Influence of different softstart polymerization techniques on marginal adaptation of Class V restorations

To investigate the influence of different curing methods used to achieve softstart polymerization on the marginal adaptation of a resin-based composite in Class V restoration.

Class V cavities, with the gingival wall located 1 mm below the cemento-enamel junction, were prepared on buccal and lingual surface of 80 extracted premolar teeth. The teeth were randomly divided into 8 groups of 10 teeth. The cavities were restored with a combination of resin-based composite (Z100) and adhesive (Single Bond) in different softstart-polymerization techniques or placement techniques. Softstart-polymerization obtained from either softstart mode (Elipar Highlight) or the modified methods using standard curing unit (Spectrum 900 and XL3000), bulk or incremental filling techniques were also used. After thermocycling between 5 degrees C and 55 degrees C for 500 cycles, the specimens were immersed in 2% methylene blue dye at 37 degrees C for 6 hours. Longitudinal sections of the specimens were scored for marginal dye penetration under the microscope. Kruskal-Wallis and Mann-Whitney tests were used for statistical analysis.

There was no statistically significant difference of dye penetration among techniques at enamel or dentin margins (P > 0.05). Dye penetration observed at dentin margins was significantly higher than that observed at enamel margins (P < 0.05) except for the group restored with a combination of incremental technique and softstart-polymerization using Spectrum curing unit. There was no statistically significant difference of microleakage between buccal and lingual cavities at enamel or dentin margins (P > 0.05).