A comparative study on 7-year results of "All-on-Four™" immediate-function concept for completely edentulous mandibles: metal-ceramic vs. bar-retained superstructures.

The study aims to document the clinical outcomes over a 7-year period of two techniques used for the rehabilitation of edentulous mandibles according to the "All-on-Four™" concept: (1) fixed complete-arch prostheses fabricated with metal-ceramic implant-supported fixed prosthesis with a titanium framework and all-ceramic crowns and (2) bar-retained implant-supported removable prosthesis with acrylic resin prosthetic teeth. The study was performed on 32 patients who received immediately loaded "All-on-Four™" fixed mandibular prostheses. (Fixed prostheses with ceramic superstructures, n:16; bar-retained removable acrylic prostheses, n:16). The patients were evaluated for up to 7 years after prosthesis completion. The endpoints included the evaluation of prosthodontic complications, bone resorption, plaque accumulation, bleeding on probing, periodontal probing depth and an oral health impact profile (OHIP). Bone loss remained under 1.2 mm in all of the implants, and no difference was observed between two groups. Plaque accumulation increased gradually in both groups, and the bar-retained acrylic-bearing implants showed significantly higher values during the first 5 years. Immediate improvement was assessed by the OHIP score in both groups. The observed bone loss and the subjective outcomes showed equivalent levels of clinical success for bar-retained and ceramic superstructures over a 7-year period. The higher level of plaque accumulation observed around implants with bar-retained superstructures requires that patients with acrylic superstructures be highly motivated to maintain their personal oral hygiene. Further studies are needed to clarify the occurrence of prosthodontic complications and assess their economic aspects.