The Swing-Lock® removable partial denture consists of a buccal retaining bar and a reciprocating lingual plate. The buccal retaining bar is hinged at one end and locked with a latch at the other. Combined this provides maximum retention and stability. Bertram Dental Lab has decades of experience doing such cases. Mesh or some form of acrylic retention is available on the buccal retaining bar in the event an acrylic veneer is needed or just to improve esthetics.
Columnist Jeffery Burton explains the indications for a Swing-Lock® Partial;
A Swing-Lock®-designed partial can stabilize mobile teeth and offer cosmetic enhancements. It can also add or repair facial contouring and work as a hidden clasp design partial where retaining struts are placed below or above the lip reflection lines. Swing-Lock® partials are also used when there is very little undercut to clasp and Swing-Lock® partials are very easy to add to in the future. This type of partial evenly distributes load among all supporting teeth, relieves the immediate stress on adjacent abutment teeth (as would occur with circumferential clasping), and passively engages all abutments during mastication.
The typical Swing-Lock® partial utilizes a lingual plate with a labial bar connected by a hinge on one side and latch on the other. The labial bar and struts, working in conjunction with the lingual plate, lock in and hold the anterior teeth. In many cases, this partial design can actually strengthen the supporting distal abutments because it relieves stress.
Here are the main concepts behind the Swing-Lock®:
Consider a typical distal free-end saddle partial design. As force is applied downward or
horizontally in the saddle areas, circumferential clasping crates tilting and lifting
of the critical abutments and irregularly compresses the periodontal membrane. This
stress to the abutments can cause premature failure of the appliance. Instead, the
Swing-Lock® design distributes stress evenly to all abutment teeth, reduces the amount
of downward pressure and leaves the abutment teeth in the same position.
The other cushioning effect has to do with direct downward force during mastication. This force is reduced by the engaging of the Swing-Lock® strut -- placed below the height of contour on some or all of the abutments -- and dispersed over the entire partial. This eliminates the possible dislodgment of the appliance as the abutment is forced under it. Unless the labial bar becomes unlocked, the partial will not dislodge.
The term I-Beam refers to the combination of three principle structures that give
the appliance additional strength: the labial bar and the lingual plate as the
ends and the supporting teeth as the connector. Combined, these elements make a
stronger supporting appliance that reduces the across arch displacement in a manner
similar to the Double Cushioning Effect -- by leveling the load and reducing the
initial displacement of the appliance.
A Swing-Lock® design is also beneficial when a bite problem is causing pressure and migration of unsupported teeth, making splinting (stabilizing mobile teeth) necessary. The design allows you to even out the force over all the load bearing abutments, not just individual abutments. Also, locking the abutments in a stationary position can stabilize the root of the tooth.
Other applications of the partial include using it for cosmetic reasons by combining the labial bar with a labial gum tissue veneer to either replace deteriorated gum tissue or help hide the bar itself. It can also be used as a tool in facial/lip contouring or as a reconstructing tool after surgery or trauma. In a recent article in the Journal of Prosthetic Dentistry, John Wahle, DDS, L. Kirk Gardner, DDS, and Mark Fiebiger, CDT, discuss the use of a Swing-Lock® labial bar in conjunction with a lingual hinge to allow the patient to collapse the partial to fit a smaller oral opening. In this case, the Swing-Lock® is used as a locking device to offset and secure the lingual hinge.
|Jeffery Burton is the manager of Bertram Dental Lab, Inc., a large casting laboratory in Wisconsin. He holds a BBA and has 15 years of partial casting laboratory experience.|
Reprinted from LMT - Lab Management Today magazine, May 1996