Angulated titanium bases screw channel abutments for single implant restorations: A systematic review and meta-analysis

Purpose: Screw-retained implant crowns are a common solution to rehabilitate single or multiple edentulous sites. Angulated screw channel (ASC) abutments have been developed as a new system of connection to correct the angulation of the implant and avoid a possible undesired emergence of the access hole. The purpose of this systematic review was to examine available literature related to the effects of ASC abutments in rehabilitating single implant crowns. Methods: A protocol was registered in the PROSPERO database (ID = CRD42022295521). An electronic search of the Cochrane Central Register of Controlled Trials and Trial Protocols, MEDLINE, SCOPUS, and Web of Science was performed up to January 16, 2024. Additionally, a manual search was carried out. The meta-analysis used a fixed or a random effects model, based on the heterogeneity between the studies, focusing on binary and continuous data. A risk of bias assessment was performed (NOS or MOGA et al.) The outcomes assessed were peri-implant marginal bone level, probing pocket depth (PPD), the prevalence of technical and mechanical complications, implant and prosthesis survival rates, and esthetics. Statistical significance was set at p < 0.05. Results: The searches resulted in a total of 10 studies included in the meta-analysis. The mean implant and prosthesis survival rates were respectively 99% (absolute quantity = 243) and 100% (absolute quantity = 239) with non-statistically significant differences observed in single crowns supported by ASC abutments compared to cemented restorations, in terms of marginal bone loss (MBL) (p = 0.22), PPD (p = 0.08), risk of complications (p = 0.53), and esthetics (p = 0.47). Follow-up intervals ranged from 14 days to more than 3 years. Conclusions: Data based on this systematic review suggest that the clinical and radiographic outcomes of single implants restored using ASC are promising if compared to the outcomes relating to screw-retained single crowns.