Steam Heat and its Implications in Sterilization of Surgical Guide in Implant Dentistry

What Are Surgical Guides?

The surgical guides in implant dentistry are a pivotal part of computer-guided implant surgery. The surgeon seeks the direction of the surgical guide for accurate placement of the implant based on position and angulation at the site of the patient's mouth. The degree of accuracy is also important for achieving long-term success rates for dental implants. Computer-guided surgeries render no scope for surgical errors. These surgical guides are made up of two kinds of materials: PMMA (polymethylmethacrylate) and copolymer resins of polyethylenes.

Why Is Sterilization Necessary for Surgical Guides?

Sterilization in dentistry plays a major role in preventing and spreading cross infections in a dental clinic or hospital setting. In implant dentistry, the surgical guides are the critical items in constant contact with the patient's blood, bone as well as oral fluids of the patient during the procedure. Numerous clinical studies and investigations have advocated steam heat sterilization as the method for sterilizing surgical implant guides. Serious microbial infections can be caused if any extra oral pathogens come in contact with or contaminate the surgical guides that are highly sensitive.

What Are Different Instruments Used in Dentistry and How Are They Classified?

Different regulations have been adopted globally for classifying medical items as semi-critical, critical, and uncritical/non-critical. The Spaulding classification is a popular classification for dental surgical instruments and can be divided into three categories. This classification system is based on the ability of the instrument to potentially infect the surroundings after using it on the patient. While low-risk instruments can be sterilized at the normal pace in a hospital setting, high-risk surgical instruments must be immediately sterilized post-usage on the patient to prevent any risk of cross-infection within the clinical setting.

Patient care items, dental instruments, dental devices, and dental equipment are categorized by Spaulding; hence the risk of disease transmission and is as follows-

• Critical Items: These instruments penetrate the soft tissue or the bone and are associated with the highest risk of transmitting infection.

• Semi-Critical Items: These instruments penetrate only up to the level of the superficial mucous membrane. These have a much lower risk of infection transmission than critical items.

• Non-Critical Items: This is the lowest infection transmission rate that only contacts the skin.

According to the American dental association (ADA), the surgical guides for implant dentistry are classified under critical items that need sterilization by steam heat.

Which Technique Is Effective In Terms of Sterilization of Surgical Guides?

Though some studies contradict this view that steam heat sterilization of surgical implant guides can create thermosensitivity, clinical trials have demonstrated this method as a reliable and practicable clinical regimen for dental implantation. Autoclave sterilization utilizes the principle of steam sterilization and is effective in the reduction of microbial load. This is done under temperatures that usually vary between 121° C (centigrade) to 134° C (centigrade). Two kinds of autoclaving cycles can be followed, which include the following-

• The Slow or Normal Cycle: This deals with the autoclaving of the surgical guide and instruments at 121° C for 15 to 20 minutes, at least ideally

• The Rapid or Fast Cycle: This deals with the autoclaving of instruments and surgical guides at 134° C for only three minutes.

According to research and literature, the autoclaving done at 121° C does not pose any risk for thermal degradation or any thermal impact on the surgical guide, nor can it induce linear shrinkage or distortion. This is because the temperature at which the thermal degradation involving molecular instability for PMMA is 180° centigrade. This temperature is considered overheating. So it is safe to use steam heat sterilization at 121° C for 20 minutes.

Nobel Biocare or NobelGuide, which is the popular implant supplier and system, usually recommends the use of high-level disinfection in implant dentistry, like the use of a 70 % diluted version of ethyl alcohol for around approximately 40 minutes to eliminate any possible risk of microbial infections for the surgical guides. In addition, research has also been done on maxillofacial implants. It has been demonstrated that accessory sterilization methods like microwave disinfection and gas plasma sterilization could induce linear shrinkage in the surgical guide material or cause morphologic distortions within the surgical guide.

Conclusion:

Most dental operators and implant surgeons consider that steam heat sterilization is much superior to chemical disinfection and accessory sterilization methods because this method greatly reduces the number of pathogens or microorganisms. In addition, it decreases their ability to penetrate the patient's body and the risk of postoperative infections or complications after dental implantation.