Effect of different light-curing methods and materials for indirect venners on Knoop hardness of resin cements

Orientador: Mario Alexandre Coelho SinhoretiDissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Odontologia de PiracicabaResumo: A crescente demanda por restaurações estéticas tem feito com que cerâmicas e compósitos sejam cada vez mais utilizados na reabilitação dental. Para a cimentação de restaurações indiretas confeccionadas com estes materiais, o agente fixador de escolha é o cimento resinoso. Este material pode polimerizar através de ativação química, física ou através de ativação química/física. Contudo, em determinadas situações clínicas a fotoativação deve ser realizada indiretamente através da cerâmica ou do compósito. Por vezes, em casos em que se prima pela estética, os cimentos fotoativados são preferidos devido a maior estabilidade de cor. Entretanto, a ativação química pode garantir polimerização mais efetiva do cimento. Assim, este estudo teve como objetivo avaliar a dureza Knoop do cimento resinoso Enforce, ativado pelo modo dual ou físico, fotoativado diretamente, sob 1,5mm de cerâmica HeraCeram ou compósito Artglass, usando diferentes aparelhos fotoativadores. Para fotoativação foram utilizados os seguintes tempos: luz halógena convencional (XL2500) - HL, por 40s; luz emitida por diodo (Ultrablue Is) - LED, por 40s; e luz emitida por arco de plasma de xenônio (Apollo 95E) - PAC, por 3s. Incisivos bovinos embutidos em resina de poliestireno tiveram suas faces vestibulares planificadas e submetidas à técnica de hibridização. Sobre a área de dentina hibridizada foi assentada uma matriz de borracha (1mm de espessura e 5mm de diâmetro), dentro da qual foi depositado o cimento devidamente espatulado. O disco de um dos materiais para prótese foi assentado sobre este conjunto, procedendo-se então a fotoativação. Após armazenagem por 24h a 37oC, as amostras foram seccionadas para mensuração da dureza (KHN) em 3 regiões distintas: próximo ao material restaurador, próximo à dentina e ao centro. As leituras de dureza foram realizadas em um microdurômetro após aplicação de carga de 50gf por 15s. Os dados obtidos foram submetidos à análise de variância e ao teste de Tukey, ambos com a=0,05. Foi verificado, de modo geral, que o cimento no modo dual apresentou maiores valores de dureza do que no modo físico, exceto para as condições HL sem material para faceta e com Artglass e LED com HeraCeram. Quando se fixou o nível dual, foi observado que com o LED foram obtidos os maiores valores de dureza nas condições sem material e sob HeraCeram, comportamento não observado sob Artglass, em que os valores de dureza foram similares para os 3 aparelhos. Para HL o menor valor de dureza foi obtido sob HeraCeram e para LED, sob Artglass. Para PAC, os menores valores foram observados sob HeraCeram e na condição sem material. Quando se fixou o nível físico para ativação do cimento, com o LED foram obtidos os maiores valores de dureza na ativação direta e sob HeraCeram, seguido pela HL e PAC, respectivamente. Sob Artglass, os maiores valores de dureza foram obtidos com HL seguido pelo LED e PAC, respectivamente. Sob Artglass e HeraCeram, não foi possível determinar os valores de dureza do cimento fotoativado com PAC. A interposição de HeraCeram mostrou influenciar negativamente a ativação com HL. Para o LED esse comportamento foi verificado sob ArtglassAbstract: The increasing demand for esthetic restorations has increased the use of ceramics and composites in oral rehabilitation. The resin-based cement is the material of choice to fix these prosthetic restorations. This material can polymerize by chemical activation, physical activation or by a combination of chemical/ physical activation. In several clinical situations light curing must be performed indirectly through ceramics or composite. Sometimes, in cases in which esthetic is the major goal, light-cured cements are preferred because their longer color stability. However, the chemical activation can guarantee the polymerization of the cement. The present study aimed to evaluate the Knoop hardness of the resin-based cement Enforce, activated by chemical/ physical mode or by physical mode solely, light-cured directly or through 1.5mm of ceramics (HeraCeram) or composite (Artglass) using different light-curing devices. For light-curing the following activation times were used: conventional halogen light (XL2500) applied for 40s - HL; light emitting diodes (Ultrablue Is) for 40s - LED; and light emitted by xenon plasma arc (Apollo 95E) for 3s - PAC. Bovine incisors embedded in polystyrene resin had its buccal faces ground flat and submitted to the hybridization technique. On the hybridized dentin area a rubber mold was seated (1mm thickness and 5mm diameter), into which the manipulated cement was deposited. A disc of one of the prosthetic materials was seated over this set to proceed the light-curing. After storage for 24h at 37oC, the samples were sectioned and submitted to hardness measurements in 3 different depths: near to restorative material, near to dentin and in the center. The hardness (KHN) measurements were performed in a micro-hardness tester after 50gf load by 15s. Data were submitted to ANOVA and to Tukey¿s test, with a=0.05. In general, it was verified that dual cement presented higher hardness compared to physical mode, exception to HL in direct light curing and with Artglass and LED with HeraCeram. When the level dual was fixed, higher hardness was observed with LED in direct light curing and with HeraCeram, what was not observed with Artglass, in which similar hardness values were obtained with different devices. For HL, the lowest hardness was observed with HeraCeram and for LED, with Artglass. For PAC, lower hardness was verified in direct light curing and with HeraCeram. When the level physical mode for cement activation was fixed, the highest hardness was obtained with LED in direct light curing and with HeraCeram followed by HL and PAC, respectively. With Artglass, the highest hardness was observed with HL followed by LED and PAC, respectively. It was not possible to determine the hardness of physical activated cement light-cured with PAC through Artglass and HeraCeram. Light curing through HeraCeram showed to be deleterious to HL. For LED, this behavior was noted with ArtglassMestradoMateriais DentariosMestre em Materiais Dentário

Effect of the increase of energy density on knoop hardness of dental composites light-cured by conventional QTH, LED and xenon plasma arc

The aim of this study was to evaluate the effect of the increase of energy density on Knoop hardness of Z250 and Esthet-X composite resins. Cylindrical cavities (3 mm in diameter X 3 mm in depth) were prepared on the buccal surface of 144 bovine incisors. The composite resins were bulk-inserted and polymerized using different light-curing units and times: conventional QTH (quartz-tungsten-halogen; 700 mW/cm²; 20 s, 30 s and 40 s); LED (light-emitting diode; 440 mW/cm²; 20 s, 30 s and 40 s); PAC (xenon plasma arc; 1700 mW/cm²; 3 s, 4.5 s and 6 s). The specimens were stored at 37°C for 24 h prior to sectioning for Knoop hardness assessment. Three measurements were obtained for each depth: top surface, 1 mm and 2 mm. Data were analyzed statistically by ANOVA and Tukey's test (p0.05) were found for QTH. Knoop hardness values decreased with the increase of depth. The increase of energy density produced composites with higher Knoop hardness means using LED and PAC.Este estudo teve como objetivo avaliar o efeito do aumento da densidade de energia na dureza Knoop das resinas compostas Z250 e Esthet-X. Cavidades cilíndricas (3 mm de diâmetro X 3mm de profundidade) foram preparadas na superfície vestibular de 144 incisivos bovinos. As resinas compostas foram inseridas em incremento único e fotopolimerizadas com diferentes unidades e tempos de fotopolimerização: luz halógena convencional (700 mW/cm²; 20 s, 30 s and 40 s); LED (diodo emissor de luz; 440 mW/cm²; 20 s, 30 s and 40 s); PAC (arco de plasma de xenônio; 1700 mW/cm²; 3 s, 4,5 s and 6 s). Os espécimens foram armazenados a 37°C durante 24 h, previamente à realização das leituras de dureza Knoop. Foram realizadas três leituras por profundidade: superfície, 1 mm e 2 mm. Os dados foram submetidos à ANOVA e ao teste de Tukey (p0.05). Os valores de dureza Knoop diminuíram com o aumento da profundidade. O aumento da densidade de energia produziu compósitos com maior dureza Knoop quando o LED e o PAC foram utilizados como fontes de polimerização.21822

The Effect of Resection Angle on Stress Distribution after Root-End Surgery

Introduction: This study aimed to investigate the influence of the resection angle on the stress distribution of retrograde endodontic treated maxillary incisors under oblique-load application.  Methods and Materials: A maxillary central incisor which was endodontically treated and restored with a fiber glass post was obtained in a 3-dimensional numerical model and distributed into three groups according to type of resection: control; restored with fiber post without retrograde obturation, R45 and R90 with 45º and 90º resection from tooth axial axis, respectively and restored with Fuji II LC (GC America). The numerical models received a 45º occlusal load of 200 N/cm2 on the middle of lingual surface. All materials and structures were considered linear elastic, homogeneous and isotropic. Numerical models were plotted and meshed with isoparametric elements, and the results were analyzed using maximum principal stress (MPS). Results: MPS showed greater stress values in the bone tissue for control group than the other groups. Groups with apicectomy showed acceptable stress distribution on the fiber post, cement layer and root dentin, presenting more improved values than control group. Conclusion: Apicectomy at 90º promotes more homogeneity on stress distribution on the fiber post, cement layer and root dentin, which suggests less probability of failure. However, due to its facility and stress distribution also being better than control group, apicectomy at 45° could be a good choice for clinicians.Keywords: Apicectomy; Cut Angle; Dental Stress Analysis; Endodontics; Finite Element Analysis; Resection Angl

Učinak bojenja i starenja na parametar translucencije CAD/CAM materijala

Objectives: To evaluate different intervals of exposure to staining solutions and artificial aging on translucency parameter (TP 00) of CAD-CAM materials. Material and Methods: One millimeter thick square-shaped specimens (N = 288) were cut from Cerasmart (CS), IPS e.max (IE), Lava Ultimate (LU), Shofu HC (SH), Vita Enamic (VE), and Vita Suprinity (VS) and were divided into laboratory and chairside polishing. Reflection wavelength spectra, CIE D65 standard illuminant, 2 ° standard observer, SCI, UV included, SAV aperture, 6 mm diameter, were recorded at 10 nm sensitivity against white and black calibration tiles using a benchtop spectrophotometer. Subsequently, they were converted into CIEDE 2000 TP 00. After baseline measurements (T0), the specimens were divided as follows (n = 8): staining in coffee (C) and wine (W), for 60 (T1) and 120 hours (T2), and accelerated artificial aging (A). Artificial aging (ISO 4892-2 standard) was performed in two cycles of 150 KJ/m 2, for T1 and T2, respectively. TP measurements were repeated at T1 and T2. Data of TP 00 retention were submitted to analysis of variance and Fisher’s PLSD multiple comparison test (α=0.05). Results: Fisher’s PLSD critical differences among materials, time intervals and staining/aging were 0.16, 0.11 and 0.11, respectively. SH showed the highest TP 00 followed by LU > CS > IE = VS > VE. For all time intervals, the lowest TP 00 retention was observed with C. W, and A presented similar values. Conclusions: Translucency Parameter was material, time and staining/aging-dependent material. In majority of cases, it decreased upon staining/aging.Svrha rada: Procijeniti utjecaj različitih intervala izloženosti otopinama za bojenje i umjetnom starenju na parameter translucencije (TP 00) CAD/CAM materijala.Materijal i metode: Uzorci kvadratnog oblika debljine 1 mm (N = 288) izrezani su iz blokova Cerasmart (CS), IPS e.max (IE), Lava Ultimate (LU), Shofu HC (SH), Vita Enamic (VE) i Vita Suprinity ( VS) te su razvrstani u skupine u kojima je provedeno poliranje ili u laboratoriju ili u ordinaciji. Mjereni su referentnim spektrofotometrom spektri valne duljine refleksije (standardno osvjetljenje CIE D65, standardni promatrač od 2°, SCI, uključen UV, otvor SAV, promjer 6 mm) pri osjetljivosti od 10 nm na bijelim i crnim kalibracijskim pločicama i pretvoreni u CIEDE 2000 TP 00 . Nakon početnih mjerenja (T0) uzorci su podijeljeni na sljedeći način (n = 8): bojenje u kavi (C) i vinu (W) 60 (T1) i 120 sati (T2) te ubrzano umjetno starenje (A) . Umjetno starenje (ISO 4892-2 standard) obavljeno je u dvama ciklusima od 150 KJ/m2, za T1, odnosno T2. Mjerenja TP-a ponovljena su nakon T1 i T2. Podatci o TP 00 podvrgnuti su analizi varijance Fisherovim PLSD- testom višestruke usporedbe (α = 0,05).Rezultati: Kritične razlike Fisherova PLSD-testa između materijala, vremenskih intervala i bojenja/starenja bile su 0,16, 0,11, odnosno 0,11. SH je imao najviši TP 00 , a zatim slijede LU > CS > IE = VS > VE. Za sve intervale zabilježeno je najmanje zadržavanje TP 00 kod C-a. Slične vrijednosti imali su W i A. Zaključci: Parametar translucencije ovisio je o materijalu, vremenu i bojenju/starenju. U većini slučajeva smanjio se nakon bojenja/starenja

Properties of type IV plaster considering variation in the mold/model position during setting stage

Objective: To assess the influence of the position of the mold during the setting stage of type IV stone plaster Durone (Dentsply Ind. Com., Rio de Janeiro, Brazil), on the following properties: surface hardness and roughness. Methods: For the roughness test, two groups (n=6) in the form of pellets were prepared. In the first group, the surface of the base of the device was turned down during the plaster setting stage (N), in the second group this position was inverted, which has been described as an act of capsize it (E). For analysis, a roughness meter with reading precision of 0.01 μm was used. With regard to the hardness analysis, two groups with conical-shaped samples were obtained. The plasters were left to set under the same conditions of the mold/model position described for the previous experiment. Hardness measurement was performed in a durometer with a spherical penetrating tip for Rockwell readout. Three measurements were performed for each test specimen in both tests. Results: The hardness (N - 39.8, standard deviation = 3.3, E - 30.8, standard deviation = 5.6) and roughness data (N - 0.67, standard deviation = 0.17, E - 0.74, standard deviation = 0.13) submitted to the Student’s-t test (5%) showed no statistically significant differences for the roughness test (0.489), but showed statistically significant differences for the hardness test (0.014). Conclusion: The variation in the mold/model position influenced the final characteristics of the specimens in terms of hardness, since those obtained with the capsize technique showed lower surface hardness, whereas for roughness these differences were not statistically significant

Analysis of bond strength between a nylon reinforcement structure and dental resins

Nylon is a polymer that its use to reinforce dental resins has shown positive results such as increased flexural strength. The aim of this study was to evaluate the bond strength between dental resins and a nylon reinforcement. Forty cylindrical nylon