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PURPOSE: Heat of composite polymerization (HP) indicates setting efficacy and temperature increase of composite in clinical procedures. The purpose of this in vitro experimental study was to evaluate the effects of 5 temperatures on HP of two new composites. MATERIALS AND METHODS: From each material (Core Max II [CM] and King Dental [KD]), 5 groups of 5 specimens each were prepared and their total HPs (J/gr) were measured and recorded, at one of the constant temperatures 0degrees C, 15degrees C, 23degrees C, 37degrees C and 60degrees C (2 x 5 x 5 specimens) using a differential scanning calorimetry (DSC) analyzer. The data were analyzed using a two-way ANOVA, a Tukey's test, an independent-samples t-test, and a linear regression analysis (alpha=0.05). RESULTS: No polymerization reactions occurred at 0degrees C; then this temperature was excluded from statistical analyses. The mean HP of the remaining 20 KD specimens was 20.5 +/- 14.9 J/gr, while it was 40.7 +/- 12.9 J/gr for CM. The independent-samples t-test showed that there were significant differences between the HP of the two materials at the temperatures 15degrees C (P=.0001), 23degrees C (P=.0163), 37degrees C (P=.0039), and 60degrees C (P=.0106). Linear regression analysis showed statistically significant correlations between environment temperatures and HP of CM (R2=0.777). CONCLUSION: Using CM is advantageous over conventional composite because of its better polymerization capacity. However due to its high HP, further studies should assess its temperature increase in vivo. Preheating KD is recommended. Refrigerating composites can negatively affect their polymerization potential.
Subject(s)
Calorimetry, Differential Scanning , Composite Resins , Dental Materials , Differential Thermal Analysis , Hot Temperature , Linear Models , Polymerization , Polymers , RefrigerationABSTRACT
Objective To prepare ?-CD(?-cyclodextrin) inclusion compounds and PEG- 4000[poly-(ethylene glycol) 4000] solid dispersions of mefenamic acid (MFA)in order to improve its dissolution. Methods The inclusion compounds of MFA were prepared using saturated ?-CD solution method by orthogonal test. The solid dispersions were prepared using melt-cool process with PEG- 4000 as a carrier. The inclusion compounds and solid dispersions were identified by differential scanning calorimetry (DSC) gram and their dissolution rates were tested in pH8.0 buffer solution. Results The suitable condition for preparing ?-CD inclusion compounds of MFA industrially was the weight ratio of 1∶4 between MFA and ?-CD, agitating for 4 h at 70 ℃. The suitable proportion for preparing solid dispersions of MFA was the weight ratio of 1∶4 between MFA and PEG- 4000. Conclusion Dissolution rates of MFA are apparently improved in inclusion compounds and PEG- 4000 solid dispersions, and the solubility of MFA is apparently increased by 2～3 times in inclusion compounds and PEG- 4000 solid dispersions.
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Objective To prepare and identify the andrographolide-hydroxypropyl-?-cyclodextrin(an- drographolide-HP-?-CD)inclusion compound.The tool ratio between andrographolide and HP-?-CD and the thermodynamic constants in inclusion were studied simultaneously.Methods The andrographolide- HP-?-CD inclusion compound was prepared with lyophilization technique.Meanwhile,the inclusion com- pound was identified by differential scanning calorimetry(DSC)methods,infrared spectrometry(IR),and X-ray diffraction(XRD),respectively.The tool ratio between host and guest moleculars and the thermo- dynamic constants during the inclusion process were also researched by phase solubility method.Results An 1:1 molar ratio inclusion complex of andrographolide with HP-?-CD could be formed at 25,35,and 45 C.The phase diagram was A_L type and the procedure of inclusion was a heat release process.Conclusion The solubility of andrographolide-HP-?-CD inclusion compound can be increased obviously by the above- mentioned preparing techniques.
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Objective In order to observe the dispersing form, the sustained release solid dispersion was prepared. Methods Sustained-release solid dispersion was prepared by taking ethyl cellulose as carrier. And the X-ray diffraction, differential scanning calotimetery (DSC) were used to evaluate the dispersing form of puerarin in the preparation and to study the solubility in vitro. Results The X-ray diffraction experiment showed that the puerarin was existed in molecuar and minicrystal form. DSC Experiment showed that there is no puerarin crystal in the solid dispersion. The test for stripping showed that thare was a better releasing results in the sustained-release capsula. Conclusion The sustained-release solid dispersion can disperse the puerarin highly to increase its bioavailability. The prepared capsula has a marked sustained-release effect.
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Objective To parperare and identify the irisquinone-hydroxypropyl-?-cyclodextrin (irisquinone-HP-?-CD) inclusion compound. The inclusion mechanism and mol ratio of irisquinone and HP-?-CD were studied simultaneously. Methods The irisquinone-HP-?-CD was prepared with lyophilization technique. The mol ratio between host and guest moleculars was also researched by molecular gradient and continuing variational methods in inclusion processing. At the same time, the inclusion compound was identified by X-ray diffraction (XRD) and differential scanning calorimetry (DSC) methods, respectively. Results The above-mentioned systems showed the mol ratio of HP-?-CD-irisquinone (2 : 1) and the inclusion compound enhanced remarkably the most solubilization and more combined constant of irisquinone in 25, 35, and 45℃. The lyophilized powder had been formed inclusion compound by identifying. Conclusion It is advantageous to increase the solubilization and to strengthen the stability of irisquinone by preparing inclusion compound.