Carabelli Trait in Australian Twins: Reliability and Validity of Different Scoring Systems

Yuh Hasegawa,Graham Scriven,Grant Townsend,James Rogers

doi:10.26575/daj.v23i1.65

Abstract

We assessed the intra- and inter-observer reliability of two methods of scoring or categorizing Carabelli trait in both primary and permanent dentitions (Hanihara, 1961; Dahlberg, 1963). By using dental casts obtained from twins, we also compared the expression of Carabelli trait within and between monozygotic (MZ) co-twins to clarify the ontogenetic processes leading to different forms of trait expression. While intra-observer concordance rates were generally good (70 - 90%), inter-observer concordance rates were poor (35 - 60%). This indicates that considerable caution is needed when comparing data for Carabelli trait derived from different samples by different researchers. By comparing categories or scores for Carabelli trait in both dentitions of MZ co-twins, we found inter-relationships between groove and cuspal forms of the feature. Although the Arizona State University system developed by Turner is commonly used nowadays to score the Carabelli trait, we would encourage researchers interested in clarifying genetic influences and ontogenetic processes in both dentitions to refer to the often over-looked plaque of Hanihara and also Dahlberg’s plaque P12B. This should improve the reliability and validity of data obtained by helping to clarify the inter-relationships between the different phenotypic expressions of Carabelli trait.

Highlights

Carabelli trait is expressed on the mesio-palatal surface trait in the permanent dentition of South Australian of human maxillary molar crowns, primary twins indicated a very strong genetic contribution to second and permanent first molars, and the feature shows observed variation, with an estimate of heritability a quasi-continuous pattern of expression (Harris, 1977). around 90% (Townsend and Martin, 1992)
By using dental casts obtained from twins, we compared the expression of Carabelli trait within and between monozygotic (MZ) co-twins to clarify the ontogenetic processes leading to different forms of trait expression
While intra-observer concordance rates were generally good (70 - 90%), inter-observer concordance rates were poor (35 - 60%). This indicates that considerable caution is needed when comparing data for Carabelli trait derived from different samples by different researchers

Summary

Introduction

Carabelli trait is expressed on the mesio-palatal surface trait in the permanent dentition of South Australian of human maxillary molar crowns, primary twins indicated a very strong genetic contribution to second and permanent first molars, and the feature shows observed variation, with an estimate of heritability a quasi-continuous pattern of expression (Harris, 1977). around 90% (Townsend and Martin, 1992). Carabelli trait is expressed on the mesio-palatal surface trait in the permanent dentition of South Australian of human maxillary molar crowns, primary twins indicated a very strong genetic contribution to second and permanent first molars, and the feature shows observed variation, with an estimate of heritability a quasi-continuous pattern of expression (Harris, 1977). (1999) extended this earlier investigation by analysing metric dental crown traits, are usually based on classifying the expression of Carabelli trait in both the primary and or scoring the feature with reference to standard plaques, permanent dentitions of a large sample of Australian leading to calculations of its frequency of occurrence twins, highlighting the importance of genetic influences and degree of expression. Carabelli trait has been studied extensively within and among human populations, there is still uncertainty about the validity of the different methods of classification, including which is the most suitable to use in primary and permanent dentitions.

Objectives

Methods

Results