The effect of casting and masticatory simulation on strain and misfit of implant-supported metal frameworks

The influence of casting and masticatory simulation on marginal misfit and strain in multiple implant-supported prostheses was evaluated. Three-unit screw retained fixed dental prosthesis (FDP) and screw retained full-arch fixed dental prosthesis (FAFDP) frameworks were made using calcinable or overcasted cylinders on conical dental implant abutment. Four groups were obtained according to the cylinder and prosthesis type (n = 10). Frameworks were casted in CoCr alloy and subjected to strain gauge analyses and marginal misfit measurements before and after 106 mechanical cycles (2 Hz/280 N). Results were submitted to ANOVA, Tukey's HSD and Pearson correlation test (α = 0.05). No difference was found on misfit among all groups and times (p > 0.05). Overcasted frameworks showed higher strain than the calcinable ones (FDP — Initial p = 0.0047; Final p = 0.0004; FAFDP — Initial p = 0.0476; Final p = 0.0115). The masticatory simulation did not influence strain (p > 0.05). No correlation was observed between strain and misfit (r = 0.24; p > 0.05). In conclusion, the marginal misfit value in the overcasted full-arch frameworks was higher than clinical acceptable data. It proved that overcasted method is not an ideal method for full-arch prosthesis. Overcasted frameworks generate higher strain upon the system. The masticatory simulation had no influence on misfit and strain of multiple prostheses.62746751CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO - CNPQFUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULO - FAPESP132946/2011-42011/02841-7 ; 2011/03032-