Objective: Performing the finishing and polishing procedures(F/P) immediately after placement of tooth-coloured restoratives is a routine measure despite concerns on their possible undesirable effects on the material's properties. For example, surface hardness is accepted as a determinant factor of the conversion rate. The aim of this study was to compare the effect of immediate versus delayed F/P procedures on the surface hardness of resin restoratives. Methods: A total of 120 disc-shaped specimens were prepared (10x2mm) using four different resins (Venus/Heraeus Kulzer; Grandio/VOCO; Tetric-Flow/Ivoclar; Dyract Extra/Dentsply). Samples were fabricated in a teflon mould in one increment and cured for 40-seconds using tungsten-halogen light (Hilux, Benlioglu) at direct contact with 550mW/cm2 light output. Each resin group then was divided into three subgroups as immediate F/P, delayed F/P (at 24 hrs), and control(cured under mylar strip) (n=10). Finishing with diamond finishing burs (Diatech, Diatech Dental AC, Heerbrugg Switzerland) and polishing with aluminum oxide discs(Sof-Lex, 3M) was performed by the same operator. Following 24hr storage in 37ºC water exposed to normal ambient light, Vickers microhardness measurements (HMV-2, Shimadzu) were performed from three locations on each specimen surface (100g load,10s dwell time). Two specimens from each group were randomly selected for scanning electron microscopy evaluation (JSM 5600-JEOL). Data was statistically analyzed by one-way ANOVA and Tukey HSD test. Results: The lowest hardness values were recorded for all restorative materials under Mylar strip. The hardness values of the rest of all delayed finished/polished restorative materials were statistically higher than immediately finished/polished samples(p<0.05).
Resin | Control(Mylar) | Immediate F/P | Delayed F/P |
Venus | 54.90(2.3) | 65.39(6.1) | 84.4(11.2) |
TetricFlow | 36.50(2.32) | 46.66 (5.07) | 51.36(4.10) |
Grandio | 89.35(11.6) | 252.78(13.3) | 280.85(11.0) |
DyractExtra | 46.03(2.7) | 61.81(2.3) | 72.07(4.1) |
Conclusion: Finishing/polishing procedure increased the surface hardness of all materials tested. Delayed F/P procedure increased the surface hardness of resin restoratives more than immediate F/P procedure.