Effect of three different attachment designs in the extrusive forces generated by thermoplastic aligners in the maxillary central incisor.

INTRODUCTION: Orthodontic aligners use have increased in dentistry. The resolution of complex movements such as extrusion demands the use of attachments to reach the aimed force, but just a few studies have been developed to evaluate the biomechanical performance of the aligners and their accessories. OBJECTIVE: The objective of this study was to evaluate on the three axes (X, Y and Z) the forces generated by three different attachment designs for the extrusion of the maxillary central incisor using esthetic orthodontic aligners. METHODS: Three prototypes of maxillary models were developed, each one with a specific attachment inserted in the central incisor. Three aligners were manufactured for each of the three attachment designs, with 0.33-mm activation in the direction of the extrusion. An analytical device was used to evaluate the forces applied to the three axes by each aligner/attachment. The data were assessed by one-way ANOVA and Tukey's test (α = 0.05). RESULTS: All of the studied attachment designs could satisfactorily perform the extrusion movement. However, force intensities were different in the three designs (design 1 = 2.5 N; design 2 = 2.2 N, and design 3 = 1.1 N). Furthermore, two of the three attachment designs (designs 1 and 2) eventually exerted significant forces on the X (mesiodistal) and Y (buccopalatal) axes. CONCLUSION: The attachment design 3 presents the best distribution of forces for extrusion movement, generating almost null forces on X and Y axes, and lower intensity of force on the Z axis.

Effect of three different attachment designs in the extrusive forces generated by thermoplastic aligners in the maxillary central incisor

ABSTRACT Introduction: Orthodontic aligners use have increased in dentistry. The resolution of complex movements such as extrusion demands the use of attachments to reach the aimed force, but just a few studies have been developed to evaluate the biomechanical performance of the aligners and their accessories. Objective: The objective of this study was to evaluate on the three axes (X, Y and Z) the forces generated by three different attachment designs for the extrusion of the maxillary central incisor using esthetic orthodontic aligners. Methods: Three prototypes of maxillary models were developed, each one with a specific attachment inserted in the central incisor. Three aligners were manufactured for each of the three attachment designs, with 0.33-mm activation in the direction of the extrusion. An analytical device was used to evaluate the forces applied to the three axes by each aligner/attachment. The data were assessed by one-way ANOVA and Tukey's test (α = 0.05). Results: All of the studied attachment designs could satisfactorily perform the extrusion movement. However, force intensities were different in the three designs (design 1 = 2.5 N; design 2 = 2.2 N, and design 3 = 1.1 N). Furthermore, two of the three attachment designs (designs 1 and 2) eventually exerted significant forces on the X (mesiodistal) and Y (buccopalatal) axes. Conclusion: The attachment design 3 presents the best distribution of forces for extrusion movement, generating almost null forces on X and Y axes, and lower intensity of force on the Z axis.

RESUMO Introdução: O uso de alinhadores ortodônticos tem aumentado na Odontologia. Porém, para a realização de movimentos complexos, como a extrusão, é necessário usar attachments para se obter as forças desejadas. Apesar disso, há poucos estudos que tenham avaliado o desempenho biomecânico dos alinhadores e de seus attachments. Objetivo: O objetivo do presente estudo foi avaliar nos três eixos (X, Y e Z) as forças geradas por três diferentes designs de attachments para extrusão de um incisivo central superior usando alinhadores ortodônticos. Métodos: Foram confeccionados três modelos superiores prototipados, cada um com um tipo de attachmentinserido no incisivo central. Três alinhadores foram fabricados para cada um dos três designs de attachment, com ativação de 0,33 mm na direção da extrusão. Foi, então, utilizado um equipamento de análise para mensurar, nos três eixos, as forças aplicadas por cada alinhador/attachment. Os dados foram submetidos à ANOVA de fator único e ao teste de Tukey (α?#8197;= 0,05). Resultados: Todos os designs de attachments utilizados foram capazes de exercer satisfatoriamente o movimento de extrusão. Entretanto, a intensidade das forças foi diferente nos três designs (attachment 1 = 2,5 N; attachment 2 = 2,2 N e attachment 3= 1,1 N). Além disso, dois dos três designs (attachments 1 e 2) exerceram forças significativas nos eixos X (mesiodistal) e Y (vestibulopalatino). Conclusões: o design do attachment 3 apresentou a melhor distribuição de forças para o movimento de extrusão, sendo o mais próximo de forças nulas nos eixos X e Y e força de baixa intensidade no eixo Z.

Influence of physical assessment of different light-curing units on irradiance and composite microhardness top/bottom ratio.

The aim of this study was to evaluate the influence of the physical assessment of different light-curing units from 55 dental offices on the irradiance and composite microhardness top/bottom ratio, and the influence of the radiometers for LED or QTH light sources on irradiance measurement. The irradiance of each light-curing unit was evaluated with two radiometers, either for LED or QTH light. A questionnaire regarding the type of source (LED or QTH), time of use, date of last maintenance and light-curing performance assessment applied. The physical assessments were evaluated regarding damage or debris on the light tip. For each light-curing unit, three composite specimens were made (diameter = 7 mm; thickness = 2 mm) with polymerizing time of 20 s, in order to perform the microhardness (Knoop) test. Data were analyzed by Kruskal-Wallis and Dunn test (α = 0.01). There was wide variation in irradiance (0-1000 mW/cm(2)). Approximately 50 % of the light-curing units presented radiation lower than 300 mW/cm(2); 10 % of light-curing units, especially those with LED source, presented values higher than 800 mW/cm(2), and 43 % of light-curing units worked with adequate irradiance between 301 and 800 mW/cm(2). In almost 60 % of cases, no maintenance of light-curing units was performed in a period of 3 to 10 years. The age of the light-curing units and the use of inadequate tips interfered negatively in irradiance. The data emphasize the importance of periodic maintenance of light-polymerizing, light-curing units.

Relationship between toothpastes properties and patient-reported discomfort: crossover study.

OBJECTIVES: This study aims to correlate patient-reported reactions with in vitro analyses of the pH, abrasive quality, and cytotoxicity of four toothpastes. MATERIALS AND METHODS: One hundred twenty-one patients received non-identified samples of toothpaste to be used for 6 days and answered a questionnaire about their sensations. In vitro analysis: the pH of toothpastes was measured with a pH meter. The abrasivity of toothpastes was evaluated against composite resin specimens (n = 10). A toothbrushing machine was used to simulate wear, which was indirectly measured by mass loss using a scale. Cell culture media conditioned with toothpaste were used to assess the cytotoxicity. Confluent cells were kept in contact with the conditioned media or control for 24 h. The cell viability was measured using the 3-(bromide, 4,5-dimethylthiazol-2yl)-2,5-diphenyltetrazolium (MTT)-reduction assay. The obtained data on the pH, weight loss, and cell viability were compared by ANOVA/Tukey's tests (p < 0.05). RESULTS: With the exception of the bleaching effect paste, the Oral B® paste produced the highest frequencies of irritation reports, tooth sensitivity, taste discomfort, and texture discomfort in the clinical study; patients also reported rougher teeth, soft tissue peeling, dry mouth, thrush, tingling, and taste changes in response to this paste. The in vitro analysis demonstrated that Oral B® had the lowest pH, the highest abrasivity, and produced the lowest cell viability (p < 0.01). CONCLUSION: Results suggest that low pH toothpastes that are highly abrasive and cytotoxic may cause undesirable reactions in patients. CLINICAL RELEVANCE: Toothpaste's properties should be well known for indication to patient therefore minimizing discomfort reports.

Flexural properties of resin composites: influence of specimen dimensions and storage conditions.

This study evaluated the influence of specimen dimensions and storage medium and temperature on the flexural properties of one dental resin composite. The material utilized throughout the study was Clearfil AP-X. Eighty specimens were built with dimensions of either 10×2×2 mm or 25×2×2 mm, stored dry or in distilled water, at 25 or 37ºC, for 24 h. Flexural strength and modulus were tested in three-point bending. Results were evaluated with three-way ANOVA and Tukey's test (α=0.05). Statistical significance was observed for all three factors: temperature (37ºC=190.8 MPa, 25ºC=165.3 MPa; p<0.01), storage medium (water=167.7 MPa, Dry=188.4 MPa; p<0.01) and specimen dimensions (10×2×2 mm=197.9 MPa, 25×2×2 mm=158.2 MPa; p<0.01). None of the interactions were significant. Within the limitations of this study, it can be concluded that factors such as specimen dimensions, storage medium and temperature significantly affect flexural strength results, which invalidates comparisons of results from studies that use different methodologies.

Effects of Nd:YAG laser irradiation on the hybrid layer of different adhesive systems.

PURPOSE: The aim of this in vitro study was to evaluate the microtensile bond strength (microTBS) and hybrid layer morphology of different adhesive systems, either followed by treatment with Nd:YAG laser irradiation or not. Previous studies have shown the effects of Nd:YAG laser irradiation on the dentin surface at restoration margins, but there are few reports about the significance of the irradiation on the hybrid layer. MATERIALS AND METHODS: The flattened coronal and root dentin samples of 24 bovine teeth were randomly divided into 8 groups, according to the adhesive system used -- Scotchbond Multi Purpose (SBMP) or Clearfil SE Bond (CSEB) -- and were either irradiated with Nd:YAG or not, with different parameters: 0.8 W/10 Hz, 0.8 W/20 Hz, 1.2 W/10 Hz, 1.2 W/20 Hz. The left sides of specimens were the control groups, and right sides were irradiated. A composite crown was built over bonded surfaces and stored in water (24 h at 37 degrees C). Specimens were sectioned vertically into slabs that were subjected to microTBS testing and observed by SEM. RESULTS: Control groups (27.81 +/- 1.38) showed statistically higher values than lased groups (21.37 +/- 0.99), and CSEB control group values (31.26 +/- 15.71) were statistically higher than those of SBMP (24.3 +/- 10.66). There were no significant differences between CSEB (20.34 +/- 10.01) and SBMP (22.43 +/- 9.82) lased groups. Among parameters tested, 0.8 W/10 Hz showed the highest value (25.54 +/- 11.74). Nd:YAG laser irradiation caused dentin to melt under the adhesive layer of both adhesive systems tested. CONCLUSION: With the parameters used in this study, Nd:YAG laser irradiation of the hybrid layer promoted morphological changes in dentin and negatively influenced the bond strength of both adhesive systems.

Early and 24-hour bond strength and degree of conversion of etch-and-rinse and self-etch adhesives.

PURPOSE: To evaluate early and 24-hour microtensile bond strength (microTBS) and the degree of conversion (DC) of one representative adhesive system from each of the four current bonding approaches. METHODS: 40 human molars were sectioned occluso-gingivally into two halves. Resin composite was bonded incrementally to flat, mid-coronal dentin, using the adhesives Adper Scotchbond MP (MP); Adper Scotchbond 2 (SB); Clearfil SE Bond (SE); and Adper Prompt L-Pop (LP) according to the respective manufacturer's instructions (n = 10). One half was immediately sectioned into sticks and subjected to muTBS test. As the sectioning process took approximately 1 hour, the results were designated as 1-hour bond strengths. The other half was stored in distilled water at 37 degrees C for 24 hours before being sectioned and tested. The DC of these systems was measured using Fourier Transform-Raman spectroscopy in three periods: immediately, 1 and 24 hours after polymerization. Data were analyzed with ANOVA and Tukey's tests. RESULTS: There were no significant differences between the 1-hour and 24-hour bond strengths (P > 0.05), or among the DC measured immediately, 1 hour and 24 hours after polymerization (P > 0.05). However, significant differences were observed among adhesives (P < 0.05). microTBS values obtained, in MPa (1 hour/24 hour), were: SB (48.6 + 1.3/48.4 + 3.5) = SE (51.9 + 4.7/53.3 +/- 2.9) > MP (35.3 +/- 10.9/38.6 + 6.7) > LP (25.5 + 1.1/26.0 + 1.5). The DC, in percentage (immediately/1 hour/24 hour), were: SE (81/82/87) > MP (79/77/81) > SB (60/63/65) > LP (39/37/42).

Polymerization stress related to radiant exposure and its effect on microleakage of composite restorations.

OBJECTIVES: Verify the influence of radiant exposure (dose) on polymerization stress and microleakage of composite restorations using two adhesive systems. METHODS: An experimental composite (1BisGMA:1TEGDMA, 75wt.% filler) was subjected to 3, 6, 12 or 24J/cm(2) under 500mW/cm(2). Stress was measured in 1-mm height specimens placed between two glass rods (Ø=5mm) attached to a testing machine. Microleakage was assessed in cylindrical restorations (Ø=5mm, h=2mm) with enamel margins, using Adper Single Bond 2 (SB) or Adper Prompt (PR). After storage, specimens were subjected to dye penetration (50% AgNO(3)) and sectioned twice, perpendicularly. Microleakage of the 8tooth/composite interfaces was recorded in millimeters. KHN was measured at both surfaces of cylindrical specimens (Ø=5mm, 1 or 2mm height). ANOVA/Tukey test were used (alpha=0.05). KHN top and bottom were compared using paired t-tests. RESULTS: Stress increased significantly with dose (3J/cm(2): 1.4+/-0.3(c); 6J/cm(2): 4.3+/-0.5(b); 12J/cm(2): 9.3+/-0.6(a); 24J/cm(2): 9.9+/-0.7(a), in MPa). For both average and maximum microleakage, interactions were not statistically significant (p>0.05). Tooth average microleakage was influenced by the adhesive system (SB

Influência da dose de energia sobre o grau de conversão, tensão de polimerização, propriedades mecânicas e microinfiltração in vitro de restaurações em compósito / Influence of the radiant exposure on the degree of conversion, polymerization stress, mechanical properties and in vitro microleakage of composite restorations

Proposição: O objetivo deste trabalho foi verificar a influência da dose de energia aplicada a um compósito resinoso sobre seu grau de conversão (GC), tensão de polimerização (TP), velocidade máxima de reação (Rp max), propriedades mecânicas (resistência à flexão/RF, módulo de elasticidade/ME, dureza Knoop/KHN) e microinfiltração de restaurações in vitro confeccionadas com dois tipos de sistema adesivo. Material e métodos: Um compósito experimental foi manipulado na proporção em peso de 1:1 de BisGMA e TEGDMA e 75 por cento de carga inorgânica. O compósito foi submetido a doses de 3, 6, 12, 24 e 48 J/cm2 com irradiância constante de 500 mW/cm2. GC e Rp max foram monitorados durante 10 min após o início da fotoativação através de FTIR-ATR em filmes com 150 μm de espessura (simulando a superfície irradiada) e na base de discos com 2 mm de altura. Após 48 h de armazenamento a seco em temperatura ambiente, novas medidas de GC foram feitas nesses espécimes. TP foi monitorada durante 10 min em espécimes com 1 ou 2 mm de altura construídos entre dois bastões de vidro (Ø=5 mm) presos às garras de uma máquina de ensaios universal. RF e ME em espécimes com 10x2x1 mm foram determinados através de ensaio de flexão em três pontos. Fragmentos dos espécimes do teste de RF foram utilizados para análise de KHN (topo e base) após 48 h. KHN aos 10 min foi determinada no topo e na base dos corpos-de-prova com 1 ou 2 mm de espessura e 5 mm de diâmetro. A microinfiltração foi avaliada em cavidades cilíndricas (Ø=5 mm e 2 mm profundidade) com término em esmalte confeccionadas na face vestibular de incisivos bovinos preenchidas em incremento único. Foram utilizados os sistemas adesivos Adper Single Bond 2 (SB) e Adper Prompt (PR). Após armazenamento em água destilada por 48 h a 37oC, os dentes foram submetidos ao protocolo de microinfiltração com solução de 50 por cento de AgNO3. As cavidades foram seccionadas com dois cortes perpendiculares entre si para análise da microinfilt...

Influence of condansation method and alloy type on mercury vapor release and residual porosity of dental amalgams / Influência do método de condensação e tipo de liga sobre a liberação de vapor de mercúrio e porosidade residual de amálgamas dentários

Objetivo: Verificar a influência do método de condensação e do tipo de liga na liberação de vapor de mercúrio e poro-sidade residual de amálgamas dentários. Material e Métodos: Três tipos de amálgama foram testados: forma de aparas (F-4000), forma esférica (Logic Plus) e mistura (Permit-C). A liga foi condensada em cavidades cilíndricas através de três técnicas: manual (Ward # 2), mecânica (Densco-Teledyne) e ultrasônica (Gnatus). Os procedimentos foram executados dentro de uma caixa de acrílico (50 x 50 x 35 cm, ou 0,0875 m3) contendo uma bomba exaustora (6 l/min). O nível do vapor de mercúrio foi monitorado durante 15 min após a trituração. A superfície dos corpos-de-prova recebeu polimento metalográfico e a porosidade foi analisada através de imagens digitais com 100x de aumento. Os resultados foram sub-metidos à análise de variância e teste de Tukey (p>0.05). Resultados: Foram encontradas diferenças significantes nos valores de liberação de vapor de Hg entre os tipos de liga (p<0.01) e técnicas de condensação (p<0.01). A liga em forma de aparas produziu liberação de Hg significantemente maior que a liga esférica. A condensação ultrasônica produziu níveis de vapor de Hg significantemente maior que as outras técnicas. Porosidade residual não foi influenciada pelo tipo de liga. Porém, quanto ao tipo de condensação, a utilização do aparelho ultrsônico produziu a maior porcentagem de porosidade no amálgama (p<0.05). Conclusão: O método de condensação e o tipo de liga têm influência na liberação de vapor de mercúrio e também na porosidade residual de amálgamas dentários.

Polymerization contraction stress of low-shrinkage composites and its correlation with microleakage in class V restorations.

OBJECTIVE: The aim of this study was to compare the behavior of two new, low-shrinkage hybrid composites (Aelite LS and Inten-S) with a microfilled (Heliomolar) and a hybrid composite (Filtek Z250), in terms of polymerization contraction stress and microleakage. METHODS: Maximum contraction stress after 10 min was recorded in a "tensilometer", using a C-factor (C) of 2.5 and energy density of 26 J/cm(2). For the microleakage test, cylindrical cavities with enamel margins prepared in bovine incisors (4 mm diameter, 1.5 mm depth, C = 2.5) were restored in bulk, applying the same energy density used in the contraction stress test. After immersion in 0.5% methylene blue for 4 h, specimens were sectioned twice, perpendicularly, and the highest dye penetration score was recorded. Contraction stress results were analyzed by one-way ANOVA/Tukey's test and microleakage was analyzed by Kruskal-Wallis test. Regression analysis between the two variables was also performed. RESULTS: Aelite LS showed significantly higher stress than the other composites tested. Inten-S and Filtek Z250 had similar stress levels, statistically higher than Heliomolar. In the microleakage test, a significant difference was observed between Aelite LS and Heliomolar only. Regression analysis showed a good linear correlation between the two variables (R2(adjusted) = 0.811). CONCLUSIONS: The low-shrinkage materials exhibited contraction stress values similar or higher than the hybrid composite. A direct relationship between contraction stress values and microleakage for the composites evaluated was verified. SIGNIFICANCE: The low-shrinkage composites tested did not seem to represent an improvement in terms of reducing contraction stress or microleakage.

Ligas para restaurações metalocerâmicas: uma revisão da literatura / Alloys for metalloceramic restorations: literature review

Durante muitos anos, as ligas nobres foram utilizadas como única alternativa para a confecção de restaurações metalocerâmicas e próteses parciais fixas. Posteriormente, o desenvolvimento de ligas básicas proporcionou um maior número de opções, com custo mais acessivel. Muitas são as ligas capazes de estabelecer união com cerâmicas odontológicas, diferindo quanto à manipulação e ao desempenho devido a variações na composição. As ligas nobres, apesar de seu excelente desempenho, perderam espaço em razão do seu alto custo; as ligas básicas por outro lado, apresentam como desvantagem problemas relacionados ao potencial alergênico de certos constituintes. Em virtude das excelentes propriedades mecânicas e de sua biocompatibilidade, o titânio surgiu como alternativa ao alto custo de ligas nobres e à sensibilidade das ligas básicas. Porém, há ainda problemas relacionados à técnica da fundição e união à porcelana, qua fazem necessárias várias pesquisas para torná-lo uma opção viável. Nesta revisão da literatura propõe-se discutir as ligas ondontológicas nobres e de metais básicos mais utilizadas para a confecção de restaurações metalocerâmicas em relação à composição e propriedades mecânicas, abordando também seus mecanismos de união com as porcelanas