Effect of etching time on shear bond strength of resin cements to reinforced all-ceramic crowns / 대한치과보철학회지

PURPOSE: The purpose of this study was to evaluate the effects of etching time on shear bond strength of four resin cements to IPS Empress 2 ceramic. MATERIAL AND METHODS: Forty rectangular shape ceramic specimens (10x15x3.5mm size) were used for this study. The ceramic specimens divided into four groups and were etched with 10% hydrofluoric acid for 0, 10, 30, 60, 180, 300, 420, 600, and 900 seconds respectively. Etched surfaces of ceramic specimens were coated with ceramic adhesive system and bonded with four resin cement (Variolink II, Panavia F, Panavia 21, Super-Bond C & B) using acrylic glass tube. All cemented specimens were tested under shear loading untill fracture on universal testing machine at a crosshead speed 1mm/min; the maximum load at fracture (kg) was recored. Shear bond strengh data were analyzed with oneway analysis of variance and Tukey HSD tests (p<.05). Etched ceramic surfaces (0-, 60-, 300-, and 600-seconds etching period) and fracture surfaces after shear testing were examined mophologically using scanning electron microscopy. RESULTS: Ceramic surface treatment with 10% hydrofluoric acid improved the bond strength of three resin cement except for Super-Bond C&B cement. Variolink II (41.0+/-2.4 MPa) resin cement at 300-seconds etching time showed ststistically higher shear bond strength than the other resin cements (Panavia F: 28.3+/-2.3 MPa, Panavia 21: 21.5+/-2.2 MPa, Super-Bond C&B: 16.7+/-1.6 MPa). Ceramic surface etched with 10% hydrofluoric acid for 300 seconds showed more retentive surface texture. CONCLUSION: Within the limitation of this study, Variolink II resin cement are suitable for cementation of Empress 2 all-ceramic restorations and etching with 10% hydrofluoric acid for 180 to 300 seconds is required to enhance the bond strength.

Influence of several posts and IPS-Empress ingot thickness on the final shade of all-ceramic crowns / 대한치과보철학회지

STATEMENT OF PROBLEM: All-ceramic restorations have been advocated for superior esthetics. Various post and core systems have been used to improve the strength of damaged teeth, but it is unclear whether they affect the final shade of finished all-ceramic restorations. PURPOSE: The influence of different types of post and core systems on light transmission through all-ceramic crowns was assessed by spectrophotometric analysis. Also the masking effect of different thickness of ceramic ingot was evaluated. MATERIAL AND METHODS: Forty-five sample disks(15mm in diameter) at several thickness(1.0, 1.5, 2.0mm) and value(shade 100, 200, 300) were made in heat pressed ceramic(IPSEmpress). Background specimens simulating gold-alloy cast posts(Type III casting gold alloy), metal posts(Ni-Cr casting alloy) and ceramic posts(CosmoPost) were fabricated. Resin composite(Z250, A3 shade) was used as a tooth substrate reference. For each combination, the change in color was measured with a spectrophotometer. Readings were performed for 2 conditions: (1) ability of ceramic to mask the core in relation to its thickness(1.0, 1.5, or 2.0mm); (2) influence of post and core types on the final color of the ceramic. Data were recorded according to the CIE L*a*b* systems and color difference(delta E) was calculated. RESULTS: 100 shade ingot: when ceramic thickness was 1.0mm, delta E value for ceramic post larger than 1 but delta E value for metal and gold post was larger than 2. For ceramic thickness of 1.5mm, only delta E value for metal was larger than 2, and the other samples' delta E value was smaller than 2. For ceramic thickness of 2.0mm, E values for all specimens was smaller than 2. 200 shade ingot: when ceramic thickness was 1.0mm, delta E value for ceramic post was smaller than 1 but delta E value for metal and gold post was larger than 2. For ceramic thickness of 1.5 mm, only the delta E value for metal was larger than 2, and the other samples' delta E value was smaller than 2. For ceramic thickness of 2.0mm, delta E values for all specimens was smaller than 1. 300 shade ingot: when ceramic thickness was 1.0mm, only delta E value for metal was larger than 2 and the other samples' delta E value was smaller than 2. For ceramic thickness of 1.5mm, delta E values for all specimens was smaller than 1. For ceramic thickness of 2.0mm, delta E values for all specimens was smaller than 1. CONCLUSION: The final esthetic result of the IPS-Empress glass-ceramic restoration was not affected by the presence of different core materials when the thickness was more than 2.0 mm. When ceramic thickness decreases to 1.5mm, it is advised to take the substrate aspects into consideration. If the ceramic thickness is less than 1.0mm, using the tooth color matched substrate is strongly recommended.

ANALYSIS OF OPTICAL TRANSMISSION CHARATERISTICS BY VISIBLE LIGHT INTO SHADE GUIDES / 대한치과보철학회지

The purpose of this study was the evaluation of spectral transmission of the commercial three shade guides and the relationship of hue, value, and chroma according to the transmission rate. The spectral transmittance of three shade guides - Vita Lumin Shade Guide, Vintage and Unibond Shade Guide, and Vitapan 3D-Master Shade Guide - were measured. For direct transmission measurements, each shade tabs were placed at the entrance port of the 1mm diameter intergrating sphere. The intensity of the light source passing through the shade tabs to the right angle was continuously recorded for wavelength from 400 to 700 nm. A transmission spectrum and digital data were obtained for each measurement and they were evaluated using Microcal Origin program. The obtained results of this study were as follows 1. In Vita Lumin Shade Guide, sum of the transmission rate of the shade tabs at the wavelength 400-700nm was decreased in agreement with the arrangement order at each A, B, C, D group, except D4 shade tab. However, there were no relationships between the transmission rate of the shade tabs and the value-oriented. 2. In Vintage and Unibond Shade Guide, sum of the total transmission rate of the shade tabs was decreased in agreement with the arrangement order at each A, B, C, D group. When all shade tabs arranged in value-oriented, transmission rate was accord with the order, except D4 shade tab. 3. When shade tabs of the Vitapan 3D-Master Shade Guide have the same value and hue, sum of their total transmission rate decreased in accordance with the chroma-oriented. When the shade tabs have the same value and chroma, there were no differences from the order of the transmission rate to the various hue type. However, in the "R" tabs of reddish hue type, the transmission rate increased at the long wavelength range area. In conclusion, we need the quantitative analyzing instruments in transmission determination. Vitapan 3D-Master Shade Guide covers the tooth color space taking into account the parameters of the systematic value, chroma, hue oriented, and the transmission rate relatively accorded with that sequence.