Development of Jaw and Deciduous Teeth in Japanese Children -Comparing Size of Crown and Alveolar Area between Today and 40 Years Ago

Digital measurement of deciduous tooth dimensions in China: A cross-sectional survey

OBJECTIVE

Crown dimensions data of deciduous teeth hold anthropological, forensic, and archaeological value. However, such information remains scarce for the Chinese population. This multi-center study aimed to collect a large sample of deciduous crown data from Chinese children using three-dimensional measurement methods and to analyze their dimensions.

DESIGN

A total of 1592 children's deciduous dentition samples were included, and the sample size was distributed according to Northeast, North, East, Northwest, Southwest and South China. Digital dental models were reconstructed from plaster dental models. Independent sample t test, paired t test, principal component analysis (PCA), and factor analysis (FA) were used to analyze the tooth crown dimensions.

RESULT

18,318 deciduous teeth from 1592 children were included. Males exhibited slightly larger values than females. The range of sexual dimorphism percentages for each measurement was as follows: mesiodistal diameter (0.40-2.08), buccolingual diameter (0.13-2.24), and maxillogingival diameter (0.48-3.37). The FA results showed that the main trend of crown dimensions changes was the simultaneous increase or decrease in mesiodistal diameter, buccolingual diameter and maxillogingival diameter in three directions.

CONCLUSION

This is the first large-scale survey of deciduous tooth crown dimensions in China, which supplements the data of deciduous tooth measurement and provides a reference for clinical application.

Sexual dimorphism in deciduous tooth crown size: Variability within and between groups

OBJECTIVES

Sexual dimorphism in deciduous tooth crown size is often used to identify sex in sub-adults from archeological sites and forensic settings. Yet sexual dimorphism in deciduous dental attributes is less well documented than in permanent teeth. This analysis was conducted to document variation in sexual dimorphism within and between a global sample of populations.

METHODS

Mean deciduous tooth crown size was culled from published literature, yielding a sample of 37 groups. Mean mesiodistal (MD) and buccolingual (BL) crown dimensions are the basis for computing percent sexual dimorphism [(M/F-1) * 100]. Three analyses were conducted: (1) a statistical analysis of mean % sex dimorphism (%SD) within and between populations, (2) an evaluation of rank-ordered %SD by tooth, and (3) an assessment of intergroup patterns in degree of sexual dimorphism. Univariate tests of significance, correlation and regression, and multivariate cluster analysis were used.

RESULTS

Mean %SD is low overall (1.77) for 26 groups and the level of dimorphism is not significantly different for MD (1.68) and BL (1.72) dimensions. The most sexual dimorphic deciduous teeth include incisor, canine and molar tooth types, while in the permanent dentition canines are consistently most sexual dimorphic. Global variation in sexual dimorphism of deciduous tooth size is low with little inter-ethnic variation.

CONCLUSIONS

Sexual dimorphism in crown size is lower and more variably expressed than in permanent teeth. Differences may relate to developmental, chromosomal, and hormonal factors. Degree of sexual dimorphism is not associated with ethnicity in this global sample.

Crown dimensions of primary teeth-A systematic review and meta-analysis

Odontometrics, also known as metric traits, includes mesiodistal, buccolingual dimensions, and crown height. The purpose of this study was to assess pancontinental odontometric variations in the crown dimensions of primary teeth. Ten electronic databases were searched to identify studies that measured crown dimensions of primary teeth, published in English language, without year restriction up to July 2020. Studies included cross-sectional research measuring on casts, subjects, and on radiographs of healthy children. Meta-analysis was performed, and risk of bias was assessed using modified Newcastle-Ottawa Scale. Eighty-seven observational studies were included, with 24,634 participants (9487 males, 11,083 females; 19 studies lacked gender information). Only one study showed a low bias risk, whereas 81 and 5 studies had moderate and high risk, respectively. Sixty-five studies included for meta-analysis revealed heterogeneity in mean mesiodistal dimensions of maxillary first molars from Asia (I² -99.7%), buccolingual measurements of mandibular first molars from Europe (I² -99.9%), crown height of mandibular second molars from Africa and Europe (I² -79.8%). Among mesiodistal and buccolingual dimensions, Australians have larger while Asians have smaller teeth. Pertaining to crown height, very few studies could be found in the literature. This review highlights the variations in crown dimensions of primary teeth among populations.

Measurement of the morphological data of primary teeth in northwest China

OBJECTIVE

This study aims to digitally obtain the morphological data of children's primary teeth in northwest China and evaluate the reliability of digitally obtaining the anatomical morphological data of primary teeth.

METHODS

A total of 308 extracted primary teeth and cone-beam computed tomography (CBCT) images of 407 primary teeth were collected in northwest China. Electronic digital Vernier callipers (accuracy: 0.01 mm) were used to measure the mesiodistal and buccolingual diameters and crown length of the extracted primary teeth and calculate the crown area and crown index. Each sample was scanned with an intraoral scanner (Trios2 3shape, Denmark), and the resulting stl format files were imported into Geomagic Wrap 2015 to measure the axial and buccolingual diameters and crown length. The crown area and crown index were then calculated. After verifying the accuracy of the CBCT image measurement, the CBCT image data of 407 samples were measured in SmartV software using the "measure length" function by referring to the coronal, sagittal, and horizontal planes to adjust the position of the reference line.

RESULTS

Northern Chinese have larger primary teeth than other populations (Japanese, white American, African, Icelander, Spanish, and Dominican Mestizo) but smaller primary teeth than native Australians. Compared to Indian primary teeth, northwest Chinese's primary teeth have larger diameters on the central axis and smaller diameters on the buccolingual surface. Male teeth are usually larger than female teeth. Compared with the results of Wang Huiyun's study, the axial and buccolingual diameters and crown length of all native tooth types in this total sample were significantly smaller at the 0.1% level, and only the axial diameters of the upper first molar and lower second molar and the crown length of the lower lateral incisor were significantly smaller at the 1% level. The results of the intraclass correlation coefficient of 308 extracted primary teeth expressed an excellent degree of agreement between the callipers and intraoral scanner for the following: mesiodistal diameter (0.956-0.991), buccolingual diameter (0.963-0.989), crown length [0.864-0.992, except for the upper canine (0.690)], crown index (0.850-0.975), and crown area (0.946-0.993).

CONCLUSION

The digital measurements of the intraoral scanner and CBCT image are in good agreement with the manual measurement of the Vernier calliper. The difference between the anatomical morphology size of the primary teeth measured in this study and the results of different populations could be due to different genetic backgrounds and environmental factors.

Supernumerary roots in maxillary deciduous canines: A rare anomaly with a long history

OBJECTIVE

To describe two maxillary deciduous bi-rooted canines, one archeological and one modern, and examine the possible etiology of this condition.

DESIGN

Two cases of bi-rooted canines were described and compared to published examples. Both specimens were radiographed and measured and compared to one-rooted samples. The archeological specimen was scanned using CBCT to facilitate detailed examination of the deciduous teeth. The extracted modern tooth was embedded in epoxy resin and two coronal sections were cut, one through the crown and one through the roots and examined with a light microscope.

RESULTS

The bi-rooted canines were larger than the control samples. They showed none of the features commonly associated with gemination. The radiographs and scans showed that the canine roots in the archeological case diverged mesio-distally like the buccal roots in the adjacent first deciduous molar. In the clinical case, the root trunk was elongated mesio-distally and the furcation was located very close to the apex with a C-shaped root canal.

CONCLUSIONS

Both variants of the condition described above are rare in deciduous canines. They do not seem to be associated with fusion or gemination. However, as the teeth are relatively flattened bucco-lingually and we tentatively propose that this form results from spatial constraints during the early stages of crown development that have contributed to the development of additional roots. The megadont dimension of the recent bi-rooted deciduous canine may affect root development and the necessity of two mesio-distally located roots for anchorage in the maxilla.

Incisor liability and its effects among East Asian children

BACKGROUND/PURPOSE

Incisor liability is the discrepancy in the sum of the mesiodistal crown width between the primary and permanent incisors. Incisor liability affects the integrity and eruption of the permanent incisors during the transition from the primary to permanent dentition. This study investigated the incisor liability in the primary dentition of Taiwanese children.

METHODS

The digital periapical films of 203 upper arches of 105 boys and 98 girls and 195 lower arches of 119 boys and 76 girls aged between 3 and 6 years were selected in this retrospective study. The mesiodistal crown widths of the primary and permanent incisors were measured using the medical imaging software for both arches. Differences in incisor liability values were statistically analyzed.

RESULTS

The mean ± standard deviation of the incisor liability values were 8.32 ± 1.88 and 6.91 ± 1.13 mm for the upper and lower arches, respectively, in all children. The incisor liability was closely related with the total crown widths of the permanent incisors for upper and lower arches. The incisor liability values were higher among boys than girls for the upper but not lower arch.

CONCLUSION

Incisor liability differs depending on ethnicity. In Taiwanese children, incisor liability was closely related with the crown widths of the permanent incisors. The incisor liability values of boys were higher than those of girls in the upper arch but not the lower arch.