In cases refractory to initial root canal therapy in which a decision is made to perform nonsurgical retreatment, the patient has the right to know the prognosis of the proposed treatment and clinicians must be able to provide this information based on the best available data. The literature answered this question when the treatment was performed in multiple visits; however, little information exists when single visit root canal retreatment was performed. Therefore, the aim of the present study is to assess the clinical and radiographic outcome of root canal retreatment performed in single visits in endodontic clinics of Dubai Health Authority (DHA).

The present study is designed to assess the clinical and radiographic outcome of root canal retreatment performed in single visits in endodontic clinics of Dubai Health Authority (DHA). This is a retrospective study where patients' treatment data will be collected and outcome criteria will be applied blindly.

The sample in this retrospective study will be selected from those patients who have undergone single visit endodontic retreatment at the DHA Endodontics clinics from January 2018, through December 2019. The teeth under investigation will be tracked in the database starting from completion of retreatment for at least 6 months, and the percentages of teeth that were retained or underwent additional procedures such as apical surgery or extraction will be recorded.

The clinical and radiographic assessment at baseline and at recall documented in clinical notes, and all data will be collected using a standardized proforma.

The quality of the existing root canal fillings and the status of the periapical tissues will be determined according to the PAI by 2 calibrated independent observers using the periapical radiographs.

A. Periapical index (PAI) The index is a radiographic method of interpretation that consists of 5 categories, numbered 1-5.

B. Quality of root canal filling

Three criteria were used to assess the quality of the existing root canal fillings as follows:

Length of root canal filling: root filling ending ≤2 mm from the radiographic apex, root filling ending >2 mm from the radiographic apex, or root filling at the radiographic apex (flush).

Density of root canal filling: the presence or absence of voids in the root filling or between the root filling and root canal walls.

Taper of the root canal filling: consistent taper from the orifice to the apex or no consistent taper from the orifice to the apex

The preoperative diagnosis is determined based on clinical and radiographic findings using the American Association of Endodontists Consensus Conference-recommended diagnostic terminology.

Retreatment Procedures

Endodontic retreatment of all cases was conducted in a single visit by endodontic specialists according to the contemporary standards of endodontic therapy.

Only those patients with at least 6 months of clinical and radiographic follow-up were included. When patients returned for recalls, one or multiple (in mutirooted teeth) periapical radiographs were taken.

Follow up

Recall appointments included a radiographic and clinical examination of the treated tooth. The examination was documented and included any signs or symptoms, the presence of a sinus tract, sensitivity to percussion and palpation, swelling, periodontal pockets, or a history of pain.

Periapical radiographs will be evaluated by 2 examiners.

The treatment outcomes will be classified into 3 categories according to the following definitions:

Healed: Functional, asymptomatic teeth with no or minimal radiographic periradicular pathosis (radiolucency) Nonhealed: Nonfunctional, symptomatic teeth with or without radiographic periradicular pathosis or asymptomatic teeth with unchanged, new, or enlarged radiographic periradicular pathosis (radiolucency) Healing: Teeth that are asymptomatic and functional with a decreased size of radiographic periradicular pathosis (radiolucency) .

Collecting data into a recording sheet:

The patients' treatment data will be collected continuously for at least 6 months in the database, and outcome criteria will applied blindly. The teeth will be tracked in the database during the entire period.

Inclusion Criteria:

• Root canal retreatment cases performed in single visits
• Age ranging from 18 - 70 years
• Follow up period of at least 6 months

Exclusion Criteria:

A case will be excluded from the study if the case was under 18 years of age or followed up period for less than 6 months.

Adult patients who underwent root canal retreatment in single visit in endodontic clinics of Dubai Health Authority (DHA).