sterilization

Gonadotropin hormone-releasing hormone (GnRH) is a peptide involved in mammals’ fertility and may also serve as a candidate target for cancer immunotherapy. Immunonsterilization is known as a proper alternative to surgical castration and has been advocated by European countries in recent years. Immunization with GnRH can effectively inhibit the secretion of gonadotropins and cause infertility in both genders of mammals. In this study, a recombinant trimer of GnRH is designed and expressed in a prokaryotic system.  A construct containing GnRH trimer was designed and prepared using gene synthesis. A cloning site was embedded and connected to the GnRH using a linker to further clone any protein of interest. The construct was subcloned into a pET-32a+ plasmid vector. The recombinant vector was transferred to BL21, an Escherichia coli strain, and the expression was induced using isopropyl β- d-1-thiogalactopyranoside (IPTG). The cell lysate was prepared using lysis buffer and nickel affinity chromatography purification. The GnRH expression was evaluated using sodium dodecyl sulfate-polyacrylamide gel electrophoresis after protein purification. The cloning was verified using a polymerase chain reaction (PCR) followed by sequencing the recombinant vector. The result of the sodium dodecyl sulfate-polyacrylamide gel electrophoresis verified the recombinant protein’s expression and the purification process’s function. The GnRH was properly cloned and expressed in BL21. The results also verified the reliability of the purification process. The construct design allows the researchers to express another peptide sequence attached to the GnRH using the embedded linker to improve the stability and antigenicity. A stable recombinant GnRH would be applied in immunocastration and cancer immunotherapies.

This study evaluated the effect of physical and chemical sterilization techniques on the fracture resistance of mini-implants.

Thirty-two titanium mini-implants of 1.5 x 8 mm were randomly divided into four groups: control, steam sterilized, dry heat sterilized, and chemically sterilized. The samples were then tested in the air for fracture resistance using a universal testing machine. A tangential load was applied to the head of the mini-implant with a 1 mm/min crosshead speed after blocking each of them in the machine. Also, the maximum load was recorded previous to screw fracture. he Kruskal-Wallis test and Mann-Whitney post hoc test were used for data analysis.

The results of this study demonstrated the mean fracture resistance difference between the four groups was statistically significant at p<0.001. Moreover it was showed the control group had significantly higher mean fracture resistance compared to dry heat and chemically sterilized groups at p=0.001 and p=0.009 respectively. This was followed by the stem sterilized group demonstrating significantly higher mean fracture resistance as compared to dry heat and chemically sterilized groups at p=0.001 and p=0.01 respectively. Later, the chemically sterilized group also showed significantly higher mean fracture resistance as compared to the dry heat group at p=0.002. However, no significant difference was observed between the control and stem sterilized groups (p=0.29).

The steam sterilized group demonstrated the highest fracture resistance that was followed by the chemically sterilized group, and the least with the dry heat sterilized group.

ntroduction:Dentures, occlusal splints, surgical guides and orthodontic appliances are examples of acrylic resin devices made in dental laboratories, which must be disinfected and even sterilized before insertion into the oral cavity. This study evaluated the antimicrobial effect of photodynamic therapy (PDT) applied to acrylic resin specimens received from different laboratories.

Three hundred standardized specimens were ordered from six randomly selected laboratories registered in the Council of Dentistry of Ceará (n = 50). The PDT consisted in the association of 22 μM erythrosine, as a photosensitizer (P), and a 520-nm LED at 38 J/cm2 (L). The specimens of each laboratory were randomly distributed into five groups: positive control, sterilized with ethylene oxide; negative control, untreated (P-L-); erythrosine control, only stained (P + L-); LED control, only irradiated (P-L + ); PDT (P + L + ). Then, the specimens were individually sonicated in saline solution; the suspension was diluted, plated on culture mediums (blood agar, sabouraud dextrose agar and a non-selective chromogenic agar), and incubated for 48 hours at 37°C. Colony-forming-unit (CFU) counts were done and statistical tests of Kruskal-Wallis/Dunn were carried out.

The specimens from all laboratories were contaminated with bacteria and yeasts. Staphylococcus aureus, Staphylococcus saprophyticus,Escherichia coli,Enterococcus spp., Klebsiella and Pseudomonas spp. were identified. The PDT significantly reduced CFU counts (P < 0.0001), compared to P-L-.

PDT was able to effectively decontaminate the acrylic resin specimens provided from dental laboratories.

Cleaning is one of the most important steps in preparing surgical instruments for reuse. Thorough cleaning can ensure more effective sterilization, protect treatment teams and patients from transmissible infections, and extend the life of surgical instruments. This study was conducted to compare the manual, automated, and ultrasonic methods of cleaning surgical instruments. 

In this quasi-experimental study, three types of surgical instruments, namely curved hemostats, suction tips, and Metzenbaum scissors, (n=90) from among 20 surgical sets were randomly selected and assigned to three cleaning groups viz manual, automated, and ultrasonic. After the instruments were cleaned, surface protein and blood residue swab tests were conducted and the results were recorded on a data-registration form. Data were analyzed using SPSS version 16 and descriptive and inferential statistical methods.

According to the research results, in manually cleaned instruments group, 8 (26.7%) tested positive for blood and 10 (33.3%) tested positive for protein. Of the 30 automatically cleaned instruments, 6 (20%) tested positive for blood and 7 (23.3%) tested positive for protein and of the 30 ultrasonically cleaned instruments, 1 (3.3%) tested positive for blood and protein. The chi-square test showed a statistically significant difference between the three methods of cleaning residual blood and protein from the surgical instruments (p<0.05).

The results revealed that according to the research results, of the three cleaning methods, ultrasonic cleaning was by far the most effective in removing blood and protein residues from the surgical instruments. Hence, we suggest that ultrasonic cleaning can be routinely utilized as an efficient cleaning method in medical centers.

Today, various sterilization methods are used for the removal of microorganisms, some of which are based on thermal methods that have negative effects on the physicochemical properties of milk. The present study aimed to investigate the effects of cold plasma at atmospheric pressure on the population of Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli) in raw milk. Initially, a plasma jet filled with argon gas was used to evaluate the antibacterial effects of cold plasma. Following that, pasteurized milk samples (1.5% and 3% fat) were infected with standard strains of E. coli and coagulase-positive S. aureus and irradiated with cold plasma at the frequency of 22, 28, and 33 kHz and voltage of 20, 12.5, and 10 kV for five minutes. The results of statistical analysis and Tukey’s test indicated that the E. coli and S. aureus microbial load was significantly lower in the 1.5% fat milk compared to the control group (P<0.05). In addition, the milk samples exposed to plasma at 20 kV and 28 kHz showed the most significant reduction in the number of E. coli bacteria compared to the control samples (P<0.05). The milk samples exposed to 10 kV and 33 kHz also showed the most significant reduction in the S. aureus microbial load. According to the results, cold plasma could decrease the microbial load of milk containing 1.5% fat more significantly compared to the 3% fat milk. Therefore, plasma could be a proper alternative to thermal decontamination methods for raw milk. However, its application requires further studies to determine the intensity and duration of the exposure of microorganisms to cold plasma at atmospheric pressure.

Infections caused by surgeries have always been considered a primary concern of medical centers and are associated with irreversible complications. Using appropriate sterilization procedures reduces these complications. This study aimed to investigate how compliant are the current sterilization procedures of operating room (OR) environment and instruments with valid scientific standards.

This cross-sectional, descriptive-analytical study examined ophthalmology, gynecology, and otorhinolaryngology ORs of Valiasr Hospital in Birjand. With the presence of the researcher in the OR, a standard 41-item checklist consisting of three parts (environmental cleaning, equipment cleaning, and sterilization procedure) was completed for each OR in each shift. The data were analyzed using the Mann-Whitney and Kruskal-Wallis test by SPSS(Version18) in significant level (a=0.05).

A total of 50 questionnaires were filled out for ORs. The highest number of questionnaires were completed for the gynecology OR, and the most elective surgeries were performed in the morning shift. There was no significant difference between the median score of OR instruments cleaning and that of valid scientific guidelines in terms of steralization (P> 0.05). The median scores of sterilization procedures and steps in hospital ORs were significantly different from those of scientific guidelines in the field of sterilization of surgical operations (P <0.05).

The study findings indicate cases of mismatch between the quality of infection control and sterilization in the ORs of Vali-asar Hospital in Birjand and those recommended by valid scientific standards and guidelines.

Decontamination of gutta-percha (GP) cones is recommended before placement in the root canal system. However, the incidence of contamination is still a matter of debate. The present study aimed to evaluate the contamination of GP cones before and during clinical use by general dentists.

In this in vitro study, 120 GP cones (#20) were examined for incidence of contamination. First, 30 GP packages were opened under aseptic laboratory conditions, and two cones were randomly selected for the laboratory tests. Next, the initially sampled packages were distributed among 30 general dentists and then they were asked to use them clinically for 7 days and then the packages were collected for the microbial tests. The collected cones were placed in tubes containing thioglycolate medium and incubated at 37℃ for 21 days. Bacterial growth was detected by presence of turbidity and comparison with the control groups. A sample was collected from the tubes showing turbidity and plated in blood agar and also underwent Gram-staining, followed by colony counting. Data were analyzed using the Chi-square and paired sample t-test (alpha=0.05).

None of the 60 samples from initial sampling of packages showed contamination. However, in secondary sampling after clinical use, 8.3% of GP samples were positive for contamination. There was a statistically significant difference in contamination of packages before and after clinical use (P= 0.02).

Within the limitations of this study, it can be concluded that GP cones can become infected after opening the package and in the process of clinical use.

Extending the lifespan and improving the physical properties of dental burs as the most extensivly used instruments have been the subject of several studies. One of the proposed methods is using surface coatings for the burs. Since the dental instruments are reused, they require sterilization. One of the possible causes of the damage to dental burs is autoclaving process. This study aimed to investigate sterilization (autoclave) effect on wear of diamond coated tungsten-carbide burs with different thicknesses.

In this in vitro study, 40 tungsten-carbide dental burs (IQ DENT, Poznan, Poland) were selected, out of which 20 burs were coated with 1.5-μm-like diamond particles, and 20 burs were coated with 3.5-μm by PVD method using Swin Plasma Coating Machine. Then, the burs were randomly divided into four groups (n=10) as follow: G1: 1.5 μm thickness coated burs without sterilization; G2: 3.5 μm thickness coated burs without sterilization; G3: 1.5 μm coated with sterilization; and G4: 3.5μm thickness coated burs with sterilization. Their weights were measured before wear test.Wear test was performed and then they were re-weighted. Data were analyzed using SPSS software (version 21) as well as Two-way ANOVA and Tukey HSD supplementary tests (α=0.05).

Mean and standard deviation of the burs weights without sterilization in the control groups were 7.31±2.63 and 7.96±1.61 mg, respectively; and mean and standard deviation of the burs weights in the sterilization groups were 7.06±0.98 and 7.12±1.11 mg, respectively. The study results showed that “sterilization application” and “thickness of coated layer” were the main factors and their intraction had no statistically significant difference (P=0.589).

The sterilization process had no effect on wear of diamond coated tungsten-carbide burs with different thicknesses.

This study aimed to evaluate the effects of repeated sterilization cycles on the surface alterations of various nickel-titanium instruments, including ProTaper Next (PTN), TF Adaptive (TFA), HyFlex CM (HCM), and 2Shape (2S).

Twenty-four new NiTi files of four different alloys were selected. The instruments in each group were divided into two equal groups, as follows: control and sterilization. The first group was chosen as the control without applying any sterilization procedure, while in group 2, five cycles of sterilization procedures were applied. The surface topographies were evaluated using scanning electron microscope (SEM) and atomic force microscope (AFM). The root mean square (RMS) and maximum height (MH) values and three-dimensional images were recorded. The data were analyzed with the Shapiro-Wilk test, one-way ANOVA, and post hoc Tukey tests. The statistical significance level was set at P≤0.05.

Before the experiment, HCM demonstrated the highest RMS value, and 2S showed the lowest. After the procedures, the RMS and MH values deteriorated on the surface of PTX, TFA, and 2S (P<0.001). The HCM was not affected by sterilization processes (P>0.05).

The initial irregularity on the surface did not affect the rate of alteration. The HCM files demonstrated superior surface properties after several cycles of sterilization. The PTN, TFA, and 2S presented similar surface responses after five cycles of autoclave sterilization.

Titanium miniscrews are used at an ever‑increasing rate to provide orthodontic anchorage. The aim of this study was to evaluate the mechanical performance of miniscrews after dry and steam sterilization.

In this experimental study, a total of 72 miniscrews from two different manufacturers with a diameter of 1.6 mm and height of 8 mm were divided into six groups (n = 12). One group of screws from each manufacturer was considered as the control group; the second underwent steam sterilization; and the last group was subjected to dry sterilization. Insertion and fracture torques of each miniscrew were assessed by a torque tester. Data were analyzed using the Kruskal–Wallis and Mann–Whitney tests (P < 0.05).

For Jeil miniscrew, no statistically significant differences were detected between the steam‑sterilized and control groups in their insertion torques (P > 0.05). There was a statistically significant difference between the steam sterilized, dry sterilized and control groups with respect to their fracture torque (P < 0.001). For Hubit miniscrew, there were no significant differences between steam sterilized, dry sterilized and control groups in their insertion torque (P > 0.05) and between steam sterilized and control groups with respect to their fracture torque (P > 0.05). There were significant differences in the mean values of insertion and fracture torques between the two different manufacturers (P < 0.001).

Steam sterilization had no detrimental effects on torque values of miniscrews, but dry heat sterilization affected their mechanical properties.

The main purpose of this research was to find a proper Poly Vinyl Chloride (PVC) stabilizer system for medical purpose. It was sterilized by ethylene oxide gas, constant ratio of metallic soap stabilizers (calcium-zinc stearate) as well as stabilizers based on organotin (octyle sn-mercaptide, which is commercially known as 17mok901) and soybean oil were studied.
PVC S-6058 with value=60 from Iran Petrochemical Commercial Company, di-2 ethyl hexil phethalate plasticizer from Iran Azarshimi Company, epoxide soya bean oil (from South Africa’s MBT Company), calcium-zinc stearate (from India’s Shital Company), octyl tin mercaptide, commercially known as 17® MOK 901, (from India’s Shital Company) and BHT (2,6-di-tert-butyl-4-methyl phenol) anti-oxidant (commercially known as Lanxess from Germany’s Volkanux Company) were provided and utilized during the research. PVC mixtures prepared by the aforementioned stabilizers were tested under mechanical testing, thermal gravimetric analysis (weight measurement under heating) (TGA) and Fourier transform infra-red (FTIR) (determination of functional groups in the stabilized PVC) before and after sterilization by ethylene oxide gas.
Assessment of blood compatibility of samples was done by Hemolysis test, according to ISO 10993 standard part 4. Results of the tensile test demonstrated that calcium-zinc stearate was the best PVC stabilizer. In order to improve its tensile properties, with 2.67 strain rate, sterilization improved its mechanical properties while preserving strength.
The results from Fourier transform infra-red (FTIR) on chemical structures of samples suggested that sterilization by ethylene oxide gas had no negative effect on the structure of the stabilized PVC. Furthermore, the mixture made from PVC had stabilized on organotin and was of higher thermal stability as well as had better blood-compatibility properties with respect to other stabilizers. This confirms acceptable efficiency of stabilizers utilized for hygienic and medical purposes.

Dental burs are among the most commonly used instruments in dental offices and have the most possible cross-contamination risks. The sterilization of dental burs is highly noted and necessary. The present study evaluated the effects of different sterilization methods on the uniformity of diamond dental burs and changes in the cutting edge carbide burs. In this descriptive study, to assess the results of sterilization, 36 burs (18 diamond burs and 18 carbide burs) were studied. In total, 18 diamond burs using R software were randomly divided into the 3 groups of 6 burs (dry-clave group, autoclave group, and cold sterilization group). Each group was divided into the 2 subgroups of 3 burs; the first subgroup received 5 cycles and the second subgroup received 15 cycles of sterilization. The same process was used for 18 carbide burs to categorize them into groups and subgroups. A pre-assessment was conducted by Scanning Electron Microscopy (SEM). After the sterilization cycles, a post-test SEM was performed. Adobe Photoshop 2017 was used in a gray scale of 12 to compare the pre-test and post-test differences. Kruskal-Wallis test, Analysis of Variance, Mann-Whitney U test, and Post Hoc Tukey test were used to analyze the obtained data in SPSS at a significance level of P=0.05. Dry-clave was the best approach in 5 cycles of sterilization for diamond and carbide burs. Moreover, autoclave was the best method for 5 cycles of sterilization (P<0.05). In 15 cycles of sterilization of diamond and carbide burs, the best method was auto-clave which exhibited a significant difference in carbide burs. Dry-clave and autoclave were the most appropriate approaches for 5 and 15 cycles of sterilization of diamond burs, respectively. In sterilization of carbide, in both 5 and 15 cycles, autoclave was the best method. All of the sterilization methods caused corrosion, discoloration, and the loss of integrity in carbide burs; however, these changes were minimum in the autoclave method. In conclusion, auto-clave method is recommended due to causing the least changes in carbide and diamond burs.