Composition, phase analysis, biaxial flexural strength, and fatigue of unshaded versus shaded Procera zirconia ceramic.

STATEMENT OF THE PROBLEM: Recent interest in shaded zirconia has raised questions about the relative stability of the tetragonal phase after colorant oxide additions. PURPOSE: The purpose of this in vitro study was to evaluate the effects of fatigue cycling on the stability of a commercially available dental zirconia (Procera) in both unshaded and shaded compositions by measuring the change in biaxial flexural strength (BFS) after 500 000 cycles at 80-N loads and in phase composition as detected by x-ray diffraction (XRD). MATERIAL AND METHODS: Partially stabilized zirconia disks (NobelProcera) were fabricated in unshaded and shaded forms (12 mm diameter × 0.8 mm thick). Specimens were analyzed by energy-dispersive x-ray spectroscopy (EDS) and by wavelength-dispersive x-ray spectroscopy (WDS) for oxide compositions which indicated the presence of small amounts of Fe-O (0.13 ±0.10 wt %) in the shaded specimens. XRD focused on the tetragonal (T) and monoclinic (M) peaks in the 20 to 40 degrees 2θ range. The disks were polished on 1 side, cyclically loaded (80N, 500 000 cycles, custom 4-station fatigue test machine), and tested for residual BFS after cycling. Unshaded (U) and shaded groups (S) were compared before (U1, S1) and after (U2, S2) load cycling with XRD and residual BFS. RESULTS: Residual BFS (MPa) for specimens before (U1=856 ±99 versus S1= 842 ±40) and after fatigue (U2=772 ±65 versus S2= 718 ±68) were statistically different (U1 versus U2; S1 versus S2; U2 versus S2, P<.05). The XRD of U1 and S1 specimens revealed tetragonal and cubic zirconia. U2 and S2 specimens contained tetragonal zirconia, with the initial appearance of small amounts of monoclinic zirconia after fatigue cycling. Monoclinic detection was measured on the tension side of the tested specimens and varied between tests at the center and radially at 4 mm. CONCLUSIONS: The results indicated shaded materials more readily transform the tetragonal to the monoclinic phase during load cycling than unshaded ones. However, extrapolating the effects of any shortening of the service life of zirconia compositions is difficult. The potential mitigating effects of other factors such as the thermal postprocessing of porcelain veneers, stains on zirconia, or effects of water have yet to be investigated.

Cyclic Loading Effect on Color Stability of Unshaded versus Shaded Zirconia.

STATEMENT OF PROBLEM: Shaded versions of dental zirconia may improve initial color matching to teeth, but might change color with cyclic mechanical loading. PURPOSE: The purpose of this study was to measure the color of unshaded and shaded zirconia dental ceramic before and after cyclic mechanical loading and calculate color differences (ΔE). MATERIAL AND METHODS: Disk-shaped specimens (N = 30, Nobel Procera, 0.8 mm thick, 12 mm diameter) of unshaded or shaded zirconia (intrinsically shaded by small oxide modifications) were fabricated by the Nobel Biocare using standard CAD-CAM processing. Milled surfaces were polished. CIE L*a*b* values were measured (Konica Minolta spectrophotometer) before and after mechanical cycling (custom modified Leinfelder test machine, biaxial flexure loading, load = 80 N × 500,000 cycles, dry), and L*a*b* individual differences and ΔE color differences were calculated and compared (ANOVA, p < 0.05). RESULTS: Mean L*a*b* values for the unshaded group before (U1 = 86.165, -0.887, 0.372) and after (U2 = 84.860, -0.805, 0.097) cyclic loading were compared to the shaded group before (S1 = 75.281, -0.679, 23.251) and after (S2 = 74.961, -1.233, 22.439) cyclic loading. All color variables for both unshaded and shaded groups were significantly different between before and after cyclic loading (p < .004) except for the L* value of the shaded group. The ΔE for unshaded (1.441 ± 0.495) versus shaded (1.252 ± 0.363) were statistically different but clinically the change would not be detectable at this point. CONCLUSIONS: The color of the unshaded and shaded zirconia specimens was influenced by cyclic loading (p < 0.05). Color changes were detectable but small at levels up to 500,000 cycles, and remained clinically acceptable at that point. CLINICAL SIGNIFICANCE: It is important to acknowledge any possible color changes that might occur in zirconia restorations, especially in the esthetic zone. Minor color changes that are individually imperceptible to the human eye within different restorative components may be compounded to produce clinically significant color change that is not aesthetically acceptable.

Material options for restoring intentionally misaligned implants on maxillary edentulous arch: a clinical report.

Without major bone grafting procedures, anatomic challenges may dictate less than ideal implant placement. When surgical correction is impossible, it may be possible to place implants on an angle and use angled abutments to compensate. This article presents 2 patient treatments where angled abutments were used to facilitate the fabrication of an implant-supported fixed complete-arch prosthesis. In both scenarios the supporting bars for the prostheses were milled in titanium. Soft tissue shaded ceramic was used to simulate the soft tissues for one patient and soft tissue shaded composite resin was used for the second. The prostheses were completed by cementing 12 individual crowns on each bar.

Nonrigid connection of tooth with implants in the esthetic zone with a ceramic restoration: a clinical report.

Restoring edentulous areas with fixed prostheses can be challenging, especially when key abutment teeth are missing and implant placement is not an option. Sometimes, clinicians are faced with situations where teeth have to be connected with implants even though long-term prognosis of those connections may be questionable. This clinical report presents a connection of 2 implants with 1 tooth in the esthetic zone with a nonrigid connection. Two zirconia custom abutments and 1 zirconia coping definitively cemented on the tooth were used. A zirconia superstructure, veneered with porcelain, was cemented with provisional cement on the abutments and the coping.

Maxillary implant-supported bar overdenture and mandibular implant-retained fixed denture using CAD/CAM technology and 3-D design software: a clinical report.

The implant-supported bar overdenture and the implant-retained fixed complete denture are appropriate treatment choices for patients with inadequate bone volume in the posterior maxilla and mandible, respectively. Computer-aided design/computer-aided manufacturing (CAD/CAM) technology has broadened the scope and application of those treatment options, allowing for prosthodontically-driven implant placement and ideal substructure design for optimal esthetics and biomechanics. This report describes the fabrication of a maxillary implant-supported milled titanium bar with attachments and an overdenture, and a mandibular implant-retained fixed complete denture with milled titanium substructure.

Translucency of shaded zirconia core material.

STATEMENT OF PROBLEM: With the development of various zirconia core shades, questions arise regarding the effect of the shaded zirconia on the translucency of ceramic crowns. PURPOSE: The purpose of this study was to investigate the translucency of the 3 Procera Zirconia shaded core materials. The hypothesis was that differences exist in the translucency of various shaded zirconia cores. MATERIAL AND METHODS: Disk-shaped (0.6 ± 0.01 × 12 mm) zirconia core (Procera Zirconia) specimens (n=90) were fabricated by the manufacturer using a CAD/CAM process. The disks were fabricated in 3 groups according to shade (light, medium, intense) (n=30). A spectrophotometer was used to measure contrast ratio (CR) which is indicative of translucency. One-way ANOVA was conducted to determine significant differences among the shades (α=.05). RESULTS: A significant difference in translucency between the light and intense shades (P=.030) and the medium and intense shades (P<.001) was observed. There was no significant difference between the light and medium shades (P=.15). CONCLUSIONS: Shaded zirconia is partially translucent. In addition, significant differences in translucency measurements were identified between specific shades.

A technique for indirect fabrication of a complete-arch, implant-supported, fixed provisional restoration from a radiographic template.

This article describes an alternative technique for the fabrication of a complete-arch, implant-supported, cement-retained, fixed provisional restoration. The definitive cast is fabricated from the surgical guide and the provisional restoration is fabricated indirectly from the radiographic guide. This technique is an easy and time-saving procedure to fabricate an interim prosthesis for immediate or delayed loading of implants.

Restoring implants in the esthetic zone after sculpting and capturing the periimplant tissues in rest position: a clinical report.

Obtaining an accurate representation of the soft tissue contours developed around an implant in the esthetic zone is crucial to the success of a restoration. The technique presented emphasizes "guiding" of the soft tissue by modifying a provisional restoration to obtain an emergence profile that appears natural and blends with the gingival contour of the adjacent teeth. The technique provides an accurate impression of the soft tissue through the intraoral use of autopolymerized acrylic resin supported by the impression coping and vinyl polylsiloxane impression material. The eventual restoration uses an esthetic zirconia custom abutment and an implant-supported single crown to fulfill the esthetic and functional expectations of the patient and the provider.