Educational Objectives
Upon completion of
this course, participants should be able to achieve the following:
• Understand what the
three classification systems in composite materials and what their indications.
• Learn clinical tips
for Class I and Class II direct posterior restorations.
• Learn layering
techniques to build in dentinal lobes, incisal edge effects and incisal halos.
• Learn simple
polishing techniques to create the appropriate finish and luster.
Introduction
Used in Class I, II
and IV restorations in the posterior and anterior regions, composite resins
represent an attractive restorative option for patients who desire minimally
invasive treatment or cannot afford more costly indirect alternatives. Among
the most versatile materials, composites might be used in direct restorations,
build-ups, cements, diagnostic mock-ups, gingival stabilization, provisionals
and prototypes. Although previous direct
composite generations have demonstrated polymerization shrinkage and the
potential for marginal leakage resulting in the development of secondary
caries, their benefits today outweigh the risks, which can be avoided when
proper materials and techniques are utilized. A viable solution to the problems of amalgam, including cusp fractures,
increased rates of secondary caries and possible toxicity due to mercury
content, has increased the demand for composite resins in recent years.
Composites
Conserving sound tooth
structure and with the potential for tooth reinforcement, adhesively bonded
composite restorations demonstrate aesthetically acceptable results. The least invasive and predictable restoration
of teeth to normal form and function, tooth-colored composites provide patients
and dentists with a cost-effective and long-lasting solution for a variety of
indications.However, four parameters dictate an ideal composite material
outcome:
• Mirror natural tooth
structure in color and translucency.
• Strength to
withstand function in high stress-bearing areas for the long term.
• Seamless or
undetectable margins from restoration to tooth for the long term.
• Appropriate polish
and luster that can be maintained throughout the life of the restoration.
Hybrids
Compared by the author
to rocks with pebbles loaded between them, hybrids or microhybrids are
heavy-loaded materials that display an average 1μ glass particle sizes and
.04μ silica in
resin.8,9 This class of materials
demonstrates high strength and opacity similar to natural dentin and enamel.
Less likely to chip, hybrids can provide strength in any of the functional
areas and, through layering techniques, can mimic dentin and enamel morphology.
A disadvantage, however, is that their polish is not long-lasting.
Microfills
Described as all pebbles
and composed of an average 0.1μ glass particles in resin, microfills display
high polishability that lasts for the long term.When compared to
hybrids, microfills demonstrate a higher resistance to wear and a
translucency similar to enamel. These materials also give dentists
the ability to replace the color, translucency, polishability, wear resistance and surface
texture of natural enamel. However, microfills lack the strength
required for many of the functional areas and can be too
translucent.
Nanofills
(Nanohybrids)
A newer-class of
composites, nanofilled materials display 20nm primary particle sizes,
consisting of zirconia-silica nanoclusters and silica nanoparticles (0.01μ glass
particles in resin). Because
this material contains even smaller particles, it has the potential to maintain
greater strength and long-term polishability.Therefore, according to the
author’s analogy of rocks and pebbles, nanofilled composites would additionally
have grains of sand. In this analogy, when wear does occur, only pebbles and
grains of sand “pluck out” leading to more favorable mechanical and optical
properties. Nanofilled composites also display opacity similar to natural enamel
and dentin, with translucency similar to enamel.
Demonstrating high
strength, nanofilled composites are less likely to chip in high stress areas.1 The only true disadvantage to nanofilled
composites, however, is the lack of in-vivo long-term studies, since the
material science is relatively new.When using the different types of
composites, it is necessary to understand that both technique and material
selection define the outcome. By using the proper composite, tints and opaquers,
along with proper layering, customization and polishing, predictable restorative
outcomes can be completed and maintained.
Aesthetics
Dentists must realize
that there are many different characteristics of the teeth, which are key to
understanding aesthetics, that need to be addressed during treatment planning. When recreating tooth shape, the line angle,
outline form and profile must be considered, along with tooth proportions,
which involves the width-to-length ratio. To develop proper symmetry, the tooth
shape must be developed first, followed by the embrasures and contact point.
Another fundamental
aspect of aesthetics, age and gender play important roles in the development of
highly aesthetic and natural appearing restorations. For example, age should be a major
consideration when building the central incisors, and gender should define the
lateral incisors. Other aesthetic considerations should include the smile line,
cant, tooth size, central dominance, axial inclination, reverse “S and S” line
angles and the natural curvature of the dentition. The location and direction of the midline is
also crucial to aesthetics and should be evaluated and developed prior to any
preparation. Once the dentition is understood and a treatment plan developed,
the facial characteristics of the patient and their skin tone must be
evaluated. By doing so, harmony between the restorations and the patient’s facial
features can be created to develop the best in aesthetics.
Basic Principles for
Adhesive Dentistry
A rubber dam should
always be used to isolate the preparation and stop contamination from blood and
saliva. Rubber dams also provide
the added benefit of preventing the patient from swallowing the potentially toxic
mercury that is present in amalgam fillings. It is important to note that once
removed, amalgam fillings should be disposed of properly. In 2007, the American
Dental Association adopted “Best Management Practices for Amalgam Waste,” which
include the voluntary use of amalgam separators. Additionally, the Environmental
Protection Agency has been reviewing options for regulating the dental industry
regarding mercury discharge, as well as for requiring the installation of amalgam
separators.The author has an amalgam separator (DRNA ISO Certified BU10 Amalgam
Separator, Dental CareWaste Management) in his office and encourages other
practitioners to incorporate one in their practices also.
Adhesive Systems
Once rubber dam
isolation is achieved, the preparation should be etched, primed and then bonded
to provide the most predictable results.Of the adhesive systems available on
the market today, total-etch, three-step systems are considered the “gold
standard” and are the author’s preference for indirect restorations. These three-step systems come in two bottles and
are indicated for use in all indirect and direct restorations. In comparison, a
self-etching, two-step system, per the manufacturer, requires pre-etching on uncut
enamel, essentially, from a technique standpoint, making a self-etching,
two-step system a total-etch, three-step system.
Class-based
Preparation and Placement
Class I
To begin preparation
of Class I indications, previous restorations and any remaining decay are first
removed. Bevels should not be used
in these situations, and rounded line angles are required internally. An incremental
filling technique must then be used when layering the new composite, being sure
not to join the buccal-lingual walls. An example of this type of restorative
procedure includes removing the decay and old restorations, then etching the dentin
and enamel. The etchant is agitated while on the surface of the tooth and left
for 15 to 30 seconds before being rinsed away. The dentin is then wet, followed
by priming and bonding using a total-etch, one-bottle system. Multiple coats
are placed and agitated before air-drying to remove the necessary contaminants (i.e.,
solvent).25 To seal the dentin and
enamel, the bonding agent is light cured.
To build the
restoration, the cuspal inclines are formed using a microhybrid or nanohybrid
composite in appropriate shades and tints where desired. Each individual layer
is light cured (ramp cured) through the tooth. The cuspal inclines are adjusted
as necessary.
Class II
Like in Class I
indications, the preparation for Class II restorations begins by removing
amalgam or old composite and any remaining decay. Once again, no bevel is used,
and rounded line angles are required. The enamel periphery ideally would
demonstrate 0.5mm to 1.0mm of enamel in height and width at the gingival floor.
Layering is similar to Class I restorations, with incremental filling without joining
the buccal-lingual walls. For
shading characteristics, 2+ shades of a microhybrid should be used, with
incisal/translucent microhybrid or microfill layered over the restoration.
Today’s nanohybrid
composites (Venus Diamond, Heraeus, South Bend, Illinois), however, can enable
us to achieve such aesthetics with a single-layer composite material. To form
the interproximal contact of Class II restorations, several options are
available, including pre-wedge before the rubber dam is placed, a sectional
matrix with proper wedging, and utilization of special instrumentation.An
example of a clinical case involves first cutting out the old amalgam filling.
The rubber dam is placed, all previous material and decay is removed, and the
matrix is placed. The preparation is then etched for 15 to 30 seconds. After
the etchant is rinsed away and the surface partially dried, the total-etch,
one-bottle adhesive is applied to the preparation with agitation in multiple coats
and, after 30 seconds, thinned with air to blow off the necessary contaminant
(i.e., solvent). The adhesive is light cured, after which incremental filling
begins, followed by carving to form anatomy. After proper anatomy is achieved
and occlusion is checked, the tooth is etched again and glazed. A surface glaze
(BisCover LV, BISCO) is then placed on the restoration to lessen micro-leakage and
post-operative sensitivity. This incremental-oblique filling technique works
well for Class II indications. Different from incremental-horizontal filling, the
use of metallic bands with oblique increments lessens the polymerization
shrinkage of composites and reduces the chance of microleakage.
In a clinical example
of this type of indication and technique, the old filling and decay are removed
first. A sectional matrix is then utilized, along with a wedge and oblique filling.
Nanofilled composite material (Venus Diamond, Heraeus) is applied to the
restoration, with an enamel layer over it.
Fig. 1: Rubber
dam isolation of broken-down teeth and restorations on teeth #30 and #31.
Fig. 2:
Incremental filling was achieved by developing dentin cuspal inclines on teeth
#30 and #31.
Note the
sectional matrix and wedge are used to assure proper interproximal contours.
Fig. 3: View of
the completed, integrated restorations with appropriate marginal ridge contact
and contours.
Class IV
Class IV indications
typically require diastema closure or full veneers and can involve no
preparation to a full 1+mm of reduction.To help with a seamless restoration, a
starburst bevel of 2+mm should be utilized, except on the gingival margin if
dentin is exposed.Layering should be completed with at least two shades of a
microhybrid material, overlaid with incisal/translucency, or microfill, to create
the dentinal lobes, incisal translucency and the incisal halo. However, today we can achieve this with a nanohybrid
composite (Venus Diamond).
Undetectable Margins
When margins are in the
aesthetic zone, a starburst bevel should be used, followed by etching beyond
the bevel.The outer layer of composite should be rolled, while wearing clean
gloves, to improve sculptability and prevent voids. The material should then be
placed and super-cured, allowing five minutes or more for the material to
settle. The margin should then be addressed first, finishing it back between
where the etch and the bevel end. Rubber wheels and polishers should not be
used on the margins, since the rubber tends to become embedded in this area.
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