Measurement of the buccolingual inclination of teeth: Manual technique vs 3-dimensional software

Introduction: In this study, we aimed tomeasure the inclination of teeth on dental casts by a manual techniquewith the tooth inclination protractor (TIP; MBI, Newport, United Kingdom) and a newly designed 3-dimensional(3D) software program. The correlation of the 2 techniques was evaluated, and the reliability of each techniquewas assessed separately.

Methods: This study was conducted on 36 dental casts of normal, well-alignedClass I occlusions; we assessed 432 teeth. All casts had a normal Class I occlusion. After determining thefacial axis of the clinical crown and the facial axis points on the dental casts, we measured the inclinationsof the incisors and posterior teeth up to the first molars in each dental arch relative to Andrews' occlusalplane and the posterior occlusal plane using the TIP. Moreover, the casts were scanned by a structuredlight3D scanner. The inclination of teeth relative to the occlusal plane was determined using the newsoftware. To assess the reliability, measurements of all teeth from 15 casts were repeated twice by the 2methods. Intraclass correlation coefficient and Dahlberg's formula were used for calculation of correlationand reliability.

Results: Overall, the 2 techniques were not significantly different in the measurements ofthe inclinations of the teeth in both jaws. The ranges of Dahlberg's formula were 3.1- to 5.8- for the maxillaand 3.3- to 5.9- for the mandible. The overall correlation of the 2 techniques according to the intraclass correlationcoefficient was 0.91. For calculation of reliability, the intraclass correlation coefficients for the TIPand the 3D method were 0.73 and 0.82, respectively.

Conclusions: The TIP and the 3D software showeda high correlation for measurement of the inclinations of maxillary and mandibular teeth relative to the occlusalplane. Also, the reproducibility of the measurements in each method was high.