Daniela Maffei Botega

Effects of Thermocycling on the Tensile Bond Strength of Three Permanent Soft Denture Liners

PURPOSE This study investigated the effect of in vitro accelerated aging reproduced with thermocycling on the bond strength of three commercially available permanent denture soft liners (PermaSoft, Dentuflex, Ufi-gel) with one heat-polymerized polymethyl methacrylate resin denture base (QC-20) by tensile test. MATERIAL AND METHODS Ten specimens were prepared for control and test groups of each material for a total of 60 specimens. All controls were stored in water (37 degrees C) for 24 hours before testing. All test groups received 3000 thermal cycles consisting of 1 minute at 5 degrees C and 1 minute at 65 degrees C. All specimens were submitted to a tensile test using a universal testing machine at a crosshead speed of 5 mm/min. Results were statistically analyzed (ANOVA, p < or = 0.05, Tukeys post-hoc test). RESULTS The mean bond strength of control specimens was (MPa): 0.32 (Ufi-gel), 0.49 (PermaSoft), and 1.19 (Dentuflex). There was no statistical difference (p > 0.05) between Ufi-gel and PermaSoft, but both were statistically different (p < 0.05) when compared to Dentuflex. After thermocycling, the mean bond strength was (MPa): 0.18 (Ufi-gel), 0.81 (PermaSoft), and 3.32 (Dentuflex). All materials were statistically different (p < 0.05). Ufi-gel had the lowest value and Dentuflex the highest in both control and test groups. Dentuflex presented only adhesive failure; in the remaining groups, there was no predominant failure mode, except Ufi-gel control with no adhesive failure. CONCLUSIONS Despite presenting greater bond strength, thermocycling had a deleterious effect in Dentuflex; Ufi-gel may be adequate for short-term use.

Artificial teeth: evaluation of wear resistance, microhardness and composition

Objective: To evaluate the Knoop hardness, composition, and wear resistance of acrylic-resin artificial teeth exposed to mechanical toothbrushing.Methods: Artificial teeth from three commercial brands - Biotone, Trilux, and Soluut PX - were used. From each brand, 10 teeth were selected for wear evaluation after mechanical brushing, 10 for microhardness testing, and 5 for composition analysis. Specimens underwent 55,000 brushing cycles, under a 200-g load and at a frequency of 250 cycles per minute, using a soft-bristled toothbrush (IndicatorPlus 30, Oral-B) soaked in a 1:1 toothpaste/water slurry (Oral B Pro Saude). Microhardness testing was performed using a 25-g load for 15 seconds in an HMV-2 hardness tester (Shimadzu). The composition of teeth from different brands was determined by scanning electron microscopy with energy-dispersive X-ray spectroscopy (SEM/EDS) (Jeol JSM 5800).Results: Wear results after mechanical brushing were compared by means of the paired t-test, whereas those obtained in microhardness testing were compared by ANOVA with Bonferroni correction. There was no statistically significant difference between brands in either trial.Conclusion: Composition analysis revealed that all of the artificial teeth analyzed contain carbon and oxygen. Trilux and Soluut PX brand teeth also contain silicon; however, the presence of filler particles did not result in increased resistance.

Resistência ao desgaste e rugosidade superficial de dentes artificiais submetidos ao ensaio de atrição

Este estudo avaliou a rugosidade superficial e a resistencia ao desgaste de dentes artificiais de resina acrilica submetidos ao ensaio de atricao. Foram selecionados 10 incisivos centrais superiores e 10 incisivos centrais inferiores de cada marca comercial: Biotone (Dentsply), Trilux (Vipi) e Soluut PX (Kota). As amostras foram submetidas a afericao da rugosidade superficial em rugosimetro (Mitutoyo SJ-201), com velocidade de 0,5 mm/s, por 30 segundos e comprimento de leitura de 0,25 mm; e a mensuracao da altura cervico-incisal utilizando paquimetro digital (MitutoyoDigimaticCaliper); assim como a afericao da massa de cada par de amostras (incisivo superior e inferior) em balanca de precisao (Shimadzu AUW220D), antes e apos o ensaio. Foi utilizada maquina de escovacao mecânica, simulando movimento de atricao entre a superficie vestibular do incisivo superior e a incisal do incisivo inferior. As amostras foram submetidas a 40.000 ciclos, imersas em agua destilada. Nao houve diferenca estatisticamente significante com relacao a rugosidade superficial antes e apos o ensaio de atricao. Todas as marcas comerciais estudadas apresentaram reducao significativa na altura cervico-incisal, mas nao apresentaram reducao de suas massas, exceto Soluut PX. Tambem constatou-se que nao houve diferenca nos valores de rugosidade entre as marcas comerciais.