the term molar incisor hypomineralization ( mih ) has been described as a clinical entity of systemic origin affecting the enamel of one or all first permanent molars and also the incisors ; less frequently , the second primary molars have also been reported to develop hypomineralization of the enamel , along with mih . various studies in relation to the prevalence of mih had been conducted round the globe , reporting its prevalence ranging 2.440.2% investigations on second primary molars with hypomineralization are scarce . were the first to report the prevalence of hypomineralized defects in second primary molars to be 4.9% . hypomineralization increases the chances of development of caries such as the advanced carious lesions masking the hypomineralized surfaces , resulting in underreporting of the prevalence of hypomineralization . among the studies reported on the prevalence of hypomineralization , many had been conducted in the european continent and very few in the asian subcontinent , especially india . therefore , we aimed to scrutinize the association between hypomineralized second primary molars ( hspms ) and mih and their prevalence in school going pupils in nagpur , maharashtra , india and associated severity of dental caries . the present study was a cross - sectional survey conducted through a school - based dental health care program among the randomly selected pupils of public schools situated in the outskirts of nagpur , maharashtra , india . after obtaining ethical approval from the institutional committee and school jurisdiction , pupils with parental informed consent were included . study samples were selected from 1,109 pupils with no medical and systemic illnesses belonging to the 312-year - old age group . children who were absent on the day of the study and those who or whose parents declined consent were excluded . the sample thus obtained was segregated into group i ( 35-year - old age group ) and group ii ( 612-year - old age group ) . the first author was trained in diagnosing hypomineralized defects and caries using photographs from a previous study . the intraexaminer consistency using kappa statistics for precisely detecting both hypomineralization as well as caries parameters was 88 and 100 , respectively . the study was conducted in public schools in natural daylight using mouth mirror ( api , ashoosons , delhi ) and cpi probe ( api , ashoosons , delhi ) . european academy of paediatric dentistry ( eapd ) criteria were used for the assessment of mih and hspm [ appendix 1 ] . all the surfaces ( except the proximal surfaces ) of the second primary molars , permanent incisors , and first permanent molars were examined for hypomineralization defects . in cases of uncertainty related to the lesion severity of hypomineralization defects , also , a defect of less than 2 mm in diameter were recorded as sound . caries in the molars was investigated using the international caries detection and assessment system ( icdas ii ) scoring criteria [ appendix 2 ] . icdas ii code 1 was excluded due to unavailability of the usage of compressed air for drying the teeth . cases exhibiting multiple carious lesions on the same surface were tackled by recording the most severe lesion . all the collected data were entered and computed by statistical software statistical package for the social sciences ( spss ) 17.0 for windows . chi - square test was used for assessing the relationship between the severity of hypomineralization defects and caries . odds ratio was used for calculating the vulnerability for caries among hypomineralized and nonhypomineralized molars . all the collected data were entered and computed by statistical software statistical package for the social sciences ( spss ) 17.0 for windows . chi - square test was used for assessing the relationship between the severity of hypomineralization defects and caries . odds ratio was used for calculating the vulnerability for caries among hypomineralized and nonhypomineralized molars . i , among the 223 subjects , 10 subjects had at least one hspm , resulting in a prevalence rate of 4.88% . in group ii , 63 out of 886 subjects were diagnosed with at least one mih resulting in a prevalence of 7.11% . distribution of hypomineralized teeth according to tooth number is illustrated in tables 2 and 3 . a total of 28 teeth in group i and 183 teeth in group ii were reported with hypomineralization defects . in group i , the mandibular right second deciduous molar ( 35.71% ) and in group ii , the mandibular right first permanent molar ( 30.60% ) were the most frequently affected . in both the groups , the recurrent type of hypomineralized defect was demarcated opacities followed by posteruptive breakdown ( peb ) . none of the subjects were diagnosed with atypical restoration or extracted molars [ table 4 ] . in group ii , out of 63 subjects diagnosed with mih , 30 subjects ( 48% ) also had at least one hspm . a significant positive association was appreciated between the severity of caries and hypomineralized lesions [ table 5 ] . distribution of study groups according to gender distribution of hypomineralized teeth according to tooth number in group i distribution of hypomineralized teeth according to tooth number in group ii distribution of hypomineralized teeth according to type of defect association between hypomineralization and caries on comparing hypomineralized molars and nonhypomineralized molars by their dental caries status in both the groups , it was found that the possibility of occurrence of caries with higher severity was greater in hypomineralized molars compared to nonhypomineralized molars [ figures 1 and 2 ] . distribution of hypomineralized and nonhypomineralized teeth by dental caries status diagnosed according to icdas ii criteria in group i distribution of hypomineralized and nonhypomineralized teeth by dental caries status diagnosed according to icdas ii criteria in group ii enamel hypoplasia is a quantitative defect resulting due to disturbance to the enamel - forming cells during the stage of formation of matrix , whereas hypomineralization is a qualitative defect resulting due to disturbance occurring during the maturation stage of enamel formation . in the literature , various terminologies had been used to describe these demarcated enamel opacities and breakdowns such as internal enamel hypoplasia , cheese molars , nonendemic enamel mottling , idiopathic demarcated opacities , and nonfluoride hypomineralization . in 2001 , weerheijm termed it mih because first permanent molars with hypomineralization are often related to affected permanent upper incisors and rarely lower incisors . the presence of hypomineralization defects can considerably affect the child 's overall well - being . various criteria had been used for the diagnosis of idiopathic enamel defects before the establishment of the eapd criteria in 2003 . these include the modified developmental defects of enamel ( dde ) index proposed by federation dentaire internationale ( fdi ) and used by jalevik et al . and weerheijm et al . , the one proposed by alalausua et al . and used by leppaniemi et al . according to the reports on mih , the large variation in the prevalence and severity in the data appearing in the various studies worldwide were partly due to the different criteria used in the past for diagnosis of mih . therefore , in the current study , assessment of hypomineralization defects was performed using the criteria recommended by the eapd in 2003 . in the present study , the studies that had used similar criteria reported a prevalence rate of 4.9% and 6.6% in the netherlands and iraq , respectively . prevalence of mih in group ii was 7.11% , which was in line with other studies conducted in gujarat ( 9.2% ) , udaipur ( 9.46% ) , and chandigarh ( 6.31% ) in india as well as in lithuania ( 9.7% ) and turkey ( 9.2% ) . variations in the prevalence rate reflect the real differences between regions and countries , and differences in recording methods , indices used and populations investigated . in group ii , 30 subjects ( n = 48% ) out of 63 subjects reported with at least one hspm , along with mih indicating that hspm could act as a predictor for mih . demarcated opacities were the most common form of hypomineralization defect , accounting for 80% in group i and 76% in group ii . second in the sequence was posteruptive breakdown , which was in accordance with the study conducted in iraq using the same diagnostic criteria . in the present study , mandibular molars were comparatively more affected in both the age groups . , baskar and hegde , and jasulaityte et al . however , it differed from studies conducted by weerheijm et al . and it had been suggested that differences in examination conditions may make it difficult to view maxillary molars as clearly as mandibular molars . in addition , the early eruption of mandibular molars with resultant early posteruptive enamel breakdown or caries makes them more prone than maxillary molars . in the present study , it has been shown that hypomineralization plays a vital role for caries development in the primary dentition . in the permanent dentition , this greater incidence of dental caries , combined with compromised , defective enamel results in substantial dental morbidity , which presents a challenge to the clinician . the present study has certain pitfalls ; first , the age group might not represent the exact prevalence as a younger age group was included and in group ii , pupils with the presence of second primary molar and first permanent molar were included . another pitfall is the small sample size used for analyzing the susceptibility of hypomineralized teeth for caries study . however , the present study had provided substantial data for future research on mih and hspm . the most commonly encountered type of hypomineralization defect was demarcated opacities . in group ii , 48% of the subjects diagnosed with mih had at least one hspm . dental caries was more common in hypomineralized molars implicating that hypomineralization plays a critical role in deterioration of the affected tooth and there is a need for increasing the awareness regarding hypomineralization defects and its early prevention . criteria for scoring hypomineralization defects ( eapd , 2003 ) international caries detection and assessment system ii ( 2007 ) criteria for scoring hypomineralization defects ( eapd , 2003 ) international caries detection and assessment system ii ( 2007 )