Structural organization of calcospherites in normal and rachitic human dentine

The structure of human dentine affected by familial hypophosphataemic rickets was investigated by polarized light and electron microscopy. Within the calcospherites both radially-orientated and collagen-orientated crystals were present, in approximately equal numbers. This was so, but less distinctly, in the calcospherites of normal dentine. It is concluded that dentine mineralizes entirely by formation of calcospherities which coalesce. It is proposed that matrix vesicles are probably responsible for the initiation of mineralization, and that growth of the calcospherites may depend on scavenging of inorganic pyrophosphate by the first-formed crystals. Growth of these crystals is thus poisoned but the resulting removal of inhibition allows deposition of further crystals by precipitation and by nucleation on collagen. The rachitic structure of dentine appeared to be due to slow calcospherite growth, probably as a result of the depressed serum phosphate characteristic of the disease.     

Micromorphologic features of dentin in vitamin D-resistant rickets: correlation with clinical grading of severity

This study was a histological analysis of 20 primary teeth from 5 patients with 3 clinical grades of vitamin D-resistant rickets (VDRR). The results showed that the degree of globular dentin formation in the histological sections may be graded into Grades I-III in increasing order of severity. In Grade I, the amount of globular dentin was less than 50% of the total dentin thickness, and the interglobular spaces were small. By contrast, in Grade III severity, globular dentin extended throughout the entire thickness of dentin, and the interglobular spaces were large. In Grade II severity, the amount of globular dentin was more than half but did not involve the entire dentin thickness. These histologic grades of severity correlated directly with the clinical grades of the patients. In addition, the study found that lack of medical treatment in affected mothers might lead to globular dentin formation in the fetus in-utero. Conversely, adequate phosphate supplementation in a hypophosphatemic mother might prevent the formation of globular dentin in the fetus.     

Dentin structure in familial hypophosphatemic rickets: benefits of vitamin D and phosphate treatment

OBJECTIVE: To evaluate the outcome of 1-(OH) vitamin D and oral phosphate treatment on dentin structure in patients with familial hypophosphatemic rickets, and expression of SIBLINGs (a family of non-collagenous proteins involved in dentinogenesis) and osteocalcin. PATIENTS AND METHODS: Seven patients with familial hypophosphatemic rickets (age 3-16 years) were studied before or during treatment. Deciduous and permanent teeth were prepared for scanning electron microscopy (SEM) analysis and immunohistochemistry. RESULTS: Untreated or inadequately treated patients had necrotic teeth with impaired dentin mineralization including unmerged calcospherites and accumulation of non-collagenous proteins in wide interglobular spaces. Most of the primary incisors analyzed displayed fissures linking enamel subsurface to pulp horn. These elements may explain the bacterial penetration and dental abscesses despite the absence of carious lesions. Well-treated patients had healthy teeth with good dentin mineralization and little evidence of calcospherites. CONCLUSION: Treatment of hypophosphatemic children with 1-(OH) vitamin D and oral phosphate insures good dentin development and mineralization, and prevents clinical anomalies such as the dental necrosis classically associated with the disease. Starting treatment during early childhood and good adherence to the therapy are mandatory to observe these beneficial effects.     

Scanning electron microscopic study of dentinal pulpal walls in relation to age and tooth area

A study was conducted to observe the surface morphological changes of human dentinal pulpal walls in specific areas of the tooth at various ages. Thirty-two extracted human non-carious teeth with single root canals were used. The teeth were divided longitudinally in the bucco-lingual plane and prepared for scanning electron microscopy (SEM). The specimens were divided into two groups (younger and older) according to age. Four central sites of the dentinal pulpal wall, including coronal, cervical, mid-root and apical sections, were selected as specific locations. Under the conditions of this study, six basic types of SEM appearance at dentinal pulpal wall surfaces were identified on the basis of calcospherite shape and mineralization. The appearance of the calcospherites varied according to tooth age and location along the dentinal pulpal walls.     

上颌第一恒磨牙髓室底的扫描电镜及其图像分析

本文采用扫描电镜(SEM)和图像分析仪对5颗上颌第一恒磨牙髓室底进行了观测,结果表明:髓室底呈现蘑菇状突起,平均密度为5234个/mm~2,每个蘑菇状突起平均含牙本质小管口9.2个,牙本质小管口分圆形(21.50％)、椭圆形(43.61％)和不规则形(34.89％)。作者并就其临床意义进行了讨论。     

SEM and EDS analysis of calcospherites in human teeth

The present study was designed to characterize the morphology and composition of calcospherites in the coronal and root predentin of human permanent teeth by scanning electron microscopy (SEM) and scanning electron microscopy – energy dispersive spectroscopy (SEM-EDS). Human incisors, premolars, and molars were used. The calcospherites in the coronal predentin were globular and 10–20 μm in diameter. The calcospherites in the root predentin were smaller and their shape was different. Polygonal calcospherites and stellate calcospherites were observed in the intermediate region of the root predentin. Calcospherites were rarely present in the apical region of the root predentin. Calcified matrix fibers were observed in the apical region of the root predentin. The Ca/P molar ratio in crown calcospherites (1.63 ± 0.27) differed significantly from that in root calcospherites (1.46 ± 0.28). Sulfur was detected from the cervical region to the root region, but not in the horn region. Odontoblast activity and the local environment of the predentin are thought to determine the shape, size, and composition of calcospherites     

Scanning electron microscopic observations of microcanals and continuous zones of interglobular dentin in human deciduous incisal dentin

Scanning electron microscopic (SEM) observation of the coronal dentin of deciduous incisors revealed microcanals and continuous zones of interglobular dentin (CID) in the labio-lingual central portion of dentin beneath the incisal edge. The microcanals, which were clearly larger than dentinal tubules, extended from the incisal edge to the vicinity of the pulp cavity. They were located essentially in the labio-lingual central portion of the dentin and were arranged linearly in the mesio-distal direction. Inside the microcanals, collagen fiber bundles were arranged almost in parallel with the canal long axis: spherical bodies 1.0-2.5 microns in size made up of assemblies of regular parallelpipedal crystals and granulated crystals were also seen. In some instances, bacteria had invaded incisal dentin that had been exposed by attrition. The CID were made up of interglobular dentin aligned with the long axis of the tooth. As was true in the case of the microcanals, several zones were arranged irregularly in the mesio-distal direction, generally in the labio-lingual central portion of the coronal dentin. The CID were confined to about half the width of the incisal edge dentin on the incisal edge side and did not appear in the vicinity of the pulp cavity. Within the interglobular dentin itself, which was surrounded by calcospherites, were longitudinal collagen fibers connected with dentinal tubule walls inside calcified dentin and collagen bundles forming a network with those fibers. Spherical bodies 1.0-1.5 microns in size were observed attached to the surfaces of the bundles or distributed among these fibers. In some instances, the microcanals penetrated the CID.     

A scanning electron and confocal laser microscope investigation of tetracycline-affected human dentine

Because of the well reported dental side-effects of tetracycline administration, the drug should not be administered to children. However, it and its derivatives are often administered over a prolonged period for treatment of acne in young adults. Dental side effects are also noticed in these patients. The aim of this study was to examine with scanning electron microscopy (SEM) and confocal laser scanning microscopy (CLSM) the root dentine of a tooth from a young adult affected by tetracycline therapy. The palatal root of an upper third molar, demonstrating distinct areas of tetracycline staining, was removed from the crown and sectioned longitudinally to produce two samples. The pulp tissue was peeled off the dentine and any remaining non-mineralized tissues were removed with sodium hypochlorite. One sample was prepared for SEM and the other as a ground section which was examined with a CLSM. It was demonstrated by SEM that the mineralizing front of unaffected dentine was of a normal calcospherite appearance; in contrast, the mineralizing front of the tetracycline-affected dentine was devoid of calcospherite formation and many surface defects were apparent. In addition, the number of dentinal tubules associated with the defects was reduced. It was shown by CLSM that tetracycline bands were made up of numerous smaller bands and that peritubular dentine not associated with fluorescent bands had incorporated tetracycline. The CLSM examination of the mineralization front of the affected dentine revealed that fluorescence of dentine was restricted to the peritubular dentine. The results confirm that dentine mineralization is affected by systemic tetracycline therapy and that tetracycline can be incorporated into peritubular dentine after mineralization of the primary dentine matrix.     

Clinical effects of glass ionomer restorations on residual carious dentin in primary molars

PURPOSE: To evaluate the mineralization and morphology of residual (infected and affected) carious dentin following the restoration of vital primary molars with viscous glass-ionomer cement (GIC). METHODS: Encapsulated Fuji IX GP and Ketac-Molar Aplicap GICs were placed in cavities that were prepared using the atraumatic restorative treatment (ART) approach. Four suitable exfoliated teeth with intact restorations were sectioned and then examined by electron probe microanalysis (EPMA) and scanning electron microscopy (SEM). RESULTS: EPMA demonstrated the presence of fluorine and strontium that had penetrated into the underlying residual carious dentin from the adjacent GIC. The concentrations of these two elements, and those of calcium and phosphorous, varied with distance from the GIC/dentin interface. SEM showed varying degrees of dentin tubule destruction and intratubular (peritubular) dentin present immediately subjacent to the GIC/dentin interface. Incomplete removal of carious dentin was observed in all specimens, and GIC remained adherent to the tissue.     

Is the morphology and activity of the occlusal carious lesion related to the lesion progression stage?

ObjectiveTo investigate the relationship between degree of dentin demineralization with both lesion activity and morphology of the occlusal carious cavity.DesignOcclusal sites (n = 138) were identified by visual examination (Nyvad’s scores 0–6) in 67 extracted teeth which were scanned in a high energy micro-CT. After 3D reconstruction, each stack was resliced in the mesio-distal direction and tooth mineral density (MD) was measured along a path from enamel to the deepest part of dentin in the slice showing the most severe carious involvement. Each site was classified in “open” or “closed” (if cavitated) depending on the morphology of the surrounding enamel walls as measured using micro-CT and as active or inactive in enamel or dentin by a clinical scoring system.ResultsLesions showing dentin cavitation presented higher demineralization degree compared to non-cavitated, or enamel cavitated lesions. Inactive lesions presented lower demineralization degree compared to active lesions, although with a low effect size. According to the morphological aspect of the carious cavity, open enamel lesions showed lower dentin demineralization degree than closed lesion environments.ConclusionActive lesions showed higher dentin demineralization degree than inactive ones, while lesions showing closed cavitation resulted in higher dentin demineralization degree only for enamel lesions. Including those parameters in treatment decisions may help to improve prognosis and increase effectiveness of the caries diagnostic systems in the clinical setting.     

Histopathology of root surface caries

The histopathology of active and arrested human root caries was examined in extracted teeth by different optical methods. Significant differences were observed between the mechanisms operating on the various dental structures. Three different patterns of initial cementum and dentin lesions could be distinguished, depending on the severity of the cariogenic attack, the degree of sclerosis of the peripheral dentin, and the presence of calculus. Advanced lesions were characterized by various patterns of demineralization. In particular, a massive lateral spread of bacteria into intertubular dentin was observed. Consequently, unaffected dentinal areas became continuously undermined. In arrested lesions, either a partial or complete mineralization of the intertubular dentin was apparent. Dentinal tubules were sclerosed passively by re- or precipitation of Ca and PO4 ions. In contrast, tubules filled with ghosts of bacteria appeared mineralized by fine-granular crystals. Our observations indicate that both the arrestment and the remineralization of active lesions depend on (1) the degree of active sclerosis of dentinal tubules in areas underlying the lesion, (2) the degree of the bacterial infection of the dentin, (3) the degree of progression of the lesions, and (4) the location of the lesions at the various root surfaces. It is suggested that remineralization of active lesions can occur. This supports the concept of non-invasive treatment of root caries lesions without cavitation.     

Effect of extreme calcium deprivation on degree of mineralization of alveolar bone, dentin and enamel in rats

abstract – The effect of an extreme and prolonged calcium-depriving regimen on the degree of mineralization of alveolar bone, dentin and enamel in adult female rats has been studied by quantitative microradiography. This method is considered to be the method of choice for disclosing differences in V % hydroxyapatite (HA). Despite the calcium-depriving regimen causing a substantial loss of bone mineral from femur and tibia, as estimated by gravimetric methods, the mineral content of alveolar bone, expressed as V % HA, did not deviate significantly from the normal, indicating that no osteolytic processes had taken place. Neither did the degree of mineralization of the fully formed molar dentin deviate from the normal. However, dentin and enamel formed during the experimental period by the continuously growing incisors disclosed a degree of mineralization which was significantly lower than normal. It was further noticed that the mineral content of the lingual dentin of the incisors, from both experimental and control animals, was significantly lower than the labial dentin.     

How does fluoride affect dentin microhardness and mineralization?

Fluoride (F) has been a useful instrument in caries prevention. However, only limited data exist on the effect of its long-term use on dentin mineralization patterns and microhardness. The objective of this study was to evaluate the influence of tooth F concentration ([F]) and dental fluorosis (DF) severity on dentin microhardness and mineralization. We collected 137 teeth in Montreal and Toronto, Canada, and Fortaleza, Brazil, where optimum or suboptimum levels of water F were 0.2 ppm, 1 ppm, and 0.7 ppm, respectively. Teeth were analyzed for DF severity, dentin [F], enamel [F], dentin microhardness, and dentin mineralization. Dentin [F] correlated with DF severity; enamel [F] correlated with dentin microhardness and dentin mineralization; DF severity correlated with dentin microhardness. Genetic factors (e.g., DF severity) and environmental factors (e.g., tooth [F]) influenced the mechanical properties (microhardness) of the teeth, while only the environmental factors influenced their material properties (e.g., mineralization). Fortaleza teeth were harder and less mineralized and presented higher dentin [F] values. Montreal teeth presented lower levels of DF when compared with both Toronto and Fortaleza teeth.     

NaOCl effects on primary and permanent pulp chamber dentin

OBJECTIVES: The dentin quality of primary and permanent pulp chamber was inspected by Fourier-transformed Raman spectroscopy (FT-Raman) and scanning electron microscopy (SEM). Fragments of pulp chamber dentin were obtained from 20 human molar crowns (primary and permanent). METHODS: The fragments were assigned to 8 groups (n=5)-Primary teeth: G1, pulp chamber dentin; G2, pulp chamber dentin irrigated with NaOCl 1% (30min); G3, pulp chamber dentin irrigated with NaOCl 1% (30min) and etched by 35% phosphoric acid; G4, pulp chamber dentin etched by 35% phosphoric acid. Permanent teeth: G5, pulp chamber dentin; G6, pulp chamber dentin irrigated with NaOCl 1% (30min); G7, pulp chamber dentin irrigated with NaOCl 1% (30min) and etched by 35% phosphoric acid; G8, pulp chamber dentin etched by 35% phosphoric acid. The spectra were subjected to the Cluster analysis. The SEM images were scored. RESULTS: Inorganic content: There was a difference between primary and permanent dentin. The groups treated with NaOCl were statistically similar between them, but differed from the groups not treated. Organic content: There was no difference between primary and permanent dentin. The groups became similar after NaOCl and phosphoric acid treatments. The microscopic images showed the presence of calcospherites on permanent dentin and their absence on primary dentin. CONCLUSIONS: The NaOCl changed the inorganic content in both dentitions; regardless of the following phosphoric acid etching. However, the chemical changes caused by NaOCl were not detected by SEM when it was followed by etching.     

Maternal diabetes and changes in the hard tissues of primary teeth. III. A histologic and microradiographic study.

According to clinical studies, infants of diabetic mothers (IDM) seem to run a higher risk of mineralization disturbances in the enamel than normal healthy infants. In order to evaluate this observation at the histologic level, exfoliated primary incisors were collected from 74 IDM, representing two types of care during gestation and the perinatal period, and from 52 healthy children. The width of the neonatal line was evaluated in the enamel and the dentin by study of bucco-lingual undemineralized sections. Pre- and postnatal enamel was classified according to discolorations, deviations of prisms and hypoplasia. Microradiographic studies included measurements of the neonatal lines and classification of the degree of mineralization in the pre- and postnatal dental hard tissues. Irrespective of treatment, the IDM showed a significantly higher incidence of widened neonatal lines and also an increased frequency of postnatal disturbances compared to the controls. The observations are discussed against the background of the neonatal hypocalcemia reported in IDM.     

Effect of removal of surface collagen fibrils on resin-dentin bonding.

OBJECTIVES: The aim of this study was to evaluate the effects of NaOCl at removing the demineralized layer by examining the morphology of the hybrid layer and measuring shear bond strengths after different dentin treatments. METHODS: Dentin disks were treated with: (1) 35% phosphoric acid (PA) 20 s; (2) PA treatment followed by 1.5% NaOCl, 2 min; (3) PA treatment, followed by a 10% NaOCl immersion for 120 h. SEM was used to analyze the morphology of dentin and its interface with dentin bonding agents (DBAs), while shear bond strength tests were used to measure adhesion. All specimens were then fractured into two halves: One half was inspected under SEM; the other half was sequentially placed in 10% PA followed by 12.5% NaOCl for 70 h, to remove all dentin from the resin replica of the original bonded interface. RESULTS: SEM observations showed that collagen fibrils were completely removed from the acid-etched surface by NaOCl treatment. The diameter and the size of dentinal tubules and the number of lateral branches of the tubules were increased following NaOCl treatment. NaOCl applied on dentin smear layers did not significantly modify their SEM morphology. Resin tags were larger in diameter after phosphoric acid/NaOCl treatment than after only phosphoric acid treatment. Resin-infiltrated dentin-layers were only observed after the single phosphoric acid (i.e. conventional etching) procedure, and were not observed after combined phosphoric acid/NaOCl treatment. Etched/NaOCl samples showed a lower bond strength using Scotchbond MP and 3M Single Bond, but were higher in Optibond FL and unmodified in Prime & Bond 2.0 groups when compared with acid-etched controls. Treatment of etched dentin with NaOCl for 120 h produced an unusual type of resin infiltration of mineralized dentin that could be called a "reverse hybrid layer" which may explain the mechanism of resin bonding to NaOCl treated dentin. SIGNIFICANCE: The use of acidic conditioners for exposure of the collagen matrix exposes a soft delicate mesh that can collapse, thereby interfering with resin infiltration. If acid-etching is followed by NaOCl treatment, high bond strengths can be achieved via "reverse hybrid layer" formation, a proposed new mechanism of micromechanical resin retention. This mechanism is not yet recommended for clinical use but demonstrates a new type of resin retention.     

牙本质的仿生再矿化

近年来,在修复由龋病等原因引起的牙本质脱矿的研究中,牙本质仿生再矿化技术以其精确控制无定形矿物质前体在脱矿牙本质胶原纤维内有序沉积、形成的磷灰石晶体与天然矿化牙本质相似、自下而上的再矿化方式不依赖于籽晶存在等优点,逐渐成为这一领域的研究热点。本文回顾了脱矿牙本质再矿化的理念和实践的进展,并着重对牙本质仿生再矿化策略的相关研究进行综述,文献复习结果表明,传统的牙本质再矿化方法通常是脱矿牙本质与矿物质晶体的无序混合,这样矿化后的牙本质在形态特征和机械性能上均无法与天然矿化牙本质相媲美;而近年逐渐兴起的牙本质仿生再矿化技术则复现了天然矿化牙本质中矿物质在牙本质胶原纤维内迭序排列的结构特点,其微观结构、理化性能均得到极大提高,有望在树脂⁃牙本质粘结混合层和龋坏牙本质脱矿层的再矿化研究领域实现新的突破。目前牙本质仿生再矿化在临床应用上需要克服的技术障碍在于如何在再矿化过程中持续补充矿化所需的各种有效成份,并在缓慢释放各成份的同时保持母体材料的机械性能不变,研究者们已相继提出了三步法输送仿生再矿化原材料,以及预先制备聚合物稳定的矿化前体、再使用介孔硅纳米材料作为输送矿化成份的系统的构想,为牙本质仿生再矿化策略向临床应用的转化提供了初步体外实验基础。     

The seeded growth of calcium phosphates on dentin and predentin.

The in vitro mineralization of predentin (PD) and of the organic component of dentin (OD) has been studied in a supersaturated solution of calcium phosphate at 37 C and pH=7.4 at total calcium and phosphate concentrations close to those in vivo. The mineralization of OD can be divided into at least three periods based upon the morphology and the specific surface area of the mineral phase formed. Dissolution of the newly precipitated mineral on OD revealed a stoichiometry close to that for octacalcium phosphate. In contrast, PD was ineffective as a crystal nucleator. The mineralization of the inorganic component of dentin (ID) and whole dentin (D) has also been examined.     

Ultrastructural properties of laser-irradiated and heat-treated dentin

Previous studies using scanning electron microscopy and infrared absorption spectroscopy reported that laser irradiation causes compositional changes in enamel. The purpose of this study was to evaluate the ultrastructural and compositional changes in dentin caused by irradiation with a short-pulse laser (Q-switched Nd:YAG). The irradiated and non-irradiated areas of the lased dentin samples were investigated by scanning (SEM) and transmission electron microscopy (TEM), micro-micro electron diffraction, and electron microprobe analysis of dispersive energy (EDX). Heat-treated dentin was similarly investigated. This study demonstrated that laser irradiation resulted in the recrystallization of dentin apatite and in the formation of additional calcium phosphate phases consisting of magnesium-substituted beta-tricalcium phosphate, beta-TCMP, beta-(Ca,Mg)3(PO4)2, and tetracalcium phosphate, TetCP, Ca4(PO4)O. TEM analyses of the modified and unmodified zones of the irradiated areas showed two types of crystal populations: much larger crystals from the modified zone and crystals with size and morphology similar to those of dentin apatite in the unmodified zone. The morphology of crystals in the modified zones in the irradiated dentin resembled those of dentin sintered at 800 or 950 degrees C. In the irradiated areas (modified and unmodified zones), the Ca/P ratio was lower compared with that in the non-irradiated dentin. The Mg/Ca ratio in the modified zones was higher than that in the unmodified zones and in the non-irradiated dentin. In sintered dentin, the Mg/Ca ratio increased as a function of sintering temperature. The ultrastructural and compositional changes observed in laser-irradiated dentin may be attributed to high temperature and high pressure induced by microplasma during laser irradiation. These changes may alter the solubility of the irradiated dentin, making it less susceptible to acid dissolution or to the caries process.     

Effect of single-dose amoxicillin on rat incisor odontogenesis: a morphological study

The effect of exposure to amoxicillin on tooth development remains to be elucidated. The purpose of this study was to investigate the effect of amoxicillin on rat incisor odontogenesis. Male Wistar rats weighing approximately 100?g were given a single intraperitoneal injection of 3.0?g/kg body weight amoxicillin. One week after injection, the rats were fixed, and the lower incisors were demineralized and prepared into paraffin sections for light microscopy (LM) and immunohistochemistry. Undemineralized samples were embedded in resin and ground for processing for contact microradiography (CMR) and scanning electron microscopy (SEM). Serum calcium, phosphate, and magnesium concentrations were measured. At 1?week after amoxicillin administration, LM, CMR, and SEM revealed a clear increase in the area of interglobular dentin, representing disruption of mineralization by odontoblasts. Immunohistochemistry demonstrated moderate levels of the small integrin-binding ligand N-linked glycoprotein family dentin matrix protein 1 in large areas of interglobular dentin. On the other hand, no morphological alteration or hypomineralization was observed in the enamel. Serum calcium values showed no significant differences between the control and experimental rats during the experimental period although both serum phosphate and magnesium levels increased at day?1 after amoxicillin injection. The results suggest that a single dose of amoxicillin specifically affects normal tooth dentin mineralization, but not enamel mineralization in rat incisor odontogenesis. The present results further our understanding of the clinical association between dentin abnormality and amoxicillin exposure during tooth development.