Biomimetic deposition of calcium phosphate minerals on the surface of partially demineralized dentine modified with phosphorylated chitosan

Antimicrobial efficacy of chitosan versus sodium hypochlorite: A systematic review and meta-analysis

AIM

This meta-analysis aimed to compare the antibacterial efficacy of chitosan/chitosan nanoparticles (Ch/Ch-NPs) versus sodium hypochlorite/chlorhexidine (NaOCl/CHX).

MATERIALS AND METHODS

A search was performed in four electronic databases until December 08, 2023. Studies with missing, unclear, and insufficient data sets were excluded. The included studies were assessed by two independent reviewers using the Joanna Briggs Institute Critical Appraisal Checklist for Quasi-Experimental Studies. The meta-analysis of standardized mean difference was performed using a random effects model. Additionally, funnel plots as well as Egger's regression intercept test were used to evaluate potential publication bias.

RESULTS

A total of 426 samples were used in nine included studies. There was no difference in antibacterial efficacy between Ch/Ch-NPs-NaOCl (SMD: 0.005; 95% CI: -0.844-0.854; p = 0.990). However, the antibacterial efficacy of NaOCl was statistically more effective than Ch/Ch-NPs (SMD: 0.807; 95% CI: 0.015-1.599; p = 0.046) using the bacterial culture method, and Ch/Ch-NPs was statistically higher than NaOCl (SMD: -1.827; 95% CI: -2.720, -0.934; p < 0.000) using confocal laser scanning microscopy.

CONCLUSIONS

Ch/Ch-NPs may be an alternative to NaOCl against Enterococcus faecalis. The methods used in the in vitro studies evaluating the antibacterial efficacy of irrigation solutions against E. faecalis may have had an impact on the results.

Application of Nanomaterials in Endodontics

Recent advancements in nanotechnology have introduced a myriad of potential applications in dentistry, with nanomaterials playing an increasing role in endodontics. These nanomaterials exhibit distinctive mechanical and chemical properties, rendering them suitable for various dental applications in endodontics, including obturating materials, sealers, retro-filling agents, and root-repair materials. Certain nanomaterials demonstrate versatile functionalities in endodontics, such as antimicrobial properties that bolster the eradication of bacteria within root canals during endodontic procedures. Moreover, they offer promise in drug delivery, facilitating targeted and controlled release of therapeutic agents to enhance tissue regeneration and repair, which can be used for endodontic tissue repair or regeneration. This review outlines the diverse applications of nanomaterials in endodontics, encompassing endodontic medicaments, irrigants, obturating materials, sealers, retro-filling agents, root-repair materials, as well as pulpal repair and regeneration. The integration of nanomaterials into endodontics stands poised to revolutionize treatment methodologies, presenting substantial potential advancements in the field. Our review aims to provide guidance for the effective translation of nanotechnologies into endodontic practice, serving as an invaluable resource for researchers, clinicians, and professionals in the fields of materials science and dentistry.

Effect of final irrigation protocols with chitosan nanoparticle and genipin on dentine against collagenase degradation: An ex-vivo study

AIM

Endodontic irrigants may affect the mechanical and chemical properties of dentine. This study evaluated the effects of various final irrigation protocols including the use of chitosan nanoparticle (CSnp) and cross-linking with genipin on the (1) mechanical and (2) chemical properties of dentine against enzymatic degradation.

METHODOLOGY

CSnp was synthesized and characterized considering physiochemical parameters and stability. The root canals of 90 single-rooted teeth were prepared and irrigated with NaOCl. Dentine discs were obtained and divided into groups according to the following irrigation protocols: Group NaOCl+EDTA, Group NaOCl+CSnp, Group NaOCl+EDTA+CSnp, Group NaOCl+CSnp+Genipin, Group NaOCl+EDTA+CSnp+Genipin and Group distilled water. (1) Mechanical changes were determined by microhardness analysis using Vickers-tester. (2) Chemical changes were determined by evaluating molecular and elemental compositions of dentine using Fourier transform infrared spectroscopy (FTIR) analysis and scanning electron microscope (SEM)/energy dispersive X-ray spectroscopy (EDS) analysis, respectively. All analyses were repeated after the discs were kept in collagenase for 24 h. Data were analysed with repeated measures analysis of variance and Bonferroni correction for microhardness analysis, and Kruskal-Wallis and Wilcoxon tests for FTIR and SEM/EDS analyses (p = .05).

RESULTS

(1) Collagenase application did not have a negative effect on microhardness only in Group NaOCl+EDTA+CSnp+Genipin when compared with the post-irrigation values (p > .05). Post-collagenase microhardness of Group NaOCl+EDTA+CSnp and Group NaOCl+CSnp+Genipin was similar to the initial microhardness (p > .05). (2) After collagenase, Amide III/PO 4 3 - ratio presented no change in Group NaOCl+EDTA+CSnp, Group NaOCl+CSnp+Genipin and Group NaOCl+EDTA+CSnp+Genipin (p > .05), while decreased in other groups (p < .05). Collagenase did not affectCO 3 2 - /PO 4 3 - ratio in the groups (p > .05). There were no changes in the groups in terms of elemental level before and after collagenase application (p > .05).

CONCLUSIONS

CSnp and genipin positively affected the microhardness and molecular composition of dentine. This effect was more pronounced when CSnp was used after EDTA.

The comparative of chitosan and chitosan nanoparticle versus ethylenediaminetetraacetic acid on the smear layer removal: A systematic review and meta-analysis of in vitro study

The purpose of this systematic review of meta-analysis was to compare the effectiveness of removing the smearing layer using EDTA versus Chitosan (Ch) and Chitosan nanoparticles (Ch-NPs). A search was performed in four electronic databases (Web of Science, PubMed, Scopus, and Cochrane). The included studies were assessed by two reviewers using Joanna Briggs Institute's critical appraisal checklist for the quasi-experimental studies. Outcomes obtained by scanning electron microscopy (SEM) and conventional methods were presented as standardized mean differences alongside 95% confidence intervals. Seven investigations employed 212 single-root teeth. In the apical section (p = .317, 95% CI = -0.820 to 0.266, Tau2  = 0.387), middle segment (p = .914, 95% CI = -1.019 to 0.912, Tau2  = 1.027), and coronal segment (p = .277, 95% CI = -1.008 to 0.289, Tau2  = 0.378). This meta-analysis found no difference between Ch, Ch-NPs, and EDTA in removing the smear layer in the three segments. This systematic review is designed to show evidence related to the PICO question, in which our outcome is smear layer removal and not the clinical success of such a treatment. RESEARCH HIGHLIGHTS: The study aimed to compare the effectiveness of chitosan and chitosan nanoparticles with ethylenediaminetetraacetic acid (EDTA) in removing the smear layer, a layer of debris and organic material on the tooth surface, through a systematic review and meta-analysis. The removal of the smear layer is crucial for successful dental treatments, as it enhances the adhesion of restorative materials and improves the penetration of antimicrobial agents into dentinal tubules. The researchers conducted a systematic review and meta-analysis, searching various databases of electron microscopy results for relevant in vitro studies comparing the effects of chitosan or chitosan nanoparticles with EDTA on smear layer removal. The results encourage further exploration of chitosan and chitosan nanoparticles for clinical use in dentistry, while considering their specific applications and long-term effects.

Remineralization of Dentinal Lesions Using Biomimetic Agents: A Systematic Review and Meta-Analysis

The objective of this article was to systematically provide an up-to-date review on the different methods of remineralizing human dentine using different biomimetic agents. The authors performed a systematic search within PubMed, Scopus, and Web of Science in addition to the grey literature in Google Scholar^® using MeSH terms. The PICO question was P: human teeth dentinal sections; I: application of biomimetic remineralizing agents; C: other non-biomimetic approaches; O: extent of remineralization and physical properties of remineralized dentine. The initially identified studies were screened for titles and abstracts. Non-English articles, reviews, animal studies, studies involving the resin-dentine interface, and other irrelevant articles were then excluded. The other remaining full-text articles were retrieved. Bibliographies of the remaining articles were searched for relevant studies that could be included. A total of 4741 articles were found, and finally, 39 full-text articles were incorporated in the current systematic review. From these, twenty-six research studies used non-collagenous protein (NCP) analogs to biomineralize dentine, six studies used bioactive materials derived from natural sources, six studies used zinc hydroxyapatite, and one study used amelogenin peptide to induce hydroxyapatite formation on the surface of demineralized dentine. Additive effects of triclosan and epigenin were assessed when combined with commonly available NCPs. Overall, a moderate risk of bias was observed and, hence, the findings of the included studies could be acceptable. A meta-analysis of some similar studies was performed to assess the depth of remineralization and elastic modulus. Despite having high heterogeneity (I² > 90), all the studies showed a significant improvement in biomimetic remineralization efficacy as compared to the control. All the included studies carried out a functional remineralization assessment and found a 90-98% efficacy in the extent of remineralization while the elastic modulus reached 88.78 ± 8.35 GPa, which is close to natural dentine. It is pertinent to note the limitations of these studies that have been carried out in vitro under controlled settings, which lack the effects of a natural oral environment. To conclude, the authors suggest that the biomimetic remineralization of dentine using NCP analogs, bioactive materials, and natural products carries significant potential in treating dentinal lesions; however, more long-term studies are needed to assess their clinical applications in vivo.

Calcium Phosphates-Chitosan Composite Layers Obtained by Combining Radio-Frequency Magnetron Sputtering and Matrix-Assisted Pulsed Laser Evaporation Techniques

In this work, we report the synthesis of calcium phosphate-chitosan composite layers. Calcium phosphate layers were deposited on titanium substrates by radio-frequency magnetron sputtering technique by varying the substrate temperature from room temperature (25 °C) up to 100 and 300 °C. Further, chitosan was deposited by matrix-assisted pulsed laser evaporation technique on the calcium phosphate layers. The temperature at the substrate during the deposition process of calcium phosphate layers plays an important role in the embedding of chitosan, as scanning electron microscopy analysis showed. The degree of chitosan incorporation into the calcium phosphate layers significantly influence the physico-chemical properties and the adherence strength of the resulted layers to the substrates. For example, the decreases of Ca/P ratio at the addition of chitosan suggests that a calcium deficient hydroxyapatite structure is formed when the CaP layers are generated on Ti substrates kept at room temperature during the deposition process. The Fourier transform infrared spectroscopy analysis of the samples suggest that the PO₄^3-/CO₃^2- substitution is possible. The X-ray diffraction spectra indicated that the crystalline structure of the calcium phosphate layers obtained at the 300 °C substrate temperature is disturbed by the addition of chitosan. The adherence strength of the composite layers to the titanium substrates is diminished after the chitosan deposition. However, no complete exfoliation of the layers was observed.

Longitudinal analyses of composite resin restoration on erosive lesions

Aim: To evaluate the influence of the biomodification of erosive lesions with a chitosan nanoformulation containing green tea (NanoCsQ) on the clinical performance of a composite resin. Methods: The study was performed in a split-mouth, randomized and double-blinded model with 20 patients with 40 erosive lesions. The patient’s teeth were randomized into two groups (n=20) according to the surface treatment: 1) Without biomodification (control), and 2) Biomodification with NanoCsQ solution (experimental). The lesions were restored with adhesive (Tetric N-bond, Ivoclar) and composite resin (IPS Empress Direct, Ivoclar). The restorations were polished and 7 days (baseline), 6 months, and 12 months later were evaluated according to the United States Public Health Service (USPHS) modified criteria, using clinical exam and photographics. Data were analyzed by Friedman’s and Wilcoxon signed-rank tests. Results: No significant differences were found between the control and experimental groups (p=0.423), and also among the follow-up periods (baseline, six months, and 12 months) (p=0.50). Regarding the retention criteria, 90% of the restoration had an alpha score in the control group. Only 10% of the restorations without biomodification (control) had a score charlie at the 12-month follow-up. None of the patients reported post-operatory sensitivity. Conclusion: The NanoCsQ solution did not negatively affect the performance of the composite resin restorations after 12 months.

Effect of 0.2% Chitosan Associated with Different Final Irrigant Protocols on the Fiber Post Bond Strength to Root Canal Dentin of Bovine Teeth: An In-vitro Study

Objective:

This in-vitro study investigated the effect of 0.2% Chitosan associated with different final irrigant protocols on the bond strength of fiber posts (FP) to root canal dentin.

Methods:

Fifty bovine incisors roots were prepared using the ProTaper Universal system, irrigated with 2.5% sodium hypochlorite, and divided into one control group (n=10) with no final irrigant protocol and four experimental groups (n=10), which were defined according to the combination of chelating solution (17% EDTA and 0.2% Chitosan) and irrigant activation/delivery method [conventional irrigation (CI), and passive ultrasonic irrigation (PUI)]. Post spaces were prepared to a depth of 12 mm using #1-5 Largo drills, and the FP were cemented using self-adhesive resin cement. Two slices of 2 mm in thickness from each third were obtained and submitted to the micropush-out test. After testing the push-out strength, the slices were analyzed under a stereomicroscope at 40× magnification for bond failure patterns determination. Statistical analysis was performed using three-way ANOVA followed by Tukey’s test (α = 0.05).

Results:

The control and 17% EDTA + CI groups exhibited significantly lower bond strength than 0.2% Chitosan + CI, 17% EDTA + PUI, and 0.2% Chitosan + PUI groups in the cervical third (P = 0.00). The cervical third had higher values than the middle and apical thirds in control (P = 0.00), 17% EDTA + PUI (P = 0.00), and 0.2% Chitosan + PUI groups (P = 0.00). Adhesive cement-dentin failure type was predominant in all groups.

Conclusion:

The use of 0.2% chitosan did not affect the bond strength of FP to root dentin. Passive ultrasonic activation of chelating solutions resulted in an improvement in bonding strength.

Impact of dentin conditioning and sealer modification with chitosan-hydroxyapatite nanocomplexes on the antibacterial and mechanical characteristics of root dentin

INTRODUCTION

This study aimed to characterize the effectiveness of dentin-conditioning with bio-mineralizable chitosan-hydroxyapatite precursor (CS-HA) nanocomplexes alone or associated with tricalcium silicate sealer (TCS/CS-HA) on the mechanical property and antibiofilm efficacy in root dentin.

METHODS

Flow tests were performed following ISO6876:2012-specifications. Solubility was measured. Micromorphology was assessed using Scanning Electron Microscopy (SEM). Nanohardness/elastic modulus were also determined. Fracture resistance was determined on lower premolars that were prepared, and randomly distributed among 7-groups (n=8/group), including the control, CS-HA dentin-conditioning and root canal filled groups. Similar canal preparation/distribution procedure was followed to test the antibacterial effect on Enterococcus faecalis-infected roots. Descriptive statistic was used to report SEM findings. Flowability results were analyzed using Paired t-test. Multiple comparisons from solubility, fracture and antibacterial assays were assessed by one-way ANOVA-Tukey's tests.

RESULTS

TCS/CS-HA showed optimal flow and no effect on solubility after immersion for 4 weeks (p>.05). TCS/CS-HA significantly increased nanohardness and elastic modulus (210±11.3MPa, 7.9±0.9GPa) compared to TCS (44.5±7.8MPa, 2.1±0.3GPa,p<.05). SEM revealed needle-shaped mineralized structures resulting in fewer voids and a well-adapted sealer-dentin interface in the TCS/CS-HA groups. NaOCl-EDTA irrigation resulted in reduced fracture resistance (444.34N) while CS-HA dentin-conditioning alone (928.28N, p<.05) and CS-HA dentin-conditioning plus CS-HA/TCS resulted in higher fracture resistance (1134.06N, p<.05). CS-HA dentin-conditioning also reduced bacteria by 2.04 log (4.50±0.43) from the initial bacterial load (6.54±0.07, p<.05). There was further bacterial reduction when CS-HA-conditioned root canals were filled with TCS or TCS/CS-HA (0.00 to 0.98±0.57, p>.05).

CONCLUSION

Dentin modification with CS-HA increased the fracture resistance of root dentin, and decreased the residual bacterial burden. TCS/CS-HA potentiated the nanomechanical and physical properties of TCS.

Procyanidins and Their Therapeutic Potential against Oral Diseases

Procyanidins, as a kind of dietary flavonoid, have excellent pharmacological properties, such as antioxidant, antibacterial, anti-inflammatory and anti-tumor properties, and so they can be used to treat various diseases, including Alzheimer’s disease, diabetes, rheumatoid arthritis, tumors, and obesity. Given the low bioavailability of procyanidins, great efforts have been made in drug delivery systems to address their limited use. Nowadays, the heavy burden of oral diseases such as dental caries, periodontitis, endodontic infections, etc., and their consequences on the patients’ quality of life indicate a strong need for developing effective therapies. Recent years, plenty of efforts are being made to develop more effective treatments. Therefore, this review summarized the latest researches on versatile effects and enhanced bioavailability of procyanidins resulting from innovative drug delivery systems, particularly focused on its potential against oral diseases.

Zn-containing Adhesives Facilitate Collagen Protection and Remineralization at the Resin-Dentin Interface: A Narrative Review

This is a narrative review of the literature assessing the potential effectiveness of doping dentin polymeric adhesives with zinc compounds in order to improve bonding efficacy, remineralization and protection against degradation. A literature search was conducted using electronic databases, such as PubMed, MEDLINE, DIMDI and Web of Science. Through our search, we found literature demonstrating that Zn-doped dentin adhesives promote protection and remineralization of the resin-dentin interfaces. The increased bioactivity has also facilitated dentinal tubules' occlusion by crystals' precipitation contributing to improved sealing efficacy of restorations. Loading dentin adhesives with zinc gives rise to an increase of both crystallinity of mineral and crosslinking of collagen. The main role of zinc, in dentin adhesives, is to inhibit collagen proteolysis. We concluded that zinc exerts a protective effect through binding at the collagen-sensitive cleavage sites of matrix-metalloproteinases (MMPs), contributing to dentin matrix stabilization. Zinc may not only act as a MMPs inhibitor, but also influence signaling pathways and stimulate metabolic effects in dentin mineralization and remineralization processes. Zn-doped adhesives increase the longevity of dentin bonding through MMPs inhibition. Zn poses a remineralization strategy in demineralized dentin.

Role of Chitosan in Remineralization of Enamel and Dentin: A Systematic Review

Aim and objective

The purpose of this research was to analyze the role of chitosan in the remineralization of enamel and dentin.

Materials and methods

An electronic search was done for articles published from January 2009 to January 2020. A manual search was done from bibliographies of selected articles for relevant articles that were unexplored. Only in vitro studies conducted on the application of chitosan for remineralization of enamel and dentin were included in the study.

Results

Of the 162 articles that were searched, only 15 in vitro studies were selected for the study. These studies met the inclusion criteria and were published from January 2009 to January 2020.

Conclusion

The review provides insight into the mechanism of remineralization of enamel and dentin. The properties of chitosan make it an ideal biomaterial that can be employed in the formulation of a novel remineralizing gel. However, more in vivo studies, clinical trials, and research are essential to transform chitosan-based remineralizing gels from research to clinical use.

Clinical significance

This review article opens a new window of opportunities for remineralizing enamel and dentin which have been long considered a challenging job.

How to cite this article

Nimbeni SB, Nimbeni BS, Divakar DD. Role of Chitosan in Remineralization of Enamel and Dentin: A Systematic Review. Int J Clin Pediatr Dent 2021;14(4):562–568.

Effect of TiF4/NaF and chitosan solutions on biofilm formation and prevention of dentin demineralization

OBJECTIVE

This study evaluated the effect of experimental solutions containing TiF₄/NaF and chitosan on bacterial species of microcosm biofilm and on dentin demineralization.

DESIGN

Microcosm biofilm was produced from human saliva mixed with McBain medium (0.2% sucrose) on bovine dentin for 5 days, under 5% CO₂ and 37 °C. From the 2nd day to 5th day, the treatments were applied (1×60s/day) as following: (1) NaF (500 ppm F^-, positive control); (2) TiF₄ and NaF (TiF₄: 190 ppm Ti⁴⁺ and 300 ppm F^-; NaF: 190 ppm F^-); (3) similar to 2 plus 0.5% chitosan (Ch 500 mPa.s, 75% deacetylation); (4) phosphate buffer solution (negative control); and (5) 0.5% chitosan (Ch 500 mPa.s, 75% deacetylation). CFU counting was performed for total microorganism, total streptococci, total lactobacilli and mutans streptococci. Dentin demineralization was measured by transverse microradiography-TMR. The data were compared using ANOVA/Tukey or Kruskal-Wallis/Dunn tests (p < 0.05).

RESULTS

No differences were found between the treatments with respect to CFU counting (p > 0.05). Dentin treated with TiF₄/NaF plus chitosan solution presented the lowest demineralization compared to the negative control and pure chitosan solution. On the other hand, this experimental solution did not significantly differ from TiF₄/NaF solution, being both able to significantly reduce mineral loss.

CONCLUSION

TiF₄/NaF plus chitosan solution, at suitable pH to be clinically applicable, had no antimicrobial effect, but it was able to reduce dentin caries development under this model.

Influence of nanoparticulated chitosan on the biomodification of eroded dentin: clinical and photographic longitudinal analysis of restorations

To evaluate the influence of the pre-treatment with 2.5% nanoparticulate chitosan (2.5% NanoChi) solution on eroded dentin before the restorative dental treatment. The sample consisted of 22 patients (age between 33 and 52 years) with shallow or medium erosion lesions located in two homologous teeth. The teeth were randomly assigned according to dentin treatment: with 2.5% NanoChi and without with chitosan (control). The NanoChi were applied immediately after acid etching. The teeth were restored with Single Bond Universal (3 M) and Charisma resin (Kulzer). Analyzes were done using modified USPHS (retention, secondary caries, marginal adaptation, and sensitivity) and photographic (color, marginal pigmentation, and anatomical form) criteria at 7 days (baseline) and 1 year. Population demographics, Kaplan-Meier estimates and log-rank test (Mantel-Cox) were calculated for 1 year (α = 0.05). No significant difference was found in the survival rates between groups (p > 0.05) at 7 days and 1 year after treatment. After 7 days, 100% of the restorations were scored as Alpha on all criteria. After 1 year, 91% of the NanoChi restorations were scored as Alpha and 9% as Charlie for the retention, marginal adaptation, and anatomical form criteria, while 86% of the control restorations (without NanoChi) received the Alpha score and 14% received the Charlie. Secondary caries, sensitivity, color, and marginal pigmentation criteria were scored as Alpha in 100% of the restorations. The biomodification of eroded dentin with 2.5% NanoChi did not influence the survival of the restorations after 1 year. The application of 2.5% NanoChi on eroded dentin did not increase failures of resin restorations after 1 year and it can be used as a pre-treatment solution.

Effect of chitosan solutions with or without fluoride on the protection against dentin erosion in vitro

The aim of this study was to assess the protective effect of experimental solutions containing chitosan at different viscosities with or without fluoride (TiF₄ /NaF) on dentin loss in vitro. Bovine dentin samples (n = 15) were prepared and allocated to one of the following treatments: (i) 0.5% chitosan (500 mPas); (ii) 0.5% chitosan (2,000 mPas); (iii) 0.042% NaF and 0.049% TiF₄ ; (iv) as (iii) with addition of 0.5% chitosan (500 mPas); (v) as (iii) with addition of 0.5% chitosan (2,000 mPas); (vi) commercial solution with SnCl₂ /AmF/NaF (positive control); or (vii) deionized water (negative control). The samples were submitted to pH cycling for 7 d (0.1% citric acid, 4 × 90 s d^-1 ). The treatment was applied once a day for 30 s. The dentin loss was quantified using a contact profilometer. Three samples per group were evaluated using scanning electron microscopy. The dentin loss (μm) was submitted to anova and Tukey's test for differences between treatments. Among the treatments tested, only chitosan 500 mPas was able to statistically significantly reduce the dentin loss compared to the negative control, being similar to the positive control. TiF₄ /NaF, whether with or without chitosan, had no protective effect. Chitosan 500 mPas and SnCl₂ /AmF/NaF solutions have comparable protective effect against dentin erosion in vitro.

Drug delivery based pharmacological enhancement and current insights of quercetin with therapeutic potential against oral diseases

The heavy burden of oral diseases such as oral cancers, dental caries, periodontitis, etc. and their consequence on the patient's quality of life demonstrated an urgent demand for developing effective therapeutics. Quercetin as a natural derived flavonoid, could be utilized in the therapeutic formulation of various diseases such as diabetes, breast cancer and asthma, owing to its prominent pharmacological values. In the last decade, the applications of quercetin as a natural compound in oral treatment have attracted increasing interest due to its multifunction including antioxidant, antibacterial, anti-inflammatory and antineoplastic activities. Besides, considering the low bioavailability of quercetin, great efforts have been made in its drug delivery systems to address the problem of limited application. Therefore, this review summarized the cutting-edge researches on versatile effects and enhanced bioavailability of quercetin resulting from innovative drug delivery systems, particularly focused on its potential against oral diseases. The application of quercetin would provide novel and promising therapeutic approach for clinical treatment, promoting the development of global dental public health.

An in vitro study on dentin demineralization and remineralization: Collagen rearrangements and influence on the enucleated phase

Dentin remineralization is of clinical relevance in the therapy of caries and dentin hypersensitivity. This study is aimed at gaining more insights on a molecular scale, through IR spectroscopy, into dentin demineralization and remineralization. The dentin demineralization by ethylenediaminetetraacetic acid, EDTA (17%, 2 h) significantly altered the secondary structure distribution of collagen, upon loss of interaction with calcium ions. To investigate dentin remineralization, previously demineralized human dentin slices were soaked in Dulbecco's Phosphate Buffered Saline (DPBS) or Hank's Balanced Salt Solution HBSS, in close contact with three commercial cements used as sustained releasing sources of Ca²⁺ and OH^- ions (i.e. calcium hydroxide- and calcium silicate-based cements). IR spectroscopy showed the occurrence of remineralization under these conditions. Collagen did not lose its ability to chelate Ca²⁺, and these interactions allowed collagen to rearrange into a conformation similar to that of sound dentin. This process appeared slower in HBSS than DPBS, as also shown by the lower degree of maturation of the inorganic phase enucleated in the former medium (amorphous calcium phosphate versus B-type carbonated apatite). Collagen appeared to act as a spatial constraint to crystal deposition, affecting crystallinity and carbonate content of the enucleated phase. Remineralization was found to strongly depend on the calcium releasing ability of the cements. The fast formation of a rough apatite biocoating may represent a favorable clinical condition in the context of mineralized tissue regeneration.

Effect of Er:YAG laser irradiation and chitosan biomodification on the stability of resin/demineralized bovine dentin bond

OBJECTIVE

The purpose of this study was to evaluate the effect of Er:YAG laser for selective removal of carious lesion, followed by biomodification with chitosan on the microtensile bond strength (µTBS), adhesive interface, dry mass loss and hydroxyproline release (HYP).

METHODS

Artificial lesions were created in 104 bovine dentin blocks. Blocks were divided according to caries removal method: bur or Er:YAG laser. Seventy-six blocks were acid etched and subdivided according to dentin biomodification: no chitosan and 2.5% chitosan. Composite resin restorations were performed. Blocks were sectioned into beams and stored in water. After 24 h, 6 and 12 months, beams were submitted to μTBS test (n = 10) and analysis of adhesive interface by SEM (n = 3). The other 28 blocks were sectioned into beams and initial dry mass (DM) was determined (n = 7). Beams were stored and after 7 days, DM was redetermined. HYP release (n = 7) was evaluated by ELISA. Data were analyzed by ANOVA and Bonferroni's tests (α = 0.05).

RESULTS

After 24 h, the highest µTBS was found for bur (p < 0.001). After 6 months, methods were similar (p = 0.432). After 12 months, laser-irradiated dentin showed the highest µTBS values (p = 0.025). Chitosan promoted higher µTBS values after 6 (p = 0.011) and 12 months (p < 0.001) preserving adhesive interface. Dry mass loss and HYP release were not influenced (p > 0.05) by caries removal method or by dentin biomodification.

CONCLUSION

The bond strength to demineralized dentin reduced over 50% in all groups after water storage. From 6 months of water storage, Er:YAG laser irradiation and biomodification with chitosan maintained the stability of the resin-dentin bonds, but did not influence dry mass loss and HYP release.

Synergistic Effect of Newly Introduced Root Canal Medicaments; Ozonated Olive Oil and Chitosan Nanoparticles, Against Persistent Endodontic Pathogens

This study was conducted to investigate the antimicrobial-biofilm activity of chitosan (Ch-NPs), silver nanoparticles (Ag-NPs), ozonated olive oil (O3-oil) either separately or combined together against endodontic pathogens. While testing the antimicrobial activity, Ch-NPs showed the least minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) values exerting eightfold higher bactericidal activity than O3-oil against both Enterococcus faecalis and Streptococcus mutans as well as fourfold higher fungicidal activity against Candida albicans. Antimicrobial synergy test revealed synergism between O3-oil and Ch-NPs against the test pathogens (FIC index ≤ 0.5). Ch-NPs was superior at inhibiting immature single and mixed-species biofilm formations by 97 and 94%, respectively. Both of O3-oil and Ch-NPs had a complete anti-fibroblast adherent effect. The safety pattern results showed that O3-oil was the safest compound, followed by Ch-NPs. The double combination of Ch-NPs and O3-oil reduced the mature viable biofilm on premolars ex vivo model by 6-log reductions, with a fast kill rate, indicating potential use in treating root canals. Therefore, the double combination has the potential to eradicate mature mixed-species biofilms and hence it is potent, novel and safe.

Effect of Phosphorylated Chitosan on Dentin Erosion: An in vitro Study

The aim of this study was to evaluate the antierosive effect of phosphorylated chitosan in dentin. Bovine dentin specimens were randomly distributed into the following groups: (1) no treatment (NoTx/negative control), (2) phosphate-buffered saline solution (PBS), (3) AmF/NaF/SnCl2 (positive control), (4) 0.5% chitosan solution (Chi), (5) 0.5% neutral phosphorylated (NP)-Chi, and (6) 0.5% alkaline phosphorylated (AP)-Chi. The specimens were submitted to de-remineralization treatment cycles for 5 days: 0.5% citric acid (2 min), remineralizing solution (30 min), and surface treatment according to assigned groups (2 min, 6×/day). The loss of dentin surface was measured by profilometry. Hardness and modulus of elasticity were measured using a nanoindenter equipped with a Berkovich diamond tip. The dentin surface was analyzed by scanning electron microscopy (SEM). The largest loss of dentin was observed in the No Tx and PBS groups (approx. 25 µm). The group treated with AmF/NaF/SnCl2 showed less loss of dentin (67% reduction vs. NoTx and PBS), followed by the groups treated with NP-Chi and AP-Chi (33% reduction), and Chi (18% reduction). Nanohardness and modulus of elasticity were similar in the NoTx and PBS groups, with a small increase in stiffness in all other groups. SEM revealed that the experimental solution of AP-Chi had a favorable effect on maintaining the integrity of collagen fibrils. AmF/NaF/SnCl2 showed a preserved mineralized collagen surface. Further studies are warranted to explore this nontoxic phosphorylated chitosan polymer as an effective agent in the prevention and treatment of dental erosion.

Remineralization Potential of Mints Containing Bioactive Agents in Artificially Induced Root Caries

This study investigated the remineralization effect of experimental mint formulations containing bioactive agents (xylitol; green tea extract, GT; and amorphous calcium phosphate, ACP) in the progression of artificially induced root caries. Root caries lesions were induced by demineralization solution (pH 4.6; 96 h; 37°C). The lesions were treated with mint A, mint B, mint C, xylitol, GT, ACP, or remineralization solution (RS; negative control). Specimens were pH-cycled through treatments (5×/day; 3 min) and 6 cycles of acidic (pH 5.0; 30 min) and neutral (pH 7.0; 10 min) buffers for 8 days. Bacterial collagenase (Clostridium histolyticum) was used overnight to simulate proteolytic challenge. Caries depth and porosity as well as mineral density were estimated using fluorescence microscopy (n = 15) and microcomputed tomography (n = 6). Analysis of variance (ANOVA, α = 0.05) showed no statistically significant difference in caries depth among all groups (p = 0.172). The highest fluorescence intensity decrease was observed for GT followed by mint C, with no significant difference between them (p = 0.868). There were significant differences among GT and mints A, B, and C when compared to RS (p < 0.001). No statistically significant differences in fluorescence intensity were observed among ACP, xylitol, and RS (p > 0.05). The mineral density of the lesions in GT, mints A, B, and C, and ACP was statistically similar (p > 0.05) and significantly higher than that in RS (p < 0.05). No significant difference was observed between xylitol and RS (p = 0.728). The experimental mints showed remineralization action on artificial root caries, and GT was found to be the main active ingredient in the investigated formulations.

Selective removal of carious lesion with Er:YAG laser followed by dentin biomodification with chitosan

The aim of this study was to evaluate the effect of Er:YAG laser for selective removal of carious lesion, followed by biomodification with chitosan gel where the subsurface microhardness, chemical composition, and morphological changes of the residual caries-affected dentin were examined. Artificial dentinal lesions were created by pH-cycling method (14 days) in 104 bovine specimens (5 × 5 mm). Specimens were randomly divided according to the carious removal method: bur (low-speed handpiece) or Er:YAG laser (250 mJ/4 Hz). Specimens were treated with 35% phosphoric acid and were subdivided into two groups according to dentin biomodification: without chitosan (control) and 2.5% chitosan. Forty specimens were restored with an adhesive system and composite resin. Subsurface microhardness tests were performed in sound dentin, caries-affected dentin, residual caries-affected dentin, and after the restoration. The other 64 specimens were subjected to SEM-EDS atomic analysis. Data were statistically analyzed (p < 0.05). After the Er:YAG laser excavation, the microhardness value of residual caries-affected dentin was higher (p < 0.05) than bur-treated dentin. A significant decrease in the amount of Ca, P, and Ca/P ratio was found after the removal of carious lesions with Er:YAG laser (p < 0.05). The biomodification with chitosan did not influence the microhardness and atomic percentage of Ca, P, and Ca/P ratio of residual caries-affected dentin (p > 0.05). SEM analysis showed morphological changes on residual caries-affected dentin (p > 0.05). The selective removal of carious dentin with Er:YAG laser increased microhardness of residual caries-affected dentin, changing its surface morphology and chemical composition. The biomodification with chitosan did not influence the structural and chemical composition of residual caries-affected dentin.

Assessment of the Amount of Calcium Ions Released after the use of Different Chelating Agents and Agitation Protocols

Background:

The main goal of endodontic treatment is to achieve cleaning and shaping prior to the filling process.

Objective:

This study aimed to evaluate, using atomic absorption spectrometry, the release of Calcium ions after the use of different chelating agents and protocols of agitation.

Method:

Ninety human canine teeth were randomly assigned to one of nine groups (n=10), as follows: 1) 0.2% Chitosan and manual agitation; 2) 0.2% Chitosan and sonic agitation; 3) 0.2% Chitosan and ultrasonic agitation; 4) 17% EDTA and manual agitation; 5) 17% EDTA and sonic agitation; 6) 17% EDTA and ultrasonic agitation; 7) distilled water and manual agitation; 8) distilled water and sonic agitation; 9) distilled water and ultrasonic agitation. Following instrumentation, all chelating substances remained inside the root canal for 3 min. Then the fluid was collected for the identification and quantification of Calcium ions. The amount of Calcium ions released in each group was compared using analysis of variance (ANOVA) and the Kolmogorov-Smirnov and Levene tests followed by Tukey’s post-hoc test. Significance was set at 5%.

Results:

The groups in which 0.2% Chitosan was used showed the highest concentration of Calcium ions (p<0.05). Concerning the agitation method, ultrasonic agitation showed the greatest values, followed by sonic and manual agitation (all comparisons, p<0.05).

Conclusion:

The present findings suggest that, among the combinations here tested, Chitosan associated with ultrasonic agitation yielded the greatest release of Calcium ions.

From molecules to macrostructures: recent development of bioinspired hard tissue repair

This review summarizes the bioinspired strategies for hard tissue repair, ranging from molecule-induced mineralization, to microscale assembly to macroscaffold fabrication.

Wettability and surface morphology of eroded dentin treated with chitosan

OBJECTIVE

To assess the effect of chitosan, at concentrations of 2.5% and 5.0%, on the wettability of the eroded dentin, followed by analysis of surface morphology by SEM.

METHODS

104 bovine dentin slabs were ground, polished and then immersed in 20mL of citric acid (pH=3.2) under continuous stirring for 2h. Specimens were randomly divided according to the dentin substrate: sound and eroded, and then, subdivided into 4 groups (n=10): without rewetting (control), 1% acetic acid, 2.5% chitosan and 5.0% chitosan. Then, a drop of the adhesive system Single Bond 2 (3M) was deposited onto surface of each specimen. The contact angle between dentin surface and the adhesive system was measured by using a goniometer. The other 24 specimens were subjected to analysis under SEM. Statistical analysis was performed using the normality test (Kolmogorov-Smirnov) and Analysis of Variance (ANOVA) (p>0.05).

RESULTS

No differences were found between the angles produced on the eroded dentin rewetting with chitosan at the concentrations of 2.5% and 5%.

CONCLUSION

The chitosan, regardless of the concentration used, did not influence the eroded dentin wettability. Through SEM analysis, it was found particles of chitosan deposited on the surface and within the dentinal tubules.

Cellular behavior of L929 and MG-63 cells cultured on electrospun nanofibers of chitosan with different degrees of phosphorylation

Phosphate groups chemically grafted onto polymer substrates can be used as biomimetic analogs for in vitro studying of function of biomacromolecules and also as tissue substitutes in clinical conditions of organ loss. Despite this inspiration, studies correlating effect of degree of phosphate grafting of a polymer on fabrication and biological properties of polymers are lacking. In this work, N-methylene phosphonic chitosan (PC) with different degrees of phosphate contents were synthesized and the effect of phosphate grafting on electrospinning behavior of substituted polymers is investigated. In PC, higher phosphate content widened concentration range for nanofiber formation. Balance between conductivity and viscosity of solutions played a determinant role in the success of electrospinning process. Culture of L929 cells showed grafting-dependent increase in cell proliferation. On the other hand, culture of MG-63 cells showed a positive correlation between grafting degree and Alkaline Phosphatase (ALP) expression. It is concluded that improvement of cell response parameters of nanofiber scaffolds can be attained as a function of controlled degree of phosphate grafting in polymeric biomaterials with implications for bone tissue engineering applications. Such studies may also be useful to develop quantitative structure activity relationships of functional polymers.

Calcifying tissue regeneration via biomimetic materials chemistry

Materials chemistry is making a fundamental impact in regenerative sciences providing many platforms for tissue development. However, there is a surprising paucity of replacements that accurately mimic the structure and function of the structural fabric of tissues or promote faithful tissue reconstruction. Methodologies in biomimetic materials chemistry have shown promise in replicating morphologies, architectures and functional building blocks of acellular mineralized tissues dentine, enamel and bone or that can be used to fully regenerate them with integrated cell populations. Biomimetic materials chemistry encompasses the two processes of crystal formation and mineralization of crystals into inorganic formations on organic templates. This review will revisit the successes of biomimetics materials chemistry in regenerative medicine, including coccolithophore simulants able to promote in vivo bone formation. In-depth knowledge of biomineralization throughout evolution informs the biomimetic materials chemist of the most effective techniques for regenerative framework construction exemplified via exploitation of liquid crystals (LCs) and complex self-organizing media. Therefore, a new innovative direction would be to create chemical environments that perform reaction-diffusion exchanges as the basis for building complex biomimetic inorganic structures. This has evolved widely in biology, as have LCs, serving as self-organizing templates in pattern formation of structural biomaterials. For instance, a study is highlighted in which artificially fabricated chiral LCs, made from bacteriophages are transformed into a faithful copy of enamel. While chemical-based strategies are highly promising at creating new biomimetic structures there are limits to the degree of complexity that can be generated. Thus, there may be good reason to implement living or artificial cells in 'morphosynthesis' of complex inorganic constructs. In the future, cellular construction is probably key to instruct building of ultimate biomimetic hierarchies with a totality of functions.

Antibacterial Properties Associated with Chitosan Nanoparticle Treatment on Root Dentin and 2 Types of Endodontic Sealers

INTRODUCTION

The aim of this study was to evaluate the efficacy of carboxymethyl chitosan (CMCS) and chitosan nanoparticles (CNps) to inactivate bacteria and prevent biofilm formation at sealer-dentin interfaces.

METHODS

The study was divided into 3 stages: first stage, the experiment was conducted to analyze the antibacterial properties of CMCS in different formulations against biofilms; second stage, direct-contact and membrane-restricted methods were used to evaluate the antibacterial properties of an epoxy resin (ThermaSeal Plus; Dentsply Tulsa Dental, Tulsa, OK) and calcium silicate (MTA Fillapex; Angelus SA, Londrina, PR, Brazil) based-sealers with or without CNps; and third stage, biofilm formation at the sealer dentin interfaces of root dentin treated with CMCS and filled with gutta-percha and CNp incorporated sealer were analyzed after 1- and 4-week aging periods. The samples were treated and filled as follows: (1) distilled water: unaltered sealer (control group), (2) CMCS: sealer+CNps (CMCS group), and (3) CMCS/rose bengal: sealer+CNps (CMCS/RB group). Enterococcus faecalis was used to infect all the samples. Microbiological and microscopic analyses were used to assess the antibacterial characteristics.

RESULTS

CMCS-based treatments effectively killed bacteria adherent on root dentin (P < .05). The addition of CNps to ThermaSeal enhanced its antibacterial ability by direct-contact and membrane-restricted tests (P < .05). The CNp incorporation significantly increased the antibacterial efficacy of root canal sealers even after a 4-week aging time (P < .05).

CONCLUSIONS

This study highlighted the ability of CMCS to disinfect root canal dentin and inhibit bacterial adhesion. CNps in root canal sealers are capable of maintaining their antibacterial activity even after prolonged aging.

Use of poly (amidoamine) dendrimer for dentinal tubule occlusion: a preliminary study

The occlusion of dentinal tubules is an effective method to alleviate the symptoms caused by dentin hypersensitivity, a significant health problem in dentistry and daily life. The in situ mineralization within dentinal tubules is a promising treatment for dentin hypersensitivity as it induces the formation of mineral on the sensitive regions and occludes the dentinal tubules. This study was carried out to evaluate the in vitro effect of a whole generation poly(amidoamine) (PAMAM) dendrimer (G3.0) on dentinal tubule occlusion by inducing mineralization within dentinal tubules. Dentin discs were treated with PAMAM dendrimers using two methods, followed by the in vitro characterization using Attenuated total reflection Fourier-transform infrared spectroscopy (ATR-FTIR), X-ray diffraction (XRD), Field emission scanning electron microscopy (FE-SEM) and Energy-Dispersive X-ray Spectroscopy (EDS). These results showed that G3.0 PAMAM dendrimers coated on dentin surface and infiltrated in dentinal tubules could induce hydroxyapatite formation and resulted in effective dentinal tubule occlusion. Moreover, crosslinked PAMAM dendrimers could induce the remineralization of demineralized dentin and thus had the potential in dentinal tubule occlusion. In this in vitro study, dentinal tubules occlusion could be achieved by using PAMAM dendrimers. This could lead to the development of a new therapeutic technique for the treatment of dentin hypersensitivity.

Chelating and antibacterial properties of chitosan nanoparticles on dentin

Objectives

The use of chitosan nanoparticles (CNPs) in endodontics is of interest due to their antibiofilm properties. This study was to investigate the ability of bioactive CNPs to remove the smear layer and inhibit bacterial recolonization on dentin.

Materials and Methods

One hundred bovine dentin sections were divided into five groups (n = 20 per group) according to the treatment. The irrigating solutions used were 2.5% sodium hypochlorite (NaOCl) for 20 min, 17% ethylenediaminetetraacetic acid (EDTA) for 3 min and 1.29 mg/mL CNPs for 3 min. The samples were irrigated with either distilled water (control), NaOCl, NaOCl-EDTA, NaOCl-EDTA-CNPs or NaOCl-CNPs. After the treatment, half of the samples (n = 50) were used to assess the chelating effect of the solutions using portable scanning electronic microscopy, while the other half (n = 50) were infected intra-orally to examine the post-treatment bacterial biofilm forming capacity. The biovolume and cellular viability of the biofilms were analysed under confocal laser scanning microscopy. The Kappa test was performed for examiner calibration, and the non-parametric Kruskal-Wallis and Dunn tests (p < 0.05) were used for comparisons among the groups.

Results

The smear layer was significantly reduced in all of the groups except the control and NaOCl groups (p < 0.05). The CNPs-treated samples were able to resist biofilm formation significantly better than other treatment groups (p < 0.05).

Conclusions

CNPs could be used as a final irrigant during root canal treatment with the dual benefit of removing the smear layer and inhibiting bacterial recolonization on root dentin.

Methods for biomimetic remineralization of human dentine: a systematic review

This study aimed to review the laboratory methods on biomimetic remineralization of demineralized human dentine. A systematic search of the publications in the PubMed, TRIP, and Web of Science databases was performed. Titles and abstracts of initially identified publications were screened. Clinical trials, reviews, non-English articles, resin-dentine interface studies, hybrid layer studies, hybrid scaffolds studies, and irrelevant studies were excluded. The remaining papers were retrieved with full texts. Manual screening was conducted on the bibliographies of remaining papers to identify relevant articles. A total of 716 studies were found, and 690 were excluded after initial screening. Two articles were identified from the bibliographies of the remaining papers. After retrieving the full text, 23 were included in this systematic review. Sixteen studies used analogues to mimic the functions of non-collagenous proteins in biomineralization of dentine, and four studies used bioactive materials to induce apatite formation on demineralized dentine surface. One study used zinc as a bioactive element, one study used polydopamine, and another study constructed an agarose hydrogel system for biomimetic mineralization of dentine. Many studies reported success in biomimetic mineralization of dentine, including the use of non-collagenous protein analogues, bioactive materials, or elements and agarose hydrogel system.

Biomimetic remineralization of demineralized dentine using scaffold of CMC/ACP nanocomplexes in an in vitro tooth model of deep caries

Currently, it is still a tough task for dentists to remineralize dentine in deep caries. The aim of this study was to remineralize demineralized dentine in a tooth model of deep caries using nanocomplexes of carboxymethyl chitosan/amorphous calcium phosphate (CMC/ACP) based on mimicking the stabilizing effect of dentine matrix protein 1 (DMP1) on ACP in the biomineralization of dentine. The experimental results indicate that CMC can stabilize ACP to form nanocomplexes of CMC/ACP, which is able to be processed into scaffolds by lyophilization. In the single-layer collagen model, ACP nanoparticles are released from scaffolds of CMC/ACP nanocomplexes dissolved and then infiltrate into collagen fibrils via the gap zones (40 nm) to accomplish intrafibrillar mineralization of collagen. With this method, the completely demineralized dentine was partially remineralized in the tooth mode. This is a bottom-up remineralizing strategy based on non-classical crystallization theory. Since nanocomplexes of CMC/ACP show a promising effect of remineralization on demineralized dentine via biomimetic strategy, thereby preserving dentinal tissue to the maximum extent possible, it would be a potential indirect pulp capping (IPC) material for the management of deep caries during vital pulp therapy based on the concept of minimally invasive dentistry (MID).

Use of multifunctional phosphorylated PAMAM dendrimers for dentin biomimetic remineralization and dentinal tubule occlusion

Phosphorylated poly(amidoamine) dendrimers can induce biomimetic remineralization of demineralized dentin as analogs of non-collagenous proteins in the presence of polyacrylic acid, an amorphous calcium phosphate stabilizing agent.

Effect of in vitro chewing and bruxism events on remineralization, at the resin-dentin interface

The purpose of this study was to evaluate if different in vitro functional and parafunctional habits promote mineralization at the resin-dentin interface after bonding with three different adhesive approaches. Dentin surfaces were subjected to distinct treatments: demineralization by (1) 37% phosphoric acid (PA) followed by application of an etch-and-rinse dentin adhesive, Single Bond (SB) (PA+SB); (2) 0.5 M ethylenediaminetetraacetic acid (EDTA) followed by SB (EDTA+SB); (3) application of a self-etch dentin adhesive, Clearfil SE Bond (SEB). Different loading waveforms were applied: No cycling (I), cycled in sine (II) or square (III) waves, sustained loading hold for 24 h (IV) or sustained loading hold for 72 h (V). Remineralization at the bonded interfaces was assessed by AFM imaging/nano-indentation, Raman spectroscopy and Masson's trichrome staining. In general, in vitro chewing and parafunctional habits, promoted an increase of nano-mechanical properties at the resin-dentin interface. Raman spectroscopy through cluster analysis demonstrated an augmentation of the mineral-matrix ratio in loaded specimens. Trichrome staining reflected a narrow demineralized dentin matrix after loading in all groups except in PA+SB and EDTA+SB samples after sustained loading hold for 72 h, which exhibited a strong degree of mineralization. In vitro mechanical loading, produced during chewing and bruxism (square or hold 24 and 72 h waveforms), induced remineralization at the resin-dentin bonded interface.

Surface microanalysis and chemical imaging of early dentin remineralization

This study reports physical and chemical changes that occur at early dentin remineralization stages. Extracted human third molars were sectioned to obtain dentin discs. After polishing the dentin surfaces, three groups were established: (1) untreated dentin (UD), (2) 37% phosphoric acid application for 15 s (partially demineralized dentin-PDD), and (3) 10% phosphoric acid for 12 h at 25° C (totally demineralized dentin-TDD). Five different remineralizing solutions were used: chlorhexidine (CHX), artificial saliva (AS), phosphate solution (PS), ZnCl2, and ZnO. Wettability (contact angle), ζ potential and Raman spectroscopy analysis were determined on dentin surfaces. Demineralization of dentin resulted in a higher contact angle. Wettability decreased after immersion in all solutions. ζ potential analysis showed dissimilar performance ranging from -6.21 mV (TDD + AS) up to 3.02 mV (PDD + PS). Raman analysis showed an increase in mineral components after immersing the dentin specimens, in terms of crystallinity, mineral content, and concentration. This confirmed the optimal incorporation and deposition of mineral on dentin collagen. Organic content reflected scarce changes, except in TDD that appeared partially denatured. Pyridinium, as an expression of cross-linking, appeared in all spectra except in specimens immersed in PS.

A Zn-doped etch-and-rinse adhesive may improve the mechanical properties and the integrity at the bonded-dentin interface

OBJECTIVE

The objective of the study was to determine if zinc-doped etch-and-rinse dentin adhesive may induce therapeutic effects within the resin-dentin interface.

METHODS

Human acid-etched dentin was infiltrated with Adper™ Single Bond Plus (SB, 3M ESPE, St. Paul, MN, USA), SB doped with 10wt.% ZnO nanoparticles (ZnO-SB) or SB doped with 2wt.% ZnCl2 (ZnCl2-SB). AFM/nanoindentation analysis was performed on fully hydrated specimens to evaluate the nanomechanical properties (Hi: hardness; Ei: modulus of elasticity) across the resin-dentin interface after different SBF storage periods (24h, 1m, 3m). Confocal laser microscopy (CLSM) was used to evaluate the ultramorphology and micropermeability at 24h and 3m of SBF storage.

RESULTS

SB control specimens exhibited a decrease in Hi in the hybrid layer (HL) and bottom of the hybrid layer (BHL) and a decrease in Ei in the HL after 3m of SBF storage, indicating that severe degradation occurred in the control interface. ZnO-SB bonded specimens preserved the initial Hi and Ei at the HL and BHL subsequent SBF storage; ZnCl2-SB bonded specimens showed a decrease in Ei, in the HL over time. CLSM analysis confirmed that both Zn-doped adhesives were able to preserve the integrity of the HL.

SIGNIFICANCE

Specific formulation of Zn-doped etch-and-rinse adhesives may offer the possibility to maintain the nano-mechanical properties along the dentin-bonded interface by inhibiting dentin MMPs and by protective mineral crystals formation within the resin-dentin interface. Clinical advantages may be expected by preserving and improving the integrity of the hybrid layer when Zn-doped adhesives are employed.

Biofilm formation within the interface of bovine root dentin treated with conjugated chitosan and sealer containing chitosan nanoparticles

INTRODUCTION

The purpose of this study was to assess biofilm formation within sealer-dentin interfaces of root segments filled with gutta-percha and sealer incorporated with chitosan (CS) nanoparticles with and without canal surface treatment with different formulations of CS.

METHODS

Standardized canals of 4-mm bovine root segments (N = 35) were filled with gutta-percha and pulp canal sealer incorporated with CS nanoparticles without surface treatment (group CS) or after surface treatment with phosphorylated CS (group PHCS), CS-conjugated rose bengal and photodynamic irradiation (group CSRB), or a combination of both PHCS and CSRB (group RBPH). The control group was filled with gutta-percha and an unmodified sealer. After 7 days of setting, specimens were aged in buffered solution at 37°C for 1 or 4 weeks. Monospecies biofilms of Enterococcus faecalis were grown on specimens for 7 days in a chemostat-based biofilm fermentor. Biofilm formation within the sealer-dentin interface was assessed with confocal laser scanning microscopy.

RESULTS

In the 4-week-aged specimens only, the mean biofilm areas were significantly smaller than in the control for the CS (P = .008), PHCS (P = .012), and RBPH (P = .034) groups. The percentage of the biofilm-covered interface also was significantly lower than in the control for the CS (P = .024) and PHCS (P = .003) groups. The CS, PHCS, and RBPH groups did not differ significantly.

CONCLUSIONS

Incorporating CS nanoparticles into the zinc oxide-eugenol sealer inhibited biofilm formation within the sealer-dentin interface. This effect was maintained when canals were treated with phosphorylated CS, and it was moderated by canal treatment with CS-conjugated rose bengal and irradiation.