Requirements for a Universal Image Analysis Tool in Dentistry and Oral and Maxillofacial Surgery

Requirements for a Universal Image Analysis Tool in Dentistry and Oral and Maxillofacial Surgery

Thomas Hierl (University of Leipzig, Germany), Heike Huempfner-Hierl (University of Leipzig, Germany), Daniel Kruber (University of Leipzig, Germany), Thomas Gaebler (University of Leipzig, Germany), Alexander Hemprich (University of Leipzig, Germany) and Gert Wollny (Universidad Politecnica de Madrid, Spain)
DOI: 10.4018/978-1-60566-292-3.ch005
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Abstract

This chapter discusses the requirements of an image analysis tool designed for dentistry and oral and maxillofacial surgery focussing on 3D-image data. As software for the analysis of all the different types of medical 3D-data is not available, a model software based on VTK (visualization toolkit) is presented. VTK is a free modular software which can be tailored to individual demands. First, the most important types of image data are shown, then the operations needed to handle the data sets. Metric analysis is covered in-depth as it forms the basis of orthodontic and surgery planning. Finally typical examples of different fields of dentistry are given.
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Image Data In Dentistry

During the last decades, image analysis in dentistry was mostly confined to 2D bitmap images. Typical examples have been:

  • Plain X-rays → cephalometric analysis in orthodontics, caries diagnostics, endodontics etc.

  • Photographs → facial analysis in oral and maxillofacial surgery and orthodontics

The advent of 3D-scanning technologies has brought a wealth of new image data to dentistry. CT-scanning, magnetic resonance imaging (MRI), cone beam tomography, and optical scanning (e. g. laser scanning, fringe projection or stereophotogrammetry) are now widely used. A short and incomplete list of reasons why such data is acquired includes:

  • Optical scanning of dental crowns for prosthodontic work (CAD-CAM design and production of crowns and bridgework)

  • CT and CBT for implant surgery (ranging from planning of implant position to surgical navigation during implant placement)

  • CT, MRI, and optical scanning for 3D cephalometry

  • Optical scanning of dental plaster casts in orthodontics

  • CT, MRI, and optical scanning in epithetics (i. e. generating artificial missing facial parts after tumor surgery, accidents or due to syndromic diseases)

A key issue of most 3D scanners is the use of proprietary file formats with an inconsistent export possibility into common file formats. Most software functions of the programmes which come alongside the scanners, however, are confined to these proprietary file formats. This implies that missing import filters are limiting the use of these programmes in daily practise. Commercially used software is free of such constraints but rarely adapted to the needs of dental professionals, is rather expensive and requires profound training.

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Requirements For A “Universal” Image Analysis Tool

An ideal image analysis tool should appeal to the typical software used by medical professionals (i.e. the look and feel of standard office software). Functions and drop down menus should be named in plain words, mathematical terms should be used sparsely. Regarding the data to be analysed, import filters for typical 2D and 3D format files should be available. These include:

  • Bitmap formats (BMP, JPEG, …)

  • Rdiologic images (DICOM standard)

  • Polygon based surface data derived from optical scanners (STL, VRML, OBJ, …)

Regarding the 3D image files export filters are required for special tasks. This includes production of rapid prototyping (RP) specimens for implant templates, epithetics or alloplastic implants (Ono et al. 2000). The most important format is STL, which is the standard language of RP-machines. Other export formats like VRML are useful in case of surgical planning if virtual skulls or bone segments are created which will undergo surgery. For DICOM data export formats are needed if the data have to be processed as the original DICOM data should not be changed (this is a key point of this format to keep the inherent medical information).

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