Root canal treated teeth with asymptomatic apical radiolucency: to treat or not to treat

Recently a referring dentist has questioned my fellow endodontist treatment plan of teeth with asymptomatic apical radiolucency. She asked why the treatment is not definitely needed but likely needed? The issue is quite perplexing and worth careful consideration here. 

Making treatment decision on these teeth is far from straight forward. There are several principles generally used to govern clinician treatment decisions.

Biological principles

If we can say that the apical radiolucency is a disease then it’s quite reasonable to assume that some kind of treatment is required.

Apical radiolucencies, however, are not always disease. They can be many things.

They can be disease, of course. In this case, treatment is reasonably required. In some circle, however, there have been ongoing debate whether disease=treatment and no disease=no treatment is scientifically, biologically or even philosophically justified. But this is for another day, another topic as it can be quite long to discuss adequately and it involves area that we are not familiar with such as social science and philosophy in medicine. 

Apical radiolucencies can be healing in progress. Radiographic changes take time i.e. six months or one year even. If we have only one radiograph, it’s only a snap shot in time, we don’t know the direction toward which radiolucencies are going. If later on radiolucencies were larger, they would be disease. If, however, they were smaller, they would be healing in progress. If we have only one radiograph, we don’t know if it’s a disease or healing in progress.

If we could access historical radiographic record of the tooth in question, it would probably help determining whether that radiolucency was a disease or healing in progress.

Failing that, there have been epidemiological study that looked in to healing dynamic of apical periodontitis and found that most of the healings occurred within four year period after treatment. Based on this finding, we could say that if treatment had been done more than four years ago and radiolucency was still present, the chance would be small that radiolucency is a healing in progress. This is, however, only a guideline not a rule as evidence is not definitive. In addition, there have also been studies documenting late healing 20-30 years after treatment. This involved very small number of cases though.

Scar tissues-radiographically, they are indistinguishable from disease most of the time. Histologically, they lack crucial features of disease i.e. inflammatory cells. By definition, therefore, scar tissues are not disease and treatment is not required. Scar tissues in non-surgical endodontic treatment are quite rare.

So seeing apical radiolucencies doesn’t automatically mean treatment. Biological principles are not very useful in making treatment decision in this case. We will now consider next principle.

Harm reduction principles

If we could say that treatment reduces or prevents potential harm, treatment would then be justified. To say that we need to know that if we did nothing on root canal treated teeth with asymptomatic apical radiolucencies, what would happen? That is to say, in epidemiologically-correct lingo, we need to know the natural history of asymptomatic apical periodontitis on endodontically treated teeth. Say that three times fast. 

Now there have been two articles that I know of that looked into this issue, one from Scandinavia/Norway and the other from Singapore. The results were quite similar, the risk of acute exacerbation in root canal treated teeth with asymptomatic apical radiolucencies is about 5%. In simple terms, it means if we do nothing, there’s 5% chance that patient will end up having pain or swelling.

On the other hand, if we decided to do something (treatment, endodontic revision) on these cases, the general risk of flare up in general population is about 3%. This number is based pretty much on initial cases, revision cases may have slightly higher risk of having flare up.

So harm reduction principles are not useful here either as do nothing or do something doesn’t make much difference in terms of reducing risk of flare up or harm.

Practical and Precautionary principles  

Given current situation and taking into account the knowns and unknowns, endodontic treatment plan could be formulated. There are a lot that we don’t know. We don’t know if radiolucency’s a disease. We don’t know if the tooth will become symptomatic necessitating treatment later on. We don’t know if remaining bacteria will cause pain/swelling etc. Precautionary principles are applied here as if the tooth became symptomatic later on and treatment was required, what would entail? If it was too complex, risky and costly, doing something now rather than later would probably be better.

Practical principles are then applied by learning about future restorative treatment plan. This is something that we could find out and could take into consideration when making treatment decision. Essentially, endodontic treatment is planned in preparation of the worst case scenario.

Restorative treatment plan.

If there’s nothing plan restoratively or only direct restoration planned, treatment decision would lean more toward monitoring (doing nothing) rather than treatment now as treatment can be started easily, inexpensively (no costly restoration involved) and without complications, if/when the tooth became symptomatic.

If crown was planned, the decision between monitoring and treatment would be 50/50 as treatment can be commenced after crown placement and tooth became symptomatic, but there’s potential complications to be considered. Crown might fracture during endodontic revision as we have to go through crown. This need to be communicated clearly to the patients. They may favour endodontic revision now for preventive purposes before crown placement rather than later when symptoms arise risking crown fracture during treatment and the need for a new crown . 

Endodontic treatment cannot eradicate bacteria from root canals. It is reasonable to assume that some bacteria were left in the canals at sub-clinical level. Bacteria and host defence mechanisms are pitted against each other and they are in delicate balance that’s why there’s no symptoms. Crown preparation has potential to disrupt this balance through vibration or introducing oxygen into canals. Once the equilibrium is disturbed, symptoms may follow. This is another reason why endodontic revision before crown preparation might be worth considering.  

If post core and crown were planned, the decision would lean more toward treatment now rather than later as treatment after completion of post core crown involved dismantle everything. It would be costly, complicated and time consuming. Also risk of root fracture during post removal cannot be completely eliminated.

Treatment decision for root canal treated teeth with asymptomatic apical radiolucency is not straight forward. It’s not as simple as seeing radiolucency=disease=treatment. There are a lot to think about. Future restorative treatment plan appears to be a major driver of endodontic treatment plan.