DOI: 10.1111/ipd.12100
Prevalence of molar incisor hypomineralization (MIH) in Singaporean children JING JING NG1, OY CHU EU2, RAHUL NAIR3 & CATHERINE HSU LING HONG4 1
Private Practice, Singapore, Singapore, 2School Dental Service, Health Promotion Board, Singapore, Singapore, 3Discipline of Oral Sciences, National University of Singapore, Singapore, Singapore, and 4Discipline of Orthodontics and Paediatric Dentistry, Faculty of Dentistry, National University of Singapore, Singapore, Singapore
International Journal of Paediatric Dentistry 2014 Background. There is a lack of data on molar inci-
sor hypomineralization (MIH) in Asia, but this is not an indication that MIH is rare in the Asian population. Early identification of MIH is important as affected teeth frequently display post-eruptive enamel loss which would result in rapid caries progression. Aim. This objective of this study was to assess the prevalence of MIH in Singaporean children. Design. Patients were recruited from 30 schools across Singapore. All children were examined by a single dentist, and the judgement criteria used were based on the 2003 European Academy of Paediatric Dentistry criteria.
Introduction
The occurrence of white to yellow-brown enamel opacities in the first permanent molars was first recognized in Sweden in the late 1970s1. This phenomenon was subsequently coined molar incisor hypomineralization (MIH). The currently accepted definition of MIH by European Academy Paediatric Dentistry (EAPD) is enamel hypomineralization of unclear origin of 1 to 4 permanent first molars, frequently associated with affected incisors2. Recent studies have also reported similar defects in second primary molars, incisors, and the tips of the canines3–5. Clinically, MIH can vary from mild demarcated opacities to severe structural loss. The defects can be white, yellow, or brown in colour, but they will show a clear demarcation between the affected and normal enamel6. Correspondence to: Catherine H. L. Hong, Discipline of Orthodontics and Paediatric Dentistry, Faculty of Dentistry, National University of Singapore, Singapore, Singapore. E-mail: [email protected]
Results. A total of 1083 children; average age of 7.7 0.3 years were examined. One hundred and thirty-five children (12.5%) had MIH. A significantly higher proportion of children of the Malay ethnicity had MIH, compared to Chinese children (P = 0.02). Post-eruptive enamel breakdown and the presence of atypical restorations were correlated with increasing number of MIH teeth/child (Rho= 0.599, P < 0.001) and the cumulative enamel opacity colour score (Rho = 0.601, P < 0.001). Conclusions. Our findings suggest the role of ethnicity in MIH occurrence and that MIH severity may be influenced by the number of MIH teeth/ child and the cumulative enamel opacity colour score.
The hypomineralized part of the tooth is weak, and the enamel may chip off easily, resulting in post-eruptive loss of enamel. Some authors have suggested that the colour of opacity may be suggestive of weaker tooth structure and subsequently higher risk for post-eruptive enamel breakdown7. Post-eruptive enamel loss is a definite risk factor for rapid caries progression which in turn can cause severe pain8. As such, it is important for clinicians to identify and manage these affected teeth early. A number of MIH studies have been published in dental journals from various parts of the world and the reported prevalence of MIH ranges from 2.4% to 40.2%9. Currently, the majority of the prevalence data are based on studies from Europe, and at the time of write up of this manuscript, there had been only two published studies from Asia (Hong Kong and India)10,11. The lack of data, however, is not an indication that MIH is a rarity in the Asian population. Based on one of the authors’ observation, MIH is not uncommon in children in Singapore and has been observed periodically during routine dental examinations conducted by the School Dental Service. The
© 2014 BSPD, IAPD and John Wiley & Sons A/S. Published by John Wiley & Sons Ltd
1
2
J. J. Ng et al.
School Dental Service is a federal/governmentfunded programme where all school-going children between the ages of 7 to 18 years are entitled to free dental examination and treatment. Presently, approximately 97% of schoolgoing children between 7 and 12 years of age are registered in this programme. As Singapore is a multiracial country with a diverse and different ethnic resident population (77% Chinese, 14% Malays, 8% Indians) from that of western countries, the prevalence of MIH in Singapore may also differ. As such, extrapolation of prevalence data from these countries to the local context may be inaccurate. There is clearly a lack of data on MIH prevalence from this region of the world based on a review of the literature; this study therefore aimed to assess the prevalence of MIH in Singaporean children. Materials and methods
Patients for this study were recruited from 30 schools across the Singapore Island. In Singapore, elementary schools are grouped into four zones (North, South, East, and West regions of the Singapore Island) by the Ministry of Health. As such, the School Dental Service also divides the school dental clinics into the same four respective zones. Each zone comprises of 40 to 45 dental clinics; the clinics are further subgrouped into seven to eight groups based on geographical location. One school was selected from each group to make up a total of 30 schools to ensure that there would not be a geographical biasness in the selected sample population. Forty-five children born in the year 2003 were randomly selected for the examination from each school. The children were chosen based on their class identification numbers. The first 15 children with odd-numbered class identification numbers were selected from the first class, the next 15 children with evennumbered class identification numbers were selected from the next class, and the remaining 15 children with odd-numbered class identification numbers were selected from the last class. All the children were examined by a single dentist (Dr Ng Jing Jing) at the school’s
on-site dental clinic. The judgement criteria used for identifying MIH were based on the 2003 EAPD criteria2. The following were also recorded: 1. colour of the demarcated enamel opacity (white: 1, yellow: 2, brown: 3); a cumulative enamel opacity colour score was created for each patient by adding the individual tooth colour opacity score (e.g., if the patient had 2 affected MIH teeth, the cumulative score would be the sum of colour opacity score from both teeth); 2. caries experience as measured by the Decayed, Missing, Filled Teeth (DMFT) and dmft indexes; and 3. second primary molars affected by MIH. These details were also elicited from the dental records: medical history, dental history, and previous dental treatment. In this study, only healthy children with no significant medical conditions (American Society of Anaesthesiologists physical status classification 1 and 2) were examined. Enamel defects other than MIH were excluded; these included teeth affected by Amelogenesis Imperfecta and chronologic enamel hypoplasia. All statistical analyses were performed using IBM SPSS (Statistical Package for the Social Sciences) version 20.0 (New York, NY, USA). Descriptive statistics were carried out followed by nonparametric bivariate analysis, which was used to determine the relationships between variables. Results
Demographics A total of 1083 children; average age of 7.7 0.3 years were examined. The male-tofemale ratio was 1:1.3. Of the 1083 children examined, 65.5% (n = 709) were Chinese, 12.7% were Malay (n = 137), 11.5% (n = 125) were Indian, and 10.3% (n = 112) were of other minority races. Further details of demographics are listed in Table 1. The overall DMFT and dmft were 0.1 0.5 and 2.4 3.2, respectively. Molar Incisor Hypomineralization One hundred and thirty-five children (12.5%) were affected with MIH. Children
© 2014 BSPD, IAPD and John Wiley & Sons A/S. Published by John Wiley & Sons Ltd
MIH in Singaporean children
Table 1. Demographics. Children without MIH Variables
n
%
Gender Male 408 42.3 Female 540 57.7 Ethnicity Chinese 626 57.8 Malay 111 10.3 Indian 108 10.0 Others 103 9.5 Caries status (Mean SD) dmft 2.4 3.2 DMFT 0.1 0.4
Children with MIH
Total sample
n
%
n
%
67 68
49.6 50.4
475 608
43.9 56.1
83 26 17 9
7.7 2.4 1.5 0.8
709 137 125 112
65.5 12.7 11.5 10.3
2.5 3.1 0.3 0.7
2.4 3.2 0.1 0.5
Table 2. Distribution of children with teeth affected by MIH.
Type of MIH in children First permanent molars affected only First permanent molars and incisors affected only First permanent molars and second primary molars affected only First permanent molars and second primary molars and incisors affected only Second primary molars affected only Second primary molars and incisors only
n by patient (%) 74 (6.8) 30 (2.8) 4 (0.4) 2 (0.2) 23 (2.1) 2 (0.2)
3
significant difference in the number of MIH teeth/child among the various ethnic groups. Two hundred and ninety-eight teeth were affected by MIH, of which 180 were first permanent molars, 52 were second primary molars, and 66 were permanent incisors (Table 3). There were no significant differences in the frequency of MIH occurrence between the maxillary and mandibular arch (P = 0.19). Among the 180 permanent molars with hypomineralization, 30% (n = 54/180) had post-eruption breakdown or atypical restorations. Seven permanent maxillary incisors had post-eruption breakdown or atypical restorations. In the primary dentition, 11 molars affected by MIH had post-eruption breakdown or atypical restorations. The most common opacity was yellow in colour (n = 128), followed by white (n = 80), and brown opacities (n = 78). Further information on individual tooth is illustrated in Table 3. The number of teeth with enamel breakdown and atypical restorations was correlated with the number of MIH teeth/child (Rho = 0.599, P < 0.001) and the cumulative enamel opacity colour score/child (Rho = 0.601, P < 0.001). Discussion
with hypomineralization only affecting the incisors were excluded as in accordance with the EAPD criteria. The average number of teeth affected by MIH per child was 2.2 (range: 1–13). Majority of children with MIH (71.1%, n = 96) had either 1 (42.2%, n = 57) or 2 (28.9%, n = 39) MIH-affected teeth/ child. The average number of molars affected/ child was 1.7 (range: 1–8). Of the 135 children, 46.7% (n = 63) had one affected permanent molar, 22.2% (n = 30) had two affected permanent molars, 8.1% (n = 11) had three affected permanent molars, and 4.4% (n = 6) had four affected first permanent molars. Table 2 illustrates the distribution of children with teeth affected by MIH. Higher proportions of children of the Malay ethnicity were found to have MIH compared to Chinese children (P = 0.02). There was no
Early identification of MIH is important as affected teeth frequently display post-eruptive enamel loss which in turn would result in rapid caries progression and ensuing pain. Despite the importance for early diagnosis, MIH prevalence data are lacking from this region of the world; as such, we embarked on a study to assess the prevalence of MIH in Singaporean children. In our study, we found that the prevalence of MIH in Singapore was 12.5% with a mean number of MIH teeth per child of 2.2; these statistics are comparable to other studies that have examined children of similar ages (between 7 and 8 years) as specified by the EAPD criteria9,12,13. As with many studies in the literature, gender was not significantly associated with the MIH in our study9,10. A handful of studies have indicated a higher prevalence of MIH in girls than boys, but authors have speculated that this may be
© 2014 BSPD, IAPD and John Wiley & Sons A/S. Published by John Wiley & Sons Ltd
4
J. J. Ng et al.
Table 3. Distribution of molars with MIH by tooth number, colour, and status of enamel integrity. Colour of enamel opacities of MIH teeth
Indexed teeth Permanent dentition 16 26 36 46 Perm. 1st molars 12 11 21 22 Max. Perm. incisors 32 31 41 42 Mand Perm. incisors Primary dentition 55 65 75 85 Pri. 2nd molars
Total number of teeth present
Number of MIH teeth n (%)
Number of MIH teeth with non-intact enamel or atypical restorations, n (%)
White n (%)
Yellow n (%)
Brown n (%)
994 1002 1048 1041 4085 354 889 900 354 2497 832 1066 1068 830 3796
45 33 55 47 180 5 11 13 4 33 9 10 14 0 33
(4.5) (3.3) (5.3) (4.5) (4.4) (1.4) (1.2) (1.4) (1.1) (1.3) (1.1) (0.9) (1.3) (0) (0.9)
8 11 17 18 54 1 2 3 1 7 0 0 0 0 0
(0.8) (1.1) (1.6) (1.7) (1.2) (0.3) (0.2) (0.3) (0.3) (0.2) (0) (0) (0) (0) (0)
7 (0.7) 3 (0.3) 19 (1.8) 10 (1.0) 39 (1.0) 1 (0.3) 5 (0.6) 7 (0.8) 2 (0.6) 15 (0.6) 1* 6 (0.6) 4* 0 (0) NA
29 (0.3) 17 (1.7) 21 (2.0) 22 (2.1) 89 (2.2) 4 (1.1) 5 (0.6) 5 (0.5) 2 (0.6) 16 (0.6) 4* 3 (0.3) 2* 0 (0) NA
9 (0.9) 13 (1.3) 15 (1.4) 15 (1.4) 52 (1.3) 0 (0.0) 1 (0.1) 1 (0.1) 0 (0.0) 2 (0.1) 0* 1 (0.1) 0* 0 (0) NA
1071 1068 1069 1069 4277
15 15 9 13 52
(1.4) (1.4) (0.8) (1.2) (1.2)
2 6 1 2 11
(0.2) (0.6) (0.1) (0.2) (0.3)
3 3 4 5 15
5 3 3 3 14
7 9 2 5 23
(0.3) (0.3) (0.4) (0.5) (0.4)
(0.5) (0.3) (0.3) (0.3) (0.3)
(0.7) (0.8) (0.2) (0.5) (0.5)
*Has missing colour data.
attributed to females having a greater number of erupted permanent molars and incisors compared to their male counterparts of the same age, resulting in the disparity of MIH prevalence between genders14. Our study is unique in that unlike the European studies, our target sample was made up of three distinct races, which is quite different from the population sampled in the studies from the western countries. We found that the prevalence of MIH in Singaporean children of Chinese ethnicity (11.7%) was much higher than in Hong Kong Chinese children (2.8%)10. This may be due to an underestimation of the MIH prevalence in the Hong Kong study, which the authors of the study also acknowledged, attributing this limitation to the retrospective nature of the study design. In the other recent study by Mittal et al., the authors found that the MIH prevalence of children from Northern India was 6.3%11. This figure is lower than the MIH prevalence of children of Indian ethnicity in our study (13.6%). Mittal’s et al. study was based in North India and
therefore sampled Northern Indians; however, Singaporean Indians are largely of Southern Indian descent, and this may have contributed to the difference in prevalence rate. Notably, the number of Indian children included in our study was lower than the other ethnic groups; this was not unexpected as Indians are a minority ethnic group in Singapore, and as such, their numbers in this study were also expectedly small. These could have contributed to the variation of MIH prevalence between this study and the study by Mittal et al.11 Of interest, we found that the children of Malay ethnicity were associated with higher MIH occurrence compared to the other groups. This finding is not in concurrence with other studies where ethnicity has not been found to be a modifying factor in the occurrence of MIH15,16. There is presently no data on MIH prevalence in the Malay ethnic group; as such, a meaningful comparison cannot be carried out. In a local study by Hong et al., the group reported that children
© 2014 BSPD, IAPD and John Wiley & Sons A/S. Published by John Wiley & Sons Ltd
MIH in Singaporean children
of Malay ethnicity were breastfed for a longer period of time compared to their counterparts of other ethnicities. Based on recent literature that proposed that prolonged breastfeeding may be a cause for MIH occurrence17, this may explain the higher frequency of MIH in the Malay population18. A more in-depth examination of the feeding habits (e.g., exclusiveness of breastfeeding), however, needs to be carried out to confirm this hypothesis. In addition to the MIH prevalence, it was also essential to assess the severity of MIH as this has significant implications for assessing treatment needs. Based on the results from our study, enamel breakdown and atypical restorations were more common in children who were affected with higher number of MIH teeth. In addition, the presence of enamel breakdown and atypical restorations was also dependent on the cumulative enamel opacity colour (white given the lowest score and brown having the highest score). The association between colour and post-eruptive enamel breakdown has been suggested by da CostaSilva et al. who concluded that darker opacities (brown) of MIH demonstrated decreased resistance to structural loss and thus were more likely to develop enamel breakdown and subsequent need for atypical restorations7. Overall, these are useful clinical indicators (i.e., cumulative colour score and mean number of affected teeth) for clinicians to assess the risk of enamel breakdown in the tooth based on the child’s profile, which would translate to customized preventive and treatment plan. These interventions may include more frequent review visits, need for fullcoverage restorations for MIH molars before enamel breakdown, and/or planning for timely extractions of these molars to allow the second permanent molars to drift into the arch with minimal orthodontic intervention. As the dental needs of these children are managed by the school dental service till they are 18 years of age, another prospective study involving dental examination of the patients with MIH when they reached 12 years of age may provide more clues to the long-term survival of these teeth. The limitations of this study include the use of a convenience sample which may not be
5
representative of the country. In addition, the prevalence of MIH in primary teeth may have been underestimated as the presence of atypical caries was not included in the judgement criteria for MIH identification in primary teeth19. The MIH prevalence data from this convenience sample in Singapore falls within the range of that previously reported in western countries14 although the rate appears to be closer to those studies that have examined children of the similar ages (between 7 and 8 years) using the EAPD criteria. The study’s results also suggest the role of ethnicity in MIH occurrence and that MIH severity (as determined by post-eruptive enamel breakdown and the presence of atypical restorations) may be influenced by the number of affected teeth/child and the cumulative enamel opacity colour score of MIH teeth for each patient. All these are important knowledge of the MIH puzzle as they provide clinicians direction on treatment planning for patients afflicted by MIH.
What this paper adds? ● There is clearly a lack of data on the prevalence of molar incisor hypomineralization (MIH) from this region of the world. At the time of the write up of this manuscript, there had been only two published studies from Asia. However, this is not indicative that MIH is a rare occurrence in Asian population. This study found that the prevalence of MIH in a cohort of 8-year-old Singaporean children was 12.5% which is comparable to other studies that have examined children of the similar ages (between 7 and 8 years) using the EAPD criteria. Why this paper is important to paediatric dentists? ● The findings from this study suggest the association between MIH occurrence and the Malay ethnicity. ● MIH severity (as determined by post-eruptive enamel breakdown and the presence of atypical restorations) may be influenced by the number of MIH teeth/child and the cumulative enamel opacity colour of MIH teeth. ● This is important as this knowledge may provide clinicians direction on treatment planning for patients afflicted by MIH.
Conflict of interest
None.
© 2014 BSPD, IAPD and John Wiley & Sons A/S. Published by John Wiley & Sons Ltd
6
J. J. Ng et al.
References 1 Koch G, Hallonsten AL, Ludvigsson N, Hansson BO, Holst A, Ullbro C. Epidemiologic study of idiopathic enamel hypomineralization in permanent teeth of Swedish children. Community Dent Oral Epidemiol 1987; 15: 279–285. 2 Weerheijm KL, Duggal M, Mejare I et al. Judgement criteria for molar incisor hypomineralisation (MIH) in epidemiologic studies: a summary of the European meeting on MIH held in Athens, 2003. Eur J Paediatr Dent 2003; 4: 110–113. 3 Lygidakis NA, Wong F, Jalevik B, Vierrou AM, Alaluusua S, Espelid I. Best Clinical Practice Guidance for clinicians dealing with children presenting with Molar-Incisor-Hypomineralisation (MIH): an EAPD Policy Document. Eur Arch Paediatr Dent 2010; 11: 75–81. 4 Elfrink ME, ten Cate JM, Jaddoe VW, Hofman A, Moll HA, Veerkamp JS. Deciduous molar hypomineralization and molar incisor hypomineralization. J Dent Res 2012; 91: 551–555. 5 Weerheijm KL. Molar incisor hypomineralisation (MIH). Eur J Paediatr Dent 2003; 4: 114–120. 6 Weerheijm KL. Molar incisor hypomineralization (MIH): clinical presentation, aetiology and management. Dent Update 2004; 31: 9–12. 7 Da Costa-Silva CM, Ambrosano GM, Jeremias F, De Souza JF, Mialhe FL. Increase in severity of molar-incisor hypomineralization and its relationship with the colour of enamel opacity: a prospective cohort study. Int J Paediatr Dent 2011; 21: 333–341. 8 Jalevik B, Klingberg GA. Dental treatment, dental fear and behaviour management problems in children with severe enamel hypomineralization of their permanent first molars. Int J Paediatr Dent 2002; 12: 24–32. 9 Jalevik B. Prevalence and diagnosis of Molar-IncisorHypomineralisation (MIH): a systematic review. Eur Arch Paediatr Dent 2010; 11: 59–64. 10 Cho SY, Ki Y, Chu V. Molar incisor hypomineralization in Hong Kong Chinese children. Int J Paediatr Dent 2008; 18: 348–352.
11 Mittal NP, Goyal A, Gauba K, Kapur A. Molar incisor hypomineralisation: prevalence and clinical presentation in school children of the northern region of India. Eur Arch Paediatr Dent 2013; 15: 11–18. 12 Jasulaityte L, Veerkamp JS, Weerheijm KL. Molar incisor hypomineralization: review and prevalence data from the study of primary school children in Kaunas/Lithuania. Eur Arch Paediatr Dent 2007; 8: 87–94. 13 Kusku OO, Caglar E, Sandalli N. The prevalence and aetiology of molar-incisor hypomineralisation in a group of children in Istanbul. Eur J Paediatr Dent 2008; 9: 139–144. 14 Lygidakis NA, Dimou G, Marinou D. Molar-incisor-hypomineralisation (MIH). A retrospective clinical study in Greek children. II. Possible medical aetiological factors. Eur Arch Paediatr Dent 2008; 9: 207–217. 15 Mahoney EK, Morrison DG. The prevalence of Molar-Incisor Hypomineralisation (MIH) in Wainuiomata children. N Z Dent J 2009; 105: 121–127. 16 Zawaideh FI, Al-Jundi SH, Al-Jaljoli MH. Molar incisor hypomineralisation: prevalence in Jordanian children and clinical characteristics. Eur Arch Paediatr Dent 2011; 12: 31–36. 17 Fagrell T. Molar incisor hypomineralization. Morphological and chemical aspects, onset and possible etiological factors. Swed Dent J 2011; 5: 11–83. 18 Hong CH, Bagramian RA, Hashim Nainar SM, Straffon LH, Shen L, Hsu CY. High caries prevalence and risk factors among young preschool children in an urban community with water fluoridation. Int J Paediatr Dent 2013; doi: 10.1111/ipd.12023. [Epub ahead of print]. 19 Elfrink ME, Veerkamp JS, Aartman IH, Moll HA, Ten Cate JM. Validity of scoring caries and primary molar hypomineralization (DMH) on intraoral photographs. Eur Arch Paediatr Dent 2009; 10(Suppl 1): 5–10.
© 2014 BSPD, IAPD and John Wiley & Sons A/S. Published by John Wiley & Sons Ltd
Prevalence of molar incisor hypomineralization (MIH) in Singaporean children JING JING NG1, OY CHU EU2, RAHUL NAIR3 & CATHERINE HSU LING HONG4 1
Private Practice, Singapore, Singapore, 2School Dental Service, Health Promotion Board, Singapore, Singapore, 3Discipline of Oral Sciences, National University of Singapore, Singapore, Singapore, and 4Discipline of Orthodontics and Paediatric Dentistry, Faculty of Dentistry, National University of Singapore, Singapore, Singapore
International Journal of Paediatric Dentistry 2014 Background. There is a lack of data on molar inci-
sor hypomineralization (MIH) in Asia, but this is not an indication that MIH is rare in the Asian population. Early identification of MIH is important as affected teeth frequently display post-eruptive enamel loss which would result in rapid caries progression. Aim. This objective of this study was to assess the prevalence of MIH in Singaporean children. Design. Patients were recruited from 30 schools across Singapore. All children were examined by a single dentist, and the judgement criteria used were based on the 2003 European Academy of Paediatric Dentistry criteria.
Introduction
The occurrence of white to yellow-brown enamel opacities in the first permanent molars was first recognized in Sweden in the late 1970s1. This phenomenon was subsequently coined molar incisor hypomineralization (MIH). The currently accepted definition of MIH by European Academy Paediatric Dentistry (EAPD) is enamel hypomineralization of unclear origin of 1 to 4 permanent first molars, frequently associated with affected incisors2. Recent studies have also reported similar defects in second primary molars, incisors, and the tips of the canines3–5. Clinically, MIH can vary from mild demarcated opacities to severe structural loss. The defects can be white, yellow, or brown in colour, but they will show a clear demarcation between the affected and normal enamel6. Correspondence to: Catherine H. L. Hong, Discipline of Orthodontics and Paediatric Dentistry, Faculty of Dentistry, National University of Singapore, Singapore, Singapore. E-mail: [email protected]
Results. A total of 1083 children; average age of 7.7 0.3 years were examined. One hundred and thirty-five children (12.5%) had MIH. A significantly higher proportion of children of the Malay ethnicity had MIH, compared to Chinese children (P = 0.02). Post-eruptive enamel breakdown and the presence of atypical restorations were correlated with increasing number of MIH teeth/child (Rho= 0.599, P < 0.001) and the cumulative enamel opacity colour score (Rho = 0.601, P < 0.001). Conclusions. Our findings suggest the role of ethnicity in MIH occurrence and that MIH severity may be influenced by the number of MIH teeth/ child and the cumulative enamel opacity colour score.
The hypomineralized part of the tooth is weak, and the enamel may chip off easily, resulting in post-eruptive loss of enamel. Some authors have suggested that the colour of opacity may be suggestive of weaker tooth structure and subsequently higher risk for post-eruptive enamel breakdown7. Post-eruptive enamel loss is a definite risk factor for rapid caries progression which in turn can cause severe pain8. As such, it is important for clinicians to identify and manage these affected teeth early. A number of MIH studies have been published in dental journals from various parts of the world and the reported prevalence of MIH ranges from 2.4% to 40.2%9. Currently, the majority of the prevalence data are based on studies from Europe, and at the time of write up of this manuscript, there had been only two published studies from Asia (Hong Kong and India)10,11. The lack of data, however, is not an indication that MIH is a rarity in the Asian population. Based on one of the authors’ observation, MIH is not uncommon in children in Singapore and has been observed periodically during routine dental examinations conducted by the School Dental Service. The
© 2014 BSPD, IAPD and John Wiley & Sons A/S. Published by John Wiley & Sons Ltd
1
2
J. J. Ng et al.
School Dental Service is a federal/governmentfunded programme where all school-going children between the ages of 7 to 18 years are entitled to free dental examination and treatment. Presently, approximately 97% of schoolgoing children between 7 and 12 years of age are registered in this programme. As Singapore is a multiracial country with a diverse and different ethnic resident population (77% Chinese, 14% Malays, 8% Indians) from that of western countries, the prevalence of MIH in Singapore may also differ. As such, extrapolation of prevalence data from these countries to the local context may be inaccurate. There is clearly a lack of data on MIH prevalence from this region of the world based on a review of the literature; this study therefore aimed to assess the prevalence of MIH in Singaporean children. Materials and methods
Patients for this study were recruited from 30 schools across the Singapore Island. In Singapore, elementary schools are grouped into four zones (North, South, East, and West regions of the Singapore Island) by the Ministry of Health. As such, the School Dental Service also divides the school dental clinics into the same four respective zones. Each zone comprises of 40 to 45 dental clinics; the clinics are further subgrouped into seven to eight groups based on geographical location. One school was selected from each group to make up a total of 30 schools to ensure that there would not be a geographical biasness in the selected sample population. Forty-five children born in the year 2003 were randomly selected for the examination from each school. The children were chosen based on their class identification numbers. The first 15 children with odd-numbered class identification numbers were selected from the first class, the next 15 children with evennumbered class identification numbers were selected from the next class, and the remaining 15 children with odd-numbered class identification numbers were selected from the last class. All the children were examined by a single dentist (Dr Ng Jing Jing) at the school’s
on-site dental clinic. The judgement criteria used for identifying MIH were based on the 2003 EAPD criteria2. The following were also recorded: 1. colour of the demarcated enamel opacity (white: 1, yellow: 2, brown: 3); a cumulative enamel opacity colour score was created for each patient by adding the individual tooth colour opacity score (e.g., if the patient had 2 affected MIH teeth, the cumulative score would be the sum of colour opacity score from both teeth); 2. caries experience as measured by the Decayed, Missing, Filled Teeth (DMFT) and dmft indexes; and 3. second primary molars affected by MIH. These details were also elicited from the dental records: medical history, dental history, and previous dental treatment. In this study, only healthy children with no significant medical conditions (American Society of Anaesthesiologists physical status classification 1 and 2) were examined. Enamel defects other than MIH were excluded; these included teeth affected by Amelogenesis Imperfecta and chronologic enamel hypoplasia. All statistical analyses were performed using IBM SPSS (Statistical Package for the Social Sciences) version 20.0 (New York, NY, USA). Descriptive statistics were carried out followed by nonparametric bivariate analysis, which was used to determine the relationships between variables. Results
Demographics A total of 1083 children; average age of 7.7 0.3 years were examined. The male-tofemale ratio was 1:1.3. Of the 1083 children examined, 65.5% (n = 709) were Chinese, 12.7% were Malay (n = 137), 11.5% (n = 125) were Indian, and 10.3% (n = 112) were of other minority races. Further details of demographics are listed in Table 1. The overall DMFT and dmft were 0.1 0.5 and 2.4 3.2, respectively. Molar Incisor Hypomineralization One hundred and thirty-five children (12.5%) were affected with MIH. Children
© 2014 BSPD, IAPD and John Wiley & Sons A/S. Published by John Wiley & Sons Ltd
MIH in Singaporean children
Table 1. Demographics. Children without MIH Variables
n
%
Gender Male 408 42.3 Female 540 57.7 Ethnicity Chinese 626 57.8 Malay 111 10.3 Indian 108 10.0 Others 103 9.5 Caries status (Mean SD) dmft 2.4 3.2 DMFT 0.1 0.4
Children with MIH
Total sample
n
%
n
%
67 68
49.6 50.4
475 608
43.9 56.1
83 26 17 9
7.7 2.4 1.5 0.8
709 137 125 112
65.5 12.7 11.5 10.3
2.5 3.1 0.3 0.7
2.4 3.2 0.1 0.5
Table 2. Distribution of children with teeth affected by MIH.
Type of MIH in children First permanent molars affected only First permanent molars and incisors affected only First permanent molars and second primary molars affected only First permanent molars and second primary molars and incisors affected only Second primary molars affected only Second primary molars and incisors only
n by patient (%) 74 (6.8) 30 (2.8) 4 (0.4) 2 (0.2) 23 (2.1) 2 (0.2)
3
significant difference in the number of MIH teeth/child among the various ethnic groups. Two hundred and ninety-eight teeth were affected by MIH, of which 180 were first permanent molars, 52 were second primary molars, and 66 were permanent incisors (Table 3). There were no significant differences in the frequency of MIH occurrence between the maxillary and mandibular arch (P = 0.19). Among the 180 permanent molars with hypomineralization, 30% (n = 54/180) had post-eruption breakdown or atypical restorations. Seven permanent maxillary incisors had post-eruption breakdown or atypical restorations. In the primary dentition, 11 molars affected by MIH had post-eruption breakdown or atypical restorations. The most common opacity was yellow in colour (n = 128), followed by white (n = 80), and brown opacities (n = 78). Further information on individual tooth is illustrated in Table 3. The number of teeth with enamel breakdown and atypical restorations was correlated with the number of MIH teeth/child (Rho = 0.599, P < 0.001) and the cumulative enamel opacity colour score/child (Rho = 0.601, P < 0.001). Discussion
with hypomineralization only affecting the incisors were excluded as in accordance with the EAPD criteria. The average number of teeth affected by MIH per child was 2.2 (range: 1–13). Majority of children with MIH (71.1%, n = 96) had either 1 (42.2%, n = 57) or 2 (28.9%, n = 39) MIH-affected teeth/ child. The average number of molars affected/ child was 1.7 (range: 1–8). Of the 135 children, 46.7% (n = 63) had one affected permanent molar, 22.2% (n = 30) had two affected permanent molars, 8.1% (n = 11) had three affected permanent molars, and 4.4% (n = 6) had four affected first permanent molars. Table 2 illustrates the distribution of children with teeth affected by MIH. Higher proportions of children of the Malay ethnicity were found to have MIH compared to Chinese children (P = 0.02). There was no
Early identification of MIH is important as affected teeth frequently display post-eruptive enamel loss which in turn would result in rapid caries progression and ensuing pain. Despite the importance for early diagnosis, MIH prevalence data are lacking from this region of the world; as such, we embarked on a study to assess the prevalence of MIH in Singaporean children. In our study, we found that the prevalence of MIH in Singapore was 12.5% with a mean number of MIH teeth per child of 2.2; these statistics are comparable to other studies that have examined children of similar ages (between 7 and 8 years) as specified by the EAPD criteria9,12,13. As with many studies in the literature, gender was not significantly associated with the MIH in our study9,10. A handful of studies have indicated a higher prevalence of MIH in girls than boys, but authors have speculated that this may be
© 2014 BSPD, IAPD and John Wiley & Sons A/S. Published by John Wiley & Sons Ltd
4
J. J. Ng et al.
Table 3. Distribution of molars with MIH by tooth number, colour, and status of enamel integrity. Colour of enamel opacities of MIH teeth
Indexed teeth Permanent dentition 16 26 36 46 Perm. 1st molars 12 11 21 22 Max. Perm. incisors 32 31 41 42 Mand Perm. incisors Primary dentition 55 65 75 85 Pri. 2nd molars
Total number of teeth present
Number of MIH teeth n (%)
Number of MIH teeth with non-intact enamel or atypical restorations, n (%)
White n (%)
Yellow n (%)
Brown n (%)
994 1002 1048 1041 4085 354 889 900 354 2497 832 1066 1068 830 3796
45 33 55 47 180 5 11 13 4 33 9 10 14 0 33
(4.5) (3.3) (5.3) (4.5) (4.4) (1.4) (1.2) (1.4) (1.1) (1.3) (1.1) (0.9) (1.3) (0) (0.9)
8 11 17 18 54 1 2 3 1 7 0 0 0 0 0
(0.8) (1.1) (1.6) (1.7) (1.2) (0.3) (0.2) (0.3) (0.3) (0.2) (0) (0) (0) (0) (0)
7 (0.7) 3 (0.3) 19 (1.8) 10 (1.0) 39 (1.0) 1 (0.3) 5 (0.6) 7 (0.8) 2 (0.6) 15 (0.6) 1* 6 (0.6) 4* 0 (0) NA
29 (0.3) 17 (1.7) 21 (2.0) 22 (2.1) 89 (2.2) 4 (1.1) 5 (0.6) 5 (0.5) 2 (0.6) 16 (0.6) 4* 3 (0.3) 2* 0 (0) NA
9 (0.9) 13 (1.3) 15 (1.4) 15 (1.4) 52 (1.3) 0 (0.0) 1 (0.1) 1 (0.1) 0 (0.0) 2 (0.1) 0* 1 (0.1) 0* 0 (0) NA
1071 1068 1069 1069 4277
15 15 9 13 52
(1.4) (1.4) (0.8) (1.2) (1.2)
2 6 1 2 11
(0.2) (0.6) (0.1) (0.2) (0.3)
3 3 4 5 15
5 3 3 3 14
7 9 2 5 23
(0.3) (0.3) (0.4) (0.5) (0.4)
(0.5) (0.3) (0.3) (0.3) (0.3)
(0.7) (0.8) (0.2) (0.5) (0.5)
*Has missing colour data.
attributed to females having a greater number of erupted permanent molars and incisors compared to their male counterparts of the same age, resulting in the disparity of MIH prevalence between genders14. Our study is unique in that unlike the European studies, our target sample was made up of three distinct races, which is quite different from the population sampled in the studies from the western countries. We found that the prevalence of MIH in Singaporean children of Chinese ethnicity (11.7%) was much higher than in Hong Kong Chinese children (2.8%)10. This may be due to an underestimation of the MIH prevalence in the Hong Kong study, which the authors of the study also acknowledged, attributing this limitation to the retrospective nature of the study design. In the other recent study by Mittal et al., the authors found that the MIH prevalence of children from Northern India was 6.3%11. This figure is lower than the MIH prevalence of children of Indian ethnicity in our study (13.6%). Mittal’s et al. study was based in North India and
therefore sampled Northern Indians; however, Singaporean Indians are largely of Southern Indian descent, and this may have contributed to the difference in prevalence rate. Notably, the number of Indian children included in our study was lower than the other ethnic groups; this was not unexpected as Indians are a minority ethnic group in Singapore, and as such, their numbers in this study were also expectedly small. These could have contributed to the variation of MIH prevalence between this study and the study by Mittal et al.11 Of interest, we found that the children of Malay ethnicity were associated with higher MIH occurrence compared to the other groups. This finding is not in concurrence with other studies where ethnicity has not been found to be a modifying factor in the occurrence of MIH15,16. There is presently no data on MIH prevalence in the Malay ethnic group; as such, a meaningful comparison cannot be carried out. In a local study by Hong et al., the group reported that children
© 2014 BSPD, IAPD and John Wiley & Sons A/S. Published by John Wiley & Sons Ltd
MIH in Singaporean children
of Malay ethnicity were breastfed for a longer period of time compared to their counterparts of other ethnicities. Based on recent literature that proposed that prolonged breastfeeding may be a cause for MIH occurrence17, this may explain the higher frequency of MIH in the Malay population18. A more in-depth examination of the feeding habits (e.g., exclusiveness of breastfeeding), however, needs to be carried out to confirm this hypothesis. In addition to the MIH prevalence, it was also essential to assess the severity of MIH as this has significant implications for assessing treatment needs. Based on the results from our study, enamel breakdown and atypical restorations were more common in children who were affected with higher number of MIH teeth. In addition, the presence of enamel breakdown and atypical restorations was also dependent on the cumulative enamel opacity colour (white given the lowest score and brown having the highest score). The association between colour and post-eruptive enamel breakdown has been suggested by da CostaSilva et al. who concluded that darker opacities (brown) of MIH demonstrated decreased resistance to structural loss and thus were more likely to develop enamel breakdown and subsequent need for atypical restorations7. Overall, these are useful clinical indicators (i.e., cumulative colour score and mean number of affected teeth) for clinicians to assess the risk of enamel breakdown in the tooth based on the child’s profile, which would translate to customized preventive and treatment plan. These interventions may include more frequent review visits, need for fullcoverage restorations for MIH molars before enamel breakdown, and/or planning for timely extractions of these molars to allow the second permanent molars to drift into the arch with minimal orthodontic intervention. As the dental needs of these children are managed by the school dental service till they are 18 years of age, another prospective study involving dental examination of the patients with MIH when they reached 12 years of age may provide more clues to the long-term survival of these teeth. The limitations of this study include the use of a convenience sample which may not be
5
representative of the country. In addition, the prevalence of MIH in primary teeth may have been underestimated as the presence of atypical caries was not included in the judgement criteria for MIH identification in primary teeth19. The MIH prevalence data from this convenience sample in Singapore falls within the range of that previously reported in western countries14 although the rate appears to be closer to those studies that have examined children of the similar ages (between 7 and 8 years) using the EAPD criteria. The study’s results also suggest the role of ethnicity in MIH occurrence and that MIH severity (as determined by post-eruptive enamel breakdown and the presence of atypical restorations) may be influenced by the number of affected teeth/child and the cumulative enamel opacity colour score of MIH teeth for each patient. All these are important knowledge of the MIH puzzle as they provide clinicians direction on treatment planning for patients afflicted by MIH.
What this paper adds? ● There is clearly a lack of data on the prevalence of molar incisor hypomineralization (MIH) from this region of the world. At the time of the write up of this manuscript, there had been only two published studies from Asia. However, this is not indicative that MIH is a rare occurrence in Asian population. This study found that the prevalence of MIH in a cohort of 8-year-old Singaporean children was 12.5% which is comparable to other studies that have examined children of the similar ages (between 7 and 8 years) using the EAPD criteria. Why this paper is important to paediatric dentists? ● The findings from this study suggest the association between MIH occurrence and the Malay ethnicity. ● MIH severity (as determined by post-eruptive enamel breakdown and the presence of atypical restorations) may be influenced by the number of MIH teeth/child and the cumulative enamel opacity colour of MIH teeth. ● This is important as this knowledge may provide clinicians direction on treatment planning for patients afflicted by MIH.
Conflict of interest
None.
© 2014 BSPD, IAPD and John Wiley & Sons A/S. Published by John Wiley & Sons Ltd
6
J. J. Ng et al.
References 1 Koch G, Hallonsten AL, Ludvigsson N, Hansson BO, Holst A, Ullbro C. Epidemiologic study of idiopathic enamel hypomineralization in permanent teeth of Swedish children. Community Dent Oral Epidemiol 1987; 15: 279–285. 2 Weerheijm KL, Duggal M, Mejare I et al. Judgement criteria for molar incisor hypomineralisation (MIH) in epidemiologic studies: a summary of the European meeting on MIH held in Athens, 2003. Eur J Paediatr Dent 2003; 4: 110–113. 3 Lygidakis NA, Wong F, Jalevik B, Vierrou AM, Alaluusua S, Espelid I. Best Clinical Practice Guidance for clinicians dealing with children presenting with Molar-Incisor-Hypomineralisation (MIH): an EAPD Policy Document. Eur Arch Paediatr Dent 2010; 11: 75–81. 4 Elfrink ME, ten Cate JM, Jaddoe VW, Hofman A, Moll HA, Veerkamp JS. Deciduous molar hypomineralization and molar incisor hypomineralization. J Dent Res 2012; 91: 551–555. 5 Weerheijm KL. Molar incisor hypomineralisation (MIH). Eur J Paediatr Dent 2003; 4: 114–120. 6 Weerheijm KL. Molar incisor hypomineralization (MIH): clinical presentation, aetiology and management. Dent Update 2004; 31: 9–12. 7 Da Costa-Silva CM, Ambrosano GM, Jeremias F, De Souza JF, Mialhe FL. Increase in severity of molar-incisor hypomineralization and its relationship with the colour of enamel opacity: a prospective cohort study. Int J Paediatr Dent 2011; 21: 333–341. 8 Jalevik B, Klingberg GA. Dental treatment, dental fear and behaviour management problems in children with severe enamel hypomineralization of their permanent first molars. Int J Paediatr Dent 2002; 12: 24–32. 9 Jalevik B. Prevalence and diagnosis of Molar-IncisorHypomineralisation (MIH): a systematic review. Eur Arch Paediatr Dent 2010; 11: 59–64. 10 Cho SY, Ki Y, Chu V. Molar incisor hypomineralization in Hong Kong Chinese children. Int J Paediatr Dent 2008; 18: 348–352.
11 Mittal NP, Goyal A, Gauba K, Kapur A. Molar incisor hypomineralisation: prevalence and clinical presentation in school children of the northern region of India. Eur Arch Paediatr Dent 2013; 15: 11–18. 12 Jasulaityte L, Veerkamp JS, Weerheijm KL. Molar incisor hypomineralization: review and prevalence data from the study of primary school children in Kaunas/Lithuania. Eur Arch Paediatr Dent 2007; 8: 87–94. 13 Kusku OO, Caglar E, Sandalli N. The prevalence and aetiology of molar-incisor hypomineralisation in a group of children in Istanbul. Eur J Paediatr Dent 2008; 9: 139–144. 14 Lygidakis NA, Dimou G, Marinou D. Molar-incisor-hypomineralisation (MIH). A retrospective clinical study in Greek children. II. Possible medical aetiological factors. Eur Arch Paediatr Dent 2008; 9: 207–217. 15 Mahoney EK, Morrison DG. The prevalence of Molar-Incisor Hypomineralisation (MIH) in Wainuiomata children. N Z Dent J 2009; 105: 121–127. 16 Zawaideh FI, Al-Jundi SH, Al-Jaljoli MH. Molar incisor hypomineralisation: prevalence in Jordanian children and clinical characteristics. Eur Arch Paediatr Dent 2011; 12: 31–36. 17 Fagrell T. Molar incisor hypomineralization. Morphological and chemical aspects, onset and possible etiological factors. Swed Dent J 2011; 5: 11–83. 18 Hong CH, Bagramian RA, Hashim Nainar SM, Straffon LH, Shen L, Hsu CY. High caries prevalence and risk factors among young preschool children in an urban community with water fluoridation. Int J Paediatr Dent 2013; doi: 10.1111/ipd.12023. [Epub ahead of print]. 19 Elfrink ME, Veerkamp JS, Aartman IH, Moll HA, Ten Cate JM. Validity of scoring caries and primary molar hypomineralization (DMH) on intraoral photographs. Eur Arch Paediatr Dent 2009; 10(Suppl 1): 5–10.
© 2014 BSPD, IAPD and John Wiley & Sons A/S. Published by John Wiley & Sons Ltd
