Objective

To evaluate prevalence, distribution, intensity and extent of physiologic gingival melanin pigmentation (GMP) in black individuals.

Materials and methods

For this cross-sectional study, GMP was evaluated on digital images by three calibrated examiners, according to de Krom (distribution), DOPI (intensity) and Melanin Index (extent) classifications. Descriptive statistics, Wilcoxon, Mann–Whitney, Kruskal–Wallis, Two-way ANOVA, chi square, and K-means cluster analysis were used.

Results

Seventy participants were recruited. The most prevalent GMP categories were: de Krom category 2 (34.3%), DOPI heavy intensity (57.2%), and Melanin index Degree IV (50%). Significant inter-group differences were found for age (p < 0.05) but not gender (p > 0.05). Significant correspondence/overlap was observed between classifications (p > 0.05). Three GMP clusters were identified: Cluster 1 (27%; n = 19) had mild asymmetric and interspersed pigmentation; Cluster 2 (46%; n = 32) had heavy pigmentation in one long continuous ribbon, with pink marginal gingiva; and Cluster 3 (27%; n = 19) had heavy pigmentation in one long continuous ribbon, symmetric, and uniform.

Conclusions

There may be overlap among GMP classification systems. In black individuals, the predominant GMP presentation is one of a broad zone of heavily pigmented attached gingiva, in a continuous strip from central incisors to canines, symmetrical across the midline, and with pink free marginal gingiva.

Clinical relevance

This is the first study to analyze distribution, intensity, and extent of gingival melanin pigmentation in the same population and to integrate the various classification systems through cluster analysis. The novel findings provide a foundation for patient assessment and counseling and for future studies.