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IJBPAS, April, 2015, 4(4): 2035-2041
ISSN: 2277–4998
A COMPARISON REVIEW OF ACCURACY AND RELIABILITY OF
TECHNIQUES TO MEASURE MARGINAL ADAPTATION RESTORATIONS IN
DENTISTRY
SANAM FANIHANIFEH1, ZEINAB BAHRANI2, ROJMAN NOSRATPOUR2* AND
EZZEDIN SADEGHKHANI1
1: Postgraduate student of Prosthodontics- School of Dentistry- Islamic Azad UniversityTehran- Iran
2: Postgraduate student of Prosthodontics-school of Dentistry- Tehran University of medical
Sciences
*Correspondence Author E Mail: [email protected]
ABSTRACT
The most important factor for long-term success of full-coverage restorations is marginal
adaptation. The terminology describing “fit” and the techniques used for measuring fit vary
considerably in the literature. Although fit can be most easily defined in terms of “misfit,”
there are many different locations between a tooth and a restoration where the measurements
can be made. The measurements of misfit at different locations are geometrically related to
each other and defined as internal and marginal gaps, vertical marginal and horizontal
marginal discrepancies, overextended and under extended margins, absolute marginal and
seating discrepancy. Preparation design is one of the important factors influencing the
marginal integrity. In this paper we compared the accuracy and reliability of techniques to
measure marginal adaptation restorations.
Key Words: Marginal adaptation; Restoration, Teeth
INTRODUCTION
New technologies introduced in the fixed
[1]. Achieving esthetically and functionally
prosthodontics in dentistry during past
ideal restorations has been the goal of dental
decades but controversial reports exist for
clinicians,
success and/or usefulness of these technics
manufacturers throughout the history of
prosthodontists
and
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dentistry [2]. Three main factors esthetic
uncomfortable for the patient because of the
value, resistance to fracture, and marginal
retraction
adaptation are responsible for success of a
anesthesia. Subsequently, time is required
dental restoration [3]. Inadequate fit leads to
by the dental laboratory technician for
plaque accumulation which increases the
careful pouring of the stone die or cast from
risk of carious lesions and can cause micro
the impression, preparation of the cast, then
leakage and endodontic inflammation [4]
fabrication of the wax pattern, investing,
and
periodontal
and casting. Considering the lower unit cost
diseases such with sub gingival margins [5].
of base metal alloys, a more economical
Misfit
dental laboratory technique
finally
could
terminates
to
contribute
to
cement
procedure
and
need
would
for
be
dissolution, so, obtain the best technique
helpful to replace the previously described
minimize subsequent abnormalities. In this
technique for preparing cast restorations [6].
paper we compared accuracy and reliability
Laser sintering
of available techniques to measure marginal
The dental computer aided design-computer
adaptation restorations in dentistry.
aided manufacturing (system was developed
Lost-wax
as an alternative to the traditional lost wax
Lost-wax is the traditional technique for
technique and casting method to produce
fabricating the metal substructure is the lost-
more effective and standardized fixed dental
wax technique and using various metal
prostheses (FDPs) [1]. Laser sintering is a
alloys for casting [6]. Conventionally, wax
novel technology which may replace casting
patterns were fabricated with wax and
of the base metal alloys. Briefly in this
waxing instruments for example the popular
system, a high-power laser can quickly fuse
PKT instruments. Wax is used to make the
small particles on the surface of a powder
patterns because it can be conveniently
bed of the base metal alloy into a mass
manipulated, precisely shaped and can also
representing the desired three-dimensional
be completely eliminated from the mold by
object by scanning cross-sections generated
heating. The fabrication of the wax pattern
from a 3 dimensional digital description of
is the most critical and labor-intensive step
the part. This can be done from a CAD file
in making the porcelain fused-metal crown
or another file created from scanned data.
[7]. To fabricate a restoration prepared
After each cross-section is scanned, the
using the lost-wax technique, the dentist
thickness of the powder bed of the base
must first make an impression and the
metal alloy is lowered by one layer, and a
impression
new layer of base metal alloy is applied on
appointment
may
be
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top. This process is repeated until the part is
the acceptable standard, the exposed soluble
completed. The physical process involved
dental
with the laser sintering can be full melting,
Cariogenic microorganisms accumulate in
partial melting or liquid-phase sintering and
the void and cause caries development
up to a hundred percent density can be
under the crown [10, 11]. Fixed dental
achieved [8].
restorations mainly aim to restore function
Selective laser sintering
and esthetics of lost intraoral structures
Selective
laser
manufacturing
sintering
(SLS)
technology
is
a
recently
cement
will
dissolve
rapidly.
without jeopardizing the oral or general
health of patients [12].
introduced in dentistry. SLS, is one of the
Accuracy of techniques
fast prototyping production techniques, uses
Several systems have been introduced for
a high-temperature laser to beam selectively
the fabrication of nonmetallic ceramic
substructure metal powder based on the
crowns. All ceramic materials are widely
CAD data with the FDP design. A thin layer
used in dentistry for restoring anterior and
of the beamed area becomes burnt and the
posterior teeth to provide a metal-free
FDP is completed by laminating these thin
structure and esthetic appearance [13, 14].
layers. The metal-ceramic crown is formerly
Ceramic crowns/copings can be made from
one of the most commonly used FDPs and
different high-strength ceramic materials,
the lower core is mostly produced by the
and various manufacturing processes can be
lost wax technique and casting method.
used. Today stronger and tougher ceramic
However, SLS system has several benefits
materials are available, such as a lithium
such as material, time and expenses saving
disilicate-reinforced glass ceramic [13].
was well as the production is simpler
All
compared to the existing methods [9].
requirements for strength and precision of
Marginal gap is the critical point for
marginal fit for clinical success [15].
accuracy of techniques
Marginal fit is one of the most important
Marginal integrity is a critical factor in the
criteria for the long-term success of all
success or failure of a cast porcelain-fused-
ceramic
to-metal
If
discrepancies expose the luting material to
margins are not managed appropriately, they
the oral environment, thus leading to cement
may contribute to the cause of many clinical
dissolution and micro leakage [10]. The
problems. If the gap between the prepared
cement seal becomes weak, permits the
tooth and the crown margins is more than
percolation of bacteria, and can cause
veneer
crown
restoration.
ceramic
restorations
crowns.
must
Increased
ensure
marginal
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inflammation of the vital pulp [13, 16]. In-
What constitutes an adequate fit has not
vivo studies have provided evidence that a
been satisfactorily resolved in the literature,
large marginal discrepancy in a fixed
and each study attempting to evaluate fit
restoration correlates with a higher plaque
must establish its own definitions then
index and reduced periodontal conditions.
attempt to draw conclusions based on those
Types
definitions. The choice of terminology and
of
finish
lines
and
ceramic
manufacturing technique are the factors that
definitions
have been investigated for all-ceramic
unavoidably introduces the bias of the
crowns. Heavy chamfers and rounded
investigator.
shoulder finish lines have been advocated
terminology and definitions of fit in the
for all-ceramic crowns, as well [13]. The fit
literature
of crowns is influenced by the quality of the
difficulty in dealing with this subject [17].
investment material and the metal, the
Lost-wax Vs. SLS
casting conditions, the firing of porcelain,
Metal ceramic is the common material for
and the polishing. Fabrication procedures
fabricating complete coverage crowns and
are also directly related to the skill of the
fixed partial dentures where is considered as
technician
the standard treatment in dentistry. Lost-
[7].
Studies
have
reported
measurement of fit relative to marginal
wax
adaptation,
technique
internal adaptation,
vertical
seating,
radiographic
appearance
clinical
adaptability
as
judged
is
often
The
subjective
wide
demonstrates
technique
for
is
and
variety
the
the
of
inherent
old-fashioned
fabricating
the
metal
and
substructure and using various metal alloys
by
for casting. Lost-wax used to make the
experienced practitioners. Two common
patterns
techniques are measurement of embedded
conveniently manipulated, precisely shaped
and sectioned specimens and measurement
and completely eliminated from the mold by
of specimens (or their replicas) by direct
heating [18]. The fabrication of the wax
visualization. Mechanical devices, such as
pattern is the most critical and labor-
the tracing jig to measure relative distortion
intensive step in making the porcelain
at the margin during porcelain firing cycles,
fused-metal crown. Disadvantages of this
have also been used frequently. Studies
system includes: time consumption, quality
concerning preparation design, marginal
of wax–up’s is dependent on the skilled
configuration,
and
labor of the individual. Also, because of the
cement thickness must ultimately address
wax pattern’s color and glossy surface,
the question of fit to reach conclusions.
small defects cannot easily identify [7].
marginal
finishing,
for
many
reason
such
as
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Owing to the increased demand for safe and
inappropriate
esthetically pleasing dental materials, new
gingival inflammation and reports the most
high strength ceramic materials have been
important factor in periodontal disease
recently introduced as materials for dental
prevalence is an unsuitable marginal fit
devices. When we started research and
[11]. Marginal fit is one of the most
development in the1980s, the design and
important criteria for the long-term success
processing
of
using
of all ceramic crowns. This paper is heading
CAD/CAM
technology
generally
of our recent research which based on that
believed to be simpler and easier than for
we want to compare effects of lost-wax and
industrial products [19]. The SLS has
SLS using sloping shoulder and a shoulder
several advantages which are impressed in
bevel on marginal integrity of metal-
section 3. So to avoid repetition we avoided
ceramic crowns. So, we are trying to
list of benefits for this system here. This
introduce new methods instead of old time
paper is part of our incoming research
consuming and costly methods which have
which based on that we want to compare
been
effects of lost-wax and SLS using sloping
restorations in dentistry.
shoulder and a shoulder bevel on marginal
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