Thermoflex/Hybrid

By now many of you are aware about the new kid on the block, the flexible non-metal partial. Advertisements are popping up here and there touting the benefits and superior aesthetics of these acrylic and resin designed appliances. However like so many things in dentistry they are not a one size fits all and depending on the particular teeth you have remaining and the design that will be required to fill in the spaces around them this may or may not be a suitable appliance for you.

First let us look at the advantages. Many patients are plainly unhappy to have anything metal in their mouth, sometimes due to allergic considerations, other times due to a more holistic philosophy. Also areas where metal clasping might be visual, and less desirable, the tooth colored clasps can blend in perfectly providing superior aesthetics. The flexibility of resin clasps often allow more engagement in the undercut areas of remaining natural teeth yielding a superior retention. Slightly lighter weight is another comment patients will commonly make.

Here are some of the down sides to consider. Being highly flexible this appliance has less rigid components an attribute that makes metal frames last so well. Patients with heavy bite force can sometimes overcome the stability of flex frame appliances causing them to bend out of shape. At particular risk are the rest components small tabs that fit on top of or in pre prepared grooves on the natural tooth surfaces. The intended function is to prevent the appliance from sliding down the tooth while under heavy chewing load. Rests that are made of flexible material will often give way over time. If an appliance is allowed to shift up and down a tooth, the delicate tissues that surround, call the gingival margins, can become irritated and even damaged to a point of receding. This is definitely not a healthy condition. Along with the concerns for tissue health the longevity and fit of this appliance is also put in jeopardy when rests fail. The same downward pressure begins to bow both the clasps and reciprocal arms outward. Over time this will see the appliance become very loose.

Sometimes a highbred between cast frame partials and flexible resin partials is the ideal answer. In these cases the components that truly need to be rigid, the main frame and rests, are done in metal. While the more visual areas where flexibility and aesthetics’ are important are fabricated with resin clasps. Now we have an appliance that is both stable, has good longevity and good visual aesthetics.

These are just a few of the very basic variations to consider. As with any dental appliance the key is in the right design for your mouth and your personal requirements. Regular checkups and proper maintenance remain key components to successful and healthy function with any dental appliance.