The purpose of this pilot study was to develop a method to quantify the surface area of interproximal wear facets present in the human dentition. Another aim was to investigate the reliability of this method and possible correlations between the amount of interproximal tooth wear and vertical craniofacial morphology. The study was carried out on 24 adolescent individuals immediately prior to orthodontic treatment. Following interproximal contact separation of one week, interproximal impressions were taken with polyvinyl siloxane and a positive stone model was fabricated with type IV dental stone. The model of the wear facet was imaged using a computer-operated optical scanner and the border of the wear facet was digitally traced. From the digital tracing, the surface area of the wear facet was calculated. The intra-observer reliability of this method showed a strong agreement in repeated measurements, however the inter-observer reliability revealed some statistically significant differences between two examiners. The limited sample size could not reveal a significant relationship between interproximal tooth wear and vertical craniofacial morphology. This study serves as a proof of concept study from which further in vitro and in vivo research can be conducted to better understand the relationship between masticatory input (as measured by interproximal wear) and craniofacial morphology.

Objective: The purpose of this study was to compare in vitro the effectiveness of Novamin powered technology Oravive and TopexRenew, with Crest and Colgate's PreviDent 5000 Plus in decreasing demineralization and preventing white spot lesion formation on extracted human teeth. Materials and Methods: Eighty-two extracted non-carious human third molar teeth without observable white-spot lesions, decalcification, or dental fluorosis were used for this in vitro study. The teeth in the study were suspended in their respective treatment slurry and cycled through remineralization and demineralization solutions for ten continuous days. Following the cycling protocol the teeth were sectioned using the hard tissue microtome producing three to five sections per tooth. The sections were photographed under a polarized light microscope and subsequently measured using Image Pro Plus computer software. Results: The post-hoc Bonferroni multiple comparison test indicated that the mean lesion depths observed in Control and Oravive groups were significantly greater than the other three treatment groups, while the mean lesion depth observed in Prevident was significantly lower than those in Renew and Crest. Moreover, no significant difference was found between Control and Oravive or between Renew and Crest. Conclusions: Renew (5% novamin; 5000 ppm F) performed at the same level as Crest (1100 ppm F) and inferior than Prevident 5000 Plus (5000 ppm F). Novamin by itself (Oravive, 5% Novamin) performed at the same level as the non-fluoridated Control group. Prevident 5000 Plus (5000 ppm F) was the most effective product in this study for the prevention of enamel demineralization and white spot lesion formation.

Objective: The purpose of this study to assess the relationship between masticatory function and symphyseal biomechanical properties using a longitudinal sample. Known differences in male and female maximum bite forces manifest during adolescence. If symphyseal bending rigidity is affected by function during ontongeny, we would expect variation in male and female growth allometries of certain biomechanical properties of the symphysis. Methods and Materials: Subjects were chosen from the Iowa Growth Study records for completeness and quality of radiographic images longitudinally. 19 females and 20 males were chosen. Lateral ceph images from 9 timepoints (age 3-20) were used to trace the external cortical outline of the symphysis. The biomechanical parameters (second moments of area (Ix, Iy, Imax, Imin)) were calculated from the external contours of the symphysis. Mandibular length was used as a proxy for overall mandibular size. All variables were scaled and growth allometries calculated by a reduced major axis regression. Clarke's T-test was used to test for significance. ANCOVA was used assess the interaction between symphyseal properties and sex, mandibular length, and sex+mandibular length. Results: No significant differences in symphyseal growth allometries of males and females were found (p>.05). No significant interactions between symphyseal properties and sex, and sex+mandibular length. (p>.05). A significant interaction between symphyseal properties and mandibular length was found (p<.05). Conclusions: Despite greater bite forces in males that manifest during adolescence, there were no differences in symphyseal growth allometries between males and females. Perhaps function does not play a significant role in development of symphyseal form. Perhaps the subtle effects of function on symphyseal morphology cannot be assessed by using only external cortical outlines for evaluation of symphyseal biomechanical parameters.

No description available.

Background: Genes predispose to disproportionate growth of the human face resulting in unbalanced maxillo-mandibular relationships and severe malocclusion. The success of genetic studies aimed at identifying causative genes for complex traits such as malocclusion depends greatly on a well-characterized phenotype to reduce heterogeneity. Purpose: The purpose of this study is to characterize the skeletal and dental variation present in Class II malocclusion into distinct homogenous phenotypic groups to help empower future genetic studies aimed at identifying the etiology of malocclusion. Research Design: Cephalometric radiographic landmarks and statistical data reduction methods will be used to find the most common phenotypic groupings in a sample of 309 Caucasian Class II adults. Results: A principle component analysis produced 7 principle components that explained 81% of the variation and a subsequent cluster analysis identified 5 distinct clusters of Class II patients.

Objective: The purpose of this study was to use the University of Iowa Meredith Growth Study to limit selection bias in selecting subjects to determine interarch tooth-size discrepancies (ITSD) by measuring and comparing the mesiodistal widths of maxillary and mandibular teeth. Methods: Thirty-two males and twenty-four females were selected from the Iowa Growth Study. They were selected on the basis of normal occlusions which were defined as Class I molars with mild (<2mm crowding/spacing) or moderate (2-4mm crowding/spacing) tooth-size arch length discrepancies. The mesiodistal widths of the maxillary and mandibular teeth were measured and anterior and overall ratios were developed. Descriptive statistics were computed. A two-sample t-test was used to detect the differences between the genders and between two crowding groups under different conditions. The Shapiro-Wilk test was used to check for the normality of the variables. Results: All subjects had a combined mean overall ITSD ratio of .914, a SD of .021 and a range of .875-.960. All subjects had a combined mean anterior ITSD ratio of .778, a SD of .025 and a range of .714-.863. No significant differences in ITSD were found between the two crowding groups nor differences found between the genders (p>0.05 in each instance). No significant differences in overall ratios were found between Bolton's data and this study's data for all subjects (p=0.7934) or anterior ratios (p=0.9786). Conclusions: The determined overall ITSD ratio of 91.4% +/- 2.1% and anterior ratio of 77.8% +/- 2.5% are remarkably similar to the original Bolton analysis that is still frequently used in orthodontics today. The results of this study validate and strengthen the findings of Bolton's study and support the use of the Bolton analysis in the determination of ITSD before orthodontic treatment as a tool to assist in the development of an orthodontic treatment plan.

Purpose: The purpose of this study is to characterize class II malocclusion phenotypes from orthodontic photographs in an effort to understand variation in the vertical and transverse dimension from the frontal view and also to identify distinct subgroups of homogenous phenotypes that could be correlated to genetic variation in an effort to identify the genetic causes of class II malocclusion phenotypes. Materials and Methods: The study sample included adult class II patients who were seeking treatment at the University of Iowa Orthodontic Graduate Clinic, University of Iowa Hospital Dentistry Clinic or surrounding private practice orthodontic clinics. The sample consisted of 330 Caucasian adult subjects (79 male, 251 female; age range 16-60 years) who met our eligibility criteria. 2D pre-treatment intraoral and extraoral photographs of 330 Class II adults were imported into Dolphin Imaging, version 11.0 (Dolphin Imaging Systems, Chatsworth, Calif). Non-digital photographs were scanned and imported into Dolphin Imaging. A total of 36 measurements were made. Fifteen were made on the extraoral frontal repose photograph, 15 were made on the extraoral smile photograph, and 6 were made on the intraoral frontal photograph. After the measurements were recorded, ratios, or proportions, were calculated from these facial measurements. Data reduction methods, principal component analysis (PCA) and cluster analysis (CA), were used due to the large number of measurement variables. The goal of these statistical tests is to identify the most homogeneous groups of individuals representing distinct class II phenotypes in an effort to reduce genetic heterogeneity. PCA was used to derive quantitative phenotypes and CA to identify phenotypically homogenous groups of individuals. The next goal of this study was to examine how the derived principal components correlate with the intraoral esthetic measurements. Descriptive statistics were derived for the esthetic variables. Pearson and Spearman correlations were used to analyze the relationship between the principle components and the esthetic measures. Results: The principal components analysis revealed that four principal components accounted for nearly 80% of the total variance in the data. The four principal components were used as the basis for the attempted formation of clusters defining subphenotypes of class II malocclusion in our study. The clustering process was repeated to assess cluster over a range for the number of clusters from 2 to 7 clusters. Each fit was examined using the pseudo F statistic, the cubic clustering criterion, and cluster visualization. Unfortunately, none of the clustering models were a good fit for our data based on the cubic clustering criterion and the relationship between the pseudo-F statistic and the cubic clustering criterion. This study shows that there is minimal correlation between the esthetic dental measurements and the phenotypic variables represented by the 4 principal components. Conclusions: A well-characterized class II malocclusion phenotype is crucial to reduce the heterogeneity when trying to find the causative genes for this complex trait. There have been numerous studies identifying environmental and genetic factors that lead to malocclusion, but none have fully characterized the class II phenotype. This study along with past and ongoing studies at the University of Iowa College of Dentistry are committed to fully characterizing the class II malocclusion phenotype using lateral cephalometric measurements, photographic measurements, 3-D cast measurements, and cone beam radiographic measurements. This data, along with DNA and environmental data will be combined to identify the causative gene for developing a class II malocclusion.

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

Thesis (M.D.S.)--University of Hong Kong, 1992. / Includes bibliographical references. Also available in print.

<p>The Aim of this study was to determine wheteher there are changes in the interdental arch widths and arch lengths of the madibular and maxillary arches during no-extraction and extraction orthodontic treatment. The records of 78 patients treated by one orthodontist were used for this study. Statistical data analysis included descriptive statistics of the data, analysis of the matrices, Wilcoxon Signed Rank tests and Kruskal-Wallis tests of the changes which occured during treatment. The study concluded that extraction treatment does not necessarily lead to the narrowing of the dental arches in the canine region.</p>