Effect of Curing Time on the Bond Strength of Orthodontic Brackets Bonded by Light Cure Resin-Modified Glass Ionomer Cement: An In vitro Evaluation

This study was designed with the aim to evaluate the effect of curing time on the shear-bond strength of orthodontic brackets bonded using light cure Resin-Modified Glass Ionomer Cements (RMGIC). This class of cement when used for luting orthodontic brackets offers certain advantages when compared to the more commonly used resin cements. Intact natural teeth (premolars) extracted for therapeutic purposes as part of orthodontic treatment was sourced for use in this study. The teeth were equally divided into four groups four testing, Group 1 - brackets bonded with RMGIC and cured for 3 seconds, Group 2 - brackets bonded RMGIC and cured for 6 seconds, Group 3 - brackets bonded with RMGIC and cured for 9 seconds and Control group - brackets bonded with composite and cured for 15 seconds. A high intensity LED light source was used to cure the cements. The Shear-Bond strength of the brackets was evaluated using a universal testing machine. One-way ANOVA test and Tukey multiple comparison tests were done to compare the difference of Shear-Bond Strengths among the groups tested. The average Shear Bond Strength among study groups was 7.64±2.86 MPa. The ANOVA and Tukey multiple comparison tests could not identify a statistically significant difference in Shear-Bond Strengths among the groups. Curing time does not appear to have a statistically significant effect on the Shear Bond Strength of orthodontic brackets bonded using Resin-Modified Glass Ionomer Cements..

Evaluation of the Surface Hardness and Roughness of a Resin-Modified Glass Ionomer Cement Containing Bacterial Cellulose Nanocrystals

The purpose of this study was to evaluate the performance of a resin-modified glass ionomer cement (RMGIC) to which bacterial cellulose nanocrystals (BCNs) were added. BCNs were incorporated into the RMGIC powder in ratios of 0.3%, 0.5%, and 1% (w/w). One control and three experimental groups were enrolled in the study: unmodified RMGIC (control), 0.3% (w/w) BCN-modified RMGIC, 0.5% (w/w) BCN-modified RMGIC, and 1% (w/w) BCN-modified RMGIC. The surface hardness and surface roughness were the parameters assessed. The materials were characterized by scanning electron microscopy (SEM). The data were analyzed using the one-way ANOVA and Kruskal–Wallis tests for surface hardness and roughness, respectively. The addition of BCN resulted in the improvement of surface roughness in all the specimens compared with the control material. The RMGIC modified by 1% (w/w) BCN showed the lowest surface roughness (decreased by 52%) among all tested groups. However, BCN had a negative effect on the surface hardness of RMGIC. The group with 0.3% (w/w) BCN had the least decrease in microhardness (13%). According to the results, the RMGIC group modified by 1% (w/w) BCN had a smoother surface than the other groups. The surface microhardness of the RMGIC decreased after BCNs were added to it.

Effect of incorporation of nano-hydroxyapatite particles on the clinical performance of conventional and resin-modified glass ionomer cement in class V cavities: split-mouth, randomized controlled trial

Background The aim of this study was to compare the clinical performance of Nano-hydroxyapatite-modified conventional glass ionomer cement (NHA-GIC) and Nano-hydroxyapatite-modified resin-modified glass ionomer cement (NHA-RMGIC) with conventional glass ionomer (CGIC) and resin-modified glass ionomer (RMGIC) in the treatment of caries class V cavities. Sixty patients with at least two cervical caries lesions participated in this study. A total of 120 class V cavities were prepared and then restored using different restorative materials. Restorations were clinically evaluated according to modified United States Public Health Service criteria at baseline and after 3, 6 and 9 months. Results There was no statistically significant difference in the clinical performance of the different restorative materials at any of the follow-up periods. However, throughout the study period there was a statistically significant change in the color match, surface texture and marginal integrity in NHA-GIC. A statistically significant change in the surface texture and marginal integrity was found in GIC. On the other hand, there was only a statistically significant change in surface texture in NHA-RMGIC. Conclusions All tested restorative materials, control (CGIC and RMGIC) as well as experimental (NHA-GIC and NHA-RMGIC), exhibited comparable clinical performance after 9 months follow-up.

Effects of Incorporation of Marine Derived Hydroxyapatite on the Microhardness, Surface Roughness, and Fluoride Release of Two Glass-Ionomer Cements

Background: The aim of this study was to evaluate the effects of incorporation of hydroxyapatite (HA) derived from cuttlefish bone on the microhardness, surface roughness (SR), and fluoride release (FR) of conventional cure, and resin-modified glass-ionomer cement. Methods: There were four groups for each tested material; experimental glass-ionomer were made by addition and of 2, 5, and 10 wt % HA respectively to conventional glass-ionomers Fuji II LC and Fuji IX GP Extra. One group was prepared without the addition of HA particles. For SR and microhardness measurements sectional Teflon molds (5 mm in diameter and 2 mm deep) were used to prepare 10 samples per group (n = 80). The samples were stored in distilled water at 37 °C for 7 days prior to testing. The SR was measured using a contact type profilometer and the microhardness was determined using a Vickers micro-hardness tester at a load of 980 g for 15 s. For FR measurements, there were six samples per group (n = 48), prepared in Teflon molds (8 mm in diameter and 2 mm deep). The FR was measured with an ionoselective electrode in triplicates after 24 h, 7 days, and 45 days. Statistical analysis was performed using one-way ANOVA with Tukey post-hoc test. Results and Conclusion: Microhardness values obtained for Fuji II modified with 10 wt % HA were significantly higher compared to the other two groups tested. Comparison of materials with respect to SR showed significant difference between them (p < 0.0001) with Fuji II and Fuji IX modified with HA having higher SR values. Regarding FR, Fuji IX showed statistically significant higher results than Fuji II, independently of HA modification, and groups modified with 2 and 5 wt % HA showed significantly increased fluoride release in all three time points.

Push-Out Bond Strength of Resin-Modified Glass Ionomer Cement and Flowable Composite Luting Systems on Glass Fiber Post of Root Canal

Background: Posts that have been properly fitted can withstand torsion forces and so provide better retention. The push-out bonding strength of glass fiber posts to the root canal was evaluated using resin-modified glass ionomer cement (RMGIC) and flowable composite (FC). Method: Forty single-rooted maxillary central incisors were used in the study. The samples were randomly divided into two groups of 20 teeth each. The crown-down procedure was used to clean and shape the pulp area. A Tenax fiber trans Coltene whaletene post was used by both groups. The first group utilized FC (Filtek Z 350 3M ESPE) to coat the post, whereas the second group used RMGIC (Rely X 3M ESPE). The specimens were cross-sectioned after 24 h. Specimens were cross-sectioned four millimeters thick into coronal and middle parts using a sectioning machine, yielding 40 specimens per group. The strength of the bond between the luting cement and the posts was measured using push-out bond strength testing. We loaded the components at a cross speed of 0.5 mm/min on a universal testing machine until the bond failed. Results: The FC group had a 4.80 N push-out bond strength, whereas the RMGIC group had a 7.11 N push-out bond strength. Conclusion: FC’s mean push-out bond strength score is lower than RMGIC’s.

Assessment of the Effect of Acid and Base Cycling on Mechanical Properties of Various Esthetic Restorative Materials

Objective: The purpose of this study is the evaluation of the effect of pH cycling, including both acidic and alkaline environments, on the mechanical properties of tooth-colored restorative materials. Methods and Materials: 20 rectangular bar specimens of one bulk-fill restorative composite, two conventional nanohybrid restorative composites, and one restorative resin-modified glass ionomer were produced according to ISO 4049. Half of the materials were stored in an acid and base cycling defined as two-day storage in acidic (pH =4) and alkaline (pH=8) solutions. The rest of the materials were incubated in distilled water as a control group. The storage lasted for 48 days. Finally, flexural strength, elastic modulus, and microhardness of the specimens in each group determined. Data analyzed with Kruskal-Wallis, Dunn, MANOVA, Tukey HSD and T-test. Results: The pH cycling model had a significant influence on all mechanical properties of the bulk-fill restorative composite and resin-modified glass ionomer than those stored in water (P <0.05). One of the conventional nanohybrid restorative composites showed a significant reduction in elastic modulus and microhardness while the other one showed a significant reduction only in flexural strength. Conclusion: pH cycling negatively affects the mechanical properties of resin composites, and the materials’ composition is an important factor in the degradation of the resin-based materials examined.