μTBS Values Research Articles

Comparison of physical and mechanical properties of three different restorative materials in primary teeth: an in vitro study

Physical and mechanical properties of three different (Ketac Molar Easymix, Dyract XP, Cention N (CN)) restoratives with different ingredients were evaluated. Four groups were obtained; Group 1: CN LightCure, Group 2: CN SelfCure, Group 3: Ketac Molar Easymix and Group 4: Dyract XP. Disk-shaped samples (n = 10) were prepared and evaluated for the surface roughness test using a profilometer. For the flexure strength test, 2 × 2 × 25mm bar-shaped samples (n = 10) were prepared, and a three-point bending test was applied to the samples. After preparing cavities for microleakage tests, teeth were restored with restoratives, immersed in dye, and microleakage was assessed. For the microtensile bond strength (µTBS) test, ten sticks were obtained for each group and were stressed under tension. According to surface roughness tests, CN SelfCure showed the lowest value (0.13μm), while Ketac Molar Easymix showed the highest value (0.28μm), and significant differences were found between the groups. In flexural strength tests, the highest values were seen in CN SelfCure (82.94MPa), with statistically significant differences between the groups. When CN SelfCure was applied with an adhesive, the teeth showed statistically decreased leakage than other groups on the gingival side. Higher leakage values were seen on the gingival side than the occlusal side in most groups, and the SelfCure groups showed decreased leakage than the LightCure groups. According to µTBS tests, the highest value was obtained in CN SelfCure-Adhesive group, while the lowest was in CN LightCure-Non-adhesive group. When µTBS was evaluated regardless of adhesive use, the SelfCure groups showed higher µTBS values than the LightCure groups. As a result of the µTBS and microleakage test, the difference between the use of CN with and without adhesive, regardless of the polymerization type, was found to be significant (p < 0.05). Cention N showed better properties in SelfCure mode, compared to the rest materials tested, but further in vitro and in vivo studies are needed to investigate the effect of different polymerization modes and the oral environmental conditions.

Effect of mesoporous silica@nano-bioactive glass complex particles on the durability of dentin bonding

This study introduced a process for synthesizing mesoporous silicon@nano-bioactive glass (nano-BAG) complex particles, and evaluated their effects on dentin bonding and remineralizing activity. Mesoporous and nonporous silica microspheres were coated with nano-BAG via a quick alkali-mediated sol–gel method at different pH values (4, 7, 9). The eight groups of particles were examined by X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, nitrogen adsorption tests, scanning electron microscopy (SEM), and transmission electron microscopy (TEM). Inductively coupled plasma optical emission spectrometry (ICP-OES) was employed to record the cumulative release of Ca2+ at 7, 14, and 28 days. The ability to promote the formation of hydroxyapatite was assessed by mineralization tests. The CCK-8 cell counting kit was used to test the cytotoxicity. Microtensile bond strength (μTBS) tests nanoleakage and were carried out to evaluate the effects of a pretreatment using mesoporous or nonporous silica microspheres coated with nano-BAG. XRD and FTIR analyses confirmed that nano-BAG coated mesoporous silica and formed a relatively ordered mesoporous structure, whereas nonporous silica did not exhibit major structural changes. In N2 adsorption tests, the specific surface area and pore volume of mesoporous silica (927.04 m2/g; 0.77 cm3/g) were much larger than those of silica (10.76 m2/g; 0.04 cm3/g). Both SEM and TEM revealed a greater homogeneity and dispersity in mesoporous silica coated with nano-BAG at pH 4. This kind of particles maintained a high level of cumulative release of Ca2+ (178.29 ± 0.950 mg/L at 28 days), showed the strongest Ca and P signal intensity after being immersed in SBF for 28 days, and exhibited higher μTBS values (41.56 ± 3.110 MPa) and minimal nanoleakage. Cytotoxicity tests indicated a well-preserved cell viability in these particles. Nano-BAG-coated mesoporous silica particles, obtained at pH 4, provided a stable release of Ca2+ in body fluid, and showed a strong ability to promote the formation of hydroxyapatite. These features are beneficial for enhancing the resin–dentin bonding and reducing nanoleakage.

Effect of the composition and manufacturing process on the resin microtensile bond strength to ceramics

The present study aimed to investigate the bond strength between resin cement and different glass-ceramics manufactured in different processing systems using two different microtensile bond strength test (μTBs) assemblies (ceramic-ceramic or ceramic-dentin). For this, ceramic blocks were fabricated with adhesive surface area of 5 × 5 mm to test the different possibilities combining the two different glass-ceramic compositions (feldspathic – FEL and lithium disilicate - LD), the three manufacturing-processes (CAD/CAM, heat-pressed or layered for FEL; CAD/CAM or heat-pressed for LD) and the two μTBS assemblies (ceramic-ceramic or ceramic-dentin). Half of the samples of each ceramic evaluated were made by cementing the ceramic blocks in another ceramic block and the other half by cementing the ceramic blocks in ground molars with exposed dentin, using resin cement (Rely X ARC, 3 M ESPE). The samples were stored for 24 h in distilled water at 37 °C and then sectioned into microbars (±1 mm 2 , n = 30). These specimens were submitted to the μTBS and the data were analyzed by specific statistical tests (α = 0.05). The fractured surfaces were examined under a stereomicroscope and the failure mode was classified. In addition, finite element analysis (FEA) was performed to observe the maximum tensile stress in the resin cement when a μTBS load was applied (10 N) and during the resin cement polymerization shrinkage. The CAD/CAM glass-ceramics have better bond strength than the other evaluated manufacturing processes, the LD groups had higher μTBS values than the FEL groups in ceramic-ceramic assembly; dentin as a substrate (ceramic-dentin assembly) had a negative influence on the results for all evaluated materials. Regarding the FEA results, the maximum tensile stress in ceramic-ceramic groups was 16.1–16.5 MPa (when 10 N load was simulated), and 50.8–51.2 MPa (during the resin cement polymerization shrinkage). For the ceramic-dentin groups, the maximum tensile stress was 16.9 and 17.1 MPa on the ceramic side and 17.6 and 17.8 MPa on the dentin side (10 N load simulation); 49.8 and 49.4 MPa on the ceramic side and 49.7 and 49.4 MPa on the dentin side (resin cement polymerization shrinkage). Different glass-ceramic compositions and manufacturing processes induced distinct bond strength values (LD had better results). Moreover, the μTBS assembly interferes with the results obtained, having the ceramic-ceramic set-up inducing higher bond results than the ceramic-dentin arrangement.

Evaluation of the Effect of the Loading Time on the Microtensile Bond Strength of Various Restorative Materials Bonded to Silver Diamine Fluoride-Treated Demineralized Dentin.

The aim of this study was to evaluate the effect of immediate versus delayed loading times on the microtensile bond strength (μTBS) of restorative materials, including resin-based composite (RBC), resin-modified glass ionomer cement (RMGIC) and glass ionomer cement (GIC), that were bonded to silver diamine fluoride (SDF)-treated demineralized dentin. Ninety caries-free extracted premolar teeth were assigned to three groups (n = 30) loaded with RBC, RMGIC and GIC restorative materials. Each group was further divided into three subgroups (n = 10): subgroup A (control specimens), immediate loading of the restorative material on sound dentin; subgroup B, demineralized dentin, SDF treatment and immediate loading of the restorative material; and subgroup C, demineralized dentin, SDF treatment and restorative material loading a week later. One-way ANOVA and Tukey’s post-hoc tests were performed to compare the μTBS values. The RBC exhibited the highest µTBS, followed by RMGIC and GIC. Multiple comparisons showed an increase in the µTBS in the delayed loading groups irrespective of the restorative material used. The majority of the failure modes were adhesive. Delayed loading of RMGIC for 1 week after SDF application showed significantly higher µTBS than that of immediate loading.

Effect of Cavity Disinfection Protocols on Microtensile Bond Strength of Universal Adhesive to Dentin

The purpose of this study was to compare the effect of different disinfection protocols of dentin on bond strength of an MDP-containing universal adhesive. Twelve extracted mandibular third molars were separated horizontally at the mid-coronal of crown to get smooth and sound dentin surfaces using low-speed diamond saw. The teeth were randomly fallen into four groups: chlorhexidine (CHX), ozone, Er,Cr:YSGG laser irradiation (LASER) and no treatment (control). After cavity disinfection application, a universal adhesive (G-Premio Bond) was applied to the surface of dentin according to self-etch mode as instructed by the manufacturer. After incremental built-up of composite resin (Charisma Smart), the specimens were immersed in distilled water at 37°C for 24h. Dentin/composite beams with 1 mm² cross sectional area were produced and micro-tensile bond strength (µTBS) was applied on these beams (n=20). Failure mods were determined under a stereomicroscope at ×40. The resin penetration of samples stained with Rhodamine B fluorochrome dye was examined with a confocal laser scanning microscope. Statistical analysis was performed with SPSS-22. Test results were analyzed using One-way Anova and Tukey HSD Post-Hoc tests (p&lt;0.05). The µTBS value of control (35.13±6.20) was the highest statistically among the groups (p&lt;0.05). The lowest µTBS were obtained by LASER (19.25±4.66) and CHX (23.07±7.01). There was no significant difference between CHX and LASER, and between CHX and ozone (p&gt;0.5). All applications of cavity disinfection procedures decreased the µTBS of the resin-dentin interface.

Effect of different surface treatments on the micro tensile bond strength to dentin, biaxial flexural strength and roughness of CAD/CAM resin composite and polymer infiltrated ceramic

ObjectivesTo evaluate the biaxial flexural strength (BFS), surface roughness (Ra) and micro tensile bond strength (μTBS) of two CAD/CAM materials after different surface treatments. Materials and methodsFor μTBS, 64 human molars were used and 32 blocks of resin composite (RC-Lava Ultimate) and polymer-infiltrated ceramic (PIC -Vita Enamic). The blocks and teeth were distributed into 16 groups according to the factors “surface treatment” (HF: 10% hydrofluoric acid; APA: Al2O3 sandblasting; SC: silicate-Al2O3 sandblasting; MEP: Monobond Etch and Prime) and “thermal cycling” (TC). After cementation, the blocks were sectioned into 1 mm2 bars. Half of the specimens were thermocycled and submitted to μTBS test. For BFS, RC and PIC discs were made and distributed according to the surface treatments and after mechanical cycling, submitted to BFS test. Roughness, EDS, SEM, and Weibull analyses were also performed. Data were analyzed by (1 or 2-way) ANOVA and Tukey test (α = 0.05). ResultsFor RC, SC and HF after TC showed significantly higher μTBS values. For PIC HF after TC showed higher μTBS than the other groups. For RC, the BFS was higher for MEP than Al2O3 and SC. For PIC, none of the surface treatments influenced BFS. ConclusionThe highest μTBS for RC was obtained with SC followed by silanization and for PIC, HF followed by silanization. The RC showed lower strength after Al2O3 blasting. For PIC all surface treatments resulted in similar BFS.

Effect of the thicknesses of bulk-fill composites on bonding strength.

This work evaluated the effects of thickness on resin bonding strength. We set the two bulk-fill composites Filtek Bulk Fill Posterior (FBF) and Tetric N-Ceram Bulk Fill (TBF) as the experimental groups and the two conventional composites Filtek Z100 (Z100) and Spectrum TPH (ST) as the control groups. The translucency parameter (TP), color difference, Vickers hardness (HV), and microtensile bond strength (μTBS) of dentine and the resin composites were measured at different depths. In each group, TP and HV decreased with the increase in thickness. At the same depth, the TP of the bulk-fill composites was higher than that of the conventional composites. At the same depth, the HV of the four different resin composites followed the order of Z100>FBF>TBF>ST (except for the upper surface). Except for FBF at 3 and 4 mm, all of the other groups showed no visible color change at all the tested thicknesses. Although the μTBS values of the four different composites obtained through the bulk-fill technique were lower than those of composites obtained through the incremental fill technique, the μTBS of the bulk-fill composites obtained through the bulk-filling technique can reach 30 MPa. Bulk-fill composites applied in single 4 mm increments can meet the requirements of clinical application. However, the color stability of some bulk-fill composites cannot be maintained.

Bond strength of bulk-fill resin composites

Aim: Evaluating the resin-dentin bond strength of Class II conventional and bulk-fill composite restorations, using different cavity sizes before and after aging. Methods: Seventy-five human molars were distributed into groups according to the buccolingual width of the cavities, conservative (n=25) and extended (n=50). They were divided according to the restorative material: conventional (Z100/control group) or bulk-fill resin composites (Filtek Bulk Fill/FBF; Tetric N Ceram Bulk Fill/TNCBF; Filtek Bulk Fill Flow/FBFF; Surefill SDR flow/SDR). The restored teeth were sectioned on sticks (n=50 per restorative materials + width cavities group), half were stored in Water/Ethanol 75% for 30 days and the other half were submitted to the immediate microtensile bond strength (μTBS) test. Data were analyzed applying the Three-Way Analysis of Variance (ANOVA), Bonferroni test, test t, and Weibull analyses (p&lt;0.05). Results: SDR and FBF presented lower μTBS values for extended preparation when compared to the conservative preparation, before aging. After aging, only for the FBFF, a decrease in the μTBS values was observed. Comparing the μTBS values, before and after aging, the SDR demonstrated lower μTBS values after aging when the conservative cavity was used. A decrease in the μTBS values was observed for the Z100, the FBF and, the FBFF, after aging, when the extended cavity was used. Conclusion: The effect of cavity preparation and aging on the resin-dentin of Class II is material dependent. Most of the bulk-fill resin composites evaluated presented a similar performance to the conventional resin composites for all the conditions of this study.

Dimethyl Sulfoxide Dentin Pretreatments Do Not Improve Bonding of a Universal Adhesive in Etch-and-Rinse or Self-etch Modes.

To evaluate the influence of dimethyl sulfoxide (DMSO) solutions used as dentin pretreatments on microtensile bond strength (µTBS), as well as the dentin/restoration interface micromorphology of a universal adhesive in etch-and-rinse or self-etch mode. Eighty blocks of dentin were submitted to acid conditioning with 35% phosphoric acid (etch-and-rinse), or not (self-etch), and distributed among the treatments (n = 10): CON: Scotchbond Universal/3M Oral Care; DMSO: pretreatment with DMSO; DMSO/water: pretreatment with DMSO in water (1:1); DMSO/ethanol: pretreatment with DMSO in ethanol (1:1). Microtensile bond strength and failure tests were performed after 24-h and 6-month storage. The tooth-restoration interface was evaluated using scanning electron microscopy to assess the hybrid layer formed. The interaction between treatments, storage time, and etching modes was not significant for µTBS (p = 0.2469). The DMSO, DMSO/water and DMSO/ethanol pretreatments did not affect µTBS values at either time point (p = 0.8732). Aging decreased µTBS over time only for the etch-and-rinse strategy, although the groups presented higher microtensile bond strengths in etch-and-rinse mode than in self-etch mode at both time points (p < 0.0001). The micromorphological images of the interface showed that different DMSO pretreatment solutions did not impair hybrid layer formation. The use of dentin pretreatments containing DMSO did not improve the bonding or the micromorphology of a universal adhesive in etch-and-rinse or self-etch modes.

Bonding performance and ultramorphology of the resin-dentine interface of contemporary universal adhesives.

This study aimed at evaluating the microtensile bond strength (μTBS) and the resin-dentine ultramorphology (24h and 10months ageing) of contemporary universal adhesives applied in self-etch (SE) or etch-and-rinse (ER) mode. Sixty-four sound human molars were collected and randomly allocated in 4 main experimental groups (n = 16) according to the adhesive system employed and subsequently divided into two subgroups depending on their application mode SE or ER (n = 8): ZipBond X (ZBX-SE; ZBX-ER), Prime and Bond Active (PBA-SE; PBA-ER), Clearfil Universal Bond Quick (CBQ-SE; CBQ-ER) or Scotchbond Universal (SCH-SE; SCH-ER). The specimens were cut into sticks with a cross-sectional area of approximately 0.9 mm2 and subjected to μTBS testing at 24h or after 10months of ageing in artificial saliva (AS). Five representative fractured specimens from each group were analysed using field-emission scanning electron microscopy (FE-SEM). Resin-dentine slabs (Ø 0.9mm2) from each experimental group were immersed in Rhodamine B and subsequently analysed using confocal microscopy analysis (CLSM). The μTBS results were analysed using a two-way ANOVA and Newman-Keuls multiple-comparison test (α = 0.05). ZBX, PBA and SCH exhibited greater μTBS values than CQB at 24h in both SE and ER modes (p < 0.05). CQB showed a significant decrease in μTBS values after ageing both when used in SE and ER mode (p < 0.05). ZBX-ER exhibited no significant differences in the μTBS test after ageing (p > 0.05), while a significant drop in μTBS was seen in SCH-ER and APB-ER after 10-month ageing (p < 0.05). Clear signs of degradation were evident in the resin-dentine interface created with CQB regardless of the application mode or the ageing time. In APB-ER and SCH-ER groups, such signs of degradation were evident after ageing in AS. ZBX showed slight dye infiltration both when used in ER and SE mode. The long-term bonding performance of modern universal adhesives is usually influenced by the adhesive strategy employed; self-etching application should be prioritised during dentine bonding. Moreover, the use of shortened bonding protocols may compromise the quality of the resin-dentine interface and the bonding performance of most modern universal adhesives. The use of etch-and-rinse bonding procedures, as well as "shortened" application protocols should be eluded when using modern universal adhesives in dentine. However, new generation universal adhesives based on innovative chemical formulations may probably allow clinicians to achieve long-term bonding performance with such simplified system also when employed in ER mode.

Resin-Based Cement Applied to Enamel and Dentin Pre-Treated with Phytic Acid: An In Vitro Study

Phytic acid (IP6) has the ability to etch tooth structure due to its acidity and chelating properties. This study aimed to evaluate the micro-tensile bond strength (μTBS) of resin-based cement to enamel and dentin using manufacturer-provided etchants, phosphoric acid (PA) for enamel and a mixture of 10% citric acid and 3% ferric chloride (CAF) for dentin and compare them to IP6. Enamel surfaces were etched for 30 s with either PA or IP6 (1%, 5% or 10%). Dentin surfaces were etched for 15 s with either CAF or 1% IP6. Pre-polymerized composite blocks were bonded to enamel and dentin surfaces. After 24 h, the specimens were sectioned into beams and subjected to μTBS testing. De-bonded specimens and smear layer removal were analyzed with a scanning electron microscope. Etching enamel with 1% and 5% IP6 resulted in μTBS values that are comparable to the control (PA) (p &gt; 0.05), while 10% IP6 negatively affected the μTBS (p &lt; 0.05). The μTBS to dentin etched with 1% IP6 was higher compared to the control (CAF) (p = 0.001). IP6 effectively removed enamel and dentin smear layer, and at specific concentrations, it may be a suitable alternative conditioner agent for bonding resin-based cement to enamel and dentin.

Comparison of Silane Heat Treatment by Laser and Various Surface Treatments on Microtensile Bond Strength of Composite Resin/Lithium Disilicate.

In the current study, we evaluated the effects of heat treatment (by Er:YAG or furnace) and various surface treatments on the microtensile bond strength (μTBS) of silanized lithium disilicate ceramic. Seventy lithium disilicate (IPS e. max Press; Ivoclar Vivadent) and composite resin (Tetric N-Ceram; Ivoclar Vivadent) blocks were made and distributed into seven groups (n = 10) at random: S: silanization alone; ALS: airborne particle abrasion (APA) and silanization; SC: APA modified with silica and silanization; SHT1: silanization and heat treatment by Er:YAG; SHT2: silanization and heat treatment performed in the furnace (100 °C, 1 min); HF: etching with HF; and HFS: etching with HF and silanization. Every ceramic specimen was cemented to a composite resin block after surface treatment. Cemented specimens were embedded into acrylic resin and were tested with the μTBS test. Data were analyzed using one-way ANOVA and Tamhane T2 tests (α = 0.05). The SHT1 group had the highest bond of strength compared to the other groups (27.46 MPa). The ALS group had the lowest strength of the groups (15.56 MPa). Between SHT2 and HFS (p = 1), the comparison of the mean µTBS values showed no significant differences. It was concluded that silane heat treatment increased the resin composite–ceramic bond strength; however, within the terms of μTBS, the Er:YAG laser treatment was more successful than other surface treatment applications.

Do universal adhesives provide the benefits from double-application or an extra bonding layer in composite repair?

This study aimed to determine whether the application of extra hydrophobic resin (EHR) or double layer (DL) improves microtensile bond strength (μTBS) of two universal adhesives to composite resin. Composite blocks were fabricated and exposed to thermal cycles. The specimens were horizontally sectioned into two halves. Scotch Bond Universal (SBU) and Clearfil S3 Bond Universal (CSBU) were applied to the ground composite surface according to the manufacturers' instructions, or with DL application or EHR application. The repair composite was incrementally placed to bonded planes. Composite sticks were achieved and tensed with a universal testing machine, followed by examining the fracture surfaces by a scanning electron microscope. Data were evaluated by Weibull analysis (shape and scale [σθ and σ0.10 ] parameters) using the maximum likelihood method. The σθ and σ0.10 , respectively, estimate strength at 63.2 and 10% probability of failure. Shape parameter values showed significant differences among treatments. DL application of CSBU did not affect μTBS values at σθ of failure but caused to decrease μTBS values at σ0.10 of failure. DL application of SBU reduced μTBS values at σθ of failure. DL or EHR coating did not improve μTBS of SBU. EHR application increased μTBS of CSBU, whereas DL application did not benefit.

Investigating a Commercial Functional Adhesive with 12-MDPB and Reactive Filler to Strengthen the Adhesive Interface in Eroded Dentin.

To compare the adhesive interface of eroded dentin formed by a functional dental adhesive and a gold standard strategy, by testing microtensile bond strength (μTBS), hardness/elastic modulus. Permanent sound human molars were randomly allocated to four experimental groups, all subject to artificial erosion (0.05 M citric acid; 3× daily, 5 days). Groups included control Clearfil SE Bond 2 (CFSE), and experimental group Clearfil SE Protect (CFP), at two different time points-immediate (24 h) and long term (3 months–3 M). Samples were sectioned into microspecimens for μTBS (n = 8) and into 2-mm thick slabs for nanoindentation assays (n = 3). Groups CFSE_3M and CFP_3M were stored in artificial saliva. Statistical analysis included two-way ANOVA for μTBS data, while hardness/modulus results were analyzed using Kruskal–Wallis H Test (significance level of 5%; SPSS v.27.0). Although no significant differences were found between mean μTBS values, for different adhesives and time points (p > 0.05), a positive trend, with μTBS rising in the CFP_3M group, was observed. Regarding hardness, no significant differences were seen in the hybrid layer, considering the two variables (p > 0.05), while the reduced elastic modulus rose in CFP_3M when compared to 24 h. Thus, CFP shows similar mechanical and adhesive performance to CFSE in eroded dentin, although it may comprise promising long-term results. This is advantageous in eroded substrates due to their increased enzymatic activity and need for remineralization.

Application of β-Tricalcium Phosphate in Adhesive Dentin Bonding.

The study aimed at synthesizing β-tricalcium phosphate (β-TCP) nanoparticles and comparing the mechanical properties and dentin interaction of two adhesives: experimental adhesive (EA) and EA with 5 wt.% β-TCP nanoparticles (β-TCP-5%). These filler nanoparticles were synthesized and then characterized with scanning electron microscopy (SEM) and micro-Raman spectroscopy. The β-TCP nanoparticles were incorporated in the adhesives to form two groups: gp-1: EA (control) and gp-2: β-TCP-5%. These adhesives were characterized by SEM, energy-dispersive X-ray (EDX) spectroscopy and were also assessed for their micro-tensile bond strength (μTBS) with (TC) and without thermocycling (NTC). Fourier Transform Infrared (FTIR) spectroscopy was performed to evaluate the degree of conversion (DC) of two adhesives. The β-TCP filler was seen as irregularly shaped agglomerates on SEM. The micro-Raman spectra revealed characteristic peaks associated with β-TCP nanoparticles. Both adhesives presented suitable dentin interaction, which was demonstrated by the formation of resin tags of variable depths. The EDX analysis verified the existence of calcium (Ca) and phosphate (P) for the β-TCP-5% group. The greatest μTBS values were shown by β-TCP-5% group samples when they were non-thermocycled (NTC) (β-TCP-5%-NTC: 34.11 ± 3.46) followed by the thermocycled (TC) samples of the same group (β-TCP-5%-TC: 30.38 ± 3.66), compared with the EA group. Although the DC presented by β-TCP-5% group was comparable to the EA group, it was still lower. The addition of β-TCP nanoparticles in the adhesive improved its μTBS and resulted in a suitable dentin interaction, seen in the form of hybrid layer and resin tag formation. Nonetheless, a decreased DC was observed for the β-TCP-5% adhesive. Future studies probing the effect of different filler concentrations on various properties of the adhesive are warranted.

Nanoparticle incorporated dentin bonding agent to caries effected dentin treated by photodynamic therapy, laser or chlorhexidine

PurposeThis study aims to evaluate the microtensile bond strength (µTBS) and failure modes of graphene nanoplatelets doped with hydroxyapatite (GNP-HA) modified self-etch dentin bonding agent (DBA) to caries effected dentin (CAD) after various conventional and laser disinfection protocols. Materials and MethodsGraphene nanoplatelets and HA nanoparticles were doped and incorporated in DBA. Fifty carious human molar teeth were used for the experiment. CAD specimens were divided into five groups (n=10/group) into CAD undergoing no disinfection treatment (Group-CAD), 2% chlorhexidine disinfection (Group-CHX), 6% NaOCl disinfection (Group-NaOCl), methylene blue assisted PDT (Group-MB-PDT), and Er,Cr:YSGG laser application (Group-Er,Cr:YSGG). Following the respective disinfection techniques, the GNP-HA modified adhesive was applied to all treated CAD surface. Subsequently µTBS and failure modes were analyzed. ResultsRepresentative scanning electron microscope images (SEM images) of the synthesized GNP-HA indicated flakes of graphene with varying size lengthwise (>500 nm) with 1-2 nm width. The doped HA showed round and spherical morphology conjugated over the surface of the GNP measuring 40 -100 nm in diameter. CAD group that underwent no treatment represented the highest µTBS (29.43 MPa). Within the tested specimens, MB-PDT (22.37 MPa) and Er,Cr:YSGG (21.85 MPa) showed the highest µTBS values than CHX (15.69 MPa) and NaOCl (11.46 MPa). However, there was no significant difference between MB-PDT and Er,Cr:YSGG (p>0.05) and a significant difference existed between CHX and NaOCl (p<0.05). Equal distribution of cohesive and adhesive failures was noted for CAD, CHX and NaOCl treated specimens. A majority of adhesive failures existed in the MB-PDT groups. While admixed and adhesive failures were higher in Er,Cr:YSGG treated samples. ConclusionsThe outcome of this study suggests that CAD restored by GNP-HA modified self-etch adhesive showed highest bond strength after MB-PDT and Er,Cr:YSGG protocols with low amount of adhesive failure.

Examining the effects of acid etching duration on the bond strength between two CAD/CAM materials and one composite resin.

This study aimed to evaluate the effect of three hydrofluoric acid (HF) etching periods on the micro-tensile bond strength between two CAD-CAM ceramic systems [Vita Suprinity (VS) and feldspathic CEREC blocs (CB)] and a composite resin. The ceramics were categorized into six groups based on the surface conditioning protocol used, as follows: G1: CB-HF 5% for 20s; G2: CB-HF 5% for 40s; G3: CB-HF 5% for 60s; G4: VS-HF 5% for 20s; G5: VS-HF 5% for 40s; G6: VS-HF 5% for 60s. Scotchbond Universal was applied onto the pretreated ceramic surfaces and covered with Filtek Z350 XT composite resin. After 24h, the specimens were cut into microbars (n = 16) and a micro-tensile bond strength test (μTBS) was carried out. An optical microscope was used to examine the fractured microbars. The results showed statistically significant differences between the factors tested (p < 0.01). Moreover, the mean MPa of G1(17.27), G2(13.03), G3(12.82), G4(15.83), G5(21.66), and G6(14.50) was seen to significantly differ. The predominant failure type observed was adhesive, and all three periods of HF etching produced satisfactory bonding between the composite resin and CB. An etching time of 40s provided the highest μTBS value for VS.

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.

Fluoride-Releasing Self-Etch Adhesives Create Thick ABRZ at the Interface.

A fluoride-releasing adhesive system is expected to promote mineralization of demineralized dentin/enamel around a composite restoration, thereby contributing to the longevity of the restoration. Scanning electron microscopic (SEM) and transmission electron microscopic (TEM) observations revealed the formation of an “acid–base resistant zone” (ABRZ) beneath the hybrid layer when dentin was treated with a self-etch adhesive system. A thicker ABRZ was formed from the upper slope to the end of the outer lesion, indicating greater resistance against an acid-base challenge, when a fluoride-releasing self-etch adhesive system was used. The slope formation of a fluoride-releasing adhesive is believed to be due to fluoride-release from the adhesive. Quantitative assessment of the acid resistance was performed at the interface using the region of interest (ROI) mode of a digital image analysis software package. The area of the ABRZ is influenced by the concentration of fluoride release from the adhesive resin. The threshold of fluoride concentration in the adhesive may exist to influence the morphology of the ABRZ. X-ray absorption fine structure (XAFS) analysis of the dentin treated with different concentrations of NaF-mouth rinses suggested that different fluoride concentrations result in the formation of different chemical compounds, such as fluorapatite and CaF2-like structures, on the dentin surface. This may explain the differences in μTBS values and morphological appearance of the ABRZ. NaF is effective in enhancing the enamel/dentin bond durability and also helps create a high quality of ARBZ to improve the clinical success of restorations.

Assessment of Bond Integrity, Durability, and Degree of Conversion of a Calcium Fluoride Reinforced Dentin Adhesive

Our study aimed to synthesize and compare the mechanical properties and dentin interaction of two adhesives; experimental adhesive (EA) and EA containing 5 wt.% calcium fluoride (CaF2) nano-crystals (CaF2 adhesive-CAFA). CaF2 nano-crystals were synthesized by reacting two solutions (containing calcium and fluoride) in a glass chamber using a heated air system. The EA was produced using a mix of monomers, photo-initiators, camphorquinone, and electron initiators. The synthesized CaF2 nano-crystals were centrifuged to guarantee that inside the adhesive there is homogenized dispersion of the filler particles. Their integration in the EA yielded two groups; Gp-1: EA (without CaF2, control) and Gp-2: (5 wt.% CaF2 containing adhesive, CAFA). Sixty teeth were prepared and set to form bonded specimens using the two adhesives. The CaF2 nano-crystals were irregularly shaped with an average particle size of 30–200 nm. The highest μTBS values were obtained for CAFA-non-thermocycled (NTC) samples (32.63 ± 3.15), followed by EA-NTC (31.80 ± 3.75) specimens. On thermocycling (TC), both adhesive groups presented lower μTBS values (CAFA-TC: 29.47 ± 3.33 and EA-TC: 24.04 ± 3.69). Hybrid layer (HL) formation and resin tags of varying depths were perceived for both adhesive groups. The EDX analysis demonstrated the presence of carbon (C), silica (Si), calcium (Ca), and fluoride (F) for CAFA group. Micro-Raman spectroscopy revealed distinct peaks for CaF2 nano-crystals. The CAFA group presented the greatest DC. The addition of CaF2 nano-crystals in the adhesive caused improved bond μTBS and DC. The incorporation also demonstrated suitable dentin interaction, depicted by appropriate HL and resin tag development.