Antibiotic Use In Endodontics

Can writing really be better than reaming??

An antibiotic is defined as: a drug which inhibits or prevents the growth of bacteria. They are drugs which are important for the control of life threatening infectious diseases and are commonly used in medicine and occasionally in branches of dentistry. In recent years their use has been the subject of much scientific debate and media stories. The main reason for concern being that their overuse has led to the development of resistant strains of bacteria.

Antibiotic resistance has been the subject of many review articles. Whilst the subject of resistance is extremely important, it is perhaps more important for dental professionals to fully understand the pathogenesis of endodontic disease. By achieving a greater understanding of the disease process it becomes apparent that antibiotics have very little place in the treatment of endodontic disease.


Apical periodontitis is caused by bacteria; it is a unique disease in the sense that it doesn’t fulfil Koch’s postulates. The reason for this is; that many of the bacteria which cause the disease are also commensal organisms within the oral cavity and therefore are found in healthy individuals. However if these commensal organisms are given the environment within the root canal: and therefore isolation from the immune system, then their numbers increase and disease ensues.  This is an important difference between apical periodontitis and other bacterial infections are treated successfully treated using antibiotics

APICAL PERIODONTITIS – The disease of the root canal system

To understand the use of antibiotics in endodontic disease we must first understand the disease process. An over simplified summary of the disease is as follows:

1. Bacteria gain entry to the pulp via the dentinal tubules through a breach in the enamel (deep restorations, caries, and hairline cracks).

2. The presence of bacteria in the pulp initiates an inflammatory reaction.

3. The inflammatory reaction can give rise to symptoms, but often goes unnoticed by the patient.

4. Pulp necrosis occurs due to constant bacterial ingress, through the defect in the enamel and dentine.

5. The remnants of the necrotic pulp are used for energy by the proteolytic bacteria

6. The bacteria shed endotoxins and bacterial waste products as a result of respiration.

7. These products exit and tooth via any portals of exit (usually the apical foramen). Their presence in the periapical tissues informs the immune system that foreign organisms inhabit the root canal system.

8. Due to  pulp necrosis the cells of the immune system cannot enter the canal and so they remain in the periapical tissues adjacent the portals of exit. Inflammatory mediators are released by the immune system cells in response to the bacterial products and this causes bone loss.

9. It is this loss of bone which produces the apical lesion we see on the radiograph. The apical lesion is almost always free from bacteria. It only contains bacteria if there is a sinus tract present, an acute exacerbation (flare up) or extra radicular infection (rare bacteria such as Actinomyces which can survive outside the root canal).

10. At some point after bacteria have colonised the root canal system, the organisms within the canal system may enter the periapical tissues. When this occurs the patient usually experiences severe pain and swelling associated with the inflammatory response. It is not clear why bacteria enter the periapical tissues but it is thought to be due to a change in the balance between the bacteria within the canal and the host’s immune system in the periapical tissues. Such situations may occur if more bacteria are added to the root canal system via a leaking temporary crown or the patient becomes unwell.

Features of Apical periodontitis which make systemic antibiotic use ineffective

Apical periodontitis has several important features that distinguish it from other diseases which can be treated with antibiotics. These differences mean that the use of systemic antibiotics to treat apical periodontitis is ineffective.

1. Apical periodontitis is rarely life threatening. The human body has developed excellent ways of draining and isolating infection such as; the creation of sinus tracts and apical bone resorption.

2. The bacteria which cause apical periodontitis live within the root canal system in a biofilm (plaque). The biofilm is akin to a ‘city’ of bacteria, providing an opportunity for bacteria to share information and making them more than 1000 times more resistant to antibiotics than if they were planktonic (existing outside a biofilm).

3. Due to pulp necrosis any antibiotics taken by the patient cannot reach the bacteria within the canal system. Any bacteria which have travelled from the canal into the periapical tissues and are causing the patient discomfort are not usually adapted to living in the periapical tissues. Given time the immune system will usually phagocytose the organisms without the assistance of antibiotics.

4. The dentition is one of the most easily accessible regions of the human body. This accessibility allows the operator to quickly and effectively locate the root canal system and disrupt the organisms causing the disease. In patients suffering from acute pulpitis the bulk of the bacterial load is located in the coronal pulp. Removing this and preventing the ingress of more bacteria by placing a good temporary restoration are all that is required to alleviate the patient’s symptoms. Antibiotics should never be prescribed for patients suffering from acute pulpitis because the breach in the enamel and dentine needs to be closed. Failure to do this will allow further ingress of bacteria into the pulp keeping the inflammation and the patient’s symptoms going.



As discussed previously the use of systemic antibiotics to treat endodontic disease is largely ineffective and unwarranted. But there are always exceptions to the rule.

In rare circumstances systemic antibiotics can assist the immune system in killing bacteria outside the root canal system, where there is a good blood supply. However antibiotics should never be prescribed alone and an attempt should always be made to drain the infection, either by accessing the root canals or incising and draining a swelling. The following are the only situations when systemic antibiotics may be prescribed.

Systemic infection.

If the patient exhibits the signs of systemic infection then antibiotics can be prescribed to help the immune system eliminate the bacteria outside the root canal system. The signs of systemic involvement are- local lymph node enlargement, fever and malaise (feeling unwell). Systemic infection from the root canal system can often occur in those patients who are immunocompromised.

Antibiotic cover

The laws for antibiotic prophylaxis differ in different parts of the world. But in most countries antibiotic cover only needs to be given if root canal treatment occurs beyond the apical foramen. The number of patients requiring antibiotic cover for dental treatment is decreasing as its criteria becomes narrower.


Interappointment medicaments

The use of antibiotics in interappointment medicaments is popular. These often comprise an antibiotic and a steroid. The theory is that the steroid suppresses any pulpal inflammation which may be giving the patient symptoms and the antibiotic prevents bacterial overgrowth. The efficacy of a single dose of antibiotics inside the root canal system is debatable, as well as its ability to reach all the organisms within the canal system. It is generally thought that most of the effectiveness of these pastes is due to the anti inflammatory effect of the steroid.

Pulp revascularisation- triple antibiotic paste

A new area which has received a lot of interest recently is pulp revascularisation. This can only be performed in teeth with a very good blood supply (open apices). The theory of the procedure is that if the pulp which is infected coronally is removed then the stem cells in the apical region of the root sheath and pulp will be allowed to multiply and differentiate causing apical formation. The first stage of the procedure involves use of a triple antibiotic paste to ‘sterilise’ the canal. The antibiotics used are ciprofloxacin, metronidazole and cefaclor. These are ground up and mixed with distilled water to create a paste which is placed within the root canal for 4 weeks. After this time the dressing is removed and a blood clot is created within the canal by intentionally instrumenting through the apex. Mineral trioxide aggregate (MTA) is then gently placed onto this clot and the tooth is restored. Discolouration of the teeth can be a problem with this treatment.

So far the treatment has been limited to case reports and there are no studies showing long term of success. However it may become an area where the use of local antibiotics becomes essential.


Prescribing antibiotics for patients suffering from swelling and discomfort due to apical periodontitis has unfortunately become commonplace in dentistry. This is despite the fact that their use is largely unwarranted. However by understanding the disease process the operator quickly realises that the best remedy for a disease which involves bacteria inside the root canal system is to access the canals directly and disrupt the bacteria using endodontic files, antimicrobial irrigants and medicaments. So next time you think of writing a prescription put the pen down and pick up the endodontic files.