Date of Degree
MS (Master of Science)
Marcos A. Vargas
Objective: To assess the effect of finishing and polishing direction on the marginal adaptation of resin-based composite restorations.
Methods: Forty human molars were collected and sectioned along their mesio-distal axis. Buccal and lingual enamel surfaces were flattened and a triangular preparation (0.87mm deep and 3mm wide) representing two 30° bevels was achieved. Specimens (n=20/per group) were randomly assigned in groups and restored with two resin-based composite materials: a nanofilled (Filtek Supreme Ultra)(FSU) and a microhybrid (Point4)(PT4) and two finishing/polishing techniques: a series of Sof-Lex discs (SL) and a sequence of diamond bur/dark-orange SL/rubber polishers (HiLuster). On each specimen, both margins were finished and polished with the same technique, one from the resin-based composite to the tooth structure (C-T) and the other from the tooth structure to the resin-based composite (T-C). Replicas were made for FeSEM observation (200X) and quantitative margin analysis was performed based on four defined marginal quality criteria. Comparisons were made between polishing directions (paired-samples t-test, Wilcoxon signed-rank test), between resin-based composites and between polishing techniques (two-sample t-test and Wilcoxon rank sum test)
Results: Significant differences were found between polishing directions (p<0.05). Data showed more continuous margins, less marginal irregularities and less gaps with the polishing direction C-T than T-C except for one group (FSU/SL) with marginally significant difference in gaps (p=0.0537). Differences between the two resin-based composites and the two polishing techniques seemed to be dependent on certain combinations of resin-based composite, polishing technique and polishing direction.
Conclusion: Within the limitations of this in vitro study, polishing from resin-based composite to tooth structure (C-T) leads to better marginal adaptation than polishing from tooth structure to resin-based composite (T-C).
Copyright 2011 Laurie St-Pierre