Effects of the photobiomodulation using different energy densities on the periodontal tissues under orthodontic force in rats with type 2 diabetes mellitus

Abstract To evaluate the impact of the GaAlAs diode laser with energy densities of 160 J/cm2, 320 J/cm2, and 640 J/cm2 on the periodontal tissues under continuous orthodontic force application and on the rate of orthodontic tooth movement in rats with type-2 diabetes mellitus. The intensity of primary alveolar bone formation was also investigated through the immune-positive osteocytes for OPN antibody. Forty adult male Wistar rats were divided into eight groups of 5 rats: normoglycemic (N), 160 J-laser-normoglycemic (160 J-LN), 320 J-laser-normoglycemic (320 J-LN), 640 J-laser-normoglycemic (640 J-LN), diabetic (D), 160 J-laser-diabetic (160 J-LD), 320 J-laser-diabetic (320 J-LD), and 640 J-laser-diabetic (640 J-LD) rats. Diabetes mellitus was induced by a single intravenous injection of 40 mg/kg monohydrated-alloxan. An orthodontic force magnitude of 20cN was applied. The laser parameters were continuous emission of 780-nm wavelength, output power of 20mW, and fiber probe with a spot size of 0.04 cm in diameter. Radiographic, histomorphological, and immunohistochemical analysis were performed after a period of 21 days. The photobiomodulation using the energy density of 640 J/cm2 strongly stimulated the alveolar bone formation and contributed the reorganization of the soft periodontal tissues, followed by the 320 J/cm2. Extensive alveolar bone loss, intense infiltration of inflammatory cells, and degradation of the PDJ tissue were mainly found in the D and 160 J-LD groups. The rate of orthodontic tooth movement was represented by the interdental distance between the cementoenamel junctions of the right mandibular first and second molars . This distance was larger in the diabetic groups (D: 39.98±1.97, 160 J-LD: 34.84±6.01, 320 J-LD: 29.82±1.73, and 640 J-LD: 35.47±4.56) than in the normoglycemic groups (N: 21.13±1.19; 160 J-LN: 22.69±0.72, 320 J-LN: 22.28±0.78, and 640 J-LN: 24.56±2.11). The number of osteopontin-positive osteocytes was significantly greater in the 640 J-LD (14.72 ± 0.82; p < 0.01) and 640 J-LN (13.62 ± 1.33; p < 0.05) groups than with D (9.82 ± 1.17) and 160 J-LD (9.77 ± 1.10) groups. Therefore, the energy density of 640 J/cm2 provided the best maintenance and integrity of the periodontal tissue microarchitecture under continuous orthodontic force when compared with the other dosages, mainly in the uncontrolled diabetic rats. The interdental distance was greater in the D and 160 J-LD groups due to presence of severe periodontitis caused by diabetes plus the mechanical stress generated by continuous orthodontic forces, implying, thus, an insufficient biostimulatory effect for the dosage of 160 J/cm2.

Microwave-induced fast decalcification of rat bone for electron microscopic analysis: an ultrastructural and cytochemical study

Bone decalcification is a time-consuming process. It takes weeks and preservation of the tissue structure depends on the quality and velocity of the demineralization process. In the present study, a decalcification methodology was adapted using microwaving to accelerate the decalcification of rat bone for electron microscopic analysis. The ultrastructure of the bone decalcified by microwave energy was observed. Wistar rats were perfused with paraformaldehyde and maxillary segments were removed and fixed in glutaraldehyde. Half of specimens were decalcified by conventional treatment with immersion in Warshawsky solution at 4ºC during 45 days, and the other half of specimens were placed into the beaker with 20 mL of the Warshawsky solution in ice bath and thereafter submitted to irradiation in a domestic microwave oven (700 maximum power) during 20 s/350 W/±37ºC. In the first day, the specimens were irradiated 9 times and stored at 40ºC overnight. In the second day, the specimens were irradiated 20 times changing the solution and the ice after each bath. After decalcification, some specimens were postfixed in osmium tetroxide and others in osmium tetroxide and potassium pyroantimonate. The specimens were observed under transmission electron microscopy. The results showed an increase in the decalcification rate in the specimens activated by microwaving and a reduction of total experiment time from 45 days in the conventional method to 48 hours in the microwave-aided method.

A preservação da estrutura de ossos é dependente da qualidade e da velocidade em que ocorre o processo de desmineralização. Neste estudo foi observada a ultraestrutura de maxila de rato descalcificada utilizando microondas. Ratos Wistar sofreram perfusão com paraformaldeído e o segmento de maxila retirado e fixado em glutaraldeído. Após esta etapa algumas amostras foram descalcificadas por imersão em solução de Warshawsky durante 45 dias a 4(0)C. Outras amostras foram submetidas a irradiação por microondas (forno de microondas doméstico 700 Watts de potência), durante 20 s/350 W/ ± 37ºC. No primeiro dia foram realizadas um total de 9 irradiações e os espécimes foram deixadas posteriormente a 4ºC por 12 h na solução descalcificadora sem agitação. No segundo dia, os fragmentos foram submetidos à nova irradiação totalizando 20 banhos, trocando-se a solução e o gelo a cada banho. A seguir algumas amostras foram pós-fixadas com tetróxido de ósmio e outras com tetróxido de ósmio e piroantimonato de potássio. As amostras foram observadas em microscópio eletrônico de transmissão. Os resultados mostraram que o processo de descalcificação ativado por microondas reduziu para 48 h o período de descalcificação, o qual pelo método tradicional ocorre em 45 dias.