Who is at risk of infection complications of oral origin?

Manipulation of infected oral tissues, such as measurement of periodontal pockets, calculus removal, over-instrumentation during root canal treatment and especially tooth extraction are known to cause bacteraemia (5). Infection in a tooth or its surrounding tissues may also lead to spontaneous bacteraemia, if the infection spreads to adjacent blood vessels. Severe underlying diseases including immunosuppressive illnesses and treatments have been shown to predispose the patient to systemic odontogenic infection complications (Table 1) (6, 7). Mortality due to odontogenic infections is also known to be highest in these patient groups. Improving the level of oral hygiene and management of general oral infection status prior to dental procedures decreases procedure-related bacteraemia significantly and is at least as important as a single-dose of antibiotics (8).

When should antibiotic prophylaxis be considered?

Antibiotic prophylaxis is used in connection with invasive procedures such as tooth extraction, calculus removal, abscess incision or other surgical procedures in an infected area involving risk of bacteraemia in patients at elevated risk of endocarditis or other systemic infection complications (Table 2). The need for prophylaxis is assessed based on general susceptibility to infection (other illnesses and medications increasing susceptibility to infections, presence of foreign bodies) and the level of infection at the operating site in addition to the invasiveness and extent of the procedure. A single dose of antibiotics is usually sufficient. Severely immunocompromised patients (Table 1) have been shown to be prone to systemic infection of oral origin even with less invasive procedures. Bacterial endocarditis has its own specific risk factors, and there are separate guidelines on antibiotic prophylaxis and its indications in connection with dental procedures (9, 10) (Table 2). Preoperative single-dose prophylaxis is also appropriate in generally healthy patients when treating infection foci surgically and if antimicrobial treatment is needed anyway.

How should prophylaxis be used to be of benefit?

There are no randomized, placebo-controlled, double-blind studies available on the impact of immunosuppression on the risk for systemic odontogenic infection complications, as due to ethical reasons patients susceptible to infections cannot be exposed to ineffective treatment of infection. However, there is evidence showing that the risk of bacteraemia is significantly reduced by the intake of a single, higher than normal, antibiotic effective against the most important oral microbes one hour prior to the procedure (1, 4).

Based on an extensive meta-analysis, antimicrobial agents reduce both ostitis of the alveoral cavity and infection of surgical wounds in connection with surgical removal of the third molar, but only if the first dose is given prior to the procedure (3). Based on the 16 controlled studies included in the meta-analysis, a course of antimicrobial treatment started postoperatively is less effective than a single dose taken an hour before the procedure, at least in generally healthy patients. Patients with poor tissue response due to an underlying illness or medication are likely to benefit from combining the single-dose prophylaxis with a postoperative antimicrobial course, i.e. so-called perioperative prophylaxis. The total duration of the course depends on the patient''s healing capacity, but in most cases it lasts no longer than 5 days. Antimicrobial treatment does not reduce the symptoms of acute pulpitis or prevent flare-up during root canal treatment, which is why prophylaxis is not recommended when treating pulpitis (11).

How to choose the agent for prophylaxis?

The most common pathogens causing purulent oral infections are aerobic and anaerobic streptococci and anaerobic gram-negative bacilli, such as Prevotella and Fusobacterium species (6, 12). Staphylococcus aureus and other staphylococci are common findings, particularly in infections seen in children and the elderly, but usually infections are due to S. aureus. In patients with systemic odontogenic infection, the most commonly cultured bacteria are those belonging to the following genera: Streptococcus, Actinomyces, Klebsiella, Bacteroides, Prevotella and Enterococcus (7).

In each group of patients, antibiotic prophylaxis should cover the most important the most important pathogens likely to be present and which can cause remote site infections. These always include common oral streptococci and anaerobic bacteria, but S. aureus must also be taken into account, if the patient is particularly at risk from infection complications caused by staphylococci (an endoprosthesis susceptible to staphylococcal infections or prior treatment with penicillin, which may have favoured staphylococcal growth). The antimicrobial treatment given to the patient during the preceding month as well as exposure to multi-resistant healthcaqre associated bacteria and carrier status must be charted, and the possibility of selection and enrichment of resistant strains must be taken into consideration in when choosing medication. Repeated courses of the same antimicrobial agent within a short period of time is not usually effective due to acquisition and enrichment of resistant microbes. However the impact of single-dose prophylaxis on oral microbiota is likely to be minimal even if repeated.

When treating a patient colonized with a multi-resistant healthcare associated bacterium it is advised to avoid targeting this microbe unnecessarily in order to avoid further resistance which would weaken possibilities for treatment in the future. In general, all use of broad spectrum antimicrobial treatment favours the growth of multi-resistant bacteria. A summary of antibiotic prophylaxis of infection complications of dental origin are presented in Table 3. Amoxicillin is the first-line drug, due to its correct antimicrobial spectrum, its excellent absorption when taken orally as well as its good tissue distribution.