The goal of this observational study is to learn about the short-term effects of MTA flow thick material in apicoectomy treatment. Participants are patients who take MTA flow to treat their apical lesion. The main question it aims to answer is:

Is MTA flow thick material effective for retrograde filling in patients who require apicoectomy for treating apical lesion? Participants already taking MTA flow as part of their regular dental care for apicoectomy will be followed-up treatment results in 6 months.

Quality assurance plan: all patients satisfy the inclusion criteria are invinted to participate the study. Radiography was performed using an standard kit. All surgical procedures were conducted by an experienced oral surgeon. Clinical signs, radiographic signs are independently evaluated by an endodontist and oral surgeon.

Data checks to compare data entered into the registry against predefined rules for range or consistency with other data fields in the registry.

Source data verification: medical records adn paper report form. Data dictionary: clinical signs, swelling, pain, fistula, radiographic signs, success rate, rarefaction, periodontal space.

Standard Operating Procedures: none. Sample size assessment: none available. Plan for missing data: exclude from the participants, missing case will be reported in the results.

Statistical analysis plan: Data were collected and analysed using JASP software, version 0.19.3 (University of Amsterdam, Amsterdam, The Netherlands). Categorical variables are presented as absolute counts and percentages, whereas numerical variables are expressed as mean values with standard errors.

The Friedman test was used to compare differences in clinical symptoms and apical lesion sizes at baseline, 3 months, and 6 months. The Bonferroni post hoc test was used for pairwise comparisons between assessment points. The chi-square test was used to compare the differences in radiographic findings and overall success between 3-month and 6-month evaluations.

Inclusion Criteria:

• age 18 years or older
• systemic health classified as I or II according to the American Society of Anesthesiologists (ASA) classification
• willingness to participate in the study
• failure of conventional or repeat endodontic treatment
• a periapical lesion with a diameter ≥ 5 mm

Exclusion Criteria:

• a crown-to-root ratio ≥ 1.0
• inability to comply with the follow-up protocol

Study population are patients who came to Dental Department of 175 Military hospital for apical lesions.

IPD will be shared when other researchers ask for specific purpose.