Severe hypodontia: identifying patterns of human tooth agenesis.

Tooth agenesis is the most common dental anomaly. The aim of this retrospective study was to identify common patterns of tooth agenesis in a sample of 92 patients (55 females and 37 males; mean age 27.7 years) with non-syndromic severe hypodontia. The Tooth Agenesis Code (TAC) procedure was used for that purpose. The patients in this study were missing between 6 and 22 permanent teeth (mean 11.6; median 10.0; SD 4.35). In the maxilla, 47.9 (left side) and 50.0 (right side) per cent can be described using only five different patterns. The most common patterns involved agenesis of the maxillary lateral incisor and both premolars. In the mandible, 35.8 (lower left) or 43.5 (lower right) per cent can be described by five patterns, the most common of which was agenesis of all mandibular premolars. When comparing patients with and without symmetric agenesis patterns (symmetry in the upper or lower arch versus no symmetry), a Student's t-test revealed no difference in the total number of missing teeth. Common patterns of tooth agenesis were successfully identified in patients with non-syndromic severe hypodontia. The present findings may be used to develop interdisciplinary treatment protocols for the most common patterns to increase the quality of interdisciplinary treatment for patients with severe hypodontia.