Inclusion Criteria:

Common to all groups:

• Age: 3 to 12
• Patient affiliated to a social security program, beneficiary not covered by the AME.
• Legal representatives who speak and understand French well enough to be able to read and understand the study information.
• Legal representatives giving written consent for their child's participation in the study.

Specific:

Case Group:

• Trisomy 21 patient with gingival inflammation (subgroup 1)
• Trisomy 21 patient with healthy gingiva on intact periodontium with no history of periodontitis (subgroup 2)

Control Group: child meeting one of these criteria:

• Patient with psychomotor retardation with no known repercussions on the orofacial sphere or immunity, presenting gingival inflammation (subgroup 1)
• Patients with psychomotor retardation and no known repercussions on orofacial health or immunity, presenting gingival health on intact periodontium with no history of gingival inflammation (subgroup 2).
• Patients with no known general pathology and gingival inflammation (subgroup 3)
• Patients with no known general pathology and healthy gingiva on intact periodontium with no history of gingival inflammation (subgroup 4)

Exclusion Criteria:

Common to all groups:

• Patient having received antibiotic prophylaxis, antibiotic therapy or anti-inflammatory treatment in the 3 months prior to inclusion

• Patient included in another interventional research protocol or in a period of exclusion.

• Patient on AME

• Patients with a contraindication to the use of MEOPA:

  • Patients requiring pure oxygen ventilation
  • Intracranial hypertension
  • Unevaluated head trauma
  • New-onset, unexplained neurological abnormalities
  • Pneumothorax
  • Emphysema bubbles
  • Gas embolism
  • Diving accident
  • Abdominal gas distension, occlusion
  • Patient recently treated with ophthalmic gas (SF6, C3F8, C2F6)
  • Known, unsubstituted vitamin B12 deficiency

Specific to Trisomy 21 group:

- Patient with no genetic diagnosis