Cushioned grind‐out technique transcrestal sinus floor elevation for simultaneous implantation in severe atrophic maxilla: A retrospective study with up to 7 years of follow‐up

Abstract Objectives This study aimed to evaluate the effects of the cushioned grind‐out technique transcrestal sinus floor elevation for simultaneous implant placement with ≤4 mm of residual bone height (RBH). Materials and Methods This was a retrospective propensity score matching (PSM) study. Five PSM analyses included the confounding variables of Schneiderian membrane perforation, early and late implant failure, and peri‐implant apical and marginal bone resorption. After PSM, we compared the difference in five aspects between the RBH ≤ 4 and >4 mm groups. Results A total of 214 patients with 306 implants were included in this study. After PSM, the generalized linear mixed model (GLMM) indicated that RBH ≤ 4 mm had no significantly higher risk of Schneiderian membrane perforation and early and late implant failure ( p = .897, p = .140, p = .991, respectively). The implant cumulative 7‐year survival rate of the RBH ≤ 4 and >4 mm groups was 95.5% and 93.9%, respectively (log‐rank test: p = .900). Within at least 40 cases per group after PSM, two multivariate GLMMs indicated that RBH ≤ 4 mm could not be identified as the promotive factor of bone resorption of either endo‐sinus bone gain or crest bone level (RBH × time interaction p = .850, p = .698, respectively). Conclusions Within the limitations, 3 months to 7 years of post‐prosthetic restoration review data indicated an acceptable mid‐term survival and success rate of applying the cushioned grind‐out technique in RBH ≤ 4 mm cases.