Root canal treatment

Inside each tooth is living tissue, consisting of connective tissue, blood vessels and nerve fibers, among other things. This tissue is called the pulp. From the bone, through feeding channels, blood vessels and nerve fibers run toward the root. They enter the root at the root tip, which is called the apex. They continue their way through the root via the root canal. To assess the number of root canals and the shape of the roots, an X-ray may help. This X-ray, like the image at the top, is two-dimensional (flat), whereas in reality, a tooth/teeth is naturally three-dimensional. The dentist will combine the information obtained from the X-ray with his knowledge, “the naked eye” and instruments to create an overall picture.

Broadly speaking, teeth and small molars have one to two canals and molars have three to four canals. Where lower molars more often have three than four and upper molars more often have four than three root canals.

The root canals come together in the pulp chamber. In children and young adults, the root canals are wide and the pulp chamber is large. Throughout life, these will become smaller and smaller as new dentin is deposited against the walls from the pulp. The nerve fibers in the pulp can send signals in the face of cold, heat and also other stimuli, e.g., touch and sweet. With tooth decay and/or tooth sensitivity, among other conditions, the nerve fibers will become more easily stimulated and these stimuli may be more likely to be painful.

Inflamed pulp

Inflammation of the living part of a tooth/teeth is called pulpitis and can cause pain/sensitivity. Tooth decay, also known as caries, is a common cause of pulpitis. If a cavity occurs then harmful products from the bacteria will reach the pulp through the porous dentin (dentin), this can also occur with leaking fillings/crowns etc. This creates an inflammatory reaction in the pulp, making it more likely to react painfully to stimuli. The pain can manifest itself differently including increased sensitivity to cold, heat and sweet or sharp pain when biting/tapping closely against a tooth/teeth. Should the inflammatory reaction worsen, there could also be a continuous nagging and/or throbbing pain.

Dead pulp

If the pulpal tissue in the root canals has died due to inflammation, bacteria have free rein in the pulpal cavity and root canals. Through the root tip (apex), the root canals are connected to the tissue surrounding them, allowing the inflammation to spread. Due to the body’s immune response, inflammation is sometimes confined to the area around the root tips for long periods of time.

Root tip inflammation can cause many different symptoms, but a symptom-free period is also possible. The symptoms that may occur range from a severe and/or throbbing pain to only pain when (chewing) pressure is applied to the affected tooth/teeth. As a reaction, the inflammation may cause the cheek to swell, sometimes pus may develop (abscess) and it is also possible for the inflammation to spread to the surrounding soft tissues. With acute inflammation, you may become ill and fever is also possible. If complaints arise, it is of course wise to seek the advice of a dentist. In some cases, inflammatory products may exit through a drain. This drainage passage is called a fistula.


Root canal treatment can be performed for several reasons. A common situation is that with a severe toothache. The living part (pulp) of the tooth/teeth is then so inflamed (pulpitis) that the dentist removes the nerve to help the patient get rid of the pain. Root canal treatment does not wait for the pulp to die and can prevent possible inflammation around the root tip. In some cases, the crown of a tooth no longer has enough hold to make a filling or a crown. After a root canal treatment, the canal can be used to insert a post, which serves as a hold for the filling or crown. Root canal treatment is also necessary if the pulp has already died, or if root tip inflammation is present, as in the image above. Root canal treatment then aims to remove the bacteria from the root canal and, of course, to prevent them from re-entering it. After cleaning the root canals, the inflammation around the root tip will also be able to heal and allow the bone to grow back. Root canal treatment is called endodontic treatment or endo for short. Treatment generally takes place under anesthesia and can often be performed painlessly without acute inflammation!

Root canal treatments can range from fairly easy, in the case of a front tooth with one canal, for example, to very difficult in the case of an upper molar with four canals and crooked roots. The average treatment time in practice can range from about half an hour to one and a half/two hours, depending on the degree of difficulty. In our practice, in the first session, the canal treatment alone is started in a short time (endo-start) and the patient is relieved of pain. This appointment usually takes 30 minutes in a relatively easy case; if there are complications, it will obviously take longer. A second appointment will then be made to conclude the root canal treatment. At its easiest, this one also takes 30 minutes. This is if there is treatment of only one channel without complications. For each additional channel, think dialing, fifteen to twenty minutes per channel are added. Of course, we assume that no complications occur.

In reality, it often takes six months before the first improvements can be clearly seen, and it can take up to several years for the inflammation to disappear completely. The symptoms generally do disappear within a few weeks to months.

Please keep in mind that a tooth that has had root canal treatment is weaker and more brittle, than a tooth that is still healthy. This is often the reason why the weaker tooth is eligible for a crown in the future.


The dentist has now cleaned, disinfected and filled the root canals up to (almost) the root tip. Intensive cleaning, disinfection and pressing (through) the filling material may have temporarily irritated the area around the root tip. This is more common and will generally allow 1 to 2 days of symptoms. In some cases, it may take several weeks for the symptoms to disappear; should the symptoms persist longer, it is wise to consult your dentist.

(Severe) pain with heat and cold and e.g. sweet are typically stimuli issued by the (inflamed) dental nerve. These stimuli generally disappear after root canal treatment, unfortunately in your case others have taken their place. At the start of a root canal treatment, the dental nerve (if still present) is removed, the canals cleaned and usually temporarily filled, so that another session can finish the treatment permanently. Residual nerve, inflammatory tissue or residual bacteria can cause post-operative pain, usually most severe during the first two days, but unfortunately this can also last a bit longer. This can be a nagging pain, but can also intensify or occur only when (chewing) pressure is applied. If the file used during treatment got past the root tip, it may have irritated the bone and root membrane which can also lead to symptoms for some time (mechanical irritation). The same goes for squeezing through the diluted chlorine solution used for disinfection (chemical irritation). In the first mentioned situations where the canals are not yet completely clean or the situation where there is inflammation around the root tip that builds up high pressure in the canals, re-opening, cleaning and flushing can help! In most situations, it is often a matter of time anyway and the symptoms will subside on their own.

Bacteria in the root canal have probably caused inflammation in you. At the start of the root canal treatment, the dentist created an opening to the root canals and cleaned them with a disinfecting chlorine solution and closed the molar with a temporary filling, after which the treatment would be completed at a later date. Unfortunately, the inflammation is now flaring up again and the swelling is also back. The dentist could reopen the canals, allowing the pressure increased by the inflammation to escape and also disinfect the canals again. In some cases, antibiotics may also be prescribed. Sometimes the swelling may also be filled with pus, indicating an abscess. By allowing the pus to escape outward (drain) through the root tip and root canal or by making an incision (a drain) in the gums, the (pain) symptoms can also diminish quickly.

A patient presenting to a dentist with an inflamed nerve will often need to be scheduled between existing appointments, the time available is likely to be limited. Therefore, initially, only the inflamed nerve is removed, so that the pain for the patient will decrease and the root canal treatment can be completed permanently at a later date. Of course, more factors can play a role why a root canal treatment is not completed in 1 session, including: difficult to access canals, failure to get the canals dry, present (active) inflammation around the root tip.

A broken file during root canal treatment is unfortunately a more common complication. Files are used to widen the channels so that they can be properly rinsed (disinfected) and filled. The more curved and narrow the channels are the more likely the files can break. Also, the probability of breakage also depends on the type, age, diameter of files and the force used by the dentist, among other things. Should a piece of the file remain in the root canal, it need not cause any problems. The file itself is not likely to cause an inflammatory reaction. The chances of success depend more on the amount of bacteria remaining in the root canal around the file or under the file. If the file has already broken off high in the canal at the beginning of treatment and there is also inflammation at the root tip (bacteria) then the prognosis may be questionable. But in the opposite case of a root canal treatment of a vital (non-infected) molar, where a piece of file is left at the bottom of the root, the prognosis may be good.

The temporary filling used to close a tooth/crown after the start of root canal treatment, among other things, may be of a soft material (cavit). This can also make it appear that the filling has fallen out, when only the top layer is gone. However, should the filling be completely lost, it is wise to contact your dentist. Access to the root canals is then open and bacteria from the oral cavity have free rein. The dentist will generally disinfect the canals and place a new temporary filling.