Storage In Artificial Saliva Research Articles

Addition of EGCG to self-etching primer: effect on adhesive properties and bond stability to dentin

This study evaluated how adding EGCG to a SEP (Clearfil SE Bond, Kuraray) affects the physicomechanical properties of adhesive, and the long-term microtensile bond strength (µTBS) to dentin. Flexural strength (FS, n = 10) and degree of conversion (DC, n = 5) of the adhesive were analyzed after adding EGCG to SEP in two forms (powder or diluted in water), and in different concentrations (0.00%–control, 0.01%, 0.02% and 0.05%). The µTBS was tested by randomly dividing dentin fragments into 4 groups (n = 10): EGCG-SEP: EGCG (0.01%) added to SEP; EGCG-PRE: EGCG (0.01%) dentin pretreatment; CHX-PRE: 2% chlorhexidine dentin pretreatment; SEP: SEP applied without modification. After restoration of the dentin surface, beam-shaped specimens were submitted to µTBS after 24 h or 12 months of storage in artificial saliva. Particle size (PS), polydispersity index (PDI) and zeta potential (ZP) of EGCG-SEP and SEP solutions were measured at different storage periods (baseline, 14 or 28 days). Data was submitted to ANOVA or Kruskal–Wallis tests (α = 0.05). FS (p = 0.485) and DC (p = 0.6067) were not different among the groups. CHX-PRE and EGCG-PRE had significantly higher µTBS means than EGCG-SEP, but none differed from SEP (p = 0.053). µTBS decreased significantly after 12 months of storage (p < 0.001). PS (p < 0.001), and ZP (p = 0.003) means in EGCG-SEP were statistically higher and more negative, respectively, than SEP. PDI did not differ among the groups (p > 0.05). Incorporation of EGCG into SEP did not change adhesive properties; however, it influenced solution stability and did not prevent the decrease in long-term µTBS to dentin.

Aging behavior of high-translucent CAD/CAM resin-based composite blocks

ObjectiveThe aim of this study was to investigate the influence of artificial aging on the mechanical properties and fracture patterns of novel CAD/CAM resin-based composite blocks (RCB). MethodsFlexural strength and modulus of RCBs from seven manufacturers (Voco, Grandio Blocs, GB; Ivoclar Vivadent, Tetric®CAD, TC; DMG, Luxacam Composite, LC; Shofu Block HC, SF; 3M, Lava™ Ultimate, LU; GC, Cerasmart®, CS; Coltene, BRILLIANT Crios, CB) were assessed in a three-point-bending test after an aging process consisting of three sequential steps (14 days storage in artificial saliva, 10,000 thermo-cycles in distilled water between 5/55 °C, 48 h storage in ethanol 75%). Fracture origins were determined in a fractographic examination using reflected light stereomicroscopy combined with transillumination and scanning electron microscopy. Effects of aging were statistically analysed using one-way ANOVA with Tukey's HSD post hoc test (α = 0.05) and Weibull statistics. Correlations regarding filler amount were analysed using linear regression analysis. ResultsThe strongest influence on the flexural modulus and strength was exerted based on the parameter material (p < 0.001, ɳP2 = 0.957; ɳP2 = 0.770), but the influence of in vitro aging was also significant (p < 0.001, ɳP2 = 0.623; ɳP2 = 0.407). Storage in artificial saliva decreased the flexural modulus and flexural strength of all materials, apart from CS, significantly (p < 0.05). The Weibull moduli varied from 5.8 to 22.4. Filler amount correlated significantly with flexural modulus (p < 0.001; R2 = 0.739).Fractography revealed four different fracture patterns with fracture origins from the corner, edge or sub-surface and a smooth fracture surface with non-identifiable fracture origin. Specimens with smooth fracture surface showed the significantly lowest flexural strength (p < 0.001). Pores, agglomerates and inclusions were identified as fracture origins. ConclusionsStorage in artificial saliva mainly reduced the mechanical properties significantly while additional thermal aging mostly maintained the results. Aging in ethanol mostly maintained the results for flexural modulus but led to an increase in flexural strength values to the level of the unaged specimens. Fractographic analysis revealed a significant accumulation of sub-surface fracture origins after storage in ethanol arising from inherent flaws.

Is the high-performance thermoplastic polyetheretherketone indicated as a clasp material for removable dental prostheses?

ObjectivesTo investigate the retention force of polyetheretherketone (PEEK) removable dental prosthesis clasps in comparison with a cobalt-chrome-molybdenum control group after storage in artificial saliva.Materials and MethodsClasps were milled (Dentokeep (PEEKmilled1), NT digital implant technology; breCAM BioHPP Blank (PEEKmilled2), bredent), pressed (BioHPP Granulat for 2 press (PEEKpressed), bredent), or cast (remanium GM 800+ (cobalt-chrome-molybdenum), Dentaurum); N = 60, n = 15/subgroup. Retention force was examined 50 times/specimen in a pull-off test using the universal testing machine (Zwick 1445), where pull-off force was applied with a crosshead speed of 5 mm/minute until the maximum force dropped by 10%, at different aging levels: (1) initial, after storage in artificial saliva for (2) 90 and (3) 180 days. Statistical analysis was performed using one-way ANOVA followed by post hoc Scheffé-test and mixed models (p < 0.05).ResultsCobalt-chrome-molybdenum presented the highest retention force. No differences were observed between polyetheretherketone materials. Cobalt-chrome-molybdenum showed a significant decrease of its values after artificial aging, while polyetheretherketone materials presented similar results over the course of aging. Regarding a repetitive insertion and removal, even though PEEKmilled2 and cobalt-chrome-molybdenum showed an initial increase, ultimately, a decrease in retention force was observed for all tested groups.ConclusionsAlthough the control group showed significantly higher results, the retention force of polyetheretherketone materials indicate a potential clinical application. Neither the manufacturing process nor artificial aging showed an impact on the retention force of polyetheretherketone clasps.Clinical relevanceMechanical properties of novel removable dental prosthesis clasp materials devised to meet the growing esthetic demands of patients need to be investigated to ensure a successful long-term clinical application.

Effects of Additional Use of Bioactive Glasses or a Hydroxyapatite Toothpaste on Remineralization of Artificial Lesions in vitro

Objectives: This in vitro study aimed to evaluate and compare the effect of two different bioactive glasses, a hydroxyapatite-containing, fluoride-free toothpaste (HTP) and a fluoride toothpaste (FTP) on the remineralization behavior of initial caries lesions. Materials and Methods: A total of 100 bovine enamel samples were randomly allocated to five groups of 20 samples each: NC = negative control group (artificial saliva); HTP = HTP group (Karex); FTP = FTP group (Elmex caries protection, 1,400 ppm); FTP + BG_nano = FTP followed by Actimins bioactive glass; FTP + BG_amorph = FTP followed by Schott bioactive glass. Radiographic documentation (advanced transversal microradiography; aTMR) was applied before and after all samples were exposed to a demineralizing gel for 10 days. Over a period of 28 days, samples were covered twice a day (every 12 h) with a toothpaste slurry of the respective test group or with artificial saliva in NC for 60 s and brushed with 15 brushing strokes. Samples in FTP + BG_nano and FTP + BG_amorph were additionally treated with the respective bioactive glass slurry for 30 s after brushing with the FTP. In the meantime, all samples were stored in artificial saliva. After 28 days, the structure of all samples was assessed again using aTMR and compared to the values measured after demineralization. The statistical evaluation of the integrated mineral loss was performed using Kruskal-Wallis test followed by a post hoc Conover test. Results: The FTP revealed the significantly highest increase of mineral content while the HTP showed the significantly lowest remineralization. Compared to artificial saliva, the use of the HTP or the combined application of FTP followed by bioactive glasses (FTP + BG_nano and FTP + BG_amorph) showed no significant remineralization. Conclusion: Under remineralizing in vitro conditions, brushing with 1,400 ppm FTP induced significantly more remineralization compared to storage in artificial saliva. The additional administration of both bioactive glasses as well as the substitutional brushing with an HTP resulted in significantly less remineralization compared to brushing with 1,400 ppm FTP.

The Effect of Silver Diamine Fluoride Versus Sodium Fluoride Varnish on the Microhardness of Demineralized Enamel: An In Vitro Study

Background: Fixed orthodontic treatment has been associated with certain side effects such as white spot lesions (WSLs). Many studies showed the positive effect of sodium fluoride (NaF) varnish in remineralizing WSLs. Studies revealed that silver diamine fluoride (SDF) is effective in arresting dentin caries, but its potential for enamel remineralization has not been investigated clearly. The present study aimed to compare the effect of SDF and NaF on the microhardness of demineralized enamel. Methods: A total of 60 intact premolar teeth were collected and divided into 4 equal groups. Group 1 remained intact (control). Groups 2 to 4 were exposed to artificial cariogenic solution to create enamel lesion. Then, groups 3 and 4 were treated with NaF 5% and SDF 38%, respectively. After one month of storage in artificial saliva, NaF and SDF were reapplied. One month later, the surface microhardness values (SMHs) of teeth were assessed. Results: The results of ANOVA showed a significant difference among the 4 groups (P<0.001). There was significantly higher enamel microhardness in the control group compared with groups 2 and 3 (P<0.001); however, it was not significant for the SDF group (P=0.160). There was significantly higher enamel surface microhardness in groups 3 and 4 compared with group 2 (P≤0.001) and significantly higher mean SMH values in the SDF group compared with the NaF group (P=0.004). Conclusions: NaF varnish and SDF can both remineralize early enamel lesion but SDF has greater remineralizing potential.

Comparison of the force decay over time of four different brands of elastomeric chains (elongated to 25 mm grey/transparent and closed/open): An in-vitro study

The present study was designed to compare the force degradation of closed, open, grey and transparent power chains from four orthodontic companies (American orthodontics® (AO®), Dentsply®, Ormco® and Rocky Mountain Orthodontics® (RMO®)) over time. Universal testing machine was used to measure the force of the power chains elongated to 25mm at 0hours, and after storage in artificial saliva at 24hours, 1 week, 2 weeks, 3 weeks, and 4 weeks. A Tukey's honestly significant difference test was performed. Most of the power chains showed less than 30% of force decay at 24hours of elongation. The AO® transparent open elastomeric chains presented the lowest percentage of force remaining at almost all times: 24hours (58.9%), 1 week (67.7%), 2 weeks (43.2%), 3 weeks (72.4%), and 4 weeks (63%). Most of the power chains had an increase of force measured after 2 weeks of storage in artificial saliva. Three of the sixteen groups (Ormco® grey open, RMO® grey and transparent closed) displayed an increase in the force at 4 weeks of elongation compared to the force registered at 0hours. The results indicated that the force generated by elastomeric chains at 4 weeks remains optimal for a physiologic tooth movement.

Influence of Prolonged Dental Bleaching on the Adhesive Bond Strength to Enamel Surfaces.

The objective of this in vitro study was to assess the influence of prolonged bleaching pre- and postrestoration on the bond strength (microshear) to enamel using 4% hydrogen peroxide (PH4). In the postrestorative bleached specimens evaluation, the composite cylinders were assembled after bleaching, while in the prebleached specimens, the cylinders were assembled before. Therefore, in the postbleached specimens, 60 bovine teeth were randomly assigned as follows: G1: control; G2: 14 days bleaching before bond strength (BS) testing; G3: 21 days; and G4: 28 days. In prebleached specimens, 180 bovine teeth were randomly assigned as follows: G1: control; G5: 14 days bleaching, storage in artificial saliva (AS) for 24 h before BS testing; G6: 14 days beaching, AS storage for 7 days before BS testing; G7: 21 days bleaching, AS storage for 24 h before BS testing; G8: 21 days bleaching, AS storage for 7 days before BS testing; G9: 28 days bleaching, AS storage for 24 hours before BS testing; and G10 : 28 days bleaching, AS storage for 7 days before BS testing. The results were submitted to ANOVA one-way (postrestoration bleaching) and two-way (prerestoration bleaching) and Tukey's post hoc test (p ≤ 0.05). In the postrestoration bleaching, no statistical difference between times was found. However, when bleached groups were compared to the control (G1), an expressive difference was detected (p ≤ 0.0001). For prerestoration bleaching, all experimental groups were statistically different from G1 (p ≤ 0.05), except G6 (p ≥ 0.01), and for G5 and G6, statistical differences were found (p ≤ 0.01). There were no significant differences between G7 and G8 and between G9 and G10, regardless of the AS storage times (p ≥ 0.05). It was concluded that prolonged bleaching with PH4 decreased adhesion resistance regardless of the moment of the bleaching (post- and prerestoration bleaching).

Mechanical Properties of Thermoplastic Polymers for Aligner Manufacturing: In Vitro Study.

The use of metal-free thermoplastic materials plays a key role in the orthodontic digital workflow due to the increasing demand for clear aligner treatments. Three thermoplastic polymers commonly used to fabricate clear aligners, namely Duran®, Biolon® and Zendura®, were investigated to evaluate the effect of thermoforming (T.), storage in artificial saliva (S.A.S.) and their combination on their mechanical properties. Elastic modulus and yield stress of the specimens were characterized. Each material was characterized for each condition through tensile tests (ISO527-1). The results showed that thermoforming does not lead to a significant decrease in yield stress, except for Zendura® that showed about a 30% decrease. An increase of the elastic modulus of Duran® and Zendura®, instead, was observed after thermoforming. The same increase was noticed for the yield stress of Duran®. For S.A.S. specimens, the elastic modulus generally decreases compared to supplier condition (A.S.) and simply thermoformed material. A decrease of yield stress, instead, is significant for Zendura®. The results demonstrated that the impact of the operating conditions on the mechanical properties can vary according to the specific polymer. To design reliable and effective orthodontic treatments, the materials should be selected after their mechanical properties are characterized in the simulated intraoral environment.

Effect of artificial saliva on the mechanical and tribological behavior of nano-/micro-filled biocomposite materials for biomedical applications

Aim: The purpose of this study is to investigate the effect of artificial saliva storage time of composite materials with different filler structure (micro/nanofiller) on the mechanical and tribological behavior. Material and Method: Mechanical and tribological behaviors of composite materials were investigated with storage in artificial saliva for the control group, 1 day, and 7 days. Composite materials were subjected to direct contact wear tests (80 N wear force, 100.000 wear cycles, 1.8 Hz wear frequency, and 37°C ambient temperature) with a computer-controlled dual-axis abrasion device. The surface hardness of composite materials after each artificial saliva test procedure was determined using the Vicker's Hardness method. Results: In this study, it was concluded that the waiting process in artificial saliva increases the tribological behavior of the composite material. Conclusion: However, for the composite test materials in this study considered, correlations between the contact-wear resistance and surface hardness were found to be statistically insignificant.

Influence of Different Surface Treatments on the Bond Strength Between Composites and Resin Cement

The aim of this study was to evaluate the influence of different surface treatments on bond strength (BS) between composite and a resin cement trough microshear bond strength test. Seventy five discs (10x2 mm) of Filtek P90, Filtek Z250 and Filtek Z350 XT (3M ESPE), were divided into 5 groups according to the treatment: C= control - no treatment; sandblasting J= aluminum oxide (50μm); sandblasting JE = + 99.3% ethanol for 5 min; silica coating S = (3M-ESPE Cojet - 30 microns); SS = silica coating + silane. PVC tubes (0.5 x 0.80 mm) were attached on the composite disc, and then, inserted resin cement (3M ESPE-RelyX ARC). After 24 hours artificial saliva storage at 37oC, the specimens were tested for microshear crosshead speed of 1.0 mm/min. Data were evaluated in two-way ANOVA and Tukey’s test (5%) for contrast. The results showed that sandblasting with aluminum oxide (J) was efficient in increasing the BS for composites Z350 and P90. For the Z250, there were no difference between treatments. Also, CS showed results similar to controls for all composites. SE showed the worst results for Z350 e P90. BS values were dependent on the type of composite and the surface treatment used. Sandblasting with aluminum oxide seems to be an effective surface treatment for composites and may lead to higher BS values, while the use of ethanol could be harmful.

Novel riboflavin/VE-TPGS modified universal dentine adhesive with superior dentine bond strength and self-crosslinking potential

ObjectiveTo modify a universal dentine adhesive with different concentrations of riboflavin and D-Alpha 1000 Succinate polyethylene (VE-TPGS) as a chemical enhancer and to assess the micro-tensile bond strength (24h/12 months), determine resin penetration, measurement of intermolecular interactions and cytotoxicity. Materials and methodsAn experimental adhesive system based on bis-GMA, HEMA and hydrophobic monomer was doped with RF0.125 (RF – Riboflavin) or RF/VE-TPGS (0.25/0.50) and submitted to μTBS evaluation. Resin dentine slabs were prepared and examined using SEM and TEM. Adhesion force was analysed on ends of AFM cantilevers deflection. Quenched peptide assays were performed using fluorescence scanner and wavelengths set to 320nm and 405nm. Cytotoxicity was assessed using human peripheral blood mononuclear cell line. Molecular docking studies were carried out using Schrödinger small-molecule drug discovery suite 2018-2. Data from viable cell results was analyzed using one-way ANOVA. Bond strength values were analysed by two-way ANOVA. Nonparametric results were analyzed using a Kruskal–Wallis test at a 0.05 significance level. ResultsRF/VE-TPGS0.25 groups showed highest bond strength results after 24-h storage in artificial saliva (p<0.05). RF/VE-TPGS0.50 groups showed increased bond strength after 12-months of ageing. RF/VE-TPGS modified adhesives showed appreciable presence of a hybrid layer. Packing fraction indicated solid angle profiles describing well sized density and topology relations for the RF/VE-TPGS adhesives, in particular with the RF/VE-TPGS0.50 specimens. Qualitative analysis of the phenotype of macrophages was prominently CD163+ in the RF/VE-TPGS0.50. Both the compounds showed favourable negative binding energies as expressed in terms of ‘XP GScore’. ConclusionNew formulations based on the incorporation of RF/VE-TPGS in universal adhesives may be of significant potential in facilitating penetration, distribution and uptake of riboflavin within the dentine surface.

Potential of high-intensity focused ultrasound in resin-dentine bonding

ObjectiveThis study introduced the potential and proof-of-concept of high intensity focused ultrasound (HIFU) technology for dentin-surface treatment for resin-dentin bonding without acid-aided demineralization. This new strategy could provide a way to enhance interface-integrity and bond-durability by changing the nature of dentin-substrate; bonded-interface structure and properties; and minimizing denuded-collagen exposure. MethodsThe interaction between HIFU waves and dentin-surface in terms of structural, mechanical and chemical variations were investigated by SEM, TEM, AFM, nano-indentation and Raman-analysis. The bonding between HIFU-treated dentin and two-step, etch-and-rinse, adhesive was preliminary explored by characterizing dentin-bound proteases activities, resin-dentin interfacial morphology and bond-durability with HIFU exposure at different time-points of 60, 90 and 120 s compared to conventional acid-etching technique. ResultsWith the increase in HIFU exposure-time from 60-to-120 s, HIFU waves were able to remove the smear-layer, expose dentinal-tubules and creating textured/rough dentin surface. In addition, dentin surfaces showed a pattern of interlocking ribbon-like minerals-coated collagen-fibrils protruding from the underlaying amorphous dentin-background with HIFU exposure for 90 s and 120 s. This characteristic pattern of dentin-surface showing inorganic-minerals associated/aligned with collagen-fibrils, with 90-to-120 s HIFU-treatment, was confirmed by the Raman-analysis. HIFU-treated specimens showed higher nano-indentation properties and lower concentrations of active MMP-2 and Cathepsin-K compared to the acid-etched specimens. The resin-dentin bonded interface revealed the partial/complete absence of the characteristic hybrid-layer formed with conventional etch-and-rinse bonding strategy. Additionally, resin-infiltration and resin-tags formation were enhanced with the increase in HIFU exposure-time to 120 s. Although, all groups showed significant decrease in bond-strength after 12 months compared to 24 h storage in artificial saliva, groups exposed to HIFU for 90 s and 120 s showed significantly higher μTBS compared to the control acid-etched group. SignificanceThe implementation of HIFU-technology for dental hard-tissues treatment could be of potential significance in adhesive/restorative dentistry owing to its ability of controlled, selective and localised combined tissue alteration/ablation effects.

Effect of benzalkonium chloride on dentin bond strength and endogenous enzymatic activity

Objective: This in vitro study evaluated at baseline (T0) and over time (T12 months), the effect of a multi-mode universal adhesive compared with two experimental formulations blended with different concentrations of benzalkonium chloride (BAC), on bond strength and endogenous enzymatic activity.Methods and materials: Specimens were assigned to the following groups according to the adhesive protocol: G1) All-Bond Universal (ABU) self-etch (SE); G2) ABU + 0.5% BAC SE; G3) ABU + 1% methacrylate BAC SE; G4) ABU etch-and-rinse (E&R); G5) ABU + 0.5% BAC E&R; G6) ABU + 1% methacrylate BAC E&R. Gelatin zymography was performed on dentin powder obtained from eight human third molars. Endogenous enzymatic activity within the hybrid layer was examined using in situ zymography after 24 h (T0) or 1-year storage in artificial saliva (T12). Forty intact molars were prepared for microtensile bond strength test at T0 and T12. Results were statistically analyzed with three-way ANOVA (α = 0.05).Results: Gelatin zymography assay and in situ zymography quantification analyses indicated that all the BAC-containing formulations decreased matrix metalloproteinase expression. However, in situ zymography showed a general trend of enzymatic activity increase after aging. Microtensile bond-strength testing showed decrease in bond strength over time in all the tested groups; performances of the 1% methacrylate BAC experimental groups were worse than the control.Conclusions: BAC-containing adhesives reduce endogenous enzymatic activity both immediately and over time. However, independently from the adhesive employed, increase in the gelatinolytic activity over time and decrease in bond strength was found (especially in the BAC + 1% methacrylate groups), probably due to impaired polymerization properties.Clinical significance: Adhesives containing protease inhibitors are practical and efficient tools in clinical practice for enhancement of the longevity of dental restorations. However, extensive investigation of the mechanical and adhesive properties of the material is necessary prior to their clinical use.

Effect of Dentin Conditioning and Erosive Coca Cola Challenge on the Micro-shear Bond Strength and SEM Evaluation of Resin-Modified Glass-Ionomer Cement- in vitro study

Objective: This study was designed to evaluate the role of an erosive beverage, Coca cola, on the microshear bond strength of a nano-fill resin modified glass-ionomer cement to dentin, after different conditioning protocols, no conditioning, GC conditioner and KN primer. Materials and Methods: The occlusal enamel of forty two third molar teeth was removed, exposing the coronal dentin. Thirty prepared teeth were randomly divided into three main groups (n=10). Group 1, flat dentin surface was left unconditioned (control). Group 2, GC cavity conditioner was applied. Group 3, Ketac Nano Primer was applied. Three pieces were cut from a polyethylene micro-bore tygon tube, for each specimen. KN resin modified glass ionomer cement was applied. Each group was further distributed into two subgroups (n=5). Subgroup i, teeth were immersed in artificial saliva (control). Subgroup ii, teeth were subjected to Coca Cola pH cycles. Each specimen was stressed in shear using a load cell of 5 KN at a crosshead speed of 0.5 mm/min. The remaining 12 teeth were divided according to the previously mentioned grouping system, and observed using SEM. Results: The data collected for µSBS were subjected to two-way ANOVA test, followed by Tukey’s post hoc test. Considering the dentin conditioning factor, with storage in artificial saliva; the control group revealed the least µSBS values, followed by the group conditioned with KNP and GC conditioning, respectively. Control group posses a significant decrease in the µSBS compared to either GC or KNP groups. With Coke pH cycling; the control group revealed the least µSBS values, followed by KNP and GC conditioning, respectively. All the tested groups are significantly different from each other Considering the erosive pH cycling factor, all the teeth revealed significant decrease in the µSBS values, when exposed to erosive Coke pH cycling. Most failure modes are adhesive, followed by mixed failures. The SEM examination showed a filler‑free zone in the conditioned groups, with the greatest thickness with KNP. Cylindrical shaped resin tags, were observed when dentin is conditioned with KNP, whereas budding configuration is formed with GC conditioner. Smear layer has been completely removed with GC conditioner. Dentin conditioning with KNP revealed partial removal of smear layer with partial obliteration of dentinal tubules, while smear layer remains unaffected in case of control group. In groups stored in AS, there is intimate adaptation between the RMGIC and dentin, whereas the groups subjected to Coke erosive cycles showed variable degrees of separation at the RMGIC/dentin interface. Conclusions: Dentin conditioning before RMGIC application is an essential step to improve bonding ability to dentin. Since Coca cola beverage revealed a deteriorating effect on bonding of RMGICs, evaluation of different acidic foodstuffs, acidic drinks and mouthwashes on the bonding efficiency of different types of glass-ionomer cements is required.

Long-term bond strength and endogenous enzymatic activity of a chlorhexidine-containing commercially available adhesive

ObjectivesThe aim of this study was to investigate, by the means of microtensile bond strength (μTBS) test, gelatin and in situ zymography, the influence of 0.2% CHX contained within a commercially available adhesive on long-term bond strength and endogenous enzymatic activity. MethodsNon-carious teeth were subjected to μTBS test (N = 15 for each group) and stressed until failure. μTBS was evaluated immediately and after 12-month storage in artificial saliva at 37 °C. Dentin powder was obtained from additional teeth (N = 7) for gelatin zymography, while for in situ zymography, 3 teeth for each group were selected. Gelatin and in situ zymography were performed in dentin powder and slices of dentin, respectively, to assess the ability of 0.2% CHX blended within the adhesive to inhibit endogenous enzymatic activity. ResultsμTBS bond strength was higher in the CHX-containing groups, immediately as well as after aging. The bond strength significantly decreased after 12-month aging. The activation of endogenous MMPs was found to be related to the presence of CHX within the adhesive system and the bonding strategy employed. ConclusionsUnder this perspective 0.2% CHX blended within Peak Universal adhesive monomer seems to increase immediate bond strength, to preserve bond strength over time and to efficiently inhibit endogenous enzymatic activity in dentin. Hence, blending the CHX in low concentrations within the adhesive could be recommended as a feasible technique in every-day clinical practice. Clinical significanceUsing CHX-containing adhesives could be recommended due to several benefits: it seems to increase the longevity of the hybrid layer; the inhibitor appears to be efficiently delivered to the dentinal substrate and to inhibit endogenous enzymatic activity, without prolonging chair time.

Influence of Er:YAG laser pulse duration on the long-term stability of organic matrix and resin-dentin interface.

The purpose of this study was to explore the influence of Er:YAG laser irradiation with different pulse durations on the organic matrix, micromorphology of the hybrid layer (HL), and bond strength over time. Sixty caries-free human molars were cut to obtain flat dentin surfaces which were randomly divided into 4 groups: control (not irradiated-G1) and laser groups (80mJ/2Hz) with pulse duration ranging between 50 (G2), 300 (G3), and 600μs (G4). A self-etch adhesive system (Universal 3M ESPE) was applied on pre-treated dentin surfaces and cylinders of resin composite were built up and stressed in a universal testing machine (μSBS) at 24h and after12months (n = 12). In addition, 3 other dentin-bonded specimens were prepared as previously described for each group with the adhesive doped with 0.1wt% Rhodamine B to analyze hybrid layer morphology under Confocal Laser Microscope Scanning (CLMS). Organic matrix and collagen fibrils were analyzed by second harmonic generation (SGH). Two-way ANOVA and Tukey's test detected significantly higher μSBS values for the control group, whereas the lower values were observed in all laser groups at 24h (p < 0.05). Storage in artificial saliva did not reduce μSBS in all groups. The low signal emitted by SHG images below the irradiated area demonstrated thermal damage of the collagen matrix. CLMS images of laser groups exhibited thicker and irregular resin-dentin interfaces than the control group. Regardless of the pulse duration, Er:YAG laser pre-treatment altered the organic matrix and HL formation which resulted in low μSBS values at 24h. The alterations on dentin's organic structure did not jeopardize the μSBS after 1year of saliva storage.

Carbodiimide inactivation of matrix metalloproteinases in radicular dentine

ObjectivesThe present in vitro study evaluated the effect of 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide (EDC), a cross-linking agent used as an additional therapeutic primer for luting fiber posts to radicular dentine to prevent hybrid layer degradation. MethodsRoot canal treatment was performed on 80 extracted single-rooted human teeth. A 10-mm post space was prepared and pecimens were randomly assigned to four groups (n=20) according to the bonding system: 1) All Bond 3 (Bisco); 2) All Bond 3 + 0.3M EDC; 3) Prime&Bond XP (Dentsply Sirona); 4) Prime&Bond XP + 0.3M EDC. In groups 2 and 4, EDC was applied on phosphoric acid-etched dentine for 1 min. Fiber posts (RelyX Fiber Post, 3M ESPE) were luted with a dual-cured resin cement (Core-X flow, Dentsply Sirona). Slices were prepared for micro push-out test and interfacial nanoleakage evaluation of the coronal and apical region of the canal space after 24 h and 1 year storage in artificial saliva. In-situ zymography was performed to investigate endogenous matrix metalloproteinase activities within the hybrid layer. Results were statistically analysed with three-way ANOVA test or Chi Square test. Statistical significance was set at α=0.05. ResultsNo significant influence was identified between the two adhesives. The use of EDC significantly improved fiber post bond strength at 1 year but not at 24 h. Application of 0.3 M EDC prior to bonding significantly reduced gelatinolytic activities within the radicular hybrid layers. ConclusionsCarbodiimide was effective in preserving fibre post bond strength over time, through reducing the activities of intra-radicular endogenous proteases. Clinical SignificanceInhibition of matrix metalloproteinases using EDC over radicular dentin could play an important role in bond strength preservation. However, the clinical relevance of these findings needs to be proven.

Effects of the Contents of Various Solvents in One-step Self-etch Adhesives on Shear Bond Strengths to Enamel and Dentin

The aim of this study was to evaluate the shear bond strengths (SBSs) of one-step self-etch adhesives containing different co-solvents to enamel and dentin and to determine the failure modes of tested specimens. Two hundred and forty (n = 240) sound human molars were used. The buccal surfaces of each tooth were ground and polished to obtain flat enamel surfaces (n = 120) or to expose the underlying dentin (n = 120). The specimens with exposed enamel or dentin were randomly divided into four main groups (n = 30) according to the one-step self-etch adhesives used: Bond-1 SF, OptiBond All-In-One, G-aenial, and Single Bond Universal adhesive. All the main groups were then subdivided into two subgroups (control and thermocycling subgroups) (n = 15). After bonding procedures, a composite restoration (Filtek Z250) was applied in a vinyl tube and condensed against the cured adhesive bonding agent, to form a resin cylinder. The specimens were stored in distilled water at 37°C for 24 hours (control and thermocycling subgroups), followed by thermocycling (5-55°C/5,000 cycles + storage in artificial saliva for 2 weeks) (thermocycling subgroup). They were subjected to SBS testing in a universal testing machine at a crosshead speed of 0.5 mm/minute. After being shear-tested, all fractured samples were examined by means of a Hirox Digital Microscope at 50× magnification for failure analysis. The data were analyzed by one-way analysis of variance followed by Tukey's post hoc analysis at a p value of ≤0.05. OptiBond All-In-One adhesive showed significantly higher mean SBS values on both types of tooth structures (enamel and dentin) and under different conditions (control and thermocycled) compared with the other three adhesives (p < 0.001), except in the enamel-thermocycled group, where the Single Bond Universal adhesive showed higher mean SBS but without a significant difference compared with the OptiBond All-In-One adhesive (p = 0.266), and there was no significant difference between OptiBond All-In-One and G-aenial Bond in the same group (p = 0.192). Conversely, Bond-1 SF showed significantly lower mean SBS values compared with those of the other three adhesives on different types of tooth structures and under different conditions (control and thermocycled) (p < 0.001). One-step self-etch adhesives containing ethanol as a solvent or co-solvent showed higher SBS compared with the other self-etching bonding agents. The bond strength values of these adhesives to dentin are significantly higher than those to enamel. The types of solvents of one-step self-etch adhesives had an effect on SBS, and the absence of solvent in those adhesives would adversely influence their performance. How to cite this article: Ageel FA, Alqahtani MQ. Effects of the Contents of Various Solvents in One-step Self-etch Adhesives on Shear Bond Strengths to Enamel and Dentin. J Contemp Dent Pract 2019;20(11):1260-1268.

Effect of topical fluoride on microshear bond strength of primary enamel to composite, microhardness of enamel and its surface morphology: An in vitro study.

Background. This in vitro study aimed to evaluate the microshear bond strength (μSBS), microhardness and morphological characteristics of primary enamel after treating with sodium fluoride (NaF) and acidulated phosphate fluoride (APF). Methods. Forty-eight primary canines were cut into mesial and distal sections and assigned to five groups randomly: group 1 (immersed in saliva as a control), group 2 (treated with NAF and immersed in saliva for 30 minutes), group 3 (treated with APF and immersed in saliva for 30 minutes), group 4 (treated with NAF and immersed in saliva for 10 days), and group 5 (treated with APF and immersed in saliva for 10 days). Composite resin (Filtek Z250) was bonded on the specimens (n=15) for measuring the μSBS. After storage in 37°C artificial saliva for 24 hours, µSBS and Vickers hardness tests (10 readings) were performed. The data were analyzed using one-way ANOVA and Kolmogorov-Smirnov, Levene’s and Tukey HSD tests (P<0.05). Morphological analysis of enamel and modes of failure were carried out under a scanning electron microscope (SEM) on two remaining specimens. Results. Significant differences in μSBS were only noted between groups 2 and 4 (P=0.024). Group 3 showed a significant decrease in hardness after storage in artificial saliva (P<0.001), with a significantly lower hardness than the other groups (P<0.001). The SEM observations showed irregular particles in groups 3 and 5; uniform, smooth and thin coats were seen in groups 2 and 4. Conclusion. Fluoride therapy with NaF and APF gels prior to restorative treatments had no adverse effects on the microshear bond strength.

Effect of Er:YAG and Burs on Coronal Dentin Bond Strength Stability.

To evaluate the immediate and aged bond strength and interfacial nanolaekage of different adhesives and protocols on dental elements prepared with diamond burs and Er:YAG laser. Forty molar crowns were flattened and a standardized smear layer was created. Teeth were divided into two main groups according to the dentin cutting technique: 1. Er:YAG laser for 30 s at 30 Hz repetition rate, 250 mJ energy per pulse, and water spray irrigation set at level 8; and 2. diamond bur. Each group was then divided into subgroups according to the adhesive protocol: SG1: dentin etching for 15 s followed by universal adhesive application (All Bond Universal, Bisco); SG2: universal adhesive application (All Bond Universal); SG3: two-step self-etch adhesive application (Clearfil SE Bond 2, Kuraray Noritake); SG4: etching followed by 3-step etch-and-rinse adhesive application (Optibond FL, Kerr). After curing the adhesives, resin composite buildups of 4 mm were made and specimens were sectioned to obtain 1-mm-thick sticks in accordance with the μTBS test technique. Sticks were stressed to failure at baseline and after 6 months of storage in artificial saliva. Three teeth per group were prepared for nanoleakage interfacial analyses. Data were statistically analyzed with three-way ANOVA and Tukey's post-hoc test (p < 0.05). A significant difference in bond strengths was found for treatment, aging, and adhesive protocol. Nanoleakage analysis showed higher marginal infiltration in Er:YAG-treated groups both at baseline and after aging. Surfaces prepared with diamond burs presented higher bond strengths than did those prepared with Er:YAG laser. Adhesive protocols and aging could influence the adhesive-dentin interface. Further studies are necessary to validate the results obtained.