Using the petrous part of the temporal bone to estimate fetal age at death.

Little is understood about the age-related changes in the petrous part of the temporal bone in fetal life. The purposes of this study were to examine documented skeletal remains of Japanese fetuses, to measure the length of the petrous part, and to develop diagnostic standards for fetal age-at-death estimation that could be applied to poorly preserved skeletons. The results indicated that it is possible to use a regression equation to estimate age at death directly from the length of the petrous part of the temporal bone. The application of the present method to a different population led to a fetal age-at-death estimation with an error of less than 1 month. We also used the Bayesian estimation, which yielded posterior probabilities of age, conditional on being of a particular length of the petrous part. The reference table of estimated gestational age may provide an easy-to-use indicator of the fetal age at death. In conclusion, measurement of the petrous part of the temporal bone may offer a new methodological basis for forensic and bioarchaeological diagnoses of fetuses.

Generational differences in tooth size in the Japanese population: analysis of cohorts with a generation gap of four to five decades.

PURPOSE: Since early modern times, tooth size has reportedly been increasing in each successive generation. A detailed analysis of these trends can provide meaningful information for elucidating the origin of various problems caused by larger teeth, such as an abnormal dentition and occlusion. By using data from most recent generations, this study aimed to clarify the time course of changes in tooth size in the Japanese. MATERIALS AND METHODS: The dentitions of two Japanese cohorts comprising young individuals born in the 1980s and the 1990s were compared with those of another cohort of Japanese individuals born in the 1940s, approximately half a century earlier. The mesiodistal diameter of the tooth crowns was measured on plaster models and subjected to statistical analyses. RESULTS: A mean difference test revealed that each recent generation showed positive generational differences in the size of more than 50% of the tooth types. In addition, a deviation graph analysis indicated that the degree of change in tooth size varied with the tooth type or sampling site. Principal component analysis clearly showed an increase in tooth size on an individual basis in the more recent generations. CONCLUSIONS: This study revealed positive generational differences in tooth size in the Japanese population. The results may aid in understanding the development of abnormal dentitions and occlusion in recent Japanese populations.

Estimation of fetal age at death from the basilar part of the occipital bone.

The purposes of this study are to examine documented fetal skeletal remains of Japanese, to measure the basilar part of the occipital bone, and to develop diagnostic standards for estimating fetal age at death which can be applied to poorly preserved skeletons. The sample is composed of 272 Japanese individuals of the early to middle twentieth century, whose ages were recorded in months from gestations of 5 to 11 months. The measurement items used here are the length, breadth, and index of the basilar part. The regression equations of gestational age in months for one or two variables were calculated. The results indicated that it is possible to use the regression equations to estimate the age at death of fetuses directly from the basilar part measurements. Another indicator for estimating age at death from the basilar part is the ratio of the width to the length, which was here expressed as the index of the basilar part. The width exceeded the length at 7 months and the basilar part changed with age from an anteriorly posteriorly long shape to a bilaterally wide one. It is concluded that the basilar part is a good indicator for estimating the fetal age at death.