THE PREVALENCE AND SEVERITY OF MOLAR INCISOR HYPOMINERALIZATION IN A GROUP OF CHILDREN LIVING IN ANKARA TURKEY

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1 CLINICAL DENTISTRY AND RESEARCH 2013; 37(1): THE PREVALENCE AND SEVERITY OF MOLAR INCISOR HYPOMINERALIZATION IN A GROUP OF CHILDREN LIVING IN ANKARA TURKEY Hayriye Sönmez, DDS, PhD Professor, Department of Pediatric Dentistry, Faculty of Dentistry, Ankara University, Ankara, Turkey Gözde Yıldırım, DDS, PhD Research Assistant, Department of Pediatric Dentistry, Faculty of Dentistry, Ankara University, Ankara, Turkey Tuğba Bezgin, DDS, PhD Research Assistant, Department of Pediatric Dentistry, Faculty of Dentistry, Ankara University, Ankara, Turkey ABSTRACT Background and Aim: Little prevalence data relating to molar incisor hypomineralization (MIH) exist for Turkey. The aim of this study was to investigate the prevalence and severity of MIH in two different age groups of Turkish children. Materials and Methods: A total of 4,018 children in Ankara, Turkey participated in the study. A younger group was comprised of children in Grade 2 aged 7-9 years (median age: 8.0), and an older group was comprised of children in Grade 5 aged years (median age: 11.1). MIH was diagnosed based on the European Association of Pediatric Dentistry criteria. The data was analyzed using Pearson s Chi-square, Fisher s Exact, Spearman s correlation and McNemar s tests. Results: MIH was found to be prevalent at a significantly higher rate (p<0.05) among the younger group (8.5%) when compared to the older group (6.5%). Mild defects (whitecream and yellow-brown demarcated opacities) affecting first permanent molars were significantly higher in the younger age group (p<0.05), whereas atypical deep, large cavities, atypical restorations and extracted first permanent molars were significantly higher in the older age group (p<0.05). Conclusion: The present study found that MIH was present in 7.7% of 4,018 children and that severity of lesions increased with age. These results indicate that preventive approaches are very important at an early developmental age. Correspondence Hayriye Sönmez, DDS, PhD Department of Pediatric Dentistry, Faculty of Dentistry, Ankara University, Besevler, 06500, Ankara, Turkey Phone: Fax: hayriyesonmez@hotmail.com Key words: Central Turkey, Hypomineralization, Molar Incisor Prevalence, Severity, Urban Submitted for Publication: Accepted for Publication :

2 CLINICAL DENTISTRY AND RESEARCH INTRODUCTION Severely hypomineralized enamel of permanent incisors and first permanent molars (FPM) of unknown etiology was first reported in an epidemiological study 1 carried out in Sweden in the 1970s. Until Weerheijm et al. 2 suggested the term Molar Incisor Hypomineralization (MIH), various terms were used to describe the hypomineralization of systemic origin in first permanent molars frequently associated with affected incisors, including Idiopathic enamel hypomineralization 1, Cheese molars 3 and Non-fluoride enamel hypomineralization 4. In 2003, a seminar was held to establish the judgment criteria for MIH and experts agreed upon the following criteria, developed by Weerheijm et al. 5, to differentiate MIH from other developmental enamel defects. MIH differs from acquired enamel disorders such as dental fluorosis and Turner s teeth and from hereditary enamel disorders such as amelogenesis imperfecta. Clinically, MIH lesions are demarcated by a whitish-yellow or yellowish-brown color on a smooth enamel surface, with no alteration in thickness. Teeth affected by MIH are highly sensitive and difficult to adequately anesthetize, which can result in behavioral problems and anxiety. 6 MIH also has functional implications due to the post-eruptive enamel breakdown of first permanent molars, which is the result of occlusal loading during mastication and which is characterized by irregular enamel loss followed by rapid caries progression. Whereas severely affected first molars sometimes require extraction within the first few years after their eruption into the oral cavity, incisors affected by MIH rarely exhibit post-eruptive breakdown. 3,7-9 Fagrell et al. 10 found the hypomineralized enamel in teeth diagnosed with MIH to have significantly lower hardness values than normal enamel. A variety of medical factors have been proposed in the etiology of MIH, including prenatal, perinatal and postnatal illnesses; low birth weight; antibiotic consumption; genetic predisposition; and exposure to toxins during breastfeeding; however, there is still no agreement as to the exact etiology of MIH Children who had a disease history during the first 3-4 years of life are believed to be more likely to be affected by more severe MIH Jalevik 16 stressed agreement on examination criteria and good, comparable studies are of utmost importance in trying to elucidate the phenomenon MIH. Earlier studies 1,3,4,7,8,11,14,17-26 reported a prevalence ranging between 2.8% and 40.2%. Comparison of the results of these various studies remains difficult because of the use of different indices and criteria, examination variability, methods of recording and different age groups. 16 A previous study of 250 Turkish children 27 that used earlier criteria found a prevalence of 14.5% in Western Turkey. Two other studies 14,22 carried out with Turkish children using the 2003 EAPD criteria to diagnose MIH in a clinical population and a school population reported a prevalence of 14.9% and 9.1%, respectively for northwestern Turkey. However, data from central Turkey is lacking, and therefore, the objective of the present study was to evaluate the prevalence and severity of MIH in two different age groups of Turkish children living in Ankara, Turkey. MATERIALS AND METHODS The present study was approved by the Ankara University, Faculty of Dentistry, Ethics Committee. A complete list of schools was obtained from the Ministry of Education. The study was comprised of a total of 4,049 children 2,024 in Grade 2 (1,015 girls, 1,009 boys) and 2,025 in Grade 5 (1,014 girls, 1011 boys) enrolled in 16 primary schools randomly selected from among the 121 primary schools located in the urban areas of the 5 central municipalities of Ankara, Turkey. Children in Grade 2 ranged in age from 7-9 yrs (median age: 8.0), whereas children in Grade 5 ranged in age from yrs (median age: 11.1). The water supply in Ankara is non-fluoridated. Children were examined for MIH in school environment in daytime classroom lighting conditions while sitting upright in an ordinary school chair. Teeth were examined wet, as suggested by the FDI Working Group, 28 using a mirror and periodontal probe, which was used to measure the diameter of the lesions; and cotton rolls were used to remove food debris, as necessary. Four first permanent molars (FPM) and eight incisors in each child were evaluated according to an index developed in line with EAPD criteria 5 : Opacities (White-cream, 1; Yellow-brown, 2); Post-eruption structural loss (Enamel defects, 3a; Atypical small cavities with enamel and dentin loss, 3b; Atypical deep or large cavities extending to the pulp and covering one or more tubercle, 3c); Restored teeth, 4; Extracted teeth, 5. Lesion severity was recorded according to Alaluusua et al. 11 as either mild, moderate, or severe (Table 1). Children with generalized enamel defects, lesions smaller than 2 mm, or FPMs that were not fully erupted were excluded from further evaluation. Teeth that were erupted to less than one-third of the crown height were considered to be unerupted. The presence of permanent incisors affected by hypomineralization was considered insufficient 36

3 Molar Incisor Hypomineralization in Turkey Table 1. Severity criteria for diagnosing MIH among first permanent molars and incisors Code Description Severity 0 No defect 1 White or creamy demarcated opacities 2 Yellow or brown demarcated opacities Mild 3a Enamel loss Moderate 3b Enamel and dentin loss Atypical large cavities extending to pulp and covering one or 3c more tubercle 4 Atypical restorations Severe 5 Extracted tooth for a diagnosis of MIH; rather, at least one affected FPM was required for a diagnosis of MIH. Extracted FPMs were recorded as affected if another FPM had a defect indicating MIH. To inform parents and indicate the need for treatment, each child affected with MIH was given a letter outlining their dental health status. All examinations and registrations were undertaken by the same pediatric dentist, and intra-examiner calibration was performed by repeating the examination of 300 children following an interval of one week. Kappa values for intraexaminer consistency were 93.5% for teeth with MIH and 99.6% for healthy teeth, and Kappa coherence was Statistical analysis was performed using the program SPSS 12.0 (SPSS 12.0 for Windows, SPSS Inc., Chicago, Illinois, USA). Data was assessed using Pearson s Chi-square, Fisher s Exact, Spearman s correlation and McNemar s tests, where a p-value of less than 0.05 considered to be statistically significant. Pearson s Chi-square or Fisher s Exact tests were utilized for nominal or ordinal variables. Spearman s correlation test was used to express the association between the number of affected incisor and molar teeth and the severity of affected FPMs. McNemar s test was used to test for differences in the occurrence of MIH between mandible and maxilla and between left and right sides of the mouth. RESULTS Initial evaluations showed 31 children from Grade 2 had FPMs that were not fully erupted, and these children were excluded from further study. MIH was observed in 308 (7.7%) of the remaining 4,018 children. MIH prevalence was higher among the younger group of children (8.5%, n=170) than the older group (6.5%, n=138), and the difference between the two groups was statistically significant (p<0.05). No significant differences were found between MIH prevalence in girls and boys (p>0.05) or right and left sides of the jaw (p>0.05). Although no difference was observed between the number of affected FPMs in the maxilla and mandible (p>0.05), more defects were seen in mandibular incisors than in maxillary incisors (p<0.05) (Table 2). Of a total 16,072 FPMs, 435 in the younger group and 362 in the older group were affected by MIH. From a total 308 children with MIH, 58 (18.8%) had lesions in all four FPMs, 85 (27.6%) had lesions in three-fpms, 145 (47.1%) had lesions in two-fpms and 20 (6.5%) had lesions in only one FPM. In a total 27,189 incisors, 164 in the younger group and 174 in the older group were affected by MIH. Of the 308 children with MIH; 115 children (37.3%) had only one incisor affected and 39 children (12.6%) had 2 incisors affected. In total, 174 children (85 in the younger group and 89 in the older group) had MIH lesions on both FPMs and incisors. Figures 1 and 2 show the intraoral distribution of affected FPMs and incisors. The mean numbers of affected FPMs and incisors were 2 and 1, respectively. Although no significant correlation was found between the number of affected FPMs and incisors (p>0.05), a significant positive correlation was found between the total number of severely affected FPMs and the total number of affected FPMs as well as the total number of affected incisors (r=0.460; r=0.150) (p<0.05). Table 3 shows the severity and types of defects of affected FPMs. Mild defects were present in 54.7% of affected molars in the younger group and 32.8% of affected molars in the older group; the difference between the groups was statistically significant (p<0.05). Moderate defects were present in 9.6% of affected molars in the younger group and 6.1% of affected molars in the older group; the difference between groups was not statistically significant (p>0.05). Severe defects were present in 35.7% of affected molars in the younger group and 61.6% of affected molars in the 37

4 CLINICAL DENTISTRY AND RESEARCH Table 2. Prevalence of MIH among maxillary and mandibular first permanent molars and incisors Mandibular Maxillary Right Left Affected Permanent First Molars Affected Permanent Incisors 80.7% 80.7% 91.5% 91.5% P>0.05 P> % 25% P<0.05 DISCUSSION Figure 1. Maxillary distribution of affected first permanent molars and incisors Figure 2. Mandibular distribution of affected first permanent molars and incisors older group; the difference between groups was statistically significant (p<0.05). Table 4 shows the severity and types of defects of affected incisors. 76.2% of the affected incisors in the younger group and 79.3% of the affected incisors in the older group presented white-creamy opacities ( 1 ) and the difference between the groups was statistically significant, but there was no difference in the rate of yellow-brown defects ( 2 ) or in the rate of defects with enamel loss ( 3a ) between the two age groups (p>0.05). Structural loss and atypical restorations were not found in incisors diagnosed with MIH. In this study, the overall prevalence of MIH in a group of school children living in Ankara Turkey was found to be 7.7%. Eight years of age has been suggested as the appropriate age for diagnosing MIH because the eruption of the FPMs and the majority of permanent incisors are usually complete by this age. 5,8,13 However, regarding the reported variation between age groups 1,29, Jalevik 16 recommended to report the frequency of MIH for different age groups separately. The present study included a group of older children in order to examine the possibility of defect progression and possible loss of affected teeth with age. A study by da Costa Silva et al. 24 stressed the importance of including the extent of the lesion defect among the criteria for diagnosing MIH. Whereas some studies have included any visible defect, regardless of size, as evidence of MIH, this study included only demarcated opacities of at least 2 mm, as suggested by Jalevik et al. 8 Differences in reported rates of MIH throughout the world have been attributed to differences in the age of study participants, geographic locations, environmental factors and evaluation criteria ,20,24 The present study was based on the 2003 EAPD criteria 5 and found MIH prevalence to be 8.5% among younger children (mean age: 8.0) and 6.5% among older children (mean age: 11.1). A previous study of 250 Turkish children 27 that used earlier criteria found a prevalence of 14.5%, which is nearly twice as high as the present study. Two other studies 14,22 carried out with Turkish children using the 2003 EAPD criteria to diagnose MIH in a clinical population and a school population reported a prevalence of 14.9% and 9.1%, respectively. Given the similarity in age groups among these studies, the difference in findings may be ascribed to differences in sample size, geographic locations and environmental factors. In this study, children were examined in school environment and in daylight conditions without using artificial light. Thus, the lower prevalence rates compared to other studies were probably related to this difference in examination procedure. The present study found the prevalence of MIH to be significantly higher among younger children (mean age: 8 38

5 Molar Incisor Hypomineralization in Turkey Table 3. Distribution of affected FPMs by age and tooth number 8 year old 11 year old Defects Mild n % n % n % n % n % n % n % n % , , , ,0 9 10, , , , , , , , , , , ,1 Moderate 3a 12 12,4 8 7,2 10 8, ,4 8 9,1 1 1,1 6 6,2 7 8,4 3b 16 16,5 11 9, , , , , ,3 3 3,6 Severe 3c 8 8, , ,3 10 8, , , , , ,3 6 5, , , , , , , , ,4 3 3, , ,5 Total Table 4. Distribution of affected incisors by age and tooth number Teeth no Defects Mild Moderate 1 2 3a Total n % n % n % n % ,5 6 15,4 2 5, , ,3 1 2, years ,6 4 14,3 2 7, ,3 3 16, ,6 3 21, ,1 5 13, ,1 3 42, years , , ,8 4 13,8 1 3, ,6 2 15, ,9 1 4,5 3 13, ,7 3 33, years) when compared to older children (mean age: 11.1 years). This finding conflicts with that of da Costa-Silva et al. 24, who reported an increasing prevalence of MIH with age. It is possible that the rate of MIH among the older group of children in the present study was affected by the fact that children with one or more extracted FPMs and defect-free incisors were not diagnosed with MIH due to the difficulty in accurately diagnosing MIH in such cases. Considering that MIH etiology is probably related to a systemic disturbance, 1 it may also be hypothesized that a specific environmental factor was present during the development of FPMs and incisors in the younger group. 39

6 CLINICAL DENTISTRY AND RESEARCH Although a few studies have indicated a higher prevalence of MIH in girls than boys, 19,20 in line with most previous studies, 4,8,18,24,30 the present study found the prevalence of MIH to be similar for boys and girls. The present study found a similar rate of defects among mandibular and maxillary FPMs, but a higher rate of defects among mandibular incisors when compared to maxillary incisors. Weerheijm et al. 3 and Cho et al. 19 also found similar distributions of hypomineralized molars between arches, whereas other studies reported contradictory findings. 17,18,20 Also, in contrast to the findings of the present study, most other studies have reported maxillary incisors to be more affected by MIH than mandibular incisors. 17,18,20,26 Differences in findings related to incisors could be attributed to the fact that this study did not classify lesions smaller than 2 mm as MIH; that opacities in incisors without molar involvement were not diagnosed as MIH; and that children were evaluated even if all 8 incisors had not erupted. The number of FPMs reported to be affected by MIH has varied from 1.6 to ,18,20,26,29,30 This study found an average number of 2 affected FPM molars and 1 affected incisor. No significant correlation was found between age groups and the number of affected teeth. However, in line with the reports of Jalevik et al. 8 and Jasulaityte et al. 30, the present study found a positive relationship between the number of severely affected molars and the total number of affected FPMs and incisors. The present study also found 56.5% of children diagnosed with MIH presented lesions in both FPMs and incisors. This finding is similar to the results of other Turkish studies, 14,22 yet in this study the results were much higher than the results reported by da Costa-Silva et al. 24 The prevalence of MIH in incisors and molars concomitantly may have been underestimated by the facts that the present study did not classify lesions smaller than 2 mm as MIH, and that children were evaluated even if all 8 incisors had not erupted; however, this methodology did not affect the overall prevalence of MIH reported in the study. The severity of MIH lesions may vary from demarcated opacities to structural loss resulting in atypical restorations or crown destruction. 5 The present study evaluated three degrees of post-eruptive structural loss, namely, cavities with enamel loss ( 3a ), cavities with enamel and dentin loss ( 3b ) and atypical large cavities extending to the pulp and covering one or more tubercle ( 3c ). The severity of hypomineralized teeth was also classified according to Alaluusua et al. 11 as either mild (color change: white or brown), moderate (loss of enamel only), or severe (loss of enamel in association with affected dentine). Mild defects in FPMs were found at significantly higher rates in the younger group, whereas severe defects were found at significantly higher rates in the older group. There were no significant differences in the rates of moderate defects between the groups. These findings are similar to those of the previous studies. 18,20,24,26 The higher rate of severely affected FPMs among older children may be explained by the fact that enamel loss due to occlusal load leads to the rapid progression of caries, and because of the sensitivity associated with MIH, children avoid brushing, resulting in destruction of the affected teeth. 9,24 Extraction of FPMs may occur as a result of MIH lesions involving pulpal tissue. In the present study, the extraction rate of affected FPMs was significantly higher among older children with MIH (17.4%) than among younger children with MIH (0.60%). This finding points to the importance of initiating prophylactic and/or restorative treatment as soon as possible after eruption when enamel breakdown of FPMs is observed. The incisors of the MIH affected children revealed demarcated enamel opacities ( 1 and 2 ) and enamel loss ( 3a ) with higher rate of opacities for both age groups. This finding tends to be in line with most other studies which found affected incisors to have rarely exhibited posteruptive breakdown because of the absence of masticatory forces upon these surfaces. 14,18,20,24,30 CONCLUSION The first step in effective management of MIH should be the implementation of comparable, representative studies of MIH prevalence among different populations throughout the world. The present paper adds new prevalence data to international MIH records. Children with MIH require therapy shortly after tooth eruption. This study shows that the severity of MIH lesions increases with age. Therefore, dentists must be aware of the clinical consequences and pay special attention to children with MIH. CONFLICT OF INTEREST We have no financial relationship with the organization that sponsored the research and all authors declare that no conflict of interest in this manuscript. REFERENCES 1. Koch G, Hallonsten AL, Ludvigsson N. 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