Drug and dental impression materials.

Guidelines to prevent cross contamination with infectious agents have been instituted for dental clinical and laboratory procedures. However, compliance by dental offices and clinics in disinfecting impression material has not been universal. Techniques for disinfecting impression materials are spraying or immersing impression materials. These techniques can reduce the surface detail and dimensional accuracy of impressions; most disinfectants are irritants. This study reviewed whether antimicrobial activity can be achieved by mixing certain drugs with the impression material and their effects on the disinfection are achieved through such additions.

Dental impression materials are a group of dental materials which are used in the patient's mouth to make a negative replica of specific oral tissues, from which are obtained positive casts in dental gypsum products which are used in the fabrication of various dental prostheses outside the mouth. The prevention of transmission of pathogenic microorganisms to various dental professionals involved in the fabrication of dental prostheses has been given a lot of attention in the past couple of decades. There is a general agreement that impressions constitute one of the main vectors in the chain of infection.[1-3]

Impression making is a routine procedure carried on at the start of any prosthodontic procedure.[4-6] Dental impressions can easily become contaminated with patient's blood and saliva. Such fluids can contain overt pathogens, including the viral agents associated with hepatitis, herpes simplex, and HIV/AIDS, in addition to tubercle bacteria. Some of these microbes can exist for extended periods outside their human hosts. It is impossible to determine all infectious patients from medical histories or patient conversations. Therefore, the only valid posture is to assume all patients are capable of transmitting highly infectious diseases.[7-9]

Sterilization and Disinfection

Sterilization and disinfection are two words which are quite inseparable from the practice of dentistry in today's world. However, with regard to dental impression materials and dental gypsum products, sterilization procedures are literally ruled out as the commonly used sterilization methods in a clinical setup may alter the properties of these materials to an extent that they may no longer be fit for dental professional use.[67] Hence, disinfection is what we were left with. Over the past two decades and more, several studies have been conducted to find effective means of disinfection of both dental impressions and dental gypsum casts, with a single objective of reducing the risk of transmission of various pathogens.[24-7]

Disinfection of impressions has been recommended as a mandatory procedure for a long time now. This has been accomplished by thorough rinsing of the impressions, followed by exposure of such impressions to one of a variety of recommended disinfecting chemicals, either as a spray or by immersion in the same. This is performed to eliminate most of the microorganisms picked up from the patient's mouth. If contaminated items were to enter the dental laboratory environment, there is a high chance that unsuspecting laboratory personnel would be placed at increased risk for cross infection.[12478]

Such procedures of disinfection should ideally be taken care of at the dental clinic level soon after the dental impression is made. Some dental laboratories also have protocol to disinfect all dental impressions received at their laboratory.[2-4] However, such highly recommended protocols for safeguarding the health of all dental professionals involved are not complied with universally. These procedures are seen as additional time-consuming procedures. And this is where the idea of incorporating certain drugs into the dental impression materials fits in. This would certainly not consume any additional time on the part of the dental clinic/laboratory personnel and also results in universal compliance.

The most commonly used dental impression materials today are the alginates, silicones, and polyether. Each of these have their exclusive advantages and disadvantages, including the cost factor.[19-13]

Alginate impression material, an irreversible hydrocolloid, is one of the most commonly used impression materials in day-to-day practice and also among the most criticized in terms of its disinfection process. Inherent limitations, such as the material's dimensional instability, set restrictions to the treatment period as well as for choosing the antimicrobial agent. Due to its hydrophilic nature, also responsible for the highest retention of bacteria, disinfection should be carried out with a product that requires the least amount of time for the disinfection process.[1910] Antimicrobial agents are applied to irreversible hydrocolloid impressions in the following ways: sprays, which do not completely expose the contaminated surface to the antimicrobial agent, resulting in a less reliable procedure and immersions, which are not considered ideal, as there may be imbibition of the gel, swelling, and change of its physical dimensions.[1912]

One new idea which has been experimented upon recently is that of including certain drugs in the dental impression materials at the manufacturer level or at the clinical practice level to aid in prevention/reduction of the bacterial load on a dental impression.[10] This article makes an attempt to review such literature.

Incorporation of the agent with the impression material and mixture with antimicrobial solutions instead of water could solve the above problems. Few studies have addressed the mixture of antimicrobial solutions. The available data report that reliability is preserved in copies and inform the working time of irreversible hydrocolloids mixed with a 0.2% solution of chlorhexidine digluconate. Moreover, studies have verified the antimicrobial activity of the mixtures against bacteria of the oral environment.[110]

Review

Miller and Cottone, in their observations, concluded that dental impressions can easily become contaminated with a patient's blood and saliva. Such fluids can contain overt pathogens, including the viral agents associated with hepatitis, herpes simplex, and HIV/AIDS, in addition to tubercle bacteria. Some of these microbes can exist for extended periods outside their human hosts.[4] Miller and Palenik observed that if contaminated items were to enter the dental laboratory environment, there is a chance that infectious materials could spread to the prostheses and appliances of other patients. Unsuspecting laboratory personnel would also be placed at increased risk for cross infection. One procedure that could reduce the chances of disease transmission would be the disinfection of orally soiled dental impression materials. Ideally, such procedures should occur chairside, prior to transportation to the office or commercial laboratory.[57]

For disinfection of these impression materials, there are various techniques such as immersion or spraying and rinsing impressions. Over 60 studies have reported on the effects disinfection has on impression integrity or on the physical characteristics of the casts produced.[56812] Very few studies have investigated the actual killing rates accomplished by the applied disinfectants.[58]

Most of these focused on only the surface phenomena. It has been demonstrated that microorganisms on and/or in impression materials can be transferred to stone casts and remain viable.[311]

Denise A. Flanagan and co-authors did extensive studies by incorporating disinfecting agents into impression materials and found out that this could serve an important role in dental laboratory infection control and would be particularly valid concerning the supplementation of alginate powders.[10]

Conclusion

The incorporation of disinfecting agents into impression materials could serve an important role in dental laboratory infection control. It is observed in this review that incorporation of disinfectants does not have any observable dimensional changes in the impression material. The classes of impression materials that can be particularly benefited by such substitutions are the irreversible hydrocolloids.