Avaliação dos tratamentos químicos e/ou mecânicos da camada de esfregaço conforme observado por microscopia eletrônica de varredura - estudo cego comparativo

A blind comparative study of chemical and/or mechanical treatments of the smear layer, according to scanning electron microscopy images, was carried out. The effect of the treatments was analyzed on the smear layer of mesio-occlusodistal cavity walls prepared in vitro in human third molars. The agents used were air/water spray, 37% phosphoric acid, 5% tannic acid, biologic detergent, 0.5% sodium hypochlorite, and enamel hatchet alone or in association with the previous agents. Electron micrographs were evaluated by three professionals according to the degree of visualization of underlying dentin or enamel. Phosphoric acid received the highest scores due to the complete removal of the smear layer. However, statistical analyses revealed diverse performances of non or slightly demineralizing agents, according to the cavity walls in dentin, while there was equivalent effect on the enamel of gingival walls.Um estudo comparativo cego de tratamentos químicos e/ou mecânicos da camada de esfregaço, de acordo com imagens da microscopia eletrônica de varredura, foi realizado. Analisou-se o efeito dos tratamentos sobre a camada de esfregaço de paredes de cavidades mésio-ocluso-distais, preparadas in vitro, em terceiros molares humanos. Os agentes empregados foram spray ar/água, ácido fosfórico a 37%, ácido tânico a 5%, detergente biológico, hipoclorito de sódio a 0,5% e machado para esmalte isoladamente ou associado a estas substâncias. Eletromicrografias foram avaliadas por três profissionais de acordo com o grau de visualização da dentina ou esmalte subjacentes. O ácido fosfórico recebeu as maiores graduações devido à remoção completa da camada de esfregaço. Análises estatísticas revelaram performances diversas entre tratamentos não/ou levemente desmineralizantes de acordo com as paredes cavitárias, em dentina e efeitos equivalentes entre si, em paredes de esmalte

Исследование свойств и состава руды с целью усовершенствования извлечения вольфрамсодержащих компонентов

The aim of this in vitro study was to investigate the effect of erbium:yttrium-aluminum-garnet (Er:YAG) laser irradiation on dentinal collagen by transmission electron microscopy and to analyze the resin-dentin interface by scanning electron microscopy. A tensile bond strength test was also applied. Specimens from 69 sound human third molars were randomly divided into three groups: control (no laser), and two irradiated groups, laser 250 (250 mJ/2 Hz) and laser 400 (400 mJ/4 Hz). Then, specimens were restored with two adhesive systems, an etch-and-rinse or a self-etch system. Although ultrastructural examination showed a modified surface in the irradiated dentin, there was no statistical difference in bond strength values between the laser groups and controls (P < 0.05). In conclusion, the use of Er:YAG laser for ablating human dentin did not alter the main adhesion parameters when compared with those obtained by conventional methods, thus reinforcing its use in restorative dentistry.Fundacao de Amparo a Pesquisa do Estado de Sao Paulo (FAPESP)[97/10823-0]Conselho Nacional de Desenvolvimento Cientfico e Tecnologico e Conselho Nacional de Pesquisa (CNPq)[303798/2005-0]Coordena ao de Aperfei oamento de Pessoal de Nivel Superior (CAPES), Brazi

Functional investigation of bone implant viability using radiotracers in a new model of osteonecrosis

OBJECTIVES: Conventional imaging methods are excellent for the morphological characterization of the consequences of osteonecrosis; however, only specialized techniques have been considered useful for obtaining functional information. To explore the affinity of radiotracers for severely devascularized bone, a new mouse model of isolated femur implanted in a subcutaneous abdominal pocket was devised. To maintain animal mobility and longevity, the femur was harvested from syngeneic donors. Two technetium-99m-labeled tracers targeting angiogenesis and bone matrix were selected. METHODS: Medronic acid and a homodimer peptide conjugated with RGDfK were radiolabeled with technetium-99m, and biodistribution was evaluated in Swiss mice. The grafted and control femurs were evaluated after 15, 30 and 60 days, including computed tomography (CT) and histological analysis. RESULTS: Radiolabeling achieved high (>;95%) radiochemical purity. The biodistribution confirmed good blood clearance 1 hour after administration. For 99mTc-hydrazinonicotinic acid (HYNIC)-E-[c(RGDfK)2, remarkable renal excretion was observed compared to 99mTc-methylene diphosphonate (MDP), but the latter, as expected, revealed higher bone uptake. The results obtained in the control femur were equal at all time points. In the implanted femur, 99mTc-HYNIC-E-[c(RGDfK)2 uptake was highest after 15 days, consistent with early angiogenesis. Regarding 99mTc-MDP in the implant, similar uptake was documented at all time points, consistent with sustained bone viability; however, the uptake was lower than that detected in the control femur, as confirmed by histology. CONCLUSIONS: 1) Graft viability was successfully diagnosed using radiotracers in severely ischemic bone at all time points. 2) Analogously, indirect information about angiogenesis could be gathered using 999mTc-HYNIC-E-[c(RGDfK)2. 3) These techniques appear promising and warrant further studies to determine their potential clinical applications

Ultrastructure of the Interface between Periodontal Tissues and Titanium Mini-Implants

Objective: To describe the ultrastructure of the interface between periodontal tissues and titanium mini-implants in rat mandibles. Materials and Methods: A titanium mini-implant was placed between the buccal roots of the mandibular first molar of 24 adult rats. After 21, 30, 45, 60, 90, and 120 days of implantation, the mandibular portion was removed and fixed in cacodylate-buffered 2% glutaraldehyde + 2.5% formaldehyde. The material was decalcified and processed for scanning and transmission electron microscopy. Results: Ultrastructural analysis revealed a thin cementum-like layer at longer times after implantation at the areas in which the periodontal ligament was in contact with the implant. Conclusions: The alveolar bone and the periodontal ligament reorganized their constituents around the implant, and a thin cementum-like layer was formed at longer times after implantation at the areas in which the periodontal ligament was in contact with the implant. (Angle Orthod. 2010;80:459-435.)FAPESPCNPq, Brazi

Clastic cells: Mineralized tissue resorption in health and disease

Clastic cells are responsible for mineralized tissue resorption. Bone resorbing cells are called osteo-clasts; however, they are able to resorb mineralized dental tissues or calcified cartilage and then they are called odontoclasts and chondroclasts, respectively. They derive from mononuclear precursors of the monocyte-macrophage lineage from hemopoietic tissue, reach target mineralized tissues and degrade them under many different physiologic or pathologic stimuli. Clastic cells play a key role in calcium homeostasis, and participate in skeletal growth, tooth movement, and other physiological and pathological events. They interact tightly with forming cells in bone and dental hard tissues; their unbalance may result in disturbed resorptive activity thus, causing local or systemic diseases. (C) 2008 Elsevier Ltd. All rights reserved.Fernanda Barrence, Gerson SilvaGaspar Lima. FapespCNPq (Brazil

Immunocytochemical detection of dentine matrix protein 1 in experimentally induced reactionary and reparative dentine in rat incisors

Objective: Although the general mechanisms of dentinogenesis are understood, several aspects regarding tertiary dentine formation still deserve investigation, especially regarding the presence and distribution of some noncollagenous matrix proteins. As dentine matrix protein 1 (DMP 1) is present in primary dentine, it is possible that this protein may also be present in the dentine matrix secreted after injury, but there are no immunocytochemical studies attempting its detection in tertiary dentine. The aim of this study was to examine the ultrastructural immunolocalization of DMP 1 in the tertiary dentine after extrusion of the rat incisor. Study design: Upper incisors were extruded 3 mm and then repositioned into their sockets. After several periods, the incisors were fixed and processed for transmission electron microscopy and for immunocytochemistry for DMP 1. Results: Extrusion yielded both types of tertiary dentine, which varied in aspect and related cells. DMP 1 was found in the mineralized matrix of all types of dentine, presenting high affinity for collagen, but rare colloidal gold particles over predentine. DMP 1 was evident in the supranuclear region and inside the nucleus of some odontoblast-like cells. Conclusion: The observed association between DMP 1 and collagen seem to be essential for reactionary and reparative dentine formation. (C) 2010 Elsevier Ltd. All rights reserved.CNPq, Brazi