Publications by authors named "Orivaldo Lopes Silva"

5 Publications

  • Page 1 of 1

Comparison of the effects of electrical field stimulation and low-level laser therapy on bone loss in spinal cord-injured rats.

Photomed Laser Surg 2010 Oct 12;28(5):669-74. Epub 2010 Oct 12.

Department of Bioscience, Federal University of São Paulo (UNIFESP), Santos, SP, Brazil.

Objective: This study investigated the effects of low-level laser therapy (LLLT) and electrical stimulation (ES) on bone loss in spinal cord-injured rats.

Materials And Methods: Thirty-seven male Wistar rats were divided into four groups: standard control group (CG); spinal cord-injured control (SC); spinal cord-injured treated with laser (SCL; GaAlAs, 830 nm, CW, 30 mW/cm, 250 J/cm(2)); and spinal cord-injured treated with electrical field stimulation (SCE; 1.5 MHz, 1:4 duty cycles, 30 mW, 20 min). Biomechanical, densitometric, and morphometric analyses were performed.

Results: SC rats showed a significant decrease in bone mass, biomechanical properties, and morphometric parameters (versus CG). SCE rats showed significantly higher values of inner diameter and internal and external areas of tibia diaphyses; and the SCL group showed a trend toward the same result (versus SC). No increase was found in either mechanical or densitometric parameters.

Conclusion: We conclude that the mentioned treatments were able to initiate a positive bone-tissue response, maybe through stimulation of osteoblasts, which was able to determine the observed morphometric modifications. However, the evoked tissue response could not determine either biomechanical or densitometric modifications.
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http://dx.doi.org/10.1089/pho.2009.2691DOI Listing
October 2010

Mechanical vibration preserves bone structure in rats treated with glucocorticoids.

Bone 2010 Jun 10;46(6):1516-21. Epub 2010 Feb 10.

Division of Endocrinology, Federal University of São Paulo, Brazil.

Glucocorticoids are an important cause of secondary osteoporosis in humans, which decreases bone quality and leads to fractures. Mechanical stimulation in the form of low-intensity and high-frequency vibration seems to be able to prevent bone loss and to stimulate bone formation. The objective of this study was to evaluate the effects of mechanical vibration on bone structure in rats treated with glucocorticoids. Thirty 3-month-old adult male Wistar rats were randomized to three groups: control (C), glucocorticoid (G), and glucocorticoid with vibration (GV). The G and GV groups received 3.5mg/kg/day of methylprednisolone 5 days/week for a duration of 9 weeks, and the C group received vehicle (saline solution) during the same period. The GV group was vibrated on a special platform for 30 min per day, 5 days per week during the experiment. The platform was set to provide a vertical acceleration of 1 G and a frequency of 60 Hz. Skeletal bone mass was evaluated by total body densitometry (DXA). Fracture load threshold, undecalcified bone histomorphometry, and bone volume were measured in tibias. Glucocorticoids induced a significantly lower weight gain (-9.7%) and reduced the bone mineral content (-9.2%) and trabecular number (-41.8%) and increased the trabecular spacing (+98.0%) in the G group, when compared to the control (C). Vibration (GV) was able to significantly preserve (29.2%) of the trabecular number and decrease the trabecular spacing (+26.6%) compared to the G group, although these parameters did not reach C group values. The fracture load threshold was not different between groups, but vibration significantly augmented the bone volume of the tibia by 21.4% in the GV group compared to the C group. Our study demonstrated that low-intensity and high-frequency mechanical vibration was able to partially inhibit the deleterious consequences of glucocorticoids on bone structure in rats.
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http://dx.doi.org/10.1016/j.bone.2010.02.009DOI Listing
June 2010

Comparative study of how low-level laser therapy and low-intensity pulsed ultrasound affect bone repair in rats.

Photomed Laser Surg 2006 Dec;24(6):735-40

Bioengineering Department, University of São Paulo, São Paulo, Brazil.

Objective: This study aimed to compare the consequences of low-level laser therapy (LLLT) and low-intensity pulsed ultrasound (LIPUS) on bone repair.

Background Data: Many studies have assessed the effects of LLLT and LIPUS on bone repair, but a comparison of them is rare.

Methods: Male Wistar rats (n = 48) with tibial bone osteotomy were used. One group had the osteotomized limb treated with LLLT (GaAlAs laser, 780 nm, 30 mW, 112.5 J/cm(2)) and the second group with LIPUS (1.5 MHz, 30 mW/cm(2)), both for 12 sessions (five times per week); a third group was the control. After 20 days, rats were sacrificed and had their tibias submitted to a bending test or histomorphometric analysis.

Results: In the bending test, maximum load at failure of LLLT group was significantly higher (p < 0.05). Bone histomorphometry revealed a significant increase in osteoblast number and surface, and osteoid volume in the LLLT group, and a significant increase in eroded and osteoclast surfaces in the LIPUS group.

Conclusion: LIPUS enhanced bone repair by promoting bone resorption in the osteotomy area, while LLLT accelerated this process through bone formation.
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http://dx.doi.org/10.1089/pho.2006.24.735DOI Listing
December 2006

Metallic biomaterials TiN-coated: corrosion analysis and biocompatibility.

Artif Organs 2003 May;27(5):461-4

Departamento de Engenharia de Materiais, Aeronautica e Automobilistica, Escola de Engenharia de São Carlos, Universidade de São Paulo, Brazil.

Corrosion processes due to contact with the physiological environment should be avoided or minimized in orthopedic implants. Four metallic substrates frequently used as biomaterials: pure Ti, Ti-6Al-4V alloy, ASTM F138 stainless steel, and Co-Cr-Mo alloy, were coated with TiN using the physical vapor deposition (PVD) technique. These coatings have been screened by polarization curves in physiological solutions. TiN prepared by PVD is efficient as coating for stainless steel. On titanium and alloy there are no benefits concerning the corrosion resistance compared to the bare Ti-materials. TiN coatings have been screened according to ISO 10993 standard tests for biocompatibility and exhibited no cytotoxicity, dermal irritation, or acute systemic toxicity response.
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http://dx.doi.org/10.1046/j.1525-1594.2003.07241.xDOI Listing
May 2003

Endurance test on a textured diaphragm for the auxiliary total artificial heart (ATAH).

Artif Organs 2003 May;27(5):457-60

Department of Bioengineering, Institute Dante Pazzanese of Cardiology, São Paulo, SP, Brazil.

We performed an endurance test on a textured diaphragm made of polyurethane (BioSpan, The Polymer Technology Group, San Francisco, CA, U.S.A.) to be used in the auxiliary total artificial heart (ATAH), an electromechanical device that can be totally implantable without removing the natural heart due to the device's reduced dimension. The objective of this endurance test was to predict whether this diaphragm would be capable of resisting in vivo tests with the ATAH implanted for fifteen days in calves. In this study, a mock loop system simulating the human circulatory system was used. The test protocol was elaborated to reproduce extreme physiological conditions. The technique to produce the textured diaphragms made of polyurethane is shown. The textured surface is used as basis to fix a layer of calf-skin gelatin. The technique used to make the diaphragm guaranteed a totally textured surface without cracking. The diaphragm demonstrated enough resistance to be used at the 15 day in vivo experiments.
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http://dx.doi.org/10.1046/j.1525-1594.2003.07238.xDOI Listing
May 2003
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