Dentin Slabs Research Articles

The Impact of Different Irrigation Protocols on the Bond Strength of Self-Adhesive Resin Cement to Radicular Dentin.

The objective of the study was to investigate the influence of different irrigation protocols on the shear bond strength (SBS) of self-adhesive resin cement (SARC) on primed radicular dentin. Radicular dentin slabs (N=58) were embedded in acrylic. Subsequently, they were polished and randomly assigned to five experimental groups (N=8-12) and one control group, CG (N=8). Irrigation solutions used were 2.5% sodium hypochlorite (H), 17% ethylenediamine tetraacetic acid (EDTA), 9% etidronic acid with hypochlorite (HEDP), 0.9% saline solution (SS), and 2% chlorhexidine (CHX). Each experimental group underwent a different irrigation protocol for two minutes: 1) H/EDTA/H, 2) HEDP, 3) H/EDTA/CHX, 4) H/EDTA/SS and 5) HEDP/SS. The CG samples were not treated with any irrigation solution. After drying, the adhesive-enhancing primer (AEP) and dual-curing SARC were applied to the radicular dentin using molds corresponding to the Ultra Tester (Ultradent Products, South Jordan, USA). The specimens were stored at 37 °C in distilled water and broken after 10 days in shear mode. The results were analyzed using ANOVA and post-hoc Games-Howell test, α=0.05. CG exhibited the highest SBS. With the exception of HEDP and HEDP/SS, all experimental groups showed significantly lower SBS compared to CG (p<0.05). HEDP appears to be an adequate solution for cleaning the root canal prior to dentin priming and fiber post cementation with SARC.

Revitalising Dentin Surfaces: Unlocking Periodontal Regeneration Potential through Cutting-edge Citric Acid Techniques

Introduction: Teeth affected by periodontitis exhibit an increased mineral content and endotoxins. They do not harmonise with the neighbouring periodontal cells, whose growth is essential for periodontal regeneration. This scanning electron microscope (SEM) study evaluated and compared the in vitro effects of different citric acid application techniques on naturally preserved dentin slabs. Materials and Methods: Thirty-two dentinal slabs were prepared for experimentation, with one group undergoing various treatments and a control group left untreated. The citric acid solution, with a pH of 1.0, was meticulously prepared and used in four different application methods on the experimental group. The dentin slabs were prepared for SEM evaluation, which assessed parameters such as exposed dentinal tubules, the surface area occupied by tubule orifices, the demineralised zone’s width and the exposed tubules’ morphological characteristics. Results: The data present the mean number of exposed dentinal tubules for different application techniques and the width of the demineralised zone. While the f-test did not show significant differences in the width of the demineralised zone, the number of exposed dentinal tubules varied significantly. Immersion treatment resulted in the highest number of open tubules, followed by cotton pellet placement and brushing. Conclusions: The study suggests that in periodontal regenerative procedures, passive citric acid application may be more effective than vigorous methods like burnishing for exposing inter-tubular fibrils and dentinal openings.

Blue Laser for Polymerization of Bulk Fill Composites: Influence on dentin bond strength and temperature rise during curing and co-curing method.

Blue diode lasers are alternative curing devices for dental composites. The aim of this study was to investigate the influence of blue diode laser polymerization on shear bond strength of bulk fill composites to human dentin and temperature rise during two types of polymerization. Composite cylinders of SDR Plus(SDR) and Ever X Flow(EX) were bonded to dentin slabs using Adhese Universal and curing devices blue diode laser (449nm, 1.6 W) and Power Cure LED. For each material and curing device there were two polymerization approaches: 1)conventional: separate curing of adhesive; 2)co-curing: simultaneous adhesive and composite curing. Polymerization modes for each material in conventional and co-curing(c) approach were: blue laser 2000 mW/cm2 for 5s (L5 and L5c); blue laser 1000 mW/cm2 for 10s (L10 and L10c); Power Cure 2000 mW/cm2 for 5s (LED5 and LED5c); Power Cure 1000 mW/cm2 for 10s (LED10 and LED10c). Temeperature was measured using thermal vision camera. For SDR, the highest bond strength was 24.3MPa in L10c, and the lowest 9.2MPa in LED5c. EX exhibited the highest bond strength(21.3MPa) in LED5, and the lowest in L5(7.7MPa). The highest temperature rise for SDR was in L10 and L5 (7.3 and 7.2°C), and the lowest in LED5(0.8°C). For EX, the highest temperature rise was in L5 (13.0°C), and the lowest in LED5 (0.7°C). Temperature rise was higher during blue laser polymerization, especially at high intensity and with conventional curing. Preferable blue laser curing mode is co-curing at 1000mW/cm2 for 10s.

Characteristics of tin-containing fluoride toothpastes related to erosive tooth wear protection

ObjectivesTo assess the effect of different tin-containing toothpastes on the control of erosive tooth wear in enamel and dentin. MethodsEnamel and dentin slabs were randomly distributed into 7 experimental groups (n = 10/substrate): C−: negative control (Artificial saliva); AmF (regular fluoridated toothpaste without tin); Sn-1 (SnF2/NaF); Sn-2 (SnF2/NaF/SnCl2); Sn-3 (SnCl2/NaF); Sn-4 (SnF2/SnCl2); Sn-5 (SnCl2/AmF/NaF/chitosan). Specimens were submitted to 5-day erosion-abrasion cycling. Surface loss (SL) was determined with an optical profilometer. Tin deposition on the tooth surfaces and some characteristics of the toothpastes (pH, potentially available F−, %weight of solid particles, and RDA) were also assessed. Data were statistically analyzed (α = 0.05). ResultsFor enamel, the Sn-2 presented the lowest SL, not differing significantly from AmF, C+, and Sn-3. The SL of these groups was significantly lower than the C−, except for Sn-3. Sn-1 and Sn-4 were also not significantly different from C−. For dentin, C− significantly showed the highest SL values, whilst, Sn-1 presented the lowest SL, not differing significantly from AmF, Sn-2, C+, and Sn-3. There was a significant positive association between enamel SL and the pH and tin deposition. Dentin SL was significantly negatively associated with the %weight of solid particles and RDA. ConclusionsMost of the tin-toothpastes were able to exhibit some protection against ETW. In this process, the toothpastes characteristics play a role, as lower enamel SL was significantly associated with lower pH values and tin deposition; and lower dentin SL was associated with higher %weight of solid particles and RDA of the toothpastes. Clinical significanceTin-containing toothpastes can be used for erosive tooth wear protection, but our study showed that their effect depends on the pH, amount of tin deposition, % weight of solid particles and RDA of the toohpastes.

Efficacy of Three Remineralizing Agents on Erosion of Root Dentin by Cola Drink: An In Vitro Study

Abstract Objective The aim of the study was to investigate the effects of silver diamine fluoride (38% SDF), sodium fluoride (NaF) varnish, and casein phosphopeptide-amorphous calcium phosphate fluoride (CPP-ACPF) on cola-eroded root dentin microhardness and mineral alteration in vitro. Materials and Methods Forty human root dentin slabs were exposed to alternating 10 cycles of cola drink and artificial saliva, repeated 3 times at 6-hour intervals. Specimens were randomly assigned to four groups: control (deionized water), 38% SDF, NaF varnish, and CPP-ACPF. All specimens underwent the second erosion process. Microhardness was measured at baseline (KHN0), pretreatment (KHN1), and posttreatment (KHN2). The mean difference of microhardness (ΔKHN2-1) was analyzed using one-way analysis of variance (ANOVA) and Tukey's post hoc tests (α = 0.05). The chemical composition and surface morphology were assessed using energy dispersive spectroscopy (EDS) and scanning electron microscope (SEM). Results All experimental groups exhibited dentinal tubule occlusion. Both 38% SDF and NaF varnish demonstrated a statistically significant increase in microhardness compared to CPP-ACPF. However, CPP-ACPF was comparable to the control group. EDS analysis showed an increase in weight percentage of fluorine in all groups. Furthermore, silver and chlorine were detected in the 38% SDF group. Conclusion All treatments enhanced eroded root dentin microhardness, with 38% SDF and NaF varnish demonstrating superior acid resistance and preventing morphological changes induced by cola re-immersion.

In Vitro Comparative of the Cutting Efficiency and Smear Layer of Ceramic Burs, Conventional Tungsten Carbide Burs and Diamond Stone

Purpose: To compare the cutting efficiency and the smear layer of three different types of burs ceramic, tungsten carbide and diamond stone. Materials and Methods:135 mica-based glass ceramics (Vita blocs Mark II) blocks were used to valuate cutting efficiency by weight loss method. Five points from each type of burs: Cera Bur (komet, Brasseler, Germany): K59, Tungsten Carbide tapered Bur (komet, Brasseler, Germany): H2 010 and diamond points (komet, Brasseler, Germany): 957AM 314 010, were used for cutting procedures. Each bur had made 30 seconds duration cut, each bur was used three times. Cutting was performed under standardized protocol using a specially designed machine for this purpose. Twelve unerupted human third molars were used to obtain Dentin slabs. Cutting was performed using the same protocol and the smear layer created was observed by means of scanning electron microscope. Results: The values of weight loss were: 0.18 ± 0.08 gm, 0.40 ± 0.07 and 0.50 ± 0.07 gm for each bur respectively. Less dense smear layer was observed with the Cera Bur when compared to the tungsten carbide and diamond burs. Conclusion: The new tapered fissure ceramic bur can be considered a promising tool for minimally dentistry, while providing a minimal reduction of the sound, hard tooth substance.

Saliva Decreases Sucrose-Induced Cariogenicity in an Experimental Biological Caries Model.

Whether a minimum quantity of saliva inhibit the caries process remains uncertain. This study aimed to investigate the impact of saliva dilutions on an in vitro caries model using Streptococcus mutans (S. mutans) biofilms. S. mutans biofilms were cultivated on enamel and root dentin slabs, in culture media containing different proportions of saliva (v/v): 0%, 5%, 10%, 25%, 50%, 75%, and 100% saliva, and exposed to a 10% sucrose solution (5 min, 3x/day), with appropriate controls. After 5 (enamel) and 4 (dentin) days, demineralization, biomass, viable bacteria, and polysaccharide formation were analyzed. The acidogenicity of the spent media was monitored overtime. Each assay was performed in triplicate across two independent experiments (n = 6). In both enamel and dentin, an inverse relationship was observed between acidogenicity, demineralization, and the proportion of saliva. Even small quantities of saliva incorporated into the media led to a noticeable reduction in enamel and dentin demineralization. Saliva presence resulted in significant reductions in biomass, viable S. mutans cells, and polysaccharides, with the effects being concentration-dependent for both tissues. High quantities of saliva can almost completely inhibit sucrose-induced cariogenicity, while even small amounts exhibit a dose-dependent caries-protective effect.

Killing Efficiency and Full Genome Sequencing of Bacteriophage BAG1 Targeting Endodontic Clinical Strain of Enterococcus faecalis

Objectives: Bacterial biofilms can increase the survival of bacteria through providing resistance to conventional disinfectants as well as antibiotics, thus biofilm considered a serious risk to human health with hug loss. Consequently, novel approaches to deal with bacterial biofilms are required. Viruses that may eradicate bacteria are known as bacteriophages, they are also known as “bacteria eaters.” Due to their activity on bacteria, bacteriophages are distinct from other organisms and do not pose a threat to human. Consequently, they are regarded as secure substitutes for antibiotics in the management of bacterial infections. Aim of the Study: In this study, we report the full genome sequencing of bacteriophage, namely BAG1 that targeting an endodontic clinical strain of Enterococcus faecalis (K3). Furthermore, we evaluate it killing efficiency to eliminate E. faecalis in both planktonic media and dentine slabs. Materials and Methods: We used the previously isolated endodontic E. faecalis clinical strain, namely K3 and enterococcus bacteriophage BAG1 in this study by spotting on the double layer agar technique. DNA extracted proceeded with NORGEN phage DNA isolation kit. Phage full genome sequencing was performed using Illumina nova Seq 600, 150 bp PE. In addition, the killing capacity of BAG1 phage against E. faecalis K3 was measured by infecting 5 × 106 E. faecalis with BAG1 phage at multiplicity of infection of 0.1. Furthermore, the biofilm fraction and the number of E. faecalis colony-forming unit in planktonic media were measured after infecting 24 dentine slabs with K3 bacteria and BAG1 phage. SYTO® 9 green LIVE/DEAD® BacLight Bacterial Viability Kits were used to visualize K3 biofilm on dentine slabs using fluorescent microscope. Results: Full Genome Organization of BAG1 phage was circular composed of 68 open reading frame with GC percentage of 34.56%. An efficient killer reflecting by completely eliminating K3 strain within 180 min in killing test. In addition, the result revealed that BAG1 highly significant to eliminate K3 bacteria in both planktonic broth and biofilm fraction obtained from dentine slabs infection with the endodontic K3 clinical strain. Conclusion: Our results support that anti E. faecalis bacteriophage BAG1 significantly eliminate biofilm of E. faecalis K3 on dentine slabs with a lytic properties due to the absence of lysogenic genes which make it a suitable substitute to adjunctive anti E. faecalis therapy.

Comparison and evaluation of the effect of polymerization of resin-modified glass ionomer cement and dual-cure resin cement on the crystalline structure of dentin using synchrotron X-ray diffraction and its clinical correlation with postoperative sensitivity.

To compare the effect of polymerization of resin-modified glass ionomer cement and dual-cure resin cement on the crystalline structure and to correlate it clinically with postoperative sensitivity. The evaluation of crystalline strain in the dentin slabs was done using Synchrotron X-ray diffraction. The post operative sensitivity was measured clinically using Schiff's sensitivity scale. A total of 44 extracted and noncarious premolars were collected. Dentin slabs of dimensions 2 mm × 2 mm × 1.5 mm were prepared from the buccal aspect of the extracted teeth. The dentin slabs were then divided into two groups, Group A dual-cured resin cement and Group B resin-modified glass ionomer cement was applied. The dentin slabs first underwent synchrotron X-ray diffraction before and after the application of cement. Forty-two patients who were undergoing complete metal fixed prostheses on vital posterior abutments were selected. In this, 21 vital abutments were included in each group. Tooth preparation and fabrication of complete metal prostheses were done in the conventional manner and cemented using the 2 luting cements in Groups A and B, respectively. Dentinal hypersensitivity was measured using Schiff 's scale, postcementation, after 1 week and 1 month. Independent t-test was done for comparing the two cements in two cements in terms of lattice strain. Mann-Whitney U-test was done for comparing the cements with respect to dentinal hypersensitivity. Spearman's correlation coefficient was used for clinical correlation between dentinal hypersensitivity and crystalline strain. The lattice strain generated in dual cure resin cement was higher than that in resin-modified glass ionomer cement and was statistically significant. Postcementation hypersensitivity was higher in dual-cured resin than resin-modified glass ionomer cement but was not statistically significant in the follow-up visits. Spearman's correlation coefficients did not reveal any significant clinical correlation between lattice strain and dentinal hypersensitivity. Dual cure resin cements generate greater lattice strain as compared to resin modified glass ionomer cements.

Biodentine Inhibits the Initial Microbial Adhesion of Oral Microbiota In Vivo.

This study aimed to evaluate the in vivo initial microbial adhesion of oral microorganisms on the biomaterial Biodentine compared to MTA and AH Plus. Cylindrical samples of the materials were prepared, and dentin slabs served as a control. An individual intraoral lower jaw splint served as a carrier for the samples and was worn by six volunteers. The specimens were worn for 120 min.&amp;nbsp;Adherent bacteria were quantified by determining the colony-forming units (CFUs), while the visualization and quantification of total adherent microorganisms were facilitated by using DAPI and live/dead staining combined with fluorescence microscopy. Bovine dentin had a significantly higher number of aerobic CFUs compared to Biodentine (p = 0.017) and MTA (p = 0.013). The lowest amounts of DAPI-stained adherent microorganisms were quantified for Biodentine (15% ± 9%) and the control (18% ± 9%), while MTA showed the highest counts of initially adherent microorganisms (38% ± 10%). Significant differences were found for MTA and Biodentine (p = 0.004) as well as for MTA and the control (p = 0.021) and for AH Plus and the control (p = 0.025). Biodentine inhibited microbial adherence, thereby yielding an antimicrobial effectivity similar to that of MTA.

Streptococcus mutans Proteases Degrade Dentinal Collagen.

Here, we explored the role of S. mutans's whole cell and discrete fractions in the degradation of type I collagen and dentinal collagen. Type I collagen gels and human demineralized dentin slabs (DS) were incubated in media alone or with one of the following: overnight (O/N) or newly inoculated (NEW) cultures of S. mutans UA159; intracellular proteins, supernatant or bacterial membranes of O/N cultures. Media from all groups were analyzed for protease-mediated release of the collagen-specific imino acid hydroxyproline. Images of type I collagen and DS were analyzed, respectively. Type I collagen degradation was highest for the supernatant (p &lt; 0.05) fractions, followed by intracellular components and O/N cultures. Collagen degradation for DS samples was highest for O/N samples, followed by supernatant, and intracellular components (p &lt; 0.05). There was lower detectable degradation for both type I collagen and DS from NEW culture samples (p &lt; 0.05), and there was no type I collagen or DS degradation detected for bacterial membrane samples. Structural changes to type I collagen gel and dentinal collagen were observed, respectively, following incubation with S. mutans cultures (O/N and NEW), intracellular components, and supernatant. This study demonstrates that intracellular and extracellular proteolytic activities from S. mutans enable this cariogenic bacterium to degrade type I and dentinal collagen in a growth-phase dependent manner, potentially contributing to the progression of dental caries.

A 58S bioactive glass for dentin hypersensitivity and erosive tooth wear: An in vitro study

ObjectivesTo assess the effect of an experimental 58S bioactive glass on dentin permeability (dP) and erosive tooth wear (dentin surface loss - dSL). Methods58S bioactive glass was synthetized using a sol-gel methodology, following by lyophilization and calcination, then mixed with phosphoric acid to obtain a paste (BGP). Forty-eight dentin disks (1 mm-thick) were used for dP, and 48 dentin slabs (3 mm × 3 mm) for dSL, which were assessed at three time intervals: post-EDTA (5 min in 17% EDTA solution); post-treatment (C: distilled water; BGP: experimental bioactive glass paste; NP: Nupro prophylaxis paste; CXT: Clinpro XT varnish); and post-erosive/abrasive cycling. Data were statistically analyzed (α=0.05). ResultsFor dP and dSL, Groups did not differ significantly post-EDTA (p>0.05). Post-treatment, all groups showed lower dP than C (p<0.05), without differing significantly among them. For the dSL analysis, Groups C, BGP and NP did not differ significantly, showing lower values than CXT (p<0.05). Post-cycling, C continued to show the highest dP (p<0.05). Specimens from Group CXT had the lowest dP and did not differ from NP (p=0.86) which did not differ from BGP (p=0.193). For C and BGP, dP value was higher post-cycling than post-treatment (p<0.05). For NP and CXT, these experimental times did not differ (p>0.05). Post-cycling, dSL for C, BGP and NP did not differ significantly; values were higher than those for CXT (p<0.05). ConclusionsBGP reduced dP after application, with a reduced effect after cycling. Nonetheless, it was not able to protect dentin against erosive tooth wear. Clinical SignificanceMinimizing dentin hypersensitivity is a challenge in the field of dentistry. The development of alternative products with potential to obliterate dentinal tubules and provide resistance to chemical/mechanical stimuli is, thus, highly desirable. We have proposed a material able to reduce dentin permeability, which has emerged as a promising alternative for this purpose.

Effect of pH and titratable acidity on enamel and dentine erosion.

The relative effect of pH and titratable acidity on tooth erosion remains unclear. We determined the effect of both properties on in vivo salivary pH recovery and on enamel and dentine early erosion in situ. Solutions simulating acidic beverages with different pHs (2.5 or 3.5) and titratable acidities (0, 25, or 100mM citric acid) were tested. In an in vivo study (n = 20 participants), the salivary pH was determined before, during, and up to 2min after exposure to the tested solutions. In situ, 12 participants exposed enamel and root dentine slabs to the tested solutions simulating a beverage consumption; early erosion was assessed by percentage of surface hardness loss (%SHL). Groups were compared by ANOVA (p < 0.05). Saliva pH was lower after exposure to solutions at pH 2.5, irrespective of titratable acidity; pH recovery took longer for solutions with higher titratable acidities, irrespective of their pHs. In situ, the highest %SHL was observed for the solution with lower pH and higher titratable acidities. The addition of citric acid increased the %SHL by 2.5-3 times in enamel, and at least 5 times in dentine. Both pH and titratable acidity may play a role on the erosive potential of acidic beverages. Acidic beverages with lower pHs promote erosion by an initial acid etching of the surface; those with a higher titratable acidity slow down the salivary pH recovery. Both properties contribute to the overall erosive potential.

An extensive description of the microbiological effects of silver diamine fluoride on dental biofilms using an oral in situ model

Silver diamine fluoride (SDF) has been long studied in laboratories, and its clinical effectiveness in the treatment and prevention of root caries has been reported. In the present study, we assessed the microbiological effects of SDF on dental biofilms grown on demineralized dentin in situ. Specifically, demineralized bovine root dentin slabs used as biofilm substrates were treated with 38% SDF, and the biofilms formed after this treatment were analyzed via real-time PCR, DEAD/LIVE cell staining, and SEM. Next, the viable cell count was determined, and microbial profiles were compared using 16S rRNA gene sequencing. Untreated slabs were used as controls. We observed significant decreases in viable cell counts (p < 0.05), number of biofilm-forming cells (p < 0.01), biofilm thickness (p < 0.01), and high proportion of dead cells with SDF treatment (p < 0.01). The microcolonies in the SDF-treated biofilms showed less complexity, and only a limited number of genera were differentially abundant between the groups. Microbial diversity index comparisons showed no significant differences between the groups with respect to treatments days (p = 0.362). Thus, SDF negatively influenced dental biofilm growth on demineralized root dentin in situ; however, its antimicrobial action did not target a specific oral taxon.

Calcium pretreatment enhances fluoride reactivity with enamel and dentine

ObjectiveHigh fluoride concentration treatments are known to react with enamel and dentine forming calcium fluoride (CaF2)-like deposits, but strategies to improve this reactivity beyond increasing fluoride concentration/reducing pH in fluoride treatments have not been explored. Here we investigated the ability of a calcium pre-treatment to improve fluoride reactivity. DesignIn a blind and randomized in vitro study, sound and carious enamel and dentine slabs (n = 11/group) were randomly allocated into one of the following treatments: Deionized water (negative control); 0.05% sodium fluoride (F, positive control); 150 mM calcium lactate solution followed by 0.05% sodium fluoride solution (Ca→F); 150 mM calcium lactate solution premixed with 0.05% sodium fluoride solution (CaF2, active control). Alkali-soluble fluoride (representing CaF2-like deposits formed on the substrates) was extracted from the slabs using 1 M KOH for 24 h and measured by an ion-specific electrode. Carious slabs were further observed under scanning electron microscopy (SEM). Data were analyzed by two-way ANOVA followed by Tukey test. ResultsThe Ca→F treatment enhanced fluoride reactivity with all tested substrates when compared with F alone. Carious substrates had a greater reactivity with F and Ca→F than their respective sound substrates, confirming that increased porosity enhances the reactivity with fluoride. Alkali-soluble fluoride concentration after the CaF2 treatment did not differ among the different substrates, suggesting this treatment causes only contamination with preformed CaF2, which was noted under SEM. ConclusionA calcium pretreatment enhances the reactivity of fluoride with enamel and dentine.

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.

Tooth Age Impact on Dental Erosion Susceptibility and Treatment Efficacy

This laboratory study investigated the impact of tooth age on dental erosion susceptibility and preventive treatment efficacy. Extracted human premolars were selected and had their age estimated (∼10–100 years old) using established dental forensic methods. Enamel and root dentin slabs were prepared, embedded in acrylic blocks, flattened, and polished. The specimens were randomly assigned to one of three treatments (n = 93): Sn+F (800 ppm Sn as SnCl₂ and 250 ppm F as NaF, pH 4.5), NaF (250 ppm F, pH 4.5), or deionized water (DIW). Each specimen was subjected for 10 days to a daily cycling protocol consisting of six 5-min erosive challenges (0.3% citric acid, pH 2.6), six 60-min remineralization periods (artificial saliva), and three 2-min treatments with the test solutions. Surface loss (SL) was measured after 3, 5, and 10 days, using optical profilometry. Effects of tooth age, antierosive treatment, and time on SL were evaluated using linear mixed effects regression analysis. SL increased with age for all substrate-treatment-time combinations (p < 0.0001). Sn+F and NaF solutions significantly reduced SL compared to DIW, regardless of substrate, time, or age (p < 0.0001), with best results shown for Sn+F. Efficacy of Sn+F increased with tooth age on enamel, but tooth age did not affect the efficacy of NaF on enamel. For dentin, increased efficacy was observed with age after 5 (for Sn+F) and 10 days (for Sn+F and NaF). In conclusion, increase of tooth age rendered enamel and root dentin more susceptible to dental erosion. NaF preventive efficacy improved with tooth age for dentin, in advanced erosion simulation. Sn+F reduced enamel SL due to erosion regardless of tooth age.

Distinct effects of polyphenols and solvents on dentin collagen crosslinking interactions and biostability

ObjectiveTo evaluate the effects of different polyphenols and solvents on dentin collagen’s crosslinking interactions and biostabilization against MMPs and collagenase degradation. MethodsTwo polyphenols [proanthocyanidin (PA) and quercetin (QC)] with different water solubility were prepared as treatment solutions using ethanol (EtOH) or dimethyl sulfoxide (DMSO) as solvents. 6-um-thick dentin films were microtomed from dentin slabs of third molars. Following demineralization, films or slabs were subject to 60-s treatment (PA or QC) or no treatment (control) with subsequent extended-rinse with original solvent (EtOH or DMSO) or distilled water (DW). Collagen crosslinking interactions were assessed by FTIR. Biostability was assessed through endogenous MMPs activity via confocal laser scanning microscopy, and exogenous collagenase degradation via weight loss, hydroxyproline release and SEM. Finally, direct collagenase inactivation was also evaluated. Data were analyzed by three-way ANOVA and post-hoc tests (α=0.05%). ResultsDistinct effects of two polyphenols and solvents on collagen crosslinking and biostabilization were observed. Higher crosslinking and biostability efficacy occurred with PA than QC (p<0.001) that demonstrated negligible collagen interactions. With DMSO solvent, efficacy results were significantly reduced with both polyphenols (p<0.05). DMSO-rinse further weakened interactions of PA with collagen, diminishing biostability (p<0.05). Low biostability was detected with QC and DW-rinse, suggesting direct enzymatic inhibition due to physical presence in collagen. SignificanceCollagen crosslinking interactions and biostability depend on polyphenol chemical characteristics. Treatment-solution solvents may affect interactions between polyphenols and collagen, specifically, DMSO showed detrimental effects on collagen crosslinking and biostability and should be used with caution.

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.

Methacrylate-functionalized proanthocyanidins as novel polymerizable collagen cross-linkers – Part 1: Efficacy in dentin collagen bio-stabilization and cross-linking

ObjectiveThe aim of the study was to investigate the effects of methacrylate-functionalized proanthocyanidins (MAPAs) on dentin collagen’s bio-stabilization against enzymatic degradation and crosslinking capability. MethodsThree MAPAs were synthesized via varying methacrylate (MA) to proanthocyanidins (PA) feeding ratios of 1:2, 1:1, and 2:1 to obtain MAPA-1, MAPA-2, and MAPA-3, respectively. The three MAPAs were structurally characterized by proton nuclear magnetic resonance (1H NMR) and Fourier transform infrared (FTIR) spectroscopic methods. 5-μm-thick dentin films were microtomed from dentin slabs of third molars. Following demineralization, films or slabs were treated with 1% MAPAs or PA in ethanol for 30 s. Collagen bio-stabilization against enzymatic degradation was analyzed by weight loss (WL) and hydroxyproline release (HYP) of films, as well as scanning electron microscopy (SEM) on dentin slabs. Crosslinking capacity and interactions of MAPAs with collagen were investigated by FTIR. Data were analyzed by ANOVA and Tukey’s test (α = 0.05%). ResultsMA:PA feeding ratios affected MAPAs’ chemical structures which in turn led to different collagen stabilization efficacy against degradation and varied collagen crosslinking capabilities. Higher collagen stabilization efficacy was detected using MAPA-1 (WL 10.52%; HYP 13.53 μg/mg) and MAPA-2 (WL 5.99%; HYP 11.02 μg/mg), which was comparable to that using PA (WL 8.79%; HYP 13.17 μg/mg) (p > 0.05), while a lower collagen stability occurred in MAPA-3 (WL 38.48%; HYP 29.49 μg/mg), indicating excessive MA-functionalization would compromise its stabilization efficacy. In comparison, complete digestion was detected for untreated collagen (WL 100%; HYP 102.76 μg/mg). The above results were consistent with collagen crosslinking efficacy of the three MAPAs revealed by SEM and FTIR. SignificanceA new class of novel polymerizable collagen cross-linkers MAPAs was synthesized and shown that, when appropriate MA:PA ratios were applied, the resulting MAPAs could render high collagen stability and the ability to copolymerize with resin monomers, overcoming the drawbacks of PA. These new polymerizable crosslinkers, when included in adhesives, could lead to long-lasting dentin bonding.