[Dimensional accuracy of dental gypsum casts after immersion in stable chlorine dioxide disinfectant].

OBJECTIVE: To evaluate the changes in dimensional accuracy of dental gypsum casts after immersion in stable chlorine dioxide (SCD) disinfectant solution. METHODS: Each of 90 specimens was made of type III,type IV and type V dental stone, respectively,which were further divided into 9 groups (n=10). The gypsum casts were immersed in 3.71,7.41 and 11.12 mmol/L SCD disinfectant solution for 5, 10 and 15 min, respectively. The dimensional accuracy of dental gypsum casts were measured with outside diameter in micrometer before and after immersion. The data were analyzed using analysis of variance (ANVOA) at 95% confidence level. RESULT: There were no significant changes in dimensional accuracy of all dental gypsum casts treated by same concentration of SCD solution for 5, 10 and 15 min. And the dimensional accuracy of all dental gypsum casts treated with different concentrations of SCD for the same duration did not change. CONCLUSION: SCD disinfectant solution has no impact on dimensional stability of dental gypsum casts.

Long-lasting anti-bacterial activity and bacteriostatic mechanism of tea tree oil adsorbed on the amino-functionalized mesoporous silica-coated by PAA.

Tea tree oil (TTO) is an efficient natural antibacterial agent. However, the bacteriostatic effect of TTO does not prevail for a long period because of the volatile nature of the oil. Therefore, a novel sustained-release formulation of TTO should be developed for improving the applicability of TTO. Herein, the mesoporous silica was selected for constructing a carrier for TTO. Mesoporous silica is non-toxic, easy to modify and exhibited an adjustable pore size. First, the mesoporous silica was modified by an aminated silane coupling agent (NH2-MCM-41). Then, the polyacrylic acid (PAA) was bonded by electrostatic bonds (PAA-NH2-MCM-41), which imparted the sustained-release effect in the TTO, supported in the mesoporous silica channel (TTO/PAA-NH2-MCM-41). The prepared bacteriostatic agent can achieve long-term sustained-release properties. At room temperature (26 ℃), the release rate of TTO after 11 h release reached 50 %. However, the release rate of TTO from TTO/PAA-NH2-MCM-8 reached only 42 % after 24 h. Furthermore, the sustained release behavior of TTO/PAA-NH2-MCM-41 was consistent with the Korsmeyer-Peppas kinetic model. Compared to TTO, TTO/PAA-NH2-MCM-41 exhibited a stable and sustained bacteriostatic effect even after 50 days in a natural environment. The minimum inhibitory concentration (MIC) value of the TTO/PAA-NH2-MCM-41 against Escherichia coli (E. coli) was 0.37∼0.44 mg/mL. TTO altered the cell morphology of E. coli and broke the integrity of the cell membrane, leading to cell death.

[Analysis on content of Ni-Cr in gingival and blood of hares after wearing non-noble porcelain-fused-to-metal crown].

OBJECTIVE: Purpose of the study was to investigate the content of Nickel (Ni) and Chromium (Cr) ion in gingival tissue and blood, and to discuss the reason of gray line in gingival after wearing non-noble Porcelain-Fused-to-Metal crown. METHODS: 38 rabbits were selected as experimental animals which were divided into three groups: control group, group 1 (3 months) and group 2 (6 months). The content of Ni and Cr ion in gingival tissue and blood was detected by atomic absorption spectrometer. RESULTS: The amount of Ni and Cr in group 2 was significantly higher than that in other groups (P < 0.05) . There was no difference between group 1 and control group (P > 0.05) . CONCLUSION: The reason of gingival colouration might be the electrochemical corrosion. The metal ion was released in gingival tissue and blood.

[Expression of proliferating cell nuclear antigen/bcl-2 in gray gingival tissue].

OBJECTIVE: To study the expression of PCNA/bcl-2 protein in gray and normal gingival tissue, and to investigate the biological effect of procelain-fused-to-metals (PFM). METHODS: Gray gingival tissue animal model was established by PFM prosthesis and immunohistochemistry S-P method was used to detect the PCNA/bcl-2 protein expression in gingival tissue after 3 months, 6 months in PFM groups and control group. RESULTS: The expression of PCNA had significant difference between the 3th month group and the control group (P < 0.05); no significant difference was found between the 6th month group and the control group (P > 0.05). The expression of bcl-2 had no significant difference between the 6th month group and the control group (P > 0.05). CONCLUSION: There were a correlation between the expression of PCNA and inflammation of the gray gingival tissue; The expression of PCNA and bcl-2 protein does not indicate that gray gingival tissue had dysplasia change.