Biomechanical and morphological changes produced by ionizing radiation on bone tissue surrounding dental implant

Abstract

Biomechanical and morphological changes produced by ionizing radiation on bone tissue surrounding dental implant Objective: This study analyzed the effect of ionizing radiation on bone microarchitecture and biomechanical properties in the bone tissue surrounding a dental implant. Methodology: Twenty rabbits received three dental morse taper junction implants: one in the left tibia and two in the right tibia. The animals were randomized into two groups: the nonirradiated group (control group) and the irradiated group, which received 30 Gy in a single dose 2 weeks after the implant procedure. Four weeks after the implant procedure, the animals were sacrificed, and the implant/bone specimens were used for each experiment. The specimens (n=10) of the right tibia were examined by microcomputed tomography to measure the cortical volume (CtV, mm 3), cortical thickness (CtTh, mm) and porosity (CtPo, %). The other specimens (n=10) were examined by dynamic indentation to measure the elastic modulus (E, GPa) and Vickers hardness (VHN, N/mm 2) in the bone. The specimens of the left tibia (n=10) were subjected to pull-out tests to calculate the failure load (N), displacement (mm) up to the failure point and interface stiffness (N/mm). In the irradiated group, two measurements were performed: close, at 1 mm surrounding the implant surface, and distant, at 2.5 mm from the external limit of the first measurement. Data were analyzed using one-way ANOVA, Tukey's test and Student's t-test (α=0.05). Results: The irradiated bone closer to the implant surface had lower elastic modulus (E), Vickers hardness (VHN), Ct.Th, and Ct.V values and a higher Ct.Po value than the bone distant to the implant (P<0.04). The irradiated bone that was distant from the implant surface had lower E, VHN, and Ct.Th values and a higher Ct.Po value than the nonirradiated bone (P<0.04). The nonirradiated bone had higher failure loads, displacements and stiffness values than the irradiated bone (P<0.02). Conclusion: Ionizing radiation in dental implants resulted in negative effects on the microarchitecture and biomechanical properties of bone tissue, mainly near the surface of the implant.

Outcome of implants placed to retain craniofacial prostheses – A retrospective cohort study with a follow‐up of up to 30 years

“…The effect of ionizing radiation on peri-implant bone was confirmed by animal studies and it seems that radiation therapy negatively influences the microarchitecture and biomechanical properties of bone tissue, especially near the surface of the implant. 22,23 Earlier research concluded, though, that the survival of nasal implants is not influenced by radiotherapy. 5,12 Our study confirms this observation as an equal proportion of nasal implants were lost by irradiated and nonirradiated patients.…”

Irradiation affects the structural, cellular and molecular components of jawbones

“…Radiation affecting the vasculature of bone induces changes in the Haversian canal and sclerosis of the connective tissue in the marrow, a phenomenon which was first reported by Ewing in 1926(Ewing 1926. Investigations with long bone, and some also in jawbone, have shown that irradiation has many detrimental effects on the vasculature supplying osteogenic cells (1) reducing the blood flow by damaging vascular endothelial cells, (2) evoking a constriction and obliteration of blood vessels in the bone-forming area, and (3) diminishing the perfusion of osteogenic cells (Curi et al 2007;Poort et al 2017Soares et al 2020). In vitro studies revealed a reduced expression of vascular endothelial growth factor (VEGF), essential for blood vessel development, with doses less than 8 Gy.…”

Radiotherapy and Dental Implant Applications in Patients with Head and Neck Cancer

“…Additionally, non-healing bone necrosis during the ORN development process can trigger a series of unfavorable incidents that cause decreased implant stability and even implant loss (37). In an in vivo study, Soares et al investigated the biomechanical and morphological changes caused by ionizing radiation in the bone tissue surrounding 20 rabbit dental implants (38). The choice of rabbits was made to provide an excellent short-term analysis of the osseointegration process because of their similar Haversian systems to human beings and a three-fold faster rate of bone turnover.…”

“…Because they are more radiosensitive than other bone cells, osteoblasts are the first to experience apoptotic cell death after direct tissue damage or hypoxic/malnourished conditions caused by ionizing radiation (52). Furthermore, it is suggested RT changes collagen modulation, which in turn slows the mineralization process and contributes to implant failure (38). Ionizing radiation may also have an effect on osteoblast activity by impeding normal deposition and the production of crystals of hydroxyapatite from the inorganic matrix (53,54).…”