Biomechanical considerations - Crown length is important for retention and resistance to occlusal forces. - Characteristics of sufficient crown length include occlusal convergence, minimum height, height:width ratio, and conservation of proximal line angles. - Lack of these characteristics may require auxiliary retention methods. - Supracrestal tissue attachment, also known as biologic width, is the distance between the base of the gingival sulcus and the height of the alveolar bone. - Invasion of supracrestal tissue attachment can lead to chronic inflammation and complications.

Ferrule effect - The ferrule effect is a metal collar surrounding the dentin of the tooth. - Adequate ferrule helps resist tooth fracture and reduce stress concentration. - Beveled tooth structure does not contribute to ferrule height. - Recent studies suggest that adequate ferrule should not come at the expense of removing too much tooth and root structure. - If adequate ferrule cannot be achieved, tooth extraction should be considered.

Crown-to-root ratio - Crown lengthening decreases the bony support available for surrounding teeth. - Alveolar bone cannot be fully restored once removed. - Implications for future treatment options, such as implant placement. - Patients should thoroughly discuss treatment options with their dentist before crown lengthening. - Extraction and replacement with a dental implant may be a reasonable alternative.

Crown lengthening techniques - Crown lengthening is often done in conjunction with other dental procedures to save the tooth. - Orthodontic extrusion can be used to achieve crown lengthening. - Apically repositioned flap with osseous recontouring is a common technique. - Consideration must be given to maintaining supracrestal tissue attachment. - Symmetry of tooth length must be maintained for esthetic reasons.

Treatment planning - Replacement of unaesthetic crowns after crown lengthening and fabrication of new restorations. - Multiple treatment procedures cost time and money with potential for failures/complications. - Tooth extraction and dental implant may be an alternative treatment option. - Orthodontic extrusion can be used to achieve crown lengthening. - Consideration must be given to maintaining supracrestal tissue attachment.

SUBTOPIC: Forced tooth eruption

Indications and contraindications - Forced tooth eruption is indicated when crown lengthening is required. - Attachment and bone from adjacent teeth must be preserved. - Forced tooth eruption requires a fixed orthodontic appliance. - Problems may arise in patients with reduced dentitions. - Alternative crown lengthening procedures should be considered in such instances.

Technique and advantages - Orthodontic brackets are bonded to the teeth requiring crown lengthening surgery and adjacent teeth. - Brackets are combined within an archwire. - A power elastic band is tied from the bracket to the archwire or bar to pull the tooth coronally. - Careful checking of the tooth movement direction is necessary to avoid tilting or movement of adjacent teeth. - Fiberotomy can be performed at intervals during treatment to maintain gingival margins and crystal bone height. - Forced tooth eruption preserves osseous structure around adjacent teeth.

References: - Glossary of Dental Clinical Terms. (www.ada.org) - Ingber, Jeffrey; Rose, LF; Coslet, JG (1977). The Biologic Width - A concept in periodontics and restorative dentistry. - Al-Harbi F, Ahmad I (February 2018). A guide to minimally invasive crown lengthening and tooth preparation for rehabilitating pink and white aesthetics. - Goodacre, Charles J.; Campagni, Wayne V.; Aquilino, Steven A. (April 2001). Tooth preparations for complete crowns: An art form based on scientific principles. - Christensen, G. J. (June 2008). Esthetic Dentistry–2008.