BACKGROUNDThe lithium disilicate-based ceramic is a newly developed all-ceramic material, which is lithium disilicate-based and could be used for fabricating almost all kinds of restorations. The extent of light attenuation by ceramic material was material-dependent. Ceramic materials with different crystal composition or crystalline content would exhibit distinct light-absorbing characteristics. The aim of this study was to analyze the influence of ceramic thickness and light-curing time on the polymerization of a dual-curing resin luting material with a lithium disilicate-based ceramic.

METHODSA lithium disilicate-based ceramic was used in this study. The light attenuation caused by ceramic with different thickness was determined using a spectral radiometer. The commercial dual-cured resin cement was light-cured directly or through ceramic discs with different thickness (1, 2 and 3 mm, respectively) for different times (10, 20, 30, 40, 50 and 60 seconds, respectively). The polymerization efficiency of resin cement was expressed in terms as Vickers hardness (VHN) measured after 24 hours storage. Two-way analysis of variance (ANOVA) and Tukey's HSD tests were used to determine differences.

RESULTSIntensity of polymerizing light transmitted through ceramic discs was reduced from 584 mW/cm(2) to about 216 mW/cm(2)2, 80 mW/cm(2) and 52 mW/cm(2) at thicknesses of 1 mm, 2 mm and 3 mm, respectively. Resin cement specimens self-cured alone showed significantly lower hardness values. When resin cement was light-cured through ceramic discs with a thickness of 1 mm, 2 mm and 3 mm, no further increasing in hardness values was observed when light-curing time was more than 30 seconds, 40 seconds and 60 seconds, respectively.

CONCLUSIONSWithin the limitation of the present study, ceramic thickness and light-curing time had remarkable influence on the polymerization of dual-cured resin cement. When resin cement is light-cured beneath a lithium disilicate ceramic with different thickness, prolonging light-curing time accordingly may still be necessary to insure complete polymerization.

Ceramics ; chemistry ; Dental Porcelain ; chemistry ; Light ; Resin Cements ; chemistry

OBJECTIVETo study the bonding characteristic of Titanium and RG experiment porcelain.

METHODS5 specimens with a size of 10 mm x 5 mm x 1.4 mm were cast from pure titanium. Then 1 mm of RG experiment opaque and body porcelain were fused on the surface of the titanium specimens. The interface of titanium and porcelain was analyzed with a scanning electron microscope with energy-despersive spectrometry; 6 metal specimens with the size of 25 mm x 3 mm x 0.5 mm were cast from Ni-Cr alloy and a uniform thickness of 1 mm of VMK 99 porcelain was veneered on the central area of 8 mm x 3 mm 18 metal specimens as the same size were cast from pure titanium. The uniform thickness of 1 mm of VITA TITANKERAMIK porcelain, of Noritake super porcelain Ti-22 and of RG experiment porcelain were veneered on every 6 specimens respectively in the central area of 8 mm x 3 mm. The specimens were subjected to a three-point bending test on a load-test machine with a span of 20 mm, then the failure loads were recorded and statistically analysised. The RG porcelain/titanium crown was fabricated by fusing RG opaque porcelain and body porcelain to cast titanium substrate crown.

RESULTSThe SEM results show no porosity and crackle were found in the interface. The energy-dispersive spectrometry show that there are Si, Ti and O in the 1 micro m layer between porcelain and titanium, which suggesting titanium and experiment porcelain bonding well. The three point test showed the fracture force for the combinations of titanium/VITA TITANKERAMIK porcelain, titanium/Noritake super porcelain Ti-22 and titanium/RG experiment porcelain were (7.233 +/- 2.539) N, (5.533 +/- 1.199) N and (6.316 +/- 1.433) N respectively. There were not statistically significant differences among them (t test, P < 0.01). The fracture force for the Ni-Cr alloy/VMK99 porcelain combination (12.733 +/- 3.297) N was significantly greater than those of the cast titanium/porcelain (t test, P > 0.05). The crown was translucent with no crack.

CONCLUSIONRG porcelain is well compatible with titanium.

Dental Porcelain ; chemistry ; Metal Ceramic Alloys ; chemistry ; Titanium ; chemistry

OBJECTIVETo research the influence of K(2)O composition in the raw material on leucite microcrystallization and to study the effect of leucite content on compressive strength of the dental glass ceramics reinforced by leucite microcrystallization.

METHODSThe raw materials with different K(2)O content were treated by a decided thermal treatment system. The products were analyzed by polaring microscope and X-ray diffractometer, and their compressive strength was also tested.

RESULTSThe microstructure of products from high K(2)O component was remarkably good, at microcrystal size of 0.8 micro m and the compressive strength was 206.6 MPa. A positive correlation was found between leucite volume and the compressive strength when leucite volume was less than 50% (Vol%).

CONCLUSIONSThe component of K(2)O has a great effect on the microstructure and the properties of the leucite-microcrystal-reinforced dental glass ceramics and the content of leucite microcrystals has a notable influence on the compressive strength of the dental glass ceramics.

Compressive Strength ; Crystallization ; Dental Porcelain ; chemistry ; Glass ; chemistry ; Materials Testing

Ceramics ; Dental Alloys ; chemistry ; Dental Porcelain ; Dental Restoration, Permanent ; Humans ; Metal Ceramic Alloys ; chemistry

OBJECTIVEThe purpose of this study was to determine the thermal, mechanical properties and density of the composite infiltrated with GI-II tinted infiltration glass.

METHODSThe bar-shaped aluminum oxide and glass/alumina composite specimens with the size of 20 mm x 5 mm x 5 mm were prepared, with two free-end surfaces perpendicular to the long axis of the specimens and parallel to each other. The thermal expansion curves were obtained on a TMA2940 thermal analyzer with heating rate of 5 degrees C/min and temperature range of 25 degrees C to 1000 degrees C. The bar-shaped specimens with the size of 25 mm x 5 mm x 2 mm were fabricated and employed to test the density using Archmede's method. The flexural strength, elastic modulus were measured by means of 3-point bending test with the same specimens. The fractured specimens were indented with Vicker's diamond pyramid under load of 49 N for 15 seconds to determine the hardness and indentation fracture toughness.

RESULTSThe thermal expansion coefficient of the glass/alumina composite was 7.620 x 10(-6) degrees C-1 (25-500 degrees C), which was higher than that of Vitadur alpha veneering porcelain. The 3-poit flexural strength, elastic modulus, Vicker's hardness, indentation fracture toughness and density were 389.6 MPa, 92 GPa, 9.409 GPa, 3.2425 MNm-3/2 and 3.662 g/cm3 respectively.

CONCLUSIONThe thermal expansion of the GI-II glass/alumina composite is compatible with that of Vitadur alpha veneering porcelain, and the material could meet the strength demands for clinical use.

Aluminum Oxide ; chemistry ; Ceramics ; Dental Materials ; Dental Porcelain ; chemistry ; Glass ; chemistry ; Tensile Strength ; Transition Temperature

OBJECTIVEMultiple layer techniques were commonly employed in fabricating all-ceramic restorations. Bond and compatibility between layers were vitally important for the clinical success of the restorations. The purposes of this study were to investigate the bond of the interface between the GI-II glass/alumina composite and Vitadur alpha veneering porcelain, and to study the thermal compatibility between them.

METHODSPrepared a bar shaped specimen of GI-II glass/alumina composite 25 mm x 5 mm x 1 mm in size, with bottom surface pre-notched. The upper surface was veneered with Vitadur alpha veneering porcelain (0.2 mm opaque dentin and 0.6 mm dentin porcelain), then fractured and the fracture surface were examined under scanning electron microscope (SEM) and electron microprobe analyzer (EMPA) with electron beam of 10 micrometer in diameter; ten all-ceramic single crowns for an upper right central incisor were fabricated and the temperatures of thermal shock resistance were tested.

RESULTSSEM observation showed tight bond between the composite and the porcelain; The results of EMPA showed that penetration of Na, Al elements from glass/alumina into veneering porcelain and Si, K, Ca elements from veneering porcelain into glass/alumina occurred after sintering baking; The temperature of thermal shock resistance for anterior crowns in this study was 158 +/- 10.3 degrees C, cracks were mainly distributed in veneering porcelain with thicker layer.

CONCLUSIONSChemical bond exists between the GI-II glass/alumina composite and Vitadur alpha veneering porcelain, and there is good thermal compatibility between them.

Aluminum Oxide ; chemistry ; Dental Porcelain ; chemistry ; Dental Stress Analysis ; Humans ; Microscopy, Electron, Scanning

OBJECTIVETo study the strengthening of fluorophlogopite-based dental machinable ceramic through developing a new type of calcium-mica-based ceramic.

METHODSBased on the analysis of the crystal structure of the fluorophlogopite ceramic of Dicor MGC, the structure of a new type of calcium-mica-based ceramic was designed and the corresponding composition of the new material was experimented. And the new glass-ceramic was obtained through the treatment of glass preparation and nucleation. Then crystal content of the glass ceramic was analyzed by X-ray diffraction analysis (XRD) and the 3-point bending strength of the new ceramic was recorded.

RESULTSA new type of calcium-mica-based glass ceramic was developed and had the 3-point bending strength of (210.2 +/- 14.7) MPa. Compared with the strength of fluorophlogopite-based dental machinable ceramic, such as Dicor MGC, which was reported in the range of 150 approximately 180 MPa within inclusive studies, the higher strength of the new ceramic was recorded.

CONCLUSIONSThe fluorophlogopite-based dental machinable ceramic could be reinforced through internal strengthening.

Aluminum Silicates ; chemistry ; Dental Materials ; Dental Porcelain ; chemistry ; Materials Testing ; Tensile Strength

OBJECTIVES: This study aimed to remove occlusal veneers of varied thicknesses and compositions by Er:Yag laser in vitro and analyze the interfacial microstructure between veneers and tooth that irradiated by laser, by which experimental evidence could be provided to support the non-invasive removal of occlusal veneerby laser. METHODS: Fresh mandibular premolars extracted for orthodontic requirements were collected for tooth preparation. Three kinds of ceramic materials (Vita Suprinity, Vita Mark Ⅱ, and Upcera Hyramic) were selected to fabricate occlusal veneer with different thicknesses (1.0, 1.5, and 2.0 mm). One week later, Er:Yag laser (2.5 W and 3.5 W) was used to irradiate and remove the occlusal veneer and recorded the timespan. After the removal operation, the micro-morphologies of samples were examined by scanning electron microscope. RESULTS: Upcera Hyramic veneer failed to be removed (>20 min); the operation span at 2.5 W, Vita Suprinity (96.0 s±16.0 s) was longer than Vita MarkⅡ(84.5 s±19.5 s) in the 1.0 mm group (P<0.05), and Vita Suprinity (246.5 s±13.5 s) was longer than Vita MarkⅡ(170.0 s±14.0 s) in the 1.5 mm group (P<0.05). At 3.5 W, Vita Suprinity (381.0 s±24.0 s) was longer than Vita MarkⅡ(341.5 s±26.5 s) in the 2.0 mm group. CONCLUSIONS Increasing laser power could shorten the operation span and facilitate the removal of occlusal veneers with the same thickness and composition. The occlusal veneer was sustained when insufficient laser power was applied. With the same laser power and ceramic thickness, laser penetration could interfere with the integral of the ceramic structure when the laser interacted with the bonding layer. With the same ceramic composition and laser power, the operation span and laser power increased with the thickness of the occlusal veneer. However, the laser was incapable of removing occlusal resin veneer directly.
Lasers, Solid-State ; Materials Testing ; Dental Porcelain/chemistry* ; Ceramics/chemistry* ; Bicuspid ; Dental Veneers

BACKGROUNDThe low-temperature resistance aging performance of Yttria-stabilized tetragonal zirconia polycrystal (Y-TZP) is the key effective factor that influences the long-term success rate of prosthesis. The objective of this study was to test and compare the aging performances for resisting low temperature of Lava Frame, Cercon Smart, and Upcera Yttria-stabilized zirconia core materials, via analyzing the micro and the crystal phases of the materials, and measure the three-point bending strength and the fracture toughness.

METHODSThe three zirconia green bodies were prepared as 60 test samples for three-point bending strength and as 60 test samples for fracture toughness. The test samples for three-point bending strength and fracture toughness were assigned to five groups and were treated respectively for 0, 5, 10, 15, and 20 hours to observe the micro and the crystal phases of the test samples. Then the three-point bending strength and fracture toughness were tested by X-ray diffraction (XRD).

RESULTSThe m phase content of Lava Frame was raised from 7.70% to 13.01%; the m phase content of Cercon Smart was raised from 4.95% to 8.53%; and Lava Frame is raised from 10.84% to 35.18%. The three-point bending strengths of the three zirconia core materials were higher than 1100 MPa and the fracture toughness was higher than 3 MPa·m(1/2). The three-point bending strength and the fracture toughness of Upcra zirconia decreased the most, followed by Lava Frame, and then by Cercon Smart.

CONCLUSIONThe aging resistance sequences of the three zirconia core materials are, from strong to weak, Cercon Smart, Lava Frame, and Upcera.

Ceramics ; chemistry ; Dental Porcelain ; chemistry ; Microscopy, Electron, Scanning ; Temperature ; X-Ray Diffraction ; Yttrium ; chemistry ; Zirconium ; chemistry

OBJECTIVEThe purposes of this study were to determine the spectral transmittance of GI-II glass/alumina composites and to explore the effects of different specimen thickness and fining arts of glass infiltration on the transmittance. Data were compared with those of Vita In-Ceram Alumina materials.

METHODSPlate-shaped specimens 12.5 mm in diameter, with 3 thickness (0.5, 1.0, 1.5 mm), 6 color groups for GI-II and 4 color groups for Vita In-Ceram Alumina were fabricated. Specimens of color AL2 for In-Ceram and IG2 for GI-II were selected in the study of relationship between different infiltration arts and transmittance. Five infiltration time duration and three temperatures were studied. A spectrophotometer with standard A light source paralleled light beam 5 mm in diameter and spectra range 380-780 nm was employed to measure the spectral transmittance.

RESULTSThe range of spectral transmittance were 2.7%-4.5% for GI-II and 2.4%-5.2% for Vita In-Ceram Alumina. Transmittance decreased with specimen thickness, but they were not linearly related. Transmittance of GI-II tended to increase and that of Vita In-Ceram Alumina decreased as the infiltration temperature elevated. The transmittance increased with infiltration time less than 4 hours and reduced with prolonged time over 6 hours for both materials.

CONCLUSIONGI-II glass/alumina composite has comparatively lower translucency. Influences of factors as color, thickness and infiltration arts on translucency of restorations should be considered in the clinical selection of the all-ceramic materials.

Aluminum Oxide ; chemistry ; Ceramics ; chemistry ; Dental Materials ; Dental Porcelain ; chemistry ; Glass ; chemistry ; Light ; Spectrophotometry ; Temperature ; Tensile Strength ; Transition Temperature