Self-Etching Adhesives Increase Collagenolytic Activity in Radicular Dentin

Is a Pre-Existent Cone-Beam Computed Tomography Able to Detect Metal Dental Posts?

(1) Background: In this study, the efficacy of cone-beam computed tomography (CBCT) in detecting dental posts was compared to periapical radiography. (2) Methods: A retrospective evaluation of 53 patients' periapical radiographs and CBCT images was performed. The presence and type of the intra-canal dental post were initially determined on the periapical images (PA) radiographs' examination and were then compared to the observer's ability to detect the dental post on a CBCT image. The effect of the post's type (metal cast or prefabricated) on its detection on CBCT images was determined. (3) Results: 10.5% of teeth that were identified as having a post on a PA radiograph were not identified as having a post on the CBCT examination (p < 0.05). Approximately 17.6% of teeth that were identified as not having a post on a PA radiograph were identified as having a post on the CBCT examination (p < 0.05). Moreover, 16.3% and 50% of teeth with a prefabricated or cast posts on PA radiographs were falsely identified on the CBCT examination, respectively (p < 0.05). (4) Conclusions: A CBCT image is an insufficient tool for the identification of metal prefabricated and cast posts. A PA image is the recommended radiographic tool for achieving information about the post-endodontic restoration status of teeth candidates for endodontic retreatment in patients with a former CBCT scan.

High-Performance Bioinspired Microspheres for Boosting Dental Adhesion

Dental adhesives are widely used in daily practice for minimally invasive restorative dentistry but suffer from bond degradation and biofilm attack. Bio-inspired by marine mussels having excellent surface-adhesion capability and high chemical affinity of polydopamine (PDA) to metal ions, herein, experimental zinc (Zn)-containing polydopamine-based adhesive formulation, further being referred to as "Zn-PDA@SiO2"-incorporated adhesive is proposed as a novel dental adhesive. Different Zn contents (5 and 10 mm) of Zn-PDA@SiO2 are prepared. Considering the synergistic effect of Zn and PDA, Zn-PDA@SiO2 not only presents excellent antibacterial potential and notably inhibits enzymatic activity (soluble and matrix-bound proteases), but also exhibits superior biocompatibility and biosafety in vitro/vivo. The long-term bond stability is substantially improved by adding 5 wt% 5 mm Zn-PDA@SiO2 to the primer. The aged bond strength of the experimentally formulated dental adhesives applied in self-etch (SE) bonding mode is 1.9 times higher than that of the SE gold-standard adhesive. Molecular dynamics calculations indicate the stable formation of covalent bonds, Zn-assisted coordinative bonds, and hydrogen bonds between PDA and collagen. Overall, this bioinspired dental adhesive provides an avenue technology for innovative biomedical applications and has already revealed promising perspectives for dental restorative dentistry.

Effects of Etching Time and Ethanol Wet Bonding on Bond Strength and Metalloproteinase Activity in Radicular Dentin

(1) Background: The objective of this in vitro study was to evaluate the impact of different etching times and ethanol pre-treatments on the immediate bond strength of a hydrophilic multi-mode universal adhesive (Clearfil Universal Bond Quick, Kuraray, UBQ) and on the consequent gelatinolytic activity of metalloproteinases (MMPs) on radicular dentin. (2) Methods: Sixty single-root teeth were selected and divided into four groups according to the adhesive protocol applied for fiber post cementation: (G1) 15 s H3PO4 application + UBQ; (G2) 30 s H3PO4 application + UBQ; (G3) 15 s H3PO4 application + ethanol pre-treatment + UBQ; (G4) 30 s H3PO4 + ethanol pre-treatment + UBQ. After adhesive procedures, fiber posts were luted into the post space with a dual-curing cement (DC Core, Kuraray) and light-cured for 40 s. To perform the push-out test and nanoleakage analyses for both coronal end apical areas, 1 mm slices were prepared, following a 24 h storage period in artificial saliva. Additionally, an in situ zymographic assay was conducted to explore endogenous MMP activity within the radicular layer. Results were statistically analyzed with ANOVA and Tukey post hoc tests. Statistical significance was set at p < 0.05. (3) Result: ANOVA revealed a statistically significant difference in push-out bond strength related to the pre-treatment variable but did not highlight any significance of etching time. Specimens pre-treated with ethanol wet bond application showed higher bond strength (p < 0.01). In situ zymography quantification analyses revealed that all tested groups, independently of etching time end ethanol pre-treatment, activated MMP gelatinolytic activity. A significant increase in MMP activity was detected for the 30 s etching time. However, ETOH pre-treatment significantly reduced MMP activity within the adhesive interface (p < 0.01). (4) Conclusions: The tested adhesive showed similar results regardless of the etching time protocol. The gelatinolytic activity of MMPs was observed in all the groups. Further investigations and extended follow-ups are required to validate the results of the present study in vivo.

Final irrigation protocols can be used to promote stable long-term bond strength of AH Plus to dentin

Irrigation solutions might affect dentin surface characteristics and, consequently, endodontic sealers adhesion. This study analyzed the effect of different final irrigation protocols on push-out bond strength (BS) of AH Plus to dentin seven days and 20 months after obturation. Scanning electron micrographs were obtained from the dentin surface of one sample/group after final irrigation. Canals of bovine incisors were instrumented and received final irrigation with (n=21): G1 - 2.5% sodium hypochlorite (NaOCl) + distilled water; G2 - 2.5% NaOCl + 17% EDTA; G3 - 2.5% NaOCl + 17% EDTA + 2.5% NaOCl; G4 - 2.5% NaOCl + 17% EDTA + 2% chlorhexidine (CHX); G5 - mixture 5% NaOCl + 18% etidronate (HEDP); and G6 - mixture 5% NaOCl + 10% tetrasodium EDTA (Na4EDTA). After irrigation, one root/group was split and images were obtained by scanning electron microscopy (SEM). The other 20 roots/group were filled with only AH Plus sealer. Three slices/root were used for push-out assessment seven days and 20 months after obturation. One-way analysis of variance and Tukey (α<0.05) were used to compare the results among experimental groups, and unpaired t-test (α<0.05) was used to compare the results of the same group over time. The photomicrographs showed that, excepting G1, all groups completely removed the smear layer from the samples. In G2 and G4, the opening of the dentin tubules enlarged. In G3, erosion was observed in the peritubular and intertubular dentin. Values of the BS in the seven days were G2=G3=G4=G5>G6=G1 and in the 20 months were G3=G5>G6=G4>G1=G2. G3, G5, and G6 presented values of BS in 20 months similar to the values of seven days (P>0.05). The final irrigation protocols tested produced dentin surfaces with different characteristics. Only G3 and G5 presented high BS values that were stable over time.

Release and MMP-9 Inhibition Assessment of Dental Adhesive Modified with EGCG-Encapsulated Halloysite Nanotubes

Degradation of the collagen fibrils at the dentin-resin interface by the enzymatic activity of matrix metalloproteinases (MMPs) has been known to permit some dental restoration complications, such as microleakage, secondary caries, and, ultimately, restoration failures. This study aimed to evaluate a modified adhesive by adding an MMP inhibitor from green tea extract with and without nanotube encapsulation to sustain the drug release. Epigallocatechin-3-gallate (EGCG) and Halloysite nanotubes (HNTs) were prepared to produce three variant combinations of modified adhesive (EGCG, EGCG-encapsulated HNT, and EGCG-free HNT). The drug loading efficiency and EGCG release over time were evaluated using UV-vis spectrometry. MMP-mediated β-casein (BCN) cleavage rate assays were used to determine the ability of the EGCG in eluates of the adhesive to inhibit MMP-9 activities. For up to 8 weeks, HNT encapsulation reduced release to a statistically significant level. MMP-mediated β-casein cleavage rate assays showed a significant decrease for the EGCG groups compared to the non-EGCG adhesive groups. Furthermore, the use of HNT for EGCG encapsulation to modify a dental adhesive helped slow down the rate of EGCG release without impacting its MMP inhibitory capabilities, which may help to maintain the dentin-resin interface's integrity over the long term after dental restoration placement.

Effect of pretreatment with matrix metalloproteinase inhibitors on the durability of bond strength of fiber posts to radicular dentin

Objectives

Application of matrix metalloproteinases inhibitors has been suggested to improve the durability of resin–dentin bonding. The purpose of this study was to evaluate the effect of dimethyl sulfoxide (DMSO), carbodiimide (EDC), and chlorhexidine (CHX) treatment on the push‐out bond strength of fiber posts to radicular dentin.

Materials and Methods

24 extracted premolars were assigned randomly to 4 groups after root canal treatment and post space preparation (n = 6). In the first, second, and third groups, radicular dentin was treated with 1 ml of 5% DMSO, 0.3 M EDC, and 2% CHX, respectively. The fourth group (control) received no treatment. The root canals were primed with ED primer II, and the fiber posts were cemented with Panavia F2.0. In each group, half of the specimens were subjected to the push‐out test and the other half to 3000 thermal cycles before testing. Data were analyzed using two‐way analysis of variance via SPSS version 20 (p < .05).

Results

Among the nonthermocycled specimens, the values of push‐out bond strength were observed in the control, EDC, CHX, and DMSO groups, in decreasing order. Among the thermocycled specimens, the values were observed in the control, EDC, DMSO, and CHX groups in decreasing order. Thermocycling had a significant adverse effect on the push‐out bond strength (p = .015), but the effect of material (p = .375), and the interaction effect of material and thermocycling (p = .998) were not significant.

Conclusions

Application of CHX, DMSO, and EDC had no significant effect on the bond strength of fiber posts to radicular dentin.

Changes to dentin extracellular matrix following treatment with plant-based polyphenols

This study investigated whether treatment with plant-based polyphenols (PB-P) affected the biochemical and/or biomechanical properties of dentin extracellular matrix (ECM). Three PB-Ps were evaluated: luteolin (LT), galangin (GL), and proanthocyanidin (PAC). Because dentin ECM requires demineralization before treatment, this study also assessed the effect of these PB-Ps on dentin demineralized by two different chemicals. Dentin samples from extracted third molars were obtained, sectioned, and randomly assigned for demineralization with either phosphoric acid (PA) or ethylenediaminetetraacetic acid (EDTA). Following demineralization, baseline infrared (IR) spectra and apparent elastic modulus (AE) of each specimen were independently acquired. Based upon these initial tests, samples were randomly assigned to one of the PB-P treatments to ensure that distribution of baseline AE was similar across treatment groups. IR and AE specimens were individually immersed in either 0.2% LT, 0.4% GL or 1% PAC for 2 min. IR spectra of treated samples were compared to baseline IR spectra, looking for any interaction of PB-Ps with the demineralized dentin. The IR spectrum and AE of each PB-P-treated specimen were compared with their own correspondent baseline measurement. The ability of PB-Ps to inhibit proteolytic activity of dentin ECM was assessed by the hydroxyproline assay. Finally, the effect of PB-Ps on immediate bond strength of a dental adhesive to PA- or EDTA-etched dentin was also evaluated. PB-Ps exhibited distinctively binding affinity to dentin ECM and promoted significant increase in AE. PB-P treatment reduced the degradation rate of dentin ECM without causing detrimental effect on immediate bond strength to dentin. Our work represents the first-time that LT and GL have been assessed as dentin ECM biomodifiers.

Riboflavin and Its Effect on Dentin Bond Strength: Considerations for Clinical Applicability-An In Vitro Study

Bioactive collagen crosslinkers propose to render the dentin hybrid layer less perceptive to hydrolytic challenge. This study aims to evaluate whether bond strength of dental resin composite to dentin benefits from riboflavin (RB)-sensitized crosslinking when used in a clinically applicable protocol. A total of 300 human dentin specimens were prepared consistent with the requirements for a macro-shear bond test. RB was applied on dentin, either incorporated in the primer (RBp) of a two-step self-etch adhesive or as an aqueous solution (RBs) before applying the adhesive, and blue light from a commercial polymerization device was used for RB photoactivation. Bonding protocol executed according to the manufacturer's information served as control. Groups (n = 20) were tested after 1 week, 1 month, 3 months, 6 months or 1 year immersion times (37 °C, distilled water). The different application methods of RB significantly influenced bond strength (p < 0.001) with a medium impact (η2p = 0.119). After 1 year immersion, post hoc analysis identified a significant advantage for RB groups compared to RBp (p = 0.018), which is attributed to a pH-/solvent-dependent efficiency of RB-sensitized crosslinking, stressing the importance of formulation adjustments. We developed an application protocol for RB-sensitized crosslinking with emphasis on clinical applicability to test its performance against a gold-standard adhesive, and are confident that, with a few adjustments to the application solution, RB-sensitized crosslinking can improve the longevity of adhesive restorations in clinics.

Effect of Cavity Cleanser With Long-Term Antibacterial and Anti-Proteolytic Activities on Resin-Dentin Bond Stability

Objective

Secondary caries caused by oral microbiome dysbiosis and hybrid layer degradation are two important contributors to the poor resin-dentin bond durability. Cavity cleansers with long-term antimicrobial and anti-proteolytic activities are in demand for eliminating bacteria-induced secondary caries and preventing hybrid layers from degradation. The objectives of the present study were to examine the long-term antimicrobial effect and anti-proteolytic potential of poly(amidoamine) dendrimers with amino terminal groups (PAMAM-NH₂) cavity cleanser.

Methods

Adsorption tests by attenuated total reflectance-infrared (ATR-IR) spectroscopy and confocal laser scanning microscopy (CLSM) were first performed to evaluate whether the PAMAM-NH₂ cavity cleanser had binding capacity to dentin surface to fulfill its relatively long-term antimicrobial and anti-proteolytic effects. For antibacterial testing, Streptococcus mutans, Actinomyces naeslundii, and Enterococcus faecalis were grown on dentin surfaces, prior to the application of cavity cleanser. Colony-forming unit (CFU) counts and live/dead bacterial staining were performed to assess antibacterial effects. Gelatinolytic activity within the hybrid layers was directly detected by in situ zymography. Adhesive permeability of bonded interface and microtensile bond strength were employed to assess whether the PAMAM-NH₂ cavity cleanser adversely affected resin-dentin bonding. Finally, the cytotoxicity of PAMAM-NH₂ was evaluated by the Cell Counting Kit-8 (CCK-8) assay.

Results

Adsorption tests demonstrated that the binding capacity of PAMAM-NH₂ on dentin surface was much stronger than that of 2% chlorhexidine (CHX) because its binding was strong enough to resist phosphate-buffered saline (PBS) washing. Antibacterial testing indicated that PAMAM-NH₂ significantly inhibited bacteria grown on the dentin discs as compared with the control group (p < 0.05), which was comparable with the antibacterial activity of 2% CHX (p > 0.05). Hybrid layers conditioned with PAMAM-NH₂ showed significant decrease in gelatin activity as compared with the control group. Furthermore, PAMAM-NH₂ pretreatment did not adversely affect resin-dentin bonding because it did not decrease adhesive permeability and microtensile strength. CCK-8 assay showed that PAMAM-NH₂ had low cytotoxicity on human dental pulp cells (HDPCs) and L929.

Conclusions

PAMAM-NH₂ cavity cleanser developed in this study could provide simultaneous long-term antimicrobial and anti-proteolytic activities for eliminating secondary caries that result from a dysbiosis in the oral microbiome and for preventing hybrid layers from degradation due to its good binding capacity to dentin collagen matrix, which are crucial for the maintenance of resin-dentin bond durability.

The effect of chlorhexidine and dimethyl sulfoxide on long-term sealing ability of two calcium silicate cements in root canal

OBJECTIVES

To evaluate the long-term effect of chlorhexidine (CHX) and dimethyl sulfoxide (DMSO) on the sealing ability and biomineralization of two different calcium silicate cements (CSC) in root canal.

METHODS

Sixty human third molar root canals were obturated with ProRoot MTA or Biodentine. Before obturation the canals were irrigated with saline (control), 2% CHX or 5% DMSO. Microleakage was tested after three days and after six months. After additional six months (12 months after root filling) the roots were cut into 2 mm thick dentine discs. The discs were stored in artificial saliva for one year. The bond strength was measured with the push-out method, and the failure mode was evaluated with a stereomicroscope. The most apical disc of each tooth was used for Vickers hardness test.

RESULTS

No significant differences between the groups was found in initial microleakage. The leakage increased significantly during the 6-month storage in all groups except in Biodentine-CHX group and Biodentine-DMSO group. CHX and DMSO irrigation significantly increased the leakage with ProRoot MTA with time, but there was no statistically significant difference compared to the ProRoot MTA-control group at six months' time point. CHX significantly reduced the push-out bond strength of ProRoot MTA. With Biodentine irrigation with CHX or DMSO resulted with significantly higher push-out strength compared to the Biodentine control group. Fracture analysis showed statistically significant difference in the distribution of the fractures between the groups, but neither CHX nor DMSO change the fracture pattern statistically significantly. With Vickers hardness test ProRoot MTA with and without DMSO as the final irrigant showed significantly higher dentin hardness than any Biodentine-group.

SIGNIFICANCE

Considering that aging increased the leakage in all groups except with Biodentine-DMSO and the differences in the push-out strength and surface microhardness data, it appears that the time-related biomineralizing effect of MTA and Biodentine does not improve sealing to dentin. CHX significantly reduced ProRoot MTA bond strength and increased pure adhesive failures with both cements.

Zinc-Calcium-Fluoride Bioglass-Based Innovative Multifunctional Dental Adhesive with Thick Adhesive Resin Film Thickness

Apart from producing high bond strength to tooth enamel and dentin, a dental adhesive with biotherapeutic potential is clinically desirable, aiming to further improve tooth restoration longevity. In this laboratory study, an experimental two-step universal adhesive, referred to as Exp_2UA, applicable in both the etch-and-rinse (E&R) and self-etch (SE) modes and combining a primer, containing 10-methacryloyloxydecyldihydrogen phosphate as a functional monomer with chemical binding potential to hydroxyapatite, with a bioglass-containing hydrophobic adhesive resin, was multifactorially investigated. In addition to primary property assessment, including measurement of bond strength, water sorption, solubility, and polymerization efficiency, the resultant adhesive-dentin interface was characterized by transmission electron microscopy (TEM), the filler composition was analyzed by energy-dispersive X-ray spectroscopy, and the bioactive potential of the adhesive was estimated by measuring the long-term ion release and assessing its antienzymatic and antibacterial potential. Four representative commercial adhesives were used as reference/controls. Application in both the E&R and SE modes resulted in a durable bonding performance to dentin, as evidenced by favorable 1 year aged bond strength data and a tight interfacial ultrastructure that, as examined by TEM, remained ultramorphologically unaltered upon 1 year of water storage aging. TEM revealed a 20 μm thick hydrophobic adhesive layer with a homogeneous bioglass filler distribution. Adequate polymerization conversion resulted in extremely low water sorption and solubility. In situ zymography revealed reduced endogenous proteolytic activity, while Streptococcus mutans biofilm formation was inhibited. In conclusion, the three-/two-step E&R/SE Exp_2UA combines the high bonding potential and bond degradation resistance with long-term ion release, rendering the adhesive antienzymatic and antibacterial potential.

Finite element analysis of immature teeth filled with MTA, Biodentine and Bioaggregate

BACKGROUND AND OBJECTIVE

Finite element based simulation has emerged as a powerful tool to analyse the tooth strength and its fracture characteristics. The aim of this study is to compare and evaluate the fracture resistance of immature teeth reinforcement with MTA, Biodentine and Bioaggregate as an apical plug and backfill material using Finite Element Method.

METHODS

A 3D finite element analysis model was generated using a simulated immature maxillary central incisor. Seven different models were developed representing (Model 1): control group having an immature tooth model without any reinforcement material; (Model 2): Mineral trioxide aggregate (MTA) as apical plug 4 mm; (Model 3): Biodentine as apical plug 4 mm; (Model 4): Bioaggregate as apical plug 4 mm; (Model 5): MTA filled in the entire root canal 8.5 mm; (Model 6): Biodentine filled in the entire root canal 8.5 mm; (Model 7): Bioaggregate filled in the entire root canal 8.5 mm. A force of 100 N was applied at an angle of 130° to the palatal surface of the tooth. Stress distribution at cemento‑enamel junction was measured using the Von Mises stress criteria.

RESULTS

It was found that the 4 mm apical plug using MTA showed higher fracture resistance when compared to 8.5 mm backfill using MTA. When MTA was replaced as backfill material by Biodentine and Bioaggregate, the von mises stress increased by 64% and 94% respectively.

CONCLUSIONS

It is not desirable to restore the entire root canal of an immature teeth using same material due to higher stress concentration at the cervical region. Considering the shorter setting time and improved handling characteristics, Biodentine can be preferred over the time‑tested MTA as an apical plug.

Effect of gallic acid addition on some mechanical properties of self-adhesive resin cements

Self-adhesive resin cements (RCs) activate matrix metalloproteinase (MMP) and cathepsin-related collagen degradation, and gallic acid (GA) inhibits the activity of both MMPs and cysteine cathepsins. The purpose of this study was to evaluate the setting time, biaxial flexural strength, and Vickers hardness of self-adhesive RCs after the addition of two different concentrations of GA. RelyX U200 (3M ESPE) and Panavia SA (Kuraray) were modified with 0.5 and 1 wt% GA. The setting time of five samples in each RC group was assessed using a thermocouple apparatus as described in the ISO 4049 test. Biaxial flexure strength was measured using a universal testing machine until failure. Vickers hardness was measured with three randomized indentations on the surface of each resin disc. RCs without GA were used as control. Data were analyzed using a one-way analysis of variance and Tukey's HSD test (α = 0.05). The setting times ranged from 2.4 to 4.6 min for RelyX and from 4.9 to 6.0 min for Panavia. The biaxial flexure strength ranged from 76.5 to 109.7 MPa for RelyX and from 73.3 to 108.2 MPa for Panavia. Vickers hardness values ranged from 41.6 to 58.6 for RelyX and 27.2 to 33.6 for Panavia. The addition of 0.5 and 1 wt% GA to improve durability of resin-dentin bonds had no adverse effects on setting time, whereas the biaxial flexure strength and Vickers hardness values for the tested materials were significantly reduced.

The Effect of Chlorhexidine and Dimethyl Sulfoxide on Long-Term Microleakage of Two Different Sealers in Root Canals

Objective

The aim of root canal obturation is to prevent leakage and inhibit microbial invasion. This study aimed to determine the effect of chlorhexidine (CHX) and dimethyl sulfoxide (DMSO) as final irrigants on microleakage of root filling immediately and after 18 months. The hypothesis was that either CHX or DMSO would not affect the immediate or long-term microleakage.

Methods

A total of 120 human third molar root canals were obturated with RealSeal SE or Topseal and gutta percha. Before obturation, the canals were irrigated with saline (control), 2% CHX or 5% DMSO. Microleakage of half of each groups (n=10) was measured after 3 days, and of the other half was measured after 18 months with fluid filtration method.

Results

In immediate measurements, RealSeal SE performed significantly better in CHX-irrigated group (p=0.035; Mann-Whitney test). For both sealers, DMSO had the lowest mean microleakage values, which were also statistically significantly lower than with CHX irrigation within sealers (p<0.009 for Topseal and p=0.04 for RealSeal SE; Mann-Whitney test). With RealSeal SE, the microleakage with CHX was significantly higher than that in controls (p=0.022; Mann-Whitney test).

Conclusion

Neither final irrigant showed statistically significant differences in the immediate microleakage within the two sealers. Irrigation with DMSO caused significantly less microleakage than CHX for both sealers after 18 months.

Effect of adhesive mode and chlorhexidine on microtensile strength of universal bonding agent to sound and caries-affected dentins

Objective:

The main objective of this study is to assess the effect of the adhesive mode and chlorhexidine (CHX) on the microtensile strength of a universal bonding agent to sound and caries-affected dentins.

Materials and Methods:

Six intact third molars and six decayed third molars were sectioned to obtain two middle dentin specimens per tooth. Prime and Bond Elect Universal (Dentsply) was applied to specimens in two different modes: Etch-and-rinse (ER, phosphoric acid for 15s) and self-etch (SE, no phosphoric acid). 2% CHX (Cavity Cleanser, Bisco) was applied to both dentins for 30 s. Specimens were randomly assigned into eight groups (n = 3) according to the treatments applied to sound and caries-affected dentins: SE; ER; SE + CHX; and ER + CHX. All specimens were restored with TPH Spectra High Viscosity (Dentsply) composite resin and sectioned to obtain specimens of 0.8 ± 0.1 mm². The microtensile bond strength test was conducted at 1 mm/min. The data were statistically analyzed by ANOVA and multiple comparisons’ test (α = 0.05).

Results:

There was no significant difference between sound dentin and caries-affected dentin (P = 0.132). The highest bond strength was obtained with the application of the ER (31.81MPa). SE + CHX promoted the lowest bond strength with no statistical difference to ER + CHX (P > 0.05).

Conclusions:

ER mode for the universal bonding agent yielded the highest bond strength to sound and caries-affected dentins. CHX reduced the bond strength to both dentins regardless the application of phosphoric acid.

Clinical Significance:

The universal bonding agent increased the bond strength to sound and caries-affected dentins when applied by the ER mode.

Quaternary ammonium silane-based antibacterial and anti-proteolytic cavity cleanser

OBJECTIVE

Secondary caries and degradation of hybrid layers are two major challenges in achieving durable resin-dentin bonds. The objectives of the present study were to investigate the effects of a 2% quaternary ammonium silane (QAS) cavity cleanser on bacteria impregnated into dentin blocks and the gelatinolytic activity of the hybrid layers.

METHODS

Microtensile bond strength was first performed to evaluate if the 2% QAS cavity cleanser adversely affected bond strength. For antibacterial testing, Streptococcus mutans and Actinomyces naeslundii were impregnated into dentin blocks, respectively, prior to the application of the cavity cleanser. Live/dead bacterial staining and colony-forming unit (CFU) counts were performed to evaluate their antibacterial effects. Gelatinolytic activity within the hybrid layers was directly examined using in-situ zymography. A double-fluorescence technique was used to examine interfacial permeability immediately after bonding.

RESULTS

The cavity cleanser did not adversely affect the bond strength of the adhesives tested (p>0.05). Antibacterial testing indicated that 2% QAS significantly killed impregnated bacteria within the dentin blocks compared with control group (p<0.05), which was comparable with the antibacterial activity of 2% chlorhexidine (p>0.05). Hybrid layers pretreated with 2% QAS showed significant decrease in enzyme activity compared with control group. With the use of 2% QAS, relatively lower interfacial permeability was observed, compared with control group and 2% chlorhexidine (p<0.05).

SIGNIFICANCE

The present study developed a 2% QAS cavity cleanser that possesses combined antimicrobial and anti-proteolytic activities to extend the longevity of resin-dentin bonds.

Optimizing resin-dentin bond stability using a bioactive adhesive with concomitant antibacterial properties and anti-proteolytic activities

Secondary caries and hybrid layer degradation are two major challenges encountered in long-term resin-dentin bond stability. As a link between resin and dentin, adhesives that possess both antimicrobial and anti-proteolytic activities are in demand for eliminating bacteria-induced secondary caries and preventing hybrid layers from degradation. In the present study, a new quaternary ammonium methacryloxy silane (QAMS) prepared from sol-gel chemistry was incorporated into experimental adhesives to examine their antimicrobial effect and anti-proteolytic potential. This functional methacrylate resin monomer contains polymerizable methacryloxy functionalities as well as a positively-charged quaternary ammonium functionality with a long, lipophilic -C₁₈H₃₇ alkyl chain for puncturing the cell wall/membrane of surface-colonizing organisms. Antibacterial testing performed using agar diffusion test, live/dead bacterial staining and colony-forming unit counts all indicated that the QAMS-containing adhesives killed Streptococcus mutans and Actinomyces naeslundii in a dose-dependent manner via a predominant contact-killing mechanism. Gelatinolytic activity within the hybrid layers created by these adhesives was examined using in-situ zymography. Hybrid layers created with 0% QAMS-containing adhesive exhibited intense green fluorescence emitted by the hydrolyzed fluorescein-conjugated gelatin, with 4-fold increase in enzymatic activity compared with an experimental adhesive containing 5% QAMS. Taken together, incorporation of 5% QAMS in the experimental adhesive provides simultaneous antimicrobial and anti-proteolytic activities that are crucial for the maintenance of long-term resin-dentin bond integrity.

STATEMENT OF SIGNIFICANCE

Durability of resin-dentin interfacial bond remains a clinically-significant challenge. Secondary caries caused by bacteria and the degradation of hybrid layers via endogenous dentin proteases are two important contributors to the poor resin-dentin bond durability. The present study developed a new 5% QAMS-containing adhesive that provides simultaneous antimicrobial and dentin protease inhibition functions to extend the longevity of resin-dentin bonds.

An ex vivo evaluation of effect of dentin pretreatment with various agents for varying time intervals on the shear bond strength of resin

Background:

This article highlights the contribution of collagen structure/stability to the bond strength. We hypothesize that induction of cross-linking in dentin collagen fibrils improves dentin collagen stability and thus bond strength with composite also improves.

Aims:

The aim of the study was to evaluate the effect of collagen cross-linking agents on the shear bond strength of composite resins.

Subjects and Methods:

One hundred human permanent teeth were randomly divided into three groups: Group I (n = 20) – no dentin pretreatment done, Group II – dentin pretreatment with 10% sodium ascorbate for 5 min (IIa) and 10 min (IIb), and Group III – dentin pretreatment with 6.5% proanthocyanidin (PA) for 5 min (IIIa) and 10 min (IIIb). A composite resin was bonded on prepared surfaces and cured. Thermocycling was done, and shear bond strength of the prepared samples was tested using a universal testing machine.

Results:

Values of Group I (control) were lowest whereas that of Group II (sodium ascorbate) were highest. The following order of shear bond strength was observed: IIb > IIa > IIIb ~ IIIa > I. Results for sodium ascorbate were found to be time dependent, whereas for PA, differences were nonsignificant.

Conclusions:

Treatment of dentinal surfaces with collagen cross-linking agent increases the shear bond strengths.

Dual function of proanthocyanidins as both MMP inhibitor and crosslinker in dentin biomodification: A literature review

Proanthocyanidin, a natural phytochemical bioactive agent, simultaneously can silence the activity of dentinal proteases and crosslink the collagen matrix; both of these phenomena would be the fundamentals for bio-stability of resin-dentin interface which is essential for a promising adhesive dentistry. This review provides an overview of the data developed by different groups of researchers and highlighted topics are proanthocyanidin chemistry, natural resources and the unique interactions between proanthocyanidincollagen and proanthocyanidin-MMPs in dentin. Besides, clinical applications of proanthocyanidin in the form of proanthocyanidin-containing adhesives, preconditioners and etchants have been reviewed. One hundred and twelve studies have been published in peer-reviewed journals from 1981 to 2017, all were comprised in this review, some of them have been actually proven to be promising from clinical point of view and others need further assessment before their adoption as clinically practicable protocols.

Effect of Baicalein on Matrix Metalloproteinases and Durability of Resin-Dentin Bonding

OBJECTIVE

In an attempt to increase resin-dentin bonding quality, this study used baicalein as a preconditioner in an etch-and-rinse adhesive to evaluate its effect on matrix metalloproteinases (MMPs) and adhesive durability.

METHODS

As a MMP inhibitor and potential collagen cross-linking agent, baicalein was used as a preconditioner in an etch-and-rinse adhesive system. The degree of conversion was evaluated by Fourier-transform infrared spectroscopy. EnzChek gelatinase/collagenase assay kits were then used to detect the MMP inhibitory effect of different concentrations of baicalein (0.1, 0.5, 2.5, and 5.0 μg/mL) on dentin powders. During in vitro bonding procedures, flat dentin surfaces on sound third molars were preconditioned with 2.5 μg/mL baicalein after being acid-etched; this step was followed by continuation of adhesive processes and build-up of resin composite. After resin-dentin stick preparation, bonding strength, failure mode, and interface nanoleakage were respectively evaluated via microtensile testing, stereomicroscopy, and field emission scanning electron microscopy either immediately or after storage in artificial saliva for three or six months. Data were analyzed by two-way analysis of variance and Tukey test (α=0.05).

RESULTS

Baicalein at a concentration of 0-5.0 μg/mL did not influence the conversion of adhesives. However, it inhibited the activities of dentin-bond gelatinase and collagenase, especially at a concentration of 2.5 μg/mL, while effectively increasing microtensile bonding strength and decreasing nanoleakage in vitro, both immediately and after aging.

CONCLUSIONS

Baicalein used as preconditioner in an etch-and-rinse adhesive system has an anti-MMP function and effectively improves resin-dentin bonding durability in vitro, which has potential value in clinical bonding procedures.

The effect of two cross-linking agents on dentin bond strength of resin-modified glass ionomer

Objectives:

The hybrid layer at the interface of resin-modified glass ionomer cements and dentin is prone to degradation by endogenous matrix metalloproteinases. We aimed to investigate the effect of two types of collagen crosslinkers, carbodiimide and proanthocyanidin (PA), on immediate and medium-term bond strength of a resin-modified glass ionomer to dentin.

Materials and Methods:

Seventy-two molars were flattened on the occlusal surface to expose dentin. The specimens were divided into control, 1-ethyl-3-(3-dimethylaminopropy) carbodiimide hydrochloride (EDC), and PA groups (n = 24). In the EDC and PA groups, carbodiimide and PA solutions were applied for 1 min, respectively. Resin-modified glass ionomer was bonded. Half of the specimens in each group were tested for shear bond strength after 24 h and the other half were tested after 6 months.

Statistical Analysis:

Data were analyzed with SPSS version 16 (SPSS Inc, Chicago, IL, USA), using two-way ANOVA, and subgroup analysis was performed using one-way ANOVA, Tukey's test, and t-test.

Results:

Two-way ANOVA showed that treatment and time affected the bond strength. Carbodiimide and PA did not affect the immediate bond strength (P = 0.51). After 6 months, the bond strength of the EDC group was significantly lower than that of the control and PA groups. Bond strength of the control and PA groups increased after 6 months (P ≤ 0.002).

Conclusion:

PA did not interfere with maturation of RMGIC unlike carbodiimide. Therefore, it can be suggested as an matrix metalloproteinase inhibitor before bonding of resin-modified glass ionomer to dentin.

Long-Term Bond Strength of Two Benzalkonium Chloride-Modified Adhesive Systems to Eroded Dentin

This study investigated the effect of benzalkonium chloride (BAC) modification of two adhesive systems on long-term bond strength to normal and artificially eroded dentin. A total of 128 extracted human molars were sectioned and the buccal and oral surfaces of each molar were ground until the dentin. One half was left untreated (normal dentin) while the other half underwent artificial erosion. Resin composite was bonded to the buccal or oral surface following treatment with Adper Scotchbond 1XT or OptiBond FL without or with 1% BAC incorporation. Shear bond strength (SBS) was measured after 24 h (100% humidity, 37°C) or 1 year (tap water, 37°C). SBS results were statistically analyzed (α = 0.05). SBS was significantly lower to artificially eroded dentin than to normal dentin (p < 0.001). Storage for 1 year had no effect on SBS to normal dentin but led to a significant decrease in SBS to artificially eroded dentin (p < 0.001). BAC incorporation decreased the 24 h SBS to normal dentin (p = 0.018), increased the 24 h SBS to eroded dentin (p = 0.001), and had no effect on the 1-year SBS for either substrate. Consequently, BAC incorporation did not improve bond durability.

The effects of 2-hydroxyethyl methacrylate on matrix metalloproteinases 2 and 9 in human pulp cells and odontoblast-like cells in vitro

AIM

To assess the effects of 2-hydroxyethyl methacrylate (HEMA) on proliferation and migration of human pulp cells, as well as on matrix metalloproteinase (MMP-2 and MMP-9) expression in human odontoblast-like cells, contributing to the goal of determining the relationship between resin materials and MMP activity in pulp-dentine complexes.

METHODOLOGY

Dental pulp cell cultures were established from pulp tissue of human teeth extracted for orthodontic purposes. Pulp cell differentiation was characterized in the presence of dentine sialophosphoprotein, bone sialoprotein and alkaline phosphatase by reverse transcription polymerase chain reaction. MMP activity was assessed by gelatine zymography with media containing HEMA. Cell viability was evaluated using methyl thiazolyl tetrazolium assay for 24-72 h. Cell migration was tested using Transwell migration assay. Western blotting was used to visualize MMP expression with the nontoxic HEMA concentrations (0-400 μg mL^-1 ) for 48 h.

RESULTS

Pulp cell proliferation decreased with HEMA exposure in a time- and concentration-dependent manner. HEMA concentrations ≤400 μg mL^-1 did not induce changes in cell viability at 48 h (P < 0.05). Pulp cells were induced to differentiate into odontoblast-like cells in media containing 5 mg mL^-1 ascorbic acid and 10 mmol L^-1 β-sodium glycerophosphate for 3-4 weeks. After incubation with HEMA, dose-dependent inhibition was observed; HEMA had a strong inhibitory effect on MMP activity. Compared with the control group, cell migration and MMP expression were inhibited significantly with increasing HEMA concentration at noncytotoxic doses (P < 0.05).

CONCLUSIONS

Cell viability was not affected at HEMA concentrations ≤400 μg mL^-1 . Within this range, HEMA inhibited MMP-2 and MMP-9 expression and activity, which may protect against type I collagen degradation effectively during dentine adhesive procedures.

Chlorhexidine-Loaded Amorphous Calcium Phosphate Nanoparticles for Inhibiting Degradation and Inducing Mineralization of Type I Collagen

A major shortcoming of contemporary dentin adhesives is their limited durability. Exposed collagen fibrils within the bonding interface are degraded by matrix metalloproteinases (MMPs), resulting in aging of the resin-dentin bond. In this study, chlorhexidine-loaded amorphous calcium phosphate (ACP) nanoparticles were synthesized to induce the mineralization of collagen fibrils. The nanoparticles sustainably released chlorhexidine to inhibit MMPs during mineralization. Three types of ACP nanoparticles were prepared: N-ACP containing no chlorhexidine, C-ACP containing chlorhexidine acetate, and G-ACP containing chlorhexidine gluconate, which had a higher drug-loading than C-ACP. Scanning and transmission electron microscopy indicated that the synthesized nanoparticles had diameters of less than 100 nm. Some had diameters of less than 40 nm, which was smaller than the width of gap zones in the collagen fibrils. Energy dispersive X-ray spectroscopy, Fourier-transform infrared spectroscopy, and high performance liquid chromatography confirmed the presence of chlorhexidine in the nanoparticles. X-ray diffraction confirmed that the nanoparticles were amorphous. The drug loading was 0.11% for C-ACP and 0.53% for G-ACP. In vitro release profiles indicated that chlorhexidine was released sustainably via first-order kinetics. Released chlorhexidine inhibited the degradation of collagen in human dentine powder, and its effect lasted longer than that of pure chlorhexidine of the same concentration. The ACP could induce the mineralization of self-assembled type I collagen fibrils. The chlorhexidine-loaded ACP nanoparticles sustainably released chlorhexidine and ACP under appropriate conditions. This is useful for inhibiting degradation and inducing the mineralization of dentine collagen fibrils.

Experimental primers containing synthetic and natural compounds reduce enzymatic activity at the dentin-adhesive interface under cyclic loading

OBJECTIVE

To evaluate the effect of experimental primers (chlorhexidine, enriched mixture of proanthocyanidins, and doxycycline) on the adhesive properties and gelatinolytic activity at dentin-resin interfaces of occlusal Class I restorations.

METHODS

The inactivation of enzymes by the experimental primers was assessed by fluorescence assay and gelatin zymography. To assess the adhesive properties, occlusal Class I cavities were prepared in sound human molars, etched with phosphoric acid and restored with one of the primers and an etch-and-rinse adhesive system (Adper Single Bond Plus-3M ESPE). After the restorative procedures, specimens were divided into two subgroups (n=6) consisting of storage in incubation buffer or axial cyclic loading at 50N and 1,000,000 cycles. Then, the specimens were sectioned and slices were assigned to in situ zymography assay and microtensile bond strength (TBS) test.

RESULTS

Fluorescence assay and gelatin zymography revealed that the experimental primers inactivated rMMPs. In situ zymography (2-way ANOVA, Tukey, p<0.05) showed that cyclic loading increased the gelatinolytic activity at the resin-dentin interface and the experimental primers decreased the gelatinolytic activity at the adhesive interface. The experimental primers had no significant effects on dentin-adhesive bond strengths with or without cyclic loading (2-way ANOVA, p>0.05).

SIGNIFICANCE

The use of experimental primers impaired the enzymatic activity at the dentin-adhesive interface after cyclic loading and the activity of rMMPs. Cyclic loading did not have a significant effect on the bond strength.

Clinical evaluation of composite restorations in Er:YAG laser-prepared cavities re-wetting with chlorhexidine

OBJECTIVES

The objective of this study was to evaluate longitudinally the composite restorations, performed in cavities prepared by Er:YAG or conventional bur, and dentin re-wetting with water or chlorhexidine.

MATERIALS AND METHODS

Twenty individuals with four active caries with cavitation reaching the dentin located on the occlusal surface of molars counterparts are selected. The teeth of each individual were randomly assigned into four groups: (I) Er:YAG laser (260 mJ/4 Hz) re-wetting with chlorhexidine, (II) Er:YAG laser (260 mJ/4 Hz) re-wetting with deionized water, (III) conventional method re-wetting with chlorhexidine, and (IV) conventional method re-wetting with deionized water. The teeth were isolated, prepared cavities, phosphoric acid etching, and re-wetting according to previously assigned method. Restoration was performed employing the Single Bond 2 and Z350XT resin. Clinical follow-up was held after the polishing of the restoration (baseline) and 6 and 12 months of the making of the restoration using the modified USPHS criteria. The restorations were qualitatively analyzed by means of photographs. In the evaluation period, replicas of the restorations were analyzed by SEM. Data were analyzed by statistics using chi-square test (p < 0.05).

RESULTS

After 12 months of clinical evaluation, groups prepared with laser and re-wetting with chlorhexidine and water showed the lowest marginal staining value. There was no statistical difference between the groups for other factors. SEM analysis revealed that a non-expressive amount of restorations showed gaps and irregularities of tooth-restoration interface after 6 and 12 months compared to the baseline.

CONCLUSION

The restorations performed in laser-prepared cavities, regardless of the re-wetting, presented the best clinical performance over the evaluated period.

CLINICAL RELEVANCE

Laser-prepared teeth, regardless of re-wetting, showed greater resistance to marginal discoloration.

In Vivo and In Vitro Effects of Chlorhexidine Pretreatment on Immediate and Aged Dentin Bond Strengths

This study evaluated the effect of 2% chlorhexidine (CHX) pretreatment of dentin on the immediate and aged microtensile bond strength (μTBS) of different adhesives to dentin in vivo and in vitro. Class I cavities were prepared in 80 caries-free human third molars of 40 patients in a split-mouth fashion. In each tooth pair, one tooth received 2% CHX pretreatment after which both teeth were randomly assigned to one of the following groups with respect to the type of adhesive system applied: Adper Single Bond 2 (etch-and-rinse), Clearfil SE Bond (two-step self-etch), Clearfil S(3) Bond (one-step self-etch), and Adper Prompt-L-Pop (all-in-one self-etch). The teeth were restored with resin composite and extracted for μTBS testing either immediately or after six months in function. In vitro specimen pairs were prepared as with the clinical protocol in intact, freshly extracted human molars, and thereafter, subjected to testing immediately or after 5000× thermocycling. Data were analyzed with four-way analysis of variance (ANOVA). Bonferroni test was utilized for pair-wise comparisons. The immediate bond strength values were significantly higher than "aged" ones for all tested adhesives (p=0.00). The in vitro immediate bond strength values were statistically higher than in vivo bond strength values (p<0.05). While the bond strength of in vitro aged, CHX-treated samples were higher than their in vivo counterparts (p<0.05), no difference was observed in non-CHX treated groups (p>0.05). In the absence of CHX pretreatment, all adhesives showed significantly higher immediate bond strength values than CHX-treated groups, while all "aged", non-pretreated adhesives exhibited significantly lower bond strength values (both p<0.05). By contrast, chlorhexidine pretreatment resulted in significantly higher aged bond strengths, regardless of the adhesive system and testing condition. Aging-associated decline in dentin bond strength of etch-and rinse and self-etch adhesives can be counteracted by chlorhexidine application.

Effect of Carbodiimide on Bonding Durability of Adhesive-cemented Fiber Posts in Root Canals

This study was undertaken to investigate whether using a protein cross-linker, 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide (EDC), improves bonding stability of fiber posts to root dentin using three resin cements. Sixty human maxillary central incisor roots were randomly divided into six groups after endodontic treatment, according to the cements used with and without EDC pretreatment. In the etch-and-rinse group, 0.3 M EDC aqueous solution was applied on acid-etched root dentin prior to Excite DSC/Variolink II for post cementation. In the self-etch and self-adhesive groups, EDC was used on EDTA-conditioned root space prior to application of ED Primer II/Panavia F2.0 and Clearfil SA, respectively. After microslicing the root dentin, a push-out bond strength (BS) test was performed immediately or after one-year of water storage for each group. Data were analyzed using three-way analysis of variance and Tukey tests (α=0.05). A significant effect of cement type, time, EDC, and Time × Cement and Time × EDC interactions were observed (p≤0.001). EDC pretreatment did not affect immediate bonding of the three cements (p>0.05). Aging significantly reduced the BS in all the groups (p≤0.001), but EDC groups exhibited a higher BS compared with the respective control groups (p<0.001). Despite the significant effect of aging on decreasing the BS of fiber post to radicular dentin, EDC could diminish this effect for the three tested cements.

Effect of carbodiimide on the fatigue crack growth resistance of resin-dentin bonds

Recent studies have shown that ethyl-3-(3-dimethylaminopropyl) carbodiimide (EDC) inactivates endogenous dentin proteases, thereby preventing collagen degradation and improving the durability of adhesive bonds to dentin. Bond durability is routinely assessed by monotonic microtensile testing, which does not consider the cyclic nature of mastication.

OBJECTIVE

To characterize the effect of an EDC pretreatment on the fatigue crack growth behavior of resin-dentin bonds.

METHODS

Bonded interface Compact Tension (CT) specimens were prepared using a three-step etch-and-rinse adhesive and hybrid resin-composite. Adhesive bonding of the treated groups included a 1 min application of an experimental EDC conditioner to the acid-etched dentin. The control groups did not receive EDC treatment. The fatigue crack growth resistance was examined after storage in artificial saliva for 0, 3 and 6 months.

RESULTS

There was no significant difference in the immediate fatigue crack growth resistance of the EDC-treated and control groups at 0 months. However, after the 3 and 6 months storage periods the EDC-treated groups exhibited significantly greater (p≤0.05) fatigue crack growth resistance than the control specimens.

SIGNIFICANCE

Although the EDC treatment maintained the fatigue crack growth resistance of the dentin bonds through 6 months of storage, additional studies are needed to assess its effectiveness over longer periods and in relation to other cross-linking agents.

Immediate human pulp response to ethanol-wet bonding technique

OBJECTIVES

To evaluate the short-term response of human pulps to ethanol-wet bonding technique.

METHODS

Deep class V cavities were prepared on 17 sound premolars and divided into three groups. After acid-etching, the cavities from groups 1 (G1) and 2 (G2) were filled with 100% ethanol or distilled water, respectively, for 60 s before the application of Single Bond 2. In group 3 (G3, control), the cavity floor was lined with calcium hydroxide before etching and bonding. All cavities were restored with resin composite. Two teeth were used as intact control. The teeth were extracted 48h after the clinical procedures. From each tooth serial sections were obtained and stained with haematoxylin and eosin (H/E) and Masson's trichrome. Bacteria microleakage was assessed using Brown & Brenn. All sections were blindly evaluated for five histological features.

RESULTS

Mean remaining dentine thickness was 463±65μm (G1); 425±184μm (G2); and 348±194μm (G3). Similar pulp reactions followed ethanol- or water-wet bonding techniques. Slight inflammatory responses and disruption of the odontoblast layer related to the cavity floor were seen in all groups. Stained bacteria were not detected in any cavities. Normal pulp tissue was observed in G3 except for one case.

CONCLUSIONS

After 48h, ethanol-wet bonding does not increase pulpal damage compared to water-wet bonding technique.

CLINICAL SIGNIFICANCE

Ethanol-wet bonding may increase resin-dentine bond durability. This study reported the in vivo response of human pulp tissue when 100% ethanol was applied previously to an etch-and-rinse simplified adhesive system.

Inhibition of matrix metalloproteinase activity in human dentin via novel antibacterial monomer

OBJECTIVE

Dentin-composite bond failure is caused by factors including hybrid layer degradation, which in turn can be caused by hydrolysis and enzymatic degradation of the exposed collagen in the dentin. The objectives of this study were to investigate a new antibacterial monomer (dimethylaminododecyl methacrylate, DMADDM) as an inhibitor for matrix metalloproteinases (MMPs), and to determine the effects of DMADDM on both soluble recombinant human MMPs (rhMMPs) and dentin matrix-bound endogenous MMPs.

METHODS

Inhibitory effects of DMADDM at six mass% (0.1% to 10%) on soluble rhMMP-8 and rhMMP-9 were measured using a colorimetic assay. Matrix-bound endogenous MMP activity was evaluated in demineralized human dentin. Dentin beams were divided into four groups (n=10) and incubated in calcium- and zinc-containing media (control medium); or control medium+0.2% chlorhexidine (CHX); 5% 12-methacryloyloxydodecylpyridinium bromide (MDPB); or 5% DMADDM. Dissolution of dentin collagen peptides was evaluated by mechanical testing in three-point flexure, loss of dentin mass, and a hydroxyproline assay.

RESULTS

Use of 0.1% to 10% DMADDM exhibited a strong concentration-dependent anti-MMP effect, reaching 90% of inhibition on rhMMP-8 and rhMMP-9 at 5% DMADDM concentration. Dentin beams in medium with 5% DMADDM showed 34% decrease in elastic modulus (vs. 73% decrease for control), 3% loss of dry dentin mass (vs. 28% loss for control), and significantly less solubilized hydroxyproline when compared with control (p<0.05).

SIGNIFICANCE

The new antibacterial monomer DMADDM was effective in inhibiting both soluble rhMMPs and matrix-bound human dentin MMPs. These results, together with previous studies showing that adhesives containing DMADDM inhibited biofilms without compromising dentin bond strength, suggest that DMADDM is promising for use in adhesives to prevent collagen degradation in hybrid layer and protect the resin-dentin bond.

Aging of adhesive interfaces treated with benzalkonium chloride and benzalkonium methacrylate

Inhibition of endogenous dentin matrix metalloproteinases (MMPs) within incompletely infiltrated hybrid layers can contribute to the preservation of resin-dentin bonds. This study evaluated the bond stability of interfaces treated with benzalkonium chloride (BAC) and benzalkonium methacrylate (MBAC), and the inhibitory properties of these compounds on dentin MMP activity. Single-component adhesive ALL-BOND UNIVERSAL, modified with BAC or MBAC at concentrations of 0, 0.5, 1.0, and 2.0%, was used for microtensile bond strength (μTBS) evaluation after 24 h, 6 months, and 1 yr. Beams produced from human dentin were treated with 37% phosphoric acid, dipped in 0.5% BAC, 1.0% BAC, or water (control) for 60 s, and then incubated in SensoLyte generic MMP substrate to determine MMP activity. A significant decrease in the μTBS after 6 months and 1 yr was observed for the control group only. No significant differences among groups were shown at 24 h. After 6 months and 1 yr, the control group demonstrated significantly lower μTBS than all treatment groups. When applied for 60 s, 0.5% BAC inhibited total MMP activity by 31%, and 1.0% BAC inhibited total MMP activity by 54%. Both BAC and MBAC contributed to the preservation of resin-dentin bonds, probably because of their inhibitory properties of endogenous dentin proteinases.

Influence of pH change and water storage on the sealing ability of two resin-based root-filling materials

AIM

To evaluate the Influence of pH change and water storage up to 90 days on the sealing ability of two resin-based root-filling materials.

MATERIALS AND METHODS

Forty-four human mandibular single-rooted teeth were instrumented and filled with gutta-percha/ AH Plus or Resilon/Epiphany SE (n=20 per group). Two teeth each were used as positive and negative controls. Specimens were set for 7 days under 100% humidity at 37°C. They were allocated into two subgroups (n=10) according to whether they were tested immediately or stored for up to 90 days in water before testing. Sealing ability was evaluated by passive dye penetration. Absorbance at 630 nm (in μg/ml) was measured by spectrophotometry. The pH values were obtained in triplicate. Data were submitted to ANOVA by post-hoc Tukey's test (α=0.05).

RESULTS

Specimens filled with Resilon/Epiphany SE exhibited more leakage than specimens filled with gutta-percha/AH Plus at the immediate time point (p<0.001). No differences were detected between the groups after storage, or between the materials with pH changes after 30, 60 and 90 days (p>0.05).

CONCLUSION

Gutta-percha/AH Plus provided superior sealing at the immediate time point. Water storage and pH changes did not Influence the sealing ability of tested materials.

CLINICAL SIGNIFICANCE

These results suggest that Resilon/ Epiphany SE sealer offered no apparent advantage over the more conventional gutta-percha/AH Plus sealer technique in terms of sealing ability.

Addition of benzalkonium chloride to self-adhesive resin-cements: some clinically relevant properties

OBJECTIVE

The clinical survival rates of the adhesive restorations are limited due to the deterioration of resin-dentin bonds over time, partly due to the endogenous enzymatic activity of dentin. Recently, benzalkonium chloride (BAC) has been shown to effectively inhibit endogenous protease activity of dentin. This study evaluated the effect of different concentrations of benzalkonium chloride (BAC) on the degree of conversion (DC), vickers hardness (VH), setting time (ST) and biaxial flexural strength (FS) of two self-adhesive resin luting cements (RC).

METHODS

Two RC SpeedCEM (Ivoclar-Vivadent) and BisCem (Bisco) were modified by addition of 0.1, 0.5, 1, 1.5, 2 wt% BAC. The luting cements without the addition of BAC served as control. The DC (FT-IR/ATR from the bottom of the resin disc), vickers hardness (from top and bottom of the light-cured specimen), setting time (ISO 4049) and biaxial flexural strength (0.6 × 6 mm discs) of the specimens were tested. Data were analyzed using ANOVA and Tukeys HSD.

RESULTS

DC results were in the range of 70-80%, with some significant changes in BisCem (p < 0.05). VH values of both materials increased significantly compared to control, with no significant change as the BAC percentage increases. BAC addition influenced the ST differently for both materials. For BisCem, a gradual decrease (p < 0.05) was observed whereas, for SpeedCEM, a gradual increase was observed until 1% BAC (p < 0.05). For FS values, a gradual decrease was observed for both materials with increased amounts of BAC (p < 0.05), compared to the control group.

CONCLUSIONS

BAC addition of up to 1% seems to be acceptable considering the properties tested. Clinical significance. Incorporation of benzalkonium chloride to self-adhesive resin luting cements during the mixing procedure does not significantly affect the degree of conversion or flexural strength of the luting agent and may be a good option to improve the durability of adhesive interface.

Telechelic poly(2-oxazoline)s with a biocidal and a polymerizable terminal as collagenase inhibiting additive for long-term active antimicrobial dental materials

Dental repair materials face the problem that the dentin below the composite fillings is actively decomposed by secondary caries and extracellular proteases. To address this problem, poly(2-methyloxazoline) with a biocidal and a polymerizable terminal was explored as additive for a commercial dental adhesive. 2.5 wt% of the additive rendered the adhesive contact-active against Streptococcus mutans and washing with water for 101 d did not diminish this effect. The adhesive with 5 wt% additive kills S. mutans cells in the tubuli of bovine dentin. Further, the additive inhibits bacterial collagenase at 0.5 wt% and reduces activity of MMP-9. Human MMPs bound to dentin are inhibited by 96% in a medium with 5 wt% additive. Moreover, no adverse effect on the enamel/dentine shear bond strength was detected.

In Vitro Evaluation of Benzalkonium Chloride in the Preservation of Adhesive Interfaces

Inhibition of endogenous dentin matrix metalloproteinases (MMPs) by benzalkonium chloride (BAC) decreases collagen solubilization and may help improve resin-dentin bond stability. Objective: This study evaluated the resin-dentin bond stability of experimental adhesive blends containing BAC and the stability of dentin matrices by assessing the mass loss and collagen solubilization from dentin beams pretreated with BAC.

Materials and Methods

Twenty-five healthy molars were used for the bond strength evaluation of a two-step etch-and-rinse adhesive (Adper Single Bond Plus, SB) modified with BAC or not. The following groups were tested: 1) SB with no inhibitor (control); 2) topical 2.0% chlorhexidine + SB; 3) 1.0% BAC etchant + SB; 4) 0.5% BAC-SB; and 5) 1.0% BAC-SB. Microtensile bond strength (μTBS) and failure mode distribution under standard error of the mean were evaluated after 24 hours and six months of storage in artificial saliva (AS). A two-way analysis of variance and Tukey test with a significance level of p&lt;0.05 was used for data analysis. In addition, 30 completely demineralized dentin beams from human molars were either dipped in deionized water (DW, control) or dipped in 0.5% and 1.0% BAC for 60 seconds, and then incubated in AS. Collagen solubilization was assessed by evaluating the dry mass loss and quantifying the amount of hydroxyproline (HYP) released from hydrolyzed specimens after four weeks of incubation.

Results

The control group demonstrated lower μTBS than some of the experimental groups containing BAC at 24 hours and six months (p&lt;0.05). When BAC was incorporated into the adhesive blend in concentrations of 0.5% and 1.0%, no reduction in dentin bond strength was observed after six months (p&lt;0.05). Less mass loss and HYP release was seen for dentin matrices pretreated with BAC relative to the control pretreated with DW (p&lt;0.05).

Conclusion

This in vitro study demonstrates that BAC contributes to the preservation of resin-dentin bonds by reducing collagen degradation.

Pre-treatment of radicular dentin by self-etch primer containing chlorhexidine can improve fiber post bond durability

We evaluated whether the pre-treatment of radicular dentin by ED Primer containing different concentrations of chlorhexidine can improve the bond durability of fiber post to radicular dentin. Experimental ED primers containing different concentrations of chlorhexidine (0%, 0.5% and 1.0%) were prepared. Thirty extracted maxillary anterior teeth were divided into 3 groups, each group corresponding to different chlorhexidine concentrations. Fiber posts were cemented in endodontically treated teeth with experimental ED primers and Panavia F. The bonded teeth were transversally sectioned into six slices and then were processed for thin slice push-out test 24 h later or after 18-months water storage. Eighteen-month storage resulted in significant bond strength reduction of all groups (p<0.05). The bond strength reduction of 1.0% group was significantly lower than that of control group and 0.5% group (p<0.05). In conclusion, the incorporation of 1.0% chlorhexidine into ED primer can extend the bond longevity of fiber post to radicular dentin.

Effect of chlorhexidine and ethanol-wet bonding with a hydrophobic adhesive to intraradicular dentine

PURPOSE

To evaluate the effect of adjunctive application of ethanol-wet bonding and chlorhexidine (CHX) with a hydrophobic adhesive on bond durability of fibre posts to intraradicular dentine.

METHODS

Ninety-six extracted human teeth with a single root and root canal were prepared for post placement after endodontic treatment. The teeth were randomly divided into four groups (n=24) after etching and rinsing for rewetting: Group 1: water-wet bonding, Group 2: water-wet bonding with CHX, Group 3: ethanol-wet bonding and Group 4: ethanol-wet bonding with CHX. Teeth in Groups 1 and 2 were treated with either distilled water or distilled water with 2% CHX for 60 s; while teeth in Groups 3 and 4 were treated with either 100% ethanol or 100% ethanol with 2% CHX. Two coats of primer, followed by neat resin were applied and light-cured for 40 s. Fibre posts were luted to bonded root dentine using dual-cure resin cement. Bonded roots were subjected to push-out bond strength testing and interfacial nanoleakage evaluation after 24 h, 6 and 12 months of storage. Data were analyzed using 3-way ANOVA (rewetting solutions, time and post space regions) and SNK tests.

RESULTS

Groups 3 and 4 showed significantly (p<0.05) higher bond strengths and lower nanoleakage than Groups 1 and 2 after 12 months of ageing. Addition of 2% chlorhexidine to ethanol-wet bonding with a hydrophobic adhesive did not further improve the bonding of a fibre post to intraradicular dentine, when compared to ethanol-wet bonding alone after 12 months of ageing.

CLINICAL SIGNIFICANCE

Ethanol-wet bonding with a hydrophobic adhesive alone could improve the bond durability of fibre post to intraradicular dentine and therefore would increase the success rate of post and core restorations of endodontically treated teeth.

Long-term chlorhexidine effect on bond strength to Er:YAG laser irradiated-dentin

This study evaluates the bond strength of dentin prepared with Er:YAG laser or bur, after rewetting with chlorhexidine on long-term artificial saliva storage and thermocycling. One hundred and twenty human third molars were sectioned in order to expose the dentin surface (n = 10). The specimens were randomly divided in 12 groups according to treatment and aging: Er:YAG laser rewetting with deionized water (LW) and 24 h storage in artificial saliva (WC); LW and 6 months of artificial saliva storage + 12.000 thermocycling (6M), LW and 12 months of artificial saliva storage + 24.000 thermocycling (12M), Er:YAG laser rewetting with 2% chlorhexidine (LC) and WC, LC and 6M, LC and 12M, bur on high-speed turbine rewetting with deionized water (TW) and WC, TW6M, TW12M, bur on high-speed turbine + 2% chlorhexidine (TC) and WC, TC and 6M, TC and 12M. The specimens were etched with 35% phosphoric acid, washed, and dried with air. Single Bond 2 adhesive was applied and the samples were restored with a composite. Each tooth was sectioned in order to obtain 4 sticks, which were submitted to microtensile bond strength test (µTBS). The two-way ANOVA, showed no significant differences for the interaction between the factors and for the aging factor. Tukey 5% showed that the LC group had the lowest µTBS. The rewetting with chlorhexidine negatively influenced the bond strength of the preparation with the Er:YAG laser. The artificial saliva aging and thermocycling did not interfere with dentin bond strength.

Effect of a chlorhexidine-containing adhesive on dentin bond strength stability

PURPOSE

The present study aimed to investigate a novel adhesive system containing 0.2% chlorhexidine digluconate (CHX) for its ability to improve the stability of the adhesive interface compared with the use of 2% CHX as a therapeutic primer. Furthermore, the study aimed to confirm the inhibitory properties of these CHX concentrations (0.2% and 2.0%) on dentin matrix metalloproteinase activity by gelatin zymography.

METHODS

Superficial dentin substrate for bonding was obtained from 120 non-carious human molars. A conventional adhesive Peak LC Bond and a CHX-containing adhesive Peak Universal Bond were used either in combination with 35% phosphoric acid (etch-and-rinse approach) or with self-etching primer (self-etch approach) for evaluation of the variables CHX treatment (2.0% therapeutic primer and 0.2% adhesive), adhesive approach (etch-and-rinse and self-etch), and storage time (24 hours and six months). A bonding jig was used to fabricate composite cylinders, which were stored for either 24 hours or six months, after which shear bond strength (SBS) was evaluated using a notched-edge testing device. A three-way analysis of variance and a Student t-test with a significance level of p<0.05 were used to analyze the data. Extracts from concentrated demineralized human dentin powder were subjected to sodium dodecyl sulfate polyacrylamide gel electrophoresis and incubated in the presence of 0.2% and 2.0% CHX.

RESULTS

No significant effect of CHX treatment, adhesive approach, storage time variables, or their interactions on mean SBS was demonstrated (p<0.05). No significant difference between the control and the CHX-treated groups was detected for either adhesive technique at 24 hours or six months (p<0.05). No significant variation in mean SBS was detected after six months of storage (p<0.05). Zymographic analysis revealed bands of enzymatic activity for the group demineralized with phosphoric acid and complete inhibition of gelatinolytic activity for the groups treated with 0.2% and 2.0% CHX.

CONCLUSIONS

CHX demonstrated inhibition of dentin proteolytic activity. However, when CHX was incorporated into a commercially available adhesive or used as a therapeutic primer, no difference in bond strength was observed at baseline or after six months of storage relative to the control group without CHX.