Compressive strength and fluoride release profile of a glass ionomer cement reinforced with silver-hydroxyapatite-silica hybrid nanoparticles: An in vitro study.

OBJECTIVES: This study aimed to prepare a glass ionomer (GI) cement reinforced with silver-hydroxyapatite-silica (Ag/HA/Si) hybrid nanoparticles and assess its compressive strength and fluoride release profile. MATERIAL AND METHODS: In this in vitro, experimental study, 60 cylindrical specimens were fabricated with 4mm diameter and 6mm height in 6 groups (n=10) using BracePaste composite, GC Fuji II LC pure RMGI, and RMGI reinforced with 0.1wt%, 0.5wt%, 1wt%, and 2wt% Ag/HA/Si hybrid nanoparticles. The specimens were subjected to compressive force in a universal testing machine to measure their compressive strength (MPa). To assess their fluoride release profile, discs with 3mm diameter and 2mm thickness were fabricated from Fuji II LC pure resin-modified glass ionomer (RMGI), and RMGI with 0.1wt%, 0.5wt%, 1wt%, and 2wt% hybrid nanoparticles, and the concentration of released fluoride was measured by a digital ion-selective electrode. Data were analysed by ANOVA and Scheffe test (alpha=0.05). RESULTS: The compressive strength was 114.14MPa for BracePaste composite, and 97.14, 97.84, 100.65, 109.5, and 89.33MPa for GI groups with 0%, 0.1%, 0.5%, 1% and 2% hybrid nanoparticles, respectively, with no significant difference among them (P=0.665). Addition of 1% (0.21±0.07µg/mL, P=0.029) and 2% (0.45±0.22µg/mL, P=0.000) hybrid nanoparticles to RMGI significantly increased the amount of released fluoride, compared with the control group (0.09±0.03µg/mL). CONCLUSIONS: Addition of Ag/HA/Si hybrid nanoparticles to RMGI in the tested concentrations had no significant effect on its compressive strength but addition of 1wt% and 2wt% concentrations of Ag/HA/Si hybrid nanoparticles increased its fluoride release potential.

Effect of incorporating silica-hydroxyapatite-silver hybrid nanoparticles into the resin-modified glass ionomer on the adhesive remnant index score and shear bond strength of orthodontic metal brackets: An in vitro study.

OBJECTIVES: This study aimed to assess the effect of addition of silica-hydroxyapatite-silver (Si-HA-Ag) hybrid nanoparticles to light-cure glass ionomer (GI) on shear bond strength (SBS) of metal brackets bonded with this adhesive and the adhesive remnant index (ARI) score. MATERIAL AND METHODS: In this in vitro experimental study, 50 sound extracted premolars were assigned to 5 groups (n=10) for orthodontic metal bracket bonding with BracePaste® composite, Fuji ORTHO™ pure resin modified GI (RMGI), and RMGI reinforced with 2wt%, 5wt% and 10wt% Si-HA-Ag nanoparticles. The SBS of brackets was measured by a universal testing machine. Debonded specimens were inspected under a stereomicroscope at×10 magnification to determine the ARI score. Data were analyzed by one-way ANOVA, Scheffe test, Chi-square test, and Fisher's exact test (alpha=0.05). RESULTS: The maximum mean SBS was recorded in BracePaste® composite followed by 2% RMGI, 0% RMGI, 5% RMGI and 10% RMGI. Only the difference between the BracePaste® composite and 10% RMGI was significant in this regard (P=0.006). The groups were not significantly different regarding the ARI scores (P=0.665). All the SBS values were within the clinically acceptable range. CONCLUSION: Addition of 2wt% and 5wt% Si-HA-Ag hybrid nanoparticles to RMGI as orthodontic adhesive caused no significant change in SBS of orthodontic metal brackets while addition of 10wt% hybrid nanoparticles significantly decreased the SBS. Nonetheless, all the SBS values were within the clinically acceptable range. Addition of hybrid nanoparticles had no significant effect on the ARI score.

Live demonstration versus multimedia: A comparison of two educational methods of orthodontic dental cast trimming.

Introduction: The aim of this study was to compare the effect of two educational methods: live practical and multimedia demonstrations of dental cast trimming. Methods: In this quasi-experimental study, all 44 dental students from Zanjan University Dental School who were studying in the 8th semester entered the study. Using simple randomization, we assigned them to two groups. Multimedia and live demonstrations were used in the intervention (n=21) and control (n=23) groups, respectively. Knowledge of students was assessed using pre-test and post-test. Practical skills were compared using the students' final semester scores. The Individual Development and Educational Assessment questionnaire was used to assess the students' reaction to instruction. For data analysis, mean and standard deviation, and independent and paired t-tests were used. Statistical analysis was performed using SPSS software. Results: In terms of knowledge, the pre-test scores of the intervention and control groups were not significantly different (p-value= 0.457), and the post-test scores of the two intervention and control groups had no significant difference (p-value= 0.053); however, in both intervention and control groups there was a significant difference between the scores before and after the test, and the scores of both groups increased after training (p-value= 0.001, p-value= 0.001). In terms of practical skills, no significant difference was observed in the mean and standard deviation of the scores in the two groups (p-value=0.902). There was no significant difference in terms of the students' reaction to instruction. Conclusion: All students passed this course successfully. Further, their knowledge and skills were improved in both groups. Similar to the live practical demonstration, that of the multimedia led to a positive reaction to instruction in students. Therefore, multimedia education can be used well with the traditional method and even replaces it.

Zinc-oxide nanocoating for improvement of the antibacterial and frictional behavior of nickel-titanium alloy.

AIM: To fabricate a friction-reducing and antibacterial coating with zinc oxide (ZnO) nanoparticles on nickel-titanium (NiTi) wire. MATERIALS & METHODS: NiTi orthodontic wires were coated with ZnO nanoparticles using the chemical deposition method. Characteristics of the coating as well as the physical, mechanical and antibacterial properties of the wires were investigated. RESULTS: A stable and well-adhered ZnO coating on the NiTi wires was obtained. The hardness and elastic modulus of the ZnO nanocoating were 2.3 ± 0.2 and 61.0 ± 3.6 GPa, respectively. The coated wires presented up to 21% reduction in the frictional forces and antibacterial activity against Streptococcus mutans. ZnO nanocoating significantly improved the surface quality of NiTi wires. The modulus of elasticity, unloading forces and austenite finish temperature were not significantly different after coating. CONCLUSION: This unique coating could be implemented into practice for safer and faster treatment to the benefit of both patient and clinician.