Review Article Dental, Oral and Craniofacial Research Dent Oral Craniofac Res, 2017 doi: 10.15761/DOCR.1000197 Volume 3(2): 1-9 ISSN: 2058-5314 Defnition and scoring system of molar incisor hypomineralization: A review Eman Allam 1,2 , Ahmed Ghoneima 1 and Katherine Kula 1 * 1 Department of Orthodontics and Oral Facial Genetics, Indiana University School of Dentistry, Indianapolis, IN, USA 2 Oral and Dental Research Division, National Research Centre, Cairo, Egypt Abstract Objectives: A defnition and classifcation system for molar incisor hypomineralization (MIH) was frst suggested by the European Academy of Pediatric Dentistry (EAPD) in 2003. Since then, there has been growing interest in these mineralization defects due to esthetic and cariogenic susceptibility concerns. Te aim of this review was to evaluate studies on MIH in an attempt to provide evidence for consistency and standardization of MIH defnition and severity scoring reporting by clinicians and researchers. Methods: Included were studies (research papers and reviews) focusing on MIH afected populations and containing a defnition and scoring system. Only English language articles published in the period 2001 to 2015 were considered. Study selection and data extraction were performed by two independent investigators. Results: More than half of the publications used the EAPD defnition and fewer than half of the prevalence reports have either used the EAPD criteria or the developmental defects of enamel (DDE) index as their classifcation system. Others have either incorporated modifcations or created their own scoring criteria. Te lack of standardized defnition and heterogeneity of scoring systems used might explain the considerable variability in prevalence fgures. Conclusion: In order to better defne the diagnostic criteria and the treatment needs for those patients, a globally accepted standardized protocol for scoring system is required. Correspondence to: Katherine Kula, Diplomate, American Board of Orthodontics, Chair and Jarabak Endowed Professor, Department of Orthodontics and Oral Facial Genetics, Indiana University School of Dentistry, 1121 W. Michigan St., Indianapolis, IN 46202, USA, Tel: 317-278-9915, E-mail: kkula@iu.edu Key words: molar incisor hypomineralization, enamel defects, scoring system Received: January 09, 2017; Accepted: January 19, 2017; Published: January 23, 2017 Introduction Molar incisor hypomineralization (MIH) is the term used to describe a special pattern of enamel defects. Te terminology was frst used by Weerheijm et al. [1] describing developmental defects afecting frst permanent molars and permanent incisors, ranging from distinct, isolated, white, yellowish, or brown-colored demarcated opacities to severe post eruptive structural breakdown. Shortly afer MIH terminology was proposed, the European Academy of Paediatric Dentistry (EAPD) announced criteria specifcally aiming at diagnosing and recording MIH [2,3]. Information available on the exact etiology of MIH is limited. A combination of factors that may afect the ameloblasts resulting in abnormal enamel formation has been suggested in most studies. Systemic or environmental insults during the maturation stages of enamel development as well as the possibility of genetic predisposition of ameloblasts to environmental stressors have been reported [4- 6]. Some authors suggest that MIH may be an autosomal recessive condition or an unrecognized form of localized amelogenesis imperfecta. Others have indicated that there is a possible association between MIH and variants in genes related to enamel formation such as AMBN, TUFT1, and TFIP11 [7,8]. A genome-wide association study identifed the SCUBE1 gene on chromosome 22 as a potential genetic locus for MIH [9]. Tere is wide disparity in the reported prevalence fgures of MIH. Te majority of reports are from European populations, with prevalence rates ranging from 5.9% to 38% [10,11]. Other Non-European prevalence data also demonstrate extreme variations with a prevalence rate as low as 2.8 % in Hong Kong [12] and a rate as high as 40.2% in Brazilian children [13]. Te extensive variation in the described rates is suggested to be either due to actual diferences in MIH prevalence between diferent populations, variations in age cohorts, masking of MIH by other conditions, or most importantly, due to the diferent clinical examination protocols used to defne this condition and the non-uniform methods of classifcation and scoring indices [14-17]. Te objective of the current review was to systematically evaluate the studies on MIH to determine the consistency of the use of the current defnition and scoring systems. Methods A broad search of MEDLINE, EMBASE, ResearchGate, and Google Scholar databases was conducted for the years 2001 to 2015, using the index terms ‘molar-incisor-hypomineralization’, ‘MIH’, ‘idiopathic enamel defects in permanent teeth’, ‘hypomineralized permanent molars’ and ‘hypomineralized permanent incisors’. Te search was limited to English language articles. All abstracts were read and the full text of available relevant articles was then reviewed and data were extracted by two authors independently. Te reference list