The effect of regular dental cast artifacts on the 3D superimposition of serial digital maxillary dental models

Eva Henninger,Demetrios Halazonetis,Georgios Vasilakos,Nikolaos Gkantidis

doi:10.1038/s41598-019-46887-1

Eva Henninger, Demetrios Halazonetis + Show 2 more

Open Access

https://doi.org/10.1038/s41598-019-46887-1

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Abstract

Superimpositions of serial 3D dental surface models comprise a powerful tool to assess morphological changes due to growth, treatment, or pathology. In this study, we evaluated the effect of artifacts on the superimposition outcome, using standard model acquisition and superimposition techniques. Ten pre- and post-orthodontic treatment plaster models were scanned with an intraoral scanner and superimposed using the iterative closest point algorithm. We repeated the whole process after manual removal of plaster artifacts, according to the current practice, as well as after re-scanning the cleaned models, to assess the effect of the model acquisition process derived artifacts on the superimposition outcome. Non-parametric multivariate models showed no mean effect on accuracy and precision by software settings, cleaning status (artifact removal), or time point. The choice of the superimposition reference area was the only factor that affected the measurements. However, assessment of individual cases revealed significant differences on the detected tooth movement, depending on artifact removal and on the model acquisition process. The effects of all factors tended to decrease with an increase in the size of the superimposition reference area. The present findings highlight the importance of accurate, artifact-free models, for valid assessment of morphological changes through serial 3D model superimpositions.

Highlights

Orthodontic diagnosis and treatment planning is traditionally done with the aid of plaster dental models
The present study showed that even the imprecision of the digital model generation process itself can have a considerable effect on the detected tooth movement measurements
If we consider that small stable reference areas are required for serial dental model superimpositions to obtain a valid assessment of changes that occur during treatment and growth, the need for accurate and artifact-free dental models becomes essential.With the increasing incorporation of 3D-imaging software and hardware tools in everyday clinical practice, it is expected that the interest for proper superimposition techniques will considerably expand in the few years

Summary

Introduction

Orthodontic diagnosis and treatment planning is traditionally done with the aid of plaster dental models. Scanning of plaster dental models is expected to have a major role in the construction of 3D oral tissue digital imprints, mainly for archiving existing physical dental models or when direct intraoral scanning is not possible. Digital dental models offer great advantages with the capability to apply 3D superimposition techniques and to use the whole amount of 3D information for a thorough assessment and visualization of morphological changes[6] For this purpose, two serial dental models of the same patient can be superimposed on a selected reference area that is considered www.nature.com/scientificreports/. During the conventional impression and physical dental model construction process, surface artifacts, usually in the form of small (0.5–2 mm) bubble-type structures, can occur[10] Such artifacts normally occur on morphologically complex areas, such as the palatal rugae, the gingival margins and the fissures of the teeth. Since such artifacts alter the original surface morphology of any structure of interest, this might have an influence on the superimposition outcomes

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