Tooth Preparation Using Guide Pin Instruments and the Biological Width

Previous surveys have shown that subgingival restoration margins generally lead to significant inflammation of the marginal periodontium 6, 13, 16, 17 and, inter alai, trauma of the “biological width”. This term is defined as the area of the coronal periodontium of the limbus aleovaris, which consists of the connective tissue and epithelial attachment as well as the gingival sulcus (Figure 1a). It is assumed that, physiologically, these structures each extend approximately 1 mm vertically. The biological width of a healthy periodontium therefore has a dimension of approximately 3 mm in total – . An injury to this area, caused, for example, by a subgingival preparation placed too deeply, will irritate the marginal periodontium. As a general rule, this is followed either by recession or by persisting gingivitis/periodontitis 6, 7, 10, . For this reason, it is desirable to always place restoration margins supragingivally. However this is frequently not possible due to defective morphology as well as for aesthetic reasons 9, particularly in the anterior region. The subgingival placing of a restoration margin required in such situations must therefore be carried out as atraumatically possible taking into consideration the biological width. It is important to ensure that the biological width follows the shape of the alveolar bone, i.e. that its arch corresponds to the circular contour of the cemento-enamel junction. (Figure 1b) . The contour of the healthy gingiva serves as a guide. When preparing intrasulcular restoration margins, these should not be embedded deeper than 0.5 mm in the sulcus, thus avoiding possible injury to the soft tissue and epithelial attachment 1, 9, . Should the retention not be sufficient due to a short clinical crown, a surgical crown extension should be performed prior to restoration, in order to prevent a subgingival preparation from extending into the area of the biological width. The restoration of the tooth can be carried out approximately 8 – 12 weeks after such surgical crown extension. At this point, the healing process of the periodontium is almost complete, clinically as well as histologically . In practice, the preparation of a chamfer has proved successful 9, 13 for crown restorations. Diamond grinding instruments with non-coated guide pins are particularly suitable, causing TOOTH PREPARATION USING GUIDE PIN INSTRUMENTS AND THE BIOLOGICAL WIDTH