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[The etiology of canine tooth impaction--a space analysis].

The aim of this study was to examine to what extent excess space must be taken into consideration as an etiological factor in upper canine impaction with special attention paid to the role of the adjacent laterals. To clarify this question the pre- and post-treatment models of 63 patients with a total of 84 impacted cuspids were measured and the cephalograms of 116 patients having 144 impacted cuspids were analyzed. The results of this study revealed: 84.5% of the cuspids were palatally impacted while 15.5% were labially impacted. An arch deficiency was found in only 18% of the palatally impacted cuspids, whereas there was an arch-length deficiency in 46% of the buccally impacted. In 35% of the cases there was a correlation between peg shaped laterals and palatal impaction, however, such was not present in the patients with vestibular retention. Finally the cephalometric data revealed horizontal growth characteristics in 80% of the palatally impacted canines as opposed to 23% in those labially impacted.

Adolescent↗

[Procedure for spiral computed tomography in the diagnosis of tooth impaction].

The paper presents a procedure for spiral computed tomography that may be used if there are some difficulties in the diagnosis of impaction of different teeth. Examples art used to show the capacities of specified diagnosis in solving the problems and difficulties in surgical or orthodontic treatment.

Adolescent↗

Absence of functional type 1 parathyroid hormone (PTH)/PTH-related protein receptors in humans is associated with abnormal breast development and tooth impaction.

Recent studies in transgenic mice have demonstrated that PTH-related protein (PTHrP), signaling through the type 1 PTH/PTHrP receptor (PTHR1), regulates endochondral bone development and epithelial-mesenchymal interactions during the formation of the mammary glands and teeth. Recently, it has been shown that loss-of-function mutations in the PTHR1 gene result in a rare, lethal form of dwarfism known as Blomstrand chondrodysplasia. These patients suffer from severe defects in endochondral bone formation, but abnormalities in breast and tooth development have not been reported. To ascertain whether PTHrP signaling was important to human breast and tooth development, we studied two fetuses with Blomstrand chondrodysplasia. These fetuses lack nipples and breasts. Developing teeth were present, but they were severely impacted within the surrounding alveolar bone, leading to distortions in their architecture and orientation. Compatible with the involvement of PTHR1 and PTHrP in human breast and tooth morphogenesis, both were expressed within the developing breasts and teeth of normal human fetuses. Therefore, impairment of the PTHrP/PTHR1 signaling pathway in humans is associated with severe abnormalities in tooth and breast development. In addition to regulating human bone formation, this signaling pathway is also necessary for the normal development of the human breast and tooth.

Breast↗

Unicystic ameloblastoma. A review of 193 cases from the literature.

Based on a world-wide literature survey of 193 published cases of unicystic ameloblastomas (UA), data have been produced allowing the presentation of a revised concept of this much debated lesion. UA is a variant of the solid or multicystic ameloblastoma. Radiographically, the unilocular pattern is more common that the multilocular, especially in cases associated with tooth impaction. However, it is stressed that although the lesion is pathomorphologically unicystic, it will far from always produce a unilocular radiolucency. The mean age at the time of diagnosis of UA is closely related to an association with an impacted tooth. Almost 20 years separate the mean age of the 'dentigerous' variant from the 'non-dentigerous' (16.5 years versus 35.2 years) The male:female ratio for the 'dentigerous' type is 1.5:1, but for the 'non-dentigerous' type it is reversed (1:1.8). Location favours greatly the mandible (mandible to maxilla = 3 to 13:1). Between 50 and 80% of cases are associated with tooth impaction, the mandibular third molar being most often involved. The 'dentigerous' type occurs on average 8 years earlier than the 'non-dentigerious' variant. The mean age for unilocular, impaction-associated UAs is 22 years, whereas the mean age for the multilocular lesion unrelated to an impacted tooth is 33 years. Histologically, the minimum criterion for diagnosing a lesion as UA is the demonstration of a single cystic sac lined by odontogenic (ameloblastomatous) epithelium often seen only in focal areas. This simple type of UA (according to the authors' modification of the classification by Ackermann et al. (Journal of Oral Pathology 1988; 17:541-546)), is one of four UA subtypes, the others being (1) simple with intralumenal proliferations; (2) simple with both intralumenal and intramural proliferations; and (3) simple with intramural proliferations only. All four subtypes occur in both the 'dentigerous' and 'non-dentigerous' variants. The simple subtype with and without intralumenal proliferations may be treated conservatively (enucleation), whereas subtypes showing intramural growths must be treated radically, i.e. as a solid or multicystic ameloblastoma. Finally, the authors disclose areas and issues pertaining to UA that still need to be addressed.

Age Factors↗