Methods Inf Med 2022; 61(03/04): 090-098
DOI: 10.1055/a-1868-6555
Original Article

Reliability of Cusp Angulation Using Three-Dimensional Digital Models: A Preliminary In Vitro Study

Xinggang Liu
1   Department of prosthodontics, Beijing Stomatological Hospital, Capital Medical University; School of Stomatology, Capital Medical University, Beijing, China
Xiaoxian Chen
2   Department of Pediatric Dentistry, First Clinical Division, Peking University School and Hospital of Stomatology, Xicheng District, Beijing, China
› Author Affiliations
Funding This investigation was supported by the Beijing Municipal Administration of Hospitals Incubating Program (code: PX2017031) and Beijing Municipal Administration of Hospitals Clinical Medicine Development of Special Funding Support (code: ZYLX201828).


Background Dental cusp angulation provides valuable insights into chewing efficiency and prosthesis safety. Artificial intelligence-enabled computing of cusp angles has potential important value, but there is currently no reliable digital measurement method as a cornerstone.

Objectives To establish a digital method for measuring cusp angles and investigate inter-rater and intra-rater reliabilities.

Methods Two cusp angles (angles α and β) of the first molar were measured on 21 plaster casts using a goniometer and on their corresponding digital models using PicPick software after scanning with a CEREC Bluecam three-dimensional (3D) intraoral scanner. Means ± standard deviations, as well as intraclass correlation coefficients (ICCs) and Pearson's correlation coefficients (PCCs) were calculated, and repeated measures analysis of variance was performed. The Bland–Altman method was used to calculate the difference and mean degree values of two measurement methods from both examiners, and the Bland–Altman diagram was drawn using MedCalc software.

Results When the examiner was experienced, angle α was 139.19° ± 13.86°, angle β was 19.25° ± 6.86°, and a very strong positive correlation between the two methods was found (r > 0.9; p < 0.001). No significant difference between the two methods was found using the repeated measures analysis of variance (p > 0.05). The Bland–Altman diagram showed that the two methods were highly consistent. For inter-rater assessments, the ICC and PCC values of the cusp angulation using the digital method were all higher than the corresponding values measured on traditional casts. For intra-rater assessments, the ICC values of cusp angulation using the digital method were higher than the corresponding values measured on traditional plaster casts for both examiners. However, repeated measurements of the angle β of the inter-examiners revealed significant differences (p < 0.05) for both methods.

Conclusions Cusp angulation using 3D digital models is a clinical option and appears to improve the reliability of cusp angulation compared with measuring plaster casts using a goniometer. This variability was still evident when measuring small cusp angles using the digital model for inexperienced examiners.

Publication History

Received: 27 January 2022

Accepted: 31 May 2022

Accepted Manuscript online:
03 June 2022

Article published online:
11 October 2022

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