Genes expressed in dental enamel development are associated with molar-incisor hypomineralization

Caries among adult patients with controlled celiac disease: A cross-sectional study

INTRODUCTION

Celiac disease (CD) is one of the most common chronic gastrointestinal disorders in the world. Currently, the literature about the dental profiles of patients with celiac disease is sparse and no studies have reported on the oral conditions and caries status of CD patients in Kuwait.

OBJECTIVE

This study investigated the association between CD and caries experience.

METHODS

Two groups were examined; study and control. The study group consisted of controlled celiac disease patients. The control group consisted of subjects who were matched for age and gender to the study group participants. Both groups received clinical and radiographic examinations of their oral cavity. Parameters recorded for the study purposes were-dental caries index (decayed, missing, and filled teeth), salivary flow rates (stimulated and unstimulated), salivary buffering capacity and Lactobacilli and mutans Streptococci bacterial counts.

RESULTS

Patients with CD had statistically significant fewer missing teeth than the controls. There were no other significant differences. Measured stimulated and unstimulated salivary flow rates and salivary buffering capacity showed no statistical differences. Bacterial counts revealed no significant differences.

CONCLUSION

Adult patients with controlled CD showed fewer missing teeth than their counterparts. Other caries and salivary parameters showed no statistical differences between the two groups.

Aesthetic perception in children with molar incisor hypomineralization

PURPOSE

To investigate the relationship between aesthetic perception and molar incisor hypomineralization (MIH) in schoolchildren aged 8-12 years.

METHODS

The study included 467 pupils enrolled in elementary schools. Once authorization was received, the students were examined for DMFT and dmft indexes (WHO criteria), and for MIH (EAPD criteria). The aesthetic perceptions were verified by the Child Perceptions Questionnaire About Tooth Appearance (CQATA), a questionnaire divided into several items, including physical, psychological and social domains; perception about tooth pleasantness, tooth alignment, tooth discoloration and tooth health; and reported pleasant colour. Data analysis was carried out using descriptive statistics, the Chi-square, the Mann-Whitney and the Kruskal-Wallis tests, and linear regression at a significance level of 0.05.

RESULTS

The tooth health perception was worse when the child had MIH, and the tooth alignment and tooth discoloration perceptions, when MIH affected the incisors. The number of teeth affected by MIH was associated with higher averages in the tooth discoloration perception.

CONCLUSIONS

Children with MIH showed more negative perceptions toward tooth health, tooth alignment and tooth discoloration. However, none of the clinically investigated variables negatively impacted the reported pleasant colour question.

Association of LTF, ENAM, and AMELX polymorphisms with dental caries susceptibility: a meta-analysis

Background

This meta-analysis evaluated the association of LTF, ENAM, and AMELX polymorphisms with dental caries susceptibility.

Methods

We searched the Scopus, PubMed/Medline, Web of Science, and Cochrane Library databases to retrieve articles published by October 2019. Review Manager 5.3 software was used to estimate the odds ratios (ORs) and 95% confidence intervals (CIs). The results of publication bias tests were retrieved by Comprehensive Meta-Analysis 2.0 software.

Results

A total of 150 relevant records were identified; out of which, 16 were entered into the analysis (4 studies assessed LTF, 11 ENAM, and 11 AMELX polymorphisms). Of all polymorphisms, there was a significant association only between ENAM rs3796704 polymorphism and dental caries susceptibility. Both ENAM rs3796704 and AMELX rs17878486 polymorphisms had a significant association with dental caries risk in the Caucasian ethnicity and the studies including caries-free control group.

Conclusions

The results of this meta-analysis showed that the G allele and the GG genotype of ENAM rs3796704 were associated with an increased risk of caries in the case group compared with the control group. But there was no association between LTF rs1126478, ENAM (rs1264848 and rs3796703), and AMELX (rs946252, rs17878486, and rs2106416) polymorphisms and dental caries susceptibility.

Molar incisor hypomineralisation and dental anomalies: A random or real association?

BACKGROUND

Clinical observations suggest molar incisor hypomineralisation (MIH) may present with other dental conditions.

AIMS

The study aimed to determine the prevalence and variety of dental anomalies in children presenting with MIH.

DESIGN

A convenience sample of children referred to a UK dental hospital was recruited. Orthopantogram radiographs, taken as part of routine care, were assessed for dental anomalies. Two calibrated examiners reviewed the films separately and determined the presence and character of anomalies.

RESULTS

Radiographs were obtained from 101 patients, with an age range of 6-15 years. Co-existing hypodontia was identified in 12%, with lower second premolars being the most commonly missing teeth. Concurrent ectopic first permanent molars were identified in 8%, and infraocclusion of one or more primary molars was identified in 9%. Abnormal morphology was found in 9%, including macrodont and microdont teeth. In total, 29% of patients had an associated dental anomaly. Examiners had perfect agreement using Cohen's kappa coefficient.

CONCLUSION

This high prevalence of dental anomalies, particularly hypodontia, in children with MIH is a novel and clinically important finding. Further research is warranted considering the potential implications for assessment and treatment planning.

The relationship between molar incisor hypomineralization, dental caries, socioeconomic factors, and polymorphisms in the vitamin D receptor gene: a population-based study

OBJECTIVES

The purpose of this cross-sectional study was to investigate whether polymorphisms in vitamin D receptor (VDR) genes increase the prevalence of dental caries, molar incisor hypomineralization (MIH), and hypomineralized primary second molars (HPSM).

MATERIAL AND METHODS

A representative population-based sample of 731 schoolchildren, 8 years of age, was randomly selected in Curitiba, Paraná, Brazil. MIH, HPSM, and dental caries were clinically assessed by four calibrated examiners (kappa > 0.80) using European Academy of Pediatric Dentistry (2003) criteria, the modified Developmental Defects of Enamel (DDE) index, and the Decayed, Missing, or Filled Teeth (DMFT) index by the World Health Organization (2013), respectively. The VDR rs739837 and rs2228570 polymorphisms were genotyped using real-time polymerase chain reaction. Associations were analyzed by Poisson regression with robust variance (α = 0.05).

RESULTS

Schoolchildren with MIH presented a higher prevalence of dental caries (DMFT > 1, PR = 2.52, confidence interval = 1.60-3.97, p ≤ 0.001). No association was observed between MIH, HPSM, and dental caries, with rs739837 and rs2228570 polymorphisms. Individuals with the GT/GG genotype in rs739837 polymorphism presented a higher prevalence of MIH in molars and incisors than individuals TT (PR = 2.34, confidence interval = 1.08-5.07, p = 0.03).

CONCLUSION

Children with MIH presented a significant higher prevalence of dental caries than children without MIH. To carry at least one G allele in rs739837 was associated to higher prevalence of MIH in molars and incisors.

CLINICAL RELEVANCE

Our findings suggested that more severe cases with incisors affected by MIH could be associated with polymorphism in VDR gene.

Evaluating the changes in molar incisor hypomineralization prevalence: A comparison of two cross-sectional studies in two elementary schools in Mexico City between 2008 and 2017

BACKGROUND

Little information is available on the trends over time of the prevalence of molar incisor hypomineralization (MIH). This condition may be preventing dental caries decline.

AIM

(a) To compare the prevalence of MIH, in Mexico City schoolchildren, evaluated in 2008 with a group evaluated in 2017, (b) to identify the association of MIH with dental caries, and (c) to assess the mother's perception of her child's oral health status.

DESIGN

Two cross-sectional studies performed in 2008 and in 2017 were compared. The oral examiner and the selected schools were the same in both surveys.

RESULTS

A total of 549 schoolchildren were evaluated. The prevalence of MIH in the first survey was 20.3%, and 31.9 % in the second survey, (p = .002). Children with MIH were more likely to have dental caries. The odds ratio was 2.24 (p = .036) and 4.18 (p ˂ .001) in the first and second surveys, respectively. Mothers of children with MIH perceived worse oral health status of their children than the mothers whose children did not have MIH (odds ratio = 4.47, p ˂ .001).

CONCLUSION

The findings portray a clear increase in prevalence of MIH and highlight the need for increased awareness about this condition among dentists and the general population.

Interactions with the aquaporin 5 gene increase the susceptibility to molar-incisor hypomineralization

OBJECTIVE

The aim of this study was to evaluate whether individual genetic factors involved in amelogenesis, the immune response and water channel proteins may increase the susceptibility to Molar-Incisor Hypomineralization (MIH) in Chinese children.

DESIGN

DNA samples were collected from 86 cases with MIH cases and 344 controls. Sixteen single-nucleotide polymorphisms (SNPs) were investigated. Logistic regression analysis was performed to assess association between SNPs and the risk of MIH.

RESULTS

Our results showed that the risk of MIH in the rs13115627-AA genotype carriers and the rs1784418-TT genotype carriers were significantly higher than that among those with the rs13115627-GG genotype (OR (95 % CI)) = 4.942 (0.658-37.131) and the rs1784418-CT genotype (OR (95 % CI)) = 2.023 (1.63-3.521). The population with the rs1800972-CC genotype and the rs1800972-C allele had a higher risk to develop MIH, OR (95 % CI) = 2.284 (1.267-4.115), OR (95 % CI) = 2.427 (1.493-3.953) respectively. In the Aquaporin 5(AQP5) gene, we individually analyzed two SNPs, rs1996315 and rs923911. We found no significant associations between them and MIH. However, in the analysis of the gene-gene interactions, we discovered a significant two-locus model (P = 0.023) involving rs1996315 and rs923911. Participants with the rs1996315-AG and rs923911-AC genotypes had the highest MIH risk, compared to participants with the rs1996315-GG and rs923911-CC genotypes, OR (95 % CI) = 3.603 (1.147-11.318).

CONCLUSION

This study showed that genetic variants in the AMBN, MMP20 and DEFB1 genes may contribute to MIH in the permanent dentition of children. Moreover, interactions among AQP5 gene may also increase the MIH susceptibility.

Tuftelin and HIFs expression in osteogenesis

Tuftelin was originally discovered and mostly studied in the tooth, but later found also in other organs. Despite its wide distribution among tissues, tuftelin's function has so far been specified only in the formation of enamel crystals. Nevertheless, in many cases, tuftelin was suggested to be associated with cellular adaptation to hypoxia and recently even with cell differentiation. Therefore, we aimed to investigate tuftelin expression along with hypoxia-inducible factors (HIFs) during the early development of the mandibular/alveolar (m/a) bone, when osteoblasts started to differentiate in vivo and to compare their expression levels in undifferentiated versus differentiated osteoblastic cells in vitro. Immunohistochemistry demonstrated the presence of tuftelin already in osteoblastic precursors which were also HIF1-positive, but HIF2-negative. Nevertheless, HIF2 protein appeared when osteoblasts differentiated, one day later. This is in agreement with observations made with MC3T3-E1 cells, where there was no significant difference in tuftelin and Hif1 expression in undifferentiated vs. differentiated cells, although Hif2 increased upon differentiation induction. In differentiated osteoblasts of the m/a bone, all three proteins accumulated, first, prenatally, in the cytoplasm and later, particularly at postnatal stages, they displayed also peri/nuclear localization. Such a dynamic time-space pattern of tuftelin expression has recently been reported in neurons, which, as the m/a bone, differentiate under less hypoxic conditions as indicated also by a prevalent cytoplasmic expression of HIF1 in osteoblasts. However, unlike what was shown in cultured neurons, tuftelin does not seem to participate in final osteoblastic differentiation and its functions, thus, appears to be tissue specific.

A systematic review and meta-analysis of systemic exposure associated with molar incisor hypomineralization

OBJECTIVE

To evaluate systemic exposures associated with molar incisor hypomineralization (MIH).

METHODS

This systematic review was performed using published observational studies that evaluated the systemic exposures associated with MIH. The sources of articles searched were PubMed, Scopus, Web of Science, LILACS, BBO, Cochrane Library and Grey literature. The risk of bias was analysed according to the Newcastle-Ottawa Scale for quality assessment. The meta-analysis was performed considering the exposures during the prenatal, perinatal and postnatal periods using the CMA software.

RESULTS

A total of 4207 articles were identified. Twenty-nine studies were eligible for inclusion and 27 were included in the meta-analysis. The studies presented low and moderate risks of bias, except for one that was classified as having a high risk of bias. Maternal illness during pregnancy (OR 1.40; 95% CI 1.18-1.65, P < 0.0001) and psychological stress (OR = 2.65; 95% CI 1.52-4.63; P = 0.001) was observed to be significantly associated with higher odds of MIH. During the perinatal period, caesarean delivery (OR = 1.32, 95% CI 1.11-1.57, P = 0.001) and delivery complications (OR = 2.06; 95% CI 1.47-2.88, P < 0.0001) were also associated with MIH. In the postnatal period, only respiratory diseases (OR = 1.98; 95% CI 1.45-2.70, P < 0.0001) and fever (OR = 1.50; 95% CI 1.22-1.84; P < 0.0001) were associated with higher prevalence of MIH. The evidence was graded as very low quality.

CONCLUSIONS

Maternal illness, psychological stress, caesarean delivery, delivery complications, respiratory diseases and fever during the first years of a child's life were significantly associated with a higher odds of MIH. However, this should be interpreted with caution, once the primary studies were observational, with serious limitations according to the risk of bias, imprecision, and inconsistency. Further, well-designed cohort studies are still required.

Molar incisor hypomineralization and pre-eruptive intracoronal lesions in dentistry-diagnosis and treatment planning

The aim of this study is to report the diagnostic features, prevalence, mineral content, clinical significance and treatment options of molar incisor hypomineralization (MIH) and pre-eruptive intracoronal lesions (PEIR), in order to minimize miss-treatment of primary and permanent teeth in young children. MIH was defined as the occurrence of hypomineralization of one up to four permanent first molars from a systemic origin and frequently associated with affected incisors. PEIR are lesions that are located in the occlusal portion of the crown of unerupted permanent or primary teeth. The prevalence of MIH was reported between 2.5%-40% in the permanent first molars and 0%-21.8% in primary second molars. PEIR was observed in 2%-8% of children, mainly in mandibular second premolars and second and third permanent molars. A number of possible causes for MIH were mentioned, including environmental changes, diet and genetics in prenatal and postnatal periods, but all are questionable. In PEIR, the resorption of the intracoronal dentine begins only after crown development is complete and is caused by giant cells resembling osteoclast observed histologically on the dentine surface close to the pulp. The mineral content in MIH is reduced in comparison to normal enamel and dependent on the severity of the lesion. In PEIR the resorbed surface of enamel showed less mineral content. The hypomineralized enamel in MIH is not suitable for restorations with amalgam or composite materials, and the best material should be based on remineralization material like glass-ionomers. Similar, the resorbed dentin surface in PEIR should be covered by the biocompatible and re-mineralizing glass-ionomer cement.

MMP13 Contributes to Dental Caries Associated with Developmental Defects of Enamel

The aim of this study was to investigate the association between genetic polymorphisms in MMP8, MMP13, and MMP20 with caries experience and developmental defects of enamel (DDE) in children from the Amazon region of Brazil. Den tal caries and DDE data were collected through clinical examination from 216 children. Genomic DNA was extracted from saliva, and genotyping of selected polymorphisms in MMP8 (rs17099443 and rs3765620), MMP13 (rs478927 and rs2252070), and MMP20 (rs1784418) was performed using TaqMan chemistry and endpoint analysis. χ2 or Fisher's exact tests were used to compare allele and genotype distributions between children with caries experience and caries-free children and between DDE-affected and -unaffected children with an established alpha of 5%. The polymorphism rs478927 in MMP13 was associated with caries experience and DDE (p < 0.05). The analysis performed comparing children with both conditions (caries experience plus DDE) and children with neither of the conditions (caries-free chil dren without DDE) demonstrated that children carrying the MMP13 rs478927 TT genotype were more likely to have concomitant occurrence of these two conditions (OR = 5.8, 95% CI 2.1-15.8; p = 0.0003). In conclusion, the genetic polymorphism rs478927 in MMP13 was associated with caries experience and DDE.

Review: modulation of the oral microbiome by the host to promote ecological balance

The indivisible relationship between the human host and its oral microbiome has been shaped throughout the millennia, by facing various changes that have forced the adaptation of oral microorganisms to new environmental conditions. In this constant crosstalk between the human host and its microbiome, a bidirectional relationship has been established. The microorganisms provide the host with functions it cannot perform on its own and at the same time the host provides its microbes with a suitable environment for their growth and development. These host factors can positively affect the microbiome, promoting diversity and balance between different species, resulting in a state of symbiosis and absence of pathology. In contrast, other host factors can negatively influence the composition of the oral microbiome and drive the interaction towards a dysbiotic state, where the balance tilts towards a harmful relationship between the host and its microbiome. The aim of this review is to describe the role host factors play in cultivating and maintaining a healthy oral ecology and discuss mechanisms that can prevent its drift towards dysbiosis.

Molar-Incisor Hypomineralization: Positive Correlation with Atopic Dermatitis and Food Allergies

AIM

Molar-incisor hypomineralization is a disturbance in dental development that involves first permanent molars as well as permanent incisors with a prevalence that ranges from 2.5% to 40%. The objective of this study was to investigate the etiology of molar-incisor hypomineralization among school children from two randomly selected towns in the province of Barcelona, Spain.

STUDY DESIGN

A cross-sectional study was conducted with 705 children ranging in age from six years-old to 14 years and 11 months-old. Full mouth examinations were carried out in accordance with the European Academy of Paediatric Dentistry criteria for the diagnosis of molar-incisor hypomineralization, from April to July 2016.

RESULTS

A total of 56 cases of molar-incisor hypomineralization were found in 22 (39.3%) boys and 34 (60.7%) girls. MIH was significantly more prevalent among those who had atopic dermatitis (OR=90.9; 33.4-247.1 CI 95%), food allergies (OR=104.2; 12.2-887.5 CI 95%), bronchitis/asthma (OR=5.3; 2.7-10.1 CI 95%), varicella (OR=96.3; 41.9-221.1 CI 95%), otitis media (OR=12.2; 6.3-23.5 CI 95%), pneumonia (OR=276.7; 35.1-2183.7 CI 95%), and febrile syndrome (OR=7.8; 4.1-14.8 CI 95%).

CONCLUSIONS

The present research reveals for the first time a statistically significant relationship between atopic dermatitis and food allergies with the presence of molar-incisor hypomineralization.

TUFT1 Promotes Osteosarcoma Cell Proliferation and Predicts Poor Prognosis in Osteosarcoma Patients

Objective

This study is aimed at exploring the role of TUFT1 in osteosarcomas.

Methods

We investigated the expression of TUFT1 in osteosarcoma cell lines and explored the correlation between TUFT1 expression and prognosis in osteosarcoma patients based on the expression data downloaded from Gene Expression Omnibus (GEO) website. The effects of TUFT1 on osteosarcoma cell proliferation, migration and invasion were investigated by silencing TUFT1 in osteosarcoma MG63 cell line. Finally, western blot was performed to determine the expression changes of MAPK signaling pathway related proteins after silencing TUFT1.

Results

We found that the expression of TUFT1 was significantly up-regulated in osteosarcoma cell lines compared with the normal control. Using Kaplan-Meier analysis, we identified that high TUFT1 expression was positively correlated with poor prognosis in osteosarcoma patients. Furthermore, knockdown of TUFT1 remarkably inhibited MG63 cell proliferation, migration and invasion. Using western blot analysis, we found that the phosphorylation levels of MEK and ERK were reduced obviously in MG63 cells after silencing TUFT1 (p<0.01).

Conclusions

Our results demonstrated that TUFT1 plays a promoting role in MG63 cell proliferation and metastasis and has the potential to be a predictor as well as a therapeutic target for osteosarcoma patients.

Molar incisor hypomineralisation (MIH) - an overview

Recent data indicates that molar-incisor hypomineralisation (MIH) is a frequently - encountered dental condition worldwide. The condition could be associated with dental complications that might affect patients' quality of life as well as create treatment challenges to dentists. The affected teeth are more prone to caries and post-eruptive enamel breakdown, therefore, it is believed that this condition might be responsible for a substantial proportion of childhood caries since the condition has high prevalence. MIH is common, and as such it should be diagnosed and managed in primary care wherever possible. Early diagnosis can lead to more effective and conservative management. This article aims to highlight different aspects related to MIH, from its prevalence to treatment options in young patients.

Host genetics role in the pathogenesis of periodontal disease and caries

BACKGROUND

This study aimed to produce the latest summary of the evidence for association of host genetic variants contributing to both periodontal diseases and caries.

MATERIALS AND METHODS

Two systematic searches of the literature were conducted in Ovid Medline, Embase, LILACS and Cochrane Library for large candidate gene studies (CGS), systematic reviews and genome-wide association studies reporting data on host genetic variants and presence of periodontal disease and caries.

RESULTS

A total of 124 studies were included in the review (59 for the periodontitis outcome and 65 for the caries outcome), from an initial search of 15,487 titles. Gene variants associated with periodontitis were categorized based on strength of evidence and then compared with gene variants associated with caries. Several gene variants showed moderate to strong evidence of association with periodontitis, although none of them had also been associated with the caries trait.

CONCLUSIONS

Despite some potential aetiopathogenic similarities between periodontitis and caries, no genetic variants to date have clearly been associated with both diseases. Further studies or comparisons across studies with large sample size and clear phenotype definition could shed light into possible shared genetic risk factors for caries and periodontitis.

The Association between Molar-Incisor Hypomineralization and Dental Caries with Socioeconomic Status as an Explanatory Variable in a Group of Finnish Children

The aim of this study was to investigate if a developmental enamel defect known as Molar-Incisor Hypomineralization (MIH) is associated with dental caries. Socioeconomic status (SES) was examined as a confounding factor between caries and MIH. In this cross-sectional study, 636 children, aged 8 to 13 years, from three towns (two rural areas and one urban area) in Finland were examined for MIH in line with the criteria of the European Academy of Paediatric Dentistry. Caries status for permanent teeth was recorded as decayed, missing and filled teeth (DMFT). Caries experience (DMFT > 0) in the first permanent molars (FPMs) was set as an outcome. SES was determined using a questionnaire completed by parents. The prevalence of MIH was 18.1%. The mean DMFT in FPMs for children with MIH was higher than for their peers, 1.03 ± 1.25 vs. 0.32 ± 0.80 (p = 0.000, Mann-Whitney U test). In a multivariate analysis using the generalized linear mixed model where locality, SES, age and MIH were taken into account as caries risk indicators, MIH was the strongest risk indicator of caries in FPMs (Odds Ratio: 6.60, 95% Confidence Interval: 3.83–11.39, p = 0.000). According to the study results, children with MIH have a higher risk for dental caries than children without MIH.

Prevalence and etiology of molar-incisor hypomineralization (MIH) in the city of Istanbul

Background/purpose

Molar-Incisor-Hypomineralisation (MIH) is the term used to depict a condition in which one or more of the permanent molar teeth and usually no less than one incisor tooth is hypomineralised and the prevalence rates vary from 2.4 to 40.2%. The aim of this study was to assess the prevalence and the risk factors of MIH in children in Istanbul, Turkey.

Materials and methods

A total of 1511 (760 M, 751 F), 8- to 11-year-old children were examined who had their first permanent molar and incisors evaluated using the EAPD criteria for MIH. Hypomineralized molars and incisors were recorded based on developmental defects of enamel index. The potential aetiological factors were retrieved through personal interview and etiological questions were asked to the parents. Statistical analysis was performed with a chi-Square test.

Results

MIH was observed in 215 (14.2%; 102 male, 113 female) children. The sample (1511 children) comprised 71 (9.9%) 8 year-olds with MIH and 144 (18.2%) 11 year-olds with MIH. A significant difference was found between 8 (9.9%) and 11-year-old (18.2%) children with MIH (p ≤ 0.001). Complications during the mother's pregnancy, birth prematurity, average breast feeding period, diarrhea frequency, digestive system diseases, asthma, frequent high fever, ear infection, renal failure, rubeola, chickenpox and parotitis were found to be significantly associated with MIH (p < 0.001).

Conclusion

There are many events that can cause MIH which we cannot control or predict. Therefore, longitudinal studies with large sample size are needed so as to determine how various likely etiological factors described affect the etiological role.

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.

The prevalence of molar incisor hypomineralization: evidence from 70 studies

OBJECTIVE

A growing number of studies have investigated the prevalence of Molar Incisor Hypomineralization (MIH) around the world. The aim of this study was to systematically estimate the pooled prevalence of MIH.

METHODS

A comprehensive literature research was completed in English and Chinese databases. Random effect models were used to calculate the pooled prevalence. To address the heterogeneity, meta-regression, and sensitivity analyzes were conducted. Publication bias was estimated by trim and fill method.

RESULTS

Seventy eligible studies were included. The pooled prevalence of MIH was 14.2% globally. In subgroup analysis, South America (18.0%, 95% CI: 13.8-22.2) and Spain (21.1%, 95% CI: 17.7-24.6) had the highest prevalence. There was no significant difference between males (14.3%, 95% CI: 12.0-16.6) and females (14.4%, 95% CI: 12.8-15.9). The prevalence of MIH among children 10 years of age or younger (15.1%, 95% CI: 12.1-18.2) was much higher than the prevalence of MIH among older children (12.1%, 95% CI: 8.0-16.3). Sample size explained 15.7% heterogeneity.

CONCLUSION

MIH has a high incidence globally, especially among children <10 years old. It is, therefore, imperative to develop more appropriate dental healthcare strategies to care for these children and to identify the etiology of MIH to prevent it occurring.

Rethinking isolated cleft lip and palate as a syndrome

OBJECTIVE

The goal of the present work was to use dental conditions that have been independently associated with cleft lip and palate (CL/P) as a tool to identify a broader collection of individuals to be used for gene identification that lead to clefts.

STUDY DESIGN

We studied 1573 DNA samples combining individuals that were born with CL/P or had tooth agenesis, supernumerary teeth, molar incisor hypomineralization, or dental caries with the goal to identify genetic associations. We tested 2 single-nucleotide polymorphisms that were located in the vicinity of regions suggested to contribute to supernumerary teeth. Overrepresentation of alleles were determined for combinations of individuals as well as for each individual phenotypic group with an α of .05.

RESULTS

We determined that the allele C of rs622260 was overrepresented in all individuals studied compared with a group of unrelated individuals who did not present any of the conditions described earlier. When subgroups were tested, associations were found for individuals with hypomineralization.

CONCLUSIONS

Although we did not test this hypothesis directly in the present study, based on associations reported previously, we believe that CL/P is actually a syndrome of alterations of the dentition, and considering it that way may allow for the identification of genotype-phenotype correlations that may be useful for clinical care.

Molar Incisor Hypomineralization and Its Prevalence

Background:

Molar incisor hypomineralization (MIH) is the hypomineralization of systemic origin of one to four permanent first molars, frequently associated with affected incisors. It is presented as demarcated enamel opacities of different colors, occasionally undergoing posteruptive breakdown. The characteristic feature of MIH is the clear demarcation between the affected and sound enamel. There is asymmetry of defects present in the molars and incisors where one molar or incisor can be severely affected, while the contralateral tooth may be clinically sound or have only minor defects.

Aim and Objective:

The aim of this study is to evaluate schoolchildren of 7–12 years of age with at least one of the first permanent molars fully or partially erupted from randomly selected government and private schools in Chennai using the European Academy of Pediatric Dentistry (EAPD) criteria for MIH, to determine the prevalence and characteristics of MIH.

Materials and Methods:

The dental examinations were performed in the classroom using a mouth mirror and explorer under a headlight. Teeth were wiped with gauze when necessary to remove plaque or the food accumulations. Surfaces that were examined were the buccal, lingual, palatal, and occlusal surfaces of permanent first molars and labial surfaces of upper and lower incisors. A single examiner was involved to avoid interexaminer bias. All the data were collected and scored using the EAPD criteria for MIH.

Results:

A total of 22 (12.9%) children out of the examined 170 had MIH.

Conclusion:

Distribution of MIH was more in males, more in 9 years of age. A total of 13 children had first molars affected and 9 children had both incisors and molars affected. Molars were affected more than the incisors. Mandible was affected more in comparison with the maxilla. Right side was affected more than the left side. The distribution of MIH was more in government schools compared to private schools.

Polymorphisms in Nonamelogenin Enamel Matrix Genes Are Associated with Dental Fluorosis

The aim of this study was to evaluate whether genetic polymorphisms in AMELX, AMBN, ENAM, TFIP11, and TUFT1 genes are associated with dental fluorosis (DF). A total of 1,017 children from 2 Brazilian cohorts were evaluated. These populations lived in cities with fluoridation of public water supplies. DF was assessed in erupted permanent teeth using the modified Dean index. The polymorphisms rs946252, rs12640848, rs4694075, rs5997096, and rs4970957 were analyzed by real-time PCR from genomic DNA. Associations between DF, genotype, and allele distribution were evaluated using the χ2 test, with an alpha of 5%. The polymorphisms rs4694075, rs5997096, and rs4970957 in AMBN, TFIP11, and TUFT1 were associated with DF (p < 0.05). In conclusion, enamel matrix genes are associated with DF.

Lack of association between ENAM gene polymorphism and dental caries in primary and permanent teeth in Czech children

OBJECTIVES

The enamelin gene (ENAM) polymorphism (rs12640848) was recently associated with dental caries in primary teeth in Polish children. The aims of the present study were to prove this association in primary dentition and to find a possible effect of this variant on caries development in permanent dentition in Czech children.

MATERIALS AND METHODS

This study comprised 905 Czech children. Totally, 187 children aged 2-6 years with primary dentition [78 healthy subjects (with decayed/missing/filled teeth, dmft = 0) and 109 patients with early childhood caries (ECC; dmft ≥ 1)] were included in this case-control study. In addition, 177 subjects aged 13-15 years without caries (DMFT = 0) and 541 children with dental caries (DMFT ≥ 1) in permanent dentition were selected from the ELSPAC study. Genotype determination of the ENAM polymorphism (rs12640848) was based on the TaqMan method.

RESULTS

No significant differences in the allele or genotype frequencies between the caries-free children and those affected by dental caries were observed in both primary and permanent dentitions.

CONCLUSIONS

Lack of association between the ENAM polymorphism (rs12640848) and dental caries in Czech children was detected.

CLINICAL RELEVANCE

Although ENAM is considered as a candidate gene for dental caries, the presence of the ENAM variant (rs12640848) cannot be used as a risk factor of this multifactorial disease in the Czech population.

Association between Single Nucleotide Polymorphisms in Vitamin D Receptor Gene Polymorphisms and Permanent Tooth Caries Susceptibility to Permanent Tooth Caries in Chinese Adolescent

Purpose

Dental caries is a multifactorial infectious disease. In this study, we investigated whether single nucleotide polymorphisms (SNPs) in vitamin D receptor (VDR) gene were associated with susceptibility to permanent tooth caries in Chinese adolescents.

Method

A total of 200 dental caries patients and 200 healthy controls aged 12 years were genotyped for VDR gene polymorphisms using the PCR-restriction fragment length polymorphism (PCR-RFLP) assay. All of them were examined for their oral and dental status with the WHO criteria, and clinical information such as the Decayed Missing Filled Teeth Index (DMFT) was evaluated. Genomic DNA was extracted from the buccal epithelial cells. The four polymorphic SNPs (Bsm I, Taq I, Apa I, and Fok I) in VDR were assessed for both genotypic and phenotypic susceptibilities.

Results

Among the four examined VDR gene polymorphisms, the increased frequency of the CT and CC genotype of the Fok I VDR gene polymorphism was associated with dental caries in 12-year-old adolescent, compared with the controls (X² = 17.813, p ≤ 0.001). Moreover, Fok I polymorphic allele C frequency was significantly increased in the dental caries cases, compared to the controls (X² = 14.144, p ≤ 0.001, OR = 1.730, 95% CI = 1.299–2.303). However, the other three VDR gene polymorphisms (Bsm I, Taq I, and Apa I) showed no statistically significant differences in the caries groups compared with the controls.

Conclusion

VDR-Fok I gene polymorphisms may be associated with susceptibility to permanent tooth caries in Chinese adolescent.

Analytical evidence of enamel hypomineralisation on permanent and primary molars amongst past populations

Molar Incisor Hypomineralisation (MIH) and Hypomineralised Second Primary Molars (HSPM) involve prevalent qualitative structural developmental anomalies of tooth enamel affecting the first permanent molars (and often incisors) and the second primary molars, respectively. These demarcated hypomineralised lesions of enamel manifest as white-cream or yellow-brown opacities, with possible post-eruptive localised loss of enamel. Aetiological hypotheses have involved contemporary life factors (i.e. environmental pollutant exposure or early childhood medications) in contrast to factors not limited to a specific time period (i.e. hypoxia at birth or genetic predisposition). Evidence of MIH in ancient populations would reinforce aetiological factors present for many centuries. By means of microtomographic and X-ray fluorescence analyses the present study provides evidence that (i) two archaeological specimens: “S407” (Sains-en-Gohelle, France, 12^th–16^th centuries) and “B335” (Beauvais, France, 15^th–18^th centuries) were MIH-affected, and (ii) one individual “S323” was affected by HSPM and MIH (Sains-en-Gohelle, France, 7^th–11^th centuries).

Survival of sealants in molars affected by molar-incisor hypomineralization: 18-month follow-up

The objective of this study was to evaluate the clinical survival of sealants applied in first permanent molars (FPMs) affected by molar-incisor hypomineralization (MIH), at 18 months of follow-up. Forty-one first permanent molars were selected from 21 children, 6-8 years of age. MIH was classified by one calibrated examiner (kappa = 0.80) according to EAPD criteria. The inclusion criteria were fully erupted FPMs with MIH or sound FPMs (without MIH) for which sealant treatment was indicated. The FPMs were assigned to two groups: CG (control group) and HG (MIH group). Both groups were treated with sealant (FluroShield). Clinical follow-up was performed from baseline to 18 months to assess anatomical form, marginal adaptation, retention and presence of caries, according to criteria set by the United States Public Health Service-Modified, and was conducted by a blinded examiner (kappa = 0.80). The actuarial method was used to evaluate the survival of the sealants. The survival rates for the groups were compared using Fisher's exact test (α = 5%). The cumulative survival rates were 81% at 1 month, 68.8% at 6 months, 68.8% at 12 months, and 62.6% at 18 months for CG, and 88% at 1 month, 84% at 6 months, 76% at 12 months, and 72% at 18 months for HG. No significant difference was found between the groups. The sealants in molars affected by MIH presented a survival rate similar to the sealants in the control, suggesting that sealants may be an adequate approach for preventing carious lesions in MIH-affected molars.

Evolutionary Analysis of the Mammalian Tuftelin Sequence Reveals Features of Functional Importance

Tuftelin (TUFT1) is an acidic, phosphorylated glycoprotein, initially discovered in developing enamel matrix. TUFT1 is expressed in many mineralized and non-mineralized tissues. We performed an evolutionary analysis of 82 mammalian TUFT1 sequences to identify residues and motifs that were conserved during 220 million years (Ma) of evolution. We showed that 168 residues (out of the 390 residues composing the human TUFT1 sequence) are under purifying selection. Our analyses identified several, new, putatively functional domains and confirmed previously described functional domains, such as the TIP39 interaction domain, which correlates with nuclear localization of the TUFT1 protein, that was demonstrated in several tissues. We also identified several sites under positive selection, which could indicate evolutionary changes possibly related to the functional diversification of TUFT1 during evolution in some lineages. We discovered that TUFT1 and MYZAP (myocardial zonula adherens protein) share a common ancestor that was duplicated circa 500 million years ago. Taken together, these findings expand our knowledge of TUFT1 evolution and provide new information that will be useful for further investigation of TUFT1 functions.

Genes Involved in the Enamel Development Are Associated with Calcium and Phosphorus Level in Saliva

Saliva components play a crucial role in the integrity of the dental enamel and in caries susceptibility. The saliva characteristics are controlled by many factors, including genetic factors. Therefore, this study aimed to evaluate the association between the genetic variations in genes expressed in enamel development with calcium and phosphorus levels in saliva. We collected 276 unrelated 12-year-old children from private and public schools. Saliva was collected for DNA extraction from oral cells and for measurement of calcium and phosphorus. Inductively coupled plasma-mass spectrometry determined calcium and phosphorus levels in whole saliva. Fifteen genetic variations in 9 genes were analyzed. The genotype was determined by real-time polymerase chain reactions. Data were analyzed using Plink with an alpha of 5%. Genetic variations in AMELX, AMNB and ESRRB were associated with the calcium level in saliva (p < 0.05). A borderline association was observed in ENAM allele distribution shown with phosphate level in saliva (p = 0.049). In conclusion, our results are the first to report that genetic variations contribute to calcium and phosphorus levels in saliva.

Significance of genetic variations in developmental enamel defects of primary dentition in Polish children

OBJECTIVES

The aim of the study was to reveal the association between developmental defects of enamel (DDE) and single nucleotide polymorphisms (SNPs) in the ENAM, AMELX, AMBN, TUFT1, and TFIP11 genes.

MATERIAL AND METHODS

The molecular analysis was carried out in 52 children, aged 10-42 months, from four nursery schools situated in the region of Poznan, Poland (26 individuals with hypomineralization and/or hypoplasia of enamel - "cases" and 26 unaffected children - "controls"), chosen from 262 individuals that had prior dental examination. Six selected SNP variants (rs17878486 in AMELX, rs4694075 in AMBN, rs3796704 in ENAM, rs134136 and rs5997096 in TFIP11, and rs3790506 in TUFT1) were genotyped by the TaqMan probes assay. Genotype and allele frequencies were calculated, and a standard chi-squared analysis was used to test for deviation from Hardy-Weinberg equilibrium. The association between genetic variations and developmental defects of enamel was assessed by the Fisher's exact test and p ≤ 0.05 was considered statistically significant.

RESULTS

Statistically significant positive correlations were found between the rare T allele (p = 0.005) and the TT genotype (p = 0.0052) for rs17878486 in AMELX and occurrence of developmental enamel defects in primary dentition of children. For rs4694075 in AMBN, a higher incidence of the rare T allele (p = 0.0157) was observed in controls compared to DDE cases, whereas the wild-type CC homozygote was more frequent in DDE cases than in controls (p = 0.0062).

CONCLUSIONS

The study showed that the single nucleotide polymorphisms in the AMELX and AMBN genes may be genetic variants that contribute to developmental defects of enamel in primary dentition of children.

CLINICAL RELEVANCE

The single nucleotide polymorphisms of enamel formation genes may increase the risk for developmental defects of enamel (DDE) occurrence in primary dentition in children.

Retinoic Acid Excess Impairs Amelogenesis Inducing Enamel Defects

Abnormalities of enamel matrix proteins deposition, mineralization, or degradation during tooth development are responsible for a spectrum of either genetic diseases termed Amelogenesis imperfecta or acquired enamel defects. To assess if environmental/nutritional factors can exacerbate enamel defects, we investigated the role of the active form of vitamin A, retinoic acid (RA). Robust expression of RA-degrading enzymes Cyp26b1 and Cyp26c1 in developing murine teeth suggested RA excess would reduce tooth hard tissue mineralization, adversely affecting enamel. We employed a protocol where RA was supplied to pregnant mice as a food supplement, at a concentration estimated to result in moderate elevations in serum RA levels. This supplementation led to severe enamel defects in adult mice born from pregnant dams, with most severe alterations observed for treatments from embryonic day (E)12.5 to E16.5. We identified the enamel matrix proteins enamelin (Enam), ameloblastin (Ambn), and odontogenic ameloblast-associated protein (Odam) as target genes affected by excess RA, exhibiting mRNA reductions of over 20-fold in lower incisors at E16.5. RA treatments also affected bone formation, reducing mineralization. Accordingly, craniofacial ossification was drastically reduced after 2 days of treatment (E14.5). Massive RNA-sequencing (RNA-seq) was performed on E14.5 and E16.5 lower incisors. Reductions in Runx2 (a key transcriptional regulator of bone and enamel differentiation) and its targets were observed at E14.5 in RA-exposed embryos. RNA-seq analysis further indicated that bone growth factors, extracellular matrix, and calcium homeostasis were perturbed. Genes mutated in human AI (ENAM, AMBN, AMELX, AMTN, KLK4) were reduced in expression at E16.5. Our observations support a model in which elevated RA signaling at fetal stages affects dental cell lineages. Thereafter enamel protein production is impaired, leading to permanent enamel alterations.

Diagnostic guide enabling distinction between taphonomic stains and enamel hypomineralisation in an archaeological context

OBJECTIVE

Molar Incisor Hypomineralisation (MIH) is a structural anomaly that affects the quality of tooth enamel and has important consequences for oral health. The developmentally hypomineralised enamel has normal thickness and can range in colour from white to yellow or brown with or without surface breakdown. The possibility of finding MIH in 'ancient populations' could downplay several current aetiological hypotheses (e.g., dioxin derivatives, bisphenols, antibiotics) without excluding the possible multifactorial aspect of the anomaly. In an archaeological context, chemical elements contained in the burial ground can stain teeth yellow or brown and therefore might create a taphonomic bias. The purpose of the present study is to test a proposed diagnostic guide enabling determination of the pathological or taphonomic cause of enamel discolouration and defects that resemble MIH present on 'ancient teeth'.

DESIGN

Two sample groups including MIH discoloration (n=12 teeth) from living patients, taphonomic discoloration (n=9 teeth) and unknown discoloration (n=2 teeth) from medieval specimens were tested. Three non-destructive methods-Raman spectroscopy, X-ray micro-computed tomography and X-ray fluorescence were utilised.

RESULTS

Hypomineralised enamel has decreased mineral density (p<0.0001) and increased phosphate/β-carbonate ratio (p<0.01) compared to normal enamel whereas relative concentrations of manganese, copper, iron and lead are similar. In taphonomic discoloration, relative concentrations of these elements are significantly different (p<0.05) to normal enamel whereas mineral density and Raman spectra profile are comparable.

CONCLUSIONS

Enamel hypomineralisation can be distinguished from taphonomic staining in archaeological teeth.

Chronic Exposure to Bisphenol A Exacerbates Dental Fluorosis in Growing Rats

Enamel defects resulting from environmental conditions and way of life are public health concerns because of their high prevalence. Because their etiology is unclear, the aim of this study was to analyze the various forms of enamel hypomineralization, and to characterize the genes involved in this process to determine the mechanisms involved in disruptions of amelogenesis. We used bisphenol A (BPA) and fluoride as models; both are commonly encountered in human populations and utilized in dentistry. Wistar rats were chronically exposed to 5 μg/kg/day BPA from day 1 of gestation to day 65 after birth (P65) and 5 mM fluoride from P21 to P65. Resulting enamel defects were comparable to the human enamel pathologies molar incisor hypomineralization (MIH) and dental fluorosis (DF) respectively, and were more severe in rats exposed to both agents than to each agent alone. Large-scale transcriptomic analysis of dental epithelium showed a small group of genes the expression of which was affected by exposure to BPA or NaF. Among the most modulated, many are directly involved in amelogenesis (Amelx, Enam, Klk4, Mmp12, Slc26a4, and Slc5a8), and can be regrouped as forming the "hypomineralization enameloma." Each of these gene expression perturbations may contribute to enamel defects. Exposure to BPA weakens enamel, making it more prone to generate frequent mineralization defects MIH and DF. Our study identifies hypomineralization genes that may enable the use of dental enamel as an early marker of exposure to environmental toxicants because of its unique ability to retrospectively record ameloblast pathophysiology. © 2016 American Society for Bone and Mineral Research.

Molar incisor hypomineralization in HIV-infected children and adolescents

The objective was to determine the prevalence of molar incisor hypomineralization (MIH) among individuals between 7 and 15 years old infected or noninfected with human immunodeficiency virus (HIV). The study was conducted with 33 HIV-infected individuals (study group; SG) and 66 non-HIV-infected schoolchildren (control group; CG), paired by gender and age. Data collection was based on medical records (SG), a questionnaire for caregivers and oral examination for diagnosis of MIH (European Academy of Pediatric Dentistry criteria) and caries (DMFT index and ICDAS). Data were analyzed with Mann-Whitney, chi-square, and Fisher's exact tests and logistic regression. In SG, MIH (45.5%) and caries (87.9%) had higher prevalence. MIH was associated with use of protease inhibitors in SG (OR: 2.14; 95% CI: 1.21 to 3.77) and incubator need in CG (OR: 2.80; 95% CI: 1.71 to 9.10). HIV-infected patients had a higher prevalence of MIH and dental caries in the permanent dentition.

Eighteen-month clinical performance of composite resin restorations with two different adhesive systems for molars affected by molar incisor hypomineralization

INTRODUCTION

The restorative management of molars with molar incisor hypomineralization (MIH) represents a challenge in the clinical practice with high failure rate.

OBJECTIVE

The aim of this study is to evaluate the clinical survival of direct composite resin restorations in first permanent molars (FPMs) that are affected by MIH, comparing two adhesive systems.

MATERIAL AND METHODS

We selected 41 FPMs with MIH from children aged 6-8 years. FPM fully erupted and with restorative treatment needed were the inclusion criteria. We excluded FPMs with destroyed crowns. The FPMs were randomly assigned to two groups: self-etching adhesive (SEA) and total-etch adhesive (TEA). Clinical evaluation was performed by a blinded examiner during 18 months according to the modified US Public Health Service (USPHS) criteria. The actuarial method was used to evaluate survival of the restorations, and Chi-square and Fisher's exact tests were used to compare differences between the groups (α = 5 %).

RESULTS

The cumulative survival rates were 100 % at 1 month, 89 % at 6 months, 73 % at 12 months, and 68 % at 18 months in SEA, and 95 % at 1 month, 72 % at 6 months, 59 % at 12 months, and 54 % at 18 months in TEA; there was no significant difference between groups.

CONCLUSIONS

There was no difference in clinical survival of restorations in FPMs affected by MIH using TEA or SEA adhesives in the end of 18 months.

CLINICAL RELEVANCE

It was suggested that SEAs as well as TEAs can be applied to restore molars affected by MIH, when it is performed a conservative cavity preparation. Once, cavosurface margins (cavity design) in hypomineralized enamel have less bonding capability.

Family-Based Genetic Association for Molar-Incisor Hypomineralization

Despite some evidence of genetic and environmental factors on molar-incisor hypomineralization (MIH), its aetiology remains unclear. This family-based genetic association study aimed more comprehensively to investigate the genetic carriage potentially involved in MIH development. DNA was obtained from buccal cells of 391 individuals who were birth family members of 101 Brazilian nuclear families. Sixty-three single nucleotide polymorphisms (SNPs) were investigated in 21 candidate genes related to amelogenesis using the TaqMan™ OpenArray™ Genotyping platform. All SNPs were genotyped in 165 birth family members unaffected by MIH, 96 with unknown MIH status and 130 affected individuals (50.7% with severe MIH). Association analysis was performed by the transmission/disequilibrium test (TDT), and statistical results were corrected using the false discovery rate. Significant results were obtained for SNPs rs7821494 (FAM83H gene, OR = 3.7; 95% CI = 1.75-7.78), rs34367704 (AMBN gene, OR = 2.7; 95% CI = 1.16-6.58), rs3789334 (BMP2 gene, OR = 2.9; 95% CI = 1.34-6.35), rs6099486 (BMP7 gene, OR = 2.2; 95% CI = 1.14-4.38), rs762642 (BMP4 gene, OR = 2.3; 95% CI = 1.38-3.65), rs7664896 (ENAM gene, OR = 2.1; 95% CI = 1.19-3.51), rs1711399 (MMP20 gene, OR = 0.4; 95% CI = 0.20-0.72), rs1711423 (MMP20 gene, OR = 2.1; 95% CI = 1.18-3.61), rs2278163 (DLX3 gene, OR = 2.8; 95% CI = 1.26-6.41), rs6996321 (FGFR1 gene, OR = 2.7; 95% CI = 1.20-5.88), and rs5979395 (AMELX gene, OR = 11.7; 95% CI = 1.63-84.74). Through this family-based association study, we concluded that variations in genes related to amelogenesis were associated with the susceptibility to develop MIH. This result is in agreement with the multifactorial idea of the MIH aetiology, but further studies are necessary to investigate more thoroughly the factors that could influence MIH.

Amoxicillin diminishes the thickness of the enamel matrix that is deposited during the secretory stage in rats

BACKGROUND

The use of amoxicillin during early childhood has been associated with molar incisor hypomineralization.

AIM

The objective of this study was to determine whether the use of amoxicillin interferes with enamel development, during secretion and early mineralization stages.

DESIGN

Fifteen pregnant rats were randomly assigned to three groups that received physiological solution (sham group), 100 mg/kg/day amoxicillin (A100G), and 500 mg/kg/day amoxicillin (A500G). After birth, the pups in each group received the same treatment until post-natal day 7 or 12. The upper first molars were analyzed histomorphometrical and immunostaining with amelogenin on day 7, and MMP-20 on day 12 was performed using a semiquantitative method (H-score).

RESULTS

At 7 days, several vacuolar structures were observed in the ameloblasts in the A100G and A500G groups. A significant reduction of the enamel thickness (P < 0.001) was found in amoxicillin-treated rats compared with the sham group. Significant differences were not observed in enamel thickness (P > 0.05) between the groups of 12-day-old rats. Moreover, significant differences were not observed in the number of amelogenin- and MMP-20-immunolabeled ameloblasts (P > 0.05) between groups.

CONCLUSION

The present results suggest that amoxicillin interferes with the initial stages of amelogenesis by causing structural changes in the ameloblasts and a reduction of the enamel matrix.

On the Etiology of Molar-Incisor Hypomineralization

Molar-incisor hypomineralization (MIH) is a condition that is defined based on its peculiar clinical presentation. Reports on the etiology of the condition and possible risk factors are inconclusive and the original suggestion that MIH is an idiopathic condition is often cited. Our group was the first to suggest MIH has a genetic component that involves genetic variation in genes expressed during dental enamel formation. In this report, we provide a rationale to explain the preferential affection of molars and incisors. We suggest that MIH is a genetic condition based on its prevalence, which varies depending on the geographic location, and the evidence that on occasion second primary molars, permanent canines, and premolars can show signs of hypomineralization of enamel when molars and incisors are affected.

Genetic influences on dental enamel that impact caries differ between the primary and permanent dentitions

Clinically, primary and permanent teeth are distinct anatomically and the presentation of caries lesions differs between the two dentitions. Hence, the possibility exists that genetic contributions to tooth formation of the two dentitions are different. The purpose of this study was to test the hypothesis that genetic associations with an artificial caries model will not be the same between primary and permanent dentitions. Enamel samples from primary and permanent teeth were tested for microhardness at baseline, after carious lesion creation, and after fluoride application to verify association with genetic variants of selected genes. Associations were found between genetic variants of ameloblastin, amelogenin, enamelin, tuftelin, tuftelin interactive protein 11, and matrix metallopeptidase 20 and enamel from permanent teeth but not with enamel from primary teeth. In conclusion, our data continue to support that genetic variation may impact enamel development and consequently individual caries susceptibility. These effects may be distinct between primary and permanent dentitions.

Association of sweet taste receptor gene polymorphisms with dental caries experience in school children

Sweet taste is a powerful factor influencing food acceptance. The peripheral taste response to sugar is mediated by the TAS1R2/TAS1R3 taste receptors. The aim of the study was to determine the relationship between TAS1R2 (rs35874116 or rs9701796) and/or TAS1R3 (rs307355) single nucleotide polymorphisms with dental caries experience in schoolchildren. A total of 184 schoolchildren aged between 7 and 12 years (101 girls, 83 boys) were included in the study. Genomic DNA was extracted from saliva samples and the genotypes were identified by qPCR. The genotype frequencies were as follows: 6.6% for homozygous wild type, 41.8% for heterozygous and 51.6% for homozygous polymorphic genotype carriers of TAS1R2 gene rs35874116; 27.8% for heterozygous and 72.2% for homozygous polymorphic genotype carriers of TAS1R2 gene rs9701796, and 83.1% for homozygous wild type and 16.9% for heterozygous genotype carriers of TAS1R3 gene rs307355 polymorphism. A significant association was observed between total caries experience (dft + DMFT - decayed filled primary teeth + decayed, missing and filled permanent teeth) and TAS1R2 rs35874116 (p = 0.008) and TAS1R3 rs307355 (p = 0.04) gene polymorphisms but not for TAS1R2 gene rs9701796 polymorphism. TAS1R3 gene rs307355 polymorphism has been found to be an independent risk factor for dental caries experience by logistic regression analysis and to have increased the risk of caries. Moderate caries experience (4-7 caries) was found to be associated with TAS1R3 rs307355 heterozygous genotype, whereas high-risk caries experience (>8 caries) was found to be associated with TAS1R2 rs35874116 homozygous polymorphic genotype.