Raising compomer surface hardness by different post-curing methods

Abstract

Purpose: To investigate whether the surface hardness of a compomer restorative material (Dyract) can be raised using two different methods (heat + pressure or heat + light) an to monitor the surface hardness changes over time (up to 16 days) of water-stored specimens. Materials and Methods: Fifteen disc specimens (7mm diameter x 2mm height) were prepared of Dyract and light-cured. Specimens were arbitararily divided into three groups of five specimens each. Group were treated as follows: Group I: no treatment (control) Group II: heat + light post-curing: 100 °C for 8 win. Group III: heart + pressure post-curing: 120° + 7 bars for 10 min. Vicker's hardness number (VHN) was measured for the specimens immediately after postcuring (T1) and at 1, 3 & 16 days of water storage (T2, T3 & T4) respectively. Data were collected and statistically analyzed using ANOVA with repeated measures and Tukey 's multiple range test. Results: The means VHN (kgF/mm 2 ) at T,for all groups were significantly different with Group III being the highest (54.2) and Group I the lowest (26.25). At T2 VHN for Group I increased significantly (38.68) such that Groups I & II became not significantly different while Group III remained higher than both. This relationship continued until the end of the study (T4). Clinical significance: Dyract restorations fabricated and post-cured by heat + pressure posses higher immediate and delayed surface hardness than non-post cured ones.