Figure 2A: Diagnosis
The patient was diagnosed with secondary caries related to class I composite restorations in worn mandibular first and second permanent molars. Following shade selection and anaesthesia, the teeth were isolated with a rubber dam, secured with a versatile, reusable plastic retainer (SoftClamp™ - KERR).
Figure 2B: Cavity preparation
Minimally invasive cavity preparation involved restoration removal and caries excavation. Cavity margins were smoothed using a composite finishing bur, but no occlusal bevelling was carried out as this increases the long-term risk of marginal failure. The cavities were then air abraded with 29µm aluminium oxide, using an Aquacut Quattro unit (Optident).
Figure 2C: Adhesion
Etching was then performed using 37% phosphoric acid gel (Ultraetch™-Optident), which has optimal consistency for selective enamel etching. Etch was left for 15 seconds, before thorough washing and careful drying using gentle air flow across the cavities. A universal adhesive material was then applied according to the manufacturer’s instructions and light cured for 10 seconds. The cavities were assessed to confirm the presence of a uniform glossy/shiny adhesive layer prior to restoration.
Figure 2D: Incremental placement
When using traditional hybrid composites (not bulk fill) incremental placement remains the standard of care for restoring cavities of depth >2.0mm.1,2 By reducing the volume of contracting material, the forces of polymerisation shrinkage stress are mitigated and light curing is maximised. Controlled incremental placement, using a material with good handling properties, also reduces excess and allows anatomical contours to be created.1,2 In this example, initial increments of ≤1.0mm were placed into each cavity. The layers in contact with the tooth may be considered as the most critical and are also furthest from the tip of the light curing unit.
Figure 2E: Anatomical shaping
All permanent mandibular and maxillary molars have oblique cusp ridges that are orientated at approximately 45° towards the centre of the occlusal surface. Lower second molars have four cusps, symmetrically positioned, to create a cruciform fissure pattern. Lower first molars are more challenging (and rewarding) to restore as their asymmetric fissure pattern consists of two similarly sized lingual cusps and mesio-buccal, centro-buccal and smaller disto-buccal cusps. By placing the cusps successively, accurate occlusal anatomy can be rapidly restored, minimising the need for finishing burs following rubber dam removal. In addition, repeated light curing cycles maximise the material’s polymerisation (20 second curing cycles were used for each increment, followed by a final 60 second light cure).
Figure 2F: Fissure staining
If preferred, subtle anatomical fissure stains can be applied using specialised tinted flowable composite. Small amounts were placed using a probe tip and excess material was then blotted with a microbrush before light curing.
Summary
As well as controlling polymerisation shrinkage stress, the successive build-up technique is a very efficient method of mastering the anatomical shaping of direct restorations, which form the majority of operative procedures carried out in general dental practice.
