Influence of activation mode, fatigue, and ceramic interposition on resin cements' diametral tensile strength

This study evaluated the influence of activation modes, on Diametral Tensile Strength (DTS) of dual cured resin cements subjected to a Mechanical Fatigue test (MF). Four dual-cured resin cements (RelyX UNICEM [U], RelyX ARC [A], ENFORCE [E] and Nexus 2 [N]) were activated by three different curing modes as follows: Self-Curing (SC), Dual Cure activation with photoactivation executed directly (DC) and Dual Cure activation with Photoactivation Through Porcelain (DCTP). After 24 hours, half of the sample was subjected to 30.000 fatigue cycles at 1 Hz frequency and 12 N load. Then, all specimens were subjected to DTS test in Instron Universal Testing Machine and data were analyzed by three-way ANOVA and Tukey's Test (5%). The results of DTS test means (MPa) and standard deviation, for each cement factor activated by SC, DC and DCTP was respectively: U (28.12 ± 5.29; 37.44 ± 6.49 and 40.10 ± 4.39), A (49.68 ± 8.42; 55.12 ± 5.16 and 63.43 ± 6.92), E (49.12 ± 3.89; 56.42 ± 8.88 and 56.96 ± 6.45) and N (61.89 ± 11.21; 59.26 ± 9.47 and 62.56 ± 10.93). Turkey's test indicated that DC is related to the highest DTS values; Nexus 2 DTS remained the same independently of activation mode and that the Porcelain disk interposition enhanced DTS only for RelyX ARC the ANOVA statistical test indicated that MF didn't alter the DTS values for all experimental groups. MF results clinical implication is that all cements tested exhibited, in an immediate loading, good cross linked bonds quality33COORDENAÇÃO DE APERFEIÇOAMENTO DE PESSOAL DE NÍVEL SUPERIOR - CAPESnão te

Effect Of Etching Time And Light Source On The Bond Strength Of Metallic Brackets To Ceramic

This study evaluated the bond strength of brackets to ceramic testing different etching times and light sources for photo-activation of the bonding agent. Cylinders of feldspathic ceramic were etched with 10% hydrofluoric acid for 20 or 60 s. After application of silane on the ceramic surface, metallic brackets were bonded to the cylinders using Transbond XT (3M Unitek). The specimens for each etching time were assigned to 4 groups (n=15), according to the light source: XL2500 halogen light, UltraLume 5 LED, AccuCure 3000 argon laser, and Apollo 95E plasma arc. Light-activation was carried out with total exposure times of 40, 40, 20 and 12 s, respectively. Shear strength testing was carried out after 24 h. The adhesive remnant index (ARI) was evaluated under magnification. Data were subjected to two-way ANOVA and Tukey's test (α=0.05). Specimens etched for 20 s presented significantly lower bond strength (p0.05) were detected among the light sources. The ARI showed a predominance of scores 0 in all groups, with an increase in scores 1, 2 and 3 for the 60 s time. In conclusion, only the etching time had significant influence on the bond strength of brackets to ceramic.223245248Barghi, N., Fischer, D.E., Vatani, L., Effects of porcelain leucite content, types of etchants, and etching time on porcelaincomposite bond (2006) J Esthet Restor Dent, 18, pp. 47-52Nagayassu, M.P., Shintome, L.K., Uemura, E.S., Araújo, J.E., Effect of surface treatment on the shear bond strength of a resin-based cement to porcelain (2006) Braz Dent J, 17, pp. 290-295Shimada, Y., Yamaguchi, S., Tagami, J., Micro-shear bond strength of dual-cured resin cement to glass ceramics (2002) Dent Mater, 18, pp. 380-388Chen, J.H., Matsumura, H., Atsuta, M., Effect of different etching periods on the bond strength of a composite resin to a machinable porcelain (1998) J Dent, 26, pp. 53-58Guler, A.U., Yilmaz, F., Yenisey, M., Guler, E., Ural, C., Effect of acid etching time and a self-etching adhesive on the shear bond strength of composite resin to porcelain (2006) J Adhes Dent, 8, pp. 21-25Kasuya, K., Miyazaki, Y., Ogawa, N., Maki, K., Manabe, A., Itoh, K., Efficacy of experimental dual-cure resin cement for orthodontic direct bond system (2006) Orthod Waves, 65, pp. 107-111Meguro, D., Hayakawa, T., Kasai, K., Efficacy of using orthodontic adhesive resin in bonding and debonding characteristics of a calcium phosphate ceramic bracket (2006) Orthod Waves, 65, pp. 148-154Dall'igna, C.M., Marchioro, E.M., Spohr, A.M., Mota, E.G., Effect of curing time on the bond strength of a bracket-bonding system cured with a light-emitting diode or plasma arc light (2011) Eur J Orthod, 33, pp. 55-59Correr, A.B., Sinhoreti, M.A., Sobrinho, L.C., Tango, R.N., Schneider, L.F., Consani, S., Effect of the increase of energy density on Knoop hardness of dental composites light-cured by conventional QTH, LED and xenon plasma arc (2005) Braz Dent J, 16, pp. 218-224Cekic-Nagas, I., Egilmez, F., Ergun, G., The effect of irradiation distance on microhardness of resin composites cured with different light curing units (2010) Eur J Dent, 4, pp. 440-446Thind, B.S., Stirrups, D.R., Lloyd, C.H., A comparison of tungstenquartz- halogen, plasma arc and light-emitting diode light sources for the polymerization of an orthodontic adhesive (2006) Eur J Orthod, 28, pp. 78-82Filipov, I.A., Vladimirov, S.B., Residual monomer in a composite resin after light-curing with different sources, light intensities and spectra of radiation (2006) Braz Dent J, 17, pp. 34-38Park, J.K., Hur, B., Ko, C.C., García-Godoy, F., Kim, H.I., Kwon, Y.H., Effect of light-curing units on the thermal expansion of resin nanocomposites (2010) Am J Dent, 23, pp. 331-334Price, R.B., Labrie, D., Rueggeberg, F.A., Felix, C.M., Irraciance differences in the violet (405 nm) and blue (460 nm) spectral ranges among dental light-curing units (2010) J Esthet Restor Dent, 22, pp. 363-377Yen, T.W., Blackman, R.B., Baez, R.J., Effect of acid etching on the flexural strength of a feldspathic porcelain and a castable glass ceramic (1993) J Prosthet Dent, 70, pp. 224-233Reynolds, I.R., Composite filling materials as adhesives in orthodontics (1975) Br Dent J, 138, p. 83Rueggeberg, F., Contemporary issues in photocuring (1999) Compend Contin Educ Dent, (SUPPL.), pp. 4-15Olsen, M.E., Bishara, S.E., Boyer, D.B., Jakobsen, J.R., Effect of varying etching times on the bond strength of ceramic brackets (1996) Am J Orthod Dentofacial Orthop, 109, pp. 403-409Sant'anna, E.F., Monnerat, M.E., Chevitarese, O., Stuani, M.B., Bonding brackets to porcelain - in vitro study (2002) Braz Dent J, 3, pp. 191-196Canay, S., Hersek, N., Ertan, A., Effect of different acid treatments on a porcelain surface (2001) J Oral Rehabil, 28, pp. 95-10

Effects Of Thermocycling And Light Source On The Bond Strength Of Metallic Brackets To Bovine Teeth

This study evaluated the effects of thermocycling and different light sources on the bond strength of metallic brackets to bovine tooth enamel using an adhesive resin. Bovine teeth were etched with 35% phosphoric acid gel for 20 s. After application of primer, metallic brackets were bonded to the buccal surface using Transbond XT, forming 8 groups (n=20), depending on the light source used for photoactivation (AccuCure 3000 argon laser - 20 s, Apollo 95E plasma arc - 12 s, UltraLume 5 LED - 40 s and XL2500 halogen light - 40 s) and experimental conditions without (Groups 1 to 4) or with thermocycling (Groups 5 to 8). Shear bond testing was carried out after 24 h of distilled water storage (Groups 1 to 4) or storage and thermocycling in distilled water (groups 5 to 8; 1,500 cycles - 5°/55°C). Data were subjected to two-way ANOVA and Tukey's test (α=0.05). The Adhesive Remnant Index (ARI) was evaluated at ×8 magnification. No significant differences (p>0.05) in bond strength were found when the conditions without and with thermocycling were compared for any of the light sources. No significant differences (p>0.05) in bond strength were found among the light sources, irrespective of performing or not thermocycling. There was a predominance of ARI scores 1 in all groups. In conclusion, light sources and thermocycling had no influence on the bond strength of brackets to bovine enamel.226486489Sfondrini, M.F., Cacciafesta, V., Scribante, A., Klersy, C., Plasma arc versus halogen light curing of orthodontic brackets: A 12-month clinical study of bond failures (2004) Am J Orthod Dentofacial Orthop, 125, pp. 342-347Dall'igna, C.M., Marchioro, E.M., Spohr, A.M., Mota, E.G., Effect of curing time on the bond strength of a bracket-bonding system cured with a light-emitting diode or plasma arc light (2011) Eur J Orthod, 33, pp. 55-59Correr, A.B., Sinhoreti, M.A., Sobrinho, L.C., Tango, R.N., Schneider, L.F., Consani, S., Effect of the increase of energy density on Knoop hardness of dental composites light-cured by conventional QTH, LED and xenon plasma arc (2005) Braz Dent J, 16, pp. 218-224Cekic-Nagas, I., Egilmez, F., Ergun, G., The effect of irradiation distance on microhardness of resin composites cured with different light curing units (2010) Eur J Dent, 4, pp. 440-446Thind, B.S., Stirrups, D.R., Lloyd, C.H., A comparison of tungsten- quartz halogen, plasma arc and light-emitting diode light sources for the polymerization of an orthodontic adhesive (2006) Eur J Orthod, 28, pp. 78-82Filipov, I.A., Vladimirov, S.B., Residual monomer in a composite resin after light-curing with different sources, light intensities and spectra of radiation (2006) Braz Dent J, 17, pp. 34-38Park, J.K., Hur, B., Ko, C.C., García-Godoy, F., Kim, H.I., Kwon, Y.H., Effect of light-curing units on the thermal expansion of resin nanocomposites (2010) Am J Dent, 23, pp. 331-334Price, R.B., Labrie, D., Rueggeberg, F.A., Felix, C.M., Irradiance differences in the violet (405 nm) and blue (460 nm) spectral ranges among dental light-curing units (2010) J Esthet Restor Dent, 22, pp. 363-377Gonçalves, P.R.A., Moraes, R.R., Costa, A.R., Correr, A.B., Nouer, P.R.A., Sinhoreti, M.A.C., Effect of etching time and light source on the bond strength of metallic brackets to ceramic (2011) Braz Dent J, 22, pp. 245-248Swanson, T., Dunn, W.J., Childers, D.E., Taloumis, L.J., Shear bond strength of orthodontic brackets bonded with light-emitting diode curing units at various polymerization times (2004) Am J Orthod Dentofacial Orthop, 125, pp. 337-341Usumez, S., Buyukyilmaz, T., Karaman, A.I., Effect of light-emitting diode on bond strength of orthodontic brackets (2004) Angle Orthod, 74, pp. 259-263Talbot, T.Q., Blankenau, R.J., Zobitz, M.E., Weaver, A.L., Lohse, C.M., Rebellato, J., Effect of argon laser irradiation on shear bond strength of orthodontic brackets: An in vitro study (2000) Am J Orthod Dentofacial Orthop, 118, pp. 274-279Klocke, A., Korbmacher, H.M., Huck, L.G., Kahl-Nieke, B., Plasma arc curing lights for orthodontic bonding (2002) Am J Orthod Dentofacial Orthop, 122, pp. 643-648Bishara, S.E., Ostby, A.W., Laffoon, J.F., Warren, J., Shear bond strength comparison of two adhesive systems following thermocycling (2007) Angle Orthod, 77, pp. 337-341Faltermeier, A., Müssig, D., A comparative evaluation of bracket bonding with 1-, 2-, and 3-component adhesive systems (2007) Am J Orthod Dentofacial Orthop, 132, pp. 144.e1-144.e5Gale, M.S., Darvell, B.W., Thermal cycling procedures for laboratory testing of dental restorations (1999) J Dent, 27, pp. 89-99Trites, B., Foley, T.F., Banting, D., Bond strength comparison of 2 self-etching primers over a 3-month storage period (2004) Am J Orthod Dentofacial Orthop, 126, pp. 709-716Yuasa, T., Iijima, M., Ito, S., Muguruma, T., Saito, T., Mizoguchi, I., Effects of long-term storage and thermocycling on bond strength of two self-etching primer adhesive systems (2010) Eur J Orthod, 32, pp. 285-290Artun, J., Berglund, S., Clinical trials with crystal growth conditioning as an alternative to acid-etch enamel pretreatment (1984) Am J Orthod, 85, pp. 333-340Oesterle, L.J., Newman, S.M., Shellhart, W.C., Rapid curing of bondingcomposite with a xenon plasma arc light (2001) Am J Orthod Dentofacial Orthop, 119, pp. 610-616Staudt, C.B., Mavropoulos, A., Bouil, L.S., Kiliaridis, S., Krejcid, I., Light-curing time reduction with a new high-power halogen lamp (2005) Am J Orthod Dentofacial Orthop, 128, pp. 749-754Yu, H.S., Lee, K.J., Jin, G.C., Baik, H.S., Comparison of the shear bond strength of brackets using the LED curing light and plasma arc curing light: Polymerization time (2007) World J Orthod, 8, pp. 129-135Rueggeberg, F., Contemporary issues in photocuring (1999) Compend Contin Educ Dent Suppl, pp. 4-15de Munck, J., van Landuyt, K., Peumans, M., Poitevin, A., Lambrechts, P., Braem, M., A critical review of the durability of adhesion of tooth tissue: Methods and results (2005) J Dent Res, 84, pp. 118-132Reynolds, I.R., Composite filling materials as adhesives in Orthodontics (1975) Br Dent J, 138, p. 8

Effect Of Refrigeration On Tensile Bond Strength Of Three Adhesive Systems.

The purpose of this study was to investigate the tensile bond strengths of three adhesive systems applied to dentin at refrigerated and room temperatures. Ninety bovine incisor teeth were obtained, embedded in self-cured acrylic resin, abraded on a lathe under water spray and polished to 400 and 600 grit to form standardized dentin surfaces before randomly assigning to six groups (n = 15). The adhesive systems Scotchbond Multi-Purpose, Single Bond and Prime & Bond NT were applied to dentin according to the manufacturers' instructions at refrigerated temperature (4 degrees C) and at room temperature (23 degrees C), before bonding resin-based composite (Z 100). The specimens were stored in distilled water at 37 degrees C for 24 hours and submitted to tensile bond strength tests on a universal testing machine (EMIC DL-2000) at a crosshead speed of 0.5 mm/min. The resulting data were statistically analyzed using analysis of variance and Tukey's test. No statistical differences were found when the adhesive systems were applied at refrigerated and room temperatures. Scotchbond Multi-Purpose and Single Bond had significantly stronger tensile bond strengths than Prime & Bond NT at room and refrigerated temperatures (p < 0.01). Scotchbond Multi-Purpose and Single Bond were statistically similar. No adverse effects upon tensile bond strength were observed when adhesive systems were taken directly from refrigerated storage.122757

Marginal adaptation of composite restorations photoactivated by LED, plasma arc, and QTH light using low-modulus resin liners

Purpose: The aim of this study was to evaluate the influence of resin liners on the marginal adaptation to dentin of resin composite restorations photoactivated by a conventional quartz-tungsten halogen lamp (QTH), light emitting diodes (LED), and a plasma arc light (PAC). Materials and Methods: The buccal surfaces of 120 bovine incisors were ground until a flat dentin area was obtained. A circular cavity (4 mm in diameter x 1.5 mm in depth) was prepared in this area. Scotchbond Multi Purpose was applied in the cavities following the manufacturer's instructions. The specimens were randomly assigned into 4 groups according to the lining technique: (1) control (1 adhesive layer); (2) three adhesive layers; (3) Filtek Flow; (4) Protect Liner F. Each group was further divided into 3 subgroups according to the light-curing method: (A) QTH; (B) LED; (C) PAC. All cavities were then restored with a single increment of Filtek Z250 restorative composite and polished. Caries Detector was applied to each specimen for 5 s. Images of dye-stained gaps were observed under a stereomicroscope and transferred to a computer measurement program. Gap values were obtained by dividing the dyed margin length by the total cavity length, then multiplying by 100. Data were analyzed using ANOVA and Tukey's test (p<0.05). Results: All the tested lining techniques significantly decreased marginal gap formation when compared with the control group only for the QTH light groups. There was no significant difference among the light-curing methods. Conclusion: The use of resin liners can effectively reduce the gap formation along dentin margins, but only when QTH light is used.8422322

Permeability, Roughness And Topography Of Enamel After Bleaching: Tracking Channels Of Penetration With Silver Nitrate

Aim: This study evaluated the surface roughness, topography and permeability of bovine enamel by profilometry and scanning electron microscopy (SEM) with and without silver nitrate solution, after exposure to different bleaching agents. Methods: Fifty-two enamel samples were randomly divided into four groups (n=13): CP16% -16% carbamide peroxide - Whiteness Perfect; HP6% - 6% hydrogen peroxide - White Class; HP35% - 35% hydrogen peroxide Whiteness HP Maxx; and Control - not bleached and kept in artificial saliva. For roughness analysis, average surface roughness (Ra) and flatness coefficient (Rku) parameters were used. The topography and permeability were examined by SEM. For permeability evaluation, the samples were immersed in a 50% silver nitrate solution and analyzed using a backscattered electron and secondary electron mode. Results: For the roughness (Ra) evaluation, Kruskal-Wallis and Wilcoxon Signed Ranks Test were used, showing an increase on the surface roughness in all bleached groups. The Rku parameter suggested changes on enamel integrity. The SEM micrographs indicated changes on enamel topography and different levels of silver nitrate penetration in the samples of the bleached groups. In the overall analysis, the bleaching agents promoted surface changes and higher silver nitrate penetration when compared to the control group. Conclusions: It may be concluded that different bleaching agents might alter the topography and roughness of enamel surface. Moreover, the higher infiltration of silver nitrate suggests an easier penetration path for the oxygen molecules into the dentin substrate.10116Nathoo, S.A., The chemistry and mechanisms of extrinsic and intrinsic discoloration (1997) J Am Dent Assoc, 128 (SUPPL.), pp. 6S-10SMcEvoy, S.A., Chemical agents for removing intrinsic stains from vital teeth. II. Current techniques and their clinical application (1989) Quintessence Int, 20, pp. 379-384Ben-Amar, A., Liberman, R., Gorfil, C., Bernstein, Y., Effect of mouthguard bleaching on enamel surface (1995) Am J Dent, 8, pp. 29-32Lynch, E., Sheerin, A., Samarawickrama, D.Y., Atherton, M.A., Claxson, A.W., Hawkes, J., Molecular mechanisms of the bleaching actions associated with commercially-available whitening oral health care products (1995) J Ir Dent Assoc, 41, pp. 94-102Bowles, W.H., Ugwuneri, Z., Pulp chamber penetration by hydrogen peroxide following vital bleaching procedures (1987) J Endod, 13, pp. 375-377Sun, G., The role of lasers in cosmetic dentistry (2000) Dent Clin North Am, 44, pp. 831-850Hegedus, C., Bistey, T., Flora-Nagy, E., Keszthelyi, G., Jenei, A., An atomic force microscopy study on the effect of bleaching agents on enamel surface (1999) J Dent, 27, pp. 509-515Park, H.J., Kwon, T.Y., Nam, S.H., Kim, H.J., Kim, K.H., Kim, Y.J., Changes in bovine enamel after treatment with a 30% hydrogen peroxide bleaching agent (2004) Dent Mater J, 23, pp. 517-521Iwamoto, N., Shimada, Y., Tagami, J., Penetration of silver nitrate into bleached enamel, dentin, and cementum (2007) Quintessence Int, 38, pp. e183-e188Cavalli, V., Arrais, C.A., Giannini, M., Ambrosano, G.M., High-concentrated carbamide peroxide bleaching agents effects on enamel surface (2004) J Oral Rehabil, 31, pp. 155-159Hosoya, N., Honda, K., Iino, F., Arai, T., Changes in enamel surface roughness and adhesion of Streptococcus mutans to enamel after vital bleaching (2003) J Dent, 31, pp. 543-548Josey, A.L., Meyers, I.A., Romaniuk, K., Symons, A.L., The effect of a vital bleaching technique on enamel surface morphology and the bonding of composite resin to enamel (1996) J Oral Rehabil, 23, pp. 244-250Lee, C.Q., Cobb, C.M., Zargartalebi, F., Hu, N., Effect of bleaching on microhardness, morphology, and color of enamel (1995) Gen Dent, 43, pp. 158-160McGuckin, R.S., Babin, J.F., Meyer, B.J., Alterations in human enamel surface morphology following vital bleaching (1992) J Prosthet Dent, 68, pp. 754-760Pinto, C.F., Oliveira, R., Cavalli, V., Giannini, M., Peroxide bleaching agent effects on enamel surface microhardness, roughness and morphology (2004) Braz Oral Res, 18, pp. 306-311Shannon, H., Spencer, P., Gross, K., Tira, D., Characterization of enamel exposed to 10% carbamide peroxide bleaching agents (1993) Quintessence Int, 24, pp. 39-44Zalkind, M., Arwaz, J.R., Goldman, A., Rotstein, I., Surface morphology changes in human enamel, dentin and cementum following bleaching: a scanning electron microscopy study (1996) Endod Dent Traumatol, 12, pp. 82-88Ernst, C.P., Marroquin, B.B., Willershausen-Zonnchen, B., Effects of hydrogen peroxide-containing bleaching agents on the morphology of human enamel (1996) Quintessence Int, 27, pp. 53-56Gultz, J., Kaim, J., Scherer, W., Gupta, H., Two in-office bleaching systems: a scanning electron microscope study (1999) Compend Contin Educ Dent, 20, pp. 965-968. , 70quiz 72Haywood, V.B., Heymann, H.O., Nightguard vital bleaching: how safe is it? (1991) Quintessence Int, 22, pp. 515-523Haywood, V.B., Leech, T., Heymann, H.O., Crumpler, D., Bruggers, K., Nightguard vital bleaching: effects on enamel surface texture and diffusion (1990) Quintessence Int, 21, pp. 801-804Oltu, U., Gurgan, S., Effects of three concentrations of carbamide peroxide on the structure of enamel (2000) J Oral Rehabil, 27, pp. 332-340Spalding, M., Taveira, L.A., de Assis, G.F., Scanning electron microscopy study of dental enamel surface exposed to 35% hydrogen peroxide: alone, with saliva, and with 10% carbamide peroxide (2003) J Esthet Restor Dent, 15, pp. 154-165Sulieman, M., Addy, M., Macdonald, E., Rees, J.S., A safety study in vitro for the effects of an in-office bleaching system on the integrity of enamel and dentine (2004) J Dent, 32, pp. 581-590Tong, L.S., Pang, M.K., Mok, N.Y., King, N.M., Wei, S.H., The effects of etching, micro-abrasion, and bleaching on surface enamel (1993) J Dent Res, 72, pp. 67-71Bagheri, R., Tyas, M.J., Burrow, M.F., Subsurface degradation of resin-based composites (2007) Dent Mater, 23, pp. 944-951Reis, A., Grande, R.H., Oliveira, G.M., Lopes, G.C., Loguercio, A.D., A 2-year evaluation of moisture on microtensile bond strength and nanoleakage (2007) Dent Mater, 23, pp. 862-870Ritter, A.V., Ghaname, E., Leonard, R.H., The influence of dental unit waterline cleaners on composite-to-dentin bond strengths (2007) J Am Dent Assoc, 138, pp. 985-991. , quiz 1022-3Sano, H., Shono, T., Takatsu, T., Hosoda, H., Microporous dentin zone beneath resin-impregnated layer (1994) Oper Dent, 19, pp. 59-64Nanci, A., (2007) Ten Cate's oral histology: development, structure, and function, , 7th ed. Saint Louis: Mosby-ElsevierCeliberti, P., Pazera, P., Lussi, A., The impact of ozone treatment on enamel physical properties (2006) Am J Dent, 19, pp. 67-72Chen, J.H., Xu, J.W., Shing, C.X., Decomposition rate of hydrogen peroxide bleaching agents under various chemical and physical conditions (1993) J Prosthet Dent, 69, pp. 46-48Reyto, R., Laser tooth whitening (1998) Dent Clin North Am., 42, pp. 755-762. , xiBitter, N.C., Sanders, J.L., The effects of four bleaching agents on the enamel surface: a scanning electron microscopic study (1993) Quintessence Int, 24, pp. 817-824Leonard Jr., R.H., Austin, S.M., Haywood, V.B., Bentley, C.D., Change in pH of plaque and 10% carbamide peroxide solution during nightguard vital bleaching treatment (1994) Quintessence Int, 25, pp. 819-823Leonard Jr., R.H., Bentley, C.D., Haywood, V.B., Salivary pH changes during 10% carbamide peroxide bleaching (1994) Quintessence Int, 25, pp. 547-550Li, Y., Biological properties of peroxide-containing tooth whiteners (1996) Food Chem Toxicol, 34, pp. 887-904Price, R.B., Sedarous, M., Hiltz, G.S., The pH of tooth-whitening products (2000) J Can Dent Assoc, 66, pp. 421-426Yeh, S.T., Su, Y., Lu, Y.C., Lee, S.Y., Surface changes and acid dissolution of enamel after carbamide peroxide bleach treatment (2005) Oper Dent, 30, pp. 507-515Justino, L.M., Tames, D.R., Demarco, F.F., In situ and in vitro effects of bleaching with carbamide peroxide on human enamel (2004) Oper Dent, 29, pp. 219-22

Influence of casting methods on marginal and internal discrepancies of complete cast crowns.

The relationship between the application of die-spacer prior to wax pattern fabrication and metal removal from the inner surface of the casting on marginal and internal discrepancies of complete cast crowns was evaluated. One hundred and twenty complete crowns were cast with palladium-silver alloy melted by gas-oxygen torch or electrical resistance and cast with a centrifuge casting machine. After casting, the crowns were seated on each type of different marginal configuration dies (90-degree shoulder, 20-degree beveled shoulder, and 45-degree chamfered shoulder) with a static load of 90 N during 1 min. Evaluation of the marginal fit of the specimens was made using a digital micrometer. The crowns were embedded in acrylic resin and longitudinally sectioned to verify the internal discrepancy that occurred in lateral and occlusal interfaces with a digital micrometer. The data were submitted to ANOVA and Tukey's test with a significance level of 5%. The best marginal and inner fits were obtained with the gas-oxygen torch source. The 45-degree chamfered shoulder showed the best marginal and inner fit, and better internal relief was obtained in the crowns abraded with 50 microm Al2O3 particles

An Alternative Method for Thermal Cycling Test: Effect on the Marginal Microleakage and Bond Strength of Dental Polymer Bonded to Dentin

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)This study evaluated an alternative method for thermal cycling test on the microleakage and bond strength of the polymer-dentin bond. For the microleakage test the cavities were restored with a TEGDMA+UDMA+bis-EMA composite polymer light cured for 20 s. Samples were immersed in 2% methylene blue solution for 2 h and sectioned. Microleakage scores were submitted to Kruskal-Wallis test. For the shear bond strength test the adhesive was applied to dentin, photoactivated for 10 s and the composite polymer incrementally photoactivated. Samples were submitted to shear bond strength test in a machine with a cross-head speed of 0.5 mm/min and data were submitted to ANOVA and Tukey's test. Studied groups were: 1 - without thermocycling; 2 - thermocycled at 5 degrees C and 55 degrees C with intermediate bath at 37 degrees C; 3 - thermocycled at 5 degrees C and 37 degrees C; 4 - thermocycled at 37 degrees C and 55 degrees C; 5 - thermocycled at 5 degrees C and 55 degrees C (traditional test). Cold baths promoted greater microleakage when compared to control and hot bath, whereas control and hot bath were similar. Cold baths presented significant lower shear bond strength than those submitted to hot bath and control. It was concluded that the alternative method for thermal cycling test showed that cold temperatures increased the microleakage and decreased the bond strength of the polymeric adhesive.15610451049Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq

Development of dental resin luting agents based on Bis-EMA4: bond strength evaluation

The aim of this study was to investigate the influence of incorporating Bis-EMA4 monomer into experimental Bis-GMA/TEGDMA-based resin luting agents on the bond strength to dentin. Seven mixtures were prepared with the following ratios (wt%) of Bis-GMA/TEGDMA/Bis-EMA4: 50/50/0, 50/30/20, 50/10/40, 50/0/50, 30/10/60, 10/10/80 and 0/0/100. Camphorquinone (0.4 wt%), N,N-dimethyl-p-toluidine (0.8 wt%) and hydroquinone (0.2 wt%) were dissolved in each mixture, which was loaded with silanated strontium glass fillers to a constant content of 60 wt%. Bond strength was evaluated by microshear testing (n = 10) on bovine dentin. Data were submitted to Analysis of Variance (p < 0.05). Modes of failure were classified under magnification (200x). Bond strength means (MPa), respective to each agent, were: 19.4, 19.8, 20.0, 19.1, 16.8, 18.7 and 17.8. No significant differences were detected among groups. Mixed failures were generally predominant for all materials. In conclusion, the addition of Bis-EMA4 presented no significant influence on the bond strength of the experimental resin luting agents to dentin.22889