Effect of laser irradiation on the adhesion of resin-based materials to zirconia: a systematic review and meta-analysis

This systematic review and meta-analysis were made to evaluate the bond strength behavior and failure mode of zirconia surfaces treated by laser irradiation and to highlight the main characteristics and parameters of each laser system. The PubMed, the Scopus, and the Web of Science databases were searched for articles without limit on year of publication, in accordance with the PRISMA guidelines. Forty-three <i>in vitro</i> studies were included and meta-analyses were performed to compare the bond strength values found after the use of lasers, and to quantify the percentage of failures. When compared to untreated groups, the bond strength values found for the lasers ranged from 1.4 to 30.16 MPa for CO₂; 1.18 to 40.33 MPa for Nd:YAG; 0 to 22.72 MPa for Er:YAG; and 0.5 to 34.92 MPa for Er,Cr:YSGG. Statistical analysis indicated high heterogeneity in-between the comparisons of different lasers (<i>p</i> ˂ 0.05). When compared to other treatments, the results of the meta-analysis were favorable for tribochemical silica coating (TSC) and airborne-particle abrasion (APA) (<i>p</i> ˂ 0.05), except for the CO₂ laser. Adhesive failures were predominant (68.28% for CO_2; 65.23% for Nd:YAG; 76% for Er:YAG and 71.91% for Er,Cr:YSGG laser), followed by mixed and cohesive failures. Based on the results of this study, the conditioning of zirconia surfaces through laser irradiation increases the bond strength values when compared to untreated surfaces, regardless of the type of laser used. However, except for CO₂ laser, TSC and APA still show superior bond strength results.