OBJECTIVE: The current study aimed to evaluate the effects of different combinations of chemical and mechanical challenges on the failure load, failure mode and composition of the resulting fracture surfaces of resin-composite restorations. METHODS: Three resin composites were used to fill dentin disks (2 mm inner diameter, 5 mm outer diameter, and 2 mm thick) made from bovine incisor roots. The model restorations, half of which were preconditioned with a low-pH buffer (48 h under pH 4.5), were subjected to diametral compression with either a monotonically increasing load (fast fracture) or a cyclic load with a continuously increasing amplitude (accelerated fatigue). The load or number of cycles to failure was noted. SEM was performed on the fracture surfaces to determine the proportions of dentin, adhesive, and resin composite. RESULTS: Both cyclic fatigue and acid preconditioning significantly reduced the failure load and increased the proportion of interfacial failure in almost all the cases, with cyclic fatigue having a more pronounced effect. Cyclic fatigue also increased the amount of adhesive/hybrid layer present on the fracture surfaces, but the effect of acid preconditioning on the composition of the fracture surfaces varied among the resin composites. SIGNIFICANCE: The adhesive or hybrid layer was found to be the least resistant against the chemomechanical challenges among the components forming the model restoration. Increasing such resistance of the tooth-restoration interface, or its ability to combat the bacterial actions that lead to secondary caries following interfacial debonding, can enhance the longevity of resin-composite restorations.
Methods: 12 impressions were made of a resin maxillary model (second premolar and second molar) with two prepared abutment teeth using vinyl polysiloxane (VPS); the margin of the second premolar was 0.5 mm subgingivally; and the margin of the second molar tooth was at the level of the gingiva. Impressions were made using two techniques: one-step and two-step putty/light materials. A three-unit metal framework was fabricated on the master model using the computer-aided design/computer-aided manufacturing (CAD/CAM) technique. The vertical marginal misfit was evaluated in the buccal, lingual, and mesial and distal surfaces of the abutments on the gypsum casts using a light microscope. Data were analyzed using the independent t-test (α < 0.05). Results: The results showed significantly lower vertical marginal misfit in all six areas evaluated around the two abutments in the two-step impression technique compared with the corresponding values in the one-step technique. Conclusion: Vertical marginal misfit in the two-step technique with a preliminary putty impression was significantly lower than in the one-step putty/light-body technique.
Objectives: This study aimed to compare the efficacy of calcium hydroxide (CH)/saline and CH/Artemisia persica (A. persica) essential oil as an intracanal medicament for radiographic resolution of periapical (PA) lesions in necrotic teeth. Materials and Methods: This randomized clinical trial was conducted on 22 patients with necrotic teeth and PA lesions presenting to two private endodontic offices. The patients were randomly divided into two groups (n = 11) to receive CH/saline (control group) and CH/A. persica essential oil (10%) (intervention group) as intracanal medicaments between treatment sessions. The size of PA radiolucency was measured on parallel PA radiographs taken before treatment and also at 1 and 3 months after completion of treatment. The mean time of healing of PA lesions was also compared between the two groups. Data were analyzed by the independent t-test, chi-square test, and Fisher's exact test (alpha = 0.05). Results: No significant difference was found between the two groups regarding the changes in the size of PA lesions, relative healing percentage, and speed of healing, neither at 1 nor at 3 months postoperatively (P > 0.05). Regarding the presence/absence of clinical symptoms in the second treatment session, the intervention group showed greater resolution of symptoms, although the difference did not reach statistical significance (P > 0.05). Conclusion: According to the present results, it appears that the addition of A. persica essential oil to CH for application as intracanal medicament does not add any particular advantage.
Background: Non-Syndromic Cleft Lip with or without cleft Palate (NSCL/P) is a common developmental disorder of the head and neck with a multifactorial etiology. The current study aimed to evaluate the potential association of PTCH1 (rs10512248) and RAD54B (rs12681366) polymorphisms with NSCL/P in the Northeast Iranian population. Methods: In the present study, blood samples were taken from 122 subjects with NSCL/P and 161 healthy controls. Polymerase Chain Reaction (PCR) followed by Restriction Fragment Length Polymorphism (RFLP) were used to conduct genotyping of single-nucleotide polymorphisms. Results: Although differences were observed between cases and controls in rs10512248 and rs12681366, our data did not support a significant association of these polymorphisms with NSCL/P in our population. Conclusion: Our findings suggest that polymorphisms of rs10512248 and rs12681366 may not be potential risk factors for NSCL/P in the Northeast Iranian population due to the multifactorial and multiethnicity characteristics of some genes.
Background: The aim of the current study was to evaluate and compare the influence of Dycal, Lime-Lite, TheraCal LC, Biodentine, resin-modified glass ionomer cement (RMGIC), and Activa BioActive as the pulp capping material on the shear bond strength of resin composite to dentin. Methods: A total of 70 extracted caries-free molars were randomly assigned to seven groups. Six test groups were covered with various protective liners: Dycal, TheraCal LC, Lime-Lite, Activa BioActive, Biodentine, and RMGIC. The control group received no liner pretreatment. Each sample was bonded to resin composite using the total-etch Tetric N bond adhesive. The samples were then tested for shear bond strength using the universal testing machine at a cross-head speed of 1 mm/min until bond failure occurred. The data were analyzed using the one-way ANOVA test followed by the Tamhane post hoc test for pairwise comparisons of the groups. Results: Independent of the type of the applied liner, all groups exhibited inferior SBS to dentin compared to the control group. TheraCal and RMGIC showed significantly higher shear bond strength than Biodentine and Dycal, which showed the lowest shear bond strength. Lime-Lite and Activa also had significantly lower SBS results than TheraCal. The mode of fracture was predominantly cohesive in Dycal, Biodentine, and TheraCal and adhesive in Activa. Conclusion: This present study concludes that the bond strength of resin composite to dentin can be affected differently using various types of liners.
Dental Bonding , Glass Ionomer Cements , Composite Resins/chemistry , Dentin , Glass Ionomer Cements/chemistry , Materials Testing , Molar , Resin Cements/chemistry , Shear Strength
OBJECTIVES: This study aimed to assess the enamel and dentin marginal microleakage and dentin microtensile bond strength (µTBS) of ACTIVA BioACTIVE Restorative with and without a bonding agent compared with conventional restorative materials. MATERIAL AND METHODS: For enamel and dentin microleakage, Class II boxes were prepared in the mesial (1 mm under the cementoenamel junction) and distal (1 mm above the cementoenamel junction) surfaces of 90 extracted human third molars. The teeth were randomly divided into five groups (n = 18): Group Z (G-Premio Bond + Filtek Z250 XT), Group X (G-Premio Bond + X-tra fil bulk-fill), Group AA (G-Premio Bond + Activa Bioactive restorative), Group A (Activa Bioactive restorative), and Group G (dentin conditioner + Fuji II LC Improve). The teeth were thermocycled, and their microleakage was quantified using the dye penetration test under a stereomicroscope. For dentin µTBS measurement, 12 specimens were fabricated in metal molds (1 × 1 × 12 mm³) for each group mentioned above, and a universal testing machine measured their µTBS. Data were analyzed using one-way analysis of variance (ANOVA), the Kruskal-Wallis test, and multiple comparisons tests. RESULTS: Significant differences were noted among the groups in marginal microleakage and µTBS (p < .001). The highest mean microleakage scores at the enamel and dentin margins were noted in Group A, which had significant differences with other groups (p < .001). The highest µTBS was found in Group X, with significant differences with Group G and Group A (p < .05). The lowest µTBS was noted in Group A, with significant differences with Groups X, Group AA, and Group Z (p < .001). CONCLUSIONS: Activa Bioactive without a bonding agent showed significantly lower µTBS to dentin, and higher microleakage at the enamel and dentin margins. Application of adhesive resin with Activa Bioactive provided a dentine bond strength and marginal seal comparable to other restorative materials.
Dental Leakage , Dental Cements , Dental Leakage/prevention & control , Dental Restoration, Permanent , Humans , Resin Cements/chemistry , Tooth Cervix
