DICOM-Daten als Basis für die FEM-Simulation zahnmedizinischer Fragestellungen – ein technischer Übersichtsartikel

Zusammenfassung

Zielsetzung:

Das Ziel der vorliegenden Arbeit war es, einen methodischen Weg aufzuzeigen, um CT-Bilder in ein rechenbares Finite-Elemente-Modell umzuwandeln.

Material und Methode:

Aus den DICOM-Daten eines Patienten-CTs wurden der für die FEM-Analyse interessante Bereich mit dem Programm 3D Slicer separiert und anschließend anhand der Grauwerte segmentiert. Aus dem im STL-Format vorliegenden Bildausschnitt wurden mit dem Programm CATIA^® das Modell eines unteren Molars mit parodontalem Ligament (PDL), der umgebende Knochen und ein kieferorthopädisches Attachment generiert. Zur Diskretisierung wurden die Oberflächenmodelle von Zahn, PDL, Knochen und der kieferorthopädischen Behandlungsapparatur knotenweise miteinander verbunden. Als Ergebnis des Diskretisierungsprozesses entstand ein FE-Netz mit insgesamt 156 982 Volumenelementen.

Ergebnisse:

Nach dem beschriebenen Weg wurden ein unterer Molar mit PDL und der angrenzende Knochen aus einer CT-Aufnahme isoliert und für die Untersuchung der initialen Zahnbewegung mittels der Finite-Elemente-Methode aufbereitet. Auf der Grundlage einer CT-Aufnahme kann die numerische Simulation der initialen Zahnbewegung durchgeführt werden. Dabei lassen sich unterschiedliche Lastsituationen analysieren und vergleichen.

Schlussfolgerung:

Die Finite-Elemente-Analyse mit Patientendaten ist eine vielversprechende Möglichkeit zur Belastungssimulation im Hinblick auf gerätespezifische Wirkungen, Nebenwirkungen und Weiterentwicklungen.

Abstract

Objectives:

The aim of the present study was to demonstrate a method of converting CT images into a computable finite element model.

Materials and methods:

The program 3D Slicer was used to separate key areas from the DICOM data of a patient’s CTs for the purpose of finite element analysis and then to segment them according to their grayscale values. The resulting digital image in STL format was processed in the program CATIA^® to generate a model of a lower molar together with the periodontal ligament (PDL), the surrounding bone and an orthodontic attachment. Discretization was carried out by creating a nodal mesh from the surface models of the tooth, PDL, the bone and the orthodontic appliance. The result of the discretization process was a finite element mesh consisting of a total of 156 982 volume elements (voxels).

Results:

Using the method described, a mandibular molar together with the PDL and the surrounding bone were isolated from a CT image and prepared for analysis of the initial tooth movement by means of the finite element method. Finally different load situation and orthodontic biomechanics can be simulated and compared.

Conclusion:

A numerical simulation of the initial tooth movement can be carried out on the basis of a CT image. By using this method it is possible to analyze and compare different load situations in order to achieve as uniform a pressure distribution as possible in the PDL and controlled initial tooth displacement. Finite element analysis of patient data could be used to determine the individual dosage of orthodontic forces.

Schlüsselwörter

CT, DICOM - Finite-Elemente-Methode - Simulation - parodontales Ligament - initiale Zahnbewegung - orthodontische Kräfte

Key words

CT, DICOM - finite element method - simulation - periodontal ligament - initial tooth movement - orthodontic forces

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