ABSTRACT
Objective@#The antibacterial properties and bonding strength of 3M orthodontic adhesive resin modified by chlorhexidine acetate (CHA) composite mesoporous silica were investigated.@*Methods@# CHA with different mass fractions was encapsulated in mesoporous silica nanoparticles (MSNs) (denoted CHA@MSNs). Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM) were used to characterize the samples. The 3M Z350XT flow resin was divided into 4 groups: group A: 3M+CHA@MSNs (0%); group B: 3M+CHA@MSNs (3%); group C: 3M+CHA@MSNs (5%); and group D: 3M+CHA@MSNs (6.4%), with mass scores of 0%, 3%, 5%, and 6.4%, respectively. The shear strength of the modified adhesive was tested by a universal electronic material testing machine, the adhesive residue was observed by a 10 × magnifying glass, and the adhesive Remnant index (ARI) was calculated. The four groups of modified adhesives were cultured with Streptococcus mutans. The OD540 value of the bacterial solution was measured by a spectrophotometer, and the amount of plaque attachment was observed by scanning electron microscopy to evaluate the antibacterial performance of the adhesives.@*Results@#Infrared spectroscopic analysis of CHA@MSNs showed that CHA was successfully loaded onto MSNs. Under scanning electron microscopy, it could be seen that, after Cha was combined with MSNs, the structure of MSNs changed, as the boundary was fuzzy and aggregated into a layered structure. A comparison of shear strength revealed a statistically significant difference between the groups containing CHA@MSNs and the groups without CHA@MSNs (P<0.05). The value of the shear strength in group D decreased the most, while there was no statistically significant difference between group B and group C (P > 0.05). There was no statistical significance across all groups (P > 0.05), suggesting that the addition of CHA@MSNs had little effect on the bracket shedding. The OD540 value of bacterial fluid indicated that the difference among groups A, B and C was statistically significant (P < 0.05), and the antibacterial effect of group C was the best; there was no statistically significant difference between group C and group D (P > 0.05).@*Conclusions@#Therefore, adding 5% CHA@MSN antibacterial agent significantly improved the antibacterial effect and did not affect the bond strength.
ABSTRACT
Objective@#To investigate the effect of a nanohydroxyapatite suspension with a 10% mass fraction on enamel demineralization after adjacent enamel removal and to provide a reference for the clinical use of nanohydroxyapatite to prevent enamel demineralization after adjacent enamel removal. @*Methods @#Forty fresh extracted premolars were incised from the coronal surface of the crown after glazing and polishing with sand strips. Each tooth was made into two specimens. Eighty teeth were randomly divided into four groups: a blank group, a dolofluoride group, a dental mousse group and a 10% nanohydroxyapatite group. After 30 days of pH cycling in vitro, a microhardness tester was used to detect the enamel surface elements before and after deglazing treatment. Scanning electron microscopy (SEM) and X-ray energy dispersive spectrometry (EDS) were used to analyze the enamel surface elements. @*Results@#After the experiment, the microhardness values of the adjacent glazed specimens of the four groups were (128.18 ± 6.89) kg/mm2 in the blank group, (216.75 ±9.87) kg/mm2 in the dolefluoride group, (198.88 ± 4.76) kg/mm2 in the dental care group and (218.44 ± 7.88) kg/mm2 in the 10% nanohydroxyapatite group, which were significantly different (F=189.14, P＜ 0.001). The LSD-t test showed that there was no significant difference between the dolefluoride group and the 10% nanohydroxyapatite group (P＜ 0.05), but the differences between the other groups were statistically significant (P > 0.05). There were significant differences in the Ca/P ratio among the blank group (1.39 ± 0.08), the dolefluoride group (1.70 ± 0.11), the dental care group (1.54 ± 0.12) and the 10% nanohydroxyapatite group (1.71 ± 0.14) (F=10.539, P＜ 0.001). There was no significant difference between the dolefluoride group and the nanohydroxyapatite group after the experiment (P > 0.05), but there were significant differences among the other groups (P＜ 0.05).@*Conclusion @#Dolerofluoride, dental protector and 10% nanohydroxyapatite can promote remineralization of enamel after enamel removal. The remineralization induced by 10% nanohydroxyapatite is similar to that induced by dolerofluoride.