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.
Highlights
Diabetes Mellitus (DM) is a chronic metabolic disorder characterized by a defect either in the secretion or in the action of insulin, or both, leading to chronic hyperglycaemia and disturbances of carbohydrate, fat and protein metabolism.[1,2] Hyperglycaemia over a long period results in various classic complications, including periodontopathy.[1,3,4,5,6] Several studies have demonstrated significant alterations to bone and mineral metabolism, which are related to the following factors: decrease of osteoclasts and osteoblasts, enhance of apoptosis of osteoblasts, and reduces osteocalcin synthesis
The energy density of 640 J/cm[2] 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, an insufficient biostimulatory effect for the dosage of 160 J/cm[2]
Summary
Diabetes Mellitus (DM) is a chronic metabolic disorder characterized by a defect either in the secretion or in the action of insulin, or both, leading to chronic hyperglycaemia and disturbances of carbohydrate, fat and protein metabolism.[1,2] Hyperglycaemia over a long period results in various classic complications, including periodontopathy.[1,3,4,5,6] Several studies have demonstrated significant alterations to bone and mineral metabolism, which are related to the following factors: decrease of osteoclasts and osteoblasts, enhance of apoptosis of osteoblasts, and reduces osteocalcin synthesis These processes lead to extensive bone loss and, as a consequence, impaired bone turnover and formation.[3,6,7,8] Alternative therapies have been proposed to stimulate alveolar bone remodeling and to favor a better response in gingival and periodontal ligament tissues, especially in the supported treatments for orthodontics. The photobiomodulation (PBM), previously known as low-level laser therapy (LLLT), has showed great effectiveness due to its analgesic, anti-inflammatory and photobiostimulatory properties, resulting in a faster tooth movement with no periodontal tissue side effects.[9,10,11,12,13,14,15,16,17] one of the key issues is to find an appropriate energy density for different experimental and clinical trials
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