The Influence of Small Quantities of Oxygen in the Structure, Microstructure, Hardness, Elasticity Modulus and Cytocompatibility of Ti-Zr Alloys for Dental Applications

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Effect of resin composites with sodium trimetaphosphate with or without fluoride on hardness, ion release and enamel demineralization

Purpose: To evaluate the effect of the addition of sodium trimetaphosphate (TMP) with or without fluoride on enamel demineralization, and the hardness and release of fluoride and TMP of resin composites. Methods: Bovine enamel slabs (4x3x3 mm) were prepared and selected based on initial surface hardness (n= 96). Eight experimental resin composites were formulated, according to the combination of TMP and sodium fluoride (NaF): TMP/NaF-free (control), 1.6% sodium fluoride (NaF), and 1.5%, 14.1% and 36.8% TMP with and without 1.6% NaF. Resin composite specimens (n= 24) were attached to the enamel slabs with wax and the sets were subjected to pH cycling. Next, surface and cross-sectional hardness and fluoride content of enamel as well as fluoride and TNT release and hardness of the materials were evaluated. Data were statistically analyzed using ANOVA (P< 0.05). Results: The presence of fluoride in enamel was similar in fluoridated resin composites (P> 0.05), but higher than in the other materials (P< 0.05). The combination of 14.1% TMP and fluoride resulted in less demineralization, especially on lesion surface (P< 0.05). The presence of TMP increased fluoride release from the materials and reduced their hardness.

Effect of Beverages and Mouthwashes on the Hardness of Polymers Used in Intraoral Prostheses

PurposeThe mechanical properties of acrylic resins used in intraoral prostheses may be altered by frequent exposure to liquids such as beverages and mouthwashes. This study aimed to evaluate the effect of thermocycling and liquid immersion on the hardness of four brands of acrylic resins commonly used in removable prostheses (Onda Cryl, QC-20, Classico, Lucitone).Materials and MethodsFor each brand of resin, seven specimens were immersed in each of six solutions (coffee, cola, red wine, Plax-Colgate, Listerine [LI], Oral B), and seven more were placed in artificial saliva (control). The hardness was tested using a microhardness tester before and after 5000 thermocycles and after 1, 3, 24, 48, and 96 hours of immersion. The results were analyzed using three-way repeated-measures ANOVA and Tukey's test (p < 0.05).ResultsThe hardness of the resins decreased following thermocycling and immersion in the solutions. Specimens immersed in cola and wine exhibited significant decreases in hardness after immersion for 96 hours, although the greatest significant decrease in hardness occurred in specimens immersed in LI. However, according to American Dental Association specification 12, the Knoop hardness of acrylic resins for intraoral prostheses should not be below 15. Thus, the median values of superficial hardness observed in most of the acrylic resins in this study are considered clinically acceptable.ConclusionsThe microhardness of polymers used for intraoral prostheses decreases following thermocycling. Among specimens immersed in beverages, those immersed in cola or wine experienced the greatest decrease in microhardness. Immersion of acrylic resins in LI significantly decreased the microhardness in relation to the initial value. Among the resins assessed, QC-20 exhibited the lowest initial hardness.

Influence of heat treatment and mechanical cycling on hardness and fracture analysis of Ti35Nb5Zr casting alloy

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

Effect of different light-curing techniques on hardness of a microhybrid dental composite resin

Coordenação de Aperfeicoamento de Pessoal de Nivel Superior (CAPES)

Long-term surface hardness and monomer conversion of a nonofilled and a microhybrid composite resin

Objective: This study aims to evaluate the degree of conversion (DC) and hydrolytic degradation through the Vickers hardness test (HV) of a nanofilled (Filtek™ Z-250, 3M) and a microhybrid (Filtek™Supreme-XT, 3M) composite resin. Materials and methods: Eight disk-shaped specimens (4 mm diameter × 2 mm thick, ISO 4049) of each material were prepared for each test. Composites were inserted into single increment in a metallic matrix and light-cured for 40 seconds. VH readings were performed for each specimen at predetermined intervals: immediately after polymerization (control), 1, 2, 3, 7, 14, 21, 30 and 180 days. After curing, initial hardness measurements were performed and the specimens were immersed in artificial saliva at 37°C. For DC (%), specimens were ground, pressed with KBr and analyzed by FT-IR spectrophotometer. Results: Student t-test showed that there was no difference between the resins for DC (p = 0.252). ANOVA analysis revealed that Z-250 VH means were all greater than S-XT, for both top and bottom surfaces, whatever the storage-period in artificial saliva (p < 0.001). After 180 days of storage, the hardness obtained for S-XT was similar with that at the baseline, for both top and bottom surfaces. While for Z-250 hardness was not significantly different from baseline only for top surface, but there was a significant decrease observed in hardness for bottom surface. Conclusion: The materials tested showed no evidence of hydrolytic degradation in a significant way, in a 6-month storagetime in artificial saliva. Nanofilled resin presents a monomer conversion comparable to the conventional microhybrid.

Influence of light source and immersion media in surface roughness and hardness of a nanofilled composite resin

The study evaluated the influence of light curing units and immersion media on superficial roughness and microhardness of the nanofilled composite resin Supreme XT (3M/ESPE). Light curing units used were: XL 3000 (3M/ESPE), Jet Lite 4000 Plus (JMorita) and Ultralume Led 5 (Ultradent) and immersion media were artificial saliva, Coke®, tea and coffee, totaling 12 experimental groups. Specimens (10mm x 2mm) were immersed in each respective solution for 5 seconds, three times a day, during 60 days and so, were submitted to measure of superficial roughness (Ra) and Vickers hardness. Data were subjected to two-way ANOVA test (p<0.05). Results showed that only the light source factor showed statistically difference for hardness. It was observed that the hardness of the composite resin Filtek Supreme XT (3M/ESPE) was influenced by the light source (p<0.01) independently of the immersion media (p= 0.35) and the Jet Lite 4000 Plus (JMorita) was the light curing unit that presented lower values. In relation to surface roughness, it was noted no-significant statistical difference for light source (p=0.84), when specimens were immersed in different beverages (p=0.35).

Effect of thermal and mechanical cycles on the hardness and roughness of artificial teeth

In this study the effects of thermal and mechanical cycles on the hardness and roughness of artificial teeth were evaluated. Materials and Methods:Specimens were prepared and stored in distilled water at 37ºC for 48 hours (n=10).The hardness and roughness readings were made in the following time intervals, according to each group:G1: after specimen storage in distilled water at 37°C for 48 hours; G2: after 600.000 constant mechanical cycles; G3: after 1.200.000 constant mechanical cycles; G4: after 2.500 thermalcycling baths, alternated between hot water (55°C) and cold water (5°C) and G5: after 5.000 thermalcycling baths, alternated between hot water (55°C) and cold water (5°C). After cycling and storage procedures, the specimens of each group were submittedto surface roughness and hardness readouts. Statistical evaluation was performed by three-way analysis of variance, complemented by the Tukey multiple comparisons of means test. The level of significance adopted was 5%. There was no significant difference between G1, G4 and G5 as regards mean roughness of different brands of artificial teeth. Groups G2 and G3 showed higher mean roughness values, and generally equivalent values in all time intervals, except for Trilux (G3> G2). Significant differences in hardness values were observed in different brands of artificial teeth, and differences in values after thermal and mechanical cycling. In conclusion, our findings suggest that thermal cyclingdid not change the roughness of the artificial teeth tested, but after the mechanical cycling the roughness values increased. Thermal and mechanical cycling influenced the hardness of the artificial teeth tested.

Surface roughness and hardness of yttria stabilized zirconia (Y-TZP) after 10 years of simulated brushing

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Chemical analysis and Vickers hardness of orthodontic mini-implants

Orthodontic mini-implants are used in clinical practice to provide efficient and aesthetically-pleasing anchorage. AIM: To evaluate the hardness Vickers hardness and chemical composition of mini-implant titanium alloys from five commercial brands. METHODS: Thirty self-drilling mini-implants, six each from the following commercial brands, were used: Neodent NEO, Morelli MOR, Sin SIN, Conexão CON, and Rocky Mountain RMO. The hardness and chemical composition of the titanium alloys were performed by the Vickers hardness test and energy dispersive X-ray spectroscopy, respectively. RESULTS: Vickers hardness was significantly higher in SIN implants than in NEO, MOR, and CON implants. Similarly, VH was significantly higher in RMO implants than in MOR and NEO ones. In addition, VH was higher in CON implants than in NEO ones. There were no significant differences in the proportions of titanium and aluminum in the mini-implant alloy of the five commercial brands. Conversely, the proportion of vanadium differed significantly between CON and MOR/NEO implants. CONCLUSIONS: Mini-implants of different brands presented distinct properties of hardness and composition of the alloy.

Effect of the addition of antimicrobial agents on shore a hardness and roughness of soft lining materials

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

Effects of short-term immersion and brushing with different denture cleansers on the roughness, hardness, and color of two types of acrylic resin

Purpose: To investigate the cumulative effects of brushing (B) or immersion (I), using different cleansing agents, on the surface roughness, hardness and color stability of a heat-polymerized denture resin, Lucitone 550 (L), and a hard chairside reline resin, Tokuyama Rebase Fast II (T). Methods: A total of 316 specimens (10 x 2 mm) were fabricated. The specimens (n= 9) were divided into brushing or immersion groups according to the following agents: dentifrice/distilled water (D), 1% sodium hypochlorite (Na0C1), Corega Tabs (Pb), 1% chlorhexidine gluconate (Chx), and 0.2% peracetic acid (Ac). Brushing and immersion were tested independently. Assays were performed after 1, 3, 21, 45 and 90 blushing cycles or immersion of 10 seconds each. Data were evaluated statistically by repeated measures ANOVA. Tukey's honestly significant difference (HSD) post-hoc test was used to determine differences between means (a= 0.05). Results: For L there was no statistically significant difference in roughness, except a significant decrease in roughness by brushing with D. T showed a significant effect on the roughness after 90 immersions with Ac. Hardness values decreased for L when specimens were immersed or brushed in Na0C1 and Pb. The hardness of T decreased with increases in the repetitions (immersion or brushing), regardless of the cleaning method. Values of color stability for L resin showed significant color change after brushing with and immersion in Ac and Pb. Brushing with D exhibited a higher incidence of color change. For T there were no significant differences between cleaning agents and repetitions in immersion. A color change was noted after three brushings with the Ac, Chx, and D. Brushing with dentifrice decreased roughness of L. Immersion in or brushing with Na0C1 and Pb decreased the hardness of L. For T, hardness decreased with increases in immersions or brushing. Color changes after the immersion in or brushing with cleaning agents were clinically acceptable according to National Bureau of Standards parameters for both resins.

Effect of ion irradiation on the structural properties and hardness of a-C:H:Si:O:F films

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

Analysis of residual stress and hardness in regions of pre-manufactured and manual bends in fixation plates for maxillary advancement

The aim of this study was to analyze, through Vickers hardness test and photoelasticity analysis, pre-bent areas, manually bent areas, and areas without bends of 10-mm advancement pre-bent titanium plates (Leibinger system). The work was divided into three groups: group I-region without bend, group II-region of 90° manual bend, and group III-region of 90° pre-fabricated bends. All the materials were evaluated through hardness analysis by the Vickers hardness test, stress analysis by residual images obtained in a polariscope, and photoelastic analysis by reflection during the manual bending. The data obtained from the hardness tests were statistically analyzed using ANOVA and Tukey's tests at a significance level of 5 %. The pre-bent plate (group III) showed hardness means statistically significantly higher (P < 0.05) than those of the other groups (I-region without bends, II-90° manually bent region). Through the study of photoelastic reflection, it was possible to identify that the stress gradually increased, reaching a pink color (1.81 δ / λ), as the bending was performed. A general analysis of the results showed that the bent plate region of pre-bent titanium presented the best results.

Effect of different solutions on knoop hardness of indirect composite

Introduction: Indirect dental composites may have adequate clinical performance. However, the literature is scarce regarding indirect composite resins and these solutions should be considered to maintain their properties. The aim of the study was to evaluate the influence of beverages, mouthwashes and bleaching agents on the hardness of indirect composite resins. Methods: Five different brands of indirect composite resins were evaluated: Adoro, Resilab, Cristobal, Sinfony and Epricord. Ten specimens of each brand were immersed in eleven different solutions: four mouthwashes (Listerine, Oral-B, Plax, Periogard), four beverages (coke soft drink, red wine, coffee, orange juice), three dental bleaching agents (16% peroxide of carbamide, 7.5% and 38% peroxide of hydrogen) and artificial saliva (control group). The Knoop hardness was measured before (baseline) and after 12, 24, 36 and 60 hours of immersion in mouthwashes; after 7, 14 and 21 days of immersion in beverages and after 7 and 14 days of immersion in dental bleaching agents. The results were analyzed using 3-way repeated measures ANOVA and Tukey’s test (p<0.05). Results: All resins presented significant decrease on hardness values after immersion process whereas this reduction was higher for Resilab and Sinfony. The latter exhibited the lowest initial values of hardness while Cristobol resin presented the highest hardness values. The mouthwashes promoted a significant decrease in the hardness of specimens.