EUROPEAN JOURNAL OF PAEDIATRIC DENTISTRY VOL. 22/4-2021 309 Subgingival periodontal pathogens in Down syndrome children without periodontal breakdown. A case-control study on deciduous teeth C. Vocale¹, M. Montevecchi², G. D’Alessandro², M. Gatto², G. Piana², L.Nibali³, M. C. Re 4 , V. Sambri 5 1 Unit of Microbiology, Regional Reference Centre for Microbiological Emergencies (CRREM), St. Orsola Malpighi Hospital, Bologna, Italy 2 Department of Biomedical and Neuromotor Sciences (DIBINEM), Unit of Dental Care for Patients with Special Needs and Pediatric Dentistry, University of Bologna, Bologna, Italy 3 Periodontology Unit, Centre for Host-Microbiome Interactions, Faculty of Dentistry and Oral Craniofacial Sciences, King´s College London, London, United Kingdom 4 Unit of Microbiology, Department of Medical and Surgical Sciences, “Alma Mater Studiorum” University of Bologna, S. Orsola-Malpighi Hospital, Bologna, Italy 5 Department of Experimental, Diagnostic and Specialty Medicine (DIMES), University of Bologna, Bologna, Italy e-mail: m.montevecchi@unibo.it DOI 10.23804/ejpd.2021.22.04.9 Aim Down syndrome is the most common form of aneuploidia compatible with a long survival. The affected subjects are more susceptible to severe early-onset periodontal disease and show a lower risk to develop dental caries than the non-affected population. This study investigated the prevalence of periodontal pathogens in the subgingival plaque of deciduous teeth in children with Down syndrome without signs of periodontal breakdown. Methods Thirty children suffering from Down syndrome and 46 matched healthy subjects were studied. A total of 228 subgingival plaque samples from deciduous teeth were separately collected and evaluated by polymerase chain reaction assays. Results The prevalence of Treponema denticola, Porphyromonas gingivalis, Prevotella intermedia, Aggregatibacter actinomycetemcomitans and Tannerella forsythia was investigated. Aggregatibacter actinomycetemcomitans and Tannerella forsythia were significantly more prevalent in Down syndrome children (respectively 8 and 9 times) than in controls. Conclusion In absence of periodontal impairment, Down syndrome children display a clear presence of periodontal pathogens already in the deciduous dentition. The hypothesis of an intrinsic predisposing condition is here supported. Abstract KEYWORDS Periodontal diseases; Down syndrome; Microbiology; Child; Tooth, deciduous. Introduction Down syndrome (DS) is the most common human aneuploidia compatible with prolonged life expectancy. The underlining genetic disorder is characterised by the presence of an extra copy of the chromosome 21. Patients affected by DS are more susceptible to early onset and severe forms of periodontal disease [Jepsen et al., 2018], while presenting a lower risk of dental caries than healthy subjects in the same age group [Castilho and Marta, 2010]. It has been hypothesised that the precocious nature and rapid progression of the periodontal disease may be due to the impaired immune response, the fragile periodontal tissue, or the early senescence typical of DS [Amano et al., 2001; Jepsen et., 2018]. However, the cause of periodontal disease tendency is not yet fully understood. In general, the onset and progression of periodontitis are clearly correlated with presence and increased numbers of specific bacteria. A recent work by Nòvoa et al. [2020] has investigated the subgingival microbiome of patients with DS and periodontitis, comparing it with the microbiome of patients with DS without periodontitis. The results show significant differences between the oral microbiome at various taxonomical levels, and this finding is in agreement with those of previous studies on the subgingival microbiota and microbiome in the general population. Several reports describing the prevalence of periodontal pathogens in young DS subjects have suggested an early colonisation of the oral cavity [Morisaki and Hamada 2000; Sakellari et al., 2001; Amano et al., 2001; Morinushi et al., 1997; Naka et al., 2009, Amano et al., 2000]. However, the available data are still scattered and insufficient to determine it. Generally, the detection of periodontal pathogens has been accomplished by cultural techniques, which are not usually sensitive enough and require special skill, especially in the isolation of anaerobic bacteria. Recently, improved methods, such as immunoassays using specific antibodies and DNA probe techniques, allowing specific and sensitive detections of periodontal and other pathogens, have been developed. However, these new methods still require approximately 103–105 targets per sample specimen. The use of polymerase chain reaction (PCR) can lower the detection limit to 102 cells per specimen. Nevertheless,