Background An apical shift in the position of the gingiva beyond the cemento-enamel junction leads to gingival recession. This study aimed to evaluate the reproducibility of digital measurements of gingival recession when compared to conventional measurements taken clinically using periodontal probes. Methods Gingival recession was measured at 97 sites in the oral cavity by four examiners using the following methods: CP, direct measurement of gingival recession using William’s periodontal probe intraorally; CC, measurements on cast models using a caliper; DP, digital measurement on virtual models obtained by intraoral scanning, and DC, digital measurements on virtual models of dental casts. Intra-class and inter-rater correlations were analyzed. Bland Altman plots were drawn to visually determine the magnitude of differences in any given pair-wise measurements. Results In this study, good inter-methods reliability was observed for almost all the examiners ranging from 0.907 to 0.918, except for one examiner (0.837). The greatest disagreements between the raters were observed for methods; CP (0.631) followed by CC (0.85), while the best agreements were observed for methods DP (0.9) followed by DC (0.872). Conclusion Variations in measurements between examiners can be reduced by using digital technologies when compared to conventional methods. Improved reproducibility of measurements obtained via intraoral scanning will increase the validity and reliability of future studies that compare different treatment modalities for root coverage. Electronic supplementary material The online version of this article (10.1186/s12903-019-0851-0) contains supplementary material, which is available to authorized users.

To evaluate the prevalence, correlation, and differences of C-shaped canal morphology in mandibular premolars and molars by means of cone-beam computed tomography (CBCT). Materials and Methods: A total of 1433 mandibular premolars and molars CBCT scans from the Saudi population were evaluated. Axial sections of the roots were acquired at coronal, middle, and apical levels to evaluate C-shaped canals types. The prevalence, correlation, differences of C-shaped canals, bilateral/unilateral presence, gender differences, and location of external grooves on roots were assessed. Results:The prevalence of C-shaped canals in the first premolars was 1.5%, 0.80% in second premolars and 7.9% in second molars, whereas C-shaped canals were absent in first molars. No correlation was found between the presence of C-shaped canals within premolars and molars and between the two groups in the same individual. Both premolars and molars exhibited different types of C-shaped canals, C2 being predominant in premolars and C3 in second molars. Longitudinal external grooves were mostly located on mesiolingual (ML) surface in premolars and lingual in molars. Females showed more prevalence of C-shaped canals in second molars and no differences in premolars. Bilateral symmetry and unilateral presence in premolars and second molars were not significant. Conclusions: Although the prevalence of C-shaped canals is significantly higher in mandibular second molars, they are also found in mandibular premolars but in small percentages. No significant differences were found between both genders and both sides. Since they exhibit unpredictable morphology and differences across the root length, the use of small field CBCT is recommended when such anatomy is presented in a tooth indicated for root canal treatment for better management.

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