Mechanical evaluation of different techniques for symphysis fracture fixation--an in vitro polyurethane mandible study.

Purpose: The aim of this study was to make a comparative evaluation of the mechanical behavior of 4 different internal fixation systems for mandibular symphysis fractures.

Materials And Methods: Forty polyurethane mandible replicas (Nacional, Jaú, SP, Brazil) were used. These were divided into 4 groups of different fixation methods: group 1P, 1 2.0-mm miniplate; group 2PLL, 2 2.0-mm parallel miniplates; group 2PERP, 2 2.0-mm perpendicular miniplates; and group LST, 2 2.0-mm lag screws. Each group was subjected to linear vertical loading in the molar region in an Instron 4411 servohydraulic mechanical testing unit (Instron Corporation, Norwood, MA). The load resistance values were measured at load application displacements of 1, 3, 5, and 10 mm. Means and standard deviations were compared with respect to statistical significance using analysis of variance (P < .05) and compared by the Tukey test.

Results: Group 1P showed the lowest peak load scores compared with other fixation methods. Group LST showed a statistically significant higher resistance than group 2PLL for all displacements. Group 2PERP showed lower resistance than group LST when displacements were 1 and 3 mm and statically significant similarity at displacements of 5 and 10 mm. However, group 2PERP showed no statistically significant differences compared with group 2PLL.

Conclusions: The LST showed better mechanical behavior for symphysis fracture fixation than the other systems when the fixation methods were subjected to linear vertical loading in the molar region.