Case Study 3

‘Magnification – so what!’
Case report 3.
Resin composite restorations.
Dr. Shamir B. Mehta BDS BSC MClinDent(Prosth) – GDP Harrow, Senior clinical teacher & Deputy
Director MSc Aesthetic Dentistry, King’s College London.
Dr.Subir Banerji BDS MClinDent(Prosth) – Programme Director MSc Aesthetic Dentistry, Senior
Clinical Teacher King’s College London Dental Institute. Private Dental Practitioner, Ealing, London
The popular use of dental amalgam as a posterior restorative material appears to be in a steady state of
decline. Indeed, in some countries the use of dental amalgam has been prohibited (largely on account of
environmental grounds), whilst in others its application is considered unsuitable amongst specific groups of
patients (primarily due to toxicological concerns). In contrast, the use of resin composite as a posterior
restorative material is becoming increasingly popular. A study in 1997 reported dental amalgam to be the
primary choice of posterior restorative material amongst 65% of American dentists surveyed (1); in contrast
another such survey in 2002 revealed the proportion to reduce to 54% (2). It would be fair to speculate (with a
reasonably high level of predictability) that this trend is likely to continue, as resin-adhesive technology is
continuing to evolve.
It has been almost half a century since Bunoncore first described the use of BisGMA based resin composites.
Whilst the first generation of resin composites were rather poor in terms of their mechanical properties and
aesthetic value, it is now possible to place posterior tooth coloured resin restorations which present superior
aesthetics, reduced need for tooth preparation and an average longevity times that are not too dissimilar to
what can be expected from silver amalgam restorations. This is largely thanks to advances in adhesive
dentistry over the past three decades, together with improvements in composite technology (at both the filler
and matrix level), as well as the fulfilment of certain criteria when planning such restorations. In general the
latter include the avoidance of extensive cavities, circumstances where good moisture control may be
unattainable, where the patient may display signs of poor oral hygiene, high caries susceptibility,
parafunctional clenching/grinding habits or indeed an allergy to any resin based materials. Clinical cases where
the centric stops may be on the restorative material, or where the gingival cavosurface margin may not be on
intact enamel, should also be viewed with increased suspicion.
Currently, it is not uncommon to open a composite resin kit to discover a large array of shades of resin , which
when applied correctly can result in almost ‘lifelike’ restorations – hence the concept of ‘composite-artistry’. In
order to master the craft of composite-artistry there are certain pre-requisites that the clinician must be fluent
with. These include a good working knowledge of:
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The principals of dental occlusion and adhesive dentistry respectively,
The product being used,
The concept of resin layering,
The establishment of anatomical form and function,
The ability to correctly finish and polish the restoration.
The use of optical magnification can be particularly beneficial when fabricating composite resin restorations,
so as to optimally form and contour restorations to also include minor subtleties, which impart a life-like
appearance, as illustrated by cases 1 and 2 respectively below. Both of these cases have been completed with
the use of a Carl Zeiss operating microscope.
Case 1 is an example of a failed resin composite restoration in a maxillary molar tooth, Figure 1. The use of
optical magnification can prove to be of great benefit when assisting the clinician in achieving an accurate
diagnosis. Following the administration of a local anaesthetic, rubber dam isolation was applied, and the failed
restoration and caries were removed. The occlusal cavity margin was then prepared to receive a butt finish,
and air abrasion applied (Dentoprep) to improve retention form.
A Teflon coated, dead soft sectional matrix band, and ring were applied (Garrision Solutions), as depicted by
Figure 2. A flexible wedge was used to support the sectional matrix. The merits of sectional matrices versus
circumferential matrices in attaining patent contact points in the inter-dental areas have been well
documented in the contemporary literature . 37% ortho-phosphoric acid was then applied to the enamel
tissues using a ‘total etch’ technique for a period of 30 seconds. The enamel was washed and air dried (taking
care to avoid dehydration of the dentinal layer), and the dentinal tissues rehydrated with the application of a
moist cotton wool pledget lightly soaked in distilled water, a technique known as ‘wet bonding’. Optibond Solo
(Kerr), was then placed into the cavity preparation with the aid of a microbrush. Following a period of 20
seconds, the latter dentine bonding agent was gently air dried to permit solvent evaporation, and light cured
for a period of 30 seconds, with the aid of a SDS Kerr VCL Complete light curing unit
Following the selection of an appropriate shade of resin composite (Miris, Coltene), the enamel shade was
applied in two separate increments to form the mesial marginal ridge. Each increment was placed in layers no
more than 1.0mm in thickness, so as to permit adequate light curing, as well as assisting an overall reduction in
the ‘C-Factor’ by minimising the ratio of the bonded to un-bonded cavity walls, thereby minimising the
undesirable effect of polymerisation shrinkage commonly associated with resin composite based materials (3).
The incremental formation of the mesial marginal ridge may also allow the clinician greater control over the
formation of a patent contact point in the inter-proximal area, as he or she has the opportunity to press the
matrix band firmly against the adjacent proximal surface with the aid of a dental probe, whilst applying the
second increment. Each increment of resin composite was light cured for a period of 30 seconds.
Figure 1. Failed resin composite restoration in a maxillary molar with extensive secondary caries.
Figure2. Teflon coated sectional band, Garrison Solutions, applied to form a patent mesial contact point.
Having established a pseudo ‘class 1 cavity form’, the sectional band and ring were removed (although the
wedge was retained in place to avoid undesired haemorrhage from the gingival papillary tissue), as can be
seen in Figure3. The first increment of dentine shade of resin composite was applied in an oblique manner, at
a thickness of no greater than 1.0- 1.5mmmm. Each cuspal slope was developed in this manner, with opposing
cusps being formed in pairs in an attempt to maintain the anatomical position of the central fissure. Each
increment was light cured for a period of 30 seconds. Subsequent layers were placed so as to attain a ‘herring
bone pattern’.
Figure 3. Following the formation of the mesial marginal ridge (in two increments) the matrix and ring have
been removed to form a ‘pseudo’ class 1 cavity.
The application of resin composite in the manner described, commonly referred to as ‘layering’, allows the
clinician to applying resins of differing properties (enamel and dentine shades) so as to not only derive a
desirable aesthetic- anatomical form in an ‘additive manner’, but also optimise the process of polymerisation,
since resin composites display limited depth of light curing. The process of layering can be significantly aided
by the use of optical magnification, so that the clinician may be able to fully appreciate the subtleties of resin
application.
Having formed the ‘dentine layer’, the chosen shade of enamel material was applied in an analogous manner
and appropriately light cured. Following a period of 8 minutes (to permit dark polymerisation), the rubber dam
was removed and occlusal contacts verified and adjusted, using a selection of composite polishing tungsten
carbide burs (West-One Dental) so as to conform to the existing occlusion. The patient was recalled after a
period of 1 week, at which point the restorations polished with the aid of Green and White Durastones (Shofu)
and polished with silicone impregnated brushes from Astrobrush (Ivoclar, Vivadent). The post-operative result
can be seen on Figure 4.
Figure4. Post-operative view.
Case #2 exhibits failed anterior resin restorations amongst both the central incisor teeth, as shown in Figure 5.
A pre-operative silicone ‘key’ was made of the existing palatal form of the central incisors so as to provide a
guide to the establishment of the desired palatal anatomy. Following the administration of a local anaesthetic
agent, the existing restorations were removed and the cavity prepared with a facial bevel and the palatal
margin finished to a butt margin. The cavity preparations were conditioned in a similar manner to that
described for case #1. The selected enamel shade was applied to the silicone key (with the key ‘in-situ’) and
the resin base material carefully adapted to the template, as shown by Figure 6. The use of resin application
brushes can be particularly helpful in achieving this. PTFE tape was applied prior to application of acid etchant,
so as to prevent the adhesion of resin to areas where its presence would be considered to be undesirable.
Having formed the palatal ‘enamel shelf’, the inter-proximal pillars were formed, Figure 7. The use of a dead
soft Teflon coated matrix as used in case #1 may permit the operator to develop this complex, critical
anatomical area to the desired level of satisfaction, by virtue of the operator being able to mould the matrix to
the required shape. The latter may prove to be challenging when using the more conventional approach of
cellulose acetate strips.
Figure5. Failing class IV resin composite restorations at UL11, UR1.
Figure 6. Silicone ‘key’ formed from the palatal contours of the existing restorations, used to guide the
placement of the new definitive restorations.
Figure 7. Palatal shelf and mesial inter-proximal pillar formed in the selected enamel shade. Note the use of
PTFE tape on the adjacent enamel surfaces to prevent unwanted adhesion.
Figure8. Dentine shade applied. Note the formation of the mamelons.
Figure 9a. Completed post-operative restorations – facial view.
Figure 9b. Completed post-operative view – profile view.
Having formed a ‘palatal envelope’, the selected dentine shade was applied, and the desired size and shape of
mamelons formed in the incisal edge area as demonstrated in Figure 8. It is possible to further customise this
area through the application of resin tints to impart subtleties to the region, which has a key bearing on the
overall smile aesthetics. The use of optical magnification may prove to be very helpful for the latter purpose.
Finally, the enamel shade was applied and the restoration finished and polished in a manner akin to that
described for case #1. Figures 9a and 9b respectively, provide a facial and profile view of the definitive
restorations.
In conclusion, it is evident from both cases described above that it is possible to attain very high quality,
functional and aesthetic dental restorations with the use of resin composite, which is indeed beginning to
challenge the need to prepare teeth to receive more ‘biologically invasive’ full coverage indirect fixed
prosthodontic restorations (. The use of optical magnification can assist the operator quite considerably with
the planning and placement of superior resin composite restorations.
References :1.
In your dental practice, is dental amalgam still the material of choice? J Am Dent Assoc 1997; 128:
1502.
2.
In your dental practice, is dental amalgam still the material of choice? J Am Dent Assoc 2002; 133(8):
1405.
3.
Tagami J, Yoshikawa T, Sano H, Burrow M, Pashley D. Effects of dentine depth and cavity
configuration on bond strength. J. Dent Res 1999; 78: 898-901.
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