*Article* **Periodontal Condition and Subgingival Microbiota Characterization in Subjects with Down Syndrome**

**Maigualida Cuenca 1, María José Marín 1, Lourdes Nóvoa 2, Ana O'Connor 1, María Carmen Sánchez 1, Juan Blanco 2, Jacobo Limeres 2, Mariano Sanz 1, Pedro Diz 2,† and David Herrera 1,\*,†**


**Featured Application: Promotion of preventive actions in Down syndrome individuals is recommended, including surveillance of thyroid hormone function, improvement of oral hygiene measures and frequent evaluation of periodontal health.**

**Abstract:** The aim was to study the subgingival microbiota in subjects with Down syndrome (DS) with different periodontal health status, using cultural and molecular microbiological methods. In this cross-sectional study, DS subjects were selected among those attending educational or occupational therapy centers in Galicia (Spain). Medical histories, intraoral and periodontal examinations and microbiological sampling were performed. Samples were processed by means of culture and quantitative polymerase chain reaction (qPCR). Microbiological data were compared, by one-way ANOVA or Kruskal-Wallis and chi-square or Fisher tests, according to their periodontal status. 124 subjects were included, 62 with a healthy periodontium, 34 with gingivitis and 28 with periodontitis. Patients with periodontitis were older (*p* < 0.01) and showed lower prevalence of hypothyroidism and levothyroxine intake (*p* = 0.01), presented significantly deeper pockets and more attachment loss (*p* ≤ 0.01). Both gingivitis and periodontitis subjects showed higher levels of bleeding and dental plaque. PCR counts of *T. forsythia and* culture counts of *E. corrodens* and total anaerobic counts were significantly higher in periodontitis patients. Relevant differences were observed in the subgingival microbiota of DS patients with periodontitis, showing higher levels of anaerobic bacteria, *T. forsythia* and *E. corrodens,* when compared with periodontally healthy and gingivitis subjects. Moreover, periodontitis subjects were older, had lower frequency of hypothyroidism and higher levels of dental plaque.

**Keywords:** periodontitis; Down syndrome; polymerase chain reaction; microbiota; gingivitis
