OBJECTIVETo survey and compare the thickness-change of different thickness thermoplastic materials under different test condition and make sure the relationship between the thickness-change and the material initial thickness in order to provide a guide in selecting the suitable thickness thermoplastic in practice.

METHODSTo choose Biolon, the thickness include 1.0 mm, 0.75 mm, 0.5 mm. Used Electron Vernier caliper to measure the thickness-change of different thickness thermoplastic materials under different processing mode. The data was analyzed by SPSS 10.0.

RESULTSAfter thermoforming the thickness of thermoplastic became thinner, the thickness of Biolon 0.75 mm decreased by 0.14 mm, Biolon 1.0 mm decreased by 0.22 mm and Biolon 0.5 mm decreased by 0.14 mm. After saliva immersion the thickness became thicker. The thickness of Biolon 0.75 mm increased by 0.02 mm, Biolon 1.0 mm increased by 0.03 mm and Biolon 0.5 mm increased by 0.02 mm.

CONCLUSION1)The influence of different processing mode to the thickness-change had relation to the material initial thickness. 2)The Biolon 0.75 mm had certain superiority in thickness stability compared to the homogeneous brand through the above research.

The purpose of this study was to investigate how cyclic loading influenced the fracture toughness of hot-press lithium disilicate and zirconia core materials and whether there was an increase in the propensity for crown failure. Two types of all-ceramic crowns including the IPS e.max Press system (n=24) and the Lava zirconia system (n=24), were selected. Sectioned specimens were subjected to cyclic loading with the maximum magnitude of 200 N (R=0.1) until two million cycles. The material properties including Young's modulus (E) and hardness (H) and the fracture toughness (KIC) of the core materials were evaluated using indentation methods (n=12 each). The load-bearing capacities of the specimens were examined by means of monotonic load to fracture (n=12 each). It was found that the material properties, including E, H and KIC, of the two types of dental ceramics, were reduced. Statistical analysis indicated that there were no significant influences of fatigue loading on material properties E and H for both types of dental ceramics or KIC for zirconia, while for the IPS e.max Press core, KIC, which was parallel to the direction of the lithium disilicate crystals, was significantly reduced (P=0.001). A conclusion was drawn that zirconia possesses high mechanical reliability and sustainable capacity to resist fatigue loading, while fatigue loading remarkably degraded the anisotropic mechanical behaviour of hot-press lithium disilicate ceramics.
Crowns ; Humans ; Mastication ; Materials Testing

OBJECTIVETo analyze chemical mechanism of bonding improvement of zirconia via 10-methacryloyloxydecyl dihydrogen phosphate (MDP) conditioning.

METHODSVarious models were created for tetragonal zirconia crystals, molecular MDP, and MDP complex, and tetragonal zirconia crystal. Thermodynamic methods were used to analyze configuration between MDP and tetragonal zirconia crystal through calculation of their Gibbs free energy values and equilibrium constants.

RESULTSTwo potential configurations (double- and single-coordinate) may occur between MDP and ZrO2 crystal clusters. Thermodynamic calculations showed that -147.761 and -158.073 kJ·mol⁻¹ Gibbs free energy were required to form single- and double-coordinate configurations; their negative signs indicate that reactions for both configurations can occur. Equilibrium constant for single-coordinate configuration was 7.72×10²⁵, which was less than that of double-coordinate configuration (4.95×10²⁷), suggesting that the latter was more stable.

CONCLUSIONSMDP can spontaneously establish a double-coordinate configuration with zirconia.
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OBJECTIVE: To explore the conversion of resin monomer, the change of inorganic component and the influencing factors on the oxygen inhibition layer formed on the cured surface of resin cement. METHODS: Three kinds of resin cement were divided into three groups: (1) light-cured group: RelyX Veneer, NX3 (light-cured), Variolink N; (2) dual-cured group: RelyX U200 Automix, NX3 (dual-cured), Multilink Speed; (3) chemically-cured group, and the above 3 types of dual-cured resin cement cured without illumination could be used as chemically-cured resin cement. Each sample was provided with and without oxygen exposure of two matching surfaces, cured respectively, and the variables of light intensity and illumination time were set in the light-cured group and the dual-cured group. Scanning electron microscopy was used to observe the samples' surface morphology. Energy dispersive spectrometer was used to analyze the samples' composition of surface elements. Confocal Raman spectroscopy was used to measure the monomer conversion of resin cement and to obtain the thickness of the oxygen inhibition layer. RESULTS: (1) On the surface of cured resin cement, the weight percentage of oxygen element in the aerobic side was higher than that in the anaerobic side (P < 0.05), and the weight percentage of inorganic element was lower than that in the anaerobic side (P < 0.05). (2) The surface monomer conversion of the cured resin cement on the aerobic surface was significantly lower than that on the anaerobic surface (P < 0.05), and the surface monomer conversion on the aerobic surface and the anaerobic surface was the lowest in the chemically-cured group (P < 0.05), the dual-cured group was the highest (P < 0.05), and the light-cured group was between them. With the increase of light intensity or illumination time, the surface monomer conversion increased (P < 0.05). (3) The thickness of the oxygen inhibition layer was the thickest in the chemically-cured group [(40.27±2.81) μm](P < 0.05), the thinnest in the dual-cured group [(21.87±5.42) μm](P < 0.05) and light-cured group [(23.73±3.84) μm] was between them. With the increase of light intensity or illumination time, the thickness of the oxygen inhibition layer of resin cement decreased (P < 0.05). CONCLUSION When resin cement is exposed to oxygen, it will form an oxygen inhibition layer, its surface's inorganic filler is less, the surface monomer conversion is lower. The surface monomer conversion and the thickness of oxygen inhibition layer are affected by curing mode and illumination factors.
Materials Testing ; Oxygen ; Resin Cements

Dental impressions are widely used in the field of oral restoration. The materials are used for making impression in oral cavity. In order to measure the thickness of impression for reference in clinic, the real impressions are taken as the object for studying. Through optical method, charge-coupled device (CCD) is used for collecting the grey image of cutting section of the impressions which are located in the same plane with steel dividing ruler. According to convert relationship between dividing ruler and pixels collecting grey image, the thickness of impression specimens can be obtained. The results show that the optical method used for measuring thickness is feasible to the task and the precision can reach micro dimension. The experiment method and technique can also be provided for measuring thickness of similar tissue engineering materials.
Dental Impression Materials ; Dental Models ; Humans ; Materials Testing ; Optics and Photonics

In China, the evaluation of hemocompatibility of biomaterials is limited to hemolysis, coagulation time,and the number and morphology of platelets adhered on biomaterials. The present research, however, is aimed to establish a method for evaluating the function of sheet biomaterials in platelet activation. Platelet activation caused by glass, polyvinyl chloride or polymethylvinylsiloxane sheets was evaluated by measuring alpha-granule membrane protein (GMP-140) in platelet poor plasma, using a reasonable blood-material contact model vibrating at different speed. The result showed that the difference in platelet activation was not significantly different among the three above-mentioned materials at 140r/m or 200r/m. However, when it comes to 230r/m, significant difference was observed among these three groups, with glass > polyvinyl chloride > polymethylvinylsiloxane. But the order was reversed at 270r/m, which may be due to the different interfacial tension of different materials. Therefore, the method is suitable to evaluate platelet activation caused by sheet biomaterials, but an appropriate vibrating speed should be chosen. The interfacial tension plays an important role in the model and should be considered for results assessment.
Biocompatible Materials ; Humans ; Materials Testing ; methods ; Platelet Activation ; Surface Properties

In-vitro test is usually conducted as a preliminary screening test in the evaluation of the haemocompatibility of biomaterials for its short-term consuming, convenience and less expense. The selection of appropriate model for blood-biomaterial interaction, the choice of sensitive and specific parameters, and the minimization of additional blood activation are most important in the in-vitro test. In addition, the time and the style of blood-biomaterial interaction, the choice of sensitive and specific parameters, and the minimization of additional blood activation are most important in the in-vitro test. In addition, the time and the style of blood-biomaterial interaction, the selection of primary reference materials and the shear rate should be considered. In recent years, though great progress has been made in the in-vitro evaluation of haemocompatibility of biomaterials, all these influencing factor should be standardized for more effective evaluation of the haemocompatibility of biomaterials.
Biocompatible Materials ; Evaluation Studies as Topic ; Humans ; Materials Testing ; standards

The flowability of a root canal sealer is clinically important because it improves the penetration of the sealer into the complex root canal system. The purpose of this study was to compare the flowabilities of four root canal sealers, measured using the simple press method (ISO 6876), and their viscosities, measured using a strain-controlled rheometer. A newly developed, calcium phosphate-based root canal sealer (Capseal) and three commercial root canal sealers (AH Plus, Sealapex and Pulp Canal Sealer EWT) were used in this study. The flowabilities of the four root canal sealers were measured using the simple press method (n=5) and their viscosities were measured using a strain-controlled rheometer (n=5). The correlation between these two values was statistically analysed using Spearman's correlation test. The flow diameters and the viscosities of the root canal sealers were strongly negatively correlated (ρ=-0.8618). The viscosity of Pulp Canal Sealer EWT was the lowest and increased in the following order: AH Plus Materials Testing ; Rheology ; Root Canal Filling Materials ; Temperature ; Viscosity

Calcium phosphate cement (CPC) is well known for the excellent bioactivity and biocompatibility, however, CPC has been used only for the repair of non-load bearing bone defects due to its brittle nature and low flexural strength. Polymer reinforced CPC has been considered as one of the most effective strategies for mechanical reinforcement. This paper summarizes various kinds of polymers loaded CPC:fiber reinforcement, microsphere reinforcement and dual setting cements. It is aimed to analyze the advantages, disadvantages and principles of the polymers reinforced CPC, and so as to lay a foundation for the further research of improving and manufacturing the CPC with ideal mechanical properties.
Biocompatible Materials ; Bone Cements ; Calcium Phosphates ; Materials Testing ; Polymers

OBJECTIVETo investigate necessity of the further processing for adsorptive resin material.

METHODSAccording to GB/ T 16886.4, coagulation tests, haematology tests, in vitro spontaneous platelet-adhesion test and complement activation tests were conducted respectively to assess the in vitro blood compatibility of adsorptive resin material.

RESULTSIn comparison with polypropylene, he adsorptive resin material appears to be a very slight activator to the endogenous blood coagulation system, it can inhibited the exogenous blood coagulation system very significantly (P < 0.01), it can adhere to fibrinogen, red blood cells, reticulocytes very significantly (P < 0.01), and platelet significantly (P < 0.05). The adsorptive resin material is also revealed to be a very significant activator (P < 0.01) to the complement system.

CONCLUSIONSThe in vitro blood compatibility assessment witnesses that it is very necessary for the adsorptive resin material to go through the certain special processing(such as the surface modification and the microencapsulation technology, etc) before its application to human being.