Clinical and radiographic outcomes following transcrestal maxillary sinus floor elevation with injectable xenogenous bone substitute in gel form: a prospective multicenter study

Purpose: To investigate clinical and radiographic outcomes of transcrestal maxillary sinus floor elevation performed with an injectable xenograft in gel form, analyzing general, local and surgical variables possibly influencing the results. Methods: Patients with residual crestal height < 5 mm underwent transcrestal sinus floor elevation with xenograft in gel form to allow the placement of a single implant. Simultaneous implant placement was performed when primary stability was >= 15 Ncm. Graft height was measured immediately after surgery (T0) and after 6 months of healing (T1). Univariate and multivariate regression models were built to assess associations between clinical variables with implant survival and graft height at T1. Results: 71 patients underwent transcrestal sinus floor elevation and 54 implants were simultaneously placed. Delayed implant placement (at T1) was possible in 5 cases out of 17 (29.4%), whereas in 12 patients (70.6%) implant insertion was not possible or required additional sinus grafting. Implant survival rate, with a follow-up varying from 12 to 32 months after loading, was 100%. Mean pre-operative bone height was 3.8 +/- 1.0 mm, at T0 was 13.9 +/- 2.2 mm and at T1 was 9.9 +/- 2.8 mm. Bone height at T1 was negatively influenced by membrane perforation at surgery (p = 0.004) and positively influenced by immediate implant insertion (p < 0.001). Conclusions: Transcrestal sinus floor elevation performed with injectable xenograft gel resulted in 100% implant survival rate. However, immediate implant insertion seems a crucial factor to preserve vertical bone gain: one-stage technique seems to be the most predictable approach to optimize clinical outcomes with this approach.