Abstract

We treated two monozygotic twins with bilateral cleft lips and palates and studied their craniofacial growth and morphology using cephalometric radiographs. The zygosity of the twins was determined using DNA short tandem repeats (STRS), which are completely specific for use in human identification to analyze patterns in the STR locus. Because these patterns were identical, the children were diagnosed as monozygotic twins. The initial age at diagnosis was 5 y and 8 m. Orthodontic treatment with expansion appliances and multiple bracket appliances was done at age 13 y and 0 m when the anterior crossbite appeared. The treatment continued to age 20 y and 4 m. We found that the S-N distances in the cranial base of the twins were longer than standard values, the ANB angles decreased with growth, and the palates were located more downward. In addition, their chins were retracted by the opening of the mandibular plane angle. The mandibular plane angle was smaller and the mandibular length was larger in child A than in child B. Child B showed skeletal Class III craniofacial morphology. The maxillary and the mandibular anterior teeth inclined lingually in both. Shika Igaku (J Osaka Odontol Soc) 2023; Sep; 86(2): 115-124.