Evaluation of Twenty Non-Metric Dental Crown Traits in Different Types of Malocclusions in a Sample from India, New Delhi Population.

Background: Dental phenotype shows variation in the form of various metric and non-metric traits, primarily due to gene-environment interplay. It gives an insight into the evolutionary trends, ancestry, and food habits. Recently, it has been explored for genetic affinity with several growth anomalies and development of craniofacial skeleton which is also responsible for dental and skeletal malocclusions.

Objectives: the current study aims to investigate the non-metric dental crown traits (NDCTs) using Arizona State University Dental Anthropology system (ASUDAS) in different types of malocclusions in Delhi, National Capital Region (NCR) population.

Materials and methods: The study design was observational and retrospective. The total sample comprised of 240 pairs of dental casts divided into four equal groups of 60 subjects each (30 male and 30 female), based on malocclusion. The four groups of malocclusions were: Angle's Class I, Class II division 1, Class II division 2, Class III. The investigator was blinded for patient ID and sex before recording the data. The data for cast were recorded by three observers independently in a modified malocclusion- non-metric dental crown traits (M-NDCT) anthropological variants chart and statistically analyzed for association with different malocclusions and sex.

Results: Significant differences were found in the expression of several NDCTs (both in presence and scoring) in different malocclusions. Class I malocclusion showed a predominantly winging, shoveling -upper central and lateral incisor, protostylid, hypoconulid absence in lower second molar, and cusp number. Class II malocclusion showed a double shoveling, interrupted groove, tuberculum dentale, canine mesial ridge, premolar accessory cusp, Carabelli's trait, lingual cusp variation, and seventh cusp in the lower left first molar. Class III malocclusion showed the absence of hypocone in upper second molar, deflecting wrinkle, distal trigonid crest, and Y groove in left lower second molar (26.7%). Besides, sexual dimorphism was seen in shoveling -upper central and lateral incisor, canine mesial ridge, Carabelli's trait, 3-cusp in upper second molar, and cusp number.

Conclusions: Significant association was found between non-metric dental traits and malocclusions (Class I, Class division 1, Class II division 2, and Class III). Significant sex-linked differences were also found. Further studies can be performed at multicenter pan-India level with a standard robust protocol and a large sample.