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European Journal of Oral Implantology



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Eur J Oral Implantol 6 (2013), No. 2     23. July 2013
Eur J Oral Implantol 6 (2013), No. 2  (23.07.2013)

Page 121-131, PubMed:23926584

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
Cannizzaro, Gioacchino / Felice, Pietro / Soardi, Elisa / Ferri, Vittorio / Leone, Michele / Lazzarini, Matteo / Audino, Salvatore / Esposito, Marco
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.

Keywords: all-on-2, dental implants, flapless, immediate loading, randomised controlled trial