Processo de esterilização de materiais odontológicos: avaliação padronização em tempos de pandemia de Covid-19 / Process of sterilization of dental materials: evaluation and standardization in times of the covid-19 pandemic

Objetivos: avaliar os processos de coleta, lavagem e esterilização de instrumentais odontológicos, evidenciando se houveram mudanças no processo em função da pandemia de COVID-19, em consultórios odontológicos tanto particulares como públicos, na cidade de Pelotas-RS, visando auxiliar no incremento da segurança e eficácia da esterilização na prática odontológica, após uma crise sanitária global e propor um Procedimento Operacional Padrão (POP). Métodos: os dados foram obtidos em um único momento através de respostas dadas pela aplicação de um questionário para o profissional responsável pelo processo de esterilização de cada local. Os dados foram compilados pelo software Microsoft Excel, foi realizada a análise descritiva e os mesmos foram expressos na forma de porcentagem. Resultados: em 100% dos locais o processo de lavagem e esterilização ocorria na mesma sala de atendimento, destes em quatro locais a operação de transporte era realizada com o auxílio de uma caixa plástica higienizável e seis locais contavam com um processo de pré-lavagem. Todos os locais faziam uso de autoclave para o processo de esterilização, 100% realizavam o monitoramento químico do processo, porém apenas quatro realizavam o monitoramento biológico. Conclusão: houve poucas mudanças nos processos de lavagem e esterilização nos locais pesquisados em razão do surgimento da pandemia de COVID -19. Nenhum local examinado possuía o POP descrito do processo de lavagem e esterilização de instrumentais odontológicos e observou-se um baixo uso dos indicadores biológicos, os quais são considerados o padrão ouro da biossegurança.(AU)

Objectives: to evaluate the processes of collection, washing, and sterilization of dental instruments, highlighting any changes in the process due to the COVID-19 pandemic, in both private and public dental clinics in the city of Pelotas, Rio Grande do Sul, with the aim of enhancing the safety and effectiveness of sterilization in dental practice after a global health crisis, and to propose a Standard Operating Procedure (SOP). Methods: data were collected at a single time point through questionnaire responses provided by the professional responsible for the sterilization process at each location. The data were compiled using Microsoft Excel software, and descriptive analysis was conducted. The results were expressed in the form of percentages. Results: in 100% of the locations, the washing and sterilization process took place in the same treatment room. Out of these, transportation was conducted using a hygienizable plastic box in four locations, and six locations had a pre-washing process. All locations used an autoclave for the sterilization process, and 100% performed chemical monitoring of the process, but only four locations conducted biological monitoring. Conclusion: there were few changes in the washing and sterilization processes at the surveyed locations due to the emergence of the COVID-19 pandemic. None of the examined locations had a described SOP for the washing and sterilization process of dental instruments, and there was a low utilization of biological indicators, which are considered the gold standard for biosafety.(AU)

Análisis microbiológico a corto y largo plazo del material usado para esterilizar instrumental odontológico / Short and long-term microbiological analysis of the material for sterilize dental instruments

Introducción: el material para empaquetar el instrumental odontológico, como pueden ser bolsas de tela, papel o plástico, es usado por profesionales de la salud; sin embargo, es necesario esclarecer la efectividad de cada uno y determinar el tiempo que permanece estéril luego del procedimiento. Objetivo: identificar la eficacia de tela, plástico y papel como materiales para esterilizar instrumental a corto y largo plazo. Material y métodos: se realizaron cultivos sólidos y líquidos de instrumental esterilizado en tres materiales y con diferentes tiempos de postesterilización. Se incubaron a 36 oC por 72 horas en condiciones aerobias y anaerobias. Los resultados se analizaron usando una prueba de Kruskal-Wallis, seguida de una prueba de Dunn. Resultados: los resultados mostraron que inmediatamente después del proceso de esterilización, los tres materiales son efectivos (Kruskal-Wallis test, p = 0.2752), 24 horas (p = 0.2492), siete (p = 0.0509) y 14 días (p = 0.0006). Veinticuatro horas posterior a la esterilización la tela no es efectiva, el plástico disminuye su efectividad y el papel sigue siendo efectivo. Conclusión: en nuestros resultados, el papel es la mejor opción para esterilizar instrumental (AU)

Introduction: material such as cloth, paper or plastic bags to wrap dental instruments is used by health professionals, however, it is necessary to clarify the effectiveness of each one and determine if it remains sterile after the procedure. Objective: to determine the effectiveness of cloth, plastic and paper as materials to sterilize dental instruments in the short and long term. Material and methods: we carry out solid and liquid cultures of sterilized instruments in three materials, at different post-sterilization times, incubated at 36 oC for 72 hours under aerobic and anaerobic conditions, and the results were analyzed using a Kruskal-Wallis test, followed by from a Dunn's test. Results: our results showed that immediately after the sterilization process the three materials are effective (Kruskal-Wallis; p = 0.2752), 24 hours (p = 0.2492), 7 (p = 0.0509) and 14 (p = 0.0006) days. Twenty-four hours after the cloth is not effective, plastic decreases its effectiveness and paper remain effective. Conclusion: in our results, paper is the best option to sterilize dental instruments (AU)

Study of some risk factors for fungal contamination of dental unit waterlines in Alexandria, Egypt.

INTRODUCTION: Monitoring the microbial quality of water in dental unit waterlines is an important part of infection control measures carried out in dental clinics. Fungal contamination of such waterlines has not been extensively studied, compared with bacterial contamination. This study aimed at assessing the magnitude and risk factors for fungal contamination of dental unit waterlines. METHODOLOGY: This cross-sectional study included 82 dental units, randomly collected from 3 private clinics and 8 governmental hospitals in Alexandria, Egypt. A total of 204 water samples from dental unit waterlines output were membrane-filtered and cultured for fungal enumeration and species identification. The biofilm forming-ability was assessed for the most prevalent fungal species. The acceptability of samples was determined according to the Swedish drinking water guidelines. RESULTS: The acceptability of samples was 89.7%. The most common mould was Aspergillus flavus, while Candida spp. was the most common yeast (10 isolates), with unusual predominance of Candida dubliniensis (9 isolates). All isolates of Aspergillus flavus and Candida dubliniensis were biofilm-formers. The risk factors for fungal contamination of dental unit waterlines included: dental specialty (p = 0.042), time of sample collection (p < 0.001), older age of dental unit (p < 0.001) and use of 5-15% of sodium hypochlorite. CONCLUSIONS: The presence of biofilm-forming fungi in dental unit waterlines is a potential hazard, even when samples have acceptable levels of fungal counts. Risk factors for contamination are numerous and should be addressed.

Bacterial colonization of a power-driven water flosser during regular use. A proof-of-principle study.

OBJECTIVES: The present proof-of-principle study assessed whether daily use of a power-driven water flosser (Sonicare AirFloss; SAF) leads to bacterial colonization in the nozzle and/or the device, resulting in contaminated water-jet. MATERIAL AND METHODS: In five participants, saliva samples at baseline and water-jet samples of devices used daily with bottled water for 3 weeks (test) were collected. Additionally, water-jet samples from devices used daily with bottled water extra-orally for 3 weeks (positive control) and from brand new devices (negative control), as well as samples from newly opened and 1- and 3-week opened water bottles were collected. Colony forming units (CFU) were recorded after 48 h culturing and 20 oral pathogens were assessed by polymerase chain reaction-based analysis. RESULTS: Distinct inter-individual differences regarding the number of detected bacteria were observed; water-jet samples of test devices included both aerobic and anaerobic bacterial species, with some similarities to the saliva sample of the user. Water-jet samples from positive control devices showed limited number of aerobic and anaerobic bacterial species, while the samples from negative control devices did not show any bacterial species. Very few aerobic bacteria were detected only in the 3-week-old bottled water samples, while samples of newly and 1-week opened water bottles did not show any bacterial growth. CONCLUSIONS: The present proof-of-principle study showed that daily use of a power-driven water flosser for 3 weeks resulted in bacterial colonization in the nozzle and/or device with both aerobic and anaerobic, not only oral, species, that are transmitted via the water-jet.

Portable ozone sterilization device with mechanical and ultrasonic cleaning units for dentistry.

A portable device for cleaning and ozone sterilization of small-sized delicate dental instruments that cannot withstand the high heat and humidity of standard autoclaving has been developed. The device contains a remote unit for magnetic mechanical washing, an ultrasonic bath for pre-cleaning treatment, and a container for ozone sterilization with a reactor based on dielectric barrier discharge. The maximum ozone concentration in water reached 8.5 mg/l for 10 min of operation at a water temperature of 19 °C. The results of inactivation of Pseudomonas aeruginosa, Escherichia coli, and Staphylococcus aureus are presented. Distilled water with such seeded micro-organisms was bubbled with an ozone-air mixture at an ozone concentration of 5.8 mg/l at 17 °C for 5 min, 10 min, 20 min, and 30 min. The maximum bactericidal effect was manifested for Pseudomonas aeruginosa cells with their total elimination within 10 min. Inactivation of Escherichia coli bacteria was monitored after 20 min of treatment, and Staphylococcus aureus-after 30 min of treatment.

Review of surface disinfection protocols in dentistry: a 2019 update.

Disinfection is a crucial aspect of patient care in dentistry. In the pre-19th century era, natural elements like acids, sulfur, mercury, and various alkaline metals were valued for their ability to obliterate pathogens. More recently aerosols, sprays, and disinfectant wipes with more powerful chemicals including quaternary ammonium compounds and aldehydes have become popular. As aerosols fall out of favor due to their health and environmental risks, disinfectant wipes are becoming the most trusted form of clinical sanitization. This article explores the history as well as the current practice of disinfection in the dental profession and further explores the variations in the use of surface disinfection based on the published literature. The current practice guidelines as recommended by agencies like Centers for Disease Control (CDC) were studied and summarized for this review.

A study of the environmental survival of Streptococcus equi subspecies equi.

BACKGROUND: Streptococcus equi represents a common hazard to equids worldwide. Environmental contamination with bacteria shed from an infected horse may represent a significant source of contagion and further knowledge of ex vivo bacterial survival under different conditions is important for disinfection and isolation protocols. OBJECTIVES: To determine the potential duration of survival and vigour of growth of S. equi inoculated onto surfaces relevant to equine veterinary practice and stabling in summer and winter. STUDY DESIGN: Repeat sampling of environmental inocula of S. equi. METHODS: Cultures of S. equi were inoculated onto wood, a shoe sole, cotton overalls, inside a nasogastric tube, inside a dental rasp, in a wet plastic bucket and onto a fence post both in the summer and winter seasons. Frequent resampling and culture from the inoculated sites was conducted until no viable bacteria were found. Bacterial viability was determined by both duration (time to first negative culture) and vigour of growth (growth score over the first 3 days of culture) and compared between inoculated sites and times of year. RESULTS: Bacterial viability was enhanced by a wet local environment and by the winter season. Survival tended to be short in the summer (up to 9 days in wet sites and up to 2 days in dry sites) but much longer in the winter (up to 34 days in wet sites and up to 13 days in dry sites). Vigour of bacterial growth was also greater in the winter than in the summer as judged by 3-day-growth scores. MAIN LIMITATIONS: Direct comparison with the variable size and nature of naturally shed infectious material is difficult. CONCLUSIONS: Veterinarians and personnel handling horses should be aware that S. equi may survive in an equine environment for longer than previously found, especially when protected by wet and cold conditions.

Effect of multiple autoclave cycles on the surface roughness of HyFlex CM and HyFlex EDM files: an atomic force microscopy study.

AIM: To compare the effect of autoclave cycles on the surface topography and roughness of HyFlex CM and HyFlex EDM instruments using atomic force microscopy (AFM) analysis. METHODOLOGY: Eight new files of each brand were subdivided into four subgroups (n = 2/each subgroup). One group was allocated as the control group and not subjected to autoclave sterilization. The other three groups were subjected to different numbers (1, 5, and 10) of autoclave sterilization cycles. After the cycle instruments were subjected to AFM analysis. Roughness average (Ra) and the root mean square (RMS) values were chosen to investigate the surface features of endodontic files. The data was analyzed using one-way ANOVA and post hoc Tamhane tests at 5% significant level. RESULTS: The lowest Ra and RMS values were observed in the HyFlex EDM files that served as the control and in those subjected to a single cycle of autoclave sterilization (P < 0.05). The highest Ra and RMS values were observed in the HyFlex CM and HyFlex EDM files that were subjected to 10 cycles of autoclave sterilization (P < 0.05). The surface roughness values of the HyFlex CM group showed a significant increase after ten autoclave cycles, whereas those of the HyFlex EDM group exhibited a significant change after five autoclave cycles (P < 0.05). CONCLUSIONS: Although the initial surface roughness values of the HyFlex EDM files were lower than those of the HyFlex CM files, the surface roughness values of the EDM files showed a statistically significant increase after 5 cycles of autoclave sterilization. In contrast, the surface roughness values of the HyFlex CM files did not increase until 10 cycles of autoclave sterilization. CLINICAL RELEVANCE: Present study indicated that autoclave sterilization negatively affected the surface roughness of the tested NiTi files.

Awareness of risk of cross-infection and infection-control measures among patients attending University Dental Hospital, Peradeniya, Sri Lanka.

AIM: The aim of the present study was to assess awareness of the risk of cross-infection and infection-control measures practiced in dental clinics for patients attending the outpatient dental department (OPD) at University Dental Hospital, Peradeniya, Sri Lanka. METHODS: A descriptive cross-sectional study was carried out among 427 patients who attended the OPD clinics at University Dental Hospital. An interviewer-administered questionnaire was used to collect data, and chi-squared-test of association was applied where appropriate. RESULTS: Most patients (75.2%) were aware that there was a chance of infection transmission during dental treatments, and nearly 72% stated that wearing gloves and masks by their dentists was important during dental treatment. Awareness was higher among patients with a higher educational level. Participants revealed their fear of potential transmission of blood-borne pathogens in the dental setting. Awareness of sterilization of dental instruments was poor. CONCLUSIONS: The public should be made aware of the possible risks of cross-infection and the importance of infection-control practices in dental clinics. Dental professionals should fill the information gap.

Phenotypic and genotypic characterization of clinically relevant bacteria isolated from dental waste and waste workers' hands, mucosas and coats.

Infectious wastes are potential sources of pathogenic micro-organisms, which may represent a risk to the professionals who manage them. In this study, we aimed to characterize the infectious bacteria present in dental waste and waste workers. The dental waste produced over 24 h was collected and waste workers were sampled by swabbing. Isolate resistance profiles were characterized by Vitek® and PCR and biofilm formation by Congo Red agar, string test and microtitre assay. To assess similarity between the waste and the workers' samples, a random amplified polymorphic DNA test was used. Twenty-eight bacteria were identified as clinically relevant. The most frequent gene was blaTEM present in five Gram-negative micro-organisms, and one blaSHV in Klebsiella pneumoniae. All Pseudomonas aeruginosa were positive to extracellular polymeric substances formation, except one isolated from a worker. Klebsiella pneumoniae had negative results for the string test. Pseudomonas aeruginosa showed better adherence at 25°C after 48 h of incubation and K. pneumonia had the best biofilm formation at the same temperature, after 24 h. The similarity between P. aeruginosa recovered from dental waste and from workers was low, however, it is important to note that a pathogen was found on a worker's hands and that improvements in biosafety are required. SIGNIFICANCE AND IMPACT OF THE STUDY: Infectious dental waste can contain clinically relevant bacteria with important resistance and biofilm profiles. These micro-organisms could be transmitted to waste workers, other professionals and patients if the principles of biosafety measures are neglected. To our knowledge, no study has ever evaluated the microbial characterization and the potential contamination risk of dental infectious waste and waste handlers. The presence of clinically relevant bacteria in the hands and nasal mucosa of waste workers highlights the need for studies in this field to clarify the risk of these pathogens in dental healthcare services, and to stress the need for an efficient waste management.

Evaluación de la portación de cándida spp en pinzas ortodóncicas post utilización / Evaluation of candida spp carriage on orthodontic pliers, after using them

Objetivo: evaluar el nivel de contaminación por Candida spp, post uso del instrumental de ortodoncia que se utiliza intrabucalmente en pacientesColombianos y Argentinos. Materiales y métodos: Se incluyeron pacientesentre 16 y 65 años, de ambos sexos, con armado de brackets superior e inferior. Criterios de Exclusión: pacientes con brackets de autoligado, con enfermedades autoinmunes, con enfermedades sistémicas con manifestaciones en el periodonto, pacientes fumadores, menores de 16 años y con armado de brackets en un solo maxilar. Se analizaron los alicates de corte distal Hu Friedy luego de ser utilizados para seccionar el arco por distal del último tubo presente enboca. Se estudiaron 80 pacientes agrupados en: Grupo A 40 pacientesColombianos, Grupo B 40 pacientes argentinos. Se realizó una primer tomaintrabucal con un hisopo estéril y se llevó a un tubo con medio de Stuart. Se cortaron las 4 secciones distales de los arcos en boca tardando al menos 1 minuto. Con un segundo hisopo estéril se frota toda la superficie del alicate post uso y se llevaron a otro tubo. Se sembraron en Chromagar Candida y se realizaron pruebas microbiológicas convencionales. Resultados: Las pinzas estériles aparecen contaminadas post corte distal delos alambres en el 95% de los casos en ambos países. Hubo diferencia entrelos pacientes colombianos y los argentinos respecto a las especies, ya que enlos primeros la especie con mayor prevalencia fue Candida tropicalis tanto en lapinza como en la cavidad bucal, mientras que en los argentinos fue Candidaalbicans. Conclusión: las pinzas de ortodoncias se contaminan con Candidaspp post utilización en boca y son un fómite a partir del cual puede generarsediseminación sistémica así como infección cruzada.

Comparison of Antimicrobial Activity between Chemical Disinfectants on Contaminated Orthodontic Pliers.

AIM: To compare the antimicrobial activity of the chemical substances--70% isopropyl alcohol, 2% glutaraldehyde (GTA) and 0.25% peracetic acid (PAA) in disinfecting orthodontic pliers contaminated in vitro with Streptococcui mutani, Staphylococci aureui and Candida albicani. MATERIALS AND METHODS: Distal end cutter pliers were divided into five groups: group 1 (negative control--sterilized pliers), group 2 (positive control--sterilized plier, subsequently contaminated), group 3 (disinfected with 70% isopropyl alcohol, friction method), group 4 (disinfected with 2% GTA, immersion method for 30 minutes), group 5 (disinfected with 0.25% peracetic acid (PAA), immersion method for 10 minutes). After the pliers were treated with one disinfectant and submitted to microbiological evaluation (by counting colony forming units), they were submitted to the same cleansing, sterilizing and contaminating processes, and were used in the following groups (crossover and washout study). The two-factor analysis of variance (ANOVA) test, followed by the Tukey test, was used to compare the groups. RESULTS: The results showed that there was no statistically significant difference between the three tested disinfectants. CONCLUSION: Although there were no statistically significant differences between the disinfectants, the chemical agents 2% glutaraldehyde and 0.25% PAA were effective in inhibiting the growth of the three microorganisms tested; however, 70% isopropyl alcohol was unable to completely eliminate S. aureui. CLINICAL SIGNIFICANCE: The chemical substances 2% glutaraldehyde and 0.25% PAA completely eliminated the microorganisms tested.

Overcoming the problem of residual microbial contamination in dental suction units left by conventional disinfection using novel single component suction handpieces in combination with automated flood disinfection.

OBJECTIVES: Decontaminating dental chair unit (DCU) suction systems in a convenient, safe and effective manner is problematic. This study aimed to identify and quantify the extent of the problems using 25 DCUs, methodically eliminate these problems and develop an efficient approach for reliable, effective, automated disinfection. METHODS: DCU suction system residual contamination by environmental and human-derived bacteria was evaluated by microbiological culture following standard aspiration disinfection with a quaternary ammonium disinfectant or alternatively, a novel flooding approach to disinfection. Disinfection of multicomponent suction handpieces, assembled and disassembled, was also studied. A prototype manual and a novel automated Suction Tube Cleaning System (STCS) were developed and tested, as were novel single component suction handpieces. RESULTS: Standard aspiration disinfection consistently failed to decontaminate DCU suction systems effectively. Semi-confluent bacterial growth (101-500 colony forming units (CFU) per culture plate) was recovered from up to 60% of suction filter housings and from up to 19% of high and 37% of low volume suction hoses. Manual and automated flood disinfection of DCU suction systems reduced this dramatically (ranges for filter cage and high and low volume hoses of 0-22, 0-16 and 0-14CFU/plate, respectively) (P<0.0001). Multicomponent suction handpieces could not be adequately disinfected without prior removal and disassembly. Novel single component handpieces, allowed their effective disinfection in situ using the STCS, which virtually eliminated contamination from the entire suction system. CONCLUSION: Flood disinfection of DCU suction systems and single component handpieces radically improves disinfection efficacy and considerably reduces potential cross-infection and cross-contamination risks. CLINICAL SIGNIFICANCE: DCU suction systems become heavily contaminated during use. Conventional disinfection does not adequately control this. Furthermore, multicomponent suction handpieces cannot be adequately disinfected without disassembly, which is costly in time, staff and resources. The automated STCS DCU suction disinfection system used with single component handpieces provides an effective solution.

[Monitoring steam sterilisation processes in the dental office]. / Het monitoren van stoomsterilisatieprocessen in de mondzorgpraktijk.

In dental offices, steam sterilisation is used to sterilise instruments and in that way to prevent the cross-contamination of patients and the dental team. In order to ensure that the sterilisation process has been executed successfully, every sterilisation process has to be monitored. The monitoring of every load in the steam steriliser is necessary and often even required, either directly (by legislation) or indirectly (by harmonised standards). The complete monitoring protocol consists of controls of the installation, the exposure, the loading, the packaging and, finally, the 'track and trace' of the instruments. For examining the installation, a steam penetration test, such as the Bowie and Dick test, can be carried out.

Efficacy of 3D conforming nickel titanium rotary instruments in eliminating canal wall bacteria from oval-shaped root canals.

OBJECTIVES: To evaluate the effectiveness of TRUShape® 3D Conforming Files, compared with Twisted Files, in reducing bacteria load from root canal walls, in the presence or absence of irrigant agitation. METHODS: Extracted human premolars with single oval-shaped canals were infected with Enterococcus faecalis. Teeth in Group I (N=10; NaOCl and QMix® 2in1 as respective initial and final irrigants) were subdivided into 4 subgroups: (A) TRUShape® instrumentation without irrigant activation; (B) TRUShape® instrumentation with sonic irrigant agitation; (C) Twisted Files without irrigant agitation; (D) Twisted Files with sonic irrigant agitation. To remove confounding factor (antimicrobial irrigants), teeth in Group II (N=10) were irrigated with sterile saline, using the same subgroup designations. Specimens before and after chemomechanical débridement were cultured for quantification of colony-forming units (CFUs). Data from each group were analyzed separately using two-factor ANOVA and Holm-Sidak multiple comparison (α=0.05). Canal wall bacteria were qualitatively examined using scanning electron microscopy (SEM) and light microscopy of Taylor-modified Brown and Brenn-stained demineralised sections. RESULTS: CFUs from subgroups in Group I were not significantly different (P=0.935). For Group II, both file type (P<0.001) and irrigant agitation (P<0.001) significantly affected log-reduction in CFU concentrations. The interaction of these two factors was not significant (P=0.601). Although SEM showed reduced canal wall bacteria, bacteria were present within dentinal tubules after rotary instrumentation, as revealed by light microscopy of longitudinal root sections. CONCLUSIONS: TRUShape® files removed significantly more canal wall bacteria than Twisted Files when used without an antibacterial irrigant; the latter is required to decontaminate dentinal tubules. CLINICAL SIGNIFICANCE: Root canal disinfection should not be focused only on a mechanistic approach. Rather, the rational choice of a rotary instrumentation system should be combined with the use of well-tested antimicrobial irrigants and delivery/agitation techniques to establish a clinically realistic chemomechanical débridement protocol.

[The influence of autoclave sterilization on surface characteristics and cyclic fatigue resistance of 3 nickel-titanium rotary instruments].

PURPOSE: To investigate the effects of autoclave sterilization on surface characteristics and cyclic fatigue resistance of 3 types of nickel-titanium rotary instruments (K3, Mtwo, ProTaper). METHODS: Three brands of NiTi rotary endodontic instruments of the same size (tip diameter 0.25 mm and constant 0.06 taper) were selected: K3, Mtwo and Protaper (F2). 24 instruments for each brand were used to evaluate the effects of autoclave sterilization on inner character in the as-received condition and after subjection to 0, 1, 5, and 10 sterilization cycles (6 for each group). Time to fracture (TtF) from the start of the test to the moment of file breakage and the length of the fractured fragment were recorded. Means and standard deviations of TtF and fragment length were calculated. The data was analyzed with SPSS13.0 software package. Another 12 NiTi rotary instruments for each brand were used, 6 subjected to 10 autoclave sterilization cycles and the other as control. Scanning electron microscope was used to observe the changes in surface topography and inner character. RESULTS: For cyclic fatigue resistance, when sterilization was not performed, K3 showed the highest value of TtF means and ProTaper the lowest. The differences between each brand were statistically significant (P<0.05).When disinfection was performed, K3 brand showed greater fatigue resistance in comparison with the control when autoclave sterilization cycled 5 times and 10 times. The difference between 10 cycles of sterilization and the control was statistically significant (P<0.05); ProTaper brand showed significantly greater fatigue resistance in all the disinfected groups compared with the control (P<0.05) and 5 cycles of sterilization led to the greatest increment; The fatigue resistance of Mtwo brands increased with sterilization cycles and the difference between 5/10 cycles and the control were statistically significant (P<0.05). For surface characteristics, under scanning electron microscope, surface and inner imperfections in all instruments were intensified greatly after 10 cycles of sterilization. CONCLUSIONS: Cycle fatigue resistance is different among instruments of different brands. Autoclave sterilization may increase fatigue resistance of the 3 brands. Autoclave sterilization may increase the surface roughness and inner defects in cross section.

Sterilization for Large Volunteer Temporary Clinics.

Large portable clinics staffed by volunteers present many unique challenges, including establishing appropriate instrument processing services. This article explores many of the specific steps an organization can take to ensure a safe care environment for patients and a safe working environment for volunteers.