Biologic width is defined as the apico-coronal component of junctional epithelium and supracrestal connective tissue attachment.In 2017, during the World Workshop on Periodontics and Peri-implant disease and conditions, the term Biologic width was recommended to be replaced by Supra crestal attached tissues. The health of the periodontal tissue supporting teeth is
essential to the health and longevity of restorations around teeth. On average, maintaining 3mm between the CEJ and bone crest for natural teeth, and restoration margin and bone crest has been noted to be essential for preventing biologic width violation and inflammation or recession that can occur from its encroachment.2 The dimensions include 1mm for the gingival
sulcus, 1mm for the Junctional epithelium and 1mm for the supra-crestal connective tissue fibers.

The term Biologic width was coined by Gargiulo and colleagues based on measurements made on the dento-gingival unit for 287 teeth from 30 cadavers.3 Based on their measurements they concluded that it was comprised of two parts, the epithelial component and the connective tissue fibrous attachment.3 While the epithelial component was found to be more variable, the connective tissue attachment was found to be more constant. The average dento-gingival unit measured 2.41mm, with the epithelial attachment of .97mm and connective tissue attachment of 1.07mm, and the sulcus depth of .69mm.3 Based on their conclusions, the role of the epithelial component is to be responsible for the biologic protection of the dento-gingival unit.

While a number of studies have evaluated dimensions of the biologic width, in 2017 the World workshop of Periodontics and Peri-implant diseases and Conditions, made conclusions based on publication by Ercoli et al that looked at Dental Prosthesis and tooth related factors and their impact on supra crestal attached tissues. In evaluation of studies about crown margins placed <1mm from the crown margin and bone crest, those placed 1-2mm from the crown margin and bone crest and those place 2mm or more between the crown margin and bone crest, the periodontal tissue around sites with crown margins less than 1mm from the bone crest had more bleeding and probing depth than the groups with margins 1-2mm and 2mm or more from the bone crest in the presence of supragingival plaque.1 Based on these findings they indicated that there is an association with periodontal health and patient compliance with plaque control and periodontal maintenance around fixed prosthesis. They also further concluded that for direct restorations, subgingival margins are associated with localized gingivitis and probing depth, while for both direct and indirect restorations, overhanging margins are associated with localized gingivitis, increased probing depth and bone loss especially for larger overhangs.1 In looking at the impact of biologic width encroachment, they found that margins of restorations placed in the gingival sulcus (Sulcular epithelium), did not cause gingivitis, while margins placed into the Supra-crestal connective tissue attachment resulted in inflammation as well as potential gingival recession.

Based on their findings and recommendations, in placing restorative margin care has to be taken to prevent biologic width encroachment, and sub-gingival margins have to be approached with care ensuring that adequate oral hygiene measures are in place by the patient and that maintenance appointments are kept by patients in order to maintain them without damage to periodontal health of teeth. To prevent Biologic width encroachment when restorative margins are less than 2- 3mm from the bone crest, crown lengthening is indicated usually combined with ostectomy in order to increase the distance between the margin and bone crest in addition to replacement of the restoration.

References:
1 Ercoli C, Caton JG. Dental Prosthesis and tooth related factors. J of Periodontology 2018;89(Suppl.1):
S223-S236.
2 Gargiulo AW, Wentz FM, Orban B. Dimensions and Relations of the Dento-gingival junction in Humans.
J of Periodontology 1961;32:261-267.
3 Bhocchighoya A, Shrestha R. Biologic Width Review. J of Nepalese Prosthodontics Society
2020(Dec);3(2): 106-116.

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