Changes in vertical tooth position and face height related to long term anterior repositioning splint therapy

This study evaluates whether extended full-time wear of a partial coverage mandibular anterior repositioning splint (MORA) causes intrusion of posterior teeth and determines the effect on jaw position. Sixty-four patients from two private orthodontic practices were studied using cephalometric radiographs to measure vertical change in position of the anterior and posterior teeth and the mandible. The splint wear time ranged from a minimum of one half year to a maximum of 4.8 years, with a mean of 1.33 years. No significant change was recorded in the distance from the mandibular molar to the mandibular plane. On average, the maxillary incisor and maxillary molar extruded about 1 mm, while the mandibular molar was unchanged and the mandibular incisor intruded about 0.6 mm. Posterior face height increased an average of 1.6 mm, and anterior face height increased an average of 2.7 mms. In 20% of the patients, intrusion of the mandibular molars of 1 mm or more occurred. In 41%, extrusion of the maxillary incisors of 1 mm or more was noted. Intrusion of the upper molars or extrusion of the lower incisors occurred in only 5% of the patients. The data indicates that only a very small proportion of patients having long term splint therapy using the MORA have clinically significant molar intrusion. Change in mandibular position was expressed in a vertical increase in posterior and anterior face height. Only very small changes occurred in antero-posterior position.