Six months evaluation of posterior occlusal restorations with five adhesive systems: results from a randomized controlled trial

Abstract

Introduction: Resin-based direct posterior restorations are routine and well-established procedures in dental practice [1,2]. Durable adhesion to enamel and dentin is a fundamental prerequisite to prevent premature marginal breakdown of the restorations. All contemporary adhesive systems contain multiple and specific molecules in their formulation that meet identical functions, thereby sharing the same basic bonding mechanism. However, molecule chemistry, specificity, proportion of the incorporated ingredients and their interaction with different tooth structures varies greatly between adhesive systems with impact on the quality of the bond provided by each system [3]. Available evidence is still quantitatively and qualitatively insufficient to indicate the most adequate adhesive strategy to use in posterior load-bearing lesions [4]. The aim of this randomized clinical trial was to evaluate the efficacy of different adhesive systems in the restoration of occlusal cavities over the course of six months (6M).

Materials and methods: The protocol and consent form for this study were reviewed and approved by the Ethics Committee (CHUC-15-09). The study enrolled 54 patients and evaluated the performance of two etch-and-rinse (Optibond™FL (G1), Prime&Bond®NT™ (G2)) and three self-etch (Clearfil™SE Bond (G3), Xeno^®III (G4), Xeno^®V⁺ (G5)) adhesive systems on 159 posterior resin composite restorations (G1 = 32; G2 = 32; G3 = 32; G4 = 31; G5 = 32). The selected teeth were distributed following a block randomization list with block sizes of 5 corresponding to the 5 possible treatments to ensure group consistency during recruitment. Allocation of the adhesives was revealed to the operator after cavity preparation by opening of a sealed envelope. The operator was not blinded to group assignment due to differences in the application protocol of the materials. Patients and evaluators were blinded to group assignment. Restorations were evaluated using the World Dental Federation (FDI) criteria and the study was reported according to the CONSORT statement. Statistical analysis was performed with Friedman-test for paired samples and inter-group analysis with Mann-Whitney test (p < 0.05).

Results: At 6 months, 49 patients attended the follow-up and 144 restorations were evaluated (G1 = 29; G2 = 28; G3 = 30; G4 = 28; G5 = 29). Among aesthetic properties, only surface staining showed statistical significant alterations from baseline (BL) to 6M in G1, G3, G4 and G5 (p < 0.05) reporting variations from score 1 to score 2. Regarding biological criteria, no significant alterations could be found. Considering functional properties, a statistically significant decrease in the number of restorations with marginal adaptation occurred for the self-etch adhesives (G3, G4 and G5), but changes were only registered from score 1 to score 2 (p < 0.01). Marginal adaptation was the only parameter with statistical significance regarding group comparison. Pairwise comparisons indicated that etch-and-rinse adhesives presented statistically better performance than any other of the self-etch systems at 6 months (p < 0.01).

Discussion and conclusions: Several studies using self-etch adhesives in posterior restorations indicate that marginal integrity is the parameter most negatively affected, which is in accordance with the present study [4,5,6]. The poorer enamel bonds provided by self-etch adhesive systems may be responsible for the premature loss of integrity of the margins. Nevertheless, at six months of follow-up all cases were successful and clinically considered no less than satisfactory. (Clinical Trial Registration number: ISRCTN87835631)

Acknowledgements

Dr. Ana Chambino, Dr Fernando Marques, Dr Ana Messias are thanked for their many useful discussions and contributions to this work.