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 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 | |
|---|---|
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| MeSH | D016556 |
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.
