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The purpose of this study was to observe histologically the sequence of events leading to resolution of periradicular tissues, with a view to advancing the perception of periapical healing. Our material consisted of periapical specimens obtained from 15 single-rooted, endodontically treated teeth of patients aged 25-40 years. All the teeth required extraction because of complicated crown-root fracture following trauma, iatrogenic aetiology (cervical root resorption following bleaching) or extensive carious lesions. The patients were informed that, based on their clinical condition, surgical procedures should be performed under flap reflection in order to extract the fractured root. Informed consent, which was necessary for the surgery, was obtained in all cases. A small block section containing the apical root tip and surrounding periapical tissues was removed prior to root extraction. The results of histological examination revealed osteoblastic activty and osteoid bone formation six days after the root canal instrumentation. Periapical tissue healing was observed despite the presence of overfilled material. The lining epithelium was infiltrated with chronic inflammatory cells and surrounded by collagen bundles and newly formed bone.

A polycystic lateral periodontal cyst was observed over a period of 25 months. The case history, a description of the natural history of this lesion and its diagnostic characteristics, and a review of the literature are presented.

Numerous papers on epithelial jaw cysts have appeared in the decade since the publication in 1971 of the WHO histological classification of odontogenic tumours, jaw cysts, and allied lesions. Despite clarification of certain cyst varieties no major revisions are necessary. The following minor modifications are proposed. In the developmental odontogenic group, the terms keratocyst and follicular are preferred to primordial and dentigerous. The alveolar cyst of infants is categorised separately from the gingival cyst of adults. The developmental lateral periodontal cyst is included as a distinctive new type. In the non-odontogenic group the globulomaxillary is deleted as a unique entity, whereas the midpalatal cyst of infants is a new inclusion. To the inflammatory category are added the inflammatory follicular and inflammatory lateral periodontal varieties.

The technique for registration of fluid pressure in jaw cysts by means of pressure transducer and cannulation of the cyst cavity or cementation of a two-way valve into a tooth communicating with the cyst is described. Twenty-six closed cysts were subjected to registration of intracystic pressure. Subsequent histologic examination showed that all cysts were non-keratinized. Initial pressure values in apical periodontal cysts averaged +47 mmHg, in follicular cysts +44 mmHg, and in residual cysts +38 mmHg. A median palatine cyst exhibited a pressure of +81 mmHg. Most cysts showed intracystic pulsation corresponding to the number of heart beats on electrocardiograms obtained simultaneously. The intracystic pulsation disappeared when the intracystic pressure was experimentally increased and reappeared when it was lowered. In three cases in which registration of pressure was performed 7-14 days after the aspiration of the cyst fluid, an intracystic pressure in the same range as the initial one was found. The findings indicate deficient lymphatic drainage of non-keratinizing jaw cysts.