Lipidhistochemical and microradiographic study of distribution of lipids in relation to mineral content in dentin caries.

Fifteen human molars were investigated using lipidhistochemical and microradiographic methods. A peripheral necrotic and totally decalcified part of the carious lesion revealed a markedly positive staining reaction for sphingomyelin, sulfatides, cholesterol- and/or triglyceride-esters. The reaction was probably conditioned by the presence of debris and plaque within this area. Pulpally and immediately below the necrotic zone, an area of demineralization was found which on the microradiographs appeared as a radiolucent zone. The zone showed a mineral gradient with an increasing mineral content towards the pulp. In the zone of demineralization a positive reaction occurred for sphingomyelin decreasing in a pulpal direction with increasing mineral content. A weakly positive reaction for cholesterol- and/or triglyceride-esters was also detected but only in the most pulpal part of the zone of demineralization; the intensity of the staining reaction was comparable to that found in normal dentin. In those areas which were represented by a sclerotized, radiopaque zone, only a very weak reaction for sphingomyelin, cholesterol-and/or triglyceride-esters could be observed of the same staining intensity as in normal dentin. The region between the lesion and the pulp showed the same staining intensity as normal dentin.     

Effect of perfusion with water on demineralization of human dentin in vitro

Dentinal fluid rarely features in caries studies of dentin. The mutual effects of in vitro perfusion and dentin demineralization were investigated. The correlation between the remaining dentin thickness and demineralization was also analyzed. Buccal cervical dentin windows in human tooth segments were demineralized either with or without perfusion with water at 3.14 kPa. Transverse microradiography revealed that dentin perfusion reduced the amount of mineral loss from the lesions by 22 vol%; the reduction in lesion depth was 8%. Perfusion rate, which was measured throughout the demineralization process by means of a fluid transport model, did not change significantly. Lesions formed closer to the pulp exhibited increased mineral loss and lesion depth. In conclusion, dentinal fluid flow offers some protection against demineralization. For a better approximation of clinical reality, therefore, in vitro studies on dentinal caries should consider the effect of dentinal fluid flow.     

Vital staining of coronal dentin in monkey teeth.

Vital staining of monkey incisor teeth with the incisal dentin exposed to the oral environment by attrition was carried out, with the use of a number of dyes (pH and redox indicators). There was a distinct staining of the coronal dentin, regardless of which dye was introduced into the pulpal cavity. The exposed dentin was stained like the unaffected dentin, with the exception of a narrow centrally located zone that extended from the tip of the original pulp horn to the incisal edge of the tooth. The suggestion is that this zone is not unstained because of exposure of the dentin to the oral environment, but because it coincides with an area of the tissue where the pulpal ends of the dentinal tubules are blocked by atubular hard tissue normally laid down in the pulp horn of incisor teeth.     

The effect of silicate cement on enamel and dentin

abstract — The effects upon enamel and dentin of mixes of two different viscosities of silicate cement were examined by polarized light microscopy and microradiography. The silicate was applied to the cut surfaces of extracted teeth for periods of time ranging from 1 h to 2 weeks. In a few cases a very slight degree of demineralization of enamel occurred. Surface demineralization of the dentin, however, was observed in all specimens. This zone of demineralization in the dentin was widest centrally over the pulp and narrowed peripherally towards the amelodentinal junction. A zone of increased mineralization was observed underlying the demineralized area. The fluid mix of silicate resulted in more rapid loss of mineral than did the more viscous mix, but in neither case did the extent of demineralization appear to increase after the first 24 h. In a number of cases, especially those to which the fluid mix had been applied for 24 h, a subsurface zone of demineralization was also observed in the dentin.     

Three-dimensional reconstruction of approximal subsurface caries lesions in deciduous molars

The present study examines the three-dimensional (3D) morphology of early approximal subsurface enamel caries lesions and subjacent dentin reactions in deciduous molars. Twenty-three extracted primary molars were embedded in Technovit 9100 and serial sections were cut using a saw microtome. Forty approximal lesions were found and investigated using polarized light microscopy for the identification of the different zones of the caries lesion. These zones were then reconstructed three-dimensionally using computer-aided 3D reconstruction methods and the dimensions and volumes of the translucent zone, the body of the lesion, and the dentin lesion were calculated. The enamel demineralization index was defined as the ratio between the translucent zone and the body of the lesion, whereas the enamel–dentin demineralization index was defined as the volumetric ratio of the early dentin lesion to the body of the enamel lesion. The 3D reconstruction of the lesions showed extremely heterogeneous micromorphological features of zone profiles. In enamel lesions, the results demonstrated a decreasing enamel demineralization index with increasing size of the lesion, which indicates a high risk of further caries progression. The enamel–dentin demineralization index indicated, in 5 out of 17 dentin lesions, a high risk of further caries progression. Computer-assisted 3D reconstruction and volumetric assessment of initial caries lesions in deciduous molars represents a valuable methodology in pathogenesis studies, which may lead to a better clinical understanding of caries progression. Received: 23 December 1997 / Accepted: 10 September 1998     

Histochemical observations on human dentin exposed by attrition

abstract – Demineralized sections of human anterior teeth with dentin exposed by attrition were studied after staining with PAS, alcian blue at pH 2.2, and the combined alcian blue-PAS method. The intertubular matrix of the primary dentin was evenly and lightly stained with PAS, with exception of the most pulpal zone which showed an intense PAS-positive reaction. No changes seemed to have occurred in the intertubular matrix of the exposed dentin. The exposed dentin, however, showed a stronger alcian blue-positive reaction than the intact dentin because of a more intense staining of the peripheries and the content of the tubules. In the innermost part of the primary dentin a zonated pattern similar to that of intact teeth was observed. In the irritation dentin the intertubular matrix as well as the periphery of many tubules reacted strongly with PAS. With alcian blue the peripheries of the tubules were either unstained or showed varying degrees of positive reaction. In some tubules this reaction was comparable with that of the primary dentin. Variation in the state of aggregation of the ground substance was considered the main reason for the differences in PAS reaction of the primary dentin and the irritation dentin.     

Effect of denture base‐resin with prereacted glass‐ionomer filler on dentin demineralization

The demineralization of dentin was studied when placed adjacent to one of four experimental denture base‐resins. These experimental resins contained polymethylmethacrylate (PMMA) and 0, 5, 10, 20 or 30 wt% surface reaction‐type prereacted glass‐ionomer (S‐PRG) filler, respectively. A dentin thin‐section was sandwiched between these resins and subjected to demineralization for 1 wk. Microradiographic analyses showed that the mineral vol% of the surface was increased, and lesion formation was inhibited, in a dose–response relationship with the amount of S‐PRG filler. Moreover, the mineral loss decreased, by up to 60%, with an increasing amount of filler. These results indicate that denture base‐resins containing S‐PRG filler possess a substantial inhibition capability against demineralization, and this may thereby assist in preventing root caries of abutment teeth.     

Effect of dentinal fluid composition on dentin demineralization in vitro

Dentin demineralization is reduced by perfusion with water. We hypothesized that a simulated dentinal fluid (SDF) that contains albumin, in addition to electrolytes, would be more effective in reducing dentin demineralization than water alone, and this effect would increase with increasing flow rate of SDF. Perfusion rate in tooth segments that carried buccal cervical dentin windows was measured in a fluid transport set-up. These windows were then demineralized under perfusion with water, or SDF at 1.47 kPa for 31 days. We analyzed integrated mineral loss and lesion depth with the use of transverse microradiography (TMR), which revealed that 38% more mineral dissolved from dentin lesions perfused with water than from those perfused with SDF. The former were also 18% deeper. Flow rate of dentinal fluid showed no correlation with demineralization. We concluded that composition of dentinal fluid is an important determinant of the rate of lesion formation and progression in dentin.     

Light microscopic study of giant tubules in bovine dentin

Abstract – Demineralized, H-E stained longitudinal and transversal sections of unerupted permanent incisors from 1/2–3-yr-old calves were studied by light microscopy. The most incisal dentin in all teeth was. characterized by a regular pattern of straight axially oriented giant tubules situated in the axiomesiodistal plane with interglobular dentin between them. In younger teeth, the pulpal part of every giant tubule contained an afferent and an efferent blood vessel, forming a hairpin loop and being surrounded by basophil cells. Incisal to the blood vessel loops, cells enbedded in an eosinophil matrix were present in the giant tubule lumina, showing increasing degenerative changes incisally. In older teeth there was a mesiodistally extended eosinophil dentin band near the pulp, with few, irregularly arranged, tortuous dentinai and gianl tubules, the latter containing single blood vessels accompanied by pulpal cells. Isolated degenerating odontoblasts in lacunar cavities were seen in the transition area of the normal circumpulpal dentin and the eosinophil dentin band. A hypothesis on the initiation and subsequent development of giant tubules is presented.     

Light microscopic study of giant tubules in bovine dentin

Demineralized, H-E stained longitudinal and transversal sections of unerupted permanent incisors from 1/2-3-yr-old calves were studied by light microscopy. The most incisal dentin in all teeth was characterized by a regular pattern of straight axially oriented giant tubules situated in the axiomesiodistal plane with interglobular dentin between them. In younger teeth, the pulpal part of every giant tubule contained an afferent and an efferent blood vessel, forming a hairpin loop and being surrounded by basophil cells. Incisal to the blood vessel loops, cells enbedded in an eosinophil matrix were present in the giant tubule lumina, showing increasing degenerative changes incisally. In older teeth there was a mesiodistally extended eosinophil dentin band near the pulp, with few, irregularly arranged, tortuous dentinal and giant tubules, the latter containing single blood vessels accompanied by pulpal cells. Isolated degenerating odontoblasts in lacunar cavities were seen in the transition area of the normal circumpulpal dentin and the eosinophil dentin band. A hypothesis on the initiation and subsequent development of giant tubules is presented.     

层粘连蛋白在修复性牙本质形成中的免疫定位

目的 研究层粘连蛋白（laminin,LN）在牙髓修复中的免疫定位和分布特征。方法 在大鼠第一磨牙制备单面洞,分别观察3d、15d和30d后修复性牙本质的形成情况。以免疫组化技术检测LN的免疫反应。结果 术后3d,修复性牙本质尚未形成。牙髓内成牙本质细胞呈阳性染色,前期牙本质为弱阳性。术后15d,可见修复性牙本质形成和成牙本质细胞样细胞的出现,成牙本质细胞样细胞和牙髓细胞免疫染色呈阳性。术后30d,已形成的修复性牙本质内LN染色阳性,免疫活性特别集中于修复性牙本质与牙髓交界处,成牙本质细胞样细胞染色呈强阳性。结论 LN的分布特征提示,在修复性牙本质形成过程中,LN可能是牙髓细胞附着的一个有利因素。     

Scanning electron microscopic, light microscopic and microradiographic study of giant tubules in bovine dentin

Giant tubules (GT) in the axiomesiodistal plane of the incisal dentin of 21 unerupted permanent incisors of 1/2-2-yr-old calves were studied by scanning electron microscopy, light microscopy and contact microradiography. A technique is described by which the incisal dentin was split along the axiomesiodistal plane exposing the GT lumina longitudinally for SEM study. The luminal organic content was carefully removed mechanically or chemically. The GT originated 50-250 microns underneath the incisal dentino-enamel junction and converged pulpally, terminating in the incisal edge of the pulp. A confluence of adjacent tubules towards the pulp was seen. Each GT had a relatively constant diameter along its length, in the range of 10-50 micron. The dentinal tubules circumvented the GT origins and pursued a straight course pulpally, parallel to the characteristic wall zone surrounding each GT. Very few dentinal tubules entered the GT lumen at any level. The luminal lining along the larger part of the GT consisted of collagen fibrils forming a criss-cross pattern, while the most pulpal part was lined by a smooth organic sheath. The GT walls at any transversal level within one tooth had a lower mineral content than the circumpulpal dentin between them. It was concluded that the GT formation is not caused by crowding of the odontoblasts.     

pH-cycling of enamel and dentin lesions in the presence of low concentrations of fluoride

F-dentifrice usage causes slightly elevated fluoride levels in saliva. Therefore, the effects of permanent low fluoride concentrations versus daily dentifrice treatments were studied on enamel and dentin lesions in a pH-cycling model of alternating demineralization and remineralization. Groups received 1) no fluoride treatment. 2) 3 μM (0.06 ppm) F continuously present during re- and demineralization or 3) daily 5–min F-dentifrice treatments. Solutions were analyzed for changes in calcium and fluoride. Cumulative results (10 d) showed that for the non-fluoride group the dentin lesions increased, while for enamel lesions mineral uptake and loss were balanced. Addition of 3 μM F caused small, non-significant, enhancement of remineralization (1–7%). while demineralization was significantly inhibited for both tissues (9–23%). The daily dentifrice treatments resulted in a balance between mineral uptake and loss of dentin, due to inhibited demineralization (-33%) and enhanced remineralization (+ 79%). For enamel, the F-dentifrice treatments resulted in 43% reduction of demineralization, with no significant effect on remineralization. Fluoride loss from the 3 μM F cycling solutions was significant (up to 50%) and constant during the experimental period. Microradiographic analysis showed remineralization at the lesion front in enamel. In dentin, the lesion depth was increased in all groups, with concomitant mineral deposition in the surface region of the dentifrice group. Results indicate that slightly elevated fluoride levels may be considerably less effective in inhibiting lesion progression in dentin than in enamel, and suggest mineral uptake and loss to occur at similar depths for enamel lesions, while demineralization and remineralization occur at different depths in dentin.     

正常、龋病牙髓免疫活性细胞分布的检测

目的研究龋病不同阶段牙髓免疫活性细胞的分布变化。方法应用六种单克隆抗体对龋病不同阶段的牙髓免疫活性细胞ABC法进行免疫组化染色。结果正常牙髓中存在着数目较多的HLA一DR ”细胞，Th／Ts比值随龋病进展略降低，当牙髓暴露后比值显著升高。结论牙髓免疫活性细胞在牙髓组织炎症和自身修复的发生、发展过程中起重要作用。牙髓暴露使免疫反应明显增强。     

Scanning electron microscopic, light microscopic and microradiographic study of giant tubules in bovine dentin

Abstract — Giant tubules (GT) in the axiomesiodistal plane of the incisal dentin of 21 unerupted permanent incisors of 1/2—2-yr-old calves were studied by scanning electron microscopy, light microscopy and contact microradiography. A technique is described by which the incisal dentin was split along the axiomesiodistal plane exposing the GT lumina longitudinally for SEM study. The luminal organic content was carefully removed mechanically or chemically. The GT originated 50–250 μm underneath the incisal dentino-enamel junction and converged pulpally, terminating in the incisal edge of the pulp. A confluence of adjacent tubules towards the pulp was seen. Each GT had a relatively constant diameter along its length, in the range of 10–50 μm. The dentinal tubules circumvented the GT origins and pursued a straight course pulpally, parallell to the characteristic wall zone surrounding each GT. Very few dentinal tubules entered the GT lumen at any level. The luminal lining along the larger part of the GT consisted of collagen fibrils forming a criss-cross pattern, while the most pulpal part was lined by a smooth organic sheath. The GT walls at any transversal level within one tooth had a lower mineral content than the circnmpulpal dentin between them. It was concluded that the GT formation is not caused by crowding of the odontoblasts.     

Cytotoxicity of low pH dentin-bonding agents in a dentin barrier test in vitro

The reaction of three-dimensional cultures of pulp-derived cells in a dentin barrier test was recorded after exposure to All-Bond 2, Prime & Bond NT, Syntac SC, Syntac Classic, and Prompt L-Pop. The materials were applied on bovine dentin disks in a perfusion chamber, and the experiments were performed with (0.3 ml/h, 2 ml/h) and without perfusion of the pulpal part of the chamber. The cell reaction was recorded (MTT assay) and related to noncytotoxic controls. Bonding agents with low pH did not show any cytotoxicity. Syntac Classic decreased the cell activities to 38% to 72%, depending on different experimental conditions, and was more cytotoxic than Syntac SC. Perfusion (2 ml/h) reduced the cytotoxicity for Syntac Classic and increased cell activities from 52% to 72%. Because low pH bonding agents did not show toxic reactions in this dentin barrier test, pulp damage caused by the tested substance is unlikely if a dentin layer protects the pulp.     

大鼠磨牙牙髓组织在程度不同的机械性损伤刺激后HSP70的表达及意义的研究

目的 检测大鼠磨牙在程度不同的机械性钻磨损伤刺激(浅磨、深磨、穿髓)后热休克蛋白70(HSP70)的动态表达。方法 采用"二步法"免疫组化法观察HSP70在正常组、浅磨组、深磨24h组、穿髓24h组、穿髓3d组和穿髓7d组牙髓组织中的表达情况。结果 浅磨组和正常组HSP70在牙髓组织中有个别标本弱阳性着色,与后4组相比P<0.01;深磨24h组可见成牙本质细胞、成纤维细胞阳性表达,血管内皮细胞弱阳性表达;穿髓24h组和3d组表现为急性炎症反应,HSP70在成牙本质细胞、血管内皮细胞、中性粒细胞中均呈强阳性表达,成纤维细胞呈阳性表达;至穿髓7d时为弱阳性表达。结论 在程度不同的钻磨刺激下,HSP70在鼠牙髓组织中的表达有强弱不同的动态变化;HSP70在牙髓损伤修复过程中可能是主要介导牙齿矿化修复的细胞因子之一。     

Cell and fiber attachment to demineralized cementum from normal root surfaces

The purpose of this study was to assess connective tissue and epithelial responses to cementum (from normal human root surfaces covered by periodontal ligament) after surface demineralization with citric acid. Each rectangular specimen had a face of cementum and an opposite surface composed of pulpal dentin. One half of the specimens were treated with citric acid (experimental group), while the remainder served as untreated control specimens. Specimens were implanted vertically into incisional wounds on the dorsal surface of rats with one end of the implant protruding through the skin. Four specimens in each group were available for examination 1, 3, 5, and 10 days after implantation. Histologic and histometric analyses of the implants included counts of adhering cells, evaluation of attached connective tissue fiber density and diameter, and assessment of epithelial migration. At day 1, a distinct lighter staining zone was present on the surface of both cementum and dentin in the experimental group which corresponded to a zone of surface demineralization produced by the acid treatment. Histometric comparisons between experimental and control groups at 10 days showed a greater number of cells attached to demineralized cementum surfaces. Also, a connective tissue fiber attachment system had developed on these experimental surfaces, but which differed morphologically from periodontal ligament fiber attachment to normal cementum. It was concluded that citric acid treatment can surface demineralize cementum from normal roots, and that the surface demineralization of this cementum facilitated a cell and fiber attachment to the cementum surface.     

Dycal��MTAֱ�Ӹ�����������BMP-2�ı��仯

目的观察Dycal和矿物三氧化物凝聚体（MTA）在大鼠磨牙直接盖髓后骨形态发生蛋白（BMP）-2的表达变化。方法本研究于2011年3月至2012年12月在中国医科大学口腔医学院中心实验室及辽宁省口腔医学研究所进行。42只雌性Wistar大鼠双侧上下第一磨牙分别用Dycal和MTA直接盖髓，在各观察时点（盖髓后12h及1、3、7、14、21、28d）处死动物取材，进行BMP-2免疫组织化学染色，用图像分析软件测定各组标本中BMP-2阳性染色的平均光密度值。用SPSS13．0统计软件对数据分别进行配对t检验和Dunnett-t检验。结果在正常牙髓组织中BMP-2表达呈阴性，Dycal和MTA直接盖髓后12h牙髓中BMP-2出现低水平表达并逐渐增强，7d时达到高峰，14d后表达开始下降，至28d时接近正常水平。MTA组修复性牙本质形成较Dycal组连续且致密，7、14d时MTA组BMP-2表达强度高于Dycal组。结论MTA组形成修复性牙本质较Dycal组连续且致密，BMP-2的表达高于Dycal组；MTA可能通过调节BMP-2的表达参与诱导修复性牙本质的形成，BMP-2的表达强度可能影响了牙髓损伤修复。     

Micromorphological and micronanalytical characterization of stagnating and progressing root caries lesions

Root caries is the predominant disease of the tooth tissues in the elderly population and differs in progression and micromorphology from coronal dentin caries. Therefore, different clinical concepts are needed for the treatment of these progressing and arrested lesions. It was the aim of this study to investigate the three-dimensional structure and volume of stagnating and progressing root caries lesions and to determine the mineral composition of the different lesion zones to achieve a better understanding of the natural history of root caries lesion formation. Of 21 extracted human teeth of patients between 42 and 77 years of age with stagnating and progressing root caries lesions serial sections were cut and investigated with polarized light and scanning electron microscopy. From the polarized light micrographs 3D reconstructions were made to determine the volumes of the lesion zones and their relations expressed in a demineralization index (DI). With increasing size of the demineralizing zone the DI increased indicating an increase in the size of the translucent zone. The 3D reconstructions showed distinct differences between stagnating and progressing root caries lesions. In the hypermineralized translucent dentin not all dentin tubules were obliterated by intratubular dentin and within the translucent dentin scattered dead tracts were found. Electron dispersive X-ray (EDX) analysis showed that the intertubular dentin of the translucent dentin was also demineralized to a certain extent. The results indicate distinct morphological differences between progressing and stagnating root caries lesions which may have consequences for treatment strategies.