Periodontal observations in twins

Twenty‐six groups of twins, with ages ranging from 12–17 years, were examined in this study. Seven sets of twins were monozygous and nineteen sets were dyzygous. The following observations were made on each set using a modification of the Ramfjord Periodontal Index: 1. Gingival recession was measured with a Williams‐Fox probe. 2. Crevicular depth was measured using a Williams‐Fox probe. Six measurements were made for each tooth on the mesial, distal, facial and lingual aspects. 3. Gingival health around each of six teeth (as outlined by Ramfjord) was scored on the basis of the degree of inflammation. 4. Supragingival calculus was scored on the basis of the amount of deposit. 5. Dental plaque was scored on the basis of amount of stainable plaque. The determination as to whether the twins were monozygous or dyzygous was based on an examination of blood factors. If any difference was noted, the set was considered to be dyzygous. The results of this study can be summarized as follows: (a) No evidence was found to support the concept that gingival recession or gingival crevice depth is an inherited characteristic. (b) No significant difference was found between both groups for the gingival score, calculus score, and plaque score.