Comparative evaluation of cylindrical and conical implants performed with alveoler ridge expansion technique and new generation wedge shaped blade implant applications in posterior resorbed mandible with finite element stress analysis method

Intraosseous implants, which are used in the treatment of partially and completely edentulous patients, have been preferred by patients and dentists with successful results in the last 50 years. Bone tissue resorption caused by tooth deficiency, especially the decrease in bone width in the horizontal direction, makes it difficult to apply standard diameter implants. This situation requires different invasive bone augmentation procedures. Alveolar crest split, distraction osteogenesis, and autogenous bone grafting, which are performed to gain bone in the horizontal direction, are successful at varying rates. However, it is known that these techniques increase patient morbidity, prolong the duration of treatment and increase the economic cost. In this study, the alveolar crest split technique followed by placement of cylindrical and conical implants are compared with the blade implant applicatıon without interfering with the alveolar bone width. As a comparison method, Finite Element Stress Analysis method was preferred instead of invasive techniques applied in living tissue. Three-dimensional models of the mandible bone with a horizontal width of 4 mm were created using a three-dimensional computer-aided software program. Simulating the alveolar crest split process in two of the models, a conical implant with a diameter of 4.1 mm and a length of 10 mm was placed in one model. In the other model, after the same procedure, a cylindrical implant with a diameter of 4.1 mm and a length of 10 mm was placed. In the third model, a wedge-shaped blade implant of 11 mm in length with 1.8 mm buccolingual and 5 mm mesiodistal width was placed without interfering with the bone width. In all models, a force of 100 N in the buccolingual direction and 100 N in the vertical direction was applied to the central fossa of the computer- designed crown at an angle of 30 degrees. Stress values created by the applied forces to the bone and implants were evaluated with FEA method. The stress values formed as a result of oblique forces in all three models were higher than the stress values resulting from vertical forces. It has been observed that the stresses are concentrated in the cervical parts of the implants and the region of the cortical bone surrounding the implant neck. Compressive stress in all models was higher than tensile stress. Von Mises stress values in the blade implant were 20% higher than the values in other implants. These values were below the resistance value at which the titanium alloy undergoes irreversible deformation. Based on the results, it can be said that the stress values in the blade implant model is tolerable. Considering the disadvantages and complications of the alveolar ridge split procedure, blade implants offer a good alternative to eliminate them. The application of the blade implant system we have chosen with piezosurgery, not with conventional rotary instruments, also provides an advantage in living tissue. Although the FEA method gives close results to the results in the tissue, it cannot express the situation in the tissue exactly because it accepts some procedures as a standard. In this study, we concluded that new clinical studies are needed to support the results obtained with the computer model with the results in the tissue. We think that the data obtained in our study contribute to the literature and form the basis for future clinical studies. Key words: Wedge – shaped blade implant, Finite Elements Analysis, Posterior resorbed mandible, Alveolar crest-split