Mechanical evaluation of the use of conventional and locking miniplate/screw systems used in sagittal split ramus osteotomy.

OBJECTIVES: The aim of this study was to compare the mechanical resistance of four different osteosyntheses modeled in two different sagittal split ramus osteotomy (SSRO) designs and to determine the linear loading in a universal testing machine. MATERIALS AND METHODS: An in vitro experiment was conducted with 40 polyurethane hemimandibles. The samples were divided into two groups based on osteotomy design; Group I, right angles between osteotomies and Group II, no right angles between osteotomies. In each group, the hemimandibles were distributed into four subgroups according to the osteosynthesis method, using one 4-hole 2.0 mm conventional or locking plate, with or without one bicortical screw with a length of 12.0 mm (hybrid technique). Each subgroup contained five samples and was subjected to a linear loading test in a universal testing machine. RESULTS: The peak load and peak displacement were compared for statistical significance using PASW Statistics 18.0 (IBM Co., USA). In general, there was no difference between the peak load and peak displacement related to osteotomy design. However, when the subgroups were compared, the osteotomy without right angles offered higher mechanical resistance when one conventional or locking 2.0 mm plate was used. One locking plate with one bicortical screw showed higher mechanical resistance (162.72±42.55 N), and these results were statistically significantly compared to one conventional plate with monocortical screws (P=0.016) and one locking plate with monocortical screws (P=0.012). The difference in peak displacement was not statistically significant based on osteotomy design or internal fixation system configuration. CONCLUSION: The placement of one bicortical screw in the distal region promoted better stabilization of SSRO. The osteotomy design did not influence the mechanical behavior of SSRO when the hybrid technique was applied.

Retention and Mechanical Behavior of Attachment Systems for Implant-Retained Auricular Prostheses.

OBJECTIVE: Auricular prostheses are artificial substitutes for facial defects. The retention of these has often been a problem. This study aimed to evaluate the mechanical behavior of 3 retained auricular prosthetic connections when submitted to a mechanical cycling test. MATERIALS AND METHODS: Twelve samples with installed implants were obtained and divided into 3 groups according to their retention system with 4 samples in each group. I: bar-clip system; II: magnet system; and III: ball/o-ring system. Each of samples was submitted to the pull-out test during 3240 cycles (f = 0.5 Hz) to determine its tensile strength. The mechanical cycling test was performed using the servo-hydraulic machine MTS 810-Flex Test 40 (Eden Prairie, MN) that had a 2.5 mm shift at a 10 mm/s velocity. The retaining strength for each of the samples was obtained at 7 intervals. RESULTS: The tensile strength for the group retained by the bar-clip system (29.60 N) was higher with statistically significant difference (P < 0.05) when compared with the group retained by the ball/o-ring system (9.41 N) and magnets system (8.61 N) for all periods assessed. The ball/o-ring system showed loss of retention during the fatigue test (Kruskal-Wallis, chi-squared = 17.28; P < 0.01). CONCLUSIONS: The evaluated systems showed a tensile strength compatible with the clinical use and no fractures of the components were observed.

Expansão cirúrgica de rebordo alveolar com instalação imediata de implantes / Edentulous ridge expansion with simultaneous implant placement

Introdução: após a perda dentária, o processo alveolar sofre atrofia gradativa, impossibilitando, em casos extremos, a reabilitação com implantes dentários. Objetivo: relatar um caso clínico de instalação de implantes imediatos em maxila edêntula atrófica, após aplicação da técnica de expansão cirúrgica do rebordo alveolar (ECR) na região anterior e levantamento do assoalho do seio maxilar (LS) nas regiões posteriores, em conjunto com enxerto ósseo autógeno removido do ramo ascendente da mandíbula. Conclusão: a ECR e o LS são alternativas viáveis, seguras e previsíveis para o aumento da espessura e altura do rebordo alveolar com finalidade reabilitadora.