Finishing and Polishing Procedures and Glaze Application on Physical Properties of a Fine-Structure Feldspathic Ceramic

The aim of this study was to verify the effect of finishing and polishing procedures and glaze application on biaxial strength and surface properties of milled feldspathic ceramic blocks. Forty disc-shaped samples (14 mm diameter, 1.2 mm thickness) were divided in four groups (n = 10): C (control): no finishing and polishing; FP: finishing and polishing; G: glaze; and GFP: finishing and polishing + glaze. The specimens were subject to surface gloss (glossmeter) and roughness (profilometer) tests followed by biaxial flexural strength (universal testing machine) and Vickers hardness (microhardness tester) tests. The surface morphological analysis was performed by scanning electron microscopy (n = 3). Data were submitted to normality tests with Shapiro-Wilk, and one-way ANOVA followed by Tukey's post hoc test (α = 0.05). Group C showed the lowest gloss. For the hardness test, groups C, FP, and GFP obtained the highest values without significant differences between them. Regarding the biaxial strength test, group C showed the lowest mean value. Both finishing and polishing methods (FP and GFP) showed surface properties similar or better than the control, and with higher biaxial strength.

Heating stability, physical and chemical analysis of calcium silicate-based endodontic sealers

AIM

To evaluate possible modifications in root canal sealers subjected to a variety of heating conditions using vibrational spectroscopy and analysis of physical and chemical properties.

METHODOLOGY

EndoSequence BC Sealer HiFlow, Bio-C Sealer, BioRoot RCS and AH Plus were analysed chemically using Raman spectroscopy (25-220 °C) and Fourier-transform infrared spectroscopy (FT-IR) (37-100 °C ). For FT-IR, the materials were tested individually and mixed with root dentine powder. Scanning electron microscopy (SEM) and coupled energy dispersive spectroscopy (EDS) were used to evaluate surface and chemical elements. ISO 6876-2012 and ASTM-C266-07 specifications were followed to evaluate flow, setting time (moist and dry), solubility and radiopacity. Also, pH analysis at 37 and 100 °C was performed. Shapiro-Wilk and Mixed ANOVA (within and between the effects of the subjects), Levene, and a post hoc analyses with Bonferroni correction were performed (P < 0.05).

RESULTS

Vibrational spectroscopy revealed peaks of tricalcium silicate, dicalcium silicate and zirconium dioxide. Chemical changes in the Raman spectra during heating were discrete, as the inorganic content predominated the signalling for all root canal sealers. FT-IR analysis exhibited spectral changes in water absorption for EndoSequence BC Sealer HiFlow and Bio-C Sealer, probably related to dehydration. For BioRoot RCS and AH Plus, no significant chemical changes were observed. Bio-C Sealer exhibited a band of polyethylene glycol only after heating to 100 °C, probably related to its thermal decomposition. SEM/EDS analysis corroborated the composition results observed in vibrational spectroscopy for all materials. Heating to 100 °C significantly changed the flowability of all calcium silicate-based sealers with a wide variation in setting times at both temperatures, along with solubility levels above ISO standards. For all tested sealers, radiopacity fulfilled the requirements, and pH exhibited alkaline values.

CONCLUSIONS

The tested calcium silicate-based sealers were affected by heating. Calcium silicate-based root canal sealers had high solubility which is a concern for their clinical use. AH Plus was the only root canal sealer that was stable after heating.

Effect of Beam Profiles From Different Light Emission Tip Types of Multiwave Light-emitting Diodes on the Curing Profile of Resin-based Composites

Light activation is an important clinical step for achieving success in restorative procedures. This study evaluated the influence of beam profile from different light emission tip types of multiwave light-emitting diodes (LEDs) on the curing profile of resin-based composites. Experimental composites were produced containing either camphorquinone (CQ) or diphenyl(2,4,6-trimethylbenzoyl)phosphine oxide (TPO) as a photoinitiator. Multiwave LEDs with either a bundle light guide tip (Bluephase G2, Ivoclar Vivadent) or a microlens tip (VALO Cordless, Ultradent) were characterized using a beam profiler. Block-shaped samples (5×5×3 mm depth) of the two composites were cured in a custom-designed mold with the multiwave LEDs positioned to compare the regions exposed to the 420-495 nm (blue) and 380-420 nm (violet) emittances. To map the curing profile, the degree of conversion (DC) of longitudinal thin cross sections from each block was evaluated using transmission FT-NIR. Radiant exposure transmitted through the composites during curing was evaluated at different thicknesses. Data were analyzed using analysis of variance and Tukey test (α=0.05; β=0.2). The results indicated that there were differences in the beam profile and the overall radiant exposures transmitted through the composites using each multiwave LED (p&lt;0.01, df=1 F=73.18). However, there were no differences in the curing profiles provided by the two multiwave LEDs (p=0.89, df=12 F=0.52), and similar effects were found according to the different LED emittance regions (p=0.09, df=5, F=2.11). When considering up to 1 mm in depth, no differences in the DC were found between the composites containing either photoinitiators. Starting at 2 mm in depth, the composite containing TPO showed a decrease in DC in the 420-495 nm emittance region, while the composite containing CQ showed a similar decrease in cure efficiency only at 3-mm depth under both 380-420 nm and 420-495 nm emittance regions. Thus, despite the fact that the nonuniform light beam emitted from the two multiwave LEDs was visually distinctly different when delivering 24 J/cm2, this difference did not seem to affect the curing profile of the composites. However, light transmission within 380-420 nm seems to be reduced with depth, directly affecting the curing profile of composites containing a photoinitiator with absorbance falling within this emission range.

Espessura de Película de Compósitos Experimentais de Viscosidades Distintas Contendo Diferentes Fotoiniciadore

Avaliou-se a espessura de película formada a partir de compósitos experimentais contendo diferentes fotoiniciadores e com a viscosidade alterada pela quantidade de carga e temperatura. Foram confeccionados 3 compósitos contendo mesma matriz: Bis- GMA (29% peso), UDMA (32,5% peso), Bis-EMA (32,5% peso) e TEGDMA (6% peso). O diferencial em cada compósito foi o fotoiniciador (CQ e/ou TPO), além de um co-iniciador (EDMAB), formando-se os grupos: G1- CQ (0,4% peso) + EDMAB (0,8% peso), G2 – CQ (0,2% peso) + TPO (0,2% peso) + EDMAB (0,4% peso), G3 – TPO (0,4% peso). Cada grupo foi subdividido em 3, de acordo com a quantidade de carga (50% ou 65%): CV- convencional, CVA- convencional aquecida a 60oC e FL- flowable. Teste de viscosidade foi feito seguindo-se a especificação ISO 4049-2009. Os dados foram submetidos a ANOVA (2-fatores) e as médias comparadas pelo teste de Tukey (5%). Não se verificou efeito do fotoiniciador na espessura de película (p0,58177). Entre as consistências, o CV apresentou maior espessura de película quando comparado com FLB e CVA (p0,0007). Não foi verificado diferença entre FLB e CVA, independente do tipo de fotoiniciador. Compósitos pré-aquecidos a 60 °C apresentaram espessuras de películas comparáveis com compósitos flowable e menores que compósitos convencionais. O tipo de fotoiniciador não influenciou na espessura de película.Palavras-chave: Estética Dentária. Cimentos de Resina. Colagem Dentária.

Avaliação de Propriedades Físicas de Dentes Bovinos Clareados com Agentes Clareadores Dopados com Fosfatos de Cálcio

O objetivo foi avaliar as propriedades físicas de dentes bovinos clareados com agentes clareadores modificados por fosfatos de cálcio. Foram avaliados quatro grupos (n10): peróxido de hidrogênio 35% (Whitening HP, FGM) sem adição de fosfato (controle), com adição de 10% de hidroxiapatita (HAP), 10% de fosfato de cálcio amorfo (ACP) ou 5% de monocálcio fosfato + 5% de þTCP (MACP-TCP). Inicialmente foram avaliadas a dureza Knoop (100g por 5 s), rugosidade média (Ra) e a cor (OE) de quarenta incisivos bovinos (n10). Os dentes foram clareados com os agentes clareadores, armazenados em saliva artificial e novas medidas de dureza, rugosidade e cor foram realizadas 24 h e 7 dias após o clareamento. A permeabilidade do esmalte após o clareamento foi avaliada em microscopia confocal de varredura a laser. Os dados foram avaliados por ANOVA de medidas repetidas e teste     de Tukey (a5%). Após 24 h houve significativamente menor redução de dureza para HAP e MCP+TCP comparado ao controle. Após 7 dias os grupos com fosfato apresentaram significativamente menor redução de dureza que o controle. A cor dos dentes não foi significativamente influenciada pelo tipo de clareador. A rugosidade de HAP e ACP em 24 h foi significativamente maior que do controle, mas após 7 dias não houve diferença entre os grupos. A maior permeabilidade do esmalte foi do controle e a menor permeabilidade do MCP+TCP. Os agentes clareadores dopados com fosfatos de cálcio não inferiram na cor e na rugosidade do esmalte após o clareamento, mas possibilitaram menor redução da dureza e menor permeabilidade do esmalte.Palavras-chave: Clareamento Dental. Remineralizacã,  o Dentária. Propriedades Físicas e Químicas.

Absorção Fotônica de Diferentes Fotoiniciadores de Acordo com a Atenuação da Irradiância de Fotoativadores Multiwave Através de Cerâmicas

O objetivo neste estudo foi avaliar a transmissão de luz através de uma peça cerâmica utilizando um fotoativador multi-wave e sua eficiência quanto a absorbância de diferentes sistemas fotoiniciadores. Para tanto, a absorbância dos fotoiniciadores canforquinona (CQ) e TPO foi avaliada por meio de espectrofotometria UV-vis. Um fotoativador multi-wave foi avaliado quanto a sua irradiância e emissão espectral nos comprimentos de onda violeta (380-420nm) e azul (420-495nm) por meio de espectrofotometria. Essa caracterização também foi realizada através de uma peça cerâmica com 0,5mm de espessura e de um cimento resinoso com 0,3mm de espessura. Na análise de absorbância, a CQ absorveu luz dentro do espectro azul com pico de absorção em 468nm e o TPO, dentro do espectro violeta com pico de absorção em 380nm. O fotoativador emitiu 1218mW/cm2 sendo que, 903mW/cm2 dentro do espectro azul e 265mw/cm2 dentro do espectro violeta. Com a interposição da cerâmica e do cimento, houve uma atenuação da emissão total de 65% (424mW/cm2), sendo 57% (406mW/cm2) para o espectro azul e 93% (18mW/cm2) para o espectro violeta. Dessa forma, foi possível concluir que para fotoativação de peças cerâmicas, a irradiância emitida pelos fotoativadores sofre grande atenuação, sendo realmente necessário o aumento do tempo de exposição para eficiência de polimerização de materiais que contenham CQ. Entretanto, a irradiância emitida por fotoativadores multi-wave não seria capaz de ativar fotoiniciadores com absorção no espectro violeta em situações de cimentação de peças cerâmicas.Palavras-chave: Fotoiniciadores Dentários. Polimerização. Cimentação.

Ângulo de Contato de Infiltrantes Resinosos Experimentais Com Partículas Bioativas

O objetivo do trabalho foi avaliar a influência da adição de partículas bioativas e da matriz resinosa no ângulo de contato (AC) de infiltrantes resinosos. Foram preparadas duas matrizes resinosas (100%TEGDMA e 75%TEGDMA/25%BisEMA) e o infiltrante resinoso comercial ICON foi utilizado como controle. Os infiltrantes foram avaliados sem adição de partículas, com adição de partículas de nano-hidroxiapatita (HAP) ou biovidro 45S5 (BAG-45S5), nas concentrações de 10 ou 15% em volume. Para a mensuração dos ângulos de contato foi utilizado goniômetro GBX Instrumentation Scientifique com câmera acoplada. Gotículas dos infiltrantes foram despejadas em esmalte dental bovino polido por meio de uma micro seringa e, após 10 s, uma imagem foi registrada e analisada usando um software para análise do formato da gota, determinando o ângulo de contato (n6). Os dados foram submetidos à análise de variância 2 fatores e teste de Tukey (a0,05). A adição de partículas não influenciou o AC no infiltrante 100%TEGDMA, mas significativa redução do ângulo de contato foi observada quando HAP foi adicionada em ICON e HAP 10% foi adicionada em 75%TEGDMA/25%BisEMA. AC significativamente menor foi encontrado para 100%TEGDMA e 75%TEGDMA/25%BisEMA comparado a ICON, exceto quando BAG-45S5 15% e HAP 15% foram adicionados. Concluiu-se que a adição de partículas bioativas não prejudica (aumenta) o ângulo de contato dos infiltrantes resinosos ao esmalte dental, mas menor AC foi encontrado para os infiltrantes com matriz resinosa experimental.Palavras-chave: Esmalte Dentário. Viscosidade. Resinas Compostas.

Avaliação da União à Dentina de Sistemas Adesivos Experimentais Multi-Modo Contendo Análogos Biomiméticos e Fosfatos de Cálcio Bioativos

O objetivo foi avaliar a resistência de união (µTBS) e nanoinfiltração (NI) de um sistema adesivo experimental multi-modo contendo análogos biomiméticos e fosfatos de cálcio bioativos. Foram utilizados 60 terceiros molares humanos. A composição base dos primers foi (% em peso): 15 % GDMA-P, 10 % HEMA, 15 % TEGDMA, 10 % UDMA, 10 % água e 40 % etanol. Nos primers, foram acrescentados ou não os análogos: 5 % ácido poliacrílico e 10 % ácido polivinilfosfônico. O adesivo foi composto por:   35% UDMA, 42% BisEMA, 10% TEGDMA, 10% GDMA-P e 3% fotoiniciadores. Nesse adesivo foram acrescentados os fosfatos bioativos: beta tricálcio fosfato e monocalciofosfato monohidrato (20% em peso da mistura). O teste de μTBS foi feito em máquina de ensaios OM100 (Odeme). Após, o tipo de fratura foi analisado em lupa estereoscópica. Um palito de cada dente de cada grupo foi usado para a análise de NI, em MEV. Metade dos dentes foram utilizados para a técnica úmida e a outra para a técnica auto- condicionante e testados em 24hs ou após 4 meses de armazenagem em SSFC. Os dados de μTBS foram submetidos a ANOVA 3-fatores e as médias ao teste de Tukey (5%). Não houve melhora da μTBS após a inclusão de fosfatos e/ou análogos, porém nesses grupos, houve a manutenção dos valores de μTBS após 4 meses de armazenagem, nas duas técnicas de aplicação. Após 4 meses, houve presença da prata em todos os grupos, porém nos grupos contendo análogos, a intensidade da NI foi menor. Os adesivos experimentais multi-modo contendo análogos no primer se mostraram promissores em preservar a união dentina-compósito da degradação em ambiente úmidoPalavras-chave: Adesivos Dentinários. Dentina. Fosfatos de Cálcio.

Light-emitting Diode Beam Profile and Spectral Output Influence on the Degree of Conversion of Bulk Fill Composites

Objectives:

To evaluate the beam profile and the spectral output of monowave and polywave light-emitting diodes (LEDs) and their influence on the degree of conversion (DC) of bulk fill composites.

Methods:

A monowave LED (Smartlite Focus, Dentsply) and a polywave LED (Valo Cordless, Ultradent) were characterized using a resin calibrator and a laser beam profile analyzer. Two bulk fill composites, Sonic Fill 2 (SF) containing camphorquinone (CQ) and Tetric EvoCeram Bulk Fill (TEB) containing CQ associated with alternative photoinitiators, were placed in custom-designed molds (n=3) and photoactivated by the monowave or polywave LED with 20 J/cm2. To map the DC, longitudinal cross sections (0.5 mm thick) from the center of the restoration were evaluated using FT-NIR microscopy. SF and TEB light transmittances (n=3) through 4-mm-thick specimens were evaluated during curing. Data were analyzed using a split-plot analysis of variance and Tukey test (α=0.05; β=0.2).

Results:

The monowave LED had a radiant emittance of 20 ± 0.5 J/cm2 over 420-495 nm, and the polywave LED had an emittance of 15.5 ± 0.4 J/cm2 over 420-495 nm and of 4.5 ± 0.2 J/cm2 over 380-420 nm. The total radiant exposure at the bottom of TEB was 2.2 ± 0.2 J/cm2 with the monowave LED and 1.6 ± 0.3 J/cm2 with the polywave LED, and for SF it was 0.4 ± 0.1 J/cm2 for both LEDs. There were no differences in the curing profiles produced either by the monowave or the polywave LED (p=0.9), according to the regions under influence of blue and/or violet emission at the same depth. There was no statistical difference in the DC for SF using the monowave or polywave LED at any depth (p=0.29). TEB had a higher DC at up to 2 mm in depth when the polywave LED was used (p&lt;0.004), but no differences were found when starting at 2.5 mm.

Conclusions:

Monowave and polywave LEDs emitted nonhomogeneous light beams, but this did not affect the DC homogeneity of bulk fill composites. For composites containing CQ associated with alternative photoinitiators, polywave LEDs had a higher DC, but only at the top part of the restoration; lower wavelength absorption photoinitiators were ineffective in deeper areas.

In Situ Surface Biodegradation of Restorative Materials

This study aimed to evaluate the surface characteristics of restorative materials (roughness, hardness, chemical changes by energy-dispersive spectroscopy [EDX], and scanning electron microscopy [SEM]) submitted to in situ biodegradation. Fifteen discs of each material (IPS e.max [EM], Filtek Supreme [FS], Vitremer [VI], Ketac Molar Easymix [KM], and Amalgam GS-80 [AM]) were fabricated in a metallic mold (4.0 mm × 1.5 mm). Roughness, hardness, SEM, and EDX were then evaluated. Fifteen healthy volunteers used a palatal device containing one disc of each restorative material for seven days. After the biodegradation, the roughness, hardness, SEM, and EDX were once again evaluated. Data obtained from the roughness and hardness evaluations were submitted to Kolmogorov-Smirnov and Tukey-Kramer tests (p&lt;0.05). All esthetic restorative materials showed a significant increase in the roughness after biodegradation. Before biodegradation, significant differences in the hardness among the materials were seen: EM&gt;AM&gt;FS&gt;KM&gt;VI. After biodegradation, the hardness was significantly altered among the materials studied: EM&gt;AM&gt;FS=KM&gt;VI, along with a significant increase in the hardness for AM, KM, and VI. SEM images indicated degradation on the surface of all materials, showing porosities, cracks, and roughness. Furthermore, after biodegradation, FS showed the presence of Cl, K, and Ca on the surface, while F was not present on the VI and KM surfaces. EM and AM did not have alterations in their chemical composition after biodegradation. It was concluded that the dental biofilm accumulation in situ on different restorative materials is a material-dependent parameter. Overall, all materials changed after biodegradation: esthetic restorative materials showed increased roughness, confirmed by SEM, and the ionomer materials and silver amalgam showed a significantly higher hardness. Finally, the initial chemical composition of the composite resin and ionomer materials evaluated was significantly altered by the action of the biofilm in situ.

Dual-Cured Etch-and-Rinse Adhesive Systems Increase the Bond Durability of Direct Coronal Dentin Restorations

This study aimed to evaluate the bond durability of dentin restorations bonded with light- or dual-cured etch-and-rinse adhesive systems. A three-step adhesive system (Scotchbond Multipurpose Plus), an acetone-based two-step adhesive system (Prime & Bond 2.1), and an ethanol-based two-step adhesive system (Excite) were tested. Both the light- and the dual-cured versions were evaluated. High C-factor dentin cavities were prepared on 120 bovine incisors, which were then restored with resin composite (n=10). The samples were stored in water for 24 hours, and half of them were subjected to additional degradation with 10% NaOCl for five hours. The push-out bond strength test was performed in a universal testing machine until failure. Failure modes were evaluated by scanning electron microscopy. Data were analyzed by three-way analysis of variance and Tukey tests (p&lt;0.05). The dual-cured adhesive system presented a higher immediate bond strength and durability than those that were light cured. The three-step adhesive system produced the highest values, whereas the acetone-based adhesive system produced the lowest result. Therefore, the use of dual-cured etch-and-rinse adhesive systems can induce increased bond durability to direct coronal dentin restorations.

Effects of Surface Treatments, Thermocycling, and Cyclic Loading on the Bond Strength of a Resin Cement Bonded to a Lithium Disilicate Glass Ceramic

Objectives

The aim of this present study was to investigate the effect of two surface treatments, fatigue and thermocycling, on the microtensile bond strength of a newly introduced lithium disilicate glass ceramic (IPS e.max Press, Ivoclar Vivadent) and a dual-cured resin cement.

Methods

A total of 18 ceramic blocks (10 mm long × 7 mm wide × 3.0 mm thick) were fabricated and divided into six groups (n=3): groups 1, 2, and 3—air particle abraded for five seconds with 50-μm aluminum oxide particles; groups 4, 5, and 6—acid etched with 10% hydrofluoric acid for 20 seconds. A silane coupling agent was applied onto all specimens and allowed to dry for five seconds, and the ceramic blocks were bonded to a block of composite Tetric N-Ceram (Ivoclar Vivadent) with RelyX ARC (3M ESPE) resin cement and placed under a 500-g static load for two minutes. The cement excess was removed with a disposable microbrush, and four periods of light activation for 40 seconds each were performed at right angles using an LED curing unit (UltraLume LED 5, Ultradent) with a final 40 second light exposure from the top surface. All of the specimens were stored in distilled water at 37°C for 24 hours. Groups 2 and 5 were submitted to 3,000 thermal cycles between 5°C and 55°C, and groups 3 and 6 were submitted to a fatigue test of 100,000 cycles at 2 Hz. Specimens were sectioned perpendicular to the bonding area to obtain beams with a cross-sectional area of 1 mm2 (30 beams per group) and submitted to a microtensile bond strength test in a testing machine (EZ Test) at a crosshead speed of 0.5 mm/min. Data were submitted to analysis of variance and Tukey post hoc test (p≤0.05).

Results

The microtensile bond strength values (MPa) were 26.9 ± 6.9, 22.2 ± 7.8, and 21.2 ± 9.1 for groups 1–3 and 35.0 ± 9.6, 24.3 ± 8.9, and 23.9 ± 6.3 for groups 4–6. For the control group, fatigue testing and thermocycling produced a predominance of adhesive failures. Fatigue and thermocycling significantly decreased the microtensile bond strength for both ceramic surface treatments when compared with the control groups. Etching with 10% hydrofluoric acid significantly increased the microtensile bond strength for the control group.

Prolonged curing time reduces the effects of simulated pulpal pressure on the bond strength of one-step self-etch adhesives

The aim of this study was to evaluate the effects of extended light-curing procedures on the microtensile bond strength (μTBS) of one-step self-etch adhesives (1-SEAs) submitted to simulated pulpal pressure. Coronal deep-dentin specimens were bonded using Clearfil S3 Bond (S3), Adper Easy Bond (EB), or G-Bond Plus (GB) following the manufacturers' recommendations and light-cured for 10 seconds or 40 seconds. The dentin-bonded specimens were stored in distilled water for 24 hours without pulpal pressure (control) or submitted to 20 cm H2O simulated pulpal pressure for 24 hours. The specimens were cut into matchsticks and subjected to μTBS testing. The data were statistically analyzed using the three-way analysis of variance and Tukey's tests (p<0.05). Debonded sticks were investigated through scanning electron microscopy. EB obtained higher bond strengths than GB and S3. However, prolonged light activation (40 seconds) provided higher μTBS for all adhesives when submitted to pulpal pressure. Conversely, pulpal pressure caused a drop in μTBS in EB and S3 when light-cured for 10 seconds. A mixed failure mode was mainly attained for the control groups, whereas the specimens submitted to pulpal pressure failed in the adhesive mode. The μTBS of GB was not affected by pulpal pressure when light-cured for 10 seconds. Adhesive was the most prevalent failure mode, except when light-cured for 40 seconds, which showed predominantly cohesive failure. Extended curing times improved the resistance of 1-SEAs to simulated pulpal pressure.

Influence of natural weathering on colour stability of materials used for facial prosthesis

Colour stability of resin and silicone is an important factor for longevity of facial prostheses. The aim of this study was to evaluate the colour stability of resins and silicone for facial prostheses. Three brands of acrylic resin and one of facial silicone were evaluated considering pigment incorporation for the colourless materials. Ten samples of each material were fabricated and submitted to measurements of chromatic alteration initially and after 90 and 180 days of weathering natural through visual analysis and spectrophotometry. Data were evaluated by ANOVA and Tukey test (p < 0.05). Statistically significant colour alteration was observed among some materials regardless of the period. The materials did not present a statistical difference between 90 and 180 days except for the pigmented heat-polymerized resin. The colour difference between pigmented Silastic MDX4-4210 and colourless Silastic was statistically significant (p < 0.01) in both periods as well as between pigmented and colourless heat-polymerized resin, and between the resins Rapidaflex and Lentaflex. The visual method demonstrated colour alteration in all materials evaluated during the first 90 days of ageing. All materials exhibited colour alteration due to exposure to environment.

Influence of the volume of composite and photoactivation method on push-out bond strength and Knoop hardness of a resin composite

AIM

The aim of this paper was to evaluate the influence of modulated photoactivation methods and volume of composite on Knoop hardness (KHN) and push-out bond strength (PBS) of Filtek Z350 to root dentin.

METHODS

Three volumes (small, medium and large) of composite were bulk inserted in cavities prepared in 90 premolars. The specimens were photoactivated with continuous light, pulse-delay, or soft-start methods and submitted to PBS and KHN tests. The failure pattern was evaluated in stereomicroscope after the bond strength test. The data were submitted to two-way ANOVA and Tukey's test (P<0.05).

RESULTS

Modulated photoactivation methods showed a higher PBS than continuous method (P<0.05). Medium volume of composite showed higher PBS than small and large volumes when photoactivated with continuous method (P<0.05). Pulse-delay significantly increased KHN for medium and large volumes in comparison to continuous method (P<0.05). Medium volume of composite showed KHN significantly higher than small and large volumes (P<0.05).

CONCLUSION

The volume of composite influenced the PBS and KHN of resin composites. Pulse-delay showed the highest bond strength to dentin, as well KHN similar to the conventional method. The analysis of the failure pattern showed predominance of adhesive failure.

Degree of Conversion of Simplified Contemporary Adhesive Systems as Influenced by Extended Air-Activated or Passive Solvent Volatilization Modes

This study evaluated the effect of five methods of solvent volatilization on the degree of conversion (DC) of nine one-bottle adhesive systems using Fouriertransform infrared/attenuated total reflectance (FTIR/ATR) analysis. Nine adhesives were tested: Adper Single Bond 2 (SB), Adper Easy One (EO), One Up Bond F Plus (OUP), One Coat Bond SL (OC), XP Bond (XP), Ambar (AM), Natural Bond (NB), GO, and Stae. The adhesive systems were applied to a zinc-selenide pellet and 1) cured without solvent volatilization, 2) left undisturbed for 10 seconds before curing, 3) left undisturbed for 60 seconds before curing, 4) air-dried with an air stream for 10 seconds before curing, and 5) air-dried with an air stream for 60 seconds before curing. FTIR/ATR spectra were obtained, and the DC was calculated by comparing the aliphatic bonds/reference peaks before and after light activation for 10 seconds (FlashLite 1401). The DC means of each material were analyzed by one-way analysis of variance and post hoc Tukey test (p&lt;0.05). The DC of GO and Stae adhesive systems was not affected by the five evaporation conditions. Air-drying for 60 seconds before curing yielded the highest DC for SB, EO, and OC. Extended solvent volatilization time (60 seconds) either with or without air-drying before curing provided the highest DC for AM, NB, XP, and OUP. Thus, the monomer conversion of adhesive systems was material dependent. In general, the 60-second passive or active air-drying modes to volatilize solvents before curing enhanced the degree of conversion for the one-bottle simplified adhesive systems.

Comparison between two methods to evaluate temperature changes produced by composite light curing units and polymerization techniques

AIM

This study evaluated the temperature change into the pulp chamber during the light curing of composite resin by direct (bovine tooth) and indirect (matrix) methods.

METHODS

Direct method: fifty standardized cavities (2x2x2 mm) were prepared in bovine incisors, which were randomly assigned to evaluation of the temperature changes in the pulp chamber. Indirect method: temperature changes were evaluated through a dentine slice of 1.0 mm thickness in a elastomer cubic mold (2x2x2 mm). Filtek Z250 composite resin (3M/ESPE) was photo-activated using three light curing units: quartz-tungsten-halogen (QTH) by continuous, soft-start or intermittent light modulations; light emitting diode (LED); and plasma arc-curing (PAC). Ten groups (N.=10) were established according to technique evaluation and photo-activation methods. All experiments were carried out in a controlled environment (37 °C and 50 ± 10% relative humidity). The temperature changes were recorded using a digital thermometer attached to a type-K thermocouple in contact with the dentin slice (indirect method) or in contact with the axial wall (dentin) of pulp chamber (direct method). The results were submitted to ANOVA and Tukey's test (α=0.05).

RESULTS

Temperature changes were statistically higher for the matrix indirect method (2.56 ºC) than bovine teeth direct method (1.17ºC). The change temperature was statistically higher for the PAC (1.77 ºC) when compared to other photo-activation modes in bovine teeth direct method.

CONCLUSION

The two methods of temperature evaluation were different, however indirect method detected the higher temperature increase. Higher energy density arising from the light curing units and polymerization techniques promoted higher temperature increase.

Radiopacity of root filling materials using digital radiography

AIM

To evaluate radiopacity of root filling materials using digital radiography.

METHODOLOGY

The sealers tested were AH Plus, Endofill, EndoREZ and Epiphany. Gutta-percha (Dentsply Maillefer) and Resilon cones were also tested. Acrylic plates, containing six wells, measuring 1 mm in depth and 5 mm in diameter, were prepared for the test, and filled with the materials. The test samples were radiographed together with an aluminium stepwedge calibrated in millimetres, according to ANSI/ADA Specification 57. For the radiographic exposures, digital imaging plates and an X-ray machine at 70 kVp and 8 mA were used. The object-to-focus distance was 30 cm, and the exposure time, 0.2 s. After the laser optic reading process, the software determined the radiopacity of the standardized areas, using grey-scale values, calculating the average radiographic density for each material.

RESULTS

The decreasing values of radiopacity of the studied materials, expressed in millimetres of aluminium equivalent, were: Resilon (13.0), AH Plus(TM) (11.2), gutta-percha (9.8), Epiphany (8.0), Endofill (6.9) and EndoREZ (6.6).

CONCLUSION

All materials had radiopacity values above 3 mm of aluminium recommended by ANSI/ADA Specification 57.