Monozygotic twins are expected to be genetically identical, yet they seldom exhibit different phenotypes. Such rare occasions present a unique opportunity to untangle the role of epigenetic and environmental influence on the genetic expression of certain traits or diseases. Dental caries is a dynamic sugar- driven and biofilm-mediated disease of the dental hard tissues that can result in demineralisation and eventual structure loss if uninterrupted. The disease involves complex interplay between environmental and genetic factors. The relative contribution of potential etiological factors can be unravelled by studying monozygotic twins.

This case study involved a pair of 6-year-old monozygotic female twin who were referred for dental treatment. A thorough relevant medical and dental histories were obtained followed by a comprehensive clinical and radiographic assessment for both patients. In addition, insights into their oral hygiene practices and dietary habits were gained. Differences in their dentition and oral health status were recorded. By presenting these differences, this report sought to highlight the impact of environmental factors in modifying the phenotypic expression in genetically-identical individuals. 

Monozygotic twins are expected to be genetically identical, yet they seldom exhibit different phenotypes. Such rare occasions present a unique opportunity to untangle the role of epigenetic and environmental influence on the genetic expression of certain traits or diseases. Dental caries is a dynamic sugar- driven and biofilm-mediated disease of the dental hard tissues that can result in demineralisation and eventual structure loss if uninterrupted. The disease involves complex interplay between environmental and genetic factors. The relative contribution of potential etiological factors can be unravelled by studying monozygotic twins.

This case study involved a pair of 6-year-old monozygotic female twins who were referred for dental treatment. A thorough relevant medical and dental histories were obtained followed by a comprehensive clinical and radiographic assessment for both patients. In addition, insights into their oral hygiene practices and dietary habits were gained. Differences in their dentition and oral health status were recorded. By presenting these differences, this report sought to highlight the impact of environmental factors in modifying the phenotypic expression in genetically-identical individuals.