Crown lengthening

Surgical crown-lengthening procedures are performed to provide retention form to allow for proper tooth preparation, impression procedures, and placement of restorative margins and to adjust gingival levels for esthetics.

A palatal view of a maxillary premolar during a crown lengthening procedure

Biologic width

It is important that crown-lengthening surgery is done in such a manner that the Biologic width is preserved. The Biologic width is defined as the physiologic dimension of the junctional epithelium and connective tissue attachment. This measurement has been found to be relatively constant at approximately 2 mm (±30%). The healthy gingival sulcus has shown an average depth of 0.69 mm. It has been theorized that infringement on the biologic width by the placement of a restoration within its zone may result in gingival inflammation, pocket formation, and alveolar bone loss. Consequently, it is recommended that there be at least 3.0 mm between the gingival margin and bone crest. This allows for adequate biologic width when the restoration is placed 0.5 mm within the gingival sulcus.

Biologic width is the natural distance between the base of the gingival sulcus (G) and the height of the alveolar bone (I). The gingival sulcus (G) is a little crevice that lies between the enamel of the tooth crown and the sulcular epithelium. At the base of this crevice lies the junctional epithelium, which adheres via hemidesmosomes to the surface of the tooth, and from the base of the crevice to the height of the alveolar bone (C) is approximately 2 mm.

Procedure

Surgical crown lengthening may include the removal of soft tissue or both soft tissue and alveolar bone. Reduction of soft tissue alone is indicated if there is adequate attached gingiva and more than 3 mm of tissue coronal to the bone crest. This may be accomplished by either gingivectomy or flap technique . Inadequate attached gingiva and less than 3 mm of soft tissue require a flap procedure and bone recontouring. In the case of caries or tooth fracture, to ensure margin placement on sound tooth structure and retention form, the surgery should provide at least 4 mm from the apical extent of the caries or fracture to the bone crest. With the advent of predictable implant dentistry, it is important to weigh carefully the value of crown lengthening for restorative ease as opposed to tooth removal and replacement with a dental implant.

Crown lengthening Resources
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