Comparative study on the effect of ultrasonic instruments on the root surface in vivo

The present study was designed to investigate the effectiveness of different ultrasonic instruments on the root surface. Fourteen patients with 35 single root teeth designated for extraction were recruited to the present study. Teeth were assigned to four experimental groups: group 1, piezoelectric ultrasonic device; group 2, magnetostrictive ultrasonic device; group 3, hand instrumentation; and group 4, untreated teeth (control). After instrumentation, the teeth were extracted and the presence of residual deposits (roughness and root surfaces characteristics) were analyzed. The results showed that residual deposits were similar in all tested groups: piezoelectric, 8.7%; magnetostrictive, 9.7%; hand instrumentation, 11.1% and control, 76.4%. There were statistically significant differences between control and all the experimental groups (p < 0.0001). With respect to roughness parameters evaluation, R_a and R_z of the roots treated with the different instruments showed a similar pattern (p > 0.05), but for R_t and R_y, a significant difference was observed (p < 0.05) among hand instrumentation and ultrasonic devices. SEM analysis revealed a similar root surface pattern for the ultrasonic devices, but curettes showed many instrumental scratches, deep gouges, and a relatively large amount of dentin was removed. Within the limits of the study, although the instruments produced similar results, root surfaces instrumentated with curettes were rougher and had more root surface tissue removed than with the ultrasonic device.     

桩核材料对牙本质应力分布的影响

目的 研究6种不同材料行桩核修复前后牙本质的应力分布情况,为临床桩材料的选择提供理论依据。方法 采用螺旋CT扫描数据建立上颌中切牙烤瓷桩核冠的三维有限元模型,在此模型上对用铸造Ni-Cr合金、铸造钛合金、铸造金合金、玻璃纤维树脂、聚乙烯纤维树脂及普通复合树脂6种材料行桩核修复前后的牙本质应力分布情况进行数值分析。结果 在6种材料中,与桩修复前的烤瓷熔附金属冠修复牙相比较,临床最常用的铸造Ni-Cr合金桩修复使桩尖周围牙本质的最大主应力和Von Mises应力分别升高了152％和162％;聚乙烯纤维树脂桩修复后,牙本质中的应力分布情况无明显改变。其他材料行桩修复后牙本质中应力分布的差异较大。桩植入后对牙本质应力分布模式的影响与桩的弹性模量密切相关。结论 与牙本质弹性模量接近的聚乙烯纤维树脂更适合用于桩修复。     

饰瓷对磨牙e.max双层全瓷冠断裂类型的影响

目的：通过抗折破坏实验研究饰瓷对磨牙e.max双层全瓷冠断裂强度和断裂类型的影响,为减少临床双层全瓷修复体崩瓷提供实验依据。方法：制作单层全瓷冠（IPS e.max Press）和双层全瓷冠（IPS e.max Press/Ce-ram）共40个（每组20个）,粘接于树脂代型后进行抗折破坏实验并记录断裂强度值;体视显微镜和扫描电子显微镜下观察断裂类型;能谱分析饰瓷-核瓷界面化学元素构成。结果：单层全瓷冠断裂强度值[（2665.4±759.2）N]与双层全瓷冠[（1431.1±404.3）N]间差异有统计学意义（P=0.000）。饰瓷内部及饰瓷-核瓷界面缺陷催生裂纹造成饰瓷崩裂是双层全瓷冠断裂的主要模式。结论：饰瓷对磨牙e.max双层全瓷冠断裂强度和断裂类型均有影响;饰瓷内部及饰瓷-核瓷界面缺陷是全瓷冠断裂的主要原因,提高饰瓷断裂强度及减少界面缺陷可减少因崩瓷造成的修复体失败。     

BLB种植体的临床应用及近期疗效观察

目的：评估BLB种植体的近期临床应用效果。方法：2003年2月-2005年12月，在北京通州区潞河医院口腔科用BLB种植体进行延期种植，共47枚，采用一期埋入、二期暴露的潜入式方法，全部为金属烤瓷冠修复，临床随诊观察半年至3年。结果：随诊期间无一例种植体脱落，4例因中央螺丝松动致修复体松动，2例发生种植体周围炎；种植体周围牙槽骨水平吸收小于0．2mm／年。结论：BLB种植体适合于常见牙列缺损的延期种植修复，近期疗效可靠     

无口腔保健干预牙菌斑液成分的研究

目的 研究长期无口腔保健干预的牙菌斑液粘代谢规律及其致龋力。方法 选择长期不刷牙者４３人,分为无龋组２７人,高龋组１６人,采集１０％蔗糖漱口前后的菌斑,检测菌斑提取液的ｐＨ值、有机酸和无机离子的浓度。结果 糖漱口后,长期菌斑提取注的ｐＨ值,、铵离子浓度降低,乳酸、甲酸升高,与禁食后新形成菌斑的糖代谢规律一致。但糖漱口前后两组菌斑提取液中的单一成分差异均无显著性。结论 长期菌斑与短期菌斑的糖代谢规律     

钛修复体的口腔生物摩擦学特性研究

目的　探讨牙用钛金属与天然牙的生物摩擦学特性 ,供临床应用参考。方法　在改进后的高精度自控微动实验台上 ,对牙用钛金属TA2与天然牙组成的摩擦副进行人工唾液润滑工况下的摩擦磨损实验。采用计算机控制、动态跟踪实验 ,显微硬度仪、轮廓仪、光镜、激光共聚焦显微镜、扫描电镜与X线衍射能谱仪等测试手段综合分析研究。结果　天然牙的动态摩擦系数为一长“S”形曲线 ;钛对天然牙的磨损过程表现为牙体组织的微切削和组织变性 ;磨损量 :纯钛 /天然牙为 (2 0 33±2 86 ) μm ,纯钛 /纯钛为 (38 0 0± 5 88) μm ,二者间的差异有显著性 (P <0 0 5 )。 结论　天然牙摩擦学性能优良 ,与纯钛的耐磨性匹配 ;咀嚼过程中 ,应该避免较大的咬合力和口腔副功能 ;选择牙科材料时 ,应考虑到材料的耐磨性     

The Influence of Precondensation Mercury Content and Mulling on the Transverse Strength of Amalgams Condensed After a Delay

The purpose of this study was to investigate the influence of changing the precondensation mercury content (initial mercury content) on the final strength of amalgams when the condensation was delayed. Another purpose was to study the effect on the transverse strength of mulling the amalgam mix after the delay. The material consisted of ten different brands of alloy. Three different alloy-mercury ratios were used with each alloy brand; Mix I about 50% Hg, Mix II about 54% Hg and Mix III about 59% Hg. Rectangular amalgam test pieces, measuring 2 × 2 × 12 mm, were condensed after a 5 minutes delay by hand using a load of about 17 kg/cm². The transverse strength test was performed after one week using three point loading. The five minutes delay of the condensation reduced the strength of the amalgams by 1 to 42 per cent depending on the brand of alloy and precondensation mercury content. The three preamalgamated amalgams were affected less by the delay than the other amalgams. Increasing the precondensation mercury content reduced the effect of the delay on the final strength. The «mulling» of the amalgam mix also decreased the effect of the delay. It was concluded that a moderate excess of initial mercury gives the dentist a longer condensing time thus allowing him to perform the condensing procedure with care.     

口腔健康宣教对拔牙患者牙科焦虑心理的作用

目的 评价口腔健康宣教能否作为预防拔牙患者牙科焦虑心理有效方法.方法 实验组和对照组各40例拔牙患者在术前30分钟、术前2分钟应用牙科焦虑量表(MDAS)测评焦虑程度,两次测评之间实验组患者接受口腔健康宣教.结果 实验组术前2分钟的焦虑程度显著性低于术前30分钟(P＜0.05),同时也显著低于对照组术前2分钟(P＜0.01),两组术前30分钟焦虑程度无显著性差异.结论 口腔健康宣教能显著减轻拔牙患者术前焦虑.     

下颌第一磨牙种植固定桥的受载分析

目的 观察下颌第一磨牙种植固定桥的位移和应力分布规律。方法 采用了三维有限元法进行受载分析。结果 发现第二双尖牙的最大位移值较大;由于固定桥的支架作用,垂直分散载荷下天然基牙和种植基牙的位移均值之间差异无显著性。基牙颈部为应力集中区,第二双尖牙根尖的应力较小。集中载荷加于基牙时,位移和应力值明显增加。结论 提示应注意末端种植基牙的载荷和咬合状态,该设计是临床可使用的特殊固定桥。     

Histologic studies on osseointegration: Soft tissues response to implant surfaces and components. A review

It is important to clarify the potential response of different types of cells to different implant materials and topographies. Thus, in vitro studies are performed using cell cultures, in order to evaluate, among other characteristics, the morphology, orientation, proliferation and adhesion of the cells. Histology evaluation are performed in animals or humans to describe the physiological response to different surfaces.     

四种树脂粘接剂与牙釉质和牙本质粘接性能的比较

目的 评价4种树脂粘接剂与牙釉质和牙本质的粘接强度以及粘接界面微观形态,以期为临床应用提供依据.方法 选取24颗新鲜拔除的无龋坏人磨牙,每颗牙制取牙釉质和牙本质试件各2片,均分为4组,每组牙釉质和牙本质试件各12片.选用4种树脂粘接剂(A组:PanaviaTMF;B组:RelyXTM ARC;C组:RelyXTM Unicem;D组:ClearfilTM SA Cement)进行粘接处理后,在扫描电镜(SEM)下观察粘接界面,并测试粘接强度.结果 B组牙釉质粘接强度[(29.38±6.28)MPa]高于D组[(27.25±7.03)MPa],但两者差异无统计学意义(P＞0.05),两者均显著高于A组[(22.92±7.13)MPa]和C组[(10.92±3.41)MPa,P＜0.05].B组牙本质粘接强度[(27.28±6.79)MPa]最高,随后依次为A组[(14.23±6.39)MPa]、D组[(10.09±3.26)MPa]和C组[(6.43±1.60)MPa],各组间差异均有统计学意义(P＜0.05).B组牙釉质粘接界面可见树脂突,A、B组牙本质粘接界面可见树脂突.结论 四种树脂粘接剂表现出不同的牙釉质、牙本质粘接性能.

Abstract：

Objective To evaluate the dentin and enamel bonding strength and resin-dentin interfaces of four resin cements. Methods Twenty-four sound freshly extracted molars were sectioned with low-speed saw under running water. Two mesial-distal enamel disc and two buccal-lingual dentin discs were sectioned from each molar. Four resin cements( A group: PanaviaTM F; B group: RelyXTM ARC; C group:RelyXTM Unicem; D group: ClearfilTM SA Cement) were applied to the surface of these enamel and dentin discs according to manufacturers' guidance. The bonded specimen were prepared for shear bond strength test and sectioned occluso-gingivally into two slabs for scanning electron microscopy(SEM) observation. Results The bonding strength between resin and enamel in B group[ (29. 38 ±6. 28) MPa] was higher than that in D group[ (27.25 ± 7.03) MPa], and both of them were significantly higher than those in A [ ( 22.92 ±7. 13) MPa] and C group [ ( 10.92 ± 3.41 ) MPa] ( P ＜ 0.05 ). The highest dentin bonding strength was shown in B group [ ( 27.28 ± 6. 79 ) MPa ], followed by A [ ( 14. 23 ± 6. 39 ) MPa ], D [ ( 10.09 ±3.26) MPa] and C group[ (6. 43 ± 1.60) MPa, P ＜ 0.05 ]. Conclusions The four resin cements have different enamel or dentin bonding properties.     

IPS Empress 全瓷贴面颜色效果的初步研究

目的 评价IPS Empress全瓷贴面的遮色性能及其颜色的匹配性和稳定性。方法 18例患者采用IPS Empress全瓷材料制作贴面86个，分为四环素牙(A组)和非四环素牙(B组)2组进行观察，分别以所选比色板和相邻正常天然牙(C组)为对照。用ShadeEyeNCC电脑比色仪分别测量贴面修复前、后牙齿L^*a^*b^*值；以粘结后为基点，分别在0．5年、1年、2年后测量贴面的L^*a^*b^*值。用SPSS10．0软件分析修复前、后牙齿颜色的变化情况，贴面颜色与天然牙颜色的匹配性及修复后贴面颜色的稳定性。结果 贴面修复前、后，A、B2组牙齿颜色L^*a^*b^*值的差异均有显著性，色差值分别为5．01和4．15。A组贴面颜色与所选比色板的色差值为2．45；与基点相比，在修复2年后贴面的明度值有显著降低，但色差值的差异无显著性。B组贴面颜色与相邻天然牙的色差值为0．22，修复后贴面颜色无显著改变。结论 IPS Empress全瓷贴面对非四环素牙具有良好的遮色效果及颜色匹配性、稳定性；对四环素牙有一定的遮色能力，但其颜色与比色板不能完全匹配，修复后明度值有所降低，对其颜色效果尚需进一步观察。     

The interplay of saliva,erosion and attrition on enamel and dentine

PurposeThis investigation aimed to compare the protective role of saliva against erosion and attrition challenges.MethodPolished enamel and dentine samples (n = 160) were prepared and randomly assigned to either the saliva or saliva-free group (n = 40 enamel and n = 40 dentine/group). Within each subgroup, they were allocated to four subgroups: negative control (deionized water exposure 10 min), erosion (0.3% citric acid 10 min), attrition (120 S of 300 g force), or combined erosion/attrition (0.3% citric acid 10 min then 120 S of 300 g force). Experimental cycles were repeated three times. Data analysis was performed using SPSS.ResultsThe mean and standard deviation (SD) of step heights produced by the attrition and erosion/attrition groups in enamel in the saliva-free group were 5.6 µm (2.4) and 13.4 µm (2.8), respectively, while they were 2.4 µm (3.8) and 12.9 µm (3.5) in the saliva group, with no significant difference between the saliva and saliva-free groups. For dentine, the corresponding step heights were 25.2 µm (5.5) and 35.9 µm (7.9) for the saliva-free group, but 21.8 µm (5.3) and 27.3 µm (6.4) for the saliva group (p < 0.001).ConclusionThere was a trend that saliva decreased wear, but this was only statistically significant for erosion/attrition dentine wear.     

Cariostatic effect of fluoride-containing restorative materials associated with fluoride gels on root dentin

Secondary caries is still the main cause of restoration replacement, especially on the root surface

Objective

This in vitro study evaluated the cariostatic effects of fluoride-containing restorative materials associated with fluoride gels, on root dentin.

Materials and Methods

A randomized complete block design was used to test the effects of the restorative systems, fluoride regimes and the interactions among them at different distances from restoration margins. Standardized cavities were prepared on 240 bovine root specimens and randomly assigned to 15 groups of treatments (n=16). Cavities were filled with the following restorative materials: Ketac-Fil (3M-ESPE); Vitremer (3M-ESPE); Dyract/Prime & Bond NT (Dentsply); Charisma/Gluma One Bond (Heraeus Kulzer) and the control, Z250/Single Bond (3M-ESPE). The specimens were subjected to a pH-cycling model designed to simulate highcaries activity. During the cycles, 1.23% acidulated phosphate fluoride, 2.0% neutral sodium fluoride or deionized/distilled water (control) was applied to the specimens for 4 min. The surface Knoop microhardness test was performed before (KHN_i) and after (KHN_f) the pH cycles at 100, 200 and 300 mm from the margins. Dentin microhardness loss was represented by the difference in initial and final values (KHN_i - KHN_f). Data were analyzed by Friedman''s and Wilcoxon''s tests, ANOVA and Tukey''s test (α=5%).

Results

The interaction of restorative systems and topical treatments was not significant (p=0.102). Dentin microhardness loss was lowest closer to the restoration. Ketac-fil presented the highest cariostatic effect. Vitremer presented a moderate effect, while Dyract and Charisma did not differ from the control, Z250. The effects of neutral and acidulated fluoride gels were similar to each other and higher than the control.

Conclusion

Conventional and resin-modified glass ionomer cements as well as neutral and acidulated fluoride gels inhibit the progression of artificial caries adjacent to restorations. The associated effect of fluoride-containing restorative materials and gels could not be demonstrated.     

磁性固位体耐蚀性能的研究

目的研究3种钕铁硼磁性固位体的外包裹容器不锈钢的耐腐蚀性能.方法将3种磁性固位体分别浸泡于人工唾液中,温度为36.5℃,时间为6个月.实验方法包括恒电位法极化曲线试验与浸泡试验,分析材料的耐腐蚀能力.结果极化曲线中,国产衔铁的自腐蚀电流密度为7.015μA/cm2,国产磁体为0.119μA/cm2.浸泡试验中,国产衔铁的腐蚀速度为3.67×10-5mg/cm2*h,国产磁体的腐蚀速度为1.77×10-5mg/cm2*h.国产磁性固位体与进口同类材料相比,其耐腐蚀性能差异无显著性.结论人工唾液环境会使3种磁性固位体的耐腐蚀能力降低,进而缩短其寿命.     

白榴石微晶化增强牙科玻璃陶瓷的热处理温度制度的研究

目的 探索白榴石微晶化的热处理温度制度。方法 根据白榴石的化学式和K20-Na2O-Al2O3-SiO2系统相图制定原材料配比，在预设的熔融、成核、析晶温度中选择最佳温度；利用偏振光显微镜和x射线衍射分析仪观察样品的形态及显微结构特性。结果 玻璃融熔温度为1600℃，成核温度为1200℃，晶化温度为1500℃；微晶化后的自榴石晶粒约0．8μm，在玻璃基质中分布均匀。结论 按照一定的热处理温度制度。白榴石可以在玻璃中微晶化。     

铸造与冷弯卡环基牙菌斑致龋菌分析

目的 初步探讨可摘局部义齿卡环对基牙健康的影响。方法 对铸造、冷弯卡环可摘局部义齿初截一周前后,基牙菌斑中的主要致龋菌进行分析比较。结果 铸造卡环组初戴一周后,基牙菌斑中粘性放线菌与变形链球菌的百分比分别上升了２．３％和３．８％;冷弯卡环组初戴一周后,上述细菌百分比分别上升了５．９％和３．３％,二者间差异有显著性;铸造卡环组粘性放线菌上升的百分比显著低于冷弯卡环组。结论 可摘局部义齿卡环会增加基牙     

铸模温度对铸钛机械性能及表面反应层结构的影响

钛在高温状态下化学性能活泼，易氧化且与包埋料发生化学反应。我们采用拉伸试验及现代表面分析技术，研究了不同铸模温度对铸钛机械性能及表面反应层结构的影响。结果表明，随着铸模温度升高，铸钛件的抗拉强度、屈服强度增加而延伸率下降，同时，铸钛表面硬化层增厚。用室温铸模铸造时钛铸件表面硬化层厚５０μｍ，用８５０℃铸模铸造时钛铸件表面硬化层厚１２５μｍ。ＳＸｍａｃｒｏ电子探针微区成分分析显示，锆、铝二元素在钛铸件表面扩散深度不随铸模温度增高而加深，但硅元素的扩散则随铸模温度升高而加深。室温铸造时硅元素的扩散深度为３０μｍ，８５０℃铸造时已达９０μｍ。研究结果提示，临床制作铸钛修复体时，必须考虑铸模温度对铸件质量的影响。     

正畸治疗后牙弓稳定性的追踪研究

目的：探讨正畸治疗后牙弓的稳定性。方法：对正畸治疗后2－8年74例错He畸形患者治疗前后及保持后模型进行弓牙测量。结果：保持后，上基骨宽度较治疗后增加2．11％；上下6－6宽度、下基骨宽度没有显著性变化，其余均出现明显减少；减少百分率最大依次为上下3－3长度（7．79％，7．56％）、上下基骨长度（7．14％，5．12％）、上下牙弓长度（3．91％，3．37％）、上下3－3宽度（2．28％，3．30％）。结论：保持停止后，上下牙弓长度、基骨长度及3－3宽度有不断减少和3－3长度有回复治疗前水平的倾向，而6－6宽度较稳定。     

Effect of veneering material on the deformation suffered by implant-supported fixed prosthesis framework

Knowing how stresses are dissipated on the fixed implant-supported complex allows adequate treatment planning and better choice of the materials used for prosthesis fabrication.

Objectives

The aim of this study was to evaluate the deformation suffered by cantilevered implant-supported fixed prostheses frameworks cast in silver-palladium alloy and coated with two occlusal veneering materials: acrylic resin or porcelain.

Material and Methods

Two strain gauges were bonded to the inferior surface of the silver-palladium framework and two other were bonded to the occlusal surface of the prosthesis framework covered with ceramic and acrylic resin on each of its two halves. The framework was fixed to a metallic master model and a 35.2 N compression force was applied to the cantilever at 10, 15 and 20 mm from the most distal implant. The measurements of deformation by compression and tension were obtained. The statistical 2-way ANOVA test was used for individual analysis of the experiment variables and the Tukey test was used for the interrelation between all the variables (material and distance of force application).

Results

The results showed that both variables had influence on the studied factors (deformation by compression and tension).

Conclusion

The ceramic coating provided greater rigidity to the assembly and therefore less distortion compared with the uncoated framework and with the resin-coated framework. The cantilever arm length also influenced the prosthesis rigidity, causing higher deformation the farther the load was applied from the last implant.