Er, Cr: YSGG激光与氟化物联合应用对牙体硬组织脱矿的影响

目的：体外研究Er，Cr：YSGG激光与氟化物联合应用对牙体硬组织抗酸性的影响。方法：标本随机分成4组，分别为对照组，激光组，氟处理组，激光＋氟组，进行不同处理后，0．1mol／L乳酸（pH4．8）脱矿24h，原子吸收分光光度计检测脱矿液中溶解的钙离子浓度，能谱分析仪进行氟原子含量分析，扫描电镜观察牙釉质和牙本质表面超微结构的变化。结果：激光组、氟处理组、激光＋氟组溶解的钙离子浓度都明显降低，与对照组有显著性差异（P〈0．05），但是激光＋氟组钙离子浓度仅略低于激光组、氟处理组，与其无显著性差异（P〉0．05）；氟含量的测定仅在氟处理组牙釉质和牙本质标本有氟峰出现；扫描电镜观察见，激光组：表面不平呈鳞片状、峭壁状，无玷污层，釉质结构清晰可见，牙本质小管开放，无熔融、炭化等热损伤的表现；氟化钠组：表面有大量玷污层和碎屑，并可见到许多小颗粒沉积在牙釉质和牙本质表面；激光＋氟组：表面结构与激光组相似，未见颗粒沉积。结论：Er，Cr：YSGG激光与氟化物无联合效应，其机制仍需进一步的研究与探讨。     

三种甲基丙烯酸酯类脱敏剂的疗效比较

目的 :比较 3种甲基丙烯酸酯类脱敏剂的疗效。方法 :将 14 0例 2 5 7个患牙随机分为 4组 ,3个实验组分别用GLUMA、Seal&Protect和SingleBond进行脱敏治疗 ,对照组用 75 0g/L氟化钠甘油脱敏 ,比较各组的即刻疗效和 3个月后疗效。结果 :3个实验组的疗效均显著高于对照组 (P <0 .0 1) ,而 3组之间无显著差异(P >0 .0 5 ) ,3个月后亦然。结论 :GLUMA、Seal&Protect和SingleBond都是较为理想的脱敏剂。     

六种粘接剂的牙本质粘接界面纳米渗漏比较

目的检测6种粘接剂粘接处理后牙本质粘接界面的纳米渗漏情况。方法选取12颗无龋人磨牙,用600目碳化硅砂纸在流水冲洗下预备出统一的牙本质粘接面玷污层。分别用6种粘接剂按使用说明进行粘接处理,切割成0.9mm厚试件,避光贮存于氨化硝酸银溶液中24h。透射电子显微镜下观察牙本质粘接界面的纳米渗漏情况,单因素方差分析比较各组银染颗粒分布面积比的均值。结果6种粘接剂的牙本质粘接界面在电子显微镜下均观察到明显的纳米渗漏,其中材料A[邦多,(16.09±2.08)%]、材料B[Single Bond,(13.39±1.81)%]和材料C[Prime&Bond NT,(11.27±1.94)%]之间的差异均有统计学意义(P<0.05);材料D[B1自酸蚀底涂剂,(12.13±2.11)%]与材料E[ClearfilTMSE Bond,(12.35±2.60)%]的差异无统计学意义,但两者的纳米渗漏均小于材料F[AdperTMPromptTM,(14.93±2.67)%],差异有统计学意义(P<0.05)。结论6种牙科粘接剂的牙本质粘接界面均存在不同程度的纳米渗漏。     

Internal adaptation and overhang formation of direct class II resin composite restorations

The aim of the present in vitro study was to evaluate different restorative concepts for posterior resin composite fillings in terms of internal adaptation and overhang formation. Eighty standard occluso-distal cavities with and without a 1.5-mm bevel were restored in a phantom head using Syntac Classic and Tetric Ceram with and without Tetric Flow as thin lining or Solid Bond and Solitaire with and without FlowLine. The restorations were finished intraorally and afterwards subjected to thermal loading (1150× +5°C/+55°C) for 24 h. The proximal margins of the original specimens were analyzed for overhangs under a stereo light microscope (100-fold magnification) before and after intraoral control with loupes, including additional polish. Afterwards the teeth were cut longitudinally, replicated, and their internal integrity analyzed under a SEM (200-fold magnification). The combination of flowable and viscous composites resulted in enhanced internal adaptation for both adhesive systems. However, Syntac Classic exhibited superior adaptation characteristics compared with Solid Bond. In terms of overhang formation, the use of flowable materials always led to higher percentages of marginal overhangs in beveled cavities. Higher viscous materials alone resulted in higher percentages of underfilled margins of beveled than box-shaped cavities. It was clear that the use of magnifying glasses during finishing was beneficial for reducing marginal overhangs up to 40%. Received: 24 June 1999 / Accepted: 24 August 1999     

Assessment of bone marrow-derived mesenchymal stem cells capacity for odontogenic differentiation and dentin regeneration in methimazole-treated albino rats (Light microscopic Study)

BackgroundMethimazole is an antithyroid drug. It has side effects on many tissues. Bone marrow-derived mesenchymal stem cells (BM-MSCs) are promising in the field of tissue regeneration.ObjectiveTo investigate the capacity of BM-MSCs on odontogenic differentiation and dentin regeneration at different time intervals in methimazole treated rats.MethodsTwenty-eight male albino rats were classified as: Group I: got distilled water. Group II: obtained therapeutic dosage of methimazole as pro-drug “Neo-Mercazole®”. Group III: received methimazole then solitary injection of BM-MSCs at day 21. Group IV: obtained methimazole and single injection of BM-MSCs at the beginning of the experiment. Light microscope was used to examine specimens. Recently formed collagen and β-catenin-immunoreactivity area% were appraised histomorphometrically and statistically.ResultsHistological examination of odontoblasts and dentin illustrated normal structure in Group I and nearly normal features in Group IV. Group II demonstrated discontinuation of odontoblastic layer and areas of different stainability in dentin. Group III showed an evidently wide layer of odontoblast-like cells and distinct dentinal tubules. Masson's trichrome results of dentin in Groups I &IV showed apparently equal areas of new and old collagen. Group II illustrated old collagen mainly. Group III explored new collagen only. β-catenin-immunoreactivity was strong in Groups I & IV, mild in Group II and moderate in Group III. Statistical results revealed that the highest mean of newly formed collagen area% was in Group III, followed by Group I, Group IV then Group II respectively. Regarding β-catenin-immunoreactivity area%, the highest mean was recorded in Group I, subsequently Group IV, next Group III then Group II.ConclusionsMethimazole has destructive consequences. BM-MSCs have a time-based increased capacity for odontogenic differentiation and regeneration of dentin.     

Matrix metalloproteinase-2 expression induced by two different adhesive systems on human pulp fibroblasts

Introduction

This study evaluated the expression of matrix metalloproteinase-2 (MMP-2) in primary cultures of human pulp fibroblasts (HPFs) when exposed to extracts from dentin-bonding systems.

Methods

Polymerized resin disks of the bonding agent of a 2-step self-etch adhesive (TechBond, Isasan, Rovello Porro, Italy) or of the primer/bonding agent a 2-step etch-and-rinse adhesive (Optibond Solo; Sybron-Kerr, Orange, CA) were immersed in HPF culture medium for 24 or 96 hours. HPFs were incubated in the adhesive-conditioned or control (untreated) culture medium for 24 hours. Western blot and immunofluorescence analyses were performed to assay MMP-2 expression.

Results

MMP-2 expression levels in HPFs cultured for 24 hours in culture medium were similar in both the control and experimental media groups showing a faint band at 67 kDa. Conversely, the HPFs incubated in the medium that contain polymerized resin disks for 96 hours showed increased MMP-2 expression compared with the untreated medium. The self-etch adhesive displayed the most pronounced induction of MMP-2 expression. These findings were confirmed by immunofluorescence analysis.

Conclusions

HPFs display increased MMP-2 expression after 96 hours of conditioning of the HPF culture medium with polymerized disks of dentin bonding systems. This MMP-2 expression/activation may represent a defence mechanism exhibited by HPFs towards monomers eluted from the dentin bonding systems.     

牙颈部非龋性硬化牙本质粘接的超微形态研究

目的观察牙颈部非龋性硬化牙本质经自酸蚀牙本质粘接剂处理后，树脂一牙本质界面的超微结构。方法选择有典型牙颈部非龋性缺损且因牙周病拔除的上颌前磨牙，使用两步法的自酸蚀粘接剂Contax粘接处理。扫描电镜观察硬化牙本质表面超微形态以及树脂一牙本质界面的混合层和树脂突的微观表现。结果硬化牙本质的牙本质小管大部分被柱状的矿化结晶体堵塞。粘接界面也可见到清晰的混合层和树脂突，但树脂突较短。结论硬化牙本质的粘接与正常牙本质存在差异，牙本质小管内的矿化结晶可能影响粘接效果。自酸蚀粘接剂对硬化牙本质具有一定的粘接能力。     

大蒜治疗牙本质过敏的临床观察及实验研究

目的评价大蒜治疗牙本质过敏的疗效。方法将82例患者的243颗患牙随机分为2组,对照组(120颗牙)用75%氟化钠甘油局部涂擦,而实验组(123颗牙)用大蒜原汁涂擦,用VAS量表评估根面敏感性,并比较其疗效。另将24个牙本质块分为4组,用50%的枸橼酸处理表面后,对照组用生理盐水涂擦,实验组用大蒜原汁、1∶1大蒜稀释液及1∶10大蒜稀释液涂擦,扫描电镜下观察样本。结果实验组2周后及半年后的疼痛分数均低于对照组(P<0.05),但扫描电镜观察实验组和对照组的牙本质小管封闭情况无明显不同。结论大蒜治疗牙本质过敏有较好的疗效,但不是通过封闭牙本质小管起作用。     

Improving the effect of NaOCl pretreatment on bonding to caries-affected dentin using self-etch adhesives

Objective

To evaluate the effect of sodium hypochlorite pretreatment on adhesion to normal and caries-affected dentin using self-etch adhesives.

Methods

Forty extracted human molars with coronal carious lesions were used in this experiment. The occlusal dentin surfaces including the caries-affected dentin in each group were treated as follows: group 1, rinsed with water; group 2, treated with 6% NaOCl for 15 s; group 3, treated with 6% NaOCl for 30 s; group 4, application with Accel for 30 s after NaOCl-30 s pretreatment. After rinsing with water and air-drying, the treated dentin surfaces were applied with self-etch systems (Bond Force and Clearfil Protect Bond) according to the manufacturers’ instructions, and built-up with resin composite. After 37 °C water storage for 24 h, the bonded normal or caries-affected dentin areas were isolated to create an hourglass configuration with a cross-sectional area of approximately 1 mm². The specimens were subjected to tensile stress at a cross-head speed of 1.0 mm/min.

Results

NaOCl-15 s pretreatment significantly improved the μTBS of both self-etch adhesives to caries-affected dentin, while the 30 s pretreatment did not affect them. For normal dentin, NaOCl-30 s pretreatment significantly reduced the μTBS of both self-etch adhesives although the 15 s pretreatment did not alter them. Furthermore, the application of Accel with a reducing effect increased the μTBS to normal and caries-affected dentin treated with NaOCl for 30 s.

Conclusions

The effects of NaOCl pretreatment on bonding of both self-etch adhesives were dependent upon type of dentin (normal and caries-affected dentin) and the treatment time.     

Dentine desensitization induced by prophylactic and air-polishing procedures: An in vitro dentine permeability and confocal microscopy study

Objectives

The exposure of dentinal tubules causes fluid movement and dentinal hypersensitivity. This study aimed at evaluating the dentine permeability after prophylactic measures performed on exposed dentine after immersion in artificial saliva and citric acid challenge. Confocal microscopy was performed to evaluate the percentage of occluded tubules (OCT%) and the changes in dentine morphology.

Methods

Prophy-powders and pastes were tested in this study. An oxalic acid liner was used as a positive control. Dentine discs from human third molars were treated with each material and the dentine permeability was evaluated using a fluid filtration system working at 20 cm H₂O. Artificial saliva and citric acid were used for the determination of changes in dentine permeability. The percentage of tubule occlusion capability (OCT%) was evaluated using confocal microscopy.

Results

All the products used in this study were able to significantly reduce the dentine permeability of acid-etched specimens. The use of the bioactive glass and sodium bicarbonate showed the highest values in dentine permeability reduction. However, the air-polishing procedures performed with Sylc bioactive glass powder created a dentine surface resistant to citric acid attack.

Conclusion

Bioactive glass is suitable for treatment of dentinal hypersensitivity by creating a dentine surface resistant to citric acid attack.