Periodontal Myths and Mysteries Series (II) The Gingival Biotype

Within couple of months, I had been asked to review three papers where authors refer to the “gingival biotype” after having assessed “visibility” of a periodontal probe through facial gingival tissue. The concept had been introduced in 2003 in a series of cases by Kan et al. where the “peri-implant” biotype was introduced and visibility of the probe through the tissue determined. Later, De Rouck et al. (2009) correlated thorough assessment of the gingival biotype (extensively quoting from my own group’s previous work while applying mostly identical analytical methods such as cluster analysis) with probe visibility. After that, a flurry of papers appeared in both our serious journals and predatory open access publications. A quick Google Scholar search using key words [gingival biotype] AND [probe visibility] reveals 243 hits since 2011.

It seems so that “visibility of a periodontal probe” is increasingly been considered an equivalent to a “thin gingival biotype” and attempts are made to replace all thorough assessments of the periodontal phenotype, a somewhat different concept which may be preferred over biotype for undeniable reason.

Originally introduced by Dr. Arnold S. Weisgold in 1977 and further extended by Dr. Jay Seibert in Lindhe’s Texbook of Clinical Periodontology in its 1989 edition, it were Olsson and Lindhe (1991) and later Olsson et al. (1993) who eventually dealt with certain observations made as regards shape of teeth and appearance of respective gingiva in a more scientific way. For the first time, a hypothesis was tested that the shape of anterior teeth in the maxilla (“long-narrow”, i.e. slender vs. “short-wide”, i.e. rather squared) may be related to thickness and width of the respective gingiva. It was also hypothesized that the shape of anterior teeth in the maxilla is related to that of teeth in the mandible. Our group largely extended these studies in the 1990s as we were able to use a new ultrasonic device which allowed us to measure gingival thickness atraumatically with reasonable accuracy and reliability. Eventually, Müller and Könönen (2005) published a paper in which site-specific measurements were used to indicate that there is a periodontal phenotype (a subject-related descriptor for a certain genotype, environmental influence and random variation) but most of the variation of gingival thickness was due to tooth type. Subject variability, in fact related to what we regard the periodontal phenotype, may add to the total variance of gingival thickness, but to a very low extent (about 4%). Realize that what might actually be called the “periodontal phenotype” consists of thickness and width of gingiva, but also of its degree of keratinization, melanin pigmentation and papilla height (a direct consequence of shape and form of the teeth).

Phenotype

All this seems now to be replaced by “visibility of a periodontal probe through the facial gingiva”, a questionable and actually unscientific concept. For instance, if one accepts that the periodontal phenotype includes, in addition to thickness and width of gingiva as well as papilla height the degree of keratinization of gingiva epithelium as well as melanin pigmentation, “visibility” may actually apply only for Caucasian populations.

Melanin

See, for example, the phenotype of a 24-yr-old Ghanese patient in the picture above. Regardless of whether the phenotype is “thick” or “thin” (I have not assessed it when I saw the patient in the 1990s), I doubt, whether a probe will be visible through heavily melanin-pigmented gingiva. So, are we again creating “novel” concepts in Periodontology by excluding any other ethnicity except Caucasians? It may in fact be criticized that “normal” gingival color is still described as pink, mauve or coral, despite the fact that in the majority of the World’s population it is light or dark brown.

30 January 2015 @ 10:30 am.

Last modified May 11, 2015.

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