Deciduous tooth crown size and asymmetry in strabismic children

Primary tooth size asymmetry in twins and singletons

OBJECTIVES

To explore asymmetry values of antimeric deciduous tooth crown dimensions in three types of twins: monozygotic (MZ), dizygotic same-sex (DZ) and opposite-sex (OS) vs. single-born controls.

SETTING AND SAMPLE POPULATION

Mesiodistal and labio-lingual crown dimensions of second deciduous molars and mesiodistal canine and first molar crown dimensions of 2159 children at 6-12 years of age were evaluated, originating from the US cross-sectional Collaborative Perinatal Study from the 1970s, including altogether MZ (n = 28), DZ same-sex (n = 33) and OS (n = 39) pairs. Single born (n = 1959) were used as controls.

MATERIAL AND METHODS

Dental casts were measured for comparison of variance relationships calculated from antimeric teeth, exhibiting fluctuating (FA), and directional (DA) asymmetry using anova.

RESULTS

Significant differences appeared in MZ and OS girls in DA of deciduous canines, which gain size in the first and second trimester, and deciduous second molars, which finally stop crown growth during the early post-natal period. Significantly, increased FA values appeared for lower deciduous canines and second molars, indicating greatest environmental stress in OS girls, MZ girls and DZ boys. Twin girls had more fluctuating and directional crown asymmetry than twin boys, but in some dimensions, the twins were more symmetric than controls.

CONCLUSIONS

Transmembrane hormonal influence between opposite-sex twins, and late gestational stress factors, caused by placental malfunction and/or monochorionicity, may be involved in asymmetric growth of antimers, during critical periods of crown size gain.

Comparison of the total length and areas of upper central incisors between males and females using computer-assisted morphometry

The determination of measurements of teeth facilitates various procedures in dentistry. The purpose of this study was to evaluate the total length and the area of the non-extracted upper central incisors (UCI). Periapical radiographies of 42 UCI were placed over a lighted box. The outlines of the teeth and the pulp cavity were traced onto sheets and then measured using an image analyzer. The area of the upper left central incisor tooth (tooth 21) was statistically significantly larger in males than in females (p = 0.02). The total length of the right UCI was similar to that of the left one. This study demonstrates that computer-assisted morphometry is an important tool for the evaluation of the total length and areas of teeth and their pulp cavities. The significantly larger area of tooth 21 in males compared to females has anthropomorphic and clinical implications.