Long-term stability of mandibular incisors following successful treatment of Class II, Division 1, malocclusions.

The purpose of this study was to evaluate the long-term stability of mandibular anterior alignment in a large group of Class II, Division 1, patients who demonstrated successful occlusal results at the end of active treatment. The specific aim was to search for predictors of relapse and associations between relapse and other post-retention changes. The sample of 78 adolescents was limited to successfully treated cases as judged by subjective evaluation of intercuspation and incisor occlusion of posttreatment study models. Neither cephalometric characteristics nor post-retention occlusion were considered in sample selection. Of these patients, study models and cephalograms were available pretreatment, at the end of active treatment, and a mean of 14 years post-retention. The results demonstrated an increase of incisor irregularity and a reduction of intercanine width and arch length post-retention. At post-retention, 9.0% had irregularity index values of 6.5 mm or more and 47.4% had values equal to 3.5 mm or less. Stepwise backward multiple regression analyses revealed that narrow pretreatment intercanine width and high pretreatment incisor irregularity were significant predictors of relapse. Treatment increase of intercanine width and post-retention decrease of intercanine width and arch length were associated with relapse.

The craniofacial skeleton in anencephalic human fetuses. II. Calvarium.

A detailed study of the calvarium of twelve anencephalic and four normal human fetuses 26 to 40 weeks gestational age using gross dissection, alizarin red S staining, silver nitrate radiography and histology revealed dramatic alterations in the presence, form, location and relationship of the individual bones. In the larger dorsal cranial defects the interparietal portions of the occipital bone were relocated anteriorly to approximate the frontal bone. The occipital components were rotated anterolaterally and inferiorly with lack of fusion of the chondrocranium posterior to the foramen magnum. The squamae of the frontal bone were collapsed horizontally and reduced in size to lie peripheral to the anterior cranial fossa forming most of the orbital roofs. In anencephaly the bones derived from the chondrocranium were not as severely affected morphologically as those derived from the neurocranium. The sutures were narrow and smooth instead of wide and serrated as in the normally developing calvarium. In general the degree of maldevelopment was proportional to the extent of the dorsal cranial defect in anencephaly.

The craniofacial skeleton in anencephalic human fetuses. III. Facial skeleton.

A sample of 12 anencephalic fetuses with gestational ages ranging from 26 to 40 weeks and exhibiting varying degrees of severity of the dorsal cranial defect was compared to three normal fetuses of comparable gestational ages with regard to the morphology and positional relationships of the maxillofacial skeletal complex. Gross dissection, alizarin red S staining, radiographs, cephalometric tracings, and histologic techniques were utilized. It was found that some facial bones were severely affected in morphology, size, spatial and angular relationships. The manner in which these were altered suggests that their morphogenesis is an adaptation to the primary defect of the neurocranium.

The craniofacial skeleton in anencephalic human fetuses. I. Cranial floor.

Twelve anencephalic and four normal fetuses 26 to 40 weeks gestational age were compared by anatomic, radiographic and histologic methods in order to gain information concerning morphogenesis. In the anencephalics, alterations located within the body of the sphenoid bone led to a reduced cranial floor angle and a more vertical clivus. The reduced lateral extension of the lesser and greater wings of the sphenoid constricted the anterior and middle cranial fossae respectively. The posterior cranial fossa tended to have an increased transverse dimension related to the supraoccipital and exoccipital bone orientation. The increased anterior and inferior position of the lateral end of the petrous temporal ridge was positively correlated with the degree of dorsal schisis in the anencephalics. Alterations in the size, form, or duration of the neural functional matrix are suggested as the cause of changes in the cranial floor.