To evaluate the marginal quality of class-II bulk-fill composite restorations with different adhesive techniques in a SEM in vitro study.
Method:
One all-in-one adhesive (Futurabond U; Voco,) with a lightcuring composite (X-tra fil; Voco) was evaluated in its ability to restore class-II cavities with focus on the cervical margin in dentin. 32 caries-free human molars were randomly assigned into four groups and treated as follows: Group I bulk-layering (2x4mm increments) and group II increment-layering (5x2mm increments) using an all-in-one adhesive (Futurabond U; Voco) and a lightcuring composite (X-tra fil; Voco). In group III (increment-layering) and group IV (bulk-layering), enamel and dentin was additionally pretreated with phosphoric acid (Vococid, Voco). Specimens were water storaged for 21 days, thermocycled (TC: 5 and 55 degrees Celsius, 2.000 cycles, Thermocycler THE-1000, SD-Mechatronic), and mechanical loaded (ML: 50N, 150.000 cycles, Chewing Simulator 4.2, SD-Mechatronic). Replicas were made after each step and a SEM analysis (200x magnitude, Sigma, Carl-Zeiss) was performed dividing the cervical margins into a horizontal and edge area for using defined margin qualities (MQ): MQ1: Margin not or hardly visible, no or slight marginal irregularities; MQ2: No gap but severe marginal irregularities MQ3: Gap visible (hairline crack up to 2 μm wide), no marginal irregularities; MQ4: Severe gap (more than 2 μm wide), slight and severe marginal irregularities.
Result:
MQ1 results (median/%) for the horizontal area were: group I (90.7/87.2), group II (81.5/79.4), group III (100/100), and group IV respectively (98.5/98.8). “Continuous margin” quality results for the edge area were: group I (79.2/75.2), group II (100/100), group III (100/100), and group IV respectively (100/100). The difference between group I and group III for the edge area was statistically significant (p=0.01).
Conclusion:
Phophoric acid pretreatment is effective for improving the margin quality as compared to the groups without additional etching.