Phase transformation of yttria-stabilized zirconia after the use of various bur types in dry and wet conditions: A systematic review and meta-analysis.

Abstract

The objective of this systematic review and meta-analysis was to analyze the impact of grinding using burs with different grain size under dry and wet conditions for conventional and translucent zirconia on the degree of phase transformation. Two independent reviewers conducted an electronic search on BBO, Embase, LILACS, MEDLINE, Scopus, Web of Science and WPRIM to identify publications in English language, from January 1995 to April 2023, conforming to PRISMA guidelines for systematic reviews for in vitro studies and reported on the outcome measure of phase transformation of zirconia as a function of grinding protocols. The data were analyzed for tetragonal to monoclinic phase transformation as a primary outcome. A total of 3157 titles were identified during the search process. Of these, 59 full-text articles were assessed, resulting in the inclusion of 34 studies for the systematic review and 12 studies for the meta-analysis. According to the study groups included, the following types of burs and conditions could be analyzed: coarse burs - wet; coarse burs - dry; medium burs - dry; fine and extra-fine burs - wet and dry conditions. With coarse burs, under dry conditions, mean phase transformation ranged from 0 to 6.3 %. Pooled mean percentage of monoclinic phase transformation was 4.308 % (95 % CI: 3.697-4.919), with a prediction interval ranging from 2.064 % to 6.552 %. In contrast, wet conditions resulted in a significantly higher pooled mean percentage of monoclinic phase transformation at 7.812 % (95 % CI: 5.878-9.745) with the prediction interval ranging from 0.181 % to 15.442 %. With medium burs, under dry conditions, phase transformation varied between 4.976 and 7.023 % with a prediction interval of 4.518 %-6.973 %. The phase transformation under dry and wet conditions for fine to extra-fine grinding ranged from 7.47 to 9.7 %. These results were statistically significant for individual sub-study groups compared to control groups (p < 0.001). The results of this meta-analysis underscored the importance of operational conditions and material processing techniques in influencing phase transformation yet demonstrating values well below the ISO 13356:2008 recommendation for monoclinic phase transformation which is to be maximum 25 % to ensure biomedical reliability. CRD42023424918.