Three dimensional evaluation of microimplants with different geometries inserted to maxillary bone by using finite element analysis study

The aim of this study was to investigate the stress disturibition on the screws and the surrounding bone as a result of the force application on the screws with different geometries used for orthodontic anchorage for different treatment modalities in three dimensions by using finite element analysis. This study based on the hypothesis that the geometric differences of miniscrews can affect the force transmitted to the surrounding bone tissue.The analysis on the 3-d modeled maxillary bone was performed by using three type of mini-screws; Neo-anchor plus (anchor plus, USA) 1.6x8 mm; Screw A, O.S.A.S (Dewimed, Germany) 1.6x8 mm; Screw B and Spider Screw (HDC Company, Italy) 2x8 mm; Screw C as defined in scenarios.In scenario 1th screws were insert for the canine retraction and 1 N force was applied. In scenario 2nd screws were inserted for the molar distalisation and 2.5 N force was applied. In scenario 3rd screws were inserted for intrusion of the incisors, and 1 N force was applied. In scenario 4th screws were inserted for intrusion of the incisors, and 0.5 N force was applied. In scenario 5th screws were inserted for the sectional molar distalisation and 2.5 N force was applied.The lowest von Misses stress values for the screws were found on screw C in all scenarios. The lowest Von Misses stress for cortical bone was recorded when screw A was used in all scenarios except scenario 4.The highest values of von Misses stress on the screws were recorded at the neck of the screws, on the first piches which corresponded to the cortical bone level. As for the bone tissue, the highest von Misses stress value was recorded on the cortical bone where the screw was inserted.Increasing the number of threats or reducing the pitch at the neck of the screws, where the maximum stress were recorded, resulted with a decrease in the von Misses stress in cortical bone whereas increasing the diameter of the mini-screw decreased the von Misses stres in the screw itself.