Novo método de sobreposição mandibular usando o programa Autodesk Inventor® para avaliação da acurácia do protocolo G8 da Invisalign®

Abstract

The use of orthodontic clear aligners has required effort and resources to ensure that the treatment outcome is as accurate as possible. In 2021 Invisalgn® G8 protocol promises better treatment predictability. It is through image superimposition that these results can be evaluated. In the literature, there are reports of various methods and software that seek reliability for superimposing three-dimensional (3D) models, but no consensus on these methods.The objectives of this study were: (1) Develop a new method for superimposing 3D models with Autodesk Inventor®, (2) evaluate the reproducibility of Autodesk Inventor® using the universal coordinate system (UCS) associated with a single point for superimposing 3D orthodontic models of the mandible and maxilla (3) Evaluate the reproducibility of Autodesk Inventor® in superimposing orthodontic 3D models of the maxilla and mandible, (4) Compare the accuracy of the G8 protocol through the result predicted by ClinCheck® with the actual result obtained in intrusion movements and posterior dental expansion. To the objectives 1, 2 and 3, 11 pairs of STL (Stereo-lithography) models of both arches treated with Invisalign® were selected at two times: initial (T0) and refinement (T1). The superpositions were performed using the Slicer® (version 4.1) and Autodesk Inventor® software using as reference the planes of the three Cartesian axes (X, Y and Z) associated with a point on the second palatal crease in the maxilla and, in the mandible, a point on the lingual mucous gingival line. After superimposition, the bucco-lingual translation movements of the canines, premolars and upper and lower molars, intrusion, rotation of the canines and mandibular incisors were analyzed by two examiners. To the objective 4, the accuracy was compared in the movements achieved and predicted by ClinCheck® between three cases in which the G8 protocol was activated and 8 cases in which it was not activated for maxillary and mandibular posterior expansion, canine and mandibular incisor intrusion. Results of objectives 1, 2 and 3 were intraclass correlation coefficients (ICC) greater than 0.90 no systematic error evaluated by the Dahlberg formula was observed.Results of objective 4, no statistically significant differences were observed between the groups. The accuracy in the G8 group when compared to the non-G8 group for posterior expansion in the mandible and maxilla increased by 12.7% and 7.8% respectively but without statistically significant differences. Intrusion movement, the accuracy of the G8 group was 7.7% higher than the non G8 group with no statistical difference between groups. It was concluded that the developed method proved reproducible for three-dimensional model superimposition. The G8 protocol, when activated, does not present greater accuracy for treatment with Invisalign®