Antibiotics are medicines which are used in dentistry to kill harmful bacteria. St. Lawrence Dentistry takes the stewardship of antibiotic use very seriously as overuse of these important medications can lead to resistance over time.

Antibiotics can be ‘bactericidal’ (destroy bacteria) or ‘bacteriostatic’ (inhibit bacterial growth).

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There are different mechanisms by which antibiotics work and some are of inhibition of the synthesis of ‘cell walls’, proteins, and nucleic acid (genetic material).

‘Beta Lactams’ are a major class of antibiotics. They include the penicillin, cephalosporins, monobactams, and vancomycin. These antibiotics are bactericidal and have a ‘beta lactam’ ring’. It inhibits bacterial enzymes called ‘transpepidase’ which is needed to form a ‘cell wall’. Penicillins have the advantage of having low toxicity because humans do not have cell walls (hence the antibiotics targets the bacteria only). However, one negative aspect of this class of antibiotics is allergic reactions penicillin occurs in about10-12% of people. Penicillin G (intravenous form) and Penicillin V (oral form) are good for oral anaerobes which do not produce beta lactamase. If a bacteria is resistant to Penicillins other antibiotics are available which may be effective. While talking about the use of Penicillin ‘V’ versus ‘G’, it is worthy of noting that intravenous antibiotics will get more concentration of antibiotics into blood vessels quicker. Penicillin V is not given generally more than 500mg at a time because that is all a typical patient can absorb though the oral route. If one of our patients needs an antibiotic like Penicillin G we will refer to the nearby Trillium Hospital for its intravenous administration.

Sometimes the Beta Lactams called Ampicillin (intravenous administered) and Amoxicillin (orally administered) are used (instead of Penicillin) because they have better absorption and have additional benefits of being useful against bacteria called ‘gram positive enterococcus, listeria, gram negative bacilli’.

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Some bacteria can produce enzymes which can destroy penicillins and these are called ‘beta lactamases’. These are mostly produced by a group of bacteria called ‘gram negative’. To combat this the ‘beta lactamase’ resistance bacteria, drugs have been developed which can attack these beta lactamases. These are called ‘clavulanic acid’ (also known as augmentin), tazobactam, and sulbactam. Often times clavulanic acid is used together with amoxicillin which can be very effective against bacteria posing resistance to penicillin. This is typically used if there is no resolution of an infection in 2-3 days with solely using a ‘beta lactam’ antibiotic.

One common prescription written is the following:

  • Rx Amoxicillin 500mg + Clavulanate 125mg (3 times a day for 7 days)

Antibiotics which work by inhibiting protein synthesis include ‘macrolides, clindamycin, tetracyclines, aminoglycosides’. These are all bacteriostatic in nature. With this group of antibiotics it is generally important not to use with dairy products or with iron supplements as they will render these less effective.

When a patient has a long term infection in their gums, sometimes an antibiotic called ‘Periostat’ is used. Another name for it is ‘doxycycline’.

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A typical prescription for this looks like this:

  • Rx Doxycycline 100mg for 21days (Periostat)

Clindamycin is a very common antibiotic used in dentistry and works by inhibiting protein synthesis. It is the drug of choice if one has a penicillin allergy. It binds into the ‘50S subunit’ of the ‘ribosomes’ in bacteria thus inhibiting the ‘translocation step’ of protein synthesis. It is bacteriostatic in nature. Clindamycin is effective against gram positive, anaerobic bacteria, and several other oral pathogens. Side effects are diarrhea, skin rashes, and liver toxicity.

In addition, one main side effect of clindamycin (and many other antibiotics is ‘pseudomembranous colitis’ which is characterized by severe diarrhea and severe abdominal pain.

Tetracyclines used to be prominently used in dentistry but their use has waned due bacterial resistance. In addition, they have a high affinity for calcium and can discolour enamel or teeth in adults, children, and fetuses. They may retard skeletal function if taken in pregnancy. Other side effects of tetracycline are gastric discomfort, fungus superinfection (ie: candidia), and blood in stool.

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Macrolides are a group of common antibiotics of which ‘erythromycin’ is the most prominent example. These were one of the first drugs available which were effective for patients with an allergy to beta-lactam antibiotics such as penicillin. Macrolides are inhibitors of the ‘cytochrome p450 enzyme’ in the liver and hence may increase the concentration of common drugs such as warfarin, phenytoin, carbamazepine, and cyclosporine. This means that macrolide could potentially cause an overdose in the above medications if is not prescribed properly.

Another set of antibiotics are those that function by inhibiting genetic information synthesis. Two examples of these are metronidazole and ciprofloxacin. Metronidazole is bactericidal and is effective against a bacteria called ‘bacteroides’. It works well in certain instances in combination with amoxicillin. In dentistry is usually given either twice or three times a day in 250-500mg doses. Its side effects are an unpleasant metallic taste, gastrointestinal issues, and dizziness. Metronidazole and may inhibit an enzyme called ‘aldehyde dehydrogenase’ which helps break down alcohol in your body. Drinking alcohol with this antibiotic can cause, among other issues redness and joint pain. For this reason is it best not to take alcohol until at least 2-3 days after finishing this drug.

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In dentistry we give antibiotics to certain patients prior to some procedures to attenuate bacteria entering their bloodstream. This is called ‘antibiotic prophylaxis’ and is indicated (among other instances) for patients with prosthetic heart valves, history of endocarditis, cardiac transplant patients with subsequent heart valve issues, some congenital heart defects, and patients who have had repair of heart defects. It is not usually indicated for surgically constructed systemic pulmonary shunts, previous coronary artery bypass surgery, physiological (functional, innocent) heart murmurs, pacemakers and implanted defibrillators. Dr. Hawryluk may consult with your physician to see if you should have antibiotic prophylaxis when having your dental work done. In general the antibiotics are prescribed for procedures which could case significant bleeding. Currently the Canadian Dental Association is not recommending administering prophylactic antibiotics for most patient who had orthopaedic pins and screws placed. However, some surgeons may recommend prophylaxis in the first 2 years post surgery if a patient is immunocompromised or had previous joint infections. In general, the Canadian Dental Association (as of 2019) recommends choosing the narrowest spectrum antibiotic drug which can be effective.

Some typical adult dosages for antibiotics prophylaxis are:

  • Amoxicillin 2grams
  • Clindamycin 600mg
  • Azithromycin 500mg
  • Clarithromycin 500mg

Not all dental abscesses are the same and each situation must be carefully assessed. The choice or combination of an antibiotic may change depending how long the dental abscess has been present. If an abscess has been festering for 7-10 days it has probably become more non-aerobic. In this case adding an antibiotic which combats aerobic bacteria may be indicated. Once example of this is the above discussed metronidazole. Sometime if an abscess is leaking into the mouth, a antibiotic rinse such as those based on clindamycin and tetracycline can help. Dr. Hawryluk will assess your individual situation to see what is best for you.

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Dental abscesses are not well vascularized and the vessels are mainly located on periphery. Therefore, antibiotics have to diffuse from vessels to the abscessed tissue along a concentration gradient. The larger the abscess, the less effective an antibiotic will be in clearing it up. To make antibiotics more effective, sometime the abscessed area is ‘drained’ first. This can make the vascular perimeter of the abscess smaller. Hence, more concentration of an antibiotic will be able to reach the interior of the abscess.

Antibiotics have been a major development which has helped not only advance dentistry but the human kind overall. We take the use of antibiotics very seriously at St. Lawrence Dentistry and will ensure they are used appropriately. If you live in the Mississauga area and would like to discuss this subject or would like a dental appointment please call usclick here.

Reference: University of Toronto, Faculty of Dentistry, Online Lecture Series, 2019.