Molecular insights into hypomineralized enamel.

Hypomineralized enamel may be found in connection with the condition molar incisor hypomineralization (MIH), which has a prevalence of around 15% in most parts of the world. Molar incisor hypomineralization is associated with extensive objective and subjective problems, such as hypersensitivity of the affected teeth, enamel breakdown, and problems with retention of restorations. The etiology behind MIH has not yet been elucidated, but a number of possible factors, which affect the same or different functions of ameloblasts during their different stages of maturation, have been suggested. The aim of this study was to utilize multi-nuclear, solid-state nuclear magnetic resonance (ss-NMR) and time-of-flight secondary ion mass spectroscopy (ToF-SIMS) to elucidate any differences, at a molecular level, between enamel powder prepared from normal, healthy teeth and enamel powder prepared from teeth diagnosed with MIH. 31 P and 23 Na ss-NMR confirmed the presence of HPO42- and two different Na+ sites in hypomineralized enamel, suggesting a heterogeneous chemical composition. The content of organic components was higher in hypomineralized enamel, as shown by both 13 C ss-NMR and ToF-SIMS, indicating the presence of higher numbers of proteins and phospholipids. The interplay between both is necessary for the formation and mineralization of enamel, which might be disturbed or halted in hypomineralized enamel.

Molecular Insights into Covalently Stained Carious Dentine Using Solid-State NMR and ToF-SIMS.

Dyes currently used to stain carious dentine have a limited capacity to discriminate normal dentine from carious dentine, which may result in overexcavation. Consequently, finding a selective dye is still a challenge. However, there is evidence that hydrazine-based dyes, via covalent bonds to functional groups, bind specifically to carious dentine. The aim of this study was to investigate the possible formation of covalent bonds between carious dentine and 15N2-hydrazine and the hydrazine-based dye, 15N2-labelled Lucifer Yellow, respectively. Powdered dentine from extracted carious and normal teeth was exposed to the dyes, and the staining reactions were analysed using time-of-flight secondary ion mass spectrometry (ToF-SIMS), solid-state 13C-labelled nuclear magnetic resonance (NMR) and 15N-NMR spectroscopy. The results showed that 15N2-hydrazine and 15N2-labelled Lucifer Yellow both bind to carious dentine but not to normal dentine. It can thus be concluded that hydrazine-based dyes can be used to stain carious dentine and leave normal dentine unstained.

Individual risk factors associated with general unintentional injuries and the relationship to traumatic dental injuries among children aged 0-15 years in the Swedish BITA study.

AIM: To investigate general unintentional injuries (GUI) and traumatic dental injuries (TDI) in relation to behavioral and psychosocial strengths and difficulties among Swedish children aged 0-17 years, and to investigate general unintentional injuries in relation to temperament and socioeconomic status among the same children. SUBJECTS AND METHODS: The study included 2363 children in four different age cohorts aged 3, 7, 11, and 15 years at the study start. Twelve Public Dental Service clinics in Sweden participated, representing different types of demographic areas, both rural and urban. Data were collected from parents and children through an interview, questionnaires, and dental records. RESULTS: Twenty-four percentage (24%) of the children had experienced a serious general unintentional injury (GUI) at some point during their lifetime up until 3 months prior to the study start. Children who were regarded by their parents as being injured more often than other children also had occasions with general unintentional injuries to a greater extent. Most general unintentional injuries occurred at home. Children with incidents of general unintentional injuries had occasions with TDI to a greater extent than children without general unintentional injury. Children, whose mothers had 11 years of school/education or less, were involved in more general unintentional injuries during the 3-month period prior to the study start, compared to children of mothers with higher education level. CONCLUSIONS: Children with general unintentional injuries had more traumatic dental injuries. Children who were assessed by their parents as being injured more often than other children also had occasions with general unintentional injuries to a greater extent. Temperament, behavioral and psychosocial strengths and difficulties had different impacts at different ages for experiencing a general unintentional injury.

Temperamental and socioeconomic factors associated with traumatic dental injuries among children aged 0-17 years in the Swedish BITA study.

AIM: The aim of the study was to identify individual risk factors for traumatic dental injuries (TDI) among Swedish children aged 0-17 years. The studied risk factors were temperamental reactivity of the child, family structure, parent's country of birth, and the socioeconomic status of the family represented by parental education and occupation. SUBJECTS AND METHODS: The study included 2363 children in four different age cohorts at 12 public dental service clinics in Sweden, representing different types of demographic areas, both rural and urban. Data were collected from parents and children through an interview and questionnaires. RESULTS: The more social and active children in the two older age cohorts showed less occasions of TDI. Having one parent/guardian protected the child from dental injury just as well as two parents/guardians. Parents born outside of the Nordic countries showed children with less TDI. Low parental education was related to more occasions of TDI among the children. CONCLUSIONS: This study has increased the knowledge on certain individual risk factors for TDI. To prevent dental injuries, information could be given to families and children at risk.

Microscopic study of dental hard tissues in primary teeth with Dentinogenesis Imperfecta Type II: Correlation of 3D imaging using X-ray microtomography and polarising microscopy.

OBJECTIVES: The aim of this study was to examine the histological appearance of dental hard tissues in primary teeth from children with DI using conventional polarised light microscopy and correlate that with 3D imaging using X-ray microtomograpy (XMT) to gain a further understanding of the dentine structure of teeth diagnosed with dentinogenesis imperfecta. DESIGN: Undecalcified sections of primary teeth from patients diagnosed with Dentinogenesis Imperfecta Type II were examined using polarised light microscopy. XMT was employed for 3D-imaging and analysis of the dentine. RESULTS: The polarised light microscopy and XMT revealed tubular structures in the dentine seen as vacuoles coinciding with the path of normal dentinal tubules but not continuous tubules. The size of the tubules was close to that of capillaries. The largest tubular structures had a direction corresponding to where the pulp tissue would have been located during primary dentine formation. The dysfunctional mineralisation of the dentine and obliteration of the pulp evidently leaves blood vessels in the dentine which have in the main been tied off and, in the undecalcified sections, appear as vacuoles. CONCLUSIONS: Although from radiographs, the pulp in teeth affected by Dentinogenesis Imperfect type II appears to be completely obliterated, a network of interconnected vessels may remain. The presence of large dentinal tubules and blood vessels, or the remnants of blood vessels, could provide a pathway for bacteria from the oral cavity. This might account for why some of these teeth develop periapical abscesses in spite of apparently having no pulp.

XRMA and ToF-SIMS Analysis of Normal and Hypomineralized Enamel.

Molar incisor hypomineralization (MIH) is a developmental disturbance of the enamel. This study presents analyses of hypomineralized and normal enamel in first molar teeth diagnosed with MIH, utilizing time-of-flight secondary ion mass spectrometry area analyses and X-ray microanalysis of area and spot profiles in uncoated samples between gold lines which provide electrical conductivity. Statistical analysis of mean values allows discrimination of normal from MIH enamel, which has higher Mg and lower Na and P. Inductive analysis using complete data sets for profiles from the enamel surface to the enamel-dentin junction found that Mg, Cl and position in the profile provide useful discrimination criteria. Element profiles provide a visual complement to the inductive analysis and several elements also provide insight into the development of both normal and MIH enamel. The higher Mg content and different Cl profiles of hypomineralized enamel compared with normal enamel are probably related to a relatively short period during the development of ameloblasts between birth and the 1st year of life.

Traumatic dental injuries among children aged 0-17 years in the BITA study - a longitudinal Swedish multicenter study.

BACKGROUND/AIM: To prevent traumatic dental injuries (TDI), there is a need for vital information. This information could be reached using certain specific variables. The aim of this study, therefore, was to investigate TDI in different age groups, their etiology, and differences by gender, in Swedish children aged 0-17 years. SUBJECTS AND METHODS: The study included 2363 children in four different age cohorts from 12 Public Dental Service clinics in Sweden. The design was a 5-year longitudinal study including yearly clinical examinations, retrospective and prospective data compiled from dental records and interviews regarding TDI. RESULTS: The prevalence for TDI was 37.6% (889) with no gender differences. Boys suffered more injuries during the spring and fall compared to girls. The incidence of 2.8% varied between the age groups where preschool children presented the highest incidence. No changes in prevalence for TDI were found for the years included in the study. The most common reason for TDI was Falling (42.1%). The frequencies for the etiological factors varied between the ages. CONCLUSIONS: The TDI prevalence showed to be stable at a high level in spite of great efforts in Sweden and worldwide to reduce it. Knowledge in why, where, and when TDI appears is therefore essential for dental personnel who will work to reduce TDI.

Analysis of carious dentine using FTIR and ToF-SIMS.

Apart from the Maillard reaction, other processes, such as esterification, take place in carious tissue. The aim of the present study was to analyse sound and carious dentine in terms of ester groups and their reaction with hydrazine derivate using Fourier Transform Infrared Spectroscopy (FTIR) and Time-of-Flight Secondary Ion Mass Spectrometry (ToF-SIMS). Carious and sound dentine from human premolars were excavated in three series (Experimental Parts I-III) and separated into inner and outer layers of carious dentine. The excavated tooth material was analysed with FTIR (Part I). Carious and sound dentine were also exposed to different chemical treatments and analysed with FTIR-Attenuated Total Reflectance (FTIR-ATR; Part II) and ToF-SIMS (Part III). The FTIR absorption spectra showed that the carious tissue contained ester groups, not detected in sound dentine. The results also indicated a higher occurrence of ester groups in the inner dental caries layer than in the outer ones. Potential binding to these ester groups by hydrazine derivative was observed after different chemical treatments with both FTIR-ATR and ToF-SIMS. The results of the present study revealed ester groups unique to the carious dentine which, after reaction with hydrazine derivative, form a covalent bond not found in sound dentine. The staining of carious unique groups would be clinically helpful in detection and prevention unnecessary removal of sound dentine.

Parental attitudes and experiences of dental care in children and adolescents with ADHD--a questionnaire study.

Attention deficit hyperactivity disorder (ADHD) is a common psychiatric condition characterized by age-inappropriate levels of inattention, hyperactivity-impulsiveness or a combination of these. The aim of this study was to analyze parental attitudes to and experience of dental care, oral hygiene and dietary habits in children/adolescents with ADHD. Twenty- six parents of 31 subjects, 20 boys and 11 girls, aged 5-19 years with ADHD registered at the Gothenburg Child Neuropsychiatric Clinic, were invited. The parents answered a questionnaire regarding different oral problems when visiting the Clinic of Pediatric Dentistry, Gothenburg, for an oral examination of their child. The parents felt the dental care at the Public Dental Service was good, but noted a lack of knowledge regarding child neuropsychiatry among the dental staff which may influence the dental treatment. Fifteen parents reported their children had experienced mouth pain and 15 reported their child had suffered from both discomfort and pain from local anesthesia. Thirteen of the children had a dental trauma and 12 parents reported pain in connection to the dental treatment. Pain related to filling therapy was stated by 11 parents. According to the parents, five children suffered from dental fear but 15 reported the child had a general fear. Pursuant to the parents, the beverage for dinner was mainly milk or water, while sweet drinks were more frequent when thirsty. Seventeen parents reported their children had poor oral hygiene or could not manage to brush their teeth and 14 of the 31 children only brushed once a day or less. The results show that the parents experience a lack of child neuropsychiatric knowledge, care and patience from the dental staff, which may influence the treatment. Oral hygiene/tooth brushing is neglected and the frequent consumption of sugar is difficult for the parents to handle.

Evaluation of X-ray microanalysis for characterization of dental enamel.

Elemental analysis of dental hard tissues is of importance. The aim of this study is to evaluate X-ray microanalysis (XRMA) of bovine enamel in a scanning electron microscope (SEM) with different coatings. The buccal surface of bovine incisors was polished flat, one-third was coated with carbon, one-third with gold, leaving one-third uncoated for XRMA in an SEM equipped with an energy-dispersive microanalysis system. The elements oxygen, sodium, magnesium, phosphorous, chlorine, potassium, and calcium were analyzed using their respective characteristic K X-ray series. Comparisons were made with analyses of glass produced by fusion of the bovine enamel, showing that oxygen analyses using the K X-ray series are reliable and preferable to calculating oxygen by stoichiometry for natural enamel. For the gold-coated and uncoated analyses, carbon was also measured using the K X-ray series. Small area Analyses in small areas (80 × 80 µm) in variable pressure-SEM mode with low vacuum (20 Pa), without any coating, midway between 40 µm wide gold lines 140 µm apart to avoid build-up of electrostatic charge is the preferred method, especially if carbon is included in the analysis. The analyses of bovine enamel are sufficiently reproducible to be regarded as quantitative for all elements except carbon.

Timing of mineralization of homologues permanent teeth--an evaluation of the dental maturation in panoramic radiographs.

Clinically the condition Molar Incisor Hypomineralization (MIH),varies considerably between individuals, where any number of molars, from one to all four permanent first molars, may be affected with different degrees of hypomineralized enamel within the same dentition. An explanation to these variations could be that the start of the enamel mineralization differs between homologues teeth. The aim of this study was to compare the dental development between homologues teeth in digital panoramic radiographs (PRs),from children aged 7 to 11 years, using the Gleiser & Hunt method on second and third molars and to calculate the crown/root ratio for the mandibular premolars.77 PRs, from individuals between 7.3 and 11.0 years of age, were studied. Differences in developmental stages between homologues teeth (second and third molars) were studied. In 72 of these PRs, the crown/root ratio of mandibular premolars was also compared. In 31 of the PRs, a difference in development was found between the right and left maxillary second molar. In 22 PRs, a difference in development between the right and left mandibular second molar was found. In 17 of the PRs, a difference in development was found between the right and left maxillary third molars. In 26 PRs,a difference in-between the right and left mandibular third molar was found. In 72 PRs, the crown/root ratio of mandibular premolars was measured and differences were found. All these differences were significant. A possible explanation to the variations in expressivity of MIH may be a result of differences in the start of mineralization between homologues teeth. Timing of mineralization of homologues permanent teeth--An evaluation of the dental maturation in panoramic radiographs.

Onset of molar incisor hypomineralization (MIH).

The etiological factors and timing of the onset of molar incisor hypomineralization (MIH) are still not clear. The aim of this study was to examine ground radial and sagittal sections from teeth diagnosed with MIH using light microscopy, polarized light microscopy and X-ray micro-computed tomography (XMCT) and to estimate the onset and timing of the MIH and to relate the hypomineralized enamel to the incremental lines. Thirteen extracted permanent first molars diagnosed MIH, were analyzed with light microscopy and XMCT. The hypomineralized areas were mainly located in the mesio-buccal cusps, starting at the enamel-dentin-junction and continuing towards the enamel surface. In a relative gray scale analysis the values decreased from the EDJ towards the enamel surface. The findings indicate that the ameloblasts in the hypomineralized enamel are capable of forming an enamel of normal thickness, but with a substantial reduction of their capacity for maturation of enamel. Chronologically, it is estimated that the timing of the disturbance is at a period during the first 6-7 months of age.

Scanning electron microscopic and X-ray micro analysis on tooth enamel exposed to alkaline agents.

The background of this study comprises two clinical cases, where patients exposed to aerosols of an alkaline and surface active cleaning agent developed loss of enamel substance on their teeth, further resulting in loss of teeth and partially destroyed soft tissues. The alkaline cleaning agent consisted of potassium hydroxide and various surfactants. The purpose of this study was to investigate possible changes in morphology and composition in human teeth enamel exposed to alkaline solutions, by means of X-ray micro analysis (XRMA), FTIR-spectroscopic analyses and scanning electron microscopy (SEM). Extracted premolars, exposed to potassium hydroxide solutions and alkaline cleaning solution,were analyzed by means of XRMA and SEM. Enamel powder, exposed to cleaning solution, was analyzed by means of FTIR. The SEM analysis revealed an increased porosity of the enamel surface and partially loss of enamel substance after exposure to alkaline solutions. The XRMA analyses revealed a decrease in carbon concentration while phosphorous and calcium showed no marked changes. The FTIR analyses showed no significant changes in peak heights or peak positions for phosphate, carbonate or hydroxide. It was concluded that human teeth enamel exposed to alkaline solutions showed loss of organic substance, marked pores in enamel surface and loss of substance in the enamel surface.

Chemical aspects on dental hard tissues in primary teeth from preterm infants.

Preterm children with very low birth weight suffer from several neonatal and postnatal complications that may affect the mineralization of teeth. Clinical and morphological studies have shown enamel aberrations in teeth from preterm children. In this study, the chemical composition in enamel and dentin was compared in primary teeth from preterm children and full-term children, and the relationship between the chemical composition and the morphological appearance was investigated. Enamel and dentin in 17 exfoliated primary teeth, from 14 children with a gestational age below 29 wk, were investigated and compared with 36 exfoliated primary teeth from full-term children, using X-ray microanalyses (XRMA). In comparison with the teeth from the controls, the teeth from preterm children had a higher relative value of carbon (C), a lower relative value of calcium (Ca), a lower ratio of calcium/phosphorus (Ca/P) and a lower ratio of Ca/C throughout the outer part of the enamel. In dentin, the relative values for P were higher, and Ca/P ratio was lower, at the dentin-pulp junction. The Ca/P ratio indicated normal hydroxyapatite in the crystals in enamel and dentin. The lower ratio of Ca/C in the bulk and outer part of the enamel indicated more porous enamel.

Altered inorganic composition of dental enamel and dentin in primary teeth from girls with Turner syndrome.

In Turner syndrome (TS) one X-chromosome is missing or defective. The amelogenin gene, located on the X-chromosome, plays a key role during the formation of dental enamel. The aim of this study was to find support for the hypothesis that impaired expression of the X-chromosome influences mineral incorporation during amelogenesis and, indirectly, during dentinogenesis. Primary tooth enamel and dentin from girls with TS were analysed and compared with the enamel and dentin of primary teeth from healthy girls. Qualitative and quantitative changes in the composition of TS enamel were found, in addition to morphological differences. Higher frequencies of subsurface lesions and rod-free zones were seen in TS enamel using polarized light microscopy. Similarly, scanning electron microscopy showed that the enamel rods from TS teeth were of atypical sizes and directions. Using X-ray microanalysis, high levels of calcium and phosphorus, and low levels of carbon, were found in both TS enamel and dentin. Using microradiography, a lower degree of mineralization was found in TS enamel. Rule induction analysis was performed to identify characteristic element patterns for TS. Low values of carbon were the most critical attributes for the outcome TS. The conclusion was that impaired expression of the X-chromosome has an impact on dental hard tissue formation.

Chemical, mechanical and morphological properties of hypomineralized enamel of permanent first molars.

OBJECTIVE: The microstructure of hypomineralized enamel in permanent teeth has been described in several studies as less distinct prism sheaths and disorganized enamel with lack of organization of the enamel crystals. The mechanical properties, hardness and modulus of elasticity of the hypomineralized enamel have lower values compared with normal. The aim of this study was to examine normal and hypomineralized enamel using scanning electron microscopy (SEM), hardness measurements and X-ray microanalysis (XRMA). MATERIAL AND METHODS: Four extracted hypomineralized permanent first molars, sectioned and cut in half, were analyzed with SEM, XRMA and hardness measurements. RESULTS: An inverse relation was found between the micro hardness and the Ca:C ratio in hypomineralized and normal enamel. The acid-etched hypomineralized enamel appeared on SEM to be covered with a structureless layer and the prisms appeared disorganized, with thick prism sheaths and loosely packed crystallites. Furthermore, bacteria were found deep in porous hypomineralized enamel close to the enamel-dentin junction. CONCLUSIONS: Teeth diagnosed with molar incisor hypomineralization have significantly lower hardness values in the hypomineralized enamel compared with normal enamel. The hardness values vary according to the morphological and chemical properties.

Polarized light and scanning electron microscopic investigation of enamel hypoplasia in primary teeth.

BACKGROUND: Enamel hypoplasia is a developmental disturbance during enamel formation, defined as a macroscopic defect in the enamel, with a reduction of the enamel thickness with rounded, smooth borders. Information on the microstructural level is still limited, therefore further studies are of importance to better understand the mechanisms behind enamel hypoplasia. AIM: To study enamel hypoplasia in primary teeth by means of polarized light microscopy and scanning electron microscopy. METHODS: Nineteen primary teeth with enamel hypoplasia were examined in a polarized light microscope and in a scanning electron microscope. RESULTS: The cervical and incisal borders of the enamel hypoplasia had a rounded appearance, as the prisms in the rounded cervical area of the hypoplasia were bent. The rounded borders had a normal surface structure whereas the base of the defects appeared rough and porous. CONCLUSIONS: Morphological findings in this study indicate that the aetiological factor has a short duration and affects only certain ameloblasts. The bottom of the enamel hypoplasia is porous and constitutes possible pathways for bacteria into the dentin.

Elemental composition of normal primary tooth enamel analyzed with XRMA and SIMS.

There is an interest to analyze the chemical composition of enamel in teeth from patients with different developmental disorders or syndromes and evaluate possible differences compared to normal composition. For this purpose, it is essential to have reference material. The aim of this study was to, by means of X-ray micro analyses (XRMA) and secondary ion mass spectrometry (SIMS), present concentration gradients for C, O, P and Ca and F, Na, Mg, Cl, K and Sr in normal enamel of primary teeth from healthy individuals. 36 exfoliated primary teeth from 36 healthy children were collected, sectioned, and analyzed in the enamel and dentin with X-ray micro analyses for the content of C, O, P and Ca and F, Na MgCl, K and Sr. This study has supplied reference data for C, O, P and Ca in enamel in primary teeth from healthy subjects. No statistically significant differences in the elemental composition were found between incisors and molars.The ratio Ca/P is in concordance with other studies. Some elements have shown statistically significant differences between different levels of measurement. These results may be used as reference values for research on the chemical composition of enamel and dentin in primary teeth from patients with different conditions and/or syndromes.

Analysis of some elements in primary enamel during postnatal mineralization.

The primary teeth start to mineralize in utero and continue development and maturation during the first year of life.The aim of this study was to investigate the concentrations of some elements, C, F, Na, Mg, Cl, K and Sr, by secondary ion mass spectrometry (SIMS) in human primary incisors at different stages of mineralization.The teeth derived from an autopsy material from children who had died in sudden infant death.The buccal enamel of specimens from the ages 1, 2, 3, 4, 6 and 19 months, respectively, was analyzed. It was evident that posteruptive effects play an important role in composition of the outermost parts of the enamel. Before the tooth erupts, the concentrations of the elements vary with the maturation grade of the mineralization in the enamel. Sodium was the element with the highest concentration of the measured elements and chlorine was the element of lowest concentration.The 19 month old specimen, considered as the only mature and erupted tooth, showed to differ from the other specimens.The concentration of fluorine, in the 19 month old specimen's outermost surface, is readily seen higher compared with the other specimens at this depth zone. In the 19 month old specimen the concentration of carbon is lower. Potassium, sodium and chlorine have higher concentrations, in general, in the 19 month old specimen compared with the immature specimens. The thickness of the enamel during mineralization was calculated from data from SIMS.The thickness of the buccal enamel of primary incisors seemed to be fully developed between 3-4 months after birth, reaching a thickness of 350-400 microm.