60 Chapter 4 Materials and methods Patients All patients that were referred to the Department of Cranio-Maxillofacial Surgery at Maastricht University Medical Centre (MUMC+) for surgical and prosthetic rehabilitation in the maxilla/midface between 2005 and 2015 were asked to participate in this comparative cross-sectional study. We compared patients with implant-supported obturator prostheses (Group 1) with patients wearing conventional obturator prostheses (Group 2). Patients with maxillary/midface defects in edentulous upper jaws were included when the prosthetic obturator treatment was completed. Brown’s classification was used to determine the defect size in the maxilla/midface [21]. The study was approved by the Ethics Committee of the MUMC+ (METC 15-4-123). Informed consent was obtained from all participating patients. Procedure Patients with a status eligible for implants after partial or total maxillectomy or partial or total loss of the maxilla/midface were treated according to the “surgical and prosthetic reconsiderations in patients with maxillectomy protocol” as defined by Lethaus, Lie et al. [8]. Implants were not placed if it was expected that there would be sufficient prosthetic options for a conventional obturator. Furthermore, some patients refused implant treatment. The decision of using implants was not based on the prognosis of the patient. Imaging for digital planning was based on computerized tomography (CT) scans acquired by multi-slice CT (Siemens) or cone-beam CT (ICAT, Hatfield). Implant sites in the remaining facial skeleton or skull base were planned based on the CT-data with the Simplant 3D® program (Dentsply Sirona, Wals bei Salzburg). When standard abutments did not comply with the required distances or angulations of our protocol, individual abutments were designed by hand or by using the Cinema 4D® planning program (Design Express). If possible, a bar construction was made on the dental implants to support the obturator. Magnet abutments were used as an alternative retention method when the space between two implants was too wide. (Figures 1 and 2). Data acquisition The mixing ability test (MAT) was used to measure the masticatory performance objectively [22, 23]. Subjective aspects were measured with three OHRQoL questionnaires: (a) the Oral Health Impact Profile for EDENTulous people (OHIPEDENT) [24], (b) the Obturator Function Scale (OFS) [7], (c) and the Dutch Liverpool Oral Rehabilitation Questionnaire version 3 (LORQv3-NL) [25-28].
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