Anterior transmandibular osteodistraction: clinical and model observations.

Introduction: The aim of this paper was to study the effect of transmandibular distraction on the periodontal and dental structures, and the initial movements of the mandibular halves, when using an axial plane non-rigid bone-borne distractor (TMD).

Material And Methods: Fourteen patients undergoing bimaxillary transverse osteodistraction had their six lower anterior teeth assessed for mobility, sensitivity, and pocket depth. Recordings were made pre-operatively, post-distraction, post-consolidation and at 1-year follow-up. Selected landmarks on pre-operative and post-consolidation models were also digitised in three dimensions to study individual tooth movements, and positional changes of the mandibular halves.

Results: Pockets depths around the incisor teeth increased during the consolidation period (probably due to reduced oral hygiene), but returned to normal by the 1-year post-operative consultation. Tooth mobility increased temporarily in the active phase (central incisors, lateral incisors) and in the consolidation phase (lateral incisors, canine teeth). Sensitivity to cold was temporarily lost in the incisor teeth, probably as a result of 'apical contusion'. One central incisor was inadvertently apically osteotomized and needed root canal treatment. The angle between the mandibular halves closed by 9.4 degrees.

Conclusion: Periodontal and dental morbidity is transient and limited to the distraction and consolidation period, as long as the tooth apices are avoided when the osteotomy is performed. A step-design osteotomy may be preferable when the central incisor apices are close to each other. The transmandibular distractor (TMD) allows for rotation at the temporomandibular joints.