[The effect of different dispersive methods on flexural strength nano-ZrO(2) reinforced denture polymethyl methacrylate].

PURPOSE: To study the effect of different dispersive methods on flexural strength of nano-ZrO(2)/polymethl methacrylate(PMMA) composite samples. METHODS: The nanometer ZrO2 particles which were modified by coupling agent Z-6030 were mixed to PMMA as the filler materials (3%) by means of handle disperse, ball milling disperse and ultrasonic wet disperse, respectively. Pure PMMA was used as blank control .With reference to the standard of ISO-1567:1999, standard samples were made and tested by three-point bending test. Then the data of flexural strength of the four groups were analyzed statistically with SAS 6.12 software package for one-way ANOVA(Newman-Keuls test). And the optimized synthesis way of the PMMA composite materials was selected. RESULTS: The flexural strength of the ball milling group and the ultrasonic group were significantly higher than the handle group and blank group(P<0.05), with an increase of 17%,10% compared with the blank group. There was no significant difference between the ball milling group and the ultrasonic group (P>0.05). CONCLUSION: Dispersal ways have effect on the flexural strength of PMMA composite materials which are filled with ZrO(2) particles.

[Influence of different amount of silane coupling agent on the flexural strength of PMMA/nanometer ZrO2 composites].

PURPOSE: To study the influence of different amount of silane coupling agent Z-6030 on the flexural strength of PMMA/nanometer ZrO(2) composites. METHODS: Nanometer ZrO(2) particles were modified by silane coupling agent Z-6030 with different percentages.In situ polymerization method was used to combine PMMA/ nanometer ZrO(2) composites of denture base plate. With reference to the standard of ISO1567:1999, standard samples of the experimental group were made. PMMA II type powder and PMMA II type liquor were used,which was not added nanometer ZrO(2) and silane coupling agent to make the standard samples of common denture base plate. PMMA II type powder and PMMA II type liquor were used,which was added nanometer ZrO(2) unmodified by silane coupling agent to make the standard samples of the control group. The data of flexural strength of the base plate materials were tested with three-point bending test. One-way ANOVA was adopted to analyze the data using SAS 6.12 software package. RESULTS: When the percentage of silane coupling agent Z-6030 was 3.5%,the flexural strength of PMMA/nanometer ZrO(2) composite resin material of denture base plate was strongest, which was significantly higher than that of the common denture base plate group,the control group,2.0% group,4.0% group,4.5% group and 5.0% group(P<0.05). 0.5% group,1.0% group,1.5% group,2.5% group,3.0% group and 3.5% group had no significant difference with each other(P>0.05). 0.5% group,1.0% group,1.5% group,2.0% group,2.5% group,3.0% group,4.0% group,4.5% group,5.0% group,the common denture base plate group and the control group had no significant difference with each other(P>0.05). CONCLUSION: Using proper percentage of silane coupling agent Z-6030 can improve the flexural strength of PMMA/nanometer ZrO(2) composite resin material of denture base plate. This study showed that the best range of the percentage of silane coupling agent Z-6030 was 3.5%.

[Clinical analysis of colour distribution in tetracycline teeth].

PURPOSE: To analyze the colour range and distribution of tetracycline teeth, and the difference from normal teeth. METHODS: 142 cases with 468 anterior tetracycline teeth and 100 cases with 200 normal anterior teeth were collected. The color was measured by a computer-aided Shade-Eye NCC colorimeter, and expressed in terms of 3 coordinate values (L,a,b) of the CIE-1976-Lab color system. Chroma (Cab)and hue (h(ab) degrees)were calculated according to the value of a and b. The data were analyzed with SAS6.12 software package for description, Student's t test and Duncan test. RESULTS: The range of L, a, b Cab, h(ab) degrees of tetracycline teeth was 42.33-77.00, -0.6-9.6, 2.67-31.5, 5.24-31.89, 38.62 degrees-95.47 degrees, respectively. Significant difference of L value and hue (h(ab) degrees) was found between tetracycline teeth and normal teeth (P < 0.01), which indicated that tetracycline teeth were darker and redder than normal teeth. There was no difference of chroma (Cab) between tetracycline teeth and normal teeth (P > 0.05). Moreover there was significant difference of L value between canine and central incisor, and of H value (h(ab) degrees) between canine and lateral incisor in tetracycline teeth, which indicated that canine was darker and redder than incisor, and redder than lateral incisor, but there was no significant difference in chroma (Cab) among all anterior teeth and no difference in L, a, b between central incisor and lateral incisor. CONCLUSIONS: The study showed the color distribution of tetracycline teeth was wider and more dispersive than normal teeth, and much darker and redder than normal teeth. Supported by Shanghai Leading Academic Discipline