The effect of the Mandibular Plane Angle on Fracture Line Stability: An Ex Vivo Experimental Study.

BACKGROUND/AIMS: The mandibular angle fractures fixated with plate osteosynthesis techniques have to withstand the effects of muscle attachments. The individual variations in the cranio-facial morphology may alter the biomechanical resistance of the bone-plate construct. The aim of the present study was to determine the influence of variations in the mandibular plane angle (MPa) on the biomechanical stability of sheep mandibular angle fractures (MAFs).

MATERIALS AND METHODS: Sixty sheep hemi-mandibles were used in this study. The mandibles were positioned on a test jig that simulated low (15°, group L), normal (25°, group N) and high (35°, group H) MPa. Unfavorable MAFs were created with thin diamond cutting discs. One four-hole, 9.0 mm spacing, standard titanium mini-plate of 2.0 mm thickness and 5.0 mm long screws were inserted at the superior border of the alveolar bone in monoplanar orientation. Specimens were then subjected to vertical loads between 10N and 150N in a universal testing machine. The displacement values at each 10 N force increment and the load magnitude at which 3.0 mm displacement limit was reached, were recorded.

RESULTS: Starting from 40N, the displacement values at each 10N increment in H group were significantly higher than those of L and N groups until 150N (P<.05). The force magnitude required to reach 3.0 mm of displacement in H group was significantly lower than those for the L and N groups (P<.05 for each).

CONCLUSIONS: The one-miniplate monoplanar fixation technique used in sheep MAF with high MPa is more likely to offer lower biomechanical resistance to the vertical forces applied over the molar region than do the normal and low MPa. This article is protected by copyright. All rights reserved.