Peripheral nervous system and grounds for the neural insult in leprosy

The mechanism of interaction between Mycobacterium leprae and neural cells has not been elucidated so far. No satisfactory interpretation exists as to the bacterium tropism to the peripheral nervous system in particular. The present study is a review of the micro-physiology of the extracellular apparatus attached to Schwann cells, as well as on the description of morphological units probably involved in the process of the binding to the bacterial wall.

Influence of irradiant energy on degree of conversion, polymerization rate and shrinkage stress in an experimental resin composite system

Objective. This study evaluated the degree of conversion (DC), maximum rate of cure (R(p)(max)), and polymerization stress (PS) developed by an experimental dental composite subjected to different irradiant energies (3,6,12, 24, or 48J/cm(2)) under constant irradiance (500 mw/cm(2)). Methods. DC and R(p)(max) were monitored for 10 min on the bottom surface of 2-mm thick disks and on 150-mu m thick films (representing the top of the specimen) using ATR-FTIR. PS was monitored for 10 min in 2-mm thick disks bonded to two glass rods (O = 5 mm) attached to a universal testing machine. One-way ANOVA/Tukey tests were used and differences in DC and R(p)(max) between top and bottom surfaces were examined using Student`s t-test. Statistical testing was performed at a pre-set alpha of 0.05. Results. For a given surface, DC showed differences among all groups, except at the top between 24 and 48 J/cm(2). R(p)(max) was similar among all groups at the same surface and statistically higher at the top surface. PS also showed significant differences among all groups. Data for 48 J/cm(2) were not obtained due to specimen failure at the glass/composite interface. Significance. Increases in irradiant exposure led to significant increases in DC and PS, but had no effect on R(p)(max) (c) 2008 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

Polymerization stress of resin composites as a function of system compliance

Objectives. Evaluate the effect of testing system compliance on polymerization stress and stress distribution of composites. Methods. Composites tested were Filtek Z250 (FZ), Herculite (HL), Tetric Ceram (TC), Helio Fill-AP (HF) and Heliomolar (HM). Stress was determined in 1-mm thick specimens, inserted between two rods of either poly(methyl methacrylate), PMMA, or glass. Experimental nominal stress (sigma(exp)) was calculated by dividing the maximum force recorded 5 min after photoactivation by the cross-sectional area of the rod. Composites` elastic modulus (E) was obtained by three-point bending. Data were submitted to one-way ANOVA/Tukey`s test (alpha = 0.05). Stress distribution on longitudinal (sigma(y)) and transverse (sigma(x)) axes of models representing the composites with the highest and lowest E (FZ and HM, respectively) were evaluated by finite element analysis (FEA). Results. sigma(exp) ranged from 5.5 to 8.8 MPa in glass and from 2.6 to 3.4 MPa in PMMA. Composite ranking was not identical in both substrates, since FZ showed or sigma(exp) statistically higher than HM in glass, while in PMMA FZ showed values similar to the other composites. A strong correlation was found between stress reduction (%) from glass to PMMA and composite`s E (r(2) = 0.946). FEA revealed that system compliance was influenced by the composite (FZ led to higher compliance than HM). sigma(x) distribution was similar in both substrates, while cry distribution showed larger areas of compressive stresses in specimens built on PMMA. Significance. sigma(exp) determined in PMMA was 53-68% lower than in glass. Composite ranking varied slightly due to differences in substrates` longitudinal and transverse deformation. (c) 2007 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

Tartrate-resistant acid phosphatase activity and glutathione levels are modulated during hFOB 1.19 osteoblastic differentiation

Tartrate-resistant acid phosphatase (TRAP) is a well-known marker of osteoclasts and bone resorption. Here we have investigated whether osteoblast-like cells (hFOB 1.19) present TRAP activity and how would be its pattern of expression during osteoblastic differentiation. We also observed how the osteoblastic differentiation affected the reduced glutathione levels. TRAP activity was measured using the p-nitrophenylphosphate substrate. The osteogenic potential of hFOB 1.19 cells was studied by measuring alkaline phosphatase activity and mineralized nodule formation. Oxidative stress was determined by HPLC and DNTB assays. TRAP activity and the reduced glutathione-dependent microenvironment were modulated during osteoblastic differentiation. During this phase, TRAP activity, as well as alkaline phosphatase and glutathione increased progressively up to the 21st day, decreasing thereafter. We demonstrate that TRAP activity is modulated during osteoblastic differentiation, possibly in response to the redox state of the cell, since it seemed to depend on suitable levels of reduced glutathione.

Influence of glutaraldehyde priming on bond strength of an experimental adhesive system applied to wet and dry dentine

Objectives: This study tested the following null hypotheses: (1) there is no difference in resin-dentine bond strength when an experimental glutaraldehyde primer solution is added prior to bonding procedures and (2) there is no difference in resin-dentine bond strength when experimental glutaraldehyde/adhesive system is applied under dry or wet demineralized dentine conditions. Methods: Extracted human maxillary third molars were selected. Flat, mid-coronal dentine was exposed for bonding and four groups were formed. Two groups were designated for the dry and two for the wet dentine technique: DRY: (1) Group GD: acid etching + glutaraldehyde primer (primer A) + HEMA/ethanol primer (primer B)-under dried dentine + unfilled resin; (2) Group D: the same as GD, except for primer A application; WET: (3) Group GW: the same as GD, but primer B was applied under wet dentine condition; (4) Group W: the same as GW, except for primer A application. The bonding resin was light-cured and a resin core was built up on the adhesive layer. Teeth were then prepared for microtensile bond testing to evaluate bond strength. The data obtained were submitted to ANOVA and Tukey`s test (alpha = 0.05). Results: Glutaraldehyde primer application significantly improved resin-dentine bond strength. No significant difference was observed when the same experimental adhesive system was applied under either dry or wet dentine conditions. These results allow the first null hypothesis to be rejected and the second to be accepted. Conclusion: Glutaraldehyde may affect demineralized dentine properties leading to improved resin bonding to wet and dry substrates. (C) 2008 Elsevier Ltd. All rights reserved.

Analytical solution and numerical model for the interface in a stratified long wave system

For a two layered long wave propagation, linearized governing equations, which were derived earlier from the Euler equations of mass and momentum assuming negligible friction and interfacial mixing are solved analytically using Fourier transform. For the solution, variations of upper layer water level is assumed to be sinosoidal having known amplitude and variations of interface level is solved. As the governing equations are too complex to solve it analytically, density of upper layer fluid is assumed as very close to the density of lower layer fluid to simplify the lower layer equation. A numerical model is developed using the staggered leap-forg scheme for computation of water level and discharge in one dimensional propagation having known amplitude for the variations of upper layer water level and interface level to be solved. For the numerical model, water levels (upper layer and interface) at both the boundaries are assumed to be known from analytical solution. Results of numerical model are verified by comparing with the analytical solutions for different time period. Good agreements between analytical solution and numerical model are found for the stated boundary condition. The reliability of the developed numerical model is discussed, using it for different a (ratio of density of fluid in the upper layer to that in the lower layer) and p (ratio of water depth in the lower layer to that in the upper layer) values. It is found that as ‘CX’ increases amplification of interface also increases for same upper layer amplitude. Again for a constant lower layer depth, as ‘p’ increases amplification of interface. also increases for same upper layer amplitude.

Monolithic CAD/CAM Lithium Disilicate Versus Veneered Y-TZP Crowns: Comparison of Failure Modes and Reliability After Fatigue

Purpose: The aim of this research was to evaluate the fatigue behavior and reliability of monolithic computer-aided design/computer-assisted manufacture (CAD/CAM) lithium disilicate and hand-layer-veneered zirconia all-ceramic crowns. Materials and Methods: A CAD-based mandibular molar crown preparation, fabricated using rapid prototyping, served as the master die. Fully anatomically shaped monolithic lithium disilicate crowns (IPS e.max CAD, n = 19) and hand-layer-veneered zirconia-based crowns (IPS e.max ZirCAD/Ceram, n = 21) were designed and milled using a CAD/CAM system. Crowns were cemented on aged dentinlike composite dies with resin cement. Crowns were exposed to mouth-motion fatigue by sliding a WC-indenter (r = 3.18 mm) 0.7 mm lingually down the distobuccal cusp using three different step-stress profiles until failure occurred. Failure was designated as a large chip or fracture through the crown. If no failures occurred at high loads (> 900 N), the test method was changed to staircase r ratio fatigue. Stress level probability curves and reliability were calculated. Results: Hand-layer-veneered zirconia crowns revealed veneer chipping and had a reliability of < 0.01 (0.03 to 0.00, two-sided 90% confidence bounds) for a mission of 100,000 cycles and a 200-N load. None of the fully anatomically shaped CAD/CAM-fabricated monolithic lithium disilicate crowns failed during step-stress mouth-motion fatigue (180,000 cycles, 900 N). CAD/CAM lithium disilicate crowns also survived r ratio fatigue (1,000,000 cycles, 100 to 1,000 N). There appears to be a threshold for damage/bulk fracture for the lithium disilicate ceramic in the range of 1,100 to 1,200 N. Conclusion: Based on present fatigue findings, the application of CAD/CAM lithium disilicate ceramic in a monolithic/fully anatomical configuration resulted in fatigue-resistant crowns, whereas hand-layer-veneered zirconia crowns revealed a high susceptibility to mouth-motion cyclic loading with early veneer failures. Int J Prosthodont 2010; 23: 434-442.

Characterization of a Local Renin-Angiotensin System in Rat Gingival Tissue

Background: The systemic renin-angiotensin system (RAS) promotes the plasmatic production of angiotensin (Ang) II, which acts through interaction with specific receptors. There is growing evidence that local systems in various tissues and organs are capable of generating angiotensins independently of circulating RAS. The aims of this study were to investigate the expression and localization of RAS components in rat gingival tissue and evaluate the in vitro production of Ang II and other peptides catalyzed by rat gingival tissue homogenates incubated with different Ang II precursors. Methods: Reverse transcription - polymerase chain reaction assessed mRNA expression. Immunohistochemical analysis aimed to detect and localize renin. A standardized fluorimetric method with tripeptide hippuryl-histidyl-leucine was used to measure tissue angiotensin-converting enzyme (ACE) activity, whereas high performance liquid chromatography showed products formed after the incubation of tissue homogenates with Ang I or tetradecapeptide renin substrate (TDP). Results: mRNA for renin, angiotensinogen, ACE, and Ang II receptors (AT(1a), AT(1b), and AT(2)) was detected in gingival tissue; cultured gingival fibroblasts expressed renin, angiotensinogen, and AT(1a) receptor. Renin was present in the vascular endothelium and was intensely expressed in the epithelial basal layer of periodontally affected gingival tissue. ACE activity was detected (4.95 +/- 0.89 nmol histidyl-leucine/g/minute). When Ang I was used as substrate, Ang 1-9 (0.576 +/- 0.128 nmol/mg/minute), Ang II (0.066 +/- 0.008 nmol/mg/minute), and Ang 1-7 (0.111 +/- 0.017 nmol/mg/minute) were formed, whereas these same peptides (0.139 +/- 0.031, 0.206 +/- 0.046, and 0.039 +/- 0.007 nmol/mg/minute, respectively) and Ang 1 (0.973 +/- 0.139 nmol/mg/minute) were formed when TDP was the substrate. Conclusion: Local RAS exists in rat gingival tissue and is capable of generating Ang II and other vasoactive peptides in vitro. J Periodontol 2009;80:130-139.

Lattice-dome design using a knowledge-based system approach

In the design of lattice domes, design engineers need expertise in areas such as configuration processing, nonlinear analysis, and optimization. These are extensive numerical, iterative, and lime-consuming processes that are prone to error without an integrated design tool. This article presents the application of a knowledge-based system in solving lattice-dome design problems. An operational prototype knowledge-based system, LADOME, has been developed by employing the combined knowledge representation approach, which uses rules, procedural methods, and an object-oriented blackboard concept. The system's objective is to assist engineers in lattice-dome design by integrating all design tasks into a single computer-aided environment with implementation of the knowledge-based system approach. For system verification, results from design examples are presented.

Bone repair in mandibular body osteotomy after using 2.0 miniplate system - histological and histometric analysis in dogs

The objective of this study was to evaluate the bone repair along a mandibular body osteotomy after using a 2.0 miniplate system. Nine adult mongrel dogs were subjected to unilateral continuous defect through an osteotomy between the mandibular 3rd and 4th premolars. Two four-hole miniplates were placed in accordance with the Arbeitgeimeinschaft fur Osteosynthesefragen Manual. Miniplates adapted to the alveolar processes were fixed monocortically with 6.0-mm-length titanium alloy self-tapping screws, whereas miniplates placed near the mandible bases were fixed bicortically. At 2, 6 and 12 weeks, three dogs were sacrificed per period, and the osteotomy sites were removed, divided into three thirds (Tension Third, TT; Intermediary Third, IT; Compression Third, CT) and prepared for conventional and polarized light microscopy. At 6 weeks, while the CT repaired faster and showed bone union by woven bone formation, the TT and IT exhibited a ligament-like fibrous connective tissue inserted in, and connecting, newly formed woven bone overlying the parent lamellar bone edges. At 12 weeks, bone repair took place at all thirds. Histometrically, proportions of newly formed bone did not alter at TT, IT and CT, whereas significantly enhanced bone formation was observed for the 12-week group, irrespective of the third. The results demonstrated that although the method used to stabilize the mandibular osteotomy allowed bone repair to occur, differences in the dynamics of bone healing may take place along the osteotomy site, depending on the action of tension and compression forces generated by masticatory muscles.