CUSPAL DEFLECTION DURING POLYMERISATION OF COMPOSITE LUTES OF CERAMIC INLAYS

Abstract Objective: The purpose of this study was to measure the cuspal deflection that occurs in teeth as a result of the dimensional changes of resin-based lutes during polymerisation. Methods: Standardised MOD cavities were cut in 15 intact human premolar teeth using a custom paralleling device. A ceramic inlay was machined by the CEREC 2 system for each tooth ensuring an interface width of 50 μm (SD=17.5) at the cavity margin. The 15 teeth were divided into three groups of five according to the cementation system employed: a microfilled hybrid posterior composite; a compomer restorative; a dual-cure luteing composite. The inter-cuspal tooth dimension was recorded continuously with a laser micrometer assembly during a 2 min photoactivation period and a further 30 min post-activation period. Results: A clear overall reduction in tooth dimension was detectable for the first 10 min of polymerisation. The mean changes ranged from −0.02% to −0.06% depending on the nature of the luting material. In addition, all samples exhibited a slight expansion of 0.03% during the time of light-activation. Conclusions: The dimensional changes that teeth experience during the polymerisation of resin-based lutes are clearly detectable. It can be postulated that an increase in the dimensions of the teeth during photoactivation occurs as a result of expansion of the lute due to the thermal energy delivered.