published_or_final_version / Dentistry / Master / Master of Dental Surgery

Delayed diagnosis of dental anomalies in the permanent dentition can lead to severe occlusal, functional and aesthetic problems. Early diagnosis is not feasible in the primary dentition stage without screening radiography, which is controversial due to possible mutagenic effects. However, some dental anomalies in the primary dentition of Caucasians have been found to be followed by anomalies of the permanent successors. Therefore, identifying individuals at high risk of having anomalies of their permanent teeth by screening children for dental anomalies in the primary dentition, will facilitate early diagnosis and appropriate treatment. The objectives of this study were to determine the prevalence of dental anomalies in the primary dentition of a southern Chinese child population, and to investigate the relationship between the presence of a talon cusp, missing or supernumerary tooth in the primary dentition and the number of the permanent successor teeth. A total of 1513 children from 12 kindergartens were invited to participate in the prevalence study. School children visiting a regional school dental clinic during a four-year period and having talon cusp, supernumerary tooth or congenitally missing tooth in the primary dentition were included in the study to determine the relationship to the permanent successors. A total of 1333 children, aged from 2 years 11 months to 5 years 5 months (mean age 4 years 4 months) were included in the prevalence study. The prevalence of the commonest dental anomaly, double tooth, was 4.28%. Almost 95% of which were in the mandibular anterior region; one third of the double teeth involved the central and lateral incisors while the other two-thirds involved a lateral incisor and canine. The prevalence of congenitally missing teeth was 3.53%; all but one were mandibular incisors, the majority of which were lateral incisors. Girls were affected twice as often as boys. Both talon cusp and a supernumerary tooth occurred rarely (0.15%) and they were only found in the maxillary incisor region. A study of 57 cases of talon cusp on primary maxillary incisors showed that, when there was a talon cusp on the lateral incisor, 78.3% of the permanent successors exhibited odontogenic abnormalities; mostly in the form of supernumerary teeth. However, a talon cusp on a maxillary central incisor had no effect on the permanent successor. A study of 30 children with supernumerary primary teeth revealed that half of the children with supernumerary primary maxillary lateral incisors also had supernumerary permanent successors. A further study of 182 children with missing primary mandibular incisors showed that normal permanent successors were present in 50% of the cases with missing central incisors but only 8.5% of cases with missing lateral incisors. The prevalence of dental anomalies in the primary dentition of a local southern Chinese population differed from that of Caucasians. Children with talon cusp on primary maxillary lateral incisors, missing mandibular incisors and supernumerary maxillary lateral incisors were found to be at high risk of having an odontogenic abnormality in the permanent dentition. Clinicians should be aware of these anomalies and prepared to implement appropriate treatment. / published_or_final_version / Dentistry / Doctoral / Doctor of Philosophy

Master of Dental Surgery / This work was digitised and made available on open access by the University of Sydney, Faculty of Dentistry and Sydney eScholarship . It may only be used for the purposes of research and study. Where possible, the Faculty will try to notify the author of this work. If you have any inquiries or issues regarding this work being made available please contact the Sydney eScholarship Repository Coordinator - ses@library.usyd.edu.au

Master of Dental Surgery / This work was digitised and made available on open access by the University of Sydney, Faculty of Dentistry and Sydney eScholarship . It may only be used for the purposes of research and study. Where possible, the Faculty will try to notify the author of this work. If you have any inquiries or issues regarding this work being made available please contact the Sydney eScholarship Repository Coordinator - ses@library.usyd.edu.au

published_or_final_version / Dentistry / Master / Master of Dental Surgery

published_or_final_version / Dentistry / Master / Master of Dental Surgery

published_or_final_version / Dentistry / Master / Master of Dental Surgery

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

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