Stability consideration for internal maxillary distractors

Abstract

Purpose: Stability in distractor design ensures distraction osteogenesis healing with good bone regenerate formation. The aim of this study was to compare the holding strengths of different fixation systems for maxillary distractor design on bone pieces of different thicknesses. Material and methods: Cross-sectional images of 10 dry skulls were obtained by computer tomography and the bone thickness of the maxillae were measured according to five individual anatomical regions (paranasal, infra-orbital, posterior sinus wall, zygomatic and alveolar regions). According to the measurements, the screws of 1.5 and 2 mm in diameter and the three-screw mini-plates in triangular and straight configurations were evaluated for holding strength by pull-out tests on fresh animal bone pieces of defined thickness. Results: The paranasal and zygomatic regions of the human skulls had the thickest cortical bone (4 mm) followed by the alveolar region (2 mm). In the bones of 2 and 4 mm thickness, the 2 mm screws were confirmed stronger than the 1.5 mm ones in pull-out tests. However, the pull-out behaviour of screws of different diameters in 1 mm thick bones and the mini-plates in two different configurations showed no significant differences. Conclusion: This study confirms that the paranasal and zygomatic bones are the thickest for fixation of internal maxillary distractors. Fixation screws of 2 mm diameter in either triangular or straight miniplates can produce good stabilization for distractors. © 2003 European Association for Cranio-Maxillofacial Surgery.