Self-mated tribological systems based on multilayer micro/nanocrystalline CVD diamond coatings

The tribological response of multilayer micro/nanocrystalline diamond coatings grown by the hot filament CVD technique is investigated. These multigrade systems were tailored to comprise a starting microcrystalline diamond (MCD) layer with high adhesion to a silicon nitride (Si3N4) ceramic substrate, and a top nanocrystalline diamond (NCD) layer with reduced surface roughness. Tribological tests were carried out with a reciprocating sliding configuration without lubrication. Such composite coatings exhibit a superior critical load before delamination (130–200 N), when compared to the mono- (60–100 N) and bilayer coatings (110 N), considering ∼10 µm thick films. Regarding the friction behaviour, a short-lived initial high friction coefficient was followed by low friction regimes (friction coefficients between 0.02 and 0.09) as a result of the polished surfaces tailored by the tribological solicitation. Very mild to mild wear regimes (wear coefficient values between 4.1×10−8 and 7.7×10−7 mm3 N−1 m−1) governed the wear performance of the self-mated multilayer coatings when subjected to high-load short-term tests (60–200 N; 2 h; 86 m) and medium-load endurance tests (60 N; 16 h; 691 m).

Novel adhesive systems based on neoprene-phenolic blends

The aim of the investigation is to develop new high performance adhesive systems based on neoprene-phenolic blends. Initially the effect of addition of all possible ingredients like fillers, adhesion promoters, curing agents and their optimum compositions to neoprene solution is investigated. The phenolic resin used is a copolymer of phenol-cardanolformaldehyde prepared in the laboratory. The optimum ratio between phenol and cardanol that gives the maximum bond strength in metal-metal, rubber-rubber and rubber-metal specimens has been identified. Further the ratio between total phenols and formaldehyde is also optimised. The above adhesive system is further modified by the addition of epoxidized phenolic novolacs. For this purpose, phenolic novolac resins are prepared in different stoichiometric ratios and are subsequently epoxidized. The effectiveness of the adhesive for bonding different metal and rubber substrates is another part of the study. To study the ageing behaviour, different bonded specimens are exposed to high temperature, hot water and salt water and adhesive properties have been evaluated. The synthesized resins have been characterized by FTIR , HNMR spectroscopy. The molecular weights of the resins have been obtained by GPC. Thermogravimetric analysis and differential scanning calorimetry are used to study the thermal properties. The fractured surface analysis is studied by scanning electron microscopy. The study has brought to light the influence of phenol/ formaldehyde stoichiometric ratio, addition of cardanol (a renewable resource), adhesion promoters and suitability of the adhesive for different substrates and the age resistance of adhesive joints among other things.

Direct pulp capping with a self-etching adhesive system: Histopathologic evaluation in dogs` teeth

Objective. This study evaluated histopathologically the response of pulp and periradicular tissues after pulp capping with an all-in-one self-etching adhesive system in dogs` teeth. Study design. Forty teeth of 4 dogs were assigned to 3 groups according to the pulp capping material: G1 (n = 20): self-etching adhesive system; G2 (n = 10): Ca(OH)(2); G3 (n = 10): zinc oxide-eugenol. The animals were killed 7 and 70 days after pulp capping. The pieces containing the pulp-capped teeth were removed and processed for histologic analysis. Results. At 7 days, no dentin bridge formation was observed; G1 and G3 exhibited inflammatory pulpal alterations, whereas G2 presented only mild inflammatory infiltrate in the pulp tissue adjacent to the capping material, the remainder being intact. At 70 days, no specimen in G1 or G3 presented dentin bridge formation. The remaining pulp tissue exhibited severe inflammatory alterations and areas of necrosis. In G2, all specimens showed dentin bridge formation and absence of inflammation and mineralized tissue resorption. No bacteria were identified using Brown and Brenn staining techniques in all 3 groups at any observation period. Conclusion. According to the conditions of this study, direct pulp capping with the self-etching adhesive system did not allow pulp tissue repair and failed histopathologically in 100% of the cases. (Oral Surg Oral Med Oral Pathol Oral Radiol Endod 2009; 108: e34-e40)

Hybrid layer thickness and resin tag length of a self-etching adhesive bonded to sound dentin

Objectives: the purpose of this study is to employ optical microscopy to measure the thickness of the hybrid layer and the penetration (tags) of an aggressive self-etching adhesive system into sound dentin.Methods: occtusat cavities were prepared in 40 extracted human posterior teeth. The prepared teeth were randomly assigned to four experimental groups with 10 specimens each. The self-etching adhesive system Adper Prompt L-Pop was applied to the dentin surface as follows: Group 1: cavosurface enamel was etched for 60 s and dentin for 20 s with 35% phosphoric acid get, immediately followed by application of the self -etching adhesive with a brush to the entire cavity for 15 s; Groups 2, 3, and 4: no pre-etching was performed, and the self -etching adhesive was applied to both enamel and dentin for 15, 30 and 45 s, respectively. After curing, the cavities were fitted with composite resin Fittek Z250. Afterwards, the teeth were decalcified and the restorations were carefully removed for later embedding in paraffin. The specimens were serially sectioned at 6 mu m of thickness and sequentially mounted in glass slides. These sections were stained with Brown and Brenn staining for posterior analysis and measurement of the hybrid layer and resin tags on a tight microscope with a micrometric ocular 40/075. The results were submitted to analysis of variance at the 5% level.Results: whenever there was significance, the Tukey test was applied at the 5% level. The specimens receiving application of acid etching before the selfetching. adhesive displayed a larger thickness of the hybrid layer; on the other hand, specimens receiving only application of the self -etching adhesive on dentin for 15, 30 and 45 s exhibited similar thickness of the hybrid layer. As regards the resin tags, no statistically significant differences could be found between the study groups.Conclusions: it could be concluded that the increase in the time of application of the self-etching adhesive Adper Prompt L-Pop did not significantly influence the formation and thickness of hybrid layer, as well as its penetration into the sound dentin surface. (c) 2005 Elsevier Ltd. All rights reserved.

Influence of the activation mode of a self-etch resin-based luting cement upon the metabolism of odontoblast-like cells

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Direct pulp capping with a self-etching adhesive system: Histopathologic evaluation in dogs' teeth

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Bond strength of Epiphany (TM) Sealer combined with different adhesive systems photo-activated with LED and QTH

The Epiphany (TM) Sealer is a new dual-curing resin-based sealer and has been introduced as an alternative to gutta-percha and traditional root canal sealers. The canal filling is claimed to create a seal with the dentinal tubules within the root canal system producing a 'monoblock' effect between the sealer and dentinal tubules. Therefore, considering the possibility to incorporate the others adhesive systems, it is important to study the bond strength of the resulting cement. Forty-eight root mandibular canines were sectioned 8-mm below CEJ. The dentine discs were prepared using a tapered diamond bur and irrigated with 1% NaOCl and 17% EDTA. Previous the application Epiphany (TM) Sealer, the Epiphany (TM) Primer, AdheSE, and One Up Bond F were applied to the root canal walls. The LED and QTH (Quartz Tungsten Halogen) were used to photo-activation during 45 s with power density of 400 and 720 mW/cm(2), respectively. The specimens were performed on a universal testing machine at a cross-head speed of 1 mm/min until bond failure occurred. The force was recorded and the debonding values were used to calculate Push-out bond strength. The analysis of variance (ANOVA) and Tukey's post-hoc tests showed significant statistical differences (P < 0.05) to Epiphany (TM) Sealer/Epiphany (TM) Primer/QTH and EpiphanyTM Sealer/AdheSE/QTH, which had the highest mean values of bond strength. The efficiency of resin-based filling materials are dependent the type of light curing unit used including the power density, the polymerization characteristics of these resin-based filling materials, depending on the primer/adhesive used.

Bond Strength of Two Resin Cements on Dentin Using Different Cementation Strategies

Purpose:This study evaluated the microtensile bond strength of two resin cements to dentin either with their corresponding self-etching adhesives or employing the three-step etch-and-rinse technique. The null hypothesis was that the etch-and-rinse adhesive system would generate higher bond strengths than the self-etching adhesives.Materials and Methods:Thirty-two human molars were randomly divided into four groups (N = 32, n = 8/per group): G1) ED Primer self-etching adhesive + Panavia F; G2) All-Bond 2 etch-and-rinse adhesive + Panavia F; G3) Multilink primer A/B self-etching adhesive + Multilink resin cement; G4) All-Bond 2 + Multilink. After cementation of composite resin blocks (5 x 5 x 4 mm), the specimens were stored in water (37 degrees C, 24 hours), and sectioned to obtain beams (+/- 1 mm2 of adhesive area) to be submitted to microtensile test. The data were analyzed using 2-way analysis of variance and Tukey's test (alpha = 0.05).Results:Although the cement type did not significantly affect the results (p = 0.35), a significant effect of the adhesive system (p = 0.0001) was found on the bond strength results. Interaction terms were not significant (p = 0.88751). The etch-and-rinse adhesive provided significantly higher bond strength values (MPa) with both resin cements (G2: 34.4 +/- 10.6; G4: 33.0 +/- 8.9) compared to the self-etching adhesive systems (G1: 19.8 +/- 6.6; G3: 17.8 +/- 7.2) (p < 0.0001). Pretest failures were more frequent in the groups where self-etching systems were used.Conclusion:Although the cement type did not affect the results, there was a significant effect of changing the bonding strategy. The use of the three-step etch-and-rinse adhesive resulted in significantly higher bond strength for both resin cements on dentin.CLINICAL SIGNIFICANCEDual polymerized resin cements tested could deliver higher bond strength to dentin in combination with etch-and-rinse adhesive systems as opposed to their use in combination with self-etching adhesives.(J Esthet Restor Dent 22:262-269, 2010).

Evaluation of the shear bond strength of a composite resin in sound, demineralized and hypermineralized bovine dentin after irradiation with Er:YAG and Nd:YAG lasers, employing a self-etching adhesive system

Background and Objectives. The adhesion of dental materials is important for the success of treatment. The aim of this study is to evaluate the bond strength of a composite resin applied with a self-etching adhesive system in different dentins after irradiation with Er:YAG and Nd:YAG lasers, observing their morphologic pattern using Scanning Electronic Microscopy (SEM). Materials and Methods. The buccal surface of 72 bovine incisors was worn until exposure of medium depth dentin. The specimens were divided into three groups; GI: normal, GII: demineralized and GIII: hypermineralized dentin. These were also divided into two subgroups; A-irradiated for 30 s with Er:YAG laser in noncontact mode at 40 mJ and 6 Hz and B- irradiated for 30 s with Nd:YAG laser in contact mode at 60 mJ and 10 Hz. The adhesive system Clearfil SE. Bond (Kuraray) and composite resin Tetric Ceram (Vivadent) were applied on the irradiated area by the incremental technique. After storage for 24 h in distilled water at 37 degrees C, the specimens were submitted to the shear strength test in a universal testing machine (EMIC) at a crosshead speed of 1.0 mm/min. Other specimens were made to be analyzed by SEM. Results. The results were statistically analyzed by Analysis of Variance and the Tukey test. Regardless of the type of dentin, the bond strength of specimens irradiated with the Nd:YAG laser (8,94 +/- 2,07) was higher compared to specimens irradiated with the Er:YAG laser (7,03 +/- 2,47); the highest bond strength was obtained for the group of hypermineralized dentin irradiated with the Nd:YAG laser. The SEM analysis showed that the Er:YAG laser caused opening of tubules and the Nd:YAG laser produced areas of fusion as well as regions of opening of dentinal tubules. Conclusions. The dentin showed different morphological patterns and the laser promote alterations on their surfaces, influencing the bond strength of the composite resin. (C) 2010 Laser Institute of America.

BOND STRENGTH DURABILITY of SELF-ETCHING ADHESIVES and RESIN CEMENTS TO DENTIN

Objectives: To evaluate the microtensile bond strength (mu TBS) of one-(Xeno III, Dentsply) and two-step (Tyrian-One Step Plus, Bisco) self-etching adhesive systems bonded to dentin and cemented to chemically cured (C&B Metabond) or light-cured paste of a dual-cure resin cement (Variolink II, Ivoclar) within a short (24 h) and long period of evaluation (90 days). Material and Methods: Forty recently extracted human molars had their roots removed and their occlusal dentin exposed and ground wet with 600-grit SiC paper. After application of one of the adhesives, the resin cement was applied to the bonded surface and a composite resin block was incrementally built up to a height of 5 mm (n = 10). The restored teeth were stored in distilled water at 37 C for 7 days. The teeth were then cut along two axes (x and y), producing beam-shaped specimens with 0.8 mm(2) cross-sectional area, which were subjected to mu TBS testing at a crosshead speed of 0.05 mm/min and stressed to failure after 24 h or 90 days of storage in water. The mu TBS data in MPa were subjected to three-way analysis of variance and Tukey's test (alpha = 0.05). Results: The interaction effect for all three factors was statistically significant (three-way ANOVA, p < 0.001). All eight experimental means (MPa) were compared by the Tukey's test (p < 0.05) and the following results were obtained: Tyrian-One Step Plus /C&B/24 h (22.4 +/- 7.3); Tyrian-One Step Plus /Variolink II/24 h (39.4 +/- 11.6); Xeno III/C&B/24 h (40.3 +/- 12.9); Xeno III/Variolink II/24 h (25.8 +/- 10.5); Tyrian-One Step Plus / C&B/90 d (22.1 +/- 12.8) Tyrian-One Step Plus/VariolinkII/90 d (24.2 +/- 14.2); Xeno III/C&B/90 d (27.0 +/- 13.5); Xeno III/Variolink II/90 d (33.0 +/- 8.9). Conclusions: Xeno III/Variolink II was the luting agent/adhesive combination that provided the most promising bond strength after 90 days of storage in water.