Effects of Particle Abrasion Media and Pressure on Flexural Strength and Bond Strength of Zirconia.

OBJECTIVES: To compare the effects of particle abrasion medium and pressure on shear bond strength and biaxial flexural strength of three generations of zirconia (Lava Frame, Lava Plus, and Lava Esthetic) with the goal of optimizing the bond to zirconia. METHODS: 280 discs (14 mm diameter; 1 mm thickness) of each zirconia were milled and sintered. Specimens of each material were randomly distributed into 14 groups (n=20); half were tested for shear bond strength and half were tested for biaxial flexural strength. The specimens were particle abraded on one surface by 2 different media (50 µm alumina particles or 50 µm glass beads) for 10 seconds at three different pressures (15, 30, and 45 psi or 0.1, 0.2, 0.3 MPa). Untreated specimens served as positive control. A tube (1.50 mm diameter) filled with dual cured resin cement (Panavia SA) was placed onto the surface and light cured. Specimens were stored in water (37°C for 24 hours) and shear bond strength was measured in a universal testing machine (Instron). Biaxial flexural strength of each specimen was measured according to ISO 6872. Shear bond strength and biaxial flexural strength were compared individually with a 2-way analysis of variance (ANOVA) for factors surface treatment and zirconia composition. RESULTS: Significant differences were seen between surface treatments (p<0.01), zirconia composition (p<0.01) and their interaction (p<0.01) for both bond strength and flexural strength. With alumina particle abrasion, higher pressure produced higher bonds for Lava Frame and Lava Plus zirconia while the bond of Lava Esthetic declined with increased pressure. Higher pressure (>0.2 MPa or 30 psi) with alumina decreased biaxial flexural strength with Lava Esthetic zirconia. CONCLUSIONS: Particle abrasion with alumina produced a significantly better combination of bond strength while maintaining biaxial strength of three zirconia materials than particle abrasion with glass beads. The bond strength also depended upon the pressure of particle abrasion and the generation of zirconia used.

Survival of In-Ceram crowns in a private practice: a prospective clinical trial.

STATEMENT OF PROBLEM: Prior reports on some all-ceramic crown systems have indicated high failure rates through fracture. PURPOSE: This study prospectively evaluated the survival of infiltrated alumina crowns (In-Ceram) in a private practice. MATERIAL AND METHODS: All the In-Ceram crowns placed in a prosthodontic practice since its introduction in 1990 were serially included. Patients were recalled at 6 monthly intervals. Those who did not attend in the previous 6 months were contacted by telephone and a series of answers to standardized questions recorded. The few patients who were lost to follow-up or who died were removed from the study from the time of last contact. RESULTS: A total of 408 crowns in 107 patients were followed for periods from 1 to 86 months. As the 3-year data combined a meaningful period of service with a large sample size, these data were focused on. The 3-year survival rate was 96% for a sample size of 223. Three-year data indicated that core fracture and porcelain fracture occurred at rates of approximately 0.6% and 0.3% per year, respectively. Otherwise sound restorations were removed at a rate of approximately 0.3% per year for esthetic, endodontic, or prosthetic reasons. Anterior crowns tended to have a slightly higher 3-year survival rate (98%) than premolars or molars (94%). CONCLUSION: Clinical failure rate of In-Ceram crowns was low. Crowns were lost because of core fracture, porcelain fracture, and removal without failure. Failure tended to be more common for molar and premolar crowns than for anterior crowns.

Glass-infiltrated zirconia/alumina-based ceramic for crowns and fixed partial dentures.

The increased demand for metal-free restorative alternatives has resulted in the proliferation of all-ceramic systems. While these materials can predictably achieve aesthetic results in the anterior, they have traditionally been contraindicated for posterior applications due to the greater stresses present in the region. This article discusses a zirconia/alumina-based ceramic system that has been developed to expand the alternatives for the aesthetic restoration of the dentition. Material properties and considerations for its use in crown restorations, fixed partial dentures, and custom implant abutments are similarly addressed.

The skeleton buildup technique: a systematic approach to the three-dimensional control of shade and shape.

Due to the limitations of current shade-matching systems, shade communication has proven inadequate. Techniques for the fabrication of porcelain crowns that match the natural definition must address numerous factors. While all-ceramic restorations are indicated for the rehabilitation of the anterior dentition, these modalities are problematic in the restoration of teeth with discolored substrates. This article presents a systematic procedure for the three-dimensional fabrication of porcelain restorations. Techniques for building porcelain and altering the translucency of ceramic cores are also presented.

All-ceramic alternatives to conventional metal-ceramic restorations.

In the search for the ultimate esthetic restorative material, many new all-ceramic systems have been introduced to the market. One such system, In-Ceram, is primarily crystalline in nature, whereas all other forms of ceramics used in dentistry consist primarily of a glass matrix with a crystalline phase as a filler. In-Cream can be used to make all-ceramic crowns and fixed partial denture frameworks. Three forms of In-Ceram, based on alumina, spinal (a mixture of alumina and magnesia), or zirconia, make it possible to fabricate frameworks of various translucencies by using different processing techniques. This article discusses clinical indications and contraindications for the use of In-Ceram Alumina and In-Ceram Spinell all-ceramic restorations. Particular attention is given to cement considerations using several clinical examples.

Using copy milling technology in restorative dentistry.

A technique for the fabrication of copy milled ceramic restorations has been presented. Both direct and indirect fabrication techniques of inlays, onlays, veneers, and crowns are possible. A copy milling machine can mill accurately fitting restorations with a marginal gap of 50 microns. The machine uses premanufactured porcelain blanks, which have improved physical properties over conventional porcelains used in standard techniques. Recently, the ability to mill In-Ceram crowns from presintered alumina blocks and Spinell crowns from alumina/magnesia blocks has been added to the system. The copings are veneered with aluminous porcelain as in the conventional In-Ceram technique.