Enamel structure in deciduous teeth from low-birth-weight infants

Ground sections of deciduous teeth from 64 infants with birth weights below 2000 g and from 43 healthy full-term infants were examined in polarized light and by microradiography. The deciduous enamel displayed various changes, which were more frequent and pronounced in the low-birth-weight group. The main findings were diffuse areas of increased porosity and distinct subsurface lesions in the postnatal enamel. Five teeth with enamel hypoplasia from the low-birth-weight group were also examined. The hypoplasias were all located along the neonatal line. The postnatal enamel seemed to be more susceptible to disturbances in the mineralization than the prenatal enamel. The subsurface lesions showed an arrest in the very late stages of enamel maturation, which frequently occurred in the cervical deciduous enamel. Enamel hypoplasia is considered to be a result of severe neonatal hypocalcemia.     

Morphological aspects of dental hard tissues in primary teeth from preterm infants

Background. Preterm children with very low birth weight suffer from several neonatal and post-natal complications that may affect the mineralization of the teeth. Clinical studies have shown enamel aberrations in both dentitions. Aims. The aims of this study were to describe enamel histo-morphology in primary teeth, and investigate the relationship between medical history and morphological appearance. Design. Dental enamels in 44 exfoliated primary teeth, from 14 children with a gestational age below 29 weeks and with a very low birth weight, were investigated, using polarized light microscopy (POLMI) and under a scanning electron microscope (SEM). Results. The neonatal line was found in 1/3 of the sections located coronally of the crown. In the post-natal enamel, 31 teeth showed a degree of porosity higher than 5% with a varying extension. More than half of the teeth showed one or more increment lines. The SEM analysis confirmed the POLMI findings with irregular prisms covered with a structure-less film. Conclusions. Enamel from primary teeth of preterm children was found to have a high frequency of mineralization disturbances found in POLMI and SEM. The morphological features of the enamel from preterm children do not reflect the disturbances on general growth and development occurred during the neonatal period.     

Preterm infants--odontological aspects

Preterm birth is associated with medical complications and treatments postnatally and disturbances in growth and development. Primary and permanent teeth develop during this postnatal period. The overall aim of the present thesis was to elucidate the effects of preterm birth and postnatal complications on oral health and the dentoalveolar development during adolescence, and to study the effects of preterm birth on caries during childhood, in a well-defined group of preterm infants. In the same group, explore the development of the primary and permanent teeth and compare the results with a matched control group and control teeth. The subjects consisted of 40 (45) of 56 surviving infants, born < 29 weeks of gestational age (GA), and matched healthy children born at term. The material consisted of 44 teeth from 14 of the preterm adolescents and 36 control teeth from healthy children. Clinical examinations and dental cast analysis were performed during adolescence and morbidity was noted. Retrospective information from medical and dental records was obtained. Dental enamel was analyzed in a polarized light microscopy, and scanning electron microscopy. Further, chemical analyses of enamel and dentin were performed with X-ray microanalysis. The results showed that during adolescence, more preterms had plaque and gingival inflammation, lower salivary secretion, more S. mutans and severe hypomineralization. Retrospectively, less caries was noted at six years of age, but more children had hypomineralization in the primary dentition. Angle Class II malocclusion, large over-bite and deep bite associated with medical diagnoses were frequent. Furthermore, smaller dental arch perimeters in girls, at 16 years of age, and smaller tooth size in the incisors, canines and first molars were found. The morphological findings were confirmed in the XRMA analyses. In postnatal enamel, varying degrees of porosities > 5% and incremental lines were seen. Lower values of Ca and Ca/C ratio and higher values of C were found. Ca/P ratio in both enamel and dentine indicates normal hydroxyapatite in both groups. No single medical diagnosis, postnatal treatment or morbidity in adolescents could explain the findings. As a conclusion, there are indications for poor oral outcome in this group of preterm infants during adolescence, and disturbed mineralization in primary teeth.     

Enamel of primary teeth--morphological and chemical aspects

Enamel is one of the most important structures of the tooth, both from a functional and esthetic point of view. Primary enamel carries registered information regarding metabolic and physiological events that occurred during the period around birth and the first year of life. Detailed knowledge of normal development and the structure of enamel is important for the assessment of mineralization defects. The aim of the thesis is to add more detailed information regarding the structure of primary enamel. The structural appearance of the neonatal line and the quantitative developmental enamel defect, enamel hypoplasia, was thoroughly investigated with a polarized light microscope, microradiography and scanning electron microscope. X-ray microanalysis of some elements was also performed across the enamel and the neonatal line. Postnatal mineralization of enamel at different ages and from different individuals was studied regarding the chemical content, by using secondary ion mass spectrometry. The enamel's response to demineralization was investigated in relation to the individual chemical content and the degree of mineralization of the enamel, by using polarized light microscope, microradiography, scanning electron microscope and X-ray microanalysis. The neonatal line is a hypomineralized structure seen as a step-like rupture in the enamel matrix. The neonatal line is due to disturbances in the enamel secretion stage. The enamel prisms in the postnatal enamel appeared to be smaller than the prenatal prisms. The hypoplasias showed a rough surface at the base and no aprismatic surface layer was seen in the defect. The enamel of the rounded border of hypoplasia appeared to be hypomineralized, with the bent prisms not being densely packed. Mineralization of enamel is a gradual process, still continuous at 6 months postnatally in the primary mandibular incisors. The thickness of the buccal enamel is reached at 3-4 months of age. Demineralization of enamel depends on the degree of mineralization and the chemical content of the enamel exposed. In a more porous enamel, deeper lesions will develop. The posteruptive maturation has a beneficial effect on the enamel's resistance to demineralization.     

Enamel development in primary molars from children with familial dysautonomia

Objectives

Familial dysautonomia (FD) is an autosomal recessive disorder, classified as a hereditary sensory and autonomic neuropathy type III, associated with growth defects affecting postnatal development. This study analysed prenatal and postnatal enamel development and postnatal calcification in upper second primary molars from FD children in comparison with healthy controls. The postnatal enamel of FD was also examined histologically for manifestation of growth insults.

Design

The analyses were carried out on two ground sections, connecting buccal and palatinal cusp tips of mesial and distal cusps. The measurements included apical location of neonatal line, width and percentage of prenatal enamel. Chemical analyses were performed using an energy dispersive X-ray spectrometer.

Results

The prenatal proliferative phase and prenatal apposition rate of enamel were faster on the distal cusps in FD. The postnatal enamel thickness was similar in both groups. The phosphate content of FD teeth was significantly higher and the Ca/P ratio was significantly lower. Postnatal traumatic lines were observed in all FD children and in only one healthy child.

Conclusions

FD upper primary second molars showed thicker prenatal enamel formation in comparison to healthy and other syndromes and better mineralisation. All FD primary molars showed large number of postnatal traumatic lines, implicating severe traumatic episodes during the first year of life.     

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

Rythén M, Sabel N, Dietz W, Robertson A, Norén JG. Chemical aspects on dental hard tissues in primary teeth from preterm infants. Eur J Oral Sci 2010; 118: 389–395. © 2010 The Authors. Journal compilation © 2010 Eur J Oral Sci 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.     

Distribution of fluoride and magnesium concentrations in deciduous tooth enamel of children with cerebral palsy and Down syndrome

BackgroundSystemic disturbance during the fetal and postnatal periods in disabled children may affect the formation and mineralization of deciduous tooth enamel.AimTo reveal differences in the status of mineralization in the surface and inner layers of deciduous tooth enamel between children with cerebral palsy (CP), those with Down syndrome (DS), and controls.MethodsUsing extracted deciduous teeth obtained from CP children (5 teeth), DS children (5 teeth), and control children (11 teeth), fluoride and magnesium concentrations, used as mineralization parameters, were measured in three regions of the enamel at different depths: the enamel surface (ES), neonatal line (NL), and dentino-enamel junction (DEJ).ResultsFluoride concentration was significantly higher in the ES region than in the NL or DEJ region in all three groups. There was no significant correlation between type of disability and fluoride concentration. Magnesium concentration was significantly higher in the DEJ region than in the NL or ES region. A significant correlation was seen between type of disability and magnesium concentration.ConclusionsMagnesium concentration was significantly higher in DS children than in control children, suggesting that DS children undergo poorer mineralization. Magnesium concentration tended to be higher in CP children than in control children.     

Aetiology of developmental enamel defects not related to fluorosis

The aetiological factors in enamel defects of a non-fluoride nature can be divided into systemic and local. The systemic factors comprise a variety of conditions: genetically determined, chromosomal anomalies, congenital defects, inborn errors of metabolism, neonatal disturbances, infectious diseases, neurological disturbances, endocrinopathies, nutritional deficiencies, nephropathies, enteropathies, liver diseases and intoxications. The genetically determined enamel defects include amelogenesis imperfecta, which may occur as an isolated phenomenon or as part of other disorders such as epidermolysis bullosa, pseudohypoparathyroidism and taurodontism. The congenital defects include heart disorders and unilateral facial hypoplasia and hypertrophy. Among the inborn errors of metabolism are: galactosaemia, phenylketonuria, alkaptonuria, erythropoietic porphyria and primary hyperoxaluria. Neonatal disturbances are important in the development of enamel hypoplasia, foremost among these are premature birth and hypocalcaemia. The latter causes postnatal hypoplasias, which, however, are never seen in breast-fed children. Haemolytic anaemia, mostly in conjunction with erythroblastosis foetalis, may cause enamel hypoplasia. In children with neurological disturbances a rather large number have enamel hypoplasias, and these changes may be a significant aid in neurological diagnosis. When the tetracyclines were introduced, many children had these drugs prescribed in the period when the teeth were undergoing mineralization. The result was a yellow-brown stain of the affected teeth. In recent years, however, there appears to have been a reduction in the incidence of tetracycline staining. As for local causes the most important are traumatic injuries and periapical osteitis of primary teeth.     

Clinical and histologic appearance in enamel of primary teeth in relation to neonatal blood ionized calcium values

The purpose of this investigation was to study the relationship between low values of blood ionized calcium measured in the first days of life postpartum and the clinical and histologic appearance of enamel of primary teeth. Twenty-five healthy children selected on the basis of optimality with known blood values of ionized calcium from the first days of life participated in a dental examination at the age of 5 yr. Twenty-four of the children contributed one exfoliated tooth each, which was histologically examined. The infants had lower mean values of ionized blood calcium on days 1 and 3 than day 5 postpartum. Thirteen of the 25 children had enamel aberrations, mainly on one tooth each. The histologic examination showed normal overall enamel morphology. The neonatal line was present in all teeth, and these lines were mostly thin. The registered findings about the enamel morphology could not, in any case, be correlated with the measured values of neonatal blood ionized calcium.     

乳牙釉质发育不全的组织学研究

本研究运用偏光显微镜和显微放射照相技术对发育不全乳牙的组织学特征进行分析,发现釉质发育不全乳牙的新生线表现为低矿化的窄带状,病损发生于生后釉质,病损底多与新生线相吻合,病损内可见不同程度的矿化不良区域。得出:釉质发育不全不仅有釉质量的减少,而且有质的改变。后者可能增加了釉质发育不全牙齿对龋的易感性。     

Distribution of fluoride across human primary enamel.

The distribution of fluoride was described in detail from the incisal to the cervical region in 10 pairs of primary lower central incisors. Fluoride analyses were done on the right incisors; optical microscopic studies were done on the left. The distribution data obtained from fluoride analyses of the right incisors were superimposed on micrographs of sections through the left incisors. An abrasive microsampling technique (Weatherell et al., 1985) was used to determine the fluoride concentration and distribution. Fluoride concentration was the highest at the enamel surface and decreased from there to the interior. The fluoride distribution did not level off to an even plateau in the enamel interior, as suggested by earlier studies. Apart from the high concentration in the surface region, the fluoride levels in prenatal and postnatal enamel were rather similar. The fluoride concentration tended to be low at the neonatal line.     

Neonatal lines in the enamel of primary teeth--a morphological and scanning electron microscopic investigation

OBJECTIVE: The neonatal line (NNL) is in principle found in all primary teeth and the line represents the time of birth. Earlier findings of the appearance of the NNL in light microscope and in microradiographs have shown not only changes in the prism direction of the enamel, but that the NNL has a hypomineralized character. METHODS: The neonatal line was analyzed in un-decalcified sections of primary lower and central incisors, collected from individuals of different ages utilizing polarized light microscopy, microradiography, scanning electron microscopy (SEM) and X-ray analysis (XRMA). RESULTS: In polarized light the NNL appeared to have a more porous structure than the enamel in general. The appearance of the NNL as a dark line in microradiographs is interpreted as the NNL being less mineralized than neighbouring enamel. Analysis with ImageJ visualized the reduction of the amount of grey value, indicating that the NNL is less mineralized. Analysis of the NNL in SEM showed a reduction of the diameter of enamel prisms, the more narrow diameters continued through the postnatal enamel. A change of the growth direction of the prisms was also observed at the NNL. In a three-dimensional image the NNL appeared as a grove, however, in non-etched enamel no grove was seen. The elemental analyses with XRMA showed no marked changes in the content of C, Ca, P, N, O or S in the area around the NNL. CONCLUSIONS: The NNL is an optical phenomenon due to alterations in height, and degree of mineralization of the enamel prisms.     

Effect of prenatal and postnatal fluoride on the human deciduous dentition. A literature review

Fluoride passes from the mother to fetal teeth. Much of the fluoride is taken up in secretory enamel, probably by the forming mineral apatite crystals. Some is retained with residual proteins. The low concentration of fluoride in the inner enamel is incorporated mainly during the secretory stage, while the enhanced concentration in the surface enamel is produced during the much longer maturation stage. Mature, hard enamel is generally absent during fetal life. The clinical question is whether prenatal fluoride imparts an additional benefit to the universally accepted effect of postnatal fluoride. In general, surface enamel fluoride levels of deciduous teeth increase with increasing pre- and postnatal fluoride administration. A consistent level of caries protection has been reported with pre- and postnatal administration of fluoride unrelated to the acquisition of fluoride in the surface enamel. Many children develop enamel opacities in their deciduous dentition related by various factors to enamel mineralization disturbances in drinking water areas even low in fluoride. Accumulation of fluoride due to an increased fluoride intake is a feature of fluorosed enamel in the deciduous as well as permanent dentition. The resulting mature fluorosed enamel retains a relatively high proportion of immature matrix proteins onto the crystal surface. The degree of fluorosis of the deciduous dentition is less compared with that of the permanent dentition, due probably to a partial protection afforded by the maternal loss of fluoride, formerly known as the "placental barrier".     

Fluoride concentrations at and near the neonatal line in human deciduous tooth enamel obtained from a naturally fluoridated and a non-fluoridated area

This study sought to obtain a precise profile of fluoride concentrations at and near the neonatal line in deciduous incisors and canines from the naturally fluoridated area (1.0--1.3 parts/10(6) F in drinking water) of West Hartlepool and the non-fluoridated area (less than 0.1 parts/10(6) F in drinking water) of Leeds in England. An abrasive microsampling method was used to determine the distribution of fluoride and phosphorus concentrations. The profile of fluoride concentrations in 100-microm layers before and after the neonatal line, that is, in the prenatal and postnatal enamel, were significantly higher in teeth from the fluoridated than non-fluoridated areas. It was concluded that the fact that the fluoride concentrations were about the same prenatally and postnatally in deciduous enamel obtained from the fluoridated and non-fluoridated areas indicates that fluoride enters the prenatal deciduous enamel and that it is transferred through the placenta.     

Light and transmission-electron microscopy study of enamel organ cells in germectomized human third mandibular molars.

Using nine serially sectioned germectomized mandibular third molars it was possible to examine light microscopical (LM) and transmission-electron microscopical (TEM) features of maturing human enamel organ cells. The degree of enamel mineralization was estimated by quantitative imbibition studies in polarized light. It was possible to distinguish between three progressive stages of enamel mineralization. The most advanced stage was characterized by external enamel porosity. In the least advanced stages the enamel porosity appeared more extensive beneath a less porous surface layer. Ruffle- and smooth-ended ameloblasts were identified corresponding to the maturing enamel. Smooth-ended ameloblasts were the most frequently observed. However, no preferences for one of the two cell types could be observed in relation to the different stages of enamel mineralization. The maturing human enamel organ cells broadly revealed the same characteristics with respect to morphology features, intracellular organization, and junctional complexes as described in the maturation zone of the rat incisor enamel organ. Our findings therefore add to the view that the basic pattern of amelogenesis is identical in human and rat incisor enamel.     

An electron microscopic study of tetracycline-induced enamel defects in rat incisor enamel

abstract – The structure of incremental bands and gross hypoplastic lesions in rat incisor enamel which resulted from single or multiple injections with tetracycline hydrochloride was studied in the electron microscope. Both types of lesions which were investigated previously using microradiography and fluorescence microscopy exhibited many unusual structural features which are discussed in relation to current concepts of normal enamel formation. Disturbances in packing and organization were common to all the lesions indicating a primary interference with the first phase of enamel formation, i.e. matrix formation and initial mineralization. These changes were the main cause of the various mineralization disturbances seen in the microradiograms. Temporary and permanent interference with the second or maturation phase, i.e. crystal growth, was also evident but only as a corollary to the principal disturbance. This, and other evidence, suggests that tetracycline as well as many other chemical agents achieve their principal effects on enamel formation by injuring pre-secretory or secretory ameloblasts. Thus it appears that most developmental mineralization disturbances are symptomatic of hypoplastic lesions or are a sequela to the cell injury which also causes the hypoplastic lesions. Because of that it is suggested · that commonly used division between hypoplastic and hypomineralized defects be abandoned.     

Clinical, histologic and micro-radiographic study of natal, neonatal and pre-erupted teeth.

A clinical, histologic and microradiographic investigation of 62 natal, neonatal and otherwise pre-erupted teeth from 51 children is presented. Such a comprehensive material has not previously been reviewed. Of the 62 teeth, 59 were mandibular incisors. A hereditary factor could be demonstrated in 12 cases. Fifty-three teeth showed more or less pronounced enamel hypoplasia. The enamel had a normal prism structure and mineralization with the exception of 22 cases where the prism structure was absent in the cervical part of the enamel. The cervical and apical dentin was atubular and in developing teeth the dentin in these regions changed to an irregularly formed hard tissue of osteodentin character, in which enclosed cells could be observed. Developing teeth often had no cementum, and in those cases where acellular cementum could be observed it was thinner than normal. In four patients atypically located carious lesions occurred.     

Histological and chemical analyses of mesiodens development and mineralization

ObjectiveThis study aimed to compare the developmental timing and mineralization quality of mesiodentes, i.e., supernumerary teeth located mainly in the midline of the maxilla between the central incisors, with the developmental timing and mineralization quality of permanent and primary central incisors.DesignSixteen mesiodentes, nine permanent and seven primary central incisors were collected. The location of the neonatal line was determined using a light microscope at 10× or 20× enlargements. Chemical composition of the enamel at two locations was analyzed using energy dispersive X-ray spectrometer.ResultsNeonatal lines were observed in eight out of 16 mesiodentes, in all primary central incisors and in none of the permanent central incisors. Chemical analyses showed that mesiodentes mineralization was impaired, resulting in higher amount of organic ions and reduced inorganic ions. Discriminant analysis showed minimal overlap of mesiodentes with either primary or permanent centrals.ConclusionsMesiodentes development begins before birth in 50% of the cases but later than the primary centrals. Mineralization of mesiodens is impaired with less mineral content and higher organic content. The results showed that mesiodentes are a special group of teeth with defective morpho-differentiation and mineralization, with little similarity to primary or permanent central incisors.     

Scanning electron microscopy of the neonatal line in human enamel.

Neonatal lines in deciduous and permanent teeth showed changes in direction of the prisms and in their widths, confirming the findings of others. Structural changes in the prisms consisted of a well-defined line crossing the prisms at the prenatal side of the neonatal line and a wider diffuse zone of reduced crystal density at the postnatal side. It is suggested that these represent disturbances in physiological activity at birth and the succeeding 3 to 4 day period.     

釉蛋白在大鼠牙胚发育过程中的转录表达

目的　观察釉蛋白在大鼠牙胚发育过程中的转录表达 ,为进一步研究釉蛋白的生物学功能提供基础。方法　采用原位杂交方法 ,检测出生后 1、3、7、10、14d龄大鼠第一磨牙牙胚中釉蛋白mRNA的表达。结果　大鼠出生后 1～ 10d在成釉细胞和成牙本质细胞中均检测到釉蛋白mRNA的表达。在成釉细胞中的表达随细胞的分化、基质分泌具有规律性 ,1d已有微弱表达 ,3d表达增强 ,7d达到最强 ,10d减弱 ,14d为阴性。釉蛋白mRNA在成牙本质细胞中的表达 1d很微弱 ,14d阴性 ,3～ 10d为持续的中等强度的表达。结论　釉蛋白在成釉细胞中的转录表达从前成釉细胞一直持续到成熟期 ,至牙冠硬组织发育完全时中止。成牙本质细胞也表达釉蛋白基因 ,提示釉蛋白可能参与早期罩牙本质的形成