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U M EA U NIVERSITY ODONTOLOGICAL DISSERTATIONS
Abstract N o 30
From the D epartm en t o f Cariology, U niversity o f Umeå, Sweden
CONVENTIONAL, MICROFILLED AND HYBRID
COMPOSITE RESINS: LABORATORY
AND CLINICAL EVALUATIONS
Jan W V van Dijken
Umeå 1987
CONVENTIONAL, MICROFILLED AND HYBRID
COMPOSITE RESINS: LABORATORY
A N D CLINICAL EVALUATIONS
AKADEMISK AVHANDLING
som med vederbörligt tillstånd av Odontologiska fakulteten
vid Umeå universitet för avläggande av odontologie doktorsexamen
kommer att offentligt försvaras i föreläsningssal
B, 9 tr By 1 D, Odontologiska kliniken, Umeå,
fredagen den 24 april 1987, kl 09.00
av
Jan W V van Dijken
Leg tandläkare
Abstract
Dijken van J W V, C onventional, M icrofilled an d H yb rid C om posite Resins:
L aboratory and Clinical Evaluations. Abstract N o 30 — ISSN 0345-7532.
Three types o f com posite resins, classified as conventional, microfilled and hybrid
resins were compared with respect to surface characteristics, effect on the gingival
margin, marginal adaptation and clinical durability in anterior cavities.
The surface characteristics were studied in in vitro systems by means o f scanning
electron microscopy. Fillings prepared in vivo were evaluated regarding surface
characteristics, marginal conditions, color stability and the effect on the develop­
ment o f gingivitis and caries.
M icrofilled resins were superior to the conventional and hybrid com posites with
regard to the possibility o f obtaining and retaining a sm ooth surface. The number
o f porosities varied greatly between the com posites investigated and could not be
related to the type or curing m ethod used in their manufacture. Marginal defects
in the form o f chip fractures and fractures in the resin parallel to the resin/enamel
border were seen more frequently in the microfilled com posite fillings than in the
conventional and hybrid resins. The severity o f the defects increased with time.
There was a great variation in clinical behaviour within each resin group. The dif­
ference in surface characteristics between the three com posites did not result in
clinically measurable differences in amount o f plaque on and degree o f gingivitis
around the com posite fillings neither during a period o f normal home care nor
during an experimental gingivitis period. Recurrent caries was the major single
reason for replacement. Patients with a greater number o f caries risk factors clearly
showed a higher caries increment, especially around com posite fillings. The short­
comings o f the three com posite resin types indicate that no material as yet meets
the demands o f an all purpose material.
Key w ords: com posite resin, caries, gingivitis.
UMEÅ UNIVERSITY ODONTOLOGICAL DISSERTATIONS
Abstract No 30
From the Department o f Cariology, University o f Umeå Sweden
CONVENTIONAL, MICROFILLED AND HYBRID
COMPOSITE RESINS: LABORATORY
AND CLINICAL EVALUATIONS
Jan W V van Dijken
Umeå 1987
Abstract
Dijken van J W V, Conventional, Microfilled and H ybrid Composite Resins:
Laboratory and Clinical Evaluations. Abstract No 30 — ISSN 0345-7532.
Three types of composite resins, classified as conventional, micro filled and hybrid
resins were compared with respect to surface characteristics, effect on the gingival
margin, marginal adaptation and clinical durability in anterior cavities.
The surface characteristics were studied in in vitro systems by means of scanning
electron microscopy. Fillings prepared in vivo were evaluated regarding surface
characteristics, marginal conditions, color stability and the effect on the develop­
ment of gingivitis and caries.
Microfilled resins were superior to the conventional and hybrid composites with
regard to the possibility of obtaining and retaining a smooth surface. The number
of porosities varied greatly between the composites investigated and could not be
related to the type or curing method used in their manufacture. Marginal defects
in the form of chip fractures and fractures in the resin parallel to the resin/enamel
border were seen more frequently in the microfilled composite fillings than in the
conventional and hybrid resins. The severity of the defects increased with time.
There was a great variation in clinical behaviour within each resin group. The dif­
ference in surface characteristics between the three composites did not result in
clinically measurable differences in amount of plaque on and degree of gingivitis
around the composite fillings neither during a period of normal home care nor
during an experimental gingivitis period. Recurrent caries was the major single
reason for replacement. Patients with a greater number of caries risk factors clearly
showed a higher caries increment, especially around composite fillings. The short­
comings of the three composite resin types indicate that no material as yet meets
the demands of an all purpose material.
Key words: composite resin, caries, gingivitis.
Jan van Dijken, Dept o f Cariology, University o f Umeå, S-901 87 Umeå, Sweden.
© Jan W V van Dijken
Printed by U m eå Universitets Tryckeri, U m eå 1987
3
CONTENTS
PREFACE
4
NOMENCLATURE OF COMPOSITE RESINS
5
INTRODUCTION
6
Background
6
Composition and curing method
8
Properties o£ composite resins
11
polymerization shrinkage
11
polymerization defects
11
water absorption
13
Clinical consequences of the properties
surface characteristics
adaptation to the cavity wall
microleakage
techniques to reduce microleakage
in vitro caries
biocompatibility
13
13
14
15
17
18
20
Clinical evaluations
22
Potential caries risk
24
Summary
25
AIMS
26
METHODS
27
RESULTS
32
GENERAL DISCUSSION
35
GENERAL SUMMARY AND CONCLUSIONS
44
ACKNOWLEDGEMENTS
46
REFERENCES
47
PAPERS
4
PREFACE
This thesis is based on the following papers, which will be referred to
by their Roman numerals.
I.
Dijken
van
JWV,
Meurman
procedures
on
surface
comparison
between
JH,
Järvinen J. Effect of finishing
textures
of some resin restoratives. A
new and old types of composite resins. Acta
Odontol Scand 1980; 38: 293-301.
II.
Dijken
van
JWV,
composite resins.
III.
Dijken
van
JWV,
characteristics
restorations
Ruyter
IE, Holland RI. Porosity in posterior
Scand J Dent Res 1986; 94: 471-8.
Hörstedt
and
after
P, Meurman JH.
marginal
3-4
adaptation
years.
SEM study of surface
of
anterior
resin
Scand J Dent Res 1985; 93: 453-
62.
IV.
Dijken
types
van
of
JWV,
composite
Period 1987;
V.
Dijken
van
gingivitis
Period 1987;
VI.
Dijken
resin
viscous
Sjöström
van
S,
Wing K. The effect of different
resin fillings on marginal gingiva. J Clin
14: In press
JWV,
Sjöström
around
different
S,
Wing
types
K. Development of initial
of composite resin. J Clin
14: In press.
JWV,
Hörstedt
restorations
placed
P. Marginal adaptation of composite
with
or
without intermediate low-
resin. A SEM investigation. Acta Odontol Scand 1987;
In
press.
VII.
Dijken
van JWV. A clinical evaluation of anterior conventional,
microfiller
and
hybrid
composite
resin
fillings. A six-year
follow-up study. Acta Odontol Scand 1986; 44: 357-67
5
NOMENCLATURE OF COM POSITE RESINS
The
nomenclature for the resin materials used in dentistry is complex
and somewhat illogical. The aim of the following section is to clarify
some expressions.
A
proper
definition
of
a
composite material is "a material system
composed of a mixture of two or more macro constituents that differ in
form
and that are essentially insoluble in one another"
According
(Glenn 1982).
to this definition, many materials used in dentistry can be
considered as composites.
reacted
particles
aluminium
of
Glass ionomer cements for example consist of
glass
polyacrylate
connected
chains.
by
a
matrix of calcium and
In dentistry the term composite resin
has been reserved for the methacrylate based resin materials which are
polymerized
with
50%
by
free
radical initiated polymerization and reinforced
at least 50 vol% (=60 wt%) of filler particles.
filler
resins
vol%.
is
arbitrary
(Glenn
1982)
The selection of
and some of the microfilled
have been marketed as composites despite a filler content < 50
In this thesis the term composite is also used for these resins.
Three groups of composites can be identified according to their filler
content.
Conventional
composite
resins,
the
first generation of composites,
contain relatively large filler (macrofiller) particles such as ground
quartz,
borosilicate glass or lithium aluminium glass. Most particles
range in size 20-50 pm, and the total range is 0.1-150 pm.
Microfilled composites contain so called microfine filler particles of
pyrolytic
silica (SiO^),
0.04
They were developed in 1974 and were marketed at the end of
pm.
in the range of 0.007-0.14 pm with a mean of
the 1970s.
Hybrid
composites.
According
"anything
of mixed origin".
used
resins
for
containing
to
Websters
dictionary
a
hybrid is
In dentistry the term hybrid composite is
a
blend
microfine pyrolitic silica particles.
of
macrofiller particles and
6
INTRODUCTION
Background
The
first
silicate
1985).
high
cement introduced in 1904 by Steinbock and Richter (Hendriks
The
popularity
compressive
cements
and
tooth-colored filling material available on the market was
known
their
protect
of
the silicate cements was related to their
strength
- they were among the strongest inorganic
at that time - their physical and esthetic properties,
slow
release
adjacent
tooth
of fluoride. The fluoride content helped to
enamel
from
caries
and
was
of
definite
therapeutic value.
Many
of
the silicate restorations, were successful and clinical life
times
have
years
(Bowen
with
the
material
been
reported
of up to 20 years, with an average of 4,5
1968, Robinson 1971). However, there were disadvantages
silicate
which
cements which prompted a search for a replacement
led
to
the
development
of
the polymeric anterior
restorative resins.
Early,
attempts
employing
were made to use resins as a restorative material by
methylmethacrylate polymers (MMA),
intended for heat-curing
crown and bridge applications. The polymer was mixed with a monomer in
order
to form a material which could be packed into the tooth cavity.
The
first
by
Kulzer
self-curing dental resins were based on a patent taken out
(1943).
temperature
with
by
benzoyl
The
methylmethacrylate
was
hardened
at
room
bringing a tertiary amine as accelerator into contact
peroxide as the catalyst. A redox reaction thus started
the polymerization of the monomer (Bauer 1949, Salisbury 1943,
1950).
Cold curing resins were widely used from the beginning of the 1950s in
Class
III
and Class V restorations and in Class IV restorations with
supplemental
technique.
manipulated,
synthetic
retention
provided
Because
of
the
dental
materials.
the
by
apparent
market
However,
very
a
pins and later by the acid-etch
ease
with which they could be
soon
number
became
of
overloaded with
problems
were quickly
manifested clinically.
The major problem was a shrinkage of up to 10 %
in
polymerization.
volume
during
The
shrinkage
could
not
be
7
compensated
leakage
for
by
allowed
pulpal
subsequent watersorption.
the ingress of bacteria leading to discoloration and
inflammation.
these
restorations
brush
technique
(Nealon
1952)
problems
Recurrent caries was frequently observed around
(Caul
and
introduced
afforded
of
The resulting marginal
Schoonover
1953, Hedegård 1955). The
for successive applications of the resin
a
slight
improvement but did not solve the
the self-curing resins. The shortcomings of the unfilled
resins led to the continued use of the silicate cements.
The
idea
of
improving
the
cold
curing resins by mixing them with
inorganic filler particles to form composite resins dates back to 1951
(Knock
and
Glenn).
appropriate
thermal
Paffenberger
et
al
suggested
in
1953
that
fillers could reduce the polymerization shrinkage and the
expansion of the dental resins. The objective was to maximize
the ratio of reinforcing filler to resin.
Pioneering
of
work
Standards
was performed by Bowen (1956) at the National Bureau
in
Washington.
modification of the
or
BIS-GMA
reaction
cured
BIS-GMA
forms
is
for
a better resin a
bisphenol
in
1962. This
resin which was a
A and glycidyl methacrylate could be
a
a
1963,
1965).
resin with less polymerization shrinkage and higher
1963). To facilitate the insertion of
into cavities the viscosity was reduced by the addition of
liquid
high
was introduced
of
than MMA (Bowen 1962,
resin
more
search
intraorally by a chemical catalysator (Bowen 1962,
viscosity
the
the
epoxy resins, known in dentistry as ”Bowens resin”
resin,
product
In
dimethacrylates
of lower molecular weight. However,
too
concentration led to undesirable polymerization shrinkage.
noteworthy
that
It
until very recently almost all dental composites
were based on the BIS-GMA resin. Bowen combined silica powder with the
BIS-GMA monomer and achieved a highly loaded (around 70%) restorative.
He
suggested
in
1964 an uneven size distribution for the fillers in
order to get maximum packing of the inorganic filler.
The
addition
of
filler particles was an improvement. The composites
exhibited
increased
increased
modulus of elasticity and hardness. They also absorbed less
water
and
had
a
compressive
lower
polymerization
shrinkage
composites
comparison
laboratory,
seventies.
in
led
They
to
coefficient
tensile strength as well as an
ofthermal expansion and less
(Glenn 1982). The superior qualities of the
with
universal
gradually
and
the unfilled resins, at least in the
acceptance
replaced
the
of
the
unfilled
resins
resins
in
the
and
the
8
silicate
cements.
disadvantages
adaptation,
adhesion
However,
as
clinical
use
increased,
the
of the composites appeared in the form of poor marginal
difficulties
to
tooth
in
maintaining a polished surface,
lack of
structure and an esthetic appearance that did not
endure.
During
the
obtain
a
1970s, microfillers were used as reinforcing particles to
more
polishable
resin.
At
the
end
of the 1970s hybrid
composite resins were introduced which contained a blend of macro- and
microfiller
particles,
conventional
improving
glass
in an attempt to combine the properties of the
and the microfilled materials.
composite
fillers,
Other approaches aimed at
resins were the introduction of finer and softer
resins with a higher load of particles and the use of
resins with porous glass (Bowen & Reed 1976, Ehrnford 1983).
A
different
1970s,
line
of
development
ionomer
cement
cement).
(the
official
seen at the beginning of the
ISO
the glass
terminology: glass polyalkenoate
It is by definition a composite resin but in dentistry it is
not referred to as such.
successful
properties
polycarboxylate
cementing
almost
was
when a new tooth colored restorative was introduced,
crowns
the
greater
cement
and
of
both
which
was
bridges.
the
silicate
cement
to
acid
and
the
used as a lining material and for
The
new cement had the strength and
translucency of the dental silicate cements,
resistance
adhesive
It was developed in an attempt to combine the
attack.
It
also
and showed a
appeared to have the
and biocompatible properties of the polycarboxylate cements.
The
filler
is
released
effective
is also an aluminosilica glass,
from
as
the
silicate
set
cement
cement
in
containing fluoride which
(Forsten 1977b).
inhibiting
It should be as
recurrent caries (van
Dijken 1986).
Composition and curing method
A
dental
composite
consists
basically
of three parts:
the organic
matrix, the coupling agent and the inorganic filler.
Matrix:
The
major
monomer
component used in most of the commercial
composite resins is the BIS-GMA or modifications of the molecule.
composites
Some
contain aliphatic or aromatic urethane diacrylate as major
9
monomer
component.
Diluent
monomers
are
used
to
facilitate
the
handling of the material (Lambrechts 1983, Ruyter 1985).
Filler:
Conventional
composite resins
contained between 55-60 vol%
(=70 wt%) filler particles, while the first microfilled composites had
a
filler
load
composite
in
the
range of 17-40 vol% (30-55 wt%). Most hybrid
materials contained a total of 75-85 wt% filler of which 7%
was pyrolitic silica.
The
inorganic
composites
is
strontium.
a
of
will
most
hybrid
resins and some conventional
glass made radiopaque by incorporation of barium or
Pyrolitic
particles
hybrid
filler
not
composites
silica
make
for
and
the
traditional
quartz
filler
the material radiopaque. During the 1980s,
posterior
use
were
introduced,
containing
smaller filler particles with an average size of 2-5 pm.
Initiator - activator:
Composite resins can be divided into chemically
cured and light-cured
resins. The
the
latter
a
two-component
into
two
most
system
commonly
by
used
a
the
reaction
the
deeper
is
initiated.
initiator
system
Simultaneously
and the matrix.
initiated
and the other an
The
is benzoyl peroxide
through
a
bond is formed
In a one-component system the
the
absorption
of light by a
In contrast to the chemically cured systems,
is
not uniform in a light-cured material.
materials
problems
in
materials.
diketone,
produce
an
the rate
It is fastest
layers (Cook 1983). Although originally developed as UV light-
resulted
1985).
monomer and filler is divided
illuminated surface and becomes progressively slower in the
polymerized
health
containing
In a
tertiary aromatic amine. Free radicals are generated
is
photo-initiator.
near
paste of the
initiator-activator
particles
polymerization
of
one
polymerization
between
the
The reaction starts when the two components are mixed.
activated
and
one-component system (Buonocore and Davila 1973).
portions;
activator.
former is a two-component system and
(absorption
associated
spectra
ca 365 n m ) , the possible
with UV radiation (Ham 1983, Pitts 1981)
the development and increased use of visible light-cured
In
these
usually
composites,
blue light is absorbed by an alpha-
camphorquinone (absorption peak at 470 nm)
(Ruyter
In the excited state it reacts with an amine reducing agent to
the
free
radicals.
leads to polymerization.
This starts a series of reactions which
10
The
no
light-cured materials have a longer manipulation time and require
mixing.
stability
and
This
may
result
in
fewer
porosities and better color
since there is no amine accelerator present. The wavelength
the
intensity
of the light used to cure the resin are important
for the result (Kilian 1981). Large variations among different visible
light
have
sources
have
been shown (Newman 1983). The light-cured resins
disadvantages
materials
are
that
chemically
sensitive
to
cured
resins
do not have. The
light and polymerization can begin even
under
an operation light. Additional equipment is necessary and there
is
a
limited cure depth.
of
the
restoration
tissue
al
reactions
1973).
with
and discoloration (Stanley et al 1972, Spångberg et
microfilled
advocated
curing
2
a
to
(Ruyter
practically
mm.
and
visible
depth
1982).
realizable
Therefore
(Buonocore
transparent
depths are obtained with macrofilled than
composites
the
approximately
attain
may lead to retention failures, pulp irritation,
Greater
composites,
Incomplete polymerization in the inner part
the
Davila
For the UV-light cured
depth
of
curing
was
use of a layering technique was
1973).
Because
the resin is more
light which is more intense, these materials
of cure of 3-5 mm (Cook 1983). Because of factors as
accessibility to the light source and direction of the light the depth
of
cure
is
clinically
mostly
less
than that achieved under ideal
laboratory conditions.
Inhibitor:
ensure
Inhibitors
are
added
to
the
filler-monomer mixture to
that the composite has an adequate shelf-life. One of the most
widely used inhibitors is hydroquinone (Lambrechts 1983).
Filler-resin
filler
bond:
during
To
achieve
polymerization
a
bond
either
between the polymer and the
a semi-porous filler, giving a
mechanical bond (Bowen and Reed 1976, Ehrnford 1983) or a silane layer
on
the
used.
filler particles giving a chemical bond (Bowen 1962,
The
composites.
to
latter
is
Söderholm
hydrolytic
the
1963) is
most commonly used bond in the commercial
(1984) showed debonding of the silane bond due
degeneration
or
slow crack growth and suggested that
this could become a major clinical problem.
11
Properties of composite resins
Polymerization shrinkage
One
major
which
drawback
allows
restoration.
and
a
of
gap
polymeric materials is the setting shrinkage
to
form
between
the
cavity
wall
and
the
This permits microleakage of oral fluids containing ions
bacterial
toxins,
giving
rise to pulpal reactions,
staining of
restoration margins and recurrent caries.
The
incorporation of filler particles in the resins reduced the level
of
shrinkage,
of
1.67
to
but various composite materials still exhibit shrinkage
5.68
voi % (Goldman 1983). Microfilled composite resins
which contain a relatively high percentage of organic matrix exhibit a
larger polymerization shrinkage than the macrofilled composites.
The
photocured
restoration
cured
resins
material.
materials
contract towards the outer surfaces of the
closest to the light source in contrast to the chemically
in
which
shrinkage
occurs
towards the center of the
The shrinkage is also dependent on e.g. the diluent monomer
content (Asmussen 1975).
Polymerization defects
Polymerization
marginal
gap
shrinkage
obviously
leads
to
the
promotion
of
a
unless a bond is formed between the resin and the tooth
structure.
When
developed
during
the
bond
is
strong enough,
polymerization
can
the contraction forces
cause internal stresses in the
composite resin, the enamel or at the material/enamel border. When the
internal
resin
stress
exceeds
the
strength of the bond between tooth and
i.e. the cohesive strength,
failures
in
the
then cracks in the enamel,
cohesive
resin, and dentinal gap formation occur (Asmussen &
Jörgensen 1972, Jörgensen et al 1975, Öilo & Jörgensen 1977, Fan 1985,
van
Dijken
&
Hörstedt
1986,
1987a).
Post-operative sensitivity -
observed in connection with larger, mostly posterior restorations - is
probably a consequence of contraction forces.
12
The
recently
introduced
technique
of incremental polymerization of
resin fillings and the use of dentin bonding agents did not reduce the
shrinkage,
measured
(Forsten
1984, Jensen
1987a).
To
cervical
at
as a reduction in microleakage and gap formation
reduce
part
the
Another
and
the
1985,
marginal
van Dijken & Hörstedt 1986,
gap - especially in the non-etched
of the cavity - the application of a low-viscous resin
opening
of
way
reducing
composite
Chan
of
inlays
the
gap
has
the
been suggested (Brännström 1984).
polymerization
shrinkage is by using
made either directly or indirectly, polymerized in
an oven at 120° C and cemented with a resin.
Another
per
major problem is incomplete polymerization. Between 25 and 60
cent
of
the
dimethacrylate
composite
resin,
Svendsen
1978, Ruyter
Asmussen
resulting
&
1982). These
polymerization
strengths,
methacrylate
öysaed
authors
produces
high
low
creep
remain unreacted in the
1982,Vankerckhoven
also
in
showed
tensile,
values
conversion
polymerization
molecules
in a poorly connecting network (Ruyter &
and
composite
temperature
that
et
a
transverse
low degree of
and
low
surface
resins
is
al 1982,
compressive
hardness.
dependant
The
on the
and the concentration and chemical nature
of the initiator and accelerator (Asmussen 1982). A maximal conversion
of
reactive
groups
temperature
of
is
seen
in
the
composite
inlays
cured at a
120°C. An additional factor in a chemically activated
system is the adequacy of the mixing of the two pastes. The entrapment
of
air
bubbles
reported
by
during
several
mixing
produces an
investigators
(Forsten
important matrix defect
1977a,
Skjörland et al
1982, Reinhardt et al 1982). The porosities are reported to constitute
up to 28% of the volume.
and
wear
mostly
resistance
contain
Porosities severely impair surface morphology
(Wilder
fewer
et
porosities
al
than
1984). Photo-activated systems
chemically activated systems
(Reinhardt et al 1982, Gotfredsen et al 1983).
In
a
photo-activated
distribution
and
system,
duration
the
light
intensity,
spectral
of curing time are influential factors on
the degree of polymerization, which decreased, with increased distance
from the top surface (Ruyter & Öysaed 1982).
The
degree
clinical
of polymerization therefore is an important factor in the
performance
characteristics
(Ruyter
&
of
(McKinney
resin
restorations,
&
1982,
Wu
de
Rijk
especially
in
wear
et al 1984), creep
öysaed 1982) and color stability (Ruyter & Svendsen 1978).
13
However,
1983)
residual
or
their
photo-initiator
by-products
and
amine
accelerator (Asmussen
are primarily responsible for the color
instability of composite resins.
Water absorption
All
composite
undergo
1982).
gap
resins
absorb
water
from
the
oral environment and
hygroscopic expansion (Asmussen & Jörgensen 1972, Bowen et al
Asmussen & Jörgensen (1972),
around
expansion
composite restorations could be closed by the hygroscopic
of
molecules
the
filling material in non-etched cavities. The water
diffuse
molecules.
showed in vitro that the marginal
through
the
open
spaces
between
the
polymer
The polymer chains are pressed apart by the uptake of water
and the degree of hydratization. The water uptake is restricted by the
extent
of cross-linking.
Porosities enclosed in the material are also
filled
with
the
water
and
total
water uptake represents a linear
expansion of 0.4-0.8 per cent. The swelling process compensates partly
for
the setting contraction. Microfilled resins show higher levels of
water
that
absorption
a
than conventional composites.
hydrolytic
degradation
of
It has been suggested
the filler-matrix bond in dental
composites (Söderholm 1984) is a negative impact of water absorption.
Clinical consequences of the properties
The
composition
respect
to
of
the
volumetric
materials
changes,
and
have
the properties, mainly with
consequences for the clinical
longevity and biocompatibility of the composite restorations.
Surface characteristics
The
structure
of the polished surface of the polymerized material is
strongly
dependent on the size, packing and hardness of the filler in
relation
to
strip
cannot
the
be
resin matrix.
maintained
The smooth surface obtained under the
when
the
restorations
are
finished
14
(Dennison & Craig 1972).
a
function
of
the
abrasive
finishing
techniques
composites
(Glantz
Gavin
hard
1975).
glass
expected
surface
glaze
to
nature
produced
of
rough
the
polishing agent. Most
surfaces
on
conventional
& Larsson 1972, Dennison and Craig 1972, Gray and
The
or
Surface roughness following polishing is also
softer
resin matrix is easily removed leaving the
quartz particles protruding. A similar surface can be
emerge
after
toothbrushing
(Asmussen
1979).
A rough
can only be made smooth again temporarily by application of a
or
Calatrava
veneer
on
et
1976,
al
the
finished
Garman
et
surface
(Heath
&
Wilson 1976,
al 1977, Mc Cabe & Caddick 1978,
Williams et al 1978, Lambrechts and Vanherle 1983).
Several
authors
accumulation
&
Stallard
have
reported
that
rough
surfaces
favor
the
and retention of debris and bacterial plaque (Gildenhuys
1975,
Mörmann
promote gingivitis,
et
al 1974, Smales et al 1979). This can
recurrent caries and staining of the fillings (von
der Fehr et al 1970, Larato 1972, Smales 1975, Smales et al 1979).
Because
than
the
the
filler
particles
wavelength
homogeneous
of
material.
of microfilled composites are smaller
visible light, the composites looked like a
The
manufacturers stated that these materials
are not liable to extrinsic discoloration and that plaque accumulation
is minimal.
Adaptation to the cavity wall
The maintenance of a tight connection between a filling and the cavity
wall is dependant on the balance between shrinkage and the strength of
bonding between the material and the cavity wall. The establishment of
a
strong
permanent
tissues
is
microleakage
reduces
highly
and
bond
between
desirable.
eliminate
the
a restorative and the hard dental
An
effective
need
bonding
may
prevent
for retentive undercuts.
This
the risk of pulp damage, marginal discoloration and recurrent
caries.
The nature of a bond can be mechanical or chemical or a combination of
both. A mechanical bond is formed by the penetration of the resin into
the
micro-irregularities
technique
introduced
phosphoric
acid
restorative
to
of
by
etch
materials.
an
enamel
Buonocore
the
enamel
etched
(1955).
prior
by
means
Buonocore
to
of
the
used
85%
the use of acrylic
Silverstone et al (1975) showed that the most
15
even
etching
patterns were found when solutions of 30-40% phosphoric
acid were applied for 60 seconds. Recently, several investigators have
shown
that
etching
for
15-20
seconds
resulted
in proper sealing
conditions (Nordenvall 1981, van Dijken and Hörstedt 1986).
Initially, enamel etching was made in the placement of pit and fissure
sealants.
The
application
restorations,
veneering
expanded
of
to
hypoplasia
include Class III, IV and V
and
other
cosmetic bonding
procedures including diastema closure and labial veneering,
bonding of
orthodontic brackets, periodontal splinting and temporary bridges.
Microleakage
Marginal
permeability
has
been
75
years.
a focus of interest amongst dental investigators for nearly
The
space
between
tooth
has
possible
the
of fluid,
bacteria, molecules or ions in the
a restorative material and a prepared cavity wall of a
called
marginal
percolation,
marginal leakage and
(Going 1972, Kidd 1976a, Browne & Tobias 1986). With the
exception of when polycarboxylate- and glass ionomer cements
used,
wall,
passage
been
microleakage
are
at the interface between restoration and tooth
there
is always a gap between the material and the cavity
caused partly by the contraction of the mass of material during
setting procedure and partly because the material does not adhere
to the tooth (Asmussen and Jörgensen 1972, Barnes 1977, van Dijken and
Hörstedt
1986).
The microleakage can be related to the properties of
the filling material itself or be dependent on the procedures used for
cavity treatment and handling of the material.
Several
methods
restorations.
et
al
Browne
(1955),
et
can
be
used
to
test
the
sealing
properties of
Harper (1912) used air pressure and Fraser (1929), Rose
al
Mårtensen
(1983)
et
for
al (1965), Brännström & Nyborg (1971),
example
used
bacterial penetration as a
qualitative measure of tightness. However, the penetration of dyes and
radioactive
al
1962,
1982,
caries
van
was
isotopes
Christens
Dijken
studied
has been most frequently studied (e.g. Brown et
& Mitchell 1966, Going et al 1960, Forsten 1978,
1980). The susceptibility of the gap to artificial
in
an
acidified gel system (Kidd 1976b, Grieve
1973, Grieve & Jones 1980) and the gap itself was observed by means of
16
direct
visualization
with
light
microscopy
and
scanning electron
microscopy (Asmussen & Jörgensen 1972, van Dijken and Hörstedt 1986).
Unfortunately,
obtained
the
there
are
considerable
variations
in
the
results
with the different in vitro methods used. This combined with
lack
of
criteria
for
when
the
sign
of a gap is of clinical
relevance makes an observation made using an in vitro method uncertain
(Shortall 1982, Kidd 1985).
Microleakage
predisposes
sensitivity,
marginal
studies
concluded
restorations
irritation
However,
and
the
emanating
to
discoloration
that
pulpal
silicate
Zander
tooth
from
(1951,
pulpal
and
recurrent
inflammation
cement
the
fillings
materials
1959)
and
irritation,
acrylic
resin
caused by chemical
(Browne
Mitchell
caries. Earlier
under
was
thermal
&
(1959)
Tobias 1986).
proposed
that
inflammation was due to bacterial ingrowth in the space between cavity
wall
and
leakage
restoration.
of
fluid
From in vivo experiments,
was
accompanied
by
it appeared that the
bacterial growth, unless the
material placed in the cavity had persistent antibacterial properties.
The
presence
between
the
different
last
of
filling
and
the
has
been demonstrated in the space
cavity
materials.
wall
in cavities filled with
Numerous investigations during the
years have shown that bacterial irritation is the main cause
pulpal
damage beneath silicates,
acrylic resins, composite resins
other restorative materials (e.g. Brännström & Nyborg 1969,
1974, Qvist 1975,
1979,
Mejare
1982,
Heys
or
microorganisms
restorative
20
and
of
et
al 1979, Tobias et al 1981,
1982, Bergenholtz et al
et al 1985, Leidal & Eriksen 1985). Through the reduction
elimination
reduced
1971,
1980, Brännström & Nordenvall 1978, Brännström et al
or
of
bacterial
prevented
leakage
beneath
inflammation has been
filled
with
silicates and
(Skogedal
Tobias
al 1982). Jörgensen et al (1976) suggested that mechanical
et
in
demonstrated
teeth
teeth.
in
She
the
oral
greater
functional
concluded
Eriksen
pulpal
composites
forces
&
cavities
1976, Brännström & Nordenvall 1978,
environment
bacterial
promote
leakage.
Qvist
(1983)
leakage around composite fillings in
occlusion than in similar cavities in unopposed
that
functional
stress on teeth was the most
important factor for penetration of bacteria through leakage.
17
Techniques to reduce microleakage
Galan et al (1976) and van Dijken (1980) found that etching the enamel
wall reduced but did not eliminate marginal leakage around composites.
Eriksen
&
Buonocore
eliminated
when
(1976)
demonstrated
that
leakage
was
only
the cavity margins were bevelled prior to etching or
when the resin was extended into the etched surface enamel adjacent to
the
cavity
fillings
in
margin.
Most
studies
of
microleakage around composite
placed with the acid-etch technique, dealt with restorations
which the margins were entirely within the enamel rather than with
restorations
dentin.
been
that
Since
in
prior
observed
etches
more
the
to
that
etching
margins
both in enamel and cementum or
tags of resin can only be achieved when the enamel has
etched
margins
contained
long axis
etching
the
of
has
the prisms, bevelling of cavity
been generally accepted.
It might be
subsurface of the enamel exposed by the bevelling
readily than surface enamel. This is one reason why long
times
are unnecessary. The bevel allows a gradation of color
as the composite resin becomes progressively thinner towards the tooth
surface
(Groper
1971, Roberts & Moffa 1972, Hill & Soetopo 1977) and
decreases the occurrence of enamel fractures (Öilo & Jörgensen 1977).
Several
thus
factors adversely impair the penetration of resin into enamel
contributing
during
to
conditioning,
reaction
products,
poor bonding. These include rubbing the enamel
incomplete
removal
contamination
of
of
the
etching agent and
the etched enamel with saliva,
blood, gingival fluid or precipitation of water vapor from exhaled air
(c.f. van Dijken and Horstedt 1987b).
Resin
viscosity
(Jacobsen
et
has
al
also
1977).
been
There
thought to affect resin penetration
is
a
controversy
over
whether an
intermediate resin system of low viscosity, would better penetrate the
acid
In
etched enamel if used prior
several
in
vitro
studies
to placement of the composite resin.
no
difference
was
seen between tag
formation from a highly viscous composite resin and from a low viscous
bonding
Bryant
agent
1984,
(Jörgensen
Barnes
&
Shimokabe 1975, Asmussen 1977, Martin &
1977), while another study showed that the tags
formed with the high viscous composite resins were shorter (Nordenvall
18
1981).
Some
studies
resins
have
little
of
bonding
if
any
strength show that the low-viscous
effect
(Rider & Tanner 1977, Mitchem &
Turner 1974, Raadal 1978, Prévost et al 1982) while others indicate an
improvement
In
some
in
retention (Ortiz et al 1979, Meurman & Nevaste 1975).
studies
it
was
observed
that
the use of a bonding agent
reduces microleakage (Galan et al 1976, Qvist & Qvist 1977, Brännström
&
Nordenvall 1978, Luscher et al 1978, Forsten 1978, van Dijken 1980,
Martin & Bryant 1984) while others showed that it has no effect (Ortiz
et
al
1979, Retief & Wood 1981, Retief et al 1982). Microleakage was
significantly
margins
greater
for
both
at
the
cervical margins than at the occlusal
conventional
and microfilled resins (Retief et al
1982).
Buonocore
et
fillings
al
to
(1956)
dentin.
intermediary
layer
considerable
effort
bonding
during
for
agent.
for
idea
between
of
using
dentin
a
and
bonding
agent
restoration
led
as
to
an
a
over many years to develop an effective dentinal
products
have become commercially available
In many cavities where there is no enamel available
on one or more cavity walls, dentin bonding is essential
retention
irritation.
His
Several
the 1980s.
bonding
also did pioneering work on the adhesion of
purposes
Gap
and
formation
to
and
prevent
microleakage
and
pulpal
marginal leakage is not prevented by
most commercial dentin bonding agents (Forsten 1984, Welsh and Hembree
1985, Gordon et al 1986, van Dijken and Hörstedt 1986,
1987a).
At the present time, glass ionomer cements and polycarboxylate cements
seem
to
serve
adaptation
to
best
both
as dentin adhesive restorative material. A good
enamel and dentin without gap formation has been
shown in vivo (van Dijken 1986,
1987a).
In vitro caries
Attempts
have
microleakage
caries
and
made
to
study
the
relationship
1975).
lesions
In
for
filling
between
caries at the tooth-filling interface. The in vitro
technique of Silverstone (1967) was used to produce
caries-like
ions
been
around
restorations
in
extracted
secondary
teeth (Kidd
this technique an acidified gelatine gel provides hydrogen
the
and
carious attack on sound enamel. The microspace between
cavity
walls allows diffusion of hydrogen ions to occur
19
along
the
appeared
cavity
along
walls.
whereas
only
lesion.
On
leakage
associated
technique
Kidd
(1975,
1976b)
showed
that lesions
the cavity walls in 77 % of the amalgam restorations,
13% of composite restorations showed evidence of a wall
the
and
other
hand, Grieve & Jones (1980) examined marginal
with
composite
demonstrated
Approximately
50%
of
caries
fillings in vitro using the same
in 95% of the unetched cavities.
the restorations in etched unbevelled cavities
showed
lesions,
caries
occurred. These observations seem incompatible and Kidd (1985)
claims
that
vivo
while
the
studies.
development
in the bevelled and etched group virtually no
in vitro models should be abandoned in favour of in
The
effect
of
the
acid-etch
technique
on
caries
around composite fillings was observed earlier by Eriksen
& Pears (1978). They studied the histology of caries lesions generated
from
bacterial
lesions
plaque
penetrated
growing
along
in
unetched
an
in vitro system. The carious
class V restorations, which also
showed bacterial leakage. However in the composites made with an acidetch
technique
no
bacterial leakage was seen and the carious lesion
was limited to the free enamel surface.
The size of many caries-inducing microorganisms is in the order of
1
pm.
Bauer
necessary
form.
and
Henson
for penetration of the bacteria and for a bacterial film to
Jörgensen
marginal
(1984) stated that a space from 2-20 pm is
and Wakumoto (1968) stated that the magnitude of the
defect
must
be
approximately
50
pm
in order to produce
recurrent caries. The penetration of a small ion like the hydrogen ion
(about
1-2
indicator
Å)
of
in
the
size
of
the
to
lesions
produced in vitro as a consequence of microleakage of hydrogen
has
development.
marginal gap and cannot be directly
related
ions
caries
the acidified gel experiments is therefore a poor
The
clinical relevance of the wall
been questioned (Kidd 1985). The in vitro studies are based
on the simple diffusion of hydrogen ions along the cavity wall whereas
caries
formed
environment
longevity
that
in
vivo is a function of several conditions.
therefore
of
on
the success and
any restoration (Goldberg et al 1981).
It seems obvious
microleakage
of
has
a
bacteria
profound
bearing
The oral
and substrate will play an important
role in the formation of recurrent caries in vivo.
20
Biocompatibility
The
aim
of
biological
testing
is
to
prevent the introduction of
materials
with local or general biological side effects.
justified
need for
(ADA
1979,
(1985)
FDI
1980, BSI
suggested
under
three
profile
testing
main
so far only guidelines have been set up
1982,
that the
Despite the
DIN 1986).
In a review Mjör et al
biological testing should be carried out
headings:
preliminary
tests to obtain a toxicity
of the material, usage tests to investigate the effect of the
material in a manner identical or similar to their use in patients and
antibacterial
property
and plaque formation tests. Mjör et al (1977)
and Wennberg et al (1983) stated that many of the preliminary tests do
not
produce
the
same results as the usage tests and questionned the
validity of in vitro methods for biological testing. Development of in
vitro
methods
been
advocated
materials
(1983)
which
is
(Brown
the
concluded
restoratives
However,
more closely simulate in vivo circumstances has
Tyas
that the
still has
the
&
1979). The pulp test for restorative
most widely accepted usage test and Wennberg et al
degree
final
biological
to be carried out in the
of
pulp
reaction
in
evaluation
of dental
form of pulp studies.
relation
to
clinical
acceptability has not yet been established.
Polymerized
composites
contain a large amount of remaining unreacted
methacrylate groups (Ruyter & Svendsen 1978, Vankerckhoven et al 1982)
and many of the
(Björkner
allergic
during
components in the composites are potential
1984, Hensten-Pettersen & Holland 1985). However,
reactions
their
Tinkelman
&
20
specific
to
sensitizors
only a few
composite resins have been reported
years of use (Katz 1977, Nathanson & Lockhart 1979,
Tinkelman
1979,
Malmgren & Medin 1981, Niinimäki et al
1983, Björkner 1984).
Composite
tooth
filling
materials
contain
biologically
reactive
chemicals which are not bound when the material is introduced into the
cavity.
during
et
In cell culture tests chemically cured resins were more toxic
and immediately after polymerization than 24 h later (Wennberg
al 1983). A light-cured composite was less toxic than a chemically
cured one. Composite materials caused less cell damage than silicates,
21
cold-curing
plastics
cement
(Mjör
et
resin
material
(Spångberg
al
et
al 1973) and zinc oxide eugenol
1977, Wennberg et al 1983). The toxicity of the
is caused by substances leaking from the resin during
the first 24 hours.
The cytotoxic effect of composite materials have mostly been evaluated
in
pulp
studies.
moderate
1977,
&
in
Pulp
reactions
different
reports
ranged
from
(Brännström
none
1971,
to slight and
1972, Bloch et al
Mjör et al 1977, Heys et al 1985, Leidal and Eriksen 1985, Mjör
Wennberg
materials
1985).
None
of
the
individual components of composite
held on the pulpal walls of cavity preparations for 21 days
caused significant pulp reactions. The average response levels did not
exceed 1 on a 0-4 scale (Stanley et al 1979).
The
tissue
gingiva.
most
The
often
in
contact
with
composite fillings is the
toxicity per se may not be a serious factor in inducing
reactions
but
the
plaque
importance.
The few studies evaluating this kind of response are based
on conventional composites.
observed
the
et
adhesive
properties
may
be
of
more
Larato (1972) and Dunkin & Chambers (1983)
gingivitis adjacent to subgingival Class V composites, while
gingiva adjacent to non-restored surfaces was not inflamed. Blank
al
(1979)
adversely
Sönju
and
plaque
on
affect
the other hand found, that such composites did not
the
health of the gingiva.
Skjörland
(1976)
accumulation
on
Skjörland (1973,
1976),
and Dummer & Harrison (1983) found more
conventional
composites
than
on
polished
amalgam,
silicate cement or tooth enamel.
It
been recommended earlier that the antibacterial properties of
has
restorative
for
materials
should
biocompatibility
microspace
do
properties
may
(Mjör
be assessed as part of their screening
et
al
1985).
If bacteria found in the
cause pulpal inflammation, the different antibacterial
explain
the varying degree of pulp response.
mixed materials show some degree of antibacterial activity,
effects
(1978)
varied
showed
properties
system.
All
when fresh,
between
that
amongst
though the
microorganisms. Örstavik & Hensten-Pettersen
there
was
a
wide
variation
in antibacterial
chemically cured dental composites in an in vitro
materials
showed
some degree of antibacterial activity
but the activity was strongly diminished,
ceased totally,
Freshly
after setting and storage.
in several cases
22
Clinical evaluations
All
active
been
testing
programs on dental materials have until recently
based on evaluation of a wide variety of mechanical and chemical
properties
in
the laboratory. These tests serve primarily as a guide
for
determining whether or not a dental restorative has the potential
for
clinical
include
that
use.
Until
recently
testing programs usually did not
requirements for clinical testing.
clinical
final
evaluation
analysis
standardization
material,
of
of
the
dental
It is now generally agreed
materials is essential for the
efficiency
of
of clinical procedures,
the
materials
and
is necessary.
Clinical assessments can be made by direct or indirect techniques.
direct
the
that
including the handling of the
technique
time
of
involves
assessement,
The
an evaluation with the patient present at
i.e.
mirror
and probe type of approach.
During
the 1970s the International Dental Association (FDI) adapted a
direct
registration
performance.
graded
In
according
system,
this
system
(Cvar
&
evaluations
of
clinical
Ryge 1971) restorations were
The criteria for the clinical evaluation of tooth
restorations
marginal
quality
to criteria describing the degree of failure at the
time of examination.
colored
for
included:
discoloration,
color matching ability,
surface roughness,
cavo-surface
loss of anatomical form or
wear, marginal adaptation and recurrent caries.
In
the
some
indirect techniques the assessments are made from replicas or
type
of representation of the original filling such as clinical
photographs,
Earlier
investigations
cavities
years.
reported
The
amalgam
form
of
no
conventional composite resins in anterior
or low recurrent caries frequency after 1 to 5
marginal adaptation of composites was superior to that of
during the first year. The composites tended to lose anatomic
sooner than amalgam and surface roughness and body discoloration
occurred
Smales
casts or scanning electron micrographs (Mjör et al 1985).
(Qvist
1975,
et
al
Ulvestad
1980, Eames et al 1974, Osborne & Gale 1980,
1978,
Liatakus
1972, Leinfelder et al 1975,
1980, Chandler et al 1973).
Ameye
et
color
stability
al
(1981)
which
reported
was
that microfilled resins showed a good
comparable
or sometimes superior to the
23
conventional resins after 18 months. Marginal adaptation was, however,
not
satisfactory
concluded
Class IV and V restorations.
that
after
of
success
percentage
high
in
degree
of
30
months
than
microfilled
Loeys et al (1982)
resins
had
a higher
the conventional composites. However,
marginal
disintegration
chip
fractures
a
of
microfilled
resins
was
(Lambrechts
et
1982). Christensen & Christensen (1982) could not
al
reported
and
by the same group in another study
demonstrate differences in marginal integrity,
color match or marginal
discoloration between a microfilled and a conventional composite resin
after
3
years.
Only a few studies with a duration up to 2 years have
compared microfilled or hybrid composites with conventional composites
(Heuer
et
al
1982,
Kullmann 1985). No study has compared the three
resin types over longer periods of time.
Mjör
(1981)
reported
anatomical
form
resins
private
in
intrinsic
within
(1985)
reported
reason
for
39%
the
was
a study based on questionnaires,
the
7
that poor
major reason (41%) for replacing composite
practice,
discoloration
replaced
that
in
followed by recurrent caries (20%) and
(13%).
years.
More than half the restorations were
In
a
later study of the same type, Mjör
that
recurrent
caries was by far the most frequent
replacing
composite
resins (43%). Crabb (1981) reported
of
the investigated anterior composite fillings and 68% of
silicate
fillings
were
replaced
after 5 years. No distinction
between the different composite resin types was made in these studies.
The interest in posterior composite resins has grown rapidly initiated
by
a
demand
toxicity.
for
esthetic
Several
studied
aspects
clinically
resistance to wear.
but
dentistry
and by a concern over mercury
of the properties of the resins have been
the
main
interest
has
been
focused
on
Inadequate resistance to wear was the major reason
for the relative short life spans of conventional composites (Phillips
et
al
1973,
resistance
amounts
of
Lambrechts
1985,
Eames
to
et
wear
al
was
1974,
improved
Leinfelder
et
al
1975). Later,
by using materials with increased
smaller and softer filler particles (Vrijhoef et al 1985,
1983,
Hendriks
van Groeningen 1984, Wilder et al 1984, Dogon et al
1985, Lambrechts et al 1985, Lutz et al 1985, Boksman
et al 1986, Leinfelder et al 1986, Council on Dentai Materials 1986).
Marginal
adaptation
fillings.
Because
of
becomes
larger
a
major
movements
problem
for
the
posterior
during polymerization it is
24
particularly
necessary
gingivo-proximal
incremental
to
improve the marginal adaptation along the
margin.
placement
Attempts
technique
have
been
(Jörgensen
made
and
by
using
Hisamitsu
an
1984),
indirect curing with light reflecting wedges (Lutz et al 1986) and the
use
of
size
glass ionomer cement as a build-up base material reducing the
of
the
composite restoration (Me Lean et al 1985). The results
from these studies cannot yet be evaluated.
Many
clinical evaluations of posterior composite fillings do not show
that
recurrent
done
on
caries is a problem. Most studies, however, have been
university
faculty
members,
dental
students
or
dental
hygienists none of whom are representative populations with respect to
caries activity.
Potential caries risk
Caries
development
properties
of
the
that
a
filling
is
a
individuals susceptibility to caries.
the
role
of
if
potential
caries
made.
a
On
the
the
filling
in
caries
It is therefore obvious
development can only be
role of the patient is known. An evaluation of the
risk for the individual member of the study must be
group basis, determination of the number of lactobacilli
Streptococcus
positive
function partly of the
of the material and the handling technique used and partly
evaluated
and
around
mutans
correlation
caries
activity
1983).
When
between
(Klock
one
in
&
saliva
the
or
number
dental plaque, has shown a
of microorganisms and the
Krasse 1978, Crossner 1981, Zickert et al
variable
at
a time
- e.g.
buffer capacity,
sugar
intake, amount of lactobacilli or S. mutans in saliva and oral hygiene
is
tested
for
correlations
Grahnén
et
its relationship to dental caries, no or only weak
with
al
caries
1977,
activity were found (Bagramian et al 1974,
Ainamo 1980, Bellini et al 1981, Eriksen et al
1986). When a concerted evaluation of several caries related variables
is made the possibility of evaluating the potential caries risk for an
individual
is
increased
(Rundegren & Ericson 1978, van Dijken et al
1986, Bergman & Ericson 1986, VII,
The
multifactorial
disqualifies
the
use
nature
of
any
of
Stecksén-Blicks 1986).
the
single
caries
disease
inevitably
test as the sole basis for an
25
evaluation
of
the
caries is improved
caries
risk
of an individual. The prediction of
when several test parameters are combined.
Summary
Despite
the
improved
resins,
the
conventional
disadvantages
which
qualities
of the composites over the unfilled
composites
still
revealed
a
number
of
led to clinical problems. Polishing difficulties
and problems in obtaining lasting smooth surfaces led to rough filling
surfaces
with
large
Discoloration
led
Porosities
within
absorption
and
shrinkage
led
internal
plaque
formed, and to gingivitis.
need for rapid revisions of the fillings.
resin
material
roughness.
led to increased wear, water
A relatively high polymerization
stress
in
the
composite
resin,
enamel
interface of the acid-etched cavity margins.
controversy
around
the
the
of
to gap formation in the unetched parts of the fillings
material/enamel
some
to
surface
and
to
amounts
composite
about
the
reported
or
There is
frequency of recurrent caries
resin fillings. No consideration was taken in these
studies to the potential caries risk of the individuals.
No
studies
resins
have
with
surface
No
study
of
the
been published comparing the conventional composite
the new microfilled- and hybrid composites regarding the
characteristics and irritating effect on the gingival margin.
has compared the marginal adaptation and clinical behaviour
three
individually.
types
of
composites
either longitudinally or intra-
26
AIMS
The aims of the present investigations were to examine
the
effect
of
commonly
used
finishing
techniques on the
surface texture of different composite resins.
porosities in different composite resins.
the
effect
of
different
types
of composite resins on the
marginal gingiva.
the effect of the use of an intermediate low-viscous resin on
the
marginal
adaptation of microfilled and hybrid composite
resin fillings.
the
clinical
quality
and
durability of different types of
composite resins in anterior cavities.
27
METHODS
Preparation of test specimens. In Study I, the specimens were prepared
by
allowing
pressure.
the
The
resin to set in plastic molds for six minutes under
specimens
were
then
kept
in
were
prepared
moist chambers before
further handling was carried out.
In
Study
pressure
II,
test
method
essentially
specimens
and
a
in
two ways: using a
condensation method. The pressure method was
the same as in Study I, but a higher pressure was exerted
by means of a clamp.
The clamp was left in place during polymerization
of
activated materials, while it was removed for the
the
chemically
light-activated
spots.
for
materials which were then activated in five different
This method is recommended in the ISO standard ISO/4049 (1985)
preparing
solubility.
glass
with
specimens
The
order
condensated
to evaluate water absorption
and
specimens were prepared in small quartz
tubes. The chemically activated resins were placed in the tubes
a
spatula
syringe.
The
circular
and
the
materials
(diameter
pressure.
The
tubes
specimens
were
cut
with
in
light-activated
were
then
condensed
2 mm) smoothfaced
were
filled
transversely
resins
in
with the delivery
the
tubes with a
amalgam condensor, using light
and cured stepwise. The 6 mm high
in the middle.
Five test specimens
a height of 2.5 mm and a diameter of 4 mm thus obtained for each
product were used.
Scanning
mounted
electron
on
surface
metal
a
stubs
roughness
photomicrographs
on
microscopy (SEM)
descriptive
quantitatively
and
taken.
as
was
made of polished specimens
and then coated with a
porosity
evaluations
layer of gold. The
were
based
on
the
Surface roughness was evaluated qualitatively
base (I), while porosity evaluations were measured
pore
size and
pore area using a semi-automated
computer based picture analysis method (II).
SEM
replica
was
characteristics
(III)
composite fillings.
cleaning
(III)
the
used
in
two in vivo studies,
to study the surface
and marginal adaptation (III, VI) of different
Replica
samples
filling surfaces with a
for SEM were prepared by first
surface active cavity cleanser
or a 5 % sodium hypochlorite (NaOCl) solution (VI), followed by
28
spraying with water and drying with compressed air.
cleaned
surface
material.
(TEM
were
made
with
a
Impressions of the
low viscous silicone impression
The replica was prepared by filling the impression with Epon
bedding-in
resin,
Fluka
AG, Buchs, Switzerland).
The positive
casting was mounted on metal stubs, covered with gold and then studied
in
the SEM. The final evaluations were based on photomicrographs.
surface
characteristics
were
evaluated
The
on a descriptive base using
photomicrograph standards (III). The marginal adaptation was evaluated
descriptively (III, VI) and quantitatively (VI).
Selection
of patients for the in vivo studies (III-VII). The patients
had to fulfill certain criteria in terms of number and localization of
fillings
required
anterior
region.
determined
by
different
patient
and
non-filled
enamel
surfaces
present
in the
The number of fillings required in each patient was
the
need
composite
received
at
materials/placement
to
resin
make intraindividual comparisons of the
fillings
least
one
or
placement
techniques. Each
filling of each of the investigated
techniques.
In this way each patient served as a
statistical unit.
The
patients included in the longitudinal evaluation of the different
types of composite resins (VII) had up to twelve caries lesions at the
start of the study.
Filling
V,
margins located subgingivally were required in Studies IV and
while
the
and
VII
in
order
fillings in the individual patients in Studies III, VI
were located either at the gingival margin or subgingivally
to
obtain
similar
conditions
for
the
different
materials/techniques in each patient.
Restorative procedure. The cavity margins in the enamel were bevelled,
whereas
the
removed
with
field
was
saliva
finishing
then
active
were
obtained
(III,
at
equipment
then
cavity
enamel, mostly at the gingival margins, was
burs
subjected
suction
cavities
at
low speed (III-VII).
The operative
to moisture control with cotton rolls and
(III,
VII) or with rubberdam (IV-VI). The
dried by an air blast and cleaned with a surface
cleanser.
When
a
dry
operation
field could not be
subgingival margins these were exposed electrosurgically
VII). A layer of calcium hydroxide base was applied before acid
etching
were
unsupported
of
the
etched
spraying
with
bevelled enamel cavity margins.
for
60
water
s
with
37
%
The bevelled margins
phosphoric acid. After thorough
(20 s) and drying with compressed air, either a
29
low-viscous
intermediate
resin followed by a composite resin (IV-VI)
or the composite resin alone (III, VI, VII) were inserted. Excess lowviscous
resin
was
removed
by
a
gentle
blast
of
compressed air
immediately after placement. During polymerization the composite resin
was
kept
under
pressure
with
a matrix. The fillings were finished
after one week.
Clinical
recordings.
Silness
index
1963),
(Silness and Löe 1964), gingival
(Löe
1976)
and flow of crevicular fluid were measured in a cross-sectional
(IV)
and
Plaque
index
bleeding on probing (Ainamo and Bay
and one experimental gingivitis study (V). The flow of crevicular
fluid
was
recorded
Holm-Pedersen
with
standardized
filter paper strips (Löe and
1965) placed at the orifice of the gingival pockets for
three minutes. The strips were then stained with an alcoholic solution
of
2 % ninhydrin (Orban and Stallard 1969). The coloured area of each
strip
was
measured
under a microscope with an ocular grid (Egelberg
and Attström 1973).
A
slight
used
to
modification of the USPHS-criteria (Ryge and Cvar 1971) was
describe
microfilled
were
evaluated
visually
extrinsic discoloration,
marginal
of
clinical behaviour of brands of conventional,
and hybrid composites (VII). Using this rating system the
restorations
regards
the
adaptation,
and
with mirror and probe as
color match, marginal discoloration,
surface roughness and the presence and location
recurrent caries. The rating system is based on the basic clinical
qualities
of
qualities
are
made
every
a
restoration:
further
six
acceptable
or
not
acceptable.
These
divided into subratings. The evaluations were
months over a six year period after polishing of the
fillings.
Caries
risk evaluation. A prediction of the caries risk, expressed as
the potential caries activity, was made for the patients involved in a
longitudinal
evaluation
of
different
types
of
composite fillings
(VII). The prediction was compared to the actual caries development in
each
patient. The potential caries activity was defined by the caries
risk
estimated from the net effect of microbial counts, oral hygiene,
intake of fermentable carbohydrates,
The
recorded
caries
parameters
development
when
were
salivary flow rate and buffer pH.
regarded as negative factors favoring
certain values were exceeded (Rundegren and
30
Ericson
1978,
van
Dijken
et al 1986). The parameters were recorded
three times during the six year evaluation period.
Oral
hygiene
was defined as a negative factor when a plaque score of
more
than
or
2
gingival
bleeding
at
more than 30 % of the tooth
surfaces were recorded on more than one occasion.
Samples
tubes
of
stimulated
whole
saliva were collected into ice-chilled
by chewing on a lump of paraffin. The numbers of colony forming
units (CFU) per ml saliva of lactobacilli (Carlsson et al 1975), total
streptococci and S. mutans (Jordan et al 1968) were determined as well
as
buffer pH (Ericsson 1959) and flow rate. The presence of more than
5x10^ CFU/ml saliva of S. mutans and 105 CFU/ml saliva of lactobacilli
on
two of three occasions, were regarded as negative factors as was a
buffer
pH
of
5.3
or
lower
(Ericson 1972) and a flow rate of 0.75
ml/min or less. A mean intake of fermentable carbohydrates six times a
day
or more was regarded as a negative factor. The dietary record was
based
on
a four day protocol (Carlgren and Rossander 1982). For each
individual a maximum of six negative factors could thus be obtained.
Statistical
analysis.
The
surface
characteristics of the composite
materials were presented on a descriptive base (I, III).
In
the
in
and/or
vivo
filling
studies, when different types of composite fillings
techniques
were
compared,
each patient received at
least
one of
each of the types of fillings investigated and served in
this
way as
a statistical unit. To eliminate the effect of an uneven
representation
of
fillings
each material with a given index score were normalized
to
from
the
materials
in
each
patient (VII), the number of
total number of fillings with that material in the particular
patient.
placed
For
example,
out
of
four fillings made from one material
in a patient, one (25 % of these fillings) may have a score of
0 for a particular factor, one (25 %) may have score 1, and two (50 %)
may
have
score
3. When the relative frequencies in each patient are
known the scores for a factor can be calculated for all patients.
For
observations
index,
frequencies
were
(%)
compared,
variance
when
on
an
ordinal scale - e.g. plaque index, gingival
the classification in the USPHS-system (IV-VII) - the relative
of
ranked and tested using Friedmans two-way analysis of
test (Siegel 1956). When the null hypothesis was rejected or
all brands
materials
the scores for each material within each patient
or
were
not
techniques
test (Siegel 1956).
represented
were
in
each patient (VII), the
compared two at a time using the sign
31
The
size
of the marginal defects (VI) between independent samples in
the
various
test
groups,
were tested using the Mann Whitney U-test
(Siegel 1956),
while the related samples -
samples
each of the test groups - were tested using the Wilcoxon
in
the one-week and one-year
matched-pairs signed rank test (Siegel 1956).
The
differences
between two materials or between one filling and the
enamel
surface regarding the amount of crevicular fluid secreted were
tested
using the
increase
Study
in
Students t-test for paired observations (IV,
V). The
the amount of exudate between day zero and day seven in
V, was compared using a two-way analysis of variance (Steel and
Torrie 1960).
32
RESULTS
I. Effect of finishing procedures on surface textures of some resin
restorations. A comparison between new and old types of composite
resins. Acta Odontol Scand 1980; 38: 293-301.
The effects of twelve finishing procedures on the surface textures of two
anterior conventional
composites, two anterior microfilled resins and a
glass ionomer cement were investigated.
The
final evaluations based on the SEM photomicrographs, showed that the
microfilled
composite resins are superior in finishability to the resins
loaded with
larger filler particles.
The use
of
fine grit devices
resulted
in smooth surfaces.
In contrast
the macrofilled composites
showed
rough surfaces with protruding filler particles. Only the Sof-lex
polishing
system produced
smooth surfaces
on all
composite resins,
whereas
the use
of a polishing paste led to very rough surfaces on the
macrofilled resins.
CONCLUSION:
Microfilled materials are superior to macrofilled materials
as regards the possibility of obtaining and retaining a smooth surface.
II. Porosity in posterior composite resins.
471-8.
Scand J Dent Res 1986; 94:
The
pore
area (%) and the pore sizes were measured in 90 specimens made
of eight
brands of posterior composites and one anterior composite. Six
materials were light-cured and three chemically cured. The specimens were
prepared
in two ways:
condensed
specimens,
in order to simulate the
clinical
situation and pressure specimens according to the ISO standards
for laboratory test specimens.
Porosities
occupied
0.01-4.5% of the surface depending on the material.
Most
of the materials, including all those chemically activated, showed
more
porosity
in the condensed than in the pressure specimens. Reversed
results
emerged
for two of the materials,
and for another two, the
specimens were similar in this respect. The mean pore sizes were smaller
in the condensed than in the pressure specimens.
CONCLUSION:
Neither mean pore size nor total amount of porosities could
be related to the curing method of the composite resins.
III.
SEM study of
surface
characteristics and marginal adaptation of
anterior resin restorations after 3-4 years. Scand J Dent Res 1985;
93: 453-62.
A SEM replica
technique was used
to study the surface roughness and
marginal
adaptation of
278 anterior resin fillings. The fillings were
made
of two conventional,
three microfilled and two hybrid composite
materials.
After 3-4 years
in v i v o , replicas were made. The surface
roughness
studied
by SEM was graded by using photomicrograph standards.
The
degradation
of the
bonding between the acid etched enamel and the
filling material was investigated in two specified areas, one located on
the
incisal
part
and one on the gingival part of the etched margin of
each filling.
The
3/4-year-old
composite
restorations showed degradation of surfaces
and margins,
with eroded
areas and exposed filler particles. Cohesive
failures were
seen as chip fractures and marginal fractures parallel to
33
cavity margins. Rough surface characteristics increased in the following
order:
1)
light-cured microfilled, 2) chemically cured microfilled, 3)
hybrid
and conventional
composites.
A
light
cured microfilled resin
showed
the
smoothest
surface
characteristics with
less
surface
degradation and porosity. Marginal defects were seen in about 50% of the
conventional
and hybrid composite fillings. Defects occured in 66-88% of
the
chemically cured microfilled resins but in only 44% of the visible
light-cured microfilled
resin.
Marginal
defects were
observed more
frequently in stress bearing fillings than in non-stress bearing ones.
CONCLUSION:
The
type
of filler particle seems to determine the final
surface characteristics.
IV. The effect of different types of composite resin fillings on
marginal gingiva. J Clin Period 1987; 14: In press.
The
effect
of conventional,
microfilled
and hybrid
composite resin
fillings
on the gingival health was evaluated in two groups of patients.
The plaque
and gingival
indices were
recorded
in both groups. In
addition,
the
flow of crevicular fluid was recorded in the first study
and
bleeding
on probing in the second group. Group one consisted of 18
adults. A total of 108 fillings were made. Two conventional fillings were
inserted
in neighbouring
surfaces
in one proximal space, two hybrid
composite
fillings
in a second proximal space and two microfilled resin
fillings in a third proximal space in each patient. One proximal space in
the
region contained two non-filled enamel
control
surfaces.
The
observations were made one year after insertion of the fillings.
Group two consisted of 24 adults with 228
subgingival, anterior Class III
and
IV composite
fillings which were
3-4 years old at the
time
registration (c.f. III). Each patient had
at least one filling of
each
the
three
composite types and at least one non-filled enamel surface to
allow for an intraindividual comparison. The patients were not informed
about the registrations in advance of the visit.
In group one the
figures
for the
amount of plaque on and degree of
gingivitis
around the
composite fillings were not significantly higher
than the figures for the enamel surfaces. Significant differences in the
amount
of crevicular fluid were found between both the conventional and
the hybrid
composites and the enamel. In group two the indices for each
resin type were significantly higher than those for the enamel surfaces
and the fillings showed greater amounts of plaque and a higher degree of
gingivitis than the 1-year old fillings.
CONCLUSION: The degree of gingivitis increased with time. As concerns the
amount
of plaque
formed and the occurrence of gingivitis, there was no
difference amongst the 3 types of composite resins.
V. Development of initial gingivitis around different types of
composite resin. J Clin Period 1987; 14: In press.
The
development
of
experimental
gingivitis
around
one-year-old
restorations made from
the three types of composite resins and around
enamel
surfaces was
studied.
18 patients (IV) started an oral hygiene
regime
aimed
at
eliminating
all marginal gingival inflammation in the
experimental
area.
When
the gingival index scores approached zero, the
experimental period of seven days started.
The
early signs of gingivitis were significantly fewer around the intact
enamel
surfaces than around the composite surfaces. Neither the clinical
indices
nor the
exudate measurements
showed
any differences in this
respect between the three composite resin types.
34
CONCLUSION:
extent.
All
types
of
composites
promote
gingivitis
to the same
VI.
Marginal
adaptation of composite resin restorations placed with or
without intermediate low-viscous resin. A SEM investigation. Acta Odontol
Scand 1987; 45: In press.
The marginal
adaptation to acid-etched enamel of hybrid and microfilled
resin fillings, placed with or without intermediate low-viscous resin was
investigated
in v i v o . Class III fillings were placed in either the upper
or
lower front teeth in 37 adults. Each patient received two hybrid and
two raicrofilled composite
resin fillings. One of each composite resin
filling
was placed using
a low-viscous
resin recommended by the
manufacturer of the composite material.
After one week no difference was
seen between fillings of the same
material
placed with or without intermediate resin. After one year the
hybrid
resin fillings
placed using
intermediate
resin showed better
adaptation than the ones without, while no differences were seen between
the microfilled
resins.
The microfilled resins showed a greater number
and more severe defects than the hybrid resins.
CONCLUSION:
Hybrid
resins placed using
bonding
agent had the best
marginal adaptation.
VII. A clinical
evaluation of anterior conventional, microfilled and
hybrid composite resin fillings. A six-year follow-up study. Acta Odontol
Scand 1986; 44: 357-67
The
clinical
behaviour and durability of 303 anterior resin fillings of
seven composite materials - 2 conventional, 3 microfilled and 2 hybrid were evaluated over a six year period. The restorations were placed in 27
patients
including patients who experienced relatively high levels of
caries.
Each patient received at least one filling of each of the three
composite
resin types.
Each restoration was evaluated with respect to
extrinsic
discoloration,
color match, marginal discoloration, marginal
adaptation,
surface roughness and the presence and location of recurrent
caries.
A prediction of potential
caries
activity was made for all
patients.
The prediction, based on six caries risk factors, was compared
to the
actual
caries development during
the six year period in each
patient.
Unacceptable
color match scores varied widely among the brands
(3.5-79.7%) after six years. Unacceptable marginal discoloration was seen
in
1.7% of the
restorations,
while unacceptable marginal adaptation
varied
among
the resins (13.7-37.3%). Recurrent caries occurring at the
margins
of the composite
fillings varied among the materials (9.3% 29.4%).
During
the
experimental
period between 14.8% and 55.1% of the
fillings of each material were replaced per patient. Recurrent caries was
the major reason for replacement.
CONCLUSION: There was
a wide variation
in clinical
behaviour and
durability within
each composite resin group. Recurrent caries was the
major
reason for replacement. Patients with a high number of caries risk
factors
showed
a clearly higher
increment
of caries, especially of
recurrent caries around composite fillings.
35
GENERAL DISCUSSION
The
In
evaluation of a filling material can be made in vivo or in v i t r o .
vivo
the
investigations
probe
and
information
and
color
on
visual
inspection
(Smales
and
Creaven
1979). The
obtained in this way about roughness, marginal adaptation
matching
systematic
1971)
are generally based on an evaluation made by
has
evaluation
the
weakness of not being quantitized.
suggested
in
The
the USHPS-system (Cvar and Ryge
helps to standardize the evaluations but as the system is based
only
small
a
few scores it is not sufficiently sensitive for testing a
number
of samples in an experimental series.
It is more suited
for use on larger populations in epidemiological evaluations. Attempts
to
increase the number of descriptive ratings have merely resulted in
poorer evaluator agreements (Mjör & Haugen 1976).
It
is
now
performed
majority
not
the
consented that clinical investigations should be
as a final evaluation of new restorative materials,
of
been
often
general
the
subjected to previous clinical investigations.
obliged
same
of
materials
Several
composites;
product,
Dentists are
to base their judgements on the information applied by
manufacturers.
studies
but the
composites introduced to date on to the market have
the
problems
arise
in
long-term
clinical
the uneven composition between batches of the
change
of
composition,
and the disappearance of
from the market before substantial clinical tests have been
performed (Lambrechts 1983, VII).
It
is
difficult to predict clinical behaviour from laboratory tests,
which determine only whether a material has the potential for clinical
use.
The
shortcomings
have
led
to
making
can
replica
be
made
evaluations
make
the
a
of the subjective clinical assessment methods
development
models
of more objective ranking methods.
of the surfaces (III, VI) direct measurements
of defects in the surface. This provides more objective
of
the quality of the surface. Another possibility is to
multipower
enlargement
of the replica sample or of a cross-
section of it (van Dijken and Horstedt 1986,
visual
that
inspection
might
probe.
surface
SEM
By
of
indicate
defects.
biological
observations
roughness
offer
qualitatively
1987a) to make possible a
Such defects although of a magnitude
risk
an
would
excellent
(I,
III,
not be recognized by a
means
VI)
and
for evaluating
the
enlarged
36
structures
can
replicating
be
used for morphometric measurements (II). By using
techniques
it
is also possible to monitor continuing in
vivo changes in surface morphology for extended periods of time.
The
finishing
problems.
The
materials
is
traditional
conventional composite resins still raises serious
difference
such
in
that
hardness of the two major parts of the
a smooth finish cannot be obtained with the
polishing procedures (I). Some microfilled materials were
introduced
could
of
in
the
seventies and the manufacturers claimed that they
be polished to a smooth surface. At the same time new polishing
devices
were
composites.
various
designed
anterior
profilometer
confirmed
to
produce
smooth
surfaces
on the various
In vitro studies of the effect of polishing procedures on
(I,
that
and
posterior
composites
with
the
SEM
and
van Dijken et al 1983, van Dijken and Ruyter 1987),
microfilled
composites could be polished to a smooth
surface. The macrofilled conventional and hybrid composites showed two
different abrasion patterns (van Dijken and Ruyter 1987). One was seen
after
the
resin
matrix
seen
in
polishing
The
polishing
polymer
system was used.
The filler particles and
resulting in low Ra values and
Products,
surface
abrasion
pattern
was
seen after brushing with
pastes resulting in the preferential removal of the organic
leading
in
Toothbrushing
macrofilled
turn
in
to
a
protrusion
of
the
filler
vitro of the smooth surfaces of various
composite resins obtained initially by Sof-lex (3M Dental
St
Paul,
roughness.
MN. USA) polish also showed a marked increase in
The SEM evaluation showed the disappearance of the
smear layer obtained with the Sof-lex polish (van Dijken et al
van
structure
Dijken
and
Ruyter
1987).
between
the
various
the
influence
of
demonstrated
filler
other
matrix
particles.
1983,
disc
flattened equally,
the SEM as having the characteristics of a relatively smooth
surface.
smooth
were
particles
on
the
The
differences
macrofilled
in
surface
composites
clearly
the size, hardness and amount of the
abrasion
pattern.
The traditional quartz
particles show very little wear compared to the glass particles in the
newer
of
hybrid composites (van Dijken and Ruyter 1987). The development
composite
particles
produced
toothbrushing
composites.
resins
with a high content of smaller and softer glass
materials
resembled
very
with
surface
closely
those
profiles
of
the
which
after
microfilled
37
The
toothbrushing
al 1983,
van
Dijken and Ruyter 1987) were also seen in vivo (III, VI).
Aged
composite
with
a
SEM
similar
newly
abrasion patterns observed in vitro (van Dijken et
fillings
replica
to those
roughness,
formation
and
chip
showed rough characteristics in vivo
on in vitro samples (III).
surfaces
increased
with large filler particles studied
technique
found
finished
microfilled
loaded
the
in
aged
the
form
fractures.
resins
patches
microfilled
of
It
of
eroded
should
In comparison to
resins
showed
an
surface areas, crack
be observed that in aged
roughness occured which gave them an
overall smoother character than the aged macrofilled composites, which
showed rough characteristics over the whole surface.
It
can
be
concluded that the final surface structure of a composite
filling
will
use
polishing
of
superficial
softer
be
determined by toothbrushing procedures in vivo. The
procedures
layers
abrasives
lasting
than
effect.
resulting in smooth but easily abraded
or polishing devices with more finely grained and
The
those found in commercial dentifrices have no
clinical
degradation of the composite surfaces
occurred not only because of the mechanical forces and abrasion of the
toothpaste
but
also as a result of a combination of thermomechanical
fatigue and chemical attack.
Differences
filler
in
surface
content
can
roughness
between
materials with a similar
be influenced by the number and size of pores in
the surface of the composite. Pores, which are caused by entrapped air
are
common
and
handling
exhibit
in dental composites and are closely correlated to mixing
in
procedures.
vitro
both
Light-activated
fewer
resins have been shown to
and proportionally smaller voids than
chemically activated resins (Reinhardt et al 1982). This was also seen
in an in vivo study (III) where a light-cured microfilled resin showed
considerably
an
in
fewer
vitro
pores than two chemically cured ones. However,
study of porosity in posterior composite resins,
in
two of
five light-cured resins showed roughly the same number of pores as the
chemically
that
resins,
this
investigated
of
cured
light-cured
resins
cannot
for
light-cured
syringe
composites.
instead
This means that even if it is possible
exhibit less porosity than chemically cured
be
treated
as
a generalization and should be
each individual material. However,
composites
of
a
properly
bulk
fillings with minimal porosity.
packing
manufactured
technique
the introduction
and
may
the use of a
give composite
38
It has been stated that rough filling surfaces favour the accumulation
and
retention
of
debris and bacterial plaque and promote gingivitis
(Larato 1972, Mörmann et al 1974, Gildenhuys et al 1975, Smales 1981).
Skjörland (1973,
and
in
vivo,
quantity
large
on
1976) and Sönju and Skjörland (1976) showed,
that
the
amount
the
amount
of
in vitro
plaque accumulation differed in
various hard surfaces of the mouth. A comparatively
was formed on conventional composites,
but its presence
was scarcely demonstrable on silicate, amalgam or enamel.
Many restorations are placed adjacent to or below the gingival margin.
The
surfaces
factors
of
contributing
inflammatory
and
to
changes
suggested
the
these restorations have been implicated as possible
rough
that
gingival disease.
Waerhaug (1956)
noted
around different types of restorative materials
they were mainly caused by plaque accumulated on
area.
Löe
(1968) reported
that
the roughness
of
restorations, probably more than chemical irritation from the material
itself,
produced
inflammation. He concluded that restorations should
be well polished to reduce plaque accumulation.
Because
of
expected
rough
their
to
surface
manufacturers
has,
when
composites.
the
however,
resins
with
Enamel
is
the
microfilled resins were
affect the health of the gingiva less adversely than the
conventional
study
smoothness,
respect
probably
This
argument
was also used by the
first
hybrid composites were introduced. No
compared
the properties of the three composite
to
plaque
accumulation and gingival reaction.
the smoothest and most acceptable surface in the
mouth and all restored surfaces should be compared to it.
There
are
a
variety
inflammation.
These
and
bleeding
shape,
histological
accurate
but
to
beside
gingival
(Ainamo
that
indices
available
include those based on
tendency,
to
assess
gingival
changes in gingival color
quantity of
sulcular
fluid
and
The histological index probably provides the most
of gingival inflammation (Appelgren et al 1979),
other objectives the time and level of expertise required
prepare
method.
developed
to
assessment
obtain,
this
data.
of
for
index
and
score the biopsies limit the application of
Alternative
clinical
(Löe
gingival
use.
Among
indices
the
have
therefore
been
most commonly used are the
& Silness 1963) and the gingival bleeding index
& Bay 1975), both of which assess the tendency of the gingiva
bleed on light probing.
The bleeding indices are based on the fact
the degree of gingivitis is reflected by vascular changes in the
39
gingiva.
The
early
inflammatory
changes
of the gingival index are
detected by the subjective observation of surface changes in color and
texture.
This
subjectivity
involves
simply
scoring
is overcome in the bleeding index, which
bleeding or no bleeding and requires little
calibration. To overcome differences in the amount of force applied to
the
probe
pressure-sensitive
(force-controlled)
probes
have
been
developed.
Another
the
on
the
the
fact that when the degree of gingival inflammation increases,
amount of exudate in the gingival sulcus increases. Poulsen et al
(1979)
of
method for evaluating gingival inflammation is measurement of
gingival crevicular fluid (Brill and Krasse 1958), a method based
showed
studying
Cimasoni
(1983)
procedure
of
that
for
and
inflammation
but
gingivitis in clinical trials,
it
is the most reliable and sensitive
quantifying
gingival
in
different
parts
inflammation.
and
The
of the gingiva and the
Improved
plaque
control
may
reduce
inflammation
Multiple
severity
of
the gingival exudate fluid may reflect different
inflammation
region.
pocket.
the
stated
index
pocket
development
available
gingival
stages
that measuring crevicular fluid is an efficient method
the
not
measurements
may
reduce
at
superficial
the base of the
may be necessary to record adequately
of the disease and to follow the effect of the patients
oral hygiene procedures.
As
the
as
well
than
rate of plaque accumulation and the development of gingivitis
as the level of oral hygiene differs more inter-individually
intra-individually,
respect
to
gingivitis
the
can
same
on
index
relatively
observed
a
comparison
removal,
plaque
of
different materials with
accumulation
and appearance of
be made only if the various materials are compared in
mouth.
registered
plaque
plaque
In
two
fillings
(Silness
good
oral
supragingival
cross-sectional
of
&
studies
(IV), plaque was
the three composite resin types with the
Löe 1964).
hygiene
were
It was shown that patients with
able
to
clean plaque from the
parts of the composite fillings regardless of
the type of composite. There were more filled surfaces than there were
control
enamel surfaces with observable plaque on them. The amount of
subgingival
To
is not registered with the Silness and Löe index.
be able to evaluate the condition of the pocket the more sensitive
method
of
plaque
the
of
gingival fluid registration was used to observe the effect
subgingivally located fillings on gingival health (IV, V). No
differences
were
seen
in
crevicular
fluid
exudation
around
the
40
fillings made from conventional, microfilled or hybrid composites,
the
but
amount of fluid around the filled surfaces was always higher than
around
the unfilled enamel surfaces. The stronger reaction around the
composite
surfaces may be due to the toxicity of the materials and/or
irritation from remains of bacterial plaque.
Differences
among
in
the
gingivitis
produced
plaque
different
model
retention
and
properties evoking gingivitis
composites were also studied in an experimental
according
to
Löe et al (1965)
(V). All composites
a strong gingival response and the materials were comparable
despite the great differences in their surface characteristics.
The
results
gingivitis
found
that
cross-sectional
on
in
(IV) and the experimental
surface
characteristics per se had only
gingival responses. However,
observations
anterior
are
based
on
it must be observed
different composite resins in
fillings. The differences in plaque accumulation may be even
pronounced
cavities.
while
two
differences
effects
the
more
the
study (V) support the observations of Waerhaug (1956), who
that
minimal
of
when
These
the
areas
resins
are
used
in
posterior proximal
are more difficult for the patients to clean,
at the same time the plaque accumulation ratio in the posterior
region
of
the
mouth is faster than in the anterior part (Lang et al
1973).
Differences
in gingival responses for the composite resins in
posterior fillings should be studied.
The
SEM
investigation
of
the
adaptation
to acid-etched enamel of
composite resins placed with or without the use of low-viscous bonding
agents (VI), showed defects such as marginal fractures,
of
the
that
resin
with
and
fractures in the enamel.
chip fractures
It should be pointed out
the SEM method used, adaptation could be evaluated only at
the surface of the fillings. The deeper parts can only be investigated
in cross sections of teeth extracted e.g.
Dijken
and
Hörstedt
1986,
for orthodontic reasons (van
1987a). The most common defects observed
were fractures in the resin material often close to the filling/enamel
border.
One
marginal
week
polymerization
there
was no difference in
defects between fillings of the same material placed with or
without
a
bonding
agent
the
after
bonding
agent. The hybrid resins both with and without a
showed a significantly better marginal adaptation than
microfilled
resins (III, VI, van Dijken and Hörstedt 1987b).
contraction
stresses
microfilled
than
for
The
during polymerization, which are larger for the
the resins loaded with larger filler particles
41
are
likely
severity
one
to
be
the main
cause
of
fractures in the resin. The
of the defects for both composite materials increased at the
year
registration
which
indicates
a
decreased
resistance to
thermo-mechanical stress in the mouth.
The
marginal
important
retention,
the
defects
when
of
their
microleakage
fillings
to
composite
severity
is
fillings will become clinically
sufficient
to
cause
loss
of
or increased plaque retention and predispose
recurrent
caries.
Retention
of
composite
resin
fillings is not improved by the use of intermediate resin (VI, Low and
Majid
1979,
Ulvestad
evaluation
of
composites,
placed
at
the
etched
cervical
margins.
with
the
observed
in
will
long
the
that
application
resin
freshly
are
In a longitudinal
and
hybrid
most prone to caries were the
technique could not be used.
occur
easily along those margins and in
acid-etched
times for bacterial acids a higher
It can be concluded that the failures
margins
the
do
studied
not
necessarily
lead to
anterior composite fillings,
low viscous resin was not used. In larger fillings it may be
assumed
the
1985).
microfilled
margins
clearance
complications in
even if a
al
acid-etch
frequency of caries could occur.
clinical
et
conventional,
The
when
penetration
combination
Smith
of
without a bonding agent (VII), no caries occurred
margins,
Bacterial
1978,
fillings
bonding
will
mixed
most
not
are
penetrate
material
essential
adaptation
agents
more
necessary.
During
longer
times the viscosity of the composite resin increases,
of
the
etched
and
enamel as easily as the
(Jacobsen et al 1977). Further investigations
so
that ways of improving the cervical marginal
composite resin fillings can be discovered possibly by
finding resins with low polymerization shrinkage.
The
clinical
quality
that
implications
problem
and
of recurrent caries is both a restoration
a caries problem.
Eriksen et al (1986) reported
an increase in the prevalence of recurrent caries around amalgam
fillings could be registered only for the fillings reaching a marginal
breakdown
ranking
surfaces
pattern
scale.
a
Goldberg
correlation
moderate/severe
the
resulting
marginal
occlusal surfaces.
primarily
a
et
in
quality scores of 5 and 6 on an 1-6
al
(1981)
existed
showed
between
that for the smooth
recurrent
caries
and
quality. No such relationship was found for
Eriksen indicated that recurrent caries is not
restoration
problem,
but
is intimately related to the
42
caries-challenge
of
the patients. Unfortunately no such studies have
been performed previously for composite resin fillings.
In
a
far
recent
the
study Mjör (1985) reported that recurrent caries was by
most
common
private practice.
5
years
with
(Chandler
(41%) for replacement of composites in
In other studies
a
et
reason
very
low
al 1973,
thefillings had lasted up to 4 and
rate of
caries
or no recurrent caries
Leinfelder et al 1980, Qvist et al 1980,
Ström
and Qvist 1986).
The
higher
compared
prevalence
to
(1986),
amalgam
was
composite
also
of recurrent caries around composite fillings
and gold restorations as shown by Eriksen et al
shown
restorations
Variations
in
considered
in
caries
before
Study
VII.
In this study 18.6% of the
exhibited caries at the end of the six years.
susceptibility
any
comparisons
among
individuals
must
be
between materials can be made as
regards evaluation of the frequency of recurrent caries. Use of dental
students
or
other
underestimation
1980),
of
the
with
a
chances
low
of
caries
risk
results in an
recurrent caries (Leidal & Dahl
a circumstance that underlines the importance of the selection
patients
evaluation
Ericson
in
caries
clinical
system
(1978).
accurately
for
studies.
caries
In
on
calculation
We
factors
thesis we have used an
risk first suggested by Rundegren and
predicting caries risk in a patient increases when several
a
factors.
this
It is based on the assumption that the possibility of
related factors are evaluated.
based
also
groups
of
find
develop
used
that
of
the
patients
more caries.
In this study the evaluation is
sum
with
of
negative evaluations of 6
a
higher number of negative
The system of Rundegren and Ericson was
in studies by Bergman and Ericson (1986) and van Dijken et
al (1986).
In
Study VII we found that patients with a high potential caries risk
clearly
showed
recurrent
46%
of
the
registered
for
contiguous to the composite fillings.
recurrent
caries
lesions
as root surface caries,
on
especially of
The fact that
the buccal surfaces were
can be seen as a contra-indication
composite resins as the material of choice in these cavities.
choice
of
depend
very
patients
use
a greater actual development of caries,
caries,
of
tooth-colored
with
much
on
the
material
patients
in
The
the individual patient should
caries susceptibility.
In older
three or more negative factors one must reconsider the
composites,
especially
in
teeth
with gingival recessions.
43
Materials
which
leak
fluor like the glass ionomer cements should be
used (van Dijken 1986).
Body
discoloration
as
a
fillings
was
fillings
in
practice
(Mjör 1981). Ulvestad
old
reported
reason
the
replacement
of anterior
reach 13% of the total number of replaced
a cross-sectional
conventional
Dogon
to
for
chemically
study
of
fillings
made in private
(1978) reported that 83% of five year
cured
fillings were cosmetically poor.
et al (1985) replaced 43.7% fillings made of a chemically cured
microfilled
years
resin
and only 1.5% of the light-cured variation after 3
of use. On the other hand,
only
2%
of
fillings
of
the
Ström and Qvist (1986) reported that
same
chemically
cured
resin showed
unsatisfactory color match after a four-year assessment.
A
yellowish/brownish
reported
with
(Eriksen
mismatch
increasing
1974, Ulvestad
1980).
The
color
resins
has
been
tertiary
amines
due
to
body
discoloration has been
age in several longitudinal investigations
1978,
Qvist
et
al 1980, Leinfelder et al
shift in connection with aging of chemically cured
ascribed
to
the oxidation of residuals of certain
present in the catalytic system and to the amount of
inhibitor (Asmussen 1983). Discoloration by oxidation of the unreacted
methacrylate groups has also been considered to be important (Ruyter &
Svendsson
1978).
they
polymerized by a mechanism in which aromatic amines are not
are
required
the
Light-cured
materials were more color stable since
(Asmussen 1983). However, the color stability will depend on
particular
brand or batch, because some products contain amines
or inhibitors that may break down and liberate colored agents.
The
do
number of fillings replaced because of discoloration in Study VII
not
necessarily
acceptable
attitude
wanted
color
and
to
represent
match.
sometimes
color
adjust
the
number
Patients
accepted
(Ulvestad
tended
a
of
to
fillings with a nonhave
a
more lenient
discoloration which the dentist
1978, VII).
From Study VII it is
clear that the color change is time dependant and varies greatly among
the materials.
years
are
composites.
The results clearly show that periods longer than three
required
to
evaluate
the
clinical
color
stability of
44
GENERAL SUMMARY AND CONCLUSIONS
Microfilled
larger
composite
filler
retaining
factors
a
with
smooth
which
varied
to
surface.
the
possibility
among
the
investigated
to the curing method employed.
composite
resins
aged
in
of
obtaining
and
Porosities in the resins was one of the
determined surface roughness.
greatly
related
resins were superior to composites loaded with
regard
vivo
The number of porosities
composites and could not be
The surface characteristics of
showed
degradation of surfaces and
margins.
The chemically cured microfilled resins showed more marginal
defects
than
a
visible
light-cured
microfilled
resin
and
the
conventional and hybrid resins.
The
difference
conventional,
clinically
in
surface
microfilled
measurable
of
gingivitis
of
normal
of
hybrid
and
composition of the
composites
did not result in
differences in the amount of plaque and degree
around the resin types measured either during a period
oral
development
characteristics
and
home care in the investigated patients or during the
plaque
and
gingivitis in an experimental gingivitis
study.
The
use of a low-viscous intermediate resin produced no effect on the
marginal
hybrid
adaptation
resin
of
fillings
microfilled resins to the etched enamel.
placed
with
a
bonding
The
agent showed better
adaptation than the ones without after one year.
Despite their smoother surface characteristics,
showed
their
of
with
on
the microfilled resins
no advantage over the conventional and hybrid resins regarding
effect on the gingival health, marginal adaptation or frequency
recurrent caries.
the
the
component
Since the materials are classified in accordance
content and size of the filler it may be suggested large
per
variations
within the resin groups -
based
that the filler
se is not the determining factor for the durability of
the composite filling.
In Table I a comparison is made of rankings for
different composites with respect to some of the selected variables in
Papers III and VII.
45
Table I. Ranking of the criteria evaluated in studies III and VII. The
material judged "best" for each individual criterion was ranked lowest
Cod*
turfac*
marginal
m a rg1 n a l
recurrent
l o s e of
color
roughness
defects
degradatIon
carles
retention
match
III
VI I
VII
III
VII
Conv.
Microf.
Hybri d
It
is
A
7
2.5
2
2.5
1.5
3
18.5
P
4
2.5
4
5
1.5
4
21
S
2
6
5
4
6
5
28
I
3
7
7
6
7
6
36
Du
1
1
1
2.5
5
1
11.5
M
5
4
3
1
3
2
18
D
6
5
6
7
4
7
35
quite
within
III-VII
VI I
VII
I ranking
clear
each type.
testperiods
that
there
are wide variations among materials
It should also be observed that judgements based on
shorter
than
3
years
long
are
unreliable.
Each new
composite resin must be evaluated on its own merits and not because it
belongs to a certain group.
ranking
this
than
it
techniques
and
a
any of the other materials tested. However,
was
adaptation.
not
superior
Great
careful
in
should
is
be
exercised
for
the
delicate
making a composite filling. A good technique
evaluation
there
in spite of
in terms of recurrent caries or marginal
respect
involved
essentialif
One of the microfilled resins has a better
to
of
the
caries
be a good result.
risk
of
a
patient are
Because recurrent caries
will certainly become the major reason for replacement it is important
to include caries risk patients in a clinical evaluation.
The
introduction
of the newer composite types has not yet completely
satisfied the demand for a durable anterior restorative.
resins
have
replaced
susceptibility
of
the
the
silicate cements regardless of the caries
patients.
It is suggested that the composites
should not be used as the only tooth colored restorative,
indication
patients
should
with
a
be
high
based
The composite
on
the
but that its
patients caries risk level.
In
caries risk level a fluoride-leaking material
such as the glass ionomer cements should be preferred.
46
ACKNOWLEDGEMENTS
I wish to express my
sincere gratitude to those who have contributed to this
investigation with special thanks to
Professor Thorild Ericson,
criticism given to me at all
my tutor, for all his support, help
stages of the work.
and constructive
Associate
Professor Jukka Meurman and Jaana Stadigh for valuable cooperation in
the first part of the investigation.
Dr Per Hörstedt
for
fruitful
discussions and help with the scanning electron
microscope.
Dr Eystein Ruyter,
NIOM,
and Dr Roy Holland,
NIOM, for their constructive
criticism and encouragement and Professor Ivar Mjör, Director of
the Scandinavian
Institute of Dental Materials, Oslo and all my friends at NIOM for their support,
help
and
care during my visit to NIOM and Mr Sten Stölen for teaching me how to
use the scanning electron microscope.
Associate Professor Kenneth Wing and Dr Staffan Sjöström for fruitful discussions
and valuable cooperation during the investigation.
Margareta Widman,
Christina
Bonnedahl,
Gun Dahlgren
and
Inga Hamberg
for
excellent chairside assistance.
Engineer Rolf
Sjöström for his never failing interest and valuable statistical
advice.
Professor Maud Bergman,
Professor
Axel
Bergenholtz, Associate Professor Lars
Matsson,
Associate
Professor Lennart Hänström and Dr Mats Ryberg for valuable
advice.
John Erik Dahlgren,
Bengt
Forsell, Christer Abraharasson and Bengt Carfors for
skilful assistance with the production of the photographs.
Mrs
Britt-Marie
Kvarnbrink for secreterial aid, Patricia Shrimpton for revising
the English and to all my
collagues and friends for their encouraging interest.
Last
but not
least I would
like
to extend my thanks to all my patients who
contributed to the performance of this investigation.
This work was supported by grants from the Faculty of Odontology, University of
Umeå,
Swedish
Dental
Society,
JC Kempes Memorial Foundation and the Swedish
Patent Revenue Fund for Dental Prophylaxis.
47
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