5种灭菌器对牙科手机性能的影响

目的 了解5种灭菌器对牙科手机机械性能的影响情况。方法 用5种灭菌器分别对4把牙科手机进行灭菌200次，每完成10次灭菌全过程检测一遍牙科手机的夹持力和转速。结果 经200次灭菌后20支牙科手机中，1支停转，另有8支转速下降，低于30万转／分钟，但高于16万转／分钟．可满足基本使用要求。灭菌时间最短的灭菌器只明显影响一支牙科手机的转速，其他灭菌器均明显影响两支牙科手机的转速。结论 灭菌时间短对牙科手机机械性能影响小，灭菌前应做好牙科手机的清洁和润滑，以减少机械性能损耗。     

The effect of steam autoclave sterilization on methyl methacrylate cranial implant materials.

The use of methyl methacrylates for cranial repairs has been well established. Procedures for sterilization of these materials include soaking in benzalkonium chloride, use of ethylene oxide gas, or cobalt 60 irradiation. Although ethylene oxide sterilization is the most common method, gas sterilization and degassing of these prefabricated implants may require almost as much time as fabrication. This study evaluated impact strength and linear dimensional change following steam autoclave sterilization of heat-processed methyl methacrylate. It was compared to an autopolymerizing methyl methacrylate for impact strength. No statistical difference was found in impact strength between nonsterile heat-processed methyl methacrylate and autoclaved heat-processed methyl methacrylate; however, both were significantly stronger than the autopolymerizing material. A statistically significant linear dimensional change of 1.211% between the autoclaved and nonsterile heat-processed methyl methacrylate was found, but was not considered clinically significant.     

Mechanical properties of 2 new addition-vulcanizing silicone prosthetic elastomers

PURPOSE: This study evaluated some mechanical properties of 2 newly introduced, addition-type silicone prosthetic elastomers (Cosmesil and Episil). MATERIALS AND METHODS: The properties evaluated were tensile strength, modulus at 100% elongation, elongation at break, tear strength, and hardness. The properties tested were selected because of their clinical significance for fabricating facial prostheses. RESULTS: Episil showed greater tensile strength (P = 0.0002), elastic modulus (P = 0.0001), hardness (P = 0.0002), and tear strength (P = 0.0004) than Cosmesil material. Cosmesil exhibited a higher elongation at break (P = 0.0002) than Episil. CONCLUSION: Cosmesil and Episil showed reasonable properties as facial prosthetic elastomers and neither was superior for all properties tested. Both materials showed favorable combinations of elongation at break and tear strength.     

Effects of sterilization on the mechanical properties and the surface topography of nickel-titanium arch wires

The effects of sterilization on the mechanical properties and the surface topography were determined on 0.017 x 0.025-inch Nitinol and Titanal arch wires. Three approved heat sterilization methods were used: dry heat, formaldehyde-alcohol vapor, and steam autoclave. Elastic moduli were obtained on 1-inch segments in 3-point bending. Laser scans of flatwise wire surfaces were conducted to detect surface alterations--whether they were caused by tarnish, corrosion, or pitting. Tensile properties were determined on 7-inch lengths: the 0.1% yield strength, the ultimate tensile strength, and the percent elongation at break. Within the confines of the present sterilization experiments, no detrimental changes were observed for either the selected mechanical properties or the surface topography. When the mean values of the two products were compared, Nitinol was less compliant but stronger than Titanal. Laser spectroscopy showed that Titanal possessed at least three times more specular reflectivity than Nitinol.     

Effect of gamma-ray sterilization on phase transformation behavior and fatigue resistance of contemporary nickel-titanium instruments

Objectives

The aim of this study was to compare body temperature cyclic fatigue resistance (CF) of heat-treated NiTi rotary instruments submitted to gamma-irradiation or autoclave sterilization.

Materials and methods

A total of 176 instruments (88 Hyflex EDM (HEDM) and 88 TRUShape (TS)) were used. Forty-four of each were submitted to gamma-irradiation. Twenty-two in each group were further autoclaved, resulting in a total of eight groups (n = 22 each): TS-γ and HEDM-γ (gamma-irradiated)/TS-γ-ac and HEDM-γ-ac (gamma-irradiated and autoclaved)/TS-non-γ and HEDM-non-γ (non-sterilized controls, non-gamma-irradiated/non-autoclaved)/TS-non-γ-ac and HEDM-non-γ-ac (non-gamma-irradiated and autoclaved). Twenty in each were tested for CF. Weibull parameters were calculated and compared. The remainder was used for differential scanning calorimetry analysis.

Results

TS instruments lasted significantly longer if not submitted to gamma-irradiation (TS-non-γ mean-life = 101.5 s, 95 CI% 91.7–112.3; TS-γ mean-life = 83.2 s, 95 CI% 76–91.1); further autoclaving did not significantly affect CF. Gamma-irradiation did not affect HEDM (HEDM-γ mean-life = 717.9 s, 95 CI% 636.8–809.3; HEDM-non-γ: mean-life = 678.8 s, 95 CI% 595.1–744.2); further sterilization significantly decreased fatigue resistance (HEDM-γ-ac mean-life = 524.1 s, 95 CI% 476.1–576.8; HEDM-non-γ-ac mean-life = 570.6, 95 CI% 512.3–635.5). Gamma irradiation benefited HEDM conversion to martensite state and its maintenance, while further autoclave sterilization reverted the benefit.

Conclusions

Gamma-irradiation and autoclaving differentially affected fatigue life span and transformation temperatures of contemporary martensitic rotary instruments manufactured with different methods.

Clinical relevance

Gamma-ray processing is increasingly utilized by manufacturers for clinician to use fully sterile packaged instruments; however, the sterilization method of choice should vary depending on the effects on the behavior of contemporary martensitic rotary instruments manufactured with different methods.

     

Effect of three sterilization techniques on finger pluggers.

The effects of different sterilization methods on the fatigue life of finger pluggers were investigated. Ninety finger pluggers for each of four sizes (A, B, C, and D) were subdivided into subgroups of 10. Each subgroup was subjected to 1, 8, or 15 cycles of steam autoclave, dry heat, or bead sterilization. Ten control pluggers for each size were not sterilized. After sterilization, experimental and control finger pluggers were subjected to cyclic bending until fracture. Only the A finger pluggers autoclaved for eight cycles had a significantly lower number of cycles to failure compared with that of the controls. Nine subgroups had significantly greater number of cycles before failure than did the control. Because all but one sterilized group had fatigue lifetimes statistically equal to or greater than nonsterilized controls, clinicians generally can use any of the three sterilization methods without fear of plugger failure.     

Sterilization of elastic ligatures for intraoperative mandibulomaxillary immobilization

Sterilization can influence the mechanical properties of elastic ligatures used for mandibulomaxillary immobilization. The aim of this study was to compare different sterilization protocols (ethylene oxide, autoclave, irradiation, plasma sterilization, povidone-iodine for 24 hours and 70% isopropyl alcohol for 24 hours) of three elastomers (natural rubber, silicone rubber, and polyurethane). Three mechanical variables were assessed in a testing machine: breaking strength, tensile strength and tensile strength after a 24-hour load (material fatigue). Natural rubber was most susceptible to mechanical alteration by sterilization and lost 46% of its breaking strength and 43% of its tensile strength after autoclaving. Polyurethane was more resistant (multiple comparison, Tukey-Kramer), but polyurethane ligatures stuck together after autoclaving. The protocols for low-temperature sterilization, ethylene oxide, irradiation, and plasma were superior to autoclaving and the disinfecting solutions. These data suggest that polyurethane sterilized with ethylene oxide is the material of choice.     

Cytotoxicity of orthodontic elastic chain bands after sterilization by different methods

IntroductionThe aim was to verify the hypothesis that orthodontic elastics in chain form become more cytotoxic after the sterilization process.Materials and methodsOrthodontic elastic in chain form with six links each was divided into eight groups according to the sterilization method to be performed. The following groups were formed: Control, alcohol 70, autoclave, glutaraldehyde, microwave, ultraviolet, ethylene oxide and gamma rays. Three additional groups were used, cell control, positive control consisting of cellular detergent Tween 80, and negative control consisting of phosphate buffer solution (PBS). After this, the elastics were immersed in culture media for 24 h to release possible toxic substances. After this period elapsed, the medium was placed in contact with L929 cells for 24 h. Next, the cells were stained and analyzed in a spectrophotometer with regard to their cell viability. The data obtained were analyzed by the analysis of variance (ANOVA) and the Tukey's test.ResultsThe groups of elastic sterilized by chemical means (alcohol 70 and glutaraldehyde) and thermal means (autoclave and microwave) led to an increase in cytotoxicity of the studied elastics, presenting statistically significant differences from the groups sterilized with ethylene, ultraviolet and gamma rays (p < 0.05).ConclusionThe hypothesis was partly confirmed, since some of the sterilization methods increased the cytotoxicity of the elastics and others did not.     

Influence of sterilization on mechanical properties and fatigue resistance of nickel-titanium rotary endodontic instruments

AIM: To evaluate the effect of repeated sterilization cycles in dry oven or autoclave, on the mechanical behaviour and fatigue resistance of rotary endodontic Ni-Ti instruments. METHODOLOGY: New Ni-Ti instruments were subjected to five consecutive sterilization cycles in a dry oven or steam autoclave. Microhardness was measured in the nonmachined parts of the shanks of instruments using a Vickers indenter. Specimens of Ni-Ti wires were submitted to the same sterilization protocol and tensile tested until rupture. A group of instruments were fatigued to one half of their average fatigue life and then sterilized. New and sterilized instruments were fatigue tested until rupture. anova tests at alpha = 0.05 were used for statistical analysis. RESULTS: Sterilization procedures resulted in no significant changes in Vickers microhardness, nor in the parameters describing the mechanical behaviour of the wires. However, the number of cycles to failure was statistically higher for all instruments after dry heat or autoclave sterilization cycles. In the instruments previously fatigued to one half of their fatigue life, autoclave sterilization gave rise to an increase of 39% in the remaining number of cycles to failure. CONCLUSIONS: Changes in the mechanical properties of Ni-Ti endodontic instruments after five cycles of commonly used sterilization procedures were insignificant. The sterilization procedures are safe as they produced a significant increase in the fatigue resistance of the instruments.     

Effect of sterilization on the strength and cutting efficiency of twist drills

Retentive-pin twist drills were subjected to four methods of sterilization and then examined to determine possible effects on resistance to fracture, cutting efficiency, and surface condition. Sterilization methods included steam autoclave, chemical vapor autoclave, dry heat, and immersion in glutaraldehyde. Although the steam and chemical vapor groups had lower mean fracture strengths after sterilization, there was no statistically significant difference among the groups. Only the steam autoclave group showed a statistically significant loss of cutting efficiency. Scanning electron microscopic evaluation revealed that only drills sterilized by steam autoclave showed changes in the surface condition or cutting edges.     

Using extracted teeth for research: the effect of storage medium and sterilization on dentin bond strengths

BACKGROUND: The Centers for Disease Control and Prevention has adopted guidelines for infection control of extracted teeth used for research and teaching, requiring that teeth be sterilized before use. The authors conducted a study to test the null hypothesis that the storage medium and sterilization method have no effect on composite-to-dentin bond strengths. MATERIALS AND METHODS: The authors collected 170 bovine incisors, cleaned them and placed them randomly into one of six storage media at 37 degrees C for 60 days: distilled water (dH(2)O), 0.9 percent sodium chloride, 0.5 percent chloramine-T, 5.25 percent sodium hypochlorite (NaClO), 2 percent glutaraldehyde and 10 percent formalin. For sterilization, they autoclaved a subset of 10 specimens from every sample, while they stored another subset of 10 specimens from every sample (except for the 10 percent formalin sample) in 10 percent formalin for 14 days. The authors then embedded the specimens in epoxy and ground flat the facial surface to expose middle-depth dentin, which they polished to 600 grit. They used a dental adhesive to apply composite to the exposed dentin. The authors tested the composite-to-dentin shear bond strength 24 hours after bonding. They analyzed the data using global analysis of variance and, when appropriate, multiple post hoc tests (P = .05). RESULTS: Storage in NaClO resulted in significantly lower bond strength than that of the other treatment specimens. Sterilization with the autoclave negatively affected the bond strength of specimens stored initially in dH(2)O or 10 percent formalin, while sterilization with formalin alone had no significant effect on bond strengths. CONCLUSIONS: Storing bovine teeth in 5.25 percent NaClO may negatively affect composite-to-dentin bond strengths. Immersion in 10 percent formalin might be the best option for storage and sterilization of bovine teeth that are to be used in dental bonding studies in vitro.     

Efficacy of sterilization of endodontic files after autoclaving in a synthetic sponge

A common way of sterilizing endodontic files for clinical use is to insert them into synthetic sponges. The files are sterilized in the sponge, and the sponge is then used on the patient tray for ease of file retrieval. The ability to sterilize the files in a sponge has been questioned. The purpose of the present investigation was to evaluate the sterility of files and spore strips following autoclaving in a sponge. Commercial spore strips and contaminated endodontic files were inserted into sponges, sealed in sterilization pouches and autoclaved. The spore strips and the files were removed from the sponge and cultured for growth of microorganisms. Results show that no microbes were cultured from spore strips or contaminated files after autoclaving them in the sponges sealed in autoclave pouches. These results indicate that the insertion of files into the sponges used in this study does not obstruct the autoclaving process.     

Experimental evaluation of cyclic fatigue resistance of four different nickel-titanium instruments after immersion in sodium hypochlorite and/or sterilization

NiTi instruments have a high risk of separation due to torsional or flexural fatigue (cyclic fatigue). Chemomechanical preparation, cleaning procedures, chemical disinfection and sterilization cause the corrosion of endodontic instruments that may weaken the fracture resistance of the instruments.

Objective

To assess the effects of NaOCl immersion and autoclave sterilization on the cyclic fatigue resistance of ProFile, FlexMaster, Mtwo and TwistedFiles NiTi instruments (tip size 25, 0.06 taper, n=160).

Material and Methods

The instruments (n=10 for each subgroup) were dynamically immersed in NaOCl; immersed in NaOCl and sterilized in one autoclave cycle; 5 cycles immersed in NaOCl and sterilized in autoclave and not immersed in NaOCl and not sterilized (control group). Dynamic cyclic fatigue resistance was tested. The number of cycles to failure (NCF) were statistically analyzed (P<0.05).

Results

Kruskall-Wallis test indicated significant differences among the tested instruments in terms of NCF (P=0.000). The mean NCF of Mtwo (556.75) was higher than that of the Twisted File, Flexmaster and ProFile, 483.1, 376.12, 365.25, respectively. NaOCl immersion and autoclave sterilization have no effect on the NCF values of the tested instruments (P>.05).

Conclusions

Cyclic fatigue resistance of the tested NiTi instruments cannot be adversely affected by NaOCl immersion and autoclave sterilization. Production process (TwistedFiles) or design (Twisted Files, FlexMaster, Mtwo and ProFile) of the instruments can influence their cyclic fatigue resistance.     

Influence of sterilization on the retention properties of magnetic attachments for dental implants

Objectives: When used with dental implants advantages of the magnetic attachments include control of load transmitted to implants, improvements in stability, support and retention for the prosthesis, and the relative ease of prostheses fabrication. Clinically, the use of sterilized components is required, and this may be problematic as magnetic alloys are sensitive to temperature. The purpose of this study was to evaluate the influence of autoclave sterilization on the maximum retentive forces and characteristic curves for magnetic attachments recommended for use with dental implants. Material and methods: Eleven SmCo and NeFeB implant magnetic attachments were evaluated as provided by the respective manufacturers. Implant magnetic abutment and the corresponding denture magnet (n=5 magnet pairs) were tested before and after standardized autoclave sterilization (10 min at 134°C). Each magnet pair was tested 10 times in a calibrated universal testing machine using a non‐magnetic test device (s=40 mm, v=20 mm/min). Results were recorded electronically and statistically analyzed using t‐test and ANOVA (Welch and Brown‐Forsythe test; P<0.05). Results: After autoclave sterilization all magnetic pairs produced lower (though statistically insignificant) overall retention forces compared with the untreated pairs. After sterilization mean maximum retentive forces (SD) ranged from 5.65 (0.33) to 1.41 (0.07) N. The characteristic force–displacement curves of the tested magnetic systems showed differences among the single products. Conclusions: Autoclave sterilization caused a non‐significant reduction in retentive force of 0.04–14.6% when compared with the unsterilized magnet pairs. There were differences between the tested magnetic pairs for both the initial breakaway forces and the characteristic force–displacement curves. Within the limitations of this study all tested magnetic attachments were sterilized in an autoclave without significant change of retention properties. Nevertheless magnetic implant abutments should be sterilized with caution to reduce the risk of alterations of the retention properties.     

不同固化方式对硅橡胶机械性能的影响

目的：考察不同的固化方式对SY—1硅橡胶的机械性能的影响。方法：采用常温24h，升温70℃ 1．5h，微波700W 3min 3种固化方式制备硅橡胶试件，按国家标准要求进行扯断强度、扯断伸长率、永久变形率（3min）、撕裂强度、硬度（邵氏A）测试。结果：3种固化方式下，各组间硅橡胶的5项机械性能都没有统计学差异俨〉0．05）。结论：在赝复体的制作中，可以考虑采用升温或微波固化的方式，加快赝复体的制作周期，为临床患者的特殊需要提供选择。     

Effect of sterilization on cyclic fatigue of rotary nickel-titanium endodontic instruments

The ability of heat treatment as a result of autoclave sterilization to extend the life of nickel-titanium rotary endodontic instruments by reducing the effect of cyclic fatigue was evaluated using 280 size 40 Lightspeed instruments. Instruments were cycled in artificial canals with angles of curvature of 30 degrees and either 2 or 5 mm radii of curvature. In a pilot study, instruments were sterilized or not sterilized and cycled to failure to obtain mean cycles-to-failure values for each group. In the first experimental protocol, instruments were cycled to either 25%, 50%, or 75% of the mean cycles-to-failure limit determined in the pilot study, then sterilized or not sterilized before being cycled to failure. In the second experimental protocol, instruments were cycled to 25% of the mean cycles-to-failure determined in the pilot study, and sterilized or not sterilized. The sequence of cycling to 25% of the predetermined cycles-to-failure limit followed by sterilization was repeated until the instruments failed. No significant increases in cycles to failure were observed between groups for either experimental protocol when instruments were evaluated at a similar radius. Significant differences in cycles to failure were only observed when instruments cycled to failure in the artificial canal with 2 mm radius were compared with instruments cycled to failure in the artificial canal of 5 mm radius. Scanning electron microscopic photos showed crack initiation and propagation in all instruments that were cycled to a percentage of the predetermined cycles-to-failure limit. It is concluded that heat treatment as a result of autoclave sterilization does not extend the useful life of nickel-titanium instruments.     

The effect of autoclave sterilization on endodontic files

This study evaluates the effect of cyclic autoclave sterilization and simulated clinical usage on a mechanical property of one brand of stainless steel endodontic files. The angular deflection moments were measured by a torque apparatus approved by the American Dental Association for such purposes. Comparisons of values for sterilized and nonsterilized files were made. 1. A significant decrease in angular deflection values exists for stainless steel endodontic files having undergone ten cycles of autoclave sterilization versus files having undergone only two or five similar cyclings. 2. All file sizes (15, 20, 25, 30, 35, 40) tested in torsion were detrimentally affected by the autoclave sterilization. 3. Of the files investigated, sizes 35 and 40 were the most adversely affected by the steam-under-pressure sterilization. 4. The angular deflection values of those files subjected to repeated autoclavings were not decreased below the minimum value accepted by the American Dental Association for resistance to torquing forces. It can therefore be concluded that repeated sterilization of a stainless steel endodontic file does result in a significant reduction in the torque resistance of that file. This reduction of the metal property is not significant clinically, however.     

Effects of different sterilization methods on surface characteristics and biofilm formation on zirconia in vitro

Objective

The current laboratory study was to investigate the effect of different sterilization treatments on surface characteristics of zirconia, and biofilm formation on zirconia surface after exposure to these sterilization treatments.

四种热压膜正畸材料力学性能的比较

目的比较临床常用的4种热压膜材料在不同条件下的力学性能,为临床制作隐形矫治器选择材料提供依据。方法A、B、C和D4种热压膜材料厚度均为1.0 mm。测试在3种处理方式下进行：未处理、热成形后和恒温水浴浸泡两周后,比较材料在以上处理后的拉伸屈服应力和断裂伸长率,并比较材料在室温条件下,1h内的应力松弛速率。结果经热成形后,4种材料拉伸屈服应力均低于未处理组,断裂伸长率均大于未处理组;经浸泡两周后,4种材料拉伸屈服应力均高于热成形组,而断裂伸长率均小于热成形组。除材料A外,不同处理方式对其他3种材料力学性能的影响具有统计学意义(P＜0.05)。在室温条件下,A材料1h内的应力松弛速率为0.01 N/s,显著低于C和D(p ＜0.05),与B相比,差异无统计学意义(P＞0.05)。结论热压膜材料的力学性能受到使用环境的影响,A材料的力学性能在不同测试条件下表现最佳,与其他3种材料相比,适宜制作隐形矫治器。     

五种灭菌器对牙科手机灭菌效果的研究

目的检测5种灭菌器对牙科手机的灭菌效果.方法用酶联免疫吸附(ELISA)法检测5种压力蒸汽灭菌器灭菌后的HBsAg人为污染的牙科手机,并对5种灭菌器灭菌后的临床污染的牙科手机进行无菌检测,同时用嗜热脂肪杆菌芽胞检测5种压力蒸汽灭菌器的灭菌效果.结果 5种灭菌器生物监测均合格,5种压力蒸汽灭菌器杀菌效果都可达100%,其中2种灭菌器灭菌的所有牙科手机HBsAg抗原性检测均为阴性,其他3种灭菌器灭菌的牙科手机各有1支HBsAg抗原性检测为阳性.结论压力蒸汽灭菌器效果可靠,乙肝病毒是否灭活,还需做其他检测.牙科手机应严格遵守灭菌保养流程,灭菌后应洁净存放.