Molecular Structure of the Bony Tissue after Experimental Trauma to the Mandibular Region followed by Laser Therapy

Abstract

Objective: We investigated the therapeutic efficiency of laser irradiation and Bio-Oss, both and separately, on the post-traumatic regeneration of bone tissue in rats using infrared spectroscopy as an informative and accurate measuring method. Background Data: The therapeutic effect of low-power laser irradiation on bone tissue regeneration processes in animal models has been studied using morphogenic, biochemical, roentgenographic and electron microscopic measurements. Natural bone minerals, such as Bio-Oss collagen, were recommended for the reconstruction of bone defects in the alveolar process. Materials and Methods: 29 male Wistar rats, divided into four random groups in a blinded manner were operated on the right alveolar process. A bone defect was made by penetrating the right alveolar process of the mandible bone using a 3-mm drill. The rats were divided into four groups as follows: Group I, left side served as intact bone and right injured side as the control; Group II, right injured side was treated by organic bovine bone (Bio-Oss); Group III, right side bone defect was treated by HeNe laser (632.8 nm, 35 mW) applied transcutaneously for 20 min to the injured area daily for the following 14 consecutive days; and Group IV, Bio-Oss was placed loosely in the right side defect followed by laser treatment. After 2 weeks, the intact bone and bone replicas of the trauma area were removed and analyzed by infra-red spectroscopy technique. The composition and the structure of the bone tissue mineral substances were determined and compared among the four groups. For quantitative analysis of the regenerative bone process, the Mineralization index was used. An increase in this index indicates regenerative bone processes. Results: The normal state analysis of the IR spectra of the normal alveolar bone tissue within the intervals of 400 to 4000 cm^-1 revealed characteristic absorption bands for the inorganic bone component in spectrum regions 450–1480 cm^-1, and the organic component at 1540–3340 cm^-1. In the case of trauma, the intensity of absorption of the inorganic component was decreased by 54%, and the absorption band became narrow, which can be interpreted as quantitative changes of the bone tissue mineral content. The wavelength characteristics of the inorganic component remained unchanged; that is, the induced trauma under these experimental conditions did not provoke alterations in the structure of the phosphate framework. The organic component showed decreased absorption by 10–15%, compared to the normal bone, and slight displacement of the wavelength, which can be interpreted as changes occurring in the quality of the organic content of the bone tissue. In the Bio-Oss–treated group, the intensity of absorption of the inorganic component increased by 43%, compared to the control injured area; however, there was a decrease of 22.6% in the normal bone. The wavelength characteristics of the inorganic component remained unchanged. The organic component showed similar absorption results in the injured non-treated group and absorption was 10–15% less than in the normal bone. Mineralization Index in the Bio-Oss–treated group was 0.93, compared to 0.63 in the control group and 2.04 in the normal bone. In the laser-treated group, the intensity of absorption of the inorganic component increased by 62, compared to the control injured area, and decreased only 11.4% in the normal bone. The wavelength characteristics of the organic component remained unchanged; that is, the organic component was similar to that of normal bone. Mineralization Index in the laser-treated group increased significantly to 1.86, compared to 0.63 in the control group and 2.04 in the normal bone. In the combined laser and Bio-Oss–treated groups, the intensity of absorption of the inorganic component and organic component was similar to that of normal bone. Mineralization Index in this group increased significantly to 1.98, compared to 0.63 in the control group and 2.04 in the normal bone. Conclusion: The results suggest that low-power laser irradiation alone and in combination with Bio-Oss enhances bone healing and increases bone repair.