{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,9,2]],"date-time":"2026-09-02T09:13:07Z","timestamp":1788340387123,"version":"build-2803163510"},"reference-count":35,"publisher":"MDPI AG","issue":"9","license":[{"start":{"date-parts":[[2026,9,2]],"date-time":"2026-09-02T00:00:00Z","timestamp":1788307200000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Dent. J.","Dentistry Journal"],"abstract":"<jats:p>Objectives: To evaluate the inter- and intra-observer reliability of three methods for measuring root canal curvature and the reliability of canal visibility ratings on periapical radiographs over repeated calibration rounds. Materials and Methods: A total of 360 clinical periapical radiographs were divided into six batches and independently evaluated by three observers. Root canal curvature was measured using the Schneider, Weine, and a novel tangency-based method, while canal visibility was classified on a three-category scale. Inter- and intra-observer reliability were assessed using intraclass correlation coefficients (ICC). Agreement between observers was evaluated using Bland\u2013Altman analysis, and differences between measurement methods were compared using repeated-measures analysis. The association between canal visibility and inter-observer measurement differences was assessed using Spearman rank correlation. Results: Inter-observer reliability for curvature measurements was predominantly good to excellent across all methods, with no consistent improvement over successive calibration rounds. Intra-observer reliability, assessed in one observer, was excellent (ICC 0.90\u20130.97). Measurement method significantly influenced angle values, with the Weine method producing larger angles than the Schneider and tangency-based methods, whereas the latter two showed comparable results. Agreement on canal visibility remained fair to moderate, and reduced canal visibility showed a weak but significant association with greater inter-observer differences in curvature measurements. Conclusions: All three methods demonstrated comparable inter-observer reliability, although the Weine method yielded systematically larger curvature angles. Agreement did not consistently improve over repeated calibration rounds. Reduced canal visibility may increase measurement variability and should be considered when interpreting root canal curvature on periapical radiographs.<\/jats:p>","DOI":"10.3390\/dj14090553","type":"journal-article","created":{"date-parts":[[2026,9,2]],"date-time":"2026-09-02T07:53:11Z","timestamp":1788335591000},"page":"553","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":0,"title":["Reliability of Root Canal Curvature Measurements and Canal Visibility Ratings over Repeated Calibration Rounds"],"prefix":"10.3390","volume":"14","author":[{"ORCID":"https:\/\/orcid.org\/0000-0003-0204-3859","authenticated-orcid":false,"given":"Mounir","family":"Ajjan Alhadid","sequence":"first","affiliation":[{"name":"Department of Conservative Dentistry, Periodontology and Digital Dentistry, University Hospital, LMU Munich, Goethestrasse 70, 80336 Munich, Germany"}],"role":[{"vocabulary":"crossref","role":"author"},{"role":"conceptualization","vocabulary":"credit"},{"role":"data-curation","vocabulary":"credit"},{"role":"formal-analysis","vocabulary":"credit"},{"role":"investigation","vocabulary":"credit"},{"role":"methodology","vocabulary":"credit"},{"role":"project-administration","vocabulary":"credit"},{"role":"validation","vocabulary":"credit"},{"role":"visualization","vocabulary":"credit"},{"role":"writing-original-draft","vocabulary":"credit"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-6565-7255","authenticated-orcid":false,"given":"Sabina Noreen","family":"Wuersching","sequence":"additional","affiliation":[{"name":"Department of Conservative Dentistry, Periodontology and Digital Dentistry, University Hospital, LMU Munich, Goethestrasse 70, 80336 Munich, Germany"}],"role":[{"vocabulary":"crossref","role":"author"},{"role":"investigation","vocabulary":"credit"},{"role":"validation","vocabulary":"credit"},{"role":"writing-review-editing","vocabulary":"credit"}]},{"given":"Falk","family":"Schwendicke","sequence":"additional","affiliation":[{"name":"Department of Conservative Dentistry, Periodontology and Digital Dentistry, University Hospital, LMU Munich, Goethestrasse 70, 80336 Munich, Germany"}],"role":[{"vocabulary":"crossref","role":"author"},{"role":"writing-review-editing","vocabulary":"credit"}]},{"given":"Chantal","family":"Herbst","sequence":"additional","affiliation":[{"name":"Department of Conservative Dentistry, Periodontology and Digital Dentistry, University Hospital, LMU Munich, Goethestrasse 70, 80336 Munich, Germany"}],"role":[{"vocabulary":"crossref","role":"author"},{"role":"investigation","vocabulary":"credit"},{"role":"supervision","vocabulary":"credit"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-2934-4627","authenticated-orcid":false,"given":"Sascha R.","family":"Herbst","sequence":"additional","affiliation":[{"name":"Department of Conservative Dentistry, Periodontology and Digital Dentistry, University Hospital, LMU Munich, Goethestrasse 70, 80336 Munich, Germany"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"1968","published-online":{"date-parts":[[2026,9,2]]},"reference":[{"key":"ref_1","unstructured":"American Association of Endodontists (2026, July 12). Case Difficulty Assessment form and Guidelines. Available online: https:\/\/www.aae.org\/specialty\/clinical-resources\/treatment-planning\/case-assessment-tools\/."},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"2381","DOI":"10.1007\/s00784-018-2341-1","article-title":"A web-based endodontic case difficulty assessment tool","volume":"22","author":"Shah","year":"2018","journal-title":"Clin. Oral Investig."},{"key":"ref_3","doi-asserted-by":"crossref","first-page":"1569","DOI":"10.1111\/iej.13377","article-title":"Comparison of two case difficulty assessment methods on cohorts of undergraduate dental students\u2014A multi-center study","volume":"53","author":"Shah","year":"2020","journal-title":"Int. Endod. J."},{"key":"ref_4","doi-asserted-by":"crossref","first-page":"656","DOI":"10.1111\/iej.13685","article-title":"Present status and future directions: Management of curved and calcified root canals","volume":"55","author":"Chaniotis","year":"2022","journal-title":"Int. Endod. J."},{"key":"ref_5","doi-asserted-by":"crossref","first-page":"104378","DOI":"10.1016\/j.jdent.2022.104378","article-title":"Preoperative risk assessment does not allow to predict root filling length using machine learning: A longitudinal study","volume":"128","author":"Herbst","year":"2023","journal-title":"J. Dent."},{"key":"ref_6","doi-asserted-by":"crossref","first-page":"169","DOI":"10.1111\/iej.12996","article-title":"Methods for measurement of root canal curvature: A systematic and critical review","volume":"52","author":"Hartmann","year":"2019","journal-title":"Int. Endod. J."},{"key":"ref_7","doi-asserted-by":"crossref","first-page":"271","DOI":"10.1016\/0030-4220(71)90230-1","article-title":"A comparison of canal preparations in straight and curved root canals","volume":"32","author":"Schneider","year":"1971","journal-title":"Oral Surg. Oral Med. Oral Pathol."},{"key":"ref_8","unstructured":"Weine, F.S. (1982). Endodontic Therapy, Mosby."},{"key":"ref_9","doi-asserted-by":"crossref","first-page":"77","DOI":"10.1016\/S0099-2399(97)80250-6","article-title":"Cyclic fatigue testing of nickel-titanium endodontic instruments","volume":"23","author":"Pruett","year":"1997","journal-title":"J. Endod."},{"key":"ref_10","doi-asserted-by":"crossref","first-page":"211","DOI":"10.1097\/00004770-200203000-00017","article-title":"Roentgenographic investigation of frequency and degree of canal curvatures in human permanent teeth","volume":"28","author":"Diez","year":"2002","journal-title":"J. Endod."},{"key":"ref_11","doi-asserted-by":"crossref","first-page":"796","DOI":"10.1097\/01.don.0000158232.77240.01","article-title":"A comparative study of three different root canal curvature measurement techniques and measuring the canal access angle in curved canals","volume":"31","author":"Sazak","year":"2005","journal-title":"J. Endod."},{"key":"ref_12","unstructured":"British Endodontic Society (2026, July 12). BES Case Assessment Tool. Available online: https:\/\/bes-endoapp.typeform.com\/bes-endoapp."},{"key":"ref_13","doi-asserted-by":"crossref","first-page":"1176","DOI":"10.1016\/j.joen.2017.02.021","article-title":"Diagnostic Accuracy of Periapical Radiography and Cone-beam Computed Tomography in Identifying Root Canal Configuration of Human Premolars","volume":"43","author":"Sousa","year":"2017","journal-title":"J. Endod."},{"key":"ref_14","doi-asserted-by":"crossref","first-page":"1682","DOI":"10.1016\/j.joen.2023.09.015","article-title":"Comparison of Curvature Severity Between Sagittal and Coronal Planes of Mesiobuccal Canals in Permanent Maxillary First Molars Using Multiple Complexity-risk Criteria: A CBCT Cross-sectional Study","volume":"49","author":"Wu","year":"2023","journal-title":"J. Endod."},{"key":"ref_15","doi-asserted-by":"crossref","first-page":"508","DOI":"10.1016\/j.oooo.2015.07.033","article-title":"AAE and AAOMR Joint Position Statement Use of Cone Beam Computed Tomography in Endodontics 2015 Update","volume":"120","author":"Fayad","year":"2015","journal-title":"Oral Surg. Oral Med. Oral Pathol. Oral Radiol."},{"key":"ref_16","doi-asserted-by":"crossref","first-page":"1675","DOI":"10.1111\/iej.13187","article-title":"European Society of Endodontology position statement: Use of cone beam computed tomography in endodontics","volume":"52","author":"Patel","year":"2019","journal-title":"Int. Endod. J."},{"key":"ref_17","doi-asserted-by":"crossref","first-page":"1189","DOI":"10.1111\/iej.13506","article-title":"The Endodontic Complexity Assessment Tool (E-CAT): A digital form for assessing root canal treatment case difficulty","volume":"54","author":"Essam","year":"2021","journal-title":"Int. Endod. J."},{"key":"ref_18","doi-asserted-by":"crossref","first-page":"554","DOI":"10.1080\/00016357.2021.1910728","article-title":"Calibration improves observer reliability in detecting periapical pathology on panoramic radiographs","volume":"79","author":"Sebring","year":"2021","journal-title":"Acta Odontol. Scand."},{"key":"ref_19","doi-asserted-by":"crossref","unstructured":"Meusburger, T., W\u00fclk, A., Kessler, A., Heck, K., K\u00fchnisch, J., Hickel, R., Dujic, H., and K\u00fchnisch, J. (2023). The Detection of Dental Pathologies on Periapical Radiographs\u2014Results from a Reliability Study. J. Clin. Med., 12.","DOI":"10.3390\/jcm12062224"},{"key":"ref_20","doi-asserted-by":"crossref","first-page":"167","DOI":"10.1111\/iej.12602","article-title":"Observer variation in the assessment of root canal curvature","volume":"50","author":"Faraj","year":"2017","journal-title":"Int. Endod. J."},{"key":"ref_21","doi-asserted-by":"crossref","first-page":"1848","DOI":"10.1111\/iej.14142","article-title":"Comparative analysis of methods for measuring root canal curvature based on periapical radiography: A laboratory study","volume":"57","author":"Hartmann","year":"2024","journal-title":"Int. Endod. J."},{"key":"ref_22","doi-asserted-by":"crossref","first-page":"96","DOI":"10.1016\/j.jclinepi.2010.03.002","article-title":"Guidelines for Reporting Reliability and Agreement Studies (GRRAS) were proposed","volume":"64","author":"Kottner","year":"2011","journal-title":"J. Clin. Epidemiol."},{"key":"ref_23","doi-asserted-by":"crossref","first-page":"101","DOI":"10.1002\/(SICI)1097-0258(19980115)17:1<101::AID-SIM727>3.0.CO;2-E","article-title":"Sample size and optimal designs for reliability studies","volume":"17","author":"Walter","year":"1998","journal-title":"Stat. Med."},{"key":"ref_24","doi-asserted-by":"crossref","first-page":"332","DOI":"10.1016\/S0099-2399(06)80095-6","article-title":"Critical analysis of the balanced force technique in endodontics","volume":"20","author":"Kyomen","year":"1994","journal-title":"J. Endod."},{"key":"ref_25","unstructured":"Zantula Inc. (2026, July 12). RedBrick AI. Available online: https:\/\/www.redbrickai.com\/."},{"key":"ref_26","unstructured":"van Rossum, G., and Drake, F.L. (2009). Python 3 Reference Manual, CreateSpace."},{"key":"ref_27","doi-asserted-by":"crossref","first-page":"155","DOI":"10.1016\/j.jcm.2016.02.012","article-title":"A Guideline of Selecting and Reporting Intraclass Correlation Coefficients for Reliability Research","volume":"15","author":"Koo","year":"2016","journal-title":"J. Chiropr. Med."},{"key":"ref_28","doi-asserted-by":"crossref","first-page":"159","DOI":"10.2307\/2529310","article-title":"The Measurement of Observer Agreement for Categorical Data","volume":"33","author":"Landis","year":"1977","journal-title":"Biometrics"},{"key":"ref_29","doi-asserted-by":"crossref","first-page":"307","DOI":"10.1016\/S0140-6736(86)90837-8","article-title":"Statistical methods for assessing agreement between two methods of clinical measurement","volume":"327","author":"Bland","year":"1986","journal-title":"Lancet"},{"key":"ref_30","first-page":"118","article-title":"Reliability of two methods on measuring root canal curvature","volume":"3","author":"Zhu","year":"2003","journal-title":"Int. Chin. J. Dent."},{"key":"ref_31","doi-asserted-by":"crossref","first-page":"502","DOI":"10.1111\/iej.70072","article-title":"Comparison of curvature severity between sagittal and coronal planes of mesial canals in permanent mandibular first molars using Schneider\u2019s and Weine\u2019s methods and multiple complexity\u2013risk criteria: A CBCT cross-sectional study","volume":"59","author":"Mathew","year":"2026","journal-title":"Int. Endod. J."},{"key":"ref_32","doi-asserted-by":"crossref","first-page":"e152","DOI":"10.1016\/j.tripleo.2009.05.046","article-title":"Measurement of the trajectory of different NiTi rotary instruments in an artificial canal specifically designed for cyclic fatigue tests","volume":"108","author":"Plotino","year":"2009","journal-title":"Oral Surg. Oral Med. Oral Pathol. Oral Radiol. Endod."},{"key":"ref_33","doi-asserted-by":"crossref","first-page":"307","DOI":"10.1016\/j.joen.2005.09.011","article-title":"Roentgenographic In Vitro Investigation of Frequency and Location of Curvatures in Human Maxillary Premolars","volume":"32","author":"Willershausen","year":"2006","journal-title":"J. Endod."},{"key":"ref_34","doi-asserted-by":"crossref","first-page":"131","DOI":"10.5603\/FM.a2017.0066","article-title":"Distal root curvatures in mandibular molars: Analysis using digital panoramic X-rays","volume":"77","author":"Fuentes","year":"2018","journal-title":"Folia Morphol."},{"key":"ref_35","doi-asserted-by":"crossref","unstructured":"Obuchowicz, B., Zarzecka, J., Strzelecki, M., Jakubowska, M., Obuchowicz, R., Pi\u00f3rkowski, A., Zarzecka-Francica, E., and Lasek, J. (2025). Improving Endodontic Radiograph Interpretation with TV-CLAHE for Enhanced Root Canal Detection. J. Clin. Med., 14.","DOI":"10.3390\/jcm14155554"}],"container-title":["Dentistry Journal"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/2304-6767\/14\/9\/553\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2026,9,2]],"date-time":"2026-09-02T08:14:13Z","timestamp":1788336853000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/2304-6767\/14\/9\/553"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2026,9,2]]},"references-count":35,"journal-issue":{"issue":"9","published-online":{"date-parts":[[2026,9]]}},"alternative-id":["dj14090553"],"URL":"https:\/\/doi.org\/10.3390\/dj14090553","relation":{},"ISSN":["2304-6767"],"issn-type":[{"value":"2304-6767","type":"electronic"}],"subject":[],"published":{"date-parts":[[2026,9,2]]}}}