Posterior composites: a practical guide revisited

Detection and diagnosis

A Class I carious lesion (ICDAS 3)1 was detected in the mesial pit of an upper second molar (Figure 1). The lesion was diagnosed as active with respect to enamel cavitation exposing dentine. In addition the patient's dietary habits, oral hygiene measures and the presence of active lesions elsewhere indicated the need for operative intervention.

Isolation

Placement of direct restorations in the molar regions can present difficulty with regard to moisture control. Use of rubber dam with a single hole and a versatile winged molar clamp (Hygenic 12A, Coltène-Whaledent, Switzerland)) provided rapid isolation, which was completed (Figure 2) by flossing the dam through the mesial contact point. The speed with which this technique achieves isolation and promotes a comfortable experience for the patient and a predicable outcome for the operator cannot be overemphasized. Although the vast majority of practitioners do not routinely use rubber dam,2 the isolation of a single tooth for an occlusal restoration is a perfect starting point for those wishing to learn and refine rubber dam techniques.

Occlusal template

As carious demineralization had left the occlusal surface virtually intact, in this case a template was used to facilitate provision of an anatomically accurate final restoration. Fabrication of a template may be achieved using a pre-operative impression gained by injecting a small amount of a clear polyvinyl siloxane material (Memosil 2, Heraeus Kulzer, Germany) onto the occlusal surface3^,4 (Figure 3). After waiting for the material to partially set, finger pressure (Figure 4) was applied to accurately capture the occlusal morphology. Once set, the template was removed (Figure 5) and the mesial surface marked with a felt pen to assist orientation when reapplied later.

Access

Using a small round bur, access to the carious lesion was gained through the cavitated pit and extended only to allow visualization and assessment of underlying dentinal caries. (Figure 6).

Minimally invasive preparation

Using appropriate burs, peripheral caries excavation was carried out to remove soft carious dentine and fragile overhanging enamel only. Pulpal caries was then excavated using a hand excavator and extended only until there was moderate resistance to gentle excavation5^,6^,7 (Figure 7).

Removal of only irreversibly demineralized tooth tissue is a fundamental aim of contemporary caries management,5–7 as it maximizes the amount of residual healthy tooth tissue5–9 and improves the prognosis for long-term pulpal health by minimizing trauma to the dentine/pulp complex.5–7

Etching

Phosphoric acid (37%) was used to etch the whole cavity and 1mm beyond the margins (Figure 8).

Etch 37 (Bisco Inc, Schaumburg, IL, USA) was chosen as it flows easily into undercut cavity forms. Etching was further optimized by agitating the etchant with an appropriate instrument.

Wash and dry

After 15 seconds the etchant was thoroughly washed off. The cavity was then dried with gentle airflow, taking care not to desiccate the dentine. The aim is to achieve a visibly moist dentine cavity floor (and walls) with no obvious pooling of water.9 When total etch adhesive systems are employed, careful control of dentine moisture is essential for optimization of adhesion and prevention of post-operative sensitivity. While the ‘frosty’ appearance of enamel walls is a reassuring sign that a predictable enamel bond (and thus marginal seal) will be achieved (Figure 9), it may also signal an increased likelihood of over dry dentine. If dentine desiccation is suspected it may be rehydrated with water,9 applied using an appropriate brush.

Adhesive

Adhesive (XP Bond, Dentsply International Inc, York, PA, USA) was applied to the whole cavity and just beyond the margins, using a Microbrush (Microbrush international Grafton, US). Gentle airflow was then used until no ripples were evident. This reduced the likelihood of adhesive pooling and confirmed that the solvent had evaporated. The adhesive was then light-cured for 40 seconds with the light tip as close to the cavity as possible. The cavity was inspected to ensure that a uniform glossy/shiny adhesive layer coated the entire cavity9 (Figure 10).

Placement (‘dentine layer’)

In this case, the entire ‘dentine layer’ was restored in one increment, using a flowable composite designed for this purpose (SDR™, Smart Dentine Replacement, Dentsply International Inc, York, PA, USA) (Figure 11).

SDR™ (Figure 12) is an innovative flowable posterior composite offering a number of potential benefits with regard to reducing placement technique sensitivity:

The SDR™ layer was then light-cured for 20 seconds.

Placement (‘Enamel layer’)

A single increment of a traditional hybrid composite was then placed over the layer of SDR™, which is not designed to restore right up to the occlusal surface as a result of:

Care was taken to apply just the right amount of hybrid material (Figure 13) to minimize excess and prevent under fill that would increase the tendency for poor marginal adaptation and void formation.

Use of the template

To facilitate adaptation and shaping of the final increment, the pre-operative occlusal template was applied to the unset material (Figure 14). The light tip was then firmly applied to the translucent template during a (minimum) 60 second light-cure (Figure 15).

This technique has three main benefits:4

Light-cure

Once the template was removed the restoration received a further 60 seconds light-cure to maximize polymerization (Figure 16).

Excess removal

The restoration was inspected for marginal excess (Figure 17), which was easily removed from unetched enamel using a sharp hand instrument. (Note: Careful volume estimation of the final increment will reduce or even eliminate this stage).

Occlusal check

Articulating paper was used to confirm that the restoration conformed precisely to the patients pre-existing occlusal scheme, in both the intercuspal position and all excursions (Figure 18).

Finished restoration

The restoration was inspected (Figure 19). At this stage the surface may be refined, polished or coated with a solvent-free surface sealer, depending on operator preference.9

Review

At review (interval based on caries risk or, as in this case, need for further dentistry) all aspects of the completed restoration were studied (Figure 20).

Discussion

Direct posterior composite restorations offer many benefits to both patient and dentist that go far beyond the fact that the restorations are tooth-coloured. New materials, equipment and techniques will continue to improve the quality, predictability and success of direct composite restorations. Such methods will also promote minimally invasive caries management, maximizing the amount of tooth tissue preserved. This will increase the longevity, not of just the fillings placed, but of the teeth that they restore.

Precise notation of the materials employed during each restorative procedure will provide each dentist with an invaluable evidence base for the long-term audit of their successful operative techniques.

With patient consent, photographic images taken before, during and after operative procedures may be used as a powerful motivational tool to help explain the disease process when encouraging patients to reduce their caries risk and to demonstrate the benefits of modern minimally invasive dentistry.