## 2 Materials and Methods
However, it most frequently occurs due to loss of temporary filling material or inadequate endodontic permanent restoration or crown sealing. A contra bevelwas prepared to produce a cast core with a collar of metal that encircles the tooth and acts as secondary ferrule and provides the adequate coronal seal to the metal post. A total of 100 patients who received post and core treatments from undergraduate students in 2016-2017, were contacted four years later for follow-up evaluation. A total of 70 patients reported to the clinic in 2020-2021. To assess the endodontically treated teeth restored with glass fiber posts and cast posts in the maxillary and mandibular arches, clinical and radiographic examinations were carried out. Intraoral peri-apical radiographs of the cemented posts were taken using the paralleling approach technique to reduce the chances of distortion. The digital periapical radiographs were assessed using the CS-R4 program (CSR4 with Practice Management Software version 4, Carestream Dental LLC, Atlanta, GA, USA). All subjects were categorized into three groups based on the gap present between the apical portion of the cemented post and the residual remaining gutta-percha in the radiograph [19]. Group I: There was no gap between the remaining gutta-percha and cemented post end. Group II: The remaining gutta-percha and the cemented post end were separated by a gap that measured more than 0 mm but less than 1 mm. Group III: The remaining gutta-percha and the cemented post end were separated by a gap that measured more than 1 mm. The same participants were divided into three groups as well, in order to determine how much gutta-percha was still present after the post- and core-procedure [10; 20; 21; 22]. Group IV: The amount of gutta-percha left was less than 3 mm. Group V: The amount of gutta-percha left was between 3 to 5 mm. Group VI: The amount of gutta-percha left was more than 5 mm. The periapical index (PAI) was used to determine the apical condition of each tooth as follows [23]:  
1. Normal periapical region present
2. Minor changes in bone structure present
3. Moderate changes in the bone structure present
4. Periodontitis with well-defined radiolucent area present
5. Severe periodontitis with exacerbating features present  
A healthy periapex was designated as PAI 1, showing a normal width of periodontal ligament space and a normal look of the surrounding bone. All other PAI score (2,3,4,5) values were indicated as apical periodontitis. In order to prevent bias, the coronal portion of every radiograph was covered with cardboard. The radiographs were assessed according to the following criteria:  
Normal: The periodontal ligament was intact and the periapical region was free of radiolucency. (PAI 1)  
Disease: Periapical radiolucency or a widening of the PDL gap was present. (PAI 2,3,4,5)  
All clinical and radiographic examinations were evaluated independently by two examiners. Both examiners went through a calibration phase before performing the clinical and radiographic evaluation. During the calibration phase, the examiners received clear explanations of the study approach. Ten teeth were initially examined in order to calibrate both examiners, and [PERSON]'s kappa (kappa 0.91) was used to find inter-examiner agreement. The examination room was made darker to regulate the ambient light and provide the best radiographic image quality and radiographic contrast. Whenever there was a disagreement between the first two examiners, a prosthodontist with ten years of professional experience, the third observer, was asked to make a final decision. Each radiographic measurement was triple recorded by one experienced investigator after software calibration for linear measurement. The average of three values was obtained in order to reduce the intra-observer error. Between December 2021 and March 2022, clinical and radiological data were gathered. The gaps between the post and remaining gutta-percha were taken into account when grouping all of the qualitative data into three different groups.