The effectiveness of two sterilization methods when different precleaning techniques are employed

The effectiveness was investigated of methods for the preparation of dental handpieces prior to sterilization procedures utilizing ethylene oxide (ETO) gas. The handpieces were cleaned using either a forced-air purging unit (group 1) or by flushing with air and water from the dental unit (group 2). They were inoculated with either Bacillus subtilis or Streptococcus mutans. After exposure to either steam or ETO gas, the handpieces were flushed with saline and the viability of recovered bacteria assessed. No viable bacteria were recovered from group 1 handpieces treated with either ETO gas or steam. However, viable S. mutans were recovered from group 2 handpieces following exposure to ETO gas. Thus, the use of a high-pressure forced-air purging unit may be required for the reliable sterilization of dental handpieces by ETO gas, as viable S. mutans could be recovered from untreated handpieces exposed to ETO gas.     

不同自锁托槽系统在牙齿排齐阶段摩擦力的对比实验研究

目的探讨牙齿排齐阶段应用不同的自锁托槽与镍钛丝组合所产生的摩擦力。材料与方法选取临床安氏Ⅰ类中度拥挤不拔牙患者的上颌模型制作Typodont,选用5种自锁托槽作为实验对象,一种普通直丝弓托槽作为对照,应用0.014镍钛圆丝,在右上中切牙处唇向移动1 mm、2 mm、3 mm时,托槽与弓丝间摩擦力的变化,从而探讨自锁托槽系统在牙齿排齐阶段摩擦力的特性。结果排齐阶段,在不同拥挤度情况下,自锁托槽摩擦力低于传统托槽,牙齿拥挤度增加,摩擦力增加,差异显著;5种自锁托槽中DamonMx,Quick,Speed摩擦力更小一些,弓丝被拉伸1mm时Quick与弓丝组合产生的摩擦力最小为119.28克,Smartclip与弓丝组合产生的摩擦力最大为251.05克。结论不同的托槽设计,不同的牙齿拥挤度对摩擦力有影响。     

单晶和多晶陶瓷托槽与金属弓丝摩擦力的对比研究

目的对单晶陶瓷托槽和多晶陶瓷托槽的摩擦力学性能进行初步测试,并与相同槽沟尺寸的金属托槽进行比较。方法使用万能材料力学实验机测试单晶陶瓷托槽、多晶陶瓷托槽及金属托槽与2种金属弓丝在弹力结扎圈结扎下的最大静摩擦力和平均动摩擦力。结果单晶及多晶陶瓷托槽与两种弓丝结合产生的摩擦力较金属托槽大,多晶陶瓷托槽的摩擦力较单晶陶瓷托槽的摩擦力大(P<0.05)。结论单晶陶瓷托槽与金属弓丝的摩擦力较多晶陶瓷托槽小,但较金属托槽大。     

Long-term results and possible complications when subperiostal implants are used in patients with considerable jaw atrophy

Analysis of the results of subperiostal implants use in 130 patients with considerable atrophy of jaws bone tissues is presented. Early and delayed complications occurring in patients after subperiostal implants use are detailed.     

局麻药与奥硝唑-甲磺酸培氟沙星联用的抑菌效果

目的：探讨口腔科4种常用局麻药分别与奥硝唑-甲磺酸培氟沙星联合的抑菌效果。方法：采用琼脂纸片扩散法，检测局麻药以0、5％、10％、15％、20％体积比例与奥硝唑-甲磺酸培氟沙星液混合制备的药敏纸片所形成的抑菌环直径变化（每张滤纸片所含奥硝唑-甲磺酸培氟沙星纯药物总量一致）。结果：所有药敏纸片形成的抑菌环相互问无统计学差异（P〉0．05）。结论：4种局麻药的分别与奥硝唑-甲磺酸培氟沙星联合的抑菌效果无影响，可以混合应用。     

Effect on the fit of removable partial denture frameworks when master casts are treated with cyanoacrylate resin

Master casts of improved dental stone were made from irreversible hydrocolloid impressions of a metal model. Half of the master casts were treated with cyanoacrylate resin and half were untreated controls. They were sent to a dental laboratory for framework fabrication. The returned frameworks were examined for acceptability and their completeness of seating was determined. The frameworks fabricated on the treated master casts fit significantly better than the controls. The improved seating may be attributed to an increased surface hardness, increased abrasion resistance, and improved surface morphology, but further study is necessary.     

Evaluation of the effect of MTAD in comparison with EDTA when employed as the final rinse on the shear bond strength of three endodontic sealers to dentine

The purpose of the study was to evaluate the effect of MTAD in comparison with EDTA as a final rinse on the shear bond strength of Kerr, Apexit and AH plus. Dentine surfaces of 135 extracted human non-carious maxillary premolars were divided into three groups (n = 45). Groups I and II were conditioned with 1.3% NaOCl for 20 min, followed by a final rinse of 17% EDTA for 1 min and MTAD for 5 min respectively. Group III was treated with distilled water. Each group was further divided into three subgroups (n = 15). Subgroup 1: Kerr, Subgroup 2: Apexit and Subgroup 3: AH plus. Three-millimetre-long sections of polyethylene tubes were filled with freshly mixed sealer and placed on the dentine surfaces. The bonding between the sealer and dentine surface was evaluated using shear bond testing. The values were statistically evaluated using one way anova followed by Tukey's test. Significant difference was found among the bond strength of the sealers and irrigating regimes. AH plus showed superior bond strength among the tested sealers, when EDTA was employed as the final rinse (P < 0.05). MTAD as a final rinse affected the bond strength of AH plus and Apexit, which were significantly lower than the control group.     

Cyclic loading of implant-supported prostheses: comparison of gaps at the prosthetic-abutment interface when cycled abutments are replaced with as-manufactured abutments

STATEMENT OF PROBLEM: Implant-supported prostheses are mechanically connected to implants. When this connection is a screw joint, it is likely that the fit will be imperfect. Previous studies demonstrate that deformation can occur at the interface between the prosthesis and implant following cyclic loading. This deformation alters the fit of components. If implant connection components, abutments, were to be reoriented or replaced, it is likely that deformed surfaces would no longer approximate each other. Likewise, it is possible that the deformation may deleteriously alter the fit to replacement components. PURPOSE: This study evaluated the changes in prosthesis-implant abutment fit when gold cylinders that have been cyclically loaded are mated to as-manufactured abutments. MATERIAL AND METHODS: Fifteen implant-supported frameworks were fabricated using conventional casting techniques and were cyclically loaded under 3 different loading conditions: anterior region, unilaterally on posterior cantilever, and bilaterally on posterior cantilever. A cyclical load of 200 N was applied to each framework for 200,000 cycles. The abutments and frameworks were returned to the definitive casts for measurements. Linear measurements (microm) of the gap between the prosthetic cylinder and the implant-supported abutment at 4 predetermined reference points were made. The cycled abutments were replaced with as-manufactured abutments, and the gaps were measured at the same reference points. The Mann-Whitney rank-sum test was applied to the 2 sets of data to determine whether significant changes in fit were observed following component replacement (alpha = .05). RESULTS: Although minor changes in component fit were seen, the data failed to show that gaps at the prosthetic-abutment interface of cycled abutments were significantly different from those of as-manufactured abutments. CONCLUSIONS: Within the limitations of this study, differences in the fit between the implant-supported prosthesis and the abutments were not significantly different when abutments worn through loading were replaced with new as-manufactured abutments.