Objectives: To determine whether dolichofacial (Frankfort horizontal mandibular plane angle (FHMPA) ≥30°) vs brachyfacial (FHMPA ≤22°) phenotypes differ in temporomandibular joint (TMJ) loads and whether these differences correlate longitudinally with mandibular ramus height (Condylion-Gonion, Co-Go). Setting and Sample Population: Lateral and posteroanterior cephalographs from ten dolichofacial and ten brachyfacial individuals made at average ages of 6 (T1), 12 (T2) and 18 (T3) years and available online (http://www.aaoflegacycollection.org/aaof_home.html) were used. Materials and Methods: Three-dimensional anatomical data were derived from cephalographs and used in numerical models to predict TMJ loads for a range of biting angles on incisors, canines and first molars. Two criteria were used to define clinically important between-group TMJ load differences: statistical significance was defined with a two-group t-test, and where differences were also ≥20%. A statistical approach called response surface analysis was used to assess correlation between TMJ loads and its predictors considered in this study. Results: The two phenotypes had significantly different FHMPA at all ages (P<.05). No differences in TMJ loads were found at T1. Ipsilateral and contralateral TMJ loads at T2 and T3 were significant and ≥20% larger in dolichofacial than brachyfacial phenotypes for specific biting angles (all adjusted P<.05). Regression analysis indicated age and ramus height contribute 53% of the variability in normalized values of TMJ loads. At higher ages, dolichofacial phenotypes had significantly higher TMJ loads which were correlated with shorter ramus heights compared to brachyfacial phenotypes. Conclusions: Craniofacial mechanics may explain, in part, mandibular growth differences between dolichofacial and brachyfacial phenotypes.

Objectives: To test whether mechanobehaviour (temporomandibular joint (TMJ) loads, jaw muscle use) was different between facial types and correlated with ramus height (Condylion-Gonion, mm). Setting and Sample Population: University of Missouri-Kansas City (UMKC) Orthodontic Clinic. Ten dolichofacial and ten brachyfacial adolescents (Sella-Nasion–Gonion-Gnathion (SN-GoGn) angles ≥37° and ≤27°, respectively) consented to participate. Materials and Methods: Numerical models calculated TMJ loads for a range of static biting based on subjects’ three-dimensional anatomy. Subjects were trained to record jaw muscle electromyography (EMG) over 2 days and 2 nights in their natural environments. Laboratory EMG/bite-force calibrations determined subject-specific EMG for 20 N bite-force (T20Nave). Jaw muscle use via duty factors (DF=muscle activity duration/total recording time, %) was determined from day and night recordings for muscle-specific thresholds from ≥5% to ≥80%T20Nave. ANOVA and Tukey's HSD post hoc tests assessed for group differences in mechanobehaviour (TMJ loads, DFs). Regression modelling correlated subjects’ normalized TMJ loads, DFs and ramus height. Results: Dolichofacial compared to brachyfacial subjects produced significantly higher (P<.05) TMJ loads, where ipsilateral loads were ≥20% larger for some biting angles, but had significantly less (all P<.05) masseter (day, night) and temporalis (night) DFs. Regression analysis showed a significant relationship amongst normalized TMJ loads, masseter DF and ramus height (R2=.49). Conclusions: Mechanobehaviour showed significant differences between facial types and was correlated with ramus height.

Indiana University-Purdue University Indianapolis (IUPUI) / Even though the molecular events and pathways that underlie craniofacial development and morphogenesis are not fully understood, it is accepted that their orchestration is influenced by the interaction of genetic and environmental factors. Inbred mouse strains represent genetically homogenous groups of individuals. It is established that mice in one strain often differ quite remarkably from mice in other inbred strains. Those phenotypic differences make mice exceptional tools for the dissection of genetic factors that influence normal and abnormal craniofacial morphogenesis. While numerous investigations have focused on abnormal morphogenesis, a comprehensive study of normal craniometric morphology across multiple inbred strains of mice has not been previously performed. The Mouse Phenome Project, an international collaboration of investigators, was formed to systematically phenotype a collection of normal inbred mouse strains. The objectives of our studies were to determine and measure differences in quantitative mandibular traits/variables within and between different inbred mouse strains, and to assess sexual di1norphism through bilateral measuren1ents of the hemimandibles. These studies were a component of the Mouse Phenome Project to collect normal craniometric data from 12 genetically heterogeneous inbred strains utilizing digital images from equal numbers of female and male mice at 7 to 8 weeks of age. Our central hypothesis was that morphometric analysis of mandibular structures from genetically disparate inbred mouse strains would reveal quantifiable differences. The null hypothesis of no difference among the strains for 1nandibular measurements was rejected. Overall, CAST/Ei and MOLF/Ei were consistently small in size measured by body weight with small skeletal structures. There was no strong pattern of body weight and site of skeletal size in the mid and heavy weighted strains. Evidence of sexual dimorphism was supported. Overall, it appears males and females that have the least significance between them are in the DBA/2J strain, followed by A/J. The strain with the most significant difference between males and females is in the C3H/HeJ strain.

Indiana University-Purdue University Indianapolis (IUPUI) / Previous studies have shown an increased growth of the tibial growth plate in rats infused with supraphysiologic doses of IGF-I. However, no one has demonstrated this effect on the TMJ in vivo. To determine the effect of a constant infusion of IGF-1 on the TMJ, 20 Sprague-Dawley rats were divided into three groups: (1) control, (2) surgical control, and (3) IGF-1 and placebo infused. IGF-I was delivered at a rate of 1 μg/day over the TMJ via osmotic minipumps. lntravital bone labels were administered at two-week intervals to monitor growth rate. Following sacrifice, seven mandibular (Mn) dimensions were measured anthropometrically. The mandibles were then imbedded in acrylic and stained with tetrachrome to visualize the Mn cartilage. Fluorescence microscopy was utilized to measure the Mn growth between bone labels and calculate growth rates. In addition, the hypertrophic cartilage layer thickness was measured photomicrographically. ANOVA showed no significant difference (P<0.05) in growth rates or cartilage thicknesses between the groups. However, multiple t tests did show an increase in several Mn dimensions (increase in length from gonion to the mental foramen; increase in length from condylion to the mental foramen; and increase in condylar head anterior-posterior length) in the experimental animals comparing the IGF-I infused side with the placebo infused control side. Therefore, it was concluded that IGF-I, when infused at a constant supraphysiologic dose, may increase mandibular growth in certain directions. The present study is not able to definitively demonstrate that these increases are due to direct effects on Mn cartilage growth.

Indiana University-Purdue University Indianapolis (IUPUI) / Even though the molecular events and pathways that underlie craniofacial development and morphogenesis are not fully understood, it is accepted that their orchestration is influenced by the interaction of genetic and environmental factors. Inbred mouse strains represent genetically homogenous groups of individuals. It is established that mice in one strain often differ quite remarkably from mice in other inbred strains. Those phenotypic differences make mice exceptional tools for the dissection of genetic factors that influence normal and abnormal craniofacial morphogenesis. While numerous investigations have focused on abnormal morphogenesis, a comprehensive study of normal craniometric morphology across multiple inbred strains of mice has not been previously performed. The Mouse Phenome Project, an international collaboration of investigators, was formed to systematically phenotype a collection of normal inbred mouse strains. The objectives of our studies were to determine and measure differences in quantitative mandibular traits/variables within and between different inbred mouse strains, and to assess sexual dimorphism through bilateral measurements of the hemimandibles. These studies were a component of the Mouse Phenome Project to collect normal craniometric data from 12 genetically heterogeneous inbred strains utilizing digital images from equal numbers of female and male mice at 7 to 8 weeks of age. Our central hypothesis was that morphometric analysis of mandibular structures from genetically disparate inbred mouse strains would reveal quantifiable differences. The null hypothesis of no difference among the strains for mandibular measurements was rejected. Overall, CAST/Ei and MOLF/Ei were consistently small in size measured by body weight with small skeletal structures. There was no strong pattern of body weight and site of skeletal size in the mid and heavy weighted strains. Evidence of sexual dimorphism was supported. Overall, it appears males and females that have the least significance between them are in the DBA/2J strain, followed by A/J. The strain with the most significant difference between males and females is in the C3H/HeJ strain.

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The purpose of this dissertation is to examine the occurrence of facial fractures in automotive collisions and to determine the tolerance of the facial bones to blunt impact. The effects of restraint use, impact severity and impact direction on facial fractures were evaluated using the NASS-CDS database. The association between brain injury and facial fractures was also examined. The tolerance of the frontal bone, nasal bone, maxilla and mandible was determined using the flat surface of a cylindrical impactor. The influence of anthropometric measures and geometrical descriptors on the tolerance of the facial bones is also presented. The force-displacement response of each impacted region was also determined and response corridors were created. These corridors were used to evaluate the biofidelity of the FOCUS headform under the same impact conditions. Mathematical models were also created to predict the force and displacement resulting from facial impact. The data contained in this dissertation can be used to determine the risk of facial fracture as a function of impact force and evaluate the biofidelity of models simulating facial impact. / Ph. D.

Este estudo avaliou a força de mordida, eletromiografia e mobilidade mandibular em pacientes submetidos à cirurgia para tratamento de fraturas que acometeram, isoladamente, a mandíbula e o complexo zigomático-orbitário. A força de mordida foi registrada por meio de gnatodinamômetro na região dos molares do lado da fratura e contra-lateral e entre os incisivos centrais. Os sinais eletromiográficos foram captados dos músculos masseteres e temporais. A mobilidade mandibular foi avaliada por mensuração, com paquímetro digital, da abertura bucal, lateralidade direita e esquerda, e na protrusão mandibular, todos em amplitude máxima. A amostra foi constituída por três grupos: Grupo 1 - Controle (sem fratura avaliação única) com 12 indivíduos; Grupo 2 - Fratura mandibular, com 8 indivíduos; Grupo 3 - Fratura do complexo zigomático-orbitário (CZO), com 5 indivíduos. As fraturas foram tratadas cirurgicamente por meio de FIR (fixação interna rígida) em todos os casos, utilizando-se acessos intra e ou extrabucais. O tempo de acompanhamento foi de 2 meses para o grupo 2 e para o grupo 3 foram 6 meses. Nas avaliações realizadas, os grupos 2 e 3, apresentaram redução da força de mordida, e elevação da atividade eletromiográfica nos períodos pós operatórios iniciais. No entanto atingiram padrão de normalidade a partir do 2º mês de pós operatório. Quanto à mobilidade mandibular, a mesma se apresentou diferentemente nos dois grupos, sendo que para o grupo 2, ela mostrou redução da amplitude de todos os movimentos mandibulares avaliados, retomando padrão de normalidade no 2º mês pós operatório. Já para o grupo 3, apenas a abertura bucal máxima mostrou-se reduzida e retomou padrão de normalidade no 1º mês pós operatório. / This study evaluated the bite force, electromyography and jaw mobility in patients undergoing surgery for treatment of fractures that attacked alone, the mandible and the zygomatic-orbital complex. The bite force was recorded by gnathodynamometer in the region of the molars on the side of the fracture and contralateral side and between the central incisors. The electromyographic signals were captured of masseter and temporal muscles. The mandibular mobility was assessed by measuring with a digital caliper, mouth opening, right and left laterality, and protruding jaw, all in the maximum amplitude. The sample consisted of three groups: Group 1 - Control (without fracture - ranking only) with 12 subjects, Group 2 - mandibular fracture, with 8 subjects and Group 3 - Fracture of the zygomatic-orbital complex (CZO), with 5 individuals. The fractures were treated surgically by means of FIR (internal fixation) in all cases, using access and intra or extraoral. The follow up was 2 months for group 2 and group 3 was 6 months. In the assessments, groups 2 and 3 had a reduction of bite force, and increased EMG activity in the early postoperative period. However reached normal range from 2 months postoperatively. The jaw mobility, it is presented differently in two groups, in Group 2, it showed a reduction in the amplitude of all mandibular movements measured, resuming normal pattern in the 2 months after surgery. As for group 3, only maximum mouth opening was reduced and resumed normal range at 1 month postoperatively.