Survival of direct resin composite onlays and indirect tooth-coloured adhesive onlays in posterior teeth: a systematic review.

Objective To compare the survival of direct resin-composite used as onlays and indirect tooth-coloured adhesive onlays in posterior teeth, along with modes of failure, deterioration and variables affecting survival.Materials and methods PubMed, Embase, The Cochrane Library, Web of Science and Scopus were searched systematically up to 16 October 2020. In total, 3,768 studies were screened, with their results for survival, failure mode, deterioration and variables affecting survival.Results In total, 30 studies were selected. Survival rates in included studies greater than three years in length were 73.1-100%, with a median survival of 92.5% and median follow-up length of 5.1 years. The most prevalent failure mode was fracture, followed by pulpal episodes, debonding and caries. The most prevalent deterioration criteria were loss of marginal integrity and discolouration.Conclusions Survival of direct resin composite onlays and indirect tooth-coloured adhesive onlays in posterior teeth is acceptable (73.1-100%) in the medium-term. There is a need for more studies on direct cusp covering resin composite restorations, zirconia onlays and studies comparing material types. Fracture was the most prevalent failure mode. Restoration margins were the most prevalent area of deterioration.Clinical significance Direct and indirect tooth-coloured adhesive onlays can be a reliable and more conservative way to restore posterior teeth across a range of material options.