Don't export STL from Solidworks to send to Ansys, that is an inferior method.
Export Parasolid from Solidworks to send to Ansys, that is a superior method.
If you open the Parasolid file in SpaceClaim, use the Repair tab and check for Extra Points and Extra Edges.
Sometimes the mesher will have an easier time meshing if you slice the part up. For example, you could create two planes through the center axis and each "tooth". Use Split Body, then on the Workbench tab, use Share to have the mesh share nodes on the coincident faces created.