[Morphological and functional analysis of dento-orofacial complex in monozygotic twins with Duchenne type muscular...

The form of dento-orofacial complex and masticatory muscle function of monozygotic twins with Duchenne type muscular dystrophy were investigated. They had no environmental difference. Morphological analysis were performed on the dental casts and cephalograms. EMG recordings were derived from the bipolar surface electrodes on the masseter muscle and the anterior belly of digastric muscle on the left side. Each consisted of the data for three years. Results obtained are as follows: 1) Based on the average data, these patients showed an elongated dental arch in the maxilla and mandible, which might be caused by enlarged tongues. There were little difference in the tooth and dental arch sizes between them. 2) Cephalometric findings indicated that the elder brother showed a clockwise rotation of the mandible with larger gonial angle than the younger brother. Both of them showed a larger gonial angle based on the mean values. 3) Analysis of EMG recordings revealed an elongated silent period induced by teeth tapping and chin tapping, and a variable masticatory rhythm compared with that of normal sample. Moreover an annually increased imbalance between masseter muscle and digastric muscle was evident, which were parallel to the change of the blood creatine kinase value. Differences in the form and function of orofacial complex between them might be caused by their polygene heredity and the large size of DMD gene (XP 21).