Avhandlingens preliminära titel: On Clinical and Mechanical Aspects in Implant Supported Screw Retained Multi-unit CAD-CAM Metal Framework

Fakultetsopponent: Docent Andreas Thor, Uppsala universitet

Vid frågor, kontakta jonas.becktor@mau.se

Delta på disputationen via Zoom 

Abstract

Conventionally casted frameworks have been considered the preferred solutions for complete and partial restorations since the beginning of implantology. However, following technological development, the computer aided design/computer aided manufacturing (CAD-CAM) with milling the frameworks has been introduced as an alternative option with the potential of minimising inaccuracies, reducing the operator dependence and offering a homogeneous structure with high mechanical properties. The CAD-CAM multi-unit reconstruction varies with fixation type, implant framework connection, and prostheses material. However, the materials developed for the use of CAD-CAM, may have different technical and biological complications with time.

The present thesis aims to provide insights into the risk of complications in screw-retained multi-unit frameworks manufactured using the CAD-CAM technique.

An in vitro test (Study I) was performed to assess the effects of misfit at implant-level FPDs and supporting bone levels on the generation of implant cracks. Three clinical studies were conducted: in Study II, partially edentulous patients were rehabilitated with either an abutment or implant level multi-unit Cobalt-Chromium metal- ceramic framework; in Study III, patients, edentulous in the maxilla, were treated with either four or six implants and rehabilitated with a fixed titanium metal-acrylic framework; in Study IV edentulous patients were treated with removable overdentures retained by titanium milled bars. In Study III and IV, Oral Health Related Quality of Life was evaluated.

The marginal bone level change was clinically not significant regardless of fixation type (Study II), retention (Study III-IV), and material used (Study II-III-IV). No framework complications were registered. Patients reported a high level of satisfaction after the treatment (Study III-IV).

Based on the studies included in this thesis, the following conclusions can be made: (i) the risk of implant cracks in screw- retained Implant Level (IL) Fixed Partial Denture (FPD) is low, even with a misfit; (ii) according to the 1-year data presented in Study II, abutment level (AL) retention is recommended for FPDs; (iii) the cost- effective for a maxillary Fixed Complete Denture (FCD) supported by four implants can be considered predictable and comparable to six implants; (iv) implant-supported FCDs and Implant supported Over- Dentures (IOD) are associated with high rates of patient satisfaction, related to aesthetics and mastication function mainly resulting from the high stability of the prostheses; (v) the technical and biological complications reported in FPDs, FCDs and IODs were limited. However, a considerable percentage of prosthetic fractures and chippings were reported for FCDs at 1-year and 3-year follow-ups. Clinicians have to be aware that additional visits may be required for maintaining the prostheses.