Does the 2D:4D Ratio Exhibit Sexual Dimorphism in Skeletal Malocclusions? A Retrospective Study

Abstract

Objective: It is noteworthy that the 2D:4D ratio, also called as the ratio of the length of the second digit (2D) to the length of the fourth digit (4D), which has the ability to remain stable lifetime, is associated with various hormones and craniofacial skeletal development as a biomarker in early diagnosis. The aim of this study was to investigate the relationship between the 2D:4D ratio and sagittal skeletal malocclusions. Materials and Method: A total of 117 patients (57 females, mean age 13.44±1.98; 60 males, mean age 13.56±2.14) with normal vertical angles were included, and the groups were divided into skeletal classes I, II and III according to the ANB angle. The skeletal class I group consisted of patients with ideal values for both SNA and SNB angles. The skeletal groups were further divided into female and male subgroups by gender. SNA, SNB, SN/GoGn and ANB angles and ANS-PNS and Go-Pog lengths were measured on pretreatment lateral cephalometric radiographs. Digit length measurements were performed with a digital caliper capable of measuring up to 0.01 mm. The 2D:4D ratio was calculated for each group by dividing the 2D length by the 4D length. Statistical analyzes were performed with independent sample t-test and one-way ANOVA in normally distributed data, and Kruskal-Wallis and Man-Whitney U tests in non-normally distributed data. Statistical significance level was accepted as p < 0.05. Results: There was no statistically significant difference between right and left 2D:4D ratios and right and left digit lengths of the same hand in skeletal classes. While statistically significant sexual dimorphism was observed in digit lengths and 2D:4D ratios in skeletal class Is, it was observed that the significance decreased as the severity of malocclusion increased. No significant difference was found in terms of sexual dimorphism in skeletal class IIIs. There was no significantly difference between the skeletal groups in terms of 2D:4D ratio and length measurements. Conclusions: Sexual dimorphism was seen in all parameters, especially in skeletal class I patients, and it was found that males had more 2D and 4D lengths and a lower 2D:4D ratio than females. It was also concluded that as the severity of malocclusion increased, the statistical significance of the parameters observed with sexual dimorphism decreased. The fact that sexual dimorphism is fully seen in skeletal class Is but not in skeletal class III has led to the use of the 2D:4D ratio as a diagnostic biomarker in the early diagnosis of sagittal skeletal malocclusions by gender.