How To Design and Incorporate Ball Attachments into an Overdenture Framework?

I strongly suggest that you take the Misch prosthetics course.

There are some problems with "O" ring (ball) attachments which include: a need for greater interarch space to accommodate the attachments height, due to the increased height any divergence between attachments is magnified which can lead to lateral stresses on the fixtures when the prosthesis is inserted. The fallacy i that the Ball attachment allows rotation in all directions under load. This would be true if you had an edentulous arch and only 1 fixture with attachment was present but as soon as you have two or more attachments the rotational motion is limited. Attachments that have lower heights to the gingiva allow less stress on the fixtures then taller attachments when the denture is inserted and also require less interarch height allowing more denture acrylic to be placed over them and allowing longer life to the denture without the need to repair it.

The "O" ring attachments seem to do better with patient has a severe bone or ridge resorption.

Don't believe everything you hear. Implants, properly integrated--especially in the mandible--are much stronger than the forces from a Locator attachment. This attachment is very popular because it works great! The only torque problem could come from improper processing. The side walls of the abutment--if it is at all above tissue height--must be blocked out. Your lab should know this. I have been doing removable lab work for 32 years and now do almost exclusively implant restorations. The greatest success I've seen with free standing implants is the Locator abutments. Also, as Dr. Kurtzman wrote in the previos comment, the vertical height of the ball attachment can cause problems in some cases. I have no ties to any implant or attachment manufacturer.

I agree with the above posts. Locators are the way to go. I personally like to deliver them one by one chairside.