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Background: To evaluate the effect of 2.5% Arginine and nano-hydroxyapatite (nHA) application on the post-bleaching hypersensitivity (HS) and color change in a randomized controlled trial. Material and Methods: Sixty-four participants were randomly allocated to four groups (n=16) according to the investigated desensitizing agents (UltraEZ gel, experimental 2.5% Arginine, 2.5% nHA pastes and control (no treatment) groups). An in-office chemical bleaching agent (40% hydrogen peroxide) was used for vital bleaching of the anterior teeth. The desensitizing agents were applied to the assigned groups and left for 30 min then rinsed off the teeth. HS was evaluated using Visual Analogue Scale (VAS) from 0-10, immediate (after bleaching), first seven days, then every week for 3-w. Color change was evaluated using VITAPAN classical A1-D4 at baseline (before bleaching), immediate (after bleaching), and after 1,2, 3-w. Results: HS results showed statistically insignificant difference between the tested groups at day-1 and -2. All groups showed no HS (0) at/and after day-3. There was a statistically significant color change between immediate, 1-w and 2-w and baseline results for investigated materials. No statistically significant difference was recorded between the baseline and 3-w for the investigated materials. Both Arginine and nHA groups showed a higher color change compared to UltraEZ group. Conclusions: Arginine and nHA present a potential treatment modality for the post-bleaching HS without jeopardizing the bleaching efficiency. Key words:Arginine, nano-hydroxyapatite, bleached enamel, hypersensitivity, color change, clinical trial.
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PURPOSE: comparing the influence of different tooth preparation and bonding techniques on the fracture resistance of tooth fragment reattachment. MATERIALS AND METHOD: Ninety bovine central incisors were selected. Fifteen teeth act as a control (Group A). Experimental specimens were sectioned at the mesial-incisal proximal edge 3 mm from the incisal edge in a labio-lingual direction at 25degree inclination apically. Experimental specimens were then divided into five groups according to the tooth reattachment techniques utilized; Group B: no tooth preparation + Cured bond + Flowable composite; Group C: no tooth preparation + Uncured bond + Flowable composite; Group D: Bevel + bond + Flowable composite; Group E: Over-contouring + bond + Nanohybrid composite; Group F: Over-contouring + bond + Flowable composite. Specimens were subjected to thermocycling between 5 °C and 55 °C for 500 cycles with 30 sec. dwell time. Fracture strength was evaluated using universal testing machine. Data was analyzed using One-way ANOVA. RESULTS: There was a statistically significant difference between Group A and all the experimental groups, p < .001. Group E showed the highest statistically significant fracture resistance mean value compared to other experimental groups, while the lowest mean value was found in Group B. CONCLUSION: Though, none of the tested techniques resulted in fracture resistance similar to that of intact teeth, over-contouring technique with nanohybrid composite application showed better performances compared to the other techniques tested in the current study. Bonding plus flowable resin composite application with no additional tooth preparation and placement of a bevel are not suggested due to the low fracture strength achieved.
ABSTRACT
The influence of using simulated body fluid (SBF) as a curing medium on some characteristics of pure single tri-calcium silicate (C3S) bio-cement was investigated. CaCl2 salt solution was used as an accelerating liquid for setting and hardening of C3S pastes in comparison with distilled water (DW). Solid state reaction was applied to synthesis C3S phase at elevated temperature followed by rapid cooling. The results showed that 10 wt.% CaCl2 solution was the optimum concentration that showed the lowest setting time (106 min). C3S pastes prepared with CaCl2 solution have better physical and mechanical properties than those mixed with DW even after curing under SBF solution for the different curing ages. However, SBF solution has an adverse effect on the hydrated compound C-S-H that results in a little decrease in strength and hardness values. The elemental analysis emphasized the presence of apatite layer on the surface of the hardened C3S paste. Scanning electron microscopy (SEM) photomicrographs and elemental analysis revealed reliable adaptation of the experimentally prepared C3S paste to the tooth structure, in addition to its bioactivity makes it a consistent material to be used as dentin substitute.
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BACKGROUND: Remineralizing of bleached enamel is a common procedure that aims to compensate enamel mineral lose. This study aimed to evaluate the remineralization effectiveness of experimentally prepared grape seed extract hydrogels (GSE) compared to fluoride gel on bleached enamel. MATERIAL AND METHODS: Thirty extracted maxillary incisor were bleached using white smile bleaching agent. Bleached specimens were divided into three groups (10/group) according to the remineralizing agents tested: [GSE 6%, GSE 10%, or fluoride gel]. After bleaching and remineralization procedure, the specimens were stored in artificial saliva at 37°C. Micro-hardness and Energy-Dispersive X-ray and ultra-morphological evaluation were tested at baseline, after bleaching and after remineralization. RESULTS: Statistical significant decrease on mean micro-hardness values had resulted after bleaching procedure compared to baseline, followed by a significant increase in GSE (10%) and fluoride groups. GSE (6%) application showed the least statistical significant mean micro-hardness, which was statistically insignificant different compared to bleaching procedure. Elemental analysis results revealed a statistical significant decrease on Ca, and Ca/P ratios (At%) values after bleaching compared to baseline, followed by a significant increase after treatment with all tested remineralizing gels. SEM photomicrograph of sound enamel shows smooth uniform appearance with few pores. Bleached enamel showed irregular pitted disorganized enamel surface. Bleached enamel exposed to GSE and fluoride gel showed occlusion of enamel surface porosities and precipitates of different sizes. CONCLUSIONS: The specially prepared GSE hydrogels has positive effects on the remineralization process of bleached enamel making it an effective natural agent with remineralizing potential. Key words:Remineralization, bleaching, grape seed extract, fluoride, enamel.
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BACKGROUND: The effectiveness of each resin composite material composition in enabling homogeneous monomer conversion and reducing polymerization shrinkage (PS) is an important issue. Thus, this study aimed to evaluate the degree of conversion (DC) and PS of low-shrinkage bulk-fill composites (BFCs) in 4-mm thickness. MATERIALS AND METHODS: Four bulk fill (Tetric EvoCeram Bulk Fill, Sonic Fill, XTra Fill, and Venus Bulk Fill) and one conventional (Filtek Z350 XT) resin composites were tested in this study. Teflon molds of 4-mm depth were used to prepare resin composite specimens. All tested resin composites were packed in bulk then light cured for the recommended time by their manufacturers. DC% was determined by Fourier transform infrared spectroscopy; PS was determined using the strain gauge method. Data were subjected to one-way ANOVA/Tukey's test (α = 0.05). RESULTS: DC% results were as follows: Venus Bulk Fill > XTra Fill > Sonic Fill > Tetric EvoCeram Bulk Fill > Filtek Z350 XT with a significant difference between each others at P ≤ 0.001. For PS %, significant difference resulted between tested groups at P ≤ 0.001. Where Venus Bulk Fill < XTra Fill = Sonic Fill < Tetric EvoCeram Bulk Fill < Filtek Z350 XT. CONCLUSIONS: Low-shrinkage resin monomers seem to be beneficial for reducing PS with enhancement in the DC. Increased filler loading in BFCs had a positive effect on reducing PS, while its effect on the DC was material dependent.
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BACKGROUND: Bulk-fill resin composite has been introduced, their manufacturers claimed that they can be applied in bulks of 4mm, without necessitating a prolonged curing time, or a light curing unit with increased irradiance. Thus this study was conducted to evaluate the effect of resin thickness, and curing time on the micro-hardness of two bulk -fill resin composites; Tetric Evo-Ceram [TE], and X-trafil [XF]. MATERIAL AND METHODS: 120 cylindrical specimens were prepared, and divided into 24 groups (n=5/group), representing the two bulk-fill resin composites, three different material thicknesses (2, 3 and 4 mm) and the four curing times used in the study (10, 20, 40, and 60 seconds). The specimens were light-cured from the top surface only. Specimens were stored in light proof containers in complete darkness at 37°C for 24 hours. Micro-hardness test was conducted on both top and bottom surfaces using Vickers micro-hardness tester with 500 g load and a dwell time of 15 seconds. Data were statistically analyzed by Four-way ANOVA of Variance. The significance level was set at P ≤ 0.05. Pearson Correlation used to determine significant correlations between mean micro-hardness (top) and (bottom) surfaces. RESULTS: Four way-ANOVA shows that different tested materials produce a statistically significant effect on mean micro-hardness (VHN) at p≤0.001, while thickness, curing time, and surface revealed statistically non significant effect on mean micro-hardness (VHN) at p≥0.05. [XF] (92.01±3.15 VHN) showed statistically significant higher mean micro-hardness than [TE] (54.13±4.96 VHN). Pearson Correlation revealed that there was a significant direct correlation between micro-hardness (bottom) and mean micro-hardness (top) (mm), r = 0.985, p (2-tailed) ≤0.001. CONCLUSIONS: Within the limitations of this study, the bulk-fill resin composites used in this study can be placed and cured properly in the 4 mm bulk. KEY WORDS: Bulk-fill resin composite, micro-hardness, thickness, curing time.
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BACKGROUND: There are different solvents presented in simplified adhesives. Bond-1 SF has been developed, which contains neither water nor organic solvents, in order to eliminate technical issues in terms of evaporation of solvents and concerns for the durability of resin-dentin bond. Thus this study was conducted to evaluate the microtensile bond strength (?TBS) of solvent-free and ethanol-based one-step self-etch adhesives to dentin under simulated intrapulpal pressure (IPP). MATERIAL AND METHODS: Occlusal surfaces of human molars were prepared to expose mid-dentin depth. Bond-1SF Solvent-Free SE [SF] and AdperTM easy one adhesives [AE] were applied on dentin specimens. Resin composite build up was done in increments. Then specimens were stored under simulated IPP 20 mmHg, immersed in artificial saliva at 37 ºC for 24 hours (24h) and 6 months (6m). Specimens were sectioned into sticks of (1 mm²) to be tested for (?TBS) using a universal testing machine. Both fractured sections of each stick were inspected using a stereomicroscope at 40× magnification to determine the mode of failure. Data were statistically analyzed by Two-way ANOVA of Variance. RESULTS: There was no statistically significant difference between the mean ?TBS of both [SF] and [AE] adhesives at both aging periods, 24h and 6m (p< 0.1103) and (p< 0.7148) respectively. Only for [AE] there was statistical significance for aging periods (p< 0.0057*). The most represented modes of failure were adhesive failure at tooth side. CONCLUSIONS: Under simulated IPP solvent-free adhesive [SF] had comparable performance as ethanol-based adhesive [AE] when bonded to dentin substrate. KEY WORDS: Bond strength, dentin, simulated intrapulpal pressure, self-etch adhesives, solvents.