Association between molar hypomineralization, genes involved in enamel development, and medication in early childhood: A preliminary study.

BACKGROUND: Molar hypomineralization (MH) is defined as a multifactorial condition, and thus, its presence may be defined by interactions between environmental and genetic factors. AIM: To evaluate the association between MH, genes involved in enamel development, and the use of medication during pregnancy in early childhood. DESIGN: One hundred and eighteen children, 54 with and 64 without MH, were studied. The data collected included demographics, socioeconomic data, and the medical history of mothers and children. Genomic DNA was collected from saliva. Genetic polymorphisms in ameloblastin (AMBN; rs4694075), enamelin (ENAM; rs3796704, rs7664896), and kallikrein (KLK4; rs2235091) were evaluated. These genes were analyzed by real-time polymerase chain reaction using TaqMan chemistry. The software PLINK was used to compare allele and genotype distributions of the groups and to assess the interaction between environmental variables and genotypes (p < .05). RESULTS: The variant allele KLK4 rs2235091 was associated with MH in some children (odds ratio [OR]: 3.75; 95% confidence interval [CI] = 1.65-7.81; p = .001). Taking medications in the first 4 years of life was also associated with MH (OR: 2.94; 95% CI = 1.02-6.04; p = .041) and specifically in association with polymorphisms in ENAM, AMBN, and KLK4 (p < .05). The use of medications during pregnancy was not associated with MH (OR: 1.37; 95% CI = 0.593-3.18; p = .458). CONCLUSION: The results of this study suggest that taking medication in the postnatal period appears to contribute to the etiology of MH in some evaluated children. There may be a possible genetic influence of polymorphisms in the KLK4 gene with this condition.

Association between genetic factors and molar-incisor hypomineralisation or hypomineralised second primary molar: A systematic review.

OBJECTIVE: To determine the association between genetic factors and molar-incisor hypomineralisation (MIH) and/or hypomineralised second primary molars by means of a systematic review. DESIGN: A search was performed in Medline-PubMed, Scopus, Embase and Web of Science databases; manual search and search in gray literature were also performed. Selection of articles was performed independently by two researchers. A third examiner was involved in cases of disagreement. Data extraction was performed using an Excel® spreadsheet and independent analysis was performed for each outcome. RESULTS: Sixteen studies were included. There was an association between MIH and genetic variants related to amelogenesis, immune response, xenobiotic detoxification and other genes. Moreover, interactions between amelogenesis and immune response genes, and SNPs in the aquaporin gene and vitamin D receptors were associated with MIH. Greater agreement of MIH was found in pairs of monozygotic twins than dizygotic twins. The heritability of MIH was 20 %. Hypomineralised second primary molars was associated with SNPs in the hypoxia-related HIF-1 gene and methylation in genes related to amelogenesis. CONCLUSION: With very low or low certainty of evidence, an association was observed between MIH and SNPs in genes associated with amelogenesis, immune response, xenobiotic detox and ion transport. Interactions between genes related to amelogenesis and immune response as well as aquaporin genes were associated to MIH. With very low certainty of evidence, hypomineralised second primary molars was associated to a hypoxia-related gene and to methylation in genes related to amelogenesis. Moreover, higher agreement of MIH in pairs of monozygotic twins than dizygotic twins was observed.

Prevalence and predisponent factors of molar-incisor hypomineralization in primary dentition

Aim: To evaluate the prevalence and predisposing factors for hypomineralization of second molars in children in primary dentition. Methods: A questionnaire was applied to parents to analyze predisposing factors and to assist in the diagnosis of hypomineralization in children between 2 and 6 years old, followed by an intraoral examination based on indices of non-fluorotic enamel defects in the primary dentition, according to the "Modified Index DDE" to determine demarcated opacity and HSPM presence / severity index to assess hypomineralization. Children from public and private schools were dived into two groups: if they presented HSPM-Group 1 (G1) and if they did not have HSPM-Control group (CG). Results: The most frequent predisposing factors associated with the child were Illness in the first year of life (X2= 6.49; p=0.01) and antibiotic use in the first year of life (X2= 41.82; p= 0.01). The factors associated with the mother were hypertension (X2= 9.36; p=0.01), infections during pregnancy (X2=14.80; p=0.01) and alcohol consumption during pregnancy (X2=97.33; p=0.01). There was a prevalence of 3.9% of HSPM in 14 children, with statistical difference regarding gender (X2 = 4.57; p <0.05), with boys presenting a higher frequency. In G1 hypomineralization was of the type with demarcated opacity, with more prevalent characteristics the yellowish spot, with moderate post-eruptive fracture and acceptable atypical restorations. All lesions were located in the labial region with 1/3 of extension. Conclusion: The prevalence of HSPM in children between 2 and 6 years old was 3.9%, with a predominance in males, with tooth 65 being the most affected. There was an association between HSPM and infection in the first year of life, as well as the use of antibiotics and sensitivity in the teeth affected by the lesion. There was an association between HSPM and hypertension, infection and mothers' alcohol use during pregnancy

Clinical and Molecular Disorders Caused by COVID-19 During Pregnancy as a Potential Risk for Enamel Defects

ABSTRACT This paper discusses the potential risk that COVID-19 generates for the development of enamel defects. This hypothesis was built based on the etiopathogenesis of enamel defects and the relationship with the symptom's characteristic of COVID-19. Pregnancy is a critical period for the child's development; exposure to pathological agents can cause systemic imbalances and risks of adverse perinatal and prenatal outcomes. The main clinical symptoms of this disease and its association with that dental outcome were considered. Fever, breathing, cardiovascular disorders, and diarrhea were related as potential etiological factors of ameloblast metabolism imbalance, which can interfere qualitatively and quantitatively in the development, maturation and mineralization of the tooth enamel. Molecular disorders derived from COVID-19, as well as their clinical symptoms, can be considered potential risk factors for the development of enamel defects. Individuals with enamel defects experienced high stress levels during pregnancy or early childhood. The approach adopted may help build new research to ensure understanding of the etiology of the development of dental enamel defects and its relationship with COVID-19. However, longitudinal studies need to be conducted to confirm the association between COVID-19 and adverse events during pregnancy.

Oral manifestations of renal tubular acidosis associated with secondary rickets: case report / Manifestações bucais da acidose tubular renal associada ao raquitismo secundário: relato de caso

ABSTRACT This report describes the oral manifestations of renal tubular acidosis (RTA) associated with secondary rickets and discusses the biological plausibility of these findings. The characteristic electrolyte changes during RTA or genetic mutations that trigger RTA may be responsible for impaired amelogenesis, dental malocclusion, impacted teeth, and absent lamina dura. This report reinforces the possibility of an association between RTA and the oral manifestations described.

RESUMO Este relato de caso descreve as manifestações bucais da acidose tubular renal (ATR) associada ao raquitismo secundário e discute a plausibilidade biológica desses achados. As alterações eletrolíticas características da ATR ou as mutações genéticas que a desencadeiam podem ser responsáveis pela amelogênese imperfeita, maloclusão dentária, dentes impactados e ausência de lâmina dura. Este relato reforça a possibilidade de uma associação entre ATR e as manifestações bucais descritas.

Estudo morfológico do efeito do trauma mecânico sobre a amelogênese em incisivos de ratos / Morphological study of the effect of mechanical trauma on amelogenesis in rat incisors

Introdução: a amelogênese compreende a formação do esmalte por células especializadas denominadas ameloblastos. Os ameloblastos secretam proteínas da matriz e são responsáveis pela criação de um ambiente extracelular que favorece a mineralização do esmalte. Contudo, diversos fatores, como o trauma dentário, podem interferir na amelogênese, contribuindo para a formação de um esmalte defeituoso. O trauma dentário tem sido responsável por muitos casos de hipoplasia que podem fragilizar o dente, além de trazer desconforto estético. Objetivo: examinar as alterações morfológicas sobre o epitélio odontogênico e a matriz de esmalte de incisivos de ratos, produzidas por um trauma dentário. Metodologia: incisivos de ratos foram extruídos e depois reposicionados em seus alvéolos originais. Decorridos 3, 7, 10, 20, 30 e 60 dias do procedimento cirúrgico, os dentes foram fixados em uma solução de formaldeído e glutaraldeído, processados histologicamente e corados com azul de toluidina. Resultados: a análise morfológica revelou a formação de uma matriz de esmalte bastante heterogênea, com espessura irregular, particularmente na porção mais apical dos incisivos. Algumas matrizes de esmalte expostas mostravam pequenas lacunas de reabsorção, muitas vezes com deposição de um material cementoide. Conclusão: o presente estudo mostrou que o trauma foi suficiente para produzir alterações hipoplásicas e de hipomineralização importantes no esmalte que se relacionaram com a fase funcional dos ameloblastos na região afetada.

Introduction: amelogenesis comprises of enamel formation by specialized cells called ameloblasts. Ameloblasts secrete matrix proteins and are responsible for the creation of an extracellular environment that favors the enamel mineralization. However, various factors, such as the dental trauma, can interfere with amelogenesis, contributing to the formation of a defective enamel. Dental trauma has been responsible for many cases of hypoplasia which can weaken the tooth, in addition to bringing aesthetic discomfort. Objective: examine the morphological changes on the odontogenic epithelium and the enamel matrix of rats incisors, produced by dental trauma. Methodology: rats incisors were extruded and then repositioned in their original alveoli. After 3, 7, 10, 20, 30 and 60 days of the surgical procedure, teeth were fixed in a solution of formaldehyde and glutaraldehyde, processed histologically and stained with toluidine blue. Results: the morphological analysis revealed the formation of enamel matrix extremely heterogeneous, with irregular thickness, particularly on the apical portion of the incisors. Some matrixes of exposed enamel showed small gaps of reabsorption, often with deposition of cementoid material. Conclusion: the present study showed that the trauma was enough to produce hypoplastic and hypomineralization changes important in the enamel that were related to the functional phase of the ameloblasts in the affected region

Genes Regulating Immune Response and Amelogenesis Interact in Increasing the Susceptibility to Molar-Incisor Hypomineralization.

Ameloblasts are sensitive cells whose metabolism and function may be affected by inflammatory stimuli. The aim of this study was to evaluate the possible association between polymorphisms in immune response-related genes and molar-incisor hypomineralization (MIH), and their interaction with polymorphisms in amelogenesis-related genes. DNA samples were obtained from 101 nuclear families that had at least 1 MIH-affected child. Eleven single-nucleotide polymorphisms (SNPs) were investigated in immune response genes using TaqMan® technology allele-specific probes. A transmission disequilibrium test was performed to verify overtransmission of alleles in all MIH families, as well as in families only with mild or severe MIH-affected children. Gene-gene interactions between the immune-related and amelogenesis-related polymorphisms were analyzed by determining whether alleles of those genes were transmitted from heterozygous parents more often in association than individually with MIH-affected children. In severe cases of MIH, significant results were observed for rs10733708 (TGFBR1, OR = 3.5, 95% CI = 1.1-10.6). Statistical evidence for gene-gene interactions between rs6654939 (AMELX) and the SNPs rs2070874 (IL4), rs2275913 (IL17A), rs1800872 (IL10), rs1800587 (IL1A), and rs3771300 (STAT1) was observed. The rs2070874 SNP (IL4) was also significantly overtransmitted from heterozygous parents with the rs7526319 (TUFT1) and the rs2355767 (BMP2) SNPs, suggesting a synergistic effect of the transmission of these alleles with susceptibility to MIH. This family-based study demonstrated an association between variation in TGFBR1 and MIH. Moreover, the polymorphisms in immune response and amelogenesis genes may have an additive effect on the risk of developing MIH.

Oral manifestations of renal tubular acidosis associated with secondary rickets: case report.

This report describes the oral manifestations of renal tubular acidosis (RTA) associated with secondary rickets and discusses the biological plausibility of these findings. The characteristic electrolyte changes during RTA or genetic mutations that trigger RTA may be responsible for impaired amelogenesis, dental malocclusion, impacted teeth, and absent lamina dura. This report reinforces the possibility of an association between RTA and the oral manifestations described.

Analysis of Polymorphisms in Genes Differentially Expressed in the Enamel of Mice with Different Genetic Susceptibilities to Dental Fluorosis.

Genes expressed during amelogenesis are candidates to increase the risk of dental fluorosis (DF). Thus, this study aimed to evaluate the association between polymorphisms in enamel development genes and susceptibility to DF in mice. Mice of both sexes, representing strains 129P3/J (n = 20; resistant to DF) and A/J (n = 20; susceptible to DF), were divided into 2 groups. Each strain received a diet with a low concentration of fluoride (F) and drinking water containing 0 or 50 mg/L of F for 6 weeks. Clinical evaluation and analysis of Vickers enamel microhardness of the incisors were performed. Livers were collected for genomic DNA extraction. Seventeen genetic polymorphisms in Amelx, Ambn, Ambn, Col14a1, Col1a1, Col5a2, Enam, Fam20a, Fam83h, Foxo1, Klk4, Mmp20, Serpinf1, Serpinh1, Smad3, Tuft1, and Wdr72 were genotyped by real-time PCR using Taqman chemistry. Overrepresentation of alleles and genotypes in DF was evaluated using the χ2 test with an alpha of 5%. The clinical aspects of the enamel and the surface enamel microhardness confirmed the DF condition. In the polymorphisms rs29569969, rs13482592, and rs13480057 in Ambn, Col14a1, and Mmp20, respectively, genotype and allele distributions were statistically significantly different between A/J and 129P3/J strains (p < 0.05). In conclusion, polymorphisms in Ambn, Col14a1, and Mmp20 are associated with the susceptibility to DF.

Pathogenesis of dental fluorosis: biochemical and cellular mechanisms / Patogénesis de la fluorosis dental: mecanismos bioquímicos y celulares

Abstract. The mechanisms involved in the development of dental fluorosis are still unknown. The development of in vivo and in vitro models using biologically relevant concentrations of fluoride for the emergence of fluorosis has allowed suggesting hypotheses that contribute to the understanding of the mechanisms that produce this defect in enamel development, with high prevalence in Colombia. This topic review presents an update on the normal mechanisms of the formation of enamel and how they are affected by exposure to high concentrations of fluoride. This is a thorough review of the deleterious effects of fluoride on the cells and the extracellular matrix, especially during the maturation stage, resulting in a delay of the removal of the protein matrix of amelogenins, as well as the appearance of mottled enamel-a characteristic of dental fluorosis. Finally, it shows the perspectives of the study of this defect in enamel development from biochemistry and cellular and molecular biology.

RESUMEN. Los mecanismos involucrados en el desarrollo de la fluorosis dental aún no se conocen a cabalidad. El desarrollo de modelos in vivo e in vitro que utilizan concentraciones de fluoruro biológicamente relevantes para la aparición de fluorosis ha permitido el planteamiento de hipótesis que aportan cada vez más al conocimiento de los mecanismos que generan este defecto del desarrollo del esmalte, de alta prevalencia en Colombia. Esta revisión presenta una actualización sobre los mecanismos normales de la formación del esmalte y cómo estos se ven afectados por la exposición a altas concentraciones de fluoruro. Se presenta una revisión en detalle de los efectos deletéreos del fluoruro sobre las células y sobre la matriz extracelular, especialmente durante la etapa de maduración, que tendrán como consecuencia el retraso de la remoción de la matriz proteica de amelogeninas y se traducirá en la apariencia de esmalte moteado, característica de la fluorosis dental. Por último, se muestran las perspectivas del estudio de este defecto del desarrollo del esmalte desde la bioquímica y la biología celular y molecular.

Expression of enamel proteins in rough endoplasmic reticulum and golgi complex in human dental germs / Expresión de proteínas del esmalte en retículo endoplásmico rugoso y complexo golgiensis en gérmenes dentales humanos

Tooth enamel is the hardest tissue in the body. The organic matrix configuration is provided by the main proteins amelogenin, ameloblastin and enamelysin (MMP20), an enzyme that helps to shape the matrix. The aim of this study was to determine by histochemistry the expression of amelogenin and enamelysin through the rough endoplasmic reticulum in the late stages of amelogenesis, and its expression in the Complexus golgiensis (Golgi complex / Golgi apparatus) in the early stages in human fetuses. In early stages a colocalization of both proteins inside the Golgi apparatus was found, being more evident the relationship between Golgi and amelogenin (99.92 %). In the late stage, a colocalization of both proteins and rugged endoplasmic reticulum was found. With enamelysin being more evident in relation with rough endoplasmic reticulum (99.95 %). Our findings demonstrated the presence of amelogenin and enamelysin in odontoblast and ameloblast. However, the presence of these two proteins in odontoblast remains unknown.

El esmalte dental es el tejido más duro del cuerpo. La configuración de la matriz orgánica es proporcionada por las proteínas principales amelogenina, ameloblastina y enamelisina (MMP20), una enzima que ayuda a dar forma a la matriz. El objetivo de este estudio fue determinar mediante histoquímica la expresión de amelogenina y enamelisina a través del retículo endoplasmático rugoso en las últimas etapas de la amelogénesis , y su expresión en el Complexo golgiensis en las primeras etapas de formación en fetos humanos. En las primeras etapas se observó colocalización de ambas proteínas en el interior del Complexo golgiensis, siendo más evidente la relación entre Golgi y amelogenina (99,92 %). En la última etapa, se identificó una colocalización de ambas proteínas y retículo endoplásmico rugoso. Resulto más evidente la enamelisina en relación con el retículo endoplasmático rugoso (99,95 %). Nuestros resultados demostraron la presencia de amelogenina y enamelisina en odontoblastos y ameloblastos, sin embargo se desconoce la presencia de estas dos proteínas en odontoblastos.

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.

Expresión de tuftelina en gérmenes dentales humanos / Expression of tuftelin in human dental germs

La tuftelina es una proteína secretada en la matriz adamantina en desarrollo durante la formación del esmalte. Su función continúa sin esclarecerse, aunque se presume que juega un papel importante en la biomineralización de esmalte y dentina, así como en el desarrollo del órgano dental. Con el presente estudio se identificó su localización en las diferentes estructuras de gérmenes dentales de fetos humanos, conforme a los resultados se observó su expresión en el estadio pre-secretor observándose en el citoplasma de los ameloblastos, retículo estrellado, papila dental, así como en el estrato intermedio; en el secretor se identificó principalmente en la unión amelodentinaria, y en la superficie externa del esmalte, observando una marcada expresión de la proteína en la porción basal del proceso odontoblástico, pero no en la matriz extracelular de la dentina. De acuerdo a los resultados obtenidos se puede considerar que su expresión se presenta tanto en la amelogénesis, como en la odontogénesis en tejidos sin mineralizar.

The tuftelin is a secreted protein in the adamantine matrix in developing during the enamel formation. Its function continues unclarified, although it plays a role in the biomineralization of the dental organ. With the present studio the location was identified in the different structures of dental germs from human fetuses, according to the results it was observed the expression in the pre-secretor stage being observed in the cytoplasm of ameloblasts, stellate reticulum, dental papilla, also in the intermediate stratum; in the secretor it was mainly identified in the amelodentinal junction and in the outer surface of enamel, observing a marked expression of the protein in the basal portion of the odontoblastic process, but not in the extracellular matrix of the dentine. According to the results obtained it can be considered that its expression occurs in both amelogenesis and odontegenesis in unmineralized tissues.

Polymorphisms in genes involved in enamel development are associated with dental fluorosis.

OBJECTIVE: To evaluate the association between polymorphisms in DLX1, DLX2, MMP13, TIMP1 and TIMP2 genes with dental fluorosis (DF) phenotype. DESIGN: Four hundred and eighty one subjects (108 with DF and 373 DF free) from 6 to 18 years of age were recruited. This population lived in Rio de Janeiro, a city with fluoridation of public water supplies. DF was assessed using the Deans index modified. Only erupted permanent teeth were assessed. Genetic polymorphisms in DLX1, DLX2, MMP13, TIMP1 and TIMP2 were analyzed by real-time PCR from genomic DNA. Association between DF, genotype, and allele distribution were evaluated using chi-square and logistic regression analyses with an alpha level of 5%. RESULTS: DF was more prevalent in Afro-descendants than in Caucasians (p=0.08; OR=1.83; CI 95%=1.18-2.82). Logistic regression analysis adjusted by the ethnicity demonstrated a statistical difference for TIMP1 genotype (p=0.033; OR=2.93, 95%CI, 1.09-7.90). When only the severer cases of DF were analyzed, polymorphisms in DLX1 and DLX2 were associated with DF (p<0.05). CONCLUSION: Our results provided evidence that polymorphisms in TIMP1, DLX1 and DLX2 genes may be associated with DF phenotypes.

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.

Proteomics of Secretory-Stage and Maturation-Stage Enamel of Genetically Distinct Mice.

The mechanisms by which excessive ingestion of fluoride (F) during amelogenesis leads to dental fluorosis (DF) are still not precisely known. Inbred strains of mice vary in their susceptibility to develop DF, and therefore permit the investigation of underlying molecular events influencing DF severity. We employed a proteomic approach to characterize and evaluate changes in protein expression from secretory-stage and maturation-stage enamel in 2 strains of mice with different susceptibilities to DF (A/J, i.e. 'susceptible' and 129P3/J, i.e. 'resistant'). Weanling male and female susceptible and resistant mice fed a low-F diet were divided into 2 F-water treatment groups. They received water containing 0 (control) or 50 mg F/l for 6 weeks. Plasma and incisor enamel was analyzed for F content. For proteomic analysis, the enamel proteins extracted for each group were separated by 2-dimensional electrophoresis and subsequently characterized by liquid-chromatography electrospray-ionization quadrupole time-of-flight mass spectrometry. F data were analyzed by 2-way ANOVA and Bonferroni's test (p < 0.05). Resistant mice had significantly higher plasma and enamel F concentrations when compared with susceptible mice in the F-treated groups. The proteomic results for mice treated with 0 mg F/l revealed that during the secretory stage, resistant mice had a higher abundance of proteins than their susceptible counterparts, but this was reversed during the maturation stage. Treatment with F greatly increased the number of protein spots detected in both stages. Many proteins not previously described in enamel (e.g. type 1 collagen) as well as some uncharacterized proteins were identified. Our findings reveal new insights regarding amelogenesis and how genetic background and F affect this process.

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.

Estudio de la microdureza de dientes permanentes con fluorosis incipiente, tratados con resina infiltrante / Micro-hardness of permanent teeth with incipient fluorosis treated with infiltrant resin / Estudo da microdureza de dentes permanentes com fluorose incipiente tratados com resina infiltrante

Objetivo: Evaluar la microdureza del esmalte afectado con fluorosis sometido a tratamiento con resina infiltrante, compa-rándolo con dientes sanos y dientes con fluorosis incipiente. Materiales y métodos: La muestra estuvo constituida por 15 dientes permanentes humanos recolectados del Banco de Dientes de la Facultad de Odontología de la Universidad Central del Ecuador. Para la selección de los dientes se tuvieron en consideración los criterios diagnósticos de fluorosis dental según Thylstrup y Ferjeskov (1978), teniendo 5 dientes con score 0 y 10 dientes con fluorosis incipiente (score 1-3). Todos los dientes considerados en el estudio no presentaron lesiones de caries, grietas ni fracturas. La muestra fue dividida en 3 grupos, G1: dientes sanos (control negativo), G2: dientes con fluorosis incipiente y G3: dientes con fluorosis incipiente tratado con resina infiltrante Icon®. A cada grupo (n=5) se le realizó una profilaxis y posteriormente al G3 se le aplicó la resina infiltrante. La microdureza knoop fue obtenida mediante tres indentaciones con microdurometro (Wilson Tukon Microhardness Tester). Los datos fueron analizados a través del método de Rho de Spearman con significancia de 5%. Resultados: La media de la microdureza knoop de los grupos y sus desviaciones estándar fueron de: G1=284,8 ± 56,2 G2=325,7 ± 95,1 G3=226,2 ± 67,4. no se encontraron diferencias estadísticamente significativas entre los grupos estudia-dos (p>0,05). Conclusión: La microdureza del esmalte afectado por fluorosis incipiente sometida a tratamiento con resina infiltrante, esmalte de dientes sanos y esmalte de dientes con fluorosis incipiente no mostró diferencia estadística.

Objective: To evaluate the microhardness of the enamel affected by fluorosis subjected to treatment with infiltrating resin, comparing it with sound teeth and teeth with incipient fluorosis. Materials and methods: The sample consisted of 15 permanent human teeth collected from the Teeth Bank of the Faculty of Odontology of the Central University of Ecuador. For the selection of the teeth, diagnostic criteria of dental fluorosis were considered according to Thylstrup and Ferjeskov (1978), having 5 teeth with score 0 and 10 teeth with incipient fluorosis (score 1-3). None of the teeth that were examined in the study had caries, cracks or fractures. The sample was divided into 3 groups. G1: sound teeth (negative control), G2: teeth with incipient fluorosis and G3: teeth with incipient fluorosis treated with Icon® infiltrating resin. To each group (n=5), dental prophylaxis was performed and afterwards to G3, infiltrating resin was applied. The Knoop micro-hard-ness was obtained through 3 indentations with microhardness tester (Wilson Tukon Microhardness Tester). The data were analyzed through the Spearman's Rho method with 5% significance. Results: The median of Knoop microhardness of the groups and their standard deviations were: G1=284.8 ± 56.2 G2=325.7 ± 95.1 G3=226.2 ± 67.4, no statistically significant differences were found between the examined groups (p>0.05). Conclusion: The microhardness of the enamel affected by incipient fluorosis subjected to treatment with infiltrating resin, enamel of sound teeth, and enamel of teeth with incipient fluorosis did not demonstrate statistical difference.

RESUMOObjetivo: Avaliar a microdureza do esmalte afetado com fluorose incipiente submetido ao tratamento com resina infiltrada, fazendo uma comparação com dentes higidos dentes com fluorose incipiente. Materiais e métodos: A amostra estava constituída por 15 dentes permanentes humanos coletados do Banco de Dientes de la Facultad de Odontología de la Uni-versidad Central del Ecuador (Banco de dentes da Faculdade de Odontologia da Universidade Central do Equador). Para a seleção dos dentes se considerou os critérios de diagnóstico de fluorose dental segundo Thylstrup y Ferjeskov (1978), tendo 5 dentes com pontuação de 0 e 10 dentes com fluorose incipiente (pontuação de 1 a 3). Todos os dentes considerados no estudo não apresentaram lesões de cárie, rachaduras nem fraturas. A amostragem foi dividida em 3 grupos: G1: dentes higidos (controle negativo); G2: dentes com fluorose incipiente e G3: dentes com fluorose incipiente tratados com resina infiltrante Icon®. Para cada grupo (n=5) uma profilaxia foi realizada, e posteriormente ao G3 se aplicou a resina infiltrante. A microdureza knoop foi obtida mediante três entalhes com microdurómetro (Wilson Tukon Microhardness Tester). Os dados foram analisados através do método de Rho de Spearman com um nivel de 5%. Resultados: A média da microdu-reza knoop dos grupos e seus desvios padrões foram de G1=284,8 ± 56,2; G2=325,7 ± 95,1; G3=226,2 ± 67,4, não foram estatisticamente encontradas diferenças significativas entre os grupos estudados (p>0,05). Conclusão: A microdureza do esmalte afetado com fluorose incipiente submetido ao tratamento com resina infiltrante, esmalte de dentes hígidos e de dentes com fluorose incipiente demostrou não ter diferença estatisticamente significativa.

The role of enamelysin (MMP-20) in tooth development: systematic review / El papel de la enamelisina (MMP-20) en el desarrollo dentario: revisión sistemática

ABSTRACT. Introduction: ameloblasts are cells responsible for the production and mineralization of the organic matrix of enamel through several stages: pre-secretory, secretory, transition, and maturation. The organic matrix components are produced in the secretory phase. In the maturation phase, the organic component is removed and the mineralization process starts. This process requires the involvement of matrix metalloproteinase 20 (MMP-20), also called enamelysin. Several studies have shown the presence of MMP-20 in tooth development and its relationship to alterations in enamel formation. The objective was: to classify the different studies and laboratory techniques used to demonstrate the involvement of enamelysin in tooth development and its relation to pathologies during enamel formation. Methods: a systematic review was conducted with the following bibliographic databases: PubMed, Science-Direct, Hinari, and SciELO, in order to classify the different studies related to the involvement of MMP-20 in tooth development and the methods to detect its expression, between the years of 2009 and 2014. Results and conclusions: 11 in vitro models show that MMP-20 has specific cleavage sites for enamel matrix proteins. This process is altered by chemical composition, ions, and the presence of hydroxyapatite. Enamel morphology is altered in the knockout models. In human studies, MMP-20 has been associated with increased susceptibility to dental caries, enamel thickness, and dental agenesis.

RESUMEN. Introducción: el ameloblasto es la célula encargada de la producción y mineralización de la matriz orgánica del esmalte. Atraviesa varias etapas: la fase pre-secretora, secretora, de transición y maduración. En la fase secretora se producen los componentes de la matriz orgánica. En la fase de maduración se elimina el componente orgánico y se inicia el proceso de mineralización. Este proceso requiere de la participación de la metaloproteinasa de matriz 20 (MMP-20) o también llamada enamelisina. Diversos estudios demuestran la presencia de MMP-20 en el desarrollo dentario y su relación con alteraciones en la formación del esmalte. El objeto fue clasificar los diferentes estudios y técnicas de laboratorio empleadas que demuestren la participación de enamelisina en el desarrollo dentario y su relación con patologías en la formación del esmalte. Métodos: se realizó una revisión sistemática de la literatura con las siguientes bases bibliográficas: PubMed, Science-Direct, Hinari y SciELO, con el fin de clasificar los diferentes estudios relacionados con la participación de MMP-20 en el desarrollo dental y los métodos utilizados para detectar su expresión, entre los años de 2009 a 2014. Resultados y conclusiones: los modelos in vitro evidencian que MMP-20 tiene sitios específicos de escisión para las proteínas de matriz de esmalte. Este proceso se ve alterado por la composición química, iones, y la presencia de hidroxiapatita. En los modelos knockout la morfología del esmalte está alterada. En los estudios en humanos, se ha relacionado la MMP-20 con una mayor susceptibilidad de caries dental, el grosor completo de esmalte y agenesias dentales.