The colonization of many putative periodontopathic microorganisms can occur quite early in childhood without clinical signs of periodontal disease. However, colonization by P. gingivalis and T. denticola was not detected in periodontally healthy children.

These results suggest that various periodontopathogens can colonize in the very early childhood of DS patients and maturation of subgingival components, including P. gingivalis, plays an important role in the initiation of gingival inflammation.

Summary. A radicular cyst arising from the primary second molar and causing displacement of the permanent successor to the lower border of the mandible, with accompanying buccal expansion, was examined clinically and radiographically. Extraction of the primary molar and extirpation of the cyst led to uneventful healing. The primary molar had received pulp treatment with therapeutic agents approximately 1·5 years prior to the patient’s first visit. The relationship between pulp treatment and rapid growth of the radicular cyst is discussed.