Dental age estimation based on DNA methylation using real-time methylation-specific PCR.

Age estimation is crucial for reconstructing the biological profiles of deceased victims in the forensic field. DNA methylation, which varies in an age-dependent manner in specific genes, is a candidate biomarker for estimating chronological age. DNA methylation-based models for estimating age have been developed using various technologies such as pyrosequencing. We recently quantified the methylation levels of elongation of very long chain fatty acids protein 2 (ELOVL2) in teeth using real-time methylation-specific polymerase chain reaction (RT-MSP) to rapidly assess the methylation value of CpG sites within a CpG island. The methylation levels of ELOVL2 were moderately correlated with chronological age, suggesting the usefulness of RT-MSP for age estimation. In this study, we designed eight and five new primer sets for ELOVL2 and ectodysplasin A receptor-associated death domain (EDARADD), respectively, and selected the best primer set. The DNA methylation level was analyzed in 59 tooth samples using the selected primer set. The ELOVL2 methylation value was positively correlated with age (R2 = 0.50), whereas the EDARADD methylation value negatively correlated with age (R2 = 0.44). A multiple regression model combining ELOVL2 and EDARADD showed high accuracy [mean absolute error (MAE) = 6.69], which was verified using 40 test samples (MAE = 8.28). Additionally, the MAE of three age groups showed no significant difference. These results indicate that the multiple regression model based on the two genes is useful for accurate age estimation across the human lifespan.

Effect of cranium structure on dose distribution during intraoral radiography.

OBJECTIVES: This study aimed to evaluate, the effect of the cranium structure on dose distribution by measuring the dose using the RANDO phantom for safe use of an X-ray unit during personal identification work at a large-scale disaster site. METHODS: As the subject, the head and neck of the RANDO Phantom (Alderson) containing a dry skull composed of a tissue-equivalent substance and having a shape similar to that of a living body were studied. With the body in the supine position, the air doses per second of irradiation time were measured for a total of six sections of the anterior, premolar, and molar teeth (molar on the left side) at a tube voltage of 60 kV and tube current of 10 mA during maxilla and mandible intraoral radiography. RESULTS: The region having the highest exposure dose was the main X-ray direction in both the mandible and maxilla. Conversely, the dose tended to be low in the range from the temporal region to the occipital region on both sides of the horizontal plane, from the frontal region to the occipital region of the sagittal plane, and in the parietal region of the frontal plane. CONCLUSIONS: It would be preferable to examine from the top of the body where the dose tends to decrease for all imaging sites.

A newly developed age estimation method based on CpG methylation of teeth-derived DNA using real-time methylation-specific PCR.

Age estimation of unidentified bodies is important in forensic medicine and crime scenes. There is accumulating evidence that DNA methylation in the human genome isolated from body fluids changes with age. Most of the data have been obtained by pyrosequencing. In the forensic field, a simple, quick, and economical method is required to evaluate the age of various types of samples. In this study, an age estimation method based on methylation levels of DNA extracted from teeth using real-time methylation-specific PCR (MSP) was developed. The CpG island in the upstream region of ELOVL2, which is known as a validated biomarker in blood samples, was selected as a target site. The CpG methylation levels highly correlated with age (r = 0.843, n = 29). Age-related increase in DNA methylation levels was not affected by sex differences. In addition, the simple regression model based on methylation status of the CpG island exhibited moderate accuracy with a mean absolute deviation between chronological age and predicted age of 8.94 years. The results imply that real-time MSP can be a new tool to perform age prediction of unidentified bodies in forensic scenes.

Comparison of air dose and operator exposure from portable X-ray units.

This study was aimed at investigating and comparing exposure dose of workers and the surrounding workers. In addition, worker's exposure was also measure about lens and finger. Four intraoral portable X-ray units were evaluated. The stray radiations were measured using Pitman 37D and ionization chamber (Pitman). MyDosemini (ALOKA) was used for measurement of the finger exposure dose. Without the shield became high in anterior 0.5 m. Comparing the air dose for the four models used in this study showed a high tendency for the two NOMAD models. And using the shields, the images could be taken 4.6 times of the baseline at a maximum and 3.6 times on average. The finger radiation exposure dose was low with both of the NOMAD models, with no significant difference found. By setting the baseline value without a shield, finger radiation exposure when using a shield was lower than the detection limit for the D3000, and was reduced by approximately 94-96% for other three models. All models can photograph around 100 bodies, so it is considered that it is not necessary to switch out the operator considering the operation limit. But even if it does not reach the operation limit, the stochastic effects of radiation exposure can be increased as well as the deterministic effects of the operation limit. The operator and the surrounding workers seek to protect themselves. It is important to perform exposure management that takes into account the stochastic effects to the operator and the surrounding workers.

Age estimation based on the volume change in the maxillary premolar crown using micro CT.

Age is often estimated using teeth because numerous external and internal changes appear due to aging. The purpose of this study was to investigate an age estimation method based on the volume ratio of the internal structure of the crown. 61 maxillary first premolars and 50 maxillary second premolars from subjects aged 20-79 years old were used. Micro CT, which can be used to analyze teeth in a non-destructive manner with high sensitivity, was employed in the present study. In consideration of individual differences among subjects, the volume ratio was calculated for the following four items: The pulp chamber was calculated separately based on the presence of enamel.In order to estimate age, regression analysis was conducted with the actual age as the dependent variable and each volume ratio as the independent variable. As a result, the highest correlation was found with PVR (E-) for each measurement item. Therefore, the regression equation using the volume change of the maxillary premolar crown as an index was as follows: Age = -12.43 × 4: PVR (E-) + 69.85. Age = -12.94 × 5: PVR (E-) + 72.54.

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.

The oral health of children in a rural area of the Lao People's Democratic Republic.

The lack of information on oral health in Laos makes it difficult to estimate the need and methods for preventing oral disease. This study identified problems concerning the oral health of Lao children. The study subjects were 59 school children who lived in Pakkading District. Dental caries, gingivitis malocclusions, temporomandibular joint (TMJ) disorders, dental plaque, and calculus were examined. We observed an average of 1.6 decayed, missing, and filled teeth (DMFT) and 4.1 decayed and filled deciduous teeth (dft) per child. 25.4% had gingivitis scores from 16 to 20 on the papillary, marginal, and attached (PMA) index; 29.6% had one or more occlusal abnormality; and 0% had signs of TMJ disorders. 93.5% of the children had at least one buccal or lingual tooth surface with plaque covering more than two thirds of the surface; 32.6% had dental calculus. Oral health promotion programs for children should prioritise prevention and treatment of caries. It is likely that the high rate of gingivitis in Lao children is due mainly to unsuccessful plaque control in daily life. In addition to descriptive epidemiological studies of dental diseases in other areas, the influence of sociological and behavioural factors on oral health should be analyzed epidemiologically to promote child health.

EDX fluorescence analysis and SEM observations of resin composites.

The purpose of this study was to evaluate the filler compositions of recently available light-cured resins. The composition of each resin paste was evaluated using an energy dispersive X-ray fluorescence spectrometer. Scanning electron microscopic observation of the polymerized resin pastes was also conducted. The main component of each resin composite was Si, while the other elements detected were Al, Ba, Sr, Zr, and K. These elementary compositions differed among the resin pastes used. Three different types of filler morphology were observed; splintered, prepolymerized and splintered, and spherical. The results of this study have thus characterized recently developed resin composites based on their filler elements and morphology.

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. © 1998 Wiley-Liss, Inc.