American Journal of Orthodontics

The effects of rapid maxillary expansion on the external root structure of thirteen appliance-attached and five unattached maxillary first premolars from nine patients have been investigated with the scanning electron microscope (SEM). Topographic features of cementum and dentine resorption, as well as initial and subsequent remineralization changes, are described in detail. All anchor premolars exhibited root resorption, which was mostly confined to the buccal surface. Generally, the longer an anchor tooth remained in fixed retention, the more extensive the buccal root resorption. In contrast, the unattached maxillary first premolars and the opposing mandibular first premolars showed no evidence of resorption. Active resorption was the dominant process in anchor premolars extracted almost immediately after rapid expansion. Subsequently, repair became the predominant process, but continuing resorption was apparent even after 9 months of retention. Repair of root defects occurred by the deposition of cellular cementum which revealed little evidence of principal periodontal fiber reattachment within the advancing mineral front. The resorption pattern identified in the scanning electron microscope was not detected by in vivo radiographic examination. The significance of the findings is discussed.

A F Barber

M R Sims

American journal of orthodontics

Am J Orthod

Rapid maxillary expansion and external root resorption in man: a scanning electron microscope study.

快速上颌扩展与人类外部牙根吸收的扫描电子显微镜研究。

Cross-sectional studies have demonstrated an association between craniocervical angulation and craniofacial morphology. It was the aim of the present study to determine if the growth coordination suggested by this association could be detected in a longitudinal analysis of growth changes in posture and craniofacial morphology. The sample comprised 43 children, 20 girls and 23 boys. Cephalometric radiographs obtained in the natural head position (mirror position) were taken on two occasions. Mean age at the first observation was 9.5 years; mean period of observation was 2.7 years with a range from 1 to 4 years. Forty-one reference points and four fiducial points were digitized on each film. Individual growth changes were determined by computerized structural superimposition of the digitized sets of points. Correlation coefficients were calculated between growth changes in 11 postural and 35 morphologic variables. Correlations of r = 0.41-0.55 (P less than 0.01) were found between the change in craniocervical angulation and the true growth rotation of the mandible as assessed by the method of structural superimposition. On the average, a reduction of the craniocervical angle was seen in connection with increased forward rotation of the mandible and an increased craniocervical angle was found in conjunction with a less-than-average forward rotation of the mandible. The true mandibular rotation was masked by remodeling of the lower mandibular border. The changes in the conventional measures of head posture--the craniovertical angles--during the observation period showed no associations with the growth changes in craniofacial morphology.

Beni Solow

Susanne Siersbaek-Nielsen

Growth changes in head posture related to craniofacial development

与颅面发育相关的头部姿势生长变化

Se Bishara

Changes in facial dimensions assessed from laterial and photographs. PartI-Methodolgy

Publication Information	Publisher: C.V. Mosby Company，Publishing cycle: ，Journal Type: journal，Open Access Journals: No
Basic data	Year of publication: 1946，Proportion of original research papers: ，Self Citation Rate:， Gold OA Rate:

American Journal of Orthodontics

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Rapid maxillary expansion and external root resorption in man: a scanning electron microscope study.

Growth changes in head posture related to craniofacial development

Changes in facial dimensions assessed from laterial and photographs. PartI-Methodolgy

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