Purpose: The purpose of the present study was to determine the effect of prolonged holding time in firing schedule to the bonding strength of zirconia core to the veneered porcelain.

Materials and Methods: Twenty cubes of zirconia (Y-TZP, Cercon Base 47) were prepared and veneering ceramics (Vintage ZR) were layered. The bond strengths of zirconia core and layered porcelain with different holding time in firing schedule were evaluated by shearing test.

Results: The shear bond strengths of zirconia core and veneered porcelain with different holding time showed a statistically significant difference, 38.8±5.6 MPa (holding time; 1 minute) and 44.0±4.2 MPa (holding time; 21 minutes).

Conclusion: Prolonged holding time in firing schedule will improve the bond strength of zirconia core and veneered porcelain which reduce chipping failure of zirconia-based all ceramic restorations.

Purpose: The purpose of this study was to determine the influence of chlorine dioxide (ClO₂) on the physical properties of commercial denture base materials.

Materials and Methods: One heat-polymerized denture base acrylic resin and three metallic materials; gold-silver-palladium alloy, pure titanium, and cobalt-chromium (Co-Cr) alloy, were used in the study. Three types of commercial denture cleansers Polident (POL), Pika (PIK), and Kirari (KIR) were used. And ClO₂ was used at the following three concentrations: 1, 10, and 100 ppm. The flexural strength and flexural modulus of denture base resin were measured using universal testing machine. And the colour stability and surface morphology of dental metal materials were measured using colorimeter and scanning electron microscope.

Results: Flexural strength of the resin blocks was 70 MPa or more for all denture cleanser after 90 days of immersion. The flexural modulus was greater than 2,000 MPa specified in ISO standards for all test specimens. The specimens of Co-Cr immersed in ClO₂ exhibited high values after immersing for 90 days at 10 ppm and for all immersing times at 100 ppm concentration.

Conclusion: The following conclusions were drawn: 1) low concentrations of ClO₂ cause less discoloration than commercially available denture cleansers; and 2) low concentrations of ClO₂ are suitable for use as denture cleanser.

This article describes the clinical course of a composite restoration applied to secondary dental caries adjacent to a single restoration. After cavity preparation, the dentin surface was treated with citric acid and ferric chloride aqueous solution. A thione primer (V-Primer) and a silane primer (Porcelain Liner M) were separately applied to the metal and porcelain surfaces. An adhesive opaque resin (Super-Bond Opaque Ivory) and two layers of composite resins (Metafil Flo Opaque and Metafil C) were placed into the cavity. After an observation period of 11 years and 1 month, the restoration is functioning. The materials and bonding technique reported here are applicable as an option for a single-visit repair treatment.

Denture retainers and pontics made of gold alloy are connected with one-piece casting, soldering, or welding. This technical report describes a fundamental soldering technique for type 4 gold alloy. The procedure reported here is applicable to frameworks to be veneered with composite facing materials. Both the advantages and disadvantages of the procedure are discussed.

Purpose: This study evaluated the effect of sodium fluoride (NaF) solution and casein phosphopeptide-amorphous calcium phosphate (CPP-ACP) paste on the prevention of re-staining after in-office bleaching in vitro using an artificial discoloration tooth model.

Materials and Methods: Fifty extracted bovine teeth were stained in black tea and bleached by an in-office beaching material (TiON In Office). The teeth were divided into five groups, with 10 teeth in each group (n=10). They were treated with 2.0% or 0.2% NaF solution, CPP-ACP paste (MI Paste) or CPP-ACP paste containing fluoride (MI Paste Plus) for 1 hour. A group left without application served as control group. Then, each tooth was immersed into the black tea again. CIE L*a*b* of the stained surface of each tooth was measured by a dental color meter (Shade Eye NCC) after bleaching, at 1, 3, and 6 hours, and 1, 2, 3, and 7 days after immersion, and the changes in color were evaluated. Other specimens were prepared and the bleached and stained surfaces were observed by a scanning electron microscope (SEM) at each period.

Results: Color change increased gradually by immersion in the black tea in all groups. The color change in all experimental groups was less than that of control group. Repeated measure ANOVA showed that both the treatment solution and the immersion time significantly affected ΔE (p<0.05). A remarkable difference was not found in the SEM images among all groups at each period.

Conclusion: It was concluded that application of NaF and CPP-ACP would be able to decrease re-staining and discoloration of teeth after office-bleaching.