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1.
2.
激光焊接间距对牙科铸造纯钛性能影响的实验研究   总被引:2,自引:0,他引:2  
目的:研究激光焊接铸造纯钛时不同的焊接间距对纯钛性能的影响。方法:将铸造钛试样按照焊接间距的大小分为4组:0.00、0.25、0.50、1.00mm组,肉眼、扫描电镜观察焊缝区外观,测试焊件的抗拉强度,整铸件为对照组。结果:各试验组焊缝区显示全层焊透、无明显气孔等焊接缺陷,断口电镜显示为延展性(韧窝)与脆性(气孔、裂纹)共存的形貌。各实验组与对照组间抗拉强度方差分析结果显示差异无显著性(P>0.05)。结论:不同的焊接间距对铸钛的机械性能无明显影响。  相似文献   
3.
激光照射对牙髓细胞形态的影响   总被引:5,自引:0,他引:5  
陈柯  藏燕 《口腔医学》1998,18(4):173-175
不同的激光能量可以产生不同的生物效应.本文应用扫描电镜、倒置显微镜观察不同能量、不同频率的激光能量设置对牙髓细胞形态的影响,结果表明:100mj20Hz、60mj40Hz、40mj50Hz以上的能量设置可使牙髓细胞产生裂纹、结构模糊.结论:Nd:YAG激光的能量、频率均可影响牙髓细胞形态  相似文献   
4.
The role of oxygen in the regulation of the pulpal microcirculation is unknown. This investigation is aimed to measure tissue oxygen tension and blood-flow changes in the pulp of rat lower incisors during graded systemic hyperoxia, and to determine the response of the pulpal vasculature to various oxygen tensions. Twenty-four Sprague-Dawley rats were anaesthetized and artificially ventilated with the appropriate gas mixture. Recessed oxygen-sensitive microelectrodes were used to measure pulpal tissue oxygen tension via a small access cavity filled with saline on the labial surface of the incisor. A laser Doppler flowmeter was used to record pulpal blood-flow. Inspired oxygen was increased stepwise from 20 to 100% in 20% steps. Systemic blood-gas concentrations were measured at each step. Systemic arterial oxygen tension at 100% oxygen ventilation reached 481.2 +/- 30.7% of the baseline at 20% oxygen breathing (n=21). Pulpal tissue oxygen tension did not change significantly whereas pulpal blood-flow fell dose-dependently to 74.6 +/- 5.0% at 100% oxygen ventilation (n=21). Systemic hyperoxia, therefore, induces a significant reduction in pulpal blood-flow whereas pulpal tissue oxygen tension remains relatively stable, indicating an oxygen-dependent local regulatory mechanism.  相似文献   
5.
Er, Cr: YSGG激光与氟化物联合应用对牙体硬组织脱矿的影响   总被引:1,自引:0,他引:1  
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。  相似文献   
6.
上颌半口义齿金属基托的计算机辅助设计   总被引:5,自引:0,他引:5  
目的 :在自行重建无牙颌三维数据模型的基础上设计上颌半口义齿金属基托数字模型。方法 :采用数控铣床及新型层析数据采集系统 ,通过对标准无牙颌模型的层切 ,二维轮廓数据获取及计算 ,重建无牙颌模型 ,在此数据基础上 ,通过SURFACER软件 ,设计上颌半口义齿金属基托。结果 :获得无牙颌三维数据及上颌金属基托的数据文件。结论 :通过新型层析系统可以实现对无牙颌三维建模 ;在此基础上设计的三维数字基托可为进一步激光立体成形制作奠定基础。  相似文献   
7.
The clasp arms are fatigued by wearing a denture, by taking it off, and by occlusion. We routinely use laser irradiation to harden only the surface layer of clasp arms consisting of gold-silver-palladium alloy partially hardened by laser irradiation to resist fatigue. Recently we tested laser irradiation on silver-palladium-copper alloys, and obtained the following results:
1)  The surface hardness of the mother alloy No. 12 (52.5Ag−12.5Pd−35.0Cu alloy (wt%)) was 299.7HV after laser irradiation, 155% harder than after casting.
2)  The surface hardness of the 18Au−40Ag−20Pd−22Cu alloy (wt%) was 235.0HV after laser irradiation, 91% harder than after being softened, 15% harder than that after being hardened. The brightness (L*) of the specimens immersed in 0.1% sodium sulfide solution at 37°C for 3 days was 73.07.
3)  The surface hardness of the 12Au−40Ag−20Pd−24Cu−4Zn alloy (wt %) was 270.0HV after laser irradiation, 165% harder than after being softened, and 78% harder than that after being hardened.
  相似文献   
8.
BACKGROUND: The aim of this study was to evaluate the influence of zero-value subtraction on the performance of two laser fluorescence (LF) devices developed to detect occlusal caries. METHODS: The authors selected 119 permanent molars. Two examiners assessed three areas (cuspal, middle and cervical) of both mesial and distal portions of the buccal surface and one occlusal site using an LF device and an LF pen. For each tooth, the authors subtracted the value measured in the cuspal, middle and cervical areas in the buccal surface from the value measured in the respective occlusal site. RESULTS: The authors observed differences among the readings for both devices in the cuspal, middle and cervical areas in the buccal surface as well as differences for both devices with and without the zero-value subtraction in the occlusal surface. When the authors did not perform the zero-value subtraction, they found statistically significant differences for sensitivity and accuracy for the LF device. When this was done with the LF pen, specificity increased and sensitivity decreased significantly. CONCLUSIONS: For the LF device, the zero-value subtraction decreased the sensitivity. For this reason, the authors concluded that clinicians can obtain measures with the LF device effectively without using zero-value subtraction. For the LF pen, however, the absence of the zero-value subtraction changed both the sensitivity and specificity, and so the authors concluded that clinicians should not eliminate this step from the procedure. CLINICAL IMPLICATIONS: When using the LF device, clinicians might not need to perform the zero-value subtraction; however, for the LF pen, clinicians should do so.  相似文献   
9.
静态拉伸应变对人牙周膜成纤维细胞的影响   总被引:4,自引:2,他引:4  
目的:研究人牙周膜成纤维细胞(PDLF)在机械拉伸应变作用下,细胞和细胞核投影面积及其细胞骨架的改变情况,探讨PDLF的形态、功能和应变之间的关系。方法:采用自制的细胞体外静态机械加载装置用不同的拉伸应变量加力于细胞上,通过激光扫描共聚焦显微镜观察细胞骨架的形态及其改变情况,并进行统计分析。结果:在8%、12%、16%力值组,细胞和细胞核投影面积随着加力时间和力值的增加而每天递增,肌动蛋白纤维也随之逐渐增粗,排列更有规律;而在20%力值组,其结果则反之。结论:静态拉伸应变可影响牙周膜成纤维细胞的骨架。  相似文献   
10.
The purpose of this study was to evaluate the microcirculation in subjects with moderate gingivitis, periodontitis, and healthy gingiva. Sixty adult volunteers with clinically healthy gingiva, moderate gingivitis, and periodontitis (20 subjects each) participated in this study. The ages of the research samples ranged from 20 to 35 years. Gingival health was evaluated by using the qualitative plaque index, gingival index, gingival bleeding index, tooth mobility, probing pocket depth, clinical attachment level, and laser Doppler flowmetry (LDF) on six maxillary anterior teeth. LDF data were recorded at the facial aspect of free gingivae, interdental gingivae, attached gingivae, and alveolar mucosae on six maxillary anterior teeth, utilizing an acrylic stent to stabilize the probe. This technique was then modified to circumvent contamination by saliva and gingival exudate. When results were compared at similar sites in each patient within a trial group, there were significant differences in blood flow measurements at all the sites examined between moderate gingivitis and periodontitis when compared with measurements in healthy human gingiva. However, blood flow measurements within the same group showed significant differences at every site, at P < 0.01. Received: December 17, 2001 / Accepted: January 23, 2002  相似文献   
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