Collagen Cross-linking Agents Research Articles

Exogenous Collagen Crosslinking is Highly Detrimental to Articular Cartilage Lubrication.

Healthy articular cartilage is a remarkable bearing material optimized for near-frictionless joint articulation. Because its limited self-repair capacity renders it susceptible to osteoarthritis (OA), approaches to reinforce or rebuild degenerative cartilage are of significant interest. While exogenous collagen crosslinking (CXL) treatments improve cartilage's mechanical properties and increase its resistance to enzymatic degradation, their effects on cartilage lubrication remain less clear. Here, we examined how the collagen crosslinking agents genipin (GP) and glutaraldehyde (GTA) impact cartilage lubrication using the convergent stationary contact area (cSCA) configuration. Unlike classical configurations, the cSCA sustains biofidelic kinetic friction coefficients (μk) via superposition of interstitial and hydrodynamic pressurization (i.e., tribological rehydration). As expected, glutaraldehyde- and genipin-mediated CXL increased cartilage's tensile and compressive moduli. Although net tribological rehydration was retained after CXL, GP or GTA treatment drastically elevated μk. Both healthy and "OA-like" cartilage (generated via enzymatic digestion) sustained remarkably low μk in saline- (≤0.02) and synovial fluid-lubricated contacts (≤0.006). After CXL, μk increased up to 30-fold, reaching values associated with marked chondrocyte death in vitro. These results demonstrate that mechanical properties (i.e., stiffness) are necessary, but not sufficient, metrics of cartilage function. Furthermore, the marked impairment in lubrication suggests that CXL-mediated stiffening is ill-suited to cartilage preservation or joint resurfacing.

Effect of collagen cross-linking agents on the depth of penetration of bioceramic sealer and release of hydroxyproline: An in vitro study.

During endodontic treatment, sealers seal off dentinal tubules and prevent microbial attack. Bioceramic sealers have excellent bioactivity, but its high alkalinity is found to have detrimental effects on radicular collagen. Collagen cross linkers have the ability to chemically modify collagen and can prevent the detrimental effects of the sealer. This research was aimed to assess the effect of collagen cross-linking agents on the integrity of radicular collagen matrix and depth of penetration of sealer. Mandibular premolars (n = 48) were taken. Teeth were decoronated; canals were prepared till ProTaper size F2 and were irrigated with 5 mL of 2.5% NaOCl, followed by 3 mL of 17% ethylenediaminetetraacetic acid between instrumentation and finally rinsed with saline following which teeth were divided into three groups based on the surface treatments: Group 1: 6.5% proanthocyanin (PA), Group 2: chlorhexidine (CHX), and Group 3: saline. Teeth were obturated using gutta-percha and bioceramic sealer and stored in artificial saliva. Hydroxyproline (HYP) release was assessed after 14 and 21 days using spectrophotometer. Sealer penetration was assessed using the scanning electron microscope. Wilcoxon signed-rank test and Kruskal-Wallis test for release of HYP and paired t-test and ANOVA for sealer penetration were performed. Significantly lower release of HYP was seen in proanthocyanin-treated group. Sealer penetration was better for both the proanthocyanin- and CHX-treated groups when compared to saline. Surface treatment with collagen cross-linkers caused a decrease in the amount of HYP released, indicating lesser degradation of collagen. Sealer penetration was better due to the removal of smear layer following the surface treatments.

A highly biocompatible CE-crosslinked collagen implant with exceptional anti-calcification and collagen regeneration capabilities for aging skin rejuvenation.

Skin aging, a complex and inevitable biological process, results in wrinkles, dermal laxity, and skin cancer, profoundly influencing appearance and overall health. Collagen serves as the fundamental element of the dermal matrix; nevertheless, collagen is susceptible to enzymatic degradation within the body. Crosslinking is employed to enhance the physicochemical properties of collagen. However, conventional crosslinking agents may harbor potential issues such as cytotoxicity and calcification risks, constraining their application in the biomedical field. Therefore, we have for the first time developed a highly biocompatible CE-crosslinked collagen implant with exceptional anti-calcification and collagen regeneration capabilities for aging skin rejuvenation. A novel collagen crosslinking agent (CE) was synthesized through a reaction involving chitosan quaternary ammonium salt with 1,4-butanediol diglycidyl ether. Compared to collagen crosslinked with glutaraldehyde (GA), the CE-crosslinked collagen implant exhibited notable stability and durability. The implant demonstrated excellent injectability and viscosity, resisting displacement after implantation. Additionally, the CE-crosslinked collagen implant displayed superior biocompatibility, effectively promoting the proliferation and adhesion of HFF-1 cells compared with the GA-crosslinked collagen. The CE-crosslinked collagen represented a safer and more biologically active implant material. In vivo experiments further substantiated that the implant significantly facilitated collagen regeneration without inducing calcification. The innovative collagen implant has made substantial strides in enhancing aesthetics and reducing wrinkles, presenting the potential for revolutionary progress in the fields of skin rejuvenation and collagen regeneration.

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.

Comparative Assessment of Novel Collagen Cross-linking Agents on Push-out Bond Strength of Two Different Sealers: An In Vitro Study.

To assess the push-out bond strength and tubular penetration of resin-based and bioceramic sealers after employing two collagen cross-linking agents, namely, cashew nut shell liquid (CNSL) and epigallocatechin-3-gallate (EGCG) on sodium hypochlorite treated root canal dentin. Fifty human permanent mandibular premolars selected were decoronated at CEJ, this was followed by cleaning and shaping protocols, root canals were enlarged up to 20 sizes with 6% taper and were randomly divided into the following 5 groups with 10 samples each based on the cross-linking agent and the sealer: • Group I: Irrigation with saline (control). • Group II: Irrigation with cashew nut shell liquid followed by bioceramic sealer obturation. • Group III: Irrigation with cashew nut shell liquid followed by resin-based sealer obturation. • Group IV: Irrigation with EGCG followed by bioceramic sealer obturation. • Group V: Irrigation with EGCG followed by resin-based sealer obturation. Five specimens in each group were evaluated for push-out bond strength with the universal testing machine while the remaining five specimens in each group were evaluated for depth of sealer penetration by a scanning electron microscope (SEM). The data was recorded, tabulated, and statistically analyzed. The push-out bond strength was found to be maximum in the apical region in all the five groups followed by the middle third and coronal region. The maximum push-out bond strength was seen in group II followed by groups III and IV, and least in group V. The mean depth of tubular penetration of sealers was found to be effective in the coronal portion followed by the middle third while the apical third region showed the least depth penetration of sealers into the tubules. The maximum penetration of sealers was revealed in group V followed by groups III and IV, and least in group II. Within the limitations of this study, it can be concluded that push-out bond strength was found to the maximum in specimens irrigated with cashew nut shell liquid and obturated with bioceramic sealer. The maximum push-out bond strength was seen in the apical third of all root canals followed by the middle and coronal region. The scanning microscopic analysis revealed maximum mean tubular penetration in the coronal portion followed by the middle third and apical third. A greater penetration was seen in specimens irrigated with EGCG and obturated with hybrid sealer. Selection of sealers plays a pivotal role in the success of endodontic therapy. Leakage-related issues can compromise the bond strength enhancing the bond strength can be achieved through the addition of cross-linking agents.

Substrate stiffness controls proinflammatory responses in human gingival fibroblasts

Soft gingiva is often compromised in gingival health; however, the underlying biological mechanisms remain unknown. Extracellular matrix (ECM) stiffness is involved in the progression of various fibroblast-related inflammatory disorders via cellular mechanotransduction. Gingival stiffness might regulate cellular mechanotransduction-mediated proinflammatory responses in gingival fibroblasts. This in vitro study aims to investigate the effects of substrate stiffness on proinflammatory responses in human gingival fibroblasts (hGFs). The hGFs isolated from two healthy donors cultured on type I collagen-coated polydimethylsiloxane substrates with different stiffnesses, representing soft (5 kPa) or hard (25 kPa) gingiva. Expression levels of proinflammatory mediators, prostaglandin E2 or interleukin-1β, in hGFs were significantly higher with the soft substrate than with the hard substrate, even without and with lipopolysaccharide (LPS) to induce inflammation. Expression levels of gingival ECM and collagen cross-linking agents in hGFs were downregulated more with the soft substrate than with the hard substrate through 14 days of culture. The soft substrate suppressed the expression of mechanotransduction-related transcriptional factors and activated the expression of inflammation-related factors, whereas the hard substrate demonstrated the opposite effects. Soft substrate induced proinflammatory responses and inhibition of ECM synthesis in hGFs by inactivating cellular mechanotransduction. This supports the importance of ECM stiffness in gingival health.

Bonding strategies to deal with caries-affected dentin using cross-linking agents: Grape seed extract, green tea extract, and glutaraldehyde - An in vitro study.

This study evaluated the effect of three collagen cross-linking agents - proanthocyanidins (grape seed extract [GSE] and green tea extract [GTE]) and glutaraldehyde [GA] on microshear bond strength (μSBS) of caries-affected dentin (CAD)-resin complex. Freshly extracted 96 teeth with caries up to the middle third of dentin were sectioned through the deepest part of the occlusal fissure, perpendicular to the long axis of the crown. Caries was excavated with large round bur until firm dentin was obtained, confirmed by visual inspection and tactile examination. Flat occlusal dentin surfaces were treated as follows: Group-1 - 6.5% GSE (n = 30), Group-2 - 2% GTE (n = 30), Group-3 - 5% Glutaraldehyde (n = 30), Group-4 - control group (no agents) (n = 6). Each group was further divided into Subgroup A - Etch-N-Rinse 15s, Subgroup B - Etch-N-Rinse 45s, and Subgroup C - Self-etch. Two increments of 1.5-mm thick composite (Tetric-N-Ceram - Ivoclar Vivadent) with a 1-mm diameter were built-up. Each sample was subjected to μSBS test in Universal Testing Machine. Student's t-test was done for intragroup comparison and one-way ANOVA for intergroup comparison. Statistically significant difference was present in mean μSBS, with Group 1B showing the best results and Group 4C, the least. Thus, the application of these collagen cross-linkers, to CAD, increases μSBS and promises a new approach to improve dentin bond strength.

Biomodification of dentin collagen by primers with crosslinking reagents using ethanol wet bonding technique

To evaluate the association between Ethanol Wet Bonding (EWB) and collagen cross-linking agents (CLA) on the mechanical properties of collagen and on the physical chemical proprieties of an etch-and-rise adhesive to dentin. Demineralized dentin bars (n = 10) were immersed, for 1 min or 1 h, according to the respective groups: distilled water control (WC); absolute ethanol (EA); absolute ethanol with the incorporation of proanthocyanidins 6,5% (PAC + AE); absolute ethanol with the incorporation of 1-ethyl-3- (3-dimethylaminopropyl) carbodiimide 0.3 M (EDC + EA); absolute ethanol with the incorporation of 5% glutaraldehyde (GA + AE). All as solutions used as dentin primer per 1-min of application, for 3-point bending test was performed to evaluate the modulus of elasticity (ME) and mass change (MC) of collagen treated with the respective solutions, at different times of application (1min and 1h). The in situ degree conversion [DC] (n = 3), microtensile bond strength testing [μTBS] (n = 6) and micropermeability [MI] (n = 3) of the teeth restored with the respective treatments were analyzed. After 1 min and 1 h of application, it was observed that WC group showed the lowest ME (p < 0,05). The groups EDC + AE, GA + AE and AE presented a better ME with 1 h of application (p < 0,05), since the PAC + AE and WC were statistically similar. Treatments did not influence DC and μTBS (p > 0,05). In the micropermeability the WA showed the worst results. The association of EWB technique and CLA improved the mechanical properties of the collagen, but it showed no influence in the adhesive procedure.

Is dentin biomodification with collagen cross-linking agents effective for improving dentin adhesion? A systematic review and meta-analysis.

ObjectivesThe aim of this investigation was to evaluate the effectiveness of collagen cross-linking agents (CCLAs) used in combination with the adhesive technique in restorative procedures.Materials and MethodsIn this systematic review, the authors followed the Preferred Reporting Items for Systematic Reviews and Meta-Analyses checklist. An electronic search was performed using PubMed, Scopus, Web of Science, Cochrane Library, LILACS, and DOSS, up to October 2020. The gray literature was also researched. Only randomized clinical trials were selected.ResultsThe selection process yielded 3 studies from the 838 retrieved. The addition of CCLAs in the retention of restorations increased the number of events. The postoperative sensitivity scores and marginal adaptation scores showed no significant difference between the CCLA and control groups, and the marginal pigmentation scores showed a significant increase in the CCLA group. There were no caries events in any group throughout the evaluation period.ConclusionsThis systematic review showed that there is no clinical efficacy to justify the use of CCLAs in the protocols performed.

Impact of Various Cross Linking Agents on Dentin Adhesive Systems - an In-vitro Study

Aims and Objectives: The main aim of this study is to compare and evaluate the shear bond strength of composite resin using a total etch adhesive and self-etch adhesive after treatment with different collagen cross-linking agents.&#x0D; Materials and Methods: Forty freshly extracted human maxillary central incisors were taken. The proximal dentin was exposed, cavities were prepared on mesial and distal of each tooth. The specimens were randomly divided into two groups based on bonding agent applied-Group A and Group B i.e universal bonding agent and all in one bonding agent respectively and are subdivided into four groups based on the surface treatment of dentin. Group I A (n=10) Control-total etch(CTE); Group II A (n=10) Sodium Ascorbate-total etch (STE); Group III A (n=10)- Proanthocyanidin total etch(PTE); Group IV A (n=10)- Chitosan total etch (CHTE); Group I B (n=10) Control-self etch (CSE); Group II B (n=10) Sodium Ascorbate-self etch(SSE); Group III B (n=10)- Proanthocyanidin self-etch (PSE); and Group IV B (n=10) - Chitosan self-etch (CHSE). Shear bond strength of the specimens are tested with universal testing machine, and the data was statistically analysed with one way ANOVA.&#x0D; Results: Significantly higher shear bond strength to dentin was observed in teeth treated with 6.5% Proanthocyanidin Total etch, 10% Sodium Ascorbate Total etch and 1% Chitosan acetate compared to the control group. No significant difference was seen with self-etch treated groups.&#x0D; Conclusion: Dentin surface pretreatment with 6.5% Proanthocyanidin, 10% Sodium Ascorbate and 1% Chitosan acetate results in significant enhancement in bond strength of composite resin to deep dentin.

Collagen cross-linking agents + dimethyl sulfoxide improving the adhesive properties of erosive lesion dentin.

To investigate the effect of the dimethyl sulfoxide combined with cross-linking agents on microtensile bond strength, silver nitrate penetration and in situ degree of conversion analysis of adhesives to the erosive dentin treatment with Cola-based soft drink. One hundred and sixty-six molars were assigned to 20 groups: (1) Treatment: Sound dentin; Erosive dentin; Erosive dentin treated with primer of dimethyl sulfoxide; Erosive dentin treated with DMSO primer containing proanthocyanidin and rivoflavin; (2) Adhesive systems: iBond Universal and Scotchbond Universal; and (3) adhesive strategy: etch-and-rinse or self-etch strategy. After restoration, specimens were sectioned into sticks to be tested. The data from microtensile bond strength (MPa), silver nitrate penetration (%) and in situ degree of conversion (%) were analyzed by (three- and two-factor ANOVA; Tukey's test α=5%). The application of dimethyl sulfoxide combined of not with cross-linkers improved all properties evaluated when compared to only erosive dentin treatment with Cola-based soft drink. However, only when dimethyl sulfoxide was combined to cross-linkers, the values of the microtensile bond strength, silver nitrate penetration and in situ degree of conversion in erosive dentin treatment with Cola-based soft drink was similar to sound dentin, for both adhesives and adhesive strategies. The application of dimethyl sulfoxide combined with the collagen cross-linking agent contributed to increasing the bond strength and degree of conversion in erosive lesion dentin, at the same time that significantly reduction of nanoleakage in this substrate.

Effect of myricetin on odontoblast-like cells and its potential to preserve resin–dentin Bonds

Stabilization of the resin–dentin interface to increase the durability of adhesive dental restorations is a challenging task. The use of naturally occurring collagen crosslinking agents has been proposed to prevent degradation of the hybrid layer. Myricetin (MYR) is a flavonoid with a wide variety of beneficial effects and it has been used for the treatment of different systemic pathologies. The chemical structure of MYR makes it a powerful antioxidant, an inhibitor of matrix metalloproteinase (MMP) activity, and a collagen cross-linker. This study presents MYR as a novel treatment in operative dentistry to stabilize the resin–dentin interface by inhibiting MMPs and crosslinking the collagen. Viability tests carried out using a resazurin assay showed that MYR had no cytotoxic effects on human odontoblast-like cells and the phenotype was preserved. Fluorometric MMP activity assay and fluorescence microscopy revealed that the MMPs in the demineralized dentin were effectively inhibited by the application of MYR (600 μM for 120 s). A microtensile bond strength test was performed immediately and after six months of storage. The bond strength to dentin was not affected by MYR and was preserved over time. Demineralized dentin beams were evaluated to determine the dentin biomodification using microtensile strength and elastic modulus assays. MYR improved the biomechanical behavior of the demineralized dentin similarly to glutaraldehyde, a recognized crosslinking agent. These findings indicated that MYR acts as an MMP inhibitor, collagen cross-linker, and preserver of the bond strength. Furthermore, MYR is an ethanol-soluble molecule with a lower molecular weight than the other polyphenols; hence, it can be applied for a short time and diffuses deeply through the dentin without any associated cytotoxicity. This molecule has beneficial effects on the biological and mechanical behavior of the resin–dentin interface and may be used to effectively stabilize the hybrid layer in a clinical setting.

Effect of proanthocyanidin and riboflavin on shear bond strength of a nanocomposite to deep dentin - An in vitro Study.

Aims:The objective of this study was to evaluate the effect of two collagen crosslinking agents on shear bond strength of a nanocomposite using total-etch adhesive to deep dentin.Materials and Methods:Thirty maxillary central incisors were selected for the study and each tooth was divided into two equal halves with diamond disc (n = 60). Proximal surfaces were prepared to expose the deep dentin until the remaining dentin thickness was approximately 1 mm. The specimens were divided into three groups based upon the biomodification of dentin with collagen crosslinking agents. In Group I (n = 20), no collagen crosslinking agent was used before bonding system. In Group II, deep dentin biomodification was done with 6.5% proanthocyanidin (PA). In Group III, deep dentin biomodification was done with Riboflavin. Shear bond strength was evaluated using universal testing machine.Statistical Analysis Used:One-way analysis (ANNOVA). Pairwise comparison of groups was done with post hoc test.Results:Biomodification of deep dentin with PA showed the highest shear bond strength followed by riboflavin and control group.Conclusion:Biomodification of dentin surface with collagen cross-linking agents results in improvement of bond strength of total-etch adhesive to deep dentin.

Effect of chemical cross-linkers on surface topography and microtensile bond strength of sound dentin: An in vitro study.

Aim and Objectives:The aim of the study was to investigate the effect of two different collagen cross-linking agents proanthocyanidin (Grape seed extract [GSE] and 1-Ethyl-3-(3-dimethylaminopropyl) carbodiimide) on the surface topography of etched dentin and microtensile bond strength (μTBS) of resin dentin bond.Materials and Methods:Fifty-two sound human 3rd molars were collected, and their occlusal surfaces were ground flat to expose dentin. Dentin surfaces were etched using phosphoric acid and then teeth were randomly divided into four groups, according to the dentin treatment: Group 1: wet bonding technique, Group 2: dry bonding technique, Group 3: 6.5% proanthocyanidin, and Group 4: 0.1M carbodiimide. Scanning electron microscope analysis was done for twenty specimens (n = 5 per group) at ×10,000 and ×30,000 magnification. Remaining 32 specimens were restored with TETRIC N-Bond adhesive systems and resin composite. After 24 h, teeth were sectioned to produce a cross-sectional surface area of 1.0 mm2 and tested for μTBS.Statistical Analysis:Data were statistically analyzed using ANOVA and post hoc least significant difference test (P < 0.05).Conclusion:When acid-etched dentin is treated by 6.5% proanthocyanidin (GSE) and 0.1M carbodiimide, followed by application of adhesives, it results in increased μTBS due to cross-linking of collagen fibrils.

Effects of short-duration treatment of cartilage with punicalagin and genipin and the implications for treatment of osteoarthritis.

Punicalagin (PA) not only binds type II collagen, but also blocks its MMP-13-mediated degradation, and genipin (GNP) is a collagen cross-linking agent. We hypothesized that these drugs could mitigate the loss of cartilage if administered in the early phase of osteoarthritis, and experiments were designed to provide proof-of-concept. Porcine cartilage was exposed to both drugs in a manner designed to simulate intra-articular (IA) injection. Based on penetration of PA into cartilage, the rate of drug diffusion was conservatively estimated at 2 μm per minute. GNP caused a measurable degree of cross-linking, increased compressive resistance and coefficient of friction, and substantially inhibited degradation by collagenase, but not by hyaluronidase. Pre-incubation of GNP with collagenase had no effect on enzymatic activity. PA did not cross-link collagen nor affect the mechanical properties of cartilage. It did, however, increase resistance to degradation by collagenase and hyaluronidase. Furthermore, it reacted with collagenase in solution and inhibited its subsequent enzymatic activity. Effects of PA and GNP were not additive. The chondroprotective effect of semi-weekly IA injections was investigated in the monoiodoacetate-induced model of OA in rats. Quantitative histology suggested that injection of PA decreased the amount of cartilage lost compared to saline-injected controls, and the addition of GNP made no difference. This study supports the notion that IA delivery of PA could mitigate OA-induced cartilage erosion.

Comparison of morphological changes of corneal collagen fibers treated with collagen crosslinking agents using second harmonic generation images

Corneal cross-linking (CXL) is a common surgical procedure used to modify corneal biomechanics and stabilize keratoconus progression which is still under discussion. Its side effects, which are mostly related to anatomical unpredictability and stromal exposure, are the reason for the search for new CXL agents. In this work we have quantitatively evaluated the porcine corneal stroma architecture treated with collagen crosslinking agents such as riboflavin solutions and açai extract, using second harmonic generation microscopy. Aimed at evaluating the morphological changes in the corneal stroma after collagen crosslinking under a CXL chemical agent, a tubeness filter based Hessian matrix to obtain a 3D fiber characterization of the SHG images was applied. The results showed a curling effect and shortening of the collagen fibers treated with açai as compared to the control. They also showed a higher degree of clustering of the collagen fibers with larger empty spaces when compared to the other two groups. We believe that studies such as these presented in this paper are a good direct nondestructive and free labeling evaluation technique that allows the observation of morphologic features of corneas treated with new CXL agents.

Comparative evaluation of the effect of decontamination protocol on the shear bond strength of eighth generation bonding agent to contaminated dentin: an in vitro study.

IntroductionThis in vitro study aims to evaluate and compare the effect of decontamination protocol - based on sodium hypochlorite - NaOCl, as a decontaminating agent, followed by the application of a collagen cross-linking agent like sodium ascorbate or Proanthocyanidin on the shear bond strength of eighth generation bonding agent to contaminated dentin (saliva, blood and blood followed by hemostatic agent).MethodsThe buccal surfaces of extracted premolars were flattened to expose the dentine. The teeth were then randomly divided into 3 groups based on the contaminant used (saliva, blood and blood followed by hemostatic agent). Decontamination protocol was carried out with sodium hypochlorite followed by application of either of the two collagen cross-linking agents (sodium ascorbate/proanthocyanidin) in each group. FuturaBond DC (eighth generation) bonding agent was used to bond composite to dentin surfaces which was subjected to shear bond strength testing. Data was analyzed by one-way ANOVA and Tukey test.ResultsAll the groups (contaminated with saliva, blood, or hemostatic agent) showed a decrease in shear bond strength of composite resin to dentin. The shear bond strength of composite resin to dentin was least affected by contamination with saliva followed by contamination with blood and was most affected by contamination with a hemostatic agent.The decontamination protocol carried out showed that the combination of NaOCl and Proanthocyanidin improved the shear bond strength of composite to dentin significantly more than the combination of NaOCl and sodium ascorbate or of sodium hypochlorite used alone.

Two-year clinical evaluation of a proanthocyanidins-based primer in non-carious cervical lesions: A double-blind randomized clinical trial

ObjectivesThis double-blind randomized clinical trial evaluated the influence of pre-treatment with proanthocyanidins (PA) from grape seed extract on the clinical behavior of a simplified etch-and-rinse adhesive placed in non-carious cervical lesions (NCCLs) over 6- and 24-months. Materials and methodsA total of 135 restorations were randomly inserted in 45 subjects. The NCCLs were etched with 37 % phosphoric acid for 15 s and distributed into 3 groups: Control (PA0) - adhesive ExciTE F applied as per the manufacturer's recommendations; PA2 and PA5 groups – 2 wt% and 5 wt% PA solution, respectively, were applied for 60 s and washed for 30 s prior to application of the adhesive. The resin composite was placed incrementally and light-cured. The restorations were evaluated at baseline, 6 months (6 m) and 24 months (24 m) using both the FDI and USPHS criteria. Statistical analyses were carried out using Friedman repeated-measures analysis of variance by rank and the Wilcoxon test (α = 0.05). ResultsThe retention rates were 98 % (PA0), 98 % (PA2) and 83 % (PA5) after 6 m and 93 % (PA0), 89 % (PA2) and 70 % (PA5) after 24 m. Only PA5 resulted in a significant lower retention rate at 6 m and at 24 m compared with that of baseline (p = 0.03). All groups resulted in a significantly worse marginal adaptation and marginal staining for the FDI criteria when the baseline vs. the 24 m recall data were compared. These differences were considered clinically acceptable under the FDI criteria. ConclusionsThe application of PA as a primer did not result in clinical advantages after 24 m of clinical service, regardless of the concentration used. Clinical RelevanceIt has been reported that PA, a collagen crosslinking agent, increases the durability of the dentin-resin interface. However, no effects were found clinically after 24 months.

Genipin inhibits the scleral expression of miR-29 and MMP2 and promotes COL1A1 expression in myopic eyes of guinea pigs.

High myopia can lead to blindness. Genipin is a collagen cross-linking agent that may be used to treat myopia. However, the mechanism of action of genipin for the treatment of myopia is unclear. This study investigated the effect of genipin on the scleral expression of the miR-29 cluster, matrix metalloproteinase 2 (MMP2), and collagen alpha1 chain of type I (COL1A1) in a guinea pig model of myopia. The model of myopia was established by treating guinea pigs with a - 8D lens on both eyes for 21days, and eyes with a refractive error of - 6D or greater were included. Quantitative reverse transcription-polymerase chain reaction (RT-PCR) and western blot were used to examine the mRNA and protein expression, respectively. A dual-luciferase assay was used to determine the direct targeting of the miR-29 cluster on the 3'-untranslated region (UTR) of the COL1A1 gene. The scleral expression of miR-29a, miR-29b, and miR-29c as well as MMP2 was significantly increased, and the scleral expression of COL1A1 was significantly decreased in the myopia group. Genipin treatment reversed these effects in myopic eyes. The dual-luciferase assay showed that the luciferase activities were significantly decreased in human embryonic kidney (HEK) cells transfected with miR-29a and miR-29b, but not miR-29c, compared with those transfected with control miRNAs. Genipin inhibits the scleral expression of the miR-29 cluster and MMP2 and promotes COL1A1 expression in a guinea pig model of myopia. Thus, genipin may promote COL1A1 expression by reducing the expression of the miR-29 cluster.

Improving bonding to eroded dentin by using collagen cross-linking agents: 2years of water storage.

The aim of this study was to investigate the effects of collagen cross-linking agents on nanomechanical and bonding properties of eroded dentin (ED), 24h and 2years after water storage. Human molar dentin surfaces, eroded by soft drinks or citric acid, were acid-etched and treated with primers containing proanthocyanidin (PA) and riboflavin (RI) or were untreated (control) and tested after 24h and 2years. After acid etching and adhesive application (Prime&Bond Elect (PBE); Scotchbond Universal (SBU); Tetric n-bond Universal (TEU)), specimens were sectioned into beams and tested for microtensile bond strength (μTBS) and silver nitrate deposition (NL) after 24h and 2years. The beams were used to evaluate the 24-h in situ conversion of degree (DC). Nanohardness (NH) and Young's modulus (YM) were evaluated via resin-bonded dentin slices after 24h and 2years. A three-way ANOVA and Tukey's test were used for statistical analysis (5%). For both storage times, ED with citric acid resulted in lower μTBS, NH, and YM and higher NL for each adhesive system than soft drink ED (p < 0.05). After 2years of water storage, cross-linking primers maintained the μTBS, NH, and YM (p < 0.05) when compared with the control group. Althougth, the NL values decreased for all groups after 2 years of water storage, PA and RI treatments showed NI values lower than control group (p < 0.001). No significant differences were observed between PA and RI treatments (p > 0.05). Cross-linking primers maintain or improve DC (p < 0.03). In general, TEU and SBU yielded higher μTBS, DC, NH, and YM and lower NL than PBE. Cross-linking agents improved the results and maintained the resin-ED interface bonding and nanomechanical properties, without jeopardizing adhesive polymerization. Cross-linking agents are a viable alternative for improving and maintaining resin-ED interface bonding and nanomechanical properties.