Edentulism is a debilitating condition which may negatively affect quality of life, particularly in relation to nutritional and social health, speech, and poor facial appearance. Prosthetic options available range from conventional complete dentures to implant-supported overdentures (ISODs) and implant-supported full arch fixed partial dentures (ISFAFDPs). The choice of treatment is connected to the patient's general health, oral status, preferences and financial means. From the point of view of the treatment provider, there is a lack of evidence to support choice of treatment, as information from randomised clinical trials is sparse. This is particularly true when it comes to cost analysis and patient-reported outcome measures (PROMs). There is consensus today that an implant-supported overdenture is a valid treatment option for the edentulous mandible, but the same recommendation cannot be made for maxillary overdentures due to a lack of evidence.

The present study investigates implant-supported maxillary overdentures regarding implant and prosthesis survival, costs and PROMs in comparison to fixed implant-supported prostheses.

The thesis comprises four studies.Study I analysed implant and prosthesis failure rates with implant-supported maxillary overdentures in a systematic review. The cumulative survival rate (CSR) for the implants and the prostheses was 70.4% and 79.8%, respectively. The main finding was that patients with few implants presented higher prosthesis failure rates than patients with more implants per prosthesis.Of the most commonly used attachment systems, the ball/O-ring and the Ceka were the ones with the highest rates of patients with at least one implant failure. Most of the failures happened within the first year after installation for both implants (52.1%) and prostheses (41.8%).Study II, a retrospective analysis, compared the clinical outcomes of implantsupported overdentures (ISODs) with either bar-clip or ball attachments. The results showed that all ISOD failures resulted from loss of implants. The bar-clip system resulted in more complications than the ball attachment system, suggesting that ISODs with the bar-clip system may necessitate a greater number of appointments and chair time for adjustments, thus increasing the maintenance costs for the patient.Studies III and IV were based on a prospective clinical trial comparing different implant-supported prosthetic rehabilitations for the edentulous maxilla: implantsupported full-arch fixed partial dentures on 4 or 6 implants (ISFAFDP 4 orISFAFDP 6) versus maxillary overdentures on 2 implants.Study III is a comparative cost analysis, the results of which showed that all implants and restorations were in function at follow-up after the first year, i.e., the survival rate was 100%. Initial costs, i.e., cost of prostheses at delivery, were higher for ISFAFDP 6 and ISFAFDP 4 due to the higher number of implants and higher cost of materials and fees. There were no statistically significant differences in post-treatment costs between the groups.In study IV, patient-reported outcomes regarding aesthetics and function were compared. The results showed that all patients, irrespective of group, showed improved patient-reported outcomes from before treatment to the one-year follow-up. There were no significant differences between groups regarding functional status of the masticatory system (Jaw Functional Limitation Scale -JFLS parameters) or how patients perceive their dental and Orofacial Aesthetic Scale (OAS), and only minor differences between the two groups with fixed restorations regarding patients’ perception of the social impact of oral disorders on their well-being (Oral Health Impact Profile - OHIP).