Storage In Artificial Saliva Research Articles

Evaluation of resin composites for dental restorations

In the production of dental restorations, there are, currently, two main types of materials: ceramics and resin composites. These latter kinds are typically suggested because of their quick fabrication, easy reparation and increased crossed link density compared with conventional light-cured materials. However, it is not clear for the specialist what is the best option among the many commercially available materials for each precise clinical case. For that reason, this work aims to clarify the real mechanical performance of resin-based composites for indirect dental restorations obtained by material removal processes and their most suitable application.Two kinds of resin CAD/CAM blocks were selected: LavaTM Ultimate and CerasmartTM, which were tested under two conditions: in the as received by the manufacturer state and after storage in artificial saliva during 30 days. The mechanical properties of both materials were analysed (density, hardness, flexural strength, fracture toughness) but also the influence on the degradation of the mechanical performance due to the contact with the saliva.Results indicate a better mechanical performance of the Lava Ultimate material in the as-received condition, despite its coarser microstructure. However, Cerasmart shows a stabilised microstructure with a smaller degradation of the mechanical properties in contact with the artificial saliva; in other words, improved durability inside the mouth.

Influence of Prolonged Bleaching with 4% Hydrogen Peroxide Containing Calcium and Different Storage Times on the Bond Strength to Enamel

To assess the influence of different bleaching protocols on the bond strength to enamel. In this laboratory experiment were used forty sound bovine incisors were divided into five groups. G1: No bleaching (control). G2: 14 days bleaching with 4% hydrogen peroxide containing calcium (4% HP+Ca2+) (2 hours/ day) and 24 hours of artificial saliva (AS) storage. G3: 14 days bleaching with 4% HP+Ca2+ (2 hours/day) and 7 days storage in AS. G4: 28 days bleaching with 4% HP+Ca2+(2 hours/day) and 24 hours storage in AS. G5: 28 days bleaching with 4% HP+Ca2+ (2 hours/day) and 7 days storage in AS. Following storage times, composite resin cylinders were built upon the enamel surfaces and tested for micros hearing. For statistical analysis, two-way ANOVA and Tukey's test was applied to the data (p≤0.05), for it was evaluated different times of bleaching and stored in artificial saliva. The highest mean was observed in G1 (14.61 MPa), and the lowest in G4 (9.22 MPa). Compared to the negative control (G1), no differences were found in 14 days bleaching and the same between G2 and G3 (p ≥0.01). However, in 28 days bleaching, the effects of the storage periods (24 hours and 7 days) were significantly different (p ≤0.05), besides G4 and G5 were statistically different from G1. Extended bleaching time (28 days) decreased the bond strength, independently of storage time in AS. If adhesive procedures are required after extended at-home bleaching they may need to be delayed for at least for 7 days for the enamel adhesion ability to recover.

Bonding durability, antibacterial activity and biofilm pH of novel adhesive containing antibacterial monomer and nanoparticles of amorphous calcium phosphate

ObjectivesThe dentin bonding often fails over time, leading to secondary caries and restoration failure. The objectives of this study were to develop an adhesive with dimethylaminohexadecyl methacrylate (DMAHDM) and nanoparticles of amorphous calcium phosphate (NACP), and investigate the effects of storage in artificial saliva for six months on the bonding durability, antibacterial activity, ion release and biofilm pH properties for the first time. MethodsDMAHDM was added at 5% (by mass) to Scotchbond Primer and Adhesive (SBMP). NACP was added at 10%, 20%, and 30% to SBMP adhesive. Dentin bonding durability, antibacterial activity against Streptococcus mutans biofilms, and calcium (Ca) and phosphate (P) ion liberation properties were investigated after 1 day and 6months of storage in artificial saliva. ResultsDentin bond strength (n = 50) had 25% loss after 6 months of aging for SBMP control. However, SBMP + DMAHDM+10NACP and SBMP + DMAHDM+20NACP showed no loss in bond strength after storage in artificial saliva for 6 months. The DMAHDM + NACP incorporation method dramatically reduced the biofilm metabolic activity and acid production, and decreased the biofilm CFU by four orders of magnitude, compared to SBMP control, even after 6 months of aging (p < 0.05). DMAHDM + NACP had long-lasting Ca and P ion releases, and raised the biofilm pH to 6.8, while the control group had a cariogenic biofilm pH of 4.5. ConclusionsIncorporating DMAHDM + NACP in bonding agent yielded potent and long-lasting antibacterial activity and ions liberation ability, and much higher long-term dentin bond strength after 6-month of aging. The new bonding agent is promising to inhibit caries at the restoration margins and increase the resin-dentin bonding longevity. Clinical significanceThe novel bioactive adhesive is promising to protect tooth structures from biofilm acids and secondary caries. NACP and DMAHDM have great potential for applications to a wide range of dental materials to reduce plaque and achieve therapeutic effects.

The The effect of different solutions and thermocycling on the vickers hardness of acrylic resin denture teeth

Aim: The aim of this study was to evaluate the effect of artificial saliva, disinfectant solution, distile water and thermocycling on Vickers hardness of 4 commercial brands of acrylic resin denture teeth.&#x0D; Methodology: Four different brands of acrylic resin denture teeth (Major Dent, Acry Lux, Acry Rock, Imident Lux) were evaluated. 15 anterior and 15 posterior teeth of each group embedded in autopolymerized acrylic resin. The occlusal surfaces of posterior teeth and the vestibule surfaces of anterior teeth were flattened by using silicone carbid paper. After polishing, microhardness measurements were repeated three times for each teeth. The teeth were submitted to different conditions: (1) storage in distilled water at 37±2°C for 7 days; (2) storage in artificial saliva at 37±2°C for 30 days and (3) storage in 1 % sodium hypochlorite. After, thermal cycling between 5 and 55 °C for 2500 cycles was made. The microhardness measurements were repeated. Data were analyzed with one-way analysis of variance (ANOVA) and Duncan test ( p&lt;0.05).&#x0D; Results: There was statistical significant differences between initial and final microhardness values of different barnds of acrylic resin denture teet. Anterior teeth showed lower microhardness values than posterior teeth.&#x0D; Conclusion: Storage in different solutions and thermal cycling significantly reduced the Vickers hardness of the acrylic resin denture teeth.

Microshear Bond Strength of Bioactive Restorative Materials to Dentin

Purpose: To evaluate the microshear bond strength of bioactive restorative (BAR) materials to human dentin surface and estimate the clinical durability and serviceability of tested restorative materials Materials and Methods: Eighty dentin samples obtained from caries free human premolars and randomly divided into four groups (n = 20) according to application tested restorative materials First group (A) specimens tested direct application of bioactive restoratives BAR material to dentin without etching step. Second group (B) specimens tested for direct application of BAR material to dentin with etching step. Third group (C) specimens tested for direct application of bioactive base (BAB) material to dentin. The fourth group (D) specimens tested for direct application of nanofilled restorative (NFR) material to dentin with etching step, before application of tested restorative materials, a hollow cylinder (2.0 mm height/0.75mm internal diameter) was placed on the treated dentin surfaces. Tested restorative material inserted into the tube and cured. After artificial saliva storage for 5 days, the tube removed and microshear bond strength was determined in a universal testing machine at a crosshead speed of 0.5 mm/min. Data presented as mean and standard deviation (SD) values. Regression model using two-way Analysis of Variance (ANOVA) used in testing significance to evaluate the microshear bond strength of tested restorative materials. Results: It was found that group (B) BAR material bonded to etched dentin recorded the highest microshear bond strength mean value (12.18±1.39 MPa) followed by group (D) NFR material mean value (12.06±1.89 MPa) then group, (C) BAB materials mean value (9.96±1.27 MPa) while group (A) BAR material to unetched dentin recorded the lowest microshear bond strength mean value (9.88±2.11 MPa). The difference between all groups was statistically significant as indicated by one-way ANOVA (P=0.003>0.05). Tukey’s post-hoc showed non-significant (P>0.05) difference between (groups A and C) or (groups B and D). Conclusions: Saliva is a necessary component as calcium and phosphate supplement for proper bond strength of BAR to etched dentin. BAR and NFR have a good and clinically accepted micreoshear bond strength. BAB difficult to be used in open sandwich techniques. NFR proper adhesive selection lead to proper collagen encapsulation with qualified bonded interface.

Do collagen cross-linkers improve dentin’s bonding receptiveness?

ObjectivesDentin biomodification using collagen cross-linkers has been proposed as one of the strategies to improve bond durability of adhesives to dentin. However, literature is not very consistent regarding their benefit, in particular when cross-linkers are applied in clinically realistic application times. This study investigated the effect of three cross-linkers on the mini-interfacial fracture toughness (mini-iFT) of four adhesives bonded to dentin following either etch&rinse (E&R) or self-etch (SE) modes. Methods60 molars were randomly divided in accordance with the three variables: cross-linker, adhesive and bonding mode (n=5). The cross-linkers glutaraldehyde (5wt%; GA), proanthocyanidin (6.5wt%; PA), or UVA-activated riboflavin (0.5wt%; RB), and distilled water (control) were applied on dentin for 60s after acid-etching (E&R) or before self-etching (SE). The 3-step E&R adhesive (3E&Ra) OptiBond FL (Kerr), the 2-step SE adhesive (2SEa) Clearfil SE Bond 2 (Kuraray Noritake) and the universal adhesives G-Premio Bond (GC) and Prime&Bond Active (Dentsply), the latter two employed in both E&R and SE modes, were applied following the respective manufacturer’s instructions. Composite buildups (8×8×8mm) were made using Filtek Supreme XTE (3M) prior to 1-week storage in artificial saliva. After the teeth were sectioned into mini-specimens (1.5×2.0×18mm), a single notch was prepared at the adhesive–dentin interface. Half of the specimens were immediately loaded until failure by 4-point bending to determine the mini-iFT, while the remaining specimen set was tested upon 6-month aging. Data were statistically analyzed with a linear model (p<0.05). ResultsNo significant decrease in mini-iFT was noted only for PA (p<0.05), while the mini-iFT decreased for both other cross-linkers and in quite a similar way as when solely water (Wa) was applied. SignificanceThe cross-linker proanthocyanidin (PA) applied in clinically relevant conditions was able to maintain a stable mini-iFT after 6-month aging. The incorporation of UVA-activated riboflavin (RB) and glutaraldehyde (GA) in the dentin-bonding protocol appeared not effective to improve the stability of adhesive–dentin interfaces.

Effects of Polyacrylic Acid Pre-Treatment on Bonded-Dentine Interfaces Created with a Modern Bioactive Resin-Modified Glass Ionomer Cement and Subjected to Cycling Mechanical Stress.

Objectives: Resin-modified glass ionomer cements (RMGIC) are considered excellent restorative materials with unique therapeutic and anti-cariogenic activity. However, concerns exist regarding the use of polyacrylic acid as a dentine conditioner as it may influence the bonding performance of RMGIC. The aim of this study was to evaluate the effect of different protocols for cycling mechanical stress on the bond durability and interfacial ultramorphology of a modern RMGIC applied to dentine pre-treated with/without polyacrylic acid conditioner (PAA). Methods: The RMGIC was applied onto human dentine specimens prepared with silicon-carbide (SiC) abrasive paper with or without the use of a PAA conditioner. The specimens were immersed in deionised water for 24 h then divided in 3 groups. The first group was cut into matchsticks (cross-sectional area of 0.9 mm2) and tested immediately for microtensile bond strength (MTBS). The second was first subjected to load cycling (250,000 cycles; 3 Hz; 70 N) and then cut into matchsticks and tested for MTBS. The third group was subjected to load cycling (250,000 cycles; 3 Hz; 70 N), cut into matchsticks, and then immersed for 8 months storage in artificial saliva (AS); these were finally tested for MTBS. The results were analysed statistically using two-way ANOVA and the Student–Newman–Keuls test (α = 0.05). Fractographic analysis was performed using FE-SEM, while further RMCGIC-bonded dentine specimens were aged as previously described and used for interfacial ultramorphology characterisation (dye nanoleakage) using confocal microscopy. Results: The RMGIC applied onto dentine that received no pre-treatment (10% PAA gel) showed no significant reduction in MTBS after load cycling followed by 8 months of storage in AS (p > 0.05). The RMGIC–dentine interface created in PAA-conditioned SiC-abraded dentine specimens showed no sign of degradation, but with porosities within the bonding interface both after load cycling and after 8 months of storage in AS. Conversely, the RMGIC–dentine interface of the specimens with no PAA pre-treatment showed no sign of porosity within the interface after any of the aging protocols, although some bonded-dentine interfaces presented cohesive cracks within the cement after prolonged AS storage. However, the specimens of this group showed no significant reduction in bond strength (p < 0.05) after 8 months of storage in AS or load cycling (p > 0.05). After prolonged AS storage, the bond strength value attained in RMGIC–dentine specimens created in PAA pre-treated dentine were significantly higher than those observed in the specimens created with no PAA pre-treatment in dentine. Conclusions: PAA conditioning of dentine prior to application of RMGIC induces no substantial effect on the bond strength after short-term storage, but its use may increase the risk of collagen degradation at the bonding interface after prolonged aging. Modern RMGIC applied without PAA dentine pre-treatment may have greater therapeutic synergy with saliva during cycle occlusal load, thereby enhancing the remineralisation and protection of the bonding interface.

Changes in hardness of addition-polymerizing silicone-resilient denture liners after storage in artificial saliva

Statement of problemThe hardness of silicone resilient denture liners was reported to be more stable than that of acrylic resin resilient denture liners. However, the changes in hardness of these materials in artificial saliva are unclear. PurposeThe purpose of this in vitro study was to evaluate changes in the hardness of addition-polymerizing silicone-resilient denture liners for long-term use after storage in artificial saliva. Material and methodsFour addition-polymerizing silicone resilient denture liners were tested: GC Reline Soft, Elite Soft Relining, Megabase, and Mucopren Soft. All were long-term relining materials of the soft type. Fifteen disk-shaped specimens were prepared for each of the tested materials (40 mm in base diameter, 8 mm in thickness). Their initial hardness was assessed with a Shore A durometer, after which they were stored in artificial saliva at a temperature of 37°C. Hardness was examined after 7, 30, and 90 days. Statistical analysis was performed using parametric ANOVA for dependent and independent variables and Tukey honest significant difference (HSD) post hoc tests (α=.05). ResultsAll resilient denture liners increased in hardness during the experiment. The change was least for Elite Soft Relining, and GC Reline Soft was the hardest material. Initially, Megabase and Mucopren Soft were significantly softer than the other 2 materials, but their hardness increased rapidly after the first 7 days of specimen conditioning, achieving values close to Elite Soft Relining. ConclusionsWithin the limitations of the study, room temperature vulcanizing addition-polymerizing polyvinyl siloxanes of the soft type have different initial hardness, and this changes with storage time in artificial saliva at the temperature of the oral cavity.

Influence of gamma radiation on microshear bond strength and nanoleakage of nanofilled restoratives in Er, Cr:YSGG laser-prepared cavities.

Objective:To evaluate the effect of gamma radiation on microshear bond strength and nanoleakage of nanofilled restoratives in laser-prepared cavities.Materials and Methods:Twenty-eight flat buccal dentin surfaces were prepared for microshear bond strength test. Er, Cr:YSGG laser was used to prepare another 28 Class V cavities on the buccal surfaces of the molars. All teeth were divided into four groups; 1st group: Application of Filtek Z350 nanocomposite material, 2nd group: As the 1st group and then exposure to gamma radiation, 3rd group: Application of Ketac N100 nanoglass ionomer, and the 4th group: As the 3rd group and then gamma irradiated. The bond strength test was performed after storage in artificial saliva for 24 h. For the nanoleakage test, teeth were submerged in a solution of ammoniacal silver nitrate, sectioned, and then examined under a scanning electron microscope. The collected data were statistically analyzed.Results:Nanocomposite showed higher bond strength values than nanoglass ionomer. Despite the fact that gamma radiation did not decrease nanocomposite bond strength, it decreased nanoglass ionomer bond strength. Nanoglass ionomer-restored cavities showed higher silver ion penetration than nanocomposite in both control and gamma-irradiated groups.Conclusion:Gamma radiation has no effect on bond strength and nanoleakage of nanocomposite so that it can be placed before radiotherapy. On the other hand, the bond strength of nanoglass ionomer was adversely affected by gamma radiation.

Selective dentin etching: A potential method to improve bonding effectiveness of universal adhesives.

To evaluate whether selective dentin etching protocols using reduced phosphoric acid (H3PO4) etching-times would affect the resin-dentin interaction of a universal adhesive to improve long-term bonding effectiveness. Mid-coronal flat dentin surfaces were produced on sound third molars, selectively etched with 32% H3PO4 for 3, 5, 10 or 15 s and bonded with a universal adhesive (Scotchbond Universal, 3 M ESPE: SU). SU in self-etch mode and a three-step etch-and-rinse adhesive were used as control groups. Bonded specimens were stored in deionized water for 24 h and sectioned into beams (cross sectional area of 0.7 mm2). Micro-tensile bond strength test (n = 6) and nanoleakage evaluation were performed immediately, after thermocycling or 6-month storage in artificial saliva. Energy dispersive X-ray analysis (n = 6) was performed to determine the residual Ca-content ratio at the hybrid layers and scanning electron microscopy (SEM) was used to observe the micromorphology of the etched dentin surfaces before and after SU application. Data were analyzed by ANOVA and Tukey test (α = 0.05). Selective dentin etching for 3 s improved the interaction depth of the tested universal adhesive without overexposing demineralized collagen or reducing Ca-content availability at the bonded interface. The improved immediate bond strengths of the selective etching protocol remained significantly higher (p < 0.05) after long-term aging producing hybrid layers without significant differences (p > 0.05) in silver uptake levels compared to those produced on non-etched dentin. Despite the adjunctive conclusion that universal adhesives used in self-etch mode produce superior long-term dentin bonding compared to the etch-and-rinse mode, selective etching for 3 s with conventionally used H3PO4 improves dentin bonding effectiveness; nonetheless, longer etching times should be strictly avoided.

The effect of dentine pre-treatment using bioglass and/or polyacrylic acid on the interfacial characteristics of resin-modified glass ionomer cements

ObjectiveTo evaluate the effect of load-cycle aging and/or 6 months artificial saliva (AS) storage on bond durability and interfacial ultramorphology of resin-modified glass ionomer cement (RMGIC) applied onto dentine air-abraded using Bioglass 45S5 (BAG) with/without polyacrylic acid (PAA) conditioning. MethodsRMGIC (Ionolux, VOCO) was applied onto human dentine specimens prepared with silicon-carbide abrasive paper or air-abraded with BAG with or without the use of PAA conditioning. Half of bonded-teeth were submitted to load cycling (150,000 cycles) and half immersed in deionised water for 24 h. They were cut into matchsticks and submitted immediately to microtensile bond strength (μTBS) testing or 6 months in AS immersion and subsequently μTBS tested. Results were analysed statistically by two-way ANOVA and Student–Newman–Keuls test (α = 0.05). Fractographic analysis was performed using FE-SEM, while further RMGIC-bonded specimens were surveyed for interfacial ultramorphology characterisation (dye-assisted nanoleakage) using confocal microscopy. ResultsRMGIC applied onto dentine air-abraded with BAG regardless PAA showed no significant μTBS reduction after 6 months of AS storage and/or load cycling (p > 0.05). RMGIC–dentine interface showed no sign of degradation/nanoleakage after both aging regimens. Conversely, interfaces created in PAA-conditioned SiC-abraded specimens showed significant reduction in μTBS (p < 0.05) after 6 months of storage and/or load cycling with evident porosities within bonding interface. ConclusionsDentine pre-treatment using BAG air-abrasion might be a suitable strategy to enhance the bonding performance and durability of RMGIC applied to dentine. The use of PAA conditioner in smear layer-covered dentine may increase the risk of degradation at the bonding interface. Clinical significanceA combined dentine pre-treatment using bioglass followed by PAA may increase the bond strength and maintain it stable over time. Conversely, the use of PAA conditioning alone may offer no significant contribute to the immediate and prolonged bonding performance.

Influence of Storage Media on Color Stability of Different Resin Composites as Determined by ΔE and ΔE00

Abstract Objective: To evaluate the color stability of 3 different resin composites when exposed to storage in water, air or artificial saliva. Materials and Methods: <span style=font-size:10.0pt; font-family: times= new= roman,serif;mso-ansi-language:en-us=>Initial color of 81 specimens was assessed by a calibrated reflectance spectrophotometer over a black as well as a white background. Specifically, 9 disc shaped specimens made out of 3 resin composite materials were kept in distilled water, air and artificial saliva (Glandosane) at 37°C. After a storage period of 4 weeks, spectrophotometric measurements were repeated and the color changes calculated by means of ΔE and ΔE00. Results: When analysed over a white background, median ΔE values varied from 0.6 (Filtek Supreme Dentin/water) to 7.1 (Filtek Supreme Enamel/Glandosane). When analysed over a black background median ΔE values varied from 0.4 (Filtek Supreme Dentin/water) to 5.0 (Filtek Supreme Enamel/Glandosane). When analysed over a white background, median ΔE00 values varied from 0.4 (Filtek Supreme Dentin/water) to 4.6 (Filtek Supreme Enamel/Glandosane). When analysed over a black background median ΔE00 values varied from 0.4 (Filtek Supreme Dentin/water) to 4.6 (Filtek Supreme Enamel/Glandosane). Statistical analysis performed by means of ANOVA and Fisher’s LSD post hoc tests showed differences between groups. The correlation between ΔE and ΔE00 was 99.09% and 99.65% over black and white background, respectively. Conclusion: Within the limits of the present study, storage media significantly influenced color stability of resin composites.

Effect of Baicalein on Matrix Metalloproteinases and Durability of Resin-Dentin Bonding.

In an attempt to increase resin-dentin bonding quality, this study used baicalein as a preconditioner in an etch-and-rinse adhesive to evaluate its effect on matrix metalloproteinases (MMPs) and adhesive durability. As a MMP inhibitor and potential collagen cross-linking agent, baicalein was used as a preconditioner in an etch-and-rinse adhesive system. The degree of conversion was evaluated by Fourier-transform infrared spectroscopy. EnzChek gelatinase/collagenase assay kits were then used to detect the MMP inhibitory effect of different concentrations of baicalein (0.1, 0.5, 2.5, and 5.0 μg/mL) on dentin powders. During in vitro bonding procedures, flat dentin surfaces on sound third molars were preconditioned with 2.5 μg/mL baicalein after being acid-etched; this step was followed by continuation of adhesive processes and build-up of resin composite. After resin-dentin stick preparation, bonding strength, failure mode, and interface nanoleakage were respectively evaluated via microtensile testing, stereomicroscopy, and field emission scanning electron microscopy either immediately or after storage in artificial saliva for three or six months. Data were analyzed by two-way analysis of variance and Tukey test (α=0.05). Baicalein at a concentration of 0-5.0 μg/mL did not influence the conversion of adhesives. However, it inhibited the activities of dentin-bond gelatinase and collagenase, especially at a concentration of 2.5 μg/mL, while effectively increasing microtensile bonding strength and decreasing nanoleakage in vitro, both immediately and after aging. Baicalein used as preconditioner in an etch-and-rinse adhesive system has an anti-MMP function and effectively improves resin-dentin bonding durability in vitro, which has potential value in clinical bonding procedures.

Effect of Over-the-counter Whitening Products associated or Not with 10% Carbamide Peroxide on Color Change and Microhardness: in vitro Study

Aim: The purpose of this in vitro study was to evaluate the color and microhardness of teeth subjected to different over-the-counter (OTC) whitening products in association or not with 10% carbamide peroxide (10% CP). Materials and methods: Enamel-dentin specimens (n = 210) were obtained from bovine incisors and stained. Half of the specimens were then subjected to daily cycles of staining (5 minutes), 10% CP bleaching (8 hours) in association with OTC products, and artificial saliva storage until complete 24 hours, for 2 weeks; the other half was subjected to daily cycles of staining, OTC treatment, and storage in artificial saliva for 12 weeks. The specimens were divided into 14 groups according to the OTC: CP-Water and Water (deionized water); CP-Listerine and Listerine (whitening mouth rinse); CP-Brushing and Brushing (mechanical brushing); CP-Colgate and Colgate (conventional toothpaste), CP-ColgateW and ColgateW, CP-OralBW and OralBW, and CP-CloseUpW and CloseUpW (whitening toothpaste). After staining and whitening, color and microhardness were measured. Data were submitted to analysis of variance (ANOVA) and the Tukey's test for multiple comparisons for color analysis and the paired t-test for microhardness analysis. Results: The CP and CloseUpW groups had the largest color change (AE00). The teeth treated with Colgate increased significantly in microhardness after whitening. Conclusion: The association of 10% CP with OTC whitening agents did not increase the whitening effect or microhardness. The OTC agents containing hydrogen peroxide and abrasives had a similar effect to one another but were not as effective as the CP groups and the subgroup brushed only with blue covarine toothpaste. Clinical significance: The current study provides information about the mechanism of OTC whitening products. None of the whitening agents evaluated damaged the enamel when used according to the manufacturers' instructions. The use of toothpaste containing hydrogen peroxide or abrasives cannot provide a whitening effect similar to at-home bleaching, and this does not improve with the association with 10% CP. However, toothpaste containing blue covarine has a satisfactory whitening effect immediately after brushing. Keywords: Laboratory research, Mouthwashes, Tooth bleaching, Toothpaste.

Evaluation of enamel remineralizing potential of self-assembling peptide P11-4 on artificially induced enamel lesions in vitro.

The purpose of this study was to evaluate the remineralizing efficacy of self-assembling peptide (SAP) P11-4 qualitatively and quantitatively using scanning electron microscopy (SEM) and energy-dispersive X-ray (EDX), respectively. Enamel samples (n = 24) were prepared by sectioning extracted premolars and subjected for demineralization to create artificial enamel lesions. The structural and elemental concentrations (calcium and phosphate weight %) were assessed to obtain baseline data using SEM and EDX spectroscopy, respectively. The samples were randomly allocated into two groups and were treated with SAP P11-4 (test group) and casein phosphopeptides-amorphous calcium phosphate (CPP-ACP) (control group) followed by storage in artificial saliva to evaluate the remineralizing efficacy at 1-week, 1-month, and 3-month intervals. Data were analyzed using the ANOVA and unpaired t-test. From the observed results, CPP-ACP showed a significant increase in Ca: P ratio (2.04 ± 0.2) with irregular surface calcific deposition at 1-week interval and this reduced with time (1.87 ± 0.11 at 3-month interval). Whereas P11-4 showed a significant increase in Ca: P ratio (1.95 ± 0.10) with uniform ion deposition suggestive of hydroxyapatite nucleation over a 3-month period. SAP P11-4 exhibited superior remineralization with uniform mineral deposition compared to CPP-ACP at 3-month interval.

Influence of light energy density, composite type, composite thickness, and postcuring phase on degree of conversion of bulk-fill composites

Context:Achieving a high degree of conversion (DC) is one of the major concerns during photopolymerization of bulk-fill composites.Aims:To evaluate the effect of light energy densities (11.2 J/cm2 and 20 J/cm2) on the DC and variation of DC in the 24-h postcuring of four bulk-fill composites: SDR, Venus Bulk Fill, MI FIL, and Tetric N-Ceram Bulk Fill at simulated clinically relevant filling depths.Settings and Design:This was an in vitro comparative study.Subjects and Methods:A total of twenty samples were prepared using a teflon mold. VALO curing light was used with two light intensity modes of 1000 mW/cm2 for curing time of 20 s and 1400 mW/cm2 for curing time of 8 s. The energy density was calculated as follows: energy density (J/cm2) is the light intensity (mW/cm2) applied during a certain time (s) divided by 1000. The DC was measured at two time intervals: immediately postcure and after 24-h storage in artificial saliva using an Fourier-transform infrared spectroscopy equipped with attenuated total reflectance accessory.Statistical Analysis Used:ANOVA and Bonferroni test at P < 0.05.Results:High energy density (20 J/cm2) leads to higher DC. Thickness, type of composites, and postcuring phase strongly influence the DC. DC values of the top surface for all the bulk-fill materials investigated were found significantly greater (P < 0.005) than those of their bottom surface. Among composites, SDR showed highest DC. DC strongly increased after 24-h postcure by 32% on top surface and 76% on bottom surface.Conclusions:Energy density more than 20 J/cm2, derived by increasing curing time and low power density, helps obtain a high DC of bulk-fill composites for adequate clinical performance.

Experimental use of an acrolein-based primer as collagen cross-linker for dentine bonding

ObjectivesThe objective of the present study was to investigate the long-term effect of 0.01% acrolein (ACR) aqueous solution, employed as an additional primer, on the mechanical durability and enzymatic activity of resin-dentine interfaces created with a simplified etch-and-rinse adhesive. MethodsDentine surfaces were etched with 35% phosphoric acid for 15s, rinsed and blot-dried. Specimens were then assigned to: Group 1: dentine pre-treated with 0.01% ACR aqueous solution for 1min and bonded with Adper Scotchbond 1 XT (SB1XT), a 2-step etch-and-rinse adhesive; Group 2: SB1XT was applied on untreated acid-etched dentine (control). Resin composite build-ups were made using Filtek Z250. Microtensile bond strength was tested by stressing sectioned specimens to failure immediately or after 1year of storage in artificial saliva at 37°C. Zymography and in-situ zymography assays were performed for examining dentine matrix metalloproteinase (MMP) activities. ResultsThe use of 0.01% ACR as conditioning primer appeared to have contributed better to preservation of bond strength over time without affecting immediate bond strength. Zymography and in-situ zymography showed reduction in MMP activities after the application of ACR. ConclusionDentine collagen cross-linking produced by an ACR-based primer increases the longevity of resin-dentine bonds by reinforcement of the adhesive interface and reduction of dentine MMP activities. Further studies are required to evaluate the potential in vivo and in vivo cytotoxicity of ACR. Clinical significanceThe acrolein-based primer is a potentially useful clinical bonding tool because it demonstrates good collagen cross-linking ability within a clinically-acceptable working time. Although a low ACR concentration was employed in the present study, the cytotoxicity of ACR should be tested prior to clinical use.

Polymerisation, antibacterial and bioactivity properties of experimental orthodontic adhesives containing triclosan-loaded halloysite nanotubes

ObjectiveTo evaluate the immediate enamel bond strength, in situ degree of conversion and the polymerisation rate of three experimental orthodontic adhesives containing triclosan-loaded halloysite nanotubes. The antibacterial and bioactivity properties of such experimental materials were also assessed. Materials and methodsThree experimental orthodontic adhesives were formulated by incorporating triclosan-loaded halloysite nanotubes (TCN-HNT) at different concentrations (5wt%, 10wt% and 20wt%) into a resin blend (Control). The maximum polymerisation rate of the tested adhesives was evaluated trough FTIR, while Raman was used to analyse the in situ degree of conversion (DC) at the bracket/enamel interface. The shear bond strength (SBS) of the enamel-bonded specimens was assessed at 24h. The antibacterial properties of the experimental materials against S. Mutans were evaluate up to 72h, while, their bioactivity was evaluated after 14days of artificial saliva (AS) storage through SEM-EDS and Raman spectromicroscopy. ResultsIncorporation of TCN-HNT increased the polymerisation properties without interfering with the immediate bonding properties of the experimental adhesives. All experimental adhesives containing TCN-HNT inhibited bacterial growth at 24h, and induced mineral deposition after 14days of AS storage. At 72h, only the experimental system containing 20% TCN-HNT maintained such a capability. ConclusionsAdhesives doped with TCN-HNT present improved polymerisation properties and suitable bonding performance. However, only the adhesives containing TCN-HNT >10% might promote long-term antibacterial activity and reliable mineral deposition. Clinical significanceThe use of adhesives containing triclosan-loaded halloysite represents a promising “smart” approach to bond orthodontic brackets and bands; these might prevent enamel demineralisation and induce enamel remineralisation during the treatment.

Fatigue resistance of dentin bonds prepared with two- vs. three-step adhesives: Effect of carbodiimide

The application of a cross-linker to demineralized dentin is reportedly effective at extending the durability of dentin bonds. ObjectiveTo compare the effect of a cross-linker pretreatment on the fatigue crack growth resistance of resin–dentin bonds prepared with a two- vs. three-step adhesive system. MethodsBonded interface Compact Tension (CT) specimens were prepared using commercial two- and three-step etch-and-rinse adhesives and compatible hybrid resin-composite. For the treated groups, adhesive bonding was preceded by a 1min application of an experimental carbodiimide (EDC) conditioner to the acid-etched dentin. The control groups received no such treatment. The fatigue crack growth resistance was examined after storage in artificial saliva at 37°C for 0, 3 and 6 months. ResultsThere was no significant difference in the immediate fatigue crack growth resistance the control and EDC-treated groups at 0 months for either adhesive system. After 3 and 6 months of storage, the EDC-treated groups exhibited significantly greater (p≤0.05) fatigue crack growth resistance than the controls. Although the EDC treatment was equally effective in deterring degradation for both adhesives, bonds prepared with the three-step system exhibited the lowest resistance to fatigue crack growth overall. SignificanceAn EDC treatment applied during dentin bonding could help maintain the durability of bonds prepared with two or three-step adhesive bonding systems.

Effect of dentin proteoglycans on the stability of resin-dentin bonds against artificial saliva storage

Objective: To investigate the potential effect of proteoglycans (PG) and glycosaminoglycans (GAG) on the stability of resin-dentin bonds against artificial saliva storage. Methods: Seventy-two extracted molars were used to obtain standard dentin bonding surface, and the specimens were etched for 15 s with 37% phosphoric acid and divided into three groups using a table of random number. Then the three groups undergone different incubating procedures as follow: specimens in chondroitinase ABC (C-ABC) group were incubated with C-ABC, specimens in trypsin (TRY) group were incubated with trypsin, and specimens in the control group were incubated with deionized water. All specimens were incubated at 37 ℃ for 48 h in the oscillators. Then specimens in each group were randomly assigned into three subgroups (n=8) as follows: immediate control subgroup, aging subgroups with artificial saliva storage for 6 months and 12 months. Microtensile bond strength (μTBS), fracture mode, bonding interface morphology and nanoleakage were evaluated. Results: Immediately and with artificial saliva storage for 6 months and 12 mouths, the μTBS of TRY group ([49.04±3.57], [37.01±3.21] and [35.27±3.56] MPa) were significantly higher than those in the control group ([40.71±3.32], [28.87±2.34] and [24.20±2.07] MPa) (P<0.05). The immediate μTBS of C-ABC group ([32.94±2.45] MPa) was significantly lower than that of the control group (P<0.05). While with artificial saliva storage for 6 months and 12 mouths, the μTBS of C-ABC group ([26.46±2.45] and [22.50±2.58] MPa) were no differences with those of the control group (P>0.05). The ratio of cohesive fracture increased with the extension of aging time. Some narrow gaps were found in hybrid layer of the control group with artificial saliva storage for 6 months and 12 mouths. Conclusions: Removal of PG increased the μTBS and durable bonds to dentin, while removal of GAG decreased the μTBS, however, it can be of help to create more durable bonds to dentin.