2026 Hong Kong Root Canal Tooth Discolouration Emergency Guide: Canossa Hospital Dentist Discusses Internal Bleaching Costs and Process

When people want whiter teeth, they typically think of blue-light whitening treatments, whitening strips, or whitening solutions. However, these methods only help patients whose tooth discolouration is limited to the surface. If a tooth has undergone root canal treatment due to severe decay, trauma, or a fractured tooth, causing it to turn yellow, grey, or even dark grey-black, how can one restore a bright, white smile?

Severe Tooth Decay May Require Root Canal Treatment, Which Can Cause Teeth to Turn Grey

Dr. Yiu Ka Ki from the Hong Kong Sanatorium & Hospital Dental Centre explains that root canal treatment is a procedure in which the dentist removes certain nerve fibres and blood vessels from within the tooth. Some patients with severe tooth decay may need to undergo root canal treatment to prevent bacterial infection of the dental pulp and to preserve the tooth. Additionally, teeth that have suffered significant trauma, fractures, or other damage may also require root canal treatment, which similarly carries a risk of causing the tooth to turn grey.

After Internal Bleaching, Teeth Gradually Return to Their Natural Colour

Once the nerve tissue inside a tooth is damaged or the blood vessels are removed, the tooth may begin to turn grey. Dr. Yiu notes that this condition can be improved through internal bleaching. The procedure involves creating a small opening at the back of the tooth — or using an existing access cavity — to introduce a peroxide-based bleaching agent, which is then sealed. The patient returns for a follow-up appointment 7 to 10 days later for the dentist to assess the results.

Following internal bleaching, the tooth gradually returns to its natural colour. However, the time required and the final outcome depend on the degree of grey or dark discolouration present. In some cases, teeth that had turned grey-black after root canal treatment began to visibly lighten within fewer than three days of internal bleaching, eventually matching the shade of the surrounding teeth.

Internal Bleaching Requires Minimal Treatment Time but Must Be Performed by a Registered Dentist

Dr. Yiu points out that internal bleaching involves a short treatment duration and does not require cutting into the already compromised tooth, thereby minimising discomfort. It is important to note, however, that the bleaching agent used in internal bleaching contains peroxide and must be administered by a registered dentist. It must also be applied in accordance with safe dosage guidelines to avoid causing damage to the teeth and gums.