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.

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.