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Accuracy of cephalometric landmark location was determined in 20 pairs of headfilms, measuring differences in 18 points in two planes of each, using five independent observers. Each pair had one film taken with a conventional (calcium tungstate) intensifying screen system and one taken with a rare earth system. Statistically significant differences in accuracy were found in only six of the 36 measurements. Three of the differences favored the accuracy of the rare earth system (Pogonion Y, S Pogonion X and Y), while the other three favored the conventional system (ANS-X, Nasion-Y, Pt. A-Y). The least reproducible point in both systems in the horizontal axis was condylion. Since these findings showed no landmark accuracy preference of one screen system over the other, the 96 percent reduction in patient radiation with the rare earth system would mandate this be used in cephalometric radiography.

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The records of 33 openbite patients treated with cribs were collected. The sample was divided into two groups with group one comprised of 26 growing patients and group two comprised of seven nongrowing patients. There was a significant increase in overbite for both groups during treatment. The nongrowing group also showed a significant increase in overbite during the posttreatment period. During the posttreatment time interval 17.4 percent of the growing sample and zero percent of the nongrowing sample exhibited relapse. However, all patients who achieved a positive overbite during treatment maintained a positive overbite posttreatment. These findings suggest that patients who achieve a positive overbite with crib therapy have a good chance of maintaining this correction after orthodontic treatment is completed. This statement appears to be true for both growing and nongrowing patients. The reason for this increased stability may be due to a modification of tongue position or posture.

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The purpose of this investigation was to provide load-deflection rate data for a variety of open and closed coil springs. Ten millimeter lengths of open and closed coil stainless steel and Cobalt-Chromium-Nickel (Co-Cr-Ni) alloys in combinations of 0.008, 0.009 and 0.010 inch wire sizes, and 0.030 and 0.032 inch lumen sizes were tested. Other groups included heat treated Co-Cr-Ni springs and springs of 15 and 20 millimeter lengths. Forces and activations were measured by a tension load cell with an lnstron universal testing instrument.

Stiffness increased dramatically with wire size and pitch angle of the coils. Stiffness decreased slightly with increased lumen size. Co-Cr-Ni closed coil springs were slightly stiffer than stainless steel, whereas stainless steel open coil springs were much stiffer than Co-Cr-Ni. Heat treatment increased the stiffness of Co-Cr-Ni coil springs. The length of the spring had a great effect on the load-deflection rate. A shorter spring is stiffer than a longer spring by an amount directly proportional to the ratio of the length of the longer spring to that of the shorter spring.

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A sample consisting of 40 young Israeli adolescents, 18 males and 22 females, was examined cephalometrically. The subjects were classified as Angle Class I, with less than three millimeters of crowding and an orthognathic profile. Steiner and Downs analyses were performed for all subjects. Each analysis was done both manually and by using a computer. The computerized results were processed and subjected to statistical tests. The Israeli sample is characterized by a convex profile, a retrusive mandible, a steep mandibular plane and protrusive incisors.

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The sagittal difference between the maxillary and mandibular apical bases in orthodontic diagnosis and treatment planning can be evaluated by means of the angle ANB or alternatively, by means of the “Wits” appraisal. The lateral cephalometric radiographs of a randomly selected sample of 101 Southern Chinese children aged 10-15 years, with 55 males and 46 females were traced and analyzed by the standardized method taught to dental undergraduates. The “Wits” appraisal and angulation of the A-B line to the functional occlusal plane were added in order to generate data relevant to the local population, on whom the flatness of the nose-nasion-forehead region imposes a genuine difficulty in the identification of the cephalometric landmark nasion. Data analyses were performed under different categories with respect to age groups, 10-12 years and 13-15 years; the types of malocclusion and sex. It was found that both the angular and linear measurements were comparable to the existing norms established for the Chinese population. The “Wits” appraisal values have to be modified in order to be applicable to this population with −4.9 millimeters and −4.5 millimeters being the normal values for male and female children respectively.

Abstract

The canine occupies the transition from anterior to posterior occlusion. Following orthodontic treatment the canine's incisal edge occlusion demonstrates the tip and torque present in the appliance that was used. The effective torque of the bracket, however, is influenced by the tooth morphology at the bracket's base. The morphology of the facial surface can be described by an angle formed between the tangent at the point of bracket placement and the long axis of the crown. In this study, tangent angles at four millimeters and five millimeters from the cusp tip of 100 maxillary and 70 mandibular canines were determined. There was a significant difference between tangent angles at the same location on different canine teeth and also at different locations on the same canine tooth. Proximal collum angles were also measured in this study and there was a significant negative proximal collum angle in maxillary canines and a significant positive proximal collum angle in mandibular canines. The presence of these normal biologic variables will either enhance or minimize the torque supplied by preadjusted appliances, depending on a combination of prescription used and biologic variable present.

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A geometric, two-dimensional model was developed, which estimates the effect of changing incisal angular position to the effective bite depth. Because of the constant lengths of incisors whose long axes can be viewed as the sides of a triangle, it is possible to calculate the amount of their overlap as a function of changing angle. Additionally, a distinction is made between controlled and uncontrolled tipping, defined in respect to their centers of rotation. It is suggested that an average of 0.1 to 0.2 millimeter change in overbite occurs for every degree of incisal angular change.

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The cephalometric literature is rich with different craniofacial analyses. However, since these analyses are only descriptive for the clear skeletal discrepancies and somewhat handicapped for borderline cases, an investigation was designed to assess the dental base relationship in the human lateral skull cephalostat radiograph. A number of existing measurements were reviewed, and a new measurement, based upon anatomical points which could prove to be more reliable, was introduced.

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