Randomized clinical trial of implant-supported ceramic-ceramic and metal-ceramic fixed dental prostheses: preliminary results

Abstract

Purpose: The aim of this study was to determine the survival rates over time of implant-supported ceramic-ceramic and metal-ceramic prostheses as a function of core-veneer thickness ratio, gingival connector embrasure design, and connector height.

Materials and methods: An IRB-approved, randomized, controlled clinical trial was conducted as a single-blind pilot study involving 55 patients missing three teeth in either one or two posterior areas. These patients (34 women; 21 men; age range 52-75 years) were recruited for the study to receive a three-unit implant-supported fixed dental prosthesis (FDP). Two implants were placed for each of the 72 FDPs in the study. The implants (Osseospeed, Astra Tech), which were made of titanium, were grit blasted. A gold-shaded, custom-milled titanium abutment (Atlantis, Astra Tech), was secured to each implant body. Each of the 72 FDPs in 55 patients were randomly assigned based on one of the following options: (1) A.

Material: ceramic-ceramic (Yttria-stabilized zirconia core, pressable fluorapatite glass-ceramic, IPS e.max ZirCAD, and ZirPress, Ivoclar Vivadent) B. metal-ceramic (palladium-based noble alloy, Capricorn, Ivoclar Vivadent, with press-on leucite-reinforced glass-ceramic veneer, IPS InLine POM, Ivoclar Vivadent); (2) occlusal veneer thickness (0.5, 1.0, and 1.5 mm); (3) curvature of gingival embrasure (0.25, 0.5, and 0.75 mm diameter); and (4) connector height (3, 4, and 5 mm). FDPs were fabricated and cemented with dual-cure resin cement (RelyX, Universal Cement, 3M ESPE). Patients were recalled at 6 months, 1 year, and 2 years. FDPs were examined for cracks, fracture, and general surface quality.

Results: Recall exams of 72 prostheses revealed 10 chipping fractures. No fractures occurred within the connector or embrasure areas. Two-sided Fisher's exact tests showed no significant correlation between fractures and type of material system (p = 0.51), veneer thickness (p = 0.75), radius of curvature of gingival embrasure (p = 0.68), and connector height (p = 0.91).

Conclusions: Although there were no significant associations between connector height, curvature of gingival embrasure, core/veneer thickness ratio, and material system and the survival probability of implant-supported FDPs with zirconia as a core material, the small number of fractures precludes a definitive conclusion on the dominant controlling factor.

Keywords: Clinical; design parameters; implants.

Conflict of interest statement

The authors deny any conflicts of interest.

© 2013 by the American College of Prosthodontists.

Figures

Figure 1

Study design.

Figure 2

Representative Class 1 fracture of MC and CC FDPs that were polished and not repaired or replaced.

Figure 3

Representative Class 2 fracture of MC repaired with composite.

Figure 4

Representative Class 3 fracture of CC FDP that extended to the zirconia core (top). Another view showing the Atlantis abutment where zirconia core fractured.

Figure 5

A. SEM image showing fracture originating from occlusal area; B. Image of critical flaw at higher magnification with view from mesio buccal occlusal area. C. Fracture stress of 108.5 MPa in veneer determined from flaw size 2b (128 µm) and a (60 µm), Y (1.24) and KIc using σF = Y√c / KIC.

Figure 5

A. SEM image showing fracture originating from occlusal area; B. Image of critical flaw at higher magnification with view from mesio buccal occlusal area. C. Fracture stress of 108.5 MPa in veneer determined from flaw size 2b (128 µm) and a (60 µm), Y (1.24) and KIc using σF = Y√c / KIC.

Figure 5

A. SEM image showing fracture originating from occlusal area; B. Image of critical flaw at higher magnification with view from mesio buccal occlusal area. C. Fracture stress of 108.5 MPa in veneer determined from flaw size 2b (128 µm) and a (60 µm), Y (1.24) and KIc using σF = Y√c / KIC.