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.

Crown lengthening (Wikipedia)

Crown lengthening is a surgical procedure performed by a dentist, or more frequently a periodontist, where more tooth is exposed by removing some of the gingival margin (gum) and supporting bone. Crown lengthening can also be achieved orthodontically (using braces) by extruding the tooth.

Crown lengthening
A palatal view of a maxillary premolar during a crown lengthening procedure.
MeSH	D016556
[edit on Wikidata]

Crown lengthening is done for functional and/or esthetic reasons. Functionally, crown lengthening is used to: 1) increase retention and resistance when placing a fabricated dental crown, 2) provide access to subgingival caries, 3) access accidental tooth perforations, and 4) access external root resorption.^{[citation needed]} Esthetically, crown lengthening is used to alter gum and tooth proportions, such as in a gummy smile. There are a number of procedures used to achieve an increase in crown length.