Influence of microwave sterilization on the cutting capacity of carbide burs

OBJECTIVE: This study compared the cutting capacity of carbide burs sterilized with microwaves and traditional sterilization methods. MATERIAL AND METHODS: Sixty burs were divided into 5 groups according to the sterilization methods: dry heat (G1), autoclave (G2), microwave irradiation (G3), glutaraldehyde (G4) or control - no sterilization (G5). The burs were used to cut glass plates in a cutting machine set for twelve 2.5-min periods and, after each period, they were sterilized (except G5) following the protocol established for each group. The cutting capacity of the burs was determined by a weight-loss method. Data were analyzed statistically by Kruskal-Wallis and Dunn's test. RESULTS: The means of the cutting amount performed by each group after the 12 periods were G1 = 0.2167 ± 0.0627 g; G2 = 0.2077 ± 0.0231 g; G3 = 0.1980 ± 0.0326 g; G4 = 0.1203 ± 0.0459 g; G5 = 0.2642 ± 0.0359 g. There were statistically significant differences among the groups (

Diametral tensile strength and film thickness of an experimental dental luting agent derived from castor oil

The need to develop new dental luting agents in order to improve the success of treatments has greatly motivated research. Objective: The aim of this study was to evaluate the diametral tensile strength (DTS) and film thickness (FT) of an experimental dental luting agent derived from castor oil (COP) with or without addition of different quantities of filler (calcium carbonate - CaCO3). Material and Methods: Eighty specimens were manufactured (DTS N=40; FT N=40) and divided into 4 groups: Pure COP; COP 10%; COP 50% and zinc phosphate (control). The cements were mixed according to the manufacturers' recommendations and submitted to the tests. The DTS test was performed in the MTS 810 testing machine (10 KN, 0.5 mm/min). For FT test, the cements were sandwiched between two glass plates (2 cm(2)) and a load of 15 kg was applied vertically on the top of the specimen for 10 min. The data were analyzed by means of one-way ANOVA and Tukey's test (alpha=0.05). Results: The values of DTS (MPa) were: Pure COP- 10.94 +/- 1.30; COP 10%- 30.06 +/- 0.64; COP 50%- 29.87 +/- 0.27; zinc phosphate- 4.88 +/- 0.96. The values of FT (pm) were: Pure COP- 31.09 +/- 3.16; COP 10%- 17.05 +/- 4.83; COP 50%- 13.03 +/- 4.83; Zinc Phosphate- 20.00 +/- 0.12. One-way ANOVA showed statistically significant differences among the groups (DTS - p=1.01E-40; FT - p=2.4E-10). Conclusion: The experimental dental luting agent with 50% of filler showed the best diametral tensile strength and film thickness.FAPESP [06/02821-8, 06/00082-3, 07/02441-3]FAPES

Topografia superficial e aderência de Streptococcus mutans no titânio após imersão e escovação com dentifrícios fluoretado e não-fluoretado simulando 10 anos de uso

Este estudo teve por objetivo avaliar a topografia e a aderência de Streptococcus mutans na superfície do titânio após procedimentos que simularam 10 anos de uso de dentifrícios fluoretado e não-fluoretado. Corpos-de-prova na forma de discos (6 mm Ø X 4 mm) de Ti-6Al-4V (Grupo L, N = 36) e de titânio comercialmente puro (Ti cp, Grupo T, N = 36) foram polidos metalograficamente e subdivididos em seis subgrupos (n=6) de acordo com a imersão (I) ou escovação (E) em água destilada (A), água destilada + dentifrício não-fluoretado (D) ou água destilada + dentifrício fluoretado (1500 ppm, pH 6,3) (DF). Os discos dos subgrupos IA, ID e IDF permaneceram submersos em suas respectivas soluções durante 244 h ( 10 anos). A escovação dos discos dos subgrupos EA, ED e EDF foi realizada em uma máquina de escovação linear com escovas macias (244 h; 60 ciclos/min). A topografia superficial dos discos foi avaliada antes (pré-tratamento) e após (pós-tratamento) a imersão ou a escovação. Para tanto, os discos foram analisados em microscópio de força atômica (MFA), no qual foram obtidas imagens tri-dimensionais (3D) e valores de rugosidade média (Ra). Após os tratamentos, discos dos subgrupos IDF e EDF foram analisados em microscopia dispersiva de raios-X (EDX) para a identificação dos elementos químicos. No teste de aderência, os discos foram contaminados com cepa padrão de Streptococcus mutans (NTCC 1023) para determinação do número de unidades formadoras de colônia (UFC/mL) das bactérias aderidas. Para averiguação do padrão de aderência dos micro-organismos, os discos foram analisados em microscópio eletrônico de varredura (MEV). As comparações entre os subgrupos foram realizadas por meio da análise de variância (one way ANOVA) e teste de Tukey HSD (α=0,05). Os valores de Ra...Titanium exposure to fluorides could degrade the metal surface, contributing to an increased roughness and providing additional sites to micro-organisms adhesion. The aim of this study was to contrasting titanium surface topography after procedures that simulated 10 years of brushing using toothpastes with or without fluoride. Ti-6Al-4V (Group L – N=36) and commercially pure titanium (cp Ti – Group T; N=36) disks (6mm Ø X 4mm) were mirror-polished and treated according to 6 subgroups (n=6) as a function of immersion (I) or brushing (B) using distilled water (W), distilled water + fluoride-free toothpaste (T) and distilled water + fluoride toothpaste (1,500 ppm; pH = 6.3) (FT). Specimens submitted to immersion were submerged in the vehicles without brushing for 244 h ( 10 years). For brushed specimens, procedures were carried out in a linear brushing machine with a soft-bristled toothbrush (244 h; 60 cycles/min). Surface topography was evaluated at baseline (pre-treatment) and post-treatment, using atomic force microscope in order to obtain three-dimensional (3D) images and mean roughness (Ra). IFT and BFT samples were analyzed under scanning electron microscope with dispersive spectrometer (EDX). For the adhesion test, the disks were contaminated with standard strain of S. mutans (NTCC 1023) and the adhesion was analyzed by the colony-forming unit counts (CFU/mL) of the adhered viable cell and by scanning electron microscopy (SEM) images. The subgroups were compared with one-way ANOVA and Tukey post-test (α=.05). Pre and post-treatment values of Ra were compared using the paired Student T test (α=.05). At baseline, there was no significant difference among the Ra values of L subgroups (p = .40), or among T subgroups (p = .99). No significant changes were seen after immersions... (Complete abstract click electronic access below)Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES

Avaliação da eficiência de corte de fresas Carbide em função dos métodos de esterilização físicos e químico. Análise gravimétrica

Este estudo avaliou o efeito de métodos de esterilização físicos e químico sobre a eficiência de corte de fresas carbide. Sessenta fresas da marca S.S. White foram utilizadas para o desgaste de vidro (30 mm X 30 mm X 10 mm) e divididas em cinco grupos experimentais em função do tratamento realizado: E1 - esterilização em autoclave, E2 - esterilização em estufa, E3 - esterilização em forno de microondas, E4 - esterilização em substância química e E0 - ausência de esterilização (controle). Com o auxílio de um aparelho padronizador de desgaste, as fresas foram utilizadas para o desgaste do vidro em um total de 30 minutos divididos em doze períodos de 2,5 minutos. Após cada 2,5 minutos de uso, as fresas foram limpas com escova de nylon sob água corrente e secas com jatos de ar e, em seguida, submetidas as seus respectivos tratamentos. A eficiência de corte das fresas foi determinada pela perda de massa do vidro, que teve sua massa aferida antes e após cada período de desgaste. A soma ( ? ) da quantidade de desgaste realizado por cada fresa após os 12 ciclos de uso foi calculada e utilizada para se determinar a eficiência de corte após 30 minutos de uso. Os valores da ? foram submetidos à análise estatística pelos testes de Kruskal-Wallis e de Dunn. Diferenças estatisticamente significantes entre os grupos experimentais foram verificadas (p<0,05). De acordo com os resultados, entre os métodos de esterilização avaliados, o uso o calor seco foi responsável pelo melhor desempenho das fresas, ao contrário da utilização de glutaraldeído, que foi considerado o pior método de esterilização.The aim of this study was to evaluate the influence of physical and chemical sterilization methods on the cutting effectiveness of carbide burs. Sixty S.S. White burs were used to cut glass plates (30 mm X 30 mm X 10 mm) and subjected to the following procedures: S1 - sterilization by autoclave; S2 - sterilization by dry heat; S3 - sterilization by microwave irradiation; S4 - sterilization by chemical substance and S0 - no sterilization (control group). The burs were used to cut glass plates in a cutting machine for twelve 2.5-minute periods. After each period, the burs were cleaned with a nylon brush under running water, dried with air spray (40 seconds), and then subjected to their procedures respectively. The cutting effectiveness was calculated by the weight loss of the glass which was weighed before and after each 2.5-minute period. The sum ( ? ) of the cutting amount performed by each bur after twelve cycles of use were calculated and used to determine the cutting effectiveness after 30 minutes of use. The ? values were statistically analyzed by Kruskal-Wallisþs and Dunnþs tests. Statistical differences among the experimental groups were observed (p <.05). According to the results, among the sterilization methods, the use of dry heat was responsible for the best carbide burs performance and, the use of glutaraldehyde was responsible for the worst burs performance.Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES

A castor oil-containing dental luting agent: effects of cyclic loading and storage time on flexural strength

Favorable results in the use of castor oil polyurethane (COP) as pulp capping, membrane material, sealer, mouthwash and in bone repair, associated with the fact that Ricinus communis is not derived from petroleum and it is abundant in Brazil, encourage researches in the development of luting agents. Objectives This study compared the flexural strength (FS) of a castor oil-containing dental luting agent with a weight percentage of 10% (wt%) of calcium carbonate (COP10) with RelyX ARC (RX) after mechanical cycling (MC) and distilled water storage. Material and Methods Sixty-four specimens (25x2x2 mm) were fabricated and divided into two groups, COP10 and RX (control). Each group was divided into 4 subgroups (n=8) according to the storage time, 24 hours (24 h) or 60 days (60 d), and the performance (MC+FS) or not (only FS) of the mechanical cycling test. The FS (10 kN; 0.5 mm/min) and MC tests (10,000 cycles, 5 Hz, 0.5 mm/min) were carried out using an MTS-810 machine. The data were analyzed using ANOVA (α=0.05). Results The obtained FS (MPa) values were: COP10 24h- 19.04±2.41; COP10 60d- 17.92±3.54; RX 24h- 75.19±3.43; RX 60d- 88.77±6.89. All the RX specimens submitted to MC fractured, while the values for COP10 after MC were as follows: COP10 24h- 17.90±1.87 and COP10 60d- 18.60±1.60. Conclusions A castor oil-containing dental luting agent with a weight percentage of 10% (wt%) of calcium carbonate is resistant to mechanical cycling without decreases in flexural strength. However, mean COP10 showed only about 25% of the RelyX ARC mean flexural strength

THE INFLUENCE of SHORT-HEATING-CYCLE INVESTMENTS on THE QUALITY of COMMERCIALLY PURE TITANIUM CASTINGS

Statement of problem. A new short-cycle, spinel-based investment was developed to minimize the long heating cycle generally required for conventional investments for titanium castings, but the quality of castings made using this material has yet to be evaluated.Purpose. The purpose of this study was to compare the Vickers hardness, castability, surface roughness, in vitro marginal misfit, and internal porosity of castings made using silica phosphate-based and spinel-based investments.Material and methods. The specimens were commercially pure titanium cast using silica phosphate-based investment, Rematitan Plus (RP), and spinel-based investments, Rematitan Ultra (RU) or short-heat-cycle Trinell (TR). Disc-shaped patterns (6 x 3 mm) were cast, and Vickers hardness was measured at the surface, and 50, 100, 150, and 200 pm beneath the surface (n=10). Microstructure was analyzed by optical microscopy (x100). Mesh patterns (14 x 14 x 0.5 mm) were used for castability testing (n=10). Surface roughness (Ra) was measured on disc-shaped patterns (13 x 3 mm) with a profilometer (n=8). Wax copings were cast, screwed to implant abutments, and the marginal misfit was measured using image analysis software (n=10). Internal porosity of the copings was evaluated by density comparisons (n=10). Hardness data were analyzed by 2-way ANOVA and the Tukey HSD test. Castability, surface roughness, and marginal misfit were analyzed by 1-way ANOVA and the Tukey HSD test, and internal porosity by Kruskal-Wallis and Student-Newman-Keuls tests (alpha=.05).Results. RP had the highest hardness values at the surface and 50 pm beneath, but the hardness values of TR, RU, and RP were statistically equivalent at 100, 150, and 200 mu m. Significant differences were seen when comparing RU and TR with RP for castability (P<.001), surface roughness (P<.001), and marginal misfit (P<.001). No significant differences were seen for internal porosity.Conclusions. The quality of castings made from the new investment, TR, was similar to the quality of those made using the conventional spinel-based investment, RU, and superior to those made using RP. (J Prosthet Dent 2010; 104:265-272)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP