Tooth Mineralization Research Articles

Manifestation and Mechanisms of Abnormal Mineralization in Teeth.

Tooth biomineralization is a dynamic and complicated process influenced by local and systemic factors. Abnormal mineralization in teeth occurs when factors related to physiologic mineralization are altered during tooth formation and after tooth maturation, resulting in microscopic and macroscopic manifestations. The present Review provides timely information on the mechanisms and structural alterations of different forms of pathological tooth mineralization. A comprehensive study of these alterations benefits diagnosis and biomimetic treatment of abnormal mineralization in patients.

Analysis of follow-up changes in incidence of oral diseases in Novosibirsk schoolchildren during the preventive treatment program

Relevance. The Russian Federation state program „Healthcare system development”, approved on April 15, 2014, relies on the introduction of the specialist „Dental Hygienist” in the system of school dentistry service as the main executor of the preventive treatment program. Government resolution #1640 as of 26.12.2017, which is to be realized during 2018-2025, included the agency project „“Primary prevention of oral diseases among the population of the Russian Federation”. The realization of the oral disease prevention project (professional cleaning, fluoride local application, permanent molar fissure sealing) is a basic program that includes necessary steps to reduce oral disease incidence rate and caries increase in schoolchildren. Administration of oral care products (fluoride varnish, sealants) immediately after tooth eruption, i.e., during formation and mineralization of the hard dental tissues, is more relevant, than the use of these products after the mineralization is complete. Aim – to assess the effectiveness of oral disease preventive measures by the analysis of the follow-up changes in the dental status of schoolchildren.Materials and methods. 115 first-grade schoolchildren of two Novosibirsk general schools participated in the study. The schoolchildren were evenly divided into 2 groups: prevention and comparison. The parents and children of both groups were trained how to take care of the oral cavity at home. The children in both groups were examined, oral hygiene indices were determined and the teeth were treated. The preventive treatment in the first groups was administered with the following materials: fluoride varnish with innovative ingredient, tricalcium phosphate, and low fill fluoride-releasing light-cured sealant. The materials are certified and approved for use in children in the Russian Federation. The individual preventive treatment was not performed in the second group. The effectiveness of the preventive treatment was assessed by the analysis of follow-up changes in the dental status of the schoolchildren.Results. The school preventive treatment program demonstrated a significant reduction of caries increase rate – up to 31.79% in the prevention group, which forms the basis for performance optimization of the school dental office where the priority belongs to a dental hygienist.Conclusions. The results of the preventive treatment program with the participation of a pediatric dentist and a dental hygienist held in three Novosibirsk schools confirmed its high medical effectiveness.

Dental effects of enzyme replacement therapy in case of childhood-type hypophosphatasia

BackgroundHypophosphatasia (HPP), a skeletal disease characterized by hypomineralization of bone and teeth, is caused by an ALPL gene mutation that leads to low activity of the tissue non-specific alkaline phosphatase enzyme. Although enzyme replacement therapy (ERT) was recently introduced for affected patients, no known studies have been reported regarding its dental effects related to permanent teeth and jaw bones. In the present study, we examined the dental effects of ERT in a case of childhood-type hypophosphatasia, including panoramic radiography findings used to estimate the dental age of permanent teeth and mandibular bone density. Furthermore, the effects of that therapy on the periodontal condition of the patient were evaluated by comparing periodontal pocket depth before and after initiation.Case presentationAn 11-year-1-month-old boy was referred to our clinic for consultation regarding oral management. Two primary incisors had spontaneously exfoliated at 1 year 8 months old and he had been diagnosed with childhood-type HPP at the age of 2 years 2 months. Obvious symptoms were localized in the dental region at the time of diagnosis, though later extended to other parts of the body such as bone pain. ERT was started at 11 years 7 months of age, after which bone pain disappeared, and motor functions and activities of daily living improved. We estimated dental age based on tooth development stage. The age gap between chronological and dental ages was expanded before treatment, and then showed a constant decrease after ERT initiation and finally disappeared. The index for mandibular bone density (mandibular cortical width / length from mesial buccal cusp to apex of first molar) was increased after ERT initiation. Furthermore, the periodontal condition for all teeth except those exfoliated was stable after starting therapy.ConclusionsERT resulted in improved tooth and mandibular bone mineralization, with notably good effects on teeth under formation. Acceleration of mineralization of roots associated with erupting teeth leads to stabilization of the periodontal condition. We concluded that ERT contributed to the improved dental condition seen in this patient.

Treatment with bone maturation and average lifespan of HPP model mice by AAV8-mediated neonatal gene therapy via single muscle injection

Hypophosphatasia (HPP) is an inherited skeletal disease characterized by defective bone and tooth mineralization due to a deficiency in tissue-nonspecific alkaline phosphatase (TNALP). Patients with the severe infantile form of HPP may appear normal at birth, but their prognosis is very poor. To develop a practical gene therapy for HPP, we endeavored to phenotypically correct TNALP knockout (Akp2−/−) mice through adeno-associated virus type 8 (AAV8) vector-mediated, muscle-directed, TNALP expression. Following treatment of neonatal Akp2−/− mice with a single intramuscular injection of ARU-2801 (AAV8-TNALP-D10-vector) at 1.0 × 1012 vector genomes/body, high plasma ALP levels (19.38 ± 5.02 U/mL) were detected for up to 18 months, and computed tomography analysis showed mature bone mineralization. Histochemical staining for ALP activity in the knee joint revealed ALP activity on the surface of the endosteal bone of mice. Throughout their lives, the surviving treated Akp2−/− mice exhibited normal physical activity and a healthy appearance, whereas untreated controls died within 3 weeks. No ectopic calcification or abnormal calcium metabolism was detected in the treated mice. These findings suggest that ARU-2801-mediated neonatal intramuscular gene therapy is both safe and effective, and that this strategy could be a practical option for treatment of the severe infantile form of HPP.

Optimizing FTIR method for characterizing diagenetic alteration of skeletal material

Diagenetic alterations may limit the potential use of archaeological bones and teeth as a reliable source of information about the origin and movement of people and animals, their diet and the environment in which they lived. Fourier transform infrared spectroscopy (FTIR) has been widely applied to determine the overall state of preservation of ancient bones. Spectral data are commonly used to quantify two diagenetic indicators related to sample crystallinity: the splitting factor (SF), the hydrogen phosphate ion index (HPO4/PO4) and the width at 85% of the height of the 604 cm-1 peak (FW85%).The aim of the present work is to determine the presence of any difference in the value of SF, HPO4/PO4 and FW85% of the 604 cm−1 peak between tissues such as enamel, dentine and bone. This method has been applied to two different modern animals: sheep and pigs.The results obtained in this study demonstrate that enamel has significantly higher values of the SF and significantly lower values of HPO4/PO4 and FW85% in comparison to bone and dentine in both animal species. Moreover, enamel has been reported to show diversification of SF index across the investigated species, which is presumably related to different tooth development and mineralisation patterns in animals with different diets (i.e. herbivorous versus omnivorous). The present study demonstrates that due to the different biogenic chemical structure of bones and teeth, the SF and HPO4/PO4 reference ranges should be determined separately for each of the three tissues, and in the case of enamel also allowing for the analysed species.

Clinical Implications of Vitamin D in Oral Diseases- A Review

Oral health is a reflection of systemic health. The various nutritional deficiencies not only affect the systemic health but also have an impact on oral health. The prevalence of Vitamin D deficiency (VDD) is rampant globally. Vitamin D (VD) is not only essential for skeletal growth during childhood and adulthood but has a great impact on oral tissues and odontogenesis. VDD has several implications on oral health from childhood to adulthood. VD can negatively influence the oral health of the mother and child and VD supplementation brings positive outcomes during and after pregnancy. In children, severe VDD can impair tooth mineralization, resulting in defects of enamel and dentin and predispose patients to caries. A remarkably high prevalence of periodontitis is seen in VDD and has implications on systemic health as well. A high prevalence of VDD is seen in oropharyngeal cancers. This review aims to provide the biological role of VD and its receptor, its implication on oral health and future strategies for targeted therapies in oral pathologies.

Six ALPL gene variants in five children with hypophosphatasia.

BackgroundHypophosphatasia (HPP) is a rare hereditary disorder characterized by defective bone and tooth mineralization caused by mutations in the alkaline phosphatase (ALPL) gene encoding tissue-nonspecific alkaline phosphatase (TNSALP). Here we performed clinical and molecular studies on 5 HPP children to investigate the pathogenic mechanisms of the ALPL gene variants.MethodsClinical and genetic analyses were performed on 5 HPP children, and the loci where ALPL variants were identified. Plasmids containing the relevant loci were constructed. The molecular and cellular mechanisms of the pathogenic ALPL variants were investigated by cellular immunofluorescence, enzyme activity assay, and protein expression assay.ResultsA total of 6 ALPL variants were identified in 5 HPP children: proband 1: c.346G>A (p.A116T); proband 2: c.346G>A (p.A116T)/deletions from c.1097 to c.1099 CCT (p.T366_S367deli) compound heterozygous variant; proband 3: insertion of G from c.1014 to c.1015 (p.H338fs)/c.1446C>A (p.H482Q) compound heterozygous variant; proband 4: c.920C>T (p.P307L); and proband 5: c.883A>G (p.M295V). Twenty-four hours after the HEK-293T was transfected with different variant plasmids, its alkaline phosphatase activity and enzyme protein content were reduced compared with the wild type, and there were differences among different variants. Except for 1014-G-1015+C1446A, the degree of reduction in enzyme activity was negatively correlated with the severity of clinical manifestations. Immunofluorescence revealed that the variants (especially c.883A>G and c.920C>T) caused a decrease in alkaline phosphatase expression in the cellular membrane.ConclusionsIn total, 3 novel variants were identified in these 5 HPP children, the discovery of which will enrich the human ALPL gene mutation database. Different variants in the ALPL gene can downregulate the activity of TNSALP enzyme (and thus affect its function) by affecting protein expression and translational modifications. The same variant may cause clinical manifestations of different severities in different individuals due to the presence of dominant negative effects, alterations in noncoding sequences, blind area of intron regulatory region sequencing, and variations in environmental and individual factors. The molecular mechanisms via which the ALPL gene exerts its expression effect in vivo are highly variable and warrant further investigation.

Карієсрезистентність – критерій стоматологічного статусу дітей та підлітків

Prevention of dental caries in children is one of the current problems of modern pediatric dentistry, which is due to the high prevalence and intensity of this disease. Analysis of the results of epidemiological studies conducted among children of different ages in the regions of Ukraine shows a significant increase in caries growth in recent years, both temporary and permanent teeth, which leads to in-depth study of the hardness of dental tissues to cariogenic factors in connection with the need in the constant improvement of methods of treatment and prevention of this pathology. The purpose of the study was to analyze the value of enamel caries resistance as a detector of resistance of dental hard tissues to carious process and its complications. The subject of the research is the work of domestic and foreign researchers on this topic. In the course of the research the bibliosemantic method and structural-logical analysis were used. Today, dental caries is the most common disease in different age groups, which is confirmed by the prevalence – 90-100% and a sharp trend of increasing its intensity. Given the high rates of this pathology, it should be remembered that its untimely treatment leads to the following complications: pulpitis, periodontitis, tooth extraction. An important concept that indicates the possibility of caries is caries resistance, which indicates the level of resistance of the enamel to caries and has an informative diagnostic value for the dentist. According to modern ideas, in the pathogenesis of dental caries the leading role is played by caries-resistant enamel. Its mineral base is formed by isomorphic crystals of apatite, which contain various chemical elements, and their amount in the body is closely related to the amount in the environment. It is established that more than 40 chemical elements take part in the process of tooth mineralization, the most important of which belongs to calcium, phosphorus, fluoride. Insufficient amount or excess of certain micronutrients in the environment, especially in soils and drinking water, can change their content in the body and, consequently, in the hard tissues of the teeth, affecting their resistance to caries. It is well known that the influence of a number of adverse environmental factors leads to a decrease in the resistance of the body as a whole and, as a consequence, to a decrease in the caries resistance of the enamel of the hard tissues of the teeth. Sensitivity to the effects of adverse factors increases significantly in the prepubertal period, a time not only of intensive growth of the child and the formation of his personality, but also a period of mineralization of more than half of permanent teeth. Therefore, exactly at this time dentists should pay special attention to the prevention of caries of permanent teeth in children by improving the conditions of secondary mineralization of tooth enamel, thereby increasing their level of caries resistance

Clinical Variability of Hypophosphatasia in Colombian Patients: Case Reports

Hypophosphatasia (HPP) is a rare inherited disorder characterized by low serum alkaline phosphatase. It affects bone and tooth mineralization, although extra-skeletal manifestations are frequent. HPP is caused by loss-of-function mutations in the ALPL gene, encoding the protein tissue-nonspecific alkaline phosphatase. The phenotype is broadly variable, from a subtype with exclusive odontological compromise (odontohypophosphatasia) to five subtypes with systemic involvement, classified according to the age of onset at first symptoms. We present seven cases of HPP, in order to perform the clinical, biochemistry and radiological description of these Colombian patients, as well as to show the clinical variability of the disease in patients who present the same mutation or genetic defect. J Endocrinol Metab. 2021;11(2):56-64 doi: https://doi.org/10.14740/jem711

Antimicrobials in Dentistry

Dental caries (decay) is caused by pathogenic bacterial species, which afflicts nearly a third of the world’s population from early childhood to old age. Treatment of tooth decay often involves the use of filling materials to restore the cavity; however, if untreated, it can cause pain, infection and eventually lead to tooth loss. Since the oral environment is colonised by many different microorganisms, bacterial biofilms can form on these filling materials, contributing to secondary caries that can eventually lead to the failure of the dental restoration. Thus, preventing the formation of bacterial biofilms is an important strategy in the management of caries, which has led to research enabling antimicrobial capabilities in dental materials. Materials and pharmaceutical sciences are in a continuous race against microbial resistance but are trying to balance between beneficial biota associated with the oral cavity, and, of course, avoiding a harmful effect on tissues is challenging. This has, therefore, stemmed a substantial interest in both preventive and restorative measures that would enable limiting the formation of secondary caries, oral microbial biofilms, and the retention of tooth mineral. Thus, innovative strategies are being explored and here we present a review with a focus on strategies that can inhibit or limit the formation of bacterial biofilms.

Clinical Variability of Hypophosphatasia in Colombian Patients: Case Reports

Hypophosphatasia (HPP) is a rare inherited disorder characterized by low serum alkaline phosphatase. It affects bone and tooth mineralization, although extra-skeletal manifestations are frequent. HPP is caused by loss-of-function mutations in the ALPL gene, encoding the protein tissue-nonspecific alkaline phosphatase. The phenotype is broadly variable, from a subtype with exclusive odontological compromise (odontohypophosphatasia) to five subtypes with systemic involvement, classified according to the age of onset at first symptoms. We present seven cases of HPP, in order to perform the clinical, biochemistry and radiological description of these Colombian patients, as well as to show the clinical variability of the disease in patients who present the same mutation or genetic defect. J Endocrinol Metab. 2021;11(2):56-64 doi: https://doi.org/10.14740/jem711

Abnormalities in Tooth Formation after Early Bisphosphonate Treatment in Children with Osteogenesis Imperfecta

Treatment with intravenous bisphosphonate (BP) in children and adolescents with osteogenesis imperfecta (OI) started in Sweden in 1991. No human studies on the role of BP therapy in development of disturbances in tooth mineralization or tooth morphology have been published. The study cohort comprised 219 individuals who were divided into four groups: group 1, BP treatment onset before 2 years of age (n = 22); group 2, BP treatment onset between 2 and 6 years of age (n = 20); group 3, BP treatment onset between 6 and 10 years of age (n = 13); and a control group of patients with OI who had not received BP therapy (n = 164). The chi-square test was used in between-group comparisons of the prevalence of tooth agenesis. The prevalence of tooth agenesis was significantly higher in children who began BP treatment before the age of 2 years (group 1; 59%,) compared to the controls (10%; p < 0.001) and to children who had begun BP therapy between ages 2 and 6 years (group 2; 10%; p = 0.009) or between ages 6 and 10 years (group 3; 8%; p = 0.003). Different types of disturbances in the enamel formation were seen in 52 premolars, where 51 were seen in those who began BP treatment before the age of 2 years. To conclude, starting BP treatment before the age of 2 years increases the risk of abnormalities in tooth formation manifesting as morphological aberrations, tooth agenesis, and enamel defects.

Clinical and molecular findings in children and young adults with persistent low alkaline phosphatase concentrations.

Hypophosphatasia is a rare inherited metabolic disease resulted by ALPL gene mutations. It is characterized by defective bone and teeth mineralization. The phenotypic spectrum is highly variable ranging from lethal perinatal form to mild forms which are only diagnosed in adulthood or remain undiagnosed despite persistently low concentrations of ALP. The aim of this study is to evaluate the clinical phenotype and frequency of ALPL mutations in a group of patient with hypophosphatasaemia. Thirty individuals with alkaline phosphatase values below 40 IU/L in at least two assessments and having no alternative explanation for their low ALP concentrations were included in the study. The clinical features and radiological data of the study group were re-investigated for hypophosphatasia-related findings. ALPL sequence analysis was performed using Sanger sequencing. No patient in the study group had severe symptoms, nor had they initially been diagnosed as having hypophosphatasia. Four different heterozygous ALPL mutations (c.542C>T, c.648 + 1G>A, c.657G>T and c.862 + 1G>C) were found in four patients. One splice site mutation (c.862 + 1G>C) was reported for the first time in this study. ALPL sequence analysis may help to diagnosing genetic defects in individuals with persistently low ALP concentrations and provide to take preventive measures before symptoms appear. As in the other populations, HPP displays allelic heterogeneity in our population.

Teeth reveal juvenile diet, health and neurotoxicant exposure retrospectively: What biological rhythms and chemical records tell us.

Integrated developmental and elemental information in teeth provide a unique framework for documenting breastfeeding histories, physiological disruptions, and neurotoxicant exposure in humans and our primate relatives, including ancient hominins. Here we detail our method for detecting the consumption of mothers' milk and exploring health history through the use of laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) mapping of sectioned nonhuman primate teeth. Calcium-normalized barium and lead concentrations in tooth enamel and dentine may reflect milk and formula consumption with minimal modification during subsequent tooth mineralization, particularly in dentine. However, skeletal resorption during severe illness, and bioavailable metals in nonmilk foods, can complicate interpretations of nursing behavior. We show that explorations of the patterning of multiple elements may aid in the distinction of these important etiologies. Targeted studies of skeletal chemistry, gastrointestinal maturation, and the dietary bioavailability of metals are needed to optimize these unique records of human health and behavior.

Vitamin D Deficiency and its Effects on Tooth Structure and pulpal changes

Vitamin D is a steroid hormone that produced primarily by sunlight exposure or obtained from dietary sources, including supplements. The persons who are normally at risk of Vitamin D deficiency are those with scarce of sun exposure and diminished intestinal absorption or limited oral intake. Teeth are nothing but mineralized structure which is enclosed by alveolar bone and are developed by 3 different hard tissues such as dentin, enamel, and cementum. Vitamin D plays a predominant vital part in the tooth and bone mineralization, and it can result in rachitic tooth when the levels get unregulated. Studies suggest that Vitamin D deficiency causes hypocalcified dentin and delayed tooth eruption; thus, representing that Vitamin D has a crucial role in dentin formation as well. The beneficial effects of vitamin D on oral health are not only limited to the direct effects on the tooth mineralization but are also applied through ability to stimulate the production of anti-microbial peptides. In this article, we will briefly discuss the influence on Vitamin D level on the oral and pulpal health.

Enamel Microabrasion Combined with in-Office Bleaching in Treating with Moderate to Severe Dental Fluorosis: A Randomized Clinical Trial

Dental fluorosis is a special enamel dysplasia caused by excessive intake of fluoride during tooth development and mineralization...

Socioeconomic differences in permanent teeth mineralization of Portuguese girls and boys from Porto, Portugal.

Purpose: Socioeconomic differences in dental maturation can be used to examine the impact of environmental factors on dental maturation. The purpose of this study is to assess socioeconomic differences in dental maturation of the seven permanent mandibular teeth (I1-M2). Methods: A total of 2114 panoramic radiographs of Portuguese children, adolescents and young adults were studied. The sample was divided into a high socioeconomic status (SES) (n = 925), and a low SES group (n = 1189). Ages ranged between 5 and 26 years. Demirjian's stages were used to assess the maturation of the seven mandibular teeth on the left side. Median-age of attainment of each stage and each tooth was calculated and compared between groups using binary logistic regression. Results: Low SES girls showed a consistent advancement in dental maturation across the entire dentition. Low SES boys, however, showed more often a delayed maturation relative to their high SES counterparts, but this pattern was not consistent and a clear socioeconomic difference seems to be absent in boys. Conclusions: While this study was not able to further explore the causes of the dental advancement in girls, it is hypothesized that it might be related to a higher prevalence of overweight/obesity, and possibly caries, in low SES girls, compared to the SES difference in prevalence in boys.

Age-related dental phenotypes and tooth characteristics of FAM83H-associated hypocalcified amelogenesis imperfecta.

Autosomal-dominant hypocalcified amelogenesis imperfecta (ADHCAI) shows phenotypic heterogeneity. Our aim was to characterise the ADHCAI phenotypes, tooth properties and genotypes. Three unrelated ADHCAI probands and seven additional affected members of the three families were recruited. Mutations were identified by exome and Sanger sequencing, and haplotypes by SNP array. Tooth colour, roughness, density, nanohardness, minerals and ultrastructure were investigated. Ten participants were heterozygous for the FAM83H mutation c.1387C>T (p.Gln463*). All shared a 3.43 Mbp region on chromosome 8q24.3 encompassing the FAM83H variant, indicating a common ancestry. The c.1387C>T was estimated to be 23.8 generations or 600years. The FAM83H enamel had higher roughness and lower lightness, density, nanohardness, and calcium and phosphorus levels than controls. Blunted enamel rods, wide interrod spaces and disorganised dentinoenamel junctions were observed. Evaluating the patients with the same mutation and reviewing others with different mutations in FAM83H revealed that the FAM83H heterogeneous phenotypes are age-influenced. Tooth colour and surface texture change with ageing. FAM83H enamel demonstrated decreased lightness, density, hardness, calcium, phosphorus and defective ultrastructure. We have identified that the phenotypic variation in FAM83H-associated ADHCAI is age-related. Awareness of the correlation between age and clinical features of FAM83H-ADHCAI can help dentists make an accurate diagnosis.

NUTRITION AND MINERAL CONTENT IN HUMAN TEETH THROUGH THE CENTURIES

ObjectivesThe objectives of the study were: (i) to compare mineral values of calcium, phosphorus, magnesium, zinc and their ratios, in teeth from Croatian populations that lived in different historical periods, namely the Medieval period, the early 20th century, and the 21 st century; and (ii) to elucidate the influence of diet and lifestyle on tooth quality in these groups. DesignDetermination of mineral content (Ca, Mg, P and Zn) in 294 teeth from three different periods of history (Medieval Period [G1], Second World War period [G2] and the contemporary period [G3]) using atomic absorption spectrometer and UV/VIS spectrometer methods. ResultsOur results showed that the mineral content in teeth has changed over the centuries. Between analysed samples from all groups, there were significant differences in the elemental content as well as in the interrelationship of the elements. The largest differences were observed in the mean values of magnesium and zinc concentrations while smaller differences were observed for changes in calcium and phosphorus. ConclusionsFrom the obtained results, it is evident that there are changes in the tooth mineral composition in specimens centuries apart that could be a reflection of changes in eating habits, food quality and the environment. In addition to differences in individual elements, differences in their mutual ratios were also observed.

Knockout fth1b affects early mineralization of zebrafish pharyngeal teeth.

A study was conducted to explore the expression pattern and function of ferritin heavy polypeptide gene (fth1b) in zebrafish pharyngeal teeth development and lay the foundation for subsequent research on teeth development and mineralization. The zebrafish embryos were harvested at 56, 72, 96, and 120 h after fertilization. The expression of fth1b in zebrafish pharyngeal teeth development was detected by whole embryo in situ hybridization and compared with the known pharyngeal teeth marker dlx2b. The specific knockout of fth1b gene was performed using clustered regularly interspaced short palindromic repeats (CRISPR)/Cas9 gene editing technology. The development of zebrafish pharyngeal teeth was detected in the fth1b-/- mutant. The expression pattern of fth1b gene was very similar to that of the known zebrafish pharyngeal teeth marker dlx2b and was specifically expressed in the zebrafish pharyngeal teeth during development. After the specific knockout of the gene fth1b, the earliest gene that can be detect in zebrafish pharyngeal teeth-pitx2 was expressed normally during early development. The dlx2b expression was not significantly different from that of wild type zebrafish, but the mineralization of pharyngeal teeth in the mutant was weaker than that of wild type zebrafish. The gene fth1b is specifically expressed in zebrafish pharyngeal teeth and acts on their early mineralization.