Nanotopography and oral bacterial adhesion on titanium surfaces: in vitro and in vivo studies

The present study aimed to evaluate the influence of titanium surface nanotopography on the initial bacterial adhesion process by in vivo and in vitro study models. Titanium disks were produced and characterized according to their surface topography: machined (Ti-M), microtopography (Ti-Micro), and nanotopography (Ti-Nano). For the in vivo study, 18 subjects wore oral acrylic splints containing 2 disks from each group for 24 h (n = 36). After this period, the disks were removed from the splints and evaluated by microbial culture method, scanning electron microscopy (SEM), and qPCR for quantification of Streptococcus oralis, Actinomyces naeslundii, Fusobacterium nucleatum, as well as total bacteria. For the in vitro study, adhesion tests were performed with the species S. oralis and A. naeslundii for 24 h. Data were compared by ANOVA, with Tukey's post-test. Regarding the in vivo study, both the total aerobic and total anaerobic bacteria counts were similar among groups (p > 0.05). In qPCR, there was no difference among groups of bacteria adhered to the disks (p > 0.05), except for A. naeslundii, which was found in lower proportions in the Ti-Nano group (p < 0.05). In the SEM analysis, the groups had a similar bacterial distribution, with a predominance of cocci and few bacilli. In the in vitro study, there was no difference in the adhesion profile for S. oralis and A. naeslundii after 24 h of biofilm formation (p > 0.05). Thus, we conclude that micro- and nanotopography do not affect bacterial adhesion, considering an initial period of biofilm formation.

The impact of chitosan in experimental resin with different photoinitiator systems

OBJECTIVE

to investigate the effect of different concentrations of chitosan added to experimental resins containing either BAPO or camphorquinone (CQ) as photoinitiators, regarding degree of conversion (DC), flexural strength (FS), flexural elastic modulus (E), Knoop microhardness (KHN), cytotoxicity, genotoxicity and antimicrobial activity.

METHODS

Experimental resins with polymeric matrix of BisGMA and TEGDMA was added either 0.5 wt% BAPO or 0.5 wt% camphorquinone/0.2% amine along with and chitosan concentrations of 0.5%; 1.0% or 2.0%. Degree of conversion was measured using Fourier transformed infrared spectroscopy. Flexural strength and elastic modulus were obtained through three-point bending test and Knoop microhardness was measured in a microidenter. Direct cytotoxicity was performed in human keratinocytes and genotoxicity test was done in murine macrophages cells. Antimicrobial activity was acessed against Staphylococcus aureus and Streptococcus mutans through the inhibition halo. Data were analyzed using two-way ANOVA and Tukey teste (α = 0.05).

RESULTS

The materials containing photoinitiator BAPO showed higher values of DC, FS, E, and KHN compared to resins with CQ. The addition of chitosan did not affect the properties of these materials. However, in resins containing CQ, the addition of chitosan improve these properties compared to control group. For the groups containing BAPO the chitosan reduced cytotoxicity and genotoxicity compared to materials with camphorquinone. The materials with 1.0% and 2.0% chitosan showed increased antibacterial activity in the materials containing BAPO as photoinitiator for both bacteria.

SIGNIFICANCE

The alternative photoinitiator BAPO and chitosan can improve physical and biological properties of photoactivated resins when compared with the materials with photoinitiator camphorquinone.

Marginal discrepancy of lithium disilicate crowns made with digital and conventional technologies

STATEMENT OF PROBLEM

Digital technologies have brought different workflows to prosthetic rehabilitations, but analyses of the available processes and their influence on the marginal fit of complete crowns are lacking.

PURPOSE

The purpose of this in vitro study was to evaluate the marginal discrepancy of lithium disilicate complete crowns made with different workflows.

MATERIAL AND METHODS

Fifty lithium disilicate crowns were made with 5 different workflows (n=10): G1-Analog (control): conventional flow/pressed crown; G2-Hybrid: hybrid flow/milled crown; G3-Hybrid: hybrid flow/pressed crown; G4-Hybrid: hybrid flow/printed wax pattern/pressed crown; G5-Digital: digital flow/milled crown. The specimens were analyzed by scanning electron microscopy, and the data were analyzed for normality and submitted to analysis of variance (ANOVA). Multiple comparisons were made by using the Tukey HSD test (α=.05).

RESULTS

G4H (18.1 ±6.6 µm) had the lowest mean ±standard deviation marginal discrepancy values, statistically different from G2H (217.9 ±81.4 µm), G5D (236.4 ±89 µm), and G3H (661.8 ±61.9 µm) (P<.05). G3H had the highest marginal discrepancy values and were statistically similar to each other (P>.05). G1A (163.2 ±10.9 µm) had intermediate values, statistically similar to those of other groups (P>.05).

CONCLUSIONS

The conventional method showed no statistical differences in marginal discrepancy compared with methods using digital technology (scanner, software, 3D printer, or milling machine).

Physical analysis of an acrylic resin modified by metal and ceramic nanoparticles

BACKGROUND

Nanoparticles (NPs) have gained significant attention in various fields due to their unique properties and potential applications. Polymethyl methacrylate (PMMA) is an acrylic resin widely used in dentistry and medicine. However, the effect of different types of NP fillers on the physical properties of PMMA-based resins has not been thoroughly explored in the literature.

OBJECTIVES

The present study aimed to evaluate the effects of 3 different types of NP fillers on the physical properties of an experimental PMMA-based resin as a function of the NP content and concentration.

MATERIAL AND METHODS

Ten groups (n = 10) were designed. The specimens were composed of an acrylic resin, silicon dioxide (SiO2), cerium dioxide (CeO2), and titanium dioxide (TiO2) at the following ratios (wt%): group 1 (G1) - control; group 2 (G2) - 0.5% SiO2; group 3 (G3) - 1% SiO2; group 4 (G4) - 3% SiO2; group 5 (G5) - 0.5% CeO2; group 6 (G6) - 1% CeO2; group 7 (G7) - 3% CeO2; group 8 (G8) - 0.5% TiO2; group 9 (G9) - 1% TiO2; and group 10 (G10) - 3% TiO2. Transmission electron microscopy (TEM) was used to assess the quality of NP dispersion. Thermal stability was assessed with thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). The effects of the abovementioned NPs on the properties of the resin were evaluated using the Archimedes principle for density, the Vickers hardness (VH) test and the impact strength (IS) test. Data analysis employed the oneand two-way analysis of variance (ANOVA), followed by Duncan's post hoc test at a significance level of 0.05.

RESULTS

Transmission electron microscopy showed partial NP dispersion. All types of NPs enhanced the mechanical properties of the acrylic resin except for IS, which was similar to that of the control group. Among the types of NPs, irrespective of the weight percentage, CeO2 showed higher thermal stability and higher IS for 0.5 wt% and 1 wt% as compared to other groups, as well as the highest values of density at 0.5 wt%, 1 wt% and 3 wt%. Titanium oxide at 1 wt% presented a higher VH as compared to other groups. The fracture pattern was the same for all groups.

CONCLUSIONS

Incorporating the tested NPs into the acrylic resin resulted in enhanced physical properties, primarily attributed to a lower NP content.

Microtensile bond strength of resin composite to dentin using different adhesive systems and directions of electric current

Thisstudy aimed to evaluate the effect of the electric current direction application on the resin composite-dentin bond strength using three adhesive systems. Human molar teeth were distributed according to the adhesive system (two-step self-etch - Clearfil SE Bond, Kuraray [CSE]; one-step self-etch - Single Bond Universal, 3M ESPE [SBU]; and two-step etch-and-rinse - Adper Single Bond 2, 3M ESPE [SB2]), electric current direction (without electric current - control, direct and reverse electric currents - 35µA), and storage time (24h - immediate and 6 months). Resin composite blocks (Filtek Z350XT, 3M ESPE) were bonded to dentin. The teeth/resin composites specimens were stored in distilled water at 37ºC for 24 hours and 6 months for the microtensile bond strength (µTBS) test (n = 10; ~12 sticks for each tooth). Failure patterns were analyzed on a stereomicroscope and classified as cohesive-dentin, cohesive-resin, adhesive or mixed. Adhesive penetration into dentin and hybrid layer formation were evaluated in a scanning electron microscope (n = 6). Data were submitted to a three-way ANOVA followed by Tukey's post hoc test (α = 0.05). There are no differences in µTBS when the adhesive systems were applied under direct and reverse electric currents, but both electric currents increased the µTBS for all adhesive systems. SBU showed the lowest µTBS values for control groups in both storage times and direct electric current in 6 months of storage. The adhesive failure pattern was more frequently observed in all groups. The electric current formed long resin tags for all adhesive systems. Storage for 6 months did not significantly decrease µTBS values. Both directions of electric current (positive and negative charges) at 35µA can increase the µTBS of the adhesive systems tested to dentin.

Stress distribution in restorations with glass fiber and polyetheretherketone intraradicular posts: An in silico analysis

This study evaluated stresses generated at maxillary central incisor (21) root restored with lithium disilicate crown (LDC), and glass fiber (GFP) or polyetheretherketone (PEEK) post. 3D models created by computed tomographic image (i-CAT Cone Beam 3D Dental Imaging System) reproduced maxillary central incisor. Each model had prosthetic LDCs (2.0 mm thick) cemented to GFP or PEEK posts with dual resin cement. Different loads were applied to each model (cervical, incisal, axial, middle). At maximum principal stress, PEEK showed higher stress than GFP in all loads, but with qualitative similarity. At minimum principal stress, PEEK and GFP showed qualitative and quantitative similarities, except axial load. Maxillary central incisor restored with GFP or PEEK and LDC presented, in general, similar stress intensity and distribution for main occlusal loads. Only two of sixteen occlusal loads tested (cervical for maximum principal; axial for minimum principal) showed significant quantitative difference.

Finite Element Analysis of Stress in Anterior Prosthetic Rehabilitation with Zirconia Implants with and without Cantilever

Objectives The aim of this study was to evaluate using finite element analysis (FEA), the stress distribution in prostheses (lithium disilicate crowns) on monotype zirconia implants with and without cantilever in the anterior region of the maxilla.

Materials and Methods From a virtual reconstruction of bone model of the toothed maxilla from a computed tomography, three models (groups) were created: Zr (11–21)—implants placed in the area of 11 and 21 with cantilever; Zr (12–22)—implants placed in the area of 12 and 22 without cantilever; and Zr (11–22)—implants intercalated placed in the area of 11 and 22. In all models, monotype zirconia implant (4.1 × 12.0 mm) was used in single-body configuration. Lithium disilicate crowns were designed on the implants and pontics for all groups. A 150-N load was applied to the prostheses. The materials used were considered isotropic, homogeneous, and linearly elastic. FEA was performed to evaluate the maximum (tensile) and minimum (compressive) principal stresses in the implant, crowns, and bone tissue. Data were analyzed qualitatively and quantitatively.

Results For all groups, the highest maximum principal stress occurred in the palatal cervical area of the implant, with the high values for the Zr (12–22) group and the low values for the Zr (11–21) group. The maximum principal stress was concentrated in the cervical palatal area of the crown, with the Zr (11–21) group presented the highest values and the Zr (12–22) group showed the lowest values. In the bone tissue all the groups presented similar values of maximum and minimal principal stress, with the palatal (maximum principal) and vestibular (minimum principal) close to the cervical of the implants the area with the highest concentration of stresses.

Conclusions The position of monotype zirconia implant did not interfere in the bone tissue stress, and the implants placed in the 11–21 present lower stress in implants and higher in the crown. The cantilever does not increase the stress in the implants, crown, and bone tissue.

Influence of the Multiple Layers Application and the Heating of Silane on the Bond Strength between Lithium Disilicate Ceramics and Resinous Cement

Objective This study aimed to evaluate the bond strength between lithium disilicate ceramic and resinous cement when silane (Prosil, FGM) was applied in different amounts of layers under heating or not.

Materials and Methods Sixty IPS E-max CAD ceramic (Ivoclar) was used. They were conditioned with 10% hydrofluoric acid for 20 seconds. The samples were distributed in six groups ( n = 10): 1Sil, 1 layer of silane without heating; 1SilAq, 1 layer of silane with heating; 2Sil, 2 layers without heating; 2SilAq, 2 layers with heating; 3Sil, 3 layers without heating; and 3SilAq, 3 layers with heating. After each layer, a jet of cold air was applied for 20 seconds in groups 1Sil, 2Sil, 3Sil, and jet of hot air (50°C) in groups 1SilAq, 2SilAq, and 3SilAq. Subsequently, an adhesive layer was applied, and fourcylinders were made on the ceramic with a resin cement AllCemVeneer and photoactivated for 20 seconds. The samples were stored at 37°C for 24 hours and analyzed to the microshear test at EMIC.

Statistical Analysis Data were submitted to ANOVA and Tukey’s test (α = 0.05).

Results The results showed that there was no statistical interaction between the factors studied. The “heating” factor was not statistically significant; however, the “silane layers” factor showed differences between groups. The analysis of the results showed that the use of one (66%) or two layers (67%) of silane regardless of heating, produced higher values of bond strength, when compared with the group of three layers (62%).

Conclusion The use of silane with one or two layers provided a greater bond strength between lithium disilicate ceramic and resinous cement and that the heating did not influence the results.

Physical and Mechanical Properties of Resins Blends Containing a Monomethacrylate with Low-polymerization Shrinkage

Objectives  The aim of this study was to evaluate the Knoop hardness (KH), cross-link density (CLD), water sorption (WS), water solubility (WSB), and volumetric shrinkage (VS) of experimental resins blends containing a monomethacrylate with low-polymerization shrinkage.

Materials and Methods  A blend of bisphenol glycidyl methacrylate (BisGMA) as base monomer was formulated with (Bis-GMA)/triethyleneglycol dimethacrylate (TEGDMA), Bis-GMA/isobornyl methacrylate (IBOMA), or Bis-GMA/TEGDMA/IBOMA in different concentrations (40, 50, or 60 wt%). The camphorquinone (CQ)/2-(dimethylamino) ethyl methacrylate (DMAEMA) was used as the photoinitiator system. The KH and CLD were measured at the top surface using an indenter. For WS and WSB, the volume of the samples was calculated in mm ³ . The samples were transferred to desiccators until a constant mass was obtained (m1) and were subsequently immersed in distilled water until no alteration in mass was detected (m2). The samples were reconditioned to constant mass in desiccators (m3). WS and WSB were determined using the equations m2 − m3/V and m1 − m3/V, respectively. VS results were calculated with the density parameters before and after curing.

Statistical Analysis  Data were submitted to ANOVA and Tukey’s test (α = 0.05).

Results  The resins containing IBOMA showed lower VS results. TEGDMA 40% and TEGDMA/IBOMA 20/20 wt% showed higher KH values. The IBOMA groups showed lower CLD, while TEGDMA groups had higher values of CLD. The BisGMA/TEGDMA resin presented the highest values of WS, and for WSB, all groups showed no significant differences among themselves.

Conclusion  The monomethacrylate with low-polymerization shrinkage IBOMA used alone or in combination with TEGDMA may decrease VS, WS, and CLD values.

Stress distribution with extra-short implants in an angled frictional system: A finite element analysis study

STATEMENT OF PROBLEM

Short and extra-short implants with Morse taper connections were developed to avoid grafting procedures. How the stresses around these implants differ with abutments of different angulations is unclear.

PURPOSE

The purpose of this finite element study was to analyze the stress distribution in different structures (abutment, implant, and bone) of an extra-short implant with a Morse taper connection to the abutment (Arcsys-FGM-Brazil) (5.0×5.0 mm and 4.3×5.0 mm) when different abutment degrees were used.

MATERIAL AND METHODS

Eight 3D models were designed according to each group under analysis: group 5DS (5.0×5.0-mm implants with straight abutment), group 5DA (5.0×5.0-mm implants with 20-degree angled abutments), group 4DS (4.3×5.0-mm implants with straight abutments), and group 4DA (4.3×5.0-mm implants with 20-degree angled abutments). Axial and oblique loads of 150 N were applied on the mandibular molar crowns.

RESULTS

The oblique loads and angled abutments had higher stress values in the whole model (implant, abutment, and bone) than the axial loads and straight abutments. Implants with a different diameter had almost the same stress distribution on the implant, abutment, and bone. The yield limit was exceeded in the cortical bone with oblique loads and was also exceeded in implant models when an angled abutment with oblique loads was used.

CONCLUSIONS

Extra-short implants with Morse taper connections to the abutment had higher stress concentrations with an angled abutment on oblique loads, and the peri-implant bone was the most damaged structure.

Influence of angulation and height of tooth preparation on the distribution of tensions in prosthetic crowns for upper central incisor

Aim: it was to use tridimensional finite element analysis (FEA) to analyze the effect of height and angulation of prosthetic preparations on the distribution of stresses for lithium disilicate prosthetic crowns, the underlying resin cement, and the prosthetic preparation of a superior central incisor. Methods: a CAD modeling software, SolidWorks 2013, was used to generate three-dimensional virtual models comprising the dimensions of the preparation parameters. Three angles (6, 12 and 16 degrees) were simulated on the prepared walls and two wall heights were utilized (4 and 5 mm), for a total of six model groups according to the height and angulation of the walls. A vertical line in the Y-axis was used as a reference for determining the degrees of convergence (inclination of the preparations). The chamfer finish and preparation width were standardized for all groups. Results: the 4 mm preparations behaved more appropriately when the axial wall convergence was approximately 6 degrees. The 5 mm preparations required 12 degrees of angulation. In relation to resin cement, there was better stress distribution when the angle of incisal convergence was between 6 and 12 degrees. An increase to 16 degrees led to a considerable increase in peak stress at the preparation margin. Conclusion: it was concluded that the convergence of the axial walls of coronal preparations with 4 and 5 mm heights should be 6 and 12 degrees, respectively, to avoid high tension spikes in the underlying resin cement.

Mechanical properties of experimental resin cements containing different photoinitiators and co-initiators

Aim

The aim of this study was to evaluate the influence of different concentrations of two photoinitiators and one co-initiator on the flexural strength (FS) and elastic modulus (E) of experimental resin cements.

Materials and methods

A mixture containing BisGMA, TEGDMA, and barium-aluminum-silicate (BaAlSi) and silanized colloidal silica (SiO₂) filler particles was prepared with two photoinitiators, viz. camphorquinone (CQ) and bisacylphosphine oxide (BAPO). Dimethylaminoethyl methacrylate (DMAEMA) was used as co-initiator. Thirty groups (n=10) were formulated with different photoinitiator systems (CQ/DMAEMA and BAPO/DMAEMA) and concentrations (wt%) of photoinitiator and co-initiator. The photoactivation was carried out for 20 s with a light-emitting diode (LED, Bluephase, Ivoclar Vivadent) with irradiance of 1200 mW/cm². The FS and E were obtained in a three-point bending test on a universal testing machine (0.5 mm/min). Data were subjected to the Kolmogorov-Smirnov normality test, followed by two-way ANOVA and Tukey’s test (α=0.05).

Results

No polymerization occurred in the CQ groups without DMAEMA (0 wt%). DMAEMA 0.5 %wt and 1 %wt groups showed statistically similar FS and E results for CQ and BAPO, except for CQ 0.3 wt% (FS), CQ 0.9wt% (E) and BAPO 1.76 wt% (FS and E) for DMAEMA 0.5 %wt. No significant difference was found for FS and E values for different concentrations of photoinitiators, except for CQ 0.25 wt% (FS and E) and BAPO 0.25 wt% (E) that showed the lowest values.

Conclusion

The wt% of the photoinitiators and co-initiator influenced the mechanical properties and the performance of CQ was dependent on the DMAEMA concentration. BAPO can be used as substitute for the conventional CQ/DMAEMA photoinitiator system.

Effect of Glass Fiber Post Adaptation on Push-Out Bond Strength to Root Dentin

The aim of this study was to evaluate the effect of different glass fiber posts (GFPs) diameters on the push-out bond strength to dentin. Forty unirradicular human teeth were endodontically treated and used for cementation of GFPs (White Post DC, FGM) with different diameters (n=10): P1 - ø 1.6 mm coronal x 0.85 mm apical; P2 - ø 1.8 mm coronal x 1.05 mm apical; P5 - ø 1.4 mm coronal x 0.65 mm apical; and PC - customized post number 0.5 with composite resin (Tetric Ceram A2, Ivoclair Vivadent). All GFPs were cemented into the root canal using a dual-curing luting composite (Variolink II, Ivoclar Vivadent). One slice (1.7 mm) of each root third of cemented GFP (cervical, middle, and apical) was submitted to push-out testing. Failure modes of all specimens were classified as: adhesive failure between resin cement and post; adhesive failure between dentin and resin cement; cohesive failure within resin cement, post or dentin; and mixed failure. The data were analyzed with two-way ANOVA and Tukey's test (a=0.05). The highest bond strength values were presented for the P2 and PC groups. There was no statistically significant difference between the GFP thirds in each group. The groups P2, P5, and PC showed predominantly adhesive failure. For P1, the most prevalent type of failure was adhesive between resin cement and post. It may be concluded that a glass fiber post that is well adapted to the root canal presents higher bond strength values, regardless of GFP third.

Antibacterial resin-based composite containing chlorhexidine for dental applications

OBJETICVE

The aim of this study was to develop a composite material with antibacterial activity using MMT loaded with clorhexidine (CHX). For that it was used a BisGMA/TEGDMA matrix and added low concentration of MMT/CHX. The aim was to evaluate the drug release capacity of MMT, and not to provide reinforcement.

METHODS

Six experimental composites were made with organic matrix of BisGMA/TEGDMA in equal proportions by weight. The composites received organophlizated montmorillonite with or without CHX. The concentrations were 2,5; 5 or 10% by weight. Degree of conversion (DC) was evaluated using FTIR (peak 6165 cm-1; n=5). Specimens for flexural properties (10×2×1mm) were immediate tested (24h). Elastic modulus(E) and flexural strength (FS) was measured using the three point bending test (n=10). Inibition halo was used to test the antibacterial activity against Staphylococcus aureus, Streptococcus mutans, and Porphyromonas gingivalis (n=5 for each bacteria). The inhibition of biofilm formation (BF) was evaluated by inserting polymerized disc of composite in to a culture media colonized with Streptococcus mutans (n=10). The release of CHX was measured using ultraviolet (255nm) for 10 days (n=5). The data of degree of conversion was analysed using Kruskal-Wallis/ Mann-Whitney, and the other variables using two-way ANOVA/Tukey, always considering a global level of significance of 5%.

RESULTS

DC ranged from 71% to 74%. E ranged from 5.7 to 8.1GPa. FS ranged from 61.4 to 74.7MPa. There were no statistical differences among the groups for all the variables. For the three bacteria tested the composites with CHX loaded presented inhibition of growth for all concentration, except for 2,5% that did not inihibited the growth of P. gingivalis. BF was lower for the groups with 10% MMT/CHX, all groups presented BF, even those without CHX loaded. All concentrations presented release off CHX during all the 28 days analyzed.

CONCLUSIONS

Within the limitation of this study it can be concluded that: all concentrations tested presented release of CHX and reduced BF. All concentration presented antibacterial activity for the three bacteria tested, except for 2,5% that did not inhibit the growth of P. gingivalis. The presence of MMT with CHX loaded did not interfere in the properties evaluated.

Resistência à compressão, flexão e tração diametral de cimentos resinosos em tempos diferentes de armazenamento

Objetivos: O objetivo desse estudo foi avaliar a resistência à compressão, tração diametral e flexão de dois cimentos resinosos de presa dual. Métodos: foi utilizado o cimento autoadesivo RelyX U200 (3M ESPE) e o cimento convencional Variolink II (Ivoclar Vivadent). Foram confeccionados corpos de prova cilíndricos com 4mm de diâmetro x 6mm de altura para o teste de compressão, 6mm de diâmetro x 2mm de altura para o teste de tração diametral (ISO 9917-1:2007) e em forma de barra com 25mm de comprimento x 2mm de altura e largura para o teste de flexão três pontos (ISO 4049:2009). As amostras foram armazenadas por 24h (n = 10) e 45 dias (n = 10) em água destilada a 37ºC. Os testes foram realizados em uma máquina universal de ensaios EMIC (DL 2000) com uma célula de carga de 2000 Kgf para o teste de compressão e 200 Kgf para os testes de tração diametral e flexão, à uma velocidade de 0,5 mm/min. Os dados foram submetidos à análise de variância dois critérios (ANOVA) e as médias comparadas pelo teste de Tukey (5%). Resultados: os resultados mostraram valores estatisticamente similares para todas as propriedades mecânicas avaliadas entre todos os cimentos e tempos de armazenamento estudados. Conclusões: A composição química dos cimentos resinosos e o armazenamento em água por 45 dias não foram suficientes para ocasionar alterações nas propriedades mecânicas avaliadas nesse estudo.

Resistência da união ao microcisalhamento de cimento resinoso e resina fluida à cerâmica de dissilicato de lítio

Objetivos: O objetivo neste estudo foi avaliar a resistência da união ao microcisalhamento de uma resina composta microhíbrida de baixa viscosidade (fluida) e de um cimento resinoso fotopolimerizável aplicados a uma cerâmica de dissilicato de lítio. Métodos: Discos de uma cerâmica de dissilicato de lítio (IPS e.max CAD, Ivoclar Vivadent) foram divididos em 2 grupos (n = 10), de acordo com material utilizado para a cimentação: cimento resinoso (Allcem Veneer, FGM) ou resina composta microhíbrida fluida (Opallis Fluida, FGM). Previamente a aplicação do material para cimentação, todas as cerâmicas receberam tratamento superficial padronizado: condicionamento com ácido fluorídrico a 10% (Condac Porcelana, FGM) por 20 s, lavagem com água por 60 s, secagem com ar por 30s e aplicação de silano (Prosil, FGM). Os materiais foram inseridos em uma matriz elastomérica (0,5 mm x 1,2 mm) sobre o bloco cerâmico. Quatro cilindros por grupo foram construídos e fotoativados por um aparelho de diodo emissor de luz (LED, Valo, Ultradent) por 40 s a uma irradiância de 1200 mW/cm2. O teste de microcisalhamento foi feito utilizando uma máquina de ensaio universal (EMIC) a uma velocidade de 0,5 mm/min. Os dados (MPa) foram submetidos ao teste de normalidade (Kolmogorov-Smirnov) e one-way ANOVA, sendo as médias comparadas pelo teste de Tukey (α=0,05). Resultados: O cimento resinoso apresentou resistência da união ao microcisalhamento estatisticamente superior à resina composta fluida (ρ=0,020). Conclusão: Melhor desempenho na união à cerâmica de dissilicato de lítio foi obtido utilizando cimento resinoso.

Effect of Different Photoiniciers of Experimental Adhesive Systems on Adhesive Interface Union Resistance

Aim: The objective of this study was to investigate the performance of experimental resinous adhesives containing different combinations of photoinitiators systems through the bending test. Material and Methods: Resinous adhesive formulations were prepared with monomer mixtures consisting of 50% by mass of bisphenol dimethacrylate glycidyl (BisGMA) and 50% by mass of triethyleneglycol dimethacrylate (TEGDMA). The photoinitiators were used, camphorquinone (CQ) and bis-alkyl phosphinic oxide (BAPO). The co-initiators were diphenyliodonium hexafluorophosphate (DFI) and the amine (dimethylamino methylmethacrylate - DMAEMA) in the 1:1 proportion by mass. The photopolymerizable initiator systems were dissolved in the organic matrix at 0.5% by mass concentrations, creating eight groups (G1- CQ, G2- CQ/amine, G3- CQ/DFI, G4- CQ/amine/DFI, G5- BAPO, G6- BAPO/amine, G7- BAPO/DFI, G8- BAPO/amine/DFI). Samples with 7.0 mm in length, 2.0 mm wide and 1.0 mm height were prepared (n=12). The curing light used was VALO – Ultradent and the curing time was 20 s. The samples were subjected to evaluation of bending test at three points at a speed of 1 mm/min to evaluate the flexural resistance (FR). Results: The results were submitted to analysis of variance with one criterion (p < 0,001) and multiple comparisons were performed using Tukey test. Systems with the photoinitiator BAPO showed higher or equivalent bending values that demonstrated by the conventional system containing CQ/amine. Systems with the DFI had higher flexural values in relation to those demonstrated by systems without the DFI to CQ. Conclusion: The use of systems with alternative photoinitiators and co-initiators allows to obtain superior properties to the conventional system, making these promising systems to act both in isolation as associated with conventional systems.

Evaluation of dimensional stability and details reproduction of alginate molds storage in different times and temperature

<p><strong>Objective:</strong> The aim of this study was to evaluate dimensional stability and detail reproduction in alginate molds stored at different times and temperatures. <strong>Material and </strong><strong>Methods:</strong> Three different commercially available alginates (Cavex Color Change, Jeltrate Plus and Hydrogum 5) were tested at four different times (0 - control, 1, 3 and 5 days) and two temperatures (25ºC and 37ºC) (n=5). The alginates were handled following the manufacturer's instructions. The impression procedures occurred in an environment with controlled room temperature (25ºC) and relative humidity (50±5%). A metallic model (ISO 1563:1990) was used to perform the impressions. The tray containing alginate remained on the metallic model under constant pressure (2 kgf) until the alginate gelation process. The molds were stored (different times and temperatures) and analyzed in stereomicroscope at 30x magnification and 0.5 μm accuracy (Olympus Measuring Microscope STM). The molds and the metallic model measurements were compared, and the data were statistically analyzed by Kolmogorov-Smirnov and three-way ANOVA tests, and the means were compared by Tukey test (5%). <strong>Results:</strong> The results showed no double interactions (p&gt;0.05) and the different alginates presented statistically similar values of dimensional stability (p=0.102). However, 25ºC (temperature) and control group (time) showed the highest values of dimensional stability (p&lt;0.05). Jeltrate Plus was the only material that presented inaccuracy in details reproduction. <strong>Conclusion</strong>: It is recommended that, for tested alginates, the stone casts should be poured immediately, even though the molds are dimensionally stable up to 5 days when stored at 25ºC.</p><p><strong> </strong></p><p><strong>Keywords</strong></p><p>Dental impression materials; Dimensional measurement accuracy; Shrinkage.<strong></strong></p>

Influence of Different Concentration and Ratio of a Photoinitiator System on the Properties of Experimental Resin Composites

Abstract The aim in this study was to evaluate the influence of different ratio of camphorquinone/tertiary amine concentration on the flexural strength (FS), elastic modulus (EM), degree of conversion (DC), yellowing (YL), water sorption (WS) and water solubility (WSL) of experimental composites. Thus, acrylate blends were prepared with different camphorquinone (CQ) and amine (DABE) concentrations and ratios by weight: (CQ/DABE%): 0.4/0.4% (C1), 0.4/0.8% (C2), 0.6/0.6% (C3), 0.6/1.2% (C4), 0.8/0.8% (C5), 0.8/1.6% (C6), 1.0/1.0% (C7), 1.0/2.0% (C8), 1.5/1.5% (C9), 1.5/3.0% (C10). For the FS and EM, rectangular specimens (7x2x1 mm, n=10) were photo-activated by single-peak LED for 20 s and tested at Instron (0.5 mm/min). Then, the same specimens were evaluated by FTIR for DC measurement. For YL, disks (5x2 mm, n=10) were prepared, light-cured for 20 s and evaluated in spectrophotometer using the b aspect of the CIEL*a*b* system. For WS and WSL, the volume of the samples was calculated (mm³). For WS and WSL, composites disks (5x0.5 mm, n=5) were prepared. After desiccation, the specimens were stored in distilled water for 7 days and again desiccated, in order to measure the WS and WSL. Data were submitted to one-way ANOVA and Tukey’s test (5%). The groups C8, C9 and C10 showed higher DC, EM and YL means, compared to other composites. Therefore, the FS and WS values were similar among all groups. Also, C1, C2 and C3 presented higher WSL in 7 days, compared to other composites. In general, higher concentrations of camphorquinone promoted higher physical-mechanical properties; however, inducing higher yellowing effect for the experimental composites

Accuracy of partially edentulous arch impressions obtained from different alginates and storage times

This study aimed to assess the dimensional accuracy of five commercial alginates verified in stone casts. Methods: Each alginate impression (Cavex ColorChange, Cavex Holland BV; Jeltrate Plus, Dentsply; Hydrogum, Zhermack; Kromopan 100, Lascod; Ezact Kromm, Vigodent) was performed on partially edentulous standard stainless steel mandibular arch cast with reference points on teeth 33, 43, 37 and 47. On the stainless steel cast, the anteroposterior (33-37 and 43-47) and transverse (33-43 and 37-47) distances were measured in a stereomicroscope at 30x magnification and 0.5 μm accuracy. The distances between these points were measured three times, obtaining an average, which was analyzed statistically and compared with the distances obtained from the stone casts. For each alginate the casts were poured gypsum (n = 5) immediately and after a period of 1, 2, 3 and 5 days of the impression procedure. Results: The dimensional accuracy values of stone and stainless steel casts were analyzed statistically by two-way ANOVA and Tukey's test (α=0.05). The results showed significant differences between the alginates; however, no differences in dimensional accuracy were found among the different storage times of alginate impression. Conclusions: It can be concluded that the alginate impressions can be stored for up to 5 days.

Evaluation of phenyl-propanedione on yellowing and chemical-mechanical properties of experimental dental resin-based materials

Objective

To evaluate the influence of phenyl-propanedione on yellowing and chemical-mechanical properties of experimental resin-based materials photoactivated using different light curing units (LCUs).

Material and Methods

Experimental resin-based materials with the same organic matrix (60:40 wt% BisGMA:TEGDMA) were mechanically blended using a centrifugal mixing device. To this blend, different photoinitiator systems were added in equimolar concentrations with aliphatic amine doubled by wt%: 0.4 wt% CQ; 0.38 wt% PPD; or 0.2 wt% CQ and 0.19 wt% PPD. The degree of conversion (DC), flexural strength (FS), Young's modulus (YM), Knoop hardness (KNH), crosslinking density (CLD), and yellowing (Y) were evaluated (n=10). All samples were light cured with the following LCUs: a halogen lamp (XL 2500), a monowave LED (Radii), or a polywave LED (Valo) with 16 J/cm2. The results were analysed by two-way ANOVA and Tukey's test (α=0.05).

Results

No statistical differences were found between the different photoinitiator systems to KNH, CLS, FS, and YM properties (p≥0.05). PPD/CQ association showed the higher DC values compared with CQ and PPD isolated systems when photoactivated by a polywave LED (p≤0.05). Y values were highest for the CQ compared with the PPD systems (p≤0.05).

Conclusion

PPD isolated system promoted similar chemical and mechanical properties and less yellowing compared with the CQ isolated system, regardless of the LCU used.

Influence of Photoinitiator and Light-Curing Source on Bond Strength of Experimental Resin Cements to Dentin

Abstract This study evaluated the bond strength (BS) of experimental resin cements formulated with different photoinitiators when activated by two kinds of light-curing units (LCUs) through a ceramic material. Seven resin blends with different camphorquinone (CQ) and/or phenylpropanedione (PPD) concentrations (weight) were prepared: C5: 0.5% CQ; C8: 0.8% CQ; P5: 0.5% PPD; P8: 0.8% PPD; C1P4: 0.1% CQ and 0.4% PPD; C4P1: 0.4% CQ and 0.1% PPD; C4P4: 0.4% CQ and 0.4% PPD. Two LCUs were used: one quartz-tungsten-halogen (QTH - 850 mW/cm²) and one light-emitting diode (LED - 1300 mW/cm²). The microtensile bond strength of each blend was assessed. Data were submitted to two-way ANOVA and Tukey's test (α=0.05). The BS values did not exhibit significant differences for LCUs, regardless of the photoinitiator type. Three cements showed significant differences: P5 and C5 had higher BS with QTH, and C4P1 with LED. For QTH, P5 showed the highest and C1P4 the lowest BS. For the LED, C4P1 showed the highest BS of all the cements. The results indicated that PPD was a viable alternative in the formulation of photocured resin cements, reducing or eliminating CQ that is yellowish without impairing the bond strength. Furthermore, both LED and QTH were effective in curing resin cements that contain PPD or CQ.

Microhardness evaluation of silorane and methacrylate composites submitted to erosion and abrasion processes

Objective: The aim of this study was to evaluate the Knoop hardness number (KHN) of methacrylate (MC) and silorane (SC) composites after being submitted to erosion and abrasion processes. Material and methods: Forty samples were made with each composite: MC and SC. The samples were divided into eight groups (n = 10) according to the type of composite (G1-G4, MC; G5-G8, SC) and the beverages involved in the erosion process (G1 and G5 - Control (C), without erosion, with abrasion; G2 and G6 - Orange Juice (OJ), abrasion; G3 and G7 - Smirnoff Ice® (SI), abrasion; G4 and G8 - Gatorade® (GA), abrasion). The KHN test was performed 24 h after the last cycle of erosion/abrasion. Results: The MC groups showed smaller KHN values for the SI group (p < 0.05) when compared to the Control and OJ groups; however, for the SC groups, no differences were found (p > 0.05). Conclusion: Methacrylate composite when submitted to acidic beverages erosive challenge combined with abrasive process might alter its surface microhardness. However, the beverages used in the present study were not able to interfere in silorane composite surface microhardness.

Minimally Traumatic Surgical Procedures in Periodontics: a Review

<p>The concept of minimally invasive procedures can be extended to all fields of dentistry. Periodontics, in particular, has been reported as one of the areas with great benefits. This review aims to describe the use of minimally invasive procedures in periodontal surgery, its concepts, applications, and possible benefits from its use. For that, 682 articles published between 1950 and 2012 focused on minimally invasive periodontal surgery were evaluated. Of them, 669 studies did not describe clearly the procedures, and did not attend the inclusion criteria. The results showed that proper lighting promotes increased visual acuity during surgical procedures, favoring the precision associated with<br />microsurgical instruments specifically designed, allowing a more accurate manipulation of the soft and hard tissues. Surgical access avoids unnecessary tissues removal, optimizing the debridement, improving vascularisation, and therefore the possibility of obtaining primary healing of surgical wounds. The microsurgical approach can improve the predictability of different periodontal procedures, providing better results and cause less postoperative discomfort. However, few controlled methodologies on the use of instruments to promote minimally invasive procedures in periodontics have been found in literature. Therefore, studies are needed to determine whether microsurgical techniques can lead to a significant difference in the successful outcome. Most of the studies are based on observations and experiences of the authors, which clearly<br />show that there are advantages in having better lighting, better vision, and a more controlled and less traumatic technique.</p>

Influence of photoinitiators and light sources on the degree of conversion of experimental resin cements

Objective: The aim of this study was to evaluate the degree of conversion (DC) of seven experimental resin cements formulated with different photoinitiators when activated by two light-curing units (LCUs) through ceramic material. Material and Methods: Seven resin blends with different camphorquinone (CQ) and/or phenyl propanedione (PPD) rates were prepared: C5: 0.5% wt CQ; C8: 0.8% wt CQ; P5: 0.5% wt PPD; P8: 0.8% wt PPD; C1P4: 0.1% wt CQ and 0.4% wt PPD; C4P1: 0.4% wt CQ and 0.1% wt PPD; and C4P4: 0.4% wt CQ and 0.4% wt PPD. Each mixture was loaded with 65% wt of silanized filler particles. For photoactivation procedures, two LCUs were used: a quartz-tungsten-halogen (QTH) and a light emitting diode (LED). Results: Irradiance (mW/cm²) was calculated by the ratio of the output power by the area of the tip. DC was assessed by Fourier transformed infrared spectroscopy. Data were submitted to a two-way ANOVA and Tukey’s test (5%). DC values do not show significant differences for LCUs regardless of the photoinitiator type. The highest DC was found for experimental cement P8 and the lowest for C5. Conclusion: Intermediate DC values were found for the other cements. However, when QTH was used, P8 exhibited differences among C1P4, C4P1 and C5; whereas when LED was employed, P8 differed only for C4P1 and C5. Thus, PPD is a viable alternative for the manufacture of photoactivated cements, and the PPD/CQ association may also be viable since C4P4 was similar to P8.

Stability of external and internal implant connections after a fatigue test

Objective:

The objective of this study was to compare the torque and detorque values of screw intermediates of external hexagon, internal hexagon, and Morse taper implants in single restorations before and after mechanical cycling.

Materials and Methods:

The study sample was divided into three groups (n = 10) as follows: group EH – external hexagon implant, group IH – internal hexagon implant, and group MT – Morse taper implant. Universal abutments were screwed on the implants, and metal crowns were cemented onto the abutment. The samples were submitted to a mechanical testing of 1 million cycles, with a frequency of 8 cycles per second under a 400 N load. The application and registration of the screw torque (T0) and detorque (T1) values of the intermediate were performed before and after the test. The results were statistically evaluated by analysis of variance (ANOVA) and Tukey's test (α = 0.05).

Results:

There was no difference between the values of T0 and T1 in the intra-group samples. However, the inter-group difference in T0 between the EH (12.8 N cm) and MT (18.6 N cm) groups and in T1 between the EH (10.4 N cm) and IH (13.8 N cm), EH and MT (19.4 N cm), and MT and IH (P = 0.001) groups were significant. The MT group showed a lower variation of T0 and T1.

Conclusion:

The internal implants, particularly MT, showed better stability in these cases when used for single restorations.

Influence of the curing mode on the degree of conversion of a dual-cured self-adhesive resin luting cement beneath ceramic

OBJECTIVE

To evaluate the effect of the delayed photoactivation and ceramic barrier on the degree of conversion (DC) of self-adhesive resin cement.

MATERIALS AND METHODS

Circular specimens (5 mm in diameter × 1 mm in thickness) of the RelyX U-100 resin cement were made using the following curing protocols (n = 10): (G1) 40 s beneath a IPS Empress II ceramic; (G2) 40 s of direct photocuring; (G3) 80 s beneath the ceramic; (G4) 80 s of direct photocuring; (G5) self-curing; (G6) 5 min in the absence of light (self-curing) followed by transceramic photocuring for 40 s; (G7) 5 min in the absence of light (self-curing) followed by transceramic photocuring for 80 s. All the specimens were photoactivated by LED (800 mW/cm(2)). After 24 h of dry storage, the DC was measured by FTIR, on the top surface of the specimens. Data were submitted to one-way ANOVA and Tukey test (p ≤ 0.05).

RESULTS

Direct photocuring with no ceramic interposition, regardless of the curing time (40 s and 80 s) promoted the highest conversion mean (56.79 ± 1.19 and 59.98 ± 2.93, respectively) and the 5 min delay time for the transceramic photocuring presented a similar mean compared to the immediate transceramic photocuring. The DC was influenced by the ceramic barrier, decreasing the conversion values (49.72 ± 1.91 for 40 s and 52.36 ± 2.50 for 80 s), with no statistical difference from the groups with the previous 5 min of photoactivation delay. The self-cure only showed the worst DC values.

CONCLUSION

Direct photocuring provided a higher degree of conversion for the self-adhesive resin cement. The delayed light activation did not influence the degree of conversion for the resin cement tested.

Dynamic mechanical thermal analysis of composite resins with CQ and PPD as photo-initiators photoactivated by QTH and LED units

OBJECTIVES

The aim of this study was to evaluate the thermal and mechanical properties of the composite resins containing the photo-initiators camphorquinone (CQ) and/or phenyl-propanodione (PPD) when photoactivated with halogen lamp (XL2500/3M-ESPE), monowave (UltraBlueIS/DMC) and polywave (UltraLume5/Ultradent) LED units.

MATERIALS AND METHODS

A blend of BisGMA, UDMA, BisEMA and TEGDMA was prepared with the same wt% of photo-initiators CQ and/or PPD and 65wt% of silaneted filler particles. Compression strength (CS), diametral tensile strength (DTS) and diametral modulus (DM) were tested. Thermogravimetric analysis (TGA) was made and the lost residual monomer were verified. Dynamic mechanical thermal analysis (DMTA) was used for to analyze the glass transition temperature (Tg) and the storage modulus in 37°C. Degree of conversion (DC) was accomplished in the same samples of DMA using middle-infrared spectroscopy (mid-IR).

RESULTS

CQ, CQ/PPD and PPD obtained the same results for all mechanical properties (CS, DTS and DM), lost residual monomer and storage modulus in 37°C, regardless LCU used. The results of Tg showed that the combination PPD-UltraLume5 produced the highest values. DC showed that the combination CQ-UltraLume5 resulted in the highest values and PPD-XL2500 in the lowest DC values.

CONCLUSION

The study shows that PPD is not only effective photosensitizers, but also photocrosslinking agents for dental composite resins with a similar efficiency to CQ.

Mechanical properties of direct and indirect composites after storage for 24 hours and 10 months

OBJECTIVE

The objective of this study was to evaluate the diametral tensile strength (DTS) and Knoop hardness (KH) of direct (Filtek Z350-3M/ESPE and Charisma-Heraeus Kulzer) and indirect composites (Sinfony-3M/ESPE and Signum-Heraeus Kulzer) kept in storage for two periods of time, 24 hours and 10 months, in distilled water.

METHODS

Twenty-five specimens of each material were prepared. DTS (n=10) was tested using a universal testing machine (Versat, model 2000) at a crosshead speed of 1.0 mm/min. KH (n=5) was measured using Knoop micro-hardness (HMV-2000; 50 gf for 15 s). All tests were performed 24 hours after polymerization and after 10 months of storage in distilled water at 37°C. The data were statistically analyzed using Kolmogorov-Smirnov, ANOVA and t-Student (P=.05).

RESULTS

Filtek Z350, Sinfony, and Signum showed higher DTS values than Charisma after 24 hours. After storage, Sinfony and Signum showed higher DTS values because the storage did not influence the DTS values of the indirect composites. Filtek Z350 showed higher KH values after 24 hours and after storage than other composites; the storage influenced the KH of all composites except Sinfony.

CONCLUSION

Storage for 10 months did not influence the properties of the indirect composite Sinfony. In general, the indirect composites showed higher DTS values than direct composites, especially after 10 months storage. The direct composite Filtek Z350 obtained the highest KH values regardless of storage.

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.

Effect of different photoactivation methods on the bond strength of composite resin restorations by push-out test

OBJECTIVE

Modulated curing methods could lead to a higher probability of bond preservation. Therefore, the aim of this study was to evaluate the effect of 7 curing methods on bond strength of composite resin restorations.

METHOD AND MATERIALS

Seventy bovine incisors were selected. A conical cavity was prepared in the buccal surface. Adper Single Bond adhesive system was applied according to the manufacturer's instructions, and the cavities were filled with a single increment of Esthet X (Dentsply/Caulk). The specimens were randomly assigned into 7 groups (n = 10) according to the photoactivation method: (1) continuous light 700 (700 mW/cm2) (control); (2) continuous light 150 (150 mW/cm2); (3) continuous light 250 (250 mW/cm2); (4) soft-start 75 (75 mW/cm2) + 700 mW/cm2); (5) soft-start 150 (150 mW/cm2 + 700 mW/cm2); (6) pulse-delay (150 mW/cm2 + 3 minutes + 700 mW/cm2); and (7) intermittent light (cycles at 600 mW/cm2). The energy density for all groups was 14 J/cm2. The bond strength of the composite restorations was measured by performing the push-out test in a universal testing machine (Instron). The results were submitted to ANOVA and Tukey test (P < .05).

RESULTS

Pulse-delay, soft-start 150, and soft-start 75 methods showed a significant increase in bond strength when compared with the control continuous light 700 method. Low power density and intermittent light groups showed intermediate results.

CONCLUSION

Modulation of the energy density during light curing of composite resins using pulse-delay or soft-start methods increased the bond strength of composite restorations.

Influence of irradiance on the push-out bond strength of composite restorations photoactivated by LED

AIM

The aim of this study was to compare the bond strength of resin composites to dental structure photoactivated with a light emitting diode (LED) curing unit.

METHODS AND MATERIALS

One hundred bovine incisors were selected and a conical cavity was prepared in the facial surface of each tooth. Clearfil SE Bond (Kuraray CO., LTD. Osaka, Japan) adhesive system was applied, and the cavities were filled with a single increment of Filtektrade mark Z250 (3M ESPE, St. Paul, MN, USA) or Esthet-X (Dentsply-Caulk - Mildford, DE, USA). The specimens were assigned to ten groups (n=10) according to the irradiance used: 100, 200, 300, 400, or 500 mW/cm(2). Photoactivation was accomplished using an Ultrablue IS LED (DMC Equipamentos LTDA, São Carlos, SP, Brazil). The radiant exposure time was kept constant. A push-out test was conducted in a universal testing machine. Bond strength values were submitted to a two-way analysis of variance (ANOVA) and a Tukey's test at the 5% significance level.

RESULTS

The bond strength of the Z250 was higher than the Eshet-X (p<0.05). However, the modulation of irradiance adjusted to the same radiant exposure had no influence on Z250. The bond strength using an irradiance of 100mW/cm(2) was higher than the other levels for Esthet-X. When composites were compared, no significant differences were detected between them for activation with irradiances of 100 and 200 mW/cm(2).

CONCLUSION

The modulation of the luminous energy emitted by LED was almost unable to provide significant differences among the groups for both composites, except for a lower irradiance of Esthet-X.

Relationship between bond strength and marginal and internal adaptation of composite restorations photocured by different methods

OBJECTIVE

This study evaluated the relationship between bond strength and marginal and internal adaptation of composite restorations photocured using different methods with a quartz-tungsten-halogen light.

MATERIAL AND METHODS

A push-out test was performed to evaluate bond strength of conical restorations in 50 bovine incisors. To evaluate marginal (external) and internal restoration adaptation, 50 circular all-enamel margin preparations were done in bovine incisors. For both tests, the preparations were filled with Esthet*X resin composite. Specimens were distributed into 5 groups (n=10) depending on photoactivation method: G1: continuous light 700; G2: continuous light 150; G3: soft-start; G4: intermittent light; and G5: pulse-delay. The energy density for each method was standardized: 14 J/cm2. Caries Detector (Kuraray) was placed in restoration margins for detection of marginal adaptation. The percentage of interfaces present as gaps was determined using digital images. Specimens were then sectioned, stained, and the internal adaptation was recorded in a similar manner. Data were submitted to ANOVA and the Tukey HSD test, pre-set alpha = 0.05.

RESULTS

Bond strength G5 (7.2 MPa+/-1.3) was significantly greater (p=0.00280) than G1 (4.6 MPa+/-1.5). G2, G3, and G4 showed equivalent, intermediate strength values. No significant difference was found in marginal adaptation of any of the groups (p=0.16911). Internal adaptation results were the inverse of strength results: G5 (2.8%+/-4.9) showed significantly less (p=0.00979) gap formation compared to G1 (10.1%+/-6.2).

CONCLUSION

Some modulated photocuring methods can increase bond strength while decreasing internal gap formation. An inverse relationship was found between push-out bond strength and internal adaptation. Marginal adaptation was not affected by any photoactivation method.