Cuspal movement and microleakage in premolar teeth restored with a packable composite cured in bulk or in increments.

INTRODUCTION: The aim of this study was to investigate the effect of two novel curing systems (a plasma arc light, and a 'turbo-boosted' conventional curing light) on cuspal movement and gingival microleakage of 'packable' resin-based composite (RBC) restorations placed in extracted maxillary premolar teeth. MATERIALS AND METHODS: Forty sound extracted upper premolar teeth were subjected to standardised preparation of a large mesio-occlusal-distal cavity before restoration with a RBC. Four curing regimens were used. Either the RBC was placed in bulk and light-cured in one increment using (a). the plasma arc light; (b). the 'turbo-boosted' curing light, or the RBC was placed in eight increments using (c). the plasma arc light; (d). the 'turbo-boosted' curing light. A deflection measuring gauge allowed a measurement of cuspal deflection at each stage of polymerisation. Restored teeth were thermocycled before immersion in a 0.2% basic fuchsin dye for 24 h. After sagittal sectioning of the restored teeth in a mesio-distal plane, the sectioned restorations were examined to assess cervical microleakage. RESULTS: Cuspal deflection measurements were significantly increased when the 'turbo-boosted' halogen curing light was compared with the plasma arc light. Total mean cuspal deflection measurements obtained with incremental cure were significantly increased compared with bulk cure for both light sources. Gingival microleakage for bulk restored teeth was significantly increased compared with teeth restored incrementally. Incremental restoration with the plasma arc light had significantly increased gingival microleakage compared with the 'turbo-boosted' halogen curing light. CONCLUSIONS: The packable composite tested could not be cured adequately to a depth of 5 mm with the plasma arc light within the specified irradiation time. Under the test conditions of the current investigation, bulk curing only appeared to be practical with the high intensity halogen light (40 s activation). Incremental build-up and polymerisation optimised marginal seal for the high intensity halogen light but led to greater cuspal deflection.