Characterization of maxillary central incisor: novel crown-root relationships.

OBJECTIVES: The periodontal biotype includes crown features of the maxillary central incisor (MCI), whereas root measures have been less studied. The aim of our study was to morphologically characterize MCI and search relationships between crown and root measures. MATERIAL AND METHODS: One hundred-fifty MCIs were used. On each tooth, several crown and root reference points were marked and the following measures were done: On crown: mesio-distal (MD = major, md = minor), axial (crown length, cervical convexity) and buccolingual diameters (Cbl); On root: mesio-distal (Rmd) and buccolingual diameters (Rbl); and tooth length. A ratio between md and MD was made in order to assess dental forms. Root diameter prediction was assessed by means of multiple and single linear regression analyses, with variable selection by backward method. Reliability of measurements was estimated by the Pearson correlation coefficient. RESULTS: Dental form groups were: Stout type 56.67 %, Intermediate type 22.67 %, and Strangled type 20.67 %. A significative association was found between Rbl and Cbl (p = 0,000), Rmd with md (p = 0.000), and Rmd with MD (p = 0.000). The results allow predicting root diameters through crown measures. CONCLUSIONS: There is a direct relationship between crown and root features, which allows the prediction of root diameters with a high accuracy (95 %), regardless of tooth form. CLINICAL RELEVANCE: The morphometric data assess tooth diameters more accurately and could improve treatment planning, offering a more comprehensive approach to the periodontal biotype concept.

Assessment of maxillary central incisor crown form.

Incisor crown form is thought to be associated with different periodontal features, and it is hypothesized that there are measures of the maxillary central incisor that can be used to characterize its form. The aim of this study was to assess maxillary central incisor crown dimensions to determine morphologic groups. One-hundred fifty sound maxillary central incisors without excessive evidence of incisal wear were utilized. On each crown, several reference points were marked and mesiodistal and axial diameters were measured using a digital caliper. A ratio between the minor and major mesiodistal diameters was determined to assess dental forms. Maxillary central incisor form was categorized into three groups based on the upper limits of three intervals as cutoff points. The measurements were performed in a double blind fashion. The reliability of measurements was estimated by the Pearson correlation coefficient for each tooth, setting a value > 0.8. The percentage of maxillary central incisors in each group was 56.67% for group 1 (stout), 22.67% for group 2 (intermediate), and 20.66% for group 3 (strangled). The results suggest that maxillary central incisor morphology can be properly assessed through quantifiable methods. The minor/major mesiodistal ratio is simple, quantitative, and easily reproduced. It is a quantifiable definition of dental forms based on characteristics that are not modified by the position of the gingival margin or incisal wear. Hence, the grade of cervical convergence could help clinicians assess tooth shape before performing restorative, orthodontic, or surgical treatments.