Predictors of Developmental Defects of Enamel in Primary Maxillary Central Incisors Using Bayesian Model Selection.

INTRODUCTION: Localized non-inheritable developmental defects of tooth enamel (DDE) are classified as enamel hypoplasia (EH), opacity (OP), and post-eruptive breakdown (PEB) using the enamel defects index. To better understand the etiology of DDE, we assessed the linkages amongst exposome variables for these defects during the specific time duration for enamel mineralization of the human primary maxillary central incisor enamel crowns. In general, these two teeth develop between 13 and 14 weeks in utero and 3-4 weeks' postpartum of a full-term delivery, followed by tooth eruption at about 1 year of age. METHODS: We utilized existing datasets for mother-child dyads that encompassed 12 weeks' gestation through birth and early infancy, and child DDE outcomes from digital images of the erupted primary maxillary central incisor teeth. We applied a Bayesian modeling paradigm to assess the important predictors of EH, OP, and PEB. RESULTS: The results of Gibbs variable selection showed a key set of predictors: mother's prepregnancy body mass index (BMI); maternal serum concentrations of calcium and phosphorus at gestational week 28; child's gestational age; and both mother's and child's functional vitamin D deficiency (FVDD). In this sample of healthy mothers and children, significant predictors for OP included the child having a gestational period >36 weeks and FVDD at birth, and for PEB included a mother's prepregnancy BMI <21.5 and higher serum phosphorus concentration at week 28. CONCLUSION: In conclusion, our methodology and results provide a roadmap for assessing timely biomarker measures of exposures during specific tooth development to better understand the etiology of DDE for future prevention.

Validity of partial protocols to evaluate the prevalence of developmental defects of enamel in permanent dentition: a birth cohort study in Southern Brazil.

OBJECTIVES: To evaluate the validity of partial protocols (PP) to assess the prevalence of developmental defects of enamel (DDE) in permanent teeth and identify the strength of the association between DDE and some risk factors, using PP compared to the full-mouth (FM) exam. MATERIALS AND METHODS: This study was conducted in a population-based birth cohort of children born in 2004 in Pelotas, Southern Brazil. Socioeconomic, demographic, pre-, per-, and post-birth variables were collected. A subsample of 994 children was clinically examined for DDE in 2017, using the modified DDE index, using the "full- mouth" (FM) protocol. After FM had been performed, a dataset was created. Two different partial protocols (PP) were simulated from FM data: "only buccal surfaces (BS)" and "incisive and molars only (IM)." Sensitivity, absolute and relative bias, and inflation factors were calculated. RESULTS: For any DDE, FM had prevalence of 40.8%. The prevalence of DDE was 38.8% and 36.0%, for BS and IM protocols, respectively. When tested for any DDE, PP "BS" and "IM" showed high sensitivity. The underestimation of the true prevalence did not exceed 6.9% for PP "BS" and 16.1% for PP "IM." All protocols showed similar magnitude of association with the selected risk factors. CONCLUSION: Both PP "BS" and "IM" can be used to estimate the prevalence of DDE in epidemiological studies. CLINICAL RELEVANCE: Oral health surveys now have the option of using PP to collect DDE prevalence and investigate their association with risk factors, being less time-consuming, expensive, and labor intensive.

Does primary trauma lead to developmental defects in permanent teeth?

Introduction A systematic review of existing evidence to determine if trauma in the primary dentition causes alteration in the development of the underlying permanent dentition.Data sources Six electronic databases (PubMed, Medline, MEDES, Scopus, Lilacs and Embase) were used to search a range of dental terms relating to dental trauma to locate studies between 1972-2020.Study selection Study selection was carried out by two authors by reviewing title, abstract and then full articles. A third author was consulted if consensus for inclusion was needed. Eligibility criteria included all scientific articles concerning sequalae to the human permanent dentition following trauma to the primary dentition. Only English, German and Spanish languages were included. For evaluation, the studies must have satisfied the following: a) minimum sample of 50 children to be representative; b) radiographic examination; and c) appropriate follow-up period up to permanent successor eruption.From 537 studies, 18 studies were identified for consideration in the review, comprising of 13 cross-sectional studies, two cohort studies and three case control studies.Data extraction and synthesis The Newcastle-Ottawa Scale was used to extract data and determine study quality. Only studies determined as high quality were included in the review. Four cross-sectional studies and three case control studies, totalling seven studies, were used. Data from these high-quality studies was summarised into table format.Results Large variation in study sample size existed from 138-753 traumatised teeth and 78-879 children. Both sexes were included in all studies and the children were aged between 0-17 years.Some studies found there was no difference in rate of trauma between girls and boys, while others found there was a higher incidence of trauma in boys than girls. The most frequently traumatised teeth were the upper primary central incisors. Whilst most studies covered all types of primary trauma, two only studied intrusion and one specified the type of primary trauma as luxation or fracture injuries.Whilst some of the studies concluded a higher frequency of defects to permanent teeth following primary intrusion trauma aged four and under, others showed no significant differences between the age of intrusion and the effect to the successor incisor.Enamel defects of the permanent teeth were the most common sequalae with a wide prevalence reported between 4.5-68.8%. Enamel defects were classified as hypoplasia and hypocalcification. Ectopic or altered eruption, crown or root dilacerations and odontoma development were observed less often, with the latter very rarely.Conclusions Primary tooth intrusion trauma causes the highest proportion of sequalae presenting as enamel defects. Younger patients experiencing primary trauma are more likely to obtain damage to the succeeding dentition. The existing quality of evidence is limited due to the observational nature of the studies available.

Glass Ionomer Sealants Can Prevent Dental Caries but Cannot Prevent Posteruptive Breakdown on Molars Affected by Molar Incisor Hypomineralization: One-Year Results of a Randomized Clinical Trial.

To evaluate the preventive effect of glass ionomer cement (GIC) against dental caries and posteruptive breakdown (PEB) on molars affected by molar incisor hypomineralization (MIH). In this randomized clinical trial, 77 children aged 5-9 years with at least 1 MIH-affected molar and without PEB or dentin caries lesions (n = 228) were included and randomly allocated to one of the following groups: (1) MIH-affected molars that remained unsealed and (2) MIH-affected molars that received GIC sealants. Dental caries and PEB were clinically evaluated after 6 and 12 months. Associations between dental caries and PEB with independent variables were evaluated using logistic regression analysis (p < 0.05). The MIH-affected molars allocated to the GIC sealant group were less likely to develop dental caries compared to those allocated to the unsealed group (OR = 0.23; 95% CI 0.06-0.95). Conversely, application of a GIC sealant was not associated with prevention of PEB (p = 0.313). Furthermore, MIH-affected molars presenting yellow-brown opacities were almost 5 times more likely to develop dental caries (p = 0.013) and PEB (p = 0.001) compared to those presenting white-creamy opacities. We can conclude that GIC sealants can prevent dental caries on MIH-affected molars; however, the same protective effect was not observed for PEB.

Epidemiology of Erosive Tooth Wear, Dental Fluorosis and Molar Incisor Hypomineralization in the American Continent.

Non-carious dental lesions such as developmental defects of enamel (DDE) and erosive tooth wear (ETW) are the subject of intensive research. This paper aims to give perspectives on both DDE, including dental fluorosis and molar incisor hypomineralization (MIH), and ETW, presenting epidemiological data from the Americas and associated diagnostic aspects. Besides, it is important to present evidence to guide the clinical assessment process, supporting the clinicians' management decisions towards better oral health of their patients. The overall increase in the worldwide prevalence of non-carious lesions discussed in this this paper may reflect the need of perceptual changes. Although the number of publications related to these conditions has been increasing in the last years, there is still a need for clinical diagnostic and management awareness to include these conditions in routine dental practice. Besides, it is important to provide recommendations for standardized clinical assessment criteria, improving the process and helping clinicians' adherence. In this sense, this paper discusses the most commonly implemented indices for each condition. Thus, despite the wide range of diagnostic indices, BEWE is proposed to be the index recommended for ETW assessment, Dean or Thylstrup & Fejerskov indices for fluorosis and preferably the EAPD criteria (or modified DDE index) for MIH. Overall, non-carious lesions are a growing concern, and it is important to implement preventive measures that control their severity and progression, and accurate diagnosis by the dental clinician.

Prenatal, perinatal and postnatal events associated with hypomineralized second primary molar: a systematic review with meta-analysis.

OBJECTIVE: The etiology of hypomineralized second primary molar (HSPM) appears to be multifactorial but remains uncertain. Thus, the objective was to systematically review studies that investigated adverse health conditions in the prenatal, perinatal and postnatal periods associated with HSPM. MATERIAL AND METHODS: The search was carried out in five databases and in gray literature. The risk of bias of observational studies was analyzed according to the Newcastle-Ottawa scale. RESULTS: A total of 1878 studies were identified. Fourteen were eligible, and seven were included in the meta-analysis. Maternal smoking (OR = 2.88; 95%CI: 1.62-5.15) and presence of maternal hypertension (OR = 2.91; 95%CI: 1.35-6.28) were significantly associated with higher odds of HSPM. In the perinatal period, factors associated with HSPM were low birth weight (OR = 1.50; 95%CI: 1.15-1.96), prematurity (OR = 1.93; 95%CI: 1.37-2.71), delivery complications (OR = 2.42; 95%CI: 1.52-3.83) and need for an incubator (OR = 1.65; 95%CI: 1.01-2.70). Not breastfeeding (OR = 1.26; 95%CI: 1.01-1.58), use of antibiotics by the child (OR = 1.24; 95%CI: 1.04-1.48), fever (OR = 1.37; 95%CI: 1.10-1.72) and asthma (OR = 1.91; 95%CI: 1.16-3.13) were the postnatal factors associated with HSPM. CONCLUSION: Maternal smoking, maternal hypertension, low birth weight, prematurity, delivery complications, need for incubation, not breastfeeding, antibiotic use, fever and childhood asthma were associated with HSPM. Well-designed prospective cohort studies are needed. Clinical relevance Understanding the etiological factors can be guiding aspects for individual clinical approaches, as well as guiding the design of preventive interventions for HSPM.

Knowledge, attitudes, and beliefs regarding molar incisor hypomineralization (MIH) amongst German dental students.

BACKGROUND: Knowledge of molar incisor hypomineralization (MIH) has relevance for paediatric dentists. AIM: To assess final-year German dental students' knowledge, attitudes, and beliefs regarding MIH. MATERIALS AND METHODS: A previously validated questionnaire was posted to the 31 German dental schools. Demographic covariates as well as knowledge regarding diagnosis and prevalence, and attitudes and beliefs around aetiology and management were collected. RESULTS: Twenty-two (71%) dental schools responded and a total of 877 students participated. Most (97%) were familiar with MIH and 88% were aware of the diagnostic criteria for MIH; however, only 42% knew how to implement them. One-third were able to identify MIH and 16% reported diagnostic confidence when doing so; 90% assumed the MIH prevalence to be <10%. Two-thirds of the respondents implicated genetic components as the main aetiological factor of MIH. Resin composite (60%) and preformed metal crowns (46%) were the dental materials most often suggested for restorative management. Almost all (98%) respondents were interested in receiving more clinical training. CONCLUSION: German students were familiar with MIH; however, they reported low levels of knowledge and confidence regarding its prevalence and diagnosis. Standardized nationwide, up-to-date curricula should be implemented to educate future dentists in Germany.

[Molar incisor hypomineralisation (MIH)-discussion of prevalence and etiology with special reference to the results from the Munich birth cohorts GINIplus and LISA]. / Molaren-Inzisiven-Hypomineralisation (MIH). Häufigkeit und mögliche Ursachen unter besonderer Berücksichtigung der Ergebnisse aus den Münchner Geburtskohorten GINIplus und LISA.

After caries, molar incisor hypomineralisation (MIH)-also known as chalky teeth-is one the most common dental diseases in children and adolescents. In addition to aesthetic limitations, especially on the anterior teeth, hypersensitivities and enamel breakdowns on permanent molars are of functional importance. While the MIH prevalence rates range from ~ 10% to ~ 30% and is well described, the situation regarding aetiology is unsatisfactory. Although efforts have been made in the past to clarify the aetiology, no plausible reason is available so far. Aetiology research has to be judged as methodologically challenging, since it should ideally be embedded in prospectively planned birth cohort studies. The aim of this article is to summarize typical clinical characteristics of MIH, epidemiological findings and potential causes with special reference to the earlier published results from the two Munich birth cohort studies GINIplus and LISA.

Photobiomodulation therapy for hypersensitivity associated with molar-incisor hypomineralization: a case report.

Molar-incisor hypomineralization (MIH) is a qualitative defect of the dental enamel on permanent first molars and may be associated with permanent incisors. There is currently no defined therapeutic protocol for managing the hypersensitivity associated with this condition. The present case report describes the treatment of a patient with MIH and the impact on the patient's quality of life as assessed using the Child Perceptions Questionnaire for children aged 11 to 14 years (CPQ11-14). The maxillary central incisors, maxillary and mandibular first molars, and mandibular right canine of an 11-year-old girl were compromised by MIH. The long version of the CPQ11-14 was self-administered before treatment. Initially, the patient reported hypersensitivity of her maxillary right central incisor, maxillary and mandibular left first molars, and mandibular right canine when consuming cold food and beverages. This was confirmed by applying a jet of air to the teeth and asking the patient to report the level of sensitivity using the Wong-Baker FACES Pain Rating Scale. The patient reported that hypersensitivity was present every day or almost every day. Desensitizing treatment included 4 applications of photobiomodulation therapy (infrared diode laser) and 4 applications of fluoride varnish. After desensitization, the maxillary central incisors received direct composite resin restorations, while the maxillary left first molar, which had an amalgam restoration and recurrent caries, received a resin-modified glass ionomer cement restoration. At the conclusion of the treatment, the patient completed the CPQ11-14 again and reported less difficulty with consuming hot and cold foods and beverages, indicating that treatment had reduced hypersensitivity and its negative impact on her quality of life.

Long-Term Survival of Enamel-Defect-Affected Teeth.

There has been considerable research focussed on the occurrence and aetiology of developmental defects of enamel, but less is known about the extent to which enamel-defect-affected teeth may be at greater risk for dental caries. The Dunedin Multidisciplinary Health and Development Study is a prospective cohort study of 1,037 children born in Dunedin, New Zealand, between April 1, 1972, and March 31, 1973. Participants were examined for the presence of developmental defects of enamel at the age of 9 years and then repeatedly for the occurrence of dental caries through to the age of 45 years. After controlling for confounding variables, incisor teeth affected by demarcated opacities at the age of 9 were 3.4 times more likely to be restored than teeth unaffected by defects. Incisors with diffuse opacities and hypoplasia or combinations of defects were 2.8 times more likely to be restored. Molars with enamel defects of any type did not have any significantly different risk for being subsequently restored or lost due to caries than unaffected molars, except those affected by diffuse opacities, which were at 0.4 times the risk of being lost due to caries. Dental clinicians should be aware that enamel-defect-affected teeth are not necessarily at greater risk for tooth loss due to caries in the long term, but permanent incisors affected by enamel defects are at higher risk of receiving restorative intervention.

Is There an Association between Asthma and Dental Caries and Molar Incisor Hypomineralisation?

This epidemiological study aimed to compare the caries and molar incisor hypomineralisation (MIH) experience in asthmatic and non-asthmatic adolescents assessed at 10 and 15 years of age. 730 adolescents from ongoing birth cohort studies (GINIplus/LISA) from Munich, Germany, were examined for carious lesions at the age of 10 and 15 years to determine caries experience under inclusion of non-cavitated carious lesions D1-2T and the tooth-related decay-missing-filled index. Furthermore, MIH was scored on all permanent teeth according to the criteria of the European Academy of Paediatric Dentistry. The association between caries and MIH prevalence at the 10-year and 15-year follow-up as well as caries incidence with ever having an asthma diagnosis was analysed using hurdle regression models adjusted for potential confounders. Of the 730 adolescents, 52 and 78 were identified as asthmatics at the 10- and 15-year follow-up, respectively. There were no significant differences in caries prevalence or experience between asthma-free participants and any of the asthma groups (taking metered-dose inhaler (MDI) medication vs. taking no MDI medication). However, a significant positive association was found for asthmatic adolescents who did not take MDI medication with higher MIH/T values (OR = 2.56, 95% CI = 1.03-6.37, p = 0.043) compared to non-asthmatics. In conclusion, asthma did not influence the caries status of adolescents in the present study. Interestingly, a significant association was found between adolescents with asthma who did not take MDI medication and the number of MIH-affected teeth. The association between asthma, medication, and MIH needs further confirmation.

Second primary molar hypomineralisation and drugs used during pregnancy and infancy. A systematic review.

OBJECTIVES: Hypomineralised second primary molars (HSPM) are due to idiopathic hypomineralisation that affects from 1- to 4-s primary molars, and its aetiology remains unclear. Our objective was to systematically review studies in which the investigators had studied the association between HSPM and drug use during pregnancy and the first year of life. MATERIALS AND METHODS: A systematic search for publications until July 2018 was conducted in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-analyses (PRISMA) statement. No restrictions were placed on year of publication. The PECO Question was as follows: P, children exposed to drugs during pregnancy and the first year of life; E, drugs to which mothers, during pregnancy and their offspring were exposed; C, control groups from studies with the same characteristics not exposed to drugs during pregnancy and the first year of life; and O, relationship between drug exposure during pregnancy and the first year of life and HSPM. Two reviewers extracted the data and assessed the risk of bias using the Newcastle-Ottawa Scale criteria. RESULTS: We initially identified 986 articles, or which seven were selected for review: two case-control studies, one cross-sectional studies and four cohort studies. Four studies reported data on drug consumption during pregnancy and four investigated drug use during the first year of life and the occurrence of enamel defects in primary dentition. CONCLUSIONS: There is no clear evidence that the use of drugs during pregnancy and during the first year of life is associated with HSPM. Further well-designed prospective studies are needed. CLINICAL RELEVANCE: Determining the etiological factors related to the development of HSPM would help to establish preventive protocols in patients at potential risk. As HSPM is predictive of molar incisor hypomineralisation (MIH), the application of preventive protocols would avoid complications in both the primary and permanent dentition.

Relationship between preterm birth and developmental defects of enamel: A systematic review and meta-analysis.

BACKGROUND: A putative relationship between preterm birth and developmental defects of enamel (DDE) has been described in the literature. Although systematic reviews have found preterm birth may lead to DDE, the effect size has not been quantified. AIM: The aim of this systematic review and meta-analysis was to determine the association between preterm birth and DDE. DESIGN: An electronic search was performed in PubMed, Cochrane Library, Scopus, and Web of Science to identify relevant studies. Two independent reviewers selected the studies in a two-stage process in accordance with the PRISMA statement. The risk of bias was also analysed using the Newcastle-Ottawa Scale criteria. RESULTS: A total of 1041 publications were considered after an electronic search, 20 of which were included in the systematic review. Of these 20 publications, 18 articles were included in a meta-analysis. The meta-analysis detected an increased risk of developing DDE in preterm children [OR: 3.27 (95% CI 2.02, 5.30; P < .001)], with a greater risk in the primary dentition. In addition to this, a subgroup analysis showed a greater risk in the development of hypoplasia in preterm children. CONCLUSIONS: The results of this meta-analysis showed a three times increased risk of developing DDE in preterm children.

Infantile hemangioma of the upper lip and enamel hypoplasia: Two case reports.

Segmental infantile hemangiomas related to PHACE syndrome have recently been associated with enamel hypoplasia. We present two cases of solitary, localized upper lip infantile hemangioma with enamel hypoplasia of deciduous teeth.

Trauma in primary teeth and its effect on the development of permanent successors: a controlled study.

Objective: This controlled study investigated the occurrence of sequelae to permanent successors (SPS) following traumatic dental injury in primary teeth (TDIp). Additionally, this study evaluated whether TDIp is a risk factor for SPS, with a focus on an association between SPS and the child's age and type of trauma. Materials and methods: The trauma group (TG) consisted of permanent teeth, whose antecessors had suffered TDIp, in a population of children with complete eruption of permanent teeth. The control group (CG) consisted of permanent teeth from the same individuals, whose antecessors had not suffered TDIp. There were 214 cases of TDIp with their respective permanent teeth. In the CG 247 permanent teeth, whose antecessor had not suffered TDIp, were included. Data concerning such teeth and when TDIp occurred (in terms of the child's age) and types of SPS were collected. The chi-square test, regression logistic with generalized estimating equations (GEE) test, and risk analyses were applied to investigate the associations. Results: Overall, 29% of the permanent teeth in the TG presented SPS. This was compared to the development disturbances in the CG, which was 7%. The TG demonstrated the highest risk for SPS (OR, 5.388; p = .0001). The discolouration of enamel (37%) was the most common type of SPS found. SPS was more prone to occur in permanent teeth whose antecessors had been intruded (39%; p < .001). TDIp when the child was 1-year old was associated with SPS (p < .001). Moreover, children who had TDIp had a 4.1 times higher risk of presenting SPS. Conclusions: TDIp is a risk factor for the development of SPS. All types of TDIp caused SPS in this research. Additionally, the younger ages at the time of the injury and intrusions were related to SPS.

Developmental Disturbance of a Maxillary Permanent Lateral Incisor Following Trauma at the Age of 16 Months: A 6-Year Follow-Up.

A 3 year and 8 months old Chinese boy was referred for a consultation regarding his missing maxillary anterior teeth. He had a history of trauma to his primary maxillary anterior teeth due to a fall at the age of 16 months. Clinical examination of the patient indicated multiple carious lesions and inadequate oral hygiene. Radiographic examination revealed intrusion of the primary left lateral incisor, with evidence of damage to the permanent tooth germ. Subsequently, the patient was followed-up for almost six years during which his permanent maxillary left lateral incisor erupted exhibiting an unusual morphology. Clinically enamel hypoplasia and radiographically dens invaginatus were evident in affected tooth.

Enamel Hypomineralization in Children With Clefts and the Relationship to Treatment: A Cross-sectional Retrospective Study.

OBJECTIVE: The aim of this study was to determine whether molar incisor hypomineralization (MIH) is greater in patients with cleft lip and palate (CLP) who underwent primary alveolar grafting (PAG) as compared with CLP waiting for secondary alveolar grafting (SAG) and with controls. DESIGN: A retrospective analysis of intraoral photographs of 13 CLP patients who underwent a PAG, 28 CLP prior to SAG, and 60 controls without CLP was performed. Mantel-Haenszel χ tests were used to compare the 3 groups for differences in MIH scores, and Wilcoxon rank sum tests were used to compare the groups for differences in average MIH scores. A 5% significance level was used for all tests. RESULTS: Molar incisor hypomineralization scores were significantly higher for the PAG and SAG groups compared with the control group (P < 0.001). The PAG group had significantly higher incisor MIH (P = 0.016) compared with the SAG group. Molar incisor hypomineralization average scores were significantly higher for the 2 graft groups compared with the controls (P < 0.0001). The PAG group had significantly higher average MIH score and average MIH score for incisors compared with the SAG group (P = 0.03). CONCLUSIONS: Cleft lip and palate patients have significantly greater MIH compared with controls, and CLP patients with PAGs have significantly greater MIH in the incisor region compared with CLP patients with SAGs, indicating that subjects with PAGs have more severely affected dentition.

Factors associated with molar-incisor hypomineralisation in schoolchildren aged 8-10 years: a case-control study.

BACKGROUND: The aetiology of molar-incisor hypomineralisation (MIH) is multifactorial and may involve genetic and environmental factors. AIM: To verify the factors associated with MIH in schoolchildren from 8 to 10 years of age. DESIGN: This is a case-control study with a sample consisting of children aged 8 to 10 years, paired by gender and school type, in a ratio of 1:3. The case group included 186 children with MIH and the control included 558 children without MIH. Data were collected through a semi-structured questionnaire and clinical examination. Chi-square, linear-by-linear, Mann-Whitney, and logistic regression tests were conducted. A value of P < 0.05 was considered significant. RESULTS: The prevalence of mild MIH was 19.5%, moderate MIH 2.2% and severe MIH 3.2%. An association was observed between MIH with treatment need and a higher mean DMF-T and decayed and missing teeth (P < 0.05). According to the aetiological factors studied, mothers who presented a fever during pregnancy had a 2.54 times greater chance of having children with severe MIH than mothers who did not present a fever (P = 0.045). CONCLUSION: The presence of fever during pregnancy and the need for treatment were associated with MIH.

Exploring the association between genetic and environmental factors and molar incisor hypomineralization: evidence from a twin study.

BACKGROUND: The etiology of molar-incisor hypomineralization (MIH) remains unknown. Studies indicate that it is multifactorial, and that genetic and environmental factors are involved. Research with twins provides important subsidy to investigate the Influence of genetics and environmental factors that act during pregnancy on the etiology of alterations. AIM: This cross-sectional study evaluated the agreement of molar incisor hypomineralization (MIH) between monozygotic and dizygotic twin pairs and the association with environmental factors. DESIGN: The sample consisted of 167 pairs of twins (8-15 years old), 94 monozygotic and 73 dizygotic. The parents answered a questionnaire on sociodemographic data and pre-, peri-, and postnatal health. A dental examination was performed by two calibrated examiners (Kappa ≥0.88) for MIH diagnosis, following the criteria proposed by the European Academy of Pediatric Dentistry in 2003. RESULTS: The prevalence of MIH was 29.3%. There was greater concordance of MIH between monozygotic twins for affected first molars and permanent incisors (P = 0.0012) and pairs of twins assessed (P = 0.0211). The presence of MIH was associated with family income between one and two wages (P = 0.009, prevalence ratio [PR] = 3.82, confidence interval [CI 95%] 1.40-10.44), above two wages (P = 0.007, PR = 4.60, 95% CI: 1.51-14.05), and gestational hemorrhage (P = 0.032, PR = 5.70, 95% CI: 1.16-28.14). CONCLUSIONS: The greater concordance in the diagnosis of MIH among monozygotic twins indicates a genetic influence, although environmental factors, such as family income and hemorrhage during pregnancy, are also associated with the occurrence of MIH.

Prevalence of molar incisor hypomineralization and regional differences throughout Japan.

BACKGROUND: Molar incisor hypomineralization (MIH) frequently occurs in children worldwide. However, MIH prevalence throughout Japan has not yet been investigated. The purpose of this study was to clarify MIH prevalence rates and to consider potential regional differences throughout Japan. METHODS: A total of 4496 children aged 7-9 years throughout Japan were evaluated in this study. MIH prevalence rates among children were evaluated in eight regions throughout Japan. A child's residence was defined as the mother's residence during pregnancy. The localization of demarcated opacities and enamel breakdown was recorded on a standard code form using a guided record chart. Logistic regression analysis was used to evaluate whether MIH prevalence rates differed among age groups, sex, and regions. RESULTS: The overall prevalence of MIH in Japan was 19.8%. The prevalence of MIH was 14.0% in the Hokkaido region, 11.7% in the Tohoku region, 18.5% in the Kanto Shin-Etsu region, 19.3% in the Tokai Hokuriku region, 22.3% in the Kinki region, 19.8% in the Chugoku region, 28.1% in the Shikoku region, and 25.3% in the Kyushu region. These regional differences were statistically significant. Moreover, MIH prevalence rates decreased with age. No significant sex differences in MIH prevalence rates were demonstrated. CONCLUSIONS: To our knowledge, this is the first MIH study carried out in several regions throughout Japan. Regional differences existed in MIH prevalence rates; particularly, MIH occurred more frequently in children residing in southwestern areas than those in northeastern areas of Japan.