[A comparison between the upper and lower jaws of the alveolar bone changes due to the extraction of frontal teeth]

The present study was designed to compare the process of structural changes which appeared in the alveolar bone and cortical bone of the frontal maxilla and mandible after extraction of the incisors. Twelve adult dogs whose upper and lower incisors on the same side were extracted at the same time were kept for 29-181 days. The dogs were injected continuously with tetracycline during the first half of the experimental period and with calcein during the latter half. Labio-palatal and labio-lingual longitudinal ground sections were first micro-radiographed and, then, examined by fluorescence microscopy. From a montage of fluorescence micrograms, color tracings of the labelling sites were made on thin plastic sheets. The two images of the control and experimental sides were precisely compared The structural changes which appeared in all the parts of the alveolar bone and cortical bone after extraction of the incisors were more prominent in the maxilla than in the mandible. New bone formation in the extraction socket appeared and was completed earlier in the maxilla than in the mandible. Secondary internal remodelling of the alveolar bone proper and the newly formed bone in the extraction socket progressed more quickly in the maxilla than in the mandible. The remodelling of cortical bone and the resorption of the alveolar crest was made very actively in the upper labial side, whereas these process very slight in the upper palatal side and in the lower labial and lingual sides, so that the contour of the frontal maxilla, especially in its labial side, was more prominently deformed than the mandible.