Abstract: Objective To compare the clinical efficacy of Lava Ultimate porcelain onlays and IPS e.max lithium disilicate glass ceramic onlays on restoring pulpless posterior teeth defect. Methods A total of 89 posterior teeth were selected as the research object from 68 patients with posterior tooth defect after complete root canal therapy(RCT) from January 2017 to December 2017 in Dental Hospital of Anhui. The type of tooth defect was the most common mesio-occlusal defect in the clinic(Black Ⅱ), of which 42 teeth were restored with Lava Ultimate porcelain onlays(Ultimate porcelain group), 47 teeth were restored with IPS e.max lithium disilicate glass ceramic onlays(Glass ceramic group). The preparation of buccolingual margin of the prosthesis was designed as plane butt joint form, and the occlusal surface was designed as full coverage or partial coverage according to the amount of residual tooth tissue. The two groups were followed up for observation after the restoration treatment. According to the revised evaluation standard of the United States public health service(USPHS), eight clinical indicators of the two kinds of ceramic onlays, including the integrity of the restoration, surface abrasion, color matching, margin staining, retention, secondary caries, marginal adaptation and periodontal status, were evaluated 12 months later. Statistical analysis was carried out by χ² test. Results According to the revised evaluation standard of USPHS, the success rate of the two groups in the integrity of the restoration, surface abrasion, color matching, margin staining, retention, secondary caries, marginal adaptation and periodontal status were more than 90% during the observation period. Among them, the success rate of various clinical indicators in the Ultimate porcelain group was 92.86%-97.62%, and that in the glass ceramics group was 91.49%-100.00%. There were no significant differences between the two groups(all P<0.05). Conclusion Lava Ultimate porcelain onlays and IPS e.max lithium disilicate glass ceramic onlays, as minimally invasive methods, both have ideal short-term effects, and can be used as the choice for the restoration of posterior tooth defect after root canal therapy.