Thomas J. Cangialosi

Comparison of measurements made on digital and plaster models.

Measuring plaster models by hand is the traditional method of assessing malocclusion. Recent technologic advances now allow the models to be digitized, measured with software tools, stored electronically, and retrieved with a computer. OrthoCAD (Cadent, Fairview, NJ) performs this service. The purpose of this study was to evaluate the reliability of the OrthoCAD system. Two independent examiners measured tooth size, overbite, and overjet on both digital and plaster models. The results were compared, and interexaminer reliability was assessed. The study sample consisted of 76 randomly selected pretreatment patients. The results showed a statistically significant difference between the 2 groups for tooth size and overbite, with the digital measurements smaller than the manual measurements. However, the magnitude of these differences ranged from 0.16 mm to 0.49 mm and can be considered clinically not relevant. No difference was found between the 2 groups in the measurement of overjet. Interexaminer reliability was consistent for both the plaster and the digital models.

Skeletal morphologic features of anterior open bite

Lateral cephalograms of sixty patients with open bite and sixty untreated subjects who were determined clinically to have Class I normal occlusions were studied. The following six values were recorded: (1) ratio of posterior to anterior face height, (2) ratio of upper to lower face height, (3) Sn GoGn angle, (4) gonial angle, (5) SN-PP angle, and (6) PP-GoGn angle. Results were compared with previous studies. The constancy of the ratios and angles with age was tested and an attempt was made to separate the open-bite sample into skeletal and dentoalveolar groups. Results were generally consistent with those reported previously, except for the Sn PP angle, which was not significantly different from the normal group. In the open-bite sample the study showed a decrease in the ratio of PFH/AFH, a decrease in the ratio of UFH/LFH, and an increase in the other angles measured. Upon further division of the sample into mixed- and permanent-dentition groups, it was found that the angles and ratios remained relatively constant with age. An attempt to divide the open-bite sample into skeletal and dentoalveolar groups resulted in more extreme values for all the measurements made. The difficulty in differentiating between the two groups and the variability of dentoskeletal patterns in open bite is discussed.

Mesiodistal crown dimensions and tooth size discrepancy of the permanent dentition of Dominican Americans.

The purpose of the study was to establish normative data on the mesiodistal crown dimensions of Americans of Dominican background. The Bolton tooth size analysis was performed on a sample of 54 Dominican Americans. The mean, range and standard deviation were calculated for the size of the teeth, and a coefficient of variation was obtained for the tooth size ratio. A 2-sample t-test was used to test for the statistical difference between means. In general, the values obtained for the Dominican American sample closely resembled previous data available for the African American population. The tooth size ratios obtained were compared to the Bolton ratios. The overall ratio was found to be 91.3, equivalent to the Bolton overall ratio, whereas the anterior ratio was 78.1, larger than the 77.1 Bolton ratio. The frequency of tooth size discrepancy outside 2 standard deviations from the Bolton mean was also calculated. An overall tooth size discrepancy was found in 11% of our sample, and 28% of the sample presented an anterior tooth size discrepancy.

Comparison of space analysis evaluations with digital models and plaster dental casts

INTRODUCTION Diagnostic measurements have traditionally been made on plaster dental casts. Now, 3-dimensional digital dental models can be used. The purpose of this study was to compare space analysis measurements made on digital models with those from plaster dental casts. METHODS Two sets of 25 alginate impressions were taken of patients who had a permanent Class I crowded dentition. Each impression was made into a plaster cast and a 3-dimensional virtual orthodontic model (OrthoCad, Cadent, Fairview, NJ). Measurements of tooth widths at their greatest mesiodistal dimension and arch length were recorded for both types of models. Tooth widths were measured on the plaster models with a digital caliper, and arch length was measured with a piece of brass wire and a millimeter ruler. The virtual models were measured by using OrthoCads dedicated software. The space analysis measurements were calculated for both types of models, and the extrapolated amount of crowding for each type of model was accessed. All measurements were made by 2 examiners. The resulting values were compared with nonparametric statistics, and method errors were calculated. RESULTS When comparing digitized models with conventional plaster dental study models, we found a slight (0.4 mm) but statistically significant difference in the space analysis measurements on the maxillary models; measurements on the mandibular models were not significantly different. No significant difference was found between the measurements of the 2 examiners. CONCLUSIONS The accuracy of the software for space analysis evaluation on digital models is clinically acceptable and reproducible when compared with traditional plaster study model analyses.

A cephalometric appraisal of edgewise Class II nonextraction treatment with extraoral force.

The purpose of this study was to determine the treatment effects of nonextraction edgewise therapy combined with cervical headgear on Class II, Division 1 malocclusions. Data from a sample of 43 treated patients with a mean age of 11 years 11 months and a mean treatment time of 2 years 8 months were recorded. A cephalometric appraisal was done and the initial and final measurements of points, lines, and angles based on accepted cephalometric analyses were compared. Students t test for paired cases was used to evaluate the significance of all measurement changes. The significant findings were as follows: the inhibition of forward growth of the maxilla, downward tipping of the anterior part of the palate, reduction of flaring of the maxillary incisors, reduction of the facial convexity, and extrusion and mesial movement of maxillary and mandibular first molars. The overall results tend to indicate the efficacy of this treatment modality in the treatment of the Class II, Division 1 malocclusion.

A cephalometric evaluation of hard- and soft-tissue changes during the third stage of Begg treatment

This study examined the effect of lingual root torque during the third stage of Begg treatment upon the maxillary central incisor, hard-tissue Point A, and soft-tissue Point A. Lateral cephalograms were taken, at the beginning and end of Stage III, of eighteen patients undergoing Begg treatment. Linear and angular measurements were made in an attempt to find the anteroposterior changes which occurred in the above structures as well as the superior-inferior changes which occurred in the maxillary first molar and the maxillary central incisor. It was found that the apex of the maxillary incisor, Point A, and soft-tissue Point A moved posteriorly a significant amount following Stage III mechanics. Also, the incisal edge of the maxillary central incisor moved anteriorly and extruded significantly. Weak correlations between hard- and soft-tissue changes may be due to changes in thickness of the upper lip related to growth and to growth of the nose.

A cephalometric appraisal of nonextraction Begg treatment of Class II malocclusions

Initial and final cephalometric evaluations are compared in a sample of 42 patients with Class II malocclusions treated in a nonextraction manner with the Begg appliance. The sample was analyzed as a group. Subgroups of patients with Division 1 and Division 2 characteristics were analyzed separately. To depict skeletal and dental changes, measurements were made using the sella nasion, palatal, and mandibular planes as reference planes. The findings show that on the average: The upper first molar maintained its anteroposterior position at the same time that SNA was reduced. This suggests a restriction of anterior maxillary growth. The mandibular first molar moved forward by 1.2 mm. Part of this change was attributed to anchorage consumption. Vertical changes in both the maxilla and the mandible were found to be within the normal range. No significant change in occlusal or mandibular plane angles was observed except for the Division 1 subgroup in whom a mild increase in the mandibular plane angle was observed.

An evaluation of growth changes and treatment effects in Class II, Division 1 malocclusion with conventional roentgenographic cephalometry and finite element method analysis

Conventional methods of roentgenographic cephalometry will yield differences in interpretation of growth or treatment changes depending on which methods of superimposition are used. The finite element method of analysis has been reported to have significant advantages since it does not require a reference frame to describe the changes that have taken place. This article describes the growth of a patient with a Class II, Division 1 malocclusion during approximately 2 years of orthodontic treatment with the use of conventional cephalometric growth and static analyses, as well as the finite element method. Thirty cephalometric points were digitized on the pretreatment and the posttreatment lateral cephalograms of a patient undergoing orthodontic treatment between the ages of 10 and 12 years. The finite element method provided a reference frame invariant description of the size, shape, change, and rotation of each of the 12 finite elements representing different anatomic structures.

Treacher Collins syndrome: A case study

Treacher Collins syndrome is a disorder of craniofacial development with high penetrance and variable expressivity. Its incidence is approximately 1 in 50,000 live births. In this article, we describe the orthodontic treatment of an 11-year-old boy with Treacher Collins syndrome.