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Data from 694 untreated children seen in a private orthodontic practice were used to analyze associations between dental and skeletal maturity. Dental ages were obtained by comparison with Bolton Standards; skeletal ages were assessed using the Greulich-Pyle atlas. In some children the difference between the dental and skeletal ages was as large as 36 months; the difference was less than 6 months in fewer than 40% of the children. Regression analyses showed only moderate associations between these measures. One measure of maturity cannot be inferred from the other.

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The purpose of this study was to evaluate treatment effects of the magnetic active vertical corrector appliance (AVC) when used to treat anterior openbites in a sample of growing patients. Twenty-five patients with a mean age of 10 years 8 months underwent AVC treatment for an average of almost 8 months. They had an average of 3 mm of anterior openbite closure during the treatment period, primarily due to maxillary and mandibular molar intrusion. Additional contributions to correction of the openbite were related to maxillary incisor eruption and lingual tipping combined with mandibular incisor lingual movement. A small amount of mandibular rotation with closure of the bite and decrease in anterior force height was observed. Anteroposterior skeletal change attributed to the AVC therapy was minimal.

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This paper evaluates the relationship between maximum mandibular vertical opening and the following variables: chronological age, craniomandibular relationships, and temporomandibular joint awareness in children. The range of mandibular movement was evaluated in 189 children between the ages of 4 and 14 years, using the method of Agerberg. Measurements were found to be accurate and reliable only in the vertical plane. Cephalometric tracings were made on 131 of the subjects. Significant relationships were noted for maximum vertical opening with age, anterior facial height, and mandibular length. A temporomandibular joint awareness questionnaire was verbally given to all subjects with no parental input. Responses to the questionnaire were found to be unreliable, based upon a retest of 25 subjects one month later. It is noteworthy that all of the changes in responses on the retest were to the same question, “Does your jaw ever feel tired? ”

This paper was presented to the North Atlantic Component of the Edward H. Angle Society of Orthodontists in Boston, April 5, 1990.

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The mechanisms controlling iatrogenic external root resorption (ERR) and repair were studied on 8 Macaca fascicularis monkeys. The animals were divided into short-term and long-term groups, and were treated with jackscrew, magnetic and sham palatal expansion appliances. Scanning electron microscopy morphometric analysis found major evidence of ERR in the tooth-borne jackscrew appliance, in the long-term group, in the maxillary premolars, on the buccal and furcation root surfaces, on the mesiobuccal root, and in the apical zone. Correspondingly, the ERR mechanism is controlled by the impulse (F.·Δt) and the critical barrier of the periodontal ligament as primary determinants and by the environmental density as a secondary determinant. ERR is initially regulated by the force component of the impulse and, with increased duration, by the time component of the impulse. The impairment/repair dynamics were found to be regulated by three principles: ERR level of irreversibility, delayed resorption response and jiggling.

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In a series of 200 consecutively debanded patients receiving comprehensive orthodontic treatment with the edgewise appliance, six (3%) showed severe resorption (greater than one-quarter of the root length) of both maxillary central incisors. For other teeth, resorption of this extent occurred in less than 1% of the patients. Using a case-control design, the characteristics of 21 patients with severe resorption were compared to randomly selected controls from the case series. There were significantly more Class III patients among the severe resorption cases than would have been expected. Risk indicators for resorption that were related to treatment procedures included approximation of the maxillary incisor roots against the lingual cortical plate (odds ratio 20), maxillary surgery (odds ratio 8), and root torque (odds ratio 4.5).

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The dental casts and cephalometric radiographs of 46 patients, treated with mandibular second premolar extraction and edgewise orthodontic mechanotherapy, were evaluated for changes over a minimum 10-year postretention period. The sample was divided into two groups: early (mixed dentition) extraction of mandibular second premolars and late (permanent dentition) extraction of mandibular second premolars. Results showed no difference in long-term stability between the two groups. Arch length and arch width decreased with time and incisor irregularity increased throughout the postretention period. No predictors or associations could be found to help the clinician in determining the long-term prognosis in terms of stability. The sample was regrouped according to the postretention degree of incisor irregularity. Statistically significant differences in cephalometric measurements were found between the minimally crowded group and the moderately to severely crowded group.

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The present study was designed to investigate biomechanical and clinical changes in the craniofacial complex resulting from orthopedic maxillary protraction by means of finite element and cephalometric analyses, respectively. An analytical model developed from a young human dry skull was used for finite element analysis. Three principal stresses were determined in the complex and its sutures. For evaluating morphological changes of patients, lateral cephalograms taken before and after maxillary protraction therapy were analyzed.

Tensile stresses were produced in the maxillary and zygomatic bones in an anterior direction with corresponding compressive stresses in a perpendicular direction. In the sutural systems, compressive stresses were induced by counter-clockwise rotation of the complex. Cephalometric investigation demonstrated that significant improvement of the maxillo-mandibular relationship was obtained by maxillary protraction, however, maxillary growth and repositioning were not as great when compared to mean growth in the control group.

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