Fractal analysis of mandibular trabecular bone: optimal tile sizes for the tile counting method

PURPOSE: This study was performed to determine the optimal tile size for the fractal dimension of the mandibular trabecular bone using a tile counting method. MATERIALS AND METHODS: Digital intraoral radiographic images were obtained at the mandibular angle, molar, premolar, and incisor regions of 29 human dry mandibles. After preprocessing, the parameters representing morphometric characteristics of the trabecular bone were calculated. The fractal dimensions of the processed images were analyzed in various tile sizes by the tile counting method. RESULTS: The optimal range of tile size was 0.132 mm to 0.396 mm for the fractal dimension using the tile counting method. The sizes were closely related to the morphometric parameters. CONCLUSION: The fractal dimension of mandibular trabecular bone, as calculated with the tile counting method, can be best characterized with a range of tile sizes from 0.132 to 0.396 mm.

The influence of X ray beam angulation on the fractal analysis of trabecular architecture in human dry mandible using standardized tile counting method / 대한구강악안면방사선학회지

PURPOSE: The purpose of this study is to examine the effects of X-ray beam angulation on the fractal dimension of trabecular bone structure of human dry mandible using the tile counting method. MATERIALS AND METHODS: We divided 5 human dry mandibles into an angle and a molar groups depending on the regions and deciding the region of interest (ROI). When contrasted with the ROI, the inferior cortex was appointed to be low and the lines perpendicular to the buccal cortex were appointed to be the standard angle. Direct digital intraoral radiographs were obtained from 9 different projection angles. We analyzed statistically the fractal dimension using the tile counting method. RESULTS: There was a statistically significant difference in the fractal dimension of the regions and the mandibles, but there was no statistically significant difference in the fractal dimension according to the X-ray beam angulation. CONCLUSION: There is no statistically significant effect of the angle of the projection on the fractal dimension of trabecular bone structure of a human dry mandible according to the tile counting method.

Evaluation of masticatory muscles of mandibular asymmetry patients by computed tomography / 대한구강악안면방사선학회지

PURPOSE: To compare the size of the masseter and lateral pterygoid muscle between the affected and the unaffected side of the patients who have the chief complaints of the mandibular asymmetry. MATERIALS AND METHODS: Twenty two patients (male: 4, female: 18, average age: 21.3 year-old) were radiographed using posterior-anterior (P-A) cephalography and computed tomography (CT). On P-A cephalography, the degree of deviation was determined by the distance from the mentum to the vertical reference line through the crista galli and the anterior nasal spine. On the scanned tracing papers of the maximum cross-sectional area of the masseter and lateral pterygoid muscle using axial CT images, the pixel number was measured. The ratio of the affected : unaffected sides were obtained. For the masseter and lateral pterygoid muscle, the relationship between the muscular volume and degree of skeletal hypoplasia was studied. RESULTS: The half cases showed no skeletal asymmetry. The lateral pterygoid muscle of the affected side was larger significantly than unaffected side (p.0.05). However, there was no significant difference between two sides in the cases of skeletal asymmetry. There was only significant difference in the cases without skeletal asymmetry (p.0.05). CONCLUSIONS: To some extent, the slight mandibular hypoplasia could affect the growth of some masticatory muscles.

A study of trabecular bone strength and morphometric analysis of bone microstructure from digital radiographic image / 대한구강악안면방사선학회지

PURPOSE: To evaluate the relationship between morphometric analysis of bone microstructure from digital radiographic image and trabecular bone strength. MATERIALS AND METHODS: One hundred eleven bone specimens with 5 mm thickness were obtained from the mandibles of 5 pigs. Digital images of specimens were taken using a direct digital intraoral radiographic system. After selection of ROI (100x100 pixel) within the trabecular bone, mean gray level and standard deviation were obtained. Fractal dimension and the variants of morphometric analysis (trabecular area, periphery, length of skeletonized trabeculae, number of terminal point, number of branch point) were obtained from ROI. Punch sheer strength analysis was performed using Instron (model 4465, Instron Corp., USA). The loading force (loading speed 1 mm/min) was applied to ROI of bone specimen by a 2 mm diameter punch. Stress-deformation curve was obtained from the punch sheer strength analysis and maximum stress, yield stress, Young's modulus were measured. RESULTS: Maximum stress had a negative linear correlation with mean gray level and fractal dimension significantly (p< 0.05). Yield stress had a negative linear correlation with mean gray level, periphery, fractal dimension and the length of skeletonized trabeculae significantly (p< 0.05). Young's modulus had a negative linear correlation with mean gray level and fractal dimension significantly (p< 0.05). CONCLUSIONS: The strength of cancellous bone exhibited a significantly linear relationship between mean gray level, fractal dimension and morphometric analysis. The methods described above can be easily used to evaluate bone quality clinically.

Removal of a submandibular duct calculus with 'SNU Sialoop': Technical report / 대한구강악안면방사선학회지

Manufacturing method and technical procedure of 'SNU Sialoop', which was a new device designed for removal of sialolith, were introduced. Two cases about removal of Wharton' duct sialolith using SNU Sialoop were presented.

A study of bracket position in Korean / 대한치과교정학회지

This study was undertaken to determine the adequate bracket positron m Korean. The subjects were consisted of casts and photographs of 30 males & 30 females. They had acceptable profile, normal occlusion, no loss of teeth and no experience of dental treatment. The following conclusions were obtained. 1. In case of no necessity of the posterior teeth movement, bracket angulation was made automatically by paralleling the bracket slot with occlusal plane. 2. Axial inclination of all teeth were measured, and those of canine & premolar were much variable. 3. Adequate bracket position of Korean occlusion were obtained.