Bond Strength of Universal Adhesives: A Systematic Review and Meta-analysis

Objectives: A systematic review was conducted to determine which is the best protocol for dentin and enamel adhesion by universal adhesives: etch-and-rinse or self-etching mode.
Methods: This report followed the Preferred Reporting Items for Systematic Reviews and Meta-Analysis: the Prisma Statement. Two reviewers independently performed literature search up to July 2014 in eight databases: PubMed, Web of Science, Scopus, BBO, SciELO, Lilacs, IBECS and The Cochrane Library. In vitro studies were selected as eligibility criteria. These studies evaluated the bond strength to dentin and/or enamel of universal adhesives by etch-and-rinse and self-etch strategy. Statistical analysis were conducted using RevMan 5.1 (The Cochrane Collaboration, Copenhagen, Denmark). A global comparison was performed with random-effects models at the significance level p≤0.01. Statistical heterogeneity among studies was assessed using the Cochran’s Q test and the inconsistency I² test.
Results: The database search retrieved 6544 eligible studies. After removal of duplicates, 5573 records were examined by the titles and abstracts; 5555 studies were excluded and 18 articles were assessed for full-text reading. A total of 9 articles met inclusion criteria and were included in the meta-analysis. The global analysis for dentin micro-tensile bond strength showed no statistically significant difference (p=0.07; I²=66%) between etch-and-rinse (38.1±11.1MPa) and self-etch strategy (34.1±13.3MPa). However, in enamel micro-tensile bond strength the adhesion with the etch-and-rinse mode (34.1±0.7MPa) was statistically different from self-etch technique (25.3±3.1MPa) in the global analysis (p<0.01, I²=0%). Besides, in enamel micro-shear bond strength the etch-and-rinse (15.6±0.5MPa) was also statistically different from self-etching mode (12.4±3.2MPa) in the global analysis (p<0.01; I²=26%).
Conclusions: It was possible to conclude that there is improvement in bond strength by universal adhesives with etch-and-rinse technique in enamel and the prior phosphoric-acid etching is needless in dentin.