Biological monitoring of sterilizers and sterilization failures in Norwegian dental offices in 1985 and 1996.

It is essential that dental office sterilizers be regularly challenged with biological indicators (BIs) in order to prove that the test spores are being killed during sterilization. The aims of the study were to biologically monitor Norwegian dental office sterilizers and to identify factors contributing to sterilization failure. In 1985, participants received a packet containing: (i) 4 BI units; (ii) a set of instructions; (iii) a questionnaire concerning operation (including biological monitoring) of the office sterilizer(s), and (iv) a return-address envelope. In 1996, offices were sent (i) a survey which included demographic questions and inquiries concerning instrument sterilization processes; (ii) 2 sets of 3 BI units with instructions for their use on 2 different days; (iii) 1 control BI unit that was not to be processed, and (iv) a return-address envelope. Both private and public offices participated. Response rate to the 1996 study was 60%, which was 9.1% of all dental offices in Norway. Testing results indicated a 6.3% overall sterilization failure rate. Three out of 163 steam autoclaves (SAs) (1.8% of total) and 14 out of 109 dry heat (DH) ovens (12.8% of total) failed. DH ovens were over 7 times more likely to fail BI testing than were SAs (chi2, P < 0.01). Demographic or hygiene procedural factors could not be correlated to sterilization performance (chi2, P > 0.05). The failure rate for SAs (n = 216) in 1985 was almost 5 times greater than in 1996 (8.8% vs 1.8%). Improvement in sterilizer performance during the decade may be related to issuance in 1986 of Norway's 1st infection control guidelines for dentistry and greater awareness of infection control practices and/or to increases over the previous 10 years in the number of postgraduate courses offered in infection control. The current Norwegian guidelines on infection control practices in public health services, including dentistry, recommend regular biological monitoring of sterilizers without specifying how often. There is a lack of information among Norwegian dentists as to how frequently dental office sterilizers should be regularly monitored by BI.     

GI—Ⅱ型牙用玻璃渗透氧化铝陶瓷的生物安全性评价

目的：研究评价GI－Ⅱ型牙用玻璃渗透氧化铝陶瓷材料的生物安全性。方法：利用仓鼠,NIH纯系小鼠,豚鼠等实验动物对材料进行急性毒性,细胞毒性,致敏性,口腔粘膜刺激性,溶血,微核等试验研究,结果：材料的溶血率低于5％,有良好的血液相容性,无明显的细胞毒性作用,未见任何急性毒性反应,对口腔粘膜无刺激性,无致敏性,微核试验未见潜在致突变性。结论：GI－II型牙用玻璃渗透氧化铝陶瓷材料的临床应用具有可靠的生物安全性。     

多媒体技术在口腔材料性能教学中的应用

为进一步优化教育管理和教学过程,适应教育改革的潮流和趋势,教育部于1999年就已提出,在高校普及和运用以多媒体计算机技术为核心的教育技术应用模式是推进教育信息化进程的关键一步.按照这一思路,北京大学口腔医学院尝试对口腔材料学材料性能的教学方式进行改革,引入多媒体技术.通过对教学内容进行深入分析,将课程讲授重点分别采用动画短片和录像方式进行详尽的讲解,其他概念多配以图片进行讲解.课件制作完成后,在2006级和2007级的八年制学生中进行了实际使用,并根据课件内容设计了调查问卷,调查问卷结果显示,课件教学效果良好.     

Outcome of sterilization by steam autoclaves in Danish dental offices

Abstract — The aims of this study were to evaluate the performance of autoclaves and the use of biologic indicators for sterilization control, and to look for predictor variables for improperly functioning autoclaves in Danish dental offices. The study population comprised 314 Danish dental offices (participation rate 94%); 177 from the public Child Dental Service (CDS) and 137 from private practice. A minor questionnaire and five biologic indicators, (Attest Biological Indicator for Steam Sterilization, 3M) were sent to the participants. CDS offices were found more inclined to use biologic indicators than PP offices ( P <0.00001). Among CDS autoclaves 2.3% (95% confidence limit: 0.9–5.7%) failed to sterilize compared to 7.3% (95% confidence limit: 4.0–12.9) of the PP autoclaves. This difference is not statistically significant, but the confidence intervals indicate a possible true difference in favor of a better outcome in the CDS offices. Looking at the whole sample no other predictor variable for inadequate sterilization could be determined as differences were statistically insignificant with regard to years of professional experience, age and brand of autoclave, and use of biological control. Recommendations from an official body stating the approved types of sterilization control in dental offices would be of value.     

Outcome of sterilization by steam autoclaves in Danish dental offices

The aims of this study were to evaluate the performance of autoclaves and the use of biologic indicators for sterilization control, and to look for predictor variables for improperly functioning autoclaves in Danish dental offices. The study population comprised 314 Danish dental offices (participation rate 94%); 177 from the public Child Dental Service (CDS) and 137 from private practice. A minor questionnaire and five biologic indicators (Attest Biological Indicator for Steam Sterilization, 3M) were sent to the participants. CDS offices were found more inclined to use biologic indicators than PP offices (P less than 0.00001). Among CDS autoclaves 2.3% (95% confidence limit: 0.9-5.7%) failed to sterilize compared to 7.3% (95% confidence limit: 4.0-12.9) of the PP autoclaves. This difference is not statistically significant, but the confidence intervals indicate a possible true difference in favor of a better outcome in the CDS offices. Looking at the whole sample no other predictor variable for inadequate sterilization could be determined as differences were statistically insignificant with regard to years of professional experience, age and brand of autoclave, and use of biological control. Recommendations from an official body stating the approved types of sterilization control in dental offices would be of value.     

The effect of steam sterilization on the properties of set dental gypsum models

The aim of this study was to investigate the viability of autoclave sterilization of set dental gypsum models. The effects of autoclaving on the strength, surface hardness and dimensions of specimens of plaster, stone and diestone were investigated. In addition, sodium succinate was used to minimize any changes produced by autoclaving. It has been shown that dental gypsum casts can be successfully steam sterilized.
The results showed that for fully-dried gypsum products, autoclaving at 132°C for 5 minutes rendered the casts unacceptable for use. Autoclaving at 121°C for 16 minutes had less effect although casts were still not satisfactory, with the main problems being excessive expansion for plaster and significant strength and surface hardness loss for stone and diestone.
The effect of three additional treatment procedures was examined and the least degradation was observed when the casts were soaked in 1 per cent sodium succinate solution and dried prior to autoclaving, then soaked in water immediately after. Using this procedure the averate change in properties for plaster, stone and diestone respectively were: loss of strength 36, 21 and 28 per cent, loss of surface hardness 34, 21 and 33 per cent, and linear expansion 0.05, 0.09 and 0.13 per cent. Further refinement may improve the procedure.     

强弱吸引器配合使用降低诊室内空气污染的研究

目的检测前牙全冠修复牙体预备时吸引器的不同使用方法对口腔诊室内空气污染的影响。方法前牙全冠修复的患者36例,随机分为3组,每组12例,A组牙体预备不使用吸引器,B组牙体预备仅使用弱吸引器,C组牙体预备同时使用强、弱吸引器。采用琼脂平皿的方法采样,牙体预备15 min和30 min时送检,记录菌落数,监测口腔诊室内空气污染的情况。结果牙体预备能造成口腔诊室内空气的污染,并且随预备时间的延长而增加;使用弱吸引器可以减少诊室内空气污染;强、弱吸引器并用能明显减少口腔诊室空气污染,且15 min与30 min无明显区别（P〉0.05）。结论前牙全冠修复牙体预备过程中强、弱吸引器并用可有效减少口腔诊室内空气污染。     

Hygiene and methods of decontamination, disinfection and sterilization in dental offices in Yaounde]

Hygiene and asepsis of the dental office depend on medical ethics and legal obligation. The survey done with the participation of 33 practitioners over the 42 practicing in Yaounde allows apprehending the reality of the daily hygiene. The ways of cleaning, decontamination, disinfection or of sterilization of the premises, the dental equipment and instruments, hand-washing, disposable materials and the vaccination protection of the practitioners were analyzed. The cleaning of the floor and door mats is daily (100%); disinfection is done daily in 83% of the departments in all of the centers. The cleaning and disinfection of the dental chair is daily and is done using soap (23%) and/or bleaching-water (56%). Cleaning or disinfection of the suction machine is done with soap (24%) or with bleaching-water (47%). The hand-pieces and the turbines are cleaned and/or disinfected after each usage in (94%) with alcohol (17%) or with bleaching-water (32%) and sterilized with a heat sterilizer (45%), an autoclave(40%) or cold disinfected(15%). The frequency of the treatment of the instruments is well-respected (83%). Nevertheless the products used are very varied and are not always used in the prescribed order. Hand-washing is systematic after each patient; 50% of the practitioners use soap bars or powered soap and 50% use an antiseptic or a disinfectant solutions. With the regard to the vaccination, only 3 practitioners were properly vaccinated against hepatitis B, tetanus, diphtheria, poliomyelitis and tuberculosis. With regard to the protection of the practitioners, 72% do not wear caps, 56% do not wear eyeglasses, 40% do not wear masks, 95% do not use rubber dams, 56% do not disinfect the radiographic films and 37% do not disinfect the impressions; the habitual attire consists of a smock worn over street clothes (78%) and street shoes (90%). The debris is burnt in 35% of the centers. Better knowledge of the different stages (cleaning, decontamination, disinfection or sterilization and the products used, absolute respect of the disposable materials, optimal vaccination protection and the elaboration of the correct procedures written and posted up in the different departments are fundamental points for quality treatment. As a matter of fact, negligence and ignorance of the rules of hygiene and asepsis should not be part and parcel of the therapeutic hazard in the dental department.     

环氧乙烷对牙科手机灭菌效果及机械性能影响的实验研究

目的 探讨环氧乙烷对人工污染牙科手机灭菌效果和机械性能的影响.方法 采用实验室代表菌种污染牙科手机,经环氧乙烷气体灭菌后,无菌检查法检查牙科手机的灭菌效果,用酶联免疫吸附实验(ELISA)法检测HBsAg;牙科手机每经20次灭菌后进行机械性能检测.结果 环氧乙烷灭菌法对实验室污染的牙科手机可全部达到灭菌效果,乙型肝炎表面抗原(HBsAg)抗原性全部灭活;经200次灭菌后10支牙科手机中,2支转速下降至30万r/min以下,仍高于16万r/min的标准转速.结论 牙科手机用环氧乙烷灭菌效果可靠,并可满足机械的使用性能.     

Autoclave sterilization of dental handpieces: A literature review

PurposeThe present review aimed to investigate autoclave sterilization of dental handpieces based on available studies.Study selectionThe sterilizing efficiency of dental handpieces with autoclave is mainly affected by the types of apparatus (N, B, and S), the packaging with sterilizing pouch, cleaning, and lubrication. These subjects were reviewed based on the in vitro experimental studies.ResultsDental handpieces can be sterilized, including inactivation of heat-resistant bacterial spores, with type B or type S sterilizers, regardless of the use of a sterilization pouch. In contrast, although type N autoclaves are capable of sterilization of general bacteria such as Streptococcus salivarius even in a sterilization pouch if instruments are washed beforehand, complete sterilization of the wrapped handpiece is not always achieved. Therefore, to achieve sterilization efficiency with type N autoclaves, processing without any packaging is recommended. As regards cleaning of handpiece, although contamination decreases with irrigation and wiping of handpieces, all reports concluded that these treatments alone do not achieve complete decontamination of reusable handpieces.ConclusionAlthough type B and type S autoclaves allow us to sterilize the dental handpieces, it is important to realize that complete sterilization of the handpiece is not always achieved by type N autoclave. Understanding autoclave processing of handpieces is essential for dental practice to deliver the safe dental care.     

牙科树脂渗透氧化锆陶瓷材料的制备与性能研究

目的 制备一种牙科树脂渗透氧化锆陶瓷（polymer infiltrated zirconia ceramic network,PICN）材料,检测其机械性能。方法 制备纯氧化锆陶瓷、纯树脂以及4种不同孔隙率的陶瓷支架,实验组的陶瓷支架用树脂进行渗透得到陶瓷树脂复合材料（PICN）。通过三点弯曲强度实验检测材料的弯曲强度和弹性模量,采用单边切口梁法检测断裂韧性,通过纳米压痕系统测得材料的硬度以及用扫描电镜观测材料的显微结构。结果 树脂渗透氧化锆陶瓷（PICN）材料的弯曲强度值为135~266 MPa,弹性模量值为41.3~99.3GPa,断裂韧性值为2.20~4.04 MPam1/2,硬度值为1.93~10.83GPa。扫描电镜显示PICN材料中树脂在陶瓷孔隙内渗透完全。结论 这类树脂渗透氧化锆陶瓷材料的机械性能与人类天然牙釉质和牙本质相似,在口腔修复领域具有良好的应用前景。     

六种常用冠修复材料的摩擦磨耗性能比较

目的 探讨6种常用冠修复材料与滑石瓷对磨时的摩擦磨耗性能,为口腔常用冠修复材料的摩擦磨耗性能与牙釉质的匹配性提供依据.方法 使用MMJ-5G微机控制高温端面磨损实验机,以滑石瓷为对磨物,以15颗因正畸拔除的上颌第一前磨牙制作的10个试件为对照组,对纯钛(A组)、钴铬合金(B组)、Superporcelain Ti-22体瓷(C组)、喜美乐体瓷(D组)、松风饰瓷(E组)、e.max饰瓷(F组)(每组均为10个试件)与滑石瓷组成的摩擦副在37℃人工唾液润滑工况下进行摩擦磨耗实验.记录动态摩擦系数曲线、计算体积磨损百分比,扫描电镜观察表面磨损形貌.结果 试件体积磨损百分比由大至小为:对照组[(90.17×10-4)％]、A组[(79.23×10-4)％]、C组[(23.31 ×10-4)％]、D组[(20.41×10-4)％]、F组[(19.22 × 10-4)％]、E组[(8.53 × 10-4)％]、B组[(2.54×10-4)％].滑动摩擦系数由大到小依次是:D组(0.65)、C组(0.45)、E组(0.40)、A组(0.35)、B组和F组(0.30).扫描电镜观察显示,E组表面最光滑,以下依次是F组、D组、C组.结论 纯钛与天然牙磨耗性能相近,是理想的修复金属材料.4种瓷粉中Surperporcelain Ti-22体瓷磨损滑石瓷最少.     

IPS-Empress 2 玻璃陶瓷结构及性能的研究

目的 研究新型IPS-Empress 2牙科高强度陶瓷的显微结构和机械性能。方法采用原子力显微镜、扫描电子显微镜和X射线衍射仪，分析IPS-Empress 2的显微结构和晶相，用三点弯曲实验和压痕法测试其弯曲强度和断裂韧性。结果IPS-Empress 2玻璃陶瓷主要由二硅酸锂晶体和磷酸锂晶体组成，二者形成相互交错的三维网络式结构；这种玻璃陶瓷在热压铸前后晶体相保持不变，其三点弯曲强度和断裂韧性分别为300MPa和3．1MPam^1/2。结论IPS-Empress 2玻璃陶瓷的高强度和韧性与高含量的二硅酸锂晶体、相互锁结的网络结构和裂纹偏转有关。     

Effect of cooling protocol on mechanical properties and microstructure of dental veneering ceramics

ObjectivesUnderstand how cooling protocols control the microstructure and mechanical properties of veneering porcelains.MethodsTwo porcelain powders were selected, one used to veneer metallic frameworks (VM13) and one for zirconia frameworks (VM9). After the last firing cycle, the monolithic specimens were subjected to two cooling protocols: slow and fast. Flexural strength (FS) was evaluated by three-point beam bending and fracture toughness (K_IC) was evaluated by the single-edge V-notch beam (SEVNB) method. Scanning electron microscopy (SEM) was performed to determine the leucite crystal volume fraction (%), particle size, and matrix microcrack density. The results were compared by analysis of variances (ANOVA) and Tukey’s multiple comparison test.ResultsThe mechanical properties were significantly (p < 0.05) higher for the VM13 porcelain (FS = 111.0 MPa, K_IC = 1.01 MPa.√m) compared to VM9 (FS = 79.6 MPa, K_IC =0.87 MPa.√m) regardless of cooling protocol due to ∼250% higher volume fraction of leucite crystals. The slow cooled VM13 and fast cooled VM9 resulted in the highest and lowest mechanical properties, respectively, while the VM9 slow cooled properties were similar to the VM13 fast cooled. The SEM revealed that the slow cooling significantly increased the volume fraction of leucite crystals by 33–41 %. Across both porcelains, a significant linear correlation between both mechanical properties (strength and toughness) and leucite crystal content was found. Slow cooling was also associated with increased crystal growth resulting in more matrix microcracking.SignificanceControlled crystallization using slow cooling can be applied as a means of strengthening dental porcelains. However, the benefits of slow cooling may be partially offset by increasing the microcrack density in the glass matrix. To achieve the maximum benefit of slow cooling, it is recommending to develop heat treatments to produce porcelain with fine-grained and homogenously dispersed leucite crystals to achieve minimal glass matrix microcracking.     

Radiodensity of base, liner and luting dental materials

The aim of this study was to determine the radiodensity of base, liner and luting dental materials and to compare them with human enamel and dentin. Four classes of materials were examined: conventional glass ionomers (CG)—Vitro Cem, Ketac Bond, Vidrion F, Vidrion C; resin-modified glass ionomers (RMGI)—Fuji II LC, Vitrebond; resinous cement (RC)—Rely-X ARC; and zinc phosphate cement (ZP)—Cimento LS. Five 2-mm-thick standard samples of each material and five 2-mm-thick enamel and dentin samples were produced. An aluminum step wedge served as control. Samples were positioned over a phosphor plate of Digora digital system, exposed to X-ray, and the radiodensity obtained in the software Digora for Windows 2.0. Data were submitted to Kruskal–Wallis and Dunnett multiple comparisons test (α=0.05). According to statistical analysis, the following sequence in degree of radiodensity could be seen among the groups: Cimento LS (ZP) > Vitro Cem (CG) = Fuji II LC (RMGI) = Rely-X ARC (RC) = Vitrebond (RMGI) > Ketac Bond (CG) > enamel = Vidrion F (CG) > Vidrion C (CG) = dentin. The presence of radiopaque fillers such as zinc, strontium, zirconium, barium, and lanthanium rather than material type seems to be the most important factor when analyzing material radiodensity. Almost all investigated materials presented an accepted radiodensity.     

Digital image correlation in dental materials and related research: A review

ObjectiveDigital image correlation (DIC) is a non-contact image processing technique for full-field strain measurement. Although DIC has been widely used in engineering and biomechanical fields, it is in the spotlight only recently in dental materials. Therefore, the purpose of this review paper is introducing the working principle of the DIC technique with some modifications and providing further potential applications in various dental materials and related fields.MethodsThe accuracy of the algorithm depending on the environmental characteristics of the DIC technique, as well as the advantages and disadvantages of strain measurement using optical measurements, have been elaborated in dental materials and related fields. Applications to those researches have been classified into the following categories: shrinkage behavior of light-cured resin composite, resin-tooth interface, mechanical properties of tooth structure, crack extension and elastic properties of dental materials, and deformation of dental restoration and prosthesis. This classification and discussion were performed using literature survey and review based on numerous papers in the international journals published over the past 20 years. The future directions for predicting the precise deformation of dental materials under various environments, as well as limitations of the DIC technique, was presented in this review.ResultsThe DIC technique was demonstrated as a more effective tool to measure full-field polymerization shrinkage of composite resin, even in a simulated clinical condition over the existing methods. Moreover, the DIC combined with other technologies can be useful to evaluate the mechanical behavior of material-tooth interface, dentine structure and restorative and prosthetic materials with high accuracy. Three-dimensional DIC using two cameras extended the measurement range in-plane to out-of-plane, enabling measure of the strain directly on the surface of dental restorations or prosthesis.SignificanceDIC technique is a potential tool for measuring and predicting the full-field deformation/strain of dental materials and actual prostheses in diverse clinical conditions. The versatility of DIC can replace the existing complex sensor devices in those studies.     

两种新材料修复楔状缺损的临床效果评估

目的 应用改良的ＵＳＰＨＳ系统评估两种新材料－－光凝单组份复体和光固化玻璃离子水六汀修复楔状缺损牙齿的临床疗效。方法 门依用Ｄｙｒａｃｔ修复楔缺 ３１７颗,用３Ｍ－Ｖｉｔｒｅｍｅｒ修复楔缺牙１９２颗,用改良ＵＳＰＨＳ系统对１年３主２年的随访结果进行评估。结果 Ｄｙｒａｃｔ组１年成功率９１．１７％,２年成功率８８．６４％;３Ｍ＿Ｖｉｔｒｅｍｅｒ组１年成功率８１．７７％,２年成功率８０．２１％。两组成