77 QOL related to mastication in maxillectomy patients 4 Discussion In this cross-sectional comparative study, we explored whether implantsupported obturator prostheses in maxillectomy patients improved masticatory performance and OHRQoL. Therefore, we evaluated both objective outcomes from the MAT and subjective outcomes from the OHRQoL questionnaires, as objective information of oral functioning may be different from personal experiences. The MAT evaluates the ability to mix a bi-coloured wax tablet and results in the MAI score. It has proven to be valid and reliable in test candidates with compromised masticatory performance [23, 34]. The study indicates that implant-supported obturator prostheses are useful in the oral functional rehabilitation of maxillectomy patients. The results show a significantly better MAI score outcome in patients of Group 1, notwithstanding the larger and more ventral defects. The patients with implant-supported obturator prostheses show similar MAI score results (18.66 ± 1.37) compared with dentate obturator patients (18.4 ± 4.2) despite severely compromised oral function due to the maxillectomy. Likewise, healthy edentulous non-maxillectomy individuals with conventional maxillary dentures and implant-supported mandibular overdentures (MAI 18.5 ± 3.1) have shown similar results. The mean MAI score of Group 2 patients (22.36 ± 3.16) was comparable to healthy full denture patients (21.2 ± 3.6) and other edentulous obturator patients (25.1 ± 5.3) [23, 35]. The added value of dental implants in prosthetic rehabilitation of patients after maxillectomy has been reported previously, both in patients receiving obturator prostheses, as well as in surgically reconstructed patients. The use of zygomatic implants increases reconstructive treatment options, especially for maxillectomy patients. To date, functional differences have not been established between the obturator and surgically reconstructed patients [20, 36, 37]. We reached an overall implant survival of 90.5%, with four out of 42 implants lost in patients in Group 1. Since the four lost implants have failed in irradiated bone, our overall implant survival in non-irradiated bone of 100% is comparable with the results published by Huang et al. [14]. In their study, implant survival in irradiated patients was 82.6%. Other studies have reported similar results; however, these studies did not refer to dental implant survival in extra-maxillary bony structures of the midface or skull base [38-40]. Moreover, current literature does not explicitly reveal information about the radiation doses at the specific implant sites. Instead, studies have reported whether the patient was irradiated
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