[Characterization of homemade fast investment material for the IPS-Empress2 castable ceramic].

The aim of this study is to evaluate the physical and mechanical properties of our homemade investment material for the IPS-Empress2 castable ceramic. The IPS specific investment material was taken as control. Results show that the setting time, density before heating, density after heating, rate of open hole, compressive strength at 2 hours after setting and the compressive strength after heating to 920 degrees C of the homemade investment material are 9 minutes, 1.813 g/cm3, 1.402 g/cm3, 38.1%, 5.42 MPa and 8.37 MPa respectively, which are comparable or even better than the specific material. Under the SEM, the crystals of the phosphate hydrate in our homemade material are smaller than those in the special material. Since the physical and mechanical properties of our homemade investment material are comparable or superior to those of the specific material, a conclusion is drawn that it has a promising prospect of future clinical application.

[Study on the expansion properties of homemade fast investment material for the IPS-Empress2 castable ceramic].

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.

[Study on alveolar ridge augment through technique combination of implant-retented titanium lattice with decalcified dental matrix implanting].

OBJECTIVE: To evaluate the effect of technique combination of implant-retented titanium lattice with decalcified dental matrix (DDM) implanting. METHODS: Six healthy male dogs (weighing of 10-20 kg) were randomly divided into 3 groups. All the premolars were extracted on both sides of the jaw in dogs. After 2 weeks, titanium lattice and implant were implanted in the maxillary premolar region with DDM on one side (experimental group), but without on the other side (control group) of each dog. After 4, 9 and 14 weeks, respectively, 2 animals were individually killed each time, and the samples were evaluated by general observation, X-ray examination, histological observation and histomorphometric analyses. RESULTS: General observation: Among the 6 dogs, there was no postoperative infection or death. The X-ray examination showed that the bone density of the experimental group was greater than the control group at 4 and 9 weeks, and had no significant difference as to the vicinity bone at 14 weeks. On the other hand, the density of the control group was very low under the titanium lattice and around the implant. The experimental group revealed a ridge augment of (1.93 +/- 0.24) mm, and control group (-1.02 +/- 1.20) mm (P < 0.05). Developed bone sponge could be found after 14 weeks. Histological observation showed that in the experimental group, the DDM surface was nearly absorbed at 4 weeks. A few new bones were formed at 9 weeks. The whole DDM was absorbed; the trabecular bone was thick and arranged regularly; and the intergradations of implant were observed at 14 weeks. In the control group, there were some inflammatory fibers around the neck of implant at 4 weeks. The inflammatory condition extended to the root of implant and the titanium lattice at 9 weeks. There was no newly-formed bone under the titanium lattice at 14 weeks. Histomorphometric analyses showed that the implant contact bone ratio approached 1:1, and showed no significant difference between the new bone fragment and former bone fragment in the experimental group. CONCLUSION: This augmentation of alveolar ridge evaluated by the study is applicable, but further study is necessary.

[A study on the mechanical properties and microstructure of Alumina-zirconia nano-composite infiltrated ceramic].

OBJECTIVE: To evaluate the mechanical properties and microstructure of a new dental full-ceramic material: alumina-zirconia nano-composite infiltrated ceramic. METHODS: 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). RESULTS: 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. CONCLUSION: Alumina-zirconia nano-composite infiltrated ceramic is a new infiltrated ceramic with favorable mechanical properties. It demonstrated a promising future for clinical application.

[A study on the thermal expansion characteristics of Alumina-zirconia nano-composite infiltrated ceramic].

OBJECTIVE: To study the characteristics of thermal expansion of the alumina-zirconia nano-composite infiltrated ceramic. METHODS: The thermal expansion coefficients of alumina-zirconia composite matrix, infiltrating glass and infiltrated ceramic were determined by various methods, respectively. RESULTS: The coefficients of thermal expansion of composite matrix with 10 wt%, 20 wt% and 30 wt% zirconia were 7.607, 7.690 and 8.111 microns/(m. degree C) respectively. The thermal expansion coefficients of AZ-8 and AZ-10 infiltration glass were 6.867 and 7.333 microns/(m. degree C), respectively. The thermal expansion coefficient of infiltrated ceramic was 8.413 microns/(m. degree C). CONCLUSION: The thermal expansion coefficients of the glass and composite matrix matched well. The thermal expansion coefficients of the alumina-zirconia nano-composite infiltrated ceramic and several common veneering porcelains matched well, too.

[The influence of surface conditioning on the shear bond strength of La-Porcelain and titanium].

OBJECTIVE: To determine the influence of different surface conditioning methods on bonding strength of low fusing porcelain (La-Porcelain) and titanium. METHODS: 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. RESULTS: 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. CONCLUSION: 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.