Geometric factors affecting composite shrinkage stress in flat surfaces

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IR, 1H-NMR and ESI-MS spectroscopic data and elementary analyses. Candida albicans(33), C. parapsilosis(2), C. famata(2), C. glabrata(2), C. lipolytica(2) and Rhodotorula mucillaginosa(2) strains were used for determining the in vitro anti-Candida activity and anti-enzymatic activity of ten new 3,5-diaryl-4,5dihydro-1H-pyrazole-1-carboximidamides. These strains of Candida spp. were collected from denture user patients with Chronic Atrophic Candidiasis (CAC) enrolled in the Center for Diagnosis of Diseases of the Mouth (CDDB), School of Dentistry, Federal University of Pelotas (FOP-UFPel) (Lund et al., 2010). The minimum inhibitory concentration (MIC) and minimum fungicidal concentration (MFC) of the new 3,5-diaryl-4,5-dihydro-1H-pyrazole-1-carboximidamides was determined by using broth microdilution techniques as described by the Clinical and Laboratory Standards Institute for yeasts (M27-A2). Tests were performed using media containing bovine serum albumin or egg-yolk to evaluate the production of proteinases and phospholipase, respectively. To evaluate the cytotoxicity of the extracts, the survival of 3T3/NIH mouse fibroblasts was measured photometrically using an 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay after a 24 h-exposure. Data were analyzed by ANOVA and Tukey’s tests. Results: The results were: MIC and MFC > 15.6 mg/ml (C. albicans), MIC and MFC = 62.5 g/ml (R. mucillaginosa) MICs and MFCs > 62.5 mg/ml (C. parapsilosis) and CIM CFM = 62.5 mg/ml (C. famata), MIC and MFC = 125 mg/ml (C. glabrata) and MIC = 15.6 g/ml (C. lipolytica). The values of proteinase and phospholipase (Pz) of C. albicans before and after exposure to the compounds were: 0.6 (±0.024) and 0.2 (±0.022) and 0.9 (±0.074) and 0.3 (±0.04). These results showed that proteinase were not significant (p = 0.69) compared to phospholipase (p = 0.01), and 15.6 mg/ml was the most effective concentration. The cytotoxicity values were similar among the tests and (p = 0.32). Conclusions: It was concluded that derivatives pyrazoles are promising antifungal agents such as fungicides or protease inhibitors for C. albicans and the low cytotoxicity. doi:10.1016/j.dental.2011.08.496 94 Subcritical crack growth and longevity of composites with different filler sizes

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ica. Granulometric analyses of the glass powders were done by a laser diffraction particle size analyzer (Sald-7001, Shimadzu, USA). n and
f0 were determined by a dynamic fatigue test (10−2 and 102 MPa/s) using a biaxial flexural device (12 mm × 1.2 mm; n = 10). 20 specimens of each composite were tested at 100 MPa/s to determine Weibull parameters. SPT diagrams were constructed using the dynamic fatigue and Weibull data. For all tests, the specimens were stored in distilled water at 37 ◦ C for 24 h. The fracture surfaces of the specimens that was subjected to the 10−2 and 10−1 MPa/s rates of the dynamic fatigue test (n = 3) were analyzed in a scanning electron microscope at a maximum magnification of 5000× (Stereoscan 400, UK). Results: Based on granulometric analyses’ data, composites were divided into two groups: with wide and narrow granulometric distribution. C1.9 and C0.5 showed the widest distributions: 9.2 and 6.0 ␮m, respectively; and, C1.2 and C0.9 showed the narrowest distributions: 4.9 and 3.3 ␮m, respectively. C0.5 (31.2 ± 6.2a ) and C1.9 (34.7 ± 7.4a ) presented higher n values than C0.9 (20.3 ± 3.0b ) and C1.2 (17.3 ± 1.8b ). C1.2 (166.42 ± 0.01a ) showed the highest
f0 value (in MPa), followed by C1.9 (159.82 ± 0.02b ), C0.9 (159.59 ± 0.02c ) and C0.5 (158.40 ± 0.02d ). There were no statistical differences among the m (6.6–10.6) and
0 (170.6–176.4 MPa) values of the composites. The reductions in fracture stress at 5% failure probability for a lifetime of 10 years estimated by the SPT diagrams were approximately 22% for C0.5 and C1.9 and 36% for C0.9 and C1.2. Near-surface and surface flaws were the main fracture origins. The crack propagated by the polymeric matrix around the fillers (crack deflection) and all the fracture surfaces showed brittle fracture features. Conclusions: Composites with broader granulometric size distribution, regardless of d50 , showed higher resistance to subcritical crack growth. There was no influence of the composites’ filler sizes in the others parameters and properties evaluated (m and
0 ). doi:10.1016/j.dental.2011.08.497 95 Geometric factors affecting composite shrinkage stress in flat surfaces L.V.S. Pabis 1,∗ , T.A. Xavier 1 , E.F. Rosa 1 , F.P. Rodrigues 2 , J.B.C. Meira 1 , R.G. Lima 1 , R.Y. Ballester 1

B.P. Ornaghi 1,∗ , M.M. Meier 2 , U. Lohbauer 3 , R.R. Braga 4

1

1

2

Objectives: To verify the influence of different filler sizes on the subcritical crack growth (n and
f0 ) and Weibull (m and
0 ) parameters and longevity estimated by the strength-probability-time (SPT) diagram of experimental resin composites. Materials and methods: Four composites were prepared, each one containing 78 wt% (59 vol%) of inorganic content, in which 67 wt% was glass powder with different filler sizes (d50 = 0.5; 0.9; 1.2 and 1.9 ␮m) and 11 wt% was pyrogenic sil-

Objectives: The study proposes a method to assess stress development in the adhesive layer of composite cylinders that shrink when bonded to a single flat surface, as when micro-specimens are obtained for microtensile bond strength testing. Correlation between geometrical parameters of the bonded composite and the stress value was also investigated. The hypothesis was that the magnitude of the stress value was not correlated with the C-Factor. Materials and methods: The deflection of a glass coverslip caused by the shrinkage of a bonded composite cylinder (diameter: d = 8 mm, 4 mm or 2 mm, height: h = 4 mm, 2 mm, 1 mm or 0.5 mm) was measured. The same setup was simulated by finite element analysis (3D-FEA). Stresses generated

Universidade Positivo, Brazil 2 Universidade do Estado de Santa Catarina and FGM Produtos Odontológicos, Brazil 3 University of Erlangen-Nuremberg, Germany 4 Universidade de São Paulo, Brazil

University of São Paulo, Brazil Bandeirante University of São Paulo-UNIBAN, Brazil

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in the adhesive layer were plotted versus three geometric variables of the composite cylinder (C-Factor, diameter/height ratio and volume) to verify the existence of correlations between them and stresses. Results: The FEA models were validated. A relationship between the stress values and the coverslip deflection when the composites were grouped by height was found. The stress values of the whole set of data showed a logarithmic correlation with the bonded composite volume (p < 0.001, Pearson’s test), but was not correlated with C-Factor, neither the other variables. The trend line indicates that small changes in volume within the range from 0 to 50 mm3 lead to a large stress variation, which may contribute to the variability in strength results. Conclusions: Within the limitations of this study, this can be concluded that: (1) The developed method to evaluate the stress at the interfaces in composites that shrink when bonded to a single flat surface by combining an experimental test and an analysis by finite elements seems to be effective. (2) The stresses at the adhesive of composites bonded to single flat surfaces are not uniform, but are distributed in concentric rings. (3) The deflection of the coverslip is correlated with the stress values, but only for composite blocks grouped by height. (4) The hypothesis was confirmed: there is no overall correlation between the magnitude of stress values and the C-Factor. (5) The stress values in the adhesive layer correlates logarithmically with the volume of the bonded composite: the volume should be considered as the main factor for standardizing the stress generated by the shrinkage of composite blocks bonded to a single flat surface, especially from 0 to 50 mm3 . doi:10.1016/j.dental.2011.08.498 96 Evaluation of the surface degradation of resin materials in diet simulating solutions G.C. Padovani 1,∗ , G.S.A. Araujo 1 , A.A. Leme 1 , R.C.B. Alonso 2 , G.M.B. Ambrosano 1 , M.A.C. Sinhoreti 1 , R.M. Puppin-Rontani 1 1 2

State University of Campinas, Brazil Bandeirantes University, Brazil

Objectives: The aim of this study was to evaluate the microhardness and surface morphology of restorative resins (Filtek P901 , Filtek Z3502 , Grandio3 , Estelite4 ) before and after erosive and abrasive challenges. Materials and methods: Twenty specimens (0.4 mm diameter and 0.2 mm thick) of each restorative material were prepared, and the initial evaluation of Knoop microhardness was carried out. Five specimens of each material were

1 2 3 4

Filtek P90 – 3M ESPE, Dental Products, USA. Filtek Z350 – 3M ESPE, Dental Products, USA. VOCO, Germany. Estelite – Tokuyama Dental Corp, Japan.

immersed in low pH beverages (wine, orange juice, energy drink, saliva) for 15 days at 37 ◦ C; saliva was used as control. Subsequently to the immersion, specimens were submitted to 30,000 brushing cycles. The hardness and surface morphology were assessed by scanning electron microscopy before and after the immersion in solutions and brushing. The results were analyzed by mixed models for repeated measures and Tukey–Kramer p < 0.05. Results: Grandio showed significantly higher hardness compared to other resins in the 4 solutions [wine = 156.74 (27.31), orange juice = 203.20 (16.20); energy drink = 134.28 (28.95); saliva = 143.27 (16.20)]. After the erosive effect, the hardness decreased for all composites (p = 0.0031). There was no significant statistical difference between the solutions. Besides, the presence of erosive areas in the experimental groups that differ morphologically from the control group was verified. Conclusions: The conclusion is that the immersion in acidic beverages followed by brushing caused degradation of the restorative materials evaluated. doi:10.1016/j.dental.2011.08.499 97 The effect of bioactive glass nanoparticles on the behavior of human periodontal ligament cells S.M. Carvalho, A.A.R. Oliveira, L.M. Andrade, M.F. Leite, M.M. Pereira ∗ Federal University of Minas Gerais, Brazil Objectives: The biologic goal of periodontal regeneration is the restoration of the periodontium to its original form and function. Bioactive glass is a tissue repairing material used for regeneration in many areas of dentistry. The purpose of this work was to evaluate the effect of bioactive glass nanoparticles (BGnp) on the behavior of HPDL cells isolated from human periodontal tissue. Materials and methods: HPDL cells from third molar teeth with orthodontic indication for extraction were isolated. BGnp were synthesized by modified Stöber method. Tests were performed according to ISO 10993. BGnp were mixed in the medium, with weight-to-solution volume ratio of 0.1 mg/mL. Control cultures and seeded materials were characterized at 72 h for cell viability (Resazurine assay), at 72 h for cell proliferation (BrdU assay), at 72 h for cell cycle (flow cytometry) and alkaline phosphatase (ALP) activity after one-week culture. Results: HPDL cells were incubated with bioactive glass nanoparticles for 72 h and cell viability, ALP activity and cell proliferation rate were evaluated in comparison to control conditions. We observed an increase of 20 ± 1.63 in HPDL cells viability when cells were exposed to bioactive glass nanoparticles, compared with control group by resazurin assay (p < 0.05, n = 5). We observed an increase of 33 ± 3.0 in cells proliferation when cells were exposed to bioactive glass nanoparticles, compared with control group by BrdU assay (p < 0.05, n = 5). It was observed an increase in ALP activity of 177 ± 2.9% in HPDL cells compared with control group (p < 0.05, n = 3). Conclusions: These results indicate that BGnp induces HPDL cells to proliferate, indicating that it is a potential mate-