Composite Build-Ups: a Review of Current Techniques in Restorative Dentistry

Composite build-ups for tooth wear

Hemmings demonstrated a higher success rate using hybrid resin composites (eg Durafil®, Herculite, Kerr®) versus a microfilled, when restoring worn teeth.⁸ This may be due to the fact that hybrid composites have been shown to offer superior rigidity, which is important in wear cases, as sufficient bulk of filling material is important for strength.^9,10 However, if restoring anterior teeth, the more recent ‘nano-hybrid’ composites have been proven to have excellent light reflectivity and handling. In these ‘nano-hybrids’ (eg HRi, Optident® 3M and Herculite Ultra™, Kerr), the individual nano-sized particles (0.05 microns) allow for good wear resistance, and were not introduced until the 2000s.¹¹

Success rates

For direct composite, many studies have been carried out over the years. For example, Hemmings et al showed that, for maxillary anterior tooth wear (ie increasing vertical dimension by 1−4 mm), 89% of restorations were still in service after 2.5 years.⁸ When using relative axial tooth movement, it was noted that occlusion was re-established after a mean of 4.8 months. In addition, Poyser et al noted that 86% of restorations had >90% of volume at 2.5 years.¹² Gulamali et al showed a median survival of 5.8 years for restorations and 4.8 years for replacement restorations.¹³ Of these, over 50% had a major failure at 10 years, and over 90% had a minor failure at 10 years. Finally, a prospective split mouth clinical trial was carried out by Al-Khayatt et al of direct composites for lower anterior tooth wear.¹⁴ At 7 years, the survival of the restorations was noted as 85% 53% of patients experienced survival of all their restorations. For the majority of patients, the restorations offered the patients a high degree of patient satisfaction and an acceptable level of maintenance. A study by Milosevic and Burnside discussed the placement of 1010 composites, and reported a 5.4% failure in the first year. This failure was greater in patients who exhibited an edge-to-edge incisal relationship.¹⁵

Composite is an ideal material for restoration of a worn dentition, especially anteriorly. Pre-heating the resin composite has been proven to increase the flow, with some operators considering that this makes easier handling, and with an improved surface finish. ¹⁶ However, there are many additional advantages to warming composite, including an improvement in marginal adaptation,¹⁷ as well as improved monomer conversion, especially between the temperatures 39°C−54°C.^18,19 Various methods of warming composite are available, including dedicated composite heaters (Figure 1).

Chairside methods

Before restoring the dentition, it is imperative that the clinician has carried out an extensive clinical and radiographic examination. This will include identification of the source of wear, such as acid erosion and/or parafunction, and elimination of the cause. This will prevent progression, and increase the longevity of any dental work carried out. Once the patient is stable, there are numerous techniques a clinician can utilize. In addition, it is important to have optimum moisture control to increase the bond strength and longevity of these restorations. Use of a dental dam frequently creates problems in checking occlusal contacts, and working at gingival margins. It is important, especially in anterior teeth, that the protrusive guidance is shared equally, with posterior disclusion, and even occlusal contacts in static and dynamic function.^2,20,21 It is equally as important that composite is placed in load-bearing areas at a minimum thickness of 1.5 mm−2 mm for strength.^13,21,22

Freehand build-ups

If the wear being restored is localized, eg anteriorly, there is a possibility that the clinician can carry out adhesive bonding, and contouring of the restorations freehand. This method is more technique sensitive, and dependent on operator skill. In this technique, layering is also still possible, and separation of the teeth is still required. Figure 2 demonstrates a case restored using a freehand technique. Table 1 summarizes various methods of composite build-ups.

Use of a matrix

For more challenging cases, the clinician may benefit from a more controlled and predictable approach. When planning an extensive wear case, adequate records must be taken for planning. This will include radiographs, study models and facebow and occlusal records.

Cases which require more extensive planning may include:²¹

For improved aesthetics and ease and predictability of treatment, the author advises a diagnostic wax-up/mock-up. A wax-up allows fabrication of the desired shape, inclination and contour of the final teeth, as well as the desired occlusal scheme.

There should be even contacts in either the intercuspal position (ICP), or the retruded contact position (RCP). Often the occlusion is reorganized to make ICP and RCP coincident, which is a prosthetic convenience. Either a canine-guided or group function dynamic occlusion is used, but this is case dependant. Once the wax-up is finalized, it may be duplicated in a stone model for fabrication of various indices (see below).^2,21,23,24

Transparent silicones/polyvinylsiloxane (PVS)

A PVS material which is transparent and fast setting not only allows chairside construction of an index, but also permits light curing. Materials include Affinity Crystal® (Optident), Memosil 2® (Heraeus Kulzer GmbH, Hanau, Germany). This can either be used chairside, by syringing the material gently around the wax-up, or by requesting the laboratory to construct a guide. The use of a stable PVS guide formed from the palatal or lingual aspect of the wax-up allows the use of an incremental build-up/layering technique, which can be useful for aesthetic cases. However, although this can be light cured through the material, it is not as rigid, thereby accurate impressions are essential. In addition, the lack of rigidity may make positioning less accurate, thereby requiring more adjustment post-curing. Robinson et al describe the fabrication of a PVS index.²⁵ Demonstration of this technique has been shown in Figure 3.

Palatal putty index

This is a useful technique for upper anterior teeth, and can be used in a layering fashion for a more aesthetic result. Usually, this material is hard body PVS, which can be extended to the incisal edge. The preparation of a putty matrix is demonstrated in Figure 4. The authors recommend leaving a bulk of putty around the premolar teeth to guide the stent in, which makes it less likely to distort.

Laboratory methods

The laboratory can be involved in constructing pre-made indices, which may reduce the need for chairside preparation. However, this will incur an additional cost.

Clear silicones

Transparent PVS materials with a syringe-like delivery system (eg Memosil 2®, Heraeus Kulzer GmbH, Hanau, Germany; Affinity Crystal®, Optident) have the advantage that they are fast setting on a wax-up model, so there is no need to duplicate it in stone.²² This will reduce laboratory costs for the clinician. The further steps taken with a laboratory constructed splint are shown in Figure 3, and involves the laboratory trimming any excess material, and smoothing the outer surface of the index. This may make it easier to handle, and be more comfortable for the patient. Demonstration of a full case using Memosil® is presented in Figure 5.

Vacuum/pressure formed splint

Another practised method involves construction of a soft blow down/pressure or a vacuum-formed splint. This is usually a polyethylene material that is vacuum/pressure formed over a duplicated stone model. Materials such as Erkoflex Soft®, Schottlander are available in 1 mm, 2 mm, 3 mm and 4 mm thick blanks. However, PVC is available in thinner sections of 0.5 mm, which may be easier to manipulate. This technique has been well described by Daoudi and Radford²⁶ and is shown in Figure 6. The thicker the matrix, the harder it will be to prepare (see later), but it is more dimensionally stable, reducing the need for changes post-curing. Mizrahi has suggested the use of a 1 mm thickness index, with ‘vents’ to prevent air entrapment, and to allow excess to flow out.²⁷ This has the added benefit that it is more rigid, therefore the wax-up may be more reproducible intra-orally. However, as the material is more rigid, it is slightly more difficult if the clinician wishes to prepare it with the methods described later.²⁶ An example of a full case using this splint is shown in Figure 7.

Alternative tooth build-ups − ‘every other tooth’

This well-established more traditional method involves restoration of alternate teeth. The authors recommend using a material such as polytetrafluoroethylene (PTFE) tape, or polyacetate strips cut short, to isolate the neighbouring teeth. This method can be adopted using either a Memosil® or a PVS/PVC splint,²¹ and has the added benefit that it does not require preparation of the splint. This is good for monochromatic build-ups, when aesthetic expectations are lower, but still requires separation of the teeth.

Palatally/lingually guided build-ups – ‘layering technique’

If the patient has high aesthetic demands, commonly found in the upper anterior region, then the composite used may require layering. This technique was originally coined by Vanini,²⁸ who used a chromatic chart to express the different characteristics enamel can display, such as white spots and intensives. These can range in distribution in the general population. If the clinician has an artistic flare, he/she may wish to incorporate these features into the final build-ups, with the help of a polarizing filter on either a light or camera. This filter, although not necessary, will visualize these defects more clearly, and is demonstrated in Figure 8.

This style of build-up involves cutting the labial surface of the chosen stent away, as demonstrated in Figure 6. Most composite systems have dedicated dentine, enamel and incisal/translucent shades. The authors recommend these teeth to be built-up constructing a palatal ‘envelope’ and a ‘dentine cone’.^21,28

The ‘injection-moulding’ technique

When minimally building up lower anterior teeth (ie between 1−3 mm incisally), a quick, predictable and aesthetic method involves preparation of the lower splint. This will only apply to transparent splints, and is aided by warming the composite to reduce viscosity. In many cases involving restoration of lower anterior teeth, it will be necessary to use the lingual enamel for bonding. This technique uses a scalpel (size 11 or 15) to incise interproximally to at least 3 mm apical to the contact point of each tooth to be built up.²¹ On more rigid splints, heating the scalpel may help. After this step, a small metal matrix band (eg Polydentia 0.05®) can be wedged between the teeth. The clinician must take care to trim the metal bands lingually and buccally, to avoid soft tissue trauma to the patient. The next step involves using a small round bur to create a ‘vent’ buccally, which will allow excess composite to flow out, reducing the likelihood of interdental excess. Excessive composite interproximally can be challenging to remove, and cause iatrogenic gingival inflammation, hence this technique is very useful.

This modified splint can then be inserted intra-orally. Care should be taken to ensure that the stent is fully seated, which is better visualized with a pressure/vacuum-formed splint, as opposed to a clear silicone. Pre-flossing contact points and ensuring that there are no deposits, will aid this process. An ill-fitting splint should be abandoned. Once the splint is well fitting, the clinician should restore all incisors simultaneously. This is a quick and effective process. Afterwards, the clinician may notice buccal ‘tags’ of composite which have flowed out of the outlet created. These can be polished using Soflex® discs (3M) or a similar system, and interproximal excess removed with a fine diamond, and a finishing strip in an ‘S’-shaped motion.²¹Figure 7 demonstrates this process using a 3 mm blow down splint.

This technique is not as effective for upper teeth when using a flat metal strip, due to lack of an aesthetic contour.

Pre-contoured matrices (eg Garrison®) are available, but are best used with the layering technique. In addition, the authors advise against use of the ‘injection moulding’ technique in extensive build-ups (>3 mm), as there is a higher risk of interproximal excess, and a poorly contoured contact area.

Table 2 summarizes the various materials that are used when constructing matrices.

Survival rates

A systematic review by Manhart et al²⁹ showed that indirect composites had a lower annual failure rate than direct composites. Specifically, Redman et al⁹ showed that, for anterior composite build-ups for tooth wear, medial survival was 4 years 9 months, and that major failure requiring replacement was uncommon in the first 5 years after placement.

Gow and Hemmings³⁰ examined indirect composite palatal veneers. Of these restorations, 100% were still in service after 2 years, 13% of which experienced minor failures at 2 years. When using the ‘Dahl’ principle, the occlusion was re-established within 9 months.