Hydrofluoric acid concentration, time and use of phosphoric acid on the bond strength of feldspathic ceramics

Abstract The objective of this study was to evaluate the influence of hydrofluoric acid (HF) concentration, etching time, and application of phosphoric acid (PA) followed by neutralization with sodium bicarbonate on the bond strength between a feldspar ceramic and resin cement. Thus, 80 blocks (10 x 12 x 2 mm) of glass ceramic (VM - Vita Mark II - Vita Zahnfabrik) were made and randomly assigned to eight groups (n = 10) according to the factors: HF concentration (5 and 10%), etching time (60 and 120 s), and use of phosphoric acid (PA) (with and without). According to the experimental group, 37% PA (Condac, FGM) was applied after HF etching for 60s. Afterwards, samples were immersed in sodium bicarbonate for 1 min then in an ultrasonic bath in distilled water (5 min) for cleaning. After surface bonding treatment, cylinders (Ø = 2 mm; h = 2 mm) of dual resin cement (AllCem / FGM) were made in the center of each block. The samples were then stored in water (37ºC) for 90 days and submitted to the shear bond test (50 KgF, 1 mm/min). Failure analysis was performed by stereomicroscope and scanning electron microscopy. Data (MPa) were analyzed with 3-way ANOVA and Tukey's test. Only the factor "HF concentration" was significant (p = 0.02). Most failures were of cohesive in ceramic (40%) and mixed types (42.5%). The 10% HF resulted in higher shear bond strength value than the 5% HF. Surface cleaning with phosphoric acid followed by sodium bicarbonate and HF time (60 or 120 seconds) did not influence the resin bond strength to feldspar ceramic.

Cerámicas: una actualización / Ceramics: an update / Cerâmica: uma atualização

Las cerámicas dentales utilizadas para restaurar y reemplazar tejido dental perdido de los dientes o las piezas dentales mismas, han sufrido una enorme transformación desde que aparecieron las primeras porcelanas hace ya varias décadas. Con las feldespáticas se podían hacer dientes, coronas y puentes pero, necesitaban un soporte de metal para que no sufran fracturas con los esfuerzos masticatorios, y por ello no tenían una apa-riencia vital. Hoy en día, han aparecido muchas otras cerámicas con diferentes y mejoradas características mecánicas y ópticas, lo que ha permitido que los odontólogos puedan por primera vez ofrecer a sus pacientes dientes artificiales con sorprendente naturalidad. Objetivo: Describir la clasificación actual, las características mecánicas y ópticas, así como la microestructura y los usos clínicos de las diferentes cerámicas dentales utilizadas hoy en día. Materiales y métodos: Revisión de la literatura acerca del tema, en tres de los más importantes buscadores de internet (Pubmed,Cochrane,Web of Science). Limitando su busca a artículos en inglés y publicados en los journals de investigación de materiales dentales con calificación Q1 y Q2. Resul-tados: Se revisaron 69 artículos publicados entre 1975 y 2019 los cuales aportaron una fuente interesante de información que permitió desarrollar el conocimiento acerca de la clasificación, microestructura, propiedades mecánicas y ópticas, usos clínicos y forma de procesamiento de las cerámicas. Conclusiones: Actualmente los odontólogos tienen a disposición una amplia variedad de materiales cerámicos con diferentes composicio-nes y características únicas que son necesarias conocer al momento de escoger la cerámica específica para cada necesidad de los pacientes.

The dental ceramics used to restore and replace lost tooth tissue or the teeth have undergone a huge trans-formation since the first porcelains appeared several decades ago. With the feldspathic teeth, crowns and bridges could be made but, they needed a metal support so that they did not suffer fractures with the mastica-tory efforts, and therefore they did not have a vital appearance. Today, many other ceramics with different and improved mechanical and optical characteristics have appeared, which has allowed dentists to offer artificial teeth to their patients for the first time with surprising naturalness. Objective: Describe the current classifica-tion, mechanical and optical characteristics, as well as the microstructure and clinical uses of the different dental ceramics used today. Materials and methods: Review about the literature on the subject, in three of the most important internet search engines (Pubmed, Cochrane, Web of Science). Limiting your search to articles in English and published in the journals of research of dental materials with qualification Q1 and Q2. Results:69 articles published between 1975 and 2019 were reviewed, which provided an interesting source of informa-tion that allowed the development of knowledge about classification, microstructure, mechanical and optical properties, clinical uses and method of processing ceramics. Conclusions: Currently, dentists have available a wide variety of ceramic materials with different compositions and unique characteristics that are necessary to know when choosing the specific ceramic for each patient need.

A cerâmica dentária usada para restaurar e substituir o tecido dentário perdido ou as próprias peças dentárias sofreram uma enorme transformação desde que as primeiras porcelanas surgiram várias décadas atrás. Com os materiais feldespáticos, podiam ser feitas coroas e pontes, mas eles precisavam de um suporte de metal para não sofrer fraturas com os esforços mastigatórios e, portanto, não tinham uma aparência de vitalidade. Hoje, outras cerâmicas com características mecânicas e ópticas diferentes e aprimoradas surgiram, o que permitiu aos dentistas oferecer dentes artificiais a seus pacientes pela primeira vez com uma naturalidade surpreendente. Objetivo: Descrever a classificação atual, características mecânicas e ópticas, bem como a microestrutura e os usos clínicos das diferentes cerâmicas odontológicas utilizadas atualmente. Materiais e métodos: Revisão da literatura sobre o assunto, em três dos mais importantes mecanismos de busca na In-ternet (Pubmed, Cochrane, Web of Science). Limitando a sua pesquisa a artigos em inglês e publicados nas revistas científicas de materiais dentários com qualificação Q1 e Q2. Resultados: Foram revisados 69 artigos publicados entre 1975 e 2019, que forneceram uma fonte interessante de informações que permitiram desen-volver conhecimento sobre a classificação, microestrutura, propriedades mecânicas e ópticas, usos clínicos e forma de processamento da cerâmica. Conclusões: Atualmente, os dentistas têm disponível uma ampla variedade de materiais cerâmicos com composição diferente e características únicas que são necessárias conhecer ao escolher a cerâmica específica para cada necessidade do paciente.

Surface morphologic evaluation of orthodontic bonding systems under conditions of cariogenic challenge

Abstract: Orthodontic bonding systems are submitted to demineralization and remineralization dynamics that might compromise their surface smoothness, and favor biofilm aggregation and caries development. The aim of the present study was to evaluate the effects of a cariogenic challenge model (in vitro pH-cycling model) on the surface roughness and topography of 3 bonding materials: Transbond™ XT (XT), Transbond™ Plus Color Change (PLUS) and Fuji Ortho™ LC (FUJI), by means of Atomic Force Microscopy (AFM). Six specimens with standardized dimensions and surface smoothness were fabricated per group, and the materials were manipulated in accordance with the manufacturers' instructions. No polishing was necessary. AFM tests were performed before and after pH-cycling, taking 3 readouts per specimen. The roughness results (Ra) were obtained at nanometric levels (nm) and surface records were acquired in two- and three-dimensional images of height and lock-in phase of the material components. The surfaces of all groups analyzed in the study were morphologically altered, presenting images suggestive of matrix degradation and loss of matrix-load integrity. FUJI presented the greatest increase in surface roughness, followed by XT and PLUS, respectively (p≤0.001). Nevertheless, the roughness values found did not present sufficient degradation to harbor bacteria. The surface roughness of all tested materials was increased by pH-cycling. The use of materials capable of resisting degradation in the oral environment is recommended, in order to conserve their integrity and of the surrounding tissues.

Brittleness index and its relationship with materials mechanical properties: Influence on the machinability of CAD/CAM materials

Abstract: The aim of this study is to evaluate the machinability of four CAD/CAM materials (n = 13) assessed by brittleness index, Vickers hardness, and fracture toughness and interaction among such mechanical properties. The materials selected in this in vitro study are Feldspathic ceramic [FC], Lithium-disilicate glass ceramic [LD], leucite-reinforced glass ceramic [LR], and nanofilled resin material [RN]. Slices were made from the blocks following original dimensions 14 × 12 × 3 mm (L × W × H), using a precision slow-speed saw device and then surfaces were regularized through a polishing device. Brittleness index and fracture toughness were calculated by the use of specific equations for each one of the properties. The Vickers hardness was calculated automated software in the microhardness device. One-way Anova and Pearson's correlation were applied to data evaluation. LD obtained the highest values for brittleness index and was not significantly different from FC. LR presented statistically significant difference compared with RN, which had the lowest mean. Vickers hardness showed LD with the highest average, and no statistical difference was found between FC and LR. RN presented the lowest average. Fracture toughness showed FC and LR not statistically different from each other, likewise LD and RN. The brittleness index, considered also as the machinability of a material, showed within this study as positively dependent on Vickers hardness, which leads to conclusion that hardness of ceramics is related to its milling capacity. In addition, fracture toughness of pre-sintered ceramics is compared to polymer-based materials.

Bond strengths of various resin cements to different ceramics

Abstract This study evaluates the shear bond strength (SBS) of various resin cements to different ceramics. Composite resin cylinders of Z100 were fabricated and cemented to disks of feldspathic ceramic (Creation), leucite-reinforced feldspathic ceramic (Empress I), and densely sintered aluminum oxide ceramic (Procera AllCeram) using five resin cements: Panavia F (PAN), RelyX ARC (ARC), RelyX Unicem (RXU), RelyX Veneer, and Variolink II. SBS was measured after three days of water storage (baseline) and after artificial aging (180 days of water storage along with 12,000 thermal cycles). Failure mode of fractured specimens also was evaluated. Data were analyzed with Kruskal-Wallis and Mann-Whitney tests (α=0.05). RXU showed 1) the lowest baseline median SBS to feldspathic ceramic, which was not statistically different from PAN; 2) the lowest median baseline SBS to leucite-reinforced feldspathic and densely sintered aluminum-oxide ceramics. All cements performed similarly after aging, except for ARC (median 0.0 MPa) and PAN (median 16.2 MPa) in the densely sintered aluminum-oxide ceramic group. Resin cements perform differently when bonded to different ceramic substrates. While all test resin cements worked similarly in the long-term to feldspathic and leucite-reinforced feldspathic ceramics, only the MDP-containing resin cement provided durable bonds to densely sintered aluminum-oxide ceramic.

Fluoride release and uptake in enhanced bioactivity glass ionomer cement ("glass carbomer™") compared with conventional and resin-modified glass ionomer cements

Abstract Objectives To study the fluoride uptake and release properties of glass carbomer dental cements and compare them with those of conventional and resin-modified glass ionomers. Materials and Methods Three materials were used, as follows: glass carbomer (Glass Fill), conventional glass ionomer (Chemfil Rock) and resin-modified glass ionomer (Fuji II LC). For all materials, specimens (sets of six) were matured at room temperature for time intervals of 10 minutes, 1 hour and 6 weeks, then exposed to either deionized water or sodium fluoride solution (1000 ppm in fluoride) for 24 hours. Following this, all specimens were placed in deionized water for additional 24 hours and fluoride release was measured. Results Storage in water led to increase in mass in all cases due to water uptake, with uptake varying with maturing time and material type. Storage in aqueous NaF led to variable results. Glass carbomer showed mass losses at all maturing times, whereas the conventional glass ionomer gained mass for some maturing times, and the resin-modified glass ionomer gained mass for all maturing times. All materials released fluoride into deionized water, with glass carbomer showing the highest release. For both types of glass ionomer, uptake of fluoride led to enhanced fluoride release into deionized water. In contrast, uptake by glass carbomer did not lead to increased fluoride release, although it was substantially higher than the uptake by both types of glass ionomer. Conclusions Glass carbomer resembles glass ionomer cements in its fluoride uptake behavior but differs when considering that its fluoride uptake does not lead to increased fluoride release.

Estimation of the prophylactic effect of the egyptian propolis extract against aluminum silicate toxicity on some organs of albino rats growth performance and histochemical studies

Background: the liver is a critical organ because it contains most of the accumulated metals where toxic effects can expected. Also, the lung is directly affected by receiving aluminum as aluminum silicate. Exposure of aluminum leads to production of free radicals that damage living organs and tissues. Aim of the work: this study aimed to evaluate the nucleic acid content in liver, lung and cerebellum tissues intoxicated by aluminum silicate (AlS) and the possible ameliorative effect of propolis extract (PP). Material and methods: Forty male albino rats (weighting 100-120 grams) were categorized randomly into four groups, ten rats on each group (n=10). The 1st group considered as the healthy control group. The 2nd group received 200 ml PP/kg b.wt., day after day by stomach gavage. The 3rd group was injected intraperitoneally by 20 mg AlS/kg b.wt., twice weekly. The 4th group was treated with AlS in addition to PP as the same doses as in the 2nd and 3rd groups. After two months for each group. Liver, lung and cerebellum organs were harvested. Results: decreased body weight gain of rats was realized with weakly stained nucleic acids contents in liver, lung and cerebellum tissues that intoxicated by AlS. While, using the supplemented treatment (PP) at the same time with the induction of AlS compound showed an ameliorative effect on the nucleic acid contents. Conclusion: propolis has anti-oxidant by inhibiting AlS toxicity on nucleic acids in the different experimental organs of rats

Color changes caused by reduction on the dentin shade composite thickness

Resumo Este estudo objetivou determinar o limiar de redução na espessura do compósito de cor da dentina necessário para resultar em mudanças de cor perceptíveis e aceitáveis em restaurações simuladas. Três sistemas de compósitos (Charisma Diamond, IPS Empress Direct e Filtek Z350 XT) foram avaliados utilizando corpos-de-prova cilíndricos construídos com cores de dentina e esmalte. A opacidade dos compósitos foi avaliada usando cilindros de 1,0 mm de espessura sobre fundo preto e branco. Uma cor inicial padrão foi estabelecida para cada sistema pela combinação de esmalte de 1,0 mm de espessura com 3,0 mm de cilindros de resina na cor de dentina sobre um fundo escuro (n = 9). Em seguida, foram calculadas as alterações de cor (∆E00) causadas por reduções sequenciais de 0,1 mm nos cilindros de resina na cor de dentina. Mudanças de opacidade em cilindros na cor de dentina e cilindros combinados de esmalte e dentina foram também avaliadas após cada redução de espessura. Regressão polinomial foi realizada com médias de ∆E00 em função da espessura dos cilindros na cor de dentina; e os limiares de aceitabilidade (∆E00 = 1,77) e perceptibilidade (∆E00 = 0,81) foram calculados. Regressões lineares também foram realizadas para ∆E00 em função da opacidade dos cilindros na cor de dentina e do par combinado de cilindros de esmalte-dentina. Com exceção da Charisma, os compósitos de esmalte apresentaram menor opacidade do que os de dentina. Alterações de cor perceptíveis e aceitáveis foram observadas quando os cilindros na cor de dentina foram mais finos que 2,0-2,4 mm e 1,1-1,4 mm, respectivamente. Nenhuma diferença entre os sistemas compostos foi observada. Em conclusão, reduções no compósito de dentina menor que 0,6 mm não produziu mudanças de cor perceptíveis, e mudanças de cor clinicamente significantes apenas foram observadas com reduções maiores que 1,6 mm.

Abstract This study determined the reduction threshold in thickness of the dentin shade composite necessary to result in perceptible and acceptable color changes on simulated restorations. Three composite systems (Charisma Diamond, IPS Empress Direct, and Filtek Z350 XT) were evaluated using cylinder-shaped specimens built-up with dentin and enamel shades. The opacity of the composites was assessed using 1.0 mm thick specimens over black and white backgrounds. A baseline color was established for each system by combining 1.0 mm thick enamel shade with 3.0 mm of dentin shade cylinders over a dark background (n = 9). Then, the color changes (∆E00) caused by sequential 0.1 mm reductions on dentin shade cylinders were calculated. Opacity changes on dentin shade cylinders and combined enamel-dentin pair cylinders were also assessed after each thickness reduction. Polynomial regression was performed with averages of ∆E00 as a function of thickness of dentin shade cylinders; and acceptability (∆E = 1.77) and perceptibility (∆E = 0.81) thresholds were calculated. Linear regressions were also performed for ∆E00 as function of opacity of dentin shade cylinders and combined enamel-dentin pair of cylinders. Except for Charisma, enamel shades presented the lowest opacity than dentin one. Perceptible and acceptable color changes were observed for dentin shade cylinders thinner than 2.0-2.4 mm and 1.1-1.4 mm, respectively, were used. No difference among the composite systems was observed. In conclusion, reductions on dentin shade composite lower than 0.6-mm did not yield perceptible color changes, and clinically significant color changes only were observed within reductions higher than 1.6-mm.

Feldspar ceramic strength and the reinforcing effect by adhesive cementation under accelerated aging

Abstract This study evaluated the effect of the accelerated artificial aging (AAA) on feldspar ceramic strength and the reinforcing effect promoted by adhesive cementation with resin luting agent. One hundred twenty feldspar ceramic disks were obtained. Sixty disks were acid-etched, silanized, and coated with an experimental resin luting agent simulating the adhesive luting procedures. Four groups were created (n=30): uncoated ceramic (control group), uncoated ceramic submitted to AAA, ceramic coated with resin luting agent, and coated ceramic submitted to AAA. Biaxial flexural testing with ball-on-ring setup was carried out. Biaxial flexural strength (s bf , MPa), characteristic strength (s 0 , MPa), and Weibull modulus (m) were calculated for axial positions z=0 (ceramic surface) and z=−t2 (luting agent surface). Data of s bf at positions z=0 and z=-t2 were separately submitted to statistical analyses (a=0.05). The uncoated ceramic submitted to AAA had no significant difference in s bf and s 0 compared with the control group. Resin coating of the ceramic increased s bf and s 0 at z=0. The AAA increased the s bf and s 0 for the resin-coated ceramic specimens at z=0 and also the s 0 at axial position z=-t2. The structural reliability at z=0 and z=-t2 was not influenced by the variables tested. In conclusion, resin coating improved the mechanical strength of the feldspar ceramic. The AAA procedure was not effective in aging the uncoated or resin-coated feldspar ceramic specimens.

Resumo Este estudo avaliou o efeito do envelhecimento artificial acelerado (EAA) na resistência da cerâmica feldspática e o reforço promovido pela cimentação adesiva com cimento resinoso. Cento e vinte discos de cerâmica feldspática foram obtidos. Sessenta discos foram condicionados com ácido, silanizados, e recobertos com um cimento resinoso experimental simulando os procedimentos de cimentação adesiva. Quatro grupos foram criados (n=30): cerâmica sem recobrimento (grupo controle), cerâmica sem recobrimento submetida ao EAA, cerâmica recoberta com cimento resinoso, cerâmica recoberta com cimento resinoso submetida ao EAA. O teste de resistência à flexão biaxial foi realizado utilizando o dispositivo pistão-anel. Resistência à flexão biaxial (s fb , MPa), resistência característica (s 0 , MPa), e módulo de Weibull (m) foram calculados para as posições axiais z=0 (superfície da cerâmica) e z=−t2 (superfície do cimento). Os dados de s fb em z=0 e z=−t2 foram submetidos a análises estatísticas separadamente (a=0,05). A cerâmica não recoberta submetida ao EAA não teve diferença significante na s fb e s 0 comparada com o grupo controle. O recobrimento com cimento resinoso da cerâmica aumentou a s fb e s 0 em z=0. O EAA aumentou a s fb e s 0 para os espécimes de cerâmica recobertos com cimento resinoso em z=0 e também a s 0 em z=−t2. A confiabilidade em z=0 e z=−t2 não foi influenciada pelas variáveis testadas. Concluindo, o recobrimento com cimento resinoso melhorou a resistência mecânica da cerâmica feldspática. O procedimento de EAA não foi efetivo em envelhecer os espécimes de cerâmica feldspática recobertos ou não com cimento resinoso.

Can heat-pressed feldspathic ceramic be submitted to multiple heat-pressing?

Abstract The aim of this study was to determine if multiple processing (heat-pressing) of a dental ceramic influences flexural strength, hardness, and microstructure. Ninety bar-shaped specimens (15 mm × 4 mm × 2 mm) of a pressed ceramic (Vita PM9) were fabricated and randomly divided into 6 groups (n = 15) according to the factors "number of pressings" (C1, C2, and C3, fired 1, 2, and 3 times, respectively) and "mechanical cycling" (M). Half of the specimens were mechanically cycled (106 cycles, 45 N, 3.4 Hz, in water) and all specimens were tested for 3-point bending (0.5 mm/min, load 1000 kgf) and Vickers hardness (19.6 N for 20 s). X-ray diffraction was used to characterize the phases and scanning electron microscopy to characterize the microstructure. The flexural strength data was statistically analyzed with Weibull analysis, ANOVA, and Tukey test. Hardness data was evaluated by 2-way ANOVA and Fisher test. All tests were performed with a significance level of 0.05. Two-way ANOVA revealed that neither "number of pressings" (p=0.085) or "mechanical cycling" (0.055) significantly affected flexural strength. But Weibull analysis showed significant difference for Weibull moduli and characteristic strength between groups. For hardness, a statistical difference was seen for the interaction "Number of pressings * Mechanical cycling", (p = 0.016). Hardness decreased in the following order: C1 (775±17.2), CM3 (751±101), CM2 (735±45), C3 (701±82), CM1 (671±82), and C2 (663±92). Fewer defects were observed with an increased number of firings. Therefore, the possibility of recycling PM9 ceramic does not interfere in the evaluated mechanical properties and improves microstructure.

Effect of cavity preparation design and ceramic type on the stress distribution, strain and fracture resistance of CAD/CAM onlays in molars

Abstract Objective This study aimed to evaluate the effect of the cavity preparation and ceramic type on the stress distribution, tooth strain, fracture resistance and fracture mode of human molar teeth restored with onlays. Material and Methods Forty-eight molars were divided into four groups (n=12) with assorted combinations of two study factors: BL- conventional onlay preparation with boxes made from leucite ceramic (IPS-Empress CAD, Ivoclar Vivadent); NBL- conservative onlay preparation without boxes made from leucite ceramic; BD- conventional onlay preparation with boxes made from lithium disilicate glass ceramic (IPS e.max CAD, Ivoclar Vivadent); NBL- conservative onlay preparation with boxes made from lithium disilicate glass ceramic cuspal deformation (µS) was measured at 100 N and at maximum fracture load using strain gauge. Fracture resistance (N) was measured using a compression test, and the fracture mode was recorded. Finite element analysis was used to evaluate the stress distribution by modified von Mises stress criteria. The tooth strain and fracture resistance data were analyzed using the Tukey test and two-way ANOVA, and the fracture mode was analyzed by the chi-square test (α=0.05). Results The leucite ceramic resulted in higher tooth deformation at 100 N and lower tooth deformation at the maximum fracture load than the lithium disilicate ceramic (P<0.001). The lithium disilicate ceramic exhibited higher fracture resistance than the leucite ceramic (P<0.001). The conservative onlay resulted in higher fracture strength for lithium disilicate ceramic. Finite element analysis results showed the conventional cavity preparation resulted in higher stress concentration in the ceramic restoration and remaining tooth than the conservative onlay preparation. The conservative onlays exhibited increased fracture resistance, reduced stress concentration and more favorable fracture modes. Conclusion Molars restored with lithium disilicate CAD-CAM ceramic onlays exhibited higher fracture resistance than molars restored with leucite CAD-CAM ceramic onlays.

Influence of glass-based dental ceramic type and thickness with identical shade on the light transmittance and the degree of conversion of resin cement / 国际口腔科学杂志·英文版

The purpose of this study was to assess the influence of the types and thicknesses of glass ceramic plates on light transmittance and compare the degrees of conversion (DC) of resin cement under the ceramic materials. Three ceramic plates with thicknesses of 0.5, 1.0, 2.0, and 4.0 mm were fabricated from each of five commercial ceramic blocks in shade A2: high-translucency and low-translucency IPS Empress CAD (Emp_HT and Emp_LT); high-translucency and low-translucency IPS e.max CAD (Emx_HT and Emx_LT); and Vita Mark II (Vita). The translucency parameter was obtained using a colorimeter. The light transmittance rate was measured using a photodetector attached to an optical power meter. The DC of a resin cement (Variolink N) underneath the ceramic plates was examined by Fourier transform infrared spectroscopy. The translucency parameter, light transmittance rate, and DC showed significant differences by ceramic type and thickness (P  0.05). Both type and thickness of the glass ceramics significantly influenced the light transmittance and DC of the light-cured resin cement beneath the ceramic of the same shade.

Influence of resin-modified glass ionomer and topical fluoride on levels of Streptococcus mutans in saliva and biofilm adjacent to metallic brackets

Abstract Decalcification of enamel during fixed orthodontic appliance treatment remains a problem. White spot lesions are observed in nearly 50% of patients undergoing orthodontic treatment. The use of fluoride-containing orthodontic materials has shown inconclusive results on their ability to reduce decalcification. The aims of this investigation were to compare the levels of Streptococcus mutans (SM) in saliva and biofilm adjacent to orthodontic brackets retained with a resin-modified glass ionomer cement (RMGIC) (Fuji ORTHO LC) and a light cured composite resin (Transbond XT), and to analyze the influence of topical application of the 1.23% acidulated phosphate fluoride (APF) on SM counts. In a parallel study design, two groups (n=14/15) were used with random allocation and high salivary SM counts before treatment. Biofilm was collected from areas adjacent to the brackets on teeth 13, 22, 33, and 41. Both saliva and biofilm were collected on the 7th, 21st, 35th, and 49th days after appliance placement. Topical fluoride application was carried out on the 35th day. Bonding with RMGIC did not alter SM counts in saliva or biofilm adjacent to the brackets. On the other hand, the biofilm adjacent to brackets retained with composite resin showed a significant increase in SM counts along the trial period. Topical application of 1.23% APF did not reduce salivary or biofilm SM counts regardless of the bonding material. In conclusion, fluoride topical application did not show efficacy in reducing SM. The use of RMGIC as bonding materials allowed a better control of SM cfu counts in dental biofilm hindering the significant increase of these microorganisms along the trial period, which was observed in the biofilm adjacent to the composite material.

Degree of conversion and bond strength of resin-cements to feldspathic ceramic using different curing modes

Abstract Resin cements have led to great advances in dental ceramic restoration techniques because of their ability to bond to both dental structures and restorative materials. Objective The aim of this study was to assess the performance of resin cements when different curing modes are used, by evaluating the degree of conversion and bond strength to a ceramic substrate. Material and Methods Three resin cements were evaluated, two dual-cured (Variolink II and RelyX ARC) and one light-cured (Variolink Veneer). The dual-cured resin cements were tested by using the dual activation mode (base and catalyst) and light-activation mode (base paste only). For degree of conversion (DC) (n=5), a 1.0 mm thick feldspathic ceramic disc was placed over the resin cement specimens and the set was light activated with a QTH unit. After 24 h storage, the DC was measured with Fourier transform infrared spectroscopy (FTIR). For microshear bond strength testing, five feldspathic ceramic discs were submitted to surface treatment, and three cylindrical resin cement specimens were bonded to each ceramic surface according to the experimental groups. After 24 h, microshear bond testing was performed at 0.5 mm/min crosshead speed until the failure. Data were submitted to one-way ANOVA followed by Tukey test (p<0.05). Scanning electron microscopy (SEM) was used for classifying the failure modes. Results Higher DC and bond strength values were shown by the resin cements cured by using the dual activation mode. The Variolink II group presented higher DC and bond strength values when using light-activation only when compared with the Variolink Veneer group. Conclusion The base paste of dual-cured resin cements in light-activation mode can be used for bonding translucent ceramic restorations of up to or less than 1.0 mm thick.

Characterization and Short-Term clinical study of clay facial mask / Caracterização e estudo clínico de curta duração de máscara facial argilosa

Clay mineral facial masks are used to treat some dermatological diseases, just for cleansing or reduce the amount of oil secreted by sebaceous glands. There are several types of clays, which vary in mineralogical and chemical composition, color and origin. However, the literature lacks studies involving clay facial masks, in particular regarding their influence on skin´s biomechanical properties. Thus, this work aimed to characterize colored clays and evaluate its influence on skin frmness and elasticity by a short-term clinical study. Different clays (named in this study magnesium aluminum silicate - MAS, white, pink and green) were chemically characterized, and facial mask formulations were prepared. The short-term clinical study was performed through the application of formulations on the skin. The skin frmness and elasticity were assessed before treatment and after mask removal. The statistical analysis showed no signifcant influence of time or formulations in those parameters, although volunteers reported the sensation of mechanical tension after the removal of the clay facial masks. Thus, the composition of the different clays did not affect the skin viscoelasticity behavior in the short-term clinical study, and a long-term use of this type of formulation must be indicated to observe all the expected benefts.(AU)

Máscaras faciais argilosas são utilizadas para tratar algumas doenças dermatológicas, apenas para a limpeza ou reduzir a quantidade de óleo secretado pelas glândulas sebáceas. Existem vários tipos de argilas, que variam em composição mineral, química, cor e origem. No entanto, a literatura carece de estudos envolvendo máscaras faciais argilosas, em particular em relação a sua influência nas propriedades biomecânicas da pele. Assim, este trabalho teve como objetivo caracterizar argilas coloridas e avaliar sua influência sobre a frmeza e elasticidade da pele por meio de um estudo clínico de curto prazo. Diferentes argilas (chamadas neste estudo de silicato de alumínio e magnésio - MAS, branca, rosa e verde) foram caracterizadas quimicamente, e formulações de máscaras faciais foram preparadas. O estudo clínico de curto prazo foi realizado por meio da aplicação das formulações na pele. A frmeza e elasticidade da pele foram avaliadas antes do tratamento e após a remoção da máscara. A análise estatística mostrou nenhuma influência signifcativa do tempo ou das formulações nesses parâmetros, embora os voluntários tenham reportado sensação de tensão mecânica, após a remoção das máscaras faciais argilosas. Assim, a composição das diferentes argilas não afetou o comportamento visco-elástico da pele no estudo clínico de curto prazo, e uma utilização de longa duração poderia ser indicada com a fnalidade de se observar todos os benefícios esperados.(AU)

Influência da erosão dentária na adesão de braquetes ortodônticos colados ao esmalte com diferentes materiais / The influence of dental erosion on bond strength of orthodontic brackets bonded to enamel with different materials

O diagnóstico das lesões incipientes de erosão em esmalte é difícil de ser realizado e, em situações clínicas, poderá ocorrer a colagem de braquetes em superfícies erodidas. Este trabalho in vitro avaliou a adesão de braquetes ortodônticos ao esmalte dentário bovino hígido e previamente erodido, utilizando dois materiais para colagem. Os fatores em estudo foram condição prévia do esmalte em 2 níveis (com e sem erosão) e tipo de material de colagem em 2 níveis (Transbond XT e Fuji Ortho LC). A amostra foi composta por 160 coroas de incisivos bovinos, sendo metade dela submetida a desafio erosivo para formação de lesões artificiais de erosão e a outra metade permaneceu hígida. Na ciclagem erosiva as coroas foram imersas 8X/dia em Coca-cola® (10 min), seguido da imersão em saliva artificial (2 h), durante 5 dias. A outra metade da amostra ficou em saliva artificial por 5 dias. Braquetes de incisivo central superior foram colados às coroas hígidas (H) e erodidas (E), seguindo orientações dos fabricantes de cada material. As variáveis de resposta foram resistência ao cisalhamento e índice de remanescente adesivo (IRA). Os dados de resistência ao cisalhamento foram analisados por ANOVA 2 critérios e Teste de Tukey (p<0,05). Os resultados, expressos em megapascal, não mostraram diferenças na resistência ao cisalhamento entre esmalte erodido e hígido, tanto no grupo colado com resina (RH = 15,25 +3,72; RE = 15,79 +4,41) quanto colado com ionômero (IH = 10,70 +3,73; IE = 11,26 +3,70). A resina apresentou resistência à colagem superior ao ionômero. Na comparação do índice de remanescente adesivo, por meio do teste de Mann Whitney, o esmalte erodido apresentou valores mais altos para o IRA, evidenciando uma maior quantidade de material remanescente no esmalte, tanto no grupo colado com resina (p=0,044) quanto com ionômero (p<0,001). Conclui-se que a presença da lesão de erosão não interfere na resistência ao cisalhamento de braquetes colados ao esmalte tanto com resina quanto com cimento de ionômero de vidro. No entanto, independentemente do material de colagem, o índice de remanescente adesivo evidenciou uma maior adesão ao esmalte com erosão.(AU)

The diagnosis of initial erosion lesions on enamel is difficult and in some clinical situations, the professional bonds brackets to eroded surfaces without noting.This in vitro study evaluated the bond strength of orthodontic brackets bonded to eroded and sound bovine enamel with two different materials. The factors under study were enamel condition in two levels (with and without erosion) and type of bonding material in two levels (Transbond® XT and Fuji Ortho LC). The sample consisted of 160 bovine lower incisor teeth, half of the specimens was subjected to erosive challenge to form artificial erosive lesions and the other half remained sound. In the erosive cycling tooth crowns were immerged 8x/day in Coca-cola® (10 min), followed by immersion in artificial saliva for (2 h), for 5 days. The other half of the sample was maintained in artificial saliva for 5 days. At sequence, brackets were bonded to eroded (E) and sound (S) enamel, according to manufacturing recommendations of each material. The response variables were shear bond strength and adhesive remnant index (ARI). Shear bond strength data were analyzed by Two-way ANOVA and Tukeys test (p<0,05). The results, expressed in megapascal, did not show any difference between eroded and sound enamel, in both composite resin (RS = 15,25 +3,72; RE = 15,79 +4,41) and glass ionomer (IS = 10,70 +3,73; IE = 11,26 +3,70) groups. Composite resin showed higher shear bond strength compared to glass ionomer cement. In the comparison of adhesive remnant index using Mann Whitney test, eroded enamel presented higher scores for ARI, showing greater amount of material remaining on enamel, in both resin (p=0,04) and ionomer (p<0,001) groups. It was concluded that the presence of erosion lesions did not interfere on shear bond strength of brackets bonded to enamel with composite resin or glass ionomer cement. However, independently of the bonding material, adhesive remnant index showed higher bond strength to eroded enamel.(AU)

Four chemical methods of porcelain conditioning and their influence over bond strength and surface integrity

OBJECTIVE: To assess four different chemical surface conditioning methods for ceramic material before bracket bonding, and their impact on shear bond strength and surface integrity at debonding.METHODS: Four experimental groups (n = 13) were set up according to the ceramic conditioning method: G1 = 37% phosphoric acid etching followed by silane application; G2 = 37% liquid phosphoric acid etching, no rinsing, followed by silane application; G3 = 10% hydrofluoric acid etching alone; and G4 = 10% hydrofluoric acid etching followed by silane application. After surface conditioning, metal brackets were bonded to porcelain by means of the Transbond XP system (3M Unitek). Samples were submitted to shear bond strength tests in a universal testing machine and the surfaces were later assessed with a microscope under 8 X magnification. ANOVA/Tukey tests were performed to establish the difference between groups (α= 5%).RESULTS: The highest shear bond strength values were found in groups G3 and G4 (22.01 ± 2.15 MPa and 22.83 ± 3.32 Mpa, respectively), followed by G1 (16.42 ± 3.61 MPa) and G2 (9.29 ± 1.95 MPa). As regards surface evaluation after bracket debonding, the use of liquid phosphoric acid followed by silane application (G2) produced the least damage to porcelain. When hydrofluoric acid and silane were applied, the risk of ceramic fracture increased.CONCLUSIONS: Acceptable levels of bond strength for clinical use were reached by all methods tested; however, liquid phosphoric acid etching followed by silane application (G2) resulted in the least damage to the ceramic surface.

OBJETIVO: avaliar quatro métodos de condicionamento químico da superfície cerâmica, previamente à colagem de braquetes, e seu impacto sobre a resistência ao cisalhamento e a integridade da superfície ao descolamento.MÉTODOS: quatro grupos experimentais (n = 13) foram delineados de acordo com o método de condicionamento da superfície cerâmica empregado: G1 = ácido fosfórico a 37%, seguido da aplicação de silano; G2 = ácido fosfórico líquido a 37%, seguido da aplicação de silano sem lavagem prévia do ácido; G3 = ácido fluorídrico a 10%; e G4 = ácido fluorídrico a 10%, seguido da aplicação de silano. Após o condicionamento da superfície, braquetes metálicos foram colados à porcelana utilizando-se o sistema Transbond XP (3M Unitek). As amostras foram submetidas a ensaios de resistência ao cisalhamento, em máquina de ensaio universal, e as superfícies cerâmicas foram posteriormente avaliadas em microscópio, com magnitude de 8X. Testes ANOVA/Tukey foram realizados para verificar-se a diferença entre os grupos (α = 5%).RESULTADOS: os maiores valores de resistência ao cisalhamento foram encontrados nos grupos G3 e G4 (22,01 ± 2,15MPa e 22,83 ± 3,32Mpa, respectivamente), seguidos por G1 (16,42 ± 3,61MPa) e G2 (9,29 ± 1,95MPa). Quanto à avaliação da superfície após a descolagem do braquete, a utilização de ácido fosfórico líquido seguido da aplicação de silano, sem lavagem do ácido (G2), produziu menores danos à porcelana. Quando ácido fluorídrico e silano foram aplicados, o risco de fraturar a cerâmica aumentou.CONCLUSÕES: níveis aceitáveis de resistência de união para uso clínico foram alcançados por todos os métodos testados. No entanto, o condicionamento com ácido fosfórico líquido, seguido da aplicação de silano (G2), resultou em menor dano à superfície cerâmica.

Surface Treatments for Repair of Feldspathic, Leucite - and Lithium Disilicate-Reinforced Glass Ceramics Using Composite Resin

The aim of this study was to evaluate the efficacy of different surface conditioning methods on the microtensile bond strength of a restorative composite repair in three types of dental ceramics: lithium disilicate-reinforced, leucite-reinforced and feldspathic. Twelve blocks were sintered for each type of ceramic (n=3) and stored for 3 months in distilled water at 37 °C. The bonding surface of ceramics was abraded with 600-grit SiC paper. Surface treatments for each ceramic were: GC (control) - none; GDB - diamond bur #30 µm; GHF - hydrofluoric acid (10%); GT- tribochemical silica coating (45-μm size particles). Treatments were followed by cleaning with phosphoric acid 37% for 20 s + silane + adhesive. The composite resin was used as restorative material. After repair, samples were subjected to thermocycled ageing (10,000 cycles between 5 °C and 55 °C for 30 s). Thereafter, the samples were sectioned into 1.0 mm2 sticks and tested for microtensile bond strength with 0.5 mm/min crosshead speed. Data were compared by two-way ANOVA and Tukey's test (α=0.05). The superficial wear with diamond bur proved to be suitable for feldspathic porcelain and for leucite-reinforced glass ceramic while hydrofluoric acid-etching is indicated for repairs in lithium disilicate-reinforced ceramic; tribochemical silica coating is applicable to leucite-reinforced ceramic. Predominance of adhesive failures was observed (>85% in all groups). In conclusion, the success of surface treatments depends on the type of ceramic to be repaired.

O objetivo deste estudo foi avaliar a eficácia de diferentes condicionamentos de superfície na resistência de união de reparos de compósitos restauradores em três tipos de cerâmicas odontológicas: reforçada por dissilicato de lítio, reforçada por leucita e feldspática. Foram confeccionados 12 blocos para cada tipo de cerâmica (n=3) e armazenados por 3 meses em água destilada a 37 oC. A superfície de união das cerâmicas foi regularizada com lixa de granulação 600 por 15 s e lavadas em ultrassom por 10 min. Os tratamentos de superfície para cada cerâmica foram: GC (controle) - nenhum; GPD - ponta diamantada com 30 µm de granulação; GAF - ácido hidrofluorídrico a 10%; GJ - jateamento com partículas de óxido de alumínio revestido por sílica (45 µm - tamanho das partículas). Após, foi realizada a limpeza da superfície com ácido fosfórico a 7% por 20 s, seguido de silano e adesivo. Como material restaurador foi utilizada resina composta. Após o reparo, as amostras foram submetidas a ciclagem térmica (10,000 ciclos entre 5 °C e 55 °C, por 30 s). Na sequência, as amostras foram seccionadas em palitos de aproximadamente 1,0 mm2 e levadas ao teste de tração em uma máquina de ensaios universal à velocidade de 0,5 mm/min. Os dados obtidos foram comparados estatisticamente por ANOVA de dois fatores e teste de Tukey (α=0,05). Sugere-se que o desgaste da superfície com ponta diamantada é mais indicado para a cerâmica feldspática e cerâmica reforçada por leucita, enquanto o condicionamento com ácido fluorídrico é indicado para reparos em cerâmica reforçada por dissilicato de lítio. O jateamento com partículas de óxido de alumínio revestido por sílica mostrou-se aplicável à cerâmica reforçada por leucita. Predominancia de fraturas adesivas acima de 85% foi observada para todos os grupos. Este estudo demonstrou que o sucesso dos tratamentos de superfície depende do tipo de cerâmica a que são aplicados.

Predictive significance of standardized uptake value parameters of FDG-PET in patients with non-small cell lung carcinoma

18F-fluoro-2-deoxyglucose (FDG) positron emission tomography (PET)/computed tomography (CT) is widely used to diagnose and stage non-small cell lung cancer (NSCLC). The aim of this retrospective study was to evaluate the predictive ability of different FDG standardized uptake values (SUVs) in 74 patients with newly diagnosed NSCLC. 18F-FDG PET/CT scans were performed and different SUV parameters (SUVmax, SUVavg, SUVT/L, and SUVT/A) obtained, and their relationship with clinical characteristics were investigated. Meanwhile, correlation and multiple stepwise regression analyses were performed to determine the primary predictor of SUVs for NSCLC. Age, gender, and tumor size significantly affected SUV parameters. The mean SUVs of squamous cell carcinoma were higher than those of adenocarcinoma. Poorly differentiated tumors exhibited higher SUVs than well-differentiated ones. Further analyses based on the pathologic type revealed that the SUVmax, SUVavg, and SUVT/L of poorly differentiated adenocarcinoma tumors were higher than those of moderately or well-differentiated tumors. Among these four SUV parameters, SUVT/L was the primary predictor for tumor differentiation. However, in adenocarcinoma, SUVmax was the determining factor for tumor differentiation. Our results showed that these four SUV parameters had predictive significance related to NSCLC tumor differentiation; SUVT/L appeared to be most useful overall, but SUVmax was the best index for adenocarcinoma tumor differentiation.

Comparative study of three bonding methods in attaching removable thermoplastic appliances / 华西口腔医学杂志

<p><b>OBJECTIVE</b>To evaluate the operation time and clinical effect of three types of materials (i.e., total-etching adhesive, self-etching adhesive, resin-modified glass ionomer cement) that are used to bond removable thermoplastic appliances.</p><p><b>METHODS</b>Thirty malocclusion patients (156 attachments) with removable thermoplastic appliances were randomly divided into three groups, with 10 individuals each. Attachments of groups A and B were bonded using 3M Adper Single Bond 2 and 3M Adper Easy One, respectively; both adhesives utilized 3M Z350 nano composite resin. Attachments of group C was directly bonded using GC Fuji Ortho LC. The operation time of each attachment was recorded. Failure rates of adhesion were evaluated during adhesion, 1 month after treatment, and 6 months after treatment.</p><p><b>RESULTS</b>The operation time of group C was shorter than those of groups A and B (P<0.01). Significant difference of adhesion failure rates was not found among the three groups (P>0.05). No significant difference of adhesion failure rates was also observed in different times of the same group (P>0.05).</p><p><b>CONCLUSION</b>The attachment stability of the three types of materials achieved satisfactory effects. However, the operation method of resin-modified glass ionomer cement is more concise and suitable for clinical promotion.</p>