A Study of Micro-Leakage in Class II Composite Restorations by Four Different Curing Techniques

There are several incremental techniques for placement of posterior composites in class II cavities that were introduced to overcome the clinical failures associated with these restorations. The purpose of this study was to evaluate micro- leakage in class II cavities restored with four different placement 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 of 1 mm above the CEJ and for distal cavities 1 mm below the CEJ. The specimens were randomly divided into 4 groups. The cavity surface was conditioned with 35% phosphoric acid, rinsed, excess water removed, and a dental bonding agent (PQ1) was used for all the cavities. The teeth were then restored with a fiber reinforced resin based composite (Neulite F) with four different placement techniques: Group 1, metal matrix with wooden wedge; Group 2, transparent matrix with reflective wedge; Group3, 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, thermo-cycled (2000 times, 5°C to 55°C, 30 s dwell time), stained, and viewed under a stereomicroscope (40×) and scored according to the micro-leakage at gingival margins on a 0-4 scale. Data were analyzed using Kruskal-Wallis and Mann-Whitney U tests. Compared with other placement techniques, significantly more micro-leakage was observed with metal matrix with wooden wedge technique. While least micro-leakage was seen with metal matrices using light conducting instruments. There was no significant difference between enamel and dentin gingival margin groups. The findings of this study demonstrated that restoration with metal matrices using light conducting instruments results in significantly less micro-leakage at gingival margins of class II composite resin restorations.