Dry-heat Oven Research Articles

Influence of Processing Techniques on Microhardness and Impact Strength of Conventional and Reinforced Heat Cured Acrylic Resin: A Comparative Study

This study determined and compared the influences of various processing techniques including air circulating oven (ACO), dry heat oven (DHO) and water bath (WB) on the impact strength (IS) and microhardness (HV) of the conventional heat cure acrylic resin (CHCAR) and rubber reinforced heat cure acrylic resin (RRHCAR). Samples were fabricated using CHCAR (control Group A; n=114) and RRHCAR (experimental Group B; n=114). Group A and B were further divided into subgroups according to processing techniques: ACO, DHO and WB (n=38 each) for both testing variables microhardness and impact strength (n=19 each). Charpy testing machine and Vickers microhardness tester were utilized. Analysis of variance was applied to determine the presence of significant differences among processing techniques while P-value ≤ 0.05 was considered as significant. Water bath (P-value [0.001) and DHO technique (p-value [0.001) showed significant differences between both groups� impact strength and microhardness. Microhardness of group A and B showed a significant difference (p-value 0.002) when processed by ACO. Impact strength and micro hardness were improved in RRHCAR compared to CHCAR processed by ACO and DHO in comparison to WB technique. Rubber reinforced heat cure acrylic resin revealed improvement in the impact strength and microhardness. The air circulating oven exhibited highest microhardness in both testing materials. Dry heat oven showed improved values of impact strength in conventional heat cure acrylic resin.

Sterilization and Biologic Monitoring in Private Dental Clinics in Lebanon

The aim of the present study was to evaluate sterilization practices and effectiveness in the Lebanese private dental sector and identify potential factors contributing to sterilization failure. A 13-item questionnaire consisting of four demographic/professional questions and nine questions related to sterilization practices along with self-contained biologic indicators (SCBIs) were delivered to a representative sample of Lebanese private offices. Univariate statistics and bivariate analyses were performed to compare sterilization failure rates according to demographic, professional, and sterilization-related conditions. Out of the 560 dentists contacted, 205 dentists returned the completed questionnaires and undamaged processed SCBIs. The tested autoclaves (n = 134) were mostly dynamic air removal (69.4%) and had a mean age of 10.5 ± 6.9 years. The dry heat ovens (n = 71) were all static air and had 12.9 ± 8.1 years. The dental assistants performed the routine sterilization procedures in nearly 62% of the practices and sterilization cycles were run 4 to 6 times per week in 75% of the offices. Correct temperature/time ratios were applied in 97% of the autoclaves and 80.3% of the ovens. Few dental practices reported having preventive maintenance (17.9% for the autoclaves and 14.1% for the ovens). Routine monitoring of sterilizer efficacy was infrequently performed and was mostly conducted using physical indicators. Sterilization failure rate was higher for the ovens (16.9%) than for the autoclaves (7.5%). Incorrect temperature/time ratio was the main significant factor associated with sterilization failures. The present study demonstrated a relatively high rate of sterilization failures in the Lebanese private dental sector and identified the human error in setting sterilization cycle parameters as the predominant cause of failure. These findings should prompt actions toward increasing knowledge of the sterilization processes and their monitoring among dental professionals and improving the quality control of sterilization through collaborative efforts among health authorities, dental schools, and associations. This study presents the first published data relative to sterilization practices and effectiveness in private Lebanese dental offices and provides a rationale to implement biologic monitoring protocols in Lebanon as long practiced in developed countries.

Efektivitas Sterilisasi Metode Panas Kering pada Alat Medis Ruang Perawatan Luka Rumah Sakit dr. H. Soemarno Sosroatmodjo Kuala Kapuas

Abstract: Effectiveness Of Sterilization Method Of Dry Heat At The Wound Care Medical Devices Hospital Room Dr. H. Soemarno Sosroatmodjo Kuala Kapuas. Hospital Dr. H. Soemarno Sosroatmodjo is a Type C hospitals that provide 24-hour medical services.Bed capacity of 145 with the number BOR (Bed Occupancy Rate) 51.36%.Efforts to prevent the occurrence of nosocomial infections from medical devices one of which is the process of sterilization with dry heat heating process.The purpose of this study was to determine the effectiveness of dry heat sterilization methods on medical devices in the Hospital Dr. H. Soemarno Sosroatmodjo. This type of research is quasi-experimental.Type variables used are the independent variables (temperature variation with the dry heat oven), the dependent variable (number of bacteria).Samples taken medication is a tool set consisting of a pair of tweezers and tub instruments. Analysis of data use Oneway Anova test. Based on the results of the examination, in the highest number of bacteria known medical tool tweezers is the average number of bacteria colonies 1.33 / cm at 125oC, and the highest number of bacteria of medical tools like instrument that is the average number of bacteria colonies 0.66 / cm at the temperature of 125oC. Statistical data analysis for medical devices tweezers with Oneway Anova test, after sterilized generate significant value of 0.09, which sig> 0.05 so that Ho is accepted, meaning there is no significant difference and statistical analysis for medical devices like instrument with Oneway Anova test produces the significant value of 0.40, which sig> 0.05 means that there is no significant difference. Keywords: Hospitals; medical device; numbers germs; sterilization.

P2-394 Infection control practices at the ministry of health dental clinics in Alexandria

IntroductionInfection control (IC) is a priority consideration in dentistry. Dental procedures are done in a septic environment posing significant hazards to dentists and patients. The Aim was to assess the...

CLEANING AND STERILIZATION EFFECT ON THE TORSIONAL PROPERTIES OF PROTAPER ROTARY TITANIUM COBALT (Ti-C0) ENDODONTIC INSTRUMENT

This study was conducted to evaluate the effect of the number of cycles of cleaning using NaOCl solution of different concentration and sterilization using autoclave and dry heat oven on the torsional properties of rotary (Ti-Co) instruments. A total of forty five rotary protaper finisher instruments were divided into 3 groups: Group 1 were subjected to neither cleaning nor sterilization cycles and assigned as the control group. Group 2 and group 3 were subjected to 5 and 10 cleaning and sterilization cycles respectively, soaked within (2% and 5%) NaOCl, were sterilized with autoclave and dry heat oven. Then, all instruments were subjected to a clockwise torsional load until fracture, the torsional moment and angular deflection at fracture were calculated. The results show a significant reduction in the torsional strength after cleaning and sterilization cycles regardless the concentration of NaOCl, type and number of sterilization cycles. For the angular deflection, there was a highly significant reduction, where, the number of cycles was the most influencing factor for reduction of the angular deflection whereas, the concentration of NaOCl and the type of sterilization were show no significant influence on the angular deflection.

Dry thermal resistance of Bacillus anthracis (Sterne) spores and spores of other Bacillus species: implications for biological agent destruction via waste incineration

To obtain needed data on the dry thermal resistance of Bacillus anthracis spores and other Bacillus species for waste incinerator applications. Tests were conducted in a pilot-scale incinerator utilizing biological indicators comprised of spores of Geobacillus stearothermophilus, Bacillus atrophaeus and B. anthracis (Sterne) and embedded in building material bundles. Tests were also conducted in a dry heat oven to determine the destruction kinetics for the same species. In the pilot-scale incinerator tests, B. atrophaeus and G. stearothermophilus demonstrated similar thermal sensitivity, but B. anthracis (Sterne) was less thermally resistant than G. stearothermophilus. For the dry heat oven tests conducted at 175°C, the D-values were 0·4, 0·2 and 0·3 min for B. atrophaeus, B. anthracis (Sterne) and G. stearothermophilus, respectively. Bacillus anthracis (Sterne) possesses similar or less dry heat resistance compared to B. atrophaeus and G. stearothermophilus. Previous studies have demonstrated conditions under which bacterial spores may survive in an incinerator environment. The data from this study may assist in the selection of surrogates or indicator micro-organisms to ensure B. anthracis spores embedded in building materials are completely inactivated in an incinerator.

Color Stability, Surface Roughness, and Surface Porosity of Acrylic Resins for Eye Sclera Polymerized by Different Heat Sources

The aim of this study was to evaluate the color stability, surface roughness, and surface porosity of acrylic resins for eye sclera polymerized by different heat sources and submitted to accelerated artificial aging (AAA). Three groups of ten specimens each were formed according to the heat source used during the polymerization cycle: GI-short cycle, GII-long cycle, and GIII-dry-heat oven. The groups were submitted to color spectrophotometry through the CIE L a b system and to surface roughness and porosity analysis using a Surfcorder IF 1700 profilometer. After the tests, specimens were submitted to AAA, with a maximum aging time of 384 hours, corresponding to a year of clinical use. After aging, the color and roughness of each group were assessed. The results showed that the variability of DeltaE was clinically unacceptable for all groups but the method of polymerization was insignificant (p > 0.05) for color change. For roughness, polymerization cycle was significant for the results. GIII (0.23 +/- 0.06) presented the highest roughness difference (before and after AAA), statistically significant (p < 0.05) from GII. No statistically significant difference could be found among groups when considering the porosity test. It may be concluded that irrespective of the type of heat used for polymerization, there was an intense color alteration, to clinically unacceptable levels, when the specimens were submitted to AAA. For the other properties, alterations were less intense.

Using Biological Indicators to Meet NELAC Certification Requirements

An increasing number of water‐testing laboratories are seeking National Environmental Laboratory Accreditation Conference (NELAC) certification. Those seeking this type of accreditation must ensure implementation of all of the NELAC quality‐assurance policies, procedures, and methods specified by NELAC for quality systems. Weekly use of biological indicators to check the efficacy of the laboratories' steam autoclaves and dry heat ovens is one requirement for meeting NELAC certification of equipment. Because many laboratories have never done this procedure before, many questions are surfacing. This article provides information that is intended to help answer many of these questions.

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 inquiriesconcerning 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 alldental 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 (χ2, P < 0.01). Demographic or hygiene procedural factors could not be correlated to sterilization performance (χ2, 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.Keywords:Asepsis; biological indicators; dentistry; infection control; spore testing

CONTINUING EDUCATION ARTICLE: Compliance with infection-control procedures among Illinois orthodontists

The authors of previous studies have reported an increasing percentage of orthodontists complying with infection-control procedures in their offices, yet compliance was found to be less than ideal. In this study we surveyed Illinois orthodontists to evaluate their compliance with the infection-control guidelines established by the American Dental Association and the Centers for Disease Control and Prevention. This study is an addition to a small number of studies in the field of orthodontics on infection-control procedures. The study population was taken from the World Directory of Orthodontists, which contains 374 listings for the state of Illinois. Responses were received from 140 orthodontists, for a response rate of 37%. Thirty-two percent of the responding orthodontists stated that they always wear masks; 13% said they never do. Almost 97% of the orthodontists said they always wear gloves, and no orthodontist reported never wearing gloves. Nearly 64% of the orthodontists reported always using eyewear, and 34% said they wear gowns, whereas only 5% do not wear eye protection and 35% never wear gowns. With regard to instruments and pliers, most of the orthodontists reported using dry-heat ovens (72% and 80%, respectively), whereas nearly 58% said they use chemical disinfection to some extent on instruments and 39% said they use chemical disinfection on pliers. Only 51% of the orthodontists surveyed in our study reported using a steam autoclave to sterilize handpieces, whereas 27% said they use dry-heat ovens, 11% reported using chemical vapor, and 37% said they use chemical disinfection. In conclusion, compliance with infection control procedures among orthodontists has improved from recent studies but is still less than full compliance. (Am J Orthod Dentofacial Orthop 1998;113:647-54.)

Effects of sterilization procedures on the cutting efficiency of stainless steel and carbon steel Gates Glidden drills

One-hundred fifty carbon steel Gates Glidden drills were compared with 150 stainless steel Gates Glidden drills before and after sterilization in an autoclave, salt beads, dry heat, or 2% alkaline glutaraldehyde. Cutting efficiency and separation rates of the drills were evaluated. Stainless steel #1 and 2 Gates Glidden drills resisted separation and maintained their cutting efficiency statistically better than the carbon steel #1 and 2 Gates Glidden drills after one sterilization cycle in an autoclave, salt bead sterilizer, or dry heat oven. Glutaraldehyde did not effect either type of drill.

A survey of sterilization practices in selected endodontic offices

Little information exists concerning the effect(s) office asepsis procedures can have on sterilization success in dental speciality offices. Therefore, 218 randomly selected private endodontic offices in five midwestern states were sent spore strips, use instructions, and a 16-question survey. The question-naire dealt with practitioner/auxillary training, continuing education practices, and office sterilization procedures. Offices returning “positive” spore strips were sent additional strips and guidelines for improving sterilizer performance. Survey data were compared with sterilizer type and spore killing results. A total of 139 sterilizers in 106 offices was monitored. Testing results indicated a 15.1% overall failure rate. Of the offices with sterilization failures, only 68.2% responded for retesting. However, all of the responding offices eventually achieved negative spore tests. Dry heat ovens were most likely to have a sterilization failure (p<0.05). None of the surveyed practices nor procedures could be related to sterilization success. Little information exists concerning the effect(s) office asepsis procedures can have on sterilization success in dental speciality offices. Therefore, 218 randomly selected private endodontic offices in five midwestern states were sent spore strips, use instructions, and a 16-question survey. The question-naire dealt with practitioner/auxillary training, continuing education practices, and office sterilization procedures. Offices returning “positive” spore strips were sent additional strips and guidelines for improving sterilizer performance. Survey data were compared with sterilizer type and spore killing results. A total of 139 sterilizers in 106 offices was monitored. Testing results indicated a 15.1% overall failure rate. Of the offices with sterilization failures, only 68.2% responded for retesting. However, all of the responding offices eventually achieved negative spore tests. Dry heat ovens were most likely to have a sterilization failure (p<0.05). None of the surveyed practices nor procedures could be related to sterilization success.

Dry-heat destruction of lipopolysaccharide: design and construction of dry-heat destruction apparatus.

A dry-heat oven with automatic, multiple-sample introduction and withdrawal has been constructed to achieve instantaneous heating and cooling of samples. The oven temperature fluctuation at set points of 170 to 250 degrees C was +/- 0.1 degrees C, with temperature variation between the replicate samples of +/- 0.2 degrees C. Correction required for a sample come-up time was minimal, i.e., less than 0.25 min of the dry-heat destruction time.

Effect of temperature and gas velocity on dry-heat destruction rate of bacterial spores.

Spores of Bacillus subtilis were dried in vacuo for use in dry-heat thermal destruction tests. Survivor curve tests were conducted in a specifically designed dry-heat oven. This oven provided accurate temperature control and permitted air or nitrogen to be passed over the spores during the lethal treatment. Experiments were carried out at various flow rates of the two gases (air and nitrogen) and various temperatures, and the data were expressed as survivor curves from which the decimal reduction time (D value) was obtained. Linear regression analysis methods were used to compute the slope of the survivor curves. The results indicated that as the flow rate of gas is increased, the effect of temperature on the destruction rate of the spores is lessened, the z value becoming very large. It is believed that the higher flow rates of dry gas cause greater dehydration of the spores and that spore moisture loss is one of the major factors in determining the dry-heat thermal destruction rate of bacterial spores.

Effect of Temperature and Gas Velocity on the Dry-Heat Destruction Rate of Bacterial Spores1

Spores of Bacillus subtilis were dried in vacuo for use in dry-heat thermal destruction tests. Survivor curve tests were conducted in a specifically designed dry-heat oven. This oven provided accurate temperature control and permitted air or nitrogen to be passed over the spores during the lethal treatment. Experiments were carried out at various flow rates of the two gases (air and nitrogen) and various temperatures, and the data were expressed as survivor curves from which the decimal reduction time (D value) was obtained. Linear regression analysis methods were used to compute the slope of the survivor curves. The results indicated that as the flow rate of gas is increased, the effect of temperature on the destruction rate of the spores is lessened, the z value becoming very large. It is believed that the higher flow rates of dry gas cause greater dehydration of the spores and that spore moisture loss is one of the major factors in determining the dry-heat thermal destruction rate of bacterial spores.