Retrospective Clinical Evaluation of Non-Engaging Abutments Used for Multi-Unit Screw-Retained Fixed Prosthesis

Background/Objectives: This retrospective study aimed at evaluating the clinical performance of non-engaging abutments in multi-unit implant-supported prostheses and assessing the influence of abutment combinations and clinical variables on biological and technical outcomes. Methods: Forty patients with 90 implants and 40 fixed dental prostheses were involved. The study population was divided into three groups: 17 patients (8 males, 9 females) in the first group, 16 patients (7 males, 9 females) in the second, and 7 patients (2 males, 5 females) in the third. All patients received multi-unit implant restorations in a private practice between January 2021 and December 2023, and each prosthesis was in function for one year after delivery, with a mean follow-up of 2.17 ± 0.32 years. Restorations involved non-engaging abutments alone or in combination with engaging abutments or multi-unit abutments. Clinical parameters included implant and prosthesis survival rates, probing pocket depth, bleeding on probing, marginal bone loss, and the prevalence of biological and technical complications. For the comparison between the three groups, the analysis of variance was used to compare group means. When appropriate, Tukey's post hoc test was applied for multiple comparisons. The significance level was set at p < 0.05. Results: The implant and prosthesis survival rates were both 100%. Mean marginal bone loss was 0.53 ± 0.33 mm, and mean probing pocket depth was 4.2 ± 0.75 mm. No cases of peri-implantitis were observed. Mucositis prevalence was 11.11% at the implant level. No significant differences were found among different abutment combinations for biological outcomes or complications. The technical complication rate was 5%. Conclusions: Non-engaging abutments demonstrated favorable short-term clinical outcomes with minimal biological and technical complications. They may represent a reliable option for the restoration of multi-unit prostheses, although long-term studies are needed.