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Biomedical subjects

D J Rudolph

Publications and source records attributed to D J Rudolph.

13 recordsLinked to original sources
PubMed2001

A finite element model of apical force distribution from orthodontic tooth movement.

This study was undertaken to determine the types of orthodontic forces that cause high stress at the root apex. A 3-dimensional finite element model of a maxillary central incisor, its periodontal ligament (PDL), and alveolar bone was constructed on the basis of average anatomic morphology. The maxillary central incisor was chosen for study because it is one of the teeth at greatest risk for apical root resorption. The material properties of enamel, dentin, PDL, and bone and 5 different load systems (tipping, intrusion, extrusion, bodily movement, and rotational force) were tested. The finite element analysis showed that purely intrusive, extrusive, and rotational forces had stresses concentrated at the apex of the root. The principal stress from a tipping force was located at the alveolar crest. For bodily movement, stress was distributed throughout the PDL; however, it was concentrated more at the alveolar crest. We conclude that intrusive, extrusive, and rotational forces produce more stress at the apex. Bodily movement and tipping forces concentrate forces at the alveolar crest, not at the apex.

Alveolar Process↗
PubMed1999

Alterations of the trabecular pattern of the jaws in patients with osteoporosis.

OBJECTIVE: The purpose of this study was to determine whether the morphologic features of the trabecular bones of the maxilla and mandible differ between patients with osteoporosis and normal controls. STUDY DESIGN: Periapical radiographs, obtained from dentists of 11 patients with osteoporosis and 12 control subjects, were digitized at 600 dpi. A custom computer program measured morphologic features of the trabecular architecture. The mean values for each feature were determined for the osteoporotic and control groups and compared by anatomic site. RESULTS: Twenty-four morphologic features of the trabeculae and marrow regions were examined in each anatomical site. A principal components analysis summarized these predictors to four. The Hotelling T (2) test found that patients with osteoporosis had significantly altered morphologic pattern in the anterior maxilla (P =.019) and the posterior mandible (P =.013) in comparison with the controls. A classification tree analysis separated all subjects into 2 groups with 92% accuracy. CONCLUSIONS: The data support the hypothesis that patients with osteoporosis have an altered trabecular pattern in the jaws in comparison with normal subjects.

Adult↗
PubMed1998

Multivariate prediction of skeletal Class II growth.

Prediction of craniofacial growth is one of the keys to successful orthodontic treatment and stability. Despite numerous attempts at growth forecasting, our ability to accurately predict growth is limited. The present study outlines a possible new approach to prediction of craniofacial growth that differs from any previous attempt because of both the methods used and type of patients studied. The purpose of this study is to create and test prediction equations for forecasting favorable or unfavorable patterns of growth in skeletal Class II preadolescents. The subjects for this study include 19 females and 12 males from the Bolton growth center in Cleveland, Ohio. The patients were all untreated orthodontically, had lateral cephalometric headfilms taken biannually from the ages of 6 through 18 and had a Class II skeletal relationship at age 8. Twenty-six skeletal and dental landmarks were identified and digitized, and 48 linear, angular, and proportional measurements were calculated. The subjects were divided into two groups based on anterior-posterior changes in the relationship between the maxilla and mandible. Eleven patients were in the favorable growth group, with an average improvement of 4.13 degrees in the ANB angle; 20 patients were in the unfavorable growth group with an average increase of 0.16 degrees in the ANB angle. The following prediction formula was created with Bayes theorem and assuming a multivariate Gaussian distribution: P(Good¿Fn) = ke (-(0.5)) ¿Fn - mu(ng)¿sigma(g)(-1)¿Fn - mu(ng)¿T. The equation's sensitivity and specificity was calculated from serial cephalometric data from ages 6, 8, 10, and 12. The results obtained with this equation indicate 82.2% sensitivity, 95% specificity with a overall positive predictive value of 91%. This corresponds to 17.8% of patients being incorrectly identified as Poor Growers and only 5% of our patients were incorrectly identified as Good Growers. We conclude that this prediction formula improves the ability to predict favorable or unfavorable patterns of growth in this sample of skeletal Class II preadolescents.

Adolescent↗
PubMed1998

Automatic computerized radiographic identification of cephalometric landmarks.

Computerized cephalometric analysis currently requires manual identification of landmark locations. This process is time-consuming and limited in accuracy. The purpose of this study was to develop and test a novel method for automatic computer identification of cephalometric landmarks. Spatial spectroscopy (SS) is a computerized method that identifies image structure on the basis of a convolution of the image with a set of filters followed by a decision method using statistical pattern recognition techniques. By this method, characteristic features are used to recognize anatomic structures. This study compared manual identification on a computer monitor and the SS automatic method for landmark identification on minimum resolution images (0.16 cm2 per pixel). Minimum resolution (defined as the lowest resolution at which a cephalometric structure could be identified) was used to reduce computational time and memory requirements during this development stage of the SS method. Fifteen landmarks were selected on a set of 14 test images. The results showed no statistical difference (p > 0.05) in mean landmark identification errors between manual identification on the computer display and automatic identification using SS. We conclude that SS shows potential for the automatic detection of landmarks, which is an important step in the development of a completely automatic cephalometric analysis.

Adolescent↗
PubMed1998

The use of tooth thickness in predicting intermaxillary tooth-size discrepancies.

Intermaxillary tooth-size discrepancies can be assessed using a diagnostic setup or predicted using a mathematical formula, such as the Bolton analysis. However, variations in tooth thickness may produce inaccuracies in the Bolton analysis ratio. To date, no method for incorporating tooth thickness into discrepancy prediction has been proposed. The purpose of this study was to design and test a new method of predicting anterior tooth-size discrepancy that takes into account tooth thickness and width. Forty-four positioner setup models were set to ideal overbite (2.5 mm) and occlusion (Class I canine relationship). Interproximal gaps between the maxillary or mandibular central incisors were allowed in order to optimize tip and torque. The mesiodistal width of all anterior teeth and the labiolingual thickness of the maxillary incisors were measured on these idealized setups to the nearest 0.1 mm. Actual intermaxillary anterior ratios were then calculated. A new method of prediction was developed by assuming a linear relationship between tooth thickness and ideal intermaxillary ratio. Errors in Bolton's method were compared with the new method. The results showed wide variations in mesiodistal tooth widths, tooth thicknesses, and intermaxillary anterior ratios in orthodontically treated patients. The correlation coefficient between the intermaxillary ratio and tooth thickness was r = 0.68 when tooth thickness was < 2.75 mm, and r = 0.28 when tooth thickness was > or = 2.75 mm. The mean absolute errors in predicting the actual intermaxillary ideal ratio was 1.29 +/- 0.81 for Bolton's ratio and 0.84 +/- 0.46 for the new prediction formula. These new formulas were better than Bolton's ratio in predicting tooth-size discrepancies (p = 0.003). Tooth thickness combined with mesiodistal width may be useful in predicting intermaxillary tooth-size discrepancies.

Algorithms↗
PubMed1997

A study of holographic interferometry on the initial reaction of maxillofacial complex during protraction.

Most extraoral appliances used for protracting small or retropositioned maxilla do not allow for variations in the point of force application or in its direction. This variation may be necessary to control vertical, anteroposterior, as well as transverse effects. The purpose of this study was to investigate the initial reaction of the maxillofacial complex according to force magnitude, force direction, and point of force application. For this purpose, an antenna-type modified protraction headgear was tested with double exposure holographic interferometry on a dry human skull with well-aligned upper teeth. Fringe patterns of each protraction condition were compared and analyzed. In most cases, upward rotation of the anterior portion of the maxilla changed to translation, or to downward rotation, as force direction was changed from parallel to the occlusal plane to 20 degrees downward to the occlusal plane. Furthermore, a 500 gm force applied 15 mm above and directed 20 degrees below the occlusal plane produced a translation of the maxillary complex, indicated by a typical circular fringe pattern on the holographic plate, which represents the center of resistance of the maxilla. In most cases, with all force variables tested, a protraction of the maxilla with palatal expansion was more effective in producing translation of the maxilla than was protraction without palatal expansion. By varying force magnitude, force direction and point of force application with maxillary protraction, the amount of maxillary rotation and translation might be controlled.

Adult↗
PubMed1997

Investigation of filter sets for supervised pixel classification of cephalometric landmarks by spatial spectroscopy.

The diagnostic process of orthodontics requires the analysis of a cephalometric radiograph. Image landmarks on this two-dimensional lateral projection image of the patient's head are manually identified and spatial relationships are evaluated. This method is very time consuming. A reliable method for automatic computer landmark identification does not exist. Spatial Spectroscopy is a proposed method of automatic landmark identification on cephalometric radiographs, that decomposes an image by convolving it with a set of filters followed by a statistical decision process. The purpose of this paper is to discuss and test appropriate filter sets for the application of Spatial Spectroscopy for automatic identification of cephalometric radiographic landmarks. This study evaluated two different filter sets with 15 landmarks on fourteen images. Spatial Spectroscopy was able to consistently locate landmarks on all 14 cephalometric radiographs tested. The mean landmark identification error of 0.841 +/- 1.253 pixels for a Multiscale Derivative filter set and 0.912 +/- 1.364 pixels for an Offset Gaussian filter set was not significantly different. Furthermore, there were no significant differences between identification of individual landmarks for the Multiscale Derivative and the Offset Gaussian filter set (P > 0.05). These results suggest that Spatial Spectroscopy may be useful in landmark identification tasks.

Cephalometry↗
PubMed1989

Radiographic measurement of total lung capacity in acute asthma.

The thoracic cage appears to be large during attacks of asthma. Lung volume measurements by body plethysmography and helium dilution have suggested that total lung capacity may be increased during an acute attack of asthma, but doubt has been cast on the accuracy of these measurements in the presence of airflow obstruction. The change in total lung capacity has therefore been investigated during and after an acute attack of severe asthma in 32 patients by a radiographic technique. There was a small decrease (0.29 l) in mean total lung capacity between admission and follow up, though a quarter of the subjects showed a slight increase. There was no correlation between change in total lung capacity and change in expiratory flow rates, arterial carbon dioxide tension on admission, body mass index, and length of stay in hospital. Our findings agree with previous reports of a decrease in total lung capacity with improving airway obstruction, but the changes were small and inconsistent.

Acute Disease↗
PubMed1988

Film-holding instruments for intraoral subtraction radiography.

Clinical application of digital subtraction radiography is limited by the reproducibility in the orientation of the x-ray source, image receptor, and object. In this study, eight dental intraoral film alignment instruments (including five replicates of each) were tested for accuracy in repositioning over a period of 6 months. Each instrument was made by adhering one of six impression materials (including acrylics, compounds, and elastics) onto the bite blocks of commercially available alignment instruments. The dimensional accuracy and reproducibility of the orientation of the x-ray source with respect to the object were determined over time for each instrument by measuring the horizontal and vertical angulation change in the position of a buccally placed marker on a dried mandible with a lingually placed film grid. Nine measurements were made during the 6-month test period. The most reproducible instrument was the combination of Regisil, an elastic impression material, and a Rinn XCP bite block. This combination yielded a mean absolute horizontal angulation error of 1.34 degrees +/- 0.63 and a mean absolute vertical angulation error of 2.04 degrees +/- 0.82, yielding a total angulation error of 2.44 degrees +/- 1.16. This was within the acceptable range of accuracy needed to produce diagnostically useful information when digital subtraction radiography is used.

Acrylic Resins↗
PubMed1987

Influence of geometric distortion and exposure parameters on sensitivity of digital subtraction radiography.

In the course of digital subtraction radiography (DSR), variation in the alignment of the x-ray source object and image receptor is an undesirable but frequent problem. The influence of angulation changes between the x-ray source and object on the quality of the subtracted image was measured with the visualization of a thin chip of bone (thickness less than or equal to 0.85 mm). Twenty radiographic image pairs that differed by known geometric distortions ranging from 0 to 9 degrees horizontal and vertical were subtracted. The ability to detect a thickness change varied strongly with angular distortion. Under optimal conditions (no distortion), DSR was able to detect a change in thickness of cortical bone of 0.12 mm. Under approximately clinical circumstances (3 degree misalignment), a thickness change of 0.35 mm was detected with 50% accuracy (three of six cases), while a thickness change of 0.42 mm was detected with 100% accuracy (six of six cases). In addition, the influence of exposure parameters on DSR was investigated. Twenty-one radiographic film pairs were subtracted with differing densities and contrasts. Images made at 70 kVp with an optical density of 0.61 in the dentin produced the best subtracted images. However, even images made with one fourth the conventional exposure produced diagnostic information when analyzed with DSR; this was not seen with conventional analysis of the normally exposed radiographic films.

Densitometry↗