FINISH LINE IN FPD FOR PARTICULAR TEETH

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 PERIO IMPLICATIONS OF RESTORATIVE MATERIALS AND MARGIN PLACEMENT

Dental crown restorations are considered a major contributing factor in the etiology of periodontal disease. Löe²⁴ in his classic 1968 paper, reviewed the reactions of the periodontal tissues to restorative procedures. His paper reviewed the reactions of the periodontal tissues and the effect of certain restorative materials on the periodontal tissues. 

While optimal periodontal health is expected to the improve success of dental care, it cannot overcome the effect of a crown restoration that extends into the subgingival area and may be responsible for causing damage to the periodontal tissue. This can occur by increasing the possibility for mechanical retention of bacteria and/or by a direct irritation effect from using a restorative material that retains more dental plaque.

Amsterdam²⁵ wrote a classic treatise on periodontal prosthesis more than 30 years ago, establishing the standard of care for a crown. He described the optimal margin/finish line which should be placed in a healthy sulcus at a minimal depth, just shy of the junctional epithelium. In guidelines still followed today, he suggested that to prevent plaque buildup, it is necessary to create optimal crown contours with proper coronal form, embrasure form, and subgingival fit at the margin.

If periodontal health is to be considered the future of success for dental care, it is imperative to use restorative materials which can help maintain a healthy periodontium. Captek (Argen) provides one example of a cosmetic (crown) restorative material that is compatible with excellent periodontal health, helping to satisfy the goal of optimal tissue health. This ceramometal crown incorporates the use of a unique metal composite gold cosmetic coping. The metal can be extended to the edge, developed into a collar, or cut back from the margin for a ceramic butt margin depending on the preparation, margin placement, and/or underlying prep tooth color. When the Captek gold was in the approximation of the margin, Goodson et al²⁶ were able to document a reduction of up to 91% in the number of bacteria surrounding this tooth versus normal tooth surfaces in the same mouth. In addition, they documented 96% less bacterial adhesion compared to conventional ceramic-fused-to-noble-metal crown restorations. These crowns have been described by the author as the "periodontal crown,"²⁷ since healthy tissue can be achieved from placement of the 22K gold margin against the subgingival tissue on any periodontally-affected tooth (Figure 4). 

For success to be achieved in dental care, it is essential that materials be fabricated in a manner that makes every attempt to develop periodontally healthy crowns, so as to prevent and/or reduce tissue inflammation. With the introduction of zirconia metal-free crowns, produced from pucks made from high quality zirconia powder (produced by TOSOH), the author employs a coping design modification to maximize soft-tissue health and protection against inflammation. One benefit of zirconia crowns is that they can be adapted to accommodate multiple finishlines at the margin, much like a traditional PFM. The "Periodontal Collar" for zirconia crowns was designed by the author and fabricated by Shaun Keating, owner of Keating Dental Arts Lab. (This dental laboratory was selected by Dr. Gottehrer based on its ability to reengineer new technology successfully.)

The collar is designed to allow removal of bacterial plaque on a regular basis to maintain optimal periodontal health. The subgingival collar is polished using a special material and, because of the special polishing process a very smooth surface is established. 

Preliminary observations by Dr. Gottehrer and Keating Dental Arts Lab, with insertion of 50 Periodontal Collar zirconia crowns, have produced healthy gingival responses. The zirconia can be made in a CAD/CAM environment and offers benefits in the way of high hardness factors and fracture resistance. Becoming more familiar with the healthiest coping designs can create optimal periodontal health resulting in long-term success. 

Restoring a tooth with compromised periodontal health with an appropriate full-crown, using modern materials that are shown to reduce the risk of additional plaque retention or a negative inflammatory response, should now be considered the treatment of choice for maintaining prolonged dental health.