OBJECTIVEThe purpose of this study is to investigate the influence of cryogenic treatment and age-hardening heat treatment on the corrosion behavior of a dental casting Ag-Pd alloy.

METHODSA low gold content dental casting alloy composed of Ag-Pd-Cu-Au was prepared for this study. Corrosion test was performed according to ISO 10271:2001 dental metallie-corrosion test methods. Experimental specimens were casted according to a standard dental lost-wax casting procedure, treated with solution by heating the specimens to 900 degrees C, and immediately quenched in ice water. The specimens were then divided into four groups and subjected to heat treatment, cryogenic treatment, and heat treatment combined with cryogenic treatment. The specimens after the solution treatment were taken as control. The metallographic structures of the specimens were observed. The electrochemical parameters and the quantity of non-precious metallic ions released were evaluated via electrochemical and static immersion tests.

RESULTSMetallographic observation revealed that all the treatments resulted in a change in the microstructure of the alloy. The treatments were effective in improving the electrochemical parameters, such as an increase in Eocp and Ecorr and a decrease in Icorr (P < 0.05). The amount of non-noble metal ions released showed no difference compared with the control group (P > 0.05).

CONCLUSIONAfter different treatments, the antierosion properties of the alloy satisfied the ISO requirements. Age-hardening heat treatment and cryogenic treatment improved the corrosion resistance of the alloy.

Alloys ; Copper ; Corrosion ; Dental Alloys ; Gold Alloys ; Hot Temperature ; Palladium ; Silver

Objective To compare the clinical effects of fiber post‐retained and metal post‐retained restorations .Methods Two hundred teeth after root canal therapy from 176 patients were divided into 2 groups randomly and each group consisted of 100 teeth .In the experimental group ,teeth were restored with fiber post‐resin core and porcelain crown ,where cast metal‐core and porcelain crown were used in the control group .The teeth were clinically examined regularly for 2 years .The data were analyzed with Chi‐square method .Results At the end of the 2‐year follow‐up ,6 fiber posts dislocated and 2 teeth showed gingival inflammation in the experimental group ,with a clinical success rate of 92% ,the loss rate of 6% .5 gingival inflammation cases ,2 periapical inflammation cases and 7 cases of root fracture occurred in the metal post group ,and the clinical success rate was 85% ,root discount rate of 7% .There was statistical significance between the two groups (P< 0 .05) .Conclusion The loss rate ogf fiber post‐retained restoration is higher than the metal post‐retained restorations ,but the root discount rate is low ,incidence of periodontal and periapical tissue similar in the two groups can be routinely used clinically instead of metal post‐retained restoration .

0.05). The maximum color differences ( ?E) in the selected firing cycles were 2.279 8 and 1.389 4 for GI Ⅱand Vita In Ceram Alumina groups respectively, the maximum ?E between the two groups was 2.295 6, which fell into the clinically acceptable threshold for color differences. Conclusion: Color stability of all ceramic restorations with GI Ⅱand Vita In Ceram Alumina as substructure can be guaranteed after repeated firing of veneering porcelain up to 10 times.

OBJECTIVEThis study aims to evaluate the optical data of the different sites of the cobalt-chrome (Co-Cr) alloy abutments covered by four different all-ceramic crowns and the color difference between the crowns and target tab using a digital dental spectrophotometer.

METHODSTen Co-Cr alloy abutments were made and tried in four different groups of all-ceramic crowns, namely, Procera aluminia, Procera zirconia, Lava zirconia (Lava-Zir), and IPS E.max glass-ceramic lithium disilicate-reinforced monolithic. The color data of the cervical, body, and incisal sites of the samples were recorded and analyzed by dental spectrophotometer. The CIE L*, a*, b* values were again measured after veneering. The color difference between the abutments covered by all-ceramic crowns and A2 dentine shade tab was evaluated.

RESULTSThe L* and b* values of the abutments can be increased by all of the four groups of all-ceramic copings, but a* values were decreased in most groups. A statistical difference was observed among four groups. After being veneered, the L* values of all the copings declined slightly, and the values of a*, b* increased significantly. When compared with A2 dentine shade tab, the ΔE of the crowns was below 4.

CONCLUSIONFour ceramic copings were demonstrated to promote the lightness and hue of the alloy abutments effecttively. Though the colorimetric baseline of these copings was uneven, veneer porcelain can efficiently decrease the color difference between the samples and thee target.

Ceramics ; Chromium Alloys ; Cobalt ; Color ; Colorimetry ; Crowns ; Dental Materials ; Dental Porcelain ; Dental Prosthesis Design ; Humans ; Metal Ceramic Alloys ; Titanium ; Zirconium

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

OBJECTIVEGlass is the weak phase in the glass-alumina composite, and it plays a key role in determining the physical, mechanical and optical properties. The purpose of this study was to explore the fabrication arts of GI-II tinted infiltration glass and determine its properties.

METHODSThe thermal properties of the glass were tested on a TMA2940 thermal analyzer with heating rate of 5 degrees C/min and temperature range of 25-750 degrees C. The bar-shaped specimens were prepared with the size of 25 mm x 5 mm x 2 mm and their flexural strengths and elastic modulus with 3-point bending test were measured. The Vicker's hardness and indentation fracture toughness were also determined. The refractive index and changes of chemical constituents were tested by means of V prismatic refractometer and 2910 DTA analyzer.

RESULTSThe results showed that the thermal expansion coefficient, Tg and Tf, refractive index, 3-point bending flexural strength, bending elastic modulus, Vicker's hardness, indentation fracture toughness and density were 6.997 x 10(-6) degrees C-1 (25-500 degrees C), 635 degrees C and 650 degrees C, 1.64 MPa, 96.27 MPa, 31.16 GPa, 5.534 GPa, 1.05 MN.m1/2, and 3.214 g/cm3 respectively. Though certain heat processing conditions did result in micro-crystalline in the glass, it remained stable under routine glass infiltration firing cycles.

CONCLUSIONGI-II tinted infiltration glass had favorable physical, mechanical properties and good thermal stability.

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

OBJECTIVETo compare the influence of polishing and glazing on ceramic surface roughness and bacterial adhesion to the resulted surfaces.

METHODSThe surface of the ceramic plates were tested and analyzed by atomic force microscope. The influence of resulted surface on Streptococcus mutans adhesion were also evaluated.

RESULTSThe ceramic surface became much smoother after polishing with diamond paste or self-glazing. A positive correlation between surface roughness and bacterial adhesion were observed. Compared with surfaces polished with rubber-wheel, surfaces polished with diamond paste or self-glazing reduced bacterial adhesion to the surface (P<0.05).

CONCLUSIONPolishing with diamond paste could be an alternative to self-glazing on ceramic surface roughness and bacterial adhesion.

Bacterial Adhesion ; Ceramics ; Dental Polishing ; Dental Porcelain ; Diamond ; Humans ; Streptococcus mutans ; Surface Properties

Objective To analyse the cost-effectiveness analysis of the focal injection treatment under the guidance of contrast enhanced ultrasound(CEUS) for the severe abdominal parenchymal organs trauma.Methods One hundred and twelve patients with severe abdominal parenchymal organs trauma,including 42 hepatic injuries,52 splenic injuries and 33 renal injuries,were rolled in this study. The cost-effectiveness of this group was compared with that of surgery group. Results Treatment duration of single organ trauma under the guidance of CEUS was 20 - 30 minutes. During the first 72 hours after the focal injection, blood pressure and heart rate were improved ( P ＜0.05). Free intraperitoneal liquid did not increase on immediate US image of post-therapy and then it disappeared gradually. Heart rate returned to normal level after injection treatment ( P ＜0. 001 ). Lengths of stay in hospital was 3 - 11 (5.4 ± 2.4)days, which was not different with 3 - 9(5.1± 1.9) of surgery group( P ＞0.05). Treatment cost was 0.32 - 0.43 (0.36 ±0. 14) ten thousand RMB, which was obviously less than 3. 1 - 4. 2 (3.6 ± 10.8) ten thousand RMB of surgery group ( P ＜ 0.01 ). Conclusions The efficacy of the focal injection treatment of the severe abdominal parenchymal organs trauma under the guidance of CEUS was consistent with that of the operative treatment, but its cost was less. Especially it benefited for reserving organs and less pain.

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

OBJECTIVEThe purpose of this study was to investigate the influence of cryogenic treatment and age-hardening heat treatment on the micro-Vicker's hardness of palladium-silver dental alloys.

METHODSA low-gold content dental casting alloy composed of Ag-Pd-Cu-Au was prepared for this study. Experimental specimens according to standard requirements were prepared following a standard dental laboratory casting procedure, cast specimens were heated to 900 degrees C and quenched in ice water. The specimens were then divided into 4 groups. They were subsequently subjected to different treatments, including age-hardening heat treatment, cryogenic treatment, heat treatment combined with cryogenic treatment. The non-treated group was used as control. The micro-Vicker's hardness value was examined. The significance of correlation was analyzed.

RESULTSThe micro-Vicker's hardness of specimens after age-hardening heat treatment, cryogenic treatment, heat treatment combined with cryogenic treatment increased by 129%, 13% and 141%, respectively, compared with that of the non-treated control group. Conclusion Age-hardening heat treatment and cryogenic treatment were effective in elevating the hardness of Ag-Pd-Cu-Au alloy.

Copper ; Dental Alloys ; Gold Alloys ; Hardness ; Hot Temperature ; Humans ; Palladium ; Silver