Journal of Dental Biomaterials
Volume:3 Issue: 1, 2016

Statement of Problem: Hertzian indentation test has been proven to be an efficient and reliable alternative upon Vickers hardness test. This method has been used to test dental ceramics, amalgams, glass ionomers and luting cements.There is limited published information about the load-bearing capacity of resin composites using Hertizian indentation test. To investigate the load-bearing capacity of hybrid and nano-hybrid resin composites stored dry or wet up to 30 days, using Hertzian indentation test. Three resin composites were used: two nano-hybrids (Filtek Supreme, and Luna) and one hybrid, (Rok). A total of 108 disc-shaped specimens (1mm thick x 10 mm diameter) were prepared using polyethylene mould. The specimens of each material were randomly divided into 6 groups of 6 (n=6) and stored at 370C either in distilled water or dry for 1, 7 and 30 days. The specimens were tested using Hertzian jig aligned in the universal testing machine. The specimen was placed on the top of a disc-shaped substrate. The load was applied at the center of each specimen and the load at the first crack was recorded. Data were analyzed by ANOVA, Tukey’sand student’s t-test using SPSS version 18.0. Three-way ANOVA showed a significant interaction between all the factors (p =. 0001). The load bearing capacity of almost all materials reduced significantly in the wet condition in comparison with the dry condition (p =. 0001). After seven days of immersion in distilled water, Filtek Supreme had significantly lower values than those of Rok and Luna, there was no significant differences between materials in the dry condition. In contrast to dry condition, the load-bearing capacity of specimens stored in distilled water decreased significantly over the 30 days of immersion. The load bearing capacity of nano-hybrid composites tested in this study was shown to be comparable with that of the hybrid composite.

Statement of Problem: Dentin hypersensitivity is one of the most common complaints of patients after periodontal treatments which occur after tissue shrinkage. The aim of this study was to determine and compare the effectiveness of sensikin gel (10% potassium nitrate and 0.22% sodium fluoride) with sodium fluoride gel (2.7%) and fluoride varnish (5%) in reducing the dentin hypersensitivity after periodontal surgery. Twenty-two patients who, after full mouth periodontal surgery, had a complaint of dentin hypersensitivity (DH) in at least three quadrants were selected. Then a specific treatment was randomly selected for each quadrant which was applied once a day for one week and then stopped. A visual analog scale (VAS) was used to assess the subjects’ responses to air blast and periodontal probe stimuli at baseline at one week, and one, three and 6 months after treatment. To analyze the data, repeated measures ANOVA test, Tukey test and variance analysis test were used. At all given intervals, almost both sodium fluoride and sensikin gel significantly reduced the dental sensitivity caused by stimulants. There were no significant differences between sensikin gel and other two desensitizers in reducing the dentin hypersensitivity after 1 week, 1 month, 3 months, and 6 months with respect to air blast stimuli. Sensikin gel was more efficient than Fluoride varnish in reducing the sensitivity caused by periodontal probe after 1 month. Sensikin gel, sodium fluoride gel and fluoride varnish can all be prescribed to reduce dental sensitivity in patients who have undergone periodontal treatments. In the case of severe sensitivity to mechanical stimulations, a treatment with a long-run effectiveness such as sensikin and/or sodium fluoride gel is preferred.

Statement of the Problem: Surface roughness is a key factor in the aesthetics of restorative dentistry as it can determine the clinical quality and success of restorative materials. The chemical process of dissolution in the presence of mechanical forces can accelerate the surface roughness of tooth-coloured restorative materials. To determine the degree of surface roughness of a microhybrid and a nanohybrid resin composite after polishing and immersion in various solutions. Two resin composites were used: a microhybrid (Gradia direct, GC), and a nanohybrid (Ice, SDI). A total of 54 disc-shaped specimens were prepared for each composite and immersed in distilled water incubated at 37 °C for 24 hours. After 24 h, the baseline measurement for surface roughness (Ra) was performed and the specimens were divided into 3 groups of 18 and tested with unpolished or after polishing with Sof-Lex disc and Enhance point systems. Specimens in each group were subdivided into 3 subgroups (n = 6) and immersed in 3 solutions (distilled water, coffee, and cola) for 7 days incubated at 37 °C. After 7 days, the specimens were rinsed with tap water for 10 seconds, dried with paper towel and Ra was measured again. Two randomly selected specimens of each group were sputter coated with gold and examined using a Field-Emission Scanning Electron Microscope (SEM). Gradia direct showed a greater Ra than ice in all solutions for all polishing systems (p < 0.001). Specimens polished with Enhance point revealed a significantly greater roughness than Sof-Lex discs and both showed greater Ra than unpolished specimens. Specimens immersed in coffee exhibited significantly greater surface roughness than that of distilled water (p < 0.05) and cola (p < 0.001). Nano-hybrid composite showed a significantly smoother surface than microhybrid. Coffee exhibited the highest Ra compared to distilled water and cola. Enhance point revealed significantly greater Ra than Sof-Lex discs and unpolished group.

Statement of Problem: Fracture of veneering porcelain has been described as the most frequent reason for the failure of zirconia-based fixed restorations. The purpose of this study was to evaluate and compare the shear bond strength of a zirconium oxide core material to three commercial veneering ceramics. Three types of veneering ceramics were selected including IPS -emax Ceram, Vita VM9, and Cerabien. Thirty block specimens of zirconia core material were prepared in 4×4×9 mm dimensions. Three groups were created and the veneering ceramic was added to each of 10 blocks. Shear bond test was conducted with universal testing machine. Data were analyzed using one-way ANOVA (p = 0.05). Mean shear bond strength values and standard deviations were 26.03 MPa (6.32), 23.85 MPa (4.01), and 19.16 MPa (3.72) for Vita VM9, IPS emax Ceram, and Cerabien, respectively. Cerabien ceramic showed more failure as compared to the other ceramics. However, there was no significant difference among the three veneering groups. Within the limitation of this study, it can be concluded that shear bond strength between zirconia core and three veneering ceramics was not significantly different.

Statement of Problem: One of the factors affecting the degree of polymerization of light-cured composites is the type of light-curing unit used. In addition, physicomechanical properties of the composite resins depend on the degree of conversion and polymerization. Since the type of initiator in new composite resins is not explained by manufacturers, this study is an attempt to compare the depth of hardening, with two LED and QTH light-curing units. Fifteen samples prepared from Gradia Direct and Filtek Z250, both of which being universal, were cured with QTH (Astralis 7) and LED (Bluephase C8) light-curing units. All the samples were molded in polyester resin and cut from the middle by a disk. The hardness of the cut area was evaluated at 0, 0.5, 1, 1.5, 2, 2.5, 3, 3.5 and 4-mm depth intervals and also at the same interval as the width of the sample, with Vickers hardness machine, while the samples were placed in a darkroom. Data were statistically analyzed using one-way ANOVA, two-way ANOVA, t-test and post Hoc Tukey’s tests in SPSS, version 16. Filtek Z250 was harder than Gradia Direct at all the depth with both light-curing units. The hardness of Filtek Z250 sample cured with Astralis 7 was higher than that cured with LED, but with Gradia Direct the LED unit resulted in higher hardness. Curing depth was not significantly different between the groups (p = 0.109). Vickers hardness number for both composites used in this study is in an acceptable range for clinical implications. The composites’ composition is important to be considered for selection of light unit. Based on the findings of the present study, LED did not present more curing depth compared with QTH.

Statement of Problem: Adhesion to root canal dentin is one of the necessary characteristics of endodontic sealers. MTA Fillapex (Angelus, Londria, PR, Brazil) is one of the recently introduced MTA-based sealer. Only a limited number of studies have evaluated the bonding of this sealer to the dentin, with conflicting results. The purpose of this study was to evaluate the bond strength of MTA Fillapex sealer) to root canal dentin compared to an epoxy resinbased sealer (AH26 sealer). Twenty root blocks (6mm length) were acquired from the middle part of the extracted single-rooted central or lateral maxillary incisor roots and their lumens were enlarged to achieve a diameter of 1.3 mm. MTA Fillapex and AH26 were placed in the lumens of root blocks (n = 10). The specimens were kept in an incubator for 7 days, the roots were sectioned perpendicular to their long axis to achieve slices with thickness of 1 mm and the push-out test was carried out by a universal testing machine. The mean value of bond strength was 1.84 ± 0.7 Mpa for AH26 and 0.19 ± 0.1 Mpa for MTA Fillapex. The difference between the two groups was statistically significant (p < 0.001). With in the limitation of this study, AH 26 showed significantly higher bond strength in comparison to MTA Fillapex.