Medium-term clinical outcomes of the all-on-4 system in different bone types: a retrospective analysis
摘要
This study aimed to determine the independent influence of bone quality and prosthetic material on medium-term implant survival, peri-implant complications, prosthetic complications, and patient-reported outcomes following All-on-4 rehabilitation.
MethodsThis retrospective, observational, multicenter cohort study included 250 edentulous patients (125 maxillary and 125 mandibular cases) who received All-on-4 implant-supported full-arch prostheses between September 2018 and September 2021. Patients were categorized by bone type (Types 1–4) according to the Lekholm and Zarb classification. Clinical parameters, insertion torque, implant stability quotient (ISQ), peri-implant and prosthetic complications, and patient satisfaction (VAS score) were recorded and analyzed. Prosthetic materials used were either metal-acrylic or monolithic zirconia prostheses.
ResultsA total of 1,000 implants were evaluated over a mean follow-up period of 3.6 ± 0.4 years. The overall implant survival rate was 94.8%, with significantly lower survival in Type 4 bone (89.1%) compared to Type 1 (98.3%) (p < 0.05). Peri-implant complications, particularly peri-implantitis and screw loosening, were significantly more frequent in lower-density bone types. Prosthetic complications were analyzed at the prosthesis level and were more frequent in the metal-acrylic group (26.9%) than in the zirconia group (8.9%) (p < 0.001). Despite these differences, patient satisfaction scores were high across all bone types (Mean VAS: 8.7 ± 1.2).
ConclusionsThe All-on-4 concept demonstrated predictable medium-term clinical outcomes, with high implant survival and favorable patient satisfaction in completely edentulous patients. However, poorer bone quality, particularly Type 4 bone, was independently associated with lower implant survival, reduced primary stability, and a higher frequency of peri-implant complications. In addition, monolithic zirconia prostheses were associated with fewer mechanical complications than metal–acrylic prostheses. These findings highlight the importance of individualized treatment planning that integrates bone quality assessment and prosthetic material selection to optimize medium-term clinical outcomes. Although the findings should be interpreted in light of the retrospective observational design and medium-term follow-up, they provide clinically relevant evidence to support risk-informed clinical decision-making in full-arch implant rehabilitation.