American Journal of Orthodontics

Published by Elsevier
Online ISSN: 0002-9416
Publications
Article
There are two frequently used methods of aligning malposed teeth by means of an arch wire. The first method is to deflect and tie the arch wire, which has a low modulus of elasticity, into the deepest part of the bracket slot. This low-modulus arch wire is not permanently deformed, and the elastic forces in it return the arch wire (which is tied to the bracket on the tooth) to its preformed shape. The second method is to stretch an elastic material (for example, Unitek ligature threads, Unitek Alastik modules, Ormco power threads, or Ormolast ligature modules) from the bracket tie wings to a preformed stiff arch wire which has a high modulus of elasticity and the teeth move from their malposed position to the stiff arch wire form. The objective of this investigation was to stretch a thermodynamic nitinol wire from 8 percent to 12 percent of its original length and measure the shrinkage of the wire in length. If the quantity of shrinkage of a 0.010-inch nitinol ligature type of wire were great enough, the second method of moving teeth to a stiff preformed arch wire by employing the thermodynamic nitinol stretched wire as a "wire rubber band" could be used to move teeth. This could serve as a possible alternative to Alastik and elastic modules in which there is a great deal of inherent force decay and permanent deformation. When the thermodynamic nitinol wire was heated through its transition temperature range, three different magnitudes of shrinkage occurred. The first was less than 1.0 percent of the original stretched length of the wire, the second was between 6 percent and 7 percent of the original stretched length of the wire, and the third was approximately 1.0 percent.
 
Article
Nitinol has a unique property which is of practical use to the orthodontist. That property is its extreme elasticity when it is drawn into high-strength wire. Nitinol wire is much more difficult to deform during handling and seating in bracket slots than stainless steel wire. At the time of this writing, it is nitinol's extreme elasticity that offers the clinician an advancement in the application of orthodontic materials. This characteristic reduces the loops formerly needed to level a dentition. The wire can be used for longer periods of time without changing it, and it can shorten treatment time needed in leveling the dentition. Nitinol has another remarkable characteristic, that of being able to return to a previously manufactured shape when it is heated through a transition temperature range (TTR). If we are to take advantage of this property, the wire must first be set into the desired shape while undergoing a high-temperature heat treatment. After the wire has cooled to room temperature, it may be deformed within certain strain limits. When heated to its unique TTR, it will "remember" its shape and return to the original configuration. It is this type of wire that is being reported on in the case report that follows.
 
Article
Self-application of a water-free 0.4 per cent SnF2 gel, daily at bedtime, was practiced by ninety-nine orthodontic patients over a treatment period of 18 to 24 months. Incidence of decalcification in these patients was compared to that found for 110 control patients who were managed in the same fashion but did not use the gel.Incidence of decalcification in the control group was 58 per cent, with the bulk of the lesions being classified as localized mild and located in the gingival area. Decalcification was found in only 2 per cent of the fifty-one patients who applied the gel as directed on a daily basis. Those who used the gel less regularly experienced higher degrees of decalcification.These results suggest that frequent self-applications of low concentrations of SnF2 provide very high levels of protection. It is also clear that “frequent” in this sense, means daily treatment.
 
Article
Israeli Arab children between the ages of 13 and 15 years, living in the town of Nazareth, were examined in order to determine the prevalence and severity of malocclusion in the permanent dentition. The survey encompassed 803 children, of whom 2.5 percent were under orthodontic treatment at the time of the study and 0.3 percent showed ideal occlusion. The remainder showed various measures of deviation from normal, distributed as follows: 85 percent had Angle Class I malocclusion, 8.5 percent had Angle Class II, Division 1 malocclusion, 1.7 percent had Angle Class II, Division 2 malocclusion, and 1.3 percent belonged to the Angle Class III category. The severity of malocclusion was appraised qualitatively by subjective evaluation, while for quantitative determination the Handicapping Malocclusion Assessment Record (HMAR) was used. There was a positive correlation between the two modes of assessment as expressed in the 12.4 percent of the children who were classified "treatment highly desirable or mandatory" and who scored 30 or more points on the HMAR chart. Further examination of the deviations underlying the scoring revealed that the 52.1 percent of the children with scores of 15 points or more would benefit greatly from orthodontic treatment. Selected items of the TPI and OI charts were incorporated into the HMAR to evaluate the latter's sensitivity. Supplementing the HMAR with some deviations from normal, such as cusp-to-cusp relationships, amplifies the sensitivity of this record.
 
Article
The purpose of this study was to examine the changes in mandibular dimensions and relationship as they relate to standing height, which is one indicator of skeletal maturation. The subjects for this study consisted of twenty males and fifteen females on whom cephalograms were taken between the ages of 8 and 17 years. Basic statistics summarized the changes in standing height and the mandibular parameters from 8 to 17 years of age. Analysis of variance was used to select five parameters to describe linear and angular changes in the mandible and also to compare the mean growth profiles of each of the facial parameters selected to the growth profile for standing height. Autocorrelation analysis provided a method of assessing the predictability of the growth profiles of the facial parameters from the profile of standing height for the same individual. The findings in the present investigation indicated that (1) the growth profile of height was significantly different from that of the parameters describing mandibular length and relationship; (2) the changes in standing height are significantly different in the maximum, premaximum,, and postmaximum periods of growth in both males and females; (3) the changes in mandibular length (Ar-Pog) are significantly different in the three periods; (4) the changes in mandibular relationship were not significantly different in the maximum and premaximum periods in either males or females, while the magnitude of change in the postmaximum period tended to be smaller than the other two periods; and (5) autocorrelation analysis revealed that the growth profile of height was found to have little predictive value in determining the growth profile of any of the mandibular parameters except for Ar-Pog for females.
 
Article
The purpose of this study was to examine the changes in the maxilla and the maxillary-mandibular relationship as they relate to standing height, which is one indicator of skeletal maturation. The subjects for this study consisted of twenty males and fifteen females for whom cephalograms were taken annually between the ages of 8 and 17 years. Descriptive statistics summarized the changes in standing height and the facial parameters from 8 to 17 years of age. Analysis of variance was used to describe the linear and angular changes and also to compare the mean growth profiles of each of the facial parameters to the growth profile for standing height. Autocorrelation analysis was used to assess the predictability of the growth profiles of the facial parameters from the profile of standing height for the same person. Three periods of growth were also compared: premaximum, maximum, and postmaximum. The findings in the present investigation indicated that (1) the growth profile of the absolute and incremental changes in standing height and the various facial parameters were in general significantly different between males and females; (2) the growth profile of standing height was significantly different from the parameters describing maxillary length and relationship as well as maxillary-mandibular relationship; (3) the changes in maxillary length (A-Ptm) were significantly larger in the maximum period of growth than the other two periods of growth for both males and females; (4) the changes in maxillary relationship were significantly different in the maximum period of growth than in the other two periods of growth in males only; (5) the change in maxillary-mandibular relationship was not significantly different in the three periods of growth; (6) autocorrelation analysis revealed that the growth profile of the facial parameters could not be predicted from the growth profile of standing height of the same individual; that is, the growth profile of height was found to have little predictive value in determining the growth profile of any of the other parameters. The present findings as well as those of a previous investigation indicate that treatment of anteroposterior discrepancies should be initiated as soon as the orthodontist believes that treatment is indicated, rather than waiting for the pubertal "spurt," since the presence, magnitude, and timing of such events in any one patient are highly unpredictable, at least to the degree that renders them clinically useful to the orthodontist.
 
Top-cited authors
James A McNamara
  • University of Michigan
Sheldon Baumrind
  • University of the Pacific
Björn U Zachrisson
  • University of Oslo
William Harrison Bell
  • University of Texas Southwestern Medical Center
Fred Bookstein
  • University of Washington Seattle