No abstract

The aim of the study was to investigate whether the properties of a pre-sintered, hot isostatic post-compacted (HIP) ZrO2 are adequate for use in three-five-unit fixed partial dentures (FPDs) and to evaluate the clinical results. Twenty three-five-unit FPDs were fabricated for 18 patients on a total of 56 abutments. They were all made on abutments cut with a shoulder preparation and cemented with a zinc phosphate cement. They were clinically followed for 24 months. After 24 months all FPDs were still in use without any fractures or clinical wear but in three cases (15%) minor chip-of fractures were observed. Marginal integrity was rated excellent at 45 abutments and acceptable at 11. Within the limitations of this 2-year clinical follow-up study, FPDs made of pre-sintered HIP ZrO2 core material veneered with a compatible ceramic is an acceptable alternative in the fabrication of FPDs with the extensions investigated in this study. Special attention, however, must be paid to designing the core for an occlusal shape that provides sufficient support for the veneer.

A clinical and radiographical study was performed to compare the outcome of oral rehabilitation in the edentulous mandible by fixed supraconstructions connected to implants installed according to either i) a 1-stage surgical procedure and immediate loading (Experimental Group-EG), or ii) the original 2-stage concept (Reference Group-RG). The EG comprised 16 subjects with edentulous mandibles. Beyond the non-smoking criteria the following specific inclusion criteria were adopted: i) all patients had to consider themselves to be in good general health, ii) the amount of bone had to enable the installation of 5-6, at least 10 mm long fixtures to be bicortically anchored (Mk II fixtures; Nobel Biocare AB, Göteborg, Sweden) between the mental foramina, and iii) the patients had to be available for the follow-up and maintenance programme. A total of 88 implants were placed in the EG (16 patients) compared to 30 in the RG (11 patients). In the EG, fixed appliances were connected to the implants within 20 days following implant installation while the fixed appliances in the RG were connected about 4 months following fixture installation. At the time for delivery of the supraconstructions all 27 patients were radiographically examined, an examination that was repeated at the 18-month follow-up. The analysis of the radiographs from the EG disclosed that during the 18-month observation period the mean loss of bone support amounted to 0.4 mm. The corresponding value observed in the RG was 0.8 mm. During the 18-month observation period no fixture was lost in any of the 2 groups examined. The implants under study as well as those in the reference material were at all observation intervals found to be clinically stable. The present clinical study demonstrated that it is, at least based on an 18-month observation period, possible to successfully load titanium dental implants immediately following installation via a permanent fixed rigid cross-arch supraconstruction. However, such a treatment approach has so far to be strictly limited to the inter-foramina area of the edentulous mandible.

A clinical and radiographical study was performed to evaluate the treatment outcome of single tooth replacements with artificial crowns retained to implants installed according to a 1-stage surgical procedure and immediate loading (Experimental Group = EG) in comparison to the original 2-stage concept (Control Group = CG). The EG comprised 14 patients (= 14 implants) and the CG comprised 8 patients (= 8 implants), all with single tooth losses anterior to the molars. Beyond the non-smoking criterion the following criteria were adopted: i) the amount of bone had to allow for installation of a fixture with a minimum length of 13 mm and Ø = 3.75 mm, ii) the jaw relationship had to allow for bilateral occlusal stability, iii) the patients should be judged to be non-bruxers, and iv) the patients had to be available for the follow-up and maintenance programme. In the EG a temporary crown was connected to the implant within 24 h following fixture installation. Six months later this crown was replaced with a permanent one. In the CG the surgical and prosthetic treatment followed the standard protocol. Out of the 14 fixtures in the EG 2 were lost up to 5 months in function and were subsequently removed. All remaining 12 implants were stable at every subsequent follow-up examination. No fixture losses were recorded in the CG and all implants in this group were stable at the follow-ups. At the 6-month observation interval all the participating 20 patients were radiographically examined, an examination that was repeated at the 18-month follow-up. The analysis of the radiographs from the EG as well as from the CG disclosed that during the 12-month observation period the mean change of bone support was about 0.1 mm. Further studies, designed as controlled multicenter ones, have to be performed before the results of this pilot study can be recommended for more general use.

This clinical study demonstrated that it is, at least based on a 5-year observation period, possible to successfully load via a permanent fixed rigid cross-arch suprastructure titanium dental implants soon after installation. However, such a treatment approach has to be strictly limited to the interforamina area of the edentulous mandible. Furthermore, the bone resorption was found to be within the same range around such implants as around implants installed and loaded according to the original two-stage protocol.