Down's syndrome is associated with all of the following except:
Skeletal ﬁnding is an underdeveloped mid-face, creating a prognathic occlusal relationship. 
Oral ﬁndings include mouth breathing, open bite, appearance of macroglossia, ﬁssured lips and tongue, angular cheilitis, delayed eruption times, missing and malformed teeth, oligodontia, small roots, microdontia, crowding, and a low level of caries. 
Children with Down syndrome experience a high incidence of rapid, destructive periodontal disease, which may be related to local factors such as tooth morphology, bruxism, malocclusion, and poor oral hygiene. 

Pediatric Dentistry / Shobha Tandon - 2nd Ed
Retrognathia
Periodontal disease
Premature exfoliation of teeth
Retained deciduous teeth