What is a Precision Attachment?
A precision attachment is a precision-machined male and female (key and lock) housing that connects a removable partial denture to fixed bridgework in cases where the fixed bridgework is not possible.
What are the Advantages of Precision Attachment Cases?
Precision attachment partial dentures are the very best restorations where fixed restorations are contraindicated. Several key advantages of this type of restoration:
• Cosmetic Appearance, avoids the need for unsightly clasps
• Maintainable Periodontal Health
• Longevity of Abutment Teeth
• Patient Comfort
• Questionable Teeth can be saved in a way that does not affect the case
• Longevity if they are lost in the future.
• Natural Tooth and/or Implant Abutments can Be Used
• Precision Attachment Partial Dentures Can Be Adapted to Compensate for Future Changes in the Mouth
• Prevent bone resorption of the ridges under the partial denture
• Confer the highest degree of patient comfort.
Even though there are no locking mechanisms, a good precision attachment partial denture will not dislodge during normal function. The reason the partial denture does not continually fall out is because it is surveyed in two directions so that the path of insertion is different from the pull of the muscles and the action of the tongue and gravity. Although the partial cannot be dislodged during function, it can move in a vertical direction slightly to release the forces instead of passing along these forces to the abutment teeth. The result is physiologic stimulation of the abutment teeth and the edentulous ridges. Clinical experience has shown that this physiologic stimulation results in increased longevity of the abutment teeth, even when a few teeth are required to carry the load of an entire arch. The stimulation of the edentulous ridge also prevents the bone resorption that typically reduces tissue support for the partial denture. The tissue under a well-fitting precision attachment partial is typically healthy and firm. There is surprisingly little wear of attachments that are used in this manner, even after many years of function! While the prosthesis may require relining or alteration of the occlusion to compensate for changes, it is rarely necessary to adjust or replace the attachments on the partial. The partial denture is never kept in a glass overnight. It is worn 24 hours a day to prevent collapse of the musculature and the occlusion and only removed for cleaning and hygiene.
IMPLANT RETAINED PRECISION DENTURES
Implants are sometimes used to retain a full denture if not enough implants can be placed to create a full arch of fixed bridge work. However, implants are quite strong and have been used successfully to support precision attachment cases for over 14 years. Because precision attachment cases work so well on the weakest teeth imaginable, they work exceedingly well on implants, which are usually strong.
An implant- supported precision attachment partial denture is far superior to an implant-supported full denture for the following reasons:
• Superior Comfort and Self-Esteem. The posterior bar can be made thin and only covers a small area of the palate, while a denture usually covers the entire palate. The patient wearing an attachment case has anterior (front) teeth that do not come out, unlike the patient wearing a denture. He or she doesn’t feel bad looking in the mirror when removing a partial denture for hygiene.
• Superior Function. Unlike a denture, the posterior bar of an attachment case frees the tongue for normal speech and allows taste buds on the anterior palate to function normally. An attachment case doesn’t have the anterior-posterior movement that an implant supported denture might have. Patients with an attachment case on implants can bite into anything. This may not be possible with any type of denture.
• Increased Longevity. A precision attachment case does not place lateral forces on implants, which can be destructive to implants as well as natural teeth. Implants are not indestructible and if overloaded they can fail. A denture connected to implants, however, is usually locked in place.
• Patients Avoid Wearing Dentures. A denture that rests on tissue can only exert 10 to 15% of the force of a patient with natural teeth. Although the placement of implants may make wearing a denture easier, most people don’t want to go through the surgery and expense unless they are going to get rid of the denture. Patients who wore an attachment case prior to wearing a denture know the difference between the two, and they are thrilled that they can have the same exact case on implants.
• Both Natural and Implant Abutments Can Be Used. Single posterior teeth that remain from a previous attachment case can be left intact, and used as part of the new attachment case! Unlike fixed bridgework, a precision attachment partial denture can link both implant and natural abutments because of the stress-breaking action of the attachment case.
• Patients Choose Implants to Avoid Wearing Dentures. Implants can usually be placed in the upper and lower anterior regions of the dental arches. The placement of just three implants is enough to make a fantastic attachment case—an anterior fixed bridge and a precision attachment posterior partial denture.
A common misconception is that implants make precision attachments dentures obsolete. The rationale for using implants with attachments is that placing enough implants for a full arch of fixed bridgework may not be possible for the following reasons:
• Anatomical Problems: Most of the anatomical problems encountered for placing implants are in the posterior regions of the mouth. Inadequate bone under the sinus (upper arch) or above the mandibular nerve (lower arch) may make it impossible to place implants of adequate length to support fixed bridgework.
• Bone Grafts: The prognosis for success is lower when bone grafts are required for implant placement and the duration of treatment is much longer. Candidates for these procedures are patients who understand the risks and accept them in order to have fixed bridgework.
• Bone Quality: The bone in some areas of the mouth may have poor quality for the placement of implants. The lowest quality bone is typically found in the upper arch-posterior molar area.
• Fixed Bridgework with teeth cantilevered may be inappropriate. Studies have proven that four or five implants in the anterior region can be used with cantilevers (unsupported teeth added) to create a successful case.
Even though the cantilever fixed bridges work well with implants, they may not be the best option if:
• Anatomical deficiencies prevent the placement of sufficient implants to support fixed bridgework.
• The patient has been comfortable with an attachment case in the past.
• The patient does not want too many implants placed. Patients who do not want the extra surgery and expense of multiple implants are very receptive to the placement of only three implants to restore an entire arch.