Boota Singh Ubhi considers the potential of surgical crown lengthening.
When approaching periodontology, we often think about the health of the gingiva and the treatment or management of disease. Whilst this is the priority, it is also often necessary to consider aesthetics too. The soft tissue is integral to the appearance and function of the teeth, so optimising every aspect of it is beneficial in achieving the best possible outcomes for patients.
Soft tissue impact on treatment
The soft tissue fulfils several roles within the mouth, including protection of the tooth roots and/or dental implants, prevention of infection and improving smile aesthetics.
When assessing the gingiva either visually or with a periodontal probe, it is commonly characterised according to its biotype. Typically, it is referred to as ‘thick’ or ‘thin’ – more specifically ‘scalloped and thin’ or ‘flat and thick’ – which relate to gingival thicknesses of ≥1mm or <1.0mm respectively.
It has been proposed that gingival biotype is one of the main factors influencing the success of root coverage procedures or restorative dental treatments. Patients with a thinner gingiva are more likely to experience recession following non-surgical periodontal therapy and mucogingival problems as a result of orthodontic treatment. Tissue biotype can also affect site preparation and surgical outcomes with regards to dental implant planning and placement. All of these have the potential to impact final aesthetics, so careful consideration should be given to minimising potential soft tissue complications when working with thinner biotypes.
However, tissue thickness is not the only aspect to think about – the position of the gingiva in relation to the teeth and smile line is also important. We would typically categorise a ‘high’, ‘average’ or ‘low’ smile line, which is generally determined by how much cervico-incisal length of the maxillary anterior teeth and adjoining gingiva is visible when smiling. A high smile line reveals the entire length of the teeth with a band of the adjoining gingiva, an average smile line 75-100 per cent of the teeth with interproximal gingiva and a low smile line less than 75 per cent of the anterior teeth with no gingiva visible. Though not an exact science, there is evidence to suggest that high smile lines (or ‘gummy smiles’) are generally perceived to be less aesthetic.
Crown lengthening indications and contra-indications
According to the American Academy of Periodontology, crown lengthening is “a surgical procedure designed to increase the extent of supragingival tooth structure, primarily for restorative purposes, by apically positioning the gingival margins with or without the removal of supporting bone”.
Indications for treatment include:
- Restorative needs
- To increase clinical crown height lost due to caries, fracture or wear
- To access subgingival caries
- To produce a ‘ferrule’ for the provision of a post crown
- To access a perforation in the coronal third of the root
- To relocate the margin of restorations that are impinging on biological width
- Aesthetics
- Short teeth
- Uneven gingival contour
- Gummy smile
Contra-indications include:
- Inadequate crown-to-root ratio
- Non restorable caries or root fracture
- Aesthetic compromise
- High furcation
- Inadequate predictability
- Tooth arch relationship inadequacy
- Compromising of adjacent periodontium or aesthetics
- Insufficient restorative space
Essentially, crown lengthening can be utilised to improve smile aesthetics by increasing the amount of tooth length visible and reducing the amount of gingiva in the smile line. The most important consideration is to ensure that surgery doesn’t make the appearance of the teeth and gums worse – the crown-to-root ratio is a crucial aspect of the treatment planning process!
Another vital factor to assess and plan for is the biological width – which is the dimension of soft tissue that is attached to the part of the tooth that is coronal to the crest of the alveolar bone. This is important for periodontal health and poor management of the biological width during any treatment, including crown lengthening, can result in increased risk of periodontitis. Other possible signs of biological width violation are chronic progressive gingival inflammation, bleeding on probing, localised gingival hyperplasia, clinical attachment loss and alveolar bone loss. For a thin biotype, there is also an increased risk of gingival recession and bone resorption, while a thick biotype is associated with vertical osseous defects around the tooth and pocket formation.
Planning for success
For all these reasons and more, pre-surgical evaluation for crown lengthening must consider periodontal health and gingival biotype, root anatomy, crown-to-root ratio, the presence of caries and endodontic prognosis. This is just the beginning of successful crown lengthening treatment for the aesthetic improvement of patients’ smiles. The Surgical Crown Lengthening Hands-on course with BPI Dental & Education is a great option for any clinicians looking to significantly develop their knowledge and skills in the field.
References available on request.