Antimicrobial Activity of Nano-Magnesium Hydroxide Against Oral Bacteria and Application in Root Canal Sealer.

BACKGROUND The goal of the present work was to assess the antibacterial activity of nano-magnesium hydroxide (NMH) against Streptococcus mutans (S. mutans) and to explore the antimicrobial function of AH Plus™ sealer incorporating NMH. MATERIAL AND METHODS The antimicrobial behavior of NMH against S. mutans was evaluated with bactericidal tests. A modified direct contact test was used to assess the antimicrobial activity of unset AH Plus containing NMH after 5 minutes, 20 minutes, and 60 minutes of contact with bacteria. The antimicrobial effects and the amount of surface-adhering bacteria of the solidified materials were explored by SEM and confocal laser scanning microscopy, respectively. RESULTS NMH powder presented excellent antimicrobial activity against S. mutans. Mg²âº and OH⁻ were not the main factors resulting in bacterial death. Approximately 93.1% and 98% of the S. mutans were killed in the AH Plus+7% NMH group after incubation for 5 minutes and 20 minutes, respectively. AH Plus with 5% or 7% NMH were more potent against S. mutans compared with AH Plus alone (P<0.05). Moreover, the antibacterial function of AH Plus was lost after setting. NMH enabled the solidified AH Plus to still have antibacterial properties on the seventh day. CONCLUSIONS NMH can be used to modify AH Plus sealer to eradicate residual bacteria and prevent reinfection.

In vitro bioactivity of AH plus with the addition of nano-magnesium hydroxide.

BACKGROUND: AH Plus (AH) has been widely used as a root canal sealer in the endodontic field due to its superior physicochemical properties. However, clinical application of AH is limited due to its weak bioactivity. METHODS: In this study, we have developed an AH cement containing nano-magnesium hydroxide (NMH) as an additive to enhance the bioactivity of AH. The NMH can neutralize pH and facilitate bone formation. The objective of this study was to evaluate the effects of NMH and modified AH on osteoblasts behavior in vitro. The CCK-8, alkaline phosphatase (ALP) staining, and real-time polymerase chain reaction (PCR) assays were used to assess the proliferation and differentiation of MC3T3-E1 cells, respectively. The adhesion and spreading of MC3T3-E1 cells were investigated in vitro by scanning electron microscopy (SEM). Meanwhile, the flow and magnesium ion release of the modified AH was also concerned. RESULTS: In vitro cell assays further showed that the addition of NMH into AH cement, which was denoted as modified AH (especially AH+3%NMH), could effectively improve the proliferation and osteogenic differentiation of MC3T3-E1 cells. CONCLUSIONS: Taken all together, we believe that the modified AH samples (especially AH+3%NMH) have outstanding biocompatibility and osteogenic properties and may have great potential in endodontic field.

[Occluding effects of desensitizer containing NovaMin combined with fluor protector on dentinal tubules:an in vitro study].

PUPPOSE: To observe the occlusion effect, acid resistance and abrasion resistance of desensitizer containing NovaMin combined with fluor protector on dentin tubules, in order to provide theoretical basis for clinical treatment of dentin hypersensitivity. METHODS: Thirty extracted intact and non-carious human premolars for orthodontic treatment were selected and made into 2 mm thick dentin slices. Each slice was cut into 4 parts to form 120 sensitive dentin models and randomly divided into 4 groups (n=30). Distilled water (group A), fluor protector (group B), Ominq desensitizer (group C) and fluor protector combined with Ominq desensitizer (group D)were applied respectively on the exposed dentin surfaces. After immersed in the artificial saliva for 24 h, each group was divided into 3 subgroups randomly to undergo direct observation, acid corrosion and tooth brushing test, then the plugging rate of dentin tubules was statistically analyzed with SPSS 13.0 software package. RESULTS: Dentin tubules in group A were completely open, while good occluding effects were found in group B, C and D. Among them, group D displayed the best occlusion effect, and ability of acid and abrasion resistance compared with other 3 groups (P

[Study on the microleakage between the composite resin and cavity wall after Er,Cr:YSGG laser preparation].

PURPOSE: To evaluate microleakage between the composite resin and cavity wall after Er,Cr:YSGG laser preparation. METHODS: Class V cavities were prepared in 30 sound extracted human premolars. The teeth were randomly divided into 3 groups (n=10).Group 1 was treated with Er,Cr:YSGG+37% phosphoric acid, group 2 was treated with Er,Cr:YSGG+FL-BOND and group 3 was treated with Er,Cr:YSGG+17% EDTA.Then the specimens were subjected to thermocycling and staining. The marginal microleakage was assessed by dye penetration method and scanning electronic microscope(SEM). The data was analyzed with SPSS11.0 software package. RESULTS: In occlusal margins,microleakage in group 2 was significantly lower than that in the other two laser groups(P<0.05).No significant difference was found between group 1 and 3 by dye penetration method.The space between the restorations and tooth structure revealed that there was significant difference between group 2 and 3(P<0.05).No significant difference was found between the other two laser groups by SEM. In gingival margins, microleakage test and the space between the restorations and tooth structure revealed that there was no significant difference among the three laser groups.There was significant difference in microleakage between the occlusal and gingival margins only in group 2(P<0.05). CONCLUSIONS: It is concluded that self-etch adhesive system was effective in reducing microleakage of the occlusal margins between the composite resin and the cavity wall after Er,Cr:YSGG laser preparation.There was no significant difference in microleakage after using a total etch adhesive system and EDTA.

[A study on acquired acid resistance of enamel and dentine irradiated by Er, Cr: YSGG laser in vitro].

OBJECTIVE: To evaluate the acid resistance of enamel and dentin irradiated by Er, Cr: YSGG laser to artificial caries formation in vitro. METHODS: Enamel and dentin samples were irradiated with Er, Cr: YSGG laser at 6 W or 4 W for 6 second, respectively. Every sample was immersed in 3 ml of lactic demineralization solution at pH 4.8 and incubated at 37 degrees C for 24 hours. The parts per million of calcium ion of each solution was measured by atomic absorption spectrophotometry, the quantities of calcium and phosphate on the surface of enamel and dentin sample were examined by SED-X and the ultrastructure was investigated by SEM. RESULTS: In the enamel and dentin samples, the dissolved Ca(2+) concentration in laser group were significantly decreased compared with that of the control group (P < 0.05). The quantities of Ca (weight%) in enamel and dentin were significantly higher in the laser group than in the control group (P < 0.05). The content of P was increased in dentin and enamel samples, but only the increase in enamel sample was significant (P < 0.05). In both samples, no significant changes on Ca/P weight ratio were found between the groups. The irradiated enamel and dentin surface lacked a smear layer and showed various patterns of microirregulation with a scaly appearance, the openings of dentinal tubules were clearly visible, but no melting or carbonization was observed. CONCLUSION: Er, Cr: YSGG laser irradiation is effective for increasing acid resistance of dental hard tissue and does not cause thermal side effect.

[A scanning electron microscopy study on morphological changes of Er, Cr: YSGG laser-cutted dental hard tissue].

OBJECTIVE: The purpose of this study was to evaluate the morphological changes of Er, Cr: YSGG laser irradiated dental hard tissues by scanning electron microscopy (SEM). METHODS: 12 freshly extracted premolars were treated with fissure bur, Er, Cr: YSGG laser at 4 watt, Er, Cr: YSGG laser at 6 watt, respectively, and then bisected transversally and longitudinally. The tooth slice were prepared with conventional methods and observed by SEM. RESULTS: Compared with fissure bur, laser treatment resulted in a rather scaly and rough surface. The sections were free of smear layer, with open dentinal tubules. No carbonization and thermal damages were observed. The laser at 6 watt appeared rougher than at 4 watt, occasionally caused micro-cracks. CONCLUSION: The utilizing of Er, Cr: YSGG laser can contribute to enhance the bond strength between restorative materials and dental hard tissues. It suggests that higher energy could be applied in cutting enamel, whereas the lower energy in dentin.