The adhesive system and root canal region do not influence the degree of conversion of dual resin cement

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

Avaliação da resistência de união metalocerâmica em função de diferentes tempos de oxidação prévia

Avaliou-se a resistência de união metal/porcelana utilizando-se uma liga de Ni-Cr, submetida a diferentes tempos de oxidação prévia com o sistema cerâmico Vita-VMK, através do teste preconizado por CHIODI NETTO3. A análise dos resultados permitiu as seguintes conclusões: a ausência da oxidação prévia possibilitou os melhores resultados, sendo que a diferença foi estatisticamente significante; diferentes tempos de oxidação prévia provocaram redução acentuada nos valores obtidos e foram semelhantes entre si; o grupo submetido ao processo de jateamento após a oxidação prévia por cinco minutos mostrou resultados similares aos grupos que também passaram pelo processo de oxidação e não sofreram jateamento posterior.

Análise da qualidade de adesão de diferentes bases de braquetes metálicos

Diante das diferenças existentes nas características das bases dos braquetes usados atualmente, objetivou-se neste trabalho comparar entre si três tipos de bases de braquetes metálicos (Monobloc, Equilibrium e Dynalock). Foram utilizados 36 pré-molares humanos, divididos em 3 grupos de 12 dentes. Os dentes foram incluídos em troquéis com gesso pedra tipo IV e posicionados com suas faces vestibulares perpendiculares à base do troquel. Todos os braquetes foram colados com o compósito Concise Ortodôntico e submetidos ao ensaio de cisalhamento em uma Máquina Universal com uma velocidade de 0,5 mm por minuto. O braquete Monobloc obteve o maior valor médio de resistência adesiva (x = 28,19 Kgf/cm²), sendo superior estatisticamente aos braquetes Equilibrium (x = 18,07 Kgf/cm²) e Dynalock (x = 18,24 Kgf/cm²). em relação ao ARI (Índice de Remanescente Resinoso), não foi encontrada diferença estatística entre os braquetes testados.

Avaliação da influência dos tipos de tratamento superficial da porcelana glazeada na colagem de braquetes ortodônticos

OBJETIVO: o objetivo deste trabalho foi avaliar a influência do tipo de tratamento superficial da porcelana na resistência adesiva da colagem de braquetes ortodônticos e o modo de fratura após a descolagem. METODOLOGIA:foram confeccionados 80 corpos-de-prova de porcelana, divididos em quatro grupos (n = 18) de acordo com os diferentes tratamentos de superfície: (G1) ponta diamantada; (G2) ponta diamantada e silano; (G3) ácido hidrofluorídrico e (G4) ácido hidrofluorídrico e silano. Após o preparo das superfícies, braquetes Edgewise (Morelli) foram colados com resina (Transbond XT, 3M) e submetidos ao teste de cisalhamento. Os resultados foram avaliados estatisticamente pelo teste de Kruskal-Wallis. RESULTADO: o grupo G1 apresentou uma média de resistência de 3,35, o G2 3,97, o G3 2,56 e o G4 3,10. CONCLUSÃO: constatou-se que não houve diferença estatisticamente significativa na resistência adesiva do braquete entre os tipos de tratamentos estudados (p > 0,05) e os modos de fratura ocorreram, em sua grande maioria, na interface braquete/resina. Este estudo indica que todos os tipos de tratamentos apresentados são eficientes para a colagem.

Adhesives with different pHs: Effect on the MTBS of chemically activated and light-activated composites to human dentin

Purpose: To evaluate the bond strength between human dentin and composites, using two light-activated single-bottle total-etch adhesive systems with different pHs combined with chemically activated and light-activated-composites. The tested hypothesis was that the dentin bond strength is not influenced by an adhesive system of low pH, combined with chemically activated or light-activated composites. Material and Method: Flat dentin surfaces of twenty-eight human third molars were allocated in 4 groups (n=7), depending on the adhesive system: (One Step Plus-OS and Prime & Bond NT-PB) and composite (light-activated Filtek Z-100 [Z100] and chemically activated Bisfil 2B [B2B]). Each adhesive system was applied on acid-etched dentin and then one of the composites was added to form a 5 mm-high resin block. The specimens were stored in tap water (37 degrees C/24 h) and sectioned into two axes, x and y. This was done with a diamond disk under coolant irrigation to obtain beams with a cross-section area of approximately 0.8 mm(2). Each specimen was then attached to a custom-made device and submitted to the microtensile test (1 mm.min(-1)). Data were analyzed using two-way ANOVA and Tukey's tests (p<0.05). Results: the anticipated hypothesis was not confirmed (p<0.0001). The bond strengths (MPa) were not statistically different between the two adhesive systems when light-activated composite was used (OS+Z100 = 24.7 +/- 7.1(a); PB+Z100 = 23.8 +/- 5.7(a)). However, with use of the chemically activated composite (B2B), PB (7.8 +/- 3.6(b) MPa) showed significantly lower dentin bond strengths than OS (32.2 +/- 7.6(a)). Conclusion: the low pH of the adhesive system can affect the bond of chemically activated composite to dentin. on the other hand, under the present conditions, the low pH did not seem to affect the bond of light-activated composites to dentin significantly.

Polymerization shrinkage: effects of boundary conditions and filling technique of resin composite restorations

Objective: To evaluate the linear polymerization shrinkage (LPS) and the effect of polymerization shrinkage of a resin composite and resin-dentin bond strength under different boundary conditions and filling techniques.Methods: Two cavities (4 x 4 x 2 MM) were prepared in bovine incisors (n = 30). The teeth were divided into three groups, according to boundary conditions: In group TE, the total-etch technique was used. In group EE, only enamel was conditioned, and in group NE, none of the watts of the cavities were conditioned. A two-step adhesive system was applied to all cavities. The resin composite was inserted in one (B) or three increments (1), and tight-cured with 600 mW/cm(2) (80 s). The LPS (%) was measured in the top-bottom direction, by placing a probe in contact with resin composite during curing. Enamel and total mean gap widths were measured (400 x) in three slices obtained after sectioning the restorations. Then, the slices were sectioned again, either to obtain sticks from the adhesive interface from the bottom of the cavity or to obtain resin composite sticks (0.8 mm(2)) to be tested for tensile strength (Kratos machine, 0.5 mm/min). The data was subjected to a two-way repeated measures ANOVA and Tukey's test for comparison of the means (alpha = 0.05).Results: the highest percentage of LPS was found for the TE when bulk fitted, and the lowest percentage of LPS was found in the Hand NE when incrementally fitted. The resin dentin bond strength was higher and the total mean gap width was tower for TE group; no significant effect was detected for the main factor fitting techniques. No difference was detected for the tensile strength of resin composite among the experimental groups.Conclusions: the filling technique is not able to minimize effects of the polymerization shrinkage, and bonding to the cavity watts is necessary to assure reduced mean gap width and high bond strength values. (C) 2004 Elsevier Ltd. All rights reserved.

Cation-oxygen interaction and oxygen stability in CaCu3Ti4O12 and CdCu3Ti4O12 lattices

The cubic perovskite related material CaCu3Ti4O12 has attracted a great deal of attention due to the high values of the static dielectric constant, of order 104, approximately constant in the temperature range 100-600 K. The substitution of Ca by Cd results in a similar temperature dependence but a static dielectric constant more than one order of magnitude lower. A theoretical electronic structure study is performed on CaCu3Ti4O12 (CCTO) and CdCu3Ti4O12 (CdCTO) using a tight binding with overlap method. Although the calculations are performed in a paramagnetic configuration, excellent agreement with experiment was found for the calculated band gap of CCTO. In spite of the fact that the band structures of both systems look practically the same, a significant difference is found in the calculated bond strength of Ca-O and Cd-O pairs, driven by the presence of Ti, with Ca-O interaction in CCTO loosened with respect to Cd-O interaction in the cadmium compound. It is suggested that O vacancies are more easily formed in CCTO, this being related to the lower electronegativity of Ca as compared to Cd. The formation of oxygen vacancies could be the origin of the difference in the static dielectric constant of the two compounds.

Localized mechanics of dentin self-etching adhesive system

The bond strength of composite resins (CRs) to dentin is influenced by the interfacial microstructure of the hybrid layer (HL) and the resin tags (TAG). The contemporary self-etching primer adhesive systems overcame the inconvenient of the etch-and-rinse protocol. Studies, however, have demonstrated that HL thickness and TAG length vary according to the wetting time and additional use of acid-etching prior to self-etching primers. This study investigated the localized stress distribution in the HL and the dentin/adhesive interface. Two HL thicknesses (3 or 6 mu m), two TAG lengths (13 or 17 mu m) and two loading conditions (perpendicular and oblique-25 degrees) were investigated by the finite element (FE) analysis. Five two-dimensional FE models (M) of a dentin specimen restored with CR (38 x 64 mu m) were constructed: M1 - no HL and no TAG; M2 - 3 mu m of HL and 13 mu m of TAG; M3 - 3 mu m of HL and 17 mu m of TAG; M4 - 6 mu m of HL and 13 mu m of TAG; and M5 - 6 mu m of HL and 17 mu m of TAG. Two distributed loadings (L) (20N) were applied on CR surface: L1 - perpendicular, and L2 - oblique (25 degrees). Fixed interfacial conditions were assigned on the border of the dentin specimen. Ansys 10.0 (Ansys (R), Houston, PA, USA) software was used to calculate the stress fields. The peak of von Mises (sigma(vM)) and maximum principal stress (sigma(max)) was higher in L2 than in L1. Microstructures (HL and TAG) had no effect on local stresses for L1. Decreasing HL decreased sigma(vM) and sigma(max) in all structures for L2, but the TAG length had influence only on the peributular dentin. The thickness of HL had more influence on the sigma(vM) and sigma(max) than TAG length. The peritubular dentin and its adjacent structures showed the highest sigma(vM) and sigma(max), mainly in the oblique loading.

The effect of ceramic surface treatment on bonding to densely sintered alumina ceramic

Statement of problem. Ceramic surface treatment is crucial for bonding to resin. High crystalline ceramics are poorly conditioned using traditional procedures.Purpose. The purpose of this study was to evaluate the effect of silica coating on a densely sintered alumina ceramic relative to its bond strength to composite, using a resin luting agent.Material and methods. Blocks (6 X 6 X 5 mm) of ceramic and composite were made. The ceramic (Procera AllCeram) surfaces were polished, and the blocks were divided into 3 groups (n = 5): SB, airborne-particle abrasion with 110-mu m Al(2)O(3); RS, silica coating using Rocatec System; and CS, silica coating using CoJet System. The treated ceramic blocks were luted to the composite (W3D Master) blocks using a resin luting agent (Panavia F). Specimens were stored in distilled water at 37 degrees C for 7 days and then Cut in 2 axes, x and y, to obtain specimens with a bonding area of approximately 0.6 mm(2) (n = 30). The specimens were loaded to failure in tension in a universal testing machine, and data were statistically analyzed using a randomized complete block design analysis of variance and Tukey's test (alpha=.05). Fractured surfaces were examined using light microscopy and scanning electron microscopy to determine the type of failure. Energy-dispersive spectroscopy was used for surface compositional analysis.Results. Mean bond strength values (MPa) of Groups RS (17.1 +/- 3.9) (P = .00015) and CS (18.5 +/- 4.7) (P=.00012) were significantly higher than the values of Group SB (12.7 +/- 2.6). There was no statistical difference between Groups RS and CS. All failures occurred at the adhesive zone.Conclusion. Tribochemical silica coating systems increased the tensile bond strength values between Panavia F and Procera AllCeram ceramic.

Composite Resin to Yttria Stabilized Tetragonal Zirconia Polycrystal Bonding: Comparison of Repair Methods

Purpose: The purpose of the current study was to evaluate different approaches for bonding composite to the surface of yttria stabilized tetragonal zirconia polycrystal (Y-TZP) ceramics.Methods: One hundred Y-TZP blocks were embedded in acrylic resin, had the free surface polished, and were randomly divided into 10 groups (n=10). The tested repair approaches included four surface treatments: tribochemical silica coating (TBS), methacryloxydecyldihidrogenphosphate (MDP)-containing primer/silane, sandblasting, and metal/zirconia primer. Alcohol cleaning was used as a "no treatment" control. Surface treatment was followed by the application (or lack thereof) of an MDP-containing resin cement liner. Subsequently, a composite resin was applied to the ceramic surface using a cylindrical mold (4-mm diameter). After aging for 60 days in water storage, including 6000 thermal cycles, the specimens were submitted to a shear test. Analysis of variance and the Tukey test were used for statistical analyses (alpha=0.05).Results: Surface treatment was a statistically significant factor (F=85.42; p<0.0001). The application of the MDP-containing liner had no effect on bond strength (p=0.1017). TBS was the only treatment that had a significantly positive effect on bond strength after aging.Conclusion: Considering the evaluated approaches, TBS seems to be the best surface treatment for Y-TZP composite repairs. The use of an MDP-containing liner between the composite and Y-TZP surfaces is not effective.

Adhesive Quality of Self-adhesive and Conventional Adhesive Resin Cement to Y-TZP Ceramic Before and After Aging Conditions

Purpose: This study evaluated the adhesive quality of simplified self-adhesive and conventional resin cements to Y-TZP in dry and aged conditions. Methods: Y-TZP ceramic blocks (N=192) (5 x 5 x 2 mm) were embedded in acrylic resin and randomly divided into two groups, based on surface conditioning: 96% isopropanol or chairside tribochemical silica coating and silanization. Conditioned ceramics were divided into four groups to receive the resin cements (Panavia F 2.0, Variolink II, RelyX U100 and Maxcem). After 24 hours, half of the specimens (n=12) from each group were submitted to shear bond strength testing (0.5 nun/minute). The remaining specimens were tested after 90 days of water storage at 37 degrees C and thermocycling (12,000x, 5 degrees C-55 degrees C). Failure types were then assessed. The data were analyzed using three-way ANOVA and the Tukey's test (alpha=0.05). Results: Significant effects of ceramic conditioning, cement type and storage conditions were observed (p<0.0001). The groups cleaned using alcohol only showed low bond strength values in dry conditions and the bond strength was reduced dramatically after aging. Groups conditioned using silica coating and silanization showed higher bond strengths both in dry and aged conditions. A high number of specimens failed prematurely prior to testing when they were cleaned using 96% isopropanol. Conclusion: Overall, silica coating and silanization showed higher, stable bond strengths with and without aging. The durability of resin-ceramic adhesion varied, depending on the adhesive cement type.

Aplicação da técnica de condicionamento total ou de primers autocondicionantes em dentes decíduos após abrasão a ar

Since the use of air abrasion has grown in pediatric dentistry, the aim of this study was to evaluate, by means of shear bond strength testing, the need to use the total etching technique or self-etching primers on dentin of primary teeth after air abrasion. Twenty-five exfoliated primary molars had their occlusal dentin exposed by trimming and polishing. Specimens were treated by: Air abrasion + Scotchbond MultiPurpose adhesive (G1); 37% phosphoric acid + Scotchbond MP adhesive (G2); Clearfil SE (G3); Air abrasion ( 37% phosphoric acid + Scotchbond MP adhesive (G4); Air abrasion + Clearfil SE (G5). On the treated surface, a cylinder of 2 mm by 6 mm was made using a composite resin (Z100). Duncan's test showed that: (G2 = G3 = G5) > (G1 = G4). The use of a selfetching primer on air abraded dentin is recommended to obtain higher bond strengths.

Interaction between total-etch and self-etch adhesives and conventional and self-adhesive resin cements

The aim of this study was to compare the bond strength to enamel between resin cements combined with total-etch and self-etch adhesive systems and a self-adhesive cement. Eighty bovine incisors had their buccal surface ground flat exposing a plane area in the enamel. Eighty Artglass resin cylinders measuring 3 mm in diameter and 4 mm in height were fabricated. The teeth were divided into eight groups of 10 teeth each and the resin cylinders were cemented with different adhesive systems and resin cements; G1: RelyX Unicem (self-adhesive cement); G2: H 3PO 4 + Single Bond + RelyX ARC; G3: AdheSE + Variolink II; G4: H 3PO 4 + Excite + Variolink II; G5: Xeno III + Enforce; G6: H 3PO 4 + Prime&Bond NT + Enforce; G7: Biatite Primers 1 and 2 + Bistite II DC; G8: H 3PO 4 + Bistite Primers 1 and 2 + Bistite II DC. After application of the adhesives, the cylinders were cemented according to manufacturer instructions. The specimens were submitted to 2000 thermal cycles at a temperature ranging from 5±5°C to 55±5°C, and shear bond strength was then tested at a variety of 1 mm/min. The data were analyzed by ANOVA and the Tukey's test (á=5%), obtaining a p value of 0.00. The following mean (±standard deviation) bond strength values were observed for each group: G1: 5.14(±0.99)a; G3: 16.23(±4.69)b; G7: 17.82(±3.66)b; G5: 18.48(±2.88)bc; G8: 20.15(±4.12)bc; G4: 22.85(±3.08)cd; G2: 24.96(±2.89)d; G6: 26.07(±1.69)d. Groups followed by the same letters did not differ significantly. For most of the resin cements tested, the application of adhesive systems using acid etching resulted in a higher bond strength when compared to the self-etch adhesive systems and to the self-adhesive cement.

Influência da contaminação da dentina por cimentos temporários na resistência da união de sistemas adesivos

Objective: The aim of this study was to assess the bond strength of adhesive systems to dentin contaminated by temporary cements with or without eugenol. Method: Flat dentin surfaces were obtained from twenty-four human third molars. With exception of the control group (n=8), the surfaces were covered with Interim Restorative Material (Caulk Dentsplay, Milford, DE, USA) or Cavit (3M ESPE, St. Paul, MN, USA) and kept in an oven at 37°C for seven days. After removing the cements, the adhesive systems Adper Single Bond (3M ESPE, St. Paul, MN, USA) or Clearfil SE Bond (Kuraray Co. Ltd., Osaka, Japan) were applied in accordance with the manufacturers' recommendations, and then the crowns were constructed in of resin composite. The teeth were sectioned into specimens with a cross-sectional bond area of 0.81mm2, which were submitted to microtensile testing in a mechanical test machine at an actuator speed of 0.5mm/min. The data were analyzed by t- and ANOVA tests, complemented by Tukey tests (α=0.05). Results: For Adper Single Bond (3M ESPE, St. Paul, MN, USA), bond strength did not differ statistically (p>0.05) for all the experimental conditions. For Clearfil SE Bond (Kuraray Co. Ltd., Osaka, Japan), only the Interim Restorative Material (Caulk Dentsplay, Milford, DE, USA) Group showed significantly lower bond strength (30.1 ± 13.8 MPa) in comparison with the other groups; control (38.9 ± 13.5 MPa) and Cavit (3M ESPE, St. Paul, MN, USA) (42.1 ± 11.0 MPa), which showed no significant difference between them. Conclusion: It was concluded that the previous covering of dentin with temporary cement containing eugenol had a deleterious effect on the adhesive performance of the self-etching system only.

In vitro lingual bracket evaluation of indirect bonding with plasma arc, LED and halogen light

Authors - Magno AFF, Martins RP, Vaz LG, Martins LP Objectives - Evaluate the shear bond strength (SBS) and the adhesive remnant index (ARI) of indirect bonded lingual brackets using xenon plasma arc light, light-emitting diode (LED) and conventional quartz-tungsten-halogen light. Material and Methods - Lingual brackets were bonded indirectly to 60 premolars divided to three groups according to the curing light used: Group 1, plasma arc for 6 s; Group 2, LED for 10 s; and Group 3, halogen light for 40 s. After bonding, the specimens were subjected to a shear force until debonding. The debonding pattern was assessed and classified according to the ARI scores. The mean shear bond strengths were accessed by anova followed by the Student-Newman-Keuls test for multiple comparisons. ARI scores were assessed using the chi-square test. Results - The three groups showed significant differences (p < 0.001), with the averages of group 1 < group 2 < group 3. Groups showed no differences regarding ARI scores. Conclusion - Bonding lingual brackets indirectly with plasma arc, during 60% of the time used for the LED, produced lower SBS than obtained with the latter. Using LED during 25% of the time of the halogen light produced lower SBS than obtained with the latter. These differences did not influence the debonding pattern and are clinically acceptable according to the literature. © 2010 John Wiley & Sons A/S.