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Correction to Volume 64, Issue 4, page 257.

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The purpose of the present study was to compare cephalometric measurements derived from a centric occlusion (CO) tracing with those of a converted centric relation (CR) tracing. The sample consisted of 68 consecutively treated patients, with a CR-CO discrepancy of 2 mm or greater in either the horizontal and/or vertical planes, measured at the condyles from mounted models. Comparisons were also made within the sample between the 39 females and 29 males; and the 35 skeletal Class I and 33 Class II patients.

In analyzing the CR-CO discrepancy, the vertical component was greater than the horizontal in 96% of the sample. Every patient had a vertical component, although 10% had no horizontal component. Correlations between the horizontal discrepancy and the two tracings showed high values for approximately 50% of the measures, whereas little correlation was found with the vertical discrepancy.

Paired t tests used to compare the CO and CR cephalometric values demonstrated significant differences (p<0.05) for the majority of the values studied. However, there generally were no differences between the groups of males and females, or between the skeletal Class I and Class II individuals. The results of this study suggest that to make a correct orthodontic diagnosis the mandible should be placed in centric relation rather than in the more traditional centric occlusion.

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The finite element method has proven to be a useful tool for morphometric analysis in craniofacial biology. However, few attempts have been made to adapt this method for routine use by clinicians. The CEFEA program incorporates the advanced features of the finite element method but bypasses the detailed understanding of the engineering and mathematics previously required to interpret results. The program uses the color graphics display of common personal computers to show size change, shape change, and angle of maximum change. These are pictured as colored triangles of clinically relevant regions between pre- and mid- or posttreatment lateral headfilms. The program is designed to have features of interest in both clinical practice and research.

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Treatment and posttreatment changes in the dental arches of patients with Class II, division 1 malocclusions were evaluated. Half the patients (N=46) were treated with a nonextraction approach; treatment for the other half (N=45) included the extraction of four first premolars. The following parameters were measured in the maxillary and mandibular arches: arch width at the incisors, canines, second premolars and first permanent molars; anterior, posterior and total arch lengths; and total and anterior tooth size-arch length discrepancies. These parameters were measured pretreatment, immediately following orthodontic treatment and at least 2 years posttreatment.

The findings indicate that the extraction of premolars significantly improves the discrepancy between the tooth size and arch length during treatment. Posttreatment both the extraction and nonextraction groups experienced an increase in tooth size-arch length discrepancies and a reduction in arch length. Extractions did not significantly alter the direction of the overall posttreatment trends for some parameters, e.g., intercanine width and tooth size-arch length discrepancies. On the other hand, the posttreatment trends for other parameters—such as intermolar width—were significantly different between the extraction and nonextraction groups. In general, the trends in the posttreatment changes were similar in males and females as well as in the maxillary and mandibular arches.

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The effects of orthodontic treatment with the use of the cervical pull facebow headgear in patients with Class II malocclusions were evaluated with special reference to the dentition, the maxillary complex, the mandible, and the facial profile. The records of 85 patients, with a mean age of 11.3±1.7 years, were selected from a sample of 125 patient records requested from the office of John S. Kloehn in Appleton, Wisconsin. Dr. Kloehn has used traditional cervical pull facebow therapy in his practice. Over 100 linear and angular cephalometric measurements were made from the pretreatment and posttreatment records. These measurements were used to evaluate growth and/or treatment changes. The treatment sample was divided by size of the pretreatment FMA, sex, and the age range in which treatment was started, i.e., prepubertal, circumpubertal, and postpubertal. Overall, the results showed that the changes were very close to what would occur as a result of normal growth in Class I individuals. The maxillary permanent first molars continued to progress forward, the maxilla continued to grow forward, and the cranial base showed very little change, if any. The mandibular plane angle did not increase appreciably with treatment, regardless of the size of the pretreatment mandibular plane angle. Very few significant differences were found between sexes, pretreatment age groups, or between groups based on pretreatment Frankfort mandibular plane angle.

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The shape and size of the craniofacial complex in 35 adults with Klinefelter syndrome (47,XXY) were analyzed cephalometrically and compared with 60 control males. Twenty-four angular and 18 linear measurements were obtained for each subject. The results showed that the 47,XXY males were different from the controls in several areas of the craniofacial skeleton. Most of the differences were located in the cranial base and the cranial base angle (p < 0.02). The length of the maxillary base was greater (p < 0.05) and more prognathic (p <0.01) in the study group. The mandible was also longer and more prognathic (p < 0.01).

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Prior to bonding, the enamel surface of the tooth is normally etched using a solution of 37%–50% phosphoric acid (H₃PO₄) for 60 seconds. The purpose of this study was to evaluate the tensile bond strength, debonding interface distribution and enamel surface detachment of various concentrations of H₃PO₄ solution, from 2% to 8O%, applied for 15 seconds. Statistically significant differences in bond strength were found among the various concentrations tested: concentrations in the 10% to 60% range produced greater bond strengths than both the weaker and stronger concentrations. The weaker the bond strength, the greater the debonding interface between resin and enamel. The greater the bond strength, the greater the debonding interface between the bracket and resin. Enamel detachment occurred as the H₃PO₄ concentration rose above 30%. To obtain greater bond strength and less enamel detachment, 10%–30% concentrations of phosphoric acid for 15 seconds etching are suggested for clinical bonding.

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The ability of resin to penetrate tooth enamel during orthodontic bonding may be affected by the viscosity of the resin and the presence of a sealant. Twenty-four extracted molars were randomly divided into six groups of four. Three resin viscosities were applied with and without sealant and resin tag formation was studied with a scanning electron microscope. Statistically larger resin tags resulted in the group using the more fluid composite resin (orthodontic Concise) in combination with the sealant, although the frequency, regularity and form of the tags did not differ significantly among the various viscosities.

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The regulation of degradative activity such as phagocytosis and bone resorption in the periodontal region is greatly influenced by factors controlling general bone modeling. The purpose of this study was to determine if thyroxine has any influence on the occurrence of force-induced root resorption. Young male rats were divided into three groups: a group of normal rats, a control group in which appliances were placed, and an experimental group in which appliances were placed and I-thyroxine was administered (5 micrograms/kg bw for 12 days).

Root resorptions were induced by orthodontic force on the maxillary incisors. Fewer force-induced root resorption lesions occurred in the thyroxine group than in the control group. Alkaline phosphatase activity in the thyroxine group was significantly different from the normal and control groups. Thus, the decrease of resorptive lesions in the thyroxine group seemed correlated to a change in the bone modeling process, especially as related to the resorption activity.

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