The sterile field in dental surgery
Article by Dr. Gema Maeso
When performing any kind of surgery, we need to make an incision or surgical wound, which could be infected by microorganisms that cover the surfaces within the operating room. If we perform the correct surgical aseptic technique then we will minimise the risk of infection caused by the presence of bacteria that do not normally live in the oral cavity. We will be going over the steps required when carrying out an aseptic technique, from the initial hand scrub, gown and glove procedure to preparing the surgical field.
Performing the correct aseptic technique will not only prevent infection of the surgical wound, it will also protect the patient and ourselves from cross infection.
Dental-implant operations and developing the aseptic protocol
The surfaces that surround us are covered with microorganisms which can contaminate the surgical wound during surgery and cause infection. But the surgery performed is not the only thing that can be affected. These microorganisms can also cause various cross infections between patients, and from patient to doctor, and vice versa.
With the invention of implants, aseptic techniques are gradually being used in the field of dentistry.
We know that the mouth is full of bacteria, so in dentistry we can’t really talk about a surgical field being completely aseptic when we create one.
In this case, we will talk about relative asepsis, since saliva by definition creates oral bacteria. The difference between ‘sterile’ and ‘clean’ conditions has been a point of discussion in the field of oral surgery,
and there is a paradox within oral implantology: Osseointegrated dental implants which are placed in an environment full of bacteria have a success rate of 98.9 and 100%; which is similar to implants placed into a near sterile environment during arthroplasty. However, if we compare these to transmucosal fixations which pass through the oral mucosa and connect the epidermis to the internal environment then the success rate drops to 77%. So, why do these implants have a much higher success rate when used in the mouth, compared to the poor success rate of these implants when used in other parts of the body? Initially, this was attributed to the antimicrobial properties of saliva, although this suggestion was later discarded as saliva is the main medium of bacterial adhesion. Gingival crevicular fluid was also ruled out as the cause of a poor success rate, as it has a similar composition to blood serum.
The first reason for the high implant success rates in the mouth: the ability of oral tissues to heal rapidly compared to other tissues. Secondly, the oral immune system has a high tolerance. In surgical wounds within the oral cavity, there are fewer inflammatory cells involved (i.e. a lower number of neutrophils, macrophages and T lymphocytes, compared to surgical wounds on the skin). This implies that there is a lower inflammatory response, which could explain this success rate (1,2).
In 1993, Scharf and Tarnow carried out a study in which they compared the success rates of osseointegration for dental implants placed under sterile versus clean conditions. The difference in the success rates was not statistically significant. However, this doesn’t mean that surgery can be performed using just any method.
Infections can occur in odontology and can compromise the viability of an implant or the postoperative stage of a surgery. (3).
Given that nowadays, reports of malpractice are fairly common, it is highly advisable to carry out a surgical procedure in the most aseptic environment possible.
In addition, it is easy to create a sterile surgical field. If the surface of the implant touches the patient’s skin or any other contaminated surface when it is being inserted, then we need to dispose of it. Since implants are expensive, we need to prevent these ‘accidents’ from happening. By using a sterile field and documenting and following the procedure, we can avoid these problems with minimum preparation time. (4).
Cross infections and an aseptic technique
We need to emphasise the significance of cross infections. The larger the surface area covered with sterile drapes, the lower the chances of contamination. Given the presence of a surgical wound, it is easy for microorganisms to spread from the patient to the environment that can contaminate the next patient or even the doctor.
Many intra- and post-operative complications could be avoided with the use of a correct aseptic technique.
During a surgery in which sterile biomaterials are used, after being inserted, the implant reacts by creating a film and an immune response to this biomaterial. Depending on the physical and chemical properties of the material, bacteria may adhere to a lesser or greater extent. The growth of microorganisms can lead to the maturation of the biofilm and the emergence of infections that are difficult to eliminate with antibiotics. (5,6).
One of the tools available to control bacteria in the oral ecosystem are antiseptics. An antiseptic is a substance that is able to destroy a large number of bacteria on living tissue without damaging it and causing a lesion. Chlorhexidine has been proven to be the most effective antiseptic in dentistry, due to its effectiveness and substantivity. Chlorhexidine mouthwash has been shown to prevent postoperative bacteraemia if used prior to surgery (6).
When used preoperatively, it has been proven that antibiotics prevent the occurrence of postoperative infections. In a study comparing the use of 500 mg, 1 g, 2 g and 3 g of preoperative amoxicillin four times a day for two days versus placebo (no antibiotic) demonstrated that there was a much lower risk of postoperative infection if patients were premedicated as opposed to not given any antibiotics. There were no statistically significant differences in terms of the use of postoperative antibiotics. (7).
How to prepare an operating theatre for dental surgery
When performing the surgery we will try to have the lowest possible number of microorganisms in the environment surrounding the patient. In order to do this, we will prepare a sterile field. An item is considered to be sterile if there is a probability of not more than one in 1 million that a viable microorganism has survived the sterilisation process, i.e. its Sterility Assurance Level (SAL) is a maximum of 10-6. (8)
When preparing for a surgery, we will divide the room into two areas:
STERILE AREA. Where the sterile material and scrub nurses will be, This is where the chair will be where we seat the patient and use the sterile drapes. We will have a table covered with a sterile field where we will put the surgical instruments and kit. The staff working in this area must have performed a surgical hand scrub. Despite the use of sterile gloves, it is essential that hands are washed properly.
Normally there will be a sterile services assistant, although in larger practices there may be a scrub nurse. The sterile services assistant is responsible for placing the material on the surgical table and laying the surgical drapes. The scrub nurse is someone who needs to have a good rapport with the surgeon, since they are they person who will supply the surgical instruments in the surgeon’s normal order, as well as the dental drills and other equipment needed for the surgery.
NON-STERILE AREA. This area is cordoned off with an imaginary line. The non-sterile staff and circulant nurses will be in this area. The role of the non-sterile staff is to help the sterile staff to wash their hands and don the surgical gown. They are also responsible for opening material in the surgical field and moving the patient with the scrub cap and shoes in to the surgical field. They will clean the peri-oral area and provide the chlorhexidine for the mouthwash.
Preparing for surgery
The room chosen for surgery:
- must have been completely cleaned with disinfectant beforehand, and countertops should be as clear as possible.
- should be as far away from patient traffic and non-surgical staff as possible.
- doors must be closed in order to prevent aerosols from circulating, which could contaminate the surgical wound.
Staff who will be in the room must wear the appropriate attire (cotton surgical scrubs with clean lines), suitable footwear, scrub cap (covering all the hair), safety glasses and mask.
Watches, rings and bracelets must be removed before starting the surgery. If there are any wounds on the hands these must be covered with a waterproof plaster. Before entering the room, staff must don scrub shoes, cap and mask. The mask should be placed snugly on the bridge of the nose with safety glasses or safety screen on top.
Before surgery it is very important that all material to be used has already been prepared. Written protocols will help us to ensure that there nothing is forgotten at the last minute. In addition to all the required items in terms of equipments, surgical instruments and biomaterials, we need to have all the disposable materials that will be used for treatment. As well as the sterile drapes, protective covers for hoses, irrigation tubes, gowns, caps, etc., there are also sterile kits which basically contain everything you need so that you don’t forget anything.
Before entering the operating room, you must don scrub shoes, mask, cap and glasses. Once you have washed your hands it is important not to touch anything that may be contaminated, which is why it is essential that everything is pre-prepared. All the bagged material will be placed in the non-sterile area.
The sterile services assistant in charge of the sterile field will perform a surgical hand wash. (9).
Despite the fact that you will be using gloves to prevent contamination, we need to take into account that gloves are only effective for a limited amount of time. In addition, gloves have micropores which, depending on the quality of the product, may be large or small in size. Gloves made from latex or nitrile are best in terms of quality and length of time they are effective for, while vinyl gloves have the most faults reported due to their structure, being the ones that break the most.
In a study on surgical gloves (which are of better quality and thicker than those usually used for examinations), 15% microperforations were observed during their 90 minutes of use.(10, 11, 12) . As well as protecting the patient, the gloves also need to protect us. In the event of accidental perforation, we need to take into account that by using gloves only 50% of the volume of blood in the syringe will penetrate, which reduces the risk of transmitting disease. Meta-analysis is not statistically significant in terms of the efficacy of double or triple gloving to prevent cross infection, although it does reduce the risk of a glove perforation occurring.
How to wash your hands for surgical purposes
Considering the above, the next step will always be hand washing prior to surgery. Studies show that washing hands with an antiseptic solution is just as effective as using aqueous alcohol solutions. Among products for pre-surgery hand washing, chlorhexidine scrubs are more effective than povidone iodine scrubs (9).
Essentially, this hand washing procedure involves vigorously scrubbing hands with a soapy solution in order to remove dirt, microorganisms and epithelial cells. This is to eliminate the maximum amount of normal and transitory flora in order to prevent infection in the surgical field and surgical infections.
Nails should have been cut beforehand. Their recesses make them difficult to clean. The enamel on the nails can also contain small spaces which are home to microorganisms.
Do not wear ring or bracelets as they make it harder to clean the area and can be home to microorganisms.
Moisturise hands regularly. Having hydrated skin on the hands increases skin integrity and resistance.
There are four types of hand washing:
- Hygienic washing
- Antiseptic washing
- Washing with alcohol-based solution
- Surgical washing.
Is done with neutral soap and must be carried out:
- Before starting the appointment
- Between patients
- After going to the toilet
- Before putting gloves on
- After touching dirty or contaminated material.
Is carried out by lathering soap and scrubbing the entirety of the hands and spaces between the fingers, completely removing any dirt in the nails, and rinsing thoroughly. After drying the hands with a disposable paper hand-drying towel, turn the tap off with a sheet of paper towel Never use your hand as then you will contaminate it again.
Antiseptic washing is made up of two stages. In the first stage, we carry out hygienic washing as previously described, and in the second stage we use a water-based alcohol disinfectant to remove dirt, organic material and transient and resident microbiota.
Washing with alcohol-based solution
This is carried out in locations where there is no water tap to carry out a standard hand wash. Scrub vigorously with the solution for 30 seconds. If they dry before this time then add more solution.
This is carried out before surgery. It involves removing both transient and resident flora.
To perform the surgical washing procedure, you need a tap that can be operated using the elbow, knee or foot, with a detachable scrubbing brush, an antiseptic scrub with either a povidone iodine or chlorhexidine base (studies show that chlorhexidine is more effective), and two sterile towels. The ideal would be to use single-use, solution-filled brushes.
When performing a hand wash, the level of the hands should always remain above the elbows. This will prevent microorganisms in the area past the elbow from running onto the hands and therefore crossing the sterile field.
- Turn on the tap and wet both arms up to the elbows.
- Cover the brush with soap. Once this has been done, wet the brush and start to scrub the arms – from the fingertips to the elbow.
- Repeat this sequence 10 times, except for the sequence on the nails and elbows which should be repeated 20 times.
- Start with one arm, scrubbing from the fingertips up to the elbow. Start with the nails, then continue to the fingers, the spaces between the fingers, the back of the hand, palm, wrist, forearm then elbow. Repeat 20 times. Rinse the arm and the brush and move on to the other arm. Repeat.
- Lastly, rinse both arms, turn the tap off with the elbow and dry both hands thoroughly. Do this by patting with a paper towel, without rubbing, from the fingertips to the elbow. (13,14)
Donning the sterile gown
After washing the hands, don the gown. Surgical gowns are folded at the back, so that the non-sterile part (touching the back) is the first part we can touch. There are two ways of donning the gown.
- Putting it on yourself: With two fingers, open the gown and put the arms through the sleeves. A non-sterile assistant will do up the tie at the back, as this area is considered to be non-sterile.
- Getting someone to help you: The sterile services assistant will open the gown up to the other person, to help them put it on. The circulant nurse’s assistant will do up the tie at the back.
How to wear gloves for a surgical operation
Go into the surgical area with arms pointing upwards. The non-sterile assistant will have opened up a surgical field for us, as well as the sterile gown. The surgical gown comes pre-folded outwards, to make it easier to put it on yourself.
Put your arms through the gown without shaking it on, and get the assistant to do up the tie at the back. The area at the back is considered non-sterile.
Next, open the glove wrapper like a book, so that the inside of the wrapper (containing the gloves) is exposed. With the thumb and index finger, in one swift movement, slide in the hand – taking the edge of the glove by the folded cuff and insert the hand, leaving the cuff turned down over the hand. Put this hand into the fold the other glove in order to grasp it, then insert the other hand into the glove with one swift movement.
The cuff of the glove can then be pulled onto the gown. Ensure that the glove does not touch the skin on the arm during the gloving process. If necessary, you can adjust the fingers. You can now roll the cuff of the glove over the cuff of the gown.
At this point, you must only touch things that are sterile. This is extremely important. You cannot do things like adjust your mask or touch any surfaces without having to recover them. If you do, you will need to put on new gloves.
How to prepare the sterile surgical field
We can now prepare the surgical field. Start by placing the sterile drapes over the surface you will be working on.
The non-sterile assistant will open up all material on the Mayo tray stand for us. Place the material in the sterile field. Without touching the suction device, insert to sterile surgical cannula.
Put the protective covers on the hoses without touching anything that isn’t sterile. After doing this you cannot put it back on the normal bracket, as the suction device will become contaminated. Seal the top part so it does not fall onto an adhesive.
In order to cover the areas of normal use, such as light handles and implant drills, there are some transparent adhesive sterile films which will help us. Place the sterile irrigation tube in the contra-angle and the non-sterile assistant will connect it to the saline solution and implant drill. In the event that an external irrigation tube is used, it is important to know that the saline will be contaminated the first time the syringe is inserted to absorb the saline. Saline dispensers are available which provide a continuous irrigation, without contaminating the saline each time you inject it.
It is now time to move on to the patient. Before coming into the room, the non-sterile assistant will provide the patient with a scrub shoes, gown and gloves.
The patient should already be dressed when they come in. Inside the room, the patient will be given a 0.12% chlorhexidine mouthwash to rinse for a period of 60 seconds. Next, the peri-oral area will be cleaned with chlorhexidine or povidone iodine. To do this, put the solution on the gauze and carry out extrinsic movements, from the lips to the peripheral area.
Introduce the patient to the sterile field.
Normally, surgical draping of the patient is carried out using cotton surgical drapes and towel clips. The drapes are applied in layers, leaving only the peri-oral area exposed. To do this, place a sterile drape over the patient’s headrest, pulling it over their face and fixing it in place with the clips.
Afterwards, add a second sterile drape by fixing it in place with the clips on both sides, so that only the peri-oral area is left exposed. This should no longer be used once the single-use drapes have been placed. Fenestrated drapes with adhesive are available, which stick firmly onto the area where you are going to work.
The ideal would be for the first drape to be a non-adhesive one, and for this to be attached to a second U-shaped cutout adhesive drape on top of the patient’s head.
Surgical drapes with a window are also available, which have a transparent window over the eyes. This prevents some patients from getting anxious.
During surgery, it is very important not to touch anything that is not covered with sterile material. Doors to the room must be closed to prevent non-surgical staff from coming in. All staff inside the room need to wear scrub shoes, mask and cap.
After completing surgery, all the contaminated drapes and gowns should be removed. Scalpels, silks and sharp materials should go in the corresponding containers. The mask should be the last item you remove. First, undo the bottom tie, then undo the top one. If you do it the other way around, the mask will fall backwards and the contaminated part will touch the neck.
All the material undergoes a thorough decontamination, washing and sterilisation process. The room will be ventilated and then meticulously cleaned; both the furniture and the suction tubes. It is very important that the whole protocol is clear and understood, to prevent cross infection in the operating room.
Safety, quality and success in dental surgery: the sterile field
All of these actions will make it easier to perform surgery in the proper and correct way, preventing the biomaterials used from being contaminated before entering the body, causing them to fail. Although this is not the only reason for performing these actions.
We are protecting the patient from any potential contamination of the surgical wound. The bacteria which is not in its normal conditions in the oral environment could infect the surgical would and cause severe post-operative complications, which could lead to serious problems.
As well as protecting the patient, we are also protecting ourselves by wearing the appropriate attire, and by having most surfaces in the room covered we are protecting any other patients who will be sat in the chair later.
The use of waterproof, sterile gowns and drapes has improved our level of safety and has made our jobs much easier. Cotton surgical gowns absorb moisture due to capillary action, and can transmit bacteria from one side of the sterile field to the other, which would compromise our safety.
Article by Dr. Gema Maeso
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