Primary failure of tooth eruption associated with secondarily inflamed dental follicle: inflammatory follicular cyst?

Primary failure of eruption represents a cessation of tooth eruption before emergence not due to a physical barrier or abnormal position and has no systemic cause. This failure of tooth eruption is rare phenomenon and it has not been associated with alterations of dental follicle. This case report describes a permanent right first molar with primary failure of eruption at the inferior border of the mandible presenting microscopic, clinical and radiographic findings compatible with follicular cystic lesion. The follicular tissues of this molar showed microscopic aspects of inflammation. Thus, pericoronal tissues surrounding long-term unerupted teeth with primary failure of eruption has potential to develop into odontogenic cysts. The lesion presented herein probably arose in association with a periodontal pocket mesial to the adjacent second molar, representing an atypical inflammatory follicular cyst. This case shares etiological, radiological and microscopic features with the usual form of the inflammatory follicular cyst associated with infected primary teeth, except for the infection pathways reaching the tooth follicle. The controversies regarding the terminology for this cyst are discussed.