The effect of various sandblasting conditions on surface changes of dental zirconia and shear bond strength between zirconia core and indirect composite resin

PURPOSE: To measure the surface loss of dental restorative zirconia and the short-term bond strength between an indirect composite resin (ICR) and zirconia ceramic after various sandblasting processes. MATERIALS AND METHODS: Three hundred zirconia bars were randomly divided into 25 groups according to the type of sandblasting performed with pressures of 0.1, 0.2, 0.4 and 0.6 MPa, sandblasting times of 7, 14 and 21 seconds, and alumina powder sizes of 50 and 110 microm. The control group did not receive sandblasting. The volume loss and height loss on zirconia surface after sandblasting and the shear bond strength (SBS) between the sandblasted zirconia and ICR after 24-h immersion were measured for each group using multivariate analysis of variance (ANOVA) and Least Significance Difference (LSD) test (alpha=.05). After sandblasting, the failure modes of the ICR/zirconia surfaces were observed using scanning electron microscopy. RESULTS: The volume loss and height loss were increased with higher sandblasting pressure and longer sandblasting treatment, but they decreased with larger powder size. SBS was significantly increased by increasing the sandblasting time from 7 seconds to 14 seconds and from 14 seconds to 21 seconds, as well as increasing the size of alumina powder from 50 microm to 110 microm. SBS was significantly increased from 0.1 MPa to 0.2 MPa according to the size of alumina powder. However, the SBSs were not significantly different with the sandblasting pressure of 0.2, 0.4 and 0.6 MPa. The possibilities of the combination of both adhesive failure and cohesive failure within the ICR were higher with the increases in bonding strength. CONCLUSION: Based on the findings of this study, sandblasting with alumina particles at 0.2 MPa, 21 seconds and the powder size of 110 microm is recommended for dental applications to improve the bonding between zirconia core and ICR.

Erratum: The effect of various sandblasting conditions on surface changes of dental zirconia and shear bond strength between zirconia core and indirect composite resin

On page 219, there was an error in the Fig. 5.

Effects of different surface conditioning agents on the bond strength of resin-opaque porcelain composite / 生物医学工程学杂志

The objective of this research is to evaluate the effects of different silane coupling agents on the bond strength between Ceramco3 opaque porcelain and indirect composite resin. Five groups of Co-Cr metal alloy substrates were fabricated according to manufacturer's instruction. The surface of metal alloy with a layer of dental opaque porcelain was heated by fire. After the surface of opaque porcelain was etched, five different surface treatments, i.e. RelyX Ceramic Primer (RCP), Porcelain Bond Activator and SE Bond Primer (mixed with a proportion of 1:1) (PBA), Shofu Porcelain Primer (SPP), SE bond primer (SEP), and no primer treatment (as a control group), were used to combine P60 and opaque porcelain along with resin cement. Shear bond strength of specimens was tested in a universal testing machine. The failure modes of specimens in all groups were observed and classified into four types. Selected specimens were subjected to scanning electron microscope and energy disperse spectroscopy to reveal the relief of the fracture surface and to confirm the failure mode of different types. The experimental results showed that the values of the tested items in all the tested groups were higher than that in the control group. Group PBA exhibited the highest value [(37.52 +/- 2.14) MPa] and this suggested a fact that all of the specimens in group PBA revealed combined failures (failure occurred in metal-porcelain combined surface and within opaque porcelain). Group SPP and RCP showed higher values than SEP (P < 0.05) and most specimens of SPP and RCP performed combined failures (failure occurred in bond surface and within opaque porcelain or composite resin) while all the specimens in group SEP and control group revealed adhesive failures. Conclusions could be drawn that silane coupling agents could reinforce the bond strength of dental composite resin to metal-opaque porcelain substrate. The bond strength between dental composite resin and dental opaque porcelain could meet the clinical requirements.

Nitric oxide and prostaglandin E2 secretion in osteocytes induced by intermittent cyclic compressive force / 生物医学工程学杂志

This paper is aimed to investigate the effect of rest-inserted loading on the mechanosensitivity of osteocytes. In the investigation, cultured MLO-Y4 osteocyte-like cells were strained on cyclic compressive force (CCF) by the self-made compressive loading device. Then we observed the effect of different rest periods-inserted loading (5 s, 15 s, 30 s, respectively) on the mechanosensitivity of osteocytes. We then determined the levels of secreted nitric oxide (NO) and prostaglandin E2 (PGE2) by Griess method and enzyme linked immunosorbent assay (ELISA), respectively. We then stained the cytoskeleton F-actin using immunofluorescence. We found that the expressions of NO and PGE2 in rest-inserted strained groups (> 15 s) were significantly increased compared to those in the continuous strained group. And rest-inserted loading promoted the parallel alignment of stress fibers. It indicates that rest-inserted loading could promote the mechanosensitivity of osteocytes, and this might be related to the parallel alignment of stress fibers.

Biological properties of biphasic tricalcium phosphate bioceramics/calcium sulfate bone cement porous three-dimensional scaffolds / 中国组织工程研究

BACKGROUND:With the development of tissue engineering, porous bioceramics are more and more used to repair bone defects. Current research focuses on the biological synthesis of this bioceramics and its performance evaluation. OBJECTIVE:To discuss the preparation of a new kind of bone cement and to determine its physicochemical properties and biocompatibility with osteoblasts. METHODS:Biphasic tricalcium phosphate powders were prepared using co-precipitation method. The powder was turned into granular stuff by arabic gum. After sintering, porous hydroxyapatite/tricalcium phosphate bioceramics were harvested, and then mixed with alpha-hemihydrate to prepare the bone cement. RESULTS AND CONCLUSION:X-ray diffraction confirmed that the synthetic substance was a kind of biphasic calcium phosphate ceramic having a porous structure. The bone cement could be in the plastic state within 3 minutes. The curing time was 15 minutes, and the curing temperature was 36.5℃. The maximum compression strength was 5.82 MPa, and the MTT toxicity was level 0. Osteoblasts could grew wel on the material surface.

A preliminary study of application of the antibacterial solution containing silver ion to the surface of soft lining material / 生物医学工程学杂志

We tried to find the effects of the application of the antibacterial solution containing silver ions on the surface of the denture soft lining material. We selected the right concentration of the silver-containing solution and coated a soft lining material with the solution so that the soft lining material could be antibacterial. The antibacterial solution containing silver ions was prepared by sol-gel method. MIC of C. a and S. a were tested by broth dilution test. The surface property and thickness were tested after coated. The in vitro antibacterial ratio against C. a and S. a were demonstrated by the method of plate-counting. A film was formed after coating, while the adequacy was not changed. Antibacterial ratio of 0.64 mg/ml group against C. a was 90.82%, and that against S. a was 94.96% in 24 hours, respectively. It was found that the antibacterial property of the soft lining material can be acquired by coating this antibacterial solution with silver ion, without changing the adequacy.

Microstructure analysis of the machinable infiltrated ceramic fracture surface / 华西口腔医学杂志

<p><b>OBJECTIVE</b>To compare the fracture surface of the machinable infiltrated ceramic (MIC) prepared in different conditions, and to relate its strength and toughness to the differences in their microstructures.</p><p><b>METHODS</b>The Al2O3 matrix were prepared, infiltrated by the machinable glass and crystallized. Based on sintering and infiltrating time and conditions, the specimens were divided into three groups: Perfect group, insufficiently infiltrated group, mal-sintered substrate group. Specimens were fabricated, three point flexural strength and elastic modulus were tested, and the microstructure of the MIC fracture surfaces was analyzed by means of scanning electron micrograph (SEM) observation.</p><p><b>RESULTS</b>The strength of the insufficiently infiltrated group and mal-sintered substrate group were lower than that of the perfect group, and faults in the microstructure of these two groups also proved this. The foreland of glass infiltrating in the Al2O3 and the interface of glass and complex demonstrated that the Al2O3 surface was smoother than the complex and there was a big crack in the glass but not in the complex which proved the crack resistibility of glass and Al2O3 were smaller than that of the complex (MIC).</p><p><b>CONCLUSION</b>Correct preparing process could make the glass infiltrate into properly sintered Al2O3 sufficiently which ensured best mechanical properties of the complex.</p>

Microdiffraction measurements of natural tooth by high resolution X-ray diffraction equipment / 生物医学工程学杂志

The main mineral component of natural tooth was determined as calcium apatite many years ago; most of them exist in the form of hydroxyapatite with different crystallites. If a tooth decayed, the crystalline of hydroxyapatite would be changed and decomposed. In our experiment, a natural tooth with caries was measured by high resolution XRD equipment: X'pert Pro. Three spots which included normal enamel, normal dentin and caries tissue were analyzed. The results showed that tooth was a kind of biological mixed crystal composed of many crystal phases, the main crystal phase was hydroxyapatite. From normal enamel to normal dentin and to caries tissue, the length of the a-axis of hydroxyapatite crystallite increased, the length of the c-axis of hydroxyapatite crystallite remained unchanged. The crystal sizes were: normal enamel D002 = 27.600 nm; normal dentin D002 = 16.561 nm; caries tissue D002 = 13.163 nm. Crystallinity: normal enamel>normal dentin>caries tissue. According to our experiment, tooth could be conveniently studied by high resolution microdiffracion XRD equipment.

Effects of fluid shear stress on bone resorption in rat osteoclasts / 生物医学工程学杂志

This study was aimed to assess the effects of fluid shear stress on the bone resorption in rat osteoclasts. The osteoclasts were derived from the lumbar vertebrae marrow cells which were isolated from the 6-month-old female Sprague Dawley rats, cultured on the slide at 1 x 10(6) cell/ml, and induced with 1, 25 (OH)2 Dihydroxyvitamin D3. The slide containing osteoclasts was taken out on day 7 after culture and then put into the flow chamber. The loads of fluid shear stress applied to the osteoclasts were 5.97, 11.36, 16.08 and 20.54 dyne/cm2, respectively, for 30 minutes. The osteoclasts unloading fluid shear stress were used as control. The bone resorptive pits were studied by light microscopy and scanning electron microscopy. The tartrate-resistant acid phosphatase (TRAP) secreted by osteoclasts was detected with ultraviolet spectrophotometry. The results showed that fluid shear stress can increase the activity of TRAP and significantly increase the number and area of bone resorptive pits made by osteoclasts,and the effect of fluid shear stress on the bone resorption of osteoclasts is the same as that on the activity of TRAP. The reaction of the osteoclasts to the fluid shear stress in this study also suggested that the bone resorption of osteoclasts be increased in a magnitude of fluid shear stress-dependent manner, and that the changes of TRAP activity be closely related to the changes of the number and area of resorptive pits of the osteoclasts.

Study on the expansion properties of homemade fast investment material for the IPS-Empress2 castable ceramic / 生物医学工程学杂志

IPS-Empress2 is a successful all-ceramic restoration system. To lower its cost, and promote its application, a kind of homemade fast investment material has been developed. The aim of this study was to evaluate the expansion properties of this investment material. The setting expansion, thermal expansion and total expansion of the homemade fast investment material were tested. The same properties of the IPS special fast investment material were also tested as control. Then the SPSS statistics software was used to evaluate the differences between the homemade material and the special material. The results show that the setting expansion rate, thermal expansion rate and total expansion rate of the special investment material for IPS-Empress2 are 0.858%, 1.11% and 1.17% respectively, while the same parameters of the homemade investment material are 0.798%, 1.09% and 1.16% respectively. There is no statistically significant difference in these expansion properties between the two investment materials. In conclusion, the expansion properties of homemade fast investment material are comparable to those of the special fast investment material, so it can compensate for the cast contraction of IPS-Empress2 castable ceramic precisely.

Effect of erosion on strength of dental infiltrated Al2O3 ceramics / 生物医学工程学杂志

The objective of the research is to investigate the elements of routine sandblast technique on the evolution of bending strength of dental infiltrated Al2O3 ceramics and the underlying erosion mechanism. The plane specimens of an infiltrated ceramic were manufactured, polished and then tested under the modified pen-like sandblasting apparatus (90 degrees erosive angle and 10 mm sandblasting distance), with different grit sizes, working pressure and disposing time. Half of samples were selected randomly and sintered subsequently with Vitadur alpha veneering porcelain. Before and after sintering, the three-point-bending strengths was measured, and the surfaces of dental porcelain were observed with SEM and LCSM. The bending strength of ceramics decreased significantly after sandblast as compared with that of empty control group. After the procedure of sintering the veneering porcelain, the descending evolution of bending strength slowed down. Under the present manufacturing conditions, grit size effect is prominent among those correlative elements of sand grit size, working pressure and disposing time. And fatigue cracking characterizes the mechanism of erosion of dental infiltrated Al2O3 ceramics.

Investigation of machinable-infiltrated-ceramic glass infiltrating through the aluminous matrix / 生物医学工程学杂志

This investigation was amied at the infiltrative capability of the machinable-infiltrated-ceramic(MIC) glass and the color of the composite after the MIC glass infiltrated through the aluminous matrix with different packing densities. By heating the components to 1100 degrees C for 2 hours, the MIC glass was made to infiltrate through the aluminous matrix with different packing densities. We measured the infiltrative depth and the color parameter and observed the rupture surface of the composite by means of SEM. There was a linear relation between the square of infiltrative depth and the packing density of aluminous matrix. The minimal depth was 3.092 mm. No relationship was noted between the composite's color coefficient and the packing density of aluminous matrix. In the rupture process of the composite, crack deflexion, crystal evulsion, and rupture through crystal could be observed. This experiment proved that the infiltrative characters of MIC glass meet the clinical requirement, the composite's color is steady and the mechanical intensity is stable.

Study on infiltration glass for machinable-infiltrated-ceramic and on its colorants / 生物医学工程学杂志

In order to develop tinted infiltration glass and its colorants, which can make the ceramic have good spectrum transmittance, color space, color stability and be suitable for clinical use, we selected the best prescription and confirm the ingredient and content of the colorants. Molten glass was prepared in Al2O3 crucible by heating the components to 1420 degrees C for 2 hours. The refractive index and thermal stability of the glass were investigated. The refractive index of the MIC infiltration glass was 1.5969(587.6 nm, nd). It was close to the index of aluminous matrix 1.759(546.07 nm, ne), which increased the spectrum transmittance of MIC. The thermal expansion coefficient of the glass was 7.565 microns/m/degree C, which was compatible with the thermal expansion coefficient of aluminous matrix(8.214 microns/m/degree C). This study proved that the tinted infiltration glass has good color stability, spectrum transmittance, and thermal expansion properties.

The influence of surface conditioning on the shear bond strength of La-Porcelain and titanium / 华西口腔医学杂志

<p><b>OBJECTIVE</b>To determine the influence of different surface conditioning methods on bonding strength of low fusing porcelain (La-Porcelain) and titanium.</p><p><b>METHODS</b>The surface of the samples were sandblasted for 2 min with 80-250 microns Al2O3 or coated for two times with Si-couple agent or conditioned by pre-oxidation. The shear bond strength was examined by push-type shear test with a speed of 0.5 mm/min in a universal testing machine. Scanning electron microscopy (SEM) and electron probe micro-analyzer (EPMA) were employed to explore the relationship between bonding strength and microstructures, as well as the element diffusion at the interface between porcelain coating and titanium when heated at 800 degrees C.</p><p><b>RESULTS</b>Bonding strength was not statistically different (P > 0.05) after sandblasting with Al2O3 in particle size ranged from 80 microns to 250 microns. When a Si-couple agent was used, bond of porcelain to titanium was significantly lower (P < 0.05). The shear bond strength of the porcelain to the pre-oxidized titanium surface remained unchanged after heating (P > 0.05). The SEM results revealed integrity of porcelain and titanium.</p><p><b>CONCLUSION</b>La-Porcelain showed a small effect of surface coarseness. Sandblasting the titanium surface with 150-180 microns Al2O3 can be recommended as a method for better bonding between La-Porcelain and titanium. The Si-couple agent coating and pre-oxidation of titanium surface is unnecessary.</p>

A study on the mechanical properties and microstructure of Alumina-zirconia nano-composite infiltrated ceramic / 华西口腔医学杂志

<p><b>OBJECTIVE</b>To evaluate the mechanical properties and microstructure of a new dental full-ceramic material: alumina-zirconia nano-composite infiltrated ceramic.</p><p><b>METHODS</b>The flexural strength was tested with three-point bending method and the fracture toughness with single edge notch bend (SENB) method. The composition of crystal phases in the infiltrated ceramic was analyzed by X-ray diffraction (XRD). The microstructure of the infiltrated ceramic was examined by scanning electronic microscope (SEM).</p><p><b>RESULTS</b>The average three-point flexural strength of the material was (610.85 +/- 37.07) MPa and the average fracture toughness determined by SENB method was (6.51 +/- 1.38) MPa.m1/2. The main crystal phases in this composite ceramic were alpha-Al2O3 and TZP-ZrO2.</p><p><b>CONCLUSION</b>Alumina-zirconia nano-composite infiltrated ceramic is a new infiltrated ceramic with favorable mechanical properties. It demonstrated a promising future for clinical application.</p>

Development of GI-II tinted infiltration glass and determination of its properties / 华西口腔医学杂志

<p><b>OBJECTIVE</b>Glass 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.</p><p><b>METHODS</b>The 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.</p><p><b>RESULTS</b>The 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.</p><p><b>CONCLUSION</b>GI-II tinted infiltration glass had favorable physical, mechanical properties and good thermal stability.</p>

A study of alumina powder used in fabrication of GI-II infiltrated ceramic / 华西口腔医学杂志

<p><b>OBJECTIVE</b>This investigation was to analyze the mechanism of formation of porous structure by studying some characteristics of the alumina powder used for GI-II Infiltrate Ceramic.</p><p><b>METHODS</b>The alumina powder crystal type was analyzed with X-diffractometer, and its size distribution was obtained by powder size analysis device, and fracture surface of alumina adobe was observed under scanning electronic microscope.</p><p><b>RESULTS</b>Alumina crystals were purely alpha type, with firmest structure and best stability. Fine powder whose size was smaller than 0.5 micron occupied 9 wt% (mass) and, coarse powder with sizes between 1 to 3.5 microns occupied 75 wt% (mass). The SEM graphs of adobe showed that fine powders were attached to the surface of coarse powders, dispersed evenly, and alumina powders contacted each other firmly.</p><p><b>CONCLUSION</b>The crystal type, size distribution and even dispersion of the studied alumina powder contributed to the formation of porous structure of alumina sintered body (preform), which was the material prerequisite in forming porous preform and one of the key factors to the rise of strength of GI-II Infiltrated Ceramic.</p>

Distraction osteogenesis for the repair of cleft palate--an ultrastructural study / 华西口腔医学杂志

<p><b>OBJECTIVE</b>The aim of this study was to explore ultrastructural characters of the newly formed bone in the correction of cleft palate (CP) bone defect by distraction osteogenesis (DO).</p><p><b>METHODS</b>The CP experimental animal models (12 cats) were established surgically, and were divided randomly into the experimental group (10 cats), in which the hard palate bone defects were corrected with DO procedure at the rate of 0.4 mm x 2/day. The specimen retrieval with euthanasia was carried out at 2, 4, 6, 8, 12 weeks after completion of distraction. Ultrastructural study was then performed; the experimental control group (2 cats) was kept for 6 weeks before euthanasia without any correction, the other extra 2 cats were used as the negative control.</p><p><b>RESULTS</b>New bone formation appeared in early 2 weeks. Exclusively intramembranous bone formation was observed in all specimens. The remodeling activities were keep observed throughout the period of study, and the bone structure matured gradually till 12 weeks after the completion of DO. No repair was observed in experimental control group.</p><p><b>CONCLUSION</b>The reconstruction of CP bone defect by means of DO could get active intramembranous bone formation and remodeling, which adapted to normal functional activities.</p>

Properties of GI-II glass/alumina composite infiltrated with GI-II tinted infiltration glass / 华西口腔医学杂志

<p><b>OBJECTIVE</b>The purpose of this study was to determine the thermal, mechanical properties and density of the composite infiltrated with GI-II tinted infiltration glass.</p><p><b>METHODS</b>The 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.</p><p><b>RESULTS</b>The 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.</p><p><b>CONCLUSION</b>The 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.</p>

Spectral transmittance of GI-II glass/alumina composite / 华西口腔医学杂志

<p><b>OBJECTIVE</b>The 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.</p><p><b>METHODS</b>Plate-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.</p><p><b>RESULTS</b>The 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.</p><p><b>CONCLUSION</b>GI-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.</p>