Dentin bonding: can we make it last?

Influence of bioceramic sealer residues on the adhesion interface with a universal adhesive in the etch-and-rinse strategy, based on the application protocol and evaluation time

The aim of this study was to evaluate the effects of the application of universal adhesive in the etch-and-rinse (ER) strategy with a manual brush (MB) or rotary brush (RB) in adhesion to dentin impregnated (WB) or not (NB) with bioceramic sealer, at 24 h and 1 year. Eighty-eight crowns of bovine incisors were divided into four groups (n=22): WB-MB, WB-RB, NB-MB, NB-RB. After the restorative protocol, dentin penetrability was evaluated by confocal microscopy. Bond strength was evaluated by microtensile test. Data were analyzed using one-way ANOVA/Tukey tests (α=0.05). NB-RB and WB-RB exhibited greater extensions of resin tags in dentin. At 24 h, WB-RB and NB-MB showed the highest and lowest values of bond strength, respectively. At 1 year, WB-MB and WB-RB demonstrated the highest bond strength values. The RB increases the formation of resin tags and residues of bioceramic sealer provides higher bond strength in the ER strategy.

Clinical evaluation of Giomer and self-etch adhesive compared with nanofilled resin composite and etch-and-rinse adhesive - Results at 8 years

OBJECTIVE

This study aimed to evaluate the long-term clinical performance of Giomer and a self-etch adhesive system compared with a nanofilled resin composite and etch-and-rinse adhesive system in Class I and Class II restorations.

METHOD

The study was designed to be double-blinded with intra-individual control. 48 patients with 54 pairs of cavities (class I or class II) were recruited. Each pair of restorations was placed with either BEAUTIFIL II (BF) and FL-BOND II (FL) or Filtek Z350 (Z350) and Scotchbond Multi-Purpose (SMP). Clinical evaluation was performed at baseline, 6-month, 18-month, 4-year and 8-year after placement according to modified USPHS criteria. Kaplan-Meier survival analysis and log rank tests were performed (SPSS 20.0, IBM Corporation, US) to compare the survival probability of different restorations.A generalized linear mixed model (GLMM) was adopted to assess the performance of the materials. The McNemar test was used to show significant changes for all the evaluation criteria and difference between them.

RESULTS

At the eight-year recall, 32 patients with 67 restorations were present. There were twelve restorations in total recorded as failure due to loss of retention, restoration fracture, secondary caries, tooth fracture or endodontic treatment due to pulp necrosis. The survival probabilities and calculated annual failure rate(AFR) of BF and Z350 restorations at 8-year were 87.2 % vs 87.8 % and 1.6 % vs 1.5 % respectively with no significant difference (p > 0.05)between the two materials. Over the recall time range of eight years, decreased possibility of alpha rating was observed for retention, marginal adaptation, marginal staining and surface roughness for both materials (p < 0.05). Decreased possibility of alpha rating was observed for surface staining and secondary caries for Z350 (p < 0.05) and restoration fracture for BF (p < 0.05), respectively. Comparing the two restorative systems over eight years, no significant difference was seen for linear decline of the possibility of alpha rating for any of the criteria evaluated (p > 0.05).

CONCLUSION

Giomer material and the self-etch adhesive system had comparable clinical performance with nanofilled resin composite and etch-and-rinse adhesive system over the observation period of eight years.

Shear bond strength of universal adhesives to human enamel and dentin

OBJECTIVE

The composition of universal adhesives is highly diverse. The purpose of this in vitro study was to compare the shear bond strength of a composite with five different universal adhesives to human enamel and dentin.

MATERIALS AND METHODS

The shear bond strength of a composite (G-aenial Universal Injectable) to human enamel and dentin was tested in selective enamel etching mode before and after thermocyclic aging (10,000 cycles) using five different universal adhesive systems (Adhese Universal VivaPen, Clearfil Universal Bond Quick, G-Premio Bond, Prime&Bond active, and Scotchbond Universal Plus). Two-bottle systems (OptiBond FL and G2-Bond Universal) were used as control. Scanning electron microscopy was conducted of the bonding interface.

RESULTS

Significant differences in shear bond strength values were found among the five evaluated universal adhesives. Lowest shear bond strength values were observed for 2-hydroxyethylmethacrylate (HEMA)-free systems. Thermocyclic aging did not significantly reduce shear bond strength values indicating that the initial bond remains stable.

CONCLUSIONS

The clinical use of universal adhesives Adhese Universal VivaPen, Clearfil Universal Bond Quick, and Scotchbond Universal Plus can be encouraged as they provided comparable or even better shear bond strength values than the two-bottle controls.

CLINICAL SIGNIFICANCE

Universal adhesives that were developed for the same indication and approved for clinical use demonstrated variety in shear bond strength values. When applied in the selective enamel etching mode, a stable bond can be expected from adhesives containing HEMA and monomers with phosphate groups.

The Evaluation of the Cervical Marginal Sealing of Direct vs. Indirect Composite Resin Restorations in MOD Cavities

INTRODUCTION

The aim of this in vitro study was to compare the quality of marginal sealing at the cervical margins of indirect and direct composite resin restorations in mesio-occluso-distal (MOD) cavities.

MATERIAL AND METHOD

MOD preparations were performed on 30 extracted teeth. The mesial cervical margin of each tooth was relocated using a flow composite resin (Enamel Plus HRi Flow, Micerium, Avegno, GE, Italy), then the samples were divided into three groups. In group A, the cavities were directly restored using a nanohybrid composite resin (Miris 2 Coltène Whaledent, Altstaetten, Switzerland) and a universal adhesive (ScotchBond Universal, 3M ESPE, St. Paul, MN, USA) by the etch-and-rinse strategy, for group B, the restoration procedure was similar but the self-etch strategy was used, and the samples in group C were filled using the inlay technique. Each sample was stored for 48 h in a 2% methylene blue solution, then it was cut in a mesio-distal direction using a Struers Secotom 50 device (Cleveland, OH, USA). The marginal sealing and adhesive interface were assessed for each sample at the cervical margin by optical microscopy (OM) and scanning electron microscopy (SEM). One-way ANOVA and Bonferroni post-hoc tests were used with a significance level of 0.05.

RESULTS

Significant differences were recorded within groups A and C, between mesial and distal margins (p = 0.02 in group A and p = 0.043 in group C).

CONCLUSIONS

The marginal sealing is more effective in MOD inlay restoration compared to direct restorations. Relocation of the cervical margin with flow composite resin and the use of different adhesive strategies do not improve the marginal sealing.

Clinical evaluation of posterior restorations over wet and dry dentin using an etch-and-rinse adhesive: A 36-month randomized clinical trial

OBJECTIVES

To evaluate the clinical performance of posterior restorations over wet and dry dentin with an etch-and-rinse adhesive after 36 months of clinical service.

METHODS

Forty-five participants were recruited, each one had at least two posterior teeth that needed restoration. Ninety restorations were placed on Class I or Class II cavities. For the restoration protocol, a simplified etch-and-rinse adhesive (Adper Single Bond 2) was applied over wet (WD) or dry dentin (DD) and later restored with a bulk-fill composite (Filtek Bulk Fill) under rubber dam isolation. Each restoration was evaluated using the World Dental Federation (FDI) criteria after 6, 12, and 36 months of clinical service, regarding the following principal restoration characteristics: postoperative sensitivity, marginal discoloration, marginal adaptation, fracture of material and retention, and recurrence of caries. Kruskal Wallis analysis of variance rank (α = 0.05) and Kaplan-Meier survival analysis were used for statistical analysis.

RESULTS

After 36 months of clinical evaluation, no significant difference between groups was observed in each FDI criterion (p > 0.05). Twenty restorations (WD=10, DD=10) showed minor marginal staining, and twenty-two restorations (WD=11, DD=11) presented small marginal adaptation defects (p > 0.05). Four restorations were lost (WD = 2, DD = 2) and the fracture rates (95% confidence interval) were 94.9% for each one, without significant difference between wet and dry dentin (p > 0.05).

SIGNIFICANCE

The degree of dentin moisture does not seem to affect the clinical performance of a simplified etch-and-rinse adhesive in posterior restorations when the adhesive is applied vigorously over the dentine surface.

Longitudinal bond strength of a universal adhesive and chemical dentin characterization under different acid etching protocols

OBJECTIVE

This study aimed to analyze the longitudinal bond strength of a universal adhesive and chemically characterize the dentin substrate under different acid etching protocols.

METHODOLOGY

Dentin samples were etched with polyacrylic acid 25% (PAA) for 10 seconds (n=3) and phosphoric acid 32% (PA) for 15 seconds (n=3) and analyzed by Fourier transform infrared spectroscopy - attenuated total reflectance (FTIR-ATR) before and after treatment. For collagen degradation, samples (n=12) were divided into 3 groups: PAA, PA, and Deionized water (control), and analyzed by the quantity of solubilized type I collagen C-terminal cross-linked telopeptides and solubilized C-terminal peptide in relation to total protein concentration (ICTPtp and CTXtp) and by their ultimate tensile strength (UTS). For the adhesive interface analysis, dentin samples (n=72) were divided into 3 groups: PAA, PA, and Self-etch (SE), and subdivided into 2 groups: 24 h (baseline) and 1 year. The following tests were performed: microtensile bond strength (μTBS) (n=48), scanning electron microscopy (SEM) (n=12), and nanoleakage (n=12).

RESULTS

The FTIR of PAA showed lower reduction of the peaks in the phosphate group when compared to PA. For ICTPtp, PA showed a significantly higher value. For CTXtp, PA and PAA groups failed to statically differ from each other. UTS was significantly lower for PA. For μTBS, storage time significantly affected bond strength. The results were unaffected by the etching protocol. For SEM, after 1 year, PA had little evidence of degradation in the upper third of the adhesive interface in comparison to the other groups. Nanoleakage showed no considerable silver impregnation after 1 year in the SE group.

CONCLUSION

The use of PAA prior to a universal adhesive (when compared to PA) represents a less aggressive type of etching to dentin. However, self-etching still seems to be the best option for universal adhesive systems that have functional monomers in their composition.

Effects of Nd:YAG laser irradiation at different energy densities on dentin bond durability under simulated pulpal pressure

OBJECTIVES

To evaluate the effects of Nd:YAG laser irradiation on the microstructures of dentin surfaces and the long-term bond strength of dentin under simulated pulpal pressure.

MATERIALS AND METHODS

Under simulated pulp pressure, 30 freshly extracted caries-free third molars were cut into 2-mm-thick dentin samples and then divided into five groups: the control and laser groups (93.3 J/cm2; 124.4 J/cm2; 155.5 J/cm2; 186.6 J/cm2). Scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD), attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR), and Vickers hardness were used to analyze the surface morphology, composition, and mechanical properties of the dentin before and after laser irradiation. Another 80 caries-free third molars were removed and treated as described above, and the resin was bonded to the dentin surface with Single Bond Universal (SBU) adhesive in self-etch mode to make stick specimens. Microtensile bond strength (µTBS), confocal laser scanning microscopy (CLSM), and interfacial silver nanoleakage tests before and after 10,000 times thermocycling were then performed to analyze the bonding properties and interfacial durability of each group.

RESULTS

SEM observations revealed that the surfaces of all laser group specimens were rough with open dentin tubules. Laser irradiation altered the surface composition of dentin while removing some collagen fibers but did not affect its surface hardness or crystallographic characteristics. Furthermore, laser irradiation with an energy density of 124.4 J/cm2 significantly promoted the immediate and aging bond strengths and reduced nanoleakage compared to those of the control group.

CONCLUSIONS

Under simulated pulp pressure, Nd:YAG laser pretreatment altered the chemical composition of dentin and improved the immediate and long-term bond strength.

CLINICAL RELEVANCE

This study investigated the optimal parameters for Nd:YAG laser pretreatment of dentin, which has potential as a clinical method to strengthen bonding.

Prolonged polymerization of a universal adhesive in non-carious cervical lesions: 36-month double-blind randomized clinical trial

OBJECTIVE

To evaluate the effect of prolonged (P) polymerization time of a universal adhesive system applied in etch-and-rinse (ER) or self-etch (SE) strategies on the clinical performance of restorations in non-carious cervical lesions (NCCLs), after 36 months of clinical service.

METHODS

A total of 140 restorations were randomly placed in 35 subjects according to the polymerization time groups: ER (10 s); ER-P (40 s); SE (10 s); and SE-P (40 s) at 1,200 mW/cm2. Composite resin was placed incrementally. The restorations were evaluated immediately and after 6, 12, 18, and 36 months using the FDI criteria. Data were analyzed using the Kaplan-Meier survival test for retention loss, and the Kruskal-Wallis' test for secondary outcomes (α = 0.05).

RESULTS

After 36 months, 19 restorations were lost: ER 6, ER-P 2, SE 9, SE-P 2. The retention rates were 82.3% for ER; 94.1 % for ER-P; 73.5 % for SE; and 94.1 % for SE-P, with a significant difference between ER vs. ER-P and SE vs. SE-P, as well as ER vs. SE-P and ER-P vs. SE (p < 0.0001). Minor defects were observed in 18 restorations for the marginal staining criteria: ER 5, ER-P 2, SE 8, SE-P 3; and in 33 restorations for the marginal adaptation criteria: ER 11, ER-P 4, SE 12, and SE-P 6 (p > 0.05). No restorations showed recurrence of caries or postoperative sensitivity.

CONCLUSIONS

A prolonged polymerization time of 40 s improves the clinical performance of the universal adhesive for both adhesive strategies evaluated, even after 36 months.

CLINICAL SIGNIFICANCE

Prolonging the polymerization time of a universal adhesive from 10 to 40 s has been shown to improve its clinical performance when used in NCCLs.

Effects of dimethyl sulfoxide pretreatment on the bonding properties of fluorotic dentin of different severity: An in vitro study

STATEMENT OF PROBLEM

Bonding to fluorotic dentin is weaker than to sound dentin, but methods to improve bonding have not been well addressed.

PURPOSE

The purpose of this in vitro study was to investigate the effects of dimethyl sulfoxide (DMSO) pretreatment on the bond strength and resin-dentin surface of fluorotic dentin of different severity.

MATERIAL AND METHODS

Phosphoric acid-etched dentin specimens exhibiting mild fluorosis (ML-F), moderate fluorosis (MD-F), and severe fluorosis (SE-F) were randomly bonded with Single Bond 2 (SB2) pretreated with 50% DMSO (experimental groups) or deionized water (control groups). The bonded teeth were sectioned for microshear bond strength (μSBS) testing immediately or after aging, for micromorphology observation of the bonding interface under a scanning electron microscope, and for resin tags and microleakage evaluation under a confocal laser scanning microscope. The degree of conversion of the adhesive resin was calculated by Fourier transform infrared spectroscopy. According to varying bonding steps, the mineralized dentin powders of ML-F, MD-F, and SE-F were randomly divided into 4 subgroups (blank, PA, PA+SB2, and PA+DMSO+SB2) and incubated in artificial saliva to examine the level of enzymatic degradation product of type I collagen. Data were analyzed by using ANOVA and the Tukey test (α=.05).

RESULTS

Dental fluorosis and thermocycling had negative effects on μSBS (P<.001), while DMSO pretreatment preserved or even improved μSBS (P<.001). DMSO had no influence on the degree of conversion (P=.618). Significant effects were found for bonding steps (P<.001), but not that of dental fluorosis (P=.131) on the enzymatic degradation product of type I collagen. Images showed sparser and more expanded collagen fibril meshwork, deeper resin penetration, and less microleakage in the experimental groups.

CONCLUSIONS

DMSO pretreatment provided increased and durable dentin bonding to fluorotic dentin probably by dispersing collagen fibrils into a sparser network and inhibiting the degradation of type I collagen.

Evaluation of the Dentinal Shear Bond Strength and Resin Interface in Primary Molars after Pre-Treatment with Various Dentin Bio-Modifiers: An In Vitro Study

Dentine adhesives have demonstrated great success with permanent teeth. Though the results in primary teeth are not well documented, some studies have demonstrated lower values of bond strength in primary teeth than those found in permanent teeth. The aim of this study was to compare and evaluate the effect of grape seed extract (6.5%) (Herbal Bio Solutions, Delhi, India), glutaraldehyde (5%) (Loba Chemie PVT. LTD., Mumbai), hesperidin (0.5%) (Herbal Bio Solutions, Delhi, India), and casein phosphopeptide-amorphous calcium phosphate (tooth mousse) (GC Corporation, Alsip, IL, USA) on the shear bond strength of dentine of primary teeth and to evaluate the resin tags at the resin tooth interface. Seventy-five caries-free human primary molars were collected, and their occlusal surfaces were ground flat. Dentin surfaces were etched using phosphoric acid. Then teeth were randomly assigned in sequential order to five groups according to the dentinal treatment method: Group I (Control group) (no treatment), Group II (5% glutaraldehyde), Group III (6.5% grape seed extract), Group IV (0.5% hesperidin), and Group V (CPP-ACP). Ten teeth from each group were assigned for Shear Bond Strength and five for SEM analysis. ANOVA and a post hoc least significant difference test (p < 0.05) were used for statistical analysis of the collected data. The grape seed extract group showed significantly increased shear bond strength than the control group (p < 0.05), and the mean length of resin tags in different dentine bio modifiers groups was also statistically significant (p < 0.05). The use of dentin bio modifiers such as 5% glutaraldehyde, 6.5% grape seed extract, 0.5% hesperidin, and CPP-ACP in the bonding process for primary teeth did not improve the dentinal bond strength.

Concentration effect of DMSO-dry bonding on the stability of etch-and-rinse bonds

OBJECTIVES

To examine whether lower dimethyl sulfoxide (DMSO) concentrations would affect long-term bond stability of simplified or multistep water-based adhesives to dry-etched dentin.

METHODS

H3PO4-etched mid-coronal dentin surfaces from human molars were randomly blot- or air-dried for 30 s and pretreated or not with 5 or 50 % (v/v) ethanolic DMSO solutions. Untreated samples served as control. Samples were bonded with a two-step or a three-step etch-and-rinse adhesive. Restored crown segments (n = 5/group) were stored in distilled water for 24 h and sectioned for microtensile bond strength testing. Resin-dentin beams (0.8 mm2) were tested under tension until fracture (0.5 mm/min) after 24 h and one year of storage in artificial saliva at 37 °C. Nanoleakage evaluation and hybrid layer characterization were performed by SEM. Bond strength data was examined by three-way ANOVA followed by the Tukey test (α = 0.05).

RESULTS

Dry bonding produced significantly lower bond strengths than conventional wet bonding for both water-based adhesive systems (p < 0.05). DMSO-dry bonding restored bond strengths and reduced nanoleakage levels, regardless of adhesive type or DMSO concentration (p < 0.05). Bond strengths of DMSO-dry bonded samples were not significantly affected by long-term ageing regardless of adhesive type or DMSO concentration (p < 0.05).

SIGNIFICANCE

Although bonding methacrylate-based resins to etched dentin is normally performed under wet conditions, hybridization of air-dried collagen can outperform conventional wet bonding by employing water-free DMSO solutions with concentrations as low as 5 %. Reduced moisture-related technique sensitivity, higher bonding performance and improved hybrid layer stability may contribute to extend the service life of resin-dentin bonding.

Analysis of the adhesive interface of dentine treated with carbodiimide and chitosan before cementation of fiberglass posts with different resin cements

The objective of this study is to evaluate the effect of 1-ethyl-3-(3-dimethylaminopropyl)-carbodiimide (EDC) and chitosan (CHI) on the adhesive interface of resin cements to root dentine. Forty-five upper canines were sectioned, endodontically treated, prepared and divided into three groups according to dentine treatment (distilled water-DW, CHI 0.2% and EDC 0.5) and in three subgroups according to resin cement: RelyX ARC, Panavia F 2.0 or RelyX U200. Slices were obtained, with five slices of each third submitted to the analysis of the adaptation of the adhesive interface through scores and the perimeter with gaps in confocal laser scanning microscopy and one slice of each third later evaluated qualitatively in scanning electron microscopy. The results were analyzed using with Kruskal-Wallis and Spearman correlation tests. There was no difference in adaptation for the different resin cements (p = .438). EDC presented better adaptation when compared to the groups treated with DW and CHI (p < .001), while the CHI and DW presented similar adaptation values (p = .365). No difference was observed in the perimeter referring to the gap areas for the different resin cements (p = .510). EDC showed a lower percentage of perimeters with gaps when compared to CHI (p < .001), with the percentage of perimeter with gaps of teeth treated with CHI being lower than DW (p < .001). A positive correlation coefficient equal to 0.763 was obtained between the perimeter with gaps and the adaptation data of the adhesive interface (p < .001). EDC resulted in better adaptation of the adhesive interface and a lower percentage of perimeters with gaps compared to chitosan.

Tooth ultrastructure changes induced by a nonsense mutation in the FAM83H gene: insights into the diversity of amelogenesis imperfecta

OBJECTIVES

The current research on single-nucleotide polymorphism (SNP) mutation sites at different positions of the FAM83H gene and their phenotypic changes leading to amelogenesis imperfecta (AI) is inconsistent. We identified a previously reported heterozygous nonsense mutation c.1192C>T (p.Q398*) in the FAM83H gene and conducted a comprehensive analysis of the dental ultrastructure and chemical composition changes induced by this mutation. Additionally, we predicted the protein feature affected by this mutation site. The aim was to further deepen our understanding of the diversity of AI caused by different mutation sites in the FAM83H gene.

METHODS

Whole-exome sequencing (WES) and Sanger sequencing were used to confirm the mutation sites. Physical features of the patient's teeth were investigated using various methods including cone beam computer tomography (CBCT), scanning electron microscopy (SEM), contact profilometry (roughness measurement), and a nanomechanical tester (nanoindentation measurement). The protein features of wild-type and mutant FAM83H were predicted using bioinformatics methods.

RESULTS

One previously discovered FAM83H heterozygous nonsense mutation c.1192C>T (p.Q398*) was detected in the patient. SEM revealed inconsistent dentinal tubules, and EDS showed that calcium and phosphorus were lower in the patient's dentin but higher in the enamel compared to the control tooth. Roughness measurements showed that AI patients' teeth had rougher occlusal surfaces than those of the control tooth. Nanoindentation measurements showed that the enamel and dentin hardness values of the AI patients' teeth were both significantly reduced compared to those of the control tooth. Compared to the wild-type FAM83H protein, the mutant FAM83H protein shows alterations in stability, hydrophobicity, secondary structure, and tertiary structure. These changes could underlie functional differences and AI phenotype variations caused by this mutation site.

CONCLUSIONS

This study expands the understanding of the effects of FAM83H mutations on tooth structure.

CLINICAL RELEVANCE

Our study enhances our understanding of the genetic basis of AI and may contribute to improved diagnostics and personalized treatment strategies for patients with FAM83H-related AI.

Adhesion to enamel and dentine: an update

With the continuous development of adhesive technology leading to a wide variety of bonding systems in the market, clinicians are often faced with a vast number of systems to choose from. Although research and manufacture of bonding systems is constantly progressing, the focus has generally been on simplifying the bonding process by reducing the number of clinical steps, with little emphasis on evidence-based performance. This article draws attention to the current strategies of common commercially available products to guide clinicians during bonding system selection and application.

Development of a bioactive dentin adhesive resin modified with magnesium-doped synthetic hydroxyapatite crystals

The aim is to evaluate the development of an experimental multi-mode/Universal resin-based dentin adhesive modified with synthetic Mg²⁺ doped hydroxyapatite crystals (HAp) having self-remineralization and antibiofilm properties. HAp doped with Mg²⁺ was prepared by the precipitation method. Experimental adhesives were subjected to degree of conversion and X-ray diffraction test for size and crystal structure. Bond strength was tested, and electron microscopy (SEM/TEM) imaging of resin-dentin interface was done along with nanoleakage, nanoindentation, confocal and Raman analyses. S. mutans was analysed using CLSM images against modified adhesive specimens. Nucleating abilities within the resin-dentin specimens are determined by measuring Ca²⁺. Alkaline phosphatase, Runx2, and Ocn transcripts are amplified using quantitative polymerase chain reaction (q-PCR). A calcium assay is performed to quantify level of mineralisation. When compared to control adhesives, the 0.5% Hap/Mg²⁺ containing experimental dentin adhesive demonstrated improved interaction with dentin. The preservation of uniform intact hybrid layer with the absence of nanoleakage indicated dentin bond integrity with 0.5% HAP/Mg²⁺ modified adhesive. Self-remineralization and antibiofilm potentials are supported.

Insight into the development of versatile dentin bonding agents to increase the durability of the bonding interface

Despite the huge improvements made in adhesive technology over the past 50 years, there are still some unresolved issues regarding the durability of the adhesive interface. A complete sealing of the interface between the resin and the dentin substrate remains difficult to achieve, and it is doubtful whether an optimal interdiffusion of the adhesive system within the demineralized collagen framework can be produced in a complete and homogeneous way. In fact, it is suggested that hydrolytic degradation, combined with the action of dentin matrix enzymes, destabilizes the tooth-adhesive bond and disrupts the unprotected collagen fibrils. While a sufficient resin–dentin adhesion is usually achieved immediately, bonding efficiency declines over time. Thus, here, a review will be carried out through a bibliographic survey of scientific articles published in the last few years to present strategies that have been proposed to improve and/or develop new adhesive systems that can help prevent degradation at the adhesive interface. It will specially focus on new clinical techniques or new materials with characteristics that contribute to increasing the durability of adhesive restorations and avoiding the recurrent replacement restorative cycle and the consequent increase in damage to the tooth.

Curing profile and marginal gap formation using a liner containing long-wavelength-absorbing photoinitiator: an in vitro study

The aim was to evaluate the marginal-gap formation and curing profile of a new restorative technique using a liner with long-wavelength-absorbing photoinitiator (LWAP). Box-shaped preparations (6 mm × 4 mm × 4 mm) were made in third molars. All samples were treated with Clearfill SE Bond and divided into 4 groups (n = 5), according to restorative technique used: (1) incremental technique (INC-Technique); (2) camphorquinone-based liner (CQ-Liner) + bulk-fill resin composite; (3) LWAP-based liner (LWAP-Liner) + bulk-fill resin composite; and (4) bulk-fill technique without liner (BF-Technique). The marginal gaps (%) for all the samples were measured using micro-computed tomography. The restorations were cross-sectioned, and the degree of conversion (DC) and Knoop microhardness were evaluated at different depths (0.3, 1, 2, 3, and 4 mm). INC-Technique, CQ-Liner, and LWAP-Liner groups showed significantly fewer marginal gaps than those from the BF-Technique group. The BF-Technique specimens had the lowest DC and microhardness in depth. All the other techniques presented similar degree of conversion and microhardness at all the depths. The use of liners, regardless of the photoinitiator system, decreased the marginal-gap formation and improved the curing profile of bulk-filling restoration technique.

Dentin primer based on a highly functionalized gelatin-methacryloyl hydrogel

Gelatin-methacryloyl hydrogels (GelMA) have demonstrated their utility as scaffolds in a variety of tissue engineering applications.

OBJECTIVES

In this study, a highly functionalized GelMA hydrogel was synthesized and assessed for degree of functionalization. As the proposed GelMA hydrogel was coupled to a visible-light photoinitiator, we hypothesized it might serve as base to formulate a model dentin primer for application in restorative dentistry.

METHODS

GelMA was mixed with photoinitiator lithium phenyl-2,4,6-trimethylbenzoylphosphinate (LAP), photopolymerized for 0-40 s using a dental light-curing device and tested for extrudability, degree of photo-crosslinking (DPxlink), water sorption/solubility/swelling (WS/SL/SW) and apparent modulus of elasticity (AE). Model dentin primer was prepared by mixing GelMA+LAP with a primer of a commercial three-step etch-and-rinse adhesive. After application of GelMA-based primer to acid-etched dentin, samples were bonded with correspondent adhesive agent, photopolymerized and had their immediate bond strength compared to control samples primed and bonded with the same commercial material.

RESULTS

Extrudability of hydrogel was confirmed using a microsyringe to write the acronym "CDMI". DPxlink of GelMA+LAP changed significantly as a function of photopolymerization time (20 s < 30 s ≤ 40 s). WS, SL and SW were significantly reduced in hydrogels polymerized for 30 and 40 s. AE of hydrogels varied significantly as a function of photopolymerization time (20 s < 30 s ≤ 40 s; 20 s ‡ 40 s). Bond strength of dentin primed with GelMA-based primer was lower (∼29.3 MPa) but not significantly of that of control (∼34.6 MPa).

CONCLUSIONS

Optimization of a GelMA-based dentin primers can lead to the development of promising biomimetic adhesives for dentin rehabilitation.

Effect of collagen cross-linkers on dentin bond strength: A systematic review and network meta-analysis

Objective: This study aimed to evaluate the role of collagen cross-linkers in the bonding performance of the resin-dentin interface through a systematic review and a network meta-analysis. Sources: The literature search was conducted in several databases like PubMed, EMBASE, Cochrane, Scopus and Web of Science from their inception till 30 April 2022. Study selection: The inclusion criteria consisted of in vitro studies evaluating the micro-tensile and micro-shear bond strengths of different cross-linkers acting on dentin. Bayesian network meta-analysis was conducted using RStudio. Data: Out of the 294 studies evaluated in the full-text analysis, 40 were included in the systematic review and meta-analysis. Most studies have used cross-linkers as primer (65.1%), followed by incorporating them into in adhesives and acid etching agents. The application methods of the adhesive system were classified as "etch-and-rinse (ER) adhesives" (77%) and "self-etching (SE) adhesives". Moreover, there were six types of cross-linkers in this presented review, of which the most numerous were polyphenols. Conclusion: Different application methods of cross-linkers, the long-term results showed that were only effective when used for longer durations, the immediate results were not statistically different. According to immediate and long-term results, etch-and-rinse (ER) adhesives showed a greater bonding performance than the control groups (p ≤ 0.05), whereas self-etching (SE) adhesives showed similar bond strength values (p ≥ 0.05). The result of network meta-analysis (NMA) showed that Dope like compound showed higher long-term bonding performance than other cross-linkers. Clinical significance: Long-term clinical studies may be needed to determine the effect of the cross-linkers on the bonding properties.

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.

Triclosan to Improve the Antimicrobial Performance of Universal Adhesives

To solve the proble ms of composite restoration failure caused by secondary caries, this study reports a light curable antibacterial triclosan derivative (TCS-IH), which was synthesized and added to the existing commercial universal adhesive to achieve a long-term antibacterial effect The effect of mixing different mass percentages of TCS-IH on the bond strength of dentin was also investigated.TCS-IH was synthesized by solution polymerization and characterized by nuclear magnetic resonance hydrogen spectroscopy (1H NMR) and Fourier transform infrared (FTIR) spectroscopy. Two commercial universal adhesives, Single Bond Universal and All Bond Universal, were selected and used as the control group, and universal adhesives with different mass percentages (1 wt%, 3 wt%, 5 wt% and 7 wt%) of TCS-IH were used as the experimental group. The antibacterial properties were analysed by means of colony count experiments, biofilm formation detection, plotting of growth curves, biofilm metabolic activity detection, insoluble extracellular polysaccharide measurements and observations by confocal laser scanning microscopy and scanning electron microscopy (SEM). The effect of adhesives on biofilm formation, metabolism, extracellular matrix production, distribution of live and dead bacteria, and bacterial morphology of Streptococcus mutans (S. mutans) was analysed. The mechanical properties were evaluated by the degree of conversion and microtensile bonding strength under different conditions. Its biosafety was tested. We found that the addition of TCS-IH significantly improved the antibacterial performance of the universal adhesive, with the 5 wt% and 7 wt% groups showing the best antibacterial effect and effectively inhibiting the formation of biofilm. In addition, the adhesive strength test results showed that there was no statistical difference (p < 0.05) in the microtensile bond strength measured under various factors in all experimental groups except for the 7 wt% group in the self-etch bonding mode, and all of them had good biosafety. In summary, the 5 wt% group of antibacterial monomer TCS-IH was selected as the optimum addition to the universal adhesive to ensure the antimicrobial properties of the universal adhesive and the stability and durability of the adhesive interface. This study provides a reference for the clinical application of adhesives with antimicrobial activity to improve the stability and durability of adhesive restorations.

Effects of Er: YAG, Er,Cr: YSGG, and Nd: YAG laser irradiation and adhesive systems on the immediate and long-term bond strength of dentin: a systematic review and meta-analysis

At present, lasers are increasingly used in the oral clinical field, and research and applications in dental hard tissue treatment are also increasing. The effect of laser etching dentin on the bonding strength of composite resin reported in the literature is still inconclusive. The purpose of this review was to evaluate whether laser etching can improve the immediate and long-term bonding strength of dentin and investigate the effect of different types of adhesives on the bonding strength of dentin. Two reviewers performed a literature search up from January 2012 to November 2021 in four databases: MEDLINE (PubMed), Web of Science, EMBASE, and the Cochrane Library. A total of 25 studies were included in the meta-analysis. The Cochrane Collaboration Bias Risk Assessment tool was used to evaluate the quality of the included literature, and an analysis was carried out using Review Manager Software version 5.3. The aging bond strength of dentin after erbium (Er): yttrium aluminum garnet (YAG) laser treatment was significantly lower than that of dentin in the bur group (P < 0.00001). At the same time, the bond strength of dentin immediately and aging after (Er), chromium-doped (Cr): yttrium scandium gallium garnet (YSGG) laser treatment was lower than that of dentin in the bur group (P < 0.05). There was no significant difference in the immediate and aging bonding strength among samples in the Er: YAG laser, Er, Cr: YSGG laser, and blank control groups (no laser or bur). The aging bond strength of samples after neodymium-doped (Nd): YAG laser treatment was higher than that of samples in the blank control group (P < 0.05); in addition, the performance of self-etching adhesive was slightly better than that of acid etching adhesive. Regardless of the applied surface treatment and the adhesive employed, dentin after aging showed significant bond degradation (P < 0.05). There was high heterogeneity of bond strength between different groups, and the small number of studies and the contradictory results may be the main reasons for this outcome.

Effect of aging and cementation systems on the bond strength to root dentin after fiber post cementation

This study evaluated the effect of aging and cementation of fiber posts using glass ionomer and resin cements on push-out bond strength, failure mode, and resin tag formation. One hundred and twenty bovine incisors were used. After post-space preparation, the specimens were randomly allocated into 12 groups (n = 10) according to the cementation system used: GC - GC Gold Label Luting & Lining); RL - RelyX Luting 2; MC - MaxCem Elite; RU - RelyX U200 and the aging periods (24 hours, 6 months, and 12 months). Slices from the cervical, middle, and apical thirds were obtained and analyzed by push-out bond strength test and confocal laser scanning microscopy. One-way ANOVA and Tukey's post-hoc test was used at a significance level of 5%. For the push-out bond strength test, no differences among GC, RU, and MC in the cervical and middle thirds were observed, regardless of the period of storage (P > 0.05). In the apical third, GC and RU showed similar bond strength but higher than other groups (P > 0.05). After 12 months, GC showed the highest bond strength (P < 0.05). Bond strength to post-space dentin decreased over time, regardless of the cementation system used. Cohesive failure was the most frequent, regardless of the period of storage, cementation system, and post-space third. Tag formation was similar among all groups. After 12 months, GC showed the highest bond strength values.

In Search of Novel Degradation-Resistant Monomers for Adhesive Dentistry: A Systematic Review and Meta-Analysis

This study aimed to assess whether degradation-resistant monomers included in experimental dental adhesives can improve long-term bond strength compared to conventional monomers. This study followed the latest PRISMA guidance (2020). The search for the systematic review was carried out in four electronic databases: PubMed/Medline, Scopus, SciELO and EMBASE, without restrictions on the year of publication and language. The last screening was conducted in July 2022. Interventions included were in vitro studies on experimental dental adhesives that tested short-term and long-term bond strength, but also water sorption and solubility data when available, in extracted human molars. Meta-analyses were performed using Rstudio v1.4.1106. A summary table analyzing the individual risk of bias was generated using the recent RoBDEMAT tool. Of the 177 potentially eligible studies, a total of 7 studies were included. Experimental monomers with acrylamides or methacrylamide−acrylamide hybrids in their composition showed better results of aged bond strength when compared to methacrylate controls (p < 0.05). The experimental monomers found better sorption and solubility compared to controls and were significantly different (p < 0.001). It is possible to achieve hydrolytically resistant formulations by adding novel experimental monomers, with chemical structures that bring benefit to degradation mechanisms.

Comparison of collagen features of distinct types of caries-affected dentin

OBJECTIVES

To compare the biodegradability, mechanical behavior, and physicochemical features of the collagen-rich extracellular matrix (ECM) of artificial caries-affected dentin (ACAD), natural caries-affected dentin (NCAD) and sound dentin (SD).

METHODS

Dentin specimens from human molars were prepared and assigned into groups according to the type of dentin: ACAD, NCAD, or SD. ACAD was produced by incubation of demineralized SD with Streptococcus mutans in a chemically defined medium (CDM) with 1% sucrose for 7 days at 37 °C under anaerobic conditions. Specimens were assessed to determine collagen birefringence, biodegradability, mechanical behavior, and chemical composition. Data were individually processed and analyzed by ANOVA and post-hoc tests (α = 0.05).

RESULTS

CDM-based biofilm challenge reduced loss, storage, and complex moduli in ACAD (p < 0.001), while the damping capacity remained unaffected (p = 0.066). Higher red and lower green birefringence were found in ACAD and NCAD when compared with SD (p < 0.001). Differently to ACAD, SD and NCAD presented higher biodegradability to exogenous proteases (p = 0.02). Chemical analysis of the integrated areas of characteristic bands that assess mineral quality (carbonate/phosphate and crystallinity index), mineral to matrix (phosphate/amide I) and post-translational modifications (amide III/CH₂, pentosidine/CH₂, and pentosidine/amide III) (p<0.05) showed that NCAD was significantly different from SD while ACAD exhibited intermediate values.

CONCLUSIONS

CDM-based biofilm challenge produced a dentin ECM with decreased mechanical properties and increased collagen maturity. The compositional and structural conformation of the ACAD suggested that CDM-based biofilm challenge showed potential to produce artificial lesions by revealing a transitional condition towards mimicking critical features of NCAD.

CLINICAL SIGNIFICANCE

This study highlights the importance of developing a tissue that mimics the features of natural caries-affected dentin ECM for in vitro studies. Our findings suggested the potential of a modified biofilm challenge protocol to produce and simulate a relevant substrate, such as caries-affected dentin.

Effects of carbodiimide combined with ethanol-wet bonding pretreatment on dentin bonding properties: an in vitro study

Purpose

This study evaluated the combined effects of Carbodiimide (EDC) and ethanol-wet bonding (EWB) pretreatment on the bond strength and resin-dentin surface.

Methods

Phosphoric acid-etched dentin specimens were randomly divided into five groups based on the following pretreatments: deionized water (control), EWB, 0.3M EDC in water (EDCw), EDC water solution combined EWB (EDCw + EWB), and 0.3M EDC in ethanol (EDCe). A scanning electron microscope (SEM) was used to observe the morphology of collagen fibrils on the demineralized dentin matrix in each group after pretreatment. The adhesives Prime & Bond NT (PB) (Dentsply De trey, Konstanz, Germany) or Single bond 2 (SB) (3M ESPE, St. Paul, MN, USA) was applied after pretreatments, and a confocal laser scanning microscope (CLSM) was used to evaluate the quality of resin tags. The degree of conversion (DC) of the adhesive was investigated by Fourier transform infrared spectroscopy (ATR-FTIR). The dentin was first bonded with resin and bathed in water at 37 °C for 24 h. Half of them were subjected to 10, 000 cycles in a thermocycler between 5 °C and 55 °C before a microshear bond strength (µSBS) test. The statistical methods were Analysis of Variance (ANOVA) and a Tukey post hoc test at α = 0.05.

Results

The µSBS was significantly affected by pretreatments (p < 0.001), adhesives (p < 0.001), and aging conditions (p < 0.001) as revealed by the three-way ANOVA. The EDCw, EDCw + EWB, and EDCe groups significantly increased the µSBS; the EDCw + EWB and EDCe groups produced the highest µSBS. In the EDC-containing groups, the SEM showed at the collagen fibrils in the dentin matrix formed a three-dimensional network structure in the tubules after cross-linking into sheets, and the hybrid layer formed thicker resin tags under a CLSM. In the EDC-containing groups, the CLSM observed an increase in the length of resin tags. PB showed a higher DC and bonding strength than SB, and the five pretreatment groups tested did not affect the DC of the two adhesives.

Conclusions

In etch-and-rinse bonding system, EDC combined with EWB pretreatment can improve the quality of the hybrid layer and enhance the mechanical properties of demineralized dentin matrix. Pretreatment with EDC-ethanol solution may be a new clinically friendly option for enhancing dentin bonding durability.

Improve Dentin Bonding Performance Using a Hydrolytically Stable, Ether-Based Primer

The objective of this study is to replace a traditional methacrylate-based primer (glycine, N-(2-hydroxy-3-(2-methyl-1-oxo-2-propenyl)propyl)-N-(4-methylphenyl) monosodium salt, NTG-GMA) with a hydrolytically stable ether-based primer (glycine, N-2-hydroxy-3-(4-vinylbenzyloxy)-propyl-N-(4-methylphenyl), monosodium salt, NTG-VBGE). The performance and durability of bonding composites to detin of two primers combined with methacrylate-based or ether-based adhesives were evaluated using shear bond strength (SBS) and micro-tensile bond strength (μTBS) combined with thermal cycling. The hydrolysis resistance of NTG-VBGE against hydrolysis was tested by challenging primed hydroxyapatite crystals with an esterase. The hydrophilicity of the primers and the resin spreading kinetics of adhesives on primed dentin were characterized by water contact angle measurements. The new primer NTG-VBGE was found to be compatible with both methacrylate-based adhesives and ether-based adhesives. The highest μTBS values were found in the test group of NTG-VBGE and ether-based adhesive, which was consistent with the resin spreading kinetics results. The more hydrophobic and hydrolytically stable primer/adhesive achieved improved dentin infiltration and bonding strength, suggesting significant potential for further developing dental restorative materials with extended service life.

Matrix transfer techniques for direct paste composite resins

This article discusses potential concerns and important considerations when selecting and using matrix transfer techniques for the direct, definitive addition of composite resin to teeth. It also provides guidance to aid these processes with the use of case studies, primarily focusing on the management of tooth wear.

Considers the advantages and disadvantages of using different matrix transfer techniques for the restoration of multiple teeth with direct paste composite.

Addresses common concerns and problems associated with using matrix transfer techniques, particularly in relation to managing the worn dentition.

Suggests guidance on selecting appropriate matrix transfer techniques to minimise complications and optimise outcomes through the exploration of case studies.

Mussel-inspired monomer - A new selective protease inhibitor against dentine collagen degradation

OBJECTIVES

To evaluate the inhibitory effect of a novel mussel-inspired monomer (N-(3,4-dihydroxyphenethyl)methacrylamide (DMA) on the soluble and matrix-bound proteases.

METHODS

The inhibitory effect of DMA (0, 1, 5, and 10 mM) and 1 mM chlorhexidine (CHX) dissolved in 50% ethanol/water on soluble recombinant human matrix metalloproteinases (rhMMP-2, -8, and -9), as well as cysteine cathepsins (B and K) were evaluated using both fluorometric assay kits and molecular docking. The effect of CHX and DMA on matrix-bound proteases was examined by in situ zymography, and the fluorescence intensity and relative area were calculated by Image J software. All data obtained were analyzed by one-way ANOVA followed by Tukey test (α = 0.05).

RESULTS

The anti-proteolytic ability of DMA increased in a dose-dependent manner except that of rhMMP-9. Inhibitory effect of 1 mM DMA against rhMMP-2, - 8, - 9, as well as cathepsin B and K was all significantly lower than 1 mM CHX (p < 0.05). The molecular docking analysis was in good agreement with the experimental results, that the binding energy of DMA was lower than CHX for all proteases. In situ zymography revealed that all DMA- and CHX-treated groups significantly inactivated the matrix-bound proteases, with a dramatic reduction of the fluorescence intensity and relative area compared with the control group (p < 0.05).

SIGNIFICANCE

Under the prerequisite condition that the overall inhibitory performance on matrix-bound proteases was comparable by DMA and CHX, the more selective property of DMA could avoid inducing potential negative effects by suppressing MMP-9 when applied in dental treatment compared with CHX.

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.

Evaluation of Novel Plant-derived Monomers-based Pretreatment on Bonding to Sound and Caries-affected Dentin

This study evaluated the influence of new monomers derived from cashew nut shell liquid (CNSL) applied for dentin biomodification on resin-dentin bond strength, nanoleakage, and micropermeability to sound and artificially-created caries-affected dentin. Human dentin specimens were assigned to five groups, according to the following dentin pretreatment solutions: Absolute ethanol (control), 2 wt% grape seed extract (Vitis vinifera), 2 wt% cardol [from cashew nut shell liquid (CNSL)], 2 wt% cardol-methacrylate or 2 wt% cardanol-methacrylate applied on sound and artificial caries-affected dentin. Specimens were analyzed after 24 hour or 1 year of water storage. Microtensile bond strength (μTBS) (n=6), interface micropermeability (n=3), and silver nanoleakage (n=6) were assessed using a universal testing machine, confocal laser scanning microscope, and scanning electron microscope, respectively. In sound dentin, no difference in bond strength was observed between the groups in either storage period. In artificial caries-affected dentin, pretreatment with cardol-methacrylate resulted in statistically higher bond strength than all the other treatments in both storage periods. Cardol-methacrylate treatment resulted in less nanoleakage, along with improved interfacial integrity, compared to further treatments in artificial caries-affected dentin. Regarding micropermeability analysis, all treatments depicted deficient sealing ability when applied on artificial caries-affected dentin, with the presence of gaps in the control group. In conclusion, cardol-methacrylate is a promising plant-derived monomer to reinforce the hybrid layer, since it preserved resin-dentin bond strength and improved dentin bonding, especially to caries-affected dentin, a well-known harsh substrate for adhesion longevity.

Mechanical Stability and Proteolytic Activity of Resin-dentin Bonds Using the Cross-linked Dry Bonding Technique

OBJECTIVE

To evaluate the mechanical stability and the proteolytic activity of bonds created by a two-step, etch-and-rinse adhesive applied to cross-linked and air-dried etched dentin.

METHODS

Flat dentin surfaces were produced in 64 extracted sound human molars. The dentin was etched with 35% phosphoric acid for 15 seconds, and then the teeth were divided into groups according to the cross-linking solution applied on the etched dentin. Group 1: 5% grape seed extract (GSE), Group 2: 5% glutaraldehyde, Group 3: Gluma Desensitizer, or Group 4: deionized water (control). Solutions were applied for 60 seconds, followed by rinse and blot drying. Then, the teeth were separated into two subgroups where the etched dentin was kept moist or air-dried. The adhesive was applied followed by a composite resin buildup. After 24 hours, the teeth were cut into beams (0.81 mm2) that were tested for microtensile strength immediately or after 12 months of aging in a 37°C saliva-like buffer. Additional teeth (n=32) were bonded as described and cut into 0.5-mm-thick slabs. The slabs were prepared for nanoleakage (scanning electron microscopy) and in situ zymography (EnzChek Protease Assay Kit). Bond strength data were submitted to ANOVA and Tukey tests (α=0.05).

RESULTS

Significant reduction in immediate bond strength (ca 65%) and increase in proteolytic activity was seen when the etched dentin was air dried without previous cross-linking biomodification. Conversely, bond strengths did not differ from those produced on wet dentin when collagen was cross-linked before air drying, irrespective of the solution applied. For both moist and air-dried etched dentin, collagen cross-linking resulted in mechanically stable bonds and reduced proteolytic activity after 12 months of storage.

CONCLUSION

Bonds produced by the application of a two-step, etch-and-rinse adhesive to cross-linked, air-dried, etched dentin were mechanically stable and revealed reduced proteolytic activity after 1 year of aging.

Enhancing resin-dentin bond durability using a novel mussel-inspired monomer

Numerous approaches have been developed to improve the resin-dentin bond performance, among which the bio-application of mussel-derived compounds have drawn great attention recently. To assess the performance of N-(3,4-dihydroxyphenethyl)methacrylamide (DMA), a mussel-derived compound, as a functional monomer in dental adhesive, its potential property to cross-link with dentin collagen and polymerize with adhesive will first be evaluated by transmission electron microscopy (TEM), attenuated total reflectance technique of Fourier transform infrared (ATR-FTIR), and atomic force microscopy (AFM) via Peakforce QNM mode. After validating the influence of DMA on collagen and adhesive separately, the overall performance of DMA/ethanol solution as a primer in dentin bonding was examined using micro-tensile bond strength (μTBS) testing, fracture pattern observation, and nanoleakage evaluation both immediately and after 10,000 times thermocycling aging. The inhibitory effect of DMA on endogenous metalloproteinases (MMPs) was evaluated by in situ zymography using confocal laser scanning microscopy (CLSM) and the cytotoxicity of DMA was evaluated using cell counting kit-8. Results demonstrated that DMA successfully cross-linked with dentin collagen via non-covalent bonds and had no influence on the polymerization and mechanical properties of the adhesive. Furthermore, even after 10,000 times thermocycling aging, the μTBS and nanoleakage expression of the DMA-treated groups showed no significant change compared with their immediate values. In situ zymography revealed reduced endogenous proteolytic activities after the application of DMA, and no cytotoxicity effect was observed for DMA concentration up to 25 ​μmol/L. Thus, DMA could be used as a novel, biocompatible functional monomer in dentin bonding.

•

DMA acts as a functional monomer in dentin bonding system with high biocompatibility.

•

DMA connects the adhesive and collagen network to resist various external attacks.

•

DMA/ethanol inhibits the activity of MMPs and improve resin-dentin bond durability.

Evaluation of resveratrol-doped adhesive with advanced dentin bond durability

OBJECTIVES

This paper aimed to evaluate the influence of resveratrol-doped adhesive on the durability and antibiofilm capability of dentin bonding.

METHODS

Experimental adhesives were prepared by incorporating resveratrol into a universal adhesive at concentrations of 0 (control), 0.1, 1, and 10 mg/mL. The microtensile bond strength, fracture modes, and adhesive-dentin interface nanoleakage were assessed after 24 h of water storage, 10,000 times of thermocycling or 1-month of collagenase ageing. Relevant antibiofilm capability on Streptococcus mutans (S. mutans), in situ zymography, degree of conversion, and cytotoxicity of resveratrol-doped adhesives were also determined.

RESULTS

Irrespective of thermocycled or collagenase ageing, the resveratrol-doped adhesive (1 mg/mL) maintained the bond strength and reduced the nanoleakage expression. Meanwhile, the inhibitory ability on endogenous protease activity and S. mutans biofilm formation with acceptable biocompatibility were obtained.

CONCLUSIONS

This study suggested that the resveratrol-doped adhesive achieved effective improvement on dentin bond durability and secondary caries management.

CLINICAL SIGNIFICANCE

The application of the resveratrol-doped adhesive indicates promising benefits to increase the lifetime of composite restorations.

Dry bonding to dentin: Broadening the moisture spectrum and increasing wettability of etch-and-rinse adhesives

OBJECTIVE

To determine whether the effect of dentin moisture on the etch-and-rinse bonding may be minimized by dry-bonding protocols utilizing aqueous or ethanolic dimethyl sulfoxide (DMSO) pretreatments.

METHODS

H₃PO₄-etched mid-coronal dentin surfaces from human molars were randomly blot- or air-dried for 30 s and pretreated with DMSO/H₂O or DMSO/EtOH solutions. Untreated samples served as control. Moisture control was performed by either blot- or air-drying. Samples were bonded with a multistep etch-and-rinse adhesive. Restored crown segments (n = 8/group) were stored in distilled water for 24 h and sectioned for microtensile bond strength testing. Resin-dentin beams (0.8 mm²) were tested under tension until fracture (0.5 mm/min) after 24 h and two years of storage in artificial saliva at 37 °C. SEM nanoleakage evaluation was performed on aged samples. Collagen wettability was also measured by sessile drops of the hydrophilic and hydrophobic bonding resins (n = 8/group). Data were examined by factorial ANOVA followed by the Tukey test (α = 0.05).

RESULTS

Dry bonding to untreated collagen produced inferior immediate and long-term bond strengths than wet bonding (p < 0.05). Regardless of initial hydration and moisture control, DMSO-dry bonding produced initially higher and stable bond strengths after aging (p < 0.05). DMSO-pretreated groups presented improved collagen wettability with lower silver uptake (p < 0.05).

SIGNIFICANCE

Despite the common belief that etch-and-rinse adhesives must be applied onto moist collagen, DMSO-dry bonding protocols not only improved bonding performance and hybrid layer integrity, but also brought more versatility to collagen hybridization by reducing overdrying-related issues.

Characterization of multiscale interactions between high intensity focused ultrasound (HIFU) and tooth dentin: the effect on matrix-metalloproteinases, bacterial biofilms and biological properties

The aim of this study was to characterize multiscale interactions between high intensity focused ultrasound (HIFU) and dentin collagen and associated matrix-metalloproteinases, in addition to the analysis of the effect of HIFU on bacterial biofilms and biological properties. Dentin specimens were subjected to 5, 10 or 20 s HIFU. XPS spectra were acquired and TEM was performed on dentin slabs. Collagen orientation was performed using Raman spectroscopy. Calcium measurements in human dental pulpal cells (hDPCs) were carried out after 7 and 14 days. For macrophages, CD36+ and CD163+ were analysed. Biofilms were analyzed using CLSM. Tandem mass spectroscopy was performed for the detection of hydroxyproline sequences along with human MMP-2 quantification. Phosphorus, calcium, and nitrogen were detected in HIFU specimens. TEM images demonstrated the collagen network appearing to be fused together in the HIFU 10 and 20 s specimens. The band associated with 960 cm-1 corresponds to the stretching ν1 PO43-. The control specimens showed intensive calcium staining followed by HIFU 20 s > HIFU 10 s > HIFU 5 s specimens. Macrophages in the HIFU specimens co-expressed CD80+ and CD163+ cells. CLSM images showed the HIFU treatment inhibiting bacterial growth. SiteScore propensity determined the effect of HIFU on the binding site with a higher DScore representing better site exposure on MMPs. Multiscale mapping of dentin collagen after HIFU treatment showed no deleterious alterations on the organic structure of dentin.

Effects of different antibacterial disinfectants on microleakage of bulk-fill composite bonded to different tooth structures

Background

This in-vitro study aimed to investigate the effect of two different antibacterial disinfectants on the microleakage performance of newly developed bulk-fill composite, bonded to different tooth structures.

Methods

Class V cavities were prepared in 30 sound premolar teeth, with enamel occlusal margins (OM) and dentin cervical margins (CM). Two disinfectants, 2% chlorhexidine gluconate (CHX) and Listerine Miswak (ListM), were used. Teeth were divided into three groups (n = 10): G1, Control; G2, CHX; and G3, ListM. Disinfectants were applied to the cavity preparation walls after they were etched with 35% phosphoric acid. The Single Bond Universal adhesive system was then used, and teeth were restored with Filtek One Bulk Fill composite. Samples were examined, after thermocycling aging, by stereomicroscopy for the evaluation of marginal dye penetration.

Results

The highest mean microleakage score was reported in the CM of G1 (2.60 ± 1.174), which was significant compared with that of G2 only (p = 0.02). OM in G1 showed no microleakage, with no significant differences found among groups (χ² = 1.39, p = 0.50). No significant differences were reported between G2 and G3 (p = 0.45 OM; p = 0.17 CM).

Conclusions

Cavity pretreatment with CHX is not significantly different to pretreatment with CHX. In contrast, CHX improved the cervical marginal seal as compare to the control group (G1).

In vitro evaluation of the anti-proteolytic and cross-linking effect of mussel-inspired monomer on the demineralized dentin matrix

OBJECTIVES

To evaluate the anti-proteolytic and cross-linking effect of N-(3,4-dihydroxyphenethyl)methacrylamide (DMA) on the demineralized dentin matrix in vitro.

METHODS

Four experimental solutions were selected: 50% ethanol/water solution (Control); 1, 5, and 10 mmol/L DMA dissolved in 50% ethanol/water solution. Sound human molars were sectioned to produce dentin beams with dimension of 1×1×6 mm. The dentin beams were demineralized with 10% phosphoric acid for 8 h to remove the apatite. The demineralized specimens were randomly separated into four groups and immersed in the four experimental solutions for 1 h. After the treatment, the ultimate tensile strength (UTS), loss of dry mass and the release of hydroxyproline by storing the treated specimens in 0.1 mg/mL collagenase solution for 24 h were assessed. The swelling ratio of another ten specimens from each group were evaluated. The interaction between DMA with dentin matrix was observed under Field Emission Scanning Electron Microscopy (FESEM). UTS data was analyzed by two-way ANOVA followed by Tukey test, and the other data was analyzed by one-way ANOVA followed by Tukey test (α = 0.05).

RESULTS

The two-way ANOVA factors, different solutions (p < 0.001), collagenase degradation (p < 0.001) and their interactions (p < 0.001) all significantly affected the UTS. The 10 mM DMA treatment significantly decreased the percentage of loss of dry mass, release of hydroxyproline and swelling ratio of demineralized dentin matrix compared to other treatment groups (p < 0.05). The FESEM observation depicted that with increasing concentration of DMA, the structure of dentin matrix was protected and the porosity within dentin collagen network was decreased.

CONCLUSIONS

The treatment by 10 mM DMA/ethanol solution for 1 hour is capable of enhancing the mechanical properties of demineralized dentin matrix against collagenase degradation and may be clinically useful to improve the durability of hybrid layer.

CLINICAL SIGNIFICANCE

The 10 mM DMA/ethanol primer may offer an alternative choice for dentists to strengthen the mechanical properties of demineralized dentin matrix and resist its degradation by collagenase.

The management of deep caries in UK primary care: A nationwide questionnaire-based study

AIM

To investigate current approaches and attitudes towards the management of deep caries in primary dental care within the United Kingdom (UK).

METHODOLOGY

Open distribution of an electronic questionnaire survey was undertaken to primary care dental professionals working in publicly funded National Health Service [NHS], privately funded, military and community dental services. Demographic variables investigated included the following: place of qualification, method of remuneration, level of restorative training, materials available, years qualified, appointment length and clinician type. Management variables focussed on case-based scenarios. Univariate analyses of responses to questions were undertaken using χ² tests with sequential Bonferroni correction. Variables with a statistical relationship of p ≤ .2 were selected for binary logistic regression modelling.

RESULTS

A total of 657 responses were received. Practitioners with formal postgraduate qualifications (PGQ) were more likely (OR, 95%CI) to undertake further tests to aid diagnosis including: gaining a patient history (1.80, 1.01-3.20), periapical radiography (1.43, 1.01-2.03), cold pulp testing (2.079, 1.46-2.97) and electric pulp testing (1.65, 1.02-2.65). Rubber dam was infrequently used for deep caries management (29.2%). Non-NHS practitioners were much more likely to use rubber dam (3.40, 2.15-5.37), as were those that had completed PGQ (2.24, 1.48-3.38). Non-selective caries removal was used in deep caries by 41.4% of practitioners. Indirect pulp caps were carried out by 56.7% of practitioners. NHS practitioners were more likely to place calcium hydroxide (3.74, 1.97-7.15), whilst non-NHS practitioners were more likely to place calcium silicate cements (CSCs) (3.303, 1.71-6.38) as were non-UK graduates (5.63, 2.47-12.86) and those with PGQ (2.12, 1.17-3.87).

CONCLUSIONS

This UK survey highlights significant variation in the management of deep caries. There is lack of consensus regarding the use of a standard systematic approach to diagnosing disease, with a reliance on history and tests with poor specificity. Non-selective caries removal for managing deep carious lesions remains common, with low rubber dam compliance underlining a lack of asepsis. Notably, a significant number of practitioners placed indirect pulp caps, but CSCs and GIC were not commonly used. At present, although clear guidelines are available this is not translating into consistent management approaches in practice, suggesting that better dissemination of current treatments is essential to undergraduate and postgraduate groups.

Effect of epigallocatechin-3-gallate and thermal cycling on the bond strength of resin cements to the root dentin

This study evaluated the effect of epigallocatechin-3-gallate (EGCG) solution and thermal cycling on the bond strength (BS) of fiber posts to the root dentin using two different resin cements (conventional or self-adhesive). One hundred and forty-four bovine roots were endodontically treated. After post space preparation, specimens were randomly divided into six groups (n = 24) according to dentin pretreatment [distilled water, 0.05% EGCG solution or 2% chlorhexidine (CHX) solution] and resin luting agent used for fiber post cementation (RelyX ARC or RelyX U200-3 M ESPE). Then, the samples were separated into two subgroups (n = 12): storage in distilled water at 37 °C for 24 h and thermal cycling (5 °C/55 °C, dwell time 30 s-12,000 cycles) during 6 months. After that, the specimens were subjected to the pull-out BS test (Universal Testing Machine-0.5 mm/min) and the failures pattern was analyzed in a stereomicroscope. According to the BS results (three-way ANOVA, Tukey's test, α = 0.05), the highest values were reported in the group EGCG + RelyX U200, showing significant statistical differences compared to all the other experimental groups. For Control and CHX groups BS values, there was no significant difference (p > .05) between the resin cements. For conventional resin cement, there was no significant difference among treatment solutions (p > .05). The thermal cycling did not influence the BS results (p > .05). As reported by the failure mode analysis, adhesive failure was predominant in all groups. EGCG solution improved the bond strength of self-adhesive resin cement to root dentin.

Effect of dentin biomodification techniques on the stability of the bonded interface

Aim:

The aim of this study is to evaluate the effect of different bonding techniques ethanol wet bonding and dimethyl sulfoxide (DMSO) wet bonding and a novel collagen cross-linker Quercetin application on the durability of resin-dentin bond and observe the bonded interface under the scanning electron microscope (SEM).

Materials and Methods:

For shear bond strength testing, flat coronal dentin surfaces were prepared on 110 extracted human molars. Teeth were randomly divided into five experimental groups according to different surface pretreatments techniques. Group A was control group without any surface pretreatment. In Group B, ethanol wet bonding pretreatment was done before the application of adhesive. In Group C, DMSO wet bonding was done before the application of adhesive and in Groups D and E, Quercetin along with ethanol and Quercetin along with DMSO pretreatment, respectively, were done before adhesive application. Composite restorations were placed in all the samples. Twenty samples from each group were subjected to immediate and delayed (9 months) shear bond strength evaluation. In addition, two samples per group were subjected to the scanning electron microscopic analysis for the observation of resin-dentin interface.

Statistical Analysis:

Data collected were subjected to the statistical analysis using the one-way analysis of variance and post hoc Tukey's test at a significance level of P < 0.05.

Results:

Dentin pretreatment with all the techniques resulted in significantly higher resin-dentin bond strength after 9 months storage with DMSO group showing the highest bond strength values.

Conclusion:

It can be concluded that these biomodification techniques can improve the durability of the resin-dentin bond.

Synergistic effect of graphene oxide/calcium phosphate nanofiller in a dentin adhesive on its dentin bond integrity and degree of conversion. A scanning electron microscopy, energy dispersive X-ray spectroscopy, Fourier transform infrared, micro-Raman, and bond strength study

The objective was to formulate and analyze a dentin adhesive incorporated with graphene oxide (GO) nanoparticle and calcium phosphate (CaP) composite. Methods comprising of scanning electron microscopy (SEM)-energy dispersive X-ray spectroscopy (EDX), micro-Raman spectroscopy, shear bond strength (SBS), and Fourier transform infrared (FTIR) spectroscopy were used to characterize nanoparticle composite, dentin bond toughness, degree of conversion (DC), and adhesive-dentin interaction. Postsynthesis of GO nanoparticles, they were functionalized with CaP using standard process. The GO-CaP composite was not added to experimental adhesive (negative control group, GO-CaP-0%), and added at 2.5 and 5 wt% to yield GO-CaP-2.5% and GO-CaP 5% groups, respectively. Teeth were set to form bonded samples utilizing adhesives in three groups for SBS testing, with and without thermocycling. The homogenous diffusion of GO-CaP composite was verified in the adhesive. Resin tags having standard penetrations were observed on SEM micrographs. The EDX analysis confirmed the occurrence of calcium, phosphorus, and carbon ions in the composite containing adhesives. The SBS test revealed highest mean values for GO-CaP-5% followed by GO-CaP-2.5%. The FTIR spectra verified the presence of apatite peaks and the micro-Raman spectra showed characteristic D and G bands for GO nanoparticles. GO-CaP composite in dentin adhesive may improve its bond strength. The addition of 5 wt% resulted in a bond strength that was superior to all other groups. GO-CaP-5% group demonstrated lower DC (to control), uniform distribution of GO and CaP composite within adhesive, appropriate dentin interaction, and resin tag formation.

A novel dentin bonding scheme based on extrafibrillar demineralization combined with covalent adhesion using a dry-bonding technique

Dentin bonding is a dynamic process that involves the penetration of adhesive resin monomers into the extrafibrillar and intrafibrillar demineralized collagen matrix using a wet-bonding technique. However, adhesive resin monomers lack the capacity to infiltrate the intrafibrillar space, and the excess water that is introduced by the wet-bonding technique remains at the bonding interface. This imperfectly bonded interface is inclined to hydrolytic degradation, severely jeopardizing the longevity of bonded clinical restorations. The present study introduces a dentin bonding scheme based on a dry-bonding technique, combined with the use of extrafibrillar demineralization and a collagen-reactive monomer (CRM)-based adhesive (CBA). Selective extrafibrillar demineralization was achieved using 1-wt% high-molecular weight (MW) carboxymethyl chitosan (CMCS) within a clinically acceptable timeframe to create a less aggressive bonding substance for dentin bonding due to its selectively extrafibrillar demineralization capacity. CMCS demineralization decreased the activation of in situ collagenase, improved the shrinking resistance of demineralized collagen, and thus provided stronger and more durable bonding than traditional phosphoric acid etching. The new dentin bonding scheme that contained CMCS and CBA and used a dry-bonding technique achieved an encouraging dentin bonding strength and durability with low technical sensitivity. This bonding scheme can be used to improve the stability of the resin-dentin interface and foster the longevity of bonded clinical restorations.

Use of antioxidants to restore bond strength after tooth bleaching with peroxides

This review compiles the literature on the antioxidants used after tooth bleaching with either low or high-concentrated carbamide and hydrogen peroxide to recover the bond strength. Antioxidants used in bleached teeth are mainly natural and non-enzymatic, except for catalase. Commonly, antioxidants are applied to remove any reactive oxygen species (ROS) residues left from bleaching gels, which adversely affect adhesive procedures, such as restorations or orthodontic brackets bonding. Even though sodium ascorbate, the most thoroughly investigated antioxidant, showed the most efficient bond strength recovery at 10% concentration, its performance depends on the type of solution and the application time. Natural extracts, such as proanthocyanidins and green tea, showed satisfactory results in the reversal of bond strength at 5% and 10% concentrations, respectively. Sodium ascorbyl phosphate, α-tocopherol, and catalase exhibited promising results, but further research is required. The adhesive system type plays an important role in the outcome of enamel bond strength after the antioxidant application. The postponement of either restorations or orthodontic brackets cementation following bleaching procedures seems to be efficiently replaced by antioxidant application prior to bonding procedures. However, the efficacy of using an antioxidant to recover bond strength depends on its type and application time.

Impact of biomineralization on resin/biomineralized dentin bond longevity in a minimally invasive approach: An "in vitro" 18-month follow-up

OBJECTIVES

To determine the impact of treating caries-affected dentin (CAD) with: 0.2% sodium fluoride (NaF), casein phosphopeptide-amorphous calcium phosphate (CPP-ACP/MI Paste™) or peptide P₁₁-4 (Curodont™ Repair) on the longevity of resin/CAD interface at storage times of 24 -h, 6- and 18-month.

METHODS

255 caries-free third molars were used, and CAD was produced by a biological method. The teeth were randomly distributed into: G1- Sound dentin (SD); G2- CAD; G3- CAD + 0.2% NaF (CAD/NaF); G4- CAD + CPP-ACP (CAD/ACP); G5- CAD + Curodont™ Repair (CAD/P₁₁-4). The Filtek Z350 composite resin block was bonded to dentin using Adper™ Single 2 (4 mm/height). Resin/dentin blocks were stored in a solution of Simulated Body Fluid at 37 °C, pressures were modified to simulate natural pulpal pressures. Specimens were investigated by microtensile bond strength (μTBS) (n = 8), Scanning Electron Microscopy (to assess the failure mode) (n = 8), nanoinfiltration (to assess the interface sealing) (n = 3), in situ zymography (to assess the gelatinolytic activity) (n = 3) and micro-computed microtomography (μ-CT) (to assess the mineralization) (n = 3). Data from μTBS, μ-CT and, nanoinfiltration and hybrid layer formation/degradation were submitted to two-way ANOVA and Tukey tests, and failure patterns and in situ zymography to Kruskal-Wallis and Dunn tests (α = 5%).

RESULTS

The highest mineral density change by μ-CT, smallest silver nitrate infiltration and proteolytic activity in the adhesive layer were obtained significantly for the groups SD, CAD/ACP and CAD/P₁₁-4, with most mixed fractures at 18-month (p < 0.001). CAD/NaF showed significantly similar values to CAD, CAD and CAD/NaF which presented a high percentage of adhesive fracture (p < 0.001) at all time periods.

SIGNIFICANCE

Treating caries-affected dentin with remineralizing agents CPP-ACP and Curodont™ Repair, has the potential to be a clinically relevant treatment protocol to increase the longevity of adhesive restorations.

Incorporation of dimethyl sulfoxide into experimental hydrophilic and hydrophobic adhesive resins: evaluation of cytotoxic activities

This study evaluated the cytotoxicity of methacrylate-based resins containing dimethyl sulfoxide (DMSO). DMSO was incorporated into hydrophobic (R2) and hydrophilic (R5) resins at weight concentrations of 0, 0.01, 0.1, 1, 5, or 10 w/w %. Resin discs (n = 10/group) were prepared. Human gingival fibroblasts (HGF-1) were exposed to resin eluates for 24 h. Furthermore, dentin barrier test was performed using 3-D cultures of odontoblast-like cells (SV40 transfected pulp derived cells) with dentin slices of 400 µm thickness (n = 8). After acid etching of dentin, DMSO-modified resins were applied into the cavity part of the device and light-cured for 20 s. Cell viability (%) was assessed by MTT and analyzed spectrometrically. Data were analyzed by ANOVA and Tukey test (α = 0.05). Resin eluates showed statistically significantly lower % cell viability for all neat and DMSO-modified resins than seen for the negative control. Moreover, DMSO-R5 eluates resulted in significantly lower % cell viability than DMSO-R2 emulates. The dentin barrier test showed that DMSO-R2 did not result in significantly lower % cell viability, whereas incorporation of 1-10 w/w % DMSO into R5 resulted in significantly lower % of cell viability. Incorporating DMSO into hydrophilic self-etching resins may increase cytotoxicity. The biocompatibility is not influenced by the addition of DMSO into hydrophobic resin.

Preserving pulp vitality: part one - strategies for managing deep caries in permanent teeth

This is the first article in a series reviewing the current literature surrounding the management of deep caries in permanent teeth. Approaches to caries management are continuing to evolve, with more conservative management increasingly favoured. This philosophy has never been more important than in managing the deep carious lesion. Evidence is emerging that the use of selective caries removal to reduce the risk of pulp exposure, in conjunction with calcium silicate cements, can be successful in maintaining pulp vitality, delaying the restorative cycle and prolonging the lifespan of the tooth.

Scoping review of trials evaluating adhesive strategies in pediatric dentistry: where do simplified strategies lie?

BACKGROUND

Adhesive restorations allow a conservative approach to caries management and are increasingly used as a restorative option in pediatric dentistry. Placement can be difficult in children because of the cooperation required for multiple bonding steps. Due to this, it is vital to assess if novel, simpler strategies have been featured in clinical trials and if clinical trials are researching the different existing adhesive strategies.

METHODS

This review followed Preferred Reporting Items for Systematic Reviews and Meta-analysis adapted for Scoping Reviews (PRISMA-ScR) guidelines. PubMed/Medline, Cochrane Central, Scopus and EMBASE were used for systematic search, using free keywords and controlled search terms. Clinical trials of children requiring a restorative intervention which featured adhesive strategies were included. Only peer-reviewed trials of primary teeth restored with resin composites, published in the last 10-year period were eligible. Data charting was accomplished independently by two reviewers, and studies were summarized according to their date, type, intervention, sample size, observation period, outcomes and conclusions. Quality assessment was performed using Cochrane's Risk of Bias 2.0 tool.

RESULTS

700 potentially relevant references were found, which after a rigorous inclusion scheme, resulted in a total of 8 eligible clinical trials. Out of these, 7 were randomized clinical trials. Most trials featured a split-mouth design and the observation period ranged from 12 to 36 months. The trials evaluated interventions of two self-adhesive composites, two bulk-fill composites, two novel composites, one compomer and eight adhesives from different strategies. Most studies (4/8) included were judged to raise some concerns regarding risk of bias, while two were classified as high risk and two as low.

CONCLUSION

Few studies comparing adhesive strategies were found, especially adhesives in sound substrates. The existing studies do not reflect all current approaches that could be used in pediatric dentistry. Further studies addressing bioactive composites and contemporary adhesives are necessary.

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.