Influence of aging on bond strength of artificial teeth to denture base acrylic resins

Aim: The aim of this study was to evaluate the bond strength of artificial teeth to different types of denture base resins when submitted to thermomechanical cycling (TMC). Methods: Sixty artificial mandibular first molars (Trilux, Vipi) were randomly divided into 3 groups according to denture base acrylic resins (Vipi Wave, Vipi Cril, and Vipi Cril Plus, Vipi). The teeth were fixed onto self-polymerizing acrylic resin bars (0.5 cm2 cross-section x 2 cm height), and the set was included in a metal flask using dental stone/silicone. After the dental stone was set, the bar was removed, and the denture base resin was packed and processed according to the group studied (Vipi Wave: 180 W/20 minutes + 540W/5 minutes; Vipi Cril and Vipi Cril Plus: Water bath at 74ºC for 9h). After polymerization, the samples were divided into 2 groups (n=10), according to the TMC treatment received (simulation of 5 years of mastication or not). The samples were submitted to tensile bond strength test (1 mm/min), and the data (MPa) were statistically analyzed (2-way ANOVA, Bonferroni, α=0.05). The fracture interfaces were evaluated using a stereomicroscope (50x). Results: The bond strength results showed no statistically significant difference (p>0.05) between the resins studied. TMC was significant (p<0.05), demonstrating lower values for the bond strength of artificial teeth to Vipi Cril Plus. The predominant fracture type was cohesive in resin. Conclusions: It was concluded that there is no difference in bond strength between artificial teeth and the resins used for denture base. However, TMC decreases the bond strength values of artificial teeth and crosslink thermo-polymerizable acrylic resin

Effect of a Bioactive Glass Ceramic on the Control of Enamel and Dentin Erosion Lesions

Abstract This study evaluated the effect of a bioactive glass ceramic for the control of erosion and caries lesions. Fragments (n=10) of bovine enamel and root dentin received daily application of different treatments (Biosilicate; Acidulated Phosphate Fluoride- APF; Untreated - control) during the performance of erosive cycles. Surfaces were analyzed with 3D optical profilometry to quantify the superficial loss in four periods (1, 7, 14 and 21 days), as well as the lesion depth with confocal laser scanning microscopy. For caries progression assessment, initial Knoop microhardness was measured on enamel bovine fragments. Initial carious lesions were developed and specimens were divided into three groups (n=10), according to the daily topical application (Biosilicate; APF; no application - control), during the de-remineralization cycles for 14 days. Final microhardness was obtained to calculate the change of surface microhardness. Subsurface demineralization was analyzed using cross-sectional microhardness (depths 10, 30, 50, 70, 90, 110 and 220 µm). Data were tested using ANOVA and Tukey's test (a=5%). Results of erosive evaluation showed that Biosilicate promoted the lowest (p<0.05) values of surface loss, regardless of time, for both enamel and dentin; APF promoted lower (p<0.05) surface loss than control; analyzing different periods of time, APF did not show difference (p>0.05) between 14 and 21 days of demineralization. Results of enamel caries assessment showed that Biosilicate resulted in higher (p<0.05) surface and subsurface microhardness than both APF and control-applications. It may be concluded that Biosilicate application showed a higher potential to reduce surface loss and development of erosion and caries lesions.

Resumo Este estudo avaliou o efeito de uma vitrocerâmica bioativa para o controle de lesões de erosão e cárie. Fragmentos (n=10) de esmalte bovino e dentina radicular receberam aplicação diária de diferentes tratamentos (Biosilicato; Fluoreto de Fosfato Acidulado - APF; não tratado - controle) durante a realização de ciclos erosivos. As superfícies foram analisadas com profilometria óptica 3D para quantificar a perda superficial em quatro períodos (1, 7, 14 e 21 dias), bem como a profundidade da lesão com microscopia confocal de varredura a laser. Para a avaliação da progressão de cárie, foi obtida a microdureza Knoop inicial de fragmentos de esmalte bovino. As lesões cariosas iniciais foram desenvolvidas e os espécimes foram divididos em três grupos (n =10), de acordo com a aplicação tópica diária (Biosilicato; APF; sem aplicação - controle) durante os ciclos de desmineralização por 14 dias. A microdureza final foi obtida para calcular a perda da microdureza superficial. A desmineralização sub-superficial foi analisada utilizando microdureza transversal (profundidades 10, 30, 50, 70, 90, 110 e 220 μm). Os dados foram testados utilizando ANOVA e teste de Tukey (α=5%). Os resultados da avaliação erosiva mostraram que o Biosilicato promoveu os menores valores (p <0,05) de perda superficial, independente do tempo, tanto para o esmalte como para a dentina; APF promoveu menor (p <0,05) perda de superfície do que controle; analisando os períodos de tempo, APF não mostrou diferença (p>0,05) entre 14 e 21 dias de desmineralização. Os resultados da avaliação da cárie no esmalte mostraram que o Biosilicato resultou em maiores (p<0,05) valores de microdureza superficial e subsuperficial do que as aplicações APF e controle. Pode-se concluir que a aplicação de Biosilicato apresentou maior potencial de redução da perda superficial e desenvolvimento de lesões de erosão e cárie.

Effect of Brushing Time and Dentifrice Abrasiveness on Color Change and Surface Roughness of Resin Composites

Abstract: Dentifrice abrasiveness and brushing time may increase color change (∆E) and surface roughness (∆Ra) of resin composites. This study aimed to evaluate the effect of mechanical brushing time of dentifrices with different abrasiveness on ∆E and ∆Ra of nanofilled (Z350, 3M ESPE) and nanohybrid (Tetric N-Ceram, Ivoclar Vivadent) resin composites. Sixteen specimens (12 mm diameter x 2 mm thick) were fabricated using a white Teflon matrix of each resin composite and a ceramic (IPS e.max Ceram, Ivoclar Vivadent), used as control. After initial color readouts on white backgrounds (Spectrophotometer PCB 6807, Byk Gardner), with D65 standard illuminant, and surface roughness (Rugosimeter Surfcorder SE 1700, Kosalab) with cut-off=0.8 mm and speed=0.25 mm/s, specimens were assigned (n=8) according to the abrasiveness of the dentifrices: RDA* 68 (Colgate) and RDA* 180 (Colgate Total Plus Whitening). Specimens were submitted to mechanical brushing (58,400 cycles) and after every 14,600 cycles (1 year of brushing by a healthy individual), new color and surface roughness readouts were taken. Color stability was calculated by CIEDE2000. Data were analyzed by 3-way repeated measures ANOVA and Bonferroni test (p<0.05), and demonstrated that the dentifrice abrasiveness (p=0.02) and brushing time (p<0.0001) affected the ∆E of nanofilled resin composite. There was no difference on surface roughness of materials (p=0.6752) or brushing time (p=0.7997). In conclusion, the longer the brushing time and dentifrice abrasiveness, the greater the color change of the nanofilled resin composite. The surface roughness was not influenced by dentifrice abrasiveness.

Resumo: A abrasividade do dentifrício e o tempo de escovação podem aumentar a alteração de cor (∆E) e rugosidade de superfície (∆Ra) das resinas compostas. Este estudo teve como objetivo avaliar o efeito do tempo de escovação mecânica com dentifrícios de diferentes abrasividades, sobre o ∆E e a ∆Ra das resinas compostas (nanoparticulada, Z350, 3M ESPE e nanohíbrida, Tetric N-Ceram, Ivoclar Vivadent). Dezesseis amostras (12 mm de diâmetro x 2 mm de espessura) foram obtidas utilizando uma matriz de teflon branca, de cada resina composta e uma cerâmica (IPS e.max Ceram, Ivoclar Vivadent), considerada como controle. Após as leituras iniciais de cor sobre fundo branco (Espectrofotômetro PCB 6807, Byk Gardner), com iluminante padrão D65, e de rugosidade de superfície (Rugosímetro Surfcorder SE 1700, Kosalab), com cut-off=0,8 mm e velocidade=0,25 mm/s, as amostras foram separadas (n=8) de acordo com a abrasividade dos dentifrícios: RDA* 68 (Colgate) e RDA* 180 (Colgate Total Plus Whitening). Amostras foram submetidas a escovação mecânica (58.400 ciclos), sendo que a cada 14.600 ciclos (1 ano de escovação por um indivíduo saudável), novas leituras de cor e rugosidade de superfície foram realizadas. A estabilidade de cor foi calculada segundo CIEDE2000. Os dados foram analisados (3-way ANOVA medidas repetidas, teste de Bonferroni, p<0,05), e demonstrou-se que a abrasividade dos dentifrícios (p=0,02) e o tempo de escovação (p<0,0001) afetaram o ∆E da resina composta nanoparticulada. A rugosidade de superfície não foi influenciada pela abrasividade dos dentifrícios (p=0,6752) ou tempo de escovação (p=0,7997). Concluiu-se que quanto maior o tempo de escovação mecânica e a abrasividade do dentifrício, maior a alteração de cor da resina composta nanoparticulada. A rugosidade de superfície não foi influenciada pela abrasividade do dentifrício.

Microleakage in conservative cavities varying the preparation method and surface treatment

OBJECTIVE: To assess microleakage in conservative class V cavities prepared with aluminum-oxide air abrasion or turbine and restored with self-etching or etch-and-rinse adhesive systems. Materials and Methods: Forty premolars were randomly assigned to 4 groups (I and II: air abrasion; III and IV: turbine) and class V cavities were prepared on the buccal surfaces. Conditioning approaches were: groups I/III - 37 percent phosphoric acid; groups II/IV - self-priming etchant (Tyrian-SPE). Cavities were restored with One Step Plus/Filtek Z250. After finishing, specimens were thermocycled, immersed in 50 percent silver nitrate, and serially sectioned. Microleakage at the occlusal and cervical interfaces was measured in mm and calculated by a software. Data were subjected to ANOVA and Tukey's test (α=0.05). RESULTS: Marginal seal provided by air abrasion was similar to high-speed handpiece, except for group I. There was SIGNIFICANT difference between enamel and dentin/cementum margins for to group I and II: air abrasion. The etch-and-rinse adhesive system promoted a better marginal seal. At enamel and dentin/cementum margins, the highest microleakage values were found in cavities treated with the self-etching adhesive system. At dentin/cementum margins, high-speed handpiece preparations associated with etch-and-rinse system provided the least dye penetration. CONCLUSION: Marginal seal of cavities prepared with aluminum-oxide air abrasion was different from that of conventionally prepared cavities, and the etch-and-rinse system promoted higher marginal seal at both enamel and dentin margins.

Surface and subsurface erosion of primary enamel by acid beverages over time

This study evaluated the influence of a cola-type soft drink and a soy-based orange juice on the surface and subsurface erosion of primary enamel, as a function of the exposure time. Seventy-five primary incisors were divided for microhardness test (n=45) or scanning electron microscopy (SEM) analysis (n=30). The specimens were randomly assigned to 3 groups: 1 - artificial saliva (control); 2 - cola-type soft drink; and 3 - soy-based orange juice. Immersion cycles in the beverages were undertaken under agitation for 5 min, 3 times a day, during 60 days. Surface microhardness was measured at 7, 15, 30, 45 and 60 days. After 60 days, specimens were bisected and subsurface microhardness was measured at 30, 60, 90, 120, 150 and 200 µm from the surface exposed. Data were analyzed by ANOVA and Tukey’s test (a=0.05). Groups 2 and 3 presented similar decrease of surface microhardness. Regarding subsurface microhardness, group 2 presented the lowest values. SEM images revealed that after 60 days the surfaces clearly exhibited structural loss, unlike those immersed in artificial saliva. It may be concluded that erosion of the surfaces exposed to the cola-type soft drink was more accentuated and directly proportional to the exposure time.

Este estudo avaliou a influência de um refrigerante a base de cola e um suco de laranja a base de soja na erosão da superfície e subsuperfície do esmalte do dente decíduo, em função do tempo de exposição. Setenta e cinco incisivos decíduos foram divididos para o teste de microdureza (n=45) ou para a análise em microscópio eletrônico de varredura (MEV) (n=30). Os espécimes foram alocados aleatoriamente em 3 grupos: I - saliva artificial (controle); II - refrigerante a base de cola; e III - suco de laranja a base de soja. Ciclos de imersão nas bebidas foram realizados sob agitação durante 5 min, 3 vezes ao dia, durante 60 dias. A microdureza superficial foi mensurada aos 7, 15, 30, 45 e 60 dias. Após 60 dias, os espécimes foram seccionados e a microdureza subsuperficial foi mensurada aos 30, 60, 90, 120, 150 e 200 μm. Os dados foram analisados pelos testes ANOVA e Tukey (α=5 por cento). Os grupos II e III apresentam uma diminuição similar da microdureza superficial. O grupo II apresentou menores valores de microdureza subsuperficial. As imagens de MEV revelaram que após 60 dias as superficies mostraram perdas de estruturas claramentes identificadas, diferentemente das superfícies imersas em saliva artificial. Pode-se concluir que a erosão das superficies expostas ao refrigerante a base de cola foi mais acentuada e diretamente proporcional ao tempo de exposição à bebida.

Effectiveness of home bleaching agents in discolored teeth and influence on enamel microhardness

OBJECTIVES: This study evaluated the effectiveness of different home bleaching agents on color alteration and their influence on surface and subsurface microhardness of discolored bovine enamel. MATERIAL AND METHODS: Forty-five fragments of bovine incisors were randomly allocated into 3 groups (n=15) according to the bleaching agent: 10 percent carbamide peroxide gel (CP10), 16 percent carbamide peroxide gel (CP16) and 6.5 percent-hydrogen-peroxide-based strip (HP6.5). Before bleaching treatment, initial values of Knoop surface microhardness and color (CIEL*a*b*) were obtained and the fragments were artificially stained in hemolyzed rat blood. Then, bleaching treatments were performed over a 21-day period. Color changes (ÄE) were assessed at 7, 14 and 21 days, and final surface microhardness reading was done after 21 days. Thereafter, the fragments were bisected to obtain subsurface microhardness. Data were subjected to ANOVA and Tukey's tests (á=5 percent). RESULTS: Color changes produced by CP16 were similar to those of CP10, and the color changes produced by these materials were significantly superior to those produced by HP6.5. Color changes at 21 days were superior to 7 days and similar to 14 days. The time did not influence color changes for CP16, which showed similarity between the 14- and 21-day results. No statistically significant differences were found among the home bleaching agents for surface and subsurface microhardness. CONCLUSIONS: Microhardness of bovine enamel was not affected by the bleaching agents. The 16 percent carbamide peroxide gel was the most effective for bleaching the stained substrate.

Evaluation of the surface hardness of composite resins before and after polishing at different times

PURPOSE: The aim of this study was to evaluate the surface hardness of six composite resins: Revolution, Natural Flow, Fill Magic Flow, Flow-it! (flowables), Silux Plus (microfilled) and Z100 (minifilled) before and after polishing at different times. MATERIALS AND METHODS: For this purpose, 240 specimens (5mm diameter, 1.4mm high) were prepared. Vickers hardness was determined before and after polishing at different times: immediately, 24h, 7 and 21 days after preparation of the samples. Statistical analysis was performed by ANOVA and Tukey test. RESULTS: There was no difference in the hardness of flowable resins, which had lower hardness than the minifilled resin. The minifilled resin showed the highest surface hardness as compared to the other materials (p<0.01). All materials exhibited higher hardness after polishing, being more evident after 7 days. CONCLUSION: It may be concluded that, regardless of the composite resin, surface hardness was considerably increased when polishing was delayed and performed 1 week after preparation of the samples.

PROPOSIÇÃO: O objetivo deste estudo foi avaliar a dureza superficial de seis resinas compostas - Revolution, Natural Flow, Fill Magic Flow, Flow-it! (flowables), Silux Plus (micropartículas) e Z100 (híbrida) - antes e após o polimento realizado em diferentes tempos. MATERIAL E MÉTODO: Foram confeccionados 240 corpos-de-prova circulares (5mm de diâmetro e 1,4mm de altura). A dureza Vickers foi obtida antes e após o polimento realizado em diferentes tempos: imediatamente, 24 horas, 7 dias e 21 dias após a confecção do corpo-de-prova. Os dados foram analisados estatisticamente por meio da ANOVA e do Teste de Tukey. RESULTADOS: Não houve diferença entre as resinas compostas flowable, as quais apresentaram os menores valores de dureza. A resina composta híbrida demonstrou os melhores resultados. Todos os materiais exibiram aumento de dureza após a realização do polimento, que foi mais evidente após 7 dias. CONCLUSÃO: Pôde-se concluir que, independente do tipo de resina composta, a dureza superficial foi consideravelmente maior quando o polimento foi realizado 1 semana após a confecção dos corpos-de-prova.

Evaluation of the surface hardness of composite resins before and after polishing at different times%Avaliação da dureza superficial de resinas compostas antes e após o polimento em diferentes tempos

PROPOSIÇÃO: O objetivo deste estudo foi avaliar a dureza superficial de seis resinas compostas - Revolution, Natural Flow, Fill Magic Flow, Flow-it! (flowables), Silux Plus (micropartículas) e Z100 (híbrida) - antes e após o polimento realizado em diferentes tempos. MATERIAL E MÉTODO: Foram confeccionados 240 corpos-de-prova circulares (5mm de diâmetro e 1,4mm de altura). A dureza Vickers foi obtida antes e após o polimento realizado em diferentes tempos: imediatamente, 24 horas, 7 dias e 21 dias após a confecção do corpo-de-prova. Os dados foram analisados estatisticamente por meio da ANOVA e do Teste de Tukey. RESULTADOS: Não houve diferença entre as resinas compostas flowable, as quais apresentaram os menores valores de dureza. A resina composta híbrida demonstrou os melhores resultados. Todos os materiais exibiram aumento de dureza após a realização do polimento, que foi mais evidente após 7 dias. CONCLUSÃO: Pôde-se concluir que, independente do tipo de resina composta, a dureza superficial foi consideravelmente maior quando o polimento foi realizado 1 semana após a confecção dos corpos-de-prova

Microinfiltração marginal em Cavidades Preparadas com Pontas CVDentUS® e Diamantadas Convencionais / Marginal Microleakage in Cavities Prepared with CVDentUS® and Conventional Diamonds Burs

O objetivo deste trabalho foi avaliar a microinfiltração marginal em cavidades restritas ao esmalte de dentes bovinos preparados com as pontas CVDentUS® e diamantadas convencionais. Foram realizados preparos cavitários medindo 1mm de profundidade em dois grupos de 15 dentes cada, utilizando ponta diamantada convencional associado à turbina de alta rotação e ponta CVDentUS® associado ao ultra-som. As cavidades foram restauradas com selante para fóssulas e fissuras Fluroshield® (Dentsply) de acordo com as instruções do fabricante. Após serem isolados com Araldite® e esmalte cosmético, os dentes foram submetidos a termociclagem em água a 5°C± 2°C e 55°C± 2°C, totalizando 500 ciclos. Em seguida, foram corados com fucsina básica a 0,5%, seccionados e lixados até ficarem com aproximadamente 0,25mm de espessura, montados em lâminas e identificados. A análise da microinfiltração foi realizada em microscópio óptico ligado a uma câmara digital e conectado a um computador, que permitiu a análise quantitativa da microinfiltração em milímetros por meio de uma imagem digitalizada e um software AxioVision. Os dados obtidos foram submetidos à análise estatística através do teste de Mann-Whitney. Foi observada acentuada microinfiltração marginal em ambos os grupos sem diferença estatistica entre eles (p > 0,05)

Avaliação da eficiência de pontas diamantadas / Cutting efficiency of diamond points

O objetivo do presente estudo foi avaliar a eficiência de desgaste sobre dentes bovinos de pontas diamantadas de diferentes marcas comerciais (KG Sorensen, Microdont, Fava e SSWhinte). Para tal finalidade, foram testados 10 pontas de cada marca comercial, cujo substrato para o desgaste constituía-se de incisivos bovinos, seccionados em 4 partes iguais (2 cervicais e 2 incisais) e incluídos em resina de poliéster, totalizando 4 espécimes para cada instrumento rotatório. Para padronização do desgaste, foi utilizado um dispositivo, no qual acoplou-se a caneta de alta-rotação. Todos os testes foram executados sob refrigeração constante e as pontas foram divididas aleatoriamente e sem identificação. Os dados forma analisados através de Análise de Variância a dois critérios (p<0,01) e teste de Tukey (p<0,05). Pode-se observar que as pontas diamantadas KG Soresen demonstraram estatisticamente maior eficiência no desgaste do que as demais pontas testadas, sendo mais evidenciado após o 2° secção de dente. Através dos resultados obtidos, pode-se concluir que as pontas diamantadas KG apresentaram melhor desempenho tanto na porção incisal quanto na cervical

In vitro evaluation of microleakage of a flowable composite in class V restorations

The aim of this study was to evaluate microleakage around class V restorations using a flowable composite compared to a hybrid composite. Forty class V cavities were prepared on buccal and lingual surfaces of 20 human teeth, with occlusal and cervical margins at the enamel and cementum/dentin levels, respectively. Specimens were divided into 2 groups with 10 samples each. Group 1: buccal cavities received Paama 2 (conventional bonding agent) + Wave (flowable composite); lingual cavities were restored with Paama 2 + Glacier (hybrid composite). Group 2: buccal cavities received Optibond Solo (self-priming bonding agent) + Wave; lingual cavities were restored with Optibond Solo + Glacier. After being stored in distilled water and finished, the teeth were thermocycled, immersed in a 50 percent silver nitrate solution and embedded in resin. They were sectioned and the depth of tracer penetration was scored. The results were analyzed using Kruskall-Wallis and Wilcoxon tests. The restorations with flowable composite and those with hybrid composite from the same group showed similar results of microleakage for both occlusal and cervical margins. Optibond Solo improved the sealing of the restorations when compared with Paama 2 (p<0.01). None of the restorative materials completely sealed the tooth/restoration interface at the cervical margins