Optical modeling of extraoral defects

Abstract

In order to reduce the stress caused to patients by conventional methods of modeling using computed tomography (CT) or magnetic resonance imaging (MRI), an optical modeling process has been developed for extraoral defects and body areas. The selected body part is digitized using optical 3-coordinate measuring technology, providing an extensive data record. This is adapted for further use by equalizing the point clouds to obtain a Computer Aided Design (CAD) model, which is converted to a physical model by means of a stereolithographic process. With this technology, the patient's physical and psychological stress may be reduced. This article describes a technique for optical modeling of an ocular prosthesis. (J Prosthet Dent 2004;91:80-4.) Unti l recently, conventional impression materials such as silicones or irreversible hydrocolloid and technologies (single or dual cycle processes with or without molding aids) have been used to fabricate maxillofacial prostheses, individual respiratory masks, and extraoral radiation devices. Depending on the impression material and the method of positioning the patient during the impression procedure, displacement of the soft tissues can occur. 1 Various materials have been used to support the impression materials during the procedure. 2 Industrially preproportioned, mechanically miscible, irreversible hydrocolloids (for example, Algicap; Ivoclar, Schaan, Fuerstentum, Liechtenstein) have been used. These materials had the advantage of preventing errors in proportioning and mixing when silicones were used; cartridge systems provided the same advantage. [3][4][5][6][7][8] Newer technologies are oriented to computed tomography (CT) or magnetic resonance imaging (MRI) data, whereby the patient undergoes considerable exposure to radiation. 9-11 To avoid these disadvantages, an optical modeling process for extraoral defects and body areas was developed. The development was based on experience in the collection of digitized data for toothrelated, model-dependent representations. 12-15 The optical 3-dimensional (3-D) scanning unit provides a point cloud or virtual model of the face. The primary principle used to obtain digitized data for extraoral areas is the method of structured light illumination with a digitallight projection unit. 16,17 Use of 3-D scanning in medical applications has specific system requirements: the body part (for example, the face) should be viewed from different directions simultaneously; the measurements should be made within seconds; and the system should be mobile and simple to use.Such a system was developed by the Fraunhofer Institute for Applied Optics and Precision Engineering in Jena, Germany. It is a mobile, multiview 3-D measuring system (called "kolibri-mobile") based on self-calibrating fringe projection technology, which facilitates the fully automatic recording of the body part from various directions in one measuring process. 17 Thus, it is possible to view the face in one complete sweep, from ear to ear and from below the chin to the forehea...

Chromatic changes to artificial irises produced using different techniques

“…14,15 Some authors suggest that the chromatic changes in artificial irises come not simply from degradation caused by exposure to environmental factors, but rather mainly from the process of polymerization in the acrylic resin that covers over the paint. [16][17][18][19][20] With the aim of increasing the stability of the prosthesis color in the face of aging caused by the artificial iris paint exposure to environmental factors and minimizing the effects of the polymerization process, the use of prefabricated caps has won favor over other techniques of ocular prosthesis production. 17,[21][22][23][24] In conjunction with this technique, a protective varnish can be applied over the paint of the artificial iris to reduce chromatic changes.…”

Bone and Skin-Supported Stereolithographic Surgical Guides for Cranio-Facial Implant Placement

“…Maintaining of the CT based 3D virtual model of the craniofacial structures as well as the defect area has been reported as the preliminary requirements for the surgeon to select an appropriate site for patients whose anatomy does not allow placement of implants conventionally [32][33][34][35].…”

“…This method consists of the production of the 3D objects by using data transferred CT image files. Craniofacial defect and neighboring hard and soft tissues, prototypes of the prostheses and surgical guides may be manufactured with stereolithography [29,30,[33][34][35]37]. The data about hard and soft craniofacial structures and the defect may be acquired by CT, magnetic resonance imaging and optic scanning of the surface by using various light sources [31,32].…”

“…On the other hand, implant locations can be planned virtually [26,28,29]. For this purpose, implant site may be scanned radiographically or optically [30][31][32] and modeled digitally [33][34][35]. Surgical guides produced with stereolithographic (STL) techniques in order to the computerized tomography (CT)-based planning, may be employed in surgical intervention [36][37][38].…”

Retracted

“…Most important disadvantages of this system are requirement of equipment and high cost. 6,7 RE or 3D digitizing 8 can be used to capture the morphology of deficient and normal ears as well as casts made by impression. 9,10 Some blind spots (undercuts) result in missing data patches and need to be manually "stitched," but the latest CT/MRI systems combined with medical modeling software can yield correct anatomical details and have been successfully used for the ear region.…”