Radiographic assessment of dental post and core placement at different educational levels in an undergraduate student clinic: a 4-year retrospective study

Background Dental post and core is one of the common procedures performed after endodontic treatment. The aim of this study was to radiographically assess the quality of post and core procedures performed by dental students at different education levels in addition to determining the most critical errors encountered during their clinical practice. Methods A retrospective cross-sectional study design was conducted in the College of Dentistry, Imam Abdulrahman Bin Faisal University. A total of 550 periapical radiographs (PAs) of cemented posts were retrieved from the records of patients treated by dental students. Parameters and guidelines for assessing the quality of post treatment have been determined and statistically analyzed. A P value <0.05 was considered statistically significant. Results The study included 502 students and most of them were females (66.5%). Data were obtained from 502 patients (62% females) with fiber posts used in 98.2% of the cases. About 50% of the posts were inserted in premolars, 62.9% in the upper arch, and 66.7% were restored with crowns as a final restoration. Regarding the quality of posts, 98.4% showed good preparation quality and 98% showed good radiographic quality. The post diameter was equal to 1/3 of the root diameter in 31.9% of the cases; post length was equal to 2/3 of root length in 5% of the cases and equal to or more than crown height in all cases (100%). Length of the remaining gutta percha (GP) was between 3–5 mm in 38.8%, and there was no gap between the post and remaining GP in 95.6% of the cases. There were no statistically significant differences between dental students at different clinical educational levels regarding the quality of post placement. Conclusions The quality of post and core procedures performed by students showed acceptable radiographic quality and were within the recommended standards.


Introduction
Endodontic treatment plays a major role in ensuring the survival of tooth and success of post and core treatment. 1estoration of endodontically treated teeth (ETT) with extensive coronal tooth loss requires the placement of dental posts and core that adds retentive features to the coronal restoration. 2Several post systems were developed either in the form of custom-made posts using gold or non-precious metals, or prefabricated stainless steel or titanium posts. 3Aesthetic posts were recently introduced as alternative options including ceramic and glass fiber posts with variable shapes and sizes. 4ccess of post and core procedures depends on following the proper sequence of the treatment plan in addition to the accuracy of each step performed prior to post placement. 5One of the reliable methods used for evaluating the post placement procedure is taking periapical radiographs (PAs) prior to, during and after post cementation. 6Several factors affect the longevity of dental posts, such as proper filling and obturation, acceptable apical seal, and absence of clinical and radiographic signs and symptoms. 7ntal students are required to perform several clinical procedures as a prerequisite for graduation.One of these procedures is post and core placement in ETT followed by a final prosthetic restoration. 5,8Students perform post and core procedures in their clinical years following well-designed rubrics for each procedure under the supervision of their faculty supervisors to achieve the optimum outcome in each step of the treatment plan. 5,6Accordingly, these rubrics provide proper assessment of the students' practice and skills level, and also helps in improving their ability to perform self-assessment for each specific dental procedure.
The evaluation criteria of the post and core quality include coronal tooth preparation, radicular canal preparation and postoperative cementation of the fiber post.Several studies illustrated the capability of undergraduate dental students in post placement in ETT among Saudi Universities. 5,8,9However, no studies were conducted to assess the students' abilities and skills in post and core placement in the Eastern Province region.The study was conducted to address the common errors encountered in post and core procedures performed by dental students.By recognizing these errors, faculty members can develop a curriculum that focuses on these specific issues and teaches students how to avoid or correct them.This will help prevent complications that may arise during these procedures.Additionally, exposing students to failure cases and teaching them how to handle clinical situations will enhance their knowledge and improve their performance.By learning from these experiences, students can develop better skills and become more proficient in their clinical practice.Hence, the aim of this study was to radiographically assess the quality of post and core performed by dental students at different educational levels in addition to determining the most critical errors encountered during their clinical practice.The null hypothesis states that there would be no statistically significant differences in the performance of dental students at different educational levels.

Methods
A retrospective cross-sectional study was conducted in the College of Dentistry, Imam Abdulrahman Bin Faisal University.The sample size was estimated assuming 80% study power and 5% alpha error. 10According to Muthar et al. 11 study, the acceptable sample size was 119 samples.The study was approved by the institution research board (IRB-2022-02-285) of Imam Abdulrahman Bin Faisal University, Dammam, Saudi Arabia.A total of 550 digital REVISED Amendments from Version 1 • Title: was changed as follows; Radiographic assessment of dental post and core placement at different educational levels in an undergraduate student clinic: a 4-year retrospective study.• Keywords: Keywords were adjusted according to the MeSH terms.
• Introduction: The introduction was improved, with a better structure including clinical/educational relevance of study and gap of knowledge, hence why the study was conducted.• Methods: More details about sample size calculation were added.Also, details and guidelines of endodontic treatment and post and core treatment were added with references.The rubrics of assessing the post and core treatment quality were clarified as well as the calibration method of investigators.• Figures: the resolution was improved to be clearer.
• Results: the results were clarified and explained in details.Also, the number of excluded data due to missing information was added.• Discussion: The information about the initiation of the endodontic pre-clinical and clinical teaching and training of the students was added.Also, justification for the absence of significant difference between the students of different educational years was added.Comparisons of our findings with similar studies were added and justified.Limitations and strengths were clarified based on the study design and findings.

• Conclusion:
The content of the conclusion was modified to match the research objectives and results.
Any further responses from the reviewers can be found at the end of the article periapical radiographs (PAs) recorded using parallel technique were saved digitally on radiographic software (MiPACS Dental Enterprise Viewer 3.1.1404,Medicor Imaging, Charlotte, NC, Weasis is a free software available as a medical DICOM viewer) at the college of dentistry.ETT restored with cemented fiber posts were retrieved from the records of patients.The cases included in this study were those treated by dental students at Imam Abdulrahman bin Faisal University Dental Hospital from 2018 till 2022.Since this study was conducted retrospectively, patient consent was achieved before starting the treatment; as a step of the routine hospital procedures.The investigators maintained the anonymity of all extracted data, ensuring that patients' identities were kept undisclosed.
Inclusion criteria were set as follows: (1) dental students started clinical practice of endodontic treatments as well as prosthetic courses, starting from 4 th year till the 6 th year as well as students of internship program, (2) cemented post and core procedures on optimum ETT, (3) non-surgical root canal treatment (4) availability of complete radiographic records (a minimum of three good quality periapical radiographs: a preoperative, working length and postoperative radiographs).Exclusion criteria were set as follows: (1) permanent teeth with uncompleted endodontic treatment, (2) retreatment cases, (3) teeth previously treated surgically with apicectomy, and (4) dental records with missing or poor quality (nondiagnostic) radiographs.
Medicor Imaging Picture Archiving and Communication System was used to evaluate PAs quality as either acceptable according to the absence of following items; cone cut, teeth overlap, elongation, or shortening or unacceptable. 15Post and core treatments quality were also assessed in the extracted PAs by two trained investigators (S.A. and D.A) according to a previously published criteria (Figure 1 and Table 1). 5,9,11Before the assessment, the investigators underwent a calibration session to review the set criteria and analyze several post-obturation radiographs.The findings were discussed and an agreement was reached on the criteria of assessment.In this study, all clinical cases treated by students in the clinical sessions were approved and supervised by endodontic and prosthetic faculty member.The assigned clinical cases to the  students were done by and endodontic faculty member where the cases were of low difficulty according to the American Association of Endodontics Case Difficulty Assessment Form and Guidelines. 12Endodontic treatments were initiated by using either SS hand or engine-driven ProTaper Universal (PTU) files (Dentsply Maillefer, Ballaigues, Switzerland) followed by lateral condensation obturation technique using gutta percha cones and epoxy resin-based sealer (AH plus sealer, Dentsply Maillefer, Ballaigues, Switzerland).Post and core treatments were performed in the presence of rubber dam isolation according to the protocol of treatment in the dental school and under supervision of prosthodontic clinical staff where the average of staff to student ratio in the clinic was 1:8.However, the ratio in the internship was higher almost 1:10.The gutta percha was removed using a Gates drill (size 3) and a low-speed drill provided by the manufacturer of the post-system (glass fiber post; RelyX (3M ESPE) ® Tapered post) Self-adhesive resin cement (RelyX U200/3M ESPE-U200; Maxcem Elite/Kerr-MAX; Clearfil SA Cement/Kuraray-CSA) was used to cement either the glass fiber or the metal posts (Dentatus Classic Surtex ® Posts, New York, USA) used.Dental arch, tooth number, and the type of post (metal or fiber) were recorded in an excel sheet.Moreover, the assessment of the quality of canal preparation (acceptable: outline of the preparation was following the canal contour and unacceptable: canal preparation did not follow the canal outline or ledge resulted during preparation) and the quality of PAs were added to the excel sheet where the followed evaluation criteria of PAs were extracted from a previous study criteria. 5,9,11,13The length of the placed post was measured starting from the beginning of the restoration to the apical tip of the post as well as the crown height and root length which were measured from the cementoenamel junction to the root apex.Additionally, the length of the remaining gutta-percha in the canal, the root width and post width at the middle half of the root, and the gap between the post and gutta-percha if available, were it was measured using a digital ruler of the viewer software.Any abnormalities noticed in the PAs were also recorded in the sheet.

Statistical analysis
Descriptive data were calculated as frequencies, percentages, means and standard deviations (SD).Comparisons between the three study groups were done using chi-square test for qualitative variables, and one-way ANOVA for quantitative variables.Data were analyzed using IBM SPSS for Windows (Version 23.0).P value <0.05 was considered statistically significant.Alternative proprietary free suggested software is ocscsistatistics.

Results
Data were obtained from 502 patients (62% females) with fiber posts used in 98.2% of the cases after excluding 48 cases due to the lack of complete data (Table 2).About 62% of the treated cases were females.The cases assessed were treated by 348 fifth and sixth year students (69%), 101(20.1%)fourth year students and 53 (10.5%) interns.Most of the students were females (66.5%).
Table 3 shows the different parameters of included posts.About 50% of the posts were inserted in premolars, followed by anterior teeth and molars respectively (28.1% and 21.7%).Also, 62.9% of treated teeth were in the upper arch, and 66.7% restored with crowns as a final restoration while the rest of the cases were restored with composite restorations only.
Regarding the quality of posts, about 98% showed good preparation and radiographic quality.The men value of post length was 15.79 mm where the longest posts were set by interns 15.97 while the shortest posts were seated by the 4 th year students 15.67 mm.The mean value of remaining GP in all treated cases was 6.19 mm with lowest reading among interns 5.77 mm followed by 4 th year 5.92 and 5 th and 6 th years 6.33 mm.No radiographic abnormalities were reported in all evaluated cases.As for post assessment according to the prosthetic criteria (Table 4); the post diameter was equal to 1/3 of the root diameter in 31.9% of the cases while 63.3% of the cemented posts were larger than 1/3 of root diameter.The post length was equal to 2/3 of root length in 5% of the cases but exceeding 2/3 of the root length in 92.6% of the cases.In case of evaluating the post length towards the crown height, all of the cemented posts were equal to or more than crown height (100%).The length of the remaining GP was between 3-5 mm in 38.8%, while 61% of the cases exceeded 5 mm of the GP remaining in the root.No gap was observed between the post and remaining GP in 95.6%.In assessing the students' performance and clinical skills in treating ETT with post and core restorations, no statistically significant differences between dental students at different clinical educational years were noticed according to the criteria mentioned in the methods.

Discussion
Success and longevity of post and core restorations depend on several criteria such as post preparation dimensions in relation to tooth dimensions, post length relative to tooth length in addition to material of the used post. 14All these criteria can be radiographically evaluated, thus, the current study aimed to radiographically assess the quality of post and core procedures performed by dental students at different education levels in addition to determining the most critical errors encountered during their clinical practice.
In the current dental school, 4 th year students start the clinical sessions of endodontic treatments and prosthodontics as well.However, in the 3 rd year, the students start the preclinical sessions of endodontics and prosthodontics.Students in all dental years are supervised by faculty member even in the internship year and all the treated cases are evaluated by the specialized faculty member for the initial approval to treat the case till finalizing the procedure required for the case.The student faculty ratio in preclinical and clinical years is 1:8, while in the internship the ration is 1:10.
The study findings showed that 98.4% of the students did post preparations of acceptable quality.According to the criteria mentioned in the methodology, about 31.9% of students placed posts of diameter equivalent to 1/3 of the root diameter, while only 5% of the students used posts of length equal to 2/3 of root length in their cases.The acceptable length of the remaining GP (3-5 mm) was reported in 38.8% of the cases.Nonetheless, no gap was noticed between the posts and remaining GP in 95.6% of the cases which ensures optimum adaptation of the posts cemented by the students.The quality of students' performance in post placement was acceptable and comparable among different clinical educational years.Thus, the null hypothesis was accepted.
Results of the current study showed that 63.3% of the posts were cemented in maxillary teeth which comes in line with previous studies. 5,9,15,16Ease of isolation, absence of saliva and absence of tongue movements that can obscure vision and affect the quality of post restoration in the maxillary arch might be a valid explanation for this percentage. 17In case of type of the teeth restored, students commonly treated premolars followed by anterior teeth, while molars were less frequently treated.Similarly, previous studies reported that premolars were the most restored teeth with post and cores by undergraduate dental students. 9,11,18Another study showed that incisors were the most frequently restored teeth with posts followed by premolars. 5Selection of teeth by students might be related to the ease of post preparation and placement, so most students prefer treating single rooted teeth as several complications can be encountered while treating multi-rooted teeth including perforations and root fractures. 19tal posts were placed in nine cases only, while fiber posts were cemented in 493 cases.The high esthetic demand of patients was the cause of this difference where metal post can affect the shade of the definitive restoration.[22] Most of the restored teeth (95.6%) showed no gap between the cemented post and GP.This comes in agreement with Almaghrabi et al. 16 who stated that about 93% of cases did not show any gaps.Also, Mathar and Almutairi 11 reported that 82.9% of cases showed no gaps between the cemented post and GP.In contrast, Baik study 18 revealed that only 65% of treated cases had no gap between post and GP.The higher percentage in the current study might be due to the different treatment protocol or materials used.Also, the number of student faculty ratio might be a crucial factor that needs to be acknowledged in improving the percentage of success or survival rates.In evaluating the post length in relation to root length, 92.6% of the cases were following the optimum guidelines of exceeding 2/3 of the root length.Similarly, Almaghrabi et al. 16 showed that post length was less than 2/3 of the root length in 61% of cases.However, Meshini et al. 5 found that the post to root length ratio in almost half of the patients was 2:1.
The study findings showed that almost 31% of the cases were treated with post diameter equivalent to 1/3 of the root diameter.In line with these findings, previous studies reported that the diameter of the cemented posts was equivalent to 1/3 of the root. 23,24Additionally, another study conducted at Qassim University dental clinics showed that 81% of the post cases were of length equal to 1/3 of the root. 11This optimum post diameter dimensions agrees with Trabert et al. 25 who recommended a post diameter not exceeding 1/3 of the root width to increase fracture resistance of the restoration 24 in addition to reducing the possibility of root fracture. 26This criteria was also shown in other studies where 89.5% and 81.6% the cases included posts of diameter 1/3 of the root diameter. 5,18On the contrary, Peutzfeldt et al. 27 reported high failure rate (68% out of 176 cases) among posts with a diameter less than or equal 1/3 of the root.Additionally, 76% out of 237 cases showed post failure with a post length equal or exceeding 50% of the root length.These conflicting results might be due to the difference in the type of the posts used as glass fiber posts were not used in Peutzfedlt 27 study.Moreover, the cases of the current study were treated under supervision of faculty members following the rubrics mentioned in the methods unlike the situation in Peutzfedlt 27 cases which were treated by unknown practitioners in private clinics.
The ideal amount of the remaining GP in the root after post preparation ranges between 3-5 mm, and this was found in 38.8% of the cases, while 61% of cases included more than 5 mm of remaining GP.Similarly, a study done by Mathar and Almutairi 11 found 28% of the assessed cases had 3-5 mm of remaining GP and 61% included more than 5 mm of remaining GP.The presence of higher percentage of cases including more than 5 mm GP remaining might be justified by the precautionary attitude of students in treating clinical cases. 11Also, Al Maghrabi et al. 16 who used the same criteria in their cases, reported 3-5 mm remaining GP in 68% of cases done in King Abdulaziz university. 16Another study performed in Jazan University found that 55.7% of the assessed cases were within the same range of remaining GP. 5 The strength of this study is inclusion of students of different educational levels starting from the initial clinical year (4 th year) to the internship year can provide comprehensive findings on the students' performance in treating ETT with post and core.The high percentages of cases following the standard guidelines of post and core placement and cementation among variable teeth (incisors, premolars, and molars) as well as the lack of difference in clinical level between the students of different educational years might be justified by the presence of faculty supervision with each student in the educational clinics to limit the complications or errors that can happen in the patient's mouth.Additionally, following explicit calibrated rubrics by students and faculty members in placing post and core restorations and assessing their quality might have positively affected the treatment outcome.Inclusion of different students of various dental educational levels presents generalized findings on the performance of students in the dental college of Imam Abdurrahman University.The variation of ETT assessed in the study can provide broad understanding to the errors encountered that might be relevant to the tooth type or arch type.This can improve the dental curriculum of undergraduate students in order to enhance their knowledge and psychomotor skills.
However, the current study had some limitations such as being restricted to Eastern province so the findings cannot be generalized to the broader dental population in Saudi Arabia.Also, it included undergraduate students with the exclusion of postgraduate students since the postgraduate endodontic and prosthodontics boards were recently introduced in the dental college, and the total number of enrolled students does not exceed ten students.Further studies are needed to compare the performance of undergraduate and postgraduate students.Moreover, assessment of post and core quality needs to be extended in other Saudi dental colleges to detect the weaknesses in students' performance.

Conclusions
The successful post and core treatment relies on multiple factors related to the success of endodontic treatment as well as the procedure and type of post and core placed.In the current study, dental students demonstrated satisfactory skill in post and core placement for endodontically treated teeth according to the guidelines.The majority of the dental students restored the endodontically treated teeth with glass fiber posts.No significant difference was noticed in the skills of dental students of different educational levels.The presence of supervision from faculty members in both endodontics and prosthodontics fields might be a fundamental cause of this high percentage of acceptable treatments in addition to treating cases of low difficulty according to AAE assessment form and guidelines.

If applicable, is the statistical analysis and its interpretation appropriate? Yes
Are all the source data underlying the results available to ensure full reproducibility?Yes

Are the conclusions drawn adequately supported by the results? Yes
Competing Interests: No competing interests were disclosed.
Reviewer Expertise: A prosthodontist and faculty member

Yuanita Lely Rachmawati
Department of Community and Preventive Dentistry, Universitas Brawijaya, Malang, East Java, Indonesia The authors have revised the manuscript as suggested.No further comments from me.Thank you.

If applicable, is the statistical analysis and its interpretation appropriate? Yes
Are all the source data underlying the results available to ensure full reproducibility?Yes

Methods
Please explain in more detail about sample size calculation.
What Intraoral X-ray imaging unit was used and how the PA technique was taken "These PAs were assessed according to the following criteria by four trained investigators".Please add information related to the investigator: who are they, how they got the training, and how to measure the agreement between them.
Figure 1 looks blurry, the writing needs to be clarified.

Results
At Methods section mentions "A total of 550 periapical radiographs" but in the Result section "The study included 502 students".Please explain whether the analysis unit was PA or student, and the reasons why there are differences in numbers.
One-way ANOVA was used in this study.One-way ANOVA is a statistical test that is used to measure differences in average data on numerical scale variables.The authors can add a table that informs the mean and SD values of the variables.

Discussion
It is necessary to add references in the first paragraph.
Please add the reference of the standard guidelines of post and core placement and cementation among variable teeth

Conclusion
The content of the conclusion is focused on the research objectives and results

Is the work clearly and accurately presented and does it cite the current literature? Partly
Is the study design appropriate and is the work technically sound?Partly

If applicable, is the statistical analysis and its interpretation appropriate? Partly
Are all the source data underlying the results available to ensure full reproducibility?Partly

Are the conclusions drawn adequately supported by the results? No
Competing Interests: No competing interests were disclosed.
Reviewer Expertise: epidemiology I confirm that I have read this submission and believe that I have an appropriate level of expertise to confirm that it is of an acceptable scientific standard, however I have significant reservations, as outlined above.
We would like to thank you for inviting us to resubmit our revised manuscript.We wanted to express our sincere appreciation for the time and effort you dedicated to reviewing our manuscript.Your thoughtful feedback and insights have been instrumental in refining the quality and impact of our work.
We have carefully incorporated your suggestions into the revised manuscript, and we are confident that these revisions have significantly strengthened the overall content and presentation.Your thorough review has contributed to elevating the manuscript's potential to make a meaningful contribution to the prosthodontics community.
In response to your invaluable comments, we have diligently revised the manuscript to address your concerns.Below, we have summarized the main points you raised and provided our responses, highlighted in yellow.
Thank you for your time, consideration, and ongoing support.

Sincerely Authors
Comments: I appreciate the hard work that all authors have put into this research.However, some details need to be added.
• Keywords 1. Please check the selected words in the MeSH • Response: Thank you for your valuable comment.Keywords were adjusted in the manuscript on page 15.
• Methods 1. Please explain in more detail about sample size calculation.
• Response: Thank you for your comment.The modifications were done in the methods section of the manuscript on page 3.
2. What Intraoral X-ray imaging unit was used and how the PA technique was taken?
• Response: Thank you for your raising this important point.The modification was done in the methods section of the manuscript on pages 4-5.
3. "These PAs were assessed according to the following criteria by four trained investigators".Please add information related to the investigator: who are they, how they got the training, and how to measure the agreement between them.
• Response: Thank you for your important comment.The assessment method was clarified in the methods section of the manuscript on page 4.
4. Figure 1 looks blurry; the writing needs to be clarified.
• Response: Thank you for your valuable comment.Figure resolution was adjusted in the methods section on page 6.

• Results
1.At Methods section mentions "A total of 550 periapical radiographs" but in the Result section "The study included 502 students".Please explain whether the analysis unit was PA or student, and the reasons why there are differences in numbers.
• Response: Thank you for your raising this important This difference in the total number mentioned in the results was due to the missing data of 48 cases, and this statement was added in the results section on page 8.
2. One-way ANOVA was used in this study.One-way ANOVA is a statistical test that is used to measure differences in average data on numerical scale variables.The authors can add a table that informs the mean and SD values of the variables.
• Response: Thank you for your valuable comment.Table 1 includes the requested information on page 8.

• Discussion
1.It is necessary to add references in the first paragraph.
• Response: Thank you for your valuable comment.References were added to the introduction and rearranged in the reference section page number 14 and 15.
2. Please add the reference of the standard guidelines of post and core placement and cementation among variable teeth • Response: Thank you for your valuable comment.The guidelines used were added in Table 1 and the reference of previous studies (5, 9, 11, 15) where the guidelines were extracted and added in the methods section pages 5-7.

• Conclusion
1.The content of the conclusion is focused on the research objectives and results.
• Response: Thank you for your valuable comment.The conclusion was adjusted on page 13.

Introduction
The introduction needs to be improved, with a better structure including clinical/educational relevance of study and gap of knowledge, hence why the study was conducted.
• Response: Thank you for your valuable comment.The introduction section was modified as requested on page numbers 1,2.
2. The authors mention "Accordingly, these rubrics provide a proper assessment of the student's practice and skills level and also helps in improving their ability to perform selfassessment for each specific dental procedure."Please elaborate on the rubrics.Consider adding it as a supplementary file.
• Response: Thank you for your comment.The rubrics were added in the methods section.They were extracted from previously published articles (5, 9, 11, 15) and verified by the prosthodontics faculty department in the dental college.The rubrics were formulated to be comprehensive including assessment of the quality of radiogragraphs, quality of obturation as well as quality of post and core preparation and placement.These criteria are explained in the methods section on pages 4-7 as well as in Table 1 and Figure 1 • Methods 5.As a general comment, the experimental design needs to be explained in more detail.I have mentioned a few of the most important points that must be included.
6. Any sample size calculation to determine the power of the study?Please explain.
• Response: Thank you for your important comment.The sample size was clarified in the methods section page number 3.
7. Please add a statement about patient consent being waived due to the nature of the study.Also please add a statement about anonymous patient information status.
• Response: Thank you for your valuable comment.The statements were added in the methods section on page 4.

Please correct; dammam To Dammam
• Response: The city name was corrected in the methods section of the manuscript on page 3. 9. Can the authors mention was the post placement placed on primary (non-surgical) root canal treatment or re-treatment cases?
• Response: Thank you for your valuable comment.The inclusion and exclusion criteria were clarified in the methods section on page 4.
10. How were cases selected for undergraduate students?Please discuss the necessity for preoperative use of the AAE case difficulty assessment form and similar tools, especially in selecting appropriate teeth for inexperienced operators.Which cases were deemed as too difficult for students, and should this strategy be revised, or recommendations made considering the results?
• Response: Thank you for your important comment.Guidelines reference was added in the methods section on page 4.
11. Please add, the average staff-to-student ratio during clinical supervision • Response: Thank you for your valuable comment.The ratio was added in the methods section in the manuscript page number 5.
12. Please provide further details about how the radiographs were taken.Parallel technique?Digital or manually developed?
• Response: Thank you for your comment.The technique was added in the methods section of the manuscript on page 3.
13. Please provide further details about; post placement and to determine if any errors.
• Response: Thank you for your comment.The errors are explained in detail in the methods section page number 4-7.
14. Please provide further details about the investigators (These PAs were assessed according to the following criteria by four trained investigators).Are they students, specialists, consultants?How many years of training?
• Response: Thank you for your valuable comment.Criteria were mentioned in the methods section on page 4.

15.
Were the investigators calibrated?This should be added.How was calibration performed?
• Response: Thank you for your valuable comment.The calibration method was added in the methods section on page 4.
16. Please clearly state inclusion and exclusion criteria.
• Response: Thank you for your valuable comment.The criteria were clarified in the methods section on page number 4. 17.Please clearly mention how root canal treatment and canal obturation were performed.
• Response: Thank you for your valuable comment.The procedure was added in the methods section on page number 4.
18.The authors mention (the assessment of the quality of canal preparation (acceptable: outline of the preparation was following the canal contour and unacceptable: canal preparation did not follow the canal outline or ledge resulted during preparation) and the quality of PAs were added to the excel sheet where the followed evaluation criteria of PAs were extracted from a previous study criteria ( REF 11).Based on what criteria was the post/core assessed?on what criteria was the quality of canal preparation assessed?Please provide a suitable reference.Also, the reference for the criteria of PAs is unsuitable, please use international guideline criteria • Response: Thank you for your comment.References to the guidelines used to assess post and core treatment quality were added in the methods section pages 4-5.

• Results
19.The authors state, "There were no statistically significant differences between dental students at different clinical educational years regarding the quality of post-placement according to the criteria mentioned in the method."These results are generally non-logical, is the quality of dental post/core placement for a 4th year dental student comparable to dental interns?
• Response: Thank you for your valuable comment.The quality of treatment was comparable because the treatment procedures were done under faculty supervision from both departments' endodontics and prosthodontics.This might explain the lack of significant difference in the treatment quality of all dental years included in the study.This justification was mentioned in pages 12 and 13.
20.The findings of the study need to be explained in more detail.
• Response: Thank you for your valuable comment.The findings were thoroughly explained in the discussion section on pages 11 and 12.
21.Is the statistical analysis the most appropriate?Please consult a statistician and report the results in detail.
• Response: Thank you for your comment.All comments were adjusted in the result section pages 8-10.25.The discussion should consist of comments on the methodologies chosen and a comparison with previous studies.
• Response: Thank you for your comment.The discussion was adjusted according to the suggestion.
26.The authors keep referring to standard guidelines, please further elaborate.Which international guidelines are the authors referring to?
• Response: Thank you for your valuable comment.The guidelines of post and core placement and endodontic case selection were added to the methods (Table 1 and Figure 1) on pages 4-7.
27. Lack of clinical data to further support radiographic assessment to determine success/survival should be added.
• Response: Thank you for your comment.The data were added in the methods section and compared with previous similar studies.
28. Please add the strengths of the study.
• Response: Thank you for your valuable comment.Strengths are available in the discussion section on page 13.
29.Additionally, limitations can be added, please add • Response: Thank you for your valuable comment.Limitations are mentioned in the discussion section on page 13.

• Conclusion
30.How was the below statement extracted from the results; "Dental students' fear of perforations of narrow canals or furcation perforations pushed them to treat mainly premolars and incisors and to use narrower posts than the proper diameter.Therefore, students need to have more confidence in their qualities to improve their clinical skills."?? Please remove if not directly extracted from the study results….Please re-write the conclusion based on the results of the study.
• Response: Thank you for your comment.The conclusion was adjusted on page 13.
• References 31.Errors in references are noted, and to be carefully edited.
• Response: Thank you for your valuable comment.All references were adjusted according to journal guidelines in the reference section.

Competing Interests: No conflict of interest is available
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Figure 1 .
Figure 1.Assessment criteria of post and core treatment quality.

22 .
All tables to be edited, as per the above comment.Please consult a statistician for improvements • Response: Thank you for your valuable comment.The result section was adjusted as recommended on pages 8-10.• Discussion 23.Please add a suitable reference to the first paragraph.• Response: Thank you for your important comment.References were added to the introduction on page 3. 24.The authors must mention the endodontic pre-clinical and clinical teaching and training that the students have been taught.Additionally, what year do they start endodontic treatment?Post placement?• Response: Thank you for your valuable comment.All details were added in the methods section page number 11.

Table 2 .
Demographic characteristics of the study sample (n=502).

Table 3 .
Evaluation parameters of the included posts (n=502).

Table 4 .
Posts' assessment according to the ideal prosthetic criteria.
One-way ANOVA was used.

confirm that I have read this submission and believe that I have an appropriate level of expertise to confirm that it is of an acceptable scientific standard.
Reviewer Report 19 April 2024 https://doi.org/10.5256/f1000research.163330.r260338© 2024 Rachmawati Y.This is an open access peer review report distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.