Accuracy of 3D Curvilinear Measurements on Digital Models Generated by Light Emitting Diode Scanned Impressions: ACross-sectional Study

Abstract

Introduction: The advantages of digital models include customisation of appliances such as retainers, expanders, and indirect bracket setups for which measurements made along a curved line (curvilinear), would offer clinically more relevant information as opposed to linear measurements. Aim: The purpose of this study was to evaluate and compare the accuracy of 3 Dimensional (3D) curvilinear measurements on Digital models generated from Light Emitting Diode (LED) scanned impressions, with manual measurements on study models. Materials and Methods: The cross-sectional study consisted of maxillary arch rubber based impressions of eight patients selected on inclusion criteria of intact dentition having complete set of teeth with erupted second molar. These impressions were scanned with LED scanner (Medit Identica) and converted to Stereolithography (STL) files to generate 3D models. With the help of Ansys software curvilinear measurements were obtained from these models. These impressions were poured in dental stone to prepare study models and manual measurements were directly carried out on it with the help of brass wire and digital caliper. Measurements were made on different locations on the dental arch in various directions as the labial and palatal surface of central incisors and canine on left side along the long axis of the tooth from the cusp tip to the gingival margin and the buccal and palatal surface between the two interdental contact points of 2nd premolars. Unpaired t test was used to check the significant difference in means of different parameters. Results: No significant differences were found between central incisors labial surface (p=0.845) and palatal surface (p=0.722) and the canine measurements labial surface (p=0.721) and palatal surface (p=0.544) on digital models compared to study models, whereas significant difference was observed in premolar measurements (p-value≤0.05). Conclusion: STL files obtained by LED scanning the impressions did not exhibit significant deformation or loss of information while curvilinear measurements were evaluated, and higher accuracy was seen in the premolar measurement on palatal surface with digital models.