American journal of orthodontics最新文献

A system of roentgen stereophotogrammetric analysis (FISA) has been developed and its value in studies of cranial growth in both man and the experimental animal (rabbit) has been delineated. This method is based on measurements from metal bone marker images on roentgenograms. Two roentgen tubes simultaneously expose the object, which is placed in one of two types of calibration cages. The object position does not need to be identical from one examination to the next. The cage, holding indicators of predetermined internal positions (in two or four planes), defines a laboratory coordinate system. Two-dimensional image coordinates are obtained by means of a highly accurate cartographic instrument. By computer reconstruction of the x-ray beams through the markers, 3-D object coordinates are calculated. For subsequent analysis of growth processes, extensive software is necessary. To control intrasegmental stability (routinely performed at each examination), a minimum of two markers is required, whereas three markers are needed in each skeletal segment for kinematic analysis using the rigid-body concept. Careful planning of marker placement before implantation minimizes implant loss and instability that otherwise might be a problem. Complications other than bone marker loosening have been nonexistent. The technical accuracy is high. Consequently, roentgen stereophotogrammetry, with the aid of metallic implants, is a superior means to obtain biometric information on cranial growth with relative ease.

The purpose of this article is to test the hypothesis that the establishment of nasal respiration in children with severe nasopharyngeal obstruction can be eliminated as a factor in determining mandibular growth direction. The article describes the changes in mandibular growth direction (MGD) in a 5-year period after adenoidectomies and the establishment of nasal breathing in a population of Swedish children. Measurements of mandibular growth directions were obtained from serial cephalometric radiographs after adenoidectomies in 38 Swedish children aged 7 to 12 years with previous nasopharyngeal obstructions. These were compared with the growth directions in a control sample of 37 Swedish children with clear airways and matched for age and sex. The adenoidectomy sample initially showed significantly longer lower face heights, steeper mandibular plane angles, and more retrognathic mandibles than the matched controls. Analysis showed that during the 5 years after adenoidectomies, the girls had a more horizontal MGD (P < 0.02) than did the female controls. A corresponding but not significant trend was found for the boys. The individual growth directions that were obtained following adenoidectomies were more variable than those found in the controls.

The wear resistance of tooth enamel that had undergone eight different treatments regarding the bonding procedure has been investigated. In comparison to sound enamel, the outer 3 microns of the etched-surface enamel show a decreased wear resistance against toothbrushing in vitro. Remineralization, either direct or preceded by acidified phosphated fluoride (APF) application, did not improve the wear resistance. The prophylactic effect of the APF treatment of etched enamel is considerable and is not lost after the soft, outer surface layer has worn off.

This article presents a retrospective study of patients treated for impacted maxillary canines by a combined surgical and orthodontic approach. All patients were assessed radiographically by means of a lateral skull radiograph and an orthopantograph. No posteroanterior radiographs were taken. Facial or lingual position within the arch was not determined, the height and inclination of the canine being deemed more important. At surgery, a facial flap was raised first in all cases. Only if access and isolation were poor was a palatal flap raised. Bone was removed as necessary. One contention of this article is that the amount of bone removed is not important. It is the manner in which the soft tissues and, in particular, the periosteum are handled that ultimately affects the results of the surgical treatment. An attachment was bonded onto the tooth and the wound closed. The tooth was then actively extruded, a removable appliance being preferable because more vertical control of anchorage is possible.

The aim of the present article was to identify morphologic characteristics in the craniofacial skeleton of the 11-year-old child that could indicate potential development of a Class III skeletal pattern. A radiographic material consisting of 24 children (13 girls, 11 boys) at an average age of 11 years 0 months, who in adulthood demonstrated a Class III skeletal pattern, was compared with a control group of 33 children (16 boys, 17 girls, average age 11 years 6 months) chosen retrospectively on the basis of Class I occlusion. The analysis was performed by means of both linear and angular variables and results are reported both as group means and individual analyses. No one morphologic trait indicative of potential Class III development could be isolated because the study clearly demonstrated the existence of different skeletal combinations. The development of the maxilla, both in size and position, was clearly demonstrated by the linear analysis to be an etiologic factor in Class III development. However, maxillary retrognathism was usually masked in the angular analysis because a reduction in length of the anterior base with subsequent effect on the position of point nasion was often seen in these cases. Mandibular prognathism was a frequent observation, although a true macrognathia was uncommon. In the majority of cases, mandibular prognathism was the result of an increase in the ratio between mandibular length and dorsal position of the glenoid fossa (articulare). The relative merits of angular and linear analyses are discussed in relation to the results presented.

The purpose of this study was to identify variables of malocclusion that might be associated with previously reported temporomandibular joint morphologic findings. Before removing the left TMJ from each of 96 cadavers (age $\text{x}\text{= 26.4 ± 6.8 years}$), an intraoral examination was performed. Angle classification, crossbite, overbite, and overjet were evaluated. These parameters were analyzed with respect to their association with the following TMJ features: overall shape of the condyle and temporal bone, gross and histologic evidence of remodeling, and position of the articular disk. When combined with age, Angle Class II and III dentitions were associated with temporal and condylar deviation in form (DIF) (P < 0.05) and more Class II dentitions were accompanied by histologic evidence of remodeling changes in the TMJs. Crossbite was associated with increasing presence of DIF in all components (P < 0.01). Anterior crossbite was associated with DIF on the articular eminence (P < 0.01). Deep overbite was more common in persons with flat condyles, open mandibular fossae, and anterior extension of the temporal articular surfaces (P < 0.05). Abnormal overjet was more evident in those with DIF in the disk (P < 0.05); greater overjet was associated with disk displacement (P < 0.05). Considered together, abnormal overbite and overjet were associated with more extensive DIF on the condyle (P < 0.05). In conclusion, malocclusion was associated with morphologic changes in the TMJ, particularly when combined with age. This evidence supports the belief that longer exposure to malocclusion may be associated with more extensive TMJ changes.