Introduction: L’ostéogenèse imparfaite (OI) est un désordre de collagène héréditaire caractérisé par du tissu conjonctif défectueux avec une incidence de 1 sur 20 000 naissances. Il y a une surreprésentation marquée des malocclusions de Classe III, une occlusion croisée antérieure et postérieure dans la population d’OI. L’objectif principal de cette recherche est d’évaluer si la sévérité des malocclusions présente chez les patients atteints d’OI est proportionnelle à la gravité du syndrome. L’objectif secondaire de cette recherche est d’évaluer si la sévérité de la malocclusion augmente avec l’âge. Matériels et méthodes: Étude rétrospective d’observation effectuée par calcul du Discrepancy Index (DI) de 56 modèles dentaires de patients atteints d’OI. Les résultats du DI ont été comparés à trois variables qui caractérisent la gravité du syndrome: type de OI, type génétique et le Z-score de la grandeur de chaque patient. En outre, l’analyse longitudinale d’un sous-ensemble de 20 modèles a été faite pour déterminer si la sévérité de la malocclusion augmente avec le temps. Résultats: La médiane du DI était de 33,5 [1, 109]. Le DI est plus augmenté chez les patients atteints d’un type de OI plus sévère (p = 0,001) ainsi chez les patients avec un Z-score de grandeur plus bas (p <0,0001). L'analyse longitudinale a démontré une augmentation statistiquement significative de DI au fil du temps. (p=0.05) Conclusion: La malocclusion des patients atteints d’OI semble liée à la gravité de ce syndrome. En outre, la sévérité de la malocclusion semble augmenter avec l'âge. / Introduction: Osteogenesis imperfecta (OI) is an inherited collagen disorder characterized by defective connective tissue with an incidence of 1 in 20,000 births. There is a marked over-representation of Class III malocclusion, negative overjet and lateral openbite in the OI population. Objectives: Primary objective is to evaluate whether the severity of the malocclusions present in OI patients is proportional to the severity of the syndrome. Secondary objective is to evaluate whether the malocclusion severity increases with age. Methods: Retrospective observational study performed by calculating the Discrepancy Index (DI) of 56 dental casts of patients with mild to severe OI. DI scores were compared to three variables that characterize the severity of the syndrome: OI type, genetic type and height z-score of each patient. In addition, longitudinal analysis of a subset of 20 OI casts was done to determine whether the malocclusion increases in severity with time. Results: The median DI score was 33.5 [1, 109]. The DI score increased with increasing severity of OI type (p=0.001) and decreasing height z-score (p<0.0001). In addition, longitudinal analysis of 20 OI patients demonstrated a statistically significant increase in DI over time (p=0.05). Conclusion: The malocclusion characteristic of OI patients seems linked to the severity of the syndrome. In addition, the malocclusion severity seems to increase with age.

A thesis submitted to the College of Dental Medicine of Nova Southeastern University of the degree of Master of Science in Dentistry. Objectives: The purpose of this study was to evaluate clinical outcomes based on the American Board of Orthodontics Objective Grading System (ABO-OGS) in a 30-month postgraduate orthodontic residency and to determine what factors affected these treatment outcomes. Methods: Consecutively debonded cases from July 1, 2010 to June 30, 2011 treated by residents in the Orthodontics Department at Nova Southeastern University were graded using the ABO-OGS. The age and sex of the patient, the treatment time, the missed appointments and the number of providers were documented. Discrepancy indices were calculated for each patient. These variables were assessed and their associations with the obtained treatment outcome scores were evaluated. Results: The average OGS score of the debonded cases was 33.87. There was no significant correlation between total OGS score and the demographic or explanatory variables. There were significant correlations found between the discrepancy index (DI) and the treatment time, the number of providers, but not the OGS. Significant correlations were also identified between treatment time and the number of failed appointments and the number of providers. Extraction cases were shown to have a significantly longer treatment time. Out of the eight objective measurements of the OGS, occlusal contacts, marginal ridges, buccolingual inclination and alignment/rotations scored the highest points in our evaluation with an average of 7.81, 6.37, 5.04, and 5.01 respectively. Conclusions: This study indicated the Nova Southeastern University Orthodontic Department average OGS score is about 6 points higher than the ABO clinical exam passing score. The initial complexity of a case was not a pre-determined factor for the final treatment results. This study identified several aspects of treatment outcomes that need improvement including, occlusal contacts, marginal ridges, correcting buccolingual inclination and improving the alignment.