[The use of osteosynthesis screws in child mandibles. Anatomical and mechanical considerations]

Thirty seven child mandibular skeletons were analysed radiographically and computer tomographically to establish if there is enough room for osteosynthesis screws. The study demonstrated that in the primary and early mixed dentition there is not enough room in the canine or post-canine region to allow the installation of an osteosynthesis screw without damaging the inferior dental nerve or teeth buds. However, in the later stage of permanent tooth eruption the entire caudal portion of the mandibular body seems to provide sufficient room for osteosynthesis screws. SEM examinations of implant beds of 100 2 mm AO miniscrews inserted into the mandibles of eight fresh cadavers aged eight to twelve years showed cracks, as well as signs of squashing, crushing and shearing stress, regardless of whether the screws were pretapped or not. When, during screw insertion, the axis of the screw deviated by at least 10 degrees from the axis of the tap, two crossing thread courses resulted.