Seymour et al developed a Gingival Overgrowth Index (GOI) for quantitating gingival hyperplasia. This can be useful for monitoring a patient taking a medication or disease that can cause gingival hyperplasia. The authors are from the University of Newcastle upon Tyne in England.

Seymour divided the teeth into gingival units, with each unit extending from the midpoint of 1 tooth to the midpoint of the adjacent tooth. The midpoint of the unit is the inter-dental space. This is flanked on either side by one half of each tooth.


20 gingival units involving the anterior upper and lower teeth are examined (10 mandibular, 10 maxillary).



(1) vertical extent (extent of gingival encroachment on adjacent teeth)

(2) horizontal extent (gingival thickening along the labial or lingual aspect)


For vertical extent, each of the tooth halves in the gingival unit is divided vertically into thirds:

(1) adjacent to inter-dental space

(2) middle

(3) adjacent to midline of tooth.

Since half of a tooth is divided into thirds, each of these vertical segments is 1/6 of the tooth width.


The horizontal extent of the gingiva anteriorly (along labial aspect) normally does not extend beyond a plane connecting the midline of the 2 teeth in the gingival unit.


The horizontal extent of the gingiva posteriorly (along the lingual aspect) is harder to measure since the normal extent is a curved plane connecting the posterior midlines of the 2 teeth in the gingival unit with the apex indented towards the teeth (concave).


NOTE: Figures 2 and 3 in Seymour et al (1985, page 415) are useful to visualize the extent of gingival hyperplasia relative to the teeth.





vertical extent

no encroachment



up to 1/6 of labial surface of tooth crown encroached



1/6 to 2/6 of labial surface of crown encroached



encroachment over the labial surface of the crown to midpoint (2/6 to 3/6)


horizontal extent

normal width



0.1 to 2 mm of thickening



> 2 mm thickening



gingival overgrowth index for each gingival unit =

= (points for vertical extent) + (points for horizontal extent)



• minimum index for a gingival unit: 0

• maximum index for a gingival unit: 5

• maximum index for all 20 gingival units: 100

• The higher the index the more marked the hyperplasia.


NOTE: The score could be modified to score the horizontal extent along the labial aspect and the horizontal extent along the lingual aspect separately. This would give a maximal index of 7 per gingival unit.

To read more or access our algorithms and calculators, please log in or register.