Aim: Congenital absence of teeth is a complex condition affecting several parameters of oral development. This is the first study to measure tooth crown dimensions using image analysis in a family with hypodontia in whom the mutation has been identified, and compare them with a control group.
Methods and results: Study models were obtained from 10 family members from three generations affected by severe hypodontia with a missense mutation in PAX9 and 10 unaffected, unrelated controls. Using established image analysis techniques all teeth up to and including the first permanent molars were digitally imaged by two operators from the occlusal (O) and buccal (B) aspects three times and an average made for the mesio-distal (MDO and MDB) bucco-lingual (BL), area (A) and perimeter (P) measurements. Intra-class correlation coefficients (ICCC) were calculated to assess intra- and inter-operator reliability. Two-sample t-tests were then used to compare these dimensions with those of the controls. Reliability of the technique was high (mean r>0.95). The majority of tooth types throughout the dentition were significantly smaller in the family members with hypodontia than in the control group for all parameters measured. The levels of significance were very high for upper lateral incisors (p<0.0001) whilst the canines and first molars were less different. The greatest number of significant differences were found in BL and P, closely followed by MD and A measurements.
Conclusions: The significantly smaller tooth crown dimensions recorded in the affected family members show that the effect of the PAX9 mutation is seen not only in the congenitally missing teeth but also in smaller crown size throughout the dentition.