Infection control in dentistry is an ever-growing perturbation. Prosthodontic patients are high-risk patients relative to their potential to transmit as well as acquire an infectious disease. An equal concern has been exhibited for cross-contamination and disease transmission from patient to patient. When addressing these problems, there are two identifiable considerations: (1) how the dentist and his staff can be safeguarded from disease acquisition and disease transmission to patients and (2) what steps should be taken to help minimize cross-contamination with prosthodontic instrumentation. The constant dangers of cross-contamination in dental practice among patients, dentists, and ancillary staff have been pointed out by Murray and Slack; they reported the possibility of absorbent cotton pledgets, air syringes, glass slabs, and hand towels acting as sources of contamination. The Centers for Disease Control and Prevention (CDC), in its infection control guidelines, indicated that dental impressions are potential sources of cross-contamination and should be handled in a manner that prevents exposure to practitioners, patients, and the environment. Based on the corroboration of data and regulation confined to the province, appreciative standards of Dental Infection Control and Occupational Safety must be followed by the dental team for patient and dental healthcare safety.
The aim is to control infections caused by patient exposure to pathogenic microorganisms or transmitted to the dentist or laboratory staff via occupational exposure.
Infections could be transmitted in the dental operatory through several routes: (1) direct contact with blood, oral fluids, or other infected materials, (2) indirect contact with contaminated objects, such as instruments, environmental surfaces, or equipment, (3) contact of conjunctival, nasal, or oral mucosa with droplets, such as spatter, containing microorganisms from an infected person and propelled by coughing, sneezing, or talking, or (4) inhalation of airborne microorganisms that can remain suspended in the air for long periods.
A study undertaken by G Lynn Powell et al., established a direct correlation between dental facilities and the identification of any organisms present. Sixty-seven percent of the impressions, dentures, crowns, and wax occlusion rims sampled showed the presence of microorganisms of varying pathogenicity. The identification of bacteria showed the presence of such organisms as Enterobacter cloacae, Escherichia coli, and Klebsiella oxytoca plus many others.
It is widely recognized that used dental pumice is a major reservoir for bacterial contaminants in the prosthodontic laboratory. Miller et al., also demonstrated that during pumicing procedures, bacteria in pumice might be aerosolized and disseminated throughout the dental suite and transmitted to patients and personnel. Although it has been reported that most bacteria isolated from contaminated pumice have been native to the oral environment, studies by Wakefield and Williams et al., indicated that many of the contaminant microorganisms recovered from used pumice or from prostheses finished with used pumice were nonoral bacteria. Because of their various degrees of pathogenic potential, these organisms may be hazardous to dentists, patients, staff, and prosthodontic laboratory personnel. In a study by Henry N. Williams, the quantitation and identification of bacterial colony types recovered from pumice collected from four dental laboratories indicated that the predominant bacteria recovered were nonoral microorganisms, including members of the genera Bacillus, Acinetobacter, Micrococcus, Pseudomonas, Moraxella, and Alcaligenes. A study by Hiroshi E Gusa et al. reported the persistent presence of microorganisms on patient-derived dental impressions and gypsum casts and highlighted important human pathogens such as Candida, methicillin-resistant Staphylococcus aureus (MRSA), and Pseudomonas aeruginosa.
Infection Control Procedures
Initial patient screening is accomplished by the prosthodontist during history-taking interactions before entering the operatory. The dentist’s review of the patient’s medical history is mandatory at the onset of every clinical appointment. Multiple reviews give the dentist opportunities to establish baseline medical history data and to compare individual patient responses over an extended period of time as well as a brief review of any infectious disease the patient is suffering.
The dentist’s personal hygiene is an absolute necessity. As patients become more aware of the potential danger to themselves from materials and instruments that are not disinfected or sterilized, their confidence and acceptance of dental treatment become directly proportional to the image the clinician presents. Specific notes of hygiene include (1) Hair is cleared away from the face. If a clinician’s hair falls in such a way that it may contact the patient or dental equipment, it is fixed at the back of the head, or a surgical cap is worn. Facial hair is covered by a face mask or shield. (2) Jewelry is removed from the hands, arms, or facial area during patient treatment. (3) Fingernails are kept clean and short to prevent perforation of gloves and accumulation of debris. Fingernail polish is not worn. (4) Thorough forearm and hand washing are mandatory before and after treatment.
Residents are required to have current immunizations against communicable diseases, including hepatitis B. Gloves, are worn at all times when treating patients. Masks are worn in the patient treatment area and when the dentist is manipulating the prostheses in the laboratory. Glasses with solid side protection must be worn by the patient, faculty member, and resident. The use of disposable plastic face shields is highly recommended. Sharps disposal protocol is followed, with particular emphasis on the use of a hemostat when handling blades. Outer barrier garments for aerosol protection are worn at all times when treating a patient and always changed between patients.
Common Methods of Sterilization
Steam at 121 degrees C for 20 to 30 minutes or 134 degrees C for 2 to 10 minutes.
Unsaturated chemical vapor – 20 minutes at 134 C
Dry heat (Oven Type) – 1 to 2 hours at 160 C
Dry heat (rapid heat transfer type) 6 to 12 minutes at 191 C
There are two general approaches to surface asepsis: (1) Clean and disinfect contaminated surfaces, and (2) Prevent surfaces from becoming contaminated by the use of surface covers. A combination of both may also be used.
According to Miller and Palenik in 1994, the following chemicals are suitable for surface and equipment asepsis:
The following procedures are required when treating patients in the clinic: Before seating the patient the operatory and chair are cleaned and wiped with a disinfectant solution; the area is sprayed and left for a minimum 10 minutes. The dental chair is covered with a plastic sheath, which is removed after treatment. Subsequent to treatment, the protective covers are removed, and the room is sprayed, wiped with phenol solution, and left to dry.
All patients rinse with chlorhexidine gluconate 0.12% before treatment. Patients wear protective eyewear. Hands are washed with an antimicrobial cleanser before gloving. Once gloved, only the patient and barrier-covered areas or areas that have been cleaned and disinfected are touched. The patient chart is not touched with contaminated gloves. If an entry must be made in the chart, gloves must be removed or a clean glove is placed over the contaminated glove and removed after finishing the chart. Alternatively, an appropriate barrier must be used on the pen and over the portion of the record that is to be touched. The doctor should not leave the operatory without removing their gloves and outer barrier garments. Large, nonsterilizable items used in the operatory, such as impression material dispensing guns, articulators, face bows, water bath, silicone spray bottles, tooth shade, and mold guides are disinfected by wiping, spraying, or immersion with the appropriate disinfectant solution.
All items leaving the clinic after being used in direct patient care or touched during patient care procedures that cannot be subjected to sterilization procedures are disinfected or placed in the phenol disinfection solution within a sealed plastic bag before departure. New latex gloves are worn for the disinfection procedures. Items bagged in disinfection solution must remain in solution for 10 minutes. Metal impression trays are hung and autoclaved before use. Adhesives for impression trays are used in individual dose quantities to prevent cross-contamination. Polyvinylsiloxane, polysulfide, impression compound, and ZOE impression materials are thoroughly rinsed with water and immersed in a 5.25% sodium hypochlorite solution for 10 minutes. Alginate and polyether impressions are rinsed with water, sprayed with a 5.25% sodium hypochlorite solution and sealed in a plastic bag for at least 10 minutes. Wax, ZOE, and resin centric relation records are rinsed under water and sprayed with a 5.25% sodium hypochlorite solution and placed in a plastic bag for 10 minutes. Stone casts requiring disinfection are sprayed with a 5.25% sodium hypochlorite solution and allowed to sit for at least 10 minutes. Complete dentures and provisional restorations that leave the operatory are immersed in a 5.25% sodium hypochlorite solution for 10 minutes. Removable partial dentures with metal bases are sprayed with 2% glutaraldehyde solution and held in a plastic bag for 10 minutes.
All prostheses that enter and leave the laboratory should be disinfected. Within the laboratory, the prosthesis of each patient is kept separate through barrier, disinfection, and sterilization systems. All prostheses entering the laboratory are scrubbed with disinfectant solution. Those leaving the laboratory are immersed in a 5.25% sodium hypochlorite solution for a minimum of 10 minutes.
New gloves should be worn in the laboratory area for grinding and polishing procedures and then discarded when the practitioner leaves the laboratory. Protective clothing is worn in the laboratory and discarded before the dentist leaves the laboratory area. Laboratory countertops are cleaned and wiped with a disinfectant solution at the end of each day. Individually packaged cold sterilized laboratory burs are available in the laboratory. After the desired procedure is accomplished, the laboratory bur is cleaned and placed in a new bag for sterilization. The burs are used for one patient only and then resterilized.
For polishing the lathe, when the technician uses pumice, he/she places a clean plastic container containing an individual dose of pumice. A phenol solution is used to wet the pumice to desired consistency. Individually packaged sterile polishing wheels, designated for use with pumice, are available. The wheel is wet with water to soften it before use. If prosthesis becomes contaminated during laboratory procedures, it is disinfected, and the laboratory procedure continued. The final polish is accomplished using a sterile wheel with noncontaminated acrilustre. The acrilustre is applied to the sterile wheel once before polishing to eliminate cross-contamination. Clean-up involves disposal of the plastic container and the contaminated pumice. Wheels are removed, rinsed with water, and bagged for autoclaving. Before returning to the main clinic, all items are disinfected by immersion or spray and placed in a lock-tight bag. All information regarding disinfection procedures that are performed on prosthodontic items sent to an outside laboratory should be clearly written on the prescription form and the plastic bag. All items received from a laboratory are treated as contaminated unless the resident is informed otherwise by the dental laboratory. Before impressions are poured in the laboratory, hydrophilic impression materials are sprayed with a sodium hypochlorite solution (5.25%) and placed in a plastic bag for a minimum time of 1 minute. Hydrophobic impression materials are immersed in the disinfectant solution for 10 minutes.
Post Exposure Prophylaxis
Several recent reports in the general media and scientific and professional journals have documented instances of infection control breaches in dental care settings, resulting in state health department investigations and patient notifications about possible infection. These breaches are the result of failures in compliance with accepted infection control practices and policies. Even though all breaches do not result in healthcare-associated infections, they are unacceptable, particularly when we have the knowledge and ability to prevent them. We must take the proper precautions to stop this needless suffering, cost, and harm to the patients we serve, as well as the damage it causes to our professional credibility. Lack of infection control is life-threatening for both the patient and the dental professional and requires more effort. Formal programs in "Infection Control and Safety" must be developed and strictly followed by the entire dental health care professional.