Principles of Attachment Selection

One of the most confusing issues for dentists is choosing the appropriate attachment assembly for implant overdenture cases. They usually ask themselves many questions when it comes to selecting the right attachment assembly. First, which attachment should one use? Would a bar or stud attachments be best? Depending on the answers to those questions, more considerations follow. For instance, which bar or stud would be best for this particular case? Learning about the mechanical properties and the load distribution characteristics of different attachments is the easiest way to determine which one to use. Most available attachments demonstrate different levels of resiliency. Attachment resiliency is associated with the movement between the abutment and the prosthesis in a predetermined direction or directions. The more directions or planes in which the prosthesis can move, the less stress is placed on the implant, in turn transferring more forces to the residual ridge. That being said, the attachment is more resilient. Various Movements Allowed by Resilient Attachments Vertical Movement: The prosthesis is allowed to move bodily toward the tissue. This type of movement results in even loading and support from the entire anterior-posterior length of the residual ridge. Typically, movement is stopped by the supporting structure of the residual ridge, meaning as soon as the prosthesis comes into contact with the residual ridge and passes the resiliency of the soft tissue, it stops. Hinge Movement: Hinge movement is that in which the prosthesis revolves around an axis that has been formed by the most posterior attachments on each side of the arch. Rotation Movement: Rotation movement allows the prosthesis to rotate around an axis that runs anterior-posteriorly. Anytime masticatory forces are applied to one side of the prosthesis, it rotates around the crest of the ridge, and the opposite side rotates up and across the arch. Translation and Spinning or Fishtailing: In this type of movement, the prosthesis moves in an anterior-posterior movement, or a bucco-lingual direction, without any