Antibiotics in Dentistry: Mechanisms, Types and Usage
Mechanisms of Action
Inhibition of the synthesis of the enzyme peptidoglycan (murein), which interrupts the formation of the bacterial wall.
Increased permeability and alterations of the plasma membrane.
Inhibition of protein synthesis (tetracyclines, aminoglycosides, macrolides).
Inhibition of nucleic acid metabolism.
Conditions an antibiotic must meet to be effective: (1) broad-spectrum activity against microorganisms; (2) good absorption by the body; (3) activity in tissues or liquid corporal fluids; (4) low-grade toxicity; (5) resistance does not develop easily.
Use of Antibiotics in Dentistry
Antibiotics should be adapted individually to each patient, considering the severity of the infection, the etiological agent, and the affected site.
Antibiotics can be used as follows:
Prophylaxis: to prevent infections.
Empirical: for the infection body that causes it.
Directed: when the responsible microorganism has been identified.
First-Line Antibiotics in Dentistry
These are the ones that can be used for outpatient treatment and are the first choice for the majority of odontogenic infections.
a) Natural penicillins: beta-lactam antibiotics (bactericidal activity, wide distribution, low toxicity, low cost). Penicillin G (sodium and potassium) has a fast effect; the usual dose is 1 to 2.4 million units per day. Effective against streptococci, anaerobes, and spirochetes.
Penicillin G procaine: procaine delays absorption, which allows a delayed first action when given intramuscularly. Procaine increases the risk of adverse reactions (especially allergies).
Penicillin G benzathine and penicillin V.
b) Aminopenicillins: semi-synthetic products, used to counteract the increasing resistance. Ampicillin (oral) has the disadvantage of low intestinal absorption and is reserved for severe infections (intravenous route). Amoxicillin has better absorption, is indicated for prophylaxis, and has good gastrointestinal tolerance (3 grams one hour before the intervention and 1.5 grams six hours after the intervention).
c) Macrolides: generally used orally:
Erythromycin: good intestinal absorption, but it can affect the digestive system (nausea, vomiting). It is used for infections where penicillin cannot be used.
Spiramycin: crosses the placental membrane and reaches the fetal matrix. It is marketed alone and associated with metronidazole. It is an antagonist of clindamycin.
Second-Line Antibiotics in Dentistry
These are indicated when the antibiotic from the first-line response fails.
Metronidazole: an active antimicrobial agent against bacteria and parasites (protozoa). It is absorbed orally, although food delays absorption. It is very well distributed in the tissues of the mouth but can produce gastrointestinal discomfort. It is effective for gum infections (acute necrotizing ulcerative gingivitis), often associated with the use of spiramycin.