Hirofumi Aboshi

Age estimation using microfocus X-ray computed tomography of lower premolars

The dental pulp, like other parts of the body, shows age-related changes. The aim of this study was to develop an age estimation method based on the ratio of the three-dimensional volume of the pulp chamber compared to the total tooth. Pulp chamber volumes were calculated using microfocus X-ray computed tomography (SMX-130CT, Shimadzu, Co., Kyoto, Japan) of the three-dimensional digital radiographic images of teeth. The specimens used in this study were 50 lower first and 50 lower second premolar teeth without caries or other abnormalities, obtained from patients in six 10-year age groups (age range 20-78 years). Each specimen was imaged by a micro-CT to reconstruct the three-dimensional structure. Using the reconstructed images, the tooth and pulp volumes at four levels (crown area (L(1)); coronal one third (L(2)); midroot (L(3)), and apical one third of the root (L(4))) were measured. Mean values of the pulp-tooth volume ratio (PTVR(1-4)) were compared between the six age groups and these values were used as the variables for the multiple regression analysis. The coronal one third of the root (L(2)) showed the greatest ratio values, followed by L(3), L(4) and L(1) in all age groups. Morphological changes of the pulp cavity in different age groups were observed. PTVR gradually reduced in value with increasing age, with the steepest reduction occurring in the 20-50 age range, and most noticeably at the L(2) level. The coefficients of determination by multiple regression analysis for four variables were 0.635 for lower first and 0.703 for lower second premolars. Among the variables used for estimating age by this method, only PTVR(2) showed a significant correlation at P<0.001. To determine the variables with the most significant contribution and to optimize the models, stepwise regression method was applied with inclusion level at P<0.05. Only the variable of PTVR(2) contributed significantly to the fit for lower first premolar whereas the two variables of PTVR(1) and PTVR(2) for lower second premolars. The coefficients of determination for the chosen variables were 0.625 for lower first and 0.698 for lower second premolars. Pulp-tooth volume ratio is an age-dependent variable that can be used to estimate age with reasonable accuracy.

Comparative study of craniofacial morphology and bite force in Fijians and Japanese

An anthropological survey was conducted in Fiji in 1994 and 1995 to study dental arch form, craniofacial morphology, and bite force of Fijians. Measurements were obtained from dental casts, cephalograms, and thin pressure‐sensitive sheets (Dental Prescale®) for bite force analysis. Results were compared with those of Japanese. In every direction, the size of the dental arch in Fijians was larger than in Japanese. Fijians displayed longer palates, longer mandibles, and bimaxillary protrusion. There was no significant difference in upper and lower facial heights. FH to lower incisor angle in Fijians was significantly larger than in Japanese. Fijians were characterized by a small palatal plane angle, occlusal plane angle and mandibular plane angle, and were thus brachyfacial. The Japanese tended to be more dolichofacial. The distances from the Cd line to the pterygoid muscles, masseter muscles, and teeth in Fijians were significantly longer than in Japanese. Occlusal contact areas of Fijians were also greater than those of Japanese. The results indicate that the masticatory muscles and craniofacial morphologies supporting them would be better integrated in Fijians than in Japanese. Am. J. Hum. Biol. 10:63–72, 1998.

Assessment of quality and interpretation of panoramic radiographs obtained in the Lao People’s Democratic Republic as part of a teleradiology collaboration with Japan

As part of quality assessment of a teleradiology program we evaluated the validity of patient information received, the quality of panoramic radiography imaging in Laos, and the ability of a Laotian radiologist to detect temporomandibular joint abnormalities. The amount of patient information gathered from 2,021 scans of panoramic radiographs was evaluated by triage before image diagnosis. Among the radiographs from 2,021 patients, primary triage indicated that there was insufficient information for 794 (39.3%) patients. Secondary triage to assess imaging failure included 1,227 radiographs, four of which were excluded from imaging diagnosis because of unacceptable image flaws. In total, 2,446 joints from 1,223 radiographs were evaluated for temporomandibular joint abnormalities in order to compare the image interpretation abilities of Laotian and Japanese radiologists. The kappa coefficient was 0.836 (P < 0.01) for the agreement between the two observers in detecting temporomandibular joint abnormalities on radiographs. We conclude that additional efforts are needed in order to overcome the challenges of maintaining quality in imaging techniques and diagnoses in Laos.