Acid etching of glass-infiltrated zirconia and its biological response

PURPOSE: The purpose of this study was to evaluate the influence of acid etching treatment on surface characteristics and biological response of glass-infiltrated zirconia. MATERIALS AND METHODS: A hundred zirconia specimens were divided into four groups depending on surface treatments: untreated zirconia (group Z); acid-etched zirconia (group ZE); glass-infiltrated zirconia (group ZG); and glass-infiltrated and acid-etched zirconia (group ZGE). Surface roughness, surface topography, surface morphology, and Vickers hardness of specimens were evaluated. For biological response test, MC3T3-E1 cell attachment and proliferation on surface of the specimens were examined. The data were statistically analyzed using one-way ANOVA and Tukey's HSD test at a significance level of 0.05. RESULTS: Group ZGE showed the highest surface roughness (Ra = 1.54 µm) compared with other groups (P < .05). Meanwhile, the hardness of group Z was significantly higher than those of other groups (P < .05). Cell attachment and cell proliferation were significantly higher in group ZGE (P < .05). CONCLUSION: We concluded that effective surface roughness on zirconia could be made by acid etching treatment after glass infiltration. This surface showed significantly enhanced osteoblast cell response.

Evaluation of marginal fit of 2 CAD-CAM anatomic contour zirconia crown systems and lithium disilicate glass-ceramic crown

PURPOSE: This study was to evaluate the marginal fit of two CAD-CAM anatomic contour zirconia crown systems compared to lithium disilicate glass-ceramic crowns. MATERIALS AND METHODS: Shoulder and deep chamfer margin were formed on each acrylic resin tooth model of a maxillary first premolar. Two CAD-CAM systems (Prettau(R)Zirconia and ZENOSTAR(R)ZR translucent) and lithium disilicate glass ceramic (IPS e.max(R)press) crowns were made (n=16). Each crown was bonded to stone dies with resin cement (Rely X Unicem). Marginal gap and absolute marginal discrepancy of crowns were measured using a light microscope equipped with a digital camera (Leica DFC295) magnified by a factor of 100. Two-way analysis of variance (ANOVA) and post-hoc Tukey's HSD test were conducted to analyze the significance of crown marginal fit regarding the finish line configuration and the fabrication system. RESULTS: The mean marginal gap of lithium disilicate glass ceramic crowns (IPS e.max(R)press) was significantly lower than that of the CAD-CAM anatomic contour zirconia crown system (Prettau(R)Zirconia) (P<.05). Both fabrication systems and finish line configurations significantly influenced the absolute marginal discrepancy (P<.05). CONCLUSION: The lithium disilicate glass ceramic crown (IPS e.max(R)press) had significantly smaller marginal gap than the CAD-CAM anatomic contour zirconia crown system (Prettau(R)Zirconia). In terms of absolute marginal discrepancy, the CAD-CAM anatomic contour zirconia crown system (ZENOSTAR(R)ZR translucent) had under-extended margin, whereas the CAD-CAM anatomic contour zirconia crown system (Prettau(R)Zirconia) and lithium disilicate glass ceramic crowns (IPS e.max(R)press) had overextended margins.

Position of maxillary central incisor and intercanine width in Korean adults / 대한치과보철학회지

PURPOSE: The aim of this study was to propose the position of maxillary anterior teeth and intercanine width measurements based on the incisive papilla in accordance with the cephalic type and gender of dentate Korean adult with normal teeth alignment. MATERIALS AND METHODS: 42 students with Class I normal occlusion, without crowding or spacing, were selected from the Chonnam National University School of Dentistry. The lateral skull radiographs of the subjects were taken and were classified as different cephalic types, based on their PFH / AFH ratios. 42 casts of their maxilla were prepared and both the distance between the upper central incisors and the middle of the incisor papilla was measured with a vernier caliper (A) and the distance between the maxillary canine cusp tips (B) were measured. Statistical analysis was performed using SPSS version 15 and their significance was investigated. RESULTS: For dolichocephalic group, the mean values for A and B were 8.43 (SD: 0.61) and 36.73 (SD: 2.17), respectively. The mean value for A was 8.51 (SD: 1.27) for the mesocephalic group and 8.76 (SD 1.03) for the brachycephalic group. The mean value for B was 35.91 (SD: 1.86) for the mesocephalic group and 37.34 (SD: 2.23) for the brachycephalic group. For the male group, the mean A value was 8.86 (SD: 1.04) and the mean B value was 37.60 (SD: 0.24). For the female group, the mean A value was 8.41 (SD: 0.93) and the mean B value was 36.18 (SD: 2.01). The difference between male and female group in A values were not statistically significant (P>.05). The B values of the male subjects were greater than those of the female subjects and was statistically significant (P<.05). CONCLUSION: 42 students with normal dentition and occlusion in korea, the distance from the incisive papilla and the incisal edge of maxillary central incisors had no difference in cephalic type or gender. However, the distance between the cusp tip of both canines had significant difference in gender where the male showed higher values than the female, while having no difference in cephalic types.

Effect of different pattern size and pattern shape on castability of commercially pure titanium / 대한치과보철학회지

PURPOSE: The purpose of this study was to investigate the effect of geometrically different wax pattern shapes and sizes on the castability of Grade2 Cp-Ti (commercially pure titanium). MATERIALS AND METHODS: Total of 40 mesh wax pattern (61 mm x 24 mm, 207 grids), (61 mm x 17 mm, 138 grids) was cast in this experiment. Depending on the geometrical shape of the wax pattern, 8 groups was organized; Flat, Semicircular, Horse-shoe and V-shape, each consisting 5 samples. Runner-bar sprue was used in all patterns. The number of completely cast grid in wax pattern served as a measure for the castability of comercially pure titanium. RESULTS: The mean value of square count in each group was as followed; 133.20 squares in group SS (96.52%), 132.40 squares in group SH (95.94%), 132.00 squares in group SF (95.65%), 127.60 squares in SV (91.43%), 198.60 squares in group LF (95.94%), 197.80 squares in group LV (95.56%), 196.40 squares in group LS (94.88%), and 188.00 squares in group LH (90.82%). CONCLUSION: Within the limitations of this study the results indicate that there were no sttistically significant difference in castability of titanium regarding wax pattern shape (P>.05). However, Small size wax patterns were showing the noticeable castability more than Large size pattern.

Effects of chromium chloride addition on coloration and mechanical properties of 3Y-TZP / 대한치과보철학회지

PURPOSE: The purpose of this study was to examine the effects of chromium chloride addition on coloration, mechanical property and microstructure of 3Y-TZP. MATERIALS AND METHODS: Chromium chloride was weighed as 0.06, 0.12, and 0.25 wt% and each measured amount was dissolved in alcohol. ZrO2 powder was mixed with each of the individual slurry to prepare chromium doped zirconia specimen. The color, physical properties and microstructure were observed after the zirconia specimen were sintered at 1450degrees C. In order to evaluate the color, spectrophotometer was used to analyze the value of L*, C*, a* and b*, after placing the specimen on a white plate, and measured according to the International Commission on Illumination (CIE) standard, Illuminant D65 and SCE system. The density was measured in the Archimedes method, while microstructures were evaluated by using the scanning electron microscopy (SEM) and XRD. Fracture toughness was calculated Vickers indentation method and indentation size was measured by using the optical microscope. The data were analyzed with 1-way ANOVA test (alpha= 0.05). The Tukey multiple comparison test was used for post hoc analysis. RESULTS: 1. Chromium chloride rendered zirconia a brownish color. While chromium chloride content was increased, the color of zirconia was changed from brownish to brownish-red. 2. Chromium chloride content was increased; density of the specimen was decreased. 3. More chromium chloride in the ratio showed increase size of grains. 4. But the addition of chromium chloride did not affect the crystal phase of zirconia, and all specimens showed tetragonal phase. 5. The chromium chloride in zirconia did not showed statistically significant difference in fracture toughness, but addition of 0.25 wt% showed a statistically significant difference (P<.05). CONCLUSION: Based on the above results, this study suggests that chromium chlorides can make colored zirconia while adding in a liquid form. The new colored zirconia showed a slight difference in color to that of the natural tooth, nevertheless this material can be used as an all ceramic core material.

Sintering behavior and mechanical properties of zirconia compacts fabricated by uniaxial press forming

PURPOSE: The purpose of this study was to compare the linear sintering behavior of presintered zirconia blocks of various densities. The mechanical properties of the resulting sintered zirconia blocks were then analyzed. MATERIAL AND METHODS: Three experimental groups of dental zirconia blocks, with a different presintering density each, were designed in the present study. Kavo Everest(R) ZS blanks (Kavo, Biberach, Germany) were used as a control group. The experimental group blocks were fabricated from commercial yttria-stabilized tetragonal zirconia powder (KZ-3YF (SD) Type A, KCM. Corporation, Nagoya, Japan). The biaxial flexural strengths, microhardnesses, and microstructures of the sintered blocks were then investigated. The linear sintering shrinkages of blocks were calculated and compared. RESULTS: Despite their different presintered densities, the sintered blocks of the control and experimental groups showed similar mechanical properties. However, the sintered block had different linear sintering shrinkage rate depending on the density of the presintered block. As the density of the presintered block increased, the linear sintering shrinkage decreased. In the experimental blocks, the three sectioned pieces of each block showed the different linear shrinkage depending on the area. The tops of the experimental blocks showed the lowest linear sintering shrinkage, whereas the bottoms of the experimental blocks showed the highest linear sintering shrinkage. CONCLUSION: Within the limitations of this study, the density difference of the presintered zirconia block did not affect the mechanical properties of the sintered zirconia block, but affected the linear sintering shrinkage of the zirconia block.

Effects of titanium surface coating on ceramic adhesion / 대한치과보철학회지

STATEMENT OF PROBLEM: The adhesion between titanium and ceramic is less optimal than conventional metal-ceramic bonding, due to reaction layer form on cast titanium surface during porcelain firing. PURPOSE: This study characterized the effect of titanium-ceramic adhesion after gold and TiN coating on cast and wrought titanium substrates. MATERIAL AND METHOD: Six groups of ASTM grade II commercially pure titanium and cast titanium specimens(13mm x 13mm x 1mm) were prepared(n=8). The conventional Au-Pd-In alloy served as the control. All specimens were sandblasted with 110micrometer Al2O3 particles and ultrasonically cleaned for 5min in deionized water, and dried in air before porcelain firing. An ultra-low-fusing dental porcelain(Vita Titankeramik) was fused on titanium surfaces. Porcelain was debonded by a biaxial flexure test at a cross head speed of 0.25mm/min. The excellent titanium-ceramic adherence was exhibited by the presence of a dentin porcelain layer on the specimen surface after the biaxial flexure test. Area fraction of adherent porcelain(AFAP) was determined by SEM/EDS. Numerical results were statistically analyzed by one-way ANOVA and Student- Newman-Keuls test at alpha=0.05. RESULTS: The AFAP value of cast titanium was greatest in the group 2 with TiN coating, followed by group 1 with Au coating and the group 3 with Al2O3 sandblasting. Significant statistical difference was found between the group 1, 2 and the group 3 (p.05). The AFAP values of the cast titanium and the wrought titanium were similar. However the group treated with Al2O3 sandblasting showed significantly lower value (p<.05).

The bond characteristics of porcelain fused by titanium surface modification / 대한치과보철학회지

STATEMENT OF PROBLEM: Titanium is well known as a proper metal for the dental restorations, because it has an excellent biocompatibility, resistance to corrosion, and mechanical property. However, adhesion between titanium and dental porcelains is related to the diffusion of oxygen to the reaction layers formed on cast-titanium surfaces during porcelain firing and those oxidized layers make the adhesion difficult to be formed. Many studies using mechanical, chemical and physical methods to enhance the titanium-ceramic adhesion have been actively performed. PURPOSE: This study meant to comparatively analyse the adhesion characteristics depending on different titanium surface coatings after coating the casts and wrought titanium surfaces with Au and TiN. MATERIAL AND METHOD: In this study, the titanium specimens (CP-Ti, Grade 2, Kobe still Co. Japan) were categorized into cast and wrought titanium. The wrought titanium was cast by using the MgO-based investment(Selevest CB, Selec). The cast and wrought titanium were treated with Au coating(ParaOne(R), Gold Ion Sputter, Model PS-1200) and TiN coating(ATEC system, Korea) and the ultra low fusing dental porcelain was fused and fired onto the samples. Biaxial flection test was done on the fired samples and the porcelain was separated. The adhesion characteristics of porcelain and titanium after firing and the specimen surfaces before and after the porcelain fracture test were observed with SEM. The atomic percent of Si on all sample surfaces was comparatively analysed by EDS. In addition, the constituents of specimen surface layers after the porcelain fracture and the formed compound were evaluated by X-ray diffraction diagnosis. RESULT: The results of this study were obtained as follows : 1. The surface characteristics of cast and wrought titanium after surface treatment(Au, TiN, Al2O3 sandblasting) were similar and each cast and wrought titanium showed similar bonding characteristics. 2. Before and after the biaxial flection test, the highest atomic weight change of Si component was found in Al2O3 sandblasted wrought titanium(28.6at.% --> 8.3at.%). On the other hand, the least change was seen in Au-Pd-In alloy(24.5at.%--> 19.1at.%). 3. Much amount of Si components was uniformly distributed in Au and TiN coated titanium, but less amount of Si's was unevenly dispersed on Al2O3 sandblasting surfaces. 4. In X-ray diffraction diagnosis after porcelain debonding, we could see Au2Ti compound and TiN coating layers on Au and TiN coated surfaces and TiO2, typical oxide of titanium, on all titanium surfaces. 5. Debonding of porcelain on cast and wrought titanium surface after the biaxial flection is considered as a result of adhesion deterioration between coating layers and titanium surfaces. We found that there are both adhesive failure and cohesive failure at the same time. CONCLUSION: These results showed that the titanium-ceramic adhesion could be improved by coating cast and wrought titanium surfaces with Au and TiN when making porcelain fused to metal crowns. In order to use porcelain fused to titanium clinically, it is considered that coating technique to enhance the bonding strength between coating kKlayers and titanium surfaces should be developed first.

Effect of surface roughness on bond strength in titanium-porcelain system / 대한치과보철학회지

STATEMENT OF PROBLEM: Titanium has many advantages of high biocompatibility, physical properties, low-weight, low price and radiolucency, but it is incompatible with conventional dental porcelain due to titanium's oxidative nature. Many previous studies have shown that they used the method of sandblast for surface treatment prior to porcelain application, the researches are processing about the method of acid etching or surface coating. PURPOSE: The purpose of this research is to study the effect on bond strength of surface roughness between titanium and porcelain with the same surface topography. MATERIAL AND METHOD: In this study, we evaluated the bond strength by using 3-point bending test based on ISO 9693 after classified 8 groups - group P : polished with #1200 grit SiC paper, group S10 : 1.0 micrometer surface roughness with sandblasting, group S15 : 1.5 micrometer surface roughness with sandblasting, group S20 : 2.0 micrometer surface roughness with sandblasting, group S25 : 2.5 micrometer surface roughness with sandblasting, group S30 : 3.0 micrometer surface roughness with sandblasting, group S35 : 3.5 micrometer surface roughness with sandblasting, group E : 1.0 micrometer surface roughness with HCl etching. RESULTS: Within the confines of our research, the following results can be deduced. 1. In the results of 3-point bending test, the bond strength of sandblasting group showed significant differences from one of polishing group, acid etching group(P<.05). 2. The bond strength of sandblasting groups did not show significant differences. 3. After surface treatments, the group treated with sandblasting showed irregular aspect formed many undercuts, in the SEM photographs. The bond strength of sandblasting group was higher than 25 MPa, the requirement of ISO 9693. CONCLUSION: In above results, bond strength of titanium and low-fusing porcelain is influenced more to surface aspect than surface roughness. And titanium has clinically acceptable bond strength below surface roughness of 3.5 micrometer.

A comparison of fracture strengths of porcelain-fused-to-titanium crown among titanium surface coating treatments / 대한치과보철학회지

STATEMENT OF PROBLEM: Titanium and its alloy, with their excellent bio-compatibility and above average resistance to corrosion, have been widely used in the field of dentistry. However, the excessive oxidization of titanium which occurs during the process of firing on porcelain makes the bonding of titanium and porcelain more difficult than that of the conventional metal-porcelain bonding. To solve this problem related to titanium-porcelain bonding, several methods which modify the surfaces, coat the surfaces of titanium with various pure metals and ceramics, to enable the porcelain adhesive by limiting the diffusion of oxygen and forming the adhesive oxides surfaces, have been investigated. PURPOSE: The purpose of this study was to know whether the titanium-porcelain bonding strength could be enhanced by treating the titanium surface with gold and TiN followed by fabrication of clinically applicable porcelain-fused-to-titanium crown. MATERIAL AND METHOD: The porcelain-fused-to-titanium crown was fabricated after sandblasting the surface of the casting titanium coping with Al2O3 and treating the surface with gold and TiN coating followed by condensation and firing of ultra-low fusing porcelain. To compare with porcelain-fused-to-titanium crowns, porcelain-fused-to-gold crowns were fabricated and used as control groups. The bonding strengths of porcelain-fused-to-gold crowns and porcelain-fused-totitanium crowns were set for comparison when the porcelain was fractured on purpose to get the experimental value of fracture strength. Then, the surface were examined by SEM and each fracturing pattern were compared with each other. RESULT: Those results are as follows. 1. The highest value of fracture strength of porcelain-fused-to-titanium crowns was in the order of group with gold coating, group with TiN coating, group with Al2O3 sandblasting. No statistically significant difference was found among the three (P>.05). 2. The porcelain-fused-to-gold crowns showed the highest value in bonding strength. The bonding strength of crowns porcelain-fused-to-titanium crowns of rest groups showed bonding strength reaching only 85%-94% of that of PFG, though simple comparision seemed unacceptable due to the difference in materials used. 3. The fracturing patterns between metal and porcelain showed mixed type of failure behavior including cohesive failure and adhesive failure as a similar patterns by examination with the naked eye and SEM. But porcelain-fused-to-gold crowns showed high incidence of adhesive failure and porcelain-fused-to-titanium crowns showed high incidence of cohesive failure. CONCLUSION: Above results proved that when fabricating porcelain-fused-to-titanium crowns, treating casting titanium surface with gold or TiN was able to enhance the bonding strength between titanium and porcelain. Mean value of masticatory force was found to showed clinically acceptable values in porcelain bonding strength in all three groups. However, more experimental studies and evaluations should be done in order to get better porcelain bonding strength and various surface coating methods that can be applied on titanium surface with ease.