Fracture resistance of bovine incisors restored with different glass fiber posts: Effect of the diameter of fiber post

Aim: Compare the effect of three post designs on the fracture resistance and failure modes of composite core-fiber post-crownless tooth sets. Materials and Methods: Ninety bovine incisors were selected and divided into nine groups of 10 specimens. The teeth were assigned to three groups based on the post design: Cylindrical, tapered, and double-tapered. Each group was subdivided into three subgroups in accordance with the diameter of the post: Small (No.1), medium (No.2), and large (No.3). The Panavia F system was used for post cementation. The specimens were mounted in acrylic resin blocks with a layer of silicone rubber covering the roots. A universal testing machine compressively loaded the specimens from the palatal side at a crosshead speed of 1 mm/min and at an angle of 135I to the long axis of the teeth, until failure occurred. The failure mode was determined by a stereomicroscope inspection of all the specimens. Data were analyzed by one-way ANOVA and the Tukey test (P < 0.05). Results: The fracture resistance was affected by the type of post (P < 0.0001). A narrower diameter for all of the post systems allowed for higher resistance. The main failure mode in the large cylindrical group was catastrophic fractures, while the main failures in the other eight groups were favorable. Conclusion: Narrower diameter posts showed higher fracture resistance. The dominant failure pattern was repairable fracture, except for those with large cylindrical groups.

Improving hierarchical document cluster labels through candidate term selection

One way to organize knowledge and make its search and retrieval easier is to create a structural representation divided by hierarchically related topics. Once this structure is built, it is necessary to find labels for each of the obtained clusters. In many cases the labels must be built using all the terms in the documents of the collection. This paper presents the SeCLAR method, which explores the use of association rules in the selection of good candidates for labels of hierarchical document clusters. The purpose of this method is to select a subset of terms by exploring the relationship among the terms of each document. Thus, these candidates can be processed by a classical method to generate the labels. An experimental study demonstrates the potential of the proposed approach to improve the precision and recall of labels obtained by classical methods only considering the terms which are potentially more discriminative. © 2012 - IOS Press and the authors. All rights reserved.

Heart rate variability in healthy adolescents at rest

Objective: to describe the cardiac autonomic function in healthy adolescents between 13 and 18 years old. Methods: data from 93 adolescents, of both sexes, were analyzed; they were divided into three groups according to age. Group A 13-14 years old (n=26), Group B 15-16 years old (n = 30) and Group C 17-18 years old (n = 17). The protocol consisted of raising the heart rate, beat by beat for twenty minutes of rest in supine position with spontaneous breathing. The cardiac autonomic behavior analysis was performed by the method of heart rate variability (HRV) through the indices of the Poincaré plot (SD1, SD2 and ratio SD1/SD2) and its qualitative analysis and indices in linear time domain (RMSSD and SDNN) and frequency (LFnu, HFnu and LF/HF). One-way ANOVA test or Kruskal-Wallis test was used for comparison between groups, with a significance level of 5%. Results: there was no significant difference in none of the indices compared the three groups. In addition,visual analysis of Poincaré plot has observed for all age groups large dispersion of RR intervals, indicating that these groups have good HRV. Conclusion: there were no changes in HRV in the different age groups analyzed, however the result allowed to establish a standard for each group that was studied, becomes an important tool for comparison of cardiac autonomic function between healthy and patients subjects or in different areas.

Meal of cassava foliage as pigment of diets with cassava meal and oil of African oil palm for laying hens

Twenty-eight White Leghorn laying hens, of the Cuban commercial hybrid L-33, were used for eight weeks within the laying peak (36 to 43 weeks of age), to evaluate the meal of root of cassava (Manihot esculenta Crantz) and the crude oil of African oil palm (Elaeis guineensis J.) as pigments of the egg yolks, out of their incorporation to the diet of laying hens during the laying peak. The birds were allocated in individual cages, with 108 g of feed/bird/d, water ad libitum, and 16 h of light. Analysis of variance was performed, according to one-way design with two treatments and fourteen repetitions (one cage with one hen). The treatments consisted of two diets (I- cassava meal + African palm oil, II- cassava meal + African oil palm + 2.5 % of cassava foliage meal). The viability was of 100 % in all the treatments. No differences were found for laying (91.59 and 90.10 %), which surpassed the potential of this hybrid during the laying peak (90 %), feed conversion/egg (118 and 120 g of feed/egg), mass of egg produced (3071 and 3027 g/bird) and mass conversion (1.98 and 2.00). The pigmentation of the egg yolk was doubled, by adding 2.5 % of meal of cassava foliage to the diets (3 and 6 in the scale of Roche). It was likeable to enhance the pigmentation of the egg yolk and reduce the feeding costs of the laying hens, when including 2.5 % of meal of cassava foliage to diets where the cassava meal and the oil of the African oil palm are basic sources of starch and lipids for the laying hens.

Efficacy and cytotoxicity of a bleaching gel after short application times on dental enamel

Objectives: This study aimed to evaluate and correlate the efficacy and cytotoxicity of a 35 % hydrogen peroxide (HP) bleaching gel after different application times on dental enamel. Materials and methods: Enamel/dentin disks in artificial pulp chambers were placed in wells containing culture medium. The following groups were formed: G1, control (no bleaching); G2 and G3, three or one 15-min bleaching applications, respectively; and G4 and G5, three or one 5-min bleaching applications, respectively. Extracts (culture medium with bleaching gel components) were applied for 60 min on cultured odontoblast-like MDPC-23 cells. Cell metabolism (methyl tetrazolium assay) (Kruskal-Wallis/Mann-Whitney; α = 5 %) and cell morphology (scanning electron microscopy) were analyzed immediately after the bleaching procedures and the trans-enamel and trans-dentinal HP diffusion quantified (one-way analysis of variance/Tukey's test; α = 5 %). The alkaline phosphatase (ALP) activity was evaluated 24 h after the contact time of the extracts with the cells (Kruskal-Wallis/Mann-Whitney; α = 5 %). Tooth color was analyzed before and 24 h after bleaching using a spectrophotometer according to the Commission Internationale de l'Eclairage L*a*b* system (Kruskal-Wallis/Mann-Whitney; α = 0.05). Results: Significant difference (p < 0.05) in cell metabolism occurred only between G1 (control, 100 %) and G2 (60.6 %). A significant decrease (p < 0.05) in ALP activity was observed between G2, G3, and G4 in comparison with G1. Alterations on cell morphology were observed in all bleached groups. The highest values of HP diffusion and color alterations were observed for G2, with significant difference among all experimental groups (p < 0.05). G3 and G4 presented intermediate color change and HP diffusion values with no statistically significant differences between them (p > 0.05). The lowest amount of HP diffusion was observed in G5 (p < 0.05), which also exhibited no significant color alteration compared to the control group (p > 0.05). Conclusions: HP diffusion through dental tissues and its cytotoxic effects were proportional to the contact time of the bleaching gel with enamel. However, shorter bleaching times reduced bleaching efficacy. Clinical relevance: Shortening the in-office tooth bleaching time could be an alternative to minimize the cytotoxic effects of this clinical procedure to pulp tissue. However, the reduced time of bleaching agent application on enamel may not provide adequate esthetic outcome. © 2012 Springer-Verlag Berlin Heidelberg.

A transmission line model developed directly in phase domain

The phases of a transmission line are tightly coupled due to mutual impedances and admittances of the line. One way to accomplish the calculations of currents and voltages in multi-phase lines consists in representing them in modal domain, where its n coupled phases are represented by their n propagation modes. The separation line in their modes of propagation is through the use of a modal transformation matrix whose columns are eigenvectors associated with the parameters of the line. Usually, this matrix is achieved through numerical methods which do not allow the achievement of an analytical model for line developed directly in the phases domain. This work will show an analytical model for phase currents and voltages of the line and results it will be applied to a hypothetical two-phase. It will be shown results obtained with that will be compared to results obtained using a classical model. © 2012 IEEE.

Effect of seating forces on cement-ceramic adhesion in microtensile bond tests

Objectives: The aim of this study was to evaluate the effect of different seating forces during cementation in cement-ceramic microtensile bond strength (μTBS). Materials and methods: Forty-five blocks (5 × 5 × 4 mm3) of a glass-infiltrated alumina-based ceramic (In-Ceram Alumina) were fabricated according to the manufacturer's instructions and duplicated in resin composite. Ceramic surfaces were polished, cleaned for 10 min in an ultrasonic bath, silica coated using a laboratory type of air abrasion device, and silanized. Each treated ceramic block was then randomly assigned to five groups (n = 9) and cemented to a composite block under five seating forces (10 g, 50 g, 100 g, 500 g, and 750 g) using a dual-cured resin cement (Panavia F). The ceramic-cement-composite assemblies were cut under coolant water to obtain bar specimens (1 mm × 0. 8 mm2). The μTBS tests were performed in a universal testing machine (1 mm/min). The mean bond strengths values were statistically analyzed using one-way ANOVA (α ≤ 0. 05). Results: Different seating forces resulted in no significant difference in the μTBS results ranging between 13. 1 ± 4. 7 and 18. 8 ± 2. 1 MPa (p = 0. 13) and no significant differences among cement thickness. Conclusions: Excessive seating forces during cementation seem not to affect the μTBS results. Clinical relevance: Excessive forces during the seating of single all-ceramic restorations cementation seem to display the same tensile bond strength to the resin cement. © 2012 Springer-Verlag.

Wound healing of dehiscence defects following different root conditioning modalities: An experimental study in dogs

Objective: The purpose of this study was to investigate the periodontal healing pattern of dehiscence-type defects following different chemical root conditioning modalities. Materials and methods: Buccal osseous dehiscence defects were created on six teeth of seven dogs. After dental plaque accumulation, defects were treated with sterile saline solution (control group) or one chemical conditioning modality: citric acid (CA group), ethylenediaminetetraacetic acid (EDTA group), tetracycline (TTC group), citric acid + tetracycline (CA + TTC group), or tetracycline + citric acid (TTC + CA group). After 3 months of healing, clinical parameters were evaluated, and the animals were killed. Histological sections were processed, and a computer-assisted histometric analysis was used to evaluate the formation of new cementum, new bone, and epithelial apical migration. Results: All treatments yielded significant improvements in terms of probing depth decrease and clinical attachment level gain compared to baseline values; however, without significant differences among the groups (p > 0.05; one-way ANOVA). The highest amount of new cementum was noted in the EDTA group (3.72 ± 0.83 mm, 77.6 %), while the lowest amount of new bone was observed in the TTC group (0.7 ± 0.94 mm, 14.3 %). However, no statistically significant differences could be observed among the groups regarding epithelial apical migration, new cementum, and alveolar bone formation (p > 0.05). Conclusion: Chemical root surface conditioning did not promote any significant improvement in periodontal healing pattern of dehiscence-type defects in dogs. Clinical Relevance: Chemical root surface conditioning after surgical debridement did not promote positive or negative effects on periodontal healing pattern of dehiscence-type defects. © 2012 Springer-Verlag Berlin Heidelberg.

Ultrasonic activation of internal bleaching agents

Aim: To evaluate the effectiveness of ultrasonic activation of bleaching agents during ex vivo internal bleaching. Methodology: Fifty canine human teeth were artificially stained, root filled and divided into five groups (n = 10) that received SP - sodium perborate plus deionized water (control group), CP - 37% carbamide peroxide gel, CPUS - 37% carbamide peroxide gel plus ultrasonic application, HP - 35% hydrogen peroxide gel or HPUS - 35% hydrogen peroxide gel plus ultrasonic application. In groups CP and HP, the bleaching agent was left inside the pulp chamber for three applications of 10 min. In groups CPUS and HPUS, the same process was performed, but ultrasonic vibration was applied to the bleaching agent by an alloy tip for 30 s, with 30 s intervals. Two sessions were performed. The colour was measured initially and after each session by an intraoral dental spectrophotometer. The variation (Δ) of the colour parameters based on the CIELab system L*, a* and b*, and the colour alteration ΔE* were calculated after first and second section. Data were analysed by one-way anova and Tukey's test. Results: There was no significant difference amongst groups for ΔL*, Δa* and ΔE*, but there was a significant difference for Δb* in the first and second sessions (P = 0.0006 and 0.0016, respectively). After the first session, Δb* was significantly greater for groups HP and HPUS, without a significant difference between them. For the second session, group HPUS had the greatest Δb* values, but they were similar to groups HP and SP; group CP had the lowest values, which were similar to groups CPUS and SP. Conclusion: Ultrasonic activation of bleaching agents during ex vivo internal bleaching was no more effective than conventional internal bleaching procedures, without activation. © 2012 International Endodontic Journal.

Efficacy of mouth rinses and toothpaste on tooth whitening.

People increasingly desire tooth whitening. Considering the wide range of whitening products on the market, this study evaluated the efficacy of whitening toothpastes and mouth rinses compared with the 10% carbamide peroxide (CP) whitening gel. We obtained 120 cylindrical specimens from bovine teeth, which were darkened for 24 hours in a coffee solution. The color measurement was performed by a spectrophotometer using the CIE L*a*b* system, and specimens were divided into six groups according to the use of the following agents: group 1, conventional fluoridated toothpaste; group 2, Close Up White Now; group 3, Listerine Whitening; group 4, Colgate Plax Whitening; group 5, experimental mouth rinse with Plasdone; and group 6, 10% CP Whiteness Perfect. After the simulation of 12 weeks of treatment for groups 1 to 5 and 14 days of treatment for group 6, the specimens were subjected to a new color reading. Data were subjected to one-way analysis of variance (α=0.05), which showed significant differences among groups after 12 weeks for ΔE (p=0.001). Results of the Tukey test revealed that groups 3, 4, and 6 presented significantly higher color alteration than groups 1, 2, and 5. The whitening toothpaste Close Up White Now and the experimental mouth rinse with Plasdone showed similar color alteration as conventional toothpaste after a 12-week treatment simulation. These groups presented significantly lower color alteration compared with whitening mouth rinses Listerine and Colgate Plax Whitening, which showed similar results to those observed after 14 days of bleaching with 10% CP treatment.

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Pathological and behavioral risk factors for higher serum c-reactive protein concentrations in free-living adults - A Brazilian community-based study

Low-grade chronic systemic inflammation is often associated with chronic non-communicable diseases, and its most frequently used marker, the C-reactive protein (CRP), has become an identifier of such diseases as well as an independent predictor for cardiovascular disorders and mortality. CRP is produced in response to pro-inflammatory signaling and to individual and behavioral factors, leading to pathological states. The aim of this study was to rank the predicting factors of high CRP concentrations in free-living adults from a community-based sample. We evaluated 522 adults (40-84 years old; 381 women) for anthropometric characteristics, dietary intake, clinical and physical tests, and blood analysis. Subjects were assigned to groups, according to CRP concentrations, as normal CRP (G1;<3.0 mg/L; n = 269), high CRP (G2; 3.0-6.0 mg/L; n = 139), and very high CRP (G3; >6.0 mg/dL; n = 116). Statistical comparison between groups used one-way ANOVA or Kruskal-Wallis tests, and prediction of altered values in increasing CRP was evaluated by proportional hazard models (odds ratio). CRP distribution was influenced by gender, body mass index, body and abdominal fatness, blood leukocytes, and neutrophil counts. The higher CRP group was discriminated by the above variables in addition to lower VO2max, serum metabolic syndrome components (triglycerides, glucose, and HDL cholesterol), higher insulin, homeostasis assessment of insulin resistance, uric acid, gamma-GT, and homocysteine. After adjustments, only fatness, blood leukocytes, and hyperglycemia remained as independent predictors for increased serum CRP concentrations. Intervention procedures to treat low-grade chronic inflammation in overweight women would mainly focus on restoring muscle mass and functions in addition to an antioxidant-rich diet. © 2012 Springer Science+Business Media, LLC.

CCL3 and CXCL12 production in vitro by dental pulp fibroblasts from permanent and deciduous teeth stimulated by Porphyromonas gingivalis LPS

Objective: The aim of this study was to compare the production of the chemokines CCL3 and CXCL12 by cultured dental pulp fibroblasts from permanent (PDPF) and deciduous (DDPF) teeth under stimulation by Porphyromonas gingivalis LPS (PgLPS). Material and Methods: Primary culture of fibroblasts from permanent (n=3) and deciduous (n=2) teeth were established using an explant technique. After the fourth passage, fibroblasts were stimulated by increasing concentrations of PgLPS (0 - 10 pg/mL) at 1, 6 and 24 h. The cells were tested for viability through MTT assay, and production of the chemokines CCL3 and CXCL12 was determined through ELISA. Comparisons among samples were performed using One-way ANOVA for MTT assay and Two-way ANOVA for ELISA results. Results: Cell viability was not affected by the antigen after 24 h of stimulation. PgLPS induced the production of CCL3 by dental pulp fibroblasts at similar levels for both permanent and deciduous pulp fibroblasts. Production of CXCL12, however, was significantly higher for PDPF than DDPF at 1 and 6 h. PgLPS, in turn, downregulated the production of CXCL12 by PDPF but not by DDPF. Conclusion: These data suggest that dental pulp fibroblasts from permanent and deciduous teeth may present a differential behavior under PgLPS stimulation.

Analysis of primary stability of dental implants inserted in different substrates using the pullout test and insertion torque

The aim of the study was to evaluate mechanical behavior of implants inserted in three substrates, by measuring the pullout strength and the relative stiffness. 32 implants (Master Porous-Conexao, cylindrical, external hexagon, and surface treatment) were divided into 4 groups (n = 8): pig rib bone, polyurethane Synbone, polyurethane Nacional 40 PCF, and pinus wood. Implants were installed with the exact distance of 5 mm of another implant. The insertion torque (N·cm) was quantified using the digital Kratos torque meter and the pullout test (N) was performed by an axial traction force toward the long axis of the implant (2 min/mm) through mount implant devices attached to a piece adapted to a load cell of 200 Kg of a universal testing machine (Emic DL10000). Data of insertion torque and maximum pullout force were submitted to one-way ANOVA and Bonferroni tests (α = 0.05). Polyurethane Nacional 40 PCF and pinus wood showed the highest values of insertion torque and pullout force, with significant statistical difference (P < 0.05) with other groups. The analysis showed stiffness materials with the highest values for primary stability. © 2013 Nathalia Ferraz Oliscovicz et al.

Effects of extreme cooling methods on mechanical properties and shear bond strength of bilayered porcelain/3Y-TZP specimens

Objectives: This study investigated the effect of extreme cooling methods on the flexural strength, reliability and shear bond strength of veneer porcelain for zirconia. Methods: Vita VM9 porcelain was sintered on zirconia bar specimens and cooled by one of the following methods: inside a switched-off furnace (slow), at room temperature (normal) or immediately by compressed air (fast). Three-point flexural strength tests (FS) were performed on specimens with porcelain under tension (PT, n = 30) and zirconia under tension (ZT, n = 30). Shear bond strength tests (SBS, n = 15) were performed on cylindrical blocks of porcelain, which were applied on zirconia plates. Data were submitted to one-way ANOVA and Tukey's post hoc tests (p < 0.05). Weibull analysis was performed on the PT and ZT configurations. Results: One-way ANOVA for the PT configuration was significant, and Tukey's test revealed that fast cooling leads to significantly higher values (p < 0.01) than the other cooling methods. One-way ANOVA for the ZT configuration was not significant (p = 0.06). Weibull analysis showed that normal cooling had slightly higher reliability for both the PT and ZT configurations. Statistical tests showed that slow cooling decreased the SBS value (p < 0.01) and showed less adhesive fracture modes than the other cooling methods. Clinical Significance: Slow cooling seems to affect the veneer resistance and adhesion to the zirconia core; however, the reliability of fast cooling was slightly lower than that of the other methods. © 2013 Elsevier Ltd.