DOI: https://doi.org/10.14710/actodont.34901

Morphological Types and Dimensions of the Cervical Line in Maxillary Premolars: A Morphometric Study in the Chongjin Population

Faculty of Dentistry, Chongjin College of Medical Science, North Korea

Received: 7 Oct 2026; Revised: 27 Oct 2026; Accepted: 4 Nov 2026; Published: 1 Jun 2027.
Open Access Copyright 2026 Hong, Gwang-Hyon; Yu, Hong-Jin; Pak, Myong-Chol; Pak, Hong-Jin; Kim, Yong-Ho
Creative Commons License This work is licensed under a Creative Commons Attribution-NonCommercial 4.0 International License.

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Abstract
This study investigated cervical line type prevalence and dimensions in 670 maxillary premolars (296 first, 374 second). Cervical line morphology on the buccal, lingual, mesial, and distal surfaces was classified as straight or curved; curved lines were subdivided into type 1 (curvature height < 1/4 of the linear distance between endpoints) and type 2 (≥ 1/4 and < 1/2). Cervical width and thickness were measured. Intra-examiner reliability was assessed on 30 random teeth after 2 weeks. Chi-square or Fisher exact tests compared categorical variables; independent t tests compared continuous variables. In first premolars, the buccal surface was straight in 52.71%, curved type 1 in 43.92%, and curved type 2 in 3.37%; the lingual surface was predominantly straight (64.19%). Mesial and distal surfaces were predominantly curved (97.97% and 90.20%), mostly type 1 (93.24% and 88.85%). Second premolars showed similar trends, with curved type 2 absent buccally and rare lingually (0.53%). Cervical width was 4.9 ± 0.02 mm and 4.8 ± 0.02 mm, and thickness 8.1 ± 0.05 mm and 8.0 ± 0.03 mm, in first and second premolars, respectively. Sex differences were not significant on buccal, lingual, or distal surfaces (P > 0.05); mesial differences (Fisher P = 0.030 for both premolars) were driven by sparse straight-type cells. Cervical width was slightly larger in first premolars (P = 0.0004). Cervical line morphology varies considerably by tooth type and surface. Given sparse cells and small effect sizes, clinical relevance should be interpreted conservatively. These data inform clinical procedures involving the cervical region.
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Keywords: Cervical line; Cementoenamel junction; Maxillary premolars; Morphometry

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Section: Original Research
Language : EN
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