Microtensile Bond Strength Research Articles

Influence of a budget single-peak light-curing unit on the microhardness and bond strength of bulk-fill resin composites to the gingival floor of proximal class II cavity preparations

ObjectiveTo evaluate the Vickers microhardness (VH) and long-term microtensile bond strength (μTBS) of bulk-fill resin-based composites (RBCs) at the bottom of the proximal boxes of Class II restorations when photo-cured using two different light-curing units (LCUs). MethodsMesio-occlusal-distal (MOD) cavities were prepared in 99 third molars (n = 7 per group) and restored with Tetric N-Ceram Bulk-Fill (TNC, Ivoclar), Filtek Bulk-Fill Flow (FBF, 3 M ESPE), or SDR flow+ (SDR, Dentsply Sirona). The RBCs were photo-cured with a dual-peak (Bluephase 20i, Ivoclar) or a single-peak budget LCU (Rainbow Curing Light, SML). The energy delivered by the lights were similar. The amount of light transmitted (% of maximum transmission) through the RBCs and the light beam profile through the restored teeth were recorded (n = 5). VH values were measured at the periphery of the RBC in the proximal box. After 24-h storage in water or after additional thermocycling, the teeth were sectioned to make 1 mm2 sticks. The μTBS of bulk-fill RBCs to the dentin on the gingival floor of the proximal boxes was then measured. Two-way repeated-measures ANOVA and 2-way ANOVA were used to analyze the VH and μTBS data, respectively, and Bonferroni's post-hoc test (α = 5%). No comparisons were made among RBCs. ResultsWhen the bonding agent was photo-cured with the budget light, all the specimens failed. Therefore, the Bluephase 20i photo-cured all the bonding resins and the budget light was only used to photo-cure the RBCs. The Bluephase 20i delivered a more homogeneous and wider light distribution through the restored teeth, higher VH values for TNC and SDR groups (p < 0.05), and higher μTBS in the TNC group (p < 0.05) than those produced by the single-peak budget LCU. The μTBS values to the dentin at the gingival floor of the proximal boxes decreased after thermocycling in the SDR group (p < 0.05). ConclusionWhen the bonding agent was photo-cured with the budget light, all the specimens failed. Photo-curing the RBC with a single-peak, budget LCU compared to the Bluephase 20i reduced the VH and μTBS values of bulk-fill RBCs to the gingival floor.

Influence of chlorhexidine 2% and sodium hypochlorite 5.25% on micro-tensile bond strength of universal adhesive system (G-Premio Bond)

Aim: One of the reasons for the failure of adhesion in composite restorations and secondary caries may be the chemical irrigants used during the endodontic treatment. NaOCl is widely used for the biomechanical preparation of root canals due to its antimicrobial properties and capacity to dissolve organic material. In addition, another very effective decontamination solution is chlorhexidine 2%. There are few studies about the effect of root canal irrigation solutions on bond strength of universal adhesives therefore, in this study we have investigated the influence of CHX 2% and NaOCl 5.25% on micro-tensile bond strength of G-Premio Bond. Methods: Twenty-four human teeth were randomly allocated to the following groups: G1, immersion in saline solution 0.9% for 30 minutes (control); G2, immersion in CHX 2% for 30 minutes; G3, immersion in NaOCl 5.25% for 30 minutes. After restoration, the dentin/resin interface was tested by micro-tensile bond strength. The surfaces morphology was analyzed by Scanning Electron Microscopy. Data were analyzed by ANOVA followed by Tukey test in SPSS software Version 24. Results: There was a statistically significant difference between G3 and G1 (P &lt; 0.05). There were no statistically significant differences among G1 and G2, G2 and G3. Conclusion: Root canal irrigation with NaOCl 5.25% significantly reduced the micro-tensile bond strength in the G-Premio Bond at self-etch mode, but the use of CHX did not make a significant difference.

Phosphoric acid containing proanthocyanidin enhances bond stability of resin/dentin interface.

Proanthocyanidin (PA) is a promising dentin biomodifier due to its ability to stabilize collagen fibrils against degradation by matrix metalloproteinases (MMPs); however, the most effective protocol to incorporate PA into bonding procedures is still unclear. This study evaluated the effect of dentin biomodification with a PA acid etchant on MMP activity, adhesive interface morphology and resin-dentin microtensile bond strength. Sound extracted human molars were flattened to expose dentin and acid-etched for 15 s according to the groups: EXP - experimental phosphoric acid; EXP+PA - experimental phosphoric acid 10% PA; TE - total-etching system; SE - self-etching system. Samples were restored with composite resin and stored in distilled water (37ºC). MMP activity and interface morphology were analyzed after 24 h by in situ zymography (n=6) and scanning electron microscopy (n=3), respectively. The resin-dentin microtensile bond strength (μTBS) was evaluated after 24 h and 6 months storage (n=6). Significantly higher MMP activity was detected in etched dentin compared with untreated dentin (p<0.05), but no difference among acid groups was found. Resin tags and microtags, indicative of proper adhesive system penetration in dentinal tubules and microtubules, were observed along the hybrid layer in all groups. There was no difference in μTBS between 24 h and 6 months for EXP+PA; moreover, it showed higher long-term μTBS compared with TE and EXP (p<0.05). The results suggest that 15 s of biomodification was not sufficient to significantly reduce MMP activity; nonetheless, EXP+PA was still able to improve resin-dentin bond stability compared with total- and self-etching commercial systems.

Delayed light activation of resin composite affects the bond strength of adhesives under dynamic simulated pulpal pressure.

To evaluate the effect of a time delay before the light activation of resin composite on the microtensile bond strength (µTBS) of self-etch adhesives under dynamic simulated pulpal pressure. One hundred twenty crown segments were prepared from human third molars. Dentin surfaces were prepared with coarse diamond burs and connected to a dynamic pulpal pressure device. The self-etch adhesives used were Clearfil SE Bond (CSE), G2-Bond Universal (G2B), Clearfil Universal Bond Quick (CBQ), and G-Premio Bond (GPB). Each adhesive was divided into 3 subgroups: immediate light activation of resin composite (T0), delayed light activation for 150s (T1), and 300s (T2). The µTBS data were obtained after 24-h water storage. Scanning electron microscopy was used to evaluate the nanoleakage at the resin-dentin surface. The µTBS data were analyzed using two-way ANOVA and Duncan's multiple comparisons. All adhesives demonstrated a significant reduction in µTBS at T2, except for CBQ where the bond strength was not affected by the delayed light activation times. The two-step self-etch adhesives (CSE and G2B) demonstrated higher bond strength than the one-step adhesives at all conditions. Nanoleakage was observed in all adhesives at T2; however, nanoleakage was detected only in CBQ and GPB at T1. Delayed light activation of resin composite adversely affected the dentin bond strength of self-etch adhesives. Two-step self-etch adhesives had better bonding performance than one-step self-etch adhesives. After adhesive application, resin composite should be adapted and cured as soon as possible.

Effect of decontamination materials on bond strength of saliva-contaminated CAD/CAM resin block and dentin.

The aim of this study was to evaluate the effect of decontamination agents against saliva contamination on the bonding of computer-aided design/computer-aided manufacturing (CAD/CAM) resin block. Three commercially available decontamination agents were used in this study. The samples were subjected to microtensile bond strength test. A saliva protein staining test was performed by the pigment binding method to investigate the effect of removing saliva protein. All the decontamination agents could significantly restore the bond strength from the saliva contamination, and KATANA Cleaner showed no significant difference with the control. From the results of the saliva protein staining test, KATANA Cleaner showed higher removal effect of saliva protein for CAD/CAM resin block surface than the other materials due to the surface active effect of MDP salt. It was suggested that cleaners containing MDP salt were more effective in removing artificial saliva contamination than cleaners containing other ingredients for CAD/CAM resin blocks.

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.

FARKLI ŞEKİLLERDE POLİMERİZE OLAN İKİ REZİN SİMANIN DEĞİŞİK SERAMİK SİSTEMLER İLE ÜRETİLEN LAMİNATE VENEERLERİN BAĞLANMA DAYANIMLARINA ETKİSİ

Amaç: Bu çalışmanın amacı; ışıkla ve dual olarak polimerize olan iki rezin simanın farklı seramik sistemleri ile üretilmiş laminate veneerlerin mikroçekme bağlanma dayanımları üzerindeki etkilerini karşılaştırmalı olarak incelemektir. Yöntemler: Altmış maksiller santral diş mine-sement birleşiminin 2 mm apikalinden akrilik rezin içine gömüldü ve laminate veneer preparasyonları tamamlandı. Restorasyonların mum modelajları 3B yazıcı yardımıyla üretildi. Dişler rastgele 3 gruba ayrıldı (n = 20) ve lityum disilikat, yüksek yoğunluklu mikronize lityum disilikat ve zirkonya ile güçlendirilmiş lityum silikat seramiklerden restorasyonlar üretildi. Seramik örnekler ayrıca rezin siman tipine göre ışıkla polimerize ve dual polimerize rezin siman olarak 2 alt gruba (n = 10) ayrıldılar ve simantasyonları yapıldı. Daha sonra dişler 1 yıllık klinik kullanıma eşdeğer hızlandırılmış yapay yaşlandırmaya maruz bırakıldı. Her dişin kronunun tam ortasından 1’er tane mikrobar elde edildi (n = 10) ve örneklere kopma gerçekleşene kadar 0,5 mm/dk yükleme hızında çekme kuvveti uygulandı. İstatistiksel analizler iki yönlü varyans analizi ve Tukey's Post-hoc testi kullanılarak yapıldı (P ≤ ,05). Bulgular: Seramik ve rezin siman alt grubundaki örnekler karşılaştırıldığında aralarında istatistiksel olarak anlamlı fark bulunmuştur (P < ,001). Zirkonya ile güçlendirilmiş lityum silikat seramiklerin mikroçekme bağlanma dayanımları hem ışıkla polimerize olan hem de dual polimerize olan rezin siman gruplarında lityum disilikat seramiklere göre anlamlı seviyede düşük bulunmuştur (P < ,001). Dual polimerize olan rezin siman grubunun bağlanma dayanımı, ışıkla polimerize olan rezin siman grubundan istatistiksel olarak anlamlı seviyede düşük bulunmuştur (P < ,001). Sonuç: Lityum disilikat laminate veneerler, zirkonya ile güçlendirilmiş lityum silikat veneerlerden daha yüksek bağlanma dayanımı göstermiştir. Yine ışıkla polimerize olan rezin siman, dual polimerize olan rezin simana göre daha etkili bağlanma dayanımı sağlamıştır. Anahtar Kelimeler: Laminate veneer, lityum disilikat, mikro gerilim bağlanma dayanımı, rezin siman, zirkonya ile güçlendirilmiş lityum silikat Abstract Objective: The aim of this study was to compare the effects of two resin cements polymerized in different ways on the microtensile bond strength of laminate veneers produced with different ceramic materials. Methods: Sixty maxillary central incisor teeth were embedded in an acrylic resin 2 mm below the enamel-cement junction and laminate veneer preparations were completed. The wax models of the restorations were produced with a 3D printer. The teeth were randomly divided into 3 groups (n = 20) and restorations were produced with lithium disilicate, high-density micronized lithium disilicate and zirconia reinforced lithium silicate ceramics. Ceramic specimens were further divided into two groups (n = 10) according to the resin cement type as light-cure and dual-cure resin cement, and their cementation was performed. The teeth were then subjected to accelerated artificial aging equivalent to 1 year of clinical use. One microbar was obtained from the middle of the crown of each tooth (n = 10) and tensile force was applied to the specimens at a loading speed of 0.5 mm/min until the fracture occurred. Statistical analyzes were performed using two-way analysis of variance and Tukey's Post-hoc test (P ≤ .05). Results: Statistically significant difference was found between the ceramic type and resin cement subgroups (P < .001). The bond strength of laminate veneers produced with zirconia reinforced lithium silicate ceramic group was found significantly lower than that of lithium disilicate ceramic’s groups in both light-cured and dual-cured resin cement groups (P < .001). The dual-cure resin cement groups showed statistically significantly lower bond strength than the light-cure resin cement groups (P < .001). Conclusion: The laminate veneers fabricated from lithium disilicate ceramics showed higher bond strength than that of zirconia reinforced lithium silicate veneers. Also, the light-cure resin cement provided more effective bond strength than dual-cure resin cement. Keywords: Laminate veneer, lithium disilicate, microtensile bond strength, resin cement, zirconia reinforced lithium silicate

Promotion Effect of Carboxymethyl Chitosan on Dental Caries via Intrafibrillar Mineralization of Collagen and Dentin Remineralization.

Objective: To observe ultrastructural changes during the process of carboxymethyl chitosan (CMC)-mediated intrafibrillar mineralization, we evaluated the biomimetic remineralization potential of CMC in type-I collagen fibrils and membranes, and further explored the bond strength as well as the bond interfacial integrity of the biomimetic remineralized artificial caries-affected dentin (ACAD). Methods: A mineralized solution containing 200 μg/mL CMC was used to induce type-I collagen biomimetic remineralization in ACAD, while traditional mineralization without CMC was used as a control. The process and pattern of mineralization were investigated by transmission electron microscopy (TEM), scanning electron microscopy (SEM), and energy-dispersive X-ray spectroscopy (EDS) as well as structured illumination microscopy (SIM). The Vickers hardness test was used to quantify the dentin hardness, while the microtensile bond strength (µTBS) test was used to assess the bond strength and durability. The bond interfacial integrity was evaluated by a confocal laser scanning microscope (CLSM). Results: TEM, SEM, and SIM images showed that CMC had a positive effect on stabilizing amorphous calcium phosphate (ACP) and promoting intrafibrillar mineralization, while extrafibrillar mineralization was formed without CMC. Furthermore, hardness evaluation and µTBS proved that CMC significantly increased dentin hardness and bond strength. CLSM indicated that CMC could create a significantly better bond interfacial integrity with less of a micro-gap in ACAD. Significance: CMC possessed the ability to promote intrafibrillar mineralization and remineralization in demineralized caries dentin lesions, as well as improve bond performance, which implied its potential in carious dentin demineralization or dentin hypersensitivity and possibly even as a possible material for indirect pulp-capping, to deal with deep caries. Highlights: CMC possessed the ability to induce intrafibrillar mineralization effectively; the bond strength and bond durability of demineralized caries dentin were improved via CMC-induced remineralization; the CMC-induced remineralization complex is a potential material for indirect pulp-capping, to deal with deep caries.

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.

Comparative Evaluation of Bond Strength and Microleakage of Three Ion-Releasing Restorative Materials at Various pH Levels

The aim of this study was a comparison of the micro-tensile bond strength (μTBS) to dentin and microleakage of in vitro class V restorations of three different ion-releasing restorative materials under various pH conditions: giomer, a resin-modified glass ionomer (RMGI), and a new alkasite material. A μTBS test was performed using a universal testing machine, immediately and after storage at different pH (4, 7, and 10) buffer solutions (n = 15) over 24 h, and the failure mode was analyzed. For microleakage analysis, class V restorations were performed on extracted premolars, which were sectioned and stored in pH 4-, 7-, and 10-buffered fluorescent 0.02% rhodamine B dye. The specimens were observed under a confocal laser scanning microscope (CLSM) and scored using the acquired images. There were no significant differences in the μTBS according to the type of material (p = 0.518). The giomer showed a decreased bond strength under the pH 4 condition compared with the immediately tested or pH 7-stored specimens (p ≤ 0.043). In the microleakage analysis, the class V restoration with giomer showed a higher microleakage than RMGI or alkasite (p = 0.001). For RMGI and alkasite, the specimens stored at pH 4 showed a significantly lower microleakage than those stored at pH 7 (p = 0.028). RMGI and alkasite can be adopted as restorative materials in generalized or localized low-pH conditions.

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.

Influence of Irradiance and Exposure Times on the Mechanical and Adhesive Properties of Universal Adhesives with Dentin

This study evaluated the influence of irradiance/exposure time on the Knoop hardness (KHN) and polymer cross-linking density (PCLD), as well as microtensile bond strength (μTBS), nanoleakage (NL), and in situ degree of conversion (DC) of universal adhesives. Two universal adhesive systems, Clearfil Universal Bond Quick (CUQ) and Scotchbond Universal Adhesive (SBU), were light-cured using various irradiance/exposure times: 1400 mW/cm2 for 5 s (1400*5); 1400 mW/cm2 for 10 s (1400*10); 3200 mW/cm2 for 5 s (3200*5); and 3200 mW/cm2 for 10 s (3200*10). Adhesive disks from each group were used to measure PCLD by KHN. One hundred and twenty-eight human molars were randomly assigned to 16 groups according to the following variables: adhesive system vs adhesive strategies vs radiance/exposure times. After restoration, specimens were sectioned into resin-dentin sticks and tested for μTBS, NL, and DC. The data from PCLD (%), KHN, μTBS (MPa), NL (%), and DC (%) data were subjected to ANOVA and Tukey's test (α=0.05). Significant reductions in KHN, μTBS, and DC (p=0.00001) values and an increase in NL and PCLD (p=0.00001) values were observed for 3200*10 when compared with other groups. Higher KHN, μTBS, and DC (p=0.000001) values were observed for 3200*5 in comparison with the other groups. The 1400*5 (7 J/cm2) and 1400*10 (14 J/cm2) groups showed intermediate values (p=0.000001). Although similar results in terms of hardness, polymer cross-linking density and nanoleakage were observed when 5 seconds at 3200 mW/cm2 and 10 seconds at 1400 mW/cm2 groups were compared, the use of higher irradiance (3200 mW/cm2) for only 5 seconds showed better results in terms of bond strength and degree of conversion for both universal adhesives to dentin. The prolonged exposure time (10 seconds) at the higher irradiance (3200 mW/cm2) showed the worst results.

The effect of atmospheric pressure on the bond strength of composites.

Background: In the current study, we investigated the effect of atmospheric pressure change on the microtensile bond strength of direct and indirect composite restorations to the teeth. Materials and Methods: A total of 16 extracted teeth were prepared after crown cutting and randomly divided into four groups. The study groups included: 1) direct restoration (Filtek™ Z250 Universal Composite Restorative System, 3M, United States) at constant pressure (control); 2) direct restoration in variable pressure; 3) indirect restoration (Z250 composite) at constant pressure (control); and 4) indirect restoration at variable pressure. Then, samples were subjected to thermal cycles. Variable pressure groups were pressurized to 0 to 5 atmospheres for 96 cycles inside the hyperbaric chamber, followed by measuring the microtensile bond strength of the specimens. Results: The mean of microtensile bond strength in both direct and indirect variable-pressure groups was significantly lower than their counterpart control groups. There was no significant difference between direct and indirect restorations in constant and variable pressure. The failure mode of the samples in the control groups was often mixed, while in the pressure groups, it was dominated by adhesive. Also, microscopic examination of restoration interfaces showed that the number and volume of voids in variable pressure groups were much more than the control groups. Conclusion: Regardless of the type of restoration, changing the atmospheric pressure is effective on the bond strength of the restorations to the teeth.

Effect of Egg Shell and White Tea Dentin Pretreatment on Microtensile Bond Strength of Universal Adhesive System

Effect of Egg Shell and White Tea Dentin Pretreatment on Microtensile Bond Strength of Universal Adhesive System

Microtensile Bond Strength of Different Universal Adhesives with /without Acid Etching to Enamel Compared to Two-Step Self-Etch System After Thermal Cycling

Microtensile Bond Strength of Different Universal Adhesives with /without Acid Etching to Enamel Compared to Two-Step Self-Etch System After Thermal Cycling

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.

The effects of experimental etchant with calcium phosphate ion clusters on the nanoleakage at dentin–resin hybrid layer

This study aimed to investigate the possibility that a calcium phosphate ion cluster (CPIC)-incorporating phosphoric acid (PA) solution promotes the remineralization of the hybrid layer and prevents nanoleakage from the dentin–resin interface, thereby minimizing dentin–resin bond failure during long-term bonding periods. The specimens were prepared using human molars and treated with three types of etching solutions (35% PA, and CPIC-incorporated PA solutions at 1:1 and 1:2 ratios). The microtensile bond strength (µTBS) of half of the specimens was measured after 24 h, and measured after thermocycling for the other half. Fourier-transform infrared spectroscopy (FTIR) was performed to chemically analyze the remineralization, and the degree of nanoleakage in each sample was observed using a scanning electron microscope (SEM). The CPIC-incorporated PA-II solution decreased the nanoleakage in the hybrid layer without reducing the µTBS, with or without thermocycling, and promoted remineralization of dentin collagen.

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.

Development of an Antibacterial Dentin Adhesive.

Nisin is a peptide that possesses potent antibacterial properties. This study evaluated the antibacterial activity of a nisin-doped adhesive against Streptococcus mutans, as well as its degree of conversion and microtensile bond strength (μTBS) to dentin. Nisin was added to the adhesive Adper Single Bond 2 (3M ESPE), resulting in four groups: Control Group (Single Bond 2); Group 1% (1 wt% nisin-incorporated), Group 3% (3 wt% nisin-incorporated) and Group 5% (5 wt% nisin-incorporated). Antibacterial activity against S. mutans was evaluated using colony-forming unit counts (CFU). The degree of conversion was tested using FTIR. Forty human teeth were restored for μTBS evaluation. Data were statistically analyzed with ANOVA and Tukey tests at α = 0.05. The nisin-doped adhesives, for all concentrations, exhibited a significant inhibition of the growth of S. mutans (p < 0.05); Incorporation of 5% and 3% nisin decreased the degree of conversion of the adhesive (p < 0.05). The μTBS (in MPa): Control Group—38.3 ± 2.3A, Group 1%—35.6 ± 2.1A, Group 3%—27.1 ± 1.6B and Group 5%—22.3 ± 1.0C. Nisin-doped adhesives exerted a bactericidal effect on S. mutans. The μTBS and degree of conversion of adhesive were not affected after incorporation of 1% nisin.

Novel bioactive adhesive containing dimethylaminohexadecyl methacrylate and calcium phosphate nanoparticles to inhibit metalloproteinases and nanoleakage with three months of aging in artificial saliva

ObjectivesThe objectives of this study were to: (1) develop a multifunctional adhesive via dimethylaminohexadecyl methacrylate (DMAHDM) and nanoparticles of amorphous calcium phosphate (NACP); and (2) investigate its ability to provide metalloproteinases (MMPs) deactivation and remineralization for long-term dentin bonding durability. MethodsDMAHDM and NACP were incorporated into Adper™ Single Bond 2 Adhesive (SB2) at mass fractions of 5% and 20%, respectively. Degree of conversion and contact angle were measured. Endogenous MMP activity of the demineralized dentin beams, Masson’s trichrome staining, nano-indentation, microtensile bond strength and interfacial nanoleakage analyses were investigated after 24 h and 3 months of storage aging in artificial saliva. ResultsAdding DMAHDM and NACP did not compromise the degree of conversion and contact angle of SB2 (p > 0.05). DMAHDM and NACP incorporation reduced the endogenous MMP activity by 53 %, facilitated remineralization, and increased the Young’s modulus of hybrid layer by 49 % after 3 months of aging in artificial saliva, compared to control. For SB2 Control, the dentin bond strength decreased by 38 %, with greater nanoleakage expression, after 3 months of aging (p < 0.05). However, DMAHDM+NACP group showed no loss in bond strength, with much less nanoleakage, after 3 months of aging (p > 0.05). SignificanceDMAHDM+NACP adhesive greatly reduced MMP-degradation activity in demineralized dentin, induced remineralization at adhesive-dentin interface, and maintained the dentin bond strength after aging, without adversely affecting polymerization and dentin wettability. This new adhesive has great potential to help eliminate secondary caries, prevent hybrid layer degradation, and increase the resin-dentin bond longevity.