Page 165 - Peri-implant health: the effect of implant design and surgical procedure on bone and soft tissue stability

FOUR-IMPLANT-SUPPORTED OVERDENTURE TREATMENT IN THE MAXILLA
■ INTRODUCTION
Nowadays, the support of an overdenture by dental implants is a widely used treatment procedure to provide higher functional comfort in the edentulous patient. Moreover, the mandibular two-implant overdenture is already for a long time considered as standard care for the edentulous patient.1 Success rates over 95% after 10 years of function are presented for overdentures in the mandible.2 A systematic review and meta-analysis reported an implant survival ranging from 73.5% to 100% for maxillary implants supporting an overdenture.3 They also concluded that a minimum of four implants is required to ensure high implant survival rates. Another systematic review with meta-analysis reported an implant survival of 98.1% per year in the case of ≥6 implants and splinted anchorage, a survival rate of 97.0% per year in case of ≤4 implants and a splinted anchorage, and a survival rate of 88.9% per year in case of ≤4 implants and a nonsplinted anchorage. They concluded an increased risk for implant loss for a nonsplinted anchorage with less than four implants.4 Success of the implant treatment is mostly determined by implant factors, such as survival rate, long-term peri-implant bone stability, and the absence of inflammation in the peri-implant tissues, or by patient factors such as the Oral Health-Related Quality of Life (OHRQoL). Part II of this study describes the patient-related outcome, more specifically Oral Health-Related Quality of Life (OHIP-14) as well as subjective opinion on speech by patients and objective speech analysis by professional speech therapists. The OHRQoL improved after connection with the implant-overdenture and this remained unchanged afterward. However, despite subjective registered improvements in speech, a professional scrutiny detected some disorders indicative of adaptation problems.
Different abutment connections have been used over time, in order to overcome abutment screw loosening, enhance long-term bone stability, and minimize crestal bone loss. In the early years of implant dentistry the most common abutment connection was the flat-to-flat abutment to implant connection, with an external hexagon to prevent abutment rotation. Nowadays, an internal conical connection or a Morse taper with an internal antirotation element is mostly used. A large review of 52 articles by Schmitt and colleagues concluded from in vitro techniques that (1) no connection yields a 100% perfect seal for bacterial contamination; (2) the implant–abutment interface geometry seems to be an influencing factor for stress
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