An analysis of paramagnetic centers in irradiated dentin using electron spin resonance

Summary The ESR spectra produced in irradiated dentin have been studied over a range of incident radiation energies from 50 kVp to 25 MVp. The behavior of the dentin ESR signal strength is similar to that of enamel as a function of the energy of the incident radiation. The magnitude of the dentin ESR signals are, however, up to 10 times smaller than the signals of dental enamel for a given radiation energy. The possible contributions of radiation interaction coefficients, chemical structure, and crystallite size to the differences in ESR spectra are discussed.     

UB-I粘结剂粘结面的微形态观察

目的：研究UB-Ⅰ粘结剂的粘结界面和粘结表面的微形态特点。方法：用扫描电子显微镜观察UB-Ⅰ和牙本质的粘结界面和粘结表面。结果：UB-Ⅰ粘结剂在牙本质小管内可聚合形成树脂突，在牙本质小管内的树脂突表面有树脂侧枝呈树枝状横行排列，并且和相邻的树脂突相连接，在牙本质和复合树脂之间有杂合层形成。结论：UB-Ⅰ粘合剂具有良好的渗透性，与牙本质之间可以形成良好的机械嵌合。     

耳脑医用粘合剂修补脑脊液漏

耳脑医用粘合剂是α－氰基丙烯酸正辛酯和α－氰基丙烯酸正丁酯及少量添加剂配伍而成的复合性医用粘合剂。应用此粘合剂粘合修补脑脊液漏２７例，其中外伤性脑脊液鼻漏５例，经鼻蝶入路垂体瘤切除术脑脊液漏６例，开颅手术后手术切口脑脊液漏１１例，脊膜膨出修补术后脑脊液漏５例。成功２５例，成功率９３％。应用此粘合剂修补脑脊液漏具有简便、迅速、有效的特点。     

Occupational allergic contact dermatitis and composition of acrylates in dentin bonding systems

Background Dentin-bonding systems contain sensitizing acrylates. They are increasingly used in dentistry, but only few cases of allergy have been encountered. Objective This study reports observations on eleven patients sensitized by acrylates in dentin-bonding compounds. Furthermore, the composition of dentin-bonding products was analysed and compared with the information given in the material safety data sheets. Methods Patch testing was performed to reveal allergic contact dermatitis, and chamber provocation tests to reveal possible respiratory sensitivity. Gas chromatography/mass spectrometry was used to analyse the chemical composition of the bonding products. Results The most common sensitizer in our material of eleven patients was 2-hydroxyethyl methacrylate (2-HEMA). Another putative sensitizer, BIS-GMA, used in dentin adhesives, did not cause sensitization. The typical allergic dermatitis localized to the fingertips (pulpitis). Seven of the eleven patients also developed paresthesia of the fingertips. One patient with positive patch test reactions to (meth)acrylates had pharyngitis hut no skin symptoms. One patient was sensitized because she had been patch tested with too high a concentration (undiluted) of dentin-bonding components. Material safety sheets gave inaccurate or wrong information about the contents. Conclusion Dentin-bonding acrylates are strong sensitizers, and even a single exposure may sensitize.     

Age estimation in biopsy specimens of dentin

Determination of age at death on the basis of aspartic acid racemization in dentin is one of the most reproducible and accurate methods. In Germany, age estimation by this method has so far generally not been applied to living persons, since the extraction of a tooth exclusively for age estimation when it is not medically indicated is regarded as ethically and legally problematic. The development of a biopsy technique applicable to dentin took place against this background. Testing the technique and analysis of dentinal biopsy specimens revealed that the biopsy technique is a low-risk procedure that causes only minor discomfort to the affected person. It is readily practicable and facilitates standardized specimen removal. The relationship between the extent of aspartic acid racemization in dentinal biopsy specimens and age is very close, facilitating age estimation. A prerequisite for accurate results is the performance of biopsies under strictly standardized conditions. If this is guaranteed, age determination on the basis of aspartic acid racemization in dentinal biopsy specimens appears to be superior in precision to most other methods in living persons and can be used for all age groups.     

Structure and properties of methacrylate based dental restorative materials

The chemistry and structure of the dimethacrylate resins and the nature of the filler systems in dental composite resins are reviewed in relation to their influence on the setting behaviour, dimensional stability, aesthetics, fracture behaviour and adhesive potential. It is clear that a deeper understanding of the structure of the polymeric matrix and the mechanism of clinical wear is required. As a result of ongoing research in this area and with the development of dentine adhesives, the future prospects of composite resins are encouraging.     

YAG激光治疗牙本质过敏症的疗效分析

目的 :为探索治疗牙本质过敏症的新疗法 ,观察激光治疗后过敏齿的临床疗效 .方法 :应用 Nd:YAG激光点射治疗过敏齿 152 1颗 ,其中 °过敏 10 17颗 , °过敏 50 4颗 .结果 :即刻有效率为98.6 8% ;经 3～ 12个月的临床观察 , °过敏痊愈 814颗 (80 .0 4 % ) ,显效 183颗 (17.99% ) ,有效率为98.0 3% ; °过敏痊愈 119颗 (2 3.6 1% ) ,显效 339颗 (6 7.2 6 % ) .结论 :两组总有效率为 95.6 6 %。操作简便 ,无痛苦 ,是一种快速有效的方法     

Competitive adsorption of magnesium and calcium ions onto synthetic and biological apatites

Summary Magnesium (Mg) is a conspicuous constituent of hard tissues but its possible role in biomineralization is poorly understood. It is possible that Mg²⁺ adsorbed onto bioapatites may contribute to the modulation of crystal growth as such inhibitory activity has been reported for synthetic apatites. The present study was undertaken to determine the adsorption isotherms of Mg ions onto synthetic apatites and biominerals in tooth and bone tissues in the presence of other ions of natural occurrence. Synthetic crystals used as adsorbents were hydroxyapatite and, as a better prototype for the biomineral, Mg-containing carbonatoapatite. Human enamel and dentin materials were obtained from extracted, caries-free, permanent teeth. Porcine dentin materials at two developmental stages were obtained from erupted deciduous and unerupted permanent teeth of a 6-month-old slaughtered piglet. Porcine bone was obtained from the cortical portion of the mandible of the same animal. All biomineral samples were pulverized and then treated by plasma ashing (deproteination) at about 60°C. Each of the powdered samples was equilibrated in solutions containing various initial concentrations of Mg²⁺, Ca²⁺, and Na⁺ (or K⁺) as nitrate salts. Following equilibration, concentrations (and activities) of magnesium and calcium ions in the experimental solution were determined. The pH values of the equilibrium solutions were in the range of 6.2–6.5. Experimental data of the Mg adsorption onto hydroxyapatite were interpreted on the basis of a Langmuir-type model for binary systems assuming competition of Mg²⁺ and Ca²⁺ for the same adsorption sites on the crystal surfaces of the apatites. According to this model, the adsorbed Mg is expressed as a function of the ionic activity ratio (Mg²⁺)/(Ca²⁺) in the equilibrium solution. The model contains two parameters, the adsorption selectivity constant K_s and the maximum number of adsorption sites N (mol/g). The numerical values of K_s were similar for all adsorbents used (synthetic and biological) and indicated the preferential adsorption of Ca²⁺ probably due to spacial restrictions extending to the very surface of the crystals. The initial level of Mg²⁺ in the surface pool was different in the various biominerals, probably reflecting the composition of fluid in which the biominerals were formed. Whereas the surface pool of Mg of human enamel was marginal, only 5% of the total Mg, significant fractions of the total Mg in human and porcine dentins (about 20–30%), and porcine bone (about 40%) existed on the crystal surfaces. There were significant differences in the total Mg and the value of the parameter N between young (unerupted) and mature (erupted) dentin minerals. It was ascertained that the occupancy of adsorption sites by Mg ions became greater with maturation of the dentin tissues. The overall results suggest that the Mg-mineral interaction in tooth and bone tissues may be a highly tissue-specific process, presumably reflecting differences in fluid composition (particularly Ca and Mg activities) responsible for biomineralization.     

Dentin Sialoprotein (DSP) Has Limited Effects on In Vitro Apatite Formation and Growth

Sialoproteins such as bone sialoprotein (BSP) and dentin sialoprotein (DSP) accumulate at the mineralization fronts in bone and dentin, respectively, suggesting they have some function in the mineralization process. BSP, a highly phosphorylated protein rich in polyglutamate repeats, is an effective nucleator of hydroxyapatite (HA) formation in vitro. The present study examines the effect of DSP, a low phosphorylated but related sialoprotein, on the formation and growth of HA. In vitro, in a gelatin gel diffusion system, DSP at low concentrations (<25 μg/ml) slightly increased the yield of HA formed at 3.5 and 5 days, while at higher concentrations (50–100 μg/ml) it slightly inhibited accumulation. Fewer mineral crystals were formed in the presence of high concentrations of DSP but they tended to aggregate (making them appear larger by electron microscopic analysis) than those formed in DSP-free gels. X-ray diffraction line broadening analysis failed to show significant changes in c-axis crystal dimensions with increasing DSP concentration. When HA-seed crystals were coated with DSP before inclusion in the gelatin gel there was a reduction in mineral accumulation relative to HA-seeds which had not been coated with DSP, but the extent of inhibition was significantly less than that seen in this system with other mineralized tissue matrix sialoproteins, such as osteopontin or BSP. The low affinity of DSP for well-characterized seed crystals and the limited effect of this protein on HA formation and growth suggest that the role of DSP in dentin is not primarily that of a mineralization regulator. Received: 25 April 2000 / Accepted: 21 July 2000 / Online publication: 2 November 2000