Effect of Polishing Direction on Marginal Adaptation of Composite Resins

Objectives: To assess the effect of polishing direction on marginal adaptation of composite-resin restorations.

Methods: Forty human molars were collected and sectioned along their mesio-distal axis. Buccal and lingual enamel was flattened and a triangular preparation (0.87mm deep and 3mm wide) representing two 60°-bevels was achieved. Specimens (n=20/per group) were randomly assigned in groups and restored with two composite-resins: 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) (R). On each specimen, both margins were finished/polished with the same technique, one from composite-resin to tooth (C-T) and the other from tooth to composite-resin (T-C). Replicas were made for FeSEM observation (200X) and quantitative margin analysis was performed based on defined marginal quality criteria. Comparisons were made between polishing directions, composite-resins and polishing techniques (paired-samples t-test, Wilcoxon signed-rank test, a=0.05).

Results: Significant differences were found between polishing directions (p<0.05). Data showed more “continuous margins” (MQ1), less “marginal irregularities” (MQ2) and less “gaps” (MQ3+MQ4) 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 two composite-resins and two polishing techniques seemed to be dependent on certain combinations of composite-resin, polishing technique, and polishing direction.

Conclusions: Within the limitations of this study, polishing from composite-resin to tooth (C-T) leads to better marginal adaptation than polishing from tooth to composite-resins (T-C).

 

GROUPS	Margin Quality	Difference in Direction (C-T vs. T-C) Mean(SD) (%)	p-value
FSU/SL	MQ1 MQ2 MQ3+MQ4	10.47(14.95) -7.27(14.65) -3.20(7.75)	0.0055 0.0388 0.0537
FSU/R	MQ1 MQ2 MQ3+MQ4	10.87(13.27) -6.40(9.76) -4.48(7.50)	0.0016 0.0085 0.0039
PT4/SL	MQ1 MQ2 MQ3+MQ4	20.22(13.46) -13.99(13.78) -6.23(8.89)	<0.0001 0.0002 0.0005
PT4/R	MQ1 MQ2 MQ3+MQ4	22.25(13.86) -12.71(10.87) -9.54(12.05)	<0.00001 <0.0001 <0.0001