Dental pulp treatment / root canal treatment (known in Hong Kong Cantonese as “du ya gen”)
When a tooth has persistent severe pain, wakes you at night, hurts when you bite, or the gum repeatedly swells and discharges pus, many people hear their dentist recommend “root canal treatment”, often called “du ya gen” in everyday Hong Kong Cantonese; the formal name is dental pulp treatment or root canal treatment. It does not mean “killing” the root. Instead, the infected, inflamed or dead dental pulp tissue is removed, and the root canals inside the root are thoroughly cleaned and filled, so that the natural tooth can be preserved.
The dental pulp lies inside the tooth and contains nerves, blood vessels and connective tissue. When tooth decay is very deep, the tooth has been knocked, a crack extends into the pulp, or an old filling leaks, bacteria can enter the pulp and cause inflammation or even infection. If left untreated, the inflammation can spread to the bone around the tip of the root, leading to apical inflammation, an abscess or facial swelling.
The purpose of root canal treatment is to control infection, relieve pain and preserve the natural tooth’s chewing function as far as possible, while the tooth is still worth keeping.
How is root canal treatment different from an ordinary filling?
A dental filling deals with decay that is still confined to the outer or middle layers of the tooth. After the dentist removes the decayed part, the defect is filled with resin or another restorative material to stop the decay from getting larger.
Root canal treatment deals with problems that have already affected the dental pulp. Once bacteria have reached the nerve and blood vessel tissue inside the tooth, a filling alone is usually not enough to clear the infection. The dentist needs to enter the pulp chamber at the centre of the tooth, remove the inflamed or dead pulp, and clean the small, complex root canal system inside the root.
In other words, a filling repairs damage on the outside of the tooth, while root canal treatment deals with infection inside it. The two do not replace each other; the choice depends on how deep the decay is and how healthy the pulp is.
When might root canal treatment be needed?
Whether root canal treatment is needed cannot be judged from the level of pain alone, because some teeth with dead pulp may not feel obvious hot or cold pain. Dentists usually assess this by combining the medical history, clinical examination, hot and cold tests, percussion tests and X-ray images.
Situations that commonly call for further examination include:
Persistent or spontaneous tooth pain, especially when it worsens at night.
After eating cold, hot, sweet or acidic food, the pain lingers for a long time before fading.
The tooth feels raised, achy or very uncomfortable when biting.
A small pus bump appears on the gum, repeatedly discharging pus or giving off a bad smell.
The tooth gradually becomes darker, grey or black.
The tooth has suffered an impact, even if it did not crack or hurt at the time.
Deep decay that is close to, or has reached, the dental pulp.
The edges of an old filling, crown or restoration leak, allowing bacteria to enter the tooth again.
In the early stage of pulpitis, because the nerve is still alive, patients may feel obvious pain from hot and cold stimuli or spontaneous pain. As the pulp gradually dies, pain from hot and cold may lessen, but the infection can still continue to develop towards the root tip, causing gum swelling or an abscess. Information from Class ONE Dental also states that root canal treatment is a way of preserving the natural tooth in cases of pulpitis, more severe decay and dental trauma.
The root canal treatment procedure
Root canal treatment is a delicate dental procedure. The number of canals, how curved they are and the extent of infection differ from tooth to tooth, so the number of visits needed may also vary. It can generally be divided into the following steps.
Step 1: Examination and diagnosis
The dentist will first ask about the pain, your past dental history and whether the tooth has ever been injured, then check the depth of decay, the condition of the gums, your bite and whether the tooth has any cracks. X-rays help show the shape of the roots, the number of canals, the bone around the root tip, and whether there is an abscess or inflammation shadow.
If the tooth has a severe crack, a fractured root, insufficient periodontal support or extensive decay, the outcome may not be good even after root canal treatment is completed. In that case the dentist will discuss with the patient whether the tooth can realistically be saved and what other options exist.
Step 2: Local anaesthesia and isolation
Before root canal treatment, the dentist will usually give a local anaesthetic to reduce discomfort during the procedure. Even if the pulp is already dead, local anaesthesia helps the patient stay comfortable while the canals are cleaned and the tissue around the root is treated.
A rubber dam is generally used to isolate the tooth. It reduces the amount of saliva and bacteria entering the treatment area, and also prevents irrigating solutions or tiny instruments from falling into the mouth. It is an important infection control measure in root canal treatment.
Step 3: Opening the tooth and removing infected pulp
The dentist creates an access opening from the biting surface or the back of the tooth to reach the pulp chamber in the centre. Special instruments are then used to remove the inflamed, infected or dead pulp tissue, and the entrance to each root canal is located.
The canal system is not the same in every tooth. Front teeth usually have fewer canals; back teeth, especially molars, have more complex canal numbers and shapes, and some canals are very fine or curved, so they need more careful handling and sufficient time.
Step 4: Measuring, enlarging and irrigating the canals
The dentist measures the length of the canals to determine the area to be cleaned and filled, then gradually enlarges and shapes them with fine canal instruments. The aim of this step is to remove infected tissue, bacteria and debris, while creating a canal shape suitable for irrigation and filling.
During the procedure, the dentist repeatedly cleans the canals with special irrigating solutions to help reduce the bacterial load and remove residue. If the infection is more severe, the canals are producing a lot of fluid, or there is obvious inflammation at the root tip, the dentist may place medication inside the canals and seal the tooth temporarily, completing the treatment at the next visit.
Step 5: Filling the root canals
Once the canals have been thoroughly cleaned, are dry and show no obvious signs of infection, the dentist seals them with a root canal filling material. The purpose of sealing is to reduce the chance of bacteria re-entering the canals and to keep the inside of the root stable.
Some cases can be completed in a single visit; if the infection is more severe, the tooth is painful or the canal structure is complex, two or more visits may be needed. The number of visits cannot be judged by the position of the tooth alone, but is arranged according to the degree of infection and how the tooth responds to treatment.
Step 6: Restoring the tooth structure
After root canal treatment the tooth is preserved, but because it has usually had deep decay, old restorations or a treatment opening, its structure is generally more fragile. Depending on how much tooth structure remains, the biting forces and the position of the tooth, the dentist will recommend a final restoration such as a filling, inlay, onlay, post or crown.
Back teeth have to withstand greater chewing forces, so after root canal treatment the dentist often needs to consider more carefully whether a crown is needed for protection, to reduce the risk of the tooth cracking. For front teeth, a suitable restoration is chosen according to the extent of the defect, the tooth colour and appearance needs.
Will it hurt after root canal treatment?
Mild tenderness when biting, sensitivity around the tooth or some local discomfort for one to several days after treatment is fairly common. Although the pulp nerve has been removed, the ligaments and tissue around the root may still be temporarily irritated by the original inflammation or by the treatment itself.
Patients may take painkillers as directed by the dentist or clinic staff, and should avoid biting very hard or sticky food with that tooth at first. If the pain eases day by day, it can generally just be observed.
However, you should contact the dental clinic as soon as possible if any of the following occurs:
The pain becomes more and more severe, or cannot be controlled even with painkillers.
There is obvious swelling of the face, gums or jaw.
Fever, difficulty swallowing or limited mouth opening.
The temporary filling falls out, the tooth cracks, or the bite is clearly uneven.
Severe pain persists several days after treatment, or pus is discharged.
How should I care for the tooth after root canal treatment?
The success of root canal treatment depends not only on the day of treatment; protection afterwards, oral hygiene and regular check-ups are equally important.
First, avoid eating until the anaesthetic has worn off
If your lips, tongue or cheeks still feel numb after treatment, avoid chewing straight away so that you do not accidentally bite the soft tissue. It is safer to eat once normal feeling has returned.
Second, avoid biting hard objects with the treated tooth
If the tooth still has a temporary restoration, or the final crown, inlay or filling has not yet been completed, avoid chewing hard foods on that side, such as ice, hard sweets, bones, nut shells or hard, crunchy foods. A tooth that has had root canal treatment may be more fragile, and taking heavy biting forces too early may cause it to crack.
Third, keep up normal but gentle oral hygiene
Having had root canal treatment does not mean the tooth can no longer decay. Patients should still brush morning and night, and clean between the teeth with floss or suitable interdental cleaning tools. The area around the treated tooth can be cleaned as normal, but if the gum feels slightly uncomfortable at first, use a gentler technique and avoid irritating the wound or the temporary restoration.
Fourth, attend follow-up visits and complete the final restoration
If the dentist arranges a further root canal visit, a change of medication or the making of a crown, attend on time. Do not stop the treatment just because the pain has lessened, because if the canals have not been fully sealed or the tooth has not been properly restored, there is still a risk of bacteria re-entering or the tooth cracking.
Fifth, pay attention to your bite and the condition of the tooth
If the tooth feels “especially high” after treatment, and it is the first to touch when you bite, let your dentist check it. A high bite puts extra pressure on the tissue around the root and may prolong discomfort. Also, if you notice a chipped tooth edge, a filling that has fallen out or a loose crown, have it dealt with early.
Can a tooth last a long time after root canal treatment?
If the root canal treatment is successful, the tooth is suitably restored, and the patient maintains good oral hygiene and has regular check-ups, a treated tooth can last for many years. However, the lifespan of the tooth is affected by many factors, including the original extent of decay, the condition of the roots, periodontal health, whether there are cracks, biting forces, teeth-grinding habits, and whether the final restoration is complete.
A tooth that has had root canal treatment is still part of your natural teeth; only the pulp has been removed. It can still contribute to chewing function, but improper biting and lack of protection should be avoided. Regular check-ups help the dentist observe whether the bone around the root tip is gradually healing, and detect decay, leakage at the crown margin or periodontal problems early.
Root canal treatment FAQ
Question 1: Is root canal treatment very painful?
Root canal treatment is generally carried out under local anaesthesia, and one of its main aims is precisely to deal with the pain caused by inflamed pulp. There may be mild tenderness when biting or some local discomfort for a few days afterwards, but it usually improves gradually. If the pain keeps getting worse, or there is obvious swelling or fever, contact your dentist for a review as soon as possible.
Question 2: Do I definitely need a crown after root canal treatment?
Not necessarily; it depends on the position of the tooth, the remaining tooth structure, the extent of decay and the biting forces. Back teeth take greater chewing forces, so if a lot of the tooth is missing, the dentist may recommend protecting it with a crown, inlay or onlay to lower the risk of cracking. If it is a front tooth, or the tooth structure is better preserved, other types of restoration may be used.
Question 3: If the tooth no longer hurts after root canal treatment, do I still need follow-up visits?
Yes. The pain going away does not mean the root canal treatment has been fully completed, nor that the tooth is adequately protected. If the dentist has arranged further cleaning, filling or a final restoration, attend on time; after treatment is completed, have regular check-ups to monitor the healing of the tissue around the root and whether the restoration is stable.
