Chlorhexidine arrests subclinical degradation of dentin hybrid layers in vivo

Effect of the anti-Alzheimer drug GSK-3β antagonist on numerical modeling of the energy dissipation through the resin-dentin interface

OBJECTIVES

The aim of this study was to determine the viscoelastic performance and energy dissipation of conditioned dentin infiltrated with polymeric nanoparticles (NPs) doped with tideglusib (TDg) (TDg-NPs).

METHODS

Dentin conditioned surfaces were infiltrated with NPs and TDg-NPs. Bonded interfaces were created, stored for 24 h and submitted to mechanical and thermal challenging. Resin-dentin interfaces were evaluated through nano-DMA/complex-loss-storage moduli-tan delta assessment and atomic force microscopy (AFM) analysis.

RESULTS

Dentin infiltrated with NPs and load cycled attained the highest complex modulus at hybrid layer and bottom of hybrid layer. Intertubular dentin treated with undoped NPs showed higher complex modulus than peritubular dentin, after load cycling, provoking energy concentration and breakdown at the interface. After infiltrating with TDg-NPs, complex modulus was similar between peri-intertubular dentin and energy dissipated homogeneously. Tan delta at intertubular dentin was higher than at peritubular dentin, after using TDg-NPs and load cycling. This generated the widest bandwidth of the collagen fibrils and bridge-like mineral structures that, as sight of energy dissipation, fastened active dentin remodeling. TDg-NPs inducted scarce mineralization after thermo-cycling, but these bridging processes limited breakdown zones at the interface.

SIGNIFICANCE

TDg-based NPs are then proposed for effective dentin remineralization and tubular seal, from a viscoelastic approach.

Investigation of the effect of Tideglusib on the hydroxyapatite formation, crystallinity and elasticity of conditioned resin-dentin interfaces

OBJECTIVES

To investigate the effect of dentin infiltration with polymeric nanoparticles (NPs) doped with tideglusib (TDg) (TDg-NPs) on hydroxyapatite formation, crystallinity and elasticity of conditioned resin-dentin interfaces.

METHODS

Dentin conditioned surfaces were infiltrated with NPs or TDg-NPs. Bonded interfaces were created, stored for 24 h and submitted to mechanical and thermal challenging. Resin-dentin interfaces were evaluated through nanoindentation to determine the modulus of elasticity, X-ray diffraction and transmission electron microscopy through selected area diffraction and bright-filed imaging.

RESULTS

TDg-NPs provoked peaks narrowing after the diffraction-intensity analysis that corresponded with high crystallinity, with an increased modulus of Young after load cycling in comparison with the samples treated with undoped NPs. New minerals, in the group of TDg-NPs, showed the greatest both deviation of line profile from perfect crystal diffraction and dimension of the lattice strain, i.e., crystallite, grain size and microstrain and 002 plane-texture. The new minerals generated after TDg-NPs application and mechanical loading followed a well defined lineation. Undoped NPs mostly produced small hydroxyapatite crystallites, non crystalline or amorphous in nature with poor maturity.

CONCLUSIONS

Tideglusib promoted the precipitation of hydroxyapatite, as a major crystalline phase, at the intrafibrillar compartment of the collagen fibrils, enabling functional mineralization. TDg-NPs facilitated nucleation of crystals randomly oriented, showing less structural variation in angles and distances that improved crystallographic relative order of atoms and maturity. Nanocrystals inducted by TDg-NPs were hexagonal prisms of submicron size. Thermal challenging of dentin treated with TDg-NPs have provoked a decrease of functional mineralization and crystallinity, associated to immature hydroxyapatite.

CLINICAL SIGNIFICANCE

New polycrystalline lattice formation generated after TDg-NPs infiltration may become correlated with high mechanical performance. This association can be inferred from the superior crystallinity that was obtained in presence of tideglusib. Immature crystallites formed in dentin treated with undoped NPs will account for a high remineralizing activity.

Endodontic irrigants from a comprehensive perspective

This review article explores the fundamental principles of modern endodontics with a focus on root canal cleaning and shaping. It reviews commonly used endodontic irrigant, namely sodium hypochlorite (NaOCl), herbal extracts, chlorhexidine (CHX), and chelating agents, highlighting their properties, applications, and potential drawbacks. NaOCl, a key antimicrobial agent, demonstrates effectiveness against various microorganisms but poses challenges such as high cytotoxicity. Herbal extracts, gaining recognition in endodontics, present an alternative with potential advantages in preserving dentin integrity. CHX, known for its broad-spectrum antimicrobial activity, is discussed in both liquid and gel formulations, emphasizing its role in reducing smear layer formation and preserving hybrid layer durability. Chelating agents, specifically ethylenediaminetetraacetic acid and citric acid, play a vital role in removing the smear layer, enhancing dentin permeability, and facilitating the penetration of antimicrobial agents. The review article underscores the importance of careful application and consideration of each irrigant's properties to ensure safe and effective endodontic procedures. It serves as a valuable guide for clinicians in selecting appropriate irrigants based on specific treatment requirements.

Polymeric functionalization of mesoporous silica nanoparticles: Biomedical insights

Mesoporous silica nanoparticles (MSNs) endowed with polymer coatings present a versatile platform, offering notable advantages such as targeted, pH-controlled, and stimuli-responsive drug delivery. Surface functionalization, particularly through amine and carboxyl modification, enhances their suitability for polymerization, thereby augmenting their versatility and applicability. This review delves into the diverse therapeutic realms benefiting from polymer-coated MSNs, including photodynamic therapy (PDT), photothermal therapy (PTT), chemotherapy, RNA delivery, wound healing, tissue engineering, food packaging, and neurodegenerative disorder treatment. The multifaceted potential of polymer-coated MSNs underscores their significance as a focal point for future research endeavors and clinical applications. A comprehensive analysis of various polymers and biopolymers, such as polydopamine, chitosan, polyethylene glycol, polycaprolactone, alginate, gelatin, albumin, and others, is conducted to elucidate their advantages, benefits, and utilization across biomedical disciplines. Furthermore, this review extends its scope beyond polymerization and biomedical applications to encompass topics such as surface functionalization, chemical modification of MSNs, recent patents in the MSN domain, and the toxicity associated with MSN polymerization. Additionally, a brief discourse on green polymers is also included in review, highlighting their potential for fostering a sustainable future.

Comparison of microtensile bond strength of prepared teeth treated with proanthocyanidin, Camellia sinensis - Polyphenols, and metal crowns luted with resin-modified glass ionomer cement: An in vitro study

AIM

The aim of this study was to evaluate the effect of proanthocyanidin and C. sinensis-polyphenols on microtensile bonding properties of prepared teeth with resin-modified glass ionomer cement (GIC).

SETTING AND DESIGN

This was an in vitro study.

MATERIALS AND METHODS

Seventy-eight maxillary premolars were selected and mounted into auto-polymerizing acrylic resin blocks. The samples were prepared and metal crowns were fabricated. The samples were randomly divided into three groups. Samples under Group 1 were not treated with any of the extracts and followed conventional bonding protocol. Samples under Group 2 and Group 3 were treated with proanthocyanidin and C. sinensis-polyphenols, respectively. After dentin treatment, these samples were luted to metal crowns using resin-modified GIC. Universal testing machine was used to measure the load at which the crowns were debonded and microtensile bond strength in MPa was calculated.

STATISTICAL ANALYSIS

The results were statistically analyzed using one-way ANOVA and post hoc Tukey HSD.

RESULTS

Samples treated with C. sinensis polyphenols (Group 3) had maximum bond strength followed by Group 2, where the samples were treated with proanthocyanidin.

CONCLUSION

C. sinensis polyphenols due to their anti-proteolytic and antioxidant properties showed improved bond strength compared to proanthocyanidin, a cross-linking agent, followed by conventional bonding protocol.

Navigating the practical-knowledge gap in deep margin elevation: A step towards a structured case selection - a review

The deep margin elevation (DME) technique has gained popularity because of numerous supporting case reports. However, some clinicians are cautious regarding using this technique owing to the lack of clear case selection criteria for DME application. This review aimed to analyze case reports and a series of DME cases to determine pre-/post-operative evaluation methods that could be used to suggest a pre-operative case selection checklist for DME. An electronic database search was conducted in June 2021 and updated by June 2023 using selected terms from PubMed, Cochrane Library, Google Scholar, EBSCO, and Scopus. The search was limited to English-language publications and was not restricted to the date. The inclusion criteria were case reports/series addressing periodontal and restorative outcomes of DME. The search identified 217 articles, 76 of which were pertinent. However, only six case reports and one case series satisfied the inclusion criteria. None of the selected studies followed any reporting guidelines, which led to significant information gaps. While the reviewed studies reported favorable outcomes, standardized protocols for evaluating pre-/post-operative restorative and periodontal status were lacking. The post-operative follow-up period varied from 3 months to 6 years. Designing and implementing pre-/post-operative guidelines hold the potential for ensuring the safe application of the DME technique. This may enhance our understanding of the suitability and efficacy of such non-invasive technique in future clinical trials.

Clinical significance

Handling deep cavities and preparing crowns are challenging. However, a lack of understanding of when to perform DME can lead to missed opportunities for conservative treatment, thereby a disservice to the patient. Provision of safe guidelines should be employed by clinicians until further evidence either supports or contradicts this treatment method.

Dentin remineralization using a stimuli-responsive engineered small molecule GSK3 antagonists-functionalized adhesive

OBJECTIVES

Tideglusib has shown great performance in terms of dentin regenerative properties. This study aims to evaluate bonding ability, of demineralized dentin infiltrated with polymeric nanoparticles (NPs) doped with tideglusib (TG) (TG-NPs).

METHODS

Dentin conditioned surfaces were infiltrated with NPs and TG-NPs. Bonded interfaces were created and stored for 24 h and then submitted to mechanical, chemical and thermal challenging. The resin-dentin interface was evaluated through a doubled dye fluorescent technique and a calcium chelator fluorophore under a confocal laser scanning microscopy, and by field emission scanning electron microscopy.

RESULTS

Dentin surfaces treated with TG-NPs and load cycled produced higher bond strength than the rest of the groups. Immersion of dentin specimens treated with undoped-NPs in collagenase solution attained the lowest microtensile bond strength (MTBS) values. Both porosity and nanoleakage decreased when dentin was infiltrated with TG-NPs, that revealed strong signals of xylenol orange stain at both hybrid layer and dentinal tubules. The presence of NPs, in general, inducted the presence of mineralized interfaces after mechanical loading and thermocycling.

CONCLUSIONS

Nanoparticles doped with tideglusib promoted the highest dentin bonding efficacy among groups, as they facilitated the maximum bond strength values with creation of mineral deposits at the hybrid layer and dentinal walls. Tideglusib enabled scarce porosity, nanoleakage and advanced sealing among dentin groups.

SIGNIFICANCE

Doping hydrophilic polymeric NPs with tideglusib, infiltrated in etched dentin represents a reproducible technique to create reparative dentin at the resin-dentin interface, by inducing therapeutic bioactivity.

Effect of the use of bromelain associated with bioactive glass-ceramic on dentin/adhesive interface

OBJECTIVES

To evaluate the effect of bromelain associated with Biosilicate on the bond strength (BS) of a universal adhesive system to sound (SD) and caries-affected dentin (CAD), and on the proteolytic activity.

MATERIALS AND METHODS

Cavities were prepared in 360 molars, half submitted to cariogenic challenge. Teeth were separated into groups (n=20): Control-No treatment; CHX-0.12% chlorhexidine; NaOCl-5% sodium hypochlorite; Br5%-5% bromelain; Br10%-10% bromelain; Bio-10% Biosilicate; NaOClBio-NaOCl+Bio; Br5%Bio-Br5%+Bio; Br10%Bio-Br10%+Bio. Following treatments, the adhesive system was applied, and cavities were restored. Samples were sectioned into sticks and stored at 37 °C for 24 h, 6 months, and 1 year. Microtensile BS (2-way ANOVA, Bonferroni's test, α=0.05), fracture patterns (SEM), and adhesive interfaces (TEM) were evaluated. Bacterial collagenase assay and in situ zymography were performed.

RESULTS

In CAD, Br10% presented higher BS (p=0.0208) than Br5%Bio. Br5% presented higher BS (p=0.0033) after 6 months than after 24 h; and association of treatments, higher BS (p<0.05) after aging than after 24 h. Mixed fractures were the most prevalent. Association of treatments promoted a more uniform hybrid layer with embedded Bio particles. Experimental groups presented lower (p<0.0001) relative fluorescence units than Control. Bromelain, associated or not with Bio, showed collagenolytic degradation.

CONCLUSIONS

Bromelain associated with Biosilicate did not affect the BS to SD. In CAD, Br5%Bio decreased immediate BS but had no long-term influence. This association decreased the proteolytic activity.

CLINICAL RELEVANCE

Bromelain and Biosilicate may enhance the longevity of adhesive restorations by inhibiting endogenous proteases.

Impact of Dentine Pretreatment with Matrix Metalloproteinase Inhibitors on Bond Strength of Coronal Composite Restorations: A Systematic Review and Meta-analysis of In Vitro Studies

Matrix metalloproteinase (MMP) enzymes participate in collagen matrix degradation, including in dentine, potentially compromising bond strength. Therefore, MMP inhibitors have been hypothesized to improve restoration bond strength and stability. This systematic review aimed to evaluate the influence of different MMP inhibitors applied as dentine surface pretreatments on the immediate (24 hours) and longer term (months) bond strength of direct coronal composite restorations. This systematic literature review followed the Preferred Reporting Items for Systematic Review and Meta-analyses (PRISMA) statement. A systematic literature search of three databases (Ovid MEDLINE, Ovid Embase, and Google Scholar) was conducted independently by two reviewers from inception to April 2022. An adapted quality assessment tool was independently applied by two reviewers for risk of bias assessment. RevMan v5.4 software was used for meta-analyses. A randomeffectsmodel was used to generatemean differences with 95% confidence intervals for treatment and control comparisons. The Q-test and I2-test were used to test for heterogeneity. The proportion of total variance across studies attributable to heterogeneity rather than chance was calculated. Overall effects were tested using the Z-test, while subgroup differences were tested using Chi-squared tests. Of 934 studies, 64 studies were included in the systematic review and 42 in the meta-analysis. Thirty-one MMP inhibitors were reported, three of which were included in the meta-analysis: 2% chlorhexidine (CHX), 0.3M carbodiimide (EDC), and 0.1% riboflavin (RIBO). Pretreatment with 2% CHX for 30 and 60 seconds did not significantly improve bond strength compared with controls either immediately or after long-termageing. However, pretreatment with 0.3MEDC and 0.1% RIBO (but not CHX) significantly improved bond strength compared with control groups both immediately and over time. Most studies showed a medium risk of bias. These in vitro findings pave the way for rationale clinical trialing of dentine surface pretreatment with MMP inhibitors to improve clinical outcomes.

Chlorhexidine-Containing Electrospun Polymeric Nanofibers for Dental Applications: An In Vitro Study

Chlorhexidine is the most commonly used anti-infective drug in dentistry. To treat infected void areas, a drug-loaded material that swells to fill the void and releases the drug slowly is needed. This study investigated the encapsulation and release of chlorhexidine from cellulose acetate nanofibers for use as an antibacterial treatment for dental bacterial infections by oral bacteria Streptococcus mutans and Enterococcus faecalis. This study used a commercial electrospinning machine to finely control the manufacture of thin, flexible, chlorhexidine-loaded cellulose acetate nanofiber mats with very-small-diameter fibers (measured using SEM). Water absorption was measured gravimetrically, drug release was analyzed by absorbance at 254 nm, and antibiotic effects were measured by halo analysis in agar. Slow electrospinning at lower voltage (14 kV), short target distance (14 cm), slow traverse and rotation, and syringe injection speeds with controlled humidity and temperature allowed for the manufacture of strong, thin films with evenly cross-meshed, uniform low-diameter nanofibers (640 nm) that were flexible and absorbed over 600% in water. Chlorhexidine was encapsulated efficiently and released in a controlled manner. All formulations killed both bacteria and may be used to fill infected voids by swelling for intimate contact with surfaces and hold the drug in the swollen matrix for effective bacterial killing in dental settings.

Some Myths in Dentin Bonding: An Evidence-Based Perspective

Laboratory investigations are essential models responsible for science development. However, laboratory discoveries must be confirmed in a clinical environment where many known and unknown variables and complex mechanisms are involved. Using conclusions from laboratory studies to make clinical recommendations can lead to widespread "unreliable truths" or so-called myths in any field of knowledge. These myths may increase the costs (financial and time) or even cause harm (side effects) that would be unnecessary, given that the current protocol or conduct was previously evaluated in a more complex and complete clinical setting. This article will discuss certain myths in dentin bonding that may influence clinical decision-making, bringing some principles of evidence-based practice to allow a more critical evaluation of the literature findings.

Evaluation of Chitosan-Oleuropein Nanoparticles on the Durability of Dentin Bonding

Purpose

To evaluate the effects of dentin pretreatment with chitosan-loaded oleuropein nanoparticles (CONPs) on the durability of resin-dentin bonding interfaces.

Methods

Eighty freshly extracted non-carious human third molars were randomly divided into four groups (n = 20 each): a de-ionized water (DW) group, a chitosan (CS) group, a chlorhexidine (CHX) group and a CONP group. The dentin in the DW, CS, CHX, and CONP groups were pretreated with de-ionized water, 1.0 mg/L CS solution, 2% chlorhexidine solution, and CONP suspension (prepared with 100 mg/L oleuropein), respectively, followed by the universal adhesive and resin composites. The bonded teeth of each group were randomly divided into two subgroups: an immediate subgroup and an aged subgroup. The bonded teeth of each group were then cut into the bonded beams. We measured their microtensile bond strength (μTBS), observed the characteristics of bonding interface by atomic force microscope, calculated the percentage of silver particles in a selected area for interfacial nanoleakage analysis, and evaluated the endogenous gelatinase activity within the bonding interface for in-situ zymogram analysis. Data were analyzed with two-way ANOVA and LSD multiple comparison test (P < 0.05).

Results

Regardless of after 24 h or after thermocycling, CONP exhibited better μTBS (P < 0.05) than the other three groups except that there was not a statistical significance (P > 0.05) in the CONP and CHX groups after 24 h. Besides, the CONP group presented significantly higher modulus of elasticity in the hybrid layers (P < 0.05), lower expression of nanoleakage (P < 0.05), and better inhibitory effect of matrix metalloproteinases than the other three groups before and after thermocycling.

Conclusion

Altogether, the CONPs had the potential to act as a dentin primer, which could effectively improve the dentin-resin binding durability.

Dexamethasone and zinc loaded polymeric nanoparticles reinforce and remineralize coronal dentin. A morpho-histological and dynamic-biomechanical study

OBJECTIVE

To investigate the effect of novel polymeric nanoparticles (NPs) doped with dexamethasone (Dex) on viscoelasticity, crystallinity and ultra-nanostructure of the formed hydroxyapatite after NPs dentin infiltration.

METHODS

Undoped-NPs, Dex-doped NPs (Dex-NPs) and zinc-doped-Dex-NPs (Zn-Dex-NPs) were tested at dentin, after 24 h and 21 d. A control group without NPs was included. Coronal dentin surfaces were studied by nano-dynamic mechanical analysis measurements, atomic force microscopy, X-ray diffraction and transmission electron microscopy. Mean and standard deviation were analyzed by ANOVA and Student-Newman-Keuls multiple comparisons (p < 0.05).

RESULTS

At 21 d of storage time, both groups doped with Dex exhibited the highest complex, storage and loss moduli among groups. Zn-Dex-NPs and Dex-NPs promoted the highest and lowest tan delta values, respectively. Dex-NPs contributed to increase the fibril diameters of dentin collagen over time. Dentin surfaces treated with Zn-Dex-NPs attained the lowest nano-roughness values, provoked the highest crystallinity, and produced the longest and shortest crystallite and grain size. These new crystals organized with randomly oriented lattices. Dex-NPs induced the highest microstrain. Crystalline and amorphous matter was present in the mineral precipitates of all groups, but Zn and Dex loaded NPs helped to increase crystallinity.

SIGNIFICANCE

Dentin treated with Zn-Dex-NPs improved crystallographic and atomic order, providing structural stability, high mechanical performance and tissue maturation. Amorphous content was also present, so high hydroxyapatite solubility, bioactivity and remineralizing activity due to the high ion-rich environment took place in the infiltrated dentin.

Shear Bond Strength and Color Stability of Novel Antibacterial Nanofilled Dental Adhesive Resins

Experimental adhesives containing co-doped metaloxide nanoparticles were demonstrated to display strong and long-term antibacterial properties against Streptococcus mutans biofilms. The present study represents an effort to characterize the shear-bond strength (SBS) and color stability (CS) of these novel biomaterials. Experimental adhesives were obtained by dispersing nitrogen and fluorine co-doped titanium dioxide nanoparticles (NF_TiO2, 10%, 20% or 30%, v/v%) into OptiBond Solo Plus (OPTB). Dentin surfaces were wet-polished (600-Grit). Specimens (n = 5/group) of Tetric EvoCeram were fabricated and bonded using either OPTB or experimental (OPTB + NF_TiO2) adhesives. Specimens were stored in water (37 °C) for twenty-four hours (T1), three months (T2), and six months (T3). At T1, T2, or T3, specimens were removed from water storage and were tested for SBS. Disc-shaped specimens (n = 10/group; d = 6.0 mm, t = 0.5 mm) of adhesives investigated were fabricated and subjected to thermocycling (10,000 cycles, 5−55 °C, 15 s dwell time). Specimens’ colors were determined with a VITA Easyshade® V spectrophotometer (after every 1000 cycles). SBS data was analyzed using two-way ANOVA and post-hoc Tukey tests, while CS data was analyzed using one-way ANOVA and post-hoc Tukey tests (α = 0.05). Mean values of SBS ranged from 16.39 ± 4.20 MPa (OPTB + 30%NF_TiO2) to 19.11 ± 1.11 MPa (OPTB), from 12.99 ± 2.53 MPa (OPTB + 30% NF_TiO2) to 14.87 ± 2.02 (OPTB) and from 11.37 ± 1.89 (OPTB + 20% NF_TiO2) to 14.19 ± 2.24 (OPTB) after twenty-four hours, three months, and six months of water storage, respectively. Experimental materials had SBS values that were comparable (p > 0.05) to those from OPTB independently of nanoparticle concentration or time-point considered. Experimental materials with higher NF_TiO2 concentrations had less intense color variations and were more color stable than OPTB even after 10,000 thermocycles. In combination, the results reported have demonstrated that experimental adhesives can establish strong and durable bonds to human dentin while displaying colors that are more stable, thereby suggesting that the antibacterial nanotechnology investigated can withstand the harsh conditions within the oral cavity without compromising the esthetic component of dental restorations.

Disinfection of caries-affected dentin using potassium titanyl phosphate laser, Rose bengal and Ozonated water on shear bond strength of deciduous teeth

AIM

To assess the efficacy of disinfection of caries-effected dentin (CAD) using KTP laser and different decontamination methods using ozonated water (OW), Rose Bengal photosensitizer (RBP), chlorhexidine (CHX), and Er, YAG laser on the shear bond strength (SBS) of adhesive resin bonded to deciduous teeth.

MATERIAL AND METHODS

A total of 50 extracted and radiographically verified carious primary molars were collected and scrutinized according to ICDAS criteria. Specimens were allocated randomly into five groups (n = 10) as per the type of CAD disinfectants. KTP laser, OW, RBP, CHX (control), and Er, YAG laser. After cavity sanitization, a resin adhesive (prime and bond NT) was smeared on the dentinal exterior followed by incremental composite filling. SBS evaluation was performed by employing specimens in the universal testing machine. The debonded surface was assessed under 40x magnification in a stereomicroscope to ascertain fracture mode. Statistical analysis was done by using the ANOVA and the Post Hoc Tukey multiple comparison tests (p < 0.05).

RESULTS

The highest SBS was exhibited by group 2 i.e., when OW was employed for CAD disinfection (10.25 ± 0.24 MPa). Whereas, the lowest SBS bond value was unveiled by samples in group 3 when RBP was applied for dentin surface sanitization (7.85 ± 0.59 MPa).CAD disinfection with KTP laser (8.25 ± 0.41 MPa), CHX (8.19 ± 0.73 MPa), and RBP displayed comparable bond values (p > 0.05).

CONCLUSION

Ozonated water and Er, YAG laser could be employed as cavity disinfectants in primary teeth as they demonstrated better shear bond strength without jeopardizing the adhesive binding capacity of restorative resins bonded to caries-affected dentin.

Adjunctive therapies for in vitro carious lesions: Antimicrobial activity, activation of dentin metalloproteinases and effects on dental pulp cells

BACKGROUND

Adjunctive therapies used before dental restorative procedures may encourage carious tissue removal. Beyond promising antimicrobial properties, treatments could positively modulate the dentin-pulp complex while not interfering with restoration survival. Herein, we evaluated a set of substances and their effects on carious lesions and the underlying dentin or pulp cells.

METHODS

Artificial caries lesions were developed in bovine teeth cavities immersed in Streptococcus mutans and Lactobacillus casei co-cultures. The cavities were treated according to the following groups: Phosphate Buffer Saline (PBS), Chlorhexidine (CHX), Papacárie® (Papain gel), Ozone (O₃), and antimicrobial Photodynamic Therapy (aPDT). After treatments, samples were cultivated to count isolated microbial colonies. The zymography assay evaluated the activity of dentin metalloproteinases (MMP-2 and MMP-9). Cell viability was indirectly assessed on human dental pulp cells after 24, 72, or 120 h, whereas the odontodifferentiation potential was evaluated after ten days of cell culture.

RESULTS

CHX and aPDT led to around 1 log bacterial load reduction. PBS, CHX, and aPDT showed the eventual expression of MMP-2 and MMP-9. Cell viability was reduced (< 30%) after 120 h for all groups compared to the control. CHX, O3, and aPDT induced greater odontodifferentiation (≈ 20% higher) than PBS and papain gel.

CONCLUSION

Adjunctive therapies presented little or no biological significance in reducing bacterial load in artificial carious lesions. Although the activation of endogenous metalloproteinases may represent a possible concern for adhesive restorations, some of these treatments may have a positive role in dental pulp tissue repair.

Effect of Cumulative Ionizing Radiation on Flexural Strength, Flexural Modulus, and Elasticity Modulus of Dentin in Unerupted Human Third Molars

Purpose

This in vitro study aimed to investigate the changes in mechanical properties in dentin of third molars after radiation therapy using variable doses and frequencies.

Methods and Materials

Rectangular cross sectioned dentin hemisections (N = 60, n = 15 per group; >7 × 4 × 1.2 mm) were prepared using extracted third molars. After cleansing and storage in artificial saliva, random distribution was performed to 2 irradiation settings, namely AB or CD (A, 30 single doses of irradiation [2 Gy each] for 6 weeks; B, control group of A; C, 3 single doses of irradiation [9 Gy each]; and D, control group of C). Various parameters (fracture strength/maximal force, flexural strength, and elasticity modulus) were assessed using a universal Testing Machine (ZwickRoell). The effect of irradiation on dentin morphology was evaluated by histology, scanning electron microscopy, and immunohistochemistry. Statistical analysis was performed using 2-way analysis of variance and paired and unpaired t tests at a significance level of 5%.

Results

Significance could be found considering the maximal force applied to failure when the irradiated groups were compared with their control groups (A/B, P < .0001; C/D, P = .008). Flexural strength was significantly higher in the irradiated group A compared with control group B (P < .001) and for the irradiated groups A and C (P = .022) compared with each other. Cumulative radiation with low irradiation doses (30 single doses; 2 Gy) and single irradiation with high doses (3 single doses; 9 Gy) make the tooth substance more prone to fracture, lowering the maximal force. The flexural strength decreases when cumulative irradiation is applied, but not after single irradiation. The elasticity modulus showed no alteration after irradiation treatment.

Conclusions

Irradiation therapy affects the prospective adhesion of dentin and the bond strength of future restorations, potentially leading to an increased risk of tooth fracture and retention loss in dental reconstructions.

Incorporation of MMP inhibitors into dental adhesive systems and bond strength of coronal composite restorations: A systematic review and meta-analysis of in vitro studies

Purpose

To systematically review in vitro studies that incorporated MMP inhibitors into adhesive systems in terms of the effect on immediate and aged bond strength of dental composite to dentine.

Materials and methods

Independently, two reviewers conducted an electronic search in three databases (MEDLINE, EMBASE, and Google Scholar) following the Preferred Reporting Items for Systematic Review and Meta-Analyses Protocols (PRISMA-P), up to 6 March 2022.

Results

The search resulted in 894 papers, 33 of which were eligible to be included in the review; of those, 13 fulfilled the meta-analysis eligibility criteria. Nineteen inhibitors were used among the studies, and those included in the meta-analysis were 2%, 0.2% chlorhexidine (CHX), 5 µM GM1489, and 0.5%, 1% benzalkonium chloride (BAC). In the meta-analysis, while above inhibitors showed no adverse effect on bond strength, 0.2% CHX and 5 µM GM1489 caused a significant increase in immediate and 12-months bond strength. All other inhibitors resulted in a significant increase in bond strength at six months of ageing.

Conclusions

Incorporation of MMP inhibitors into the adhesive system has no unfavourable effect on immediate bond strength but a favourable effect on longer-term bond strength. Additionally, inhibitors other than CHX could have similar or better effects on bond strength.

Role of Natural Cross Linkers in Resin-Dentin Bond Durability: A Systematic Review and Meta-Analysis

BACKGROUND

The role of endogenous Matrix Metallo Proteinases in resin dentin bond deterioration over time has been well documented. The present study aimed to systematically review the literature; in vitro and ex vivo studies that assessed the outcomes of natural cross-linkers for immediate and long-term tensile bond strength were included.

METHODS

The manuscript search was carried out in six electronic databases-PubMed/MEDLINE, LILACS, SciELO, Cochrane, Web of Science and DOAJ, without publication year limits. Only manuscripts in English (including the translated articles) were selected, and the last search was performed in December 2020. The Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) statement was followed.

RESULTS

From the 128 potentially eligible studies, 48 full-text articles were assessed for eligibility. After eligibility assessment and exclusions, 14 studies were considered for systematic review and seven studies for meta-analysis. Amongst the selected studies for meta-analysis, three had a medium and four had a low risk of bias.

CONCLUSIONS

It was evidenced by the available data that Proanthocyanidin is the most efficient natural cross-linker to date, in preserving the bond strength even after ageing.

Degradation and Stabilization of Resin-Dentine Interfaces in Polymeric Dental Adhesives: An Updated Review

Instability of the dentine-resin interface is owed to the partial/incomplete penetration of the resin adhesives in the collagen fibrils. However, interfacial hydrolysis of the resin-matrix hybrid layer complex activates the collagenolytic and esterase enzymes that cause the degradation of the hybrid layer. Adequate hybridization is often prevented due to the water trapped between the interfibrillar spaces of the collagen network. Cyclic fatigue rupture and denaturation of the exposed collagen fibrils have been observed on repeated application of masticatory forces. To prevent interfacial microstructure, various approaches have been explored. Techniques that stabilize the resin–dentine bond have utilized endogenous proteases inhibitors, cross linking agents’ incorporation in the exposed collagen fibrils, an adhesive system free of water, and methods to increase the monomer penetration into the adhesives interface. Therefore, it is important to discover and analyze the causes of interfacial degradation and discover methods to stabilize the hybrid layer to execute new technique and materials. To achieve a predictable and durable adhesive resin, restoration is a solution to the many clinical problems arising due to microleakage, loss of integrity of the restoration, secondary caries, and postoperative sensitivity. To enhance the longevity of the resin-dentine bond strength, several experimental strategies have been carried out to improve the resistance to enzymatic degradation by inhibiting intrinsic collagenolytic activity. In addition, biomimetic remineralization research has advanced considerably to contemporary approaches of both intrafibrillar and extrafibrillar remineralization of dental hard tissues. Thus, in the presence of biomimetic analog complete remineralization of collagen, fibers are identified.

Inhibitory activity of S-PRG filler on collagen-bound MMPs and dentin matrix degradation

OBJECTIVES

To evaluate the inhibitory activity of an ion-releasing filler (S-PRG) eluate on dentin collagen-bound metalloproteinases (MMPs) and dentin matrix degradation.

METHODS

Dentin beams (5 × 2 × 0.5 mm) from human molars were completely demineralized to produce dentin matrix specimens. The dry mass was measured, and a colorimetric assay (Sensolyte) determined the initial total MMP activity to allocate the beams into four treatment groups (n = 10/group): 1) water for 1 min (negative control); 2) 2% chlorhexidine digluconate (CHX - inhibitor control) for 1 min; 3) S-PRG eluate for 1 min; 4) S-PRG eluate for 30 min. After the treatments, the total MMP activity was reassessed. The specimens were stored in simulated body fluid (SBF) at 37 °C for up to 21 days. The dry mass was reassessed weekly. On day 7, the dentin matrix degradation was analyzed for the presence of collagen fragments (CF; Sirius Red) and hydroxyproline (Hyp) in the SBF. Statistical analyses were performed with ANOVA/Tukey, paired t-tests, and RM-ANOVA/Sidak (α = 5%).

RESULTS

S-PRG eluate exposure for 1 and 30 min reduced (p < 0.0001) MMP activity. S-PRG exposure for 30 min presented MMP activity inhibition equivalent to CHX (p = 0.061). S-PRG and CHX decreased CF (p ≤ 0.007) and Hyp (p < 0.046) release. After 21 days of storage, S-PRG-treated beams, regardless of exposure time, presented a reduced (p ≤ 0.017) mass loss, intermediate between CHX and control.

CONCLUSION

Treating demineralized dentin with S-PRG eluate for 1 or 30 min reduced matrix-bound MMP activity and dentin matrix degradation for up to 21 days.

CLINICAL SIGNIFICANCE

S-PRG filler may hinder the progression of dentin carious/erosive lesions and enhance the stabilization of dentin bonding interfaces.

Effect of irrigation protocols on chemical smear layer formation over the post-space dentin

This study evaluated the effect of irrigation protocols using 95% ethanol (ET) or 1% peracetic acid (PA) prior the use of 2% chlorhexidine (CHX) compared to distilled water (DW) on the chemical smear layer (CSL) formation and incidence of open dentin tubules at the apical, medium, and cervical third of the post-space dentin. Scanning electron microscopy (SEM) and electron dispersive spectroscopy (EDS) images were used. Forty bovine roots were endodontically treated. After, post-space preparation was performed and the roots were randomized in four groups (n = 10) according to the irrigation protocol: DW, CHX, CHX-ET and CHX-PA. The chemical composition of CSL and the incidence of open dentin tubules at the post-space thirds were evaluated by EDS (500× magnification) and SEM (2000× magnification) images, respectively. Data from chemical composition of CSL were descriptively analyzed, while the incidence of open dentin tubules was evaluated by scores and submitted to Kruskal-Wallis and Dunn test (p = .05). Cl, Bi, and Si were the chemical elements most found over the dentin after the irrigation with CHX and CHX-ET. Moreover, CHX and CHX-ET showed the highest incidence of CSL (p < .05), but without difference between them (p > .05), regardless of the post-space third. DW and CHX-PA showed similar incidence of CSL (p > .05). No difference on the incidence of open dentin tubules was found for any irrigation protocol and post-space third (p > .05). The use of 1% PA prior the post-space irrigation with CHX decrease the incidence of CSL. RESEARCH HIGHLIGHTS: The post-space irrigation with chlorhexidine results in the formation of chemical smear layer. Ethanol is not capable to remove the chemical smear layer. Peracetic acid is more effective to remove the chemical smear layer.

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.

Comparison of the effect of QMix and conventional root canal irrigants on push-out bond strength of fiber post to root dentin

OBJECTIVES

This study aimed to assess the effect of application of QMix and common root canal irrigating solutions on the bond strength of fiber post to root dentin.

MATERIAL AND METHODS

In this in-vitro study, 60 extracted incisor teeth were decoronated such that 15 mm of root length remained. The canals were prepared with ProTaper rotary system to F5 and filled with gutta-percha and AH26 sealer. Prior to post placement, the teeth were divided into four groups based on the type of final irrigating solution namely saline, 5.25% NaOCl, 2% chlorhexidine, and QMix. The fiber posts were then cemented with Panavia F2 resin cement. The roots were sectioned perpendicular to their longitudinal axis, and four sections with 1 mm thickness were made at the middle and coronal thirds of the roots. The push-out bond strength of fiber posts was measured by a universal testing machine in megapascals. Data were analyzed by two-way ANOVA and Tukey's test.

RESULTS

The maximum and minimum bond strength values were noted in QMix and NaOCl groups in both the middle and coronal third of the root, respectively. But, there was no significant difference between the push-out bond strength in the middle or coronal third of the root (p = 0.054). Adhesive failure was the most common mode of failure in all groups.

CONCLUSION

Use of QMix for post space irrigation does not compromise the bond strength of fiber post to root dentin, and can be used for final rinsing of the post space.

Captopril inhibits matrix metalloproteinase activity and improves dentin bonding durability

OBJECTIVES

We investigated the inhibitory effects of captopril on matrix metalloproteinases (MMPs) and its effect as a primer on dentin bonding durability.

MATERIALS AND METHODS

One hundred fifty human third molars were selected. Flat surfaces of the middle dentin were exposed, etched 15 s, and followed by pretreatment with a primer for 60 s, including distilled water (control, the negative control primer), 2% chlorhexidine digluconate (CHD, the positive control primer), and captopril solution. Inhibitory effects of primers on MMPs were evaluated by hydroxyproline and gelatinase activity tests. All primers were applied on dentin followed by bonding. Some of the samples were sliced into slabs, placed in a fluorescent solution containing gelatin, and incubated for in situ zymography. Some were cut into sticks, and after aging for 1 day, 12 months, or 24 months, microtensile bonding strength was tested. Some were cut into slabs, aged for 1 day, 12 months, or 24 months, and taken out for nanoleakage tests to reveal interface defects.

RESULTS

Hydroxyproline and gelatinase activity analyses showed that captopril exerted better inhibitory effects on MMPs, relative to 2% CHD (p < 0.05). A 0.2% captopril aqueous solution (0.2% CapW) was chosen to apply to the dentin. In situ zymography showed that inhibitory effects of captopril on gelatinase were significantly higher compared to 2% CHD (p < 0.01). Microtensile strength revealed that the bonding effects of the 0.2% CapW group lasted longer, compared to the control and 2% CHD groups (p < 0.05). Interface defects, detected by nanoleakage, were significantly reduced in the 0.2% CapW group, compared to the control and 2% CHD groups (p < 0.05).

CONCLUSIONS

Captopril inhibits dentin MMP activities and effectively improves dentin bonding durability.

CLINICAL RELEVANCE

Captopril is a promising dentin bonding primer for improving bonding durability.

Assessing the antimicrobial properties of copper-iodide doped adhesives in an In vitro caries model: A pilot study

Context:

Recurrent caries are the leading cause of composite resin failure.

Aims:

The purpose of this pilot study was to test the efficacy of a novel copper iodide (CuI) containing dental adhesive in an in vitro caries model.

Subjects and Methods:

Streptococcus mutans and Lactobacillus acidophilus were grown individually on the complex medium for 48 h at 37°C. The pH of the mixed medium was 7.0 initially and tested every 24 h. 40 extracted teeth were prepared with standardized cavity preparations and coated with control or experimental CuI adhesives and imaged using a micro-computed tomography (microCT). Four study groups were evaluated: (1) control (2) 0.5 μg/ml CuI (3) 1.0 μg/ml CuI, 4) 5.0 μg/ml CuI. After incubation, the teeth were re-imaged using the microCT. Utilizing AnalyzePro software the three-dimensional data sets were overlaid and demineralization was measured and statistics were run.

Statistics:

Stratified ANOVA models were run to determine if there were differences between the control and experimental adhesive groups. Similarly, pH and bacterial concentrations were evaluated to ensure the viability of polymicrobial specimen.

Results and Conclusions:

Significant differences were found between the control group and the 1.0 and 5.0 CuI adhesive groups. No differences in pH were noted between the groups. Overlaid changes in demineralization were recorded as volume loss. CuI adhesives with 5 mg/ml or higher have the potential to limit tooth demineralization after bacterial penetration of a dental restoration in an in vitro caries model. Further testing is needed.

Adhesive systems applied to dentin substrate under electric current: systematic review

Objectives

The purpose of this systematic review was to collect and discuss the technique of adhesive systems application on dentin substrate under electric current.

Materials and Methods

The first search strategy was based on data available at PubMed, LILACS, Scielo, Scopus, and Cochrane Library, using a combination of descriptors such as “dentin bond agents OR adhesive system AND electric current OR electrobond” or “dentin bonding agents OR dentin bonding agent application OR adhesive system AND electric current OR electrobond”, with no limit regarding the publication year. The second search strategy was based on the articles' references found previously. An additional search strategy was applied that concerned the proposed theme in the SBU-UNICAMP (Unicamp's Library System Institutional Repository).

Results

Twelve studies published between 2006 and 2020 were found. The analyses of the selected studies showed that the use of electric current during adhesive systems application on dentin, whether conventional or self-conditioning, increases resinous monomer infiltration in the dentin substrate, which improves the hybridization processes and the bond strength of the restorative material to dentin.

Conclusions

Despite the favorable results related to the use of this technique, there is still no specific protocol for the application of adhesive systems under electric current.

Proteolytic activity and degradation of bovine versus human dentin matrices

Non-human teeth have been commonly used in research as replacements for human teeth, and potential dissimilarities between the dental tissues should be considered when interpreting the outcomes.

Long-term effect of curcuminoid treatment on resin-to-dentin bond strength

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

CHX Stabilizes the Resin/demineralized Dentin Interface

The aim of this study was to evaluate the effect of 2% chlorhexidine digluconate (CHX) on microtensile bond strength (µTBS) between an adhesive system and under 3 dentin conditions. For that, this study evaluated the adhesive interface at initial, after 6 months and 1 year of storage. Forty-eight human third molars were prepared and randomly divided into 3 groups, according to dentin substrates: sound dentin (Sd), caries-infected dentin (Ci) and caries-affected dentin (Ca). The groups were subdivided into two according to the dentin pre-treatment: application of 2% CHX or without pre-treatment (control). The dentin surfaces were etched with 35% phosphoric acid gel and bonded with Adper Single Bond 2 (3M ESPE) adhesive system according to manufacturer's instructions. Subsequently, the specimens were stored in deionized water at 37°C for 24h, 6 months and 1 year. Two additional teeth were used to analyze the bonding interfaces by SEM. Data was submitted to three-way ANOVA in a split plot design and Tukey's test (α = 0.05). The results showed that Ci decreased µTBS values when compared to Ca and Sd, regardless storages time or treatment. Stored samples for 6 months and 1 year decreased the µTBS for the control group, but no difference was found between storages time for the CHX group. As a conclusion, the 2% CHX application after etching showed improved dentin bond strength in the storage time, regardless of the substrates evaluated.

Short- and Long-Term Dentin Bond Strength of Bioactive Glass-Modified Dental Adhesives

This study investigated the short- and long-term effects of dental adhesives doped with nano-sized bioactive glass 45S5 (BAG) on the resin-dentin interfacial bond strength. Two etch-and-rinse adhesives (Adper Scotchbond Multi-Purpose (ASB) and Solobond Plus (SB)) and one self-etch adhesive (Clearfil SE Bond (CF)) were doped with different concentrations of BAG (5, 10, and 20 wt%). The unmodified (0 wt% BAG) commercial adhesives served as control groups. Dentin of 120 molars (n = 10 per group) was treated with the different adhesives, followed by buildups with a conventional composite restorative material. From each tooth, 14 sticks were prepared for micro-tensile bond strength (µTBS) testing. The sticks were stored in simulated body fluid at 37 °C and tested after 24 h or six months for µTBS and failure mode. Data were analyzed using Kruskal-Wallis tests in combination with post-hoc Conover-tests and Wilcoxon signed-rank tests at a level of significance of α = 0.05. After 24 h and six months, both etch-and-rinse adhesives with a low BAG content (up to 10 wt% for ASB and 5 wt% for SB) showed similar µTBSs as their respective control groups (0 wt% BAG). CF showed a significant decrease in µTBS even after addition of 5 wt% BAG. At a high concentration of added BAG (20 wt%), all three adhesives showed a significant decrease in µTBS compared to the unmodified controls. The CF control group showed significantly lower µTBS after 6 months of storage than after 24 h. In contrast, the µTBS of all CF groups modified with BAG was unaffected by aging. In conclusion, the tested etch-and-rinse adhesives can be modified with up to 5 wt% (SB), or 10 wt% (ASB) of BAG without reducing their short- and long-term dentin bond strength. Moreover, the addition of nano-sized BAG may prevent long-term bond strength deterioration of a self-etch adhesive.

Influence of two carbodiimides on the bond strength of universal adhesives to dentin

The pretreatment of dentin with cross-linking agents during bonding procedures has been proposed to improve the mechanical properties of the collagen in the hybrid layer and reduce the biodegradation of the adhesive interface. The aim of this study was to evaluate the influence of pretreatment with two carbodiimides on the dentin bond strength of universal adhesives, after thermocycling. Three universal adhesives in the self-etching mode were used (Single Bond Universal-SBU, Clearfil Universal-CLU and Ambar Universal-ABU). A self-etching adhesive system (Clearfil SE Bond-CSB) was used as control. Two carbodiimides, 1-ethyl-3-(3'-dimethylaminopropyl)-carbodiimide (EDC) and N,N'-dicyclohexylcarbodiimide (DCC), were applied for 1 min. The excess solution was removed with absorbent paper and the universal adhesives were applied. The specimens were stored for 24 h in distilled water at 37 °C or 10,000 thermal cycles (5-55 °C, 30 s) and then were prepared for microtensile bond strength test (n  =  4 teeth, average of 21 sticks per group). Data were analyzed using three-way ANOVA and Tukey's (α  =  5%). After 24 h, SBU and CSB had statistically similar bond strength values for the control groups (22.07  ±  9.03 and 19.82  ±  7.28 MPa), with EDC (30.21  ±  11.30 and 19.67  ±  5.36 MPa) and DCC (30.12  ±  13.43 and 19.82  ±  7.28 MPa) pretreatments (p  >  0.05). The use of EDC (32.57  ±  9.60 MPa) and DCC (24.71  ±  9.87 MPa) showed statistically higher bond strength for CLU than for the control group (14.62  ±  6.16 MPa; p  <  0.05). After thermocycling, the SBU, CLU, and CSB groups showed statistically similar bond strengths with the use of EDC (27.08  ±  8.44; 18.74  ±  5.41; and 24.55  ±  10.43 MPa) and without the use of cross linkers (20.06  ±  7.99; 22.55  ±  9.04; and 26.54  ±  10.13 MPa; p  >  0.05). Groups tested after 24 h in distilled water presented higher bond strength than those submitted to thermocycling. It can be concluded that the use of cross linkers influenced the immediate bond strength of the universal adhesives, and this was dependent on the combination of the adhesive system and type of carbodiimide. The use of EDC increased the immediate bond strength of CLU. DCC increased the bond strength of ABU at 24 h, but the values were lower than those of the control group after aging for three out of the four adhesives.

Characteristics of biofilm-induced degradation at resin-dentin interfaces using multiple combinations of adhesives and resins

OBJECTIVE

We aimed to evaluate morphological, mechanical and chemical characteristics at resin-dentin interfaces using multiple combinations of adhesives and resins after a short-term biofilm-induced degradation.

METHODS

Cervical cavities were prepared in bovine incisors, treated by Clearfil SE Bond 2 (SE) or FL-Bond II (FL), restored by Clearfil Majesty ES Flow (ES) or Beautifil Flow Plus (BFP) and grouped into SE-ES, SE-BFP, FL-ES and FL-BFP. After biofilm challenge, interfacial gaps and dentin wall lesions were examined by optical coherence tomography (OCT). Gap depth (GD), gap pattern scale (GPS) and dentin wall lesion depth (WLD) were evaluated from confocal laser scanning microscope. Microhardness of dentin lesions was measured with a Vickers microhardness tester. Chemical elements in resins and dentin wall lesions were analyzed by scanning electron microscopy and energy dispersive X-ray spectrometry (SEM/EDS). Morphological structures of interfacial gaps were observed by SEM.

RESULTS

OCT could detect adhesive-dentin-bonded and adhesive-dentin-debonded gaps. SE-containing groups showed significantly lower GPS than FL-containing groups. FL-BFP showed significantly lower WLD than FL-ES. Microhardness of dentin wall lesions was higher than that of outer lesions and they showed significant differences in FL-BFP. SE-BFP showed a lower GPS curve and higher intensities of Ca and P in the upper half of dentin wall lesions than other groups. From SEM, microgaps between filler and matrix, break and loss of matrix, separation of adhesive matrix with hybrid layer occurred at interfacial gaps.

SIGNIFICANCE

The morphological, mechanical and chemical characteristics of resin-dentin interfacial degradation depend on the component and chemistry of restorative materials.

Performance of a Universal Bonding System Associated With 2% Digluconate Chlorhexidine in Carious and Eroded Dentin

CLINICAL RELEVANCE

Carious and eroded dentin represent clinical challenges. The use of a universal bonding system, in a self-etching mode, associated with chlorhexidine (CHX) seems to not improve its longevity. This may be attributed to the competition for calcium between the bonding agent functional monomer and CHX.

SUMMARY

Effect of Cavity Disinfectants on Adhesion to Primary Teeth-A Systematic Review

Some authors have been proposing the use of cavity disinfectants in order to reduce, or even eliminate, the effect of the microorganisms present in a dental cavity before a restoration is placed. The aim of this study was to evaluate the effect of different cavity disinfectants on bond strength and clinical success of composite and glass ionomer restorations on primary teeth. The research was conducted using Cochrane Library, PubMed/MEDLINE, SCOPUS, and Web of Science for articles published up to February 2021. The search was performed according to the PICO strategy. The evaluation of the methodological quality of each in vitro study was assessed using the CONSORT checklist for reporting in vitro studies on dental materials. Sixteen in vitro studies and one in situ study fulfilled the inclusion criteria and were analyzed. Chlorhexidine was the most studied cavity disinfectant, and its use does not compromise dentin bonding. Sodium hypochlorite is a promising alternative, but more research on its use is required to clearly state that it can safely be used as a cavity disinfectant for primary teeth. Although other disinfectants were studied, there is a low-level evidence attesting their effects on adhesion, therefore their use should be avoided.

Development and characterization of self-etching adhesives doped with 45S5 and niobophosphate bioactive glasses: Physicochemical, mechanical, bioactivity and interface properties

OBJECTIVE

The aim of study was to develop and characterize experimental bioactive glasses (45S5 and niobophosphate bioactive glass (NbG)) and evaluate the effects of their addition in self-etching adhesive systems on physicochemical, mechanical, and bioactive properties, microtensile bond strength (μTBS), and nanoleakage (NL).

METHODS

Two-step self-etching adhesive systems containing 5, 10, and 20 wt.% of 45S5 and NbG bioactive glasses were developed. An experimental adhesive without microparticles and a commercial adhesive (Clearfil SE Bond) were used as control groups. The materials were evaluated for their degree of conversion (DC%), ultimate tensile strength (UTS), softening in solvent, radiopacity, sorption and solubility, alkalizing activity (pH), ionic release, and bioactivity. μTBS and NL were evaluated after 24 h and 1 year of storage. The data were subjected to analysis of variance and post-Holm-Sidak tests (α = 0.05).

RESULTS

The addition of the two bioactive glasses did not change the values of the degree of conversion, ultimate tensile strength, and softening in solvent. The adhesive system containing 20% NbG showed the highest radiopacity. The incorporation of 45S5 increased water sorption and solubility, raised the pH, and allowed the release of large amounts of calcium. After 28 days of immersion in simulated body fluid, the 45S5 adhesive precipitated hydroxyapatite and calcium carbonate (SEM/EDX, ATR/FTIR, and XDR). The addition of 45S5 and NbG to the adhesives improved the stability of the resin-dentin interface after 1 year.

SIGNIFICANCE

The incorporation of microparticles from 45S5 bioactive glass in self-etching adhesive systems is considered an excellent alternative for the development of a bioactive adhesive that improves the integrity of the hybrid layer on sound dentin.

The effect of phytic acid on enzymatic degradation of dentin

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

Polymeric zinc-doped nanoparticles for high performance in restorative dentistry

OBJECTIVES

The aim was to state the different applications and the effectiveness of polymeric zinc-doped nanoparticles to achieve dentin remineralization.

DATA, SOURCES AND STUDY SELECTION

Literature search was conducted using electronic databases, such as PubMed, MEDLINE, DIMDI, Embase, Scopus and Web of Science. A narrative exploratory review was undertaken.

CONCLUSIONS

Polymeric nanospheres (NPs) were efficiently loaded with zinc. NPs sequestered calcium and phosphate in the presence of silicon, and remained effectively embedded at the hybrid layer. NPs incorporation did not alter bond strength and inhibited MMP-mediated dentin collagen degradation. Zn-loaded NPs remineralized the hybrid layer inducing a generalized low-carbonate substitute apatite precipitation, chemically crystalline with some amorphous components, and an increase in mechanical properties was also promoted. Viscoelastic analysis determined that dentin infiltrated with Zn-NPs released the stress by breaking the resin-dentin interface and creating specific mineral formations in response to the energy dissipation. Bacteria were scarcely encountered at the resin-dentin interface. The combined antibacterial and remineralizing effects, when Zn-NPs were applied, reduced biofilm formation. Zn-NPs application at both cervical and radicular dentin attained the lowest microleakage and also promoted durable sealing ability. The new zinc-based salt minerals generated covered the dentin surface totally occluding cracks, porosities and dentinal tubules.

CLINICAL SIGNIFICANCE

Zinc-doped NPs are proposed for effective dentin remineralization and tubular occlusion. This offers new strategies for regeneration of eroded cervical dentin, effective treatment of dentin hypersensitivity and in endodontically treated teeth previous to the canal filling. Zn-NPs also do reduce biofilm formation due to antibacterial properties.

Effect of natural primer associated to bioactive glass-ceramic on adhesive/dentin interface

OBJECTIVES

This study evaluated the effect of propolis associated with Biosilicate on the bond strength (BS) and gelatinolytic activity at the adhesive/dentin interface.

METHODS

Occlusal cavities were prepared in 320 human molars. Half of them were submitted to cariogenic challenge. All the teeth were separated into eight groups (n = 20): Control - Adhesive System (Single Bond Universal, 3 MESPE); CHX - 0.12 % Chlorhexidine; Bio - 10 % Biosilicate; P16 - Propolis with low levels of polyphenols; P45 - Propolis with high levels of polyphenols; CHX Bio - CHX + Bio; P16 Bio - P16+Bio; P45 Bio - P45+Bio. The adhesive was applied (self-etch mode) after treatments. Restorations (Filtek Z350, 3 MESPE) were performed and samples sectioned into sticks, separated and stored in distilled water at 37 °C for 24 h, 6 months and 1 year. Microtensile BS (0.5 mm/min) was tested and analyzed (2-way ANOVA, Bonferroni's Test, p < .05 and Weibull analysis). Fracture patterns (VH-M100, Keyence) and adhesive interfaces (SEM, EVO-MA10, ZEISS and TEM, JEM-1010, JEOL) were observed; and biodegradation and in situ zymography performed.

RESULTS

P16 presented the highest BS values on sound dentin after 6 months. In caries-affected dentin (CAD), the association of treatments promoted the highest BS after 24 h. Sound dentin obtained significantly higher Weibull modulus than CAD. SEM displayed resin tags in P16, P45 and association of treatments. TEM showed good interaction between adhesive and dentin. According to the in situ zymography and biodegradation assay all natural primers reduced the gelatinolytic activity. P45 presented the lowest biodegradation and enzymatic activity.

CONCLUSIONS

Propolis and the association of treatments promoted the highest bond strength results and preserved the dentin. All the experimental groups exhibited low gelatinolytic activity.

CLINICAL SIGNIFICANCE

Propolis and the association of treatments with Biosilicate could preserve the dentin substrate and improve the longevity of composite restorations.

Evaluating the effect of pretreatment with matrix metalloproteinase inhibitors on the shear bond strength of composite resin to primary teeth dentin: A 6-month in vitro study

Objective:

The purpose of this study was to evaluate the effect of pretreatment with of matrix metalloproteinase inhibitors on the shear bond strength (SBS) of Adper Single Bond 2 total etch adhesive to the primary teeth dentin following 6 months of storage in artificial saliva.

Materials and Methods:

One hundred and twenty primary anterior teeth extracted for orthodontic reasons were selected. After etching, dentin blocks from each tooth were pretreated for 60 s with: (i) phosphate-buffered saline (0.01 M, pH 7.2) as the control group, (ii) 17% ethylenediaminetetraacetic acid (EDTA), (iii) 2% doxycycline (DO) solution, and (iv) 2% chlorhexidine (CHX) solution, with subsequent application of an etch-and-rinse adhesive system (Adper Single Bond 2). The composite was placed in clear Teflon cylinders. The SBS values were determined immediately and following 6 months of aging with a universal testing machine. Failure mode was evaluated using the stereomicroscope and scanning electron microscope. Data were analyzed by the SPSS software using the one-way analysis of variance and post hoc tests (P = 0.05).

Results:

At baseline, no significant difference was observed between control, EDTA, CHX, and DO groups (P = 0.554). Following 6 months of aging, the SBS of the CHX group was significantly higher than the control group (P = 0.013). However, the SBS of the control, EDTA, and DO groups was not statistically different (P < 0.05).

Conclusions:

Following 6 months of aging, among different groups of the study, only CHX significantly preserved the SBS of composite resin to primary teeth dentin using Adper Single Bond 2 adhesive.

Evaluation of the effect of natural versus synthetic matrix metalloproteinase silencers in preservation of dentin collagen and long-term bond strength of total etch adhesive

Aim

This study investigated the effect of various synthetic (galardin [Gal] and benzalkonium chloride [BAC]) and natural agents (hesperidin [HES] and epigallocatechin gallate) on the stability of dentin collagen matrix to resist collagenase degradation and improve long-term microtensile bond strength.

Materials and Methods

Ten sound-impacted third molars were collected and manual removal of pulp, periodontal ligament, cementum, and enamel was done. Remaining dentin fragments were pulverized under liquid nitrogen to obtain dentin powder. 2 mg aliquot of dentin powder was allocated to each of the test solutions and subjected to hydroxyproline assay. Another 60 sound human third molars were collected and occlusal enamel was ground flat to reach dentinoenamel junction. Class I cavities were prepared in dentin, followed by etching using 37% phosphoric acid for 15 s. Samples were then subjected to surface treatment with different agents for 60 s, followed by application of Optibond S and restoration with P 60 composite resin. Samples of all groups except control were subject to thermocycling. Samples were sectioned to 1 mm thick slabs which were subject to universal testing machine to determine ultimate tensile strength. One-way analysis of variance and Bonferroni post hoc test with a significance level of P < 0.05 were used to analyze data.

Results

HES resulted in maximum resistance to collagen degradation, followed by epigallocatechin gallate (EGCG), Gal, and BAC with a significant difference among the groups. Samples of Gal group showed the highest microtensile bond strength values, followed by HES, EGCG, BAC with a significant difference between the groups except HES and EGCG where the difference was nonsignificant.

Conclusion

The use of matrix metalloproteinase silencers could improve the mechanical properties of collagen and resist enzymatic degradation, leading to an improved long-term intimate restoration.

Antioxidants and Collagen-Crosslinking: Benefit on Bond Strength and Clinical Applicability

Antioxidants are known for their potential of strengthening the collagen network when applied to dentin. They establish new intra-/intermolecular bonds in the collagen, rendering it less perceptive to enzymatic hydrolysis. The study evaluated the benefit on shear bond strength (SBS) of a resin–composite to dentin when antioxidants with different biomolecular mechanisms or a known inhibitor of enzymatic activity are introduced to the bonding process in a clinically inspired protocol. Specimens (900) were prepared consistent with the requirements for a macro SBS-test. Four agents (Epigallocatechingallate (EGCG), Chlorhexidindigluconate (CHX), Proanthocyanidin (PA), and Hesperidin (HPN)) were applied on dentin, either incorporated in the primer of a two-step self-etch adhesive or as an aqueous solution before applying the adhesive. Bonding protocol executed according to the manufacturer’s information served as control. Groups (n = 20) were tested after one week, one month, three months, six months, or one year immersion times (37 °C, distilled water). After six-month immersion, superior SBS were identified in PA compared to all other agents (p < 0.01) and a higher reliability in both primer and solution application when compared to control. After one year, both PA incorporated test groups demonstrated the most reliable outcome. SBS can benefit from the application of antioxidants. The use of PA in clinics might help extending the lifespan of resin-based restorations.

Is it possible for a simultaneous biomodification during acid etching on naturally caries-affected dentin bonding?

OBJECTIVES

This study investigated the ability of modified phosphoric acids containing chlorhexidine (CHX) or grape seed extract (GSE) for promoting simultaneous biomodification during acid etching on bonding properties in caries-affected dentin (CAD).

MATERIALS AND METHODS

Thirty-two human molars (8 with sound dentin [SD] and 24 naturally CAD) were selected for the study. The SD and CAD were initially exposed, then randomized and etched according to the following groups: (1) SD (SD-CT) and CAD (CAD-CT) both with 37% phosphoric acid, (2) CAD with 2% CHX containing 37% phosphoric acid (CAD-CHX), and (3) CAD with 2% GSE containing 10% phosphoric acid (CAD-GSE). The bonding procedure and composite build-ups were performed after acid etching. Subsequently, they were sectioned in resin-dentin specimens. The specimens were submitted for chemical profiling by micro-Raman, microtensile bond strength (μTBS), failure mode with chemical characterization by FEG/SEM-EDX, and in situ zymography by CLSM. The data from μTBS and CLSM were statistically analyzed (1-way ANOVA and Tukey's test; α = 0.05).

RESULTS

The highest μTBS results were shown for SD-CT in comparison with all CAD groups (p < 0.001), and the lowest for CAD-CT and CAD-CHX (p < 0.001). The etching with CHX did not increase the μTBS for CAD when compared with CT (p = 0.52). However, the etching with GSE improved significantly the μTBS for CAD when compared with CT and CHX (p < 0.001). The chemical profile detected chemical and structural changes in collagen peaks for CAD-CT, which were not detected when the CAD was etched by modified acids. Also, the poorest hybridization ability was detected in CAD for CT, which was significantly improved with modified acids, especially the GSE, as evaluated by chemical profile and failure mode. A significant reduction of MMP activity on CAD was promoted by modified acids in comparison with CT (both p < 0.001).

CONCLUSIONS

The GSE-containing acid was able to promote biomodification during the acid etching, increasing the bonding properties and reducing the activity of the MMPs within the hybrid layer.

CLINICAL RELEVANCE

The use of GSE-containing phosphoric acid can be a promising alternative to improve the bonding performance on caries-affected dentin, since it is capable of biomodifying the dentin during the acid etching, without adding any extra step in bonding procedures.

Does Q-MIX pretreatment improve the dentin bond durability of a two-step self-etch adhesive?

This study aims to analyze and assess the effects of three particular dentin pretreatment solutions on the bond durability of a two-step self-etch adhesive (Optibond XTR) applied to dentin after ageing for 2 years. Thirty-five third molars which were extracted (n = 5 for μTBS, n = 2 for nanoleakage) were divided into five groups: Group 1:Control (no pretreatment), Group 2:17% EDTA, Group 3:2% CHX, Group 4:17% EDTA plus 2% CHX, Group 5: Q-Mix. After the pretreatments of dentin, the dentin adhesive was applied as per the guidelines provided by the manufacturer. Half of the specimens were subjected to μTBS tests for 24 hr, while the remaining half were subjected to the tests after being kept for 2 years in water storage. Also, nanoleakage was evaluated with FE-SEM by examining silver nitrate deposits. The data obtained were evaluated using a two-way analysis of variance and Tukey Post Hoc test. The dentin pretreatments did not affect the 24 hr and 2 years μTBS values for OptiBond XTR. At 24 hr, the EDTA + CHX group (50.3 ± 4.9) showed that the highest μTBS value was obtained. Water ageing significantly reduced the μTBS results and after 2 years the highest μTBS value was obtained from the Q-Mix group (37.7 ± 5.2). Different dentin pretreatments do not alter the 24-hr μTBS and were not able to preserve the bond strength after 2 years of ageing. Q-Mix was able to slow down the regression in the strength of the dentin bond as well as nanoleakage over time.

In situ effect of a proanthocyanidin mouthrinse on dentin subjected to erosion

Proanthocyanidin has been shown to be efficient in inhibiting matrix metalloproteinases.

Could applying gels containing chlorhexidine, epigallocatechin-3-gallate, or proanthocyanidin to control tooth wear progression improve bond strength to eroded dentin?

STATEMENT OF PROBLEM

A consensus on whether or how to treat eroded dentin to bond to composite resins is lacking. The role of gels containing chlorhexidine (CHX), epigallocatechin-3-gallate (EGCG), and proanthocyanidin (PAC) in controlling erosive wear progression needs to be evaluated for bonding.

PURPOSE

The purpose of this in vitro study was to evaluate the effect of gels containing antiproteolytic agents (CHX or EGCG) or an antiproteolytic and also collagen crosslinking agent (PAC) to control tooth wear progression on the microtensile bond strength (μTBS) of an adhesive system plus a composite resin to simulated eroded dentin.

MATERIAL AND METHODS

Superficial occlusal dentin surfaces obtained from sectioned third molars were ground with SiC paper (600-grit; 1 minute; N-normal dentin) or subsequently submitted to an initial erosive challenge (Coca-Cola; 5 minutes). They then received one of the following treatments: application of a placebo (P), a 0.12% CHX digluconate, an EGCG at 400 μM, or a 10% PAC gel (vehicle: hydroxyethylcellulose, propylene glycol, methylparaben, imidazolidinyl urea, and deionized water; active principle: as per the experimental groups when applicable) or no treatment (C: control). Initially demineralized dentin was also submitted to pH cycling (Coca-Cola; 5 minutes, 3×/day, 5 days) to simulate eroded dentin (E). After acid etching all the specimens, adhesive Adper Single Bond 2 was applied, and composite resin (Filtek Z350 XT) was placed. After 24 hours storage in distilled water at 37 °C, the specimens were sectioned into beams, and the μTBS was tested at 0.5 mm/minute. The μTBS values obtained were evaluated considering each tooth as an experimental unit, and 2-way ANOVA and the Tukey post hoc test for multiple comparisons were applied (α=.05).

RESULTS

Immediate μTBS values for the eroded dentin were always lower than those for the normal dentin, irrespective of whether any of the gels were applied for wear control.

CONCLUSIONS

CHX, EGCG, PAC, and placebo gels, applied after the initial demineralization and before the pH cycling to simulate the eroded dentin, had a similar effect on the μTBS of the adhesive system plus the composite resin to simulated eroded dentin when compared with nonapplication (control).

Current perspectives on dental adhesion: (1) Dentin adhesion - not there yet

The essential goal of any adhesive restoration is to achieve a tight and long-lasting adaptation of the restorative material to enamel and dentin. The key challenge for new dental adhesives is to be simultaneously effective on two dental substrates of conflicting nature. Some barriers must be overcome to accomplish this objective. While bonding to enamel by micromechanical interlocking of resin tags within the array of microporosities in acid-etched enamel can be reliably achieved and can effectively seal the restoration margins against leakage, bonding effectively and durably to organic and humid dentin is the most puzzling task in adhesive dentistry.

Much of the research and development of dental adhesives has focused on making the clinical procedure more user-friendly by reducing the number of bottles and/or steps. Although clinicians certainly prefer less complicated and more versatile adhesive materials, there is a trade-off between simplification of dental adhesives and clinical outcomes. Likewise, new materials are launched with claims of being novel and having special properties without much supporting evidence.

This review article discusses dental adhesion acknowledging pioneer work in the field, highlights the substrate as a major challenge to obtain durable adhesive restorations, as well as analyzes the three adhesion strategies and their shortcomings. It also reviews the potential of chemical/ionic dental adhesion, discusses the issue of extensively published laboratory research that does not translate to clinical relevance, and leaves a few thoughts in regard to recent research that may have implications for future adhesive materials.