New prospects of intra oral scanning in maxillofacial surgery

This thesis is based on human studies conducted at the Department of Oral and Maxillofacial Surgery, Radboud University Medical Centre Nijmegen, the Netherlands, and approved by the CMO Arnhem-Nijmegen (2014-1484, 2016-2690, 2017-3671). Since the introduction of the first intraoral digital scanner (IOS), CEREC, in 1985, IOS technology has advanced rapidly, offering faster, more accurate alternatives to conventional dental impressions. While the accuracy of IOS for dentition is well established, little research has explored its use for scanning oral soft tissues, which could improve clinical examinations in oral and maxillofacial surgery. The thesis focuses on the capabilities of the TRIOS® IOS for soft tissue assessment. In the first study (chapter 2), the palatal mucosal surface of dentate patients was scanned and compared to conventional impressions, showing high accuracy and precision. The scanner also objectively recognized color variations using the HSV color scale and successfully measured surface irregularities such as palatal rugae, demonstrating its potential for soft tissue analysis. Chapter 3 introduces a novel method for matching IOS scans with cone-beam computed tomography (CBCT) using soft tissue surfaces, particularly in edentulous patients where traditional dental landmarks are absent. A patient-specific algorithm for soft tissue gray value was developed, yielding low registration errors (0.49 mm in dentate jaws and 0.16 mm in edentulous jaws), enhancing the precision of fully edentulous jaw registration. Chapter 4 evaluated the reproducibility of both IOS and the soft tissue-based registration in fully edentulous jaws. Results showed high reproducibility and inter-observer agreement, highlighting the method’s reliability. In chapter 5, the scanner's ability to quantify tissue color changes was tested as a potential indicator of vascular perfusion issues. By scanning skin during arterial and venous occlusion, the scanner detected significant color differences, distinguishing between arterial and venous congestion within one minute. This could lead to better monitoring of tissue viability, such as in free vascularized tissue transplants after oral reconstruction in cancer patients. This thesis underscores the potential of IOS beyond traditional dental impressions, proposing its broader application in oral and maxillofacial surgery for objective clinical assessments and enhanced treatment outcomes.