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This study analyzed the amounts of solubilized telopeptides cross-linked carboxyterminal telopeptide of type I collagen (ICTP) and C-terminal crosslinked telopeptide of type I collagen (CTX) derived from matrix-metalloproteinases (MMPs) and cysteine cathepsins (CTPs) subsequent to application of a filler-free (Res.A) or an ion-releasing resin (Res.B) to ethylenediaminetetraacetic acid (EDTA)-demineralized dentin with or without zoledronate-containing primer (Zol-primer) pre-treatment. The chemical modification induced following treatments and artificial saliva (AS) storage was also analyzed through attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR). Totally EDTA-demineralized specimens were infiltrated with Res.A or Res.B with or without Zol-primer pre-treatment, light-cured, and immersed in AS for up to 4 wk. ICTP release was reduced following infiltration with Res.B and further reduced when Res.B was used with Zol-primer; remarkable phosphate mineral uptake was attained after AS storage. CTX release was increased in Res.A- and Res.B-treated dentin. However, when Zol-primer was used with Res.A, the CTX release fell significantly compared to the other tested resin-infiltration methods. In conclusion, zoledronate offers an additional inhibitory effect to the ion-releasing resins in MMP-mediated collagen degradation. However, Zol-primer induces a modest reduction in CTX release only when used with resin-based systems containing no ion-releasing fillers. [ABSTRACT FROM PUBLISHER]

This study determined if dentin proteases are denatured by phosphoric acid (PA) used in etch-and-rinse dentin adhesives. Dentin beams were completely demineralized with EDTA for 30 days. We “acid-etched” experimental groups by exposing the demineralized dentin beams to 1, 10, or 37 mass% PA for 15 sec or 15 min. Control beams were not exposed to PA but were incubated in simulated body fluid for 3 days to assay their total endogenous telopeptidase activity, by their ability to solubilize C-terminal crosslinked telopeptides ICTP and CTX from insoluble dentin collagen. Control beams released 6.1 ± 0.8 ng ICTP and 0.6 ± 0.1 ng CTX/mg dry-wt/3 days. Positive control beams pre-incubated in p-aminophenylmercuric acetate, a compound known to activate proMMPs, released about the same amount of ICTP peptides, but released significantly less CTX. Beams immersed in 1, 10, or 37 mass% PA for 15 sec or 15 min released amounts of ICTP and CTX similar to that released by the controls (p > 0.05). Beams incubated in galardin, an MMP inhibitor, or E-64, a cathepsin inhibitor, blocked most of the release of ICTP and CTX, respectively. It is concluded that PA does not denature endogenous MMP and cathepsin activities of dentin matrices. [ABSTRACT FROM PUBLISHER]

Matrix metalloproteinases (MMPs) cause collagen degradation in hybrid layers created by dentin adhesives. This in vitro study evaluated the feasibility of using a cross-linking agent, 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide (EDC), to inactivate soluble rhMMP-9, as an example of dentin MMPs, and matrix-bound dentin proteases. The inhibitory effects of 5 EDC concentrations (0.01-0.3 M) and 5 incubation times (1-30 min) on soluble rhMMP-9 were screened with an MMP assay kit. The same EDC concentrations were used to evaluate their inhibitory effects on endogenous proteinases from completely demineralized dentin beams that were incubated in simulated body fluid for 30 days. Decreases in modulus of elasticity (E) and dry mass of the beams, and increases in hydroxyproline content of hydrolysates derived from the incubation medium were used as indirect measures of matrix collagen hydrolysis. All EDC concentrations and pre-treatment times inactivated MMP-9 by 98% to 100% (p < 0.05) compared with non-cross-linked controls. Dentin beams incubated in 0.3 M EDC showed only a 9% decrease in E (45% decrease in control), a 3.6% to 5% loss of dry mass (18% loss in control), and significantly less solubilized hydroxyproline when compared with the control without EDC cross-linking (p < 0.05). It is concluded that EDC application for 1 min may be a clinically relevant and effective means for inactivating soluble rhMMP-9 and matrix-bound dentin proteinases if further studies demonstrate that EDC is not toxic to pulpal tissues. [ABSTRACT FROM PUBLISHER]

Highlights • The novel mini-interfacial fracture-toughness approach (mini-iFT) was applied to evaluate if collagen cross-linkers can improve bond durability of adhesives to dentin. • Any benefit from the use of cross-linking agents in the dentin-bonding protocol appeared dependent on the adhesive/adhesive mode and the cross-linker used. • Applied following clinically relevant conditions, proanthocyanidin enhanced the collagen fibrillar resistance against enzymatic degradation. Abstract Objectives Dentin 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. Methods 60 molars were randomly divided in accordance with the three variables: cross-linker, adhesive and bonding mode (n = 5). The cross-linkers glutaraldehyde (5 wt%; GA), proanthocyanidin (6.5 wt%; PA), or UVA-activated riboflavin (0.5 wt%; RB), and distilled water (control) were applied on dentin for 60 s 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 × 8 mm) 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 × 18 mm), 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). Results No 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. Significance The 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. [ABSTRACT FROM AUTHOR]

This study investigates the effect of ions released from S-PRG fillers on host-derived enzymatic degradation of dentin collagen matrices. Dentin beams (n=80) were demineralized and distributed to eight groups following baseline dry mass and total MMP activity assessments. Each group treated with boron, fluoride, sodium, silicone, strontium, aluminium, or S-PRG eluate solutions for 5 min. Untreated beams served as control. After pre-treatment, MMP activity was reassessed, beams were incubated in complete medium for 1 week, dry mass was reassessed. Incubation media were analyzed for MMP and cathepsin-K-mediated degradation fragments. Data were analyzed with ANOVA and Tukey's test. All pretreatment groups showed significant reduction in total MMP activity (p<0.05) that was sustainable after incubation in all groups except for boron and silicone groups (p<0.05). Cathepsin-K activity did not differ between control or treatment groups. The results indicated that ions released from S-PRG fillers have the potential to partly inhibit MMP-mediated endogenous enzymatic activity.

Cariogenic biofilms produce strong acidic microenvironments, which is the primary cause of dental caries. Streptococcus mutans is a dominant species in cariogenic biofilms. Herein, we report a pH-responsive, charge-switching smart copolymer to selectively target and eradicate bacteria in cariogenic biofilms. To that end, the copolymer is designed to be activated in an acidic environment. The smart copolymer, Poly-1A, consists of ternary compositions of monomers with a cationic ethyl ammonium group, a carboxylic group, and a hydrophobic group in the side chains. The net charge of Poly-1A was charge neutral at neutral pH, but it switched to be cationic because the acidic carboxylate side chains were protonated and became neutral; however, the ammonium groups remained positive. Poly-1A with a net positive charge bound to the anionic surface of oral bacteria by electrostatic interactions and disrupted the bacterial membranes, causing bacterial death. Poly-1A reduced the cell viability of planktonic and biofilm S. mutans at pH 4.5, while it was not bactericidal at pH 7.4. Poly-1A did not reduce the cell viability of human gingival fibroblasts and periodontal ligament stem cells for a 1 h incubation.

Objectives: To study phytic acid (IP6) effect on collagen solubilization by assessing hydroxyproline (HYP) release, evaluate its binding to demineralized (DD) and mineralized dentin (MD) and determine the effect of different media on debinding of IP6., Methods: Demineralized dentin beams were incubated in 1%, 2% or 3% IP6 and HYP release was evaluated at 1 or 3 weeks and compared to those obtained in untreated control or phosphoric acid (PA)-treated beams. DD or MD powder was treated with 1%, 2% or 3% IP6 and the decrease in IP6 amount was quantitated by ultraviolet-visible spectroscopy. IP6-treated samples were re-suspended in distilled water, ethanol, urea or sodium chloride and the amount of IP6 displaced was determined., Results: At 1 week, the control group and IP6 showed lower HYP release when compared to PA (P < 0.05). There was no difference among PA, IP6 and control at 3 weeks (P = 0.22). IP6 binding was concentration dependent. 1% IP6 had higher binding potential with MD compared to DD while 2% IP6 showed the opposite result (P<0.05). 3% IP6 had similar binding values between DD and MD (P = 0.53). The highest debinding in MD occurred with urea for 2%, 3% and 1% IP6 in descending manner. Within each concentration of IP6 in DD, the highest debinding effect was reported with ethanol., Conclusions: IP6 bound to DD and MD in a concentration-dependent manner. IP6 was debound from DD mostly by the action of ethanol, while in MD, urea caused the most displacement. Collagen solubilization of IP6-treated DD was comparable to untreated DD., Clinical Significance: These findings add to the potential use of IP6 as an alternative to PA for dentin etching which possibly results in long-term stability of resin-dentin adhesion., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022 Elsevier Ltd. All rights reserved.)

Objective: To determine whether smear layer management, via conservative etching protocols, and the hydrophobic-rich content of hybrid layers would affect the fatigue strength of resin-dentin interfaces., Methods: Bar-shaped dentin beams obtained from sound third molars were wet-polished for 30 s. Dentin was etched with 32 % ortho-phosphoric acid for 3 or 15 s, 10 % meta-phosphoric acid for 15 s or by a prime-and-rinse application using a mild universal adhesive (Scotchbond Universal, 3M ESPE). Self-etch application served as control. Coating was performed with a solvent-free bisGMA-based resin. Composite buildups were made with a nanofilled composite. Resin-dentin beams with twin-bonded interfaces were sectioned and stored in deionized water for 24 h at 37 ℃ before 4-point flexural quasi-static monotonic testing (n = 16). Stress-life fatigue behavior was evaluated under cyclic loading (n = 35) by the staircase method at 4 Hz. The tension side of cyclic-loaded unfractured beams were evaluated under SEM, along with the micro-morphology of etched dentin surfaces. Monotonic data was analyzed by two-way ANOVA followed by the Tukey Test and cyclic-loaded data by Kruskal-Wallis on Ranks (α = 0.05)., Results: Etching protocols and higher hydrophobic-rich content produced significantly higher fatigue life distributions (p < 0.05). Dentin demineralization was ranked as OPA 15 s > MPA 15 s > OPA 3 s > P + R > SE. Less aggressive etching and coating reduced crack formation at hybrid layers., Significance: Current oversimplification trends in resin-dentin bonding constitute a trade-off between hybridization quality and easier adhesive handling. Controlled dentin etching and increasing the hydrophobic-rich content of hybrid layers may be necessary to extend the longevity of mild universal adhesives., (Copyright © 2022 The Authors. Published by Elsevier Inc. All rights reserved.)

Endogenous dentin proteases contribute to the degradation of collagen fibrils in the hybrid layer. Recently, inhibition of host-derived proteases by curcuminoids has shown promising results. The aim of this study was to evaluate the effect of curcuminoid treatment on the microtensile bond strength (μTBS) after 24 h or 12 months of storage. Fifty-four extracted sound human molars were flattened to mid-coronal dentin and divided into nine groups. After phosphoric acid-etching for 15 s, the dentin was experimentally treated for 60 s using 100 μM or 200 μM of curcumin, diflourobenzocurcumin, or demethoxycurcumin dissolved in 1% and 2% dimethyl sulfoxide (DMSO)/water solutions. Untreated and DMSO-treated groups served as controls. After bonding agent application, each tooth was restored with dental composite. The molars were sectioned into 0.9 × 0.9 × 6 mm beams. The μTBS testing was performed after 24 h and 12 months of storage in artificial saliva. Data were analyzed using regression analyses. Failure patterns were evaluated using scanning electron microscopy. Dentin treatment with curcuminoids did not adversely affect 24-h μTBS compared to controls. After 12 months, the μTBS of curcuminoid groups was statistically significantly higher than the controls. This study indicates the feasibility of using curcuminoids as protease inhibitors., (© 2021 Scandinavian Division of the International Association for Dental Research. Published by John Wiley & Sons Ltd.)

Objectives: The objective of this study was to determine the effects of antimicrobial photodynamic therapy (aPDT) with indocyanine green (ICG) and toluidine blue (TB) on protease activity (matrix-bound cathepsin K and matrix metalloproteinase (MMP) and dentin bond strength., Methods: Caries-free human third molars were assigned to five groups: 1-control group, 2-application of ICG with activation using an 810 nm diode (aPDT), 3-application of ICG, 4-application of TB with activation using a 660 nm diode (aPDT), and 5-application of TB. For the enzymatic investigation, dentin beams were incubated for either 3 days or 3 weeks. Aliquots of the incubation media were analyzed by ELISA for CTX (C-terminal cross-linked telopeptide of type I Collagen) and ICTP (cross-linked carboxy-terminal telopeptide of type I collagen). For microtensile bond strength testing (μTBS), composite resins were layered onto the tooth surface; the samples were then subjected to μTBS. Kruskall-Wallis and Mann-Whitney U tests were applied for statistical analysis of CTX and ICTP, one way-ANOVA and Tukey's test were applied for statistical analysis of μTBS., Results: Pretreating the dentin matrices with aPDT decreased the endogenous protease activity. ICG with laser activation resulted in the highest μTBS. Therefore, aPDT should be considered as a treatment method because it can reduce MMP-mediated dentin degradation and increase the μTBS., Significance: Inhibiting endogenous protease activity improves the stability of the dentin-adhesive bond and the durability of the bond strength., (Copyright © 2021 The Academy of Dental Materials. Published by Elsevier Inc. All rights reserved.)

We evaluated the effect of phytic acid on matrix metalloproteinase (MMP)- or cysteine cathepsin (CC)-mediated dentin degradation. Demineralized dentin beams were divided into five groups (n = 12) and treated with 1%, 2%, or 3% phytic acid or with 37% phosphoric acid. Untreated demineralized beams served as controls. After incubation for 1 or 3 wk, dry mass loss was determined and aliquots of incubation media were analysed for cross-linked telopeptide of type I collagen (ICTP) fragments for MMP-mediated and c-terminal telopeptide of type I collagen (CTX) for cathepsin-k-mediated degradation. The direct effect of phytic acid was evaluated using MMP activity assay. Data were analysed using repeated-measures anova. ICTP releases with 1% and 2% phytic acid treatment were statistically significantly lower than those following phosphoric acid treatment at 3 wk. The CTX release for phytic acid-treated beams at 3 wk was not significantly different from that of untreated control beams, but it was significantly lower than that of phosphoric acid-treated beams. Their MMP activities at 3 wk were not significantly different from those of the controls but they were significantly lower than those seen for phosphoric acid-treated beams. Compared to phosphoric acid, phytic acid treatment resulted in a reduced dentinal host-derived endogenous enzymatic activity and collagen degradation., (© 2021 The Authors. European Journal of Oral Sciences published by John Wiley & Sons Ltd on behalf of Scandinavian Division of the International Association for Dental Research.)

This study evaluated the cytotoxicity of methacrylate-based resins containing dimethyl sulfoxide (DMSO). DMSO was incorporated into hydrophobic (R2) and hydrophilic (R5) resins at weight concentrations of 0, 0.01, 0.1, 1, 5, or 10 w/w %. Resin discs (n = 10/group) were prepared. Human gingival fibroblasts (HGF-1) were exposed to resin eluates for 24 h. Furthermore, dentin barrier test was performed using 3-D cultures of odontoblast-like cells (SV40 transfected pulp derived cells) with dentin slices of 400 µm thickness (n = 8). After acid etching of dentin, DMSO-modified resins were applied into the cavity part of the device and light-cured for 20 s. Cell viability (%) was assessed by MTT and analyzed spectrometrically. Data were analyzed by ANOVA and Tukey test (α = 0.05). Resin eluates showed statistically significantly lower % cell viability for all neat and DMSO-modified resins than seen for the negative control. Moreover, DMSO-R5 eluates resulted in significantly lower % cell viability than DMSO-R2 emulates. The dentin barrier test showed that DMSO-R2 did not result in significantly lower % cell viability, whereas incorporation of 1-10 w/w % DMSO into R5 resulted in significantly lower % of cell viability. Incorporating DMSO into hydrophilic self-etching resins may increase cytotoxicity. The biocompatibility is not influenced by the addition of DMSO into hydrophobic resin., (© 2021 European Journal of Oral Sciences.)

The study evaluated changes in total enzymatic activity and degradation of demineralized dentin following the application of universal or self-etch adhesives. The universal adhesives -Scotchbond Universal (SU) and All-Bond Universal (ABU) and self-etch adhesives -Adper Easy Bond (EB) and G-aenial Bond (GB) were used for 2 min pretreatment of the dentin beams. Phosphoric acid (PA) treatment as well as no treatment served as controls. Total enzymatic activity was analyzed before and after treatment, collagen degradation was assessed using mass loss, C-terminal telopeptide (CTX) and C-terminal-telopeptide of type I collagen (ICTP) release (24 h, 3-day, 3-week). Over three weeks of incubation, ICTP release of ABU treated beams was significantly higher than other groups (p<0.05), except for SU treated beams (p>0.05) and CTX release of GB treated beams was the highest among the groups with statistically significant difference (p<0.05). The results confirm that the universal adhesives tested have also potential to increase the enzymatic activity in dentin.

Objectives: Matrix metalloproteinases (MMPs) are dentinal endogenous enzymes claimed to have a vital role in dentin organic matrix breakdown. The aim of the study was to investigate presence, localization and distribution of MMP-7 in sound human dentin., Methods: Dentin was powdered, demineralized and dissolved in isoelectric focusing buffer. Resolved proteins were transferred to nitrocellulose membranes for western blotting (WB) analyses. For the zymographic analysis, aliquots of dentin protein were electrophoresed in 12% sodium dodecyl sulfate-polyacrylamide gel electrophoresis containing fluorescently labeled gelatin. Further, the concentrations of dentinal MMPs were measured using Fluorescent Microsphere Immunoassay with a human MMP-MAP multiplex kit. Pre- and post-embedding immunolabeling technique was used to investigate the localization and distribution of MMP-7 in dentin. Dentin was cryo-fractured, the fragments partially decalcified and labeled with a primary monoclonal anti-MMP-7 and a secondary antibody conjugated with gold nanoparticles. MMP-7 labelings were identified in the demineralized dentin matrix as highly electron-dense dispersed gold particles., Results: WB and zymographic analysis of extracted dentin proteins showed presence of MMP-7 (∼20-28 KDa). Further, MMP-7 was found in the supernatants of the incubated dentin beams using Fluorescent Microsphere Immunoassay. FEI-SEM and TEM analyses established MMP-7 as an intrinsic constituent of the human dentin organic matrix., Conclusion: This study demonstrated that MMP-7 is an endogenous component of the human dentin fibrillar network., Clinical Significance: It is pivotal to understand the underlying processes behind dentin matrix remodeling and degradation in order to develop the most optimal clinical protocols and ensure the longevity of dental restorations., (Copyright © 2018 Elsevier Ltd. All rights reserved.)

In dentistry, the wet-bonding approach relies on water to maintain demineralized collagen expanded for proper resin infiltration; nevertheless, hydrolytic instability of the resin-dentin interface is inevitable with current bonding techniques. Considering dimethyl sulfoxide's (DMSO) ability to "biomodify" collagen and precipitate enzymes, the aim was to test whether the use of DMSO would permit adequate resin bonding to H 3 PO 4 -etched dehydrated dentin and assess its impact on collagen degradation by host-derived enzymes. Etched dentin surfaces from extracted sound human molars were randomly bonded in wet or dry conditions using aqueous or ethanolic DMSO solutions as pretreatments and bonding resins with or without DMSO. Bonded teeth were sectioned into resin-dentin slabs for confocal in situ zymography and beams for microtensile bond strength test. Demineralized powdered dentin was incubated in the tested DMSO -media and a hydroxyproline assay evaluated dissolution of collagen peptides. Zymography was performed on protein extracts obtained from dry and wet H 3 PO 4 -ecthed dentin powder treated with the DMSO- media. The correlative biochemical analysis demonstrated that reduction of water content during dentin hybridization by the innovative dry-bonding approaches with DMSO is effective to inactivate host-derived MMP-2 and MMP-9 and thus reduce collagen degradation while simultaneously optimizing resin-dentin bonding.

The aim of this study was to evaluate the effect of curcuminoids on the dentin endogenous protease activity. Demineralized dentin were pretreated with 50 or 100 µM of three different curcuminoids for 60 s and incubated up to 3 months. Untreated beams served as controls. Dry dentin mass was measured after incubation. Aliquots were analyzed for the quantity of ICTP and CTX releases for MMP and cathepsin-K mediated degradation, respectively. The effect of curcuminoids on matrix-bound MMP and soluble rhMMP-9 were measured using an activity assay. Data were subjected to repeated-measures-ANOVA (α=0.05). Gelatinolytic activity was analyzed using zymography. ICTP and CTX release and dry mass loss of curcuminoid-treated groups were significantly lower than the control. Inhibition of rhMMP-9 varied from 29-49% among curcumonoid-treated groups, whereas no inhibition was observed at untreated control (p>0.05). Results were confirmed by zymography. The study showed that the pretreatment of dentin matrices by curcuminoids decreases endogenous protease activity-mediated degradation in dentin.

A water-soluble crosslinking agent, 1-ethyl-3-(3-dimethylaminopropyl)-carbodiimide (EDC), has been used as a pretreatment of acid-etched dentin to inactivate matrix-bound endogenous dentin proteases. The aim of this study was to evaluate the effect of pH on the inactivation capacity of EDC. Demineralized dentin beams (1 × 2 × 6 mm) were divided into six groups (n = 8 per group). Then, EDC (0.3 M) was solubilized in distilled water with pH of 2, 4, 6, 7, 9, or 11. Control EDC was solubilized in 0.1 M 2-(N-morpholino) ethanesulfonic acid (MES) buffer and its pH was adjusted to 6. The dentin beams were pretreated for 1 min with EDC at each pH or with EDC in MES buffer at pH 6.0 and then incubated in 1 ml of simulated body fluid (pH 7.2) for 1, 3, 7, or 14 d. Untreated beams served as controls. At each study time-point, the dry mass of dentin beams was assessed and the incubation media were analyzed for carboxyterminal telopeptide of type-I collagen (ICTP) and C-terminal telopeptide of type I collagen (CTX) using specific ELISAs. Data were subjected to repeat-measures anova. The results of the study indicated that specimens pretreated with EDC in MES buffer showed the lowest collagen degradation in terms of mass loss and release of telopeptides, while specimens pretreated in alkaline media showed the highest collagen degradation. This study indicates that the pH of the EDC solution plays an important role in the stability of dentin protease inactivation., (© 2017 Eur J Oral Sci.)

The aim of this study was to evaluate the degradation of completely demineralized dentin specimens in contact with a filler-free or 2 ion-releasing resins containing micrometer-sized particles of Bioglass 45S5 (BAG) or fluoride-containing phosphate-rich bioactive glass (BAG-F). Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM) were also used to evaluate the remineralization induced by the experimental ion-releasing resin-based materials. Dentin beams were totally demineralized in H 3 PO 4 (10%) and placed in direct contact with a filler-free (RESIN) or 2 experimental ion-releasing resins (BAG or BAG-F) and immersed in artificial saliva (AS) up to 30 d. Further specimens were also processed and submitted to FTIR and SEM analysis to evaluate the remineralization induced by such ion-releasing resins before and after AS immersion. BAG and BAG-F alkalinized the incubation media. A significant decrease of the dry mass was observed between the specimens of all groups stored for 3 and 30 d in AS. However, the fluoride-containing phosphate-rich bioactive glass incorporated into a resin-based material (BAG-F) showed greater ability in reducing the solubilization of C-terminal cross-linked telopeptide (ICTP) and C-terminal telopeptide (CTX) after prolonged AS storage. Moreover, after 30 d of AS storage, BAG-F showed the greatest remineralizing effect on the stiffness of the completely demineralized dentin matrices. In conclusion, fluoride-containing phosphate-rich bioactive glass incorporated as micrometer-sized filler in dental composites may offer greater beneficial effects than Bioglass 45S5 in reducing the enzyme-mediated degradation and remineralization of demineralized dentin.

Objective: Inactivation of dentin proteases by crosslinkers has been suggested as a way to prevent the degradation of dentin collagen in the hybrid layer. However, it is not known if the inhibition is reversible. The aim of this study was to evaluate the inactivation effect of various crosslinkers on dentin protease activity over a period of 6 months., Methods: Demineralized dentin beams (1×2×6mm, n=10/group) were treated with (1) 1% glutaraldehyde (GA1), (2) 5% glutaraldehyde (GA5), (3) 1% grape seed extract (GS1), (4) 5% grape seed extract (GS5), (5) 10% sumac berry extract (S), (6) 20μM curcumin (CR20), and (7) 200μM curcumin (CR200) for 5min. Untreated beams served as control. The beams were incubated up to 6 months and incubation media were used to analyze solubilized telopeptide (ICTP and CTX) fragments as indicators of MMP- and cathepsin K-mediated degradation after 1, 3 and 6 months of incubation. The relative MMP activity of dentin beams was tested using a generic MMP assay. Data were analyzed using repeated-measures ANOVA, α=0.05., Results: All treated groups showed significant decrease in CTX release (32.2-469.5pg/mg dentin) and ICTP (1.8-47.6ng/mg dentin) fragments during the first month of incubation compared to control (1159pg/mg and 72.9ng/mg dentin, respectively). GA5, GS5 and CR200 maintained their inhibitory effect during 6-month incubation. The results were confirmed by dry mass loss and relative MMP activity following 6 months., Significance: The results of this study indicate that the long-term effect is both crosslinker and dose dependent., (Copyright © 2016 The Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.)

The enzymatic degradation of dentin organic matrix occurs via both the action of matrix metalloproteinases (MMPs) and cysteine cathepsins (CCs). Zinc can prevent collagen hydrolysis by MMPs. However, its effect on the activity of dentin-bound CCs is not known. The aim of this study was to investigate the effect of zinc on matrix-bound cathepsin K and MMP activity in dentin. Completely demineralized dentin beams were divided into test groups (n = 9) and incubated at 37°C in an incubation media (1 mL) containing ZnCl2 of 0.02 (physiological level, control), 0.2, 0.5, 1, 5, 10, 20, 30, or 40 mM. The dry mass changes of the beams were determined, and incubation media were analyzed for cathepsin K- and MMP-specific collagen degradation end products - CTX (C-terminal cross-linked telopeptide of type I collagen) and ICTP (cross-linked carboxy-terminal telopeptide of type I collagen) - at 1, 3, and 7 days of incubation. The mass loss of the beams decreased when the zinc level in the incubation media was ≥5 mM (p < 0.05). The release of liberated collagen degradation telopeptides decreased in accordance with the decrease in the mass loss rates of the beams. Cathepsin K-induced dentin collagen degradation can be strongly inhibited by zinc. Zinc levels of ≥5 mM can be considered as a reliable threshold for the stabilization of dentin matrices., (© 2017 S. Karger AG, Basel.)

Matrix metalloproteinases (MMPs) and cysteine cathepsins (CCs) degrade the collagen fibrils of demineralized dentin. Sodium fluoride (NaF) has previously been shown to inhibit recombinant MMP-2 and MMP-9. This study aimed to evaluate the efficacy of NaF on the inhibition of dentin-bound MMPs and CCs. Dentin beams were completely demineralized in 10% phosphoric acid. The baseline total MMP activity and dry masses were measured. Beams were assigned to test groups based on similar MMP activity and dry mass (n = 10/group), and incubated in artificial saliva (control) or artificial saliva with NaF containing 6-238 mM fluoride for 1, 7 and 21 days. The dry mass loss and MMP activities were reassessed at each time point. The proteolytic activity was screened by gelatin zymography. ICTP and CTX released to the incubation medium were analyzed as indices of MMP and cathepsin K activity, respectively. The beams were examined under scanning electron microscopy. All NaF doses reduced the dry mass loss after 21 days (p < 0.05). NaF inhibition of the total MMP activity ranged between 5 and 80%. In gelatin zymography, the bands of MMP-2 and MMP-9 became less prominent with increasing NaF levels. NaF did not decrease the released ICTP (p > 0.05). Less CTX release was detected with F ≥179 mM (p < 0.05). CaF2-like minerals were observed on the beams. High levels of NaF may slow the degradation of the dentin matrix due to the inhibition of cathepsin K. Fluoride does not seem effective in the direct inhibition of proteolysis by dentin matrix-bound MMPs., (© 2016 S. Karger AG, Basel.)

Objectives: The aim of this study was to evaluate the effect of using UVA-induced crosslinking with or without riboflavin as photosensitizers on degradation of dentin matrix by dentin proteases., Methods: Demineralized dentin specimens (0.4×3×6 mm(3), n=10/group) were subjected to: (RP1), 0.1% riboflavin-5 phosphate/UVA for 1 min; (RP5), 0.1% riboflavin-5 phosphate/UVA for 5 min; (R1), 0.1% riboflavin/UVA for 1 min; (R5), 0.1% riboflavin-UVA for 5 min; (UV1), UVA for 1 min; (UV5), UVA for 5 min. Specimens were incubated in 1 mL zinc and calcium containing media for 1 day and 1 week. An untreated group served as control (CM). After incubation, the loss of dry mass of samples was measured and aliquots of media were analyzed for the release of C-terminal fragment telopeptide (ICTP vs. CTX) of collagen to evaluate for cathepsin K (CA-K) and total matrix metalloproteinase (MMP)-mediated degradation. Data were analyzed using repeated measures ANOVA at α=0.05., Results: Although UVA radiation alone reduced dentin degradation, UVA-activated riboflavin or riboflavin-5 phosphate inhibited MMP and CA-K activities more than UVA alone. The effects of crosslinking were more pronounced in 7-day samples; only with CA-K were the effects of crosslinking with or without photosensitizer significantly different from controls in 1-day samples., Significance: The use of bioactive forms (RP) or longer treatment time did not result with better effect. The use of UVA crosslinking reduces dentin matrix degradation, especially with photosensitizers., (Copyright © 2015 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.)

Objective: The clinical survival rates of the adhesive restorations are limited due to the deterioration of resin-dentin bonds over time, partly due to the endogenous enzymatic activity of dentin. Recently, benzalkonium chloride (BAC) has been shown to effectively inhibit endogenous protease activity of dentin. This study evaluated the effect of different concentrations of benzalkonium chloride (BAC) on the degree of conversion (DC), vickers hardness (VH), setting time (ST) and biaxial flexural strength (FS) of two self-adhesive resin luting cements (RC)., Methods: Two RC SpeedCEM (Ivoclar-Vivadent) and BisCem (Bisco) were modified by addition of 0.1, 0.5, 1, 1.5, 2 wt% BAC. The luting cements without the addition of BAC served as control. The DC (FT-IR/ATR from the bottom of the resin disc), vickers hardness (from top and bottom of the light-cured specimen), setting time (ISO 4049) and biaxial flexural strength (0.6 × 6 mm discs) of the specimens were tested. Data were analyzed using ANOVA and Tukeys HSD., Results: DC results were in the range of 70-80%, with some significant changes in BisCem (p < 0.05). VH values of both materials increased significantly compared to control, with no significant change as the BAC percentage increases. BAC addition influenced the ST differently for both materials. For BisCem, a gradual decrease (p < 0.05) was observed whereas, for SpeedCEM, a gradual increase was observed until 1% BAC (p < 0.05). For FS values, a gradual decrease was observed for both materials with increased amounts of BAC (p < 0.05), compared to the control group., Conclusions: BAC addition of up to 1% seems to be acceptable considering the properties tested. Clinical significance. Incorporation of benzalkonium chloride to self-adhesive resin luting cements during the mixing procedure does not significantly affect the degree of conversion or flexural strength of the luting agent and may be a good option to improve the durability of adhesive interface.