强化氟水门汀物理性能及释放氟研究

目的：探讨市售磷酸锌水门汀、聚羧酸锌水门汀、玻璃离子水门汀粉末中添加复合氟化物制剂（Co-F）对其物理性能及氟释放的影响。方法：在上述各水门汀粉末中按质量分数添加复合氟化物0％～20％，调和水门汀测定其固化时间、抗压强度、氟离子释放量。结果：添加适量复合氟化物对水门汀的抗压强度没有影响，添加复合氟化物的玻璃离子水门汀释放氟量增加，添加复合氟化物的聚羧酸锌水门汀、磷酸锌水门汀也能够释放氟离子。添加复合氟化物对聚羧酸锌水门汀及玻璃离子水门汀固化时间有明显影响。结论：强化氟水门汀通过释放氟，使充填材料附近牙齿发挥防治继发龋作用，基于此观点强化氟水门汀是牙科应用有希望的材料。     

氟化微量元素制剂对牙釉质脱钙影响的实验研究

目的：比较氟化微量元素制剂对酸蚀下牙釉质脱钙的抑制作用，为找到低毒高效的防龋制剂提供依据。方法：牙釉质样本分别经含相同氟浓度的5种氟化微量元素制剂（氟化锌、氟化镧、氟化亚锡、氟化锶、氟钼酸铵）及氟化钠处理后酸蚀，甲基麝香草酚蓝法检测酸蚀液中钙浓度的变化。结果：氟化钠及氟化微量元素均有抑制酸蚀下釉质脱钙的作用（p〈0．05）；其中氟化亚锡作用最为明显，与氟化钠等比较有显著性差异（p〈0．01）。结论：锡可明显提高氟化物的防龋生物活性，在抑龋防龋方面，氟化微量元素有广泛的应用前景。     

氟化微量元素制剂对牙釉质显微硬度变化影响的实验研究

目的：比较氟化微量元素制剂对酸蚀下牙釉质显微硬度降低的抑制作用，为找到低毒高效的防龋制剂提供依据。方法：牙釉质样本分别经含相同氟浓度的5种氟化微量元素制剂（氟化锌、氟化镧、氟化亚锡、氟化锶、氟钼酸铵）及氟化钠处理后酸蚀，MH-5型显微硬度计测量牙釉质酸蚀前后显微硬度，观察牙釉质显微硬度的变化。结果：氟化钠、氟化锌、氟化锶、氟化亚锡、氟化镧、氟钼酸铵均有抑制酸蚀下釉质显微硬度降低的作用，其中氟化亚锡对酸蚀下牙釉质显微硬度降低的抑制作用明显强于氟化钠（P〈0．05）。结论：含锡氟化物可显著提高牙釉质的抗酸能力，在抑龋防龋方面，氟化微量元素拥有广泛的应用前景。     

氟化微量元素制剂对变形链球菌产酸影响的实验研究

目的比较氟化微量元素制剂对变形链球菌产酸及乳酸脱氢酶活性的抑制作用。方法含相同氟浓度的5种氟化微量元素制剂(氟化锌、氟化镧、氟化亚锡、氟化锶、氟钼酸铵)和氟化钠分别加入到含变形链球菌菌悬液的BHI培养基中,采用二硝基苯肼法并利用720A型离子仪,观察变形链球菌乳酸脱氢酶活性及培养液pH的变化。结果氟化锌、氟化亚锡对变形链球菌乳酸脱氢酶活性的抑制作用强于氟化钠(P<0.01);氟化锌、氟化亚锡抑制变形链球菌产酸的作用亦强于氟化钠(P<0.05)。结论锡、锌等微量元素可提高氟化物的防龋生物活性。     

氟化微量元素对变形链球菌葡萄糖基转移酶影响的比较研究

目的比较氟化微量元素制剂对变形链球菌葡萄糖基转移酶活性的抑制作用。方法含相同氟浓度的5种氟化微量元素制剂(氟化锌、氟化镧、氟化亚锡、氟化锶、氟钼酸铵)和氟化钠分别加入到含变形链球菌悬液的TYC培养基中,采用Ne-son-Somogyi法,观察变形链球菌葡萄糖基转移酶活性的变化。结果氟化钠、氟化锌、氟化锶、氟化亚锡、氟化镧、氟钼酸铵制剂均有抑制变形链球菌ATCC25175葡萄糖基转移酶活性的作用,其中尤以氟化亚锡抑制作用最强(P<0.05)。结论锡可提高氟化物的防龋生物活性,在抑菌防龋方面,氟化微量元素有广泛的应用前景。     

氟化微量元素制剂对变形链球菌抑制作用的实验研究

目的 :比较氟化微量元素制剂对变形链球菌的抑制作用 ,为找到低毒高效的抑龋制剂提供依据。方法 :五种氟化微量元素制剂 (氟化锌、氟化镧、氟化亚锡、氟化锶、氟钼酸铵 )和氟化钠分别以不同浓度加入含变形链球菌悬液的BHI培养基中 ,采用厌氧菌连续培养技术 ,观察菌落计数变化。结果 :氟化锌、氟化亚锡的抑菌强度在各浓度时均最强 (p <0 .0 5 ) ,且含较低氟浓度的氟化锌、氟化亚锡制剂比含较高氟浓度的氟化钠制剂抑菌强度更高。结论 :锡、锌等微量元素可明显提高氟化物的抑菌生物活性 ,在抑菌防龋方面 ,氟化微量元素具有广泛的应用前景     

氟纳米羟基磷灰石对早期根面龋再矿化效果的实验研究

目的:通过实验研究氟纳米羟基磷灰石对早期根面龋的再矿化效果,并与纳米羟基磷灰石、氟化泡沫和氟化钠溶液的再矿化效果进行比较。方法:制备人工早期根面龋模型41个,使用扫描电镜观察脱矿后的根面的表面形态及用数显显微硬度计测量脱矿后根面的显微硬度。将40个根面龋模型随机分为5组:空白对照组、氟纳米羟基磷灰石组、纳米羟基磷灰石组、氟化泡沫组和氟化钠溶液组。每组使用其相应的试剂处理,经7 d pH循环及20d再矿化处理,于扫描电镜观察和显微硬度计测量。统计采用单因素方差分析并作LSD-t检验,实验前后采用单样本t检验。结果:氟纳米羟基磷灰石组扫描电镜观察根表面有大量晶粒沉积且平滑,其硬度值与脱矿后和其他组硬度值比较,有统计学意义(P<0.05)。结论:氟纳米羟基磷灰石对早期根面龋有较好的再矿化效果。     

氟化物涂膜后唾液氟浓度的变化

目的 观察并比较使用氟化物涂膜及氟化钠溶液后，唾液中氟离子浓度的变化。方法 选取20例5岁儿童。随机分为氟化钠涂膜组和氟化钠溶液组，每组10例。使用氟化物前及使用后0．25h、0．5h、lh、2h、6h、12h、24h分别留取非刺激性全唾液，唾液离心后用氟离子选择电极法测定唾液中的氟离子浓度。结果 使用氟化钠涂膜后0．25h、0．5h、lh、2h、6h，唾液中氟离子浓度高于用氟前；使用后0．5—6h，唾液中氟离子浓度高于使用氟化钠溶液组。结论 氟化钠涂膜与氟化钠溶液相比。能延长氟化物和牙釉质接触的时间和浓度。     

表面活性剂对氟一釉质相互作用影响的体外研究

目的探索表面活性剂影响氟在釉质中渗透的机理。方法采用合或不合表面活性剂的氟化钠溶液处理牛釉质块5分钟，然后用改良酸蚀法研究釉质表层20um即刻渗入的氟化物总量和氛磷灰石形成量，及24小时后氮磷灰石形成量。结果阳离子表面活性剂ZonylFSC能在使用后立刻促进氟的渗透，而阴离子表面活性剂则不能；但是，延长反应时间24小时后，两种表面活性剂都增加了氟磷灰石的形成。结论表面活性剂影响氟一釉质界面作用与其所带的电荷有关。     

氟钼酸铵溶液提高根部牙本质抗酸性机理探讨

目的：探讨氟钼酸铵溶液提高根部牙本质抗酸性的机理。方法：用X光衍射、等离子发射光谱、光量法对10%氟钼酸铵溶液、2.86%氟钼酸铵溶液、2%氟化钠溶液、7.26%钼酸铵溶液及去离子水处理过的根部等量牙本质粉进行产物分析；并用氟电极测定产物中氟的含量；钙电极测定用乳酸溶解出的产物中钙的含量。结果：氟钼酸铵溶液处理过的牙本质粉中有氟化钙、钼酸钙生成，其中碳酸磷灰石的含量有所减少，牙本质抗酸溶液性得到提高。结论：氟钼酸铵溶液可能通过促进根表面对氟吸收生成难溶性的盐类；降低易溶解的碳酸磷灰石的含量等作用提高根表面的抗酸溶解性。     

Dental specialty,career preferences and their influencing factors among final year dental students in Saudi Arabia

Objective

The purpose of this study was to investigate evolving trends in dental post graduate specialty preferences and career aspirations among final year dental students in Saudi Arabia.

Physicochemical and mechanical characterization of a fiber-reinforced composite used as frameworks of implant-supported prostheses

ObjectivesTo characterize the physicochemical and mechanical properties of a milled fiber-reinforced composite (FRC) for implant-supported fixed dental prostheses (FDPs).MethodsFor FRC characterization, scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), X-ray diffraction, Fourier-transformed infrared spectrometry, simultaneous thermogravimetric analysis and differential scanning calorimetry were performed. For fatigue testing, 3-unit FRC frameworks were fabricated with conventional (9 mm² connector area) and modified designs (12 mm² connector area and 2.5 mm-height lingual extension). A hybrid resin composite was veneered onto the frameworks. FDPs were subjected to step-stress accelerated-life fatigue testing until fracture or suspension. Use level probability Weibull curves at 300 N were plotted and the reliability for 100,000 cycles at 300, 600 and 800 N was calculated. Fractographic analysis was performed by stereomicroscope and SEM.ResultsThe FRC consisted of an epoxy resin (∼25%) matrix reinforced with inorganic particles and glass fibers (∼75%). Multi-layer continuous regular-geometry fibers were densely arranged in a parallel and bidirectional fashion in the resin matrix. Fatigue analysis demonstrated high probability of survival (99%) for FDPs at 300 N, irrespective of framework design. Conventional FDPs showed a progressive decrease in the reliability at 600 (84%) and 800 N (19%), whereas modified FDPs reliability significantly reduced only at 800 N (75%). The chief failure modes for FRC FDPs were cohesive fracture of the veneering composite on lower loads and adhesive fracture of the veneering composite at higher loads.SignificanceMilled epoxy resin matrix reinforced with glass fibers composite resulted in high probability of survival in the implant-supported prosthesis scenario.     

牙菌斑液对牙釉质矿物的饱和程度与龋活动性的关系

为了解菌斑液对牙齿矿物饱和度随糖漱口的变化，以及与龋活动性的关系，作者选择２２例年龄相同的大学生，按龋齿情况，将其分为３组。第１组无龋（无龋组），第２组ＤＭＦＳ大于１０但无活动性龋（普通龋组），第３组ＤＭＦＳ大于１０且有活动性龋（活动性龋组），测定各受试者在静止时、用蔗糖液漱口后３ｍｉｎ和７ｍｉｎ时的菌斑液中有机酸、ｐＨ值、钙离子活度（有效离子浓度）和无机成分的含量，并计算对于釉质矿物的饱和度。结果表明，糖漱口之后菌斑液乳酸浓度升高、ｐＨ值降低、总钙和离子钙浓度增加。活动性龋组的菌斑液在糖漱口后ｐＨ值和饱和度降低的幅度明显大于无龋组和普通龋组。结论：牙菌斑液对牙齿矿物的饱和度是指示个体接受致龋食物后牙齿脱矿倾向的敏感指标。     

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。     

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.     

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     

INFLUENCE OF MICROLEAKAGE,SURFACE ROUGHNESS AND BIOFILM CONTROL ON SECONDARY CARIES FORMATION AROUND COMPOSITE RESIN RESTORATIONS: AN IN SITU EVALUATION

This study was carried out to evaluate in situ the influence of microleakage, surface roughness and biofilm control on caries formation around composite resin restorations. During 28 days, 12 volunteers wore palatal devices containing bovine enamel slabs restored with composite resin. Restorations were made without leakage, when the adhesive system was applied, or with leakage, when adhesive system was omitted. Half of the restorations in each group were finished and the remaining were finished and polished. In one side of the palatal device, biofilm was left to accumulate over the restored slabs, and in the other side dental slabs were brushed, to allow biofilm removal. There was an extraoral application of 20% sucrose solution (8x/day) over the enamel slabs. The formation of caries lesions (white spots) was evaluated by visual inspection under stereomicroscopy. Additionally, the dental slabs were sectioned and observed under polarized light microscopy. Data were submitted to Kruskal-Wallis test and Spearman''s correlation test at 5% significance level. Polishing and bonding were not significant factors regarding white spot formation (p>0.05). Biofilm control (brushing) was associated with reduction of caries formation close to the restorations (p<0.01). Polarized light microscopy confirmed the visual inspection findings. These results suggest that while microleakage and surface roughness did not influence caries lesion formation, biofilm control may prevent the enamel demineralization.     

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.