Satoru Matsunaga

Age estimation based on three-dimensional measurement of mandibular central incisors in Japanese

The purpose of this study was to investigate an age estimation method that considers gender as well as three-dimensional measurement of the components, specifically enamel and dentin. A total of 155 mandibular central incisors aged 12-79 years old which was chosen from the collection stored at the Department of Anatomy in Tokyo Dental College and had no opened apex, caries or restorative treatment, were examined. Samples were scanned using micro-CT HMX225 ACTIS4. Based on the sliced image data, three-dimensional structures were obtained and the volumes of enamel, dentin, and pulp cavity were measured. Regression equations for age estimation were then determined. The accuracy of age estimation equations for each region, volume ratio, and sex was assessed using the determination coefficient R(2) as well as the standard errors of estimated values. The root region alone had a comparable accuracy to that of the whole tooth and the crown region had a relatively lower accuracy. In the whole tooth and the crown region, slightly higher correlations were observed for pulp/tooth volume ratios in which enamel was excluded. Females tended to have higher accuracy compared to males. The estimated age was higher in males compared to females for the same volume ratio of the pulp cavity. The highest correlation in both genders with age was observed for the volume ratio of the pulp cavity to the whole tooth excluding the enamel (males, R(2)=0.67; females, R(2)=0.76). The 95% confidence intervals for the population regression showed different distributions for each sex. In the 95% prediction intervals for age estimation, females tended to have narrower intervals and higher accuracy compared to males. Therefore, the use of gender-specific equations is recommended for age estimation.

Biomechanical role of peri-implant trabecular structures during vertical loading.

The aim of this study was to identify the load transfer paths in cortical bone and trabecular structure of cancellous bone in the jawbones for loads from endosseous implants. Maxillae were resected from beagle dogs 6xa0months after implant surgery and imaged using micro-computed tomography (micro-CT). A three-dimensional structure was produced based on the CT data and peri-implant trabecular structure was observed. Load transfer paths were analyzed from the results of three-dimensional finite element analysis. Furthermore, buffer actions in bone trabeculae when strain increased during stress analysis and when loads were applied were observed. Peri-implant bone trabeculae were seen extending into the upper and lower cortical bone from the fixture. The direction of bone trabecular alignment corresponded with the load transfer paths. In addition, analysis with increased strain confirmed that trabecular structures could serve as load buffers. These results suggest that bone trabeculae supporting load transfer from implants undergo remodeling.

Evaluation of cortical bone thickness and root proximity at maxillary interradicular sites for mini‐implant placement

OBJECTIVESnThe purpose of this study was to evaluate the interradicular cortical bone thickness, alveolar process width and root proximity for planning mini-implant placement in the maxillary alveolar process.nnnMATERIAL AND METHODSnEighty maxillae (right and left sides) of 40 Japanese adult skulls were examined. The samples were imaged and measured using a micro-CT system. Buccal and palatal interradicular cortical bone thickness, alveolar process width, and root proximity were measured in six interradicular sites from distal of central incisor to mesial of second molar. Buccal and palatal interradicular cortical bone thickness and alveolar process width were measured at 10 different vertical levels. Root proximity was measured at four different vertical levels.nnnRESULTSnBuccal and palatal interradicular cortical bone thickness and alveolar process width tended to increase from crest to base of alveolar process. The buccal interradicular cortical bone thickness between canine and first premolar or between first premolar and second premolar was the greatest, and between central incisor and lateral incisor was the least. The palatal interradicular cortical bone was significantly thicker than the buccal. The root proximity between second premolar and first molar or first premolar and second premolar was the widest and between central incisor and lateral incisor it was the narrowest.nnnCONCLUSIONSnThe findings of this study suggest that recommendations when low dose 3D multislice CT or low dose cone beam imaging is not available, the results of this research may be useful in providing indicators for selecting the design of the placement site.

Three-Dimensional Analysis of the Internal Structure of the Mandibular Condyle in Dentulous and Edentulous Jaws Using Micro-CT

Abstract This study clarifies the internal structure of the mandibular condyle in dentulous and edentulous jaws; three-dimensional observation and morphological measurements were performed using micro-CT. The materials used in this study were 14 mandibular condyles each removed from the dentulous and edentulous cadavers. Internal structures of the mandibular condyle were morphologically analyzed in three anatomical planes. Additionally, morphometrical observations of the trabecular bone structure at five regions of interest and cortical bone thickness were performed. The mandibular condyle of dentulous jaws consisted predominantly of regularly aligned plate-shaped trabeculae. Conversely, edentulous jaws were predominantly irregularly aligned narrow rod-shaped trabeculae. The results of morphometrical analysis showed that trabecular separation (Tb.Sp) in the central region of the mandibular condyle most closely reflected the difference between dentulous and edentulous jaws. These results suggest that, in edentulous jaws, reduced masticatory function due to tooth loss affects the internal structures of mandibular condyle.

Evaluation of the Palatal Bone for Placement of Orthodontic Mini-Implants in Japanese Adults

Abstract Mini-implants are increasingly being used for orthodontic anchorage in the palate. The anatomical structure of the jaw must be properly evaluated prior to use; however, there are a few research reports providing basic data regarding the palate. Bone thickness was measured and bone morphology evaluated in the palates of Japanese people. The palates of five Japanese adult cadavers and 15 skulls were examined. The samples were imaged and measured using the micro-CT system. In the mid-palatine suture region, the cortical bone had a complex mesh-like structure and was thicker than surrounding areas. Cortical bone thickness varied depending on the site. The mid-palatine suture region is an ideal site for mini-implant insertion; however, because bone and cortical bone thickness markedly decrease in the lateral region, careful attention should be paid when inserting mini-implants in the midpalatine suture.

Biomechanics of Jaw Bone Considering Structural Properties of Trabecular Bone

Abstract Mechanical stress is an important factor in bone homeostasis, which is impossible to visualize and therefore difficult to evaluate. Biomechanical analysis based on the three-dimensional finite element method (3D FEW has become more accurate, and it is now possible to analyze load transfer pathways taking into consideration the trabecular structures. It has even become feasible to develop treatment plans based on mechanical factors using image data acquired from the patient. This review describes the usefulness and prospects of biomechanical analysis of the jaw bones, specifically finite element analysis (FEA) based upon the consideration of internal microstructures.

Three-dimensional analysis of pulp chambers in mandibular first deciduous molars

Abstract In crown restoration, it is important to understand the internal anatomical feature of each tooth, as the morphology of human deciduous teeth is particularly complex. The purpose of this study was to clarify threedimensionally the topographic relationship between the crown contour and the pulp chamber of the mandibular first deciduous molars using a micro-CT system. Fifteen mandibular first deciduous molars obtained from the dried skulls of Indian children in the deciduous dentition period were used as specimens. Three-dimensional reconstructed images were reproduced by combining the two-dimensional slice imaging data using a micro-CT system. Crown contours and shapes of the pulp chamber were observed from various directions. In addition, the thickness of tooth substance at each pulp horn was also measured. In observations of the topographic relationship between the crown contour and the pulp chamber, the pulp horn of the mesiobuccal pulp chamber was found to project the most to the cusp side. The distance between the pulp horn and enamel surface was also shortest (2.45±0.30mm) in this region. Furthermore, in teeth with a deep, wide trigonid notch, the lateral wall of the mesiobuccal pulp chamber projected in the mesial direction. These results suggest that in preparation of cavities in mandibular first deciduous molars, close attention must be focused on pulp exposure in the pulp horn of the mesiobuccal pulp chamber. In addition, the lateral wall of the mesiobuccal pulp chamber should be noted in teeth with the deep, wide trigonid notch.