Unilateral Condylar Hyperplasia (UCH) is a rare and complex asymmetric growth disorder affecting the mandible. The disease is characterized by growth resembling hyperactivity in one of the condyles. Treatment of UCH requires a personalised approach that aims to stop the progression and/or correct the deformity caused by the disease. The choice and timing of UCH treatment are determined by the expression, severity, and progression of the disease. One of the most recognized classifications, introduced by Obwegeser and Makek, delineates three primary UCH categories: hemimandibular elongation (HE), hemimandibular hyperplasia (HH), and a hybrid form combining the first two categories (HY). Despite efforts to effectively differentiate between UCH expressions, these classification systems heavily rely on qualitative assessments. Hence, there is a need for a tool to objectively determine the expression, severity, and progression of UCH. This study introduces a novel tool, MASQ, to quantify asymmetrical mandibular growth and aims to objectively distinguish between the three UCH categories described by Obwegeser and Makek.

In Chapter 3, asymmetry of the mandible was quantified in an unaffected population using the MASQ tool. These results were used to establish the amount of asymmetry present in an unaffected population. This enables the comparison of new mandibular samples to an unaffected population, which could facilitate the identification of asymmetrical growth caused by UCH in Chapter 5.

In Chapter 4, a machine learning model was developed for the MASQ tool to predict the expected mandibular shape of new samples. The model predicted unaffected mandibular shapes using the patients’ age and gender. Comparisons were made between the predicted model and the unaffected dataset (DFE-score), which could enable the identification and localisation of pathological growth caused by UCH.

In Chapter 5, the asymmetry and predicted model of the UCH samples were computed using the MASQ tool including the methodologies described in Chapter 2, 3, and 4. These UCH results were compared to the unaffected samples to help determine whether the growth deviations caused by UCH were significantly different. The UCH samples were classified in the three classifications described by Obwegeser and Makek. The results were used to identify characteristic growth patterns caused by the different expressions, which were used to confirm or refute the classification system.

The results revealed significant differences in asymmetry and DFE scores between UCH and unaffected samples. Additionally, the tool was able to objectively differentiate between the HE and HH class but could not fully confirm the classification of Obwegeser and Makek. This prompts the reconsideration of the existing classification system. Local results confirmed and revealed new characteristic deviations caused by the UCH expressions. These may be used in the future to establish a new UCH classification system using the MASQ tool. The current results not only deepen our understanding of mandibular variation but might also empower clinicians to make more informed decisions which could eventually result in a more effective, reliable, and patient-focused treatment.