Zirconia-based All-ceramic Crowns Research Articles

Effect of substrate and cement on the final color of zirconia-based all-ceramic crowns.

To evaluate the influence of the substrate and the cement on the final color of ceramic crowns. Prosthetic crowns (framework + porcelain) were fabricated using two all-ceramic systems (YZ, 3mol% yttria-stabilized tetragonal zirconia; IZ, alumina-based zirconia-reinforced glass-infiltrated ceramic) and a metal-ceramic system (MC; n=8). Metal (M) and resin (R) were used as substrate abutments. For R substrate, crowns were evaluated as seated (R) and after cementation (R-C). CIELAB color coordinates were obtained using a dental spectrophotometer with D65 light illumination. CIELAB, CIEDE2000 (1:1:1) and CIEDE2000 (2:1:1) color difference metrics were used. Data were analyzed using 95% confidence intervals and compared to perceptibility (PT) and acceptability (AT) thresholds. The , ∆E00 (1 : 1 : 1), and ∆E00 (2 : 1 : 1) values of the restorative systems evaluated using different substrates (M.R) were similar to the AT values of each metric. When non-cemented and cemented crowns were evaluated (R.R-C), MC had color difference values at PT and below AT; while YZ and IZ showed similar values to AT, for and ∆E00 (1 : 1 : 1) metrics. The substrate and cement affected the final color of zirconia-based all-ceramic crowns, but the color differences corresponded to an acceptable match. As both substrate and cement influence the final color of multi-layered ceramic prosthesis, dentists and dental technicians should understand the optical properties of dental ceramics to reproduce the natural appearance of dental structures and maximize the chance for excellent color matches.

Fracture resistance of zirconia-based all-ceramic crowns after bur adjustment.

Is the use of a fine grit diamond bur before polishing the best approach to carry out occlusal adjustment of all-ceramic crowns?

Clinical evaluation of zirconia-based all-ceramic single crowns: an up to 12-year retrospective cohort study.

This study aims to investigate the incidence of clinical complications with tooth-supported zirconia-based all-ceramic single crowns and identify pertinent risk parameters. A retrospective cohort study (May 2004 to April 2016) utilizing clinical records of patients receiving yttrium-oxide-partially stabilized zirconia (Y-TZP)-based all-ceramic crowns placed at Tohoku University Hospital was performed. The length of time of treatment success (complication event-free) and restoration survival (including minor complication events and remaining clinically functional) were estimated using Kaplan-Meier analysis. Multilevel survival analysis was used to identify risk factors. One hundred thirty-seven crowns were evaluated (mean follow-up time, 7.0years). A total of 21 crowns experienced at least one complication with fracture of veneering ceramic being the most common (16 crowns). Estimated success and survival rates at 5years (96.9 and 98.5%, respectively) decreased at 10years to 62.1 and 67.2%, respectively. The risk of complications was significantly higher for molar crowns compared to anterior crowns (p<0.01). A significant association of complications with metal antagonist restorations was shown by univariate analysis (p<0.01). Given the study limitations, Y-TZP single crowns placed on anterior teeth demonstrated encouraging clinical results over a period of up to 10years. However, there is a substantial risk of complications with posterior teeth within 10years of restoration placement. Treatment with zirconia-based all-ceramic crowns for molar teeth with metal antagonist occlusion should be undertaken with caution.

Low-temperature Degradation of Zirconia-based All-ceramic Crowns Materials: A Mini Review and Outlook

Zirconia-based bioceramics have been widely applied in the field of prosthodontics owing to its desirable mechanical performance, biocompatibility and aesthetics. However, the low-temperature degradation (LTD) of tetragonal zirconia (ZrO2) under intraoral condition can lead to the deterioration of mechanical properties of ZrO2 dental crowns, which contribute to many clinical failures in long-term observations. The long-term tetragonal phase stability and mechanical properties of yttria-stabilized tetragonal zirconia polycrystal (Y-TZP) are influenced by grain size of ZrO2 crystals, distribution and properties of stabilizers, the humid environment, etc. However, it is still difficult to control the abovementioned factors at the same time. This review summarizes the major advances in researches dealing with LTD and clarifies the obstacles to stabilization of the tetragonal ZrO2. Furthermore, the suggestions on improving the LTD resistance of tetragonal ZrO2 are proposed, which is the catalyst to promote the long-term stability of ZrO2-based all-ceramic crowns.

Fracture resistance of single‐tooth implant‐supported zirconia‐based indirect composite‐layered molar restorations

This study evaluated the fracture resistance of single-tooth implant-supported zirconia-based indirect composite-layered molar restorations. Forty-four titanium abutments (GingiHue Post) were placed on dental implants (Osseotite Implant). Standardized single-tooth cement-retained implant-supported mandibular molar restorations were fabricated for each of four test groups (n = 11) as follows: porcelain-fused-to-metal crowns (PFM), zirconia-based all-ceramic crowns (ZAC), zirconia-based indirect composite-layered crowns primed with Estenia Opaque Primer for zirconia frameworks (ZIC-E), and zirconia-based indirect composite-layered crowns (ZIC). The crowns were luted with a glass-ionomer cement (Ketac Cem Easymix). Fracture resistance (N) was determined by force application of a perpendicular load to the crowns with a universal testing machine. One-way analysis of variance (ANOVA) and the Tukey's HSD test were used to assess differences in fracture resistance values (α = 0.05). Mean fracture resistances (SD) were 3.09 (0.22) kN, 3.11 (0.34) kN, 2.84 (0.21) kN, and 2.50 (0.36) kN for the PFM, ZAC, ZIC-E, and ZIC groups, respectively. Fracture resistance in the ZIC specimens was significantly lower (P < 0.044) than that in the other groups, which did not significantly differ. The fracture resistance of single-tooth implant-supported zirconia-based indirect composite-layered molar crowns primed with Estenia Opaque Primer for zirconia frameworks (ZIC-E) is comparable to that of porcelain-fused-to-metal (PFM) and zirconia-based all-ceramic (ZAC) restorations. Application of Estenia Opaque Primer to zirconia ceramic framework provides superior fracture resistance in implant-supported zirconia-based indirect composite-layered molar crowns.

Effect of the shades of background substructures on the overall color of zirconia-based all-ceramic crowns

PURPOSEThe objective of this study was to determine the effect of the color of a background substructure on the overall color of a zirconia-based all-ceramic crown.MATERIALS AND METHODSTwenty one posterior zirconia crowns were made for twenty subjects. Seven premolar crowns and six molar crowns were cemented onto abutments with metal post and core in the first and second group. In the third group, eight molar crowns were cemented onto abutments with a prefabricated post and composite core build-up. The color measurements of all-ceramic crowns were made before try-in, before and after cementation. A repeated measure ANOVA was used for a statistical analysis of a color change of all-ceramic crowns at α=.05. Twenty four zirconia specimens, with different core thicknesses (0.4-1 mm) were also prepared to obtain the contrast ratio of zirconia materials after veneering.RESULTSL*, a*, and b* values of all-ceramic crowns cemented either on a metal cast post and core or on a prefabricated post did not show significant changes (P>.05). However, the slight color changes of zirconia crowns were detected and represented by ΔE*ab values, ranging from 1.2 to 3.1. The contrast ratios of zirconia specimens were 0.92-0.95 after veneering.CONCLUSIONNo significant differences were observed between the L*, a*, and b* values of zirconia crowns cemented either on a metal cast post and core or a prefabricated post and composite core. However, the color of a background substructure could affect the overall color of posterior zirconia restorations with clinically recommended core thickness according to ΔE*ab values.

Retention of zirconia copings on zirconia implant abutments cemented with provisional luting agents

The purpose of this study is to measure and compare the retentive force of zirconia-based all-ceramic crowns cemented on zirconia abutments using five provisional luting agents. In addition, the effect of sandblasting and thermocycling on the retentive force was evaluated. Two hundred zirconia abutments and copings were fabricated (Procera system; Nobel Biocare) and divided into five groups. Hy bond temporary cement hard (Hard), Hy bond temporary cement soft (Soft), experimental temporary cement (New), Tempbond NE (Temp) and Freegenool temporary pack (Pack) were used according to the manufacturers' instructions. Each group was divided into two groups, one with and one without sandblasting. Furthermore, thermocycling up to 2000 cycles was conducted on half of each group. After 24 h and thermocycling, the retentive force was measured using a universal testing machine. The data were subjected to analysis of variance, and comparisons of the means were performed with a Games-Howell test at a level of 95%. As a result, Hard showed the highest retentive force, sandblasting was effective for improving the durability, and no effect of sandblasting was detected in the others. New showed stability of the retentive force even after thermocycling. The retentive force of Temp and Pack decreased significantly after thermocycling even with sandblasting. The retentive forces were different from the provisional cement and sandblasting, and Temp and Pack may not be appropriate for the retention of single-tooth zirconia abutments and coping restorations.

Porcelain-Fused-to-Metal Versus Zirconia-Based Ceramic Restorations, 2009

P orcelain-fused-to-metal (PFM) restorations have been the dominant option in esthetic crown and fixedprosthesis restorations for about 50 years. When these restorations were introduced, there was pessimism about their value and their potential for long-term service. However, both research and clinical observation since have shown that they serve well. Research regarding the longevity of service of PFM crowns and fixed prostheses shows variable but relatively impressive results, depending on the number of units replaced, period of observation and location of the study. The method of PFM failure is apparent to clinical practicing dentists. The most destructive type of failure is breakage of a large piece of ceramic from the metal substructure. If the piece is small, the restoration can be smoothed and continue to serve. If it is a larger piece of ceramic, the restoration must be replaced. Another challenge arises when, across time, the gingival tissues recede, the crown margins become visible and the restoration is easily identified by a lay observer as a “false tooth.” Additionally, superficial color placed on crowns and fixed prostheses may abrade or dissolve from the restorations, leaving them chalky and often a lighter color than when they were placed. Again, they appear to be unnatural. Nevertheless, from a purely functional standpoint, the PFM restorations continue to serve long after they have become relatively unesthetic, and if a chip breaks from the restoration, the underlying metal substructure protects the tooth structure until some other restoration can be placed. Dentists trust PFM restorations because of their clinically observable service longevity when compared with several previous generations of all-ceramic crowns. The current generation of zirconia-based all-ceramic crowns and fixed prostheses is becoming popular. I have observed in the continuing education (CE) courses I teach that many general dentists and prosthodontists have used these restorations to a significant degree. Jim Schuck, vice president of sales and marketing of Glidewell Laboratories, Newport Beach, Calif. (the largest laboratory in the United States), estimates that use of all-ceramic restorations is increasing (J. Schuck, oral communication, April 2009). He also estimated Porcelain-fused-to-metal versus zirconia-based ceramic restorations, 2009

A comparison of the fidelity of various zirconia-based all-ceramic crowns fabricated with CAD/CAM systems

A comparison of the fidelity of various zirconia-based all-ceramic crowns fabricated with CAD/CAM systems

Zirconia-Based All-Ceramic Crowns and Bridges:Three Case Reports

The search for a clinically viable all-ceramic bridge framework has been monotonous. Until recently, few materials appear to have the necessary physical and aesthetic properties. However, the development of yttrium tetragonal zirconia polycrystals, and its adoption for use in dentistry by CAD CAM technology, may hold promise as a crown and bridge framework, this being considered suitable for single and multiple units. However, to date, no long-term clinical studies have been reported. This paper describes three cases in which zirconia frameworks were used in crowns and bridges. For the patient wishing to receive a non-metal crown or bridge, novel zirconia-based systems hold promise.