氯丙嗪对大鼠牙齿矿化抑制作用的实验研究

目的：探讨氯丙嗪(chlorpromazine,CPZ)对大鼠切牙硬组织矿化的影响。方法;采用酶联反应仪及高压液相色谱仪（HPLC）检测CPZ对培养不同时间牙胚ALP及Ca^2 的含量,利用显微放射照相技术观察CPZ对大鼠硬组织矿化的情况。结果：培养0-7d牙胚Ca^2 含量及ALP逐渐上升,培养7-10d的牙胚中,实验组Ca^2 含量及ALP活性的上升幅度显著减弱;CPZ剂量依赖性地抑制大鼠牙本质形成,并且对血浆中Ca、P无明显影响。结论：CPZ对大鼠牙齿矿化过程具有抑制作用。该作用是通过成牙本质细胞的钙调节系统实现的。     

Fluoride uptake in human dentine from glass-ionomer cement in vivo

The purpose was to examine F uptake and distribution in dentine from a F-containing glass-ionomer cement in vivo. Nine volunteers were selected from dental students who were scheduled for extraction of their third molars. Two cavities were prepared on the same occlusal surface of the third molars for each subject; one was restored with glass-ionomer cement (Virtabond), the other with zinc phosphate cement as a control. After 3 months the teeth were extracted. F profiles in the dentine from the cavity floor to the pulpal surface were determined in tissue immediately adjacent to the restorations. An abrasive micro-sampling technique was used. The F concentration of the dentine was highest immediately beneath glass-ionomer cement filling, decreasing towards the pulpal surface. Overall F concentrations were greater in the dentine beneath the glass-ionomer cement than in that beneath the zinc phosphate cement. It was concluded that the glass-ionomer cement markedly enhanced fluoride uptake by underlying dentine in vivo.     

In vitro cytotoxicity of three dentine bonding agents

While several studies have been reported on the physical testing of dentine bonding agents, very few studies have been involved with their biological evaluation. This report describes a new in vitro method for assessing the cytotoxicity of these materials through dentine simulating their clinical use. An experimental bonding agent, now marketed as Tripton by ICI Dental, Scotchbond 2 and GLUMA were exposed to BHK-fibroblasts through 100 and 500 μm slices. All materials were significantly cytotoxic compared with controls through both thicknesses of slice. The ICI Dental experimental material was the least toxic through 100 μm slices (68·8 per cent of controls) followed by Scotchbond 2 (54·2 per cent) with GLUMA the most cytotoxic (26·9 per cent). However, with 500 μm slices values for the ICI Dental experimental material and GLUMA were similar (70·8 and 66·6 per cent respectively), with Scotchbond 2 exhibiting greatest toxicity (52·6 per cent). The results indicate that these materials are considerably more cytotoxic than most restorative materials which have been tested using a similar system. It is anticipated that all materials, in particular Scotchbond 2, could cause severe reactions in deep cavities in vivo in the absence of an adequate lining.     

In vivo confocal microscopy in clinical dental research: An initial appraisal

Until recently, the in vivo microscopic investigation of intraoral tissues at high resolution has been virtually impossible. Confocal microscopy enables high-resolution imaging to be achieved below semitransparent surfaces in intact living specimens, but this may still be impractical for intraoral applications because of the need to stabilize the sample. The development of a steadying objective (x 240 overall mag.) which is held against the sample surface and is focused by moving internal elements, avoids the need for fine adjustment of the living sample under the microscope to achieve a change of focus. It is therefore more comfortable and also reduces the problems of movement due to the pulse. The objective was used with a tandem scanning microscope, with images recorded via a SIT video camera. Using this system internal tooth structure (e.g. enamel prisms/adhesive restoration interfaces) and the lining cells of the gingival crevice through to the junctional epithelium may be examined. It is also possible to image the oral mucous membrane, focusing to the capillary loops in the basal layers, where streaming red blood cells can be seen. Access is limited to the anterior regions as far back as the premolar teeth. Applications could include caries research, soft and hard tissue responses to biomaterials (e.g. implants), wound healing and monitoring the effect of periodontal treatment regimens. This new technique offers numerous exciting opportunities for the microscopic investigation of many clinical operative procedures in vivo, allowing the response of the tissues to be non-destructively monitored, over time, at high resolution.     

Artificial salivas for in vitro studies of dental materials

Objectives: An artificial saliva (AS) of defined composition is necessary for testing the performance of materials that serve in the mouth as natural saliva is too variable. The chemistry involved is critically important. Many AS recipes can be found in the literature, but the stability of tooth material, i.e. hydroxyapatite (HAP), in most of these has not been addressed. In fact, few contain all major ionic components with concentrations in the physiological range. The aim of the present study was (a) to review reported AS formulae from their inception in 1931 to date, (b) to compare the stability of HAP in various reported AS, and (c) to investigate the individual effects of ionic components present in the reported formulae on the stability of HAP.

Methods: A computer algorithm, RAMESES, for solving multiple equilibrium equations, was employed for all calculations.

Results: There was a marked difference between two groups, i.e. those with and without the presence of Ca; those with Ca were supersaturated with respect to HAP in the physiological pH range, the saturation pH ranging from about 4.5 to 6.0. There was also an approximately 180-fold range in solubility at pH 7, due to the individual effects of components such as phosphate, carbonate and citrate. Acetate, lactate and sulphate showed smaller effects, others have no appreciable effect.

Conclusions: All components and equilibria of relevance to saliva must be included in the system for detailed models. Continued systematic development of a standardized AS is essential.     

Biometric analyis of tooth migration after approximal contact removal in the rat

Nineteen 8-week-old female Sprague-Dawley rats were used to observe macroscopically the direction of tooth movements following removal of approximal contacts. In 10 rats, under anaesthesia, approximal contact between the second and third right maxillary molars (M2–M3) was removed by grinding. These animals and a control group of nine rats were housed with normal diet and water ad libitum for 7 weeks. After killing, the skulls of all animals wre removed, dried, and fixed in a standardized position on a Horsley-Clarke type stereotaxic frame. Using a micromanipulator graduated to 1/100 mm and mobile in three orthogonal directions, distances between the teeth (M1 or M3) and some bone structures that served as landmarks were measured. These measurements showed the direction of tooth movements in the experimental approximal space. After statistical analysis of the data, the results showed that the approximal space between M2 and M3 was closed by both a distal drift of M1-M2 and a mesial migration of M3. It was concluded that, in the rat, a mesial drift exists that can be induced by the loss of approximal contact. This movement is distinct from the distal physiological dental migration classically described in histological studies.     

cbfa1反义核酸对体外培养小鼠牙胚发育与矿化的影响

目的:采用反义核酸技术,用特异的与cbfa1mRNA互补的AS ODN抑制cbfa1在体外培养牙胚的翻译,利用电镜及ALP、OC等指标观察其对牙齿发育及矿化的影响,探讨其在牙齿发育中的作用。方法:设计合成cbfa1反义核酸,应用所建立的牙胚体外培养系统,用电镜观察小鼠牙胚被cbfa1反义核酸阻断表达后发育的情况,并且检测ALP、OC表达量的变化。结果:在缺乏cbfa1的情况下,与对照组相比,形成的基质较薄,且基质中胶原纤维排列稀疏,粗细不等,方向杂乱,ALP、OC表达量均有明显变化。结论:cbfa1可能是通过调控ALP和OC等靶基因的表达参与了牙齿发育矿化过程。     

The effects of immunoglobulins on the convective permeability of human dentine in vitro

Immunoglobulin molecules are localized in the dentinal tubules of non-carious and carious teeth, but their possible role in caries invasion is not understood. This study sought to examine the effects of immunoglobulin molecules on dentine permeability using a fluid-filtration method. Crown segments cut from impacted human third molars were treated by filtration with 100 μg/ml IgG, 100 μg/ml IgA or 30 μg/ml IgM under a constant pressure. Flow rates were recorded and percent changes in flow rate analysed over time. Filtrates collected at various times were tested for changes in immunoglobulin concentrations by an enzyme-linked immunosorbent assay, and the percent retention of immunoglobulins to dentine was calculated. There was a decreasing non-linear exponential relation between the percent changes in flow rate and filtration time for all three immunoglobulins. The percentage of retained immunoglobulins was significantly related to the filtration time for all three classes of immunoglobulins. Immunoglobulin retention contributed to significant changes in flow rate with time. These in vitro results indicate the potential mechanism of immunoglobulins in decreasing tabular permeability.     

碱性成纤维细胞生长因子对体外大鼠牙胚分化的影响

目的：观察外源性ｂＦＧＦ对体外培养牙胚发育和分化的作用。方法：采用体外培养１７ｄＳＤ胎鼠第一磨牙牙胚，培养液中加入１０ｎｇ／ｍｌ人重组ｂＦＧＦ（ｈｂＦＧＦ），分别培养３、６、９ｄ，组织学观察。结果：外源性ｈｂＦＧＦ可使大鼠牙胚的细胞分化和牙本质基质分泌加快。结论：外源性ｂＦＧＦ可以促进大鼠牙胚的发育，加速牙齿发育。     

In situ localization of tenascin mRNA in developing mouse teeth

Tenascin is a large extracellular-matrix glycoprotein found in developing connective tissue. A cDNA probe to mouse tenascin, mTN2, was used to determine the cellular origins of this molecule in the murine tooth germ by in situ hybridization. At embryonic day 19, a hybridization signal significantly greater than background was detected with mTN2 in the subodontoblastic layer of the dental mesenchyme and in the inner enamel epithelium of the enamel organ. At postnatal day 1, a signal was detected over pre-odontoblasts and the strata intermedium and externum. No tenascin mRNA was detected in odontoblasts or the stellate reticulum at either age, and hybridization in ameloblasts was not significantly greater than background at postnatal day 1. Thus, much of the tenascin found throughout developing teeth appears to be synthesized by pre-odontoblasts and the inner enamel epithelium, the two populations of cells destined to generate mineralized matrix.     

Expression, localisation and synthesis of versican by the enamel organ of developing mouse molar tooth germ: An in vivo and in vitro study

Objective

Versican is a large, aggregating chondroitin sulphate proteoglycan. In dental tissue, versican expression occurs primarily in mesenchymal tissue but rarely in epithelial tissue. We investigated the expression, localisation and synthesis of versican in the enamel organ of the developing tooth germ.

Design

To elucidate versican localisation in vivo, in situ hybridisation and immunohistochemistry were conducted in foetal ICR mice at E11.5–E18.5. Epithelium and mesenchyme from the lower first molars at E16.0 were enzymatically separated and versican mRNA expression was investigated by semi-quantitative RT-PCR. Organ culture of the separated samples combined with metabolic labelling with [³⁵S], followed by gel filtration, was performed to analyse secreted proteoglycans.

Results

Versican mRNA was first expressed in the thickened dental epithelium at E12.0 and continued to be expressed in the enamel organ until the bell stage. Versican immunostaining was detected in the stellate reticulum areas from the bud stage to the apposition stage. The enamel organ at E16.0 expressed versican mRNA at a level comparable to that in dental mesenchyme. Furthermore, when compared to dental mesenchyme, about 1/2–3/4 of the [³⁵S]-labelled versican-like large proteoglycan was synthesised and released into tissue explants by the enamel organ.

Conclusions

The dental epithelium of developing tooth germ is able to synthesise significant amounts of versican.     

2种镁基材料的体内外生物相容性研究

目的 探讨高纯镁和镁-1钙合金2种镁基材料的体内外生物相容性,为其临床应用提供安全性数据.方法 选择高纯镁和镁-1钙合金2种镁基材料,参照ISO 10993系列标准,开展细胞毒性、遗传毒性、皮内反应、致敏性、急性全身毒性和26w肌肉植入后组织反应的研究,探讨细胞活力的影响因素,评价其生物相容性.结果 高纯镁和镁-1钙合...     

A comparison between osteoclasts in vitro and in vivo in the periodontal ligament of the adult mouse

Twelve expiants of the first mandibular molar and surrounding periodontium of young adult mice were cultured for 7 days in vitro. The number and size of osteoclasts, the number of nuclei per osteoclast and the distribution of the osteoclasts in the periodontal ligament were compared with osteoclasts in periodontal ligament in vivo in mice of the same age as the mice from which the expiants were taken. Light microscope comparison of the two groups indicated that resorption of bone had occurred in vitro. There was a significant increase in the number and size of osteoclasts in the cultured expiants compared with the in vivo material. The numbers of nuclei per osteoclast and the distribution of osteoclasts in the periodontal ligament was similar in the two groups, but the greatest increase in osteoclast numbers occurred on the distal aspect of the distal root where there were most osteoclasts in vivo. It was concluded that there was active bone resorption and that osteoclasts formed de novo during culture of these expiants.     

裂纹尺寸对隐裂牙折裂模式和临床风险影响的体外研究

目的探讨隐裂牙的裂纹尺寸对于其折裂模式及临床风险的影响。 方法将纳入的50颗上颌前磨牙简单随机抽样法分为5组,前4组通过对试样进行测量调磨制备成隐裂牙模型,调模为颊尖斜度为59°、腭尖斜度为50°。隐裂牙模型根据不同的预裂纹尺寸进行分组,将牙冠近远中边缘嵴最外缘中点间的距离设为裂纹长度（a）,该两点所在平面至近中釉牙骨质界最凸点的距离为裂纹深度（h）,第1组至第4组的裂纹长度及宽度分别为（a/3-h/2）、（2a/3-h/2）、（a/3-h）、（2a/3-h）。第5组不做处理即对照组。所有试样采用压应力实验,记录抗折力、折裂模式及临床风险分级。采用单因素t检验比较各组间最大抗折力,利用统计图表对折裂模式分析,使用非参数秩和检验统计折裂试样临床风险等级。检验水准α=0.05。 结果每组抗折力分别为（1126 ± 126）、（974 ± 159）、（1114 ± 240）、（608 ± 105）和（1205 ± 216）N。第2组与第4组最大抗折力与其余各组比较差异均有统计学意义（P<0.05）,其余各组间比较无统计学意义。对于折裂模式：所有试验组多发生偏向腭侧的斜折,每组冠折与冠根折各占的比例分别50%~50%、40%~60%、20%~80%、0~100%、100%~0。对于临床风险评估：所有隐裂牙组（第1~4组）同对照组（第5组）相比差异均有统计学意义（P<0.05）。对于隐裂牙组,第1组同第4组间比较差异有统计学意义（P = 0.003）,其余各组间比较差异无统计学意义。第1组和第5组试样折裂后均可保留,第2组和第3组均有20%的试样发生了不可保留性冠根折。第4组临床评估风险最大,40%的试样为不可保留性的冠根折,并且折裂部位多位于根尖区。 结论隐裂牙的抗折力显著低于正常牙,易发生折裂。并且隐裂牙的折裂情况同其裂纹尺寸有着密切关系,裂纹尺寸越深越宽,越易发生冠至根尖区方向的折裂,临床风险逐渐增加。     

Cariogenic potential in vitro in man and in vivo in the rat of lactate dehydrogenase mutants of Streptococcus mutans

Human tooth fragments transferred daily in sucrose containing cultures of Streptococcus mutans strain BHT-2 developed visible white spots, the characteristic lesion of early dental caries, within 10 days. By contrast, tooth fragments exposed to an L(+)-lactate dehydrogenase (LDH)-deficient derivative of BHT-2 showed no visible lesions, even after 21 days of transfer. More direct evidence for the non-cariogenic nature of LDH-deficient mutants was provided by gnotobiotic and conventional rat models, in which the mutants could colonize the mouth to approximately the same extent as their parent, but produced a significantly lower incidence and severity of dental caries. Reversion studies suggested that single gene mutations are responsible for the deficiency in lactate dehydrogenase catalytic activity, which in turn is responsible for the observed decreases in acid production and cariogenic potential of the mutants. These results lend strong support to the acidogenic theory of caries aetiology.     

A study of the interfacial shear and tensile stresses in a restored molar tooth

Dentine bonding agents are widely used without any knowledge of their ability to ensure satisfactory clinical performance other than by clinical trials. This study is concerned with the determination of the magnitude of the tensile and shear stresses at the interface between tooth tissue and the restorative material developed as a consequence of occlusal loading. The aim is to assess the adequacy of dentine bonding agents in this respect.

A two-dimensional finite element model of a buccal-lingual section through the crown of a lower first molar was created. The cavity design consisted of a Black-type cavity which was restored with dental amalgam or composite resins of different moduli.

The results showed that the interfacial stresses between tooth tissues and a bonded restoration increased as the modulus increased, suggesting that adhesive failure is more likely with highly filled composite resins. Stresses at the interface appeared to be sufficient to cause debonding of composite resin restorations according to available data on bond strengths. However, current methods of estimating bond strengths of dentine bonding agents to dentine do not necessarily reflect the true stresses at the point of failure.     

A study in vitro of the combined effects of soft drinks and tooth brushing with fluoride toothpaste on the wear of dentine

The aim of this study was to measure loss of dentine produced by soft drinks alone and combined with tooth brushing with and without toothpastes. Groups of flat human dentine specimens were exposed for 10 min and then 30 min to orange juice (OJ), carbonated cola (CC) or modified blackcurrant (MB) drinks alone or after the exposures brushed with a fluoride toothpaste for 10 s. Further groups were exposed to OJ as before but brushed with water or non-fluoride toothpaste or placed in slurries of fluoride paste. Five cycles of each regimen were carried out. Tissue loss was determined by profilometry. Water immersion/brushing and brushing controls were included. OJ and CC produced similar erosion and significantly more than MB. Compared with drinks alone, dentine loss was reduced by fluoride toothpaste brushing but increased by water and non-fluoride toothpaste brushing. Fluoride toothpaste slurry had no significant effect on soft drink erosion. Very little abrasion with brushing alone was recorded over the time frame of these experiments. It is concluded that fluoride toothpaste could provide protection, albeit small, against erosion. The data again support the concept of brushing before meals.     

The fungicidal effect of human lactoferrin on Candida albicans and Candida krusei

Five oral isolates each of Candida albicans and Candida krusei were studied for their sensitivity to the fungicidal effect of human lactoferrin. Significant inter- and intraspecies variations were observed and with most isolates the sensitivity of C. krusei to lactoferrin was greater than that of C. albicans. Fungicidal activity of lactoferrin was dose-dependent and observable only with the irondashfree form of the molecule (apo-lactoferrin). Irondashsaturated lactoferrin was ineffective against all isolates. Supernatant protein assays and scanning electron microscopy indicated cell surface alterations—leakage of proteins and formation of surface blebs—only in those Candida isolates that were sensitive to apo-lactoferrin. As lactoferrin is a common, nondashimmune, mucosal defence protein, its varying mode of action against C. albicans and C. krusei may be related to their different oral carriage rates.     

Microradiography and light microscopy of mineralization in the pulp of undemineralized human primary molars

This study was undertaken to investigate the prevalence, location and histologic features of the different types of mineralization observed in the pulp of human primary molars. Microradiography and light microscopy of undemineralized material disclosed that 95% of primary molars contain pulp calcifications. Histologically, their structure may be classified into four different types: (1) pulp stones, (2) diffuse calcifications, (3) eburnoid tissue and (4) spherulitic calcifications.     

氢化镁颗粒对牙周致病菌具核梭杆菌的体外抗菌作用

目的 评价微米氢化镁（MgH₂）颗粒对牙周炎致病菌具核梭杆菌的体外抗菌作用,研究可能的抗菌机制。方法 通过扫描电镜（SEM）和X射线衍射仪（XRD）对实验材料MgH₂颗粒的尺寸大小、表面形貌和晶相结构进行表征。使用电子顺磁共振技术（EPR）研究其释放行为,同时使用菌落计数实验（CFU）、溴化四甲基偶氮唑盐法（MTT）研究了MgH₂颗粒对具核梭杆菌的抗菌效应。结果 MgH₂颗粒呈现为尺寸不均一的微米级球状颗粒,平均尺寸为10.52 μm。XRD谱图具有属于MgH₂的（110）、（101）、（200）及（211）特征面的衍射信号。在菌落计数实验（CFU）实验中,当材料浓度达到 1.5 mg/mL和 2 mg/mL时有显著的抑菌效果,抗菌率分别为45.69 %和79.24 %。在MTT实验中,具核梭杆菌的活性随着MgH₂颗粒浓度的增加而逐渐降低,当MgH₂颗粒浓度达到2 mg/mL时,其活性接近于零。结论 MgH₂颗粒对具核梭杆菌有着良好的抑菌效果,在临床应用方面具有良好的前景。