Bulk fill restoratives: to cap or not to cap--that is the question?

OBJECTIVES: To assess the cuspal deflection and cervical microleakage scores of standardised large mesio-occlusal-distal (MOD) cavities filled with different restoration protocols: (1) conventional resin restoratives, (2) bulk fill flowable base materials 'capped' with a conventional dimethacrylate resin-based composite (RBC) or (3) bulk fill resin restorative materials. METHODS: Standardised MOD cavities were prepared in sixty-four sound maxillary premolar teeth and randomly allocated to eight groups. Restorations were placed in conjunction with a universal bonding system and resin restorative materials were irradiated with a quartz-tungsten-halogen light-curing-unit. Restoration protocol (eight oblique increments of conventional resin restorative, bulk fill flowable base and two occlusal 'capping' RBC increments (three increments in total) or bulk fill resin restorative (two increments)) was the dependent variable. A twin channel deflection measuring gauge measured the buccal and palatal cuspal deflections. Teeth were thermally fatigued, immersed in a 0.2% basic fuchsin dye for 24h, sectioned and examined for cervical microleakage score. RESULTS: Post hoc Tukey's tests highlighted significant differences in the mean total cuspal deflection values between resin restoratives (p < 0.0001) and restoration protocol (p < 0.005). In general (albeit product dependently), an increase in mean total cuspal deflection and concomitant decrease in cervical microleakage score was evident for bulk fill flowable base materials with occlusal 'capping' RBC increments (restoration protocol 2) compared with bulk fill resin restoratives (restoration protocol 3). CONCLUSIONS: Not all bulk fill flowable materials or bulk fill resin restoratives behave in a similar fashion when used to restore standardised MOD cavities in maxillary premolar teeth and material selection is vital in the absence of clinical data. CLINICAL SIGNIFICANCE: Poorly performing bulk fill flowable materials or bulk fill restoratives can be identified using the cuspal deflection and cervical microleakage protocol which could save the complications encountered clinically when restoring Class II restorations.

Cuspal deflection and cervical microleakage scores to determine the adhesive potential of universal bonding systems.

OBJECTIVES: To assess the adhesive performance of three universal bonding systems (self-etch and total-etch protocols) with cuspal deflection and cervical microleakage score. METHODS: Fifty-six standardised sound maxillary premolar teeth with uniform mesio-occlusal-distal (MOD) cavities were randomly allocated to six groups. Restoration with resin-based composite (RBC) was performed in conjunction with a universal bonding system facilitated by a quartz-tungsten-halogen light-curing-unit. The dependent variable was the universal bonding protocol (self-etch or total-etch). Buccal and palatal cuspal deflections were recorded at 0, 30, 60 and 180s post-irradiation using a twin channel deflection measuring gauge. Following restoration, the teeth subjected to 500 thermocycles, immersed in a 0.2% basic fuchsin dye for 24h, sectioned and examined for cervical microleakage. RESULTS: Comparing between bonding protocol (self-etch or total-etch), a decrease in total cuspal deflection and a concomitant increase in cervical microleakage were evident when employing the total-etch compared with the self-etch protocol for two of the three universal dental adhesives. CONCLUSIONS: The 'Adhesion-Decalcification concept' suggests a trend towards 'mild self-etch' adhesives. Differences in adhesive performance (cuspal deflection and cervical microleakage) between the teeth restored using the self-etch or total-etch protocols is suggested to be a result of the pH of the self-etch solutions. 'Mild self-etch' (pH∼2.0) adhesives out-performed ultra-mild (pH>2.5) or strong (pH<1.5) self-etch solutions. CLINICAL SIGNIFICANCE: Poorly performing adhesives could be identified using the cuspal deflection and cervical microleakage protocol reported which could save the complications encountered clinically with Class II RBC restorations.