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.

Photoelastic and finite element stress analysis reliability for implant-supported system stress investigation

Aim: To compare the reliability between photoelastic and finite element (FE) analyses by evaluating the effect of different marginal misfit levels on the stresses generated on two different implant-supported systems using conventional and short implants. Methods: Two photoelastic models were obtained: model C with two conventional implants (4.1×11 mm); and model S with a conventional and a short implant (5×6 mm). Three-unit CoCr frameworks were fabricated simulating a superior first pre-molar (P) to first molar (M) fixed dental prosthesis. Different levels of misfit (µm) were selected based on the misfit average of 10 frameworks obtained by the single-screw test protocol: low (<20), medium (>20 and <40) and high (>40). Stress levels and distribution were measured by photoelastic analysis. A similar situation of the in vitro assay was designed and simulated by the in silico analysis. Maximum and minimum principal strain were recorded numerically and color-coded for the models. Von Mises Stress was obtained for the metallic components. Results: Photoelasticity and FE analyses showed similar tendency where the increase of misfit generates higher stress levels despite of the implant design. The short implant showed lower von Mises stress values; however, it presented stresses around its full length for the in vitro and in silico analysis. Also, model S showed higher µstrain values for all simulated misfit levels. The type of implant did not affect the stresses around pillar P. Conclusions: Photoelasticity and FEA are reliable methodologies presenting similarity for the investigation of the biomechanical behavior of implant-supported rehabilitations

Ilusão / Ilusion

A Odontologia Restauradora e a Protése devem satisfazer as exigências estéticas do paciente e contribuir para a saúde gengival e articular (oclusão). Para tanto, muitas vezes nos deparamos com desproporções dentoalveolares, maus posicionamentos, desvios de longo-eixo, inclinações axiais desfavoráveis, presenças de diastemas, etc. Para criar a percepção ilusória de dimensões e rotações diferentes das reais, podem ser utilizados artifícios ópticos dentro dos limites de tolerância visual. Esses artifícios vão desde o trabalho com a estratificação das cores utilizadas na restauração/prótese ao planejamento adequado da área plana (ou reflexiva), ângulos incisais, área de transição, linhas de brilho, textura, pontos de con-tatos proximais, etc. Este artigo aborda alguns princípios que podemos utilizar para alterar a percepção ilusória de um dente, aproveitando-se de fenômenos ópticos na superfície do esmalte.

Restorative dentistry and dental prosthesis must meet patients' aesthetic expectations and preserve gingival and articular health. In such circumstances it is common to observe dentoalveolar disproportion, poorly positioned teeth, large, deviations of the long axis, unfa-vorable axial inclination, diastema, etc. In order to create the illusion of different dimension and rotations, optical resources can be applied respecting visual tolerance limits. These resources range from the stratification of the colors used on the restoration/prostheses to proper planning of reflexive area, incisal angles, transition areas, texture, brightness, texture and proximal contact points. The present study approaches some principles that may be used in order to improve dental appearance through optical resources over enamel surface

The research on optical properties of four all-ceramic veneer materials / 中华口腔医学杂志

<p><b>OBJECTIVE</b>To analyze the color parameters and translucency of four frequently-used veneer materials.</p><p><b>METHODS</b>Forty disc specimens[(1.00±0.01) mm in thickness, 10 mm in diameter] were fabricated according to the manufacturer's instructions with IPS Empress(®) CAD[A2, high translucency (HT)], IPS e.max(®) Press(A2, HT), IPS e.max(®) CAD (A2, HT) and VITABLOCS(®) Mark II (A2) respectively and were divided into Groups A, B, C, D. All of the specimens were ground and polished on a grinding machine. Then color parameters (L*, a*, b*) and transmittance (τ) were measured using spectrocolorimeter and transmissivity testing device. The color parameters of the specimens were compared to the color parameters of A2 shade of Ivoclar Vivadent A-D shade guide. The data were analyzed with one-way analysis of variance (ANOVA), and mean values were compared by the Tukey's test (α = 0.05).</p><p><b>RESULTS</b>There was no statistical difference between the color parameters L*, a*, b* and C*ab of Group A and Group D (P > 0.05). But the color parameters of those two ceramic materials were statistically different from the color parameters of Group B and Group C (P < 0.05). There was no statistical difference between color parameters b* and C*ab of Group B and Group C(P > 0.05). However, the color parameters L* and a* of the two materials were statistically different(P < 0.05). The color differences (ΔE) between Group A, B, C, D and standard A2 were 6.05±0.12, 5.11±0.27, 3.73±0.27, 6.30±0.38 respectively. The transmittances of Group A, B, C, D were (29.69±0.31)%, (25.83±0.36) %, (28.92±0.47)% and (26.94±0.33)% respectively.</p><p><b>CONCLUSIONS</b>The color parameters of these four materials are different. Their transmittance are relatively high but statistically different. The color difference (ΔE) between IPS e.max(®) CAD (A2, HT) and standard A2 is lowest among all the groups.</p>

Lentes progressivas: análise dos campos intermediário e de perto por deflexometria / Progressive addition lenses: analysis of intermediate and near vision zones by deflectometry

OBJETIVO: Avaliar por deflexometria as diferentes regiões das lentes progressivas e determinar as áreas dos campos de visão intermediário e de perto. MÉTODOS: Foram incluídas vinte e duas lentes progressivas com poder +1,00 DE para longe e duas adições diferentes (adição 1,00 e 2,00, 11 de cada). Mediram-se as áreas dos campos intermediário e de perto entre as isoastigmáticas de 0,5 DC. RESULTADOS: Encontraram-se diferenças significativas entre as áreas dos campos intermediário e de perto das lentes estudadas. Entre a área do campo intermediário e a adição observou-se correlação inversa; entre a área do campo intermediário e a extensão vertical do corredor encontrou-se correlação direta. CONCLUSÃO: Com esses dados permitem-se recomendar as lentes de acordo com o campo de maior necessidade visual de cada usuário.

PURPOSE: To determine near and intermediate vision areas of progressive addition lenses by means of a deflectometer. METHODS: Twenty-two progressive addition lenses with +1.00 SD far power and two different additions (add 1.00 and 2.00; eleven subjects in each addition) were studied. Near and intermediate vision areas within 0.50 CD isoastigmatic lines were determined. RESULTS: There are significant differences between near and intermediate vision areas of the studied lenses. There is also an inverse correlation between the addition and intermediate areas as well as direct relation between the vertical length of the corridor and its area. CONCLUSION: Based on those findings, progressive addition lenses can be selected to suit the wearer's visual requirements.

Development of standardization platform for optical density value based on an improved method / 生物医学工程学杂志

Due to the high variation in test results of indirect enzyme-linked immuno sorbent assay (ELISA) and complicated steps involved in the process of standardization, a platform used for standardizing the test results from indirect ELISA was developed. The platform was designed based on 'Improved Standardization Method for Optical Density' (I-STOD). Gauss-Newton iteration was applied to estimate parameters in a standard formula. Programming Language VB was used for developing interface of platform. The results indicated that the validity of experiment could be verified through platform. A well determined scope of standardization could be generated. The sample with concentration within the scope was standardized and the degree of dilution was calculated for those outside the scope. The platform was successfully developed which normalized the process of standardization. The function provides the researchers with an effective and convenient tool for quickly achieving standardization of ELISA test results.

[ comparative study of optical purity of some generic and under license solid pharmaceutical products of esomeprazole using validated HPLC method]

This method was applied to perform a comparative study of optical purity of some generic solid pharmaceutical products of esomeprazole [capsules, tablets] manufactured locally and in some neighbouring countries for the determination the percentage of R enantiomer. A product of under license company was used for comparison of the results. The study was performed by using a validated HPLC method on chiral column Nucleocel Alpha S and a mixture ethanol: hexane [70:30, v/v] as a mobile phase, the flow rate was 0.65 ml/min, and the detection was carried out using UV detector at 302nm. The temperature of column was set at 25[degree]C. The study showed that some samples were not polluted with R enantiomer, while the others contained this enantiomer in the range of 0.1-2.24%

Construction of a copper stepwedge with aluminum equivalent mean gray values

OBJECTIVES: To produce a copper (Cu) stepwedge with aluminum (Al) equivalent mean gray values (MGV). MATERIAL AND METHODS: The thicknesses of Cu steps that were equivalent to those of the Al were formulated using the X-ray attenuation properties of the materials. The Al and fabricated Cu stepwedges were radiographed, but the MGVs of the Cu stepwedge were mismatching to those of the Al. Using a mathematical function to adjust the pixel MGV of Cu stepwedge to those of the Al, new Cu stepwedges were created. In vitro iterations were performed until best approximation to Al was reached. RESULTS: The MGV of the Cu stepwedges fabricated by formularization were different than those of Al (p=0.001). Iteration method led to MGV similar to those of the Al stepwedge (p=0.207). CONCLUSIONS: Construction of a Cu stepwedge according to the basic rules of radiophysic failed to result in a stepwedge with similar radiodensity values to those of Al stepwedge. Further studies may use the formularization method only for prototype Cu wedge production, but consecutive iterations shall be compassed to obtain the best approximation to Al MGV.

Wavefront analysis and modulation transfer function of three multifocal intraocular lenses.

Purpose: To evaluate wavefront performance and modulation transfer function (MTF) in the human eye after the implantation of diffractive or refractive multifocal intraocular lenses (IOLs). Materials and Methods: This was a prospective, interventional, comparative, nonrandomized clinical study. Uncorrected distance and near visual acuity, and wavefront analysis including MTF curves (iTrace aberrometer, Tracey Technologies, Houston, TX, USA) were measured in 60 patients after bilateral IOL implantation with 6 months of follow-up. Forty eyes received the diffractive ReSTOR (Alcon), 40 eyes received the refractive ReZoom (Advanced Medical Optics) and 40 eyes, the Tecnis ZM900 (Advanced Medical Optics). The comparison of MTF and aberration between the intraocular lenses was performed using analysis of variance (ANOVA), followed by the Dunn test when necessary. Results: The mean uncorrected distance visual acuity was similar in all three groups of multifocal IOLs. The ReSTOR group provided better uncorrected near visual acuity than the ReZoom group (P < 0.001), but similar to the Tecnis group. Spherical aberration was significantly higher in the ReZoom group (P = 0.007). Similar MTF curves were found for the aspheric multifocal IOL Tecnis and the spheric multifocal IOL ReSTOR, and both performed better than the multifocal IOL ReZoom in a 5 mm pupil (P < 0.001 at all spatial frequencies). Conclusions: Diffractive IOLs studied presented similar MTF curves for a 5 mm pupil diameter. Both diffractive IOLs showed similar spherical aberration, which was significantly better with the full-diffractive IOL Tecnis than with the refractive IOL ReZoom.

Effects of radio-opacifier addition in dental impression material.

Objective: The aim of this in vitro study was to determine the effects of barium sulfate addition in two dental impression materials previously proved as radiolucent. Materials and Methods: An irreversible hydrocolloid (IH) and polyether (PE) were tested for optical density, linear dimension stability and detail reproduction. Statistical Analysis Used: The optical density data were submitted to Kolmogorov-Smirnov normality test and compared with two-way ANOVA and Tukey (alpha=0.05). Results: The results of optical density (pixel) were: IH control 45.24 f (±7.6), PE control 54.93 e (±4.45), PE 5Wt% 60.43 d (±6.27), IH 1Wt% 61.54 cd (±5.3), PE 1Wt% 66.9 bc (±5.05), IH 5Wt% 67.17 b (±6.01), PE 10Wt% 84.55 a (±5.14), IH 10Wt% 85.33 a (±5.53). On detail reproduction, polyether control was able to copy the 6 μm line. Adding 1 or 5Wt% of barium sulfate have not change this characteristic. For the irreversible hydrocolloid, the control group was able to copy a line with 14 μm, however, adding 1Wt% barium sulfate, the capability decreased to 22 μm. Adding barium sulfate in the polyether promoted an increase in between the copied lines, for the control, the average distance was 931.6 μm, 936 μm to 1Wt% and 954.5 μm to 5 Wt%. For the IH, the control presented 975 μm in comparison to 987.25 μm for 1 Wt% samples. Conclusion: The addition of barium sulfate was capable of increasing significantly the optical density of tested material, have changed the linear dimension stability, however, have not interfered in detail reproduction only for PE.

Comparison of silorane and methacrylate-based composite resins on the curing light transmission

The aim of this study was to investigate the influence of different composite resins - Filtek P90 (silorane-based composite) and Heliomolar (methacrylate-based composite) - on light transmission and decrease in Knoop hardness between the bottom and top of cured specimens. The irradiance of a light-curing unit (LCU) was measured with a power meter (Ophir Optronics; 900 mw/cm2) and spectral distributions were obtained using a spectrometer (USB 2000). Twenty standardized cylindrical specimens (2 mm thick x 7 mm diameter) of each composite resin were obtained by curing using the LCU for 40 s. Light energy transmission through the composite was calculated (n=10). The Knoop hardness number for each surface was recorded as the mean of 3 indentations. The difference in Knoop hardness between the top and bottom (DKH) of the same specimen was calculated (n=10). The irradiance of light that passed through Filtek P90 (272 mW/cm2) was not significantly greater than that the passed through Heliomolar (271 mW/cm2). The DKH of Filtek P90 (25 percent) was significantly higher than that of Heliomolar (12 percent). There was a greater degree of subsurface polymerization of the methacrylate-based composite compared to the silorane-based composite.

O objetivo deste estudo foi avaliar a influência da diferença entre a dureza do topo e da base em compósitos restauradores. Foram utilizados os compósitos restauradores Filtek P90 (compósito à base de silorano) e Heliomolar (compósito à base de metacrilato). A irradiância da unidade foto-ativadodora (UF) foi mensurada com um potenciômetro Ophir Optronics (900 mw/cm2) e o espectro de luz foi obtido usando um espectrofotômetro (USB 2000). Vinte espécimes cilíndricos padronizados (2 mm de espessura por 7 mm de diâmetro) foram obtidos pela fotoativação utilizando UF (40 s) para cada compósito. A irradiância que passou através do compósito foi mensurada (n=10). O número de dureza Knoop para cada superfície foi calculado pela média de 3 penetrações. A diferença da dureza Knoop entre o topo e base (DDK) de um mesmo espécime foi calculada (n=10). A irradiância que passou através da Filtek P90 (272 mW/cm2) não foi estatisticamente superior a Heliomolar (271 mW/cm2). A DDK da Filtek P90 (25 por cento) foi estatisticamente superior a Heliomolar (12 por cento). O compósito a base de metacrilato apresentou melhor grau de polimerização na base quando comparado ao compósito à base de silorano.

The optical analysis of the abdominal wall using the biospeckle after implants of polypropylene mesh in rats / Análise ótica da parede abdominal pelo biospeckle após implante de prótese de polipropileno em ratos

PURPOSE: To evaluate an experimental animal model to study the abdominal tissue activity considering its interaction with a polypropylene mesh, through the use of one of the optical phenomena of light Laser, the biospeckle. METHODS: Fifty Wistar male rats were divided into four groups: Group 1: ten animals not submitted to surgery; Group 2: ten animals submitted to surgery without polypropylene mesh; Group 3: 20 animals submitted to surgery followed by the mesh placement; Group 4: (sham) with ten animals. None of the animals presented post surgical complications being submitted to the optical tests at the 20th postoperative day. RESULTS: The analysis from the biospeckle tests, comparing the medians and standard deviations with T Student test, indicated that no significative difference was observed on the abdominal wall tissue activity in the four groups considered, with and without polypropylene mesh prosthesis implantation. CONCLUSION: The animal model is viable and the biospeckle open ways for a great number of experiments to be developed in evaluating tissue activity.

OBJETIVO: Avaliar o modelo experimental animal para o estudo da atividade tecidual da parede abdominal em sua interação com a prótese de polipropileno, através da utilização de um dos fenômenos ópticos da luz Laser, o biospeckle. MÉTODOS: Foram utilizados 50 ratos Wistar machos, divididos em quatro grupos: Grupo 1 com 10 animais não operados e controles; Grupo 2 com 10 animais submetidos a cirurgia sem a colocação de prótese; Grupo 3 com 20 animais submetidos a cirurgia com colocação de prótese de polipropileno pré-peritonial; Grupo 4 (Sham) com 10 animais. Nenhum animal apresentou complicações pós-operatórias, sendo que no 20º PO foram submetidos ao ensaio óptico. RESULTADOS: A comparação das médias e o desvio padrão das medidas da atividade tecidual da parede abdominal, com e sem implantação da prótese de polipropileno obtidas dos grupos de animais, pelo teste T de Student, não evidenciou diferença estatística significativa (p>0.05). CONCLUSÃO: A análise dos dados obtidos permitiu concluir que o modelo animal é viável e que o biospeckle abre caminhos para toda uma linha de experimentos a ser desenvolvida em avaliar atividade tecidual.

Optical density and chemical composition of microfilled and microhybrid composite resins

This study evaluated the optical density of two microfilled and two microhybrid resins, as well as the composition of these materials with regard to their optical density. Cavities prepared in 12 2-mm- or 4-mm-thick acrylic plastic plates were filled with Z250 (3M-ESPE), A110 (3M-ESPE), Charisma (Heraeus-Kulzer) and DurafillVS (Heraeus-Kulzer). The resin increments (2-mm-thick) were light-cured for 40 s. Three 0.12-s radiographic exposures were made of each #2 acrylic plastic plate. DenOptix system optical plates were used to obtain the digital images. Three readings of the composite resin surface were made in each radiograph, totalizing 216 readings. The mean of highest and lowest grey-scale values was obtained. Two specimens of each composite resin were prepared for SEM analysis of the chemical elements related to optical density, using energy dispersive x-ray analysis (EDX). The results were subjected to Shapiro-Wilk's test, ANOVA, Tukey's test at 1 percent level of significance and Pearson's correlation. The mean grey-scale values at 2 mm and 4 mm were: Z250 = 154.27a and 185.33w; A110 = 46.77b and 63.05y; Charisma = 163.40c and 200.46z; DurafillVS = 43.92b and 58.99x, respectively. Pearson's test did not show any positive correlation between optical density and percentage weight of optical density chemical elements. It was concluded that the microhybrid resins had higher optical density means than the microfilled resins; among the evaluated resins, Charisma had the highest optical density means.

Infrared spectroscopy: a tool for determination of the degree of conversion in dental composites

Infrared spectroscopy is one of the most widely used techniques for measurement of conversion degree in dental composites. However, to obtain good quality spectra and quantitative analysis from spectral data, appropriate expertise and knowledge of the technique are mandatory. This paper presents important details to use infrared spectroscopy for determination of the conversion degree.

Interrogando as teorias sobre o arco-íris / Understanding the theories about the rainbow

Tentar entender as teorias do arco-íris é uma maneira de pensar sobre as argumentações entre a lógica científica e o pensamento mítico na história da ciência. Este trabalho segue três percursos relacionados: primeiramente, expõe um resumo das descontinuidades e recorrências históricas na explanação do arco-íris; em segundo lugar, examina registros de etnógrafos estrangeiros na Amazônia, na primeira metade do século XX; por último, aborda a 'teoria nativa' sobre o fenômeno nas terras baixas da América do Sul, visando compreender a lógica das classificações nativas, que opera como um pensamento mítico. A simetria das disciplinas permite uma complementaridade entre as teorias científicas e as humanidades, bem como analogias entre diferentes leituras dos códigos biológicos e sociais.

Trying to understand the theories of the rainbow we focus the debate between scientific logic and mythic thinking in the history of science. This paper follows three paths. Firstly, it presents a summary of the discontinuities and recurrences in the explanation of the fenomena in history of thinking. Secondly, registrations of foreign ethnographers in the Amazon in the first half of the twentieth century are examined. Thirdly, the approach is directed to the 'native theory' about the rainbow in the low lands of South America, trying to understand the logic behind the native classifications as mythic thinking. Symmetry among disciplines supposes complementarities between biological theories and humanities and allows for analogies involving biological and social codes.