Dry Sterilization Research Articles

DBD plasma as a practical approach to sterilization of dental instruments

Microbe control and decontamination are necessary for medical equipment that will be used again. Several wet and dry sterilizer technologies, like as autoclaves, ovens, UV systems, and chemical agents, have been widely used to eliminate the possibility of cross-infection between contaminated dental instruments or materials and dental patients. The development of a sterilizer device capable of sterilizing dental equipment through non-toxic materials has been shown to significantly decrease the overall procedure time compared to conventional approaches. Therefore, an investigation was conducted to assess the efficacy of a dielectric barrier discharge (DBD) plasma device in sterilizing dental instruments under atmospheric pressure conditions. Also, due to Reactive Oxygen and Nitrogen Species (RONS) existence at low temperatures, researchers have been examining the biological effects of cold plasmas for medical applications with promising results. The dental Tweezer, one of the dental tools, was chosen to perform the sterilization process using the DBD plasma device. The Dental Tweezers samples were contaminated with Escherichia coli and Staphylococcus aureus bacteria, and then the DBD plasma device was used to sterilize them for 1, 2, 3, and 4 min, respectively, to figure out the best time to do this. The DBD plasma device successfully killed E. coli and S. aureus. Based on the findings derived from our present investigation, the cold plasma device has impressively proven its efficiency in sterilization.

The novel sterilization device: the prototype testing

Currently, there are numerous methods that can be used to neutralize pathogens (i.e., devices, tools, or protective clothing), but the sterilizing agent must be selected so that it does not damage or change the properties of the material to which it is applied. Dry sterilization with hydrogen peroxide gas (VHP) in combination with UV-C radiation is well described and effective method of sterilization. This paper presents the design, construction, and analysis of a novel model of sterilization device. Verification of the sterilization process was performed, using classical microbiological methods and flow cytometry, on samples containing Geobacillus stearothermophilus spores, Bacillus subtilis spores, Escherichia coli, and Candida albicans. Flow cytometry results were in line with the standardized microbiological tests and confirmed the effectiveness of the sterilization process. It was also determined that mobile sterilization stations represent a valuable solution when dedicated to public institutions and businesses in the tourism sector, sports & fitness industry, or other types of services, e.g., cosmetic services. A key feature of this solution is the ability to adapt the device within specific constraints to the user’s needs.

SYNTHESIS AND RESEARCH OF THE NEW POLYURETHANE UREAS THAT CONTAINE 1,8-DIAMINO-3,6-DIOXAOCTANE AS EXTENDER OF MACROCHAINE

A number of polyurethane ureas (PUUs) containing 1,8-diamino-3,6-dioxooctane (DOODA) in their structure as a macrochain extender were synthesized with a different molar ratio of 4,4'-diaminodiphenylmethane (DADPh) to DOODA as 30:70; 50:50; 70:30. Synthesized polymers are elastic, transparent films with a thickness of 0.3 mm. According to the results of physical and mechanical tests, the tensile strength of the synthesized PUUs is in the range of (0.7-2.0) MPa, and the relative elongation at break is in the range of (73.9-584.7)%. The best physical and mechanical characteristics have the polymer synthesized with a ratio of DADPh:DOODA as 0.3:0.7 with a tensile strength of 2.0 MPa and a relative elongation of 522%. The formation of PUUs was confirmed by the method of IR-spectroscopy. Thermophysical properties synthesized by DSC, TGA methods were studied. It was established that the glass transition temperature (Tg) in a number of synthesized PUUs with DOODA is in the range from (minus) 18.50 °C to (minus) 34.52 °C. An increase in the content of 1,8-Diamino-3,6-dioxaoctane in the PUUs structure leads to a decrease in Tg and a slight increase in ΔCp during the second heating. According to the TGA, the heat resistance characteristics of the synthesized PUUs depend on the content of DOODA. When entering the structure of the PUUs DOODA, a decrease of the temperature of the start of the decomposition (T0) and the temperature of the maximal speed of the decomposition (Tmax), which is non-linear nature. T0 of the synthesized PUUs is in the range (275.16-289.8)°C and is accompanied by a slight loss of mass (0.007-0.093)%. Synthesized PUUs are heat-resistant to a temperature of 275.16 °C, which makes it possible to carry out dry sterilization of samples without changing their characteristics. Synthesized PUUs are promising materials for the immobilization of medicinal substances for further use in medicine.

Sterilisasi Peralatan dan Media Kultur Jaringan

Plant tissue culture is a technology used to propagate plants under controlled and aseptic environmental conditions. One of the obstacles in tissue culture activities is the presence of bacterial and fungal contamination. Equipment and growing media that are used for tissue culture can be the source of contamination. The method that can be used to reduce contamination is using sterilization. Sterilization is used to kill or eliminate microorganisms so that the equipment and media are free from contaminants. Equipment sterilization can be done through several methods such as wet sterilization and dry sterilization. Wet sterilization is carried out using an autoclave, while dry sterilization can be carried out using an oven, fire, and glass bead sterilizer. Media sterilization is generally carried out using an autoclave or membrane filter.

Nine Channels Temperature Data Logger Design for Dry Sterilizer Calibration

In the process of sterilizing medical devices, a sterilizer that is able to produce an accurate and even temperature is needed. If the resulting temperature is not in accordance with the regulated temperature and is not evenly distributed, it will be fatal/damage to the material sterilized. Periodic calibration should be applied to the sterilizer to monitor its function. Based on the research that has been done, no one has done research on making a temperature data logger with 9 channels to calibrate the sterilizer. This study aims to design a temperature measuring device with 9 sensors that can measure simultaneously, so that the accuracy and the distribution of the temperature of a sterlisator can be obtained. This tool used a K thermocouple-type temperature sensor which will detect the temperature and further enters the analog signal conditioning circuit. This then enters the ATMegga 2560 which has been programmed and processed in such a way, leading to the display of the temperature on the 4x20 character LCD. Temperature measurement data will be further stored to SD Card every 10 seconds in the form of a txt file. Tests were carried out on sterilizers, continued by comparison with the Madgetech OctTemp2000 data logger. Based on the measurement and comparison data, the average error was obtained at a temperature of 50ºC with the smallest error value of 0.7% and the largest error value of 3.9%. At a temperature of 100ºC, the smallest error value is 1.6% and the largest error value is 10.5%. Furthermore, at a temperature of 120ºC, the smallest error value is 0.0% and the largest error value is 8.5%. The module resulting from this research is stable in response to temperature by looking at the very small uncertainty value. This research can be further used to help analyze the temperature distribution in a sterilizer. With these measurement results, this study is considered having a fairly high error value at several measurement points.

Nine Channel Temperature Data Logger in Measuring the Effectiveness of the Sterilization Process of Medical Instruments with Dry Sterilization

Measuring the temperature on the dry sterilizer is very necessary because the temperature inside the dry sterilizer has the possibility that the temperature is not the same as the temperature that has been set and is displayed on the display. If the temperature in the dry sterilizer does not match the standard setting temperature for the sterilization process, then the sterilization process is said to be imperfect The purpose of this study is to record and monitor whether the distributed temperature in the sterilization chamber corresponds to the setting temperature. The workings of the temperature data logger tool is that the type K thermocouple temperature sensor will detect the temperature which then enters the analog signal conditioning circuit which then enters the ATMegga 2560 which has been given a program and processed in such a way, then the temperature will be displayed on a 4x20 character LCD. Temperature measurement data will be saved to the SD Card every 10 seconds in the form of a TXT file. This research has been used to record 2 sterilizers and compared with the Madgetech OctTemp2000 data logger. Based on data measurements and comparisons, the average error was obtained at a temperature of 50ºC with the smallest error value of 0.7% and the largest value of 3.9%. At a temperature of 100ºC, the smallest error value is 1.6% and the largest is 10.5%. Then at a temperature of 120ºC the smallest error value is 0.0% and the largest is 8.5%. This research can be used to help analyze the distribution of temperature in a room. With these measurement results, it can be said that this study still has afairly high error value at several measurement points.

DEVELOPMENT AND RESEARCH OF POLYURETHANE FOAM COMPOSITE MATERIALS WITH LYSOZYME

The article is devoted to the development and research of the structure and properties of polyurethane foam (PUF) composite materials with the antibacterial enzyme lysozyme. A series of PUF composite materials with lysozyme of various concentrations (1, 3 and 5 wt %) were obtained. It is established that the immobilization of lysozyme occurs due to intermolecular hydrogen bonds by the method of IR spectroscopy. According to the results of physical-mechanical tests the adhesive strength of polyurethane foam compositions with lysozyme is in the range of 0,82–1,16 MPa. The introduction of lysozyme into the composition of polyurethane foams and an increase its amount causes a decrease in the values of adhesion strength by 18,1–29,3 %. According to differential scanning calorimetry the tested systems are single-phase with a glass transition temperature in the range of -49,20 to -49,86 °C. The introduction of lysozyme into the composition causes an increase heating capacity at the glass transition, which can be associated with a decrease of the packing density of macrochains resulting in an increase in free volume, which leads to an increase molecular mobility. According to the results of the analysis of transmission optical microscopy micrographs the studied PUF have a microporous structure, which depends on the content of filler in their composition. It was found that the presence of lysozyme in the composition of composite materials leads to a decrease in the percentage of porosity, an increase in the number of pores with a diameter of up to 300 μm, which is 76,7–82,4 % (while for PUF – 69,5 %) and the absence of pores with a diameter larger than 990 μm. Thermogravimetric characteristics indicate the heat resistance of the synthesized PUF to a temperature of 179,95 °C, which allows dry sterilization of samples without changing their characteristics. PUF composite materials with lysozyme are promising materials that can be used in medical practice as polymer compositions for the treatment of wounds and burns.

Development and Research of Polyurethane Foam Composite Materials with Albucid

In modern surgery there is a need for restorative and reconstructive operations in the orbit and periorbital area as a result of eye injuries. This study is aimed at the development and research of the structure and properties of polyurethane foam (PUF) composite materials filled by antimicrobial drug substance albucid as implants for ophthalmic surgery. PUF composite materials with albucid (in the amount of 5 wt.%) based on diisocyanate prepolymer (synthesized from polyoxypropylene glycol and 2.4-; 2.6-toluylene diisocyanate) were obtained. The structure, adhesive, thermophysical and thermogravimetric properties, morphology of composite materials have been characterized using Fourier transform infrared (FTIR), mechanical tests, differential scanning calorimetry (DSC), thermogravimetric analysis (TGA) and transmission optical microscopy (TOM). It is established that the immobilization of albucid occurs due to intermolecular hydrogen bonds by the method of IR spectroscopy. According to the results of physical-mechanical tests the presence of albucid in the composition of polyurethane foams does not affect the value of the adhesive strength of composite materials. According to DSC the investigated systems are single-phase with a glass transition temperature from minus 48.40 to minus 48.64°C. The introduction of albucid into the PUF causes a decrease of the specific heat capacity at the glass-transition temperature and does not affect on the T_g of composite materials. According to the results of analysis of TOM photomicrograph, it was found that the presence of albucid in the composite materials leads to a decrease in the porosity percentage, an increase in the quantity of pores with a diameter less than 300 μm, which is 82% (while for PUF it is 69.5%) and the absence of pores with a diameter more than 954 μm. Thermogravimetric characteristics indicate the heat resistance of the synthesized PUF to a temperature of 162.84°C, which makes it possible to carry out dry sterilization of samples without changing their characteristics. Therefore, the obtained PUF composite materials with albucid exhibit adhesion, heat resistance and have a microporous structure. It allows us to conclude that they are promising materials that can be used in medical practice, in particular in ophthalmic surgery as implants with antimicrobial action.

A dry sterilization process for sterilized products after pressure steam sterilization

A dry sterilization process is designed as a post-processual technology of the pressure-steam sterilization. Three experiments are carried out to study the effects of negative pressure, pulsating air, and pulsating steam, respectively, on the process. Antoine's formula is used to predict the relationship between the vapor pressure and the temperature, which can be applied in practice.

Dry Sterilization of Paprika (Capsicum annuum L.) by Short Time-Intensive Microwave-Infrared Radiation: Establishment of Process Using Glass Transition, Sorption, and Quality Degradation Kinetic Parameters

The present study was undertaken for inactivation of S. Typhimurium and A. flavus in paprika by short time intensive microwave-infrared (MW-IR) radiation. The MW-IR heating experiments were carried out using the central composite design with the microwave power density, infrared heater temperature, the distance between the infrared heater and paprika layer, and heating time in the range of 4–12 W g−1, 75–375 °C, 6–14 cm and 15–75 s, respectively. It was observed that whenever the temperature of paprika was exceeded its corresponding glass transition temperature, it resulted in accelerated moisture diffusion and quality degradation. Also, the correlation of overall color degradation with sorption and thermal characteristics of paprika was established. The spatial changes in the temperature and water activity of paprika during short time intensive MW-IR heating resulted in 8.849 log reduction of total plate count (S. Typhimurium) and 7.372 log reduction of yeast and mold count (A. flavus) in presence of natural microbial flora. Industrial relevanceIndia is the largest producer, consumer, and exporter of spices in the world. The steam-assisted sterilization is widely practiced in Indian spice industry but steam treatment is problematic particularly for paprika because of moisture condensation and additional drying cycle resulting in excess quality degradation which fetches a low price in the export market. The present work has been carried out based on industry demand for alternative technology considering spice growers and processors with the special requirement on the quality profile, bactericidal efficacy, ease of operations, cost-effectiveness, and affordability. The results of the present study showed that the short time intensive MW-IR assisted heating process would be an alternative method for finish drying, microbial and enzyme inactivation, and restriction of moisture deteriorative reactions in low moisture products like spices considering demand of spice growers, processors, and exporters.

4 Channel Sterilizer Calibrator

Thermocouple (Thermocouple) is a type of temperature sensor used to detect or measure temperature through two types of metal conductors, whose working principle is that each end of a metal conductor is combined to create a "Thermoelectric" effect. One type of metal conductor contained in a thermocouple will serve as a reference with a constant temperature (fixed), while a metal conductor functions as a metal conductor that detects hot temperatures. Sterilisator is a device used to sterilize medical instruments to avoid the bacteria that attach to the remainder of the use of medical instruments. The temperature of the sterilizer varies but generally for dry sterilizers ranges from 175 ° Celsius. From the above problems, the author wants to develop a "4 Channel Sterilizer Calibrator", Using the Arduino Nano Atmega328 as a minimum system, K type thermocouple and MAX6675 module as a sensor. Measurements were made by comparing modules with standard measuring instruments, obtained the smallest error 0.2% at T3 and T4 when measuring 100 ° C, and the largest 4.4% at T2 when measuring 150 ° C.

Effect of steam and dry heat sterilization on the insertion and fracture torque of orthodontic miniscrews

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.

Knowledge of Nurses in Prevention of Hospital Infection in Hospital "Sheikh Zayed" Vushtrri.

Introduction:Hospital infections are the major challenge of modern health care, and they are indicative of the quality of the services provided, a hospital or other health institution. Hospital infections also belong to gastric infections, which are the result of the mistakes of health workers during various diagnostic and therapeutic procedures.Aim:This study deals with the research of knowledge, experiences, and the work of nurses and their interventions in the prevention of hospital infections in the Vushtrri regional hospital center.Material and Methods:We used dry Sterilization (exposure at 160 ° C for 120 minutes or 170 ° C for 60 minutes) which is considered less safe than the first method especially for some devices with many tubes, pits, etc. Ethylene oxide and formaldehyde are released from use for safety reasons with the emission of gases.Results:From the research conducted we found that about 70% of nursing staff have satisfactory knowledge of hospital infections and the role of nursing care in preventing hospital infections, while only 55% have sufficient knowledge about the ways of spreading hospital infections. Over 77% of respondents have sufficient knowledge about the measures and prevention of hospital infections.Conclusion:The reason why we have been researching this topic has to do with many interventions, applications, nursing procedures is a series of actions that can contribute both to prevention and to the appearance of hospital infections. For their definition around the world, definitions of hospital infections are used according to the Center for Disease Control (CDC) from Atlanta.

A formulation of neem cake seeded with Bacillus sp. provides control over tomato Fusarium crown and root rot

ABSTRACTFusarium crown and root rot (FCRR) caused by the fungus Fusarium oxysporum f. sp. radicis-lycopersici is a damaging soil-borne disease of tomato. A plant growth rhizobacterium, Bacillus sp. strain HN09 isolated from neem tree rhizosphere soil, was shown to inhibit the growth, germination and development of normal morphology of the FCRR pathogen. A substantial level of disease control was achieved in greenhouse trials by soil supplementation with a preparation of neem cake seeded with HN09. Dry sterilisation of neem cake before fermentation gained comparable disease control effect as those in the unsterilised treatment, whereas moist sterilisation treatment decreased the effect significantly. This bioformulation also led to significantly raised activities in tomato genes encoding pathogenesis-related proteins, hence providing an effective alternative for the control of FCRR, reducing the need for chemical fungicide and fertilisers that impact the environment.

Inactivation of pathogenic micro-organisms in hospital waste using a microwave

The aim of this study was to investigate the efficiency of dry sterilization by microwave in the inactivation of pathogenic bacteria in blood wastes. Eight bacteria strains were selected for this purpose and these are S. aureus, Salmonella sp., E. faecalis, K. pneumonia, P. aeruginosa, E. coli, Streptococcus Group B and Bacillus sp. Sterilization by microwave was carried out at 385, 450 and 700 watts for 1, 5 and 10 min, respectively. Isolation and enumeration of pathogenic bacteria before and after treatments were carried out using direct plate technique and inactivation was determined in terms of log reduction. Increasing the running time and power to 10 min and 700 watts did not increase log reduction of most of pathogenic bacteria especially of gram negative bacteria. Revival of pathogenic bacteria during the storage period might be aided by the presence of a low moisture content which helps bacterial cells to revive but not to reproduce or over-grow. It can be concluded that dry sterilization of blood wastes by microwave reduces the number and limited re-growth of these pathogenic bacteria during storage time, due to the lower moisture content in the blood wastes.

Beneficial effect of protracted sterilization of lentils on phytase production by Aspergillus ficuum in solid state fermentation

Water addition to the solid substrate preceding autoclaving increased substrate porosity and phytase production in solid state fermentation. In comparison with dry sterilization, the phytase activity increased 6-, 8.5-, and 10-fold when the autoclaving time was 20, 40, and 60 min, respectively. Autoclaving increased the void space of sterilized lentils, and the increase was 16% higher when water was supplemented to the lentils before sterilization. Image analysis of SEM pictures of the solid substrate showed that water supplementation presterilization portended greater micro-fissure surface area, which also increased with increasing the sterilization time. SEM pictures of the fermentation product showed that fungal growth into the center of the solid substrate was ubiquitous when water was supplemented before sterilization but was absent when water was supplemented post sterilization. Similarly, spore formation on the substrate surface for the presterilization water supplementation samples far exceeded spore formation for samples that received supplementation poststerilization. This evidence suggests that improved mass transfer into the solid substrate resulting from additional pore volume and the formation of micro-fissures on the substrate surface is responsible for the observed gains in phytase productivity in solid state fermentation.

Development of a Wound Dressing Composed of Hyaluronic Acid and Collagen Sponge with Epidermal Growth Factor

This study was designed to investigate the effect of a wound dressing composed of hyaluronic acid (HA) and collagen (Col) sponge containing epidermal growth factor (EGF) on various parameters of wound healing in vitro and in vivo. High-molecular-weight (HMW) HA solution, hydrolyzed low-molecular-weight (LMW) HA solution and heat-denatured Col solution were mixed, followed by freeze-drying to obtain a spongy sheet. Cross-linkage between Col molecules was induced by UV irradiation to the spongy sheet (Type-I dressing). In a similar manner, a spongy sheet containing EGF was prepared (Type-II dressing). The efficacy of these products was firstly evaluated in vitro. Fibroblast proliferation was assessed in culture medium in the presence or absence of a piece of each wound dressing. EGF stimulated cell proliferation after UV irradiation and dry sterilization at 110°C for 1 h. In the second experiment, fibroblasts-embedded Col gels were elevated to the air–liquid interface to create a wound surface model, on which wound dressings were placed and cultured for 1 week. Cell proliferation and the production of vascular endothelial growth factor (VEGF) and hepatocyte growth factor (HGF) were investigated. With Type-II dressings, the amounts of VEGF and HGF released from fibroblasts in the Col gel were significantly increased compared with Type-I dressing. Next, the efficacy of these products was evaluated in vivo using Sprague–Dawley (SD) rats. Wound conditions after 1 and 2 weeks of treatment with the wound dressings were evaluated based on the gross and histological appearances. Type-II dressings promoted a decrease in wound size, re-epithelialization and granulation tissue formation associated with angiogenesis. These findings indicate that the combination of HA, Col and EGF promotes wound healing by stimulating fibroblast function.

Initial Determination of Polymorphism and In Vitro Conservation of Some Ramonda Serbica and Ramonda Nathaliae Populations from Albania, Macedonia and Bulgaria

ABSTRACTThe “resurrection plant” Ramonda serbica is included in the Albanian and Bulgarian list of endangered plants as a rare, Balkanic-endemic species and tertiary relic species, while R. nathaliae is characteristic in the FYROM area. Our research groups have established national in vitro collections of R. serbica in Albania and Bulgaria and R. nathaliae in Macedonia. The aim of this joint study is (1) the choice of successful micropropagation methods as the basis for the in vitro collections and (2) the evaluation of polymorphism of some natural populations. In both collections, seeds were used as a convenient starting point for micropropagation in the nutrient medium JG-B. In the Bulgarian in vitro collection, a dry sterilization of seeds was applied for a first time for Gesneriaceae family. The micropropagation and conservation of Ramonda seeds and plantlets were similar in Albanian and Bulgarian collections. The plantlets in vitro as an explant material were developed in JG-B medium with different phytohormones. The direct organogenesis of two Ramonda species is very similar models. The method of conservation in vitro with minimal growth method (modification of nutrient medium) was used. Meiosis and mitosis examinations of the natural populations and plantlets cultivated in vitro were carried out by standard Squash method. Cytogenetical study of natural populations showed polyploid forms as a mixture (2n=72) and (2n=96). Mitosis preparations in plantlets in vitro showed a predominance of the most frequent form (2n=96). The biodiversity in interspecific level of the natural populations of Ramonda serbica of Central Albania, R. nathaliae from Macedonia and cultivated plantlets in vitro from Albania and Bulgaria was evaluated via molecular markers (RAPDs). The micropropagation method is a convenient way for the international exchange of germplasm of rare and endemic plants. From the data obtained in this study it can be concluded that RAPD markers provided a useful technique to study genetic diversity in Ramonda serbica and R. nathaliae populations. This technology allows the identification of different populations as well as the assessment of the genetic similarity among different populations.

Difference between post curing composite hardness with heating using dry sterilizer and radiation using light box

Introduction: Composite resin has been used as a restoration material for quite a long time. Two different methods were expected to show result of which method that would be the most promising. Aim of study is to analyzed differences the hardness of one composite resin subjected to two post curing treatments. Methods: This study was a true experimental research (in vitro). The subjects were 30 specimens of the hybrid light cured resin composites made in a mold (6 mm diameter and 4 mm high). The hardness of all specimens were tested using Rebound Hardness Tester. Data were compared using ANOVA and post hoc analysis (for pairwise independent groups) using t-tests. Results: This study showed that post curing treatment by heat (for 10 min at 110 oC ) showed higher hardness (p&lt;0.005). Conclusion: There was difference of hardness between two methods of post curing. Moreover, post curing with dry heat sterilizer at 110oC for 10 min was found to be the most promising post curing method.

Deformations of the manual endodontic instruments during root canal instrumentation

Introduction. Mechanical instrumentation of the complex root canal system is very demanding procedure which requires use of the various manual and rotary instruments. The aim of this study was to assess the frequency and to verify the possible deformation of the working part of endodontic instruments after their multiple clinical use. Material and Methods. New sets of the manual endodontic instruments (reamers, K-files and Hedstroem) used in routine clinical use (44 instruments) and for root canal instrumentation of extracted teeth (44 instruments) were included in the study. Instrumentation was performed by Step-Back technique and constant irrigation with 0.5% NaOCl solution, 10 ml for each root canal. All the instruments were used 10 times and after use sterilized in a dry sterilizer or autoclave. The working parts of deformed instruments were analyzed using optimagnetic print. Results. The results obtained after clinical use showed deformations of the working part of the reamers in 50%, K-files in 43% and Hedstroem in 66.7% of used instruments. After instrumentation the canal of the extracted teeth, deformations were observed in 87.5% of the reamers, in 50% of the K-files and in 62.5% of Hedstroem files. The difference in frequency of the deformations was not statistically significant. On the instruments used for the preparation the canals of the extracted teeth and sterilized in autoclave, malformations were observed in 86.4%, comparing to the instruments sterilized in a dry sterilizer where malformations of the working part were registered in 59.1% of the cases. That difference was statistically significant (?2=5.250; p=0.072). Conclusion. Multiple use of the manual endodontic instruments in clinical conditions leads to increased frequency of malformations of the working part in all types of manual endodontic instruments.