ORIGINAL ARTICLE Dental arch dimensions in oligodontia patients Xianghhong Bu, a Khaled Khalaf, b and Ross S. Hobson c Yanan, China, and Newcastle upon Tyne, United Kingdom Introducton: The aim of this study was to compare the dental arch sizes in a group of oligodontia patients with a group of age- and sex-matched untreated Class I control patients. Methods: Dental casts were measured of 50 oligodontia patients and 50 untreated Class I patients between 8 and 16 years old. For each subject, dental arch length and width parameters were measured in the maxillary and mandibular arches with digital calipers. The various dental arch parameters were compared between the 2 groups by using ANOVA. Results: The mean age of the subjects was 12.5 years. The average number of teeth missing in the oligodontia group was 11. The mean maxillary and mandibular arch lengths in the oligodontia group were reduced by 4.40 and 2.80 mm, respectively, when compared with the control group. The intercanine widths were reduced in the oligodontia group compared with the control group by 2.82 mm in the maxillary arch and 2.70 mm in the mandibular arch. The intermolar widths of the maxillary and mandibular arches in the oligodontia group were reduced by 3.40 and 1.80 mm, respectively, compared with the control group. These differences were statistically significant (P 0.01). Conclusions: The findings indicate that arch length and width are reduced in oligodontia patients; this should be taken into account when planning orthodontic treatment. (Am J Orthod Dentofacial Orthop 2008;134:768-72) H ypodontia is the developmental absence of at least 1 tooth; when 6 or more teeth are congenitally absent, it is called oligodontia. 1,2 The prevalence of hypodontia has been estimated between 2.3% and 10.1% in the permanent dentition. 3-5 The prevalence of severe hypodontia is less than that of moderate hypodontia, which in turn is less than that of mild hypodontia. Sarnas and Rune 6 estimated the prev- alence of advanced hypodontia (congenital absence of 4 or more permanent teeth) at 0.25% in a Swedish population. The prevalence was reported to be as low as 0.084% for 6 or more congenitally missing teeth (oligodontia) in a Norwegian population. 2 Patients seek orthodontic care because of an unes- thetic and socially unacceptable malocclusion when teeth are missing. The absence of teeth can affect social interaction and masticatory function. 7 Comprehensive management of hypodontia is best undertaken in mul- tidisciplinary clinics, and these have been established in some centers for diagnosis, treatment planning, and coordination of treatment. 8-14 The etiology of oligodontia is not yet known. How- ever, various genetic and environmental factors have been implicated in the etiology of congenitally missing teeth. Brook 15 suggested a multi-factorial model with an under- lying scale of continuous variation related to tooth number and size. Environmental influences such as trauma, infec- tions (eg, rubella), ionizing radiation, drugs, and hormonal influences have been suggested as possible insults that might have impinged on tooth formation during the embryologic stages of dental development. 15,16 Various homeobox genes— eg, Msx-1, Msx-2, Dlx-1, Dlx-2, Barx-1, Parx-9, and Pitx-2— have been found to be expressed in various regions of future tooth devel- opment in mice. 17 Further studies have shown that oligodontia is most likely a genetic trait, and various gene defects have been proposed as the cause. 18-25 Although several studies have investigated dental arch dimensions in hypodontia patients, there are no similar reports in oligodontia patients. 26-29 Our aim in this study was to compare dental arch lengths and widths in a group of oligodontia patients with those in an age- and sex-matched control group. MATERIAL AND METHODS Fifty oligodontia patients were selected randomly from the database of the hypodontia clinic at New- castle upon Tyne in the United Kingdom. This database contain the records of more than 400 patients who have attended the multidisciplinary hypodontia clinic. The patients’ records were ob- tained and their radiographs examined to confirm the absence of teeth. a Lecturer in orthodontics, Department of Orthodontics, Yanan Municipal Hospital, Yanan, China. b Clinical lecturer and FTTA in orthodontics, School of Dental Sciences, Newcastle upon Tyne, United Kingdom. c Senior lecturer and honorary consultant in orthodontics, School of Dental Sciences, Newcastle upon Tyne, United Kingdom. Reprint requests to: Ross S. Hobson, School of Dental Sciences, Framlington Place, Newcastle upon Tyne NE2 4BW, United Kingdom; e-mail, R.S.Hobson@ ncl.ac.uk. Submitted, September 2005; revised and accepted, March 2007. 0889-5406/$34.00 Copyright © 2008 by the American Association of Orthodontists. doi:10.1016/j.ajodo.2007.03.029 768