it is the destruction or removal of all pathogenic micro - organisms which give rise to infection , but not necessarily their spore forms . it is the process by which an article , surface , or medium is freed of all microorganisms either in the vegetative or spore state . with the whole world looking at the eradication of existing infectious diseases and preventing any new infections , sterilization of instruments is significant to ensure optimal patient care . in contemporary dental practice , the instruments directly come in contact with tissues , blood and tissue fluids , saliva , and gingival crevicular fluid which may seep through the rubber dam if not properly placed . dental health personnel are constantly exposed to the potential threat of developing an infection by occupational exposures to a variety of microbial pathogens ; most common of all are hepatitis b virus ( hbv ) , hepatitis c virus ( hcv ) , tuberculosis ( tb ) , and acquired immunodeficiency syndrome ( aids ) . the prevention of cross - contamination of infectious diseases among dentists , dental staff , and patients is a major concern in dental practice . also , aseptic technique is especially important in endodontics because microorganisms are the major cause of endodontic disease . diseases may be transmitted by indirect contact when dental instruments contaminated by one patient are reused for another patient without adequate disinfection or sterilization between uses . apart from maxillofacial surgery , the potential for cross - infection is highest in the prosthodontic environment . dental burs have been identified as a source of cross - contamination between patient and dental personnel . they may become heavily contaminated with necrotic tissues , saliva , blood , and potential pathogens during use . however , it is difficult to do the pre - cleaning and sterilization of burs because of their complex architecture . endodontic files are slender , tapered instruments , about 25 mm long , with intricate topography and spiral cutting edges , and are used for cleaning and shaping root canals during endodontic treatment . because of their size and shape , it is difficult to remove all the biologic material during resterilization procedures . hence , a strict sterilization protocol is essential as the risk of cross - infection is higher . various methods have been proposed by many manufacturers for this purpose , namely , the autoclave , dry - heat sterilization , laser , chemical sterilization , etc . therefore , the present study was designed to investigate the pathological evaluation for sterilization of routinely used prosthodontic and endodontic instruments . to investigate the effectiveness of various sterilization procedures commonly applied to used burs . to investigate the effectiveness of various sterilization procedures commonly applied to used endodontic files . it is the destruction or removal of all pathogenic micro - organisms which give rise to infection , but not necessarily their spore forms . it is the process by which an article , surface , or medium is freed of all microorganisms either in the vegetative or spore state . with the whole world looking at the eradication of existing infectious diseases and preventing any new infections , sterilization of instruments is significant to ensure optimal patient care . in contemporary dental practice , the instruments directly come in contact with tissues , blood and tissue fluids , saliva , and gingival crevicular fluid which may seep through the rubber dam if not properly placed . dental health personnel are constantly exposed to the potential threat of developing an infection by occupational exposures to a variety of microbial pathogens ; most common of all are hepatitis b virus ( hbv ) , hepatitis c virus ( hcv ) , tuberculosis ( tb ) , and acquired immunodeficiency syndrome ( aids ) . the prevention of cross - contamination of infectious diseases among dentists , dental staff , and patients is a major concern in dental practice . also , aseptic technique is especially important in endodontics because microorganisms are the major cause of endodontic disease . diseases may be transmitted by indirect contact when dental instruments contaminated by one patient are reused for another patient without adequate disinfection or sterilization between uses . apart from maxillofacial surgery , the potential for cross - infection is highest in the prosthodontic environment . dental burs have been identified as a source of cross - contamination between patient and dental personnel . they may become heavily contaminated with necrotic tissues , saliva , blood , and potential pathogens during use . however , it is difficult to do the pre - cleaning and sterilization of burs because of their complex architecture . endodontic files are slender , tapered instruments , about 25 mm long , with intricate topography and spiral cutting edges , and are used for cleaning and shaping root canals during endodontic treatment . because of their size and shape , it is difficult to remove all the biologic material during resterilization procedures . hence , a strict sterilization protocol is essential as the risk of cross - infection is higher . various methods have been proposed by many manufacturers for this purpose , namely , the autoclave , dry - heat sterilization , laser , chemical sterilization , etc . therefore , the present study was designed to investigate the pathological evaluation for sterilization of routinely used prosthodontic and endodontic instruments . to investigate the effectiveness of various sterilization procedures commonly applied to used burs . to investigate the effectiveness of various sterilization procedures this is an in vitro study in which used burs and files were considered for sterilization . after sterilization , they were incubated for a period of 72 h. ethical clearance was obtained from sridevi institute of medical sciences and research centre . procedure and purpose of the study was explained to the participants from whom used burs and files were obtained , and their consent was taken . an unused bur was placed in a sterilized hand piece and used for cavity preparation . 20 file used for endodontic purpose was collected in a sterile tube and cleaned properly by scrubbing . out of the total 60 burs and 60 files , 12 burs and 12 files were taken as the control group ( group e ) ; the remaining 48 burs and 48 files were divided into four groups of 12 each and they were tested for the efficacy of sterilization with different methods such as autoclave ( group a ) , glass bead ( group b ) , glutaraldehyde ( group c ) , and quitanet plus solution ( group d ) . the 12 contaminated burs and files in group a were placed in an endodontic instrument box and subjected to autoclave at 121c for 15 min at a pressure of 15 pounds . the 12 contaminated burs and files in group b were wiped for 10 s with surgical spirit and placed in the periphery of the glass - bead sterilizer and sterilized for 45 s at 240c . the 12 contaminated burs and files in group c were placed in a sterile plastic container containing 2.4% glutaraldehyde solution and left in it for 12 h. the 12 contaminated burs and files in group d were placed in a sterile plastic container containing quitanet plus solution and left in it for 12 h. the 12 contaminated burs and files in group e ( control group ) were put in separate tubes without doing any sterilization . on completion of the procedure , the burs and files were transferred in a sterile fashion into test tubes containing a culture medium selected to grow oral bacteria ( todd - hewitt broth ) . all samples ( n = 120 ) were then placed in an incubator maintained at 37c to mimic body temperature . the burs and files were examined daily over 72 h to check for evidence of bacterial growth . a color change , cloudy broth , and visible precipitate in the test tube were all considered as indicative of bacterial growth [ figure 1 ] . if the solution remained clear throughout the incubation period , the sample was considered sterile . an unused bur was placed in a sterilized hand piece and used for cavity preparation . 20 file used for endodontic purpose was collected in a sterile tube and cleaned properly by scrubbing . out of the total 60 burs and 60 files , 12 burs and 12 files were taken as the control group ( group e ) ; the remaining 48 burs and 48 files were divided into four groups of 12 each and they were tested for the efficacy of sterilization with different methods such as autoclave ( group a ) , glass bead ( group b ) , glutaraldehyde ( group c ) , and quitanet plus solution ( group d ) . the 12 contaminated burs and files in group a were placed in an endodontic instrument box and subjected to autoclave at 121c for 15 min at a pressure of 15 pounds . the 12 contaminated burs and files in group b were wiped for 10 s with surgical spirit and placed in the periphery of the glass - bead sterilizer and sterilized for 45 s at 240c . the 12 contaminated burs and files in group c were placed in a sterile plastic container containing 2.4% glutaraldehyde solution and left in it for 12 h. the 12 contaminated burs and files in group d were placed in a sterile plastic container containing quitanet plus solution and left in it for 12 h. the 12 contaminated burs and files in group e ( control group ) were put in separate tubes without doing any sterilization . on completion of the procedure , the burs and files were transferred in a sterile fashion into test tubes containing a culture medium selected to grow oral bacteria ( todd - hewitt broth ) . all samples ( n = 120 ) were then placed in an incubator maintained at 37c to mimic body temperature . the burs and files were examined daily over 72 h to check for evidence of bacterial growth . a color change , cloudy broth , and visible precipitate in the test tube were all considered as indicative of bacterial growth [ figure 1 ] . if the solution remained clear throughout the incubation period , the sample was considered sterile . in the study , the endodontic files sterilized by autoclaving in an instrument box at 121c for 15 min at a pressure of 15 pounds ( group a ) showed total sterility . ten burs ( 83.3% ) subjected to sterilization by glass - bead sterilizer and seven files ( 58.33% ) after wiping for 10 s with surgical spirit and sterilized for 45 s at 240c ( group b ) showed incomplete sterilization [ figures 2 and 3 ] . sterilization efficiency of different methods for burs sterilization efficiency of different methods for files burs and files sterilized by immersing in glutaraldehyde ( 2.4% ) for 12 h ( group c ) showed complete sterilization . ten burs ( 83.3% ) and nine files ( 75% ) showed incomplete sterilization with quitanet plus ( group d ) solution . the control group ( group e ) , for which the files after contamination were not sterilized by any method , showed growth in all samples . statistical analysis of the four sterilized groups using k analysis of variance ( anova ) showed a statistically significant difference between groups with regard to their efficacies in sterilization of both with burs and files ( p  0.05 ) [ tables 1 and 2 ] . comparison of different methods of sterilization for burs comparison of different methods of sterilization for files the risk of disease transmission is unknown in endodontic procedures ; even if the risk of disease transmission is minimal during endodontic procedures , the high frequency of root canal treatments could increase the possibility of an adverse event . this is one example of why it is so important to ensure that resterilization procedures are effective . there are three principal methods currently available for sterilization of instruments : steam under pressure ( autoclave ) , dry heat , and chemiclave . steam autoclaving and glass - bead sterilizers are among the commonly recommended methods of sterilization . the goal of instrument sterilization in dentistry is to protect patients from cross - contamination via instruments . at present , only a few dental instruments can not be sterilized and these are either disinfected or disposable . the complex miniature architecture of dental burs and endodontic files makes precleaning and sterilization difficult . for decades , clinicians have searched for the ideal chair - side sterilization method and several different mediums have been used . the present study showed that complete sterilization was possible by autoclaving the instruments in an endodontic box . this is significantly similar to the findings from studies of other researchers like hurtt et al . damaging alterations of proteins by dry heat are a result of oxidation , desiccation , and changes in osmotic pressure owing to evaporation of moisture . dry heat sterilization is slower and requires temperatures higher than those used in moist heat sterilization . this study showed that sterilization by a glass - bead sterilizer was not able to completely eliminate microorganisms and that total sterility was not found . the present study result was contradictory to that of previous research done by rajkumar et al . , but it was the same as that of hurtt et al . who performed their study with salt instead of glass bead . in the present study , immersing the files in glutaraldehyde solution for 12 h resulted in complete sterilization , which is similar to the results of the study done by hurtt et al . but glutaraldehyde solution can not be relied upon completely to sterilize endodontic instruments as it is used in a limited number of applications , rather than as a general disinfectant , as it is a toxic chemical . contact with glutaraldehyde liquid and vapor can severely irritate the eyes , and at higher concentrations , it burns the skin . breathing glutaraldehyde can irritate the nose , throat , and respiratory tract , causing coughing and wheezing , nausea , headaches , drowsiness , nosebleeds , and dizziness . quitanet plus is commonly used nowadays in the dental office for sterilization of burs and files . it can be concluded that it is not an effective means of sterilizing burs and files . routine sterilization procedures were not effective for previously used burs and files , and further research is warranted to devise an effective sterilization protocol . future studies should focus on determining the best method of pre - cleaning these devices . if such procedures can not be devised , perhaps the instruments should be considered single - use devices . glass - bead sterilizer can be used as an alternative when these two methods are not available , but the problem with glutaraldehyde sterilization is tissue toxicity . though autoclave is an effective method for sterilizing endodontic files , the time taken by it to sterilize is more . hence there is a need for an alternative method which has a good sterilization capacity and involves less time .