ABSTRACT
BACKGROUND:Due to limitations of the physicochemical properties of soft denture liner material itself, whisker has been added in the soft lining material in recent years, so as to enhance its mechanical properties. OBJECTIVE:To investigate the effect of different additive amount of anhydrous calcium sulfate whisker on the mechanical function of self-curing soft denture liner. METHODS: There were six groups in this experiment. Anhydrous calcium sulfate whisker at the mass fraction of 0 (control), 1%, 2%, 3%, 4%, 5% was respectively added into self-curing soft liner materials, 10 test specimens in each group, a total of 60 test specimens. The shear bond strength, Shore hardness and tensile strength were detected. RESULTS AND CONCLUSION: With the increasing amount of the anhydrous calcium sulfate whisker, the Shore hardness of the soft lining material was increased continuously, and the tensile strength was increased firstly and then reduced. When 3% anhydrous calcium sulfate whisker was added, the bond strength and tensile strength of soft lining material reached the peak. Taken together, the mechanical properties of the soft lining materials became perfect when 3% anhydrous calcium sulfate whisker was added. These results demonstrate that anhydrous calcium sulfate whisker may affect the mechanical properties of self-curing soft liner.
ABSTRACT
BACKGROUND:Microleakage between restoration, tooth structure and bonding agent can cause the entry of bacteria and liquid in the mouth into the gap, thereby damaging the bonding interface between the restoration and tooth tissues, and leading to bond failure. Microleakage detection can directly show whether the closure of the root canal of post and core system is good or bad. The severity of microleakage directly affects the restorative effects of post and core. OBJECTIVE: To evaluate the effects of different root canal cleaning methods on the microleakage between the fiber post and root canal dentin. METHODS: Thirty fresh non-caries premolar posts with free root canalin vitro were randomly divided into five groups, and the root canal wal was respectively washed with saline, 5.25% sodium hypochlorite solution+17% ethylenediamine tetra-acetic acid (EDTA)+saline, 3% hydrogen peroxide solution+5.25% sodium hypochlorite+ saline, 3% hydrogen peroxide solution+2% chlorhexidine solution+saline, and 2% chlorhexidine solution+17% EDTA+saline in different groups. Super-bond C&B adhesive agent was used for bonding fiber post, and the microleakage of each sample was observed under stereomicroscope. RESULTS AND CONCLUSION: The severity of microleakage in the al groups was ranged as folows: saline group > 3% hydrogen peroxide solution+5.25% sodium hypochlorite+saline group > 5.25% sodium hypochlorite solution+17% EDTA+saline and 3% hydrogen peroxide solution+2% chlorhexidine solution+saline groups > 2% chlorhexidine solution+17% EDTA+saline group.
ABSTRACT
BACKGROUND:Studies have confirmed that the surface treatment methods such as silane coupling agent and sand blasting could improve bonding strength of zirconia ceramics and resin binder. In addition, the increase of micro cracks on the surface of zirconia ceramics can also improve the bonding strength of zirconia ceramics and resin binder. But there is a lack of related studies addressing whether repeatedly sintering would have an impact on shear bond strength of zirconia ceramics. OBJECTIVE:To determine the effect of decorative porcelain temperature firing on the shear bond strength between dental zirconia ceramics and resin binder. METHODS:Twenty pieces of zirconia ceramics specimens were selected from 40 tablets, and then randomly divided into five groups according to the number of sintered times:control group (without sintering), sintering groups for 2, 4, 6, 8 times. Heat starting temperature was 500 ℃, and final temperature was 1 000 ℃ with a heating rate of 55 ℃/min. The vacuum time was 7 minutes. During the sintering, the final temperature was constant. Unsintered ceramic pieces were bonded using resin binder. Universal testing machine was used to test the shear strength of the interface between the two pieces of zirconia ceramics. The interface after shearing was characterized by scanning electron microscope. RESULTS AND CONCLUSION:The shear strength of sintering groups for 4, 6, 8 times was significantly higher than that of the control group (P0.05). Shear strength of specimens sintered 8 times was slightly higher than that sintered 4 and 6 times (P<0.05). Under the scanning electron microscope, there was no crack on the surface of non-sintered zirconia ceramics. After 2 times sintering, the surface appeared to have fine cracks. After sintering 4 times, visible cracks were increased. After six rounds of sintering, the surface began to have significant changes;cracks rose along with slight gaps and a smal amount of adhesive residues were found. After sintering for 8 times, cracks and voids were obviously increased on the sintered surface and adhesive residues were found. It indicated that after sintering for 4, 6 and 8 times, zirconia ceramics could have a good shear strength binding to resin adhesives;with the increasing of sintering times, the shear bond strength could be increased.
ABSTRACT
BACKGROUND:At present, there are stil differences in the studies of total-etch, self-etch and self-bonding resin cement effect on the coronal microleakage and bonding strength of fiber posts. OBJECTIVE:To evaluate the coronal microleakage and the bonding strength of fiber posts treated with three kinds of resin cements. METHODS:Total y 32 upper incisors were randomly divided into five groups, including three experimental groups and two control groups. After the root canal preparation, three kinds of resin cements (EMBRACE WetBond, LuxaCore, Medental Multi-cure) were used to fiber posts with the bond diameter of 1.4 mm. Stereomicroscope was used to observe the microleakage. Then, the specimens were cut into 2 mm wafer along the axis of tooth, and universal testing machine for push-out test was used to observe the failure mode. In the positive control group, no root canal preparation was done, the root was coated with nail polish, and the crown was directly exposed to the dye. In the negative control group, no root canal preparation was done, the root canal orifice was covered with the resin, the tooth was overal coated with nail polish and then embedded 1 mm below the section. RESULTS AND CONCLUSION:The microleakage was observed in al the three resin cements, Medental Multi-cure showed the least microleakage and LuxaCore showed the largest microleakage, and there was significantly different among the three kinds of resin cements (P<0.05). The bonding strength of three cements had significant differences (P<0.05), and ranked from high to low:Mdental Multi-cure, LuxaCore, and EMBRACE WetBond. The main fracture modes were binder/fiber post fracture and mixed failure. The results suggest that the total-etch resin cement binds tightly with the dentin, and owns a superiority in the microleakage and bonding property as compared with the self-etch resin cements and self-bonding resin cements.