Modulus of rupture of the Procera All-Ceramic System

Color- and strength-graded zirconia: Strength, light transmission, and composition

STATEMENT OF PROBLEM

Natural teeth are graded in terms of translucency and strength. Graded zirconia materials are now available with a higher yttria content on the top or in the enamel zone to increase surface translucency and a lower yttria content on the bottom or in the dentin zone to increase strength. Such materials could provide multiple advantages over uniform materials and reduce the need for porcelain veneering in anterior artificial crowns; however, studies on the properties of these materials are lacking.

PURPOSE

The purpose of this in vitro study was to measure and compare the biaxial flexural strength, percentage light transmission, elemental content, and phase content of zones within and among color graded zirconia blocks and color- and strength-graded zirconia blocks.

MATERIAL AND METHODS

Disks of a color graded material (Katana STML) and a strength- and color-graded material (IPS e.max ZirCAD Prime) were fabricated (Zircom Furnace). Biaxial flexural strength was measured using a piston-on-3-ball test in a universal testing machine (n=10). Absolute light transmission was measured with a spectrophotometer. Elemental compositions were quantified for 3 zones in each of the 2 zirconia materials using X-ray fluorescence analysis. Zirconia phase fractions were quantified for 3 zones using X-ray diffraction analysis (XRD). Where appropriate, 2-way ANOVA, 1-way ANOVA, and Tukey multiple pairwise comparison testing were used to determine which of the 6 zones differed from one another (α=.05).

RESULTS

The color-graded zirconia exhibited gradients in light transmission and differences in phase content in the 3 zones measured. The color- and strength-graded zirconia exhibited gradients in light transmission, biaxial flexural strength, elemental composition, and phase content in the 3 zones measured. The bottom, dentin, or intaglio layer of a strength graded zirconia material was substantially stronger than all other zones of either material (P<.05). The top, enamel, zones of both materials possessed high light transmissibility (P<.05). The 2 materials differed with respect to biaxial strength (P<.001), light transmission (P<.02), elemental composition, and phase composition overall, as well as in most zone-by zone comparisons (P<.05). The performance and composition of the color graded material was consistent with it being a 5Y material throughout. The performance and composition of the color and strength graded material was consistent with it having a 3Y bottom zone and a 5Y top zone.

CONCLUSIONS

A strength-graded and color-graded zirconia material offers potential advantages in both strength and translucency.

The all-ceramic, inlay supported fixed partial denture. Part 3. Experimental approach for validating the finite element analysis

In a previous study, the authors used a finite element analysis (FEA) to evaluate the stresses developed during the loading of an all-ceramic, inlay supported fixed partial denture and compared it with the more traditional full crown supported prosthesis. To date there has been little research into correlating the responses of the numerical model against physical mechanical tests; such validation analysis is crucial if the results from the FEA are to be confidently relied upon. This study reports on the experimental methods used to compare with the FEA and thereby to validate the predictive fracture behaviour of the numerical model. This study also outlines the methods for manufacture and testing of the ceramic structure along with observations of the fracture tests. In addition the procedure used for developing the FEA model for the test system is outlined.

Bonding between titanium and dental porcelain: a systematic review

OBJECTIVES

The aims of this literature review are to provide answers to questions on how to improve bonding between titanium and dental porcelain and how to further implement, in clinical practice, ceramic-veneered titanium as an alternative to conventional metal-ceramic systems.

MATERIAL AND METHODS

A literature search of PubMed and also among referenced published scientific papers was performed and 24 fulfilled the search criteria, namely mentions of titanium, ceramics and bond strength. These papers were compiled for comparison and evaluated regarding the bond strength achieved with different methods.

RESULTS

The results strongly indicate that there are possibilities to improve both the present materials and methods for titanium-ceramic veneering.

CONCLUSIONS

The results indicate that present knowledge is sufficient to conclude that veneering titanium with low-fused porcelain for crowns and fixed partial dentures can be recommended for routine clinical use.

Flexural strength of a layered zirconia and porcelain dental all-ceramic system

STATEMENT OF PROBLEM

New processing techniques have facilitated the use of zirconia core materials in all-ceramic dental prostheses. Zirconia has many potential advantages compared to existing core materials; however, its performance when layered with porcelain has not been evaluated.

PURPOSE

This study investigated the strength of a wide variety of layered zirconia and porcelain beams to determine whether the inclusion of zirconia cores results in improved strength.

MATERIAL AND METHODS

Eight types of layered or simple zirconia and porcelain beams (n = 10), approximately fixed partial denture-size, were made of a tetragonal polycrystalline zirconium dioxide partially stabilized with yttria core (Lava System Frame) and a feldspathic dental porcelain (Lava Ceram veneer ceramic). Elastic moduli of the materials were measured using an acoustic method. Maximum force and modulus of rupture were determined using 3-point flexural testing and a universal testing machine. Descriptive statistical methods were used.

RESULTS

Beams with porcelain tensile surfaces recorded mean tensile strengths or moduli of rupture from 77 to 85 MPa, whereas beams with zirconia tensile surfaces recorded moduli of rupture almost an order of magnitude higher, 636 to 786 MPa. The elastic moduli of the porcelain and zirconia materials were 71 and 224 GPa, respectively. Crack propagation following initial tensile cracking often involved the porcelain-zirconia interface, as well as bulk porcelain and zirconia.

CONCLUSION

The layered zirconia-porcelain system tested recorded substantially higher moduli of rupture than have been previously reported for other layered all-ceramic systems.

The influence of surface topography of ceramic abutments on the attachment and proliferation of human oral fibroblasts

As different implant abutments are introduced to obtain a sufficient soft tissue barrier, the aim of this study was to determine the effect of three different surface modifications of densely sintered high-purity aluminium oxide on morphology, attachment and proliferation of human gingival fibroblasts. Fibroblasts were cultured on pressed aluminium oxide, milled, and then sintered to full density (1), on pressed, densely sintered (2), and on pressed, densely sintered and then polished surfaces (3). The different surfaces were analyzed using a confocal laser scanner, an atomic force microscope and a scanning electron microscope. The cell profile areas were measured using a semiautomatic interactive image analyzer and the figures were expressed as percent of attachment. The polished specimens had the smoothest surfaces and the roughest were the milled surfaces in terms of height deviation. No difference was found in the spacing between the peaks on the polished surfaces compared to the milled surfaces. Fibroblasts on the milled ceramic appeared to follow the direction of the fine irregularities on the surface. The analyses showed the polished surfaces had significantly higher percentages of initial cell attachment than the other surfaces (P < 0.05). After 3 days of cell culture, significantly more cells were attached to the milled and sintered surfaces than to the polished one, possibly indicating higher proliferation capacity on those types of surfaces.

Precision of fit and clinical evaluation of all-ceramic full restorations followed between 0.5 and 5 years

Currently CAD-CAM systems are rapidly gaining importance in dental practice as some of their products aim to combine aesthetics with strength and are free of metals. This study reports on the crown adaptation, marginal fit and clinical behaviour of 300 all-ceramic full coverage restorations (Procera, Gothenburg, Sweden) placed in one clinical centre and followed up to 5 years. The marginal fit and coping adaptation before and after luting was determined by direct measurement as well as after sectioning in a laboratory study. Three hundred all-ceram restorations were installed in 165 patients between 1994 and 1998. Before the end of 2000, patients were recalled to assess their restorations, using the California Dental Association quality evaluation index, their own appreciation, as well as the reaction towards the periodontium. The in vitro data revealed a mean marginal adaptation of 30 microm, before and after luting of the Al(2)0(3)-coping onto the tooth. However, at the deepest part of the chamfer, the distance increased to 135 microm. In the clinical study only one restoration fractured, while in 6% small porcelain infractions occurred. After polishing the latter, no persistent patient complaints remained. At the last recall visit 1.8% of the margins were rated unacceptable. Dentists rated 72 and 78% of the restorations excellent for surface, colour and anatomic form respectively. Eighty-seven per cent of the patients rated their restorations more than 7/10 on an ordered analogue scale for aesthetics as well as for function.

Contemporary materials and technologies for all-ceramic fixed partial dentures: A review of the literature

High-strength all-ceramic systems for fixed partial dentures (FPDs) are available for replacing a missing tooth. New core/framework materials have been developed and have evolved in the last decade. With the advancement of CAD/CAM technology, various fabrication techniques have been developed for fabricating improved, consistent, and predictable restorations in terms of strength, marginal fit, and esthetics and for managing core/framework materials that could not otherwise be managed. This article reviews the evolution and development of materials and technologies for all-ceramic FPDs through data published between 1966 and 2004 in the English language. Peer-reviewed articles were identified through a MEDLINE search and a hand search of relevant textbooks and annual publications. The available information suggests that clinical data on the success of these restorations are limited, and that the results of long-term clinical studies are critical to the assessment of these restorations to provide more specific guidelines for usage.

Contemporary all-ceramic fixed partial dentures: a review

High-strength all-ceramic systems for fixed partial dentures (FPDs)have become available for replacing missing teeth. New core materials have been developed and have evolved in the last decade,with yttrium tetragonal zirconia polycrystals (Y-TZP)-based materials being the most contemporary. With the emphasis on the use of computer-assisted design/computer assisted-manufacturing technology, various production techniques have been developed for enhancing the fabrication of consistent and predictable restorations in terms of strength, marginal fit, and esthetics. Although initial results are limited, results reported in scientific abstracts of ongoing clinical studies assessing the long-term success of three unit all-ceramic FPDs and anecdotal evidence published in peer reviewed articles on the use of Y-TZP-based restorative systems are encouraging. This article reviews the evolution and development of materials and technologies for all-ceramic FPDs.

Colorimetric Evaluation of the Influence of Five Different Restorative Materials on the Color of Veneered Densely Sintered Alumina

PURPOSE

Since the introduction of densely sintered alumina ceramic material in prosthetic dentistry for the fabrication of all-ceramic crowns, no scientific data have been presented on the color of these restorations in combination with different restorative materials. The purpose of this in vitro study was to evaluate the influence of five different restorative materials used for implant abutments or posts and cores on the color of veneered densely sintered alumina.

MATERIALS AND METHODS

Sixty discs, 0.6 mm in thickness and 10 mm in diameter, were made out of densely sintered alumina ceramic material (Procera, Nobel Biocare, Gothenburg, Sweden) and veneered using feldspathic porcelain (AllCeram, Ducera, Rosbach, Germany) for a total thickness of 2 mm. Ten of the discs were evaluated colorimetrically using the CIE, L*, a*, b* system (control group). In addition, 50 discs, 3 mm in thickness and identical diameter, were fabricated using the following restorative materials (five different materials used on 10 specimens each): (1) high-precious gold alloy, (2) aluminum-oxide ceramic material, (3) titanium metal alloy, (4) yttrium-stabilized zirconium dioxide ceramic material, and (5) glass-ceramic material. The 50 veneered densely sintered alumina specimens were bonded to the 50 restorative specimens using an autopolymerizing luting composite. L*, a*, b* color coordinates were measured 10 times for each veneered densely sintered alumina specimen. Color differences were calculated using the equation DeltaE = [(DeltaL*)2 + (Deltaa*)2 + (Deltab*)2] 1/2. DeltaE values correspond to differences between the control group and each of the five materials groups.

RESULTS

Mean color differences (DeltaE) and SDs for each group were as follows: DeltaE (1) = 1.42 +/- 0.5, DeltaE (2) = 1.53 +/- 0.5, DeltaE (3) = 1.55 +/- 0.4, DeltaE (4) = 1.95 +/- 0.5, DeltaE (5) = 1.23 +/- 0.3. All restorative materials induced changes to the densely sintered alumina color relative to the original color. One-way analysis of variance (ANOVA) tests showed statistically significant differences in DeltaE between the groups; however, the Student-Newman-Keuls test revealed that the only statistically significant difference was between groups 4 and 5. Color differences between the groups were not visually perceivable (DeltaE < 2).

CLINICAL SIGNIFICANCE

Within the limits of this in vitro study, veneered densely sintered alumina adhesively fixed with dentine-like cement, successfully masks the shade of different metal or ceramic restorative materials.

Validation of finite element analysis in dental ceramics research

STATEMENT OF PROBLEM

In vitro dental materials strength testing of ceramic restorations primarily has involved mechanical evaluations of simplified models. The finite element method (FEM) provides a mathematic analysis to predict strength values, but neither methodology is without the potential for errors.

PURPOSE

The purpose of this study was to demonstrate the advantages of combining mechanical testing results and FEM data to determine the strengths of a layered ceramic beam when the layered materials and positions are varied.

MATERIAL AND METHODS

Eight finite element 5 x 20 x 1-mm layered beams were modeled. Four of the modeled beams were of the same layered arrangements as physical specimens from a previously published study. The remaining 4 modeled beams provided intermediate layered arrangements not evaluated in the earlier study. A force in newtons was applied in the center of the top layer of each beam until fracture. finite element analysis was performed, and the data were compared with mechanical strength test results from the earlier study.

RESULTS

The FEM data of the 8 models demonstrated a linear decrease in load-bearing capacity as the layer thickness of the core material decreased and the layer thickness of the veneer material increased. The progressively decreasing values for the FEM beams were 170, 144, 140, 134, 72, 43, 34, and 27 N. The mean load-bearing capacities of 3 of the 4 mechanically tested beams compared favorably with the FEM data. The strength of the fourth mechanically tested beam, a veneer/core layered arrangement, was 110 N, which was lower than the corresponding FEM value (140 N). The 110 N value fell outside the decreasing linear progression for load, indicating that the FEM data were more accurate and reliable than the mechanical data.

CONCLUSION

No one perfect method exists for testing the strength of dental materials. The best approach is to use the results from both mechanical testing and finite element analysis, which together may provide more reliable and valid data than either method alone.

The safety and efficacy of anterior ceramic fixed partial dentures: A review of the literature

As a result of the successful use of ceramic crowns and patient demands for metal-free, tooth-colored restorations, ceramic systems for anterior fixed partial dentures (FPDs) have become available. Although numerous in vitro studies have been published, clinical studies that evaluate anterior ceramic FPDs are few and limited. This article reviews data on ceramic FPDs published between 1966 and 2001 in the English language. Peer-reviewed articles were identified through a MEDLINE search and a hand search of relevant textbooks and annual publications; abstracts were not considered for inclusion. The available data suggest that more clinical studies (preferably randomized clinical trials) that assess the long-term outcome of anterior ceramic FPDs are required to determine whether they can serve as a viable replacement for a maxillary anterior missing tooth and, at the same time, provide patients with a safe and effective restoration, oral health, and social comfort.

Anterior esthetic rehabilitation on teeth and dental implants optimized with Procera technology: a case report

With the latest developments of the Procera system, all-ceramic crowns have become an attractive solution to provide functional and esthetic rehabilitation on teeth and dental implants. The Procera AllCeram crown and Procera Abutment embrace the concept of computer-assisted design and computer-assisted machining (CAD/CAM) and can be used together for optimal esthetic result. The purpose of this case report was to illustrate the advantages of these new components for complex anterior rehabilitation. Three natural teeth and a Procera Abutment were restored using four Procera AllCeram crowns. Treatment planning and esthetic benefits are discussed.

All-ceramic surveyed crowns for removable partial denture abutments

All-ceramic restorations may have limitations when used in combinations with other treatment modalities. Removable partial denture (RPD) abutment crowns are typically shaped to provide guide planes, rest seats, and retentive areas. Porcelain-to-metal crowns are routinely fabricated with retentive contours in the veneering porcelain, but until recently, the contours of the other portions of the restoration were developed in metal. This article describes the fabrication of all-ceramic crowns for RPDs with rest seats and guide planes in densely sintered aluminum oxide and retentive areas in veneering porcelain. Within the limitations outlined, this procedure allows the practitioner to use all-ceramic crowns in situations previously reserved for metal or metal-ceramic restorations.

Procera all-ceramic crowns: a new approach to an old problem?

Increasing patient expectations regarding the appearance of restorations continue to test the ingenuity and skill of the dental team. To this end the quest for sufficiently strong, metal-free, all-ceramic restorations to function in all areas of the mouth continues apace. We report on a possible solution to this problem that uses computer-aided design/computer-aided milling (CAD/CAM) technology coupled with a novel, densely sintered, ceramic material. In this article we offer suggestions for case selection, preparation design, and luting procedures, and in addition illustrate these with a number of completed cases.

A procedure for a modified cylindric titanium abutment

In the restoration of a single anterior edentulous space with a dental implant, there are three transmucosal elements that could be used within the Nobel Biocare system: the CeraOne abutment, the Estheticone abutment with a nonrotating gold cylinder, and the CerAdapt abutment. This article describes a procedure to modify the CeraOne cylindric titanium abutment with titanium ceramics to achieve an anatomically shaped transmucosal element that does not show evidence of the metal through thin gingival tissue.