Purpose: This study was an in in-vitro study conducted to compare the stress distribution pattern in implant retained maxillary obturators with three different attachment systems with the aid of three dimensional finite element analysis.
Methods: CT scan was made for a patient with hemi-maxillectomy defect. The CT scan file was exported to a personal computer with Materialize Mimics 10.01 program (Materialize, interactive medical image (Materialize Leuven, Belgium). Mimics were utilized to modify the CT scan of the maxilla to construct 3-D model with Solid Works, Concord, Massachusetts, USA) for finite element stress analysis. All components of the models were constructed thereafter, superimposed till construction of maxillary obturator models. Three implants were inserted in the alveolar bone on the intact side. Ball & Nova-lock locator/ bar attachment systems were simulated according to their structural configurations. A static load of 100 N load was applied vertically & obliquely on the defect side. ANSYS program (Canonsburg, PA, USA) was utilized to solve the problems, The resultant Von Misses stresses in bone surrounding implants were evaluated and compared in the 3 studied models.
Results: The highest Von Misses stresses were found in cortical bony layers around the implant adjacent to defect & the least stresses at the area of 3rd implant. Nova-lock retained implant obturtors had recorded the least Von Misses stresses (20. 479 &21.675 Mpa) in comparison to Ball (40.762 & 41.488 Mpa) & locator bar attachment systems (43.526 & 47.203 Mpa) under vertical & oblique load application respectively. All models had shown the highest stresses on oblique load application on the defect side.
Conclusions: Within the limitations of this study various conclusions could be drawn:
The load direction has more important role than the attachment type in stress distribution pattern in implant retained maxillary obturators.
Nova- lock attachment system may induce the least stresses onto implant/ bone interface followed by Ball & locator bar attachment systems.
The Locator/ bar attachment may allow better stress distribution in implant retained maxillary obturators than other Bar systems.