FEA of Treatment Success in Ball-attachment and Locator-retained Implant-supported Complete-dentures

Method: Impressions were taken from a U-shaped human mandible. Two complete-dentures were constructed for resorbed and non-resorbed ridges.

In order to accomplish FEA, the mandible, prostheses, implants and retainers were 3-dimentionally scanned and solid models were obtained using SolidWorks 2010 program. 1mm of mucosa was added. Forces of 40 N perpendicular from the incisal, 55 N from canine region in 45⁰, 150 N perpendicular from first molar and the combination of these three forces in 45⁰from the lingual were applied. Stress analysis was accomplished with ANSYS Workbench 10.0.

Result: Bone- Minimal principal stress was lower in resorbed mandible for ball-attachment group with loads from the canine region, but higher from the molar region. Loads from the incisal and combined regions generated similar stresses in the resorbed mandible. In all the loading scenarios lower stress values were observed in the higher mandibular ridge. Maximum principal stress values were lower in the locator group for the molar region. Higher stress and strain values were obtained for the resorbed mandible in all the other loading scenarios.

Implant- Higher values were obtained in the resorbed mandible with ball attachments, similar results were observed in the higher ridge for both of the retainers.

Screw and retainers- Except for the canine region, highest von Misses stresses were with retainers in the resorbed mandible. Stresses on screws were lower than retainers.

Conclusion: According to the FEA results, both retainers can safely be used in the  resorbed and non-resorbed mandibular ridges, locators would be preferable in the resorbed mandibles than ball-attachments.