Surface hardness and pressing accuracy of reused IPS empress 2 / 대한치과보철학회지

STATEMENT OF PROBLEM: IPS Empress2 system was developed and used in prosthodontic treatment, but the cost of ingot is expensive for wide application. PURPOSE: This study was to investigate the possibility on recycling of IPS Empress 2 ceramic for wide application of IPS Empress 2 ceramic in prosthodontic treatment. MATERIAL AND METHOD: 1st, 2nd and 3rd pressed disc-shaped(10x1.5mm) IPS Empress 2 specimens were made with IPS Empress ingot(200, Ivoclar, Liechtenstein) and pressing furnace(IPS Empress EP 500, Ivoclar, Liechtenstein). Vicker's surface hardness and fracture toughness, acid resistance, and pressing accuracy of IPS Empress 2 ceramic were measured and analyzed. Surface hardness was measured by microhardness tester(MTX 70, Matsuzawa, Japan). before and after surface treatment with 0.5% hydrofluoric acid and carbonic acid(Coca cola) for evaluation of acid resistance. RESULTS: The surface hardness of 1st pressed specimen was the higher(5.11 GPa) than those of 2nd pressed( 4.89 GPa) and 3rd pressed specimen(4.86 GPa). and the fracture toughness of 1st pressed (1.58 MPam1/2)and 2nd pressed specimen(1.51 MPam1/2) were higher than that of 3rd pressed specimen(1.39 MPam1/2). The changes of surface hardness of 1st, 2nd, and 3rd pressed specimens after treatment with fluoric acid were 0.17, 0.06, 0.05(GPa) respectively, and those of 1st, 2nd, and 3rd pressed specimens after treatment with carbonic acid were 0.07, 0.00, 0.05(MPa) respectively. The pressing accuracy of 1st, 2nd and 3rd specimen were 77.22%, 85.681%, and 75.05%. The pressing accuracy of 2nd pressed specimen was higher than that of the 3rd specimen. CONCLUSION: The changes of physical properties according to recycling of IPS Empress 2 from this study were insignificant. Therefore the possibility of recycling of IPS Empress 2 can be suggested from the results.

Effect Of Dentin Desensitizers On Shear Bond Strength Of Resin Cements / 대한치과보철학회지

The purpose of this study was to investigate the effects of desensitizer on shear bond strength of adhesive resin cements for all ceramic crown. For this study,Gluma desensitizer(R)(Heraeus Kulzer, Germany)and MS Coat(R)(Sun medical, Japan)were used as desensitizer,and Bistite II(R) resin cement(Tokuyama, Japan)and VariolinkII(R) resin cement(Ivoclar, Liechtenstein) were used. IPS Empress ceramics were bonded to dentin surfaces after application of desensitizer and shear bond strength of specimens were measured using UTM(Zwick 1456 41, Zwick, Germany)at a crosshead speed of 1mm/min. The obtained results were as follows: 1. The shear bond strength of both resin cements were not affected by Gluma desensitizer(R) containing HEMA. 2. The shear bond strength of Bistite II(R) resin cement was significantly decreased by MS Coat(R). 3. The failure mode in MS Coat(R)-Bistite II(R) group was mainly adhesive type between dentin and resin cement, but that of Gluma desensitizer(R)-Variolink II(R) group was mainly mixed type, combined adhesive failures between dentin and resin cement or porcelain and resin cement.

A STUDY ON THE STAIN RESISTANCE OF DENTAL CERAMICS FOR ALL CERAMIC CROWN / 대한치과보철학회지

Simulation of naturally appearing enamel in fixed prosthodontics could be achieved with all ceramics. The purpose of this study was to investigate the stain resistance of 4 different all ceramics materials (In-ceram, IPS Empress, Celay, Vintage). Forty specimens were prepared using manifacture's instruction and the samples were divided into two groups. The specimens for one group were glazing and those for other group wee ground to remove the glazing layer. All specimens were immersed in methylene-blue for 24hours. The color values for each specimen was measured with colorimeter (Mode Tc-6Fx, Tokyo Denshoku Co.) prior to and after immersion in methylene-blue. The following conclusions were drawn from this study. 1. The stain resistance of glazing ceramics was higher than that of unglazing ceramics. 2. The changes of E* and L* values were revealed in Vintage and unglazing Celay. 3. The changes of a* values were revealed in unglazing vintage, Celay, In-cream. 4. The changes of b* value were revealed in Vintage, IPS Empress and unglazing Celay.