A study of microleakage in class II composite restorations using four different curing techniques

There are several incremental techniques for the placement of posterior composites in Class II cavities that were introduced to overcome clinical failures associated with these restorations. This study evaluated microleakage in Class II cavities restored with four different curing techniques. On 40 non-carious, freshly extracted human premolars, Class II cavities were prepared following a standard pattern in which the mesial cavities had a cervical margin 1.0 mm above the CEJ, and for distal cavities, 1.0 mm below the CEJ. The specimens were randomly divided into four groups. Each cavity surface was conditioned with 35% phosphoric acid and rinsed to remove the excess water, followed by a dental bonding agent (PQ1) being used for all the cavities. The teeth were then restored with a fiber reinforced resin-based composite (Neulite F), using four different techniques: Group 1, metal matrix with wooden wedge; Group 2, transparent matrix with reflective wedge; Group 3, metal matrix with wooden wedge and light tip and Group 4, metal matrix with wooden wedge and bio-glass cylinder. Then, the restorations were finished and polished, rebonded, thermocycled (2000 times, 5 degrees C to 55 degrees C, 30 second dwell time), stained, sectioned vertically and viewed under a stereomicroscope (40x). They were then scored on a 0-4 scale based on microleakage at the gingival margins. The data were analyzed using the Kruskal-Wallis and Mann-Whitney U tests. The results showed that Group 1 demonstrated the most leakage, while the other three groups showed less leakage than Group 1. There was no significant difference between the enamel and dentin gingival margin groups. As a result of these findings, the authors concluded that restoration with metal matrices, using light conducting instruments, results in significantly less microleakage at the gingival margins of Class II resin composite restorations.