Class I restoration margin quality in direct resin composites: A double-blind randomized controlled clinical trial

To evaluate the margin quality of direct resin composite restorations comparing the enamel-dentin adhesive standard procedure with additional use of adhesive layer at the external outline.

A total of 648 teeth with Class I occlusal lesions in molars and premolars were randomly selected and distributed into two groups of 324 each in order to compare the margin quality with two restoration strategies. Lesions were sealed with the standard adhesion procedure for direct resin composite restorations (Group 1) and with an additional procedure of enamel adhesive on the outer boundary of the finished restoration (Group 2). Evaluation of marginal quality at 6, 12, 24, 36 and 48 months was performed and described as good marginal adaption or as poor quality defined as Inadequacy A (IA): overhanging resin or change of color; Inadequacy B (IB): the presence of a gap at the enamel-composite interface that retained the probe tip; or Inadequacy C (IC) presence of gap at the enamel-composite interface with explorer tip penetration of more than 1 mm.

Data showed a higher number of Inadequacy A for restorations with the additional technique for marginal seal (Group 2): 16 of 24 total (57%) at 6 months; 28 of 37 total (76%) at 12 months; 36 of 44 total (82%) at 18 months; 22 of 33 total (67%) at 24 months; 14 of 21 total (70%) at 36 months and 16 of 25 total (64%) at 48 months. The Inadequacy B and C of marginal seal were more prevalent for restorations without the additional marginal seal (Group 1): 18 of 28 total (64%) at 12 months with inadequacy B; 19 of 25 total (76%) with inadequacy B and 16 total (100%) with inadequacy C at 18 months; 9 of 17 total (53%) with Inadequacy B and 13 total (100%) with Inadequacy C at 24 months; 12 of 17 total (70%) with Inadequacy B and 9 of 13 total (73%) with Inadequacy C at 36 months; 14 of 24 total (58%) with Inadequacy B and 7 of 11 total (63%) with Inadequacy C at 48 months.