Background and objectives: Unilateral condylar hyperplasia (UCH) is a rare asymmetric condition of the mandible due to condylar pathology resembling growth, with unknown aetiology. Obwegeser et al. described a classification in 3 categories: hemimandibular elongation (HE), hemimandibular hyperplasia (HH) and a combination of these two (hybrid form), using panoramic radiographs and clinical features. Three dimensional quantification of asymmetry in UCH is not reported yet, but would be useful for diagnosing and evaluating the degree of deformity in this disease. The aim of this study is to quantify the asymmetry of the mandible in UCH patients and to evaluate whether Obwegeser’s classification (HE/HH/hybrid) can be confirmed.

Methods: 36 UCH-patients were included and a group of age and gender matched controls was formed from an existing CBCT database. UCH inclusion-criteria were progressive mandibular asymmetry supported with a positive bonescan and/or performed condylectomy. Demographic data were noted and CBCT-data were collected. Using Maxillim software, 3D images were reconstructed. Validated linear measurements were performed, including length of condyle, length of mandibular ramus and length of mandibular body. Volumes were calculated for these skeletal units on the affected and non-affected side for both patients and controls. Differences were calculated using an unpaired Student’s t -test.

Results: The patient group consisted of 20 females and 16 males. In 22 cases the left side was affected, and in 14 cases the right side. The mean age at presentation was 20.5 years (range 9.2–40.5 yrs). Significant differences between affected and non-affected sides were found in the condyle region ( p = 0.0001), but not in the ramal and body region ( p = 0.07; p = 0.4).

Conclusions: Mandibular asymmetry in unilateral condylar hyperplasia is mainly situated in the condylar region. Conebeam computed tomography proves to be an useful and accurate modality for diagnosis, quantification and evaluation of mandibular asymmetry in UCH.