ORIGINAL ARTICLE Effects of early unilateral first molar extraction on skeletal asymmetry Murat Çag ˘ larog ˘ lu, a Nihat Kilic, a and Abdulvahit Erdem b Erzurum, Turkey Introduction: The purpose of this study was to investigate dental and skeletal asymmetry in patients who had unilateral first molar extractions. Methods: Two study groups were formed according to the location of the extracted first molars. Group I included 25 subjects who had a maxillary permanent first molar extracted (mean age, 18.25 years). Group II included 26 subjects who had a mandibular permanent first molar extracted (mean age, 17.75 years). The control group included 30 subjects with no missing teeth and normal occlusion (mean age, 18.50 years). Dental and skeletal asymmetry values were computed on posteroanterior radiographs for all subjects. Data were analyzed statistically with paired t tests to determine intragroup differences and with ANOVA and Scheffé tests to determine intergroup differences. Results: Unilateral first molar extractions caused dental midline deviations in both arches, but this was more prominent in the mandibular arch. Unilateral first molar extraction during growth and development can result in remarkable skeletal asymmetry, especially in the lower third of face. Conclusions: Patients who had early unilateral first molar extraction can have skeletal and dental asymmetries. (Am J Orthod Dentofacial Orthop 2008;134:270-5) T he study of beauty and harmony of facial appearance has been central to the practice of orthodontics from its earliest days. 1 Perhaps an important objective of orthodontic treatment is obtain- ing a balanced and harmonious face, which greatly depends on skeletal form and craniofacial symmetry. Symmetry is defined as the correspondence in size, form, and arrangement of parts on the opposite sides of a plane, line, or point; and regularity of form or arrangement in terms of like, reciprocal, or correspond- ing parts. 2 Craniofacial symmetry is the similarity and equality in shape, volume, and appearance of the right and left sides of the face with respect to the median sagittal plane. However, perfect symmetry does not exist between the left and right parts of living organ- isms. Some authors stated that subjects with normal facial appearance might have facial asymmetry. 3-8 Peck et al 9 found a slight skeletal asymmetry in esthetically pleasing faces. Some researchers stated that the left side of the face was larger, 3-5 but others reported that the right side was larger. 6,7,9 Bishara et al 10 classified dentofacial asymmetries as dental, skeletal, muscular, and functional according to their origins. The development of craniofacial asymmetry still is a phenomenon. According to Sarver et al, 11 the possible etiologies of asymmetry are: (1) genetic or congenital malformations (hemifacial microsomia, unilateral cleft lip, and palate problems) and (2) environmental factors such as bad habits, trauma, functional deviation of the mandible as a result of maxillary constriction or maloc- clusion, hard- and soft-tissue tumors, condylar hyperplasia or hypoplasia, asymmetric mandibular growth caused by reduced growth of the condyle, and masseter hypertrophy. Lundstrom 12 studied asymmetry of the face and the dental arches, and classified the possible causes of asymmetries as genetic, environmental, or a combina- tion. The author stated that environmental factors such as tooth caries, early tooth loss, and trauma might result in asymmetric chewing habits. Andrews 13 emphasized the importance of the first molars in a balanced and normal occlusion. Early extraction of these teeth can negatively affect both arches and consequently the whole occlusion. Unfortu- nately, the first molars are the most commonly ex- tracted teeth because of caries. 14,15 Early extraction of permanent first molars might also cause problems such as tipping of adjacent teeth toward the extraction site, extrusion of the corresponding opposite teeth, dental midline shifts toward the extraction side, asymmetric or unilateral chewing habits, and periodontal problems from alveolar bone atrophy in the extraction cavity. 14,16 From the Department of Orthodontics, Faculty of Dentistry, Atatürk Univer- sity, Erzurum, Turkey. a Research assistant. b Professor. Reprint requests to: Murat Çag ˘larog ˘lu, Atatürk U ¨ niversitesi Dis ¸ Hekimlig ˘i Fakültesi Ortodonti Anabilim Dalı, 25240 Erzurum, Turkey; e-mail, drcaglaroglu@ gmail.com. Submitted, May 2006; revised and accepted, July 2006. 0889-5406/$34.00 Copyright © 2008 by the American Association of Orthodontists. doi:10.1016/j.ajodo.2006.07.036 270