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A pilot study for the digital replacement of a distorted dentition acquired by Cone Beam Computed Tomography (CBCT)

Nairn, Neil J (2011) A pilot study for the digital replacement of a distorted dentition acquired by Cone Beam Computed Tomography (CBCT). MSc(R) thesis, University of Glasgow.

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Abstract

Abstract Introduction: Cone beam CT (CBCT) is becoming a routine imaging modality designed for the maxillofacial region. Imaging patients with intra-oral metallic objects cause streak artefacts. Artefacts impair any virtual model by obliterating the teeth. This is a major obstacle for occlusal registration and the fabrication of orthognathic wafers to guide the surgical correction of dentofacial deformities. Aims and Objectives: To develop a method of replacing the inaccurate CBCT images of the dentition with an accurate representation and test the feasibility of the technique in the clinical environment. Materials and Method: Impressions of the teeth are acquired and acrylic baseplates constructed on dental casts incorporating radiopaque registration markers. The appliances are fitted and a preoperative CBCT is performed. Impressions are taken of the dentition with the devices in situ and subsequent dental models produced. The models are scanned to produce a virtual model. Both images of the patient and the model are imported into a virtual reality software program and aligned on the virtual markers. This allows the alignment of the dentition without relying on the teeth for superimposition. The occlusal surfaces of the dentition can be replaced with the occlusal image of the model. Results: The absolute mean distance of the mesh between the markers in the skulls was in the region of 0.09mm ± 0.03mm; the replacement dentition had an absolute mean distance of about 0.24mm ± 0.09mm. In patients the absolute mean distance between markers increased to 0.14mm ± 0.03mm. It was not possible to establish the discrepancies in the patient’s dentition, since the original image of the dentition is inherently inaccurate. Conclusion: It is possible to replace the CBCT virtual dentition of cadaveric skulls with an accurate representation to create a composite skull. The feasibility study was successful in the clinical arena. This could be a significant advancement in the accuracy of surgical prediction planning, with the ultimate goal of fabrication of a physical orthognathic wafer using reverse engineering.

Item Type: Thesis (MSc(R))
Qualification Level: Masters
Keywords: Cone beam computed tomography, CBCT, laser scanning, iterative closest point, composite skull, image fusion, virtual reality, maxillofacial, orthognathic surgery, orthognathic wafer, dentition
Subjects: R Medicine > RK Dentistry
Q Science > QM Human anatomy
Colleges/Schools: College of Medical Veterinary and Life Sciences > School of Medicine > Dental School
Supervisor's Name: Ayoub, Professor Ashraf F and Khambay, Dr Balvinder S
Date of Award: 2011
Depositing User: Mr Neil J Nairn
Unique ID: glathesis:2011-3019
Copyright: Copyright of this thesis is held by the author.
Date Deposited: 24 Nov 2011
Last Modified: 10 Dec 2012 14:02
URI: http://theses.gla.ac.uk/id/eprint/3019

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