Análise do efeito da fotobiomodulação em duplo comprimento de onda no reparo ósseo e na osseointegração de implantes em áreas enxertadas com osso bovino desproteinizado

Abstract

The objective of this dissertation was to evaluate different photobiomodulation (PBMT) protocols using red and infrared lasers both alone and in combination for bone repair and the osseointegration of implants placed in areas grafted with deproteinized bovine bone. Additionally, a method for automating the analysis of implant osseointegration was developed and evaluated. Chapter 1: A total of 48 rats were used and assessed over two experimental periods (30 and 90 days – n=6). A teflon capsule filled with deproteinized bovine bone (DBB) was bilaterally installed in the mandible of each animal. The groups were divided according to the type of treatment applied to the grafted area: CTR: DBB without additional treatment; IRL: DBB associated with PBMT using infrared light; RL: DBB associated with PBMT using red light; IRL/RL: DBB associated with PBMT using both infrared and red light. The following analyses were performed: Microtomography to assess the volume and microstructure of the grafted area, and Histomorphometry to evaluate the volume of new bone formation and the composition of the repaired tissue. It was observed that the IRL/RL group exhibited greater trabecular thickness than the CTR group at the 90-day mark (p < 0.05), while the CTR group showed a higher number of trabeculae than the IRL group at 90 days (p < 0.05). Regarding the histomorphometric analysis, it was noted that the IRL/RL group presented a greater amount of bone at 90 days compared to all other groups (p < 0.05) and a lower amount of soft tissue than the CTR and RL groups at 90 days (p < 0.05). PBMT with infrared and red lasers enhances repair in areas grafted with DBB. Chapter 2: Sixty-four rats were randomly distributed into 4 groups. The animals underwent grafting procedures in the tibias, and after 60 days, implants were installed. Following the placement of the implants, PBMT was performed by applying 4J around the implants in the IRL, RL, and IRL/RL groups. The groups were divided according to the irradiation protocol applied: CTR - Implants not subjected to PBMT; IRL - Implants treated with infrared PBMT; RL - Implants treated with red PBMT; IRL/RL - Implants treated with combined red and infrared PBMT. After 15 and 45 days, the animals were euthanized (n=8). Through microtomography, analyses of the amount of mineralized tissue around the implants (BV/TV%), microstructure of the bone tissue (Thickness, spacing, and number of trabeculae - Tb.Th; Tb.Sp; and Tb.N) were conducted, and through histomorphometry, evaluations were carried out the osseointegration (Bone and implant contact - %BIC and Bone between the threads - 10 %BBT). The IRL/RL group presented better BV/TV% values, while the RL group showed better Tb.N values when compared to the CTR group at 45 days (p < 0.05). The IRL/RL group had better BV/TV% and Tb.N values than the CTR group at 45 days (p < 0.05). Although no statistical difference was found, the IRL/RL group exhibited higher %BIC and %BBT. The combination of red and infrared lasers increases the amount of mineralized tissue, which has been associated with an increased number of trabeculae around implants installed in grafted areas with OBD. Chapter 3: %BIC (bone-implant contact) and %BBT (bone between the threads of the implant) were analyzed using histological slides of implants installed in the tibias of 40 rats through the manual method and the ImageJ software. In the automated histomorphometric analysis method, the similarity of the RGB color channels was analyzed and the black background region of the image was excluded to select the region of interest. The contour curve was extracted by excluding points that did not belong to the contact between the implant and the bone, i.e., the edges of the image. A Gaussian filter was applied to smooth small imperfections in the curve. An analysis of the points of the curve in relation to their neighboring points was conducted, and the local maximum of the curve was selected, excluding points that were too close and keeping only those that represent the peaks of the implant curve. The peaks and the corresponding portion of the curve were used to select the region of the original image and calculate the %BIC and %BBT values. A comparison of the results obtained for both parameters in both evaluation methods was then performed using the Pearson correlation test. A strong correlation between the analyses was observed (r = 0.99) (p < 0.05). Thus, the proposed automated histomorphometric analysis method proved to be reliable for assessing the bone integration of implants. Overall, this study concluded that dual-wavelength laser therapy improved bone repair in areas grafted with OBD, but did not improve the integration of implants installed in those areas. Furthermore, the proposed automation method proved to be reliable for the assessment of implant integration.