Systematic review of in vitro studies evaluating tooth bleaching efficacy.

PURPOSE: To review and assess the literature on in vitro studies evaluating tooth bleaching efficacy considering the use of a negative control, type of tooth substrate, storage medium, color evaluation methods, and evaluation time points. METHODS: The following databases were searched: PubMed (MEDLINE), Web of Science. Search used Medical Subject Headings (MeSH) in PubMed in addition to free text. The following limits were applied: English, articles published between January 1989 and October 2017. Additional free text key terms included: in vitro, tooth bleaching, placebo, negative control, overall CIELAB color change (DeltaE*ab), change in shade guide units (DeltaSGU), tooth color stabilization, evaluation time points, bovine teeth, and staining. Search was repeated in Web of Science but no additional articles were identified. A total of 11 studies were included for qualitative and quantitative analysis. RESULTS: The meta-analysis of nine included studies that reported DeltaE*ab values, revealed that the NC statistically exceeded the perceptibility threshold (PT) of 1.2 (P< 0.05). The estimate was 2.872 with lower and upper bounds of 1.955 and 3.790, respectively. CLINICAL SIGNIFICANCE: Randomized controlled trials are gold standards to evaluate bleaching efficacy of different materials. However, in vitro studies offer a way to screen for potential bleaching efficacy. It is vital to determine an appropriate cut-off value for determining bleaching efficacy in vitro and further apply for clinical relevance.