Suleyman Demirel University Faculty of Dentistry Pediatric Dentistry Department

In this study, the study groups comprised MZ and DZ twin pairs, triplets and singletons between the ages of 2 and 17 who attended the Department of Pediatric Dentistry at Suleyman Demirel University between January 2018 and September 2020. Twins and triplets who had developmental anomalies such as cleft lip and palate, premature tooth loss, systemic diseases or syndromes that could influence oral health or had already undergone or were undergoing orthodontic therapy, as well as those whose family did not give consent, were excluded from the study.

All children were assessed by the same experienced pedodontist (E.O.) to avoid interexaminer variability. The oral examination was performed using sterile mouth mirror and probe. The prevalence of dental caries was recorded using dmft index (decayed, missing and filled teeth) in primary dentition and DMFT index (Decayed, Missing and Filled teeth) in permanent dentition. When evaluating patients over 6 years old, the missing tooth component was not included in the primary dft scores.

Oral hygiene practices, such as tooth brushing frequency and the children's past or present oral habits (digit sucking, nail biting, tongue thrust, bruxism, lip biting, pencil biting, cheek biting and mouth breathing), were also recorded.

The primary molar relationships were evaluated as flush terminal plane and mesial and distal step. The permanent molar relationships were recorded as Class I, Class II (Division 1 and 2) and Class III. Occlusal traits such as increased overjet, deep bite, open bite and anterior and posterior crossbite were recorded as present (1) or absent (0) with the help of a dental probe