Variance of occlusion among preschool monozygotic twins

Aim The aim of this study was carried to assess the occlusion in primary dentition among preschool monozygotic pairs. Participants and methods A cross‑sectional study was performed on 20 pairs of healthy monozygotic twins of both sexes, aged 3–5 years. Occlusal measures included primary molar and canine relationships, the degree of overjet, overbite, anterior and posterior cross‑bite. Space discrepancies included primate and physiologic spaces, and crowding. Arch dimensions included arch circumference, crown tooth width, palatal depth, and primary intermolar and intercanine widths. Results The results showed a very strong and significant relation for primary molar and canine relationships, for mandibular and maxillary tooth widths, and for palatal depth. A strong relation was found for overbite and for mandibular and maxillary arch circumferences. Meanwhile, a moderate and significant relation was found for overjet, and for intercanine and intermolar widths in both arches. Conclusion The occlusal variables showed a very strong intrapair correlation coefficient for all parameters except for arch circumferences and overbite which showed a strong correlation, whereas interarch widths and overjet showed moderate correlation. Therefore, the variance of occlusion in this study is suggested that the pairs are similar but not identical.