Bonding of self-etch and total-etch adhesives to carious dentin

Carbon nanotube-modified adhesive to caries affected dentin conditioned with Nd: YAP laser, Phosphoric acid, and Photoactivated-erythrosine

AIM

DENTIN CONDITIONED: with phosphoric acid (PA) Nd: YAP laser, and photoactivated-Ery(Erythrosine) on microleakage, shear bond strength (SBS) degree of conversion (DC), and rheological assessment of adhesive-infused with carbon nanotubes (CNTs).

MATERIAL AND METHOD

Carious ninety-six human mandibular molars were included. Specimens were disinfected and allocated into three groups based on surface pretreatment (n=32) Group 1 (PA), Group 2 (Nd: YAP) laser, and Group 3 (Photoactivated-Ery). Conditioned groups were further divided into two 2 subgroups based on the application of unmodified ERA and CNTs-modified ERA. Composite restorations were placed on the CAD surface and thermal aging of the samples was performed. The microleakage assessment was conducted using a dye penetration test. Universal testing machine (UTM) assessed SBS bond failure was evaluated using a stereomicroscope. Scanning electron microscopy (SEM), energy-dispersive X-ray (EDX) analyses of CNT, and Fourier Transform Infrared FTIR of adhesives were performed. One-way ANOVA and Tukey post hoc analyzed the outcomes.

RESULTS

Group 1B samples (PA+ CNTs modified adhesive) presented the minimum marginal leakage and highest bond integrity. Group 2A (Nd:YAP laser+Unmodified adhesive) displayed the maximum scores of microleakage and lowest bond strength.

CONCLUSION

Photoactivated Ery-PS can serve as an alternative to phosphoric acid for conditioning CAD. Incorporating CNT in adhesive significantly enhanced bond integrity and marginal seal with no significant difference in DC.

Mechanical properties of simulated dentin caries treated with metal cations and L-ascorbic acid 2-phosphate

This pH cycling study aimed to investigate the effects of L-Ascorbic acid 2-phosphate (AA2P) salts of Mg, Zn, Mn, Sr, and Ba on the surface microhardness, compressive strength, diametral tensile strength (DTS), and solubility of root canal dentin. 186 cylindrical dentin specimens from 93 teeth were fortified with optimal concentrations of AA2P salts of Mg (0.18 mM), Zn (5.3 µM), Mn (2.2 × 10-8 M), Sr (1.8 µM), and Ba (1.9 µM). Saline was used as the control group. These dentin specimens underwent a 3-day cycling process simulating dentin caries formation through repeated sequences of demineralization and remineralization. Surface microhardness at 100 and 500 µm depths (n = 10/subgroup), scanning electron microscopy (n = 3/group), compressive strength (n = 10/group), DTS (n = 6/group), and solubility (n = 5/group) tests were performed to analyze the dentin specimens. Data were analyzed using Kolmogorov-Smirnov, one-way ANOVA, and Post Hoc Tukey tests (p < 0.05). The control group had significantly lower microhardness at both depths (p < 0.001), reduced DTS (p = 0.001), decreased compressive strength (p < 0.001), and higher weight loss (p < 0.001) than all other groups. The Sr group had the highest compressive strength and microhardness among all the groups. The microhardness was significantly higher for the 500 µm depth than the 100 µm depth (p < 0.001), but the difference in microhardness between depths across groups was not significant (p = 0.211). All fortifying solutions provided some protection against artificial caries lesions. Therefore, these elements might have penetrated and reinforced the demineralized dentin against acid dissolution.

Enhanced Bonding to Caries-Affected Dentin Using an Isocyanate-Based Primer

Dental caries is the most common oral disease and the most common cause of resin restorations. In minimally invasive dentistry, the principle behind cavity preparation is to remove external caries-infected dentin (CID) and preserve internal caries-affected dentin (CAD) and sound dentin (SD). The cavity floor is mainly composed of CAD, but the poor bonding performance of CAD has become a widespread concern. This study evaluated the performance of a new collagen-reactive monomer (ITCM) used as a primer to improve the bonding performance of CAD. The experimental specimens were grouped as follows: SD, CAD, and ITCM-pretreated CAD (CAD-ITCM). Dentin slices were obtained for attenuated total reflectance-Fourier transform infrared (ATR-FTIR) analysis. The bonded samples were subjected to microtensile bond strength analysis after 24 h of water storage or aging by thermocycling, and the bonding interface quality was evaluated by nanoleakage assessment, interfacial nanoindentation testing, and in situ zymography. Cytotoxicity experiments with ITCM were performed. ATR-FTIR showed that the isocyanate groups in ITCM can covalently bind and form hydrogen bonds with the collagen in CAD to mediate chemical bonding. ITCM pretreatment significantly improved the bond strength of CAD (P < 0.05), reduced interfacial nanoleakage, improved the sealing of the bonding interface, enhanced the homogeneity of the hybrid layer, and inhibited matrix metalloproteinase activity. In addition, ITCM presented acceptable biocompatibility for dental restorative application. Taken together, this study reported the application of ITCM to induce collagen-based chemical bonding in the CAD bonding system, which fills the gap in strategies to improve the bonding performance of CAD immediately and after aging and has important clinical application prospects.

Selective Removal to Soft Dentine versus Full Pulpotomy for Management of Proximal Deep Carious Lesions: A Randomized Controlled Non-Inferiority Trial

The management of the deep carious lesion with reversible pulpitis is a dilemma for the dentist. The current study compared selective removal to soft dentine (SRSD) and full pulpotomy (FP) for treating proximal deep carious lesions in teeth with reversible pulpitis. Visual-tactile examination and bitewing radiographs were used to determine the depth of carious lesion, and American Association of Endodontists recommendations were used to formulate pulp diagnosis. Sixty mandibular molar teeth from healthy patients between the ages of 16-35 years and a diagnosis of proximal deep carious lesion with reversible pulpitis were included. Teeth were randomly allocated to two study groups. SRSD group (n = 30): soft dentine was preserved over the pulpal aspect. A hard-setting calcium hydroxide cement liner and resin-modified glass ionomer cement base were applied over the remaining soft carious dentine. FP group (n = 30): complete caries removal followed by mineral trioxide aggregate FP was performed. The teeth in both groups were restored with composite resin restoration. The established criteria for outcome assessment of SRSD and pulpotomy were used. Accordingly, only asymptomatic teeth with no radiological evidence of periapical rarefaction were considered successful at the 12-month follow-up. Two-sample t test, Pearson χ2 test/Fisher's exact test, and percentage agreement were used for statistical evaluation. According to the per-protocol analysis, the success rate of both SRSD and FP treatment was 95.45% and 95.65%, respectively, and the actual difference between the two treatments was 1% (95% CI: [-10, 9]). The data suggests that both treatments (SRSD and FP) appear to have a good success rate (>95%) when used to manage permanent mandibular molar teeth with proximal deep carious lesion and reversible pulpitis. As SRSD is a noninvasive procedure, it should be favored over FP in these instances.

Theobromine versus casein phospho-peptides/Amorphous calcium phosphate with fluoride as remineralizing agents: effect on resin-dentine bond strength, microhardness, and morphology of dentine

BACKGROUND

This study aimed to assess the impact of theobromine and casein phospho-peptides/amorphous calcium phosphate with fluoride (CPP-ACPF) on the resin-dentine bond strength, microhardness, and dentine morphology.

METHODS

A total of 18 sound human molars for micro-tensile bond strength (µTBS), 20 sound human premolars for microhardness, and 30 premolars for Scanning electron microscopy/energy-dispersive X-ray spectroscopy (SEM/EDX) were used. Based on the pre-treatment used, teeth were split into six groups; sound dentine, demineralized dentine, and demineralized dentine treated with theobromine (Sigma Aldrich) and MI paste plus (GC International, USA) for two-time intervals; 5 min and 1 month. The bonded teeth were sectioned to produce 1 mm² resin-dentine sticks which were evaluated for µTBS using a universal testing device (Instron 3365, USA). The dentine microhardness was tested by using the Vickers microhardness tester (Nexus 4000 TM, Netherlands). The pre-treated dentine surface was examined using SEM/EDX (Neoscope JCM-6000 plus Joel benchtop SEM, Japan). µTBS results were analysed with two-way ANOVA. Microhardness and EDX results were analysed with two-way mixed model ANOVA. The significance level was set at (p ≤ 0.05).

RESULTS

While both remineralizing materials at the two-time intervals demonstrated µTBS comparable to sound dentine (46.38 ± 12.18), the demineralized group demonstrated statistically the lowest µTBS (p < 0.001). Whether used for 5 min or 1 month, theobromine significantly increased the microhardness (50.18 ± 3.43) and (54.12 ± 2.66) respectively (p < 0.001), whereas MI paste only increased the hardness (51.12 ± 1.45) after 1 month (p < 0.001).

CONCLUSIONS

The pre-treatment of demineralized dentine with theobromine for 5 min or 1 month could enhance its bond strength and microhardness while for MI paste plus, only 1-month application was efficient to ensure remineralization.

Theobromine versus Casein phospho-peptide/Amorphous Calcium Phosphate with Fluoride as remineralizing agents: Effect on resin-dentine bond strength, microhardness, and morphology of dentine.. [DOI: 10.21203/rs.3.rs-2722167/v1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0]

Background: This study aimed to assess the impact of theobromine and casein phospho-peptides/amorphous calcium phosphate with Fluoride (CPP/ACPF) on the resin-dentine bond strength, microhardness, and dentine morphology. Methods: Based on the pre-treatment used, 18 sound human third molars were split into six groups.; sound dentine, demineralized dentine, and demineralized dentine treated with theobromine and MI paste plus for two-time intervals; 5 minutes and 1 month. The bonded teeth were sectioned to produce 1 mm2 resin-dentine sticks which were evaluated for micro-tensile bond strength (µTBS) using a universal testing device. The dentine microhardness was tested by using the Vickers microhardness tester. The pre-treated dentine surface was examined using Scanning electron microscopy/energy-dispersive X-ray spectroscopy (SEM/EDX). µTBS results were analysed with two-way ANOVA. Microhardness and EDX results were analysed with two-way mixed model ANOVA. Results: While both remineralizing materials at the two-time intervals demonstrated µTBS comparable to sound dentine, the demineralized group demonstrated statistically the lowest µTBS. Whether used for 5 minutes or 1 month, theobromine significantly increased the microhardness, whereas MI paste only increased the hardness after 1 month. Conclusions: The pre-treatment of demineralized dentine with theobromine and MI paste plus could enhance its bond strength and microhardness.

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.

Minimally invasive selective caries removal: a clinical guide

An evolving understanding of the carious process, along with new research in adhesive restorative materials, has led to a more conservative, minimally invasive and biologically-based approach to managing dental carious lesions. The growing volume of literature has also demonstrated prognostic success in the selective caries excavation technique, subsequently preventing excessive tooth structure removal and injury to the dentine-pulp complex, which maintains pulp vitality and improves the long-term prognosis of the tooth. However, at present, there remains a limited volume of high-quality evidence to support selective caries removal, which subsequently could partly explain some resistance to its use in clinical practice. This clinical technique guide aims to demonstrate the management of carious lesions of moderate-to-deep depth in permanent teeth based on current minimally invasive dental literature.

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.

Effect of Method of Removing Caries-Affected Dentin on the Bond Strength of Composite Resin to Root Canal Dentin

The adhesion of composite resin to caries-affected dentin differs from the adhesion of resin to sound dentin. We evaluated the bond strengths of dual-cure resin composites applied to caries-affected root canal dentin under various clinical conditions and using several caries removal indicators. In the dye stain 1 group, caries were removed to a pale pink stain level using a caries detector. In the dye stain 2 group, caries were removed to a stain-free level using a caries detector. In the probing group, caries were removed to the level of hardness based on probing with a sharp explorer. Additionally, a sound dentin group was used as a control. We compared the resin composite microtensile bond strengths and failure mode distribution among the groups. The bond strengths (MPa) of the probing (64.6 ± 11.9) and the sound dentin (68.7 ± 11.1) groups were significantly higher than those of the dye stain 1 (46.9 ± 7.9) and 2 (47.5 ± 8.4) groups (p < 0.05). The removal of caries-affected dentin using a dentin-hardness-based technique showed higher tensile strength than that using a dye stain technique involving removal to any color level. Thus, the caries removal technique used on root canal dentin affects the bond strength of the resin composite.

Assessment of Caries-Affected Dentin Adhesive Interface Treated with Contemporary Conditioning Techniques

Objective: The aim of this study was to assess shear bond strength (SBS) and failure analysis of adhesion of composite resin (CR) to caries-affected dentin (CAD) pretreated with the Er,Cr:YSGG (ECY) laser, photodynamic therapy (PDT), and etch and rinse (ER) used for cavity disinfection. Materials and methods: Methods used in this study included scanning electron microscopy (SEM), SBS analysis, failure analysis, and digital microscopy. The methods were adopted to assess bond integrity, CAD interface, smear layer, and hybridization. Thirty human third molars assessed clinically and having scores of 4 and 5 based on International Caries Detection and Assessment System (ICDAS) criteria were inspected. Infected dentin was removed. Dentin that was hard and stained pink was categorized as CAD. Ten samples were used in each group for pretreatment of CAD. Ten samples of healthy dentin [sound dentin (SD)] were collected separately and taken as controls. Samples were divided into the following groups: group 1: SD+ER; group 2: CAD+ER; group 3: CAD+ECY; and group 4: CAD+PDT after the pretreatment bonding agent was applied and the restorative procedure was performed using CR. Results: CAD conditioned with PDT before bonding to CR demonstrated the lowest SBS values (11.22 ± 0.77 MPa), whereas the highest SBS values were observed in the SD surface treated with ER (18.25 ± 1.22 MPa). In CAD and SD pretreated with ER, majority of failure modes were cohesive failure and admixed failure, whereas in CAD pretreated with PDT and the ECY laser, the adhesive failure mode was pertinent. Conclusions: The use of the ECY laser and PDT on CAD for cavity disinfection does not have potential for application in clinical settings as it decreases bond integrity of CR. Moreover, the ER pretreatment method for CAD and SD remains the gold standard.

Does the Application of Additional Hydrophobic Resin to Universal Adhesives Increase Bonding Longevity of Eroded Dentin?

This paper evaluates the effect of an additional hydrophobic resin coat (extra HL) associated with universal adhesives on sound and eroded dentin and evaluated immediately or after 2 years of water storage to improve the microtensile bond strength (μTBS) and nanoleakage (NL) when compared to the use of universal adhesives only. Sixty-four molars were assigned to eight groups using the following combinations: 1. dentin substrate, including sound and eroded dentin; 2. treatment, including the control and extra HL and storage time (immediately and after two-years of storage). Two universal adhesives (Prime & Bond Active or Scotchbond Universal) were evaluated. Before restoration, half of the teeth were subjected to soft-drink erosion. Composite buildups were bonded; specimens were stored (37 °C/24 h), sectioned into resin−dentin bonded sticks and tested for microtensile bond strength and nanoleakage using SEM (immediately and after two-years of storage). Three-way ANOVA and Tukey’s test (α = 0.05%) were used. In the immediate testing, the application of extra HL did not increase microtensile bond strength values compared with the control group in either substrate (p > 0.05). However, extra HL significantly decreased nanoleakage values when applied to eroded and sound dentin (p = 0.0001). After two years, the application of extra HL produced significantly higher microtensile bond strength and lower nanoleakage values than the control group for both adhesives (p = 0.0001). In all cases, sound dentin showed higher microtensile bond strength and lower nanoleakage values than eroded dentin (p = 0.000001). An extra HL increased the bond strength and reduced nanoleakage in eroded dentin after two-years of storage.

Extrusion bond strength of glass fiber post to radicular dentin after final irrigation using MTAD, EDTA, Pineapple peel extract, and riboflavin

INTRODUCTION

The present study aims to determine the effect of different post-space final irrigants ethylenediaminetetraacetic acid (EDTA), a mixture of Doxycycline citric acid and detergent (MTAD), Riboflavin (RF) and Pineapple peel extract (PPE) on the bond integrity of GFPs bonded to radicular dentin.

MATERIALS AND METHODS

Crowns of forty human mandibular premolars teeth were sectioned up to cementoenamel junction CEJ. Root canal treatment was performed. Gates Glidden drills were used to retrieve gutta-percha from the canal. All the specimens were randomly divided into four groups based on the final irrigant used. Group 1 (NaOCl with EDTA), group 2 NaOCl+ MTAD, group 3 NaOCl+RF and group 4 NaOCl+PPE. Cementation of glass fiber posts (GFPs) was performed using self-etch dual-cure resin cement. Sectioning was performed using a slow-speed saw from the coronal, middle, and apical third under constant water irrigation. A universal testing machine was used to assess push-out bond strength (PBS) and failure mode was evaluated using a Stereomicroscope at 40x magnification. One-way analysis of variance (ANOVA) and Tukey multiple comparison tests were used for statistical analysis (p=0.05).

RESULTS

Group 4 (2.5% NaOCl+ PPE) displayed the highest PBS at all three root levels (Cervical: 11.22±0.74 MPa, Middle: 8.99±0.97MPa, and Apical: 6.00±0.88 MPa). However, Group 1 (2.5% NaOCl+17% EDTA) demonstrated the lowest EBS (Cervical: 9.25±0.17 MPa, Middle: 7.01±1.84 MPa, and Apical: 4.41±0.17 MPa). Inter-group comparison displayed that PBS to be comparable between group 1 and group 3 (2.5% NaOCl+ Riboflavin) (Cervical: 9.74±0.41 MPa, Middle: 7.44±1.18 MPa, and Apical: 4.21±0.05 MPa) (p > 0.05). Whereas, group 2 (1.3% NaOCl+ MTAD) (Cervical: 9.32±1.36 MPa, Middle: 7.17±1.75 MPa, and Apical: 4.85±0.19 MPa) and group 4 demonstrated comparable values of PBS (p >0.05).

CONCLUSION

Pineapple peel extract and a mixture of Doxycycline citric acid and a detergent when used as a final irrigant demonstrated better bond integrity of GFPs to radicular dentin at all three levels coronal, middle and apical.

Dentin collagen denaturation status assessed by collagen hybridizing peptide and its effect on bio-stabilization of proanthocyanidins

OBJECTIVE

To assess dentin collagen denaturation from phosphoric acid and enzyme treatments using collagen hybridizing peptide (CHP) and to investigate the effect of collagen denaturation on bio-stabilization promoted by proanthocyanidins (PA).

METHODS

Human molars were sectioned into 7-µm-thick dentin films, demineralized, and assigned to six groups: control with/without PA modification, H₃PO₄-treated collagen with/without PA modification, enzyme-treated collagen with/without PA modification. PA modification involved immersing collagen films in 0.65% PA for 30 s. H₃PO₄ and enzyme treatments were used to experimentally induce collagen denaturation, which was quantitated by fluorescence intensity (FI) from the fluorescently-conjugated-CHP (F-CHP) staining (n = 4). FTIR was used to characterize collagen structures. All groups were subject to collagenase digestion to test the bio-stabilization effect of PA on denatured collagen using weight loss analysis and hydroxyproline assay (n = 6). Data were analyzed using two-factor ANOVA and Games-Howell post hoc tests (α = 0.05).

RESULTS

FTIR showed collagen secondary structural changes after denaturation treatments and confirmed the incorporation and cross-linking of PA in control and treated collagen. F-CHP staining indicated high-degree, medium-degree, and low-degree collagen denaturation from H₃PO₄-treatment (FI = 83.22), enzyme-treatment (FI = 36.54), and control (FI = 6.01) respectively. PA modification significantly reduced the weight loss and hydroxyproline release of all groups after digestion (p < 0.0001), with the results correlated with FI values at r = 0.96-0.98.

SIGNIFICANCE

A molecular method CHP is introduced as a sensitive technique to quantitate dentin collagen denaturation for the first time. PA modification is shown to effectively stabilize denatured collagen against collagenase digestion, with the stabilization effect negatively associated with the collagen denaturation degree.

New Dual-cure Resin-based Material in Occlusal and Occluso-proximal Restorations of Primary Teeth: Results of a Randomized Clinical Trial

Background

The clinical performance of new restorative materials must be evaluated before recommending its use in primary teeth.

Aim

This randomized clinical trial evaluated the survival rates of restorations in single and occluso-proximal cavities of primary teeth performed with a new dual-cure resin-based material in comparison with a resin-modified glass ionomer cement after 12 months of follow-up.

Materials and methods

A total of 107 restorations were placed in 27 children by one experienced pediatric dentist. Two materials were tested: Vitremer and a dual-cure resin-based material with (CentionN+Adh) and without (Cention N-Adh) adhesive system application. Two calibrated and blinded examiners evaluated the restorations at 3, 6, and 12-month. The longevity of the restorations was analyzed using Kaplan-Meier survival curves and Log-rank test (α = 5%).

Results

The overall survival rates after 12-month were 81.9% for Vitremer, 70.4% for Cention N+Adh, and 66.7% for Cention N-Adh, which had the poorer performance (HR = 0.54; 95% CI= 0.31-0.95; p = 0.031). When considering the type of the cavities, the difference was significant only for occluso-proximal cavities when Cention N-Adh was used (HR = 0.46; CI = 0.26-0.81; p = 0.008).

Conclusion

All evaluated materials are suitable for restoring occlusal cavities after selective caries removal. However, Cention N needs to be used with adhesive in occluso-proximal cavities.

Clinical significance

Cention-N can be used for deciduous teeth restorations, with similar longevity rates as resin modified glass ionomer cements.

Trial registration number RBR-9nqszr

How to cite this article

da Cunha CM, Wambier LM, Paris Matos TD, et al. New Dual-cure Resin-based Material in Occlusal and Occluso-proximal Restorations of Primary Teeth: Results of a Randomized Clinical Trial. Int J Clin Pediatr Dent 2022;15(1):38-46.

CHX Stabilizes the Resin/demineralized Dentin Interface

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

Biodentine or Mineral Trioxide Aggregate as Direct Pulp Capping Material in Mature Permanent Teeth with Carious Exposure? A Systematic Review and Meta-analysis

OBJECTIVE

To evaluate the success rate of direct pulp capping (DPC) with Biodentine in mature permanent teeth with carious vital pulp exposure compared to that of DPC with mineral trioxide aggregate (MTA) by means of a systematic review and meta-analysis.

DATA SOURCES

The two authors searched independently the literature published through July 31, 2020, in five electronic databases (PubMed, the Cochrane Central Register of Controlled Trials, Web of Science Core Collection, the Wiley Online Library, and the SCOPUS database).

STUDY SELECTION

The research protocol was previously registered in the PROSPERO database (CRD42020192511). Clinical studies that met the inclusion criteria were chosen and independently screened by the authors.

DATA EXTRACTION

A custom-designed spreadsheet was used to extract the data. The quality of each study was evaluated by means of the revised Cochrane risk of bias (ROB) tool or the ROB of nonrandomized studies of interventions tool.

DATA SYNTHESIS

Three randomized controlled trials and one retrospective study met the inclusion criteria. Only one study had a high risk of bias. The included studies reported data on a total of 95 participants with an age range of 8-51 years. No significant difference was observed in the overall treatment outcome when comparing Biodentine with MTA (Risk ratio=1.00, 95% confidence interval [0.93-1.07], p=1.00).

CONCLUSIONS

Biodentine had comparable clinical and radiographic success to that of MTA when used as a DPC agent in mature permanent teeth with carious vital pulp exposure. Additional high-quality studies are needed.

Development of dental inspection method: Nondestructive evaluation of an adhesive interface by ACTIVE acoustic emission

PURPOSE

This study aims to confirm the usefulness of active acoustic emission (Active AE) for reproducible and non-invasive generation of physical external force which is required for conventional AE.

METHODS

Experiment 1: A root dentin-resin adhesive interface was observed. The post space was filled with a dual-cure resin composite core material with and without adhesive. The vibration characteristics of the data obtained from the time-frequency analysis were evaluated. Experiment 2: A crown-abutment tooth adhesive interface was observed. Adhesive resin cement was used for luting the crown and adhesion states in the same specimen over time were analyzed with three measurements: at trial-fitting, immediately after luting, and 2 weeks after luting. Data were subjected to time-frequency analysis and relationships between amplitude (indicating loudness) and frequency (indicating the sound component) were analyzed.

RESULTS

Experiment 1: Time-frequency analysis confirmed multiple peak frequencies for each specimen without adhesive and monomodal peak frequency in all specimens using adhesive. Experiment 2: Two weeks after luting, all specimens showed a single major peak except one which showed multiple weak peaks.The three-dimensional visualization of time-frequency analysis revealed one specimen with multiple weak peaks while all others displayed a single, low-amplitude band at 2 weeks after luting.

CONCLUSIONS

The state of the adhesive interface can be evaluated using active AE. This basic technique may prove useful to evaluate changes in the adhesive interface of prostheses over time.

Synthesis of an urushiol derivative and its use for hydrolysis resistance in dentin adhesive

Hydrolysis resistance is essential to the durability of the dentin bonding interface. Urushiol is a natural monomer that has been used in different fields over thousands of years but has the disadvantage of a long drying time. In this study, we evaluated a novel photocurable derivative of urushiol as the main monomer for polymerization in dentin adhesive and its effect on hydrolysis resistance. The derivative was characterized by Fourier transform infrared spectroscopy and ¹H nuclear magnetic resonance spectroscopy. Compared with the Adper Single Bond 2, the experimentally synthesized adhesives had higher contact angles. In particular, the water sorption/solubility of the experimental samples were significantly lower than that of Adper Single Bond 2. The microtensile bond strengths of the test groups were higher than that of the control group, even after 5000 thermocycles. Cytotoxicity test results showed that adhesives based on the original derivative induced low toxicity to L929 cells. The results of this study may shift the focus of future research to natural monomers and even their derivatives which may perform well in dentistry.

Development of dental inspection method: nondestructive evaluation of a dentin-adhesive interface by acoustic emission

PURPOSE

The state of adhesion between root dentin and a resin composite core material was inspected using acoustic emission (AE).

METHODS

A total of 14 human incisors and premolars were used to prepare "no-adhesive group" and "adhesive group" specimens. For "adhesive group" specimens, a bonding agent was applied to root canal dentin. The entire post space was subsequently filled with a resin composite for both specimen groups. The prepared specimens were fixed onto a jig on which an AE sensor was installed. A zirconia ball was used for the impact test, and a vibration wave generated by the collision was measured by the system using an AE sensor. The obtained data were subjected to time-frequency analysis using analysis software (LabVIEW), and the relationship between the amplitude indicating the loudness and the frequency indicating the sound component was analyzed.

RESULTS

Zirconia-ball collision tests using AE revealed differences between the groups with respect to the waveform of vibration waves transmitted to the root dentin through the root dentin-resin interface. The time-frequency analysis of the obtained data confirmed that multiple peaks were observed for each specimen in the no-adhesive group, whereas a single characteristic vibration peak was observed for all specimens in the adhesive group.

CONCLUSIONS

The state of the adhesive interface was successfully evaluated by AE. This demonstration is expected to lead to the development of a device that can detect problems at the bonding interface between the prostheses and tooth substances.

Substantial regional differences in the biomechanical behavior of molar treated with selective caries tissue removal technique: a finite element study

OBJECTIVES

Selective caries removal (SCR) is recommended over non-selective removal for managing deep carious lesions to avoid pulp exposure and maintain pulp vitality. During SCR, residual carious dentin is left behind and sealed beneath the restoration. The biomechanical effects of such residual lesions on the restored tooth remain unclear and were assessed using finite element modeling (FEM).

METHODS

Based on μ-CT images of a healthy permanent human third molar, we developed five finite element models. Generic class I and II cavity restorations were modeled where residual lesions of variable sizes were either left or fully removed on occlusal and proximal surfaces. The cavities were restored with adhesive composite. All 3D-FE models were compared with a model of a healthy, non-treated molar. A vertical load of 100 N was applied onto the occlusal surface.

RESULTS

Regardless of the lesion size, in molars with occlusal lesions higher mean stresses were predicted along the filling-lesion interface than in all other models. The smallest occlusal lesion (Ø₁ = 1 mm) resulted in the highest maximum stresses at the filling-lesion interface with large stress concentrations at the filling walls indicating failure risk. In conclusion, lesion site and extent are influencing parameters affecting the filling-lesion interactions and thus the biomechanical behavior of the tooth after SCR.

SIGNIFICANCE

Retaining carious lesions around the pulpal floor affects the deformation and stress states in tooth-filling complexes. The higher stresses observed in molars with occlusal lesions may affect restoration stability and longevity. Suprisingly, more extended occlusal lesions may provide a more favorable tooth performance than less extended ones. In contrast, in molars with proximal lesions the residual lesion had only limited effect on the tooth's biomechanical condition.

Etching time and bonding of adhesive systems to dentin of primary teeth: A systematic review and meta-analysis

BACKGROUND

Due to the chemical and morphological differences between primary vs. permanent teeth, the time reduction of the acid etching or acidic primer can result in higher values of bond strength.

AIM

To assess through a systematic review and meta-analysis the influence of the reducing etching (acid etching or acidic primer) time on the bond strength of adhesive systems to primary dentin.

DESIGN

A systematic search was carried out in 3 databases: PubMed, Web of Science and Scopus. Studies that evaluated the effect of reducing the etching time on the bond strength of adhesive systems to primary dentin were included. Meta-analyses were performed using a random-effects model, with subgroups for etch-and-rinse and self-etching adhesives, with a significance level of P < .05. The risk of bias and heterogeneity between studies (Cochrane and I2 tests) were assessed.

RESULTS

Eight studies were included in the systematic review and seven in the meta-analyses. The shortening etching time did not influence the immediate dentin bond strength for etch-and-rinse (Z = 0.07, P = .95) and self-etching adhesives (Z = 0.41, P = .69). After ageing, however, the shorting etching time improved the bond strength for etch-and-rinse adhesives (Z = 2.01, P = .04). All studies presented high bias risk.

CONCLUSIONS

Reducing the acid-etching time to primary dentin improves the long-term bond strength to this substrate.

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

OBJECTIVES

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

MATERIALS AND METHODS

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

RESULTS

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

CONCLUSIONS

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

CLINICAL RELEVANCE

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

Current perspectives on dental adhesion: (2) Concepts for operatively managing carious lesions extending into dentine using bioactive and adhesive direct restorative materials

This article reviews the current concepts for operatively managing carious lesions extending into dentine with minimal removal of tooth structure and restoring with dentine adhesives and direct composite resin. It looks sequentially at the operative steps involved including remineralisation with bioactive cements, bonding to caries-affected dentine including smear-layer modification using HOCl, creation of an acid-base resistance zone,steps to optimise the performance of all-in-one adhesives, and incremental placement of direct composite resin to improve bond strengths to cavity floor dentine. It explores how understanding the phenomenon of colour-shifting at the composite resin-enamel/dentine restoration borders can help in creating near "invisible" restoration margins through a "chameleon" effect. With the increased risks of transmission of Covid-19 when aerosol generating procedures are carried out in Dentistry, following a minimally invasive approach to managing dental caries should be given serious consideration.

Shortening of etching time of the dentin in primary teeth restorations: a randomized clinical trial

The aim of this study was to investigate the influence of shortening of etching time for dentin on the restoration survival after selective carious tissue removal in primary molars. This two-arm randomized clinical trial included sixty-two subjects (5-8 year-old) and 100 primary molars presenting moderate dentin carious lesions on occlusal surface. The sample was randomly assigned into groups previously to adhesive application (Adper Single Bond 2; 3M ESPE): etching time recommended by manufacturer (15 s) or reduced (7 s). Resin composite (Filtek Bulk Fill Posterior Restorative; 3M ESPE) was inserted in a single increment for all restorations. Restorations were evaluated at 1, 6, 12, and 18 months using FDI criteria. Survival estimates for restorations' longevity were evaluated with Kaplan-Meier method. Multivariate Cox regression analysis with shared frailty was used to assess the factors associated with failures (p < 0.05). The etching time did not influence the restorations' survival (HR 0.35 95%CI 0.11-1.12; p = 0.06). Mean estimated time of survival was 17.6 months (95%CI, 17.2-17.9). The survival rates at the 18-month follow-up were 75.7% and 91.4% (AFR: 16.9% and 5.7%) when primary dentin was acid etched for 15 and 7 s, respectively (log-rank p = 0.06). In conclusion, the etching time for dentin did not influence the clinical behavior of adhesives restorations. However, there was a tendency for better clinical outcome when using etching time of 7 s.

Effect of silver diamine fluoride on the bond durability of normal and carious dentin

Background

Silver diamine fluoride (SDF) has attracted attention because of its clinical success in arresting dentin caries. It has been shown that it can inhibit matrix metalloproteinases and cysteine cathepsins. These two properties might be beneficial in bonding to caries-affected dentin (CAD). Therefore, the present study aimed to investigate the effect of SDF on the durability and bond strength to the CAD.

Material and Methods

Forty-eight third molars with occlusal caries were used. The roots were cut, and the occlusal enamel was removed. The CAD area surrounded by the normal dentin (ND) was exposed. All the specimens were bonded with an etch-and-rinse adhesive, but half of them were treated with SDF after acid etching (NT or SDF). Two cylinders of composite (0.9 mm in diameter and 0.7 mm in height) were built-up on each specimen, one on the CAD and the other on the ND area. The specimens in each group (NT-ND, NT, CAD, SDF-ND, SDF-CAD) (n=24) were equally divided into two subgroups. One subgroup was tested for microshear bond strength 24 hours after bonding (T0), and the other subgroup was tested after six months of water storage (T6). The bond strength data were analyzed using three-way ANOVA. Subgroup analysis was performed using independent samples t-test. Fracture patterns were also evaluated.

Results

At T0, the bond strength of NT-ND was higher than that of NT-CAD (p<0.00), but the bond strength of SDF-ND and SDF-CAD were not different (p=0.77). Comparison of the bond strength of the groups between the two time intervals yielded the following results: NT-ND-T0> NT-ND-T6 (p=0.04), SDF-ND-T0=SDF-ND-T6 (p=0.39), NT-CAD-T0=NT-CAD-T6 (p=0.51) and SDF-CAD-T0>SDF-CAD-T6 (p<0.00).

Conclusions

The SDF treatment increased the bond strength to CAD but did not affect the bond strength to the ND. SDF hindered the decrease in the bond strength to the ND caused by aging. However, the effect of SDF on increasing the bond strength to CAD disappeared after aging. Key words:Silver diamine fluoride, caries-affected dentin, bond strength.

Bonding Performance of Universal Adhesive Systems Applied in Etch-and-Rinse and Self-Etch Strategies on Natural Dentin Caries

Objective:

This study investigated the bonding performance of three universal adhesive systems applied using etch-and-rinse (ER) or self-etch (SE) strategies on natural dentin caries.

Materials and Methods:

Sixty human third molars were selected for this study: 30 naturally carious (CAD) and 30 sound (SD) teeth. The dentin surfaces were exposed, and teeth were randomly assigned to each evaluated adhesive system: Scotchbond Universal (SBU), Futurabond U (FBU), and Prime&Bond Elect (PBE) and an adhesive strategy: ER or SE. The adhesive systems were applied following the manufacturer's instructions, and the teeth were restored using a resin composite (Filtek Supreme Ultra, 3M). After 24 hours (distilled water at 37°C), samples were sectioned and evaluated using microtensile bond strength analysis (μTBS), micro-Raman spectroscopy to evaluate the degree of conversion within the hybrid layer (DC), and scanning electronic microscopy (SEM) to describe the morphology of the hybrid layer. The μTBS and DC data were analyzed using three-way analysis of variance and Tukey's test for means comparison (α=0.05). The SEM images were analyzed qualitatively.

Results:

Reduced μTBS values were observed when comparing CAD with SD, regardless of adhesive system or strategy (p&lt;0.0001). SBU showed statistically higher μTBS for both dentin substrates and strategies (p&lt;0.0001). Furthermore, SBU showed greater integrity of the hybrid layer and resin tag formation compared with FBU and PBE. Mean μTBS values for FBU were higher for SD in the SE mode, whereas higher mean μTBS values were observed for CAD in the ER mode, both compared with PBE (p&lt;0.001).

Conclusion:

Bonding performance is reduced on a caries-affected substrate. The ER strategy was not able to improve the bonding performance on natural CAD for universal adhesive systems. Improved bonding performance was obtained when using the Scotchbond Universal system.

Performance of Adhesives and Restorative Materials After Selective Removal of Carious Lesions: Restorative Materials with Anticaries Properties

Selective carious tissue-removal strategies require specific considerations in selection of restorative materials. A tight marginal seal placed over hard dentin and sound enamel is essential. For selective removal of carious tissue with permanent restoration, bioactive materials, such as high-viscosity glass-ionomer cement (HV-GIC) or calcium silicates, may be preferred over caries-affected firm or leathery dentin to improve remineralization. HV-GICs have the best clinical evidence of caries-arresting effect and demonstrate sufficient longevity as long-term provisional restorations that can later be used in open or closed sandwich restorations. As with any material, oral health maintenance remains important for long-term survival of restorations.

Does selective carious tissue removal of soft dentin increase the restorative failure risk in primary teeth?: Systematic review and meta-analysis

BACKGROUND

The authors conducted a systematic review of randomized controlled trials comparing the risk of experiencing restoration failure in primary teeth after complete and selective carious tissue removal of soft dentin.

METHODS

The authors searched electronic databases (PubMed [MEDLINE], Scopus, Cochrane Central Register of Controlled Trials) and the ClinicalTrials.gov Web site with manual searching and cross-referencing for trials reporting restoration failure after follow-up of 6 months or longer. Two reviewers independently selected studies, extracted data, and assessed the risk of bias and quality of evidence using the Grading of Recommendations Assessment, Development, and Evaluation approach. The authors performed intention-to-treat and per-protocol meta-analyses and calculated odds ratios (OR) as effect estimates in the random-effects model.

RESULTS

From 327 potentially eligible studies, the authors selected 23 for full-text screening and included 4. Results showed increased risk of experiencing restoration failure (intention-to-treat analysis, OR [95% confidence interval] 1.74 [1.01 to 3.00], and per-protocol analysis, OR [95% confidence interval] 1.79 [1.04 to 3.09]) after selective carious tissue removal of soft dentin. The risk of bias was high, and the quality of evidence was low.

CONCLUSIONS

Selective carious tissue removal of soft dentin may increase the risk of experiencing restoration failure in primary teeth. However, the evidence level is insufficient for definitive conclusions.

PRACTICAL IMPLICATIONS

Patients with restorations performed after selective carious tissue removal of soft dentin should have shorter recall visit intervals to evaluate the restorations' quality and control caries disease, allowing for more conservative approaches, such as repair, in cases of defective restorations.

Tailored Dentistry: From "One Size Fits All" to Precision Dental Medicine?

Over the past 30 years and fueled by both a rapidly evolving understanding of dental diseases and technological advances in diagnostics and therapy, dentistry has been changing dramatically. Managing dental caries and carious lesions had, for nearly a century, encompassed only a small number of basic concepts that were applied to virtually all patients and lesions, namely, invasive removal of any carious tissue regardless of its activity or depth and its replacement with restorative materials (amalgams or crowns for most of the past) or tooth removal and prosthetic replacement. Grounded in a deeper understanding of the disease "caries," its management-aiming to control the causes of the disease, to slow down or alleviate existing disease, and, only as a last resort, to remove its symptoms using a bur or forceps-has become more complex and diverse. In parallel and at nearly unprecedented speed, our patients are changing, as mirrored by ongoing debates as to the demographic and, with it, the social future of most high-income countries. This article describes how these changes will have a profound future impact on how we practice dental medicine in the future. It will deduce, from both demographic and epidemiologic trends, why there is the need to apply not one but rather the whole range of existing evidence-based concepts in an individualized (personalized) manner, hence increasing the effectiveness and efficiency of dental management strategies, and also describe how these strategies should be tailored according not only to our patients (their age and risk profiles) but also to the specific tooth (or site or lesion).

Comparison of the micro-tensile bond strengths of four different universal adhesives to caries-affected dentin after ER:YAG laser irradiation

The micro-tensile bond strengths (micro-TBSs) of four universal adhesive systems, applied in two different bonding techniques, to carries-affected dentin after Er:YAG laser irradiation were investigated. Twenty-four extracted human molars were divided into four groups, according to the adhesive systems used. Each group was subdivided into two subgroups, depending on the bonding method used: the etch-and-rinse procedure or self-etch procedure. The carious lesions were irradiated using an Er:YAG laser. Resin composites were used to restore the adhesive-treated dentin surfaces. After 2,500 thermal cycles, the vertical composite resin-dentin sticks obtained were subjected to micro-TBS tests. One tooth in each group was examined using scanning electron microscopy (SEM). There were statistically significant differences (p<0.001) in micro-TBS values between universal adhesives. The results of this study suggested that universal adhesives applied both with self and total etch technique can be used for adhesive restorations to caries-affected dentin after Er:YAG laser irradiation. If lasers are preferred as a caries removal method, choosing a dentin bonding agent containing MDP may be recommended in clinical practice due to the property of increasing the bonding strength.

The Evolution of Dental Materials over the Past Century: Silver and Gold to Tooth Color and Beyond

The field of dental materials has undergone more of a revolution than an evolution over the past 100 y. The development of new products, especially in the past half century, has occurred at a staggering pace, and their introduction to the market has been equally impressive. The movement has mostly come in the area of improved esthetics, marked by the gradual replacement of dental amalgam with dental composite and all-metal and porcelain-fused-to-metal indirect restorations with reinforced dental ceramics, all made possible by the rapid improvements in dental adhesive materials. This article covers the time course of dental materials development over the past century in which the Journal of Dental Research has been published. While there have been advances in nearly all materials used in the field, this article focuses on several areas, including dental amalgam, dental composites and light curing, dental adhesives and dental cements, ceramics, and new functional repair materials. A few short statements on future advances will be included at the end.

Degradation of Multimode Adhesive System Bond Strength to Artificial Caries-Affected Dentin Due to Water Storage

The purpose of this study was to evaluate the influence of water storage on bond strength of multimode adhesive systems to artificially induced caries-affected dentin. One hundred twelve sound bovine incisors were randomly assigned to 16 groups (n=7) according to the dentin condition (sound; SND, artificially induced caries-affected dentin; CAD, cariogenic challenge by pH cycling for 14 days); the adhesive system (SU, Scotchbond Universal Adhesive; AB, All-Bond Universal; PB, Prime & Bond Elect; SB, Adper Single Bond 2; and CS, Clearfil SE Bond), and the etching strategy (etch-and-rinse and self-etch). All adhesive systems were applied under manufacturer's instructions to flat dentin surfaces, and a composite block was built up on each dentin surface. After 24 hours of water storage, the specimens were sectioned into stick-shaped specimens (0.8 mm2) and submitted to a microtensile test immediately (24 hours) or after six months of water storage. Bond strength data (MPa) were analyzed using three-way repeated-measures analysis of variance and post hoc Tukey test (α=5%), considering each substrate separately (SND and CAD). The etching strategy did not influence the bond strength of multimode adhesives, irrespective of the dentin condition. Water storage only reduced significantly the bond strength to CAD. The degradation of bond strength due to water storage was more pronounced in CAD, regardless of the etching strategy.

Biological response to self-etch adhesive after partial caries removal in rats

OBJECTIVES

The purposes of this study were to evaluate a model of slow caries progression and to investigate the performance of a self-etch adhesive system for partial caries removal.

MATERIALS AND METHODS

Rat molars were infected with Streptococcus sobrinus 6715 culture. Different time points were analyzed: days 78, 85, and 95 (± 2). After this, the samples were processed for morphological analysis. Additionally, the first molars were restored with zinc oxide and eugenol (IRM™; Dentsply; Brazil) or adhesive system (Clearfil SE Bond™; Kuraray Medical; Japan) 78 days after caries induction. After, 3 or 15 days post-treatment, the animals were euthanized, and their mandibles were processed for morphological analysis, classified by means of scores, and submitted to statistical analysis. Subsequently, immunohistochemical analysis was performed for osteonectin (OSN) and transforming growth factor-ß1 (TGF-ß1) expression.

RESULTS

According to the caries induction model used, on day 95 greater inflammatory infiltration (p < 0.001), and more extensive degradation of secondary/primary dentin were demonstrated than on day 78 (p < 0.05). Furthermore, the restorative materials presented similar performance (p > 0.05) and proved to be fundamental to control the carious lesion. The TGF-ß1 and OSN were shown to be active during the caries process.

CONCLUSIONS

The slow caries lesion model was feasible for morphological analysis of the dentin-pulp complex. The self-etch adhesive system triggered no acute inflammatory infiltration or pulp necrosis, instead it seemed to stimulate early pulp repair.

CLINICAL RELEVANCE

Clearfil SE Bond™ applied directly on caries-affected dentin did not predispose to pulp inflammation; instead, it appeared to provide early biological benefits.

Efficacy of removal of cariogenic bacteria and carious dentin by ablation using different modes of Er:YAG lasers

The primary objective of this in vitro study was to evaluate the efficiency of removal of cariogenic bacteria and carious dentin by ablation using two lasers: fluorescence-feedback controlled (FFC) Er:YAG laser and different pulses of Er:YAG laser based on variable square pulse technology (VSPt). The secondary objective was to measure the temperature during laser ablation of carious tissue. Seventy-two extracted human molars were used in this study. Sixty teeth with carious dentin were randomly divided into four experimental groups according to the treatment for caries removal: group 1: 400 µs (FFC group); group 2: super short pulse (SSP group, 50 µs pulse); group 3: medium short pulse (MSP group, 100 µs pulse); group 4: short pulse (SP group, 300 µs pulse) and one positive control group with no treatment. Twelve teeth without carious lesion were used as a negative control group. After caries removal, swabs were taken with cotton pellets and real-time PCR analysis was performed. During caries ablation, a thermal infrared camera was used to measure the temperature changes. In all experimental groups, specimens were free of bacterial contamination after the treatment. In the SSP, MSP and SP groups, temperatures measured during caries ablation were significantly higher compared to temperatures in the FFC group (P<0.001). In this in vitro study, laser treatment for removal of carious dentin and cariogenic bacteria was an efficient treatment modality without causing excessive temperatures that might adversely affect pulp vitality.

The impact of artificially caries-affected dentin on bond strength of multi-mode adhesives

Aim:

The aim of this study is to evaluate the impact of dentin condition on bond strength of multi-mode adhesive systems (MMAS) to sound and artificially induced caries-affected dentin (CAD).

Methods:

Flat dentin surfaces of 112 bovine incisors were assigned to 16 subgroups (n = 7) according to the substrate condition (sound and CAD– pH-cycling for 14 days); adhesive systems (Scotchbond Universal, All-Bond Universal, Prime and Bond Elect, Adper Single Bond Plus and Clearfil SE Bond) and etching strategy (etch-and-rinse and self-etch). All systems were applied according to the manufacturer's instructions, and resin composite restorations were built. After 24 h of water storage, specimens were sectioned (0.8 mm²) and submitted to the microtensile test.

Statistical Analysis:

Data (MPa) were analyzed using three-way analysis of variance and Tukey's test (α = 0.05).

Results:

MMAS presented similar bond strength values, regardless etching strategy in each substrate condition. Bond strength values were lower when MMAS were applied to CAD in the etch-and-rinse strategy.

Conclusion:

The etching strategy did not influence the bond strength of MMAS to sound or CAD, considering each substrate separately. However, CAD impact negatively on bond strength of MMAS in etch-and rinse mode.

Bond strength of adhesive systems to sound and demineralized dentin treated with bioactive glass ceramic suspension

OBJECTIVE

The objective of this study was to evaluate the effect of a Biosilicate®, associated with dentin adhesive system, on microtensile bond strength (μTBS) to sound and demineralized dentin.

MATERIALS AND METHODS

Eighty sound-extracted molars had their middle occlusal dentin exposed. In forty teeth, dentin was artificially demineralized (pH cycling). Sound and demineralized dentin teeth were separated into four groups (n = 10), according to the substrate treatment before restoration: Group 1-total-etching adhesive Adper TM Single bond 2 (ASB) + Biosilicate®, Group 2-ASB (without Biosilicate®), Group 3-AdheSE self-etching adhesive system (AdSE) + Biosilicate®, and Group 4-AdSE (without Biosilicate®). Each tooth was restored with a hybrid composite and stored in water at 37 °C for 6 months. After water aging, teeth were cut in sticks (≈ 1 mm² cross-sectional area) and all samples were submitted to μTBS test. The fracture modes of the samples were analyzed by stereomicroscopy. The representatively fractured samples were observed by scanning electron microscopy. Representative samples of each group were analyzed on energy dispersive X-ray spectrometry (EDX). The μTBS and Ca-P ratio values were analyzed by 2-way ANOVA, Bonferroni, and Tukey test, respectively, p < .05.

RESULTS

ASB + Biosilicate® presented the highest μTBS values (p < .05), and lowest μTBS values (p < .05) were found in AdSE Group. There was no statistical difference (p < .05) on μTBS when substrates were compared, except for Group 2. The fracture pattern analysis showed prevalence of adhesive fractures in all groups.

CONCLUSION

Biosilicate® enhanced bond strength of self-etching and etch-and-rinse adhesives to sound and demineralized dentin.

CLINICAL RELEVANCE

Bioactive glass ceramic suspension could be recommended to be used to improve the dentin bond strengths of the total-etching and self-etching adhesives after acid-etching and priming.

Histological evaluation of three techniques for caries removal

A number of concepts and devices have been proposed for caries removal. Among these, the Er:YAG laser is a potential alternative to conventional mechanical treatment. This study compared the effectiveness of the Er:YAG laser with that of low-speed rotary instruments for removal of carious tissue in 26 extracted human molars and premolars with severe decay (i.e., large occlusal or proximal decay but no pulpal contact). The teeth were divided into three groups of eight teeth, and two teeth were used as controls. After sectioning all the teeth through the center of the carious lesion before excavation, each group was randomly assigned to three groups-Er:YAG laser versus tungsten bur, Er:YAG laser versus polymer bur, and polymer bur versus tungsten bur-to evaluate the efficacy of the three techniques. The time required for carious treatment of each half was recorded, and samples were then histologically examined. Mean duration of caries removal did not significantly differ in relation to the technique used. Histological analysis of tooth halves treated with the Er:YAG laser revealed a regular 5-µm-thick stained layer that appeared to be denatured collagen. A smear layer was often detectable in halves treated with carbide burs. A superficial disorganized layer, which was found to be affected dentin, was observed in halves treated with polymer burs. The present findings indicate that the three techniques were clinically and histologically effective in removing the infected dentin layer.(J Oral Sci 58, 583-589, 2016).

Effects of silver nanoparticles on the bonding of three adhesive systems to fluorotic enamel

The objective was to evaluate the effect of adding silver nanoparticles into three commercial adhesive systems (Excite™, Adper Prompt L-Pop™ and AdheSE™). Nanoparticles were prepared by a chemical method then mixed with the commercial adhesive systems. This was later applied to the fluorotic enamel, and then micro-tensile bond strength, contact angle measurements and scanning electron microscopy observations were conducted. The commercial adhesive systems achieved the lowest micro-tensile bond strength (Excite™: 11.0±2.1, Adper Prompt L-Pop™: 14.0±5.4 and AdheSE™: 16.0±3.0 MPa) with the highest adhesive failure mode related with the highest contact angle (46.0±0.6º, 30.0±0.5º and 28.0±0.4º respectively). The bond strength achieved in all the experimental adhesive systems (19.0±5.4, 20.0±4.0 and 19.0±3.5 MPa respectively) was statistically higher (p<0.05) than the control and showed the highest cohesive failures related to the lowest contact angle. Adding silver nanoparticles in order to decrease the contact angle improve the adhesive system wetting and its bond strength.

Effect of Different Intermediary Bases on Microleakage of a Restorative Material in Class II Box Cavities of Primary Teeth

Introduction

The aim of this in vitro study was to assess and compare the effect of different intermediary bases on microleakage between tooth and a nanocomposite interface in Class II box cavities in primary teeth.

Methods

Standard Class II box cavities were prepared in 52 primary molars and randomly divided into 9 groups according to the intermediary base used (Multicore Flow, Fuji II LC, SDR, Smart Dentin Replacement, and Biodentine). All specimens were subjected to thermocycling and prepared for microleakage testing and evaluation.

Results

There was significant difference in the mean ranks of microleakage between the 9 groups, which was observed in the gingival side (p<0.0001) and the occlusal side (p<0.0001). The mean ranks microleakage was significantly higher with experimental SDR, experimental Multicore Flow, and positive control materials when compared with the other 6 groups. The microleakage mean ranks were statistically significantly lower in experimental Fuji II LC, experimental Biodentine, and all negative control groups when compared with the other 3 groups.

Conclusions

Microleakage is affected by the application of intermediate material. Experimental Biodentine and Fuji II LC showed the lowest microleakage while experimental SDR and experimental Multicore Flow showed the highest microleakage.

Influence of Different Dentin Substrate (Caries-Affected, Caries-Infected, Sound) on Long-Term μTBS

Abstract The aim of this study was to evaluate the μTBS in different dentin substrates and water-storage periods. Twenty-four dentin blocks obtained from sound third molars were randomly divided into 3 groups: Sound dentin (Sd), Caries-affected dentin (Ca) and Caries-infected dentin (Ci). Dentin blocks from Ca and Ci groups were subjected to artificial caries development (S. mutans biofilm). The softest carious tissue was removed using spherical drills under visual inspection with Caries Detector solution (Ca group). It was considered as Ci (softer and deeply red stained dentin) and Ca (harder and slightly red stained dentin). The Adper Single Bond 2 adhesive system was applied and Z350 composite blocks were built in all groups. Teeth were stored in deionized water for 24 h at 37 ºC and sectioned into beams (1.0 mm2 section area). The beams from each tooth were randomly divided into three storages periods: 24 h, 6 months or 1 year. Specimens were submitted to µTBS using EZ test machine at a crosshead speed of 1.0 mm/min. Failure mode was examined by SEM. Data from µTBS were submitted to split plot two-way ANOVA and Tukey’s HSD tests (a=0.05). The µTBS (MPa) of Sd (41.2) was significantly higher than Ca (32.4) and Ci (27.2), regardless of storage. Ca and Ci after 6 months and 1 year, presented similar µTBS. Mixed and adhesive failures predominated in all groups. The highest µTBS values (48.1±9.1) were found for Sd at 24 h storage. Storage of specimens decreased the µTBS values for all conditions.