Effects of Remineralizing Agents Based on Calcium Phosphate, Sodium Phosphate, or Sodium Fluoride on Eroded Cervical Dentin

SUMMARY Objectives: To evaluate the effect of remineralizing agents on collagen matrix pattern, precipitate formation, and dentinal tubule obliteration in eroded cervical dentin. Methods and Materials: One hundred bovine cervical dentin specimens were previously eroded (0.6% hydrochloric acid, pH 2.3, 5 minutes) and then randomized into five groups (n=20): G1, control (without treatment); G2, Desensibilize Nano P (FGM); G3, MI Paste Plus (Recaldent); G4, Regenerate (NR-5); and G5, Desensibilize KF 2% (FGM). These treatments were applied in four sessions with 7-day intervals. During this period, the samples were subjected to an erosive challenge with orange juice (pH 3.8, 5 minutes). The specimens were analyzed by polarized light microscopy with picrosirius red staining, scanning electron microscopy (SEM), and energy-dispersive X-ray spectroscopy (EDX). Results: The G3 showed a higher concentration of type I collagen than G2 and G5 (p<0.05). The G3 showed greater formation of surface precipitates than that of G1 and G5 (p<0.05). In addition, G4 and G5 showed a greater number of open dentinal tubules than that of G3 (p<0.05). Conclusions: Calcium phosphate-based remineralizing agents have shown to be a promising alternative treatment for preventing deleterious effects on the eroded dentin collagen matrix. In addition, they promoted precipitate formation and dentinal tubule obliteration on the eroded dentin.

Reconstructing the childhood diet of the individuals from the Middle Late Bronze Age Bezdanjača Cave, Croatia (ca. 1430 1290 BCE) using stable C and N isotope analysis of dentin collagen

This paper investigates the childhood diet of 16 individuals from the Middle Late Bronze Age (1430 1290 BCE) Bezdanjača Cave (Lika region, Croatia) using stable isotope analysis of dentin collagen from permanent first molars. Results from the analysis reveal that the individuals from Bezdanjača consumed notable quantities of C4 plants during their childhood. The most common C4 plant is millet, whose spread throughout Southern Europe was recently dated to the second half of the 2nd millennium BCE, which agrees with the results obtained in this research. Comparisons between the data collected for the individuals from Bezdanjača and other Middle and Late Bronze Age sites in Croatia suggest that only the individuals from the site of Veliki Vital (Middle Bronze Age, inland Croatia) exhibit similar isotopic values to those from Bezdanjača. Human isotopic values from coastal sites, however, reveal that during the Middle and Late Bronze Age people from the coast had diet that still predominantly contained C3 plant-based foods, which appears to suggest that the dispersion of this crop in Croatia during the Bronze Age followed an east-west trajectory, appearing earlier (Middle and Late Bronze Age) in inland settlements such as Veliki Vital and Bezdanjača and only later (Late Bronze Age and mostly Iron Age) in coastal sites.

Theaflavins as a novel cross-linker quickly stabilize demineralized dentin collagen against degradation

To investigate the ability of theaflavins (TF) from black tea to protect dentin collagen against enzymatic degradation via cross-linking effect under clinically relevant conditions. 10-µm-thick dentin films were microtomed from dentin slabs of human molars. Following demineralization, films or slabs were treated with TF at two concentrations (0.4% and 2%) for 30 s. A well-known collagen cross-linker grape seed proanthocyanidins (PA) was used as control. Collagen cross-linking interactions and stabilization against enzymatic degradation were investigated by Fourier transform infrared spectroscopy, weight loss, hydroxyproline release, and scanning/transmission electron microscopy. Data were analyzed by ANOVA, Tukey’s and Student’s T test (α = 0.05%). The results showed collagen cross-linking and stabilization efficacy was dependent on TF/PA concentrations. At 2.0%, TF and PA offered nearly full protection to collagen; at 0.4%, TF exhibited a significantly better collagen stabilization effect than PA (P < 0.05), while untreated collagen was completely digested. It’s concluded that TF cross-links dentin collagen within a clinically relevant time (30 s) and offers excellent collagen protection against enzymatic degradation, with efficacy comparable to or better than PA. The study supports the potential use of TF as a novel, promising collagen cross-linker for degradation resistant, long-lasting dentin bonding in composite restorations.

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

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

Dual-Functionality Evaluation of a Novel Collagen Crosslinking Resin

Current adhesives bond to dentin via a micro-interlocking mechanism within the hybrid layer. Besides such mechanical retention, bonding to dentin would benefit from additional chemical interaction between collagen and resin. This study aims to synthesize a novel light-curable collagen crosslinker methacrylate (MA) functionalized grapeseed extract (GSE) and to assess MAGSE’s ability to crosslink dentin collagen in a clinically relevant setting as well as its role in light-cure as a resin. MA functionalization was accomplished by reacting GSE with methacryloyl chloride to obtain MAGSE, which was characterized by 1H-NMR and Fourier transformed infrared spectroscopy (FTIR). The 6-µm-thick dentin films were microtomed from dentin slabs of third molars. Following demineralization, they were treated for 30 s by 1% MAGSE. Collagen crosslinking and resistance to digestion of MAGSE were evaluated by FTIR, matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF) assay of films, and scanning electron microscopy (SEM)/transmission electron microscopy (TEM) on slabs. Meanwhile, 1% MAGSE or GSE was added to an experimental adhesive formulated with 2-hydroxyethyl methacrylate and a tricomponent photoinitiator system. Polymerization kinetics were monitored continuously in real time for 10 min using FTIR–attenuated total reflection. The results indicated that MAGSE could bind to dentin collagen and protect it from collagenase degradation as strong as GSE. Dentin collagen treated by 1% MAGSE for 30 s was scarcely digested (1.6 ± 1.6%) after 1 h in 0.1% collagenase, while untreated collagen was completely digested (100.9 ± 20.2%). SEM/TEM images indicated MAGSE efficiently crosslinked dentin collagen in 30 s and rendered it almost inert to digestion under clinically relevant settings. Unlike GSE that hindered light-curing of HEMA, MAGSE accelerated the rate of polymerization and exhibited typical traits of a resin monomer with multiple polymerizable units. In conclusion, a novel collagen crosslinking resin MAGSE is synthesized, which inherits collagen crosslinking ability from GSE and polymerization function from MA. Inclusion of this light-curable collagen crosslinker into adhesives might be a revolutionary way to improve durability of dentin bonding in composite restorations.

Quercetin as an Auxiliary Endodontic Irrigant for Root Canal Treatment: Anti-Biofilm and Dentin Collagen-Stabilizing Effects

(1) Background: Bacterial reinfection and root fracture are the main culprits related to root canal treatment failure. This study aimed to assess the utility of quercetin solution as an adjunctive endodontic irrigant that strengthen root canal dentin with commitment anti-biofilm activity and bio-safety. (2) Methods: Based on a noninvasive dentin infection model, dentin tubules infected with Enterococcus faecalis (E. faecalis) were irrigated with sterile water (control group), and 0, 1, 2, 4 wt% quercetin-containing ethanol solutions. The live and dead bacteria proportions within E. fae-calis biofilms were analyzed using confocal laser scanning microscopy (CLSM). Elastic modulus and hydroxyproline release and X-ray photoelectron spectroscopy (XPS) characterization was tested on irrigant-treated demineralized dentin to evaluate irrigants&rsquo; biostability. The cytotoxicity of irrigants was tested by CCK-8 assay. (3) Results: Quercetin increased the proportion of dead bacteria volumes within E. faecalis, and improved the flexural strength of dentin collagen com-pared to control group. The XPS characterization revealed an increase in C-O peak area under both C1s and O1s narrow-scan spectra. The CCK-8 assay confirmed no cytotoxicity of quercetin solutions. (4) Conclusions: Quercetin exhibited anti-biofilm activity, collagen-stabilizing effect as well as cytocompatibility, supporting quercetin as a potential candidate for endodontic irrigant.