What oral manifestation is most commonly associated with Down syndrome?

The most characteristic oral findings in Down syndrome include: relative macroglossia (the tongue appears large relative to a smaller oral cavity, often protruding), open mouth posture and mouth breathing, fissured tongue (scrotal tongue), high-arched palate, delayed or abnormal tooth eruption, hypodontia (missing teeth), microdontia (small teeth), and increased periodontal disease susceptibility. Absolute macroglossia (truly enlarged tongue) may be present. True cleft palate is not a characteristic Down syndrome feature. Hyperdontia is more associated with cleidocranial dysplasia. Macroglossia with open-mouth posture is the most clinically recognizable oral feature.