The study design is a double blinded randomized controlled trial and 170 subjects (teeth) , 85 in each of the 2 groups, will be enrolled from the patients at the NUH dental centre endodontic unit. The study aims to assess how the use of TotalFill® bioceramic sealer affects the healing outcome of apical periodontitis compared to a control AH plus®.

Conventional root canal treatment will be done during this study. Radiographs will be taken at each study visit during the study for root canal. The preoperative, postoperative and review clinical and radiographic data will be analysed.

Randomization and Blinding Study subject (tooth) will be randomized in a 1:1 allocation ratio between the two treatment groups. Allocation will be by random permuted block and stratified by gender to enhance balance. Computer generated randomized allocation for each subject will be concealed in opaque envelope. The envelope will only be opened by the operator on the obturation visit of the enrolled patient and the randomization number assigned to them.

In the event that a patient has more than 1 tooth eligible for the study, only one tooth on left and/or right side of the mouth will be recruited for the study. Therefore, a patient could contribute a maximum of two teeth for this study (i.e. a maximum of one tooth on each side of the mouth). Selection of tooth will be done using computer generated randomization number.

Study Visits and Procedures After cleaning and shaping and the patients are deemed ready for obturation, the patients will be randomly assigned to one of the 2 groups for obturation using AH plus® or TotalFill® bioceramic sealer.

• The patients and the examiners will be blinded to the type of sealer used but it would not be possible to blind the operators.

  b. Post Study Follow up and Procedures

• A follow up phone call will be made to collect the patient pain experience on day 1, day 3 and day 7 post treatment which they have recorded on their pain/discomfort diary.

• At the 6-month and 12-month review, patients will be examined for any clinical signs and symptoms and a review radiograph will be taken to assess the size of the periapical lesion.

  c. Radiographic assessment

• All radiographs will be taken with a localising device to control for angulation and magnification.

• Calibrated measurement tools in the dental practice management software will be used to measure the diameter of the lesion across the longest diameter.

Statistical and Analytical Plans

a. General Considerations Intention-to-treat population is considered the main analysis population. The intention-to-treat population includes all subjects who were assigned a randomization number. Study subject's demographic and pre-operative characteristics will be summarized for each treatment group.

Inclusion Criteria:

• A preoperative periapical radiograph will be required for diagnosis.
• Subjects at least 21 years old.
• Medically healthy
• In a patient with multiple teeth requiring root canal treatment, only 1 tooth from each side will be included and selected at random.

Exclusion Criteria:

• Patient below 21 years old
• Pregnant women.
• Patients with autoimmune diseases and uncontrolled diabetes.
• Teeth with periodontal probing depths of 5mm or more.
• Incomplete root formation that is detected radiographically.
• Cracked teeth
• Teeth are deemed to have poor restorative prognosis.
• Teeth with adjacent teeth on the same side that require root canal treatment

Blinding will be done to the assessors to reduce bias to healing assessment. As well, participants won't know which treatment they are undergoing.