Effect of fibula flap positioning on biomechanical properties of prosthetic structures supported on dental implants in patients with segmental mandibular defects

Background. Defects of the lower jaw can be formed after surgery due to a tumor process and also be the result of gunshot wounds to the maxillofacial area. The use of vascularized combined fibula flaps is clinically effective and obvious from the standpoint of choice. The positioning of the bone graft relative to the preserved part of the lower jaw determines the option for further dental implant procedure and high-quality prosthetic treatment. However, each of the fixation positions has its advantages and disadvantages. The goal is to study the peculiarities of the stress-strain state of bone tissue of a fibula free flap that replaces a segmental defect of the jaw in a model experiment. Materials and methods. The method of simulation computer modeling of the stress-strain state of the lower jaw with segmental defects replaced in different ways after the prosthetic rehabilitation of patients with fixed structures supported on dental implants was used. In total, 4 models were generated and calculated, reproducing 2 types of geometry and 2 types of loading. Results. In bone tissue, stresses were concentrated around the first 2–3 turns of the thread with maximum values around the first turn. In the implant itself, the stresses were concentrated in the area of the abutment. It was found that under conditions of vertical and horizontal loading, which corresponds to the occlusion under phy­siological conditions of chewing load, the location of the fibula flap in the area of the base of the alveolar process was associated with a decrease in the maximum values of equivalent stresses in implants by 16–63 %. In bone tissue, load reduction occurred by 30–53 % compared to the model where the bone graft was located along the lower edge of the jaw. Conclusions. With a higher location of the bone component of the fibula flap, adequate stress-strain state conditions and normal distribution of local loads occurred, which obviously determines a better prognosis of osseointegration, survival and functioning of dental implants.