Immersion In Artificial Saliva Research Articles

Observations of Enamel Microstructure in Incipient Lesions Remineralized by NaF Dentifrices

Synchrotron Radiation (SR) Wide-angle X-ray Diffraction (WAXD) and Small-angle X-ray Scattering (SAXS) techniques were used to assess microstructure of bovine enamel white-spot lesions (WSL) evaluated in a 10-day pH cycling model comprising three different dentifrice groups: (A) 0.21% NaF plus TCP (Clinpro Tooth Crème), (B) 1.1% NaF plus TCP (Clinpro 5000), or (C) 0% NaF (Tom’s of Maine) dentifrice. Each day consisted of four 2-minute treatments, one 4-hour acid challenge (pH=5.0), and immersion in artificial saliva (pH=7.0) between these events. These specimens were also examined with cross-sectional microhardness, digital light microscopy and FE-SEM (field emission scanning electron microscope), and demonstrated the remineralization model effected changes in subsurface microstructure. X-ray diffraction data from WAXD and SAXS were collected on enamel slab cross-sections extending from 0 μm to 150 μm, in 6 μm microbeam increments. A primary outcome of this observational study was that simultaneous WAXD and SAXS measurements were able to resolve significant differences (ANOVA, Student’s t-test, p<0.05) between the effects of the two fluoridecontaining dentifrices on subsurface lesion microstructure. In particular, enamel lesions treated with 1.1% NaF dentifrice group manifested an abundance of nanometer-sized crystallites, while treatment with the 0.21% NaF dentifrice produced larger apatite-like crystals. While the presence of fluoride in both cases promoted regularity in crystal size and orientation, this was not observed for lesions treated without fluoride. Altogether, our observations demonstrate the pathological processes for remineralization are markedly influenced by the presence and concentration of fluoride, the microstructural characteristics of which can be distinguished using the simultaneous WAXD and SAXS technique.

Evaluation of Five Different Desensitizers: A Comparative Dentin Permeability and SEM Investigation In Vitro.

Background/Objective:The purpose of this study was to evaluate the efficacy and durability of five different dentin desensitizers (Gluma Desensitizer Powergel, Bifluorid 12, Gluma Self Etch Bond, D/Sense Crystal, Nupro Sensodyne Prophylaxis Paste with Novamin) on tubule occlusion and dentin permeability reduction in vitro.Method:The quantitative changes in permeability of 100 dentin discs were measured after desensitizer treatments and following post-treatments of 6% citric acid challenge for 1 min or immersion in artificial saliva for 24 hours under hydrostatic pressure generated by a computerised fluid filtration meter. Qualitative SEM analyses were also carried out.Results:Dentin permeability decreased after desensitizer application in all groups. Nevertheless, only the difference between ‘Gluma Self Etch Bond’ and ‘Nupro Sensodyne Prophylaxis Paste with Novamin’ groups was significantly different (p<0.05). Dentin permeability increased significantly after post-treatments (p<0.05). There was no statistically difference among the citric acid-subgroups (p>0.05). Of all the artificial saliva-subgroups, only the difference between ‘D/Sense Crystal’ and ‘Bifluorid 12’ was significantly different (p<0.05). In SEM analysis, morphological changes were detected on the dentin surface and within the tubules following desensitizer treatments and post-treatments.Conclusion:All the desensitizers significantly reduced dentin permeability by changing the morphology of the dentin surface and/or dentinal tubules. Following post-treatments, there was some reduction in the efficacy of the desensitizers which was represented by the reduction in permeability values. SEM analysis revealed some physical changes in the dentin structure which can partly give an explanation to the reduced efficacy of tested desensitizers.

To Compare and Evaluate the Sorption and Solubility of Four Luting Cements after Immersion in Artificial Saliva of Different pH Values.

Introduction:The word ‘luting’ is derived from a latin word ‘Lutum’ which means ‘mud’. ‘Luting’ is a word that is often used to describe the use of a mouldable substance to seal a space or to cement two components together. Therefore in view of the clinical importance of dissolution of luting cements in the oral environment, an in vitro study was designed to compare the sorption and solubility of commercially available luting cements mainly zinc phosphate, Glass Ionomer cement, Resin Modified Glass Ionomer Cement and Resin Cement after immersion in artificial saliva of different ph values of 5 and 7.Aim:To Compare and Evaluate the sorption and solubility of four luting cements after immersion in artificial saliva of different pH values.Materials and Method:A total of 120 test samples were prepared of which 30 samples of each luting cement were prepared for the purpose of assessing the water solubility and sorptionThese luting cements were grouped as: GROUP- A (Zinc Phosphate cement), GROUP- B (Glass Ionomer Cement), GROUP-C (Resin Modified Cement), GROUP- D (Resin Cement) In these groups, based on immersion of artificial saliva of acidic pH 5 and neutral pH7, the luting cement specimens were subdivided into 2 groups of 15 samples each. The volume (V) of each specimen was calculated using mathematical formula.Conclusion:Resin cement had the highest resistance to solubility and sorption followed by resin modified GIC, Conventional GIC, and Zinc Phosphate which exhibited the least resistance to solubility in both artificial saliva of pH 5 and pH 7.

Effect of 15% Carbamide Peroxide on the Surface Roughness and Adhesion of Streptococcus mutans to Microhybrid Composite Resin and Giomer

ABSTRACT Introduction Adhesion of bacteria, especially Streptococcus mutans (S. mutans), to the surface of tooth restorations is a factor in the etiology of secondary caries. Given the ever-increasing popularity of bleaching procedures, the aim of the present study was to evaluate adhesion of S. mutans and surface roughness (SR) of microhybrid composite resin and giomer subsequent to the application of 15% carbamide peroxide. Materials and methods Twenty disk-shaped samples were prepared from each material, measuring 8 mm in diameter and 2 mm in thickness. Then, the samples of each material were divided into two groups (n = 10): (a) microhybrid without bleaching; (b) microhybrid with bleaching; and (c) giomer without bleaching; and (d) giomer with bleaching. The samples in groups I and III were immersed in artificial saliva for 14 days without any bleaching procedure; the samples in groups II and IV underwent a bleaching procedure on their polished surfaces with 15% carbamide peroxide for 14 days (4 hours of bleaching and 20 hours of immersion in artificial saliva). The SR of all the samples was determined with the use of a profilometer. The samples were added to the culture medium after 4 hours of placement in a microbial suspension at 37°C; after 24 hours of incubation at 37°C, the bacterial counts, indicating the number of bacteria adhering to the surface, were determined by counting them in the plates containing the solid culture medium. Results The type of the restorative material had a significant effect on SR, with greater SR in giomer (p = 0.03). However, bleaching had no significant effect on SR (p = 0.099). In relation to the rate of bacterial adhesion (BA), both the types of the restorative materials and bleaching procedures were significantly effective; in this context, there was more BA in microhybrid composite resin samples that did not undergo bleaching (p &lt; 0.001). Bleaching resulted in the adhesion of S. mutans to the surface of both materials decrease. Pearson's correlation coefficient did not reveal any correlation between BA and SR (p = 0.42). Conclusion The BA was higher in microhybrid composite resin, and SR was higher in giomer. The BA was higher in samples that did not undergo a bleaching procedure. Clinical significance There is no change in the SR of microhybrid composite resin and giomer after application of 15% carbamide peroxide; therefore, it is not necessary to polish or replace these restorative materials after bleaching. In addition, use of 15% carbamide peroxide does not increase caries risk. How to cite this article Mohammadi N, Mowlaie S, Savadi- Oskoee S, Ebrahimi ME, Rikhtegaran S, Rahbar M, Pirzadeh T. Effect of 15% Carbamide Peroxide on the Surface Roughness and Adhesion of Streptococcus mutans to Microhybrid Composite Resin and Giomer. World J Dent 2017;8(4):288-295.

Protective performance of Zr and Cr based silico-oxynitrides used for dental applications by means of potentiodynamic polarization and odd random phase multisine electrochemical impedance spectroscopy

Zr and Cr based silico-oxynitrides were deposited on CoCr dental alloys by cathodic arc evaporation method, at two bias voltages. Potentiodynamic polarization and ORP-multisine EIS were employed to assess the performance of the coatings during 72h of immersion in artificial saliva. Enhanced corrosion resistance was exhibited by coatings deposited at higher bias voltage, ascribed to the beneficial effect of the more intense ion bombardment during the deposition, which determined a defect-free structure. Among them, ZrSiON200 coating exhibited the highest protective performance in time to the CoCr substrate ascribed to the formation of a stable passive layer inhibiting the corrosion.

Effect of plasma nitriding and titanium nitride coating on the corrosion resistance of titanium

Statement of problemThe passive film on the surface of titanium can be destroyed by immersion in a fluoridated acidic medium. Coating with titanium nitride (TiN) may improve the corrosion resistance of titanium. PurposeThe purpose of this in vitro study was to investigate the effect of duplex treatment with plasma nitriding and TiN coating on the corrosion resistance of cast titanium. Material and methodsCast titanium was treated with plasma nitriding and TiN coating. The corrosion resistance of the duplex-treated titanium in fluoride-containing artificial saliva was then investigated through electrochemical and immersion tests. The corroded surface was characterized by scanning electron microscopy (SEM) with energy-dispersive spectroscopy surface scan analysis. The data were analyzed using ANOVA (α=.05) ResultsDuplex treatment generated a dense and uniform TiN film with a thickness of 4.5 μm. Compared with untreated titanium, the duplex-treated titanium displayed higher corrosion potential (Ecorr) values (P<.001) and lower corrosion current density (Icorr) values (P<.001). SEM results showed that the surface of untreated titanium was more heavily corroded than that of duplex-treated titanium. Surface scan analysis of duplex-treated titanium that had been immersed in artificial saliva containing 2 g/L fluoride revealed fluorine on the titanium surface, whereas fluorine was not observed on the surface of untreated titanium after immersion in fluoride-containing artificial saliva. The concentration of titanium ions released from the treated titanium was less than the amount released from untreated titanium (P<.001). ConclusionsDuplex treatment by plasma nitriding and TiN coating significantly improved the corrosion resistance of cast titanium in a fluoride-containing environment.

Influence of Adhesive on Shear Bond Strength Between Denture Base Materials and Self-Cured Silicon Soft Liner

Background: Soft lining materials play an important role in modern prosthodontics because of their capability of restoring health of inflamed and distorted mucosa. Gradual changes of oral tissues require that complete or partial dentures be relined to improve their adaptation to the supporting tissue. This study aimed to evaluate the shear bond strength (SBS) of heat cured acrylic and injection-molded ValplastTM denture base materials to silicone self-cure soft lining materials, with and without adhesive, after storage in two different times in artificial saliva. Materials and Methods: 40 rectangularspecimens were prepared from two types of self-cured silicone soft lining material,one with adhesive and the other without adhesive were applied to two types of denture base materials ( heat polymerized Polymethyl methacrylate and injection-molded nylon denture base materials). Shear bond strength of the specimens was measured, after immersionin artificial saliva for different periods (72 hours or 10 weeks), using Lloyd universal testing machine. Results: Acrylic denture base bonded to soft liner with adhesive at 72 hours of immersion in artificial saliva showed the highest shear bond strength. Comparing SBS values of the tested soft lining materials revealed significant differences between adhesively bonded and non-adhesively bonded types. Conclusions: This study concluded that the bond strength of the silicone soft lining materials with denture base materials increased with adhesive. Silicone soft lining materials are affected by artificial saliva storage.

Changes in the permeability and morphology of dentine surfaces after brushing with a Thai herbal toothpaste: A preliminary study.

Objectives:The aim of this study was to evaluate dentine permeability after brushing with Twin Lotus®, Thai herbal toothpaste by comparing with Sensodyne Rapid Relief®, a commercial desensitizing toothpaste, and also after artificial saliva (AS) immersion or citric acid challenge.Materials and Methods:Dentine discs from human mandibular third molars were divided into three groups (n = 20) and brushed with either experimental toothpaste or water (control) for 2 min with an automated toothbrush. Then, 10 discs were immersed in AS, and the other 10 discs were immersed in 6% citric acid to simulate the conditions of the oral environment. The dentine permeability of each specimen was measured before brushing and after each treatment using a fluid filtration system. Morphological changes in the dentine were observed using scanning electron microscopy (SEM).Results:Both toothpastes significantly reduced dentine permeability, and a crystalline precipitate was observed on the dentine surface under SEM observation. No significant difference was found between the two toothpaste groups with regard to dentine permeability after brushing and AS or acid immersion.Conclusions:The dentine permeability reduction caused by the two toothpastes did not differ after brushing or after AS or citric acid immersion.

An investigation into bisphenol A leaching from materials used intraorally

BackgroundIn this study, the authors quantitatively determined the bisphenol A (BPA) leached from intraoral materials during simulated intraoral exposure. MethodsThe authors subjected samples of intraoral materials to simulated abrasion, immersion in artificial saliva, thermal shock via temperature cycling, and simulated intraoral exposure. The authors collected sample aliquots for up to 2 weeks after artificial saliva immersion, derivatized, and then analyzed the aliquots for BPA by gas chromatography and mass spectroscopy. ResultsQuantifiable amounts of leached BPA were observed from only 1 of 13 intraoral materials tested: a silicone baby bottle nipple (20 micrograms). BPA leaching was only observed after 3 days of artificial saliva immersion, with no additional leaching thereafter. ConclusionsUnder the test conditions, BPA was observed to leach from a silicone baby bottle nipple. Practical ImplicationsAlthough the quantities of leached BPA were below the reference dose for daily intake, investigators have shown a possible association between low levels of BPA and many medical disorders. BPA exposure, and thus the use of the leaching material identified in this study, should be reduced or eliminated.

An Evaluation of Corrosion Pits in Esthetic Coated Stainless Steel Orthodontic Archwires in Dry and Wet Environment at Different Intervals : An in Vitro Study

Background: The demand for esthetic orthodontic appliances is increasing; so the esthetic orthodontic archwires were introduced. Among them, Teflon and Epoxy coated stainless steel archwires. The amount of force available from the archwire depends on the structural properties and susceptibility to corrosion. All metallic alloys are changed during immersion in artificial saliva, chlorhexidine mouthwash andtoothpaste, but their behaviors differ from one type to another. They corrode at different rates, which lead to decrease the amount of force applied to the teeth. This in vitro study was designed to evaluate the corrosion pits in stainless steel archwires coated with Teflon and with Epoxy in dry and after immersion in artificial saliva, chlorhexidine(0.2%( (Parodontax) and toothpaste media (Sensodyne) for (1, 7 and 28) days intervals. Moreover, this study is intended to compare the corrosion pits for each type of archwires at these different media among all intervals. Materials and Methods: In this study, two hundred forty pieces of orthodontic wires of Teflon (Hubit) coated Stainless steel (120 pieces) and epoxy (Orthotechnology) coated Stainless steel (120 pieces), rectangular in cross section, size (0.019 x 0.025) inch and 15mm in length divided into four groups according to immersion media: (dry environment group, artificial saliva group, chlorhexidine group and toothpaste group). The atomic force microscope was used to measure the corrosion pits for all samples at dry and wet conditions and after different immersion periods. Results: Statistical analysis showed that there was a highly significant increase in the corrosion pits of Teflon coated stainless steel archwires (P ≤ 0.05) in wet environment at 28 days immersion period.The highest corrosion pits were found in the toothpaste medium for the two archwire types at 28 days immersion period. Conclusion: We can conclude that Epoxy coatedstainless steel archwires are indicated to be used above Teflon coated stainless steel archwires in terms of corrosion resistance. IfTeflon coated stainless steel archwires should to be used, they should be change in shorter periods than Epoxy coated stainless steel archwires type Key words: Esthetic coated archwire, corrosion, Teflon, Epoxy, wet environment, AFM.

In vitro antibacterial and remineralizing effect of adhesive containing triazine and niobium pentoxide phosphate inverted glass.

White spot lesions are still a concern for orthodontic patients. The objective of this study was to assess the remineralizing and antibacterial effect of a newly developed orthodontic adhesive. The compounds 1,3,5-tryacryloylhexahydro-1,3,5-triazine (TAT) and phosphate invert glass containing 10mol% of niobium pentoxide (PIG-Nb) were added at 20 and 5wt%, respectively, to an experimental adhesive (75wt% BisGMA, 25wt% TEGDMA, 5wt% fummed silica, and photo-initiator system), called TPN. A group without the addition of these compounds was used as Control and the orthodontic adhesive Transbond XT (TXT) was used for comparison. Antibacterial activity was evaluated through surface biofilm formation, mineral deposition, and degree of conversion (DC) through Raman microscopy, Knoop hardness after softening in solvent, and bracket dislodgement (BD). TPN group presented a reduction in bacterial growth when compared to Control and TXT. Mineral deposits were observed on the surface of TPN adhesive after 14 and 28days of immersion in artificial saliva. There was an increase in DC after 28days, whereas TPN group presented the highest DC. All groups underwent some degree of softening. No significant changes were observed in BD after 28days of immersion in artificial saliva. The newly developed orthodontic adhesive, with addition of 20wt% TAT and 5w% PIG-Nb, exhibited antibacterial activity and was capable to induce mineral deposition on its surface in vitro. The orthodontic adhesive developed in this study with antibacterial activity and mineral deposition could be a reliable choice for brackets adhesion.

In vitro Degradation of Pure Mg for Esophageal Stent in Artificial Saliva

Magnesium and its alloys as biodegradable implant materials can be potentially used in cardiovascular and orthopedic devices. However, few studies have focused on its application in esophageal stents. In this paper, time-lapse degradation characteristics of pure Mg were analyzed by scanning electron microscopy, energy dispersive spectroscopy, X-ray diffraction, Fourier transform infrared spectroscopy, hydrogen evolution, pH and electrochemical measurements after immersion in artificial saliva for different times. Results revealed that a dense degradation product film formed on samples, which mainly consisted of two kinds of layers: one was calcium phosphate compounds with different structures; the other was thin magnesium hydrate layer close to the substrate. Less pH increase and low degradation rate were observed in the first 5 days of immersion, which can be ascribed to the formation of a thicker and denser layer on the sample surface with increasing immersion time. And then there was an increase in degradation rate and pH values; the deposition layer remained almost intact after immersion for 6 and 8 days. After 10 days of immersion, the degradation rate and pH value remained stable, and the calcium phosphate layer was delaminated and the inner magnesium hydrate layer was exposed. This study indicated that pure Mg exhibited desirable degradation resistance in artificial saliva, which provided magnesium-based materials with the potential to be used as esophageal stents.

Influence of removing excess of resin-based materials applied to eroded enamel on the resistance to erosive challenge

ObjectivesThe aim of this study was to evaluate the effect of removing excess of resin-based materials applied to eroded enamel, subjected to erosive challenge. MethodsBovine enamel blocks were immersed in HCl 0.01M, pH 2.3, for 30s under agitation at 50rpm in room temperature, in order to form a softened erosion lesion. The blocks were then randomly divided into eight groups (n=12) and treated as follows: Cn- and Ce-control without treatment, Hn- and He-fissure resin sealant (Helioseal Clear®), An- and Ae-self-etch adhesive (Adhese®), In- and Ie-infiltrant (Icon®); being n-with excess removal and e-without excess removal of the material. After application of the materials, the blocks were immersed in HCl for 2min, followed by immersion in artificial saliva for 120min. This cycle was repeated four times a day for five days. Material thickness and enamel wear were assessed using profilometry. Data were analyzed by two-way ANOVA and Tukey’s test (P<0.05). ResultsGroups He, Ae, and Ie resulted in the formation of a layer of material over enamel, being similar effective in inhibiting erosion progression (P>0.05). Groups Hn, An, and In (with excess removal) were similar to controls (Cn, Ce) and resulted in near enamel loss after application and after erosive challenge (P>0.05). ConclusionsResin-based materials are able to protect enamel against erosion only when they are present over enamel, as a physical barrier. Clinical significanceThe resin-based materials demonstrated potential to prevent the progression of erosion lesions when the material remains on the dental surface.

Tunicate-Inspired Gallic Acid/Metal Ion Complex for Instant and Efficient Treatment of Dentin Hypersensitivity.

Dentin hypersensitivity is sharp and unpleasant pains caused by exposed dentinal tubules when enamel outside of the tooth wears away. The occlusion of dentinal tubules via in situ remineralization of hydroxyapatite is the best method to alleviate the symptoms caused by dentin hypersensitivity. Commercially available dental desensitizers are generally effective only on a specific area and are relatively toxic, and their performance usually depends on the skill of the clinician. Here, a facile and efficient dentin hypersensitivity treatment with remarkable aesthetic improvement inspired by the tunicate-self-healing process is reported. As pyrogallol groups in tunicate proteins conjugate with metal ions to heal the torn body armor of a tunicate, the ingenious mechanism by introducing gallic acid (GA) as a cheap, abundant, and edible alternative to the pyrogallol groups of the tunicate combined with a varied daily intake of metal ion sources is mimicked. In particular, the GA/Fe(3+) complex exhibits the most promising results, to the instant ≈52% blockage in tubules within 4 min and ≈87% after 7 d of immersion in artificial saliva. Overall, the GA/metal ion complex-mediated coating is facile, instant, and effective, and is suggested as an aesthetic solution for treating dentin hypersensitivity.

Surface properties of Ti-35Nb-7Zr-5Ta: Effects of long-term immersion in artificial saliva and fluoride solution

Statement of problemThe mechanical properties of new titanium alloys with an elastic modulus closest to cortical bone have been studied. However, potentially damaging conditions experienced in the oral cavity, such as fluoride ions, can initiate a localized or crevice process of corrosive degradation in the alloy surfaces. PurposeThe purpose of this in vitro study was to evaluate the effects of long-term immersion in artificial saliva or in fluoride solution on mean roughness (Ra), Vickers hardness, and topography of the new titanium alloy Ti-35Nb-7Zr-5Ta (TNZT) compared with those of cp Ti and Ti-6Al-4V (TAV). Material and methodsDisks (N=210) were divided into cp Ti, TAV, and TNZT and subdivided according to the following treatments: no immersion (N−, control), immersion in artificial saliva (S), and immersion in fluoride (F) during periods equivalent to 5, 10, 15, and 20 years. The Ra and Vickers hardness were measured with a profilometer and a hardness tester. The topography was analyzed by scanning electronic microscopy. Data were compared using the Kruskal-Wallis and Dunn tests (α=.05). ResultsValues of Ra and hardness were significantly different among the metals (Ra: TAV<TNZT<cp Ti; P<.05); and hardness (cp Ti<TNZT<TAV; P<.05); with a tendency for Ra to increase for TAV after 20 years of fluoride immersion and changes in hardness values of TAV and TNZT after immersion. TAV surfaces showed a heterogeneous appearance. ConclusionsLong-term immersion in NaF did not change the roughness of Ti-35Nb-7Zr-5Ta. However, the hardness of the alloys increased with immersion.

Electrochemical impedance investigation of Ni-free Co-Cr-Mo and Co-Cr-Mo-Ni dental casting alloy for partial removable dental prosthesis frameworks

Statement of problemThe pH level of the oral environment influences corrosion in dental materials. Corrosion behaviors of Co-Cr-Mo and Co-Cr-Mo-Ni alloys in different pH environments remain undetermined. PurposeThe purpose of this in vitro study was to evaluate the surface properties and corrosion behaviors of Co-Cr-Mo and Co-Cr-Mo-Ni dental casting alloys in artificial saliva at pH values of 5.0 and 2.5. Material and methodsFifty specimens were divided into 2 groups according to the alloy composition. The surface compositions, hardness values, and microstructures of the alloys were measured before immersion in artificial saliva. The corrosion behaviors of the specimens in artificial saliva at pH values of 5.0 and 2.5 were studied using electrochemical impedance spectroscopy (EIS). The microstructures were examined again after a 7-day immersion test. Data were analyzed by a 1-way analysis of variance (ANOVA) test (α=.05). ResultsAs expected, the relative levels of Co and Cr of the surface composition were higher in the Co-Cr-Mo alloy. The Co-Cr-Mo alloy had statistically higher surface hardness than the Co-Cr-Mo-Ni alloy (P<.05). In the pH 2.5 environment, both of the alloys showed decreased corrosion resistance (P<.05). The microstructure of the Co-Cr-Mo-Ni alloy corroded more than that of the Co-Cr-Mo alloy in the pH 2.5 environment. The oxide-layer corrosion resistance of the Co-Cr-Mo alloy was better than that of the Co-Cr-Mo-Ni alloy in Fusayama artificial saliva solutions at pH values of both 5.0 and 2.5 (P<.05). ConclusionsThe corrosion resistance of the Co-Cr-Mo alloy was better in the oral environment, especially at a low pH value.

In vitro Effect of Erosive Challenge on Surface Microhardness of Orthodontic Composites

Objective: To evaluate in vitro the effect of erosive challenge and continuous immersion in cola drink on surface microhardness of orthodontic composites. Material and Methods: Forty samples of three composites (Transbond XT, Quick Cure and Ortho Cem) were prepared (4 x 2 mm) and distributed into 4 groups (n=10): erosive challenge, artificial saliva immersion (control 1), continuous cola immersion and artificial saliva immersion (control 2). Erosive challenge was performed 4 times per day (5 min) in cola drink for 2 h in artificial saliva for 7 days. Samples of continuous cola immersion group were soaked in cola drink for 5 weeks and the beverage was renewed every two days. Control samples were immersed in artificial saliva for 7 days (control 1) and 5 weeks (control 2). Vickers microhardness (VHN) measurements were performed before and after erosive challenge and continuous immersion. Data were evaluated by paired Student’s T-test, ANOVA one-way and Tukey tests (α = 0.05). Results: After 7 days of erosive challenge, there was no statistical difference between VHN values before and after erosive challenge and artificial saliva immersion. However, after 5 weeks of cola drink and artificial saliva immersion, significant reduction in VHN values was observed for all composites when compared to baseline values, and specimens immersed in cola drink showed lower VHN compared to those immersed in saliva, regardless of composite composition. Conclusion: After 7 days of erosive challenge, there was no alteration in superficial VHN of orthodontic composites. However, after 5 weeks of immersion in cola drink, significant reduction of VHN values was observed for all composites.

Effect of sodium ascorbate and delayed treatment on the shear bond strength of composite resin to enamel following bleaching.

The effect of bleaching on enamel surfaces, as well as exploring methods of preventing the weakening of bond strength of two different adhesives to bleached enamel surfaces. This study compared the shear bond strength (SBS) of two different adhesives on bleached enamel immediately after bleaching, with a 1-week delay, and following application of an antioxidizing agent after bleaching. Materilas and Method: The enamel surfaces of 140 incisors were divided into 14 groups. Two unbleached enamel groups (n = 20) were prepared as negative controls of the Adper Single Bond 2 total-etch and Clearfil Tri S Bond self-etch adhesives. The remaining surfaces were randomly divided into two bleaching groups treated with 35% Beyond Max (n = 60) and 38% Opalescence Xtra Boost (n = 60). Each bleaching group was then divided into two subgroups using the total and self-etch adhesive systems. Specimens were bonded immediately after bleaching, after treatment with 10% sodium ascorbate (SA) gel, or after 1-week of immersion in artificial saliva. All groups were restored with composite resin. After thermocycling, SBS was measured and data were analyzed. In the control groups, there was no statistically-significant difference in SBS between self-and total-etch adhesives. Among all bleaching groups, no statistically-significant differences in SBS were noted, although the SA-treated delayed bonding (1-week) groups had the highest values. The lowest values were noted for the groups bonded immediately after bleaching.

The effect of red and white wine on color changes of nanofilled and nanohybrid resin composites

ObjectivesThis study investigated the effect of red and white wine on color changes of nanofilled and nanohybrid resin composite.Materials and MethodsSixty specimens of each resin composite were prepared. Baseline data color values were recorded using a spectrophotometer. Three groups of discs (n = 20) were then alternately immersed in red, white wine, and deionized water (as a control) for twenty five minutes and artificial saliva for five minutes for four cycles. Specimens were then stored in artificial saliva for twenty two hours. This process was repeated for five days following immersion in artificial saliva for two days. Subsequently, the process was repeated again. Data were analyzed by two-way repeated ANOVA, one-way ANOVA, and Tukey's HSD.ResultsRed wine caused significantly higher color change (ΔE* > 3.3) than did white wine and deionized water (p < 0.05). Nanohybrid resin composites had significantly more color changes than nanofilled resin composite (p < 0.05).ConclusionsThe effect of red and white wine on the color changes of resin composite restorative materials depended upon the physical and chemical composition of the restorative materials and the types of wine.

Surface roughness and erosion of nanohybrid and nanofilled resin composites after immersion in red and white wine

Aims:This study aimed to investigate the effects of red and white wine on the surface roughness and erosion of nanohybrid and nanofilled resin composites.Materials and Methods:Sixty specimens of each resin-based composite (RBC) were prepared. Before immersion, baseline data roughness values were recorded using a profilometer. Three groups of discs (n = 20) were then alternately immersed in red wine, white wine, and deionized water (as a control) for 25 min and artificial saliva for 5 min over four cycles. The specimens were then stored in artificial saliva for 22 h. This process was repeated for 5 days following immersion in artificial saliva for 2 days. Subsequently, the process was repeated. After immersion, the specimens were evaluated and data were analyzed by two-way repeated analysis of variance (ANOVA) and Tukey's honestly significant difference (HSD) (α = 0.05).Results:Red wine caused significantly greater roughness and erosion than did white wine and deionized water (P < 0.05). Nanohybrid resin composites were significantly rougher than nanofilled resin composites (P < 0.05).Conclusion:The effects of red and white wine on the surface roughness and erosion of resin composite restorative materials depended upon the physical and chemical composition of the restorative materials and the types of wine.