Objectives 1. To define the normative airway of Chinese population using three-dimensional imaging and computer analysis 2. To evaluate the upper airway differences in patients with normal facial profile and those with skeletal class III deformity 3. To evaluate the differences in upper airway models among patients with different dentofacial deformities and describe the role of computational fluid dynamics (CFD) in the human upper airway Materials and Methods Part I : Three-Dimensional Analysis of the Normative Upper Airway in Chinese This was a cross-sectional observational study. Cone beam computerized tomography (CBCT) scans of one hundred patients were analyzed. Computer analysis of the different upper airway parameters were studied including airway length and volume, as well as airway dimensions at the axial level of the soft palate, hard palate, base of tongue, and epiglottis. The most constricted airway location was identified and correlation analysis with variables of interest was done. Part II: A Cone Beam Computerized Tomography Study of Airway in Skeletal Class I and Class III Cone-beam computed tomography (CBCT) records of 200 patients were used to evaluate the upper airway dimensions. This sample consisted of patients with normal facial profile (Class I) and those demonstrating skeletal class III deformities. Computer analysis of the upper airway parameters such as airway length, airway volume, airway anterior-posterior and cross-sectional area dimensions at the hard palate, soft palate, base of tongue and epiglottis were performed. The most constricted airway sites were identified. Part III: Computational fluid dynamics study of upper airway in different dentofacial deformities Cone-beam computed tomography records of 12 patients were used to evaluate the upper airway. This sample consisted of facial skeletal Class I, II and III subjects. The upper airway models were constructed to allow CFD simulations in the airway from the epiglottis to the hard palate. Cross-sectional area, pressure, velocity and resistance were measured based on the reconstructed meshed models. Results Part I : Three-Dimensional Analysis of the Normative Upper Airway in Chinese In 100 subjects (40 males, 60 females) aged 16-40 years with normal facial profile, we found that the most constricted site occurs at the level of the soft palate. This surface area of this site was found to be linearly correlated to the airway volume, suggesting a significant relationship between the most constricted area and the total airway volume. Gender differences were found in airway length, volume, and in the dimensions at the base of tongue and epiglottis region. The mean airway length was 54.12 mm + 6.19 for males and 49.25 mm + 4.86 for females; airway volume of 15.09 cm3 + 4.92 for males and 13.12 cm3 + 4.72 for females. Part II: A Cone Beam Computerized Tomography Study of Airway in Skeletal Class I and Class III The sample consisted of 100 Class I (41 males, 59 females) with a mean age of 25.4 years and 100 Class III (38 males, 62 females) with a mean age of 23.5 years. Gender differences were noted in the airway length, airway volume and dimensions at the base of tongue and epiglottis for both groups. Males showed longer airway length, larger airway volume, larger airway dimensions at the base of tongue and epiglottis compared to females. Significant differences in all the airway parameters between the two groups were found except for airway length. The soft palate was found to be the most constricted airway site observed in the Class I subjects while Class III subjects showed restriction in both the soft palate and epiglottis region. Part III: Computational fluid dynamics study of upper airway in different dentofacial deformities The airflow was variable among airway in different skeletal deformities. The pressure changes along airway of Class II were the largest, followed by Class I. The pressure drop in the airway of Class III subjects were the smallest. The larger pressure differences would cause greater resistance in the airway. The highest resistance was observed in the airway of Class II subjects. Conclusion Part I : Three-Dimensional Analysis of the Normative Upper Airway in Chinese This airway data provide a normative reference that can be used in various dentofacial analysis as well as for diagnosis and treatment planning for related dentofacial deformities and in understanding the pathophysiology for sleep-related breathing disorders. Part II: A Cone Beam Computerized Tomography Study of Airway in Skeletal Class I and Class III The upper airway is larger in patients with Class III deformity than those with a normal facial profile. The site of restriction is commonly observed at the soft palate in the Class I group whereas patients with Class III deformity, the airway restriction sites are at both the soft palate and epiglottis. Understanding of the upper airway differences in between class I and class III facial deformities can have implications on treatment planning for orthognathic surgery. Part III: Computational fluid dynamics study of upper airway in different dentofacial deformities The results in this study suggest that skeletal pattern showed a significant correlation with pressure and resistance along the upper airway. / published_or_final_version / Dental Surgery / Master / Master of Dental Surgery

Background: Jaw corrective surgery can cause significant psychosocial impacts on patients. This prospective study aimed to investigate the longitudinal changes of psychosocial characteristics of patients with dentofacial deformities after corrective surgery and the factors that predict the psychological resilience of Hong Kong Chinese undergoing this type of surgery. Materials and Methods: A prospective cohort study was carried out from 1st June 2011 to 31st December 2012 on Hong Kong Chinese patients, who had corrective surgery as treatment for their dentofacial deformities. Self-completed questionnaires, including Brief Symptom Inventory (BSI), Adult Trait Hope Scale (AHS), Hospital Anxiety and Depression Scale (HADS), Life Orientation Test (LOT), Social Avoidance and Distress Scale (SADS) and Satisfaction with Life Scale (SWLS), were administered to each patient at the surgical consent signing date (T1), one pre-operative day (T2), 1-2 post-operative week (T3) and 3rd post-operative month (T4). Psychological outcome trajectories were established using the BSI General Severity index (GSI) at T1, T3 and T4. Five patterns of outcome trajectories were created using specified outcome measures of psychological distress level, including chronic dysfunction, recovery, delayed dysfunction, resilience and others. They were then categorized into two patterns of outcome trajectories (resilience and non-resilience groups) for analysis. Independence sample t-test and logistic regression analyses were conducted to investigate the significance of life orientation level at baseline to predict resilience. Results: 67 participants (23 males, 44 females; mean age 25.6) were recruited in the study. Highest hope level and psychological distress level was noted pre-operatively at the surgical consent signing date. The levels then dropped post-operatively in the first 3 months. No statistically significant difference was noted on the depression and anxiety level, social avoidance and distress level, optimism level and life satisfaction level from pre-operative to post-operative stages. The proportion of the five patterns of outcome trajectories was chronic dysfunction (22.4%), recovery (7.5%), delayed dysfunction (3%), resilience (43.3%) and others (23.8%). The logistic regression analyses showed that the pre-operative baseline optimism level of LOT was a significant predictor on the resilience characteristic of a patient after orthognathic corrective surgery. Conclusion: Patients with dentofacial deformities have high level of hope and equally high level of psychological distress at the surgical consent stage of orthognathic surgery. Their psychological distress and hope levels tend to drop during the first three post-operative months. There is no expected peri-operative change on the depression and anxiety symptoms, social avoidance and distress, optimism level as well as life satisfaction level in these patients. Optimism level can predict the psychological resilience of a Hong Kong Chinese in going through orthognathic surgery. Brief Symptom Inventory (BSI) and Life Orientation Test (LOT) are recommended as preoperative psychological screening tools. / published_or_final_version / Dental Surgery / Master / Master of Dental Surgery

Call number: LD2668 .T4 1963 S66 / Master of Science

published_or_final_version / Dentistry / Master / Master of Dental Surgery

Dentofacial deformities have an adverse impact on functional as well as psychological wellbeing. Being highly visible, they may lead to a host of psychological problems particularly in youths and young adults as concerns about bodily identity and integrity are likely to be most prominent. Body image and self-esteem have been noted to play an important role in adjusting to disfigurement. Those who opted for corrective orthognatic surgery with realistic expectations were found to have a higher level of satisfaction with the outcome of the surgery. In contrast, undue and unrealistically positive aspirations towards the surgery are implicated in increased post-operative psychological difficulties. This study aimed to systematically document the variability of psychological adjustment and study the predictors of well-being in individuals with dentofacial deformity after orthognathic surgery. Seventy patients pending to go through orthognathic surgery were recruited from a university based dental hospital. Assessments of the patients’ overall psychological condition and adjustment towards their dentofacial deformity were conducted with standardized questionnaires and compared with similar assessment conducted with control subjects. The patients’ motivations for orthognathic surgery, psychological well-being, as well as expectations on the outcomes of surgery were studied through individually conducted psychological assessment interviews. Patients were re-assessed at 6 and 12 months after surgery on their level of satisfaction toward the outcome of surgery as well as to gauge possible changes in their psychological condition. There was no excess of significant psychopathology in patients with dentofacial deformity compared to the normal control group. However, as predicted, people with dentofacial deformity were more dissatisfied with their facial attractiveness. They also have more problems in interpersonal sensitivity. In the patient group, functional impairment or disability was a lesser concern compared to body image and presentation. Improvement of physical attractiveness was a strong underlying motivation for treatment. Longitudinal data on patients’ level of satisfaction with the treatment outcomes and perceived benefits associated with the improved facial esthetics will be further analyzed in the light of their underlying psychological vulnerabilities or resilience. The results are expected to cast light on factors that may affect patients’ satisfaction with the treatment. The results of the study confirmed that dissatisfaction with facial appearance prompted acceptance of surgery despite its associated discomfort and hazards. The findings of the study are expected to be useful in better informing clinical psychological interventions with aims of enhancing adjustment and forestalling psychological morbidity through early intervention with individuals coping with facial disfigurement. / published_or_final_version / Psychiatry / Doctoral / Doctor of Philosophy