Comparision of the eruption of the maxillary impacted canine teeth using ballista spring and elastic thread procedures by finite elementh method

The maxillary canines are the most frequently impacted teeth following the third molar. Preserving the surrounding periodontium and keeping the erupting force within the normal physiologic force limit is as important as while traction of impacted tooth. The finite element analysis method has considered to be an effective computerized method in simulation which is ferequently used in engineering for solving the stress and strain problems. It has recently been used in orthodontics for determining areas of stress distribution on the teeth and the adjacent periodontal structures. In our study, effects of ballista spring and elastic thread on the surrounding periodontial tissues has been compared, as they both considered to be the most frequently used methods for stimulating eruption of impacted teeth in our clinics . For this purpose, force has been applied to two different impacted canine models by using elastic thread which was attached to the arch wire, and by balista spring which was made from 0.016 inch stainless steel wire. Results were compared by finite element analysis. It has been found that the compression and tensile stress values on the impacted canine, anchor teeth and adjacent periodontal tissues are higher in the elastic thread model than in the balista spring model,inspite of applying equal force in both groups . The concentrated stress in the left posterior region following force application by using ballista spring method, resulted in tipping force especially on the first premolar and the first molar teeth. Thus, tipping movement of the teeth adjacent to the impacted canine was considered to be the most obvious disadvantage of using elastic tread, while in balista spring model tipping of the posterior teeth found to be most significantly happened. Key words: ballista spring, elastic thread, finite element, maxillary impacted canine, tooth eruption.