# Unilateral Condylar Hyperplasia in Surgeons' Perspective--A Narrative Review
###### Abstract  
The following paper focuses on the topic of mandibular unilateral condyle hyperplasia (UCH). This form of mandibular asymmetry (MA) is one of the less common but still known pathologies that requires detailed surgical and orthodontic planning and treatment. Since this pathology is mostly related to a high number of individual dental, bone, and overgrowth factors, until now the treatment methods were individually driven. It seems that the scope of surgical intervention is greatly dependent on the degree of bone overgrowth and the occurrence of asymmetry. Many treatment modalities and possible surgical perspectives are known, yet, so far, no adequate detailed guidelines are known. This detailed review of this type of mandibular asymmetry will focus on diagnostics and treatment plans and outcomes. The following paper underlines the authors' own clinical experiences in MA and UCH treatment, which are compared with the literature review. The authors intend to investigate what has changed in the treatment and diagnostics of one-sided mandibular condyle and bone overgrowth. c 2023 13 1839 19 January 20  
soft/hard tissue disproportions might occur, which are related to maxillary bone tilting and the scope of asymmetry, mainly impacted by time and the intensity of pathological growth [1; 2]. Present bone and teeth discrepancies influence facial contour and balance, which influence facial appearance aspects, such as lip contour and symmetry, the angle of the lips, chin position, subnasal and sublabial balance, zygomaticomalar area prominence, and others [5; 6; 7; 8; 9; 10; 11; 12]. The presented pathology might start early, at 9-12 years of age (\(\pm\)2 years), and can have various forms of intensity and growth activity, and even have a natural cessation period and self-limiting over time [6; 7; 8; 9; 10; 11]. In most cases, mandibular asymmetry should be carefully examined and established, especially in young, growing patients. Growing children and young adults are most affected by this condition, and a higher female predominance (F:M ratio) is noted and estimated at 2:1 or 3:1 [11; 12; 13; 14; 15]. On the other hand, some authors emphasize no sex-related occurrence of this pathological condition, while others underline a higher occurrence rate in the left condyle area [11; 12]. [PERSON] et al. 's meta-analysis study in 2012 explored 10 studies with 275 patients with UCH [12]. The presented results indicated a female predominance, along with a higher occurrence rate on the left side of the mandible, which has also been confirmed in other studies [13]. A study on two Indian families by [PERSON] suggests a possible Y-linked or autosomal dominant etiology of UCH [14]. Both mother- and son-related genetics need further genetic evaluation. A similar rare genetic link was reported by [PERSON] et al. in two siblings with mirror image UCH [15]. The role of potential etiological factors is still not fully known; however, some endocrine and hormone-related factors are also taken into consideration [11; 12; 13; 14; 15]. Possible etiological factors may be various since no evidence-based relationship has so far been noted in the literature. Some literature reviews suggest the following factors: trauma-related, metabolic hyperactivity, endocranial distortions (growth factors, insulin growth factors (IGF), hormonal estrogen-progesterone related, and others), arthrosis, genetic factors, hereditary or acquired factors, or others [15; 16; 17; 18; 19]. The timing of early diagnostics greatly influences the types of possible treatment modalities that can be used. Moreover, the scope of each asymmetry is different for individual dentoalveolar discrepancies and teeth relations; therefore, the presented narrative review underlines only the selected special cases of UCH from the literature where active asymmetrical growth affected the condyle and those which became self-limiting over time, causing visible mandibular asymmetry, but where the pathological growth is inactive, has ceased, or is not present at all.