Reference Edition
This chapter is part of the Air Force Dental Laboratory Manual (2005) – Digitally Restored Edition.
This edition preserves the original publication while correcting OCR errors, restoring formatting, reconstructing damaged tables where necessary, and improving digital readability.
The technical content has not been rewritten, modernized, expanded, or altered.
It is provided as a professional reference. Modern instructional material is published separately throughout DentalTechnology.org.
The mission of the dental laboratory specialty is “to support the Department of Defense personnel in building the world’s most respected air, land, sea, and space forces by fabricating dental prostheses and specialized products, supporting research activities, and providing consultation services to dental health care providers.” The foundation of our country’s national security is based on the strength and readiness of its military services. As part of the medical mission, each person assigned to the Dental Service plays a vital role in establishing and maintaining the dental health of uniformed military personnel.
The dental laboratory specialty is an integral element of the Dental Service. It deals with the design, fabrication, and repair of dental prostheses (crowns, complete dentures, and fixed and removable partial dentures [RPD]) under the supervision of a dentist. Prosthesis is a general term that applies to any artificial replacement for a lost body part. Prosthetic dentistry (prosthodontics) is the art and science of fabricating artificial replacements for missing oral structures.
The duties and responsibilities of personnel assigned to the dental laboratory specialty increase as a person grows in knowledge, skill, and grade. These duties begin by performing routine procedures in the various areas of fixed, partial, and complete dentures. As skills and knowledge increase, more advanced procedures are learned through on-the-job training or in advanced training courses. The technician who demonstrates personal and professional maturity is expected to assume supervisory responsibilities. These duties include laboratory training, laboratory supervision, and administrative and leadership positions. A more extensive breakdown of skill and career progression is described in the Air Force Dental Laboratory Specialty Career Field Education and Training Plan.
A special standard of ethical behavior is required of all people involved in health care delivery. That is, a spirit of service and personal commitment must be the controlling factor in duty performance. Supporting patient care requires committed and responsible duty performance. Your performance affects the health of others.
1.4.1. Dentist's Relationship to the Technician. The dentist should treat the technician as a professional. The dentist is responsible for giving the technician very specific directions (a prescription) for each case to be fabricated, being available to answer the technician's validity questions, and providing assistance as necessary. After determining the patient can wear the prosthesis made by the technician, the dentist assumes legal responsibility for the entire procedure.
1.4.2. Technician's Relationship to the Dentist. As a professional, a technician must maintain knowledge and proficiency by continuing his or her education. Every restoration the technician makes must represent his or her best effort. The technician must follow the dentist's prescription exactly. In the technician's judgment, if a prescription change is indicated, the dentist must be consulted. Technicians must conduct themselves in a professional manner, especially when patients are present. Professionally oriented conversations between a technician and a dentist are privileged communications that must not be repeated to others.
1.4.3. Technician's Relationship to the Patient.
1.4.3.1. The technician must fabricate each prosthesis to the highest standard of which he or she is capable. The technician is responsible for any deliberate inappropriate actions resulting in failure of the prosthesis.
1.4.3.2. The technician's moral responsibility is to the patient. The technician must behave in a professional manner at all times. NOTE: Because the technician and dentist are judged on the basis of observed behavior, they must ensure their behavior is always acceptable.
1.4.3.3. The patient's dental condition and progress of treatment are privileged information; therefore, this information must not be repeated in anything other than a professional conversation. Anything the technician learns about a patient's personal life or habits is privileged information.
Improper posture can produce fatigue, pain, and discomfort. Sitting with your head lowered forward can cause a feeling of cramping in the back of your neck, and a curved spine can cause backache. General health can be impaired because poor posture could cause displacement of the internal organs. The following are proper postures for the positions in dental laboratory work:
1.5.1. Standing Position. Stand erect, with your legs comfortably parted. This posture ensures maximum stability. The weight is carried mainly on the balls of your feet. In this position, an imaginary line dropped from the base of the ear would pass through your shoulder, hip joint, and kneecap and just in front of your ankle.
1.5.2. Sitting Position. Sit erect. In this position, an imaginary line would pass through your ear, shoulder, and hip joint. Sit as far back in your chair as possible. When you work at a desk or bench, your body should bend forward from the waist without breaking the straight line previously described.
The exactness of dental laboratory work demands good lighting. When possible, place the equipment so natural light comes from behind and above your shoulders. When artificial light is in front of the operation, it must be shielded so there is no glare and it should be directed onto the work being performed.
1.7.1. Properly filtered ventilation is essential for good health and maintaining a positive working attitude. Ventilation supplies clean air at a controlled temperature so the environment is kept safe and comfortable. A controlled temperature is also essential when working with dental materials. Waxes and investments require a controlled temperature of approximately 70 - 72 degrees to achieve proper expansion for accurate-fitting restorations.
1.7.2. Ventilation should be sufficient to remove fumes, gases, and excessive heat and dust. In some areas of dental laboratories, some form of mechanical ventilation is required to remove air contaminants such as dust and fumes. This is done by using exhaust hoods located at the areas where contaminants are generated.
1.8.1. Prolonged exposure to noise and vibration can affect your hearing ability, general health, and working efficiency. Many noises can be eliminated at their source, while others can be guarded against by individual protective measures. Proper location and lubrication of machinery are essential.
1.8.2. The Air Force Occupational Safety and Health (AFOSH) Standard 48-19, Hazardous Noise Program, enforces Occupational Safety and Health Administration (OSHA) standards and requires the use of devices (such as soft rubber earplugs when you work close to noisy equipment) and rubber mats placed under equipment and in places where people stand to operate equipment, thus reducing the effects of vibration. These measures reduce the effects of long term exposure to noise and vibration detrimental to your general health.
A dental laboratory must be neat and orderly at all times. Clean, orderly surroundings are conducive to the best efforts and safety of all concerned. Continuous, routine care of the laboratory is everyone's responsibility. The easiest way to maintain a neat work area is to clean the area after each procedure. When this becomes habit, only a short cleanup period is necessary each evening to prepare the laboratory for use the next day. When the day's work is completed, work benches, lathes, and bench engines must be cleaned and dusted. Sinks must be emptied and scoured, and water baths must be drained. As required by clinic policy, floors should be swept, mopped, and waxed. Instruments must be cleaned and returned to their proper storage areas.
You must constantly be alert to hazards that might harm your eyes. Intense light from gas-oxygen torches, acids, corrosive fumes, and flying particles pose serious safety hazards in the laboratory. All personnel must be trained to use an approved eyewash station which should be located in the laboratory for easy access by all personnel. This station will be used to flush the eyes with cold water in the event hazardous materials get into the eyes. (For guidelines on eyewash station requirements, see AFOSH Standard 91-32, Emergency Shower and Eyewash Units.) Neutralizers for chemicals used in the laboratory must be available. Refer to material safety data sheets (MSDS) for specific neutralizers.
WEAR PROTECTIVE GLASSES OR GOGGLES WHEN THE REMOTEST POSSIBILITY OF EYE DAMAGE EXISTS.
1.11.1. Fingernails should be trimmed short so they do not collect dirt or become torn and cause injury to fingertips. Certain laboratory procedures require wearing rubber gloves; other procedures require wearing insulated gloves or mitts. Using hand creams frequently during cold weather helps prevent chapping.
1.11.2. Give immediate care to all scratches, cuts, burns, or bruises to lessen the risk of infection. Appliances worn by patients can harbor organisms that may cause serious infection or disease through cuts or breaks in the skin. Therefore, always wear latex or rubber gloves when pouring impressions, cleaning impression trays, or handling a prosthesis that was in the patient's mouth.
1.11.3. Keep hands clean by frequently brushing them with a handbrush, soap, and water. Remove rings and bracelets to prevent catching them in equipment.
Hair should be trimmed short to prevent tangling it in lathes. Long hair will almost certainly be singed or set on fire near an open flame. If the need is obvious, use hairnets or bobby pins.
As with long hair, dangling shirttails, sleeves, and neckties can pose a problem near lathes and flames. A securely fastened, well-fitting lab coat provides protection. Use an apron over your lab coat when pouring impressions or cleaning impression trays. This clothing may be disposable or cleaned by a laundry service.
As a general rule, sharp instruments are less dangerous than dull ones. Rather than straining to use a dull tool, you can exercise more deliberate control with a sharp one. Keep all cutting tools sharply pointed or edged, but don't carry dangerous, unshielded instruments on your person. Dispose of broken instruments and worn or broken lab blades in an appropriate "sharps" container.
1.15.1. Wear protective goggles or glasses during finishing and polishing procedures. Do not leave a running lathe unattended; turn it off when it is not in use.
1.15.2. Ensure all chucks and attachments are securely mounted before starting the lathe. Do not use attachments that vibrate or do not run true. Do not adjust or replace chucks, wheels, or similar attachments while the lathe is running unless the machine is equipped with an automatic chuck. Do not attempt to stop a running lathe by grasping the attachment with your hands.
1.15.3. Adjust the glass shield of high speed lathes to an angle that deflects flying debris away from the face. Follow the manufacturer's directions for inserting attachments, starting and stopping the lathe, and releasing the attachments.
1.16.1. ALL DENTAL LABORATORY PERSONNEL MUST KNOW LOCAL PROCEDURES FOR REPORTING FIRES, WHERE THE FIRE EXTINGUISHER IS KEPT, AND HOW TO USE IT.
1.16.2. After use, turn off equipment having electric heating elements. Be aware that these units have a tendency to stay hot long after they are switched off.
1.16.3. Do not leave a Bunsen burner or blowtorch flame unattended. Turn off these flames immediately after use. Control the height of a Bunsen burner flame. (A 3-inch flame is sufficient for almost all laboratory procedures.) Close the outlet valve at once when a gas flame is accidentally extinguished. Make sure a Bunsen flame is not burning through the hose that supplies the unit.
1.16.4. Replace damaged lengths of hose immediately. Store flammables (in permissible volumes) in proper containers and inside approved storage facilities. Keep flames away from storage areas containing flammables. Avoid heating both ends of a double-ended instrument. Use care in handling hot waxes and liquids.
Ensure all positive exhaust machinery is working properly. When working with acids or any other substance having toxic fumes, place and use these substances under a power exhaust hood. Keep all acid containers properly marked and covered when they are not in use. Position them to prevent spills. Use a proper mask to prevent inhalation of airborne dust during grinding and polishing procedures when adequate exhaust machinery is not available.
Report all electrical defects (frayed cords, loose plugs, etc.) as soon as they are discovered. Treat all electrical wires as “live” wires. Unplug all equipment not in use unless it is required to be plugged in at all times for proper function (for example, porcelain ovens).
1.19.1. Do not allow horseplay around compressed air. (NOTE: Serious injuries have occurred by the entry of compressed air into the body. Laboratory air pressure is routinely 30 lb/in2, and it is estimated that a pressure of 4 lb/in2 will rupture intestines.)
1.19.2. Wear eye protection at all times when compressed air is being used. Do not use more than the recommended pressure in pressurized curing units or other compressed air-powered equipment. Do not use more than 30 lb/in2 for cleaning purposes. Label each air outlet according to the air pressure available (lb/in2).
1.20.1. Preventing the spread of infectious disease is a factor less obvious than safety, but equally as important in maintaining the health and well-being of patients and clinic personnel. Infection control procedures reduce the spread of pathogenic microorganisms by breaking the chain of infection at critical points in the fabrication, repair, and delivery of prostheses.
1.20.2. The key concept in dental laboratory infection control is to clean and disinfect all contaminated items before they are allowed to reach the production area of the laboratory. If this is done, dental laboratory personnel and equipment will not become contaminated.
1.21.1. Dental health care workers (DHCW) are routinely exposed to blood, saliva, and other potentially infectious materials. Because of the potential for cross-contamination, dental personnel must follow strict infection control precautions.
1.21.2. Dental laboratory technicians are also susceptible to infection via cross-contamination. For example, it has been documented that they are almost three times more likely to be exposed to hepatitis B than the general population. Because of this potential for exposure, dental laboratory personnel are included in the hepatitis B high-risk population.
1.21.3. Some of the other potential pathogens the dental laboratory technician may be exposed to include the human immunodeficiency virus (HIV), tubercle bacillus (tuberculous), and herpes virus (primary and secondary herpes).
1.21.4. The potential for transmission of various types of infectious microorganisms from impressions and prostheses to dental laboratory personnel is always present, and universal precautions form the foundation for the prevention of cross-contamination. As described by OSHA, “Universal Precautions” indicates all blood, saliva, and bodily fluids in the dental workplace should be treated as potentially infectious.
1.21.5. In addition, routine infection control procedures should be developed and implemented for every patient. The term Standard Universal Precautions refers to the standard precautions applied universally to all patients, regardless of the infectious status, to reduce the risk of transmission of bloodborne pathogens. (See https://www.afms.mil/afdental/almajltr/1997/970414.pdf.) Various methods have been developed to minimize exposure of dental personnel to potentially infectious microbes. For example, engineering principles, personal protective equipment, chemical disinfection, sterilization, and vaccination all play a role in minimizing exposure to pathogenic microorganisms.
The following terms apply to infection control:
1.22.1. Antiseptic. An antiseptic is a chemical agent applied to a tissue to inhibit the growth of microorganisms.
1.22.2. Asepsis. Asepsis is a pathogen-free condition; that is, the process of preventing the access of microorganisms.
1.22.3. Aseptic Technique. Proper use of dental instruments to ensure sterilized and disinfected items are not contaminated before use is the aseptic technique.
1.22.4. Bioburden. Bioburden is the number and type of microorganisms that must be removed via mechanical debridement to allow proper disinfection.
1.22.5. Dental Item Classifications. Dental items can be classified as critical, semicritical, or noncritical in their need for sterilization or various levels of disinfection. As follows, these classifications are determined by where and how the items are used:
1.22.5.1. Critical Items. Critical items are objects that enter the skin, mucous membrane, or vascular system and present the greatest risk of infection. CRITICAL ITEMS MUST BE STERILE PRIOR TO USE. Scalpel blades, hypodermic needles, surgical instruments, and suture needles are examples of critical items.
1.22.5.2. Semicritical Items. Semicritical items are objects that frequently contact mucous membranes and are often contaminated by oral secretions and blood, but they do not enter the tissue or vascular system. THESE ITEMS MUST HAVE HIGH TO INTERMEDIATE LEVEL DISINFECTION. Shade guides, facebows, jaw relationship records, impressions, and prosthetic devices are examples of semicritical items.
1.22.5.3. Noncritical Items. Noncritical items are objects that don’t ordinarily contact mucous membranes or broken skin. THESE ITEMS SHOULD HAVE INTERMEDIATE TO LOW LEVEL DISINFECTION. Receiving areas, case pans, and articulators are examples of noncritical items. NOTE: The term “noncritical” does not imply “nonimportant.”
1.22.6. Disinfection.
1.22.6.1. The destruction or inhibition of most pathogenic bacteria (while they are in their active growth phase) and the inactivation of some viruses are termed disinfection. In most cases, the disinfecting process does not kill spores and cannot be easily verified. In addition to their normal spectrum, disinfectants used in a dental clinic environment also need to be tuberculocidal.
1.22.6.2. The Environmental Protection Agency (EPA) is tasked with classifying sterilants and disinfectants. They classify high-level disinfectants, which are sporicidal, as sterilizing agents. Defined levels of disinfection are based on the biocidal activity of an agent against bacterial spores, tubercle bacilli, vegetative bacteria, and viruses as well as the contact time of the solution.
1.22.6.3. High-level disinfectants (sterilizing agents) are biocidal against all classes of microbes, and they are used for all critical and some semicritical items.
1.22.6.4. Intermediate-level disinfectants will not routinely kill spores, but they are biocidal against all other classes. Intermediate-level disinfectants are used for semicritical and some noncritical items.
1.22.6.5. Low-level disinfectants are not effective against tubercle bacilli, bacterial spores, or certain nonlipid viruses. Low-level disinfectants are used only for noncritical items.
1.22.7. Personal Protective Equipment (PPE)
Specialized clothing or equipment (such as gloves, masks, protective eyeglasses, and gowns) that provide a physical barrier between the body and the source of contamination are called PPE.
1.22.8. Sanitation. Sanitation is the process that removes gross debris and reduces the number of microorganisms or nonliving material.
1.22.9. Sterilization. The process of totally destroying all forms of life within an environment, including viruses and spores, is called sterilization. Heat sterilization can be monitored and verified, but sterilization by high-level disinfectant solutions cannot easily be monitored or verified.
1.22.10. Unit Dose. Dispensing only those materials or supplies required for treating a single patient (or prosthesis) is the unit dose method.
1.22.11. Standard-Universal Precautions. DHCWs must assume all body fluids and contaminated instruments and materials are infectious and routinely use standardized infection control procedures. The use of standard-universal precautions protects both the patient and the dental team.
1.23.1. Laboratory personnel can be protected against infection by the establishment of a strict barrier system. This is usually initiated by establishing a receiving area (an engineering control) that is physically separate from the rest of the dental laboratory. If it is not possible to create a physically separate receiving area, a portion of the laboratory should be designated as the receiving area which would be considered contaminated. (The rest of the laboratory would be considered uncontaminated.)
1.23.2. All items needing disinfecting will first be processed through the receiving area (paragraph 1.24). This barrier system is essentially a series of cleaning and disinfecting procedures that removes blood, saliva, and other potentially infectious material from the impression or prosthesis. After an item has passed through the barrier system, dental laboratory personnel may safely work on the case with minimum PPE. In practice, this means sterilizing or disinfecting dental items that have had contact with the patient before and after any laboratory work is performed (paragraphs 1.25 through 1.38). After a prosthesis has been through the barrier system, it can then be processed through the laboratory.
Dental personnel working in the receiving area should wear the appropriate PPE (gloves, mask, eye protection, and smocks). They should wash their hands as they enter and leave the receiving area. Dirty and clean cases must be separated. Every item with a potential for contamination must not leave the receiving area until it has been cleaned and disinfected. Rush cases should not be allowed to break the infection control barrier. The bench top must be disinfected between each case and at the end of the day with an intermediate disinfectant solution.
1.25.1. After removal from the mouth, each impression should be carefully rinsed with running water in the dental treatment room before it is transported to the receiving area. Small amounts of dental stone may be sprinkled in the impression and gently scrubbed into the impression with a camel hair brush. This addition of the stone will aid in cleaning the impression. The impression should then be gently rinsed under running water. After rinsing, the impression will be transported to the receiving area in a plastic bag.
1.25.2. In the receiving area, the impression will be sprayed with an appropriate disinfectant solution and placed in a sealed plastic bag. Alginate impressions should be disinfected with a spray because they will absorb moisture if placed in a solution. Sealing the impression in a plastic bag creates a “charged atmosphere” which enhances disinfection. The most accurate casts have been produced when the spray and plastic bag technique was used to disinfect alginate and reversible hydrocolloid impressions. Appropriate disinfectant sprays include iodophors, sodium hypochlorite (1:10 solution), 2 percent glutaraldehyde, and chlorine dioxide products.
1.25.3. After the recommended time of disinfection, the impression will again be gently rinsed under running water and then poured in the traditional manner. Because reversible hydrocolloid and alginate impressions lose dimensional accuracy as a function of time, they should be poured within 12 minutes after removal from the mouth. A disinfectant should be selected that produces an appropriate level of disinfection in as short a time as possible.
These impressions may be managed like the hydrocolloid impressions (paragraph 1.25), or they may be immersed in an appropriate hospital level disinfectant. (EXCEPTION: These impressions should not be immersed in neutral glutaraldehyde.) Immersion with any acceptable disinfectant will not adversely affect the accuracy of the impression or the surface detail of the resulting cast. The surface detail of the cast seems to be enhanced if these impressions are immersed in a 2 percent acidic glutaraldehyde disinfectant.
Polyether impressions are hydrophilic and should not be immersed in a disinfectant solution. These impressions are disinfected in the same manner as reversible hydrocolloid and alginate impressions (paragraph 1.25). A chlorine-based disinfectant with a short disinfectant time is recommended for these impressions.
1.28.1. Carefully rinse fixed and removable prostheses under running water after removal from the mouth. This is the precleaning step. Then scrub the prosthesis with an antimicrobial soap and rinse it. This procedure can occur in the dental treatment room, professional work area, or the receiving area. If this cleaning step is performed in the dental treatment room, place the cleaned prosthesis in a plastic bag and take it to the receiving area.
1.28.2. In the receiving area, place the prosthesis in an ultrasonic cleaner with the appropriate cleaning solution. Place the cover on the ultrasonic cleaner and clean the prosthesis according to the manufacturer's recommended time. Then immerse the prosthesis in an accepted tuberculocidal disinfectant. Examples of acceptable disinfectants are sodium hypochlorite (1:10 solution), iodophors, and glutaraldehyde. The immersion time is 10 minutes or the manufacturer's specified time. Metal components of prostheses can be corroded by many disinfectants, but this is unlikely to occur if proper disinfectant times are followed.
1.28.3. After the disinfectant procedure is accomplished, the prosthesis will again be rinsed and can be processed through the laboratory. This procedure allows the laboratory technician to work on the prosthesis with minimum PPE.
1.28.4. If the prosthesis is to be shipped to another laboratory, the prosthesis will be disinfected and sealed in a plastic bag, which prevents contamination of the shipping materials. Also, a statement should be included in the shipping container stating the prosthesis has been disinfected. NOTE: Disinfectant is not added to the plastic bag containing the prosthesis because the exposure time to the disinfectant will be excessive and may damage the prosthesis.
Dental equipment that has minimal contact with oral fluids will be cleaned and disinfected with an acceptable disinfectant. Examples of such items are shade tabs, dental torches, case pans, articulators, facebows, spatulas, and rubber bowls. Equipment that has been placed in the patient's mouth will be sterilized. Examples of such items are the facebow's bitefork and reusable impression trays.
The prosthesis will be cleaned, disinfected, and placed in a plastic bag before it is returned to the dentist. A statement may be affixed to the bag stating the prosthesis has been disinfected.
Prepare the SDS from fresh set stone that has never been poured against a potentially contaminated impression.
1.32.1. Ideally, an impression will be disinfected before it is poured in dental stone. If the impression was poured before disinfection, the subsequent cast will be considered contaminated. Spraying the cast with an iodophor or a chlorine disinfectant can disinfect the cast. The cast will then be placed upright and allowed to completely dry. Care must be taken not to damage the stone cast's surface.
1.32.2. Another method is to place a 0.5 percent solution of sodium hypochlorite in a solution of clear SDS and soak the cast for 30 minutes. The cast will be removed from the solution and allowed to dry completely. This solution will not damage the surface of the cast. The solution must be prepared daily to maintain its effectiveness.
As a minimum, to minimize the possibility of contamination in the workplace, (1) PPE should be used when necessary, (2) excellent personal hygiene should be maintained, (3) hepatitis B vaccination should be accomplished, (4) eating or drinking should not be permitted in the dental laboratory, and (5) the receiving and shipping area should be controlled.
1.33.1. Rush Cases. Do not allow rush cases to jeopardize the barrier system. If a prosthesis is adjusted or modified in the dental treatment room and additional laboratory support is required, make one of the following two choices:
1.33.1.1. Recognize that, depending on the disinfectant, up to a 20-minute turnaround time is required to protect the dental laboratory.
1.33.1.2. Establish a unit dose polishing area physically removed from the dental laboratory. In the isolated area include a polishing unit, individually wrapped wheels, abrasive points, and polishing agents. Enclose catch pans for pumice in sealed plastic bags for single patient use. Ensure all pumice and polishing wheels used on contaminated appliances are sterilized after each use.
1.33.2. Hand Cleansing. Personnel involved with patient care must follow the rigid handwashing regimine below:
1.33.2.1. Hands must be thoroughly washed and free of rings to remove resident bacteria and transient organisms acquired from contact with patients or contaminated surfaces.
1.33.2.2. Cleanse hands at the beginning of each duty day. Fingernails should be free of nail polish and trimmed and cleaned, using a nail cleaner. (DO NOT wear false fingernails because contamination may occur from fungal growth occurring between the false and natural nail.)
1.33.2.3. Wet hands, apply an antiseptic solution, and scrub hands and nails with a surgical sponge or brush. Rinse thoroughly because some antiseptic handcleansing agents may irritate the skin if they are not thoroughly removed. Finally, dry hands, using a clean paper towel.
1.33.2.4. Repeat handcleansing is required after working with contaminated dental items, before lunch, and before leaving the dental clinic.
1.34.1. Although heat sterilization is the preferred method, certain instruments and many dental materials cannot be placed in a heat sterilizer. Therefore, they require chemical sterilization or disinfection. Many different chemical disinfectants are available with varying degrees of effectiveness.
1.34.2. It is important to remember that disinfectants can be rendered ineffective by soiled or heavily contaminated prostheses. Therefore, adequate debridement and cleaning are necessary for effective disinfection.
1.34.3. The American Dental Association (ADA) Council on Dental Therapeutics recommends the following five disinfectants; iodophor (paragraph 1.35), glutaraldehyde (paragraph 1.36), phenolic (paragraph 1.37), chlorine (paragraph 1.38), and formaldehyde compounds. Formaldehyde compounds are usually used as surface or immersion disinfectants in dentistry.
Examples include Wescodyne® and Biocide®.
1.35.1. Iodophor compounds contain 0.05 to 1.6 percent iodine and surface-active agents (usually that of detergents), which carry and release free iodine. Because the antimicrobial activity of an iodophor compound is greater than iodine alone, it can be used as a chemical disinfectant.
1.35.2. Because the vapor pressure of iodine is reduced in the iodophor, its odor is not as offensive. Also, iodophors do not stain as readily as iodine.
1.35.3. Intermediate levels of disinfection can be achieved after 10 to 30 minutes of contact when mixed with water according to the manufacturer's directions.
1.35.4. Antiseptic iodine compounds approved by the Federal Drug Administration (FDA) must not be used as disinfectants.
1.36.1. Examples. Examples of glutaraldehyde include, Cidex®, Sporicidin®, Sterilize®, Glutarex®, and Banicide®.
1.36.2. Chemical Sterilization.
1.36.2.1. The types of available glutaraldehyde are alkaline, neutral, and acidic. Most formulations contain 2 percent glutaraldehyde and come in two containers. When the proper amounts from each container are mixed, the solution is activated.
1.36.2.2. Glutaraldehyde sterilization cannot be verified by using sterilization monitors. Because it is caustic to the skin, forceps or rubber gloves should be used to handle prostheses that have been immersed in glutaraldehyde. A 2-percent, room-temperature solution of alkaline or neutral glutaraldehyde should be used to sterilize heat-sensitive items. (Read the manufacturer's directions carefully because some formulations cannot be used on carbon-steel instruments.)
1.36.2.3. Immersion for 6 3/4 to 10 hours in a fresh solution of alkaline or neutral glutaraldehyde usually achieves sterilization, but metallic items cannot be left in any glutaraldehyde solution for longer than 24 hours.
1.36.2.4. After activation, the shelf life and reuse life of each solution may vary depending on the formulation. Place an expiration date on each container of fresh solution to ensure only active solutions are used. Acidic glutaraldehydes heated to 60 oC in a closed system will sterilize instruments in 1 hour. Because of the need for frequent heating and a closed system to eliminate toxic vapors, the use of acid glutaraldehyde is impractical for sterilization.
1.36.3. Chemical Disinfection. The types of glutaraldehydes used for disinfection are the same as for sterilization, but their usage differs. A 10-minute immersion in glutaraldehyde normally provides an intermediate level of disinfection. The label states shelf life (after activation), reuse life, and dilution factors. Glutaraldehydes are best used as immersion disinfectants. They are not practical to use as surface disinfectants because surfaces wiped down with glutaraldehydes must have the residual disinfectant film wiped off with sterile water.
Synthetic phenolics have been accepted as disinfectants. In high concentrations, phenolics are protoplasmic poisons; in low concentrations, they inactivate essential enzyme systems. As disinfectants, phenolics are usually combined with a detergent. Some phenolic compounds have also been shown to be bactericidal, fungicidal, virucidal, and tuberculocidal.
Chlorine is available as sodium hypochlorite (common household bleach) or as chlorine dioxide. If improperly used, chlorine-containing compounds can cause corrosion of dental instruments and materials.
1.38.1. Sodium Hypochlorite. Sodium hypochlorite is thought to oxidize microbial enzymes and cell-wall components. It is used as a chemical disinfectant. A 10-percent solution (one part bleach to nine parts water) yields 10,000 parts per million of available chlorine which achieves an intermediate level of disinfection in 30 minutes. Because a sodium hypochlorite solution tends to be unstable, a fresh solution must be prepared daily. This solution possesses a strong odor and can be harmful to eyes, skin, colored clothing, and metals.
1.38.2. Chlorine Dioxide. This new chemical sterilant has been approved by the EPA.
1.38.2.1. It contains no glutaraldehyde, is economical to use, and is nontoxic and nonsensitizing. It is safe to use on most nonmetal items, but very corrosive to nonstainless steel metal instruments.
1.38.2.2. It requires an immersion time of 6 hours for sterilization. After activation, it has a shelf life of 14 days, but a reuse life of only 1 day. It is biodegradable, does not stain hands or equipment, and does not have to be wiped off environmental surfaces.
1.38.2.3. If used within 24 hours of preparation, it requires an immersion time of only 1 minute to achieve an intermediate level of disinfection. However, if used 24 or more hours after its preparation, 3 minutes of immersion or wetting are required.
Ethylene oxide is the most reliable agent for chemical sterilization. It sterilizes objects that are heat stable without producing rust or corrosion.
1.39.1. Like heat sterilization, it can be verified with biological spore monitors. Monitoring with the B subtilis spore should be performed with each sterilization cycle.
1.39.2. Certain disadvantages prohibit the routine use of ethylene oxide in the dental laboratory. First, it is very slow acting, taking 4 to 6 hours to complete sterilization. In addition, certain sterilized items retain ethylene oxide gas so they must be aerated for a minimum of 12 hours before they can be used in the oral cavity. Finally, there is some concern about whether ethylene oxide vapors may be mutagenic and (or) carcinogenic.
1.39.3. Ethylene oxide must be used according to OSHA standards.
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