Effect of phototherapy on shear bond strength of resin cements to zirconia ceramics: A systematic review and meta-analysis of in-vitro studies

Background: The present study systematically reviewed the literature to investigate the effect of phototherapy on the shear bond strength (SBS) of resin cement to zirconia ceramic. Methods: Electronic databases including MEDLINE (PubMed), ISI Web of Science, Scopus, ScIELO, LILACS and EMBASE until April 2018. The addressed focused question was: Does phototherapy increase the SBS of resin cement to zirconia ceramics?" Results: A total of 8 in-vitro studies were included in the qualitative and quantitative analysis. The mean SBS for phototherapy ranged from 4.1 to 18.95 MPa while mean SBS for sandblasted zirconia-composite specimens ranged from 3.98 to 23.35 MPa in the included studies. Qualitative analysis showed 3 studies favoured application of phototherapy in significantly increasing SBS, while 4 studies indicated sandblasting showed significantly greater SBS of resin cement to zirconia ceramics. Considering the effects of phototherapy, significant heterogeneity for SBS (Q value = 136.37, p < 0.0001, I-2 = 94.87%) was noticed among both the groups. The overall mean difference for SBS (SMD = -0.59, 95% CI = -1.99 to -0.80, p = 0.402) was not significant between phototherapy and sandblast (control) groups. Conclusion: Whether the effect of phototherapy on increasing the SBS of resin cement to zirconia ceramic is debatable. Further in-vitro studies should be performed in order to obtain strong conclusions.