气体加压技术对两步法自酸蚀粘接系统树脂牙本质粘接效果的影响

探讨使用不同压力气体吹拂两步法自酸蚀粘接剂对树脂牙本质粘接界面微观形貌及微拉伸粘接强度的影响。20颗离体的完整无龋第3磨牙去除冠釉,按粘接过程中气体吹拂处理方法不同随机分为4组(处理剂和粘合剂均轻吹;处理剂强吹,粘合剂轻吹;处理剂轻吹,粘合剂强吹;处理剂和粘合剂均强吹。轻吹气压为0.1MPa,强吹气压为0.3 MPa),每组5颗牙。各组粘接完成后,37℃水浴24 h,每颗牙切出1片薄片状试件利用场扫描电子显微镜(SEM)观察4组粘接界面微观形貌(n=5),另外每颗牙制成8根长方体形试件测试微拉伸强度(μTBS)(n=40)。SEM观察显示,第1组的粘接剂层最厚,树脂突最短小稀疏;第2组和第3组的粘接剂层较薄,树脂突更长更致密更均匀;第4组的粘接剂层最薄,但是树脂突更长更致密更均匀。第2组的μTBS最高(41.32±3.76)MPa,其次为第3组(31.17±4.80)MPa、第1组(26.24±5.21)MPa,第4组最低(14.89±2.31)MPa。在两步法自酸蚀粘接中,采用气体加压技术吹拂处理剂可显著提高树脂牙本质粘接强度。     

Shear bond strength to dentine of dental adhesives containing hydroxyapatite nano-fillers

The aim of this study was to compare the effect of hydroxyapatite (HAP) nano-rods (HAP_rods) and HAP nano-sticks (HAP_sticks) added to commercial adhesives on the macro-shear bond strength (SBS) to dentine and morphology of the adhesive–dentine interface. HAP was added to Single Bond Universal (SBU, 3M ESPE) and Te-Econom Bond (TeE; Ivoclar Vivadent), in the form of water suspensions to avoid agglomeration of nano-particles and to achieve HAP concentrations of 0.5, 1.0 and 1.5 wt%. Following a ‘total-etch’ or a ‘self-etch’ protocol, the adhesives were applied to flat dentine surface of 162 intact human, third molars (N = 6/group). Composite (Z250, 3M ESPE) was built-up using a split stainless steel mould, 3 mm in diameter. SBS was tested using a universal testing machine at 1 mm/min until fracture. Data were statistically analysed using two-way and one-way analysis of variance with Tukey’s post-test (α = 0.05). HAP_rods had no significant effect on SBS of the tested adhesives while HAP_sticks improved bond strength to dentine only of adhesives applied following the ‘total-etch’ total-etch protocol. SBS values of SBU containing 1% HAP_sticks (15.10 ± 2.96 MPa) and TeE containing 0.5% HAP_sticks applied following the total-etch protocol (12.96 ± 4.48 MPa) were higher than those of their respective control groups (10.36 ± 2.68 and 7.97 ± 3.64 MPa). Samples with higher SBS showed more ‘mixed’ failures. HAP nano-fillers may improve bond strength of total-etch adhesives without an adverse effect on adhesive dispersion on dentine and its ability to infiltrate dentinal tubules.     

One-year bonding performance of one-bottle etch-and-rinse adhesives to dentin at different moisture conditions

Abstract

This study aimed to investigate the one-year bond strengths to dentin of one-bottle etch-and-rinse adhesive systems applied under different moisture conditions. Class V cavities were prepared in bovine incisors and randomly allocated (n?=?8) according to the type of adhesive system used – SB (Adper? Single Bond 2); PB (Prime & Bond 2.1); and XPB (XP Bond) – and the moisture condition kept in the cavity – moist, over-wet, and over-dry. Filtek? Z250 was used for teeth restoration. Specimens for microtensile bond strength (µTBS) test were obtained and stored in water for 24?h or 1?year, and submitted to mechanical testing. Data were analyzed using t-tests, ANOVA and the Holm–Sidak post hoc test (α?=?0.05). Weibull analysis was used to verify the reliability of specimens. The type of adhesive and the moisture condition of the substrate affected the µTBS. At 24?h, SB performed better under the moist and over-wet conditions. At 1?year, SB, PB, and XPB showed the greatest percentage reduction at the moist (～38%), over-wet (100%), and over-dry (100%) conditions, respectively. The reliability of adhesives was affected by the variable factors tested. In conclusion, the solvent composition of adhesives and the moisture condition of the substrate play an important role in the bond strength and bonding stability of resin-based restorations, as well as on the reliability of the adhesive interfaces over time.     

Prime-and-rinse approach for improving the enamel micro-tensile bond strengths of self-etch adhesives

The study investigated the effects of prime-and-rinse approach using 15% MDP (10-methacryloyloxydecyl dihydrogen phosphate)-containing primer on the enamel micro-tensile bond strengths (MTBS) of (ultra-) mild self-etch adhesives, enamel surfaces and enamel-resin interfaces. The buccal enamel surfaces of 69 human third molars were polished and randomly assigned to three groups: Group A (control, self-etch approach): Polished enamel surfaces were not further pre-treated. The enamel surfaces were acid-etched (Group B, (selective) enamel etching) or primed with 15% MDP-containing primer (Group C, prime-and-rinse approach) for 15?s and thoroughly water-sprayed. The enamel surfaces were applied with self-etch adhesives and placed with composite resins (Adper Easy One?+?Filtek Z350 (3?M ESPE); Clearfil S3 Bond?+?Clearfil Majesty (Kuraray-Noritake Co.); G Bond?+?Gradia Direct (GC); iBond?+?Charisma (Heraeus-Kulzer)), respectively. The specimens were prepared for MTBS test and scanning/transmission electron microscopy observations. Compared with group A, groups B and C produced significantly higher enamel MTBS (p?<?.01), regardless of the adhesives used. Groups B and C possessed similar enamel MTBS (p?>?.05). The SEM findings showed that smear layer remained on the polished enamel surface was completely removed by acid etching and almost completely removed by prime-and-rinse approach. The TEM microphotographs reveal that smear layer was detectable at the resin-enamel interface in group A, not in groups B and C. The novel prime-and-rinse approach using MDP-containing primer before the application of (ultra-) mild self-etch adhesives could greatly increase the enamel MTBS. That might be an alternative to selective enamel etching.     

Effect of saliva contamination on shear bond strength and microleakage of one-bottle etch-and-rinse and self-etch adhesives: scanning electron and confocal laser microscopic analyses

Purpose: To evaluate the effect of saliva contamination on shear bond strength, microleakage, and microstructure of the adhesive interface in two different adhesive systems by using scanning electron microscopy (SEM) and confocal laser microscopy (CLSM). Materials and methods: Randomly, 228 third molars were allocated to six groups for an etch-and-rinse adhesive One-Step Plus (Bisco Inc.) and a self-etch adhesive G Bond (GC Corp.): Group 1 – manufacturer’s instructions were followed; Group 2 – involved contamination and drying before adhesive application; Group 3 – involved contamination, washing, and blot drying before adhesive application; Group 4 – involved contamination, etching, washing, and blot drying before adhesive application; Group 5 – involved contamination and drying after adhesive application, followed by adhesive reapplication; Group 6 – involved contamination and washing after adhesive application, followed by adhesive reapplication. Shear bond strength was tested after specimens were stored in distilled water at 37?°C for 24?h. Specimens were evaluated under a stereomicroscope for microleakage. Dentin–resin interfaces were evaluated by SEM and CLSM. Results: Group 2 for One-Step Plus and Group 3 for G Bond showed significantly lower bond strengths than control groups. Microleakage values were significantly greater at dentin than at enamel margins for all groups. In Group 2, for both adhesive systems, the highest microleakage was observed at dentin margins. Further, dentin–adhesive interfaces were not uniform and gaps were found by SEM and CLSM. Conclusions: The SEM and CLSM images demonstrated high variability of dentin–resin interfaces among saliva-contaminated groups. Rinsing the saliva and re-applying adhesive might be the best way to reduce the effect of saliva contamination on bond strength and microleakage.     

Effect of different application techniques on microshear bond strength of self-etch adhesives to dentin

Objectives: To investigate the effect of different self-etch adhesive systems application techniques: active or passive in a single or double layer on adhesive–dentin microshear bond strength.

Methods: Occlusal surfaces of 48 extracted human molars were ground to expose flat superficial dentin surfaces. Specimens were randomly divided into two main groups according to the tested self-etch adhesive system either: One-step self-etch (Adper^TM easy-one) or two-step self-etch (Adper^TM SE Plus). Each adhesive system was applied on the prepared dentin surfaces followed one of these techniques: (1) Passive application of a single layer, (2) Active application of single layer, (3) Passive application of double adhesive layer (with light curing in between), and (4) Active application of double adhesive layers. Resin composite was packed inside micro-tubes fixed on the bonded dentin surfaces and light cured for 40 s. All specimens were stored in artificial saliva either for 24 h or 3 months before testing. Microshear bond strength test was employed using a universal testing machine at a crosshead speed of 0.5 mm/min.

Results: Adper^TM SE Plus showed higher significant microshear bond strength in compared with Adper^TM easy-one. For both adhesive systems active application showed higher significant microshear bond strength to dentin than passive application. Double application of adhesive systems showed lower microshear bond strength than single application.

Conclusion: Active application of self-etch adhesives could improve the dentin microshear bond strength. Double application with curing in between the layers did not improve the bond strength to the tested adhesive.     

Effect of polymerization protocol on the degree of conversion of photo- and dual-polymerized self-etch adhesives

This study investigated the effect of different polymerization protocols on the degree of conversion (DC%) of various photo-polymerized and dual-polymerized self-etch adhesive resins. Five different photo-polymerized (All-Bond Universal, Bisco; G-ænial Bond, GC; Futurabond M+ LC, VOCO; Single Bond Universal LC, 3M ESPE and Peak Universal Bond, Ultradent) and four dual-polymerized self-etch adhesives (Futurabond U, VOCO; Gradia Core SE, GC; Futurabond M+ DC, VOCO and Single Bond Universal DC, 3 M ESPE) were tested. All adhesives were applied on potassium bromide pellets (KBr) following the manufacturer’s instructions. The KBr pellets were divided into 10 experimental groups for the photo-polymerized adhesives and 12 experimental groups for the dual-polymerized adhesives according to the two levels of the study, Level 1: polymerization protocol and Level 2: adhesive system. For the photo-polymerized adhesives, the adhesives were polymerized either at 1 or 10 mm from the KBr pellets. For the photo-polymerized adhesives, the adhesives were photo-polymerized either at 1 or 10 mm distance or polymerized chemically. The DC% of the unpolymerized and polymerized adhesives was assessed using Fourier transform infrared spectroscopy. Data were analyzed using two-way ANOVA to evaluate the effect of polymerization protocol, adhesive system, and their interaction on the DC% of the self-etch adhesives. For the photo-polymerized and dual-polymerized adhesives, one-way ANOVA and Tukey HSD post hoc test was used to evaluate the effect of adhesive system within each polymerization protocol and the effect of polymerization protocol within each adhesive for the dual-polymerized adhesives (p = 0.05). Student t-test was used to compare the effect of polymerization distances within each photo-polymerized adhesive. For both photo- and dual-polymerized adhesives, the polymerization protocol and adhesive system had a significant effect on the DC (p = 0.000). The interaction between the two factors (polymerization protocol and adhesive system) revealed also a significant effect on the DC% of the different adhesives (p = 0.000). Polymerization distance of 1 mm showed significantly higher DC% compared to 10 mm distance. When the dual-polymerized adhesives were left to set chemically, they showed the lowest DC% among all polymerization protocols. DC varied depending on the chemical composition of the self-etch adhesives. The tip of the polymerization device should be positioned as close as possible to the surface to achieve higher DC% of the tested adhesives. Photo-polymerization of the dual-polymerized self-etch adhesives is a mandatory step to improve their DC.     

The sonic application of universal adhesives in self-etch mode improves their performance on enamel

The objective of this study was to evaluate the effect of sonic application of universal adhesives on the enamel microshear bond strengths (µSBS), in situ degree of conversion (DC) and etching pattern. Ninety-six extracted third molars were sectioned in four parts (buccal, lingual, proximal) and divided into 12 groups, according to the combination of 1) adhesive system (All-Bond Universal [ABU], G-Bond Plus [GBP], Prime&Bond Elect (PBE), and Scotchbond Universal Adhesive [SBU]), and 2) adhesive application mode (manual active etch-and-rinse [M-ER], manual active self-etch [M-SE], and sonic vibration self-etch [S-SE]). Specimens were stored in water at 37 °C during 24 h and tested at 1.0 mm/min (µSBS). DC was evaluated in the enamel-resin interfaces using micro-Raman spectroscopy. The enamel-etching pattern was evaluated under a field- emission scanning electron microscope. Data were analyzed with two-way ANOVA and Tukey's test (α = 0.05). S-SE application increased µSBS and DC for all universal adhesives when compared to M-SE (p < 0.05). S-SE application resulted in mean bond strengths that were statistically similar to those obtained with the respective ER application mode (p > 0.05). A deeper enamel-etching pattern was observed for all universal adhesives in the etch-and-rinse strategy. An improvement in etching ability was observed in S-SE application compared to M-SE application. In light of the improved performance of universal adhesives when applied sonically in SE mode, selective enamel etching with phosphoric acid may not be crucial for their adhesion to enamel. The sonic application of universal adhesives in self-etch mode may be a practical alternative to enamel etching.     

Evaluation of resin/dentin bonded interfaces formed by different adhesive strategies and exposed to NaOCl challenge

This study evaluated the importance of encapsulated collagen on resin/dentin interface created by different adhesive strategies. Composite build-ups were bonded to dentin using one of the following adhesive systems: Scotchbond Multi-Purpose (SBMP), Adper Scotchbond 2 (SB2), Clearfil SE (CSE) and Scotchbond SE Plus (SBSE), and cut into non-trimmed dentin–composite beams. Half of those beams were deproteinized using 10% NaOCl for 1 h and the other half was stored in water. Beams were pulled to failure and data were statistically analyzed by a two-way ANOVA and Tukey for multi-comparison test (α=0.05). Additional dentin disks were stained with Masson׳s trichrome acid and processed with light microscopy in order to identify the exposed collagen zones. All groups showed a significant reduction on bond strength after proteolytic challenge (p<0.05). Adhesive systems were ranked in the following order: SBMP>SB2=CSE>SBSE (p<0.05) for control and treated groups. Microscopy analysis showed different collagen exposed zones in relation with the adhesive strategy used. It can be concluded that collagen encapsulation affects the quality of bond interface, which is related to the adhesive system used.     

Adhesion of dual-polymerized luting cement on superficial and deep dentin using different one-step self-etch mild adhesive systems

This study evaluated adhesion of dual-polymerized resin cement to superficial dentin (SD) and deep dentin (DD) using one-step self-etch adhesives at varying pH. After smear layer was created on third molars (N?=?60, n?=?15 per group), adhesive resins, 1- Clearfil S3 Bond Plus-CBP (Kuraray) (pH: 2.3), 2- Bisco All Bond Universal-BAU (Bisco) (pH: 3.2), 3- Single Bond Universal Adhesive-SBU (3M ESPE) (pH: 2.7), 4- Nova Compo-B Plus-NCBP (Imicryl) (pH: 2.5–3), were applied on SD and DD. Resin cement (Variolink II, Ivoclar Vivadent) was adhered incrementally on the SD surfaces using polyethylene molds and photo-polymerized for 40?s from 5 directions (output: 1200?mw/cm²). After macroshear and microshear test, in order to achieve DD specimens, SD were removed 1?mm in the pulp direction and the same bonding and test procedures were performed. The specimens were kept at 37?°C for 24?h. The adhesion tests were conducted in the Universal Testing Machine and failure types were analyzed. The data were analyzed using Univariate ANOVA, Tukey`s, Kruskal-Wallis and Mann-Whitney tests (α?=?.05). Test method, dentin level and the adhesive resin significantly affected the results (MPa) (p?<?.05). After macroshear test, more incidences of cohesive failures in DD were observed with NCBP Plus. On SD, NCBP presented the highest results followed by BAU using macroshear test. On DD, NCBP presented the highest results followed by SBU. Not only the pH but the chemical composition affected adhesion especially to SD while in DD, the difference between the adhesive resins was less significant.     

The influence of endodontic sealer dentine penetration on fibreglass post retention

This study aimed to evaluate the influence of endodontic sealer inside dentinal tubules on the retention of fibreglass posts. One hundred eighty extracted teeth were instrumented with rotary instruments and divided into two groups (n = 90) according to their filling technique: (LC) lateral condensation and (CT) controlled technique, and subdivided into three subgroups according to the endodontic sealer used: (A) epoxy resin sealer, (B) zinc-oxide and eugenol sealer, and (C) bioceramic endodontic sealer. After root preparation, each subgroup received a fibreglass posts cemented with (1) adhesive resin cement, (2) self-adhesive resin cement, and (3) glass ionomer cement. After stored for 15 days at 37 °C and 100% humidity, the teeth were sectioned transversely into 1-mm thick slices and subjected to laser confocal scanning microscopy and push-out test. The failure mode was analyzed by stereo microscope, and scanning electron microscopy images of representative fractures were made. Although there were no significant differences in the dislocation resistance among the filling techniques (p > 0.05), the type of sealer used affected bond strengths on the cervical and middle thirds. Fibreglass posts cemented with glass ionomer cement presented higher values for the push-out test than those cemented with resin cements (p < 0.05). Mix failure modes were predominant and occurred in all experimental groups. The use of bioceramic endodontic sealer was able to reduce the bond strength, mainly when the fibreglass posts was cemented by resin cement.     

Effect of Etching Time on Resin-Primary Dentin Adhesion and Degradation of Interfaces

Abstract

The purpose of this research was to evaluate the resin–dentin bond degradation in primary teeth after reducing the etching time. The dentin surfaces were bonded with: an etch and rinse adhesive (single bond-SB); a two step self-etching adhesive (Clearfil self etching bond-CSEB); and a one-step self-etching adhesive (one up bond F-OUB). For half the specimens, the recommended etching time was used (the manufacturer’s instructions); for the other half the etching time was reduced by 50%. The bonded teeth were divided according to different challenging procedures: (a) 24 h storage in distilled water and sectioned into beams (1.0 mm2); (b) immersion of the bonded beams in 10% NaOCl aqueous solution for 5 h; (c) load cycled (5000 cycles, 90 N) and then sectioned into beams. The micro-tensile bond strength (MTBS) was measured and fractographic analysis performed. The data were statistically analyzed using an analysis of variance (ANOVA) technique, together with multiple comparisons tests. The results showed that the OUB produced the lowest MTBS values, regardless of the challenging procedure. After NaOCl immersion, the MTBS decreased in all groups, with the Clearfil self etching bond (immersed for half the time) attained the highest MTBS. Following the instructions for each of the adhesive systems, after load cycling, no differences in MTBS were observed in the samples after 24 h. However when the etching time was shortened, a decrease in MTBS were observed for all groups. In conclusion, shortening the etching/conditioning time caused a significant change to the bond strength which was material dependent. The OUB produced the lowest bond strengths, regardless of other variables; and a reduced conditioning time resulted in an increased bond strength for CSEB adhesive.     

Influence of different surface treatments on zirconia/resin shear bond strength using one-bottle universal adhesive

ABSTRACT

This study was designed to evaluate the effect of different treatments on the zirconia/resin shear bond strength (SBS) using commercial one-bottle universal adhesive. Zirconia discs with different surface treatments (blank control; airborne-particle-abrasion; glazing) were bonded to the bovine enamel surfaces using one-bottle universal adhesive. All specimens were tested for SBS (MPa) before and after 10000 thermocycles. Statistically analysis were conducted by using one-way analysis of variance and multiple-comparison least significant difference tests (α = 0.05). Airborne-particle-abrasion group showed higher SBS (36.19 ± 11.86) than control group (14.98 ± 5.90) and glazing group (10.63 ± 5.39) (p < 0.05). After thermocycling test, the SBS significantly decreased for control group (8.84 ± 2.55) and glazing group (6.18 ± 2.78) while not for airborne-particle-abrasion group (41.5 ± 7.95). One-bottle universal adhesives combined with airborne-particle-abrasion showed quite high SBS of zirconia/resin, which was appropriate for bonding of zirconia restoration.     

In vitro degradation and cytotoxicity of alkyl 2‐cyanoacrylate polymers for application to tissue adhesives

To investigate the in vitro degradability and cytotoxicity of long alkyl cyanoacrylate polymers [polycyanoacrylates (PCAs)], we synthesized five kinds of alkyl cyanoacrylates (ethyl, 2‐octyl, n‐octyl, ethylhexyl, and ethyl cyanoacryloyllactate). In vitro degradation in buffer solutions and cell cultures for cytotoxicity were performed with PCAs prepared by various polymerization methods. Lower alkyl homologues such as ethyl cyanoacrylate revealed a higher tissue toxicity than higher alkyl homologues. The amounts of formaldehyde released from various PCAs were not proportional to the rate of degradation. The apparent form of the cyanoacrylate polymers greatly affected the degradation rate, as the powdery polymers degraded much more quickly than the films. A new biodegradable polymer, prepared from ethyl 2‐cyanoacryloyllactate, degraded more quickly than the others. The amount of formaldehyde released from the polymer degradation was high because it degraded rapidly. It was observed from cell culture experiments that the viability of the cells was higher with a lower release of formaldehyde because the alkyl side groups were bigger. Therefore, octyl cyanoacrylate polymers demonstrated lower amounts of formaldehyde by degradation and higher cell viability, and these monomers may be desirable for use as tissue adhesives. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 3272–3278, 2003     

Strength, deformation and relaxation of joints bonded with modified cyanoacrylate adhesives

The introduction of high molecular weight poly(methyl methacrylate) or poly(butadiene-co-acrylonitrile) into ethyl 2-cyanoacrylate produced viscous adhesives with a homogeneous or heterogeneous structure after cure. Steel joints bonded with these adhesives are shown to have improved tensile shear strength, deformability and stress relaxation of bonds compared with pure cyanoacrylate adhesive. Poly(methyl methacrylate)-modified adhesive is recommended for static load-bearing joints while poly(butadiene-co-acrylonitrile)-modified adhesive is more suited to cyclic or vibrating loads.     

The bonding effect of adhesive systems and bulk-fill composites to sound and caries-affected dentine

Purpose: To investigate the influence of adhesive type and increment thickness on shear bond strength of flowable bulk-fill resin composites compared with a flowable conventional resin composite, in both sound and caries-affected dentine.

Methods: Shear bond strength was tested in 100 extracted human molars with coronal dentine caries. Half of the teeth were restored with Adper? Easy Bond and the other half with Adper? Single Bond Plus. Bonded surfaces were restored with Filtek? Ultimate Flow and two bulk-fill composites (SDR and X-tra base) (n = 10 teeth for each subgroup). Restorations of 4 mm were performed with incremental or bulk-fill technique. The shear bond was determined and statistically analysed using three-way ANOVA and Bonferroni multiple comparison post hoc tests (p ≤ 0.05). Dentine–resin interfaces were evaluated by scanning electron microscopy.

Results: For both adhesives, the highest shear bond strength values were obtained for sound dentine. In sound dentine, the highest bond strength observed with Easy Bond when used in 2-mm increments of SDR. In caries-affected dentine, Single Bond in combination with SDR displayed significantly lower bond strength.

Conclusion: There was no significant difference in shear bond strength between the incremental and bulk-fill groups for molars with sound dentine when the etch-and-rinse adhesive system was used; however, for the self-etch adhesive system, incremental application caused higher bond strength than bulk application.     

Effects of chemical and physico-chemical surface conditioning methods on the adhesion of resin composite to different mineral trioxide aggregate based cements

This study investigated the adhesion of resin composite to mineral trioxide aggregate based cements after different chemical and physico-chemical surface conditioning methods. Mineral trioxide aggregate based cements (Biodentine, ProRoot MTA, Imicryl MTA) were embedded in Teflon disks (N?=?180). After storing at 37?°C at 100% humidity for 72?h, substrate surfaces were polished using silicon carbide papers. Specimens were allocated to 3 groups to be conditioned with one of the following (n?=?15 per group): a) Adhesive resin (Clearfil SE Bond, CSE), b) Adhesive resin (Adper Single Bond 2, SB2), c) air-abrasion with 30?μm alumina coated with silica?+?silane?+?adhesive resin (ALB), d) no surface conditioning, control group (CON). Microhybrid resin composite (Filtek Z250) was applied on the conditioned substrate surfaces and photo-polymerized. After storage at 37?°C at 100% humidity for 24?h, adhesive interfaces were loaded under shear (1?mm/min) in a universal testing machine. After debonding failure types were analyzed. Data were analyzed using 2-way ANOVA and Tukey’s test (alpha = 0.05). SBS results were significantly affected by surface conditioning (p?<?0.05) and materials (p?<?0.05). Interaction terms were significant (p?<?0.05). Biodentine-ALB resulted in significantly higher SBS values (3.96?±?1.24) compared to those of other combinations, while ALB and SB2 resulted in no significant difference for ProRoot MTA and Imicryl MTA (p?>?.05). CSE (1.36?±?0.5- 1.98?±?0.76) did not significantly increase SBS for all MTA materials compared to the control group (0.8?±?0.52 – 2?±?0.91) (p?>?9.05). While CON groups resulted in exclusively adhesive failures, ALB presented the highest incidence of mixed failures for all materials tested (60–100%).     

Mechanical behavior of polyurethane adhesive bonded joints as a function of temperature and humidity

The temperature and humidity were found to be the most effective parameters in the behavior of polyurethane flexible adhesive bonded aluminum joints. In order to obtain the effect of environment on bond strength, toughness, failure displacement, joints stiffness and failure model, in this work, aluminum single-lap joints were tested under various temperatures (25, 40, 60 and 80 °C) and relative humidity (RH, 55, 65, 75, 85, 95 and 99%) using an environmental chamber. The results showed that as the humidity increased from 55 to 99%, bond strength decreased as linear function. As the temperature increased from 25 to 80 °C, the bond strength decreased as exponential function. The joints stiffness reduced gradually with the increase of temperature and humidity. The analysis of the failure section of the ageing joints showed that the humidity caused the transition of the failure model, and the increase of the temperature promoted the change of the failure model. Besides, at low humidity (55 and 65%), failure displacement decreased gradually with the increase of temperature, and at high humidity (95 and 99%), failure displacement increased. This study will help engineers design a reliable, safe and effective bonding structure. And it is conducive to solve the problem of joint strength degradation in the hygrothermal environment.     

Effect of root canal sealers on the push-out bond strengths of tooth-colored posts to root dentine

Objectives: This study evaluated the effect of different root canal sealers on the push-out bond strength of tooth-colored posts to root dentin. Material and methods: Eighty human mandibular premolar teeth with single roots were decoronated and randomly divided into two groups according to post material: G1–G5: Cytec blanco; G6–G10: Cosmopost. In each group, the specimens were further subgrouped according to the filling material plus sealer (n = 8): G1, G6: Gutta-percha + AH Plus; G2, G7: Resilon + Epiphany SE; G3, G8: Gutta-percha + Sealite; G4, G9: Gutta-percha + iRoot SP; and G5, G10: control (unobturated). Cytec blanco and Cosmopost of 1.4 mm diameter were adhesively luted to samples using Variolink II. Push-out test was performed in a universal testing machine, and failure modes were examined under stereomicroscope. Data were analyzed with the two-way ANOVA and post hoc Tukey’s tests. Statistical significance was set to 0.05. Results: Roots obturated with AH Plus (3.48 ± 1.41 MPa), Sealite (3.47 ± 0.65 MPa), and Resilon (3.36 ± 1.23 MPa) had the lowest bond strength (p < 0.005). iRoot SP and control group samples showed the highest bond strength values (7.38 ± 0.89 MPa and 6.43 ± 1.16 MPa, respectively) (p < 0.05). Significant differences were observed among tooth-colored posts and sealers (p < 0.05). Adhesive failures were predominant in all groups (48%). Conclusions: When the resin cement Variolink II was used, the types of root canal filling materials and sealers could affect the retentions of the fiber/zirconium posts; the fiber post revealed the higher bond values than the zirconium post; and the calcium silicate-based sealer (iRoot SP) revealed the highest bond strengths.     

In situ paired electrooxidative degradation of formaldehyde with electrogenerated hydrogen peroxide and hypochlorite ion

Formaldehyde was degraded with hydrogen peroxide and hypochlorite ion electrogenerated by paired electrolysis of dissolved oxygen and chloride ion in aqueous solution. Degradation of formaldehyde in the cathodic compartment was significantly affected by the ratio of electrolyte volume to cathodic surface area, oxygen sparging rate and stirring rate. The model calculations correlated sufficiently well with the experimental results. The average current efficiency and degradation fraction of the in situ paired electrooxidative degradation of formaldehyde were experimentally found to be 62.0% and 93.2%, respectively.