Considerations for Preparation Design and Facial Margin Placement: Part III

(For Part I of this series, click here. For Part II, click here.)

Here is a patient with malpositioned lower incisors who desires her alignment to be corrected. She has seen two different orthodontists, but refuses any orthodontic correction. In addition the incisors have varying amounts of recession, but the CEJs are intact.

The ideal solution for this patient, like many others, is orthodontic correction, but for many personal reasons she refuses treatment. A diagnostic wax up was performed and preparation guides made to assist in the tooth reduction, but what I would like to focus on in this article is the recession and the facial margin placement.

The key elements I would look at are:

1. Tooth color. The teeth are all a uniform and acceptable shade; this makes placing supragingival margins much easier. If one or several of the teeth were dark, they would require a subgingival margin to look acceptable.

2. Recession is present, but the CEJs are all intact. As long as the CEJs haven’t been undermined by erosion or old restorations, I prefer to keep my margins supragingival and above the CEJs, assuring a bond to enamel. This also always leaves open the possibility of future grafting to cover the recession.

3. Tooth length. Anytime you have recession, especially if it varies in amount from tooth to tooth, you face potential tooth length issues, especially if you extend the margin of the restoration to the gingiva. Obviously there are times do to caries, loss of the CEJ due to deep cervical lesions, or existing restorations that extend to the gingiva that you must go all the way to the tissue.

4. Lip level. These are lower incisors, and she doesn’t show the gingiva either at rest, during speech or in a high smile. This makes it much easier to use supragingival margins.

The actual margin location was determined by the left lateral incisor, the shortest tooth with the least recession. The margin location of the other incisors were prepped to match the position of the margin of the left lateral.

As with all tooth-colored restorations with supragingival margins, if you want them to be relatively invisible you will use a translucent material that is easily etched and bonded, either feldspathic porcelain (powder and liquid ceramics), leucite reinforced ceramics (Empress, Authentic), or lithium disilicate (e.max). They are then placed using a dentin adhesive and translucent resin cement, typically a light cure only cement as the restorations are highly translucent.

(Click this link for more articles by Dr. Frank Spear.)