Reinforcing plastic with fiber is certainly not new. Probably the best known is the generic term fiberglass, which of course, is used to make numerous products. Composite reinforcement fibers are materials that presumably increase the flexural strength and thus help resist fracturing of high stress restorations and appliances such as bridges (definitive and provisional), natural tooth pontics, endodontic posts and cores (direct and lab-fabricated), periodontal splints, orthodontic retainers, and even dentures. Reinforcing various types of restorations/prostheses with a fiber is a reasonably simple technique to gain strength and will be necessary until composites are developed that are intrinsically much stronger.
For these materials to function properly, it is believed that they must be incorporated into the restoration during its initial fabrication and not merely added on after the fact. In other words, the reinforcement material must be completely integrated into the resin before any curing takes place.
When a reinforced restoration fails, it is rarely catastrophic. Usually the resin will fracture, but the fiber will hold the restoration together. In this vein, most of the failed restorations as reported from an Editorial Team survey point to bridges as the one most likely to fracture.
One universal problem is that the ends of these materials tend to fray. However, once resin is incorporated into them, this problem can be minimized. Another problem is when you try to repair a fiber-reinforced restoration that has fractured. If you try to roughen the surrounding composite with a sandblaster, the remaining fiber has a tendency to turn black. Roughening the adjacent composite with a coarse diamond instead of a sandblaster will usually solve the problem.
Some of these materials can either be used directly in the mouth or used in the fabrication of an indirect restoration. Others are only designed for laboratory fabrication of indirect restorations. In general, fabrication on a model is easier than direct use. Even though each material has its own peculiarities, the general principles are similar.
Procedure for Periodontal Splint or Orthodontic Retainer
Step 1 Decide what length you need by using deadsoft matrix material, which can be adapted to the surfaces of the teeth to be included and pushed into embrasures to simulate the final position of the fibers. Then remove the deadsoft material and measure its length. This then becomes the length of the fiber that will be necessary to complete the splint.
Step 2 Treat the fiber as indicated by the manufacturer.
Step 3 Etch the teeth, apply an adhesive, and place a thin "ribbon" of composite on the teeth that are to be splinted.
Step 4 Carefully adapt the reinforcement material into the composite, which should help in preventing the fiber from rebounding off the teeth. Push the fiber into the embrasures and as close to the surfaces of the teeth as possible with an instrument and/or your clean, gloved fingers that have been lubricated with unfilled resin. Cure each area that your light tip covers for 10 seconds.
Step 5 Apply another layer of composite over the fiber-reinforced layer to completely cover any exposed fiber, including the facial embrasures. Cure again 20-40 seconds for each light coverage area.
Step 6 Smooth the cured splint with finishing burs and/or finishing discs followed by rubber polishing instruments for further smoothing and polishing. Finish with polishing paste if necessary.
The same type of splint can also be made extraorally on a conventional gypsum study model or a flexible model made from a stiff elastomeric impression material. If you use a study model, be sure to lightly lubricate it with a water-soluble separating medium before applying the first layer of composite.
Once the splint has been cured and removed from the model, sandblast its tooth surface prior to taking it to the mouth.
NOTE: Most of these materials are white, but tend to become translucent when incorporated into the restorative material.