There are many infectious diseases that can be transmitted in the dental clinic, one of the main routes of transmission being the use of contaminated material.Recent literature and increased publicity about the potential for transmission of infectious agents in the dental office have focused attention on dental instruments as potential pathogen transmission agents.In this review study, we intend to collect what are the main causes of poor sterilization and, therefore, of the transmission of infectious diseases.Keywords: Sterilization, effectiveness, safety, hepatitis, disease transmission, cross infection, biological indicators.There are many infectious diseases that can be transmitted in the dental clinic, one of the main routes of transmission being the use of contaminated material.Some of the diseases that can be transmitted by this route are of special importance due to their high morbidity and mortality.Among them, we can highlight hepatitis B, hepatitis C and HIV (1-2).The risk of transmission in a percutaneous exposure with contaminated blood is greater in hepatitis B (6-30%) than in hepatitis C (1-7%) and HIV (0.3%) (17).Currently there is greater concern about infection with the hepatitis C virus (HCV), since despite the fact that the risk of transmission of the hepatitis B virus is greater, only 10% of those infected become Chronic carriers, moreover, thanks to the existence of an effective vaccine, this high risk is reduced, while the risk of HIV transmission is very low, especially in the dental clinic (2).The main problem with the hepatitis C virus (HCV) is that 80% of those infected are chronic carriers and, to a great extent, it contributes to the appearance of cirrhosis and hepatocellular carcinoma.There are currently 130-170 million chronic carriers, which means that 2.2-3% of the world population has the capacity to transmit the disease (3).The most recent literature, and increased publicity about the potential for transmission of infectious agents in the dentist, have focused attention on dental instruments as possible pathogen transmission agents (4).In the present study, which has included a review of the literature available in the last 10 years, it is intended to collect what are the main causes of poor sterilization and, consequently, of the transmission of infectious diseases.Sterilization is any physical or chemical process that destroys all forms of microbial life, including resistant forms (spores) and viruses.It is the highest possible level of microbial destruction and, therefore, the method that provides the highest level of protection to the patient (5-7).Sterilization methods can be physical or chemical.Among the physical sterilization methods, we can use steam or dry heat sterilization, while chemical sterilization can be carried out by immersing the instruments in chemical liquids, the main one being 2% glutaraldehyde, or by means of gas. ethylene oxide or hydrogen peroxide gas-plasma (7-8).It uses moist heat that has a greater and faster effect on microorganisms, since water is a good conductor, so that the heat penetrates better and is distributed more evenly.When applied as steam, it destroys microorganisms by coagulation and denaturation of proteins and enzymes.This system is the most widely used and most reliable, since it is non-toxic, inexpensive, a fast-acting microbicide, sporicidal, and rapidly heats and penetrates tissue.Thus, this system is used for the vast majority of materials, except in those cases that can be damaged by moisture or heat, since it produces corrosion and combustion on some materials such as lubricants associated with handpieces.The procedure consists of the generation of water vapor in a water chamber and the consequent displacement of the air to the outside.In this process, four fundamental parameters must be taken into account: steam, pressure, temperature and time.The principle on which this sterilization system is based is to expose each element with steam at the required temperature and pressure for the time necessary to destroy the biological organisms contained in said material.Air extraction is carried out beforehand, since its presence is an impediment to the sterilization process.Minimum exposure times for sterilization of wrapped medical devices are 30 minutes at 250ºF (121ºC) in a gravity displacement sterilizer, or 4 minutes at 270ºF (132ºC) in a pre-vacuum sterilizer.This difference in the duration of the process is due to the fact that in the case of gravity sterilization it is not possible to eliminate all the air.In addition, there are rapid sterilization or flash cycles in which the unwrapped material is kept at 134ºC for 3 minutes, however, its routine use is not recommended due to the lack of adequate biological indicators to verify its effectiveness, the absence of protection after sterilization (due to the absence of packaging) since the parameters of the sterilization cycle are minimal (5, 8-10).The basis of this method lies in the heating of the air and the transfer of heat energy to the instruments to be sterilized, achieving the death of microorganisms by coagulation or dehydration of proteins, with the usual loss of vital functions (9) .Dry heat, having less heat penetration and transfer capacity than moist heat, requires higher temperatures and a longer period of heating and holding to achieve sterilization.The main advantage of this type of sterilization is that the steel instruments do not corrode with carbon, unlike what happens with steam sterilization.Dry heat sterilizers can be of two types: static air or forced air circulation.In the former, the hot air generated by a resistance rises by natural convection into the interior of the chamber.Sterilization occurs after 2 hours at 160ºC or 1 hour at 170ºC.The heating time (until 160ºC or 170ºC is reached) varies according to the quality and quantity of the load (9).In those of forced air, the heated air is propelled and circulates at high speed through the chamber, this allows the rapid transfer of heat to the instruments, so that the time necessary to achieve sterilization is reduced.When the temperature reaches 190ºC, the holding time begins, which ranges from 12 minutes for wrapped instruments to 6 minutes for items that are not packaged.Bead sterilizers apply dry heat to instruments.It is an electric heater that makes pearls reach temperatures close to 220ºC.This method has the drawbacks that the temperature is not homogeneous and that it is not possible to carry out a biological control of the sterilization process.For it to be effective, the sterilization time must be greater than 60 seconds (11).It is used for the sterilization of thermosensitive materials (rubber, plastic, etc.), since the temperature reached does not exceed 30-60ºC.The duration of the cycle is 90 minutes, however, subsequently, it requires an aeration period of 12 hours to eliminate the gas residues, since it is flammable, toxic and reactive, this excessive time being the main drawback of this method (5 -6).It consists of the diffusion of hydrogen peroxide in the plasma phase (between liquid and gas).The temperature reached, as in the previous case, is low and subsequent aeration of the material is not necessary because the hydrogen peroxide, at the end of the process, is converted into water and oxygen, leaving no toxic residue.Complete sterilization is achieved in 55 minutes.However, it has a number of drawbacks: materials containing cellulose and liquids cannot be sterilized (instruments must be perfectly dry before being inserted into the chamber).It is also the most expensive method of those mentioned (5-6).It should be used at temperatures of 25º C (77ºF) keeping the instruments submerged for 10 hours.This product, being toxic, subsequently requires washing the instruments with boiled or sterile water (6,12).Almost as important as the prevention of contagion by direct contact, is the prevention of contagion by indirect contact.In this sense, it is essential to emphasize that it can be prevented by proper processing of the material.In the first place, we must take into account the degree of disinfection that we want the material to present: sterile, disinfected or clean.It depends on the type of instrument:– Critical: they are intended to be introduced into the bloodstream or into normally sterile areas, such as soft tissues and bone, and must be sterilized after each use.These include forceps, chisels, bone files, elevators, etc.– Semi-critical: they will come into contact with intact mucous membranes, but do not penetrate them or bone.They must be sterilized after each use.They include dental mirror, amalgam condensers, etc.– Non-critical: they will come into contact with intact skin.They are instruments such as external components of radiographic heads.Because these surfaces have a low risk of transmitting infections, the instruments can be treated between patients with medium or low level disinfectants, or detergents and washed with water depending on the nature of the surface and the degree of contamination (5,13).When using critical instruments, there are two options: use single-use sterile material or reusable material subjected to sterilization between one patient and another.For sterilization to be effective, it is essential that the material is previously washed and packaged (so that after sterilization it does not become contaminated).Table 1 compares the effectiveness of the different methods according to the available bibliography (14-17).As a summary, we can point out that steam sterilization is the only method that achieves 100% effectiveness in any of the cases.The second most effective method is ethylene oxide sterilization (close to 100%), followed by dry heat sterilization and by immersion in glutaraldehyde, these methods being less safe.Sterilization processes must be routinely subjected to controls that demonstrate their effectiveness.These controls can be of three types: physical, chemical or biological.All three forms of control must be used.Physical controls consist of a cycle record that documents that the appropriate pressure, temperature and time have been reached, being elements such as: thermometers, pressure gauges, load sensors, among others.If any anomaly is observed in these parameters, the load cannot be considered sterile, so despite being useful, they are not an effective means of verifying sterilization.They must be performed every day and in all cycles, at the beginning, during and at the end of the cycle (7,18).Chemical controls are commonly carried out using commercial products, consisting of chemical substances that change color if one or more key elements (temperature, humidity, pressure, concentration of the sterilizing agent) are met in the sterilization process.Like the previous ones, they do not guarantee that the equipment is carrying out an effective sterilization, although they do guarantee its operation, since they react when said parameters are reached.They are different according to the sterilization process used (dry, moist, gas heat).– External chemical controls: they are placed on the outside of the package or the elements to be sterilized and are used to check whether the material has been subjected to a sterilization cycle or not.– Internal chemical controls: They are placed inside the package.In dry heat cycles these indicators change color at a certain temperature and after a certain time, while for moist heat cycles temperature and steam indicators are used.Both types must be placed in each package.There are also chemical operating controls for autoclaves such as the Bowie and Dick, which consist of placing a control sheet in the center of a standard textile package, to detect the penetration of steam inside the package.It is always carried out under the same conditions: first cycle of the day, empty chamber, the package is placed in the coldest area (front lower, on the bleeder valve), horizontally, at 134ºC for 210 seconds.The indicator should change uniformly and throughout its length (7,18).Biological controls are the only ones that are universally accepted and serve to verify the effectiveness of sterilization.They consist of standardized preparations of spores of highly resistant microorganisms, which are processed in the sterilizer to check whether or not they have been destroyed and, therefore, whether or not the sterilization process has been carried out.They use two types of spores:Bacillus stearotermophilus (for steam or chemical vapor sterilization processes) and Bacillus subtilis (for ethylene oxide or dry heat processes), which are marketed on paper strips or disks.After the sterilization process, they are incubated for 24-48 hours and, subsequently, if there are live spores, they will return to their vegetative form and reproduce, producing bacterial growth that will be detectable by the appearance of turbidity or by the color change in the culture medium, which will reveal a sterilization failure.Rapid reading biological indicators are also available on the market, in the form of ampoules that contain a culture medium inoculated with the same spores, which also contains a non-fluorescent substrate that, due to the action of the enzyme of theBacillus stearothermophilus is transformed, after 3 hours of incubation, into a fluorescent product (5,7,18).In a study carried out by Villalobos (2001) it was shown that the results obtained with both types of biological indicators were identical, with a reliability and efficiency of 100% (19).According to the available bibliography, in Mexico the NOM recommends, for the prevention of oral diseases, that equipment with BI be evaluated once a month, while in the US the ADA, OSAP and CDC recommend applying it once a week .A record of the result must also be kept for each piece of equipment analysed.BI sampling has shown that even the safest method of sterilization can fail.Table 2 shows the published adverse events related to the transmission of infectious diseases due to defects in sterilization in the dental field (4).Table 3 specifies the percentage of failure found in the various studies, being notable for its habitual use of the autoclave that ranges between 2 and 37%, according to the data consulted (10,12, 20-22).Despite these data, the application of biological indicators is scarce and is often confused with heating indicators (control tapes), endangering patient safety by not identifying failures in the sterilization process (20).In 2001, Patiño evaluated the percentage of dentists that used indicators: 73% did not use any type of indicator, 10.7% used chemical indicators and only 16.2% used biological indicators.It is noteworthy that according to this study, 57.6% do not know the biological indicators (20).Despite the high efficiency of the main sterilization methods, being 100% that of the autoclave, these methods sometimes fail, causing the instruments to be non-sterile.Currently, due to the little use of biological indicators, these errors are not adequately detected in the sterilization process, turning said instruments into carriers of diseases.1. Araujo M, Andreana S. Risk and prevention of transmission of infectious diseases in dentistry.Quintessence International 2002;33: 376-82.2. Thomas MV, Jarboe G, Frazer RQ.Regulatory Compliance in the Dental Office.Dent Clin N Am 2008;52: 629-639.3. Lavanchy D. Chronic viral hepatitis as a public health issue in the world.Rev Lat Am Enfermagem 2008;22: 991-1008.4. Kohn WG, Collins AS, Cleveland JF, Harte JA, Eklund KJ, Malvitz DM.Guidelines for Infection Control in Dental Health: Care Settings.MMWR Recommend Rep 2003;52 (RR-17):1-61.5. Count M. Sterilization in Dentistry.www.dentisnet.com6. Silvestre C, Fagoaga L, Garciandía MJ, Lanzeta I, Mateo MC, Zapata MC.Sterilization.An Sist Sanit Navar 2000;23: 95-103.7. Sanz P. Sterilizer.Esteripharma, Mexico.8. Rojo M, Sardiñas S, Sosa MC, García I, Garay MI.Biosafety Manual for Stomatological Services.National Directorate of Stomatology.National HIV/AIDS Program.MINSAP, 2008.9. Diaz Alfonso GR.Current status of sterilization processes.Cuban Society of Bioengineering, 2003.10. Healy CM, Kearns HP, Coulter WA, Stevenson M, Burke FJ.Autoclave use in dental practice in the Republic of Ireland.Int Dent J 2004;54: 182-6.11. Zadik Y, Peretz A. The effectiveness of glass bead sterilizer in the dental practice.Refuat Hapeh Vehashinayim 2008;25:36-9.12. Acosta-Gío E. Infection prevention and control in your dental office.www.dentgra.com.13. Casillas E, Morán MA.Biosafety in dentistry.Current Dentistry 2008;59: 16-8.14. Van Eldik DA, Zilm PS, Rogers AH, Marin PD.Microbiological evaluation of endodontic files after cleaning and steam sterilization procedures.Austin Dent J 2004;49: 122-7.15. Venkatasubramanian R, Das Um, Bhatnagar S. Comparison of the effectiveness of sterilizing endodontic files by 4 different methods: an in vitro study.J Indian Soc Pedod Prev Dent 2010;28:2-5.16. Lopes C, Graziano KU, Pinto TJ.Evaluation of single-use reprocessed laparoscopic instrument sterilization.Best Practice Res Clin Gastroenterol 2011;19: 370-7.17. Yoon JH, Yoon BC, Lee HL, Kim YT, Lee DH, Choi IJ et al.Comparison of sterilization of reusable endoscopy biopsy forceps by autoclaving and ethylene oxide gas.Dig Dis Sci 2012;57: 405-12.18. Negroni M. Stomatologic Microbiology: Fundamentals and Practical Guide.2nd edition.Buenos Aires, Pan American Medical Editorial, 2009.19. Villalobos SG.Comparison of the result of the sterilization process with two biological indicators.Rev Nursing IMSS 2001;9:143-6.20. Patiño N, Loyola JP, Tovar LF.Use and verification with biological indicators in sterilizers of dental surgeons in San Luis de Potosí, Mexico.Public Health Mex 2001;43: 455-8.21. Reyes CA, Castillo JM, Martínez MP, Galan D, Aranda I. Biological sampling of dental autoclaves, 2008.22. Coulter WA, Chew-Graham CA, Cheung SW, Burke FJ.Autoclave performance and operator knowledge of autoclave use in primary care: a survey of UK practices.J Hosp Infect 2001;48: 180-5.Dr. Maria Garrido Garcia.Degree in Dentistry (UCM).Collaborator of the Spanish Patient Safety Observatory (OESPO)Dr. Bernardo Perea.Director of the Spanish Observatory for Dental Patient Safety (OESPO).Director of Legal and Forensic Medicine at the Complutense University of Madrid (UCM).Director of the Spanish Observatory for Dental Patient Safety (OESPO).Director of Legal and Forensic Medicine at the Complutense University of Madrid (UCM)Dr. Elena Labajo González.Doctor of Dentistry (UCM).Secretary of the Spanish Observatory for Dental Patient Safety (OESPO)Login to leave a commentThis website uses its own and third-party cookies to improve the user experience, perform user navigation analysis, show advertising related to your preferences and improve our services.If you continue browsing, we consider that you reject the use of cookies, and navigation errors or display problems of certain contents may occur.For more information, consult our cookies policy in advance.