Immediate loading of three (fixed-on-3) vs four (fixed-on-4) implants supporting cross-arch fixed prostheses: 1-year results from a multicentre randomised controlled trial.

PURPOSE: To evaluate the outcome of three (fixed-on-3 = Fo3) vs four (fixed-on-4 = Fo4) implants immediately restored with metal-resin screw-retained cross-arch prostheses in fully edentulous jaws. MATERIALS AND METHODS: Forty-eight edentulous or to be rendered edentulous patients were randomised in six centres (eight patients per centre) to the Fo3 group (24 patients: 12 maxillae and 12 mandibles) and to the Fo4 group (24 patients: 12 maxillae and 12 mandibles) according to a parallel group design. To be immediately loaded, implants had to be inserted with a minimum torque of 40 Ncm. Outcome measures were prosthesis and implant failures, complications and peri-implant marginal bone level changes evaluated up to 1 year post-loading. RESULTS: One maxillary prosthesis per group was delayed loaded because implants could not be placed with a torque of at least 40 Ncm. Ten patients in the Fo3 group and four in the Fo4 group had implants placed flapless. One year after loading no drop out occurred. One patient of the Fo3 group lost three implants vs three patients of the Fo4 group who lost four implants, the difference being no statistically significant (risk difference = -0.08; 95% CI: -0.27 to 0.10; Fisher's exact test P = 0.609). One mandibular Fo3 and one maxillary Fo4 prosthesis failed. Six Fo3 patients were affected by complications vs three Fo4 patients (risk difference = 0.12; 95% CI: -0.10 to 0.34; Fisher's exact test; P = 0.461). Both groups lost marginal bone in a statistically significant way (0.22 ± 0.20 mm for Fo3 patients and 0.40 ± 0.21 mm for Fo4 patients), with Fo3 group showing less marginal peri-implant bone loss than Fo4 group (estimate of the difference = -0.18 (standard error: 0.06) mm; 95% CI: -0.30 to -0.06; P = 0.005). There were no differences in clinical outcomes between the six operators. CONCLUSIONS: These preliminary results suggest that immediately loaded cross-arch prostheses of both jaws can be supported by only three dental implants at least up to 1 year post-loading, though longer follow-ups are definitively needed.

Immediate loading of 2(all-on-2) versus 4 (all-on-4) implants placed with a flapless technique supporting mandibular cross-arch fixed prostheses: 1-year results from a pilot randomised controlled trial.

PURPOSE: To evaluate the outcome of 2 versus 4 implants placed flapless in fully edentulous mandibles and immediately restored with metal-resin screw-retained cross-arch prostheses. MATERIALS AND METHODS: Sixty patients from two different centres were randomised: 30 to the allon- 2 group and 30 to the all-on-4 group according to a parallel group design. To be immediately loaded, implants had to be inserted with a minimum torque of 40 Ncm. Outcome measures were prosthesis and implant failures, complications, and marginal bone level changes. RESULTS: Flaps were raised in 18 patients. A total of 2 implants in 2 patients did not reach the planned insertion torque and were immediately replaced by larger diameter ones. One year after loading, no drop-out or implant failure occurred. Eight biomechanical complications occurred in the all-on-2 group versus 8 complications in the all-on-4 group. There were no statistically significant differences for complications between groups. There were no statistically significant differences for marginal peri-implant bone levels between the two groups (estimate of the difference = -0.16; 95%CI -0.40 to 0.08; P (ANCOVA) = 0.074), with both groups losing a statistically significant amount of marginal bone (0.74 mm for all-on-2 implants and 0.58 mm for all-on-4 implants). There were statistically significant differences between the two centres, with more bone being lost for the Bologna centre (0.26 mm versus 1.07 mm). CONCLUSIONS: These preliminary results, up to 1 year after loading, suggest that immediately loaded mandibular cross-arch fixed prostheses can be supported by only 2 dental implants. Longer followups (approximately 10 years) are needed to properly evaluate this therapeutic option.