Demineralized Dentin Surfaces Research Articles

Correlating immediate vapour reactivity with dentin remineralization and tubule occlusion capacity of a bioactive sol-gel borate glass

The use of bioactive glass as a mineralization agent in treating dentin hypersensitivity has been established for almost two decades where the melt-quench-derived silicate glass, 45S5, may be regarded as the gold standard formulation. Compared to silicate glasses, borate glasses are less chemically durable and have the potential to mineralize (i.e., convert to apatite) more rapidly. This study compared the apatite forming capacity of a sol-gel-derived calcium-borate glass, 40CaO–60B2O3 (SGB60), to that of 45S5, on demineralized dentin discs and its ability to occlude tubules on non-demineralized dentin discs, in vitro. Moreover, it investigated the vapour sorption reactivity of the glasses to explore the potential correlation between their immediate aqueous interactions and bioactivity in remineralization solution. Compared to 45S5, SGB60 demonstrated more rapid calcium-phosphate layer formation on demineralized dentin surfaces. On the other hand, after 24 h immersion in remineralization solution, the 45S5-induced calcium-phosphate layer occlusion of tubules in non-demineralized dentin surfaces appeared to be qualitatively greater than that induced by SGB60. Moreover, vapour sorption analysis under either air or nitrogen gas, demonstrated that the reactivity of 45S5 with vapour varied under the different purge gasses, with significant carbonate formation under air. In contrast, SGB60 showed a more rapid rate of initial weight increase with vapour under both purge gasses, and this vapour reactivity may be correlated to its more rapid calcium-phosphate layer formation on demineralized dentin surfaces when immersed in remineralization solution.

Comparison of Shear Bond Strength of Three Types of Adhesive Materials Used in the Restoration of Permanent Molars after Treatment with Silver Diamine Fluoride: An In Vitro Study.

Permanent blackish discoloration of the tooth structure post application of silver diamine fluoride (SDF) is one of its drawbacks. Several restorative materials have been used to restore and mask the blackish discoloration of SDF-treated teeth. Recently, a new self-adhesive material has been introduced and is marketed as an all-in-one etchant, adhesive, and restorative material indicated for use in all clinical situations. This study aimed to assess the shear bond strength of the new self-adhesive restorative material and compare it with adhesive restorative materials- resin-based composite and resin-modified glass ionomer cement to dentin of extracted permanent teeth treated with 38% SDF. Thirty-nine caries-free extracted teeth (n = 39) were grouped into three groups. Following 38% SDF application, the specimens were loaded with resin-based (Group I), the new self-adhesive restorative material (SDR) Surefil (Group II), and resin-modified glass ionomer cement (RMGIC) (Group III). Shear bond strength (SBS) was calculated, and failure modes were evaluated using the universal testing device (3) Results: The composite showed the highest bond strength, followed by Group II while Group III had the lowest bond strength of all tested materials. Regarding failure type, the composite showed 100% adhesive failure, while Group III and Group II showed mostly adhesive failure with some combination. (4) Conclusions: RBC had a significantly stronger SBS to demineralized dentin surfaces of permanent molar teeth treated with SDF when compared to SDR Surefil and RMGIC.

The cross-linking and protective effect of artemisinin and its derivatives on collagen fibers of demineralized dentin surface

ObjectiveTo investigate the cross-linking and protective effect of artemisinin (ART), dihydroartemisinin (DHA), and artesunate (AST) on collagen fibers of demineralized dentin surface. MethodsMolecular docking was used to predict potential interactions of ART, DHA, and AST with dentin type I collagen. Human third molars without caries were completely demineralized and treated with different solutions for 1 min. The molecular interactions and cross-linking degree of ART and its derivatives with dentin collagen were evaluated by FTIR spectroscopy, total extractable protein content, and a ninhydrin assay. Scanning electron microscopy, hydroxyproline release, and ultimate microtensile strength tests (μUTS) were employed to confirm the mechanical properties and anti-collagenase degradation properties of dentin collagen fibers. ResultsART, DHA, and AST combined with dentin type I collagen mainly through hydrogen bonding and hydrophobic interactions, and the cross-linking reaction sites were mainly C=O and CN functional groups. Compared to the control group, ART and its derivatives significantly increased the degree of cross-linking. Additionally, significant increases were observed in resistance to enzymatic digestion and mechanical properties of the artemisinin and its derivatives group. ConclusionART, DHA, and AST could cross-link with demineralized dentin collagen, through improving the mechanical properties and anti-collagenase degradation properties. Clinical significanceThe study endorses the potential use of ART and its derivatives as a prospective collagen cross-linking agent for degradation-resistant and long-period dentin bonding in composite resin restorations.

Evaluation of a novel primer containing isocyanate group on dentin bonding durability.

To evaluate the benefits of a novel dentin-bonding primer, namely, isocyanate-terminated urethane methacrylate precursor (UMP), which can form covalent bonds with demineralized dentin collagen. The synthesized and purified UMP monomer was characterized and tested its effects on the degree of conversion (DC) and wettability of an acetone-based dental adhesive. Then UMP primers of different concentrations were formulated and used to prepare adhesive specimens, which were compared with solvent-treated groups. Primer-treated specimens with and without aging were also compared. To evaluate the bonding interface, microtensile strength tests, nano-indentation tests and nanoleakage- eavaluation were performed using a field-emission scanning electron microscope and nano-indenter. Data were analyzed using SPSS 20.0 software with significance set at α=0.05 using one-way analysis of variance (ANOVA) and two-way ANOVA to characterize the effects of the primer. Treatment with the UMP primer promoted the DC and wettability of the adhesive on the demineralized dentin surface (P<0.05); it also increased the bond strength of the aged dentin bonding interface (P<0.05). Nanoleakage was reduced; the bonding interface became more stable, and the continuity and strength of the hybrid layer improved (P<0.05) following UMP treatment. The application of 5mM UMP as a primer for dentin bonding could lead to a stable bonding interface and long-lasting bonding effects. The use of 5mM UMP primer developed in this study could improve dentin bonding durability and has excellent clinical application prospects.

Chlorhexidine-loaded poly (amido amine) dendrimer and a dental adhesive containing amorphous calcium phosphate nanofillers for enhancing bonding durability

ObjectiveA novel method of combining chlorhexidine (CHX) loaded poly (amido amine) (PAMAM) dendrimers with a dental adhesive containing amorphous calcium phosphate (ACP) nanofillers are proposed for etch-and-rinse bonding system to enhance resin-dentin bonding durability. MethodsThe CHX-loaded PAMAM and ACP nanofillers were synthesized and characterized. Their effects on the cytotoxicity were tested by MTT assay. Micro-tensile bond strength (μTBS) before and after thermomechanical challenges were used to evaluate the bonding durability. Anti-matrix metalloproteinase (MMPs) property was examined using in-situ zymography. A double-fluorescence technique was used to examine interfacial permeability after bonding. Dentin remineralization in Ca/P lacking solution was observed under scanning electron microscopy. ResultsCompared with a 0.2 wt% CHX solution, the PAMAM loaded CHX had less cytotoxicity, while the in situ zymography showed it could still inhibit MMPs activity within the hybrid layer after released from PAMAM. The application of the novel method maintained the μTBS better than the control group after thermomechanical challenges, and it did not negatively affect water permeability of the bonding interfaces. CHX-loaded PAMAM regulated the calcium (Ca) and phosphate (P) ions provided by the ACP-containing adhesives to remineralize the demineralized dentin surfaces without initial Ca/P in the environment. SignificanceThe novel method can reduce the cytotoxicity of CHX, inhibit MMPs activities, maintain μTBS, and induce dentin remineralization, which are crucial factors for enhancing bonding durability.

81 - Improvement of methacrylate-based polymer networks by introduction of catechol moieties

Dental adhesives mainly consist of methacrylate-based monomers as well as solvents and initiators. The bonding mechanism is based on the penetration of adhesive resins into the demineralized dentin surface and formation of interlocking with exposed collagen fibrils. However, phase separation into hydrophilic/hydrophobic domains leads to water sorption and deterioration of mechanical properties. Furthermore, the esterases and matrix metalloproteinases (MMPs) present in oral environment contribute to methacrylate hydrolysis and collagen degradation, respectively. All these factors accelerate decay along the adhesive interface and cause sub-optimal longevity of the resin filling. A bio-inspired moiety, catechol, has been found to form strong bidentate hydrogen bonds with a variety of surfaces. The purpose of the present study was to design a novel bio-inspired adhesive with catechol moieties and evaluate whether catechol can reduce the heterogeneity of methacrylate-based network structure, decrease water sorption, inhibit the enzyme activities, and improve the longevity of adhesive materials. Catechol methacrylate was synthesized by Steglich esterification which is described in the previous literature. The control adhesive formulations include urethane dimethacrylate (UDMA) as crosslinker (50 wt%), 2-hydroxyethyl methacrylate (HEMA) as monomer (50 wt%), and additional 0.5 wt% 2,2-Dimethoxy-2-phenylacetophenone (DMPA) as photoinitiator. In the novel catechol-contained adhesive, 25 wt% of the HEMA was replaced by catechol methacrylate, with the other components unchanged. To evaluate the performance of these two formulations, dynamic mechanical analysis (DMA), Fourier-transform infrared spectroscopy (FT-IR), water sorption and enzyme (esterases) degradation were conducted to characterize the performance. The novel catechol-contained adhesive showed similar photopolymerization kinetics (final conversion and maximum polymerization rate) to the control one, although multiple works showed that catechol exerts an inhibitory effect on the radial photopolymerization. The water sorption of the novel adhesive, however, was nearly 50% lower than the control adhesive. Moreover, the catechol-contained adhesive showed a higher resistance of the esterase hydrolysis, with less weight loss and lower release of 2-hydroxyethyl methacrylate (HEMA) and methacrylic acid (MMA). The addition of catechol to adhesive formulations reduces the water sorption and improves the resistance of enzyme degradation of methacrylate. These might contribute to the formation of extra hydrogen bonding of catechol in the low-density domains and the inhibitory behaviors of catechol to esterases. Introducing catechol into dental adhesive formulations provides a promising way to enhance the long-term performance of dental adhesive materials. Cytotoxicity and micro-tensile bonding strength tests are essential for the future works.

Bioactive remineralization of dentin surface with calcium phosphate-based agents: An in vitro analysis.

Background:With the increasing prevalence of erosive tooth wear affecting both adults and children; designing optimum protocols of management in a noninvasive manner is gaining precedence.Aim:Comparative evaluation of topically applied calcium phosphate-based agents casein phosphopeptide-amorphous calcium phosphate (CPP-ACP) and beta tricalcium phosphate (β-TCP) on the surface of eroded dentin.Materials and Methods:Dentin blocks from human third molars in four groups were subjected to the surface treatment: (G1) sound dentin (G2) demineralized dentin (G3) CPP-ACP (G4) β-TCP. All the samples except control (G1) were immersed in an acidic solution incubated at 37°C for 96 h. The samples in G3 and G4 were topically treated with CPP-ACP and β-TCP for 4 min twice daily for 14 days; followed by pH-cycling for 21 days. Surface hardness testing and surface morphology were observed using the scanning electron microscopy. Data were analyzed using the Statistical Package for the Social Sciences (SPSS) software with Kruskal-Wallis test and post hoc test.Results:Dentin treated with both CPP-ACP (37.25) and β-TCP (32.05) recorded significantly higher VHN than demineralized (G2-23.51) but lower compared to sound control (G1-57.06).Conclusion:The topical application of CPP-ACP and β-TCP agents shows definite potential in promoting the hardening of demineralized dentin surface.

The Amelogenin-Derived Peptide TVH-19 Promotes Dentinal Tubule Occlusion and Mineralization.

In this study, the amelogenin-derived peptide, TVH-19, which has been confirmed to promote mineralization, was evaluated to derive its potential to induce dentinal tubule occlusion. The binding capability of fluorescein isothiocyanate (FITC)-labeled TVH-19 to the demineralized dentin surface was analyzed by confocal laser scanning microscopy (CLSM). Additionally, the sealing function of the peptide was studied through the remineralization of demineralized dentin in vitro. The adsorption results showed that TVH-19 could bind to the hydroxyapatite and demineralized dentin surfaces, especially to periodontal dentin. Scanning electron microscopy analysis further revealed that TVH-19 created mineral precipitates. The plugging rate in the TVH-19 group was higher than that in the PBS group. Moreover, energy-dispersive X-ray spectroscopy (EDX) results indicated that the calcium/phosphorus (Ca/P) ratio of the new minerals induced by TVH-19 was close to that of the hydroxyapatite. Attenuated total internal reflection-Fourier transform infrared (ATR-FTIR) spectrometry and X-ray diffraction (XRD) results indicated that the hydroxyapatite crystals formed via remineralization elongated the axial growth and closely resembled the natural dentin components. These findings indicate that TVH-19 can effectively promote dentin sealing by binding to the periodontal dentin, promoting mineral deposition, and reducing the space between the dentin tubules.

Cranberry Juice Extract Rapidly Protects Demineralized Dentin against Digestion and Inhibits Its Gelatinolytic Activity.

Improving the longevity of composite restorations has proven to be difficult when they are bonded to dentin. Dentin demineralization leaves collagen fibrils susceptible to enzymatic digestion, which causes breakdown of the resin–dentin interface. Therefore, measures for counteracting the enzymatic environment by enhancing dentin collagen’s resistance to degradation have the potential to improve the durability of dental composite restorations. This study aimed to evaluate the effects of polyphenol-rich extracts and a chemical cross-linker on the cross-linking interaction, resistance to digestion, and endogenous matrix metalloproteinase (MMP) activities of dentin collagen under clinically relevant conditions. Ten-µm-thick films were cut from dentin slabs of non-carious extracted human third molars. Following demineralization, polyphenol-rich extracts—including grape seed (GSE), green tea (GTE), and cranberry juice (CJE)—or chemical cross-linker carbodiimide with n-hydroxysuccinimide (EDC/NHS) were applied to the demineralized dentin surfaces for 30 s. The collagen cross-linking, bio-stabilization, and gelatinolytic activities of MMPs 2 and 9 were studied by using Fourier-transform infrared spectroscopy, weight loss, hydroxyproline release, scanning/transmission electron microscopy, and in situ zymography. All treatments significantly increased resistance to collagenase degradation and reduced the gelatinolytic MMP activity of dentin collagen compared to the untreated control. The CJE- and GSE-treated groups were more resistant to digestion than the GTE- or EDC/NHS-treated ones (p < 0.05), which was consistent with the cross-linking interaction found with FTIR and the in situ performance on the acid-etched dentin surface found with SEM/TEM. The collagen films treated with CJE showed the lowest MMP activity, followed by GSE, GTE, and, finally, EDC/NHS. The CJE-treated dentin collagen rapidly increased its resistance to digestion and MMP inhibition. An application of CJE as short as 30 s may be a clinically feasible approach to improving the longevity of dentin bonding in composite restorations.

Novel Bioactive Glass-Modified Hybrid Composite Resin: Mechanical Properties, Biocompatibility, and Antibacterial and Remineralizing Activity.

Secondary caries seriously limits the lifetime of composite resin. However, integrating all desirable properties (i.e., mechanical, antibacterial, bioactivity, and biocompatibility) into one composite resin is still challenging. Herein, a novel bioactive glass (BAG)-modified hybrid composite resin has been successfully developed to simultaneously achieve excellent mechanical properties, good biocompatibility, and antibacterial and remineralizing capabilities. When the mass fractions of BAG particles were added from 8 to 23 wt %, the original mechanical properties of the composite resin, including flexural strength and compressive strength, were not obviously affected without compromising the degree of conversion. Although the BAG incorporation of mass fractions of 16 wt % to 23 wt % in composite resins reduced cell viability, the viability could be recovered to normal by adjusting the pH value. Moreover, the BAG-modified composite resins that were obtained showed good antibacterial effects against Streptococcus mutans and enhanced remineralizing activity on demineralized dentin surfaces with increasing incorporation of BAG particles. The possible mechanisms for antibacterial and remineralizing activity might be closely related to the release of bioactive ions (Ca2+, Si4+), suggesting that its antibacterial and biological properties can be controlled by modulating the amounts of bioactive ions. The capability to balance the mechanical properties, cytotoxicity, antibacterial activity, and bioactivity makes the BAG-modified composite resin a promising prospect for clinical application. Our findings provide insight into better design and intelligent fabrication of bioactive composite resins.

Effects of bioactive glass incorporation into glass ionomer cement on demineralized dentin

The effects of the incorporation of sodium-free bioactive glass into glass ionomer cement (GIC) on the demineralized dentin are studied. Four experimental groups with various amounts of BAG in GIC were considered: BG0 group: 0 wt% (control); BG5 group: 5 wt%; BG10 group: 10 wt%; BG20 group: 20 wt%. The GIC surface and GIC-approximated demineralized dentin surfaces were evaluated using field emission scanning electron microscopy (FE–SEM). X-ray diffraction (XRD) analysis was performed to evaluate the chemical changes in the GIC-approximated dentin surface. In addition, a shear bond strength test was performed to evaluate the effects of BAG incorporation on the bond strength of GIC. FE–SEM analysis indicated that BAG-incorporated GICs formed distinct precipitates on their surface. Precipitates were also formed on the GIC-approximated demineralized dentin surface. It was more obvious when the amount of BAG increased. In the XRD analysis, fluorapatitie (FAP) peaks were detected in the BG5, BG10, and BG20 groups. There was no significant difference in the shear bond strength among all experimental groups. BAG-incorporated GIC precipitated FAP crystals underlying demineralized dentin surface without affecting bond strength. This study suggests the possibility of BAG as a beneficial additive in GIC.

Effects of mechanical abrasion challenge on sound and demineralized dentin surfaces treated with SDF

This study evaluated the effect of mechanical abrasion on the surface integrity, color change (ΔE) and antibacterial properties of demineralized and sound dentin surfaces treated with silver-diammine-fluoride (SDF). The dentin specimens were divided into two groups: sound and demineralized dentin, then divided into three sub-groups, control (no-treatment), SDF, and SDF + potassium-iodide (KI). Each sub-group was further divided into two groups, one exposed to mechanical brushing and the other without brushing. Specimens were analyzed for the ΔE, surface roughness/surface loss and antibacterial properties (CFU, optical density and fluorescent microscope). Repeated Measures ANOVA was used for statistical analysis of color change while one-way ANOVA was used for CFU analysis. SDF and SDI + KI groups showed significant reduction in ΔE with brushing in the sound dentin group unlike the demineralized group. The surface roughness values were higher for both SDF and SDF + KI groups but roughness values significantly decreased after brushing. Both SDF and SDF + KI groups revealed significantly less surface loss than control. The SDF group showed high anti-bacterial effect after brushing, unlike SDF + KI group. So, we concluded that mechanical brushing improved the esthetic outcome. While, SDF and SDF + KI could protect the dentin surface integrity. SDF-treated dentin possesses an antibacterial property even after mechanical brushing.

EFFECT OF POLYMER-INDUCED LIQUID PRECURSOR PROCESS CONTAINING POLYASPARTIC ACID ON INTRAFIBRILLAR DENTIN REMINERALIZATION (MICRO-COMPUTED TOMOGRAPHY ANALYSIS)

Objective: Caries treatment can be performed by minimal intervention, i.e., by removing the infected dentin and leaving the affected dentin and theninducing remineralization in the affected dentin. The affected dentin still consists of collagen cross bonds. Polymer-induced liquid precursor processis a guided tissue remineralization method that aims to remineralize intrafibrillar and extrafibrillar dentin by adding polymers that are similar tonon-collagen protein. One of the non-collagen protein analog materials is polyaspartic acid. The aim of this study was to evaluate the remineralizationof dentin on the demineralized dentin surface after immersed in remineralization solutions containing polyaspartic acid as a non-collagen proteinanalog.Methods: Human premolar teeth extracted for orthodontic purposes were divided into four groups, namely, one control and three treatment groups.Teeth in the control group were immersed only in the demineralization solution containing acetate buffer (pH 5.0, 66 h). Teeth in the three treatmentgroups were immersed in acetate buffer (pH 5.0, 66 h) and then continue to immersed in the remineralization solution containing polyaspartic acidfor 3, 7, and 14 days. Remineralization was evaluated by micro-CT.Results: Remineralization appeared on the demineralized dentin surface, characterized by an increase in the grayscale index, after immersion inthe remineralization solution containing polyaspartic acid. Significant differences were observed in the mean grayscale index values among the fourgroups.Conclusion: Polyaspartic acid has the potential to induce dentin remineralization.

Bioinspired catechol chemistry for dentin remineralization: A new approach for the treatment of dentin hypersensitivity

ObjectiveDentin remineralization is of considerable clinical interest for dentin hypersensitivity and developing biomimetic analogs that can regulate hydroxyapatite (HAp) nucleation and growth remains a challenge. This study aimed to evaluate in vitro the potential for dentin remineralization using the following biomimetic in situ prepared poly(catechols): poly(dopamine), poly(DOPA), poly(caffeic acid) and a synthesized DOPA-peptide possessing collagen and calcium-binding domains (DOPA-Ahx-(Gly)3-(Glu)5). MethodsDentin samples were immersed in a freshly prepared phosphate-buffered saline (PBS) containing the respective catechol and laccase. After the reaction, they were immersed in calcium and phosphate remineralization solution, which was changed every day for 10 days. Samples of intact and demineralized dentin were used as control groups and kept in deionized water under the same experimental conditions. The remineralized dentin was characterized by scanning electron microscopy (SEM), Micro-energy dispersion X-ray fluorescence spectroscopy (μEDX) and X-ray diffraction (XRD). ResultsThe application of different poly(catechols) and DOPA-peptide promoted crystal nucleation and the formation of HAp, which partially covered both the dentin surface and dentinal tubules walls. SignificanceBy mimicking the role of charged non-collagenous proteins in vivo, polymers consisting of catechol groups showed the ability to modify demineralized dentin surface properties, promoting mineral formation. The use of poly(catechols) may be encouraged for the development of a therapeutic technique for dentin hypersensitivity.

Effect of Using Biomimetic Analogs on Dentin Remineralization with Bioactive Cements.

This study evaluated the impact of using biomimetic analogs (poly-acrylic acid and sodium tri-meta-phosphate) on dentin remineralization using two cement materials, the first is calcium silicate based and the second is calcium hydroxide based materials. Two standardized occlusal cavities (mesial and distal) were prepared within dentin after removal of occlusal enamel. Artificial demineralized dentin was induced through pH cycling (8 h in demineralizing and 16 h in remineralizing solutions). Demineralized cavities were divided into four groups; two groups received cement materials. The other groups were first treated with biomimetic analogs then restored with pulp cement materials. Teeth were sectioned buccolingually into two halves. Treated cavities with analogs were stored in simulated body fluid containing poly-acrylic acid. Untreated cavities were stored in simulated body fluid only. Ground unstained sections of demineralized dentin were examined using light microscope. Specimens were examined after 1, 6 and 12 weeks of storage using energy dispersive X-ray Spectroscopy (EDX) and Vickers microhardness was evaluated. Two-way ANOVA was used to analyze data statistically. Calcium silicate-based cement group with biomimetic analogs showed the highest statistically significant calcium and phosphorous wt% in addition to highest surface hardness values after 12 weeks of storage. Demineralized dentin ground sections showed increase in light zones after total period of storage. Calcium silicate-based cement showed the best ability to enrich the artificial carious dentin with ions for remineralization. Using biomimetic analogs had a significant impact on demineralized dentin surface hardness improvement.

Therapeutic Management of Demineralized Dentin Surfaces Using a Mineralizing Adhesive To Seal and Mineralize Dentin, Dentinal Tubules, and Odontoblast Processes.

Dentin hypersensitivity is attributable to the exposed dentin and its patent tubules. We proposed the therapeutic management of demineralized dentin surfaces using a mineralizing adhesive to seal and remineralize dentin, dentinal tubules, and odontoblast processes. An experimental self-etch adhesive and a mineralizing adhesive consisting of the self-etch adhesive and 20 wt % poly-aspartic acid-stabilized amorphous calcium phosphate (PAsp-ACP) nanoparticles were prepared and characterized by X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, transmission electron microscopy (TEM), and scanning electron microscopy. After 60 acid-etched midcoronal dentin disks were treated with distilled water (control), a desensitizing agent (Gluma), the experimental self-etch adhesive, and the mineralizing adhesive, dentin permeability was measured and mineralization was evaluated by Raman, FTIR, XRD, TEM, and selected-area electron diffraction, irrespective of abrasive and acidic challenges. In vitro cytotoxicity of the adhesive and the mineralizing adhesive was assessed by Cell Counting Kit-8. The mineralizing adhesive possessed excellent biocompatibility. We proposed a hybrid mineralization layer composed of the light-cured mineralizing adhesive and the mineralized dentin surfaces, as well as interiorly mineralized resin tags and odontoblast processes inside of the dentinal tubules. This hybrid mineralization not only reduced dentin permeability but also resisted abrasive and acidic attacks.

Effect of Chitosan pretreatment of the demineralized dentin surface on the durability of resin dentin bonding. An in vitro study

Abstract: the aim of this study was to evaluate the effect of pretreatment of the demineralized dentin surface with Chlorohexidine (CHX), Chitosan (Ch), riboflavin (RF) and Chitosan/riboflavin (RF) combination on the shear bond strength and short-term bond durability with total etch adhesives. Fifty sound extracted human permanent molars were used in this study. The teeth were embedded in plastic tube containers and a flat dentin surface was then prepared by grinding the occlusal enamel exposing superficial dentin surfaces. Specimens were etched for 15 sec with 35% phosphoric acid and were then randomly divided into five groups (10 teeth each), one control group and four experimental groups according to the surface pretreatment (Chlorohexidine, Chitosan, riboflavin and Chitosan/riboflavin combination). This is followed by application of total etch adhesive system and resin composite restoration. The resin composite samples were then divided to be stored either for 24 h or 6 months in distilled water at 37 C followed by shear bond strength testing using Instron Testing Machine. The data were analyzed using ANOVA test. The results revealed that, pretreatment of the demineralized dentin surface with CHX, Ch, RF, and Ch/RF 1:1 significantly improved the shear bond strength mean values at both 24 h and 6 months storage in distilled water compared to the control group. Within control group, significant reduction in shear bond strength mean values were found after 6 months storage in distilled water compared to the baseline measurements at 24 h. The immediate pretreatment of the demineralized dentin with collagen cross linkers could be safely recommended as an effective chairside procedure to improve shear bond strength of resin composite to dentin.

Effect of a novel cold atmospheric plasma jet treatment with different temperatures on resin-dentin bonding

To investigate the effect of different treatment temperatures of a novel cold atmospheric plasma jet treatment on the resin-dentin bonding. (1) Fifty-two freshly extracted, non-carious and intact third molars were collected. The occlusal one-third of the crown was removed by means of a water-cooled low-speed Isomet saw. One dentin disc [(900 ±100) μm] was prepared for each tooth. The fifty-two dentin discs were randomly divided into control group and experimental groups, of which four were in control group, and forty-eight were divided into four experimental groups according to the different treatment temperatures (4 °C, 10 °C, 20 °C and 30 °C) of the novel radio-frequency atmospheric-pressure glow discharge (RF-APGD) plasma jet, twelve in each group. Each experimental group was divided into three subgroups according to different treatment time (10 s, 20 s and 30 s), with four in each subgroup. The occlusal one-third of the crown was removed by means of a water-cooled low-speed Isomet saw. The morphology of demineralized dentin surfaces was analyzed using field emission scanning electron microscopy. (2) Twenty unerupted, non-carious and intact third molars were randomly divided into five groups, four in each group: control group, untreated; 4 °C, 10 °C, 20 °C and 30 °C experimental groups, each group was treated with the RF-APGD plasma jet for 20 s. The micro-tensile resin dentin bond strength was tested after 20 s RF-APGD plasma jet treatment with different temperatures, using a universal mechanical machine. (1) The field emission scanning electron microscopy results indicated that when compared with the control group, a 10 s RF-APGD plasma jet treatment with 30 °C and 20 °C collapsed the collagen scaffold. Collagen fibrils maintained an uncollapsed three-dimensional structure after the 4 °C RF-APGD plasma jet treatment for even 30 s treatment. (2) The microtensile resin dentin bond strength results of the 4 °C RF-APGD plasma jet treatment group (57.8±0.7) MPa were significantly higher than that of the control group [(47.4±0.5) MPa] and 10 s, 20 s and 30 s RF-APGD plasma treatment group [(51.9±0.7) MPa,(29.7±1.0) MPa and (22.2±1.5) MPa] with statistically significant difference (P<0.05). Compared with the control group, the micro-tensile bond strength increased about 21.9% and 9.5% after 4 °C and 10 °C RF-APGD plasma jet treatment, respectively. Compared with other treatment temperatures, this novel RF-APGD plasma jet treatment with the temperature of 4 °C can preserve the three-dimensional morphology of demineralized dentin better, and can improve the resin-dentin bonding.

Silver improves collagen structure and stability at demineralized dentin: A dynamic-mechanical and Raman analysis

ObjectiveThis study aimed to evaluate the effect of silver loaded nanoparticles (NPs) application on dentin remineralization. MethodsPolymethylmetacrylate-based NPs and silver loaded NPs (Ag-NPs) were applied on demineralized dentin surfaces. Dentin was characterized morphologically by scanning electron microscopy, mechanically probed by a nanoindenter to test nanohardness and Young modulus, and chemically analyzed by Raman spectroscopy after 24 h and 7 d of storage. Untreated surfaces were used as control. Data were submitted to ANOVA and Student-Newman-Keuls multiple comparisons tests (P < 0.05). ResultsAfter Raman analysis, dentin treated with Ag-NPs obtained the lowest mineralization and intensity of stoichiometric hydroxyapatite when compared with specimens treated with undoped-NPs. The lowest relative mineral concentration, expressed as the ratio phosphate or carbonate/phenyl group, and crystallinity was attained by dentin treated with Ag-NPs, after 7 d. Ag-NPs application generated the highest values of collagen crosslinking (intensity at 1032 cm−1 band). The molecular conformation of the collagen’s polypeptide chains, amide-I and CH2 also attained the highest peaks in dentin treated with Ag-NPs. Staggered and demineralized collagen fibrils were observed covering the dentin surfaces treated with Ag-NPs, at both 24 h and 7 d. Samples treated with Ag-NPs attained the lowest values of nanohardness and Young’s modulus at 7 d of storage. ConclusionsPeritubular and intertubular dentin were remineralized when using undoped-NPs. After 7 d, collagen treated with NPs was remineralized but dentin treated with Ag-NPs attained an improved collagen matrix structure and stability but the lowest mineralization and crystallinity. Clinical significancePreservation of the demineralized organic matrix is fundamental in operative dentistry. Silver contributed to improve crosslinking, nature and secondary structure of demineralized dentin collagen, for further long-term intrafibrillar mineralization.

Influences of the cold atmospheric plasma jet treatment on the properties of the demineralized dentin surfaces

Improvement of the bonding strength and durability between the dentin surface and the composite resin is a challenging job in dentistry. In this paper, a radio-frequency atmospheric-pressure glow discharge (RF-APGD) plasma jet is employed for the treatment of the acid-etched dentin surfaces used for the composite restoration. The properties of the plasma treated dentin surfaces and the resin–dentin interfaces are analyzed using the x-ray photoemission spectroscopy, contact angle goniometer, scanning electron microscope and microtensile tester. The experimental results show that, due to the abundant chemically reactive species existing in the RF-APGD plasma jet under a stable and low energy input operating mode, the contact angle of the plasma-treated dentin surfaces decreases to a stable level with the increase of the atomic percentage of oxygen in the specimens; the formation of the long resin tags in the scattered clusters and the hybrid layers at the resin–dentin interfaces significantly improve the bonding strength and durability. These results indicate that the RF-APGD plasma jet is an effective tool for modifying the chemical properties of the dentin surfaces, and for improving the immediate bonding strength and the durability of the resin-dentin bonding in dentistry.