|Year : 2015 | Volume
| Issue : 3 | Page : 213-217
Prevalence and severity of molar incisor hypomineralization in children aged 11-16 years of a city in Karnataka, Davangere
M Kirthiga1, P Poornima2, R Praveen3, P Gayathri4, M Manju1, M Priya1
1 Department of Pedodontics and Preventive Dentistry, Syamala Redddy Dental College, Bengaluru, Karnataka, India
2 Department of Pedodontics and Preventive Dentistry, College of Dental Sciences, Davangere, Karnataka, India
3 Department of Conservative Dentistry and Endodontics, Dr. M R Ambedkar Dental College, Bengaluru, Karnataka, India
4 Department of Pedodontics and Preventive Dentistry, Saveetha Dental College, Chennai, India
|Date of Web Publication||9-Jul-2015|
Dr. M Kirthiga
Department of Pedodontics and Preventive Dentistry, Syamala Redddy Dental College, Bengaluru, Karnataka
Source of Support: None, Conflict of Interest: None
| Abstract|| |
Introduction: Molar incisor hypomineralization (MIH) describes the clinical picture of hypomineralization of systemic origin affecting one or more first permanent molar. There is a rarity of prevalence studies in Indian population. Objectives: The main aim of this study was to investigate the prevalence of MIH in a population of South Indian children. Settings and Design: A cross-sectional epidemiological survey, included 2000 children aged 11-16 years chosen by stratified random sampling from government and private schools of Davangere, a city in South India. Materials and Methods: Evaluation of MIH and decayed, missing and filled teeth was carried out in these children by a calibrated examiner. The severity of hypomineralization was recorded according to the Wetzel and Reckel scale. Statistical Analysis: Chi-square test was used to analyze the categorical data. P ≤ 0.05 was considered for statistical significance. Results: About 8.9% of all examined children showed at least one ill-structured first permanent molar in terms of MIH. The male and female ratio was found to be 1:1.1. The decreasing order of occurrence of MIH affected teeth were permanent maxillary molars, maxillaryincisors, mandibular molars and the mandibular incisors. Conclusion: The prevalence of MIH in the permanent dentition of south Indian children was 8.9%. There is a need for a proper planned preventive and restorative program with regard to the increasing prevalence of MIH.
Keywords: Molar incisor hypomineralization, permanent incisor, permanent molar
|How to cite this article:|
Kirthiga M, Poornima P, Praveen R, Gayathri P, Manju M, Priya M. Prevalence and severity of molar incisor hypomineralization in children aged 11-16 years of a city in Karnataka, Davangere. J Indian Soc Pedod Prev Dent 2015;33:213-7
|How to cite this URL:|
Kirthiga M, Poornima P, Praveen R, Gayathri P, Manju M, Priya M. Prevalence and severity of molar incisor hypomineralization in children aged 11-16 years of a city in Karnataka, Davangere. J Indian Soc Pedod Prev Dent [serial online] 2015 [cited 2019 Jul 16];33:213-7. Available from: http://www.jisppd.com/text.asp?2015/33/3/213/160366
| Introduction|| |
The molar incisor hypomineralization (MIH) is defined as a qualitative defect of the enamel characterized by the progressive and simultaneous hypomineralization of the enamel structure of the first permanent molars of systemic origin, which may be associated frequently with incisors. The first article on MIH was from Koch 1987. It was first described by Weerheijm et al. in 2001. It is also called as "hypomineralized permanent first molars (PFMs)," "idiopathic enamel hypomineralization," "nonfluoride hypomineralization" dysmineralized PFMs and "cheese molars." , The author suggested that in such a condition one or more molars are always affected and they may or may not involve incisors.  These lesions vary from white to yellow to brown demarcated opacities sometimes combined with enamel breakdown. The characteristic feature of MIH would be clear a demarcation between the affected and sound enamel. These lesions should not be confused with smooth and rounded margins seen in hypoplasia, diffuse opacities typically present in fluorosis, generalized opacities present in amelogenesis imperfecta, or opacities present only on permanent incisors that may indicate traumatic injuries. , Another feature seen in MIH is the asymmetry of defects present in the molars and incisors, that is, one molar or incisor can be severely affected while the contralateral tooth may be clinically sound or have only minor defects. 
Knowledge about the magnitude of MIH seems desirable as it is vulnerable for consequences like rapid caries development, early enamel loss, soft structure and sensitivity. Most of the prevalence studies of MIH have been carried out in the European countries; and reported rates are between 2.9% and 25%. , In India, there has been just one study conducted on the prevalence of MIH and knowledge in this area has been confusing and inadequate. Thus, the aim of this study was to evaluate the prevalence and severity of MIH in a group of children aged from 11 to 16 years of Davangere city. This data could be useful as a baseline for Indian population in order to assess the etiological factor and treatment for this condition which is still under research.
| Materials and Methods|| |
Ethical approval from the Institutional Review Board of College of Dental Sciences, Davangere was obtained prior to the study. Verbal consent from parents, concerned authorities of schools were sought prior to start of the study. The duration of the study was for a period of 75 days and was conducted between the months of June and August 2013.
A cross-sectional study was conducted in a city named Davangere in Karnataka state, India where 2000 school children (1173 boys and 827 girls) aged 11-16 years were screened for MIH and decayed, missing and filled teeth (DMFT). The investigator was trained to diagnose MIH by a gold standard examiner among children who visited the Out Patient Department of the College of Dental Sciences for duration of 2 months. The Intra examiner reliability was calculated by 30 children who were randomly selected and were examined at two different occasions. The kappa statistics was found to be 0.93 and 0.95 for MIH and DMFT respectively, which reflected a high degree of conformity in the examination. Two stage sampling procedure was adopted for selection of the sample. In the first stage, 6 government schools and 6 private schools were selected from the total number of schools (190) with the help of simple random sampling. In the second stage children were selected from the already selected schools with the help of proportionate stratified random sampling. The examinations took place in a suitable room at the individual school with the help of natural light using mouth mirrors, probes, tweezers and cotton for removing the plaque whenever necessary. The diagnostic criteria included the following which was in accordance with Cho et al.: 
- Well demarcated opacities when examined under wet condition.
- At least one of the permanent molars was affected.
- The hypomineralization was limited to PFMs and incisors but were not generalized or diffused as in cases of enamel hypoplasia or amelogenesisimperfecta.
- The defects in the permanent incisors were not associated with a history of trauma or infection in the primary dentition.
- PFM with caries, restorations or posteruption enamel breakdown due to unknown reasons would be diagnosed as MIH if demarcated opacities remained at the borders or on the other surfaces.
The teeth with discoloration due to tetracycline staining, nonvitality, white spot lesions, demineralized areas, erosion, fluorosis and extracted PFMs were not included in the study. After the diagnosis of MIH was made, the teeth being affected were recorded in the form of a master chart according to the individual tooth. The severity of hypomineralization was also recorded according to the Wetzel and Reckel scale. 
Degree 1 (mild): Isolated white and cream to yellowish-brown discolorations on the chewing surface and upper part of the crown.
Degree 2 (moderate): Hypomineralized yellowish-brown enamel affecting more or less all the humps on top of the crown, but with only a slight loss of substance.
Degree 3 (severe): Large scale mineral deficiency with distinct yellowish brown discolorations and defects in crown morphology resulting from extensive loss of enamel.
It will be expressed in the form of numbers and percentages. The Chi-square test was used to analyze the categorical data. P = 0.05 or less was considered for statistical significance.
| Results|| |
A total number of 2000 school children were reviewed, of which 179 cases of MIH were identified with a prevalence rate of 8.9%. The tooth-wise prevalence was found to be 3.3%. Out of 30,400 teeth examined, 1016 teeth showed MIH. Among the children with MIH, the percentage of girls and boys affected were 9.3 and 8.7 respectively, and the male to female ratio was 1:1.1 showing no significant difference between males and females.
Among the affected population, the percentage of molars and incisors affected by them were 4.3% and 2.4%, respectively, which showed that the molars were affected more than that of incisors (P < 0.001). Both molars and incisors were affected to a significantly greater extent in the maxilla than in the mandible. The difference between the number of teeth affected in the maxilla and mandible also proved to be highly significant with the maxilla being affected more than the mandible (P < 0.001) [Table 1].
|Table 1: Percentage of molars and incisors affected with MIH in maxilla and mandible|
Click here to view
When the degrees of severity according to Wetzel and Reckel were evaluated, out of 179 cases affected by MIH, 67% belonged to degree 1, 29.6% to degree 2 and 3.4% to degree 3. The mean DMFT score of those with MIH was 3.2, which was significantly higher than the controls (0.8) (P < 0.05).
| Discussion|| |
In our study, the prevalence of MIH was found to be 8.9%, which was well within the range observed in other studies conducted in various parts of the world. As far as Asia was concerned the prevalence rate was estimated to be the least (2.8%) in Hong Kong and highest (18.6%) in Iraq (2003-2011). ,, The prevalence of MIH in European countries conducted during the years 1996 and 2008 ranged from 2.9% in Germany to 25% in Finland.  A very high prevalence of 40.2% was seen in a study conducted in Brazilian children in 2009.  This would be the highest prevalence found till date. This difference in MIH prevalence seen in various parts of the world may be due to the heterogeneity in ethnic and age groups being studied and the retrospective nature of the study.  It could also be explained by the differences in the diagnostic criteria like exclusion of the genetically based hypomineralization and hypomineralization of unknown etiology. 
Only one study has been done so far in India in the Northern region (Gujarat) where prevalence rate was 9.2%, which was comparable to our result.  This study shows the prevalence of MIH between 7.5% and 10.3% if 95% confidence interval was taken. Nevertheless, this study gave a baseline data in a South Indian population, which at the time of writing was not available in the literatures.
The age group selected in this study was 11-16 years, reason being all PFMs and incisors were fully erupted at the time of examinations. The second molars were present only in 1600 individuals and the calculations were done accordingly in order to avoid bias. The male:female ratio in the present study was found to be 1:1.1, showing no significant difference between the sexes which was consistent with the studies performed earlier. ,,,
The percentage of individual teeth affected were also calculated taking the sample size as a whole and it clearly showed that the first molars were the most commonly affected (7.5%) followed by the central incisors (3.9%) then the lateral incisors (0.9%) and finally the second molars (0.3%) [Table 1]. This could be very well explained by the fact that the first molars are the first teeth to get mineralized, followed by the same order just as the order of prevalence mentioned above and as we know for MIH to occur, ameloblasts must be affected in the later mineralization or mature phase of amelogenesis. Since, the first molar is the tooth which is most exposed to environmental changes it is said to be most vulnerable to MIH than incisors.  This was in contrast to another study done by Weerheijm et al. where the results showed that percentage of molars and incisors affected were almost the same.  The order of association of the affected teeth noticed in our study was 4 molars/2 incisors, 4 molars/4 incisors, only 4 molars and finally only 2 molars which were in agreement with Lygidakis et al.
The present study showed significant difference in MIH occurring more in maxilla compared to the mandible [Table 1] which is in contrast to most of the studies' findings done namely, Weerheijm and Jälevik and Norén. , However, our study was in agreement with another study done by Leppäniemi et al. where he also concluded that maxillary molars were affected much more than mandibular teeth.  This could be explained by the contribution of Lunt and Law who modified the chronology of the deciduous human dentition and concluded that maxillary teeth are generally ahead of the mandibular teeth in development.  Another study conducted by Calderara et al. concluded no significant difference between the maxilla and mandible with respect to MIH. 
The mean DMFT value of those affected with MIH was 3.2, which was significantly higher than the mean DMFT value of the controls (0.8). This result is in accordance with other studies done by Cho et al.  and Preusser et al.  An obvious explanation for this would be that the presence of enamel defects increases the risk of dental caries in the affected teeth. 
Also, according to a recent study by Grošelj and Jan in Slovenia it was seen that MIH was found in 21.4% children and they had significantly higher caries experience in their permanent teeth, but not in their primary teeth. 
The severity chart showed that among the teeth affected by MIH, majority belonged to a mild form of MIH and a very few belonged to the most severe form which was consistent with the study done by Preusser et al. This may be attributed to the onset and duration of the influence of the causative agent on the mineralizing dental tissue. Further, it has to be considered that the occlusal third of the crown is exposed to the environmental influences of the oral cavity earlier, and more intensively than the middle and gingival portions of the tooth. Such influences may include mastication, bacterial plaque, or acidic beverages. 
The etiology of MIH has not been clear till date. The main problems in diagnosing any single etiological factor would be nonspecific appearance of enamel defects, threshold levels of etiological agents not being known and difficulty in timing of events. The possible causes could be attributed to environmental changes during a specific time period, infections such as chicken pox or respiratory diseases during childhood and dioxin in breast milk. ,
Further studies applying the same diagnostic criteria are needed especially in Asia where they are lacking in order to make them comparable and to confirm the etiology of MIH. Knowledge of the extent of this phenomenon seems necessary for future treatment estimates.
| Conclusion|| |
The prevalence of MIH in a representative sample of school children aged 11-16 years of Davangere was 8.9%. This data could be helpful in estimating the baseline data of MIH among the Indian population. In our study, there was no significant difference with regard to gender. The maxillary molars are the teeth most commonly affected followed by maxillary incisors mandibular molars, and the mandibular incisors are the least affected ones. Thus, awareness about the condition would help in the preventive and therapeutic measures for combating this alarming developmental disturbance of teeth which is also of relevance for public health authorities.
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