Influence of Er,Cr: YSGG laser on bond strength of self-adhesive resin cement

The purpose of this study was to investigate the bond strength of fiber post previously laser treated root canals. Forty single-rooted bovine teeth were endodontically treated, randomly and equally divided into two main groups according to the type of pretreatment: G1: 2.5% NaOCl (control group); and G2: Er,Cr:YSGG laser. Each group was further subdivided into 2 groups based on the category of adhesive systems/ luting materials used: a: an etch-and-rinse resin cement (Single Bond/RelyX ARC; 3M ESPE), and b: a self-adhesive resin cement (Rely X Unicem; 3M ESPE). Three 1.5 mm thick slabs were obtained per root and the push-out test was performed at a crosshead speed of 0.5 mm/min until post dislodgement occurred. Data were analyzed by ANOVA and post-hoc Tukey's test at a pre-set alpha of 0.05. Analysis of variance showed no statistically significant difference (p > 0.05) among the groups G1a (25.44 ± 2.35) and G1b (23.62 ± 3.48), G2a (11.77 ± 2.67) and G2b (9.93 ± 3.37). Fractures were observed at the interface between the dentin and the resin in all groups. The Er,Cr:YSGG laser irradiation did not influence on the bond strength of the resin cements and the etch-and-rinse resin cement had better results on bond strength than self-adhesive resin cement.

Bond strength of different endodontic sealers to dentin: push-out test

Objective: The aim of this in vitro study was to evaluate the bond strength of different root canal sealers to dentin. Material and Methods: Forty extracted single-rooted human teeth were examined and the coronal and middle thirds of the canals were prepared with a 1.50 mm post drill (FibreKor Post System, Pentron). The teeth were allocated in two experimental groups, irrigated with 2.5% NaOCl+17% EDTA or saline solution (control group) and instrumented using Race rotary files (FKG) to a size #40 at the working length. Then, the groups were divided into four subgroups and filled with Epiphany sealer (Group 1), EndoREZ (Group 2), AH26 (Group 3) and Grossman's Sealer (Group 4). After 2 weeks of storage in 100% humidity at 37 degrees C, all teeth were sectioned transversally into 2-mm-thick discs. Push-out tests were performed at a cross-head speed of 1 mm/min using a universal testing machine. The maximum load at failure was recorded and expressed in MPa. Results: Means (+/- SD) in root canals irrigated with 2.5% NaOCl and 17% EDTA were: G1 (21.6 +/- 6.0), G2 (15.2 +/- 3.7), G3 (14.6 +/- 4.5) and G4 (11.7 +/- 4.1). Two-way ANOVA and Tukey's test showed the highest bond strength for the Epiphany's group (p < 0.01) when compared to the other tested sealers. Saline solution decreased the values of bond-strength (p < 0.05) for all sealers. Conclusion: Epiphany sealer presented higher bond strength values to dentin in both irrigating protocols, and the use of 2.5% NaOCl and 17% EDTA increased the bond strength values for all sealers.

Factors affecting on bond strength of glass fiber post cemented with different resin cements to root canal

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Nd:YAG Laser Irradiation of Etched/Unetched Dentin Through an Uncured Two-step Etch-and-Rinse Adhesive and its Effect on Microtensile Bond Strength

Purpose: To evaluate whether Nd:YAG laser irradiation of etched and unetched dentin through an uncured adhesive affected the microtensile bond strength (pTBS).Materials and Methods: Flat dentin surfaces were created in 19 extracted human third molars. Adper Single Bond (SB) adhesive was applied over etched (groups 1 to 3) or unetched dentin (groups 4 to 6). The dentin was then irradiated with a Nd:YAG laser through the uncured adhesive, using 0.75 or 1 W power settings, except for the control groups (groups 1 and 4). The adhesive was light cured and composite crowns were built up. After 24 h, the teeth were sectioned into beams, with cross-sectional areas of 0.49 mm(2), and were stressed under tension. Data were statistically analyzed using two-way ANOVA and Tukey's test (alpha = 5%). Dentin surfaces of fractured specimens and the interfaces of untested beams were observed under scanning electron microscopy (SEM).Results: Acid etching, laser irradiation, and their interaction significantly affected bonding (p < 0.05). Laser irradiation did not improve bonding of etched dentin to resin (p > 0.05). However, higher pTBS means were found on unetched lased dentin (groups 5 and 6), but only in comparison to group 4, where neither lasing nor etching was performed. Groups 4 to 6 showed the lowest pTBS means among all groups tested (p < 0.05). Laser irradiation did not change the characteristics of the hybrid layers created, while solidification globules were observed on lased dentin surfaces under SEM.Conclusion: Laser irradiation of dentin through the uncured adhesive did not significantly improve the pTBS in comparison to the suggested manufacturer's technique.

Phospholipase A(2) myotoxins from Bothrops snake venoms: Structure-function relationship

Phospholipases A(2) constitute the major components from Bothrops snake venoms and have been extensively investigated not only because they are relatively very abundant in these venoms but mainly because they display a range of many relevant biological effects, including: myotoxic, cytotoxic, edema-inducing, artificial membrane disrupting, anticoagulant, neuromuscular, platelet aggregation inhibiting, hypotensive, bactericidal, anti-HIV, anti-tumoural, anti-malarial and anti-parasitic. The primary structures of several PLA(2)s have been elucidated through direct amino acid sequencing or, inderectly, through the corresponding nucleotide sequencing. Two main subgroups were thus described: (i) Asp49 PLA(2)s, showing low (basic, highly myotoxic) to relatively high (acidic, less or non myotoxic) Ca++-dependent hydrolytic activity upon artificial substrates; (ii) Lys49 PLA(2)s (basic, highly myotoxic) , showing no detectable hydrolytic activity on artificial substrates. Several crystal structures of Lys49 PLAs from genus Bothrops have already been solved, revealing very similar fold patterns. Lack of catalytic activity of myotoxic Lys49-PLA(2)s, first related solely with the fact that Lys49 occupies the position of the calcium ion in the catalyticly active site of Asp49 PLA(2)s, is now also attributed to Lys122 which interacts with the carbonyl of Cys29 hyperpolarising the peptide bond between Cys29 and Gly30 and trapping the fatty acid product in the active site, thus interrupting the catalytic cycle. This hypothesis, supported for three recent structures, is also discussed here. All Asp49 myotoxins showed to be pharmacologically more potent when compared with the Lys49 variants, but phospholipid hydrolysis is not an indispensable condition for the myotoxic, cytotoxic, bactericidal, anti-HIV, anti-parasitic, liposome disrupting or edema-inducing activities. Recent studies on site directed mutagenesis of the recombinant Lys49 myotoxin from Bothrops jararacussu revealed the participation of important amino acid residues in the membrane damaging and myotoxic activities.

Crystal structure of a myotoxic Asp49-phospholipase A(2) with low catalytic activity: Insights into Ca2+ -independent catalytic mechanism

A myotoxic Asp49-phospholipase A(2) (Asp49-PLA(2)) with low catalytic activity (BthTX-II from Bothrops jararacussu venom) was crystallized and the molecular-replacement solution has been obtained with a dimer in the asymmetric unit. The quaternary structure of BthTX-II resembles the myotoxic Asp49-PLA2 PrTX-III (piratoxin III from B. pirajai venom) and all non-catalytic and myotoxic dimeric Lys49-PLA(2)s. Despite of this, BthTX-II is different from the highly catalytic and non-myotoxic BthA-I (acidic PLA(2) from B. jararacussu) and other Asp49-PLA(2)s. BthTX-II structure showed a severe distortion of calcium-binding loop leading to displacement of the C-terminal region. Tyr28 side chain, present in this region, is in an opposite position in relation to the same residue in the catalytic activity Asp49-PLA(2)s, making a hydrogen bond with the atom 0 delta 2 of the catalytically active Asp49, which should coordinate the calcium. This high distortion may also be confirmed by the inability of BthTX-II to bind Na+ ions at the Ca2+-binding loop, despite of the crystallization to have occurred in the presence of this ion. In contrast, other Asp49-PLA(2)s which are able to bind Ca2+ ions are also able to bind Na+ ions at this loop. The comparison with other catalytic, non-catalytic and inhibited PLA(2)s indicates that the BthTX-II is not able to bind calcium ions; consequently, we suggest that its low catalytic function is based on an alternative way compared with other PLA(2)s. (c) 2008 Elsevier B.V All rights reserved.

Crystal structure of a phospholipase A(2) homolog complexed with p-bromophenacyl bromide reveals important structural changes associated with the inhibition of myotoxic activity

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

Effect of Cement Type, Relining Procedure, and Length of Cementation on Pull-out Bond Strength of Fiber Posts

Introduction: As opposed to the cementation metal posts, the cementation of fiber posts has several details that can significantly influence the success of post retention. This study evaluated the effect of the relining procedure, the cement type, and the luted length of the post on fiber posts retention. Methods: One hundred eighty bovine incisors were selected to assess post retention; after endodontic treatment, the canals were flared with diamonds burs. Post holes were prepared in lengths of 5, 7.5, and 10 mm; the fiber posts were relined with composite resin and luted with RelyX ARC, RelyX Unicem, or RelyX Luting 2. All cements are manufactured by 3M ESPE (St. Paul, MN). Samples were subjected to a pull-out bond strength test in a universal testing machine; the results (N) were submitted to a three-way analysis of variance and the Tukey post hoc test (alpha = 0.05). Results: The improvement of post retention occurred with the increase of the post length luted into the root canal; the relining procedure improved the pull-out bond strength. RelyX Unicem and RelyX ARC showed similar values of retention, both showing higher values than RelyX Luting 2. Conclusion: Post length, the reining procedure, and the cement type are all important factors for improving the retention of fiber posts. (J Endod 2010;36:1543-1546)

INFLUENCE of DIFFERENT SURFACE CONDITIONING PROTOCOLS on MICROTENSILE BOND STRENGTH of SELF-ADHESIVE RESIN CEMENTS TO DENTIN

Statement of problem. According to manufacturers, bonding with self-adhesive resin cements can be achieved without any pretreatment steps such as etching, priming, or bonding. However, the benefit of saving time with these simplified luting systems may be realized at the expense of compromising the bonding capacity.Purpose. The purpose of this study was to assess whether different dentin conditioning protocols influence the bond performance of self-adhesive resin cements to dentin.Material and methods. Flat dentin surfaces from 48 human molars were divided into 4 groups (n=12): 1) control, no conditioning; 2) H(3)PO(4), etching with 37% H(3)PO(4) for 15 seconds; 3) SEBond, bonding with self-etching primer adhesive (Clearfil SE Bond); and 4) EDTA, etching with 0.1M EDTA for 60 seconds. The specimens from each dentin pre-treatment were bonded using the self-adhesive cements RelyX Unicem, Maxcem or Multilink Sprint (n=4). The resin-cement-dentin specimens were stored in water at 37 degrees C for 7 days, and serially sectioned to produce beam specimens of 1.0 mm(2) cross-sectional area. Microtensile bond strength (mu TBS) testing was performed at 1.0 mm/min. Data (MPa) were analyzed by 2-way ANOVA and Tukey multiple comparisons test (alpha=.05). Fractured specimens were examined with a stereomicroscope (x40) and classified as adhesive, mixed, or cohesive. Additional bonded interfaces were evaluated under a scanning electron microscope (SEM).Results. Cement-dentin mu TBS was affected by the dentin conditioning approach (P <.001). RelyX Unicem attained statistically similar bond strengths to all pre-treated dentin surfaces. H(3)PO(4)-etching prior to the application of Maxcem resulted in bond strength values that were significantly higher than the other groups. The lowest mu TBS were attained when luting Multilink Sprint per manufacturers' recommendations, while H(3)PO(4)-etching produced the highest values followed by Clearfil SE bonding and EDTA. SEM observations disclosed an enhanced potential of the self-adhesive cements to form a hybrid layer when applied following manufacturer's instructions.Conclusions. When evaluated self-adhesive resin cements are used, selectively etching dentin with H(3)PO(4) prior to luting results in the most effective bonding. (J Prosthet Dent 2011;105:227-235)

Does Adhesive Resin Application Contribute to Resin Bond Durability on Etched and Silanized Feldspathic Ceramic?

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

The Influence of Cutting Speed and Cutting Initiation Location in Specimen Preparation for the Microtensile Bond Strength Test

Purpose: This study evaluated the effect of cutting initiation location and cutting speed on the bond strength between resin cement and feldspathic ceramic.Materials and Methods: Thirty-six blocks (6.4 x 6.4 x 4.8 mm) of ceramic (Vita VM7) were produced. The ceramic surfaces were etched with 10% hydrofluoric acid gel for 60 s and then silanized. Each ceramic block was placed in a silicon mold with the treated surface exposed. A resin cement (Variolink II) was injected into the mold over the treated surface and polymerized. The resin cement-ceramic blocks were divided into two groups according to experimental conditions: a) cutting initiation location - resin cement, ceramic and interface; and b) cutting speed - 10,000, 15,000, and 20,000 rpm. The blocks were sectioned to achieve non-trimmed bar specimens. The microtensile test was performed in a universal testing machine (1 mm/min). The failure modes were examined using an optical light microscope and SEM. Bond strength results were analyzed using one-way ANOVA and Tukey's test (alpha = 0.05).Results: Significant influences of cutting speed and initiation location on bond strength (p < 0.05) were observed. The highest mean was achieved for specimens cut at 15,000 rpm at the interface (15.12 +/- 5.36 MPa). The lowest means were obtained for specimens cut at the highest cutting speed in resin cement (8.50 +/- 3.27 MPa), and cut at the lowest cutting speed in ceramic (8.60 +/- 2.65MPa). All groups showed mainly mixed failure (75% to 100%).Conclusion: The cutting speed and initiation location are important factors that should be considered during specimen preparation for microtensile bond strength testing, as both may influence the bond strength results.

Evaluation of thermal compatibility between core and veneer dental ceramics using shear bond strength test and contact angle measurement

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Effect of Acid Neutralization and Mechanical Cycling on the Microtensile Bond Strength of Glass-ceramic Inlays

Objectives: To evaluate the hypothesis that a process of hydrofluoric acid precipitate neutralization and fatigue load cycling performed on human premolars restored with ceramic inlays had an influence on microtensile bond strength results (MTBS). Methods: MOD inlay preparations were performed in 40 premolars (with their roots embedded in acrylic resin). Forty ceramic restorations were prepared using glass-ceramic (IPS Empress). The inner surfaces of all the restorations were etched with 10% hydrofluoric acid for 60 seconds, rinsed with water and dried. The specimens were divided into two groups (N=20): 1-without neutralization; 2-with neutralization. All the restorations were silanized and adhesively cemented (self-curing and self-etching luting composite system, Multilink). Ten premolars from each group were submitted to mechanical cycling (1,400,000 cycles, 50N, 37 degrees C). After cycling, the samples were sectioned to produce non-trimmed beam specimens (vestibular dentin-restoration-lingual dentin set), which were submitted to microtensile testing. Results: Bond strength was significantly affected by the surface treatment (p<0.0001) (no neutralization > neutralization) and mechanical cycling (p<0.0001) (control > cycling) (2-way ANOVA and Tukey test, alpha=.05). Conclusion: Hydrofluoric acid precipitate neutralization appears to significantly damage the resin bond to glass-ceramic and should not be recommended. The clinical simulation of the specimens, by using mechanical cycling, is important when evaluating the ceramic-dentin bond.

Durability of Microtensile Bond to Nonetched and Etched Feldspar Ceramic: Self-adhesive Resin Cements vs Conventional Resin

Purpose: The objective of this study was to evaluate the effect of thermocycling (TC), self-adhesive resin cements and surface conditioning on the microtensile bond strength (mu TBS) between feldspathic ceramic blocks and resin cements.Materials and Methods: Fifty-six feldspathic ceramic blocks (10 x 7 x 5 mm) (Vita Mark II) were divided into groups according to the factors "resin cement" (3 cements) and "surface conditioning" (no conditioning or conditioning [10% hydrofluoric acid etching for 5 min + silanization]) (n = 8): group 1: conditioning+Variolink II (control group); group 2: no conditioning+Biscem; group 3: no conditioning+RelyX U100; group 4: no conditioning+Maxcem Elite; group 5: conditioning+Biscem; group 6: conditioning+RelyX U100; group 7: conditioning+Maxcem Elite. The ceramic-cement blocks were sectioned to produce non-trimmed bar specimens (adhered cross-sectional area: 1 +/- 0.1 mm(2)), which were divided into two storage conditions: dry, mu TBS immediately after cutting; TC (12,000x, 5 degrees C/55 degrees C). Statistical significance was deterimined using two-way ANOVA (7 strategies and 2 storage conditions) and the post-hoc Tukey test (p<0.05).Results: Resin cement and thermocycling affected the mu TBS significantly (p = 0.001). In the dry condition, group 5 (18 +/- 6.5 MPa) presented the lowest values of mu TBS when compared to the other groups. TC decreased the mean mu TBS values significantly (p<0.05) for all resin cements tested (9.7 +/- 2.3 to 22.1 +/- 6.3 MPa), except for the resin cement RelyX U100 (22.1 +/- 6.3 MPa). In groups 3 and 4, it was not possible to measure mu TBS, since these groups had 100% pre-test failures during sectioning. Moreover, the same occurred in group 2 after TC, where 100% failure was observed during thermocycling (spontaneous failures).Conclusion: Hydrofluoric acid etching and silanization of the feldspathic ceramic surface are essential for bonding self-adhesive resin cement to a feldspathic ceramic, regardless of the resin cement used. Non-etched ceramic is not recommended.

Bond strength durability of a resin composite on a reinforced ceramic using various repair systems

Objectives. This study compared the durability of repair bond strength of a resin composite to a reinforced ceramic after three repair systems.Methods. Alumina-reinforced feldspathic ceramic blocks (Vitadur-alpha(R)) (N=30) were randomly divided into three groups according to the repair method: PR-Porcelain Repair Kit (Bisco) [etching with 9.5% hydrofluoric acid + silanization + adhesive]; CJ-CoJet Repair Kit (3M ESPE) [(chairside silica coating with 30 mu m SiO2 + silanization (ESPE(R)-Sil) + adhesive (Visio(TM)-Bond)]; CL-Clearfil Repair Kit [diamond surface roughening, etching with 40% H3PO4 + Clearfil Porcelain Bond Activator + Clearfil SE Bond)]. Resin composite was photo-polymerized on each conditioned ceramic block. Non-trimmed beam specimens were produced for the microtensile bond strength (mu TBS) tests. In order to study the hydrolytic durability of the repair methods, the beam specimens obtained from each block were randomly assigned to two conditions. Half of the specimens were tested either immediately after beam production (Dry) or after long-term water storage (37 degrees C, 150 days) followed by thermocyling (12,000 cycles, 5-55 degrees C) in a universal testing machine (1 mm/min). Failure types were analyzed under an optical microscope and SEM.Results. mu TBS results were significantly affected by the repair method (p=0.0001) and the aging conditions (p=0.0001) (two-way ANOVA, Tukey's test). In dry testing conditions, PR method showed significantly higher (p < 0.001) repair bond strength (19.8 +/- 3.8 MPa) than those of CJ and CL (12.4 +/- 4.7 and 9.9 +/- 2.9, respectively). After long-term water storage and thermocycling, CJ revealed significantly higher results (14.5 +/- 3.1 MPa) than those of PR (12.1 +/- 2.6 MPa) (p < 0.01) and CL (4.2 +/- 2.1 MPa) (p < 0.001). In all groups when tested in dry conditions, cohesive failure in the composite accompanied with adhesive failure at the interface (mixed failures), was frequently observed (76%, 80%, 65% for PR, CJ and CL, respectively). After aging conditions, while the specimens treated with PR and CJ presented primarily mixed failure types (52% and 87%, respectively), CL group presented mainly complete adhesive failures at the interface (70%).Significance. Hydrolytic stability of the repair method based on silica coating and silanization was superior to the other repair strategies for the ceramic tested. (C) 2009 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.