The most significant factor in the long term
prognosis of a restored tooth is the preservation of a healthy periodontal
The best restorative margin is placed coronal
to soft tissue. It is cleansable and can be maintained more easily.
The term "biologic width" denotes
the combined connective tissue- epithelial attachment from the crest of the
alveolar bone to the base of the gingival sulcus. This includes the width of
supra-alveolar connective tissue fibres (average 1.07) and the junctional
epithelium (average 0.97), which totals an average of 2.04 mm.
During placement of restorative margins, an
additional 1-2 mm of sound structure coronal to the epithelial attachment is
needed, hence the minimum distance between the alveolar crest and the
restorative margin should be 3-4 mm (to allow a gingival sulcus of approx. 1 mm)
This can be determined radio graphically.
Impinging on this width by a restoration will
trigger loss of bone and epithelial attachment. An interproximal encroachment
leads to osseous crater that will be unmanageable from oral hygiene standpoint.
The width of keratinized gingiva needed to
maintain periodontal health and unaltered attachment levels is a controversial
topic. The keratinized gingiva provides a protective fibre barrier against
inflammation and attachment loss.
There is increasing evidence that periodontal
health can be maintained in areas with minimal zones of keratinized gingiva as
long as the patient can maintain the area and there are no restorations in the
area of the gingival margin. When restorative procedures enter the gingival
crevice, a minimum of 5 mm of keratinized tissue is required (2 mm of free
gingiva and 3 mm of attached gingiva).
There are situations where we are forced to
take the restorative margins sub-gingivally. When such conditions as fracture
and caries force us to violate biologic width, periodontal surgery or crown
lengthening procedures should be performed. Orthodontic extrusion or forced
eruption is useful in the premolar and anterior region, where gingival width is
important. When indicated, this procedure is to be completed before the
To conclude, the points to remember are:-
· To preserve
biologic width and prevent attachment loss, restorative margins should be at
least 3-4 mm from crestal bone.
· Sub gingival
restorative margins should be properly contoured
· An adequate
band of keratinized tissue is mandatory.
· Plan the
treatment carefully and consider the benefits that periodontal surgery and
orthodontic extrusion can provide.