Evidence of chemisorption of maleic acid to enamel and hydroxyapatite

Maleic acid has been used as an etchant or non-rinse conditioner in adhesive dentistry. However, the inherent mechanisms of the interaction of maleic acid with hydroxyapatite/enamel have never been fully elucidated. The purpose of this study was to provide evidence for the chemisorption of maleic acid onto hydroxyapatite/enamel, and to identify the reaction products obtained following the interaction of maleic acid with hydroxyapatite. Hydroxyapatite particles were dissolved in a 15% (w/v) aqueous solution of maleic acid (pH = 0.98). Half of the solution was dried to obtain a desiccated mixture. This mixture, hydroxyapatite, maleic acid and self-prepared calcium maleate were analysed by X-ray diffraction (XRD). Acetone was added to the other half of the solution to obtain a precipitate. This precipitate, hydroxyapatite, maleic acid, unetched enamel and maleic acid-etched enamel were analysed by X-ray photoelectron spectroscopy (XPS). The precipitate was also analysed by (1)H NMR. A new binding energy, indicating carboxylate groups, was detected by XPS on the precipitate and maleic acid-etched enamel surface. XRD data indicated the formation of calcium maleate and calcium hydrogen phosphate after the reaction. NMR data revealed that one carboxylic group of maleic acid reacted with hydroxyapatite. Hence, maleic acid can chemisorb to hydroxyapatite and enamel via ionic interactions.     

Clinical evaluation of different treatment methods for oral submucous fibrosis. A 10-year experience with 150 cases

Over a 10-year period (1982–1991), a total of 150 patients divided into two groups with varying degrees of oral submucous fibrosis (OSF) were treated by either medical or surgical therapies. Medical treatment involved (a) conservative oral administration of vitamin B-complex, buflomedial hydrochloride and topical triamcinolone acetonide 0.1%, or (b) conventional submucosal injections of a combination of dexamethasone and hyaluronidase, or (c) a combination of both (a) and (b). The surgical group was treated by the excision of fibrotic tissues and covering the defect with split-thickness skin, fresh human amnion, or buccal fat pad (BFP) grafts. Treatment was chosen according to the stage of clinical progression to gain maximal interincisal distance (ID). The cases were followed up by monthly examinations for at least two years, or when possible even longer. A combination of (a) and (b) medical treatment was satisfactory in cases of mild impairment (ID > 20 mm) but in the long term it led to symptomatic relief only. Surgical therapy, on the other hand, when accepted by the patients, led to a significant improvement of trismus in cases of severe limitation (ID < 20 mm). Following this strategy, an additional ID increase was observed in all patients. BFP grafting was particularly successful in diminishing scarring after two years as compared with the other two grafts. Together with a cessation of the betel quid chewing habit before and after therapy, these treatment regimens combined with daily mouth opening exercises were found to be necessary to manage OSF cases in early and advanced stages of progression.     

应用植入控释系统进行一次法根管治疗术的动物实验研究

目的：利用自制含氯霉素、甲硝唑等药物的控释系统，对实验家兔的血药浓度、药物抗菌活性和家兔根管、尖周组织的病理观察，为今后临床应用提供理论和实验依据。方法：应用组织病理观察和液相色谱分析技术。结果：用ＨＰＬＣ法得出实验用家兔血药浓度和抗菌活性均为阴性，根管及尖周组织病理切片无特殊表现。结论：自制控释系统是一种无毒、无副作用、有效的根管治疗药物剂型，可进行临床应用。     

Surface analysis and corrosion resistance of different stainless steel orthodontic brackets in artificial saliva

The purpose of this study was to investigate the variation in corrosion resistance of commercial stainless steel (SS) brackets with different brands and types for the same application, using the electrochemical technique. The linear polarization test was used to evaluate the corrosion resistance, in terms of polarization resistance (Rp), of as-received commercial SS brackets in acidic artificial saliva. A two-way analysis of variance was used to analyze the Rp with the factors of brand and type. A scanning electron microscope and an atomic force microscope were used to analyze the surface morphology and roughness, respectively. The X-ray photoelectron spectroscopy was used to identify the chemical composition of the passive film on SS brackets. Results showed that different brands of SS brackets had a statistically significant difference in Rp (P < .0001), whereas there was no statistical difference between the bracket types ("Roth" and standard) (P = .27). Different surface topography, including surface roughness and defect, was present among the tested SS brackets. The same passive film structure, containing Cr2O3/Fe2O3 with small amounts of NiO, was observed on all SS brackets. The surface topography of the commercial SS brackets with identical surface passive film structure did not correspond with the difference in corrosion resistance.     

The inhibitory effect of MI paste, fluoride and a combination of both on the progression of artificial caries-like lesions in enamel

This in-vitro study evaluated the inhibition of demineralization in enamel sections produced by MI paste, fluoride and a combination of both, compared to artificial saliva and NaF 5000 ppm in a caries progression pH-cycling model. Twenty-one teeth were demineralized to create subsurface enamel lesions (approximately 200 microns in depth). The teeth were sectioned and characterized using polarized-light-microscopy (PLM). A single section from each lesion was assigned to a treatment group: Artificial saliva, NaF 5000 ppm (Prevident, Colgate), MI paste (Recaldent, GC America Inc), NaF 1100 ppm (Crest, Procter & Gamble) and NaF 1100 ppm plus MI paste. The sections were covered with varnish except for an exposed window on the external surface of the lesion and placed in a six-day pH-cycling model with two daily treatment applications of two minutes each. The sections were characterized by PLM, and the lesion areas were measured using a digital image analysis system. Based on a paired-sample t-test, significant differences (p < .05) in percentage of change in lesion size were found between the high fluoride group and all the other groups. No significant difference was found between the artificial saliva and MI paste group, neither was there any significant difference between the NaF 1100 ppm, the combined application group or the MI paste group alone. In conclusion, the higher concentration of NaF (5000 ppm) reduced lesion progression to the greatest extent. The MI paste group did not show any effect on the inhibition of lesion progression. Further studies on the preventive effect and longer treatment applications are recommended.     

Calbindin-D28k与肌动蛋白在人健康及龋坏牙齿中的分布

目的 探讨calbindin—D28k与肌动蛋白在健康和龋坏人恒牙中的分布相关性及意义。方法 用免疫组化方法分别检测calbindin—D28k与肌动蛋白在正常、中龋和深龋人牙中的表达并观察比较。结果 正常组Calbindin—D28k在前期牙本质远髓2／3区域染色阳性，肌动蛋白在成牙本质细胞及住于矿化牙本质中的细胞突呈阳性；中龋组位于前期牙本质中的成牙本质细胞突Calbindin—D28k与肌动蛋白均呈强阳性，Calbindin—D28k在病损区前期牙本质全层呈阳性且较正常组明显增强；深龋组Calbindin—D28k染色部位主要位于成牙本质细胞核。结论 在第三期牙本质形成活跃的成牙本质细胞中Calbindin—D28k与肌动蛋白的分布变化具有一致性，均与牙本质基质的分泌有关。     

舌大小二维超声成像测量分析方法的建立及其评价

目的：建立一种舌大小测量分析方法，为舌大小在错He发病中的作用研究奠定基础。方法：采用B超超声像方法取舌正中纵断面和横切面图像，选取代表舌大小的参数进行测量，从而分析舌大小。结果：通过对测量结果的可重复性和准确性检验。认为这一测量方法是准确可行的，结论：建立的舌大濒分析方法可以作为研究手段使用。