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Symmetry is considered an attractive facial characteristic, though it is very rare as most humans have some degree of asymmetry. Though most cases are subtle enough to go undetected, more severe cases of asymmetry can result in marked facial deformity. It has been found that facial asymmetry presents as a comorbid condition with other severe malocclusions. While many causes of facial asymmetry have been thoroughly investigated, such as cleft lip/palate, unilateral craniosynostosis and hemifacial microsomia, the genetic cause of asymmetries associated with dentofacial malocclusions has yet to be investigated. Studies have shown that muscle strength, size, and fiber type can influence bone size and density. The masseter muscle is frequently involved in development of sagittal malocclusion, and left/right fiber-type differences have been previously found in subjects with facial asymmetry. Still, the contribution of muscle function to the development of facial asymmetry is unclear. Symmetry is a genetically controlled human characteristic, as is the careful breaking of symmetry during development to allow for appropriate organ formation necessary for life. Many genes have been identified to play a role in this initial breaking of symmetry, as well as the maintenance of left-right differential expression. Among these genes, the Nodal Pathway plays a particularly important role. Expression of Nodal Signaling Pathway (NSP) genes, which provide positional and patterning information during embryogenesis, vary significantly in facial asymmetry subjects. PITX2, a downstream NSP effector, patterns changes in gene expression on left-right sides through gradient density signaling. PITX2 is reportedly expressed in adult human skeletal muscle satellite cells suggesting NSP gene activity is a key factor in both development and maintenance of facial asymmetry in adulthood. A human transcript microarray was used to evaluate whether these genes involved with normal coding of symmetry during development were differentially expressed in masseter muscle from patients with or without facial asymmetry. This study evaluated orthognathic surgery patients with varying skeletal malocclusions. The patients were categorized based on vertical, transverse, and sagittal discrepancies, as well as the presence or absence of facial asymmetry (n= 93). The subjects were appropriately diagnosed as open or deep bite, class I, II, or III, and treatments planned for the appropriate surgical correction. All of the patients required bimaxillary sagittal split osteotomy, at which point masseter muscle samples were collected. Eleven patients were included in this study. Of the eleven, two of the patients were classified with facial asymmetry. Samples were disrupted in QIAzol Lysis Reagent, RNA was isolated using a Qiagen miRNeasy Mini Kit according to the manufacturer’s instructions, and quality of the total RNA was tested by Agilent Bioanalyzer and Nanodrop spectrophotometry. Samples were used for quantitative Reverse Transcriptase Polymerase Chain Reaction (RT-PCR) and protocols for microarray analysis were conducted as described in the Ambion WT Expression Manual and the Affymetrix GeneChip Expression Analysis Technical Manual. The eleven samples were analyzed by Principal Components Analysis (PCA) to detect fold-changes for each transcript. From this, differences in global gene expression between the two asymmetric and eight remaining subjects were evident, as the two asymmetric patients clustered separately from the malocclusion patients without asymmetry. To find differentially expressed transcripts step-up t-tests were performed to correct for false discovery rate (FDR) comparing the two asymmetric samples to the eight symmetric samples. Differences were considered significant if step-up p-values were ±2 between groups. Differential gene expression was confirmed with ten of the 22 Nodal Pathway genes in asymmetric patients. Extracellular mediators Nodal and Lefty expression was 1.39 and 1.84 fold greater (P< 3.41 x 10-5) whereas integral membrane Nodal-modulators NOMO1,2,3 were -5.63 to -5.81 (P < 3.05 x 10-4) less in asymmetric subjects. Two of the three Nodal Pathway mediators decreased significantly with negative fold differences (-7.02, -2.47; P < 0.003). PPM1a, one of the two negative intracellular mediators, had a significantly decreased fold difference of -3.79 with asymmetry (P , 4.59 x 10-6). PITX2, an asymmetry factor known to influence the size of type II skeletal muscle fibers in adults was also decreased in facial asymmetry (P< 0.05). The down regulation of Nodal Pathway genes suggests its involvement in development of asymmetry. PITX2 expression differences also contribute to skeletal and muscle development in this condition. The overall data trend was for moderate to large decreases in gene expression for approximately 60% of the Nodal pathway genes. Further histological analysis of masticatory muscle fiber types will be necessary to determine how variations in bilateral masticatory muscle phenotype contribute to jaw asymmetry in subjects with posterior facial asymmetry. Finally, the methods used in this study should be conducted with a larger sample population, including a wider variety of different types of asymmetry. / Oral Biology

A public orthodontic system generally is designed to prioritize patients so that those who have the greatest need receive treatment. The aim of this study was to compare the subjective perceptions of the occlusal appearance of 11 to 12 year-old schoolchildren of Nairobi with the modified Aesthetic Component (AC) scale of the Index of Orthodontic Treatment Need (IOTN). The objectives were to assess the children&rsquo / s perception of their occlusal appearance, categorise the occlusal appearance using the AC scale, by both the children and researcher / and to compare the children&rsquo / s&rsquo / perception and the AC of the IOTN.

Epidemiological studies on malocclusion have been primarily concerned with its aetiology and distribution. However, due to the varied and often subjective methods of assessment, many of these studies provide conflicting data related to malocclusions (Solow, 1970). To address this, the F&eacute / d&eacute / ration Dentaire Internationale (FDI) in close collaboration with the World Health Organisation (WHO) developed an objective method for measuring occlusal traits (Baume et al., 1973). This method was used to obtain the epidemiological data on occlusal traits for 14-year-old children Kampala in order to provide baseline data related to malocclusion. A total of 402 subjects were examined. Of these 65% were female and 35% were male. Thirty percent of the sample had at least one dental anomaly. The most commonly extracted teeth were mandibular first molars (43.6%) and maxillary canines (17.3%). The high frequency of extracted permanent canines in this sample is unique. By and large, many of the occlusal traits related to the canine are attributable to the practice of ebinyo, a form of dental mutilation, which still seem to be rife in many communities in Uganda. Similar to other studies (Massler and Frankel, 1951 / de Muňiz, 1986 / Ferguson, 1988 / Kaka, 1993), mandibular first molars were five times more likely to be missing than maxillary first molars while the ratio of missing maxillary to mandibular canines was found to be 2.5:1. Crowding was most frequently observed in the mandibular incisal segment while spacing was mostly in the maxillary incisal region, thus supporting the view of Brunelle et al., (1996) that although prevalence may vary from study to study, more people have malaligned mandibular incisors than maxillary incisors concurs with these studies. Of the subjects studied, 6.8% had a diastema of 3mm and more. Regarding space measurements, 17.9% of the sample population had at least one segment with crowding, 18.2% had at least one segment with spacing while 33.6% had some degree of incisor malalignment and 54.2% of the sample population had some form of space anomaly. About 70% of the subjects had symmetric molar relationships of which 54.2% were Class I, 9.2% Class II and 3.2% Class III similar to the universal distributional pattern. Crossbites were not a major finding, and were present in only 7% of the sample. The distribution of overjet was relatively symmetrical on the left and right. Negative overjet (anterior open bite) was a rare occurrence in an average of 2.4% of the population. In 77.6% of the population, the overjet ranged from 1 to 4mm, and in 22.4%, the overjet was either edge-to-edge, reverse or 5mm and over. About 7.3% had an overjet of 5-6mm while only 2.1% had an overjet greater than 6mm. Approximately 53.7% of the population had an overbite of 1-3mm. Edge-to-edge and open bite incisor relationships were found in less than 10% of the sample. Although ideal occlusion as described by Angle (1907) in the Ugandan sample is very rare, using the data derived from this study, normal occlusion as defined by statistical distribution can be described.

Thesis (M.S.)--West Virginia University, 2001. / Title from document title page. Document formatted into pages; contains vii, 73 p. : ill. Vita. Includes abstract. Includes bibliographical references (p. 64-69).

Epidemiological studies on malocclusion have been primarily concerned with its aetiology and distribution. However, due to the varied and often subjective methods of assessment, many of these studies provide conflicting data related to malocclusions (Solow, 1970). To address this, the F&eacute / d&eacute / ration Dentaire Internationale (FDI) in close collaboration with the World Health Organisation (WHO) developed an objective method for measuring occlusal traits (Baume et al., 1973). This method was used to obtain the epidemiological data on occlusal traits for 14-year-old children Kampala in order to provide baseline data related to malocclusion. A total of 402 subjects were examined. Of these 65% were female and 35% were male. Thirty percent of the sample had at least one dental anomaly. The most commonly extracted teeth were mandibular first molars (43.6%) and maxillary canines (17.3%). The high frequency of extracted permanent canines in this sample is unique. By and large, many of the occlusal traits related to the canine are attributable to the practice of ebinyo, a form of dental mutilation, which still seem to be rife in many communities in Uganda. Similar to other studies (Massler and Frankel, 1951 / de Muňiz, 1986 / Ferguson, 1988 / Kaka, 1993), mandibular first molars were five times more likely to be missing than maxillary first molars while the ratio of missing maxillary to mandibular canines was found to be 2.5:1. Crowding was most frequently observed in the mandibular incisal segment while spacing was mostly in the maxillary incisal region, thus supporting the view of Brunelle et al., (1996) that although prevalence may vary from study to study, more people have malaligned mandibular incisors than maxillary incisors concurs with these studies. Of the subjects studied, 6.8% had a diastema of 3mm and more. Regarding space measurements, 17.9% of the sample population had at least one segment with crowding, 18.2% had at least one segment with spacing while 33.6% had some degree of incisor malalignment and 54.2% of the sample population had some form of space anomaly. About 70% of the subjects had symmetric molar relationships of which 54.2% were Class I, 9.2% Class II and 3.2% Class III similar to the universal distributional pattern. Crossbites were not a major finding, and were present in only 7% of the sample. The distribution of overjet was relatively symmetrical on the left and right. Negative overjet (anterior open bite) was a rare occurrence in an average of 2.4% of the population. In 77.6% of the population, the overjet ranged from 1 to 4mm, and in 22.4%, the overjet was either edge-to-edge, reverse or 5mm and over. About 7.3% had an overjet of 5-6mm while only 2.1% had an overjet greater than 6mm. Approximately 53.7% of the population had an overbite of 1-3mm. Edge-to-edge and open bite incisor relationships were found in less than 10% of the sample. Although ideal occlusion as described by Angle (1907) in the Ugandan sample is very rare, using the data derived from this study, normal occlusion as defined by statistical distribution can be described.

A public orthodontic system generally is designed to prioritize patients so that those who have the greatest need receive treatment. The aim of this study was to compare the subjective perceptions of the occlusal appearance of 11 to 12 year-old schoolchildren of Nairobi with the modified Aesthetic Component (AC) scale of the Index of Orthodontic Treatment Need (IOTN). The objectives were to assess the children&rsquo / s perception of their occlusal appearance, categorise the occlusal appearance using the AC scale, by both the children and researcher / and to compare the children&rsquo / s&rsquo / perception and the AC of the IOTN.

Thesis (M.S.)--University of Michigan, 1975.

Thesis (M.S.)--University of Michigan, 1983.

Thesis (M.S.)--University of Michigan, 1966.