Artificial methods of dentine caries induction: A hardness and morphological comparative study

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

The Efficacy of Laser Fluorescence to Detect in Vitro Demineralization and Remineralization of Smooth Enamel Surfaces

Objective: The purpose of this study was to evaluate the efficacy of the laser fluorescence (LF) device in detecting in vitro demineralization and remineralization of smooth surface caries-like lesions. Background Data: The early detection of smooth surface caries-like lesions is important to provide proper management of carious lesions, and allows monitoring of them over time. Also, some authors suggest that LF could be useful in monitoring the caries pathological process. Materials and Methods: Seventy-eight blocks of bovine teeth were obtained, and then submitted to artificial caries lesion induction and to a pH-cycling process. Superficial microhardness (SMH) and laser fluorescence analysis were performed at baseline, after induction of caries-like lesions, and after the pH-cycling regimen to promote remineralization. Results: Friedman's and multiple comparison tests were performed for all variables. SMH analysis showed significant differences (p < 0.05) between baseline (286.77 +/- 1.49 Vickers hardness number [VHN] units), before (38.48 +/- 0.85 VHN), and after remineralization (131.93 +/- 2.63 VHN). Baseline values for LF were extremely low (2.71 +/- 0.05), and a statistically significant difference was observed only after remineralization (3.61 +/- 0.08), as demonstrated by the increase in LF values. Conclusion: The LF device did not show efficacy for monitoring in vitro demineralization and remineralization of smooth enamel surfaces.

Mechanical, physical, and chemical characterization of Ti-35Nb-5Zr and Ti-35Nb-10Zr casting alloys

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

The effect of disinfectant solutions on the hardness of acrylic resin denture teeth

This investigation studied the effects of disinfectant solutions on the hardness of acrylic resin denture teeth. The occlusal surfaces of 64 resin denture teeth were ground flat with abrasives up to 400-grit silicon carbide paper. Measurements were made after polishing and after the specimens were stored in water at 37 degreesC for 48 h. The specimens were then divided into four groups and immersed in chemical disinfectants (4% chlorhexidine; 1% sodium hypochlorite and sodium perborate) for 10 min. The disinfection methods were performed twice to simulate clinical conditions and hardness measurements were made. Specimens tested as controls were immersed in water during the same disinfection time. Eight specimens were produced for each group. After desinfection procedures, testing of hardness was also performed after the samples were stored at 37 degreesC for 7, 30, 60, 90 and 120 days. Data were analysed using two-way analysis of variance (anova) and Tukey's test at 95% confidence level. According to the results, no significant differences were found between materials and immersion solutions (P > 0.05). However, a continuous decrease in hardness was noticed after ageing (P < 0.05). It was conclude that the surfaces of both acrylic resin denture teeth softened upon immersion in water regardless the disinfecting solution.

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

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

The effect of long-term disinfection procedures on hardness property of resin denture teeth

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

HARDNESS and SURFACE ROUGHNESS of RELINE and DENTURE BASE ACRYLIC RESINS AFTER REPEATED DISINFECTION PROCEDURES

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Flexural strength and hardness of reline and denture base acrylic resins after different exposure times of microwave disinfection

Objectives: To evaluate the effect of microwave disinfection on the flexural strength and Vickers hardness of 4 autopolymerized resins (Kooliner [K], Tokuso Rebase Fast [T], Ufi Gel Hard [U], and New Truliner [N]) and 1 denture base resin (Lucitone 550 [L]). Method and Materials: For each material, 48 specimens (64 x 10 x 3.3 mm) were made and divided into 6 equal groups (n = 8). In the control group, specimens were untreated. Before testing, specimens were immersed in 200 mL of distilled water and submitted to disinfection for 1 of the following irradiation times: 1, 2, 3, 4, or 5 minutes. The irradiation procedure was performed twice. The flexural strength was determined using a testing machine MTS-810 and measurements of Vickers hardness were made on Micromet 2100. The values were submitted to ANOVA and Tukey's test (P = .05). Results: The K material showed a significant increase (P = .0010) in flexural strength following 5 minutes of disinfection compared to control specimens. The flexural strength mean values of materials T, U, and N were not significantly affected (P > .05) by disinfection. Compared to the control group, the K material showed a significant increase in hardness (P < .001) following disinfection for 3, 4, and 5 minutes. For material U, disinfection for 4 and 5 minutes produced specimens with significantly increased hardness values (P < .001) compared to the control group. For material N, disinfection for 5 minutes resulted in significantly higher hardness values (P < .001) than the control group. Conclusion: Regardless of the irradiation time, the flexural strength and hardness of the materials evaluated were not detrimentally affected by microwave disinfection. (Quintessence Int 2008;39:833-840)

Influence of light guide tip used in the photo-activation on degree of conversion and hardness of one nanofilled dental composite

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Effect of compression load and temperature on thermomechanical tests for gutta-percha and Resilon (R)

Tanomaru-Filho M, Silveira GF, Reis JMSN, Bonetti-Filho I, Guerreiro-Tanomaru JM. Effect of compression load and temperature on thermomechanical tests for gutta-percha and Resilon (R). International Endodontic Journal, 44, 1019-1023, 2011.Aim To analyse a method used to evaluate the thermomechanical properties of gutta-percha and Resilon at different temperatures and compression loads.Methodology Two hundred and seventy specimens measuring 10 mm in diameter and 1.5 mm in height were made from the following materials: conventional gutta-percha (GCO). thermoplastic gutta-percha (GTP) and Resilon (R) cones (RE). After 24 h, the specimens were placed in water at 50 degrees C. 60 degrees C or 70 degrees C for 60 s. After that, specimens were placed between two glass slabs, and loads weighing 1.0, 3.0 or 5.0 kg were applied. Images of the specimens were digitized before and after the test and analysed using imaging software to determine their initial and final areas. The thermomechanical property of each material was determined by the difference between the initial and final areas of the specimens. Data were subjected to ANOVA and SNK tests at 5% significance. To verify a possible correlation between the results of the materials, linear regression coefficients (r) were calculated.Results Data showed higher flow area values for RE under all compression loads at 70 degrees C and under the 5.0 kg load at 60 degrees C (P < 0.05). Regarding gutta-percha, GTP showed higher flow under loads weighing 3.0 and 5.0 kg. at 60 and 70 degrees C (P < 0.05). GCO presented higher flow at 70 degrees C with a load of 5.0 kg. Regression analyses showed a poor linear correlation amongst the results of the materials under the different experimental conditions.Conclusion Gutta-percha and Resilon (R) cones require different compression loads and temperatures for evaluation of their thermomechanical properties. For all materials, the greatest flow occurred at 70 degrees C under a load of 5.0 kg: therefore. these parameters may be adopted when evaluating endodontic tilling materials.

Flexibility and Torsional Strength of ProTaper and ProTaper Universal Rotary Instruments Assessed by Mechanical Tests

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)