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PubMed2005

All-ceramic full-coverage restorations: concepts and guidelines for material selection.

UNLABELLED: High-strength, all-ceramic systems for full-coverage restorations use all-ceramic core materials for the fabrication and processing of infrastructures (eg, crown copings, fixed partial denture frameworks) that are then veneered with porcelain. Not all of these all-ceramic core materials are alike, and as such, they present with different properties that may affect their indications and limitations, the laboratory procedures used for their processing, and their clinical handling. This article reviews their clinically relevant properties and discusses the effect of these characteristics on their indications and recommended clinical procedures. LEARNING OBJECTIVES: This article provides an overview of the clinically relevant properties of high-strength, all-ceramic systems used for aesthetic restorative dentistry. Upon reading this article, the reader should: Be able to differentiate among the principal all-ceramic material systems. Understand the clinical indications for contemporary, high-strength ceramics.

Aluminum Oxide↗
PubMed2006

Study of yttrium containing bioactive glasses behaviour in simulated body fluid.

The influence of yttrium oxide on the bioactivity of glasses in the system SiO(2)-Na(2)O-P(2)O(5)-CaO-B(2)O(3)-K(2)O-MgO was studied in a simulated body fluid (SBF). Two series of glasses with different bioactivity were investigated. The reaction layers formed on the surface of the exposed glasses were evaluated by means of back scattered electron imaging of scanning electron microscopy equipped with energy dispersive X-ray analysis (BEI-SEM/EDXA). The concentration of Y, Ca and P released from the glasses into SBF, during 21 days was determined using inductively coupled plasma-emission spectroscopy ICP-AES and inductively coupled plasma-mass spectroscopy ICP-MS. Introducing yttrium in the selected bioactive glass tended to diminish the bioactivity of the glasses. The thickness of the calcium phosphate layer decreased with increasing yttrium oxide content. The same effect was also observed when yttrium oxide partially replaced only calcium, magnesium and phosphorous oxide in the precursor glass. The data show that we can produce bioactive glasses with yttrium oxide as a component. By suitable tailoring of the rest of the glasses the yttrium effect on the glass behavior in SBF should be possible to control and thus produce yttrium containing glasses with desired bioactivity.

Biocompatible Materials↗
PubMedDate not supplied

Finite element analysis studies of an all-ceramic crown on a first premolar.

PURPOSE: This study examined the effects of using four different core-ceramic materials on the stresses that developed in a single all-ceramic first premolar crown. MATERIALS AND METHODS: This was done by analyzing models constructed in an axisymmetric fashion with finite element analyses. The model had a 600-N vertical load applied uniformly over a circular area on top of the crown. Particular emphasis was placed on the tensile stresses that developed. RESULTS: For this particular type of model and loading configuration, radial tensile stresses were predominant in magnitude. Peak hoop and axial tensile stresses were approximately 80% and 2% of this value, respectively. The peak radial and hoop tensile stresses were located on the inside of the coping and scaled with the elastic modulus of the coping. For the axial component, the peak was located in the veneer ceramic on its outermost perimeter. CONCLUSION: Under normal loading, a near-uniform tensile stress field developed within the coping, directly beneath the contact area. The magnitude of this stress for realistic bite forces using current design recommendations was significantly lower than the fracture strength of the four ceramic materials investigated. The stresses developed within the porcelain were in all instances well below typical strength values.

Aluminum Oxide↗
PubMed2005

Evaluation of different bonded investments for dental titanium casting.

The properties of several different investments were investigated including phosphate bonded, magnesia bonded, and alumina cement investments. Measurements included the setting expansion, thermal expansion, and compressive strength of investments, as well as the tensile strength, elongation, Vickers hardness (VHN) and surface roughness of titanium castings. For phosphate bonded investment, the setting expansion after being mixed with its own mixing solution was 2.10%, which was larger than the other investments; the thermal expansion was -0.25% at 200 degrees C, the compressive strength 14 and 5 MPa after heating. For titanium cast in phosphate bonded investment, the hardness on its top surface was 655 Hv, the tensile strength was 379 MPa, the elongation was 19.4%, and the surface roughness was 2.29 microm. Although the thermal expansion of phosphate bonded investment is small, the setting expansion is large enough to compensate for the shrinkage of titanium castings. As its thermal expansion at T > or = 600 degrees C was constant and its heating-cooling cycle was almost reversible, these two properties can reduce the thermal shock and thus avoid cracking of the investment.

Aluminum Oxide↗
PubMed1999

Antibacterial activity of resin composites with silver-containing materials.

Resin composites with antibacterial activity may be useful to decrease the frequency of secondary caries around restorations. The purposes of this study were to investigate the antibacterial activity of light-activated resin composites incorporating one of three silver-containing materials and to evaluate their long-term inhibitory effect against Streptococcus mutans The three types of silver-containing materials, Novaron (N), Amenitop (AM), and AIS, were incorporated into TEGDMA-UDMA-based light-activated resin composites, and the antibacterial activities, mechanical properties and release of silver ions were examined. Minimum inhibitory concentrations in suspensions of N, AM, and AIS against S. mutans were 1.1, 1.2, and 23.0 mg/ml, respectively. Resin composites incorporating 5 wt% of Novaron (N-5) and 7 wt% of Amenitop (AM-7) inhibited the growth of S. mutans after immersion in water for 3 months, whereas the resin composite incorporating 10 wt% of AIS did not. No significant difference in either compressive or flexural strength was observed between the control and N-5 composites after 1 d and 3 months storage in water. However, for AM-5 composite, there was a significant difference in both strength parameters between the two immersion periods. There was no or extremely little release of silver ions from the N-5 and AM-5 composites after 1 d or 3 months immersion in water. These results indicated that a light-activated resin composite incorporating silver-containing materials such as Novaron may be clinically useful due to its long-term inhibitory effect against S. mutans and favorable mechanical properties.

Aluminum Oxide↗
PubMed2002

Relative translucency of six all-ceramic systems. Part I: core materials.

STATEMENT OF PROBLEM: All-ceramic restorations have been advocated for superior esthetics. Various materials have been used to improve ceramic core strength, but it is unclear whether they affect the opacity of all-ceramic systems. PURPOSE: This study compared the translucency of 6 all-ceramic system core materials at clinically appropriate thicknesses. MATERIALS AND METHODS: Disc specimens 13 mm in diameter and 0.49 +/- 0.01 mm in thickness were fabricated from the following materials (n = 5 per group): IPS Empress dentin, IPS Empress 2 dentin, In-Ceram Alumina core, In-Ceram Spinell core, In-Ceram Zirconia core, and Procera AllCeram core. Empress and Empress 2 dentin specimens also were fabricated and tested at a thickness of 0.77 +/- 0.02 mm (the manufacturer's recommended core thickness is 0.8 mm). A high-noble metal-ceramic alloy (Porc. 52 SF) served as the control, and Vitadur Alpha opaque dentin was used as a standard. Sample reflectance (ratio of the intensity of reflected light to that of the incident light) was measured with an integrating sphere attached to a spectrophotometer across the visible spectrum (380 to 700 nm); 0-degree illumination and diffuse viewing geometry were used. Contrast ratios were calculated from the luminous reflectance (Y) of the specimens with a black (Yb) and a white (Yw) backing to give Yb/Yw with CIE illuminant D65 and a 2-degree observer function (0.0 = transparent, 1.0 = opaque). One-way analysis of variance and Tukey's multiple-comparison test were used to analyze the data (P<.05). RESULTS: Contrast ratios in order of most translucent to most opaque were as follows: Vitadur Alpha 0.60 +/- 0.03, Empress (0.5 mm) 0.64 +/- 0.01, In-Ceram Spinell 0.67 +/- 0.02, Empress 2 (0.5 mm) 0.68 +/- 0.02, Empress (0.8 mm) 0.72 +/- 0.01, Procera 0.72 +/- 0.01, Empress 2 (0.8 mm) 0.74 +/- 0.01, In-Ceram Alumina 0.87 +/- 0.01, In-Ceram Zirconia 1.00 +/- 0.01, and 52 SF alloy 1.00 +/- 0.00. CONCLUSION: Within the limitations of this study, there was a range of ceramic core translucency at clinically relevant core thicknesses. In order of decreasing translucency, the ranges were Vitadur Alpha dentin (standard) > In-Ceram Spinell > Empress, Procera, Empress 2 > In-Ceram Alumina > In-Ceram Zirconia, 52 SF alloy.

Aluminum Oxide↗
PubMed1994

Intracanal isolating barriers as they relate to bleaching.

Four restorative materials were evaluated for effectiveness as intracanal isolating barriers to prevent leakage of bleaching agents into the coronal part of the root canal. Fifty-five teeth were stained in vitro, instrumented, and filled with gutta-percha. In the experimental groups, gutta-percha was removed 2 mm apical to the labial cementoenamel junction, and an intracanal isolating barrier (zinc oxide-eugenol, IRM, Ketac-Cem, or Scotchbond Multipurpose) was placed even with the facial and proximal cementoenamel junction areas in a sloped manner. All were bleached with a thermocatalytic and walking bleach technique until the crown was one shade lighter than the original shade. The roots were then examined for the occurrence of bleaching. The results indicate that none of the materials used was a totally effective intracanal isolating barrier. Although a significant difference was found when IRM was compared with Ketac-Cem or Scotchbond Multipurpose (p < 0.05), all restorative materials evaluated showed a high incidence of leakage as demonstrated by bleached roots. There was no significant difference between zinc oxide-eugenol and IRM.

Chi-Square Distribution↗
PubMed2004

Shear bond strength of different types of luting cements to an aluminum oxide-reinforced glass ceramic core material.

OBJECTIVE: The aim of this study was to find the optimal choice of luting cement to Synthoceram, an aluminum oxide-reinforced glass ceramic material. The bond strength of five different commercial luting cements to the ceramic material was evaluated. The effect of surface treatments, etching, sandblasting, silanizing, and combinations of these treatments was also investigated. METHODS: Shear bond strength tests were performed using the ceramic material as substrate with each of the luting cements. Cements rods were prepared on pre-treated ceramic surfaces. The shear bond strength was determined 24 h after cementation. The effect of surface treatments: etching, sandblasting, and sandblasting followed by etching, respectively, on the morphology of the material, was investigated with SEM. RESULTS: The shear bond strength increases significantly from Ketac Cem, Rely X Luting, Fuji Plus, Panavia F to Xeno Cem. The surface treatments etching and/or sandblasting followed by silanization generally provide the highest bond strength values. SIGNIFICANCE: Based on the results of this study, the use of resin composite based cements is preferred for cementation of an all-ceramic restoration with an aluminum oxide-reinforced glass ceramic base. Surface treatment of etching and/or sandblasting followed by silanization is recommended.

Aluminum Oxide↗
PubMed1999

Contact damage resistance and strength degradation of glass-infiltrated alumina and spinel ceramics.

All-ceramic crowns are coming into widespread use because of their superior esthetics and chemical inertness. This study examines the hypothesis that glass-infiltrated alumina and spinel core ceramics are resistant to damage accumulation and strength degradation under representative oral contact conditions. Accordingly, Hertzian indentation testing with hard spheres is used to evaluate damage accumulation in alumina and spinel ceramics with different pre-form grain morphologies and porosities. Indentation stress-strain curves measured on fully infiltrated materials reveal a marked insensitivity to the starting pre-form state. The glass phase is shown to play a vital role in providing mechanical rigidity and strength to the ceramic structures. All the infiltrated ceramics show subsurface cone fracture and quasi-plastic deformation above critical loads P(C) (cracking) and P(Y) (yield), depending on sphere radius, with P(Y) < P(C). Strength degradation from accumulation of damage in Hertzian contacts above these critical loads is conspicuously small, suggesting that the infiltrated materials should be highly damage-tolerant to the "blunt" contacts encountered during mastication. Failure in the strength tests originates from either cone cracks ("brittle mode") or yield zones ("quasi-plastic mode"), with the brittle mode more dominant in the spinels and the quasi-plastic mode more dominant in the aluminas. Multi-cycle contacts at lower loads, but still above loads typical of oral function, are found to be innocuous up to 10(5) cycles in air and water, although contacts at 10(6) cycles in water do cause significant strength degradation. By contrast, contacts with Vickers indenters produce substantial strength losses at low loads, suggesting that the mechanical integrity of these materials may be compromised by inadvertent "sharp" contacts.

Aluminum Oxide↗
PubMedDate not supplied

A comparison of all-ceramic restorative systems: Part 2.

Overall, any of these systems can provide well-fitting, natural looking restorations as long as care is taken during the preparation and fabrication procedures. A key to successful use of all-ceramic materials is proper selection based on the clinical conditions involved in specific restorative procedures (see table). All systems have limitations on their use and when we try to stretch those limits, success rates may fall drastically. High stress areas should shift selection to high strength, clinically documented materials. Low stress areas requiring high translucency may be restored successfully using the lower strength castable glasses. Intermediate areas may shift selection to higher strength yet still translucent materials such as In-Ceram Spinell or Empress 2. Posterior regions might best be addressed with the use of In-Ceram Alumina or Procera. The case of posterior bridges would lock the selection into In-Ceram Zirconia. Finally, it is important for each of us to continually educate ourselves and to examine the evidence in order to make an informed decision and maximize clinical success.

Aluminum Oxide↗
PubMed2002

Relative translucency of six all-ceramic systems. Part II: core and veneer materials.

UNLABELLED: STATEMENT OF PROBLEM All-ceramic core materials with various strengthening compositions have a range of translucencies. It is unknown whether translucency differs when all-ceramic materials are fabricated similarly to the clinical restoration with a veneered core material. PURPOSE: This study compared the translucency of 6 all-ceramic materials veneered and glazed at clinically appropriate thicknesses. MATERIALS AND METHODS: Core specimens (n = 5 per group) of Empress dentin, Empress 2 dentin, In-Ceram Alumina, In-Ceram Spinell, In-Ceram Zirconia, and Procera AllCeram were fabricated as described in Part I of this study and veneered with their corresponding dentin porcelain to a final thickness of 1.47 +/- 0.01 mm. These specimens were compared with veneered Vitadur Alpha opaque dentin (as a standard), a clear glass disc (positive control), and a high-noble metal-ceramic alloy (Porc. 52 SF) veneered with Vitadur Omega dentin (negative control). Specimen reflectance was measured with an integrating sphere attached to a spectrophotometer across the visible spectrum (380 to 700 nm); 0-degree illumination and diffuse viewing geometry were used. Measurements were repeated after a glazing cycle. Contrast ratios were calculated from the luminous reflectance (Y) of the specimens with a black (Yb) and a white backing (Yw) to give Yb/Yw with CIE illuminant D65 and a 2-degree observer function (0.0 = transparent, 1.0 = opaque). One-way analysis of variance and Tukey's multiple-comparison test were used to analyze the data (P<.05). RESULTS: Significant differences in contrast ratios were found among the ceramic systems tested when they were veneered (P<.0001) and after the glazing cycle (P<.0001). Significant changes in contrast ratios (P<.0001) also were identified when the veneered specimens were glazed. CONCLUSION: Within the limitations of this study, a range of translucency was identified in the veneered all-ceramic systems tested. Such variability may affect their ability to match natural teeth. The glazing cycle resulted in decreased opacity for all test materials except the completely opaque In-Ceram Zirconia and metal-ceramic specimens.

Aluminum Oxide↗
PubMedDate not supplied

An up to 5-year clinical evaluation of posterior in-ceram CAD/CAM core crowns.

PURPOSE: This study evaluated the clinical performance of posterior CAD/CAM-generated In-Ceram Alumina and In-Ceram Spinell core crowns. MATERIALS AND METHODS: Nineteen In-Ceram Spinell core crowns (four premolars and 15 molars) and 24 In-Ceram Alumina core crowns (two premolars and 22 molars) in 21 patients were examined using modified USPHS criteria at baseline and after a mean service time of 39 +/- 11 months. The crown copings were machined from Vitablocs In-Ceram Alumina and Vitablocs In-Ceram Spinell using the Cerec 2 CAD/CAM system. RESULTS: Two molar In-Ceram Alumina core crowns fractured after respective service times of 14 and 17 months in the same patient. The Kaplan-Meier survival rate regarding fracture of the ceramic was 92% for In-Ceram Alumina and 100% for In-Ceram Spinell. At the follow-up examination, 80% alpha ratings and 18% beta ratings for In-Ceram Alumina core crowns and 84% alpha ratings and 15% beta ratings for In-Ceram Spinell core crowns were recorded. CONCLUSION: Despite the two fractures, the clinical quality of CAD/CAM-generated In-Ceram Alumina and In-Ceram Spinell posterior crowns was excellent. Within the limitations of this study, both types of crowns appeared to be feasible.

Adult↗
PubMed2006

Kinetic model of energy transfer processes between low-coordinated ions on MgO by photoluminescence decay measurements.

Photoluminescence decay studies of emitting species on MgO nanocubes at room temperature provide evidence of three surface species characterized by an excitation and emission wavelength couple {lambda(exc);lambda(em)}. Species A corresponds to {lambda(exc)=240 nm; lambda(em)=380 nm}, whereas the couple {lambda(exc)=280 nm; lambda(em)=470 nm} is assigned to two species: B and B', the former is involved in energy transfer from excited state A* and the latter in direct emission from excited state B'*. A simple model for energy transfer from species A* to B is proposed. The numerical resolution of equations corresponding to this model is in good agreement with experimental data. This method quantifies the kinetics of intrinsic emission and energy transfer processes. Lifetime values indicate that phosphorescence is taking place, and species A, B and B' are identified as edge O(2-) (4 C), corner O(2-) (3 C) and kink O(2-) (3 C) oxide ions respectively.

Energy Transfer↗