Inhibition of human gelatinases by metals released from dental amalgam

18-month clinical evaluation of a copper-containing universal adhesive in non-carious cervical lesions: A double-blind, randomized controlled trial

OBJECTIVE

This study aimed to evaluate the addition of copper nanoparticles (CuNp) on the clinical performance of a universal adhesive system used as etch-and-rinse (ER) and self-etch (SE).

METHODS

216 restorations were randomly placed in 36 subjects according to the following groups: ERcu = etch-and-rinse with 0.1% CuNp; ERct = etch-and-rinse without CuNp; SEcu = self-etch with 0.1% CuNp; SEct = self-etch without CuNp. Resin composite was placed incrementally and light-cured. The restorations were evaluated at baseline and 6, 12 and 18 months using the FDI and USPHS criteria. Statistical analyses were performed using appropriate tests (α = 0.05).

RESULTS

The addition of CuNp did not increase the clinical performance (FDI / USPHS) of the universal adhesive tested after 18-month when applied in the ER mode (p > 0.05). The addition of CuNp in SE restorations increased the retention rate significantly and decreased the marginal discrepancies after 18 months (p < 0.05).

CONCLUSION

The clinical performance of universal adhesive was significantly increased when applied in the SE mode with the addition of copper nanoparticles.

CLINICAL RELEVANCE

This is the first study that demonstrates a slight improvement in the clinical performance of universal adhesive systems in non-carious cervical lesions when added CuNp in lower concentration.

The cytotoxic and oxidative effects of restorative materials in cultured human gingival fibroblasts

The aim of this study was to evaluate the cytotoxic and oxidative effects of the most commonly used dental restorative materials on human gingival fibroblast cells (HGFCs). HGFCs were obtained from healthy individuals. The tested restorative materials were a microhybrid resin based composite, a compomer resin, a glass ionomer cement, and an amalgam alloy. One hundred eight cylindirical samples, 10 mm in diameter and 2 mm in height, were prepared according to ISO 10993-12:2002 specifications (n = 9 in the tested subgroups). Freshly prepared and aged samples in artificial saliva at 37 °C (7 and 21 d) were placed into well plates and incubated. Wells without dental materials were constituted as the control group. After 72 h incubation period, cytotoxicity was determined using the neutral red (NR) assay. Oxidative alterations were assessed using total antioxidant capacity (TAC) and total oxidant status (TOS) assay kits. Data were analyzed using the ANOVA and LSD post hoc tests. All tested materials led to significant decreases in the cell viability rates (33-73%) compared to the control group. Glass ionomer and resin composite were found to be more cytotoxic than amalgam alloy and compomer. The highest TAC level was observed in glass ionomer after seven-day aging and these changes prevented an increase in TOS levels. Increases in TAC levels after seven-day aging in all groups exhibited significant differences with freshly prepared samples (p < 0.05). In all material groups, TOS levels of freshly prepared samples differed statistically and significantly from samples aged for 7 and 21 d (p < 0.05). The data obtained suggested that all the tested materials exhibited cytotoxic and pro-oxidant features. Freshly prepared samples caused higher TOS levels. However, oxidant status induced by materials decreased over time.

Effect of zinc on the collagen degradation in acid-etched dentin

BACKGROUND/PURPOSE

Matrix metalloproteinases (MMPs) play a crucial role in the pathogenesis of dental caries, collapse of adhesive interface, and chemical erosion of teeth. The objective of this study was to investigate the inhibitory effect of zinc on collagen degradation.

MATERIALS AND METHODS

Human dentin was ground and demineralized by citric acid (pH 2.0). The demineralized ground dentin was incubated in six different media: artificial saliva (AS); 5 mg/ml doxycycline in AS; 3.33, 6.82, 13.63, and 27.26 mg/ml of zinc chloride (Zn) in AS. Each group was divided into two subgroups, and active MMP-2 was incorporated into one subgroup. Specimens were incubated for 24 h, 1 week, and 2 weeks. Collagen degradation product was assessed using ELISA. The results were analyzed using repeated measured ANOVA and Duncan's post hoc analysis (α = 0.05).

RESULTS

The amount of collagen degradation was the lowest in Doxy group. Zn groups showed a significant inhibitory effect in collagen degradation for all concentrations (P < 0.05). In subgroups without exogenous MMP-2, zinc-mediated inhibition increased in a concentration-dependent manner with increasing zinc concentration. The amount of collagen degradation product slightly increased with increased incubation time from 24 h to 2 weeks. However, in subgroups with exogenous MMP, the inhibitory effect of zinc on collagen degradation did not depend on zinc concentration.

CONCLUSION

All Zn groups for the four concentrations tested exhibited statistically significant inhibitory effect on collagen degradation.

[Progress on matrix metalloproteinase inhibitors]

Continuing advances in dentin bonding technology and adhesives revolutionized bonding of resin-based composite restorations. However, hybrid layers created by contemporary dentin adhesives present imperfect durability, and degradation of collagen matrix by endogenous enzymes is a significant factor causing destruction of hybrid layers. Bond durability can be improved by using enzyme inhibitors to prevent collagen degradation and to preserve integrity of collagen matrix. This review summarizes progress on matrix metalloproteinase inhibitors (including chlorhexidine, ethylenediaminetetraacetic acid, quaternary ammonium salt, tetracycline and its derivatives, hydroxamic acid inhibitors, bisphosphonate derivative, and cross-linking agents) and suggests prospects for these compounds.

Role of Host-Derived Proteinases in Dentine Caries and Erosion

Demineralization in dentinal caries and erosion exposes dentine organic matrix. This exposed matrix, containing type I collagen and non-collagenous proteins, is then degraded by host collagenolytic enzymes, matrix metalloproteinases (MMPs) and cysteine cathepsins. The knowledge of the identities and function of these enzymes in dentine has accumulated only within the last 15 years, but has already formed a field of research called ‘dentine degradomics'. This research has demonstrated the role of endogenous collagenolytic enzymes in caries and erosion development. In demineralized dentine, the enzymes degrade triple-helical collagen molecules, leading to the gradual loss of collagen matrix. Even before that, they can cleave off the terminal non-helical ends of collagen molecules called telopeptides, leading to the structural changes at the intramolecular gap areas, which may affect or even prevent intrafibrillar remineralization, which is considered essential in restoring the dentine's mechanical properties. They may also cause the loss of non-collagenous proteins that could serve as nucleation sites for remineralization. Here we review the findings demonstrating that inhibition of salivary or dentine endogenous MMPs and cysteine cathepsins may provide preventive means against the progression of caries or erosion. Furthermore, we also suggest the future directions for the new experimental preventive research to gain more knowledge of the enzymes and their function during and after dentine demineralization, and the pathways to find the clinically acceptable means to prevent the functional activity of these enzymes.

The crude skin secretion of the pepper frog Leptodactylus labyrinthicus is rich in metallo and serine peptidases

Peptidases are ubiquitous enzymes involved in diverse biological processes. Fragments from bioactive peptides have been found in skin secretions from frogs, and their presence suggests processing by peptidases. Thus, the aim of this work was to characterize the peptidase activity present in the skin secretion of Leptodactylus labyrinthicus. Zymography revealed the presence of three bands of gelatinase activity of approximately 60 kDa, 66 kDa, and 80 kDa, which the first two were calcium-dependent. These three bands were inhibited either by ethylenediaminetetraacetic acid (EDTA) and phenathroline; thus, they were characterized as metallopeptidases. Furthermore, the proteolytic enzymes identified were active only at pH 6.0-10.0, and their activity increased in the presence of CHAPS or NaCl. Experiments with fluorogenic substrates incubated with skin secretions identified aminopeptidase activity, with cleavage after leucine, proline, and alanine residues. This activity was directly proportional to the protein concentration, and it was inhibited in the presence of metallo and serine peptidase inhibitors. Besides, the optimal pH for substrate cleavage was determined to be 7.0-8.0. The results of the in gel activity assay showed that all substrates were hydrolyzed by a 45 kDa peptidase. Gly-Pro-AMC was also cleaved by a peptidase greater than 97 kDa. The data suggest the presence of dipeptidyl peptidases (DPPs) and metallopeptidases; however, further research is necessary. In conclusion, our work will help to elucidate the implication of these enzymatic activities in the processing of the bioactive peptides present in frog venom, expanding the knowledge of amphibian biology.

Effect of strontium-substituted biphasic calcium phosphate on inflammatory mediators production by human monocytes

Calcium phosphate materials are widely used as bone substitutes because of their properties close to those of the mineral phase of bones. Nevertheless, after several months, calcium phosphate-based materials release particles that may be phagocytosed by monocytes, leading to an inflammatory reaction. Strontium is well known to counteract the osteoporosis process, but little is known about its effect on inflammatory processes. The purpose of this work was to study the effect of biphasic calcium phosphate (BCP) particles substituted with strontium on the inflammatory reaction. Human primary monocytes stimulated or not by lipopolysaccharide (LPS) were exposed to BCP particles containing strontium for 6 and 24 h. Inflammatory mediators (cytokines and matrix metalloproteinases (MMPs)) production was then quantified by ELISA and zymography. We observed that the presence of strontium had few effects on unstimulated cells, but it decreased the production of pro-inflammatory cytokines and the chemokine interleukin 8 in LPS-stimulated cell-conditioned medium. This work suggests for the first time that strontium may be involved in the control of inflammatory processes following BCP phagocytosis by human monocytes.

The inhibitory effects of silver diamine fluoride at different concentrations on matrix metalloproteinases

OBJECTIVE

To study the inhibitory effect of various commercially available concentrations of silver diamine fluoride (SDF) solutions on matrix metalloproteinases (MMPs).

METHODS

Three SDF solutions with concentrations at 38%, 30% and 12% were studied. Two sodium fluoride (NaF) solutions at 10% and 3% were prepared, and they had the same fluoride ion concentrations as 38% and 12% SDF, respectively. Two silver nitrate (AgNO(3)) solutions at 42% and 13% were also prepared, and they had the same silver ion concentrations as 38% and 12% SDF, respectively. Ten samples of each experimental solution were used to study their inhibitory effect on three MMPs, which were MMP-2 (gelatinase A), MMP-8 (neutrophil collagenase) and MMP-9 (gelatinase B) using MMP assay kits. Positive control containing assay buffer at pH 9 and MMPs dilution was used to calculate the percentage inhibition.

RESULTS

The percentage inhibition of 38%, 30% and 12% SDF on MMP-2 were 79%, 60% and 17%, respectively (p<0.001); on MMP-8 were 94%, 85% and 77%, respectively (p<0.001); on MMP-9 were 82%, 65% and 60%, respectively (p<0.001). The percentage inhibition on MMP-2, MMP-8 and MMP-9 by 38% SDF was significantly higher than the corresponding percentage inhibition by 10% NaF and 42% AgNO(3).

SIGNIFICANCE

Greater inhibitory effect on MMPs was found with higher concentration of SDF solution. SDF had more inhibition on MMPs than solutions of NaF and AgNO(3) containing equivalent concentration of fluoride and silver ions, respectively.

Characterization of an antimicrobial dental resin adhesive containing zinc methacrylate

This study evaluates the effect of zinc methacrylate (ZM) on the degree of conversion (DC), cytotoxicity and antimicrobial activity (AA) of an experimental resin. Tetraethyleneglycol dimethacrylate was used as the experimental resin and it was photo activated using camphoroquinone and ethyl 4-dimethylamine benzoate. Additionally, 1.0, 2.5, 5.0, 10, 20 and 30 wt% of ZM was added to the various experimental resins. The DC was accessed by Fourier Transform infrared spectroscopy. For cytotoxicity, immortalized mouse fibroblasts were exposed to the experimental resin extracts. An MTT assay was used to access the cytotoxicity. The AA against Streptococcus mutans UA159 was accessed by the agar diffusion method. An improvement in the DC in all concentrations of ZM was observed. The greater the amount of ZM on the experimental resin, the less the cytotoxicity was provoked. Three ZM concentrations showed AA that exhibited various inhibition growth zones with 10, 20 (10 mm) and 30 wt% (15 mm).

Addition of zinc methacrylate in dental polymers: MMP-2 inhibition and ultimate tensile strength evaluation

This study evaluated the effect of zinc methacrylate (ZM) on the inhibition of matrix metalloproteinase 2 (MMP-2) and the ultimate tensile strength (UTS) of an experimental polymer. Enzymes secreted from mouse gingival tissues were analyzed by gelatin zymography in buffers containing 5 mM CaCl(2) (Tris-CaCl(2)) in 50 mM Tris-HCl buffer with various concentrations of ZM (0.5, 1, 2, 4, 8, and 16 mM). The matrix metalloproteinases present in the conditioned media were characterized by immunoprecipitation. The polymer UTS evaluation was performed in eight groups with various concentrations of ZM (0, 0.5, 1, 2.5, 5, 10, 20, and 30 wt.%), in a mechanical testing machine. MMP-2 (62 kDa) was detected in the zymographic assays and inhibited by ZM in all tested concentrations. UTS data were submitted to one-way ANOVA and Tukey's test (α = 0.05), and no significant differences were observed among groups, except in the polymer containing 30% ZM, presenting a significantly lower value when compared with the control group (p < 0.05). The results suggest that ZM inhibits MMP-2 expression in all concentrations tested, while small concentrations did not affect the ultimate tensile strength of the polymer. Zinc methacrylate is a metalloproteinase inhibitor that can be copolymerized with other methacrylate monomers. Yet, the addition of ZM did not affect the resin bond strength. Thus, in vivo tests should be performed to evaluate the performance of this material.

Zinc reduces collagen degradation in demineralized human dentin explants

OBJECTIVES

Dentin matrix metalloproteinases are implicated in the pathogenesis of caries and contribute to collagen degradation in resin-dentin interfaces. The objective was to determine if collagen degradation may be modulated by an excess of zinc or zinc chelators.

METHODS

Mineralized and phosphoric acid demineralized human dentin specimens were tested. Chlorhexidine digluconate, doxycycline or ZnCl₂ were added to the media. In half of the groups, active exogenous metalloproteinase-2 was incorporated into the solution. C-terminal telopeptide determinations (radioimmunoassay) were performed after 24 h, 1 and 3 weeks.

RESULTS

Collagen degradation was prominent in demineralized dentin. Doxycycline fully blocked dentin proteolysis. Chlorhexidine digluconate reduced the degradation at the 24-h period. Zinc in excess strongly inhibits hydrolysis of collagen and its effect was maintained for 3 weeks.

CONCLUSIONS

Zinc in excess reduces MMP-mediated collagen degradation. The hypothesis that binding of zinc to collagen results in protection of sensitive cleavage sites of metalloproteinases requires further validation.

The requirement of zinc and calcium ions for functional MMP activity in demineralized dentin matrices

The progressive degradation of resin-dentin bonds is due, in part, to the slow degradation of collagen fibrils in the hybrid layer by endogenous matrix metalloproteinases (MMPs) of the dentin matrix. In in vitro durability studies, the storage medium composition might be important because the optimum activity of MMPs requires both zinc and calcium.

OBJECTIVE

This study evaluated the effect of different storage media on changes in matrix stiffness, loss of dry weight or solubilization of collagen from demineralized dentin beams incubated in vitro for up to 60 days.

METHODS

Dentin beams (1mm×2mm×6mm) were completely demineralized in 10% phosphoric acid. After baseline measurements of dry mass and elastic modulus (E) (3-point bending, 15% strain) the beams were divided into 5 groups (n=11/group) and incubated at 37°C in either media containing both zinc and calcium designated as complete medium (CM), calcium-free medium, zinc-free medium, a doubled-zinc medium or water. Beams were retested at 3, 7, 14, 30, and 60 days of incubation. The incubation media was hydrolyzed with HCl for the quantitation of hydroxyproline (HOP) as an index of solubilization of collagen by MMPs. Data were analyzed using repeated measures of ANOVA.

RESULTS

Both the storage medium and the storage time showed significant effects on E, mass loss and HOP release (p<0.05). The incubation in CM resulted in relatively rapid and significant (p<0.05) decreases in stiffness, and increasing amounts of mass loss. The HOP content of the experimental media also increased with incubation time but was significantly lower (p<0.05) than in the control CM medium, the recommended storage medium.

CONCLUSIONS

The storage solutions used to age resin-dentin bonds should be buffered solutions that contain both calcium and zinc. The common use of water as an aging medium may underestimate the hydrolytic activity of endogenous dentin MMPs.

Inhibition of the activity of matrix metalloproteinase 2 by triethylene glycol dimethacrylate

The aim of this study was to evaluate the effect of different concentrations of triethylene glycol dimethacrylate (TEGDMA) on the inhibition of matrix metalloproteinase 2 (MMP-2). Mouse gingival explants were cultured overnight in DMEM and the expression of secreted enzymes was analyzed by gelatin zymography in buffers containing 5 mM CaCl(2) (Tris-CaCl(2)) in 50 mM Tris-HCl buffer with the addition of TEGDMA at different concentrations (0.62%, 1.25%, 2.5%, or 5.0% (v/v)). The gelatinolytic proteinase present in the conditioned media was characterized as matrix metalloproteinase by means of specific chemical inhibition. The matrix metalloproteinases present in the conditioned media were characterized as MMP-2 by immunoprecipitation. The eletrophoretic bands were scanned and the transmittance values were analyzed. Data was plotted and submitted to linear regression to investigate MMP-2 inhibition as a function of TEGDMA concentration. Three major bands were detected in the zymographic assays. These bands were characterized as MMP-2. Zymogene (72 kDa), intermediate (66 kDa) and active forms of MMP-2 (62 kDa) were inhibited by TEGDMA in a dose-dependent way. These findings suggest that TEGDMA could inhibit MMP-2 expression even at small concentrations.

2-hydroxyethyl methacrylate as an inhibitor of matrix metalloproteinase-2

This study evaluated the effect of different concentrations of 2-hydroxyethyl methacrylate (HEMA) on the inhibition of matrix metalloproteinase-2 (MMP-2) in vitro. Mouse gingival explants were cultured overnight in Dulbecco's modified Eagle's minimal essential medium, following which the expression of secreted enzymes was analyzed by gelatin zymography and the effects of different amounts of HEMA on enzyme activity were investigated. The gelatinolytic proteinases present in the conditioned media were characterized as being matrix metalloproteinases (MMPs) by means of specific chemical inhibition. The MMPs present in the conditioned media were identified, using immunoprecipitation, as MMP-2. Three major bands were detected in the zymographic assays and were characterized, according to their respective molecular weights, into the following forms of MMP-2: zymogene (72 kDa), intermediate (66 kDa), and active (62 kDa). All forms of MMP-2 were inhibited by HEMA in a dose-dependent manner, implying that MMP-2 may be inhibited by HEMA in vivo.

Relaxation of the mouse pubic symphysis during late pregnancy is not accompanied by the influx of granulocytes

In some animals, such as mice and guinea pigs, a hormonally controlled mechanism increases the flexibility of the pubic symphysis and enhances the cervical remodeling necessary for safe delivery. Cervical ripening during pregnancy is associated with a paradoxical influx of leukocytes. However, the changes in cell metabolism during relaxation of the mouse pubic symphysis for delivery have not been extensively studied. In this work, we used light microscopy and transmission and scanning electron microcopy, as well as immunohistochemistry and Western blotting for MMP-8, to investigate the involvement of granulocytes or resident stromal cells in the relaxation of the virgin pubic symphysis during late pregnancy (days 18 and 19, before delivery) in vivo and in explanted joints. MMP-8 was studied because this collagenase is a hallmark for cervical ripening associated with the influx of granulocytes during late pregnancy. Extensive dissolution and disorganization of the extracellular matrix was seen around fibroblastic-like cells in late pregnancy. In contrast to the cervix (positive control), morphological and immunohistochemical analyses revealed that there was no characteristic cellular inflammatory response in the interpubic tissue. Staining for MMP-8 was observed in chondroid and fibroblastic-like cells of virgin and relaxed interpubic ligament, respectively. However, no granulocytes were seen during the extensive remodeling of the pubic joint in late pregnancy. These results indicate that constitutive stromal cells may have an important role in tissue relaxation during remodeling of the pubic symphysis in pregnancy.