Sphenoid bone changes in rapid maxillary expansion assessed with cone-beam computed tomography / 대한치과교정학회지

OBJECTIVE: Rapid maxillary expansion (RME) is used to expand the maxilla and increase arch perimeter; yet, there are few reports on its effects on the sphenoid bone. With cone-beam computed topography (CBCT), it is possible to visualize sphenoid bone changes. The purpose of this study was to investigate sphenoid bone changes observed in conjunction with RME treatments, using CBCT. METHODS: Sixty patients (34 women and 26 men, aged 11–17 years) underwent RME as part of their orthodontic treatment. Patients were randomly assigned to one of three groups: a tooth-anchored group, a bone-anchored group, or a control group. Initial CBCT scans were performed preceding the RME treatment (T₁) and again directly after the completion of expansion (T₂). Statistical analysis included ANOVA, descriptive statistics, and the intraclass correlation coefficient (ICC). RESULTS: The reliability of the landmark location was at least 0.783, and the largest ICC mean measurement error was 2.32 mm. With regard to distances, the largest change was 0.78 mm, which was not statistically significant (p > 0.05). Statistical significance was established in patient groups of the same sex and treatment type for the following distance measurements: right anterior lateral pterygoid plate to the right edge of the hypophyseal fossa (d₂), anterior distance between the medial pterygoid plates (d₄), and anterior distance between the left medial and lateral plates (d₈). CONCLUSIONS: In this study, there were no clinically significant changes in the sphenoid bone due to RME treatments regardless of sex or treatment type.

Accuracy of Bolton analysis measured in laser scanned digital models compared with plaster models (gold standard) and cone-beam computer tomography images / 대한치과교정학회지

OBJECTIVE: The aim of this study was to compare the accuracy of Bolton analysis obtained from digital models scanned with the Ortho Insight three-dimensional (3D) laser scanner system to those obtained from cone-beam computed tomography (CBCT) images and traditional plaster models. METHODS: CBCT scans and plaster models were obtained from 50 patients. Plaster models were scanned using the Ortho Insight 3D laser scanner; Bolton ratios were calculated with its software. CBCT scans were imported and analyzed using AVIZO software. Plaster models were measured with a digital caliper. Data were analyzed with descriptive statistics and the intraclass correlation coefficient (ICC). RESULTS: Anterior and overall Bolton ratios obtained by the three different modalities exhibited excellent agreement (> 0.970). The mean differences between the scanned digital models and physical models and between the CBCT images and scanned digital models for overall Bolton ratios were 0.41 +/- 0.305% and 0.45 +/- 0.456%, respectively; for anterior Bolton ratios, 0.59 +/- 0.520% and 1.01 +/- 0.780%, respectively. ICC results showed that intraexaminer error reliability was generally excellent (> 0.858 for all three diagnostic modalities), with < 1.45% discrepancy in the Bolton analysis. CONCLUSIONS: Laser scanned digital models are highly accurate compared to physical models and CBCT scans for assessing the spatial relationships of dental arches for orthodontic diagnosis.

New Statistical Method to Analyze Three-Dimensional Landmark Configurations Obtained with Cone-Beam CT: Basic Features and Clinical Application for Rapid Maxillary Expansion

OBJECTIVE: To describe a statistical method of three-dimensional landmark configuration data and apply it to an orthodontic data set comparing two types of rapid maxillary expansion (RME) treatments. MATERIALS AND METHODS: Landmark configurations obtained from cone beam CT scans were used to represent patients in two types (please describe what were two types) of RME groups and a control group over four time points. A method using tools from persistent homology and dimensionality reduction is presented and used to identify variability between the subjects. RESULTS: The analysis was in agreement with previous results using conventional methods, which found significant differences between treatment groups and the control, but no distinction between the types of treatment. Additionally, it was found that second molar eruption varied considerably between the subjects, and this has not been evaluated in previous analyses. CONCLUSION: This method of analysis allows entire configurations to be considered as a whole, and does not require specific inter-landmark distances or angles to be selected. Sources of variability present themselves, without having to be individually sought after. This method is suggested as an additional tool for the analysis of landmark configuration data.

Esthetic perception towards different combinations of facial contours and upper incisor shape

Aim: The aim of this study was to assess the esthetic perception of adults with primary, secondary and higher education and recent dental graduates towards different combinations of facial contours and upper central incisor shapes. Methods: Photographs of 6 individuals with square, tapered and ovoid facial contours (2 per type) were modified to have the 3 different types of tooth shapes (square, tapered and ovoid) in each facial contour (total of 18 photographs). The 195 participants rated each photograph using visual analogue scales. Comparison between groups was performed using the Chi-square t-test ('alfa'=0.05). Results: No statistically significant differences (p>0.05) were found in the esthetic perception towards the frontal facial outline and upper incisor shape by participants’ educational level. In addition, the shapes of teeth perceived as the most esthetically pleasing were not always similar to the form of frontal facial outline evaluated. Conclusions: No general agreement was found in the esthetic perception towards the frontalfacial outline and upper incisor shape by educational level. Dentists tend to prefer ovoid shape tooth for almost all frontal facial outline.