Shear Bond Strength of Orthodontic Brackets Bonded with a Self-Adhering Composite in Dry and Saliva-Contaminated Conditions.

OBJECTIVES: The purpose of this study was to evaluate the effect of saliva contamination on shear bond strength (SBS) of orthodontic brackets bonded by a self-adhering composite compared with a conventional adhesive. MATERIALS AND METHODS: This in vitro, experimental study investigated 40 human premolars. The teeth were randomly divided into four groups based on the adhesive type and bonding condition: (I) Vertise Flow composite without saliva contamination (VF), (II) Vertise Flow composite with saliva contamination (VF/S), (III) Transbond XT composite without saliva contamination (TXT), and (IV) Transbond XT composite with saliva contamination (TXT/S). After the preparation step, brackets were bonded to the buccal surface of the teeth, and samples were mounted in acrylic blocks, incubated at 37°C for 24 hours, and underwent thermocycling between 5- 55°C. Next, the SBS was measured by a universal testing machine. Data were analyzed by ANOVA and Tukey's test. P<0.05 was considered statistically significant. RESULTS: ANOVA showed a significant difference in SBS among the groups (P<0.001). The highest SBS was achieved in the TXT group (26.63±9.09 MPa), followed by TXT/S (13.69±4.23 MPa), VF/S (3.68±1.49 MPa), and VF (3.04±1.73 MPa). CONCLUSION: Saliva contamination did not have a significant effect on SBS of brackets bonded with Vertise Flow. However, it did not provide acceptable bond strength for orthodontic bracket bonding in the clinical setting.

In Vitro Comparison of Cytotoxicity and Genotoxicity of Three Vital Pulp Capping Materials.

INTRODUCTION: Direct pulp capping (DPC) is a treatment for maintaining pulp vitality and its biological function. Ideally, pulp capping agents are expected to induce pulp cells to form hard tissue. This in vitro study assessed the cytotoxicity and genotoxicity of three vital pulp capping (VPC) agents naming Biodentine (Septodont, Saint-Maur-des-Fosses, France), mineral trioxide aggregate (ProRoot MTA; Dentsply, Tulsa Dental, Tulsa, OK, USA) and TheraCal LC (Bisco Inc, Schamburg, IL, USA) on human dental pulp fibroblasts. METHODS AND MATERIALS: Human fibroblasts were exposed to 100 µL of ProRoot MTA, TheraCal LC and Biodentine in 0-1000 µg/mL concentrations and incubated at 37°C for 24 h. Their cytotoxicity and genotoxicity were assessed using the methyl thiazol tetrazolium (MTT) and the comet assays, respectively. The data were analyzed by Kruskal-Wallis test at the level of significance set at 0.05. RESULTS: None of the tested materials had cytotoxicity or genotoxicity. CONCLUSION: TheraCal LC, Biodentine and ProRoot MTA can be alternately used for VPC treatment of teeth.

Efficacy of Modified Bioactive Glass for Dentin Remineralization and Obstruction of Dentinal Tubules.

OBJECTIVES: This study assessed the efficacy of modified bioactive glass (MBG) for dentin remineralization and obstruction of dentinal tubules. MATERIALS AND METHODS: Thirty-six dentin discs were made from 20 third molars and were stored in 12% lactic acid solution for two weeks to induce demineralization. The samples were divided into three groups (n=12): 1- BG, 2- BG modified with 5% strontium (Sr) and 3- BG modified with 10% Sr. After applying the BG, the samples were stored in artificial saliva for 7, 14 and 21 days. Attenuated Total Reflection-Fourier Transform Infrared Spectroscopy (ATR-FTIR), X-ray Diffraction (XRD) analysis, Scanning Electron Microscopy (SEM), and Energy-Dispersive X-ray (EDX) analysis were used to assess remineralization. Also, 6 dentin discs were divided into three groups of BG, BG modified with 5% Sr and BG modified with 10% Sr, to examine tubular occlusion. The discs were etched using 0.5M of EDTA for two minutes and were stored in artificial saliva for 7 days. Changes in dentin surface morphology were evaluated under SEM. RESULTS: Group 3 showed high rates of remineralization at days 7 and 14, although the rate decreased at day 21. Group 2 exhibited high rates of remineralization at days 7, 14 and 21. Dentinal tubules were partially occluded by BG and BG modified with 5% Sr, while they were almost completely obstructed after the use of BG modified with 10% Sr. CONCLUSIONS: Strontium increases remineralization. Addition of 10% Sr to BG enhances apatite formation; however, the apatite dissolves over time. Addition of 5% Sr to BG stabilizes the apatite lattice and increases the remineralization.