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Biomedical subjects

T E Southard

Publications and source records attributed to T E Southard.

At least 19 recordsLinked to original sources
PubMed1999

Geometric and densitometric standardization of intraoral radiography through use of a modified XCP system.

OBJECTIVE: The purposes of this study were to examine the density correction afforded by curve-fitting algorithms and to investigate whether the device we developed significantly improves the reliability of longitudinal alveolar process bone radiographic density measurements. STUDY DESIGN: Stepwedges were radiographed over a range of impulse settings, and curve-fitting algorithms were fitted to sets of step images on each digitized film. Differences between the actual thicknesses of an alternate set of steps and their corresponding thickness estimates were calculated. Next, clinicians made periapical radiographs from interproximal bony sites on a dry skull using our imaging device. Differences in bone densities between corresponding regions of interest taken 1 week apart were calculated. RESULTS: Analysis of variance and Duncan's Multiple Range test demonstrated that piecewise linear, third-degree polynomial, and fourth-degree polynomial curves provided significantly better estimates of stepwedge thickness than did sigmoid or first degree polynomial-curves (P < .05) and that the differences between repeat bone density measurements made with density correction were significantly less than those made without density correction (P < .05). CONCLUSIONS: Piecewise linear, third-degree polynomial, and fourth-degree polynomial curve-fitting algorithms provided the best densitometric correction. The use of our imaging device increased the reliability of longitudinal bone density measurements.

Absorptiometry, Photon↗
PubMed1998

Prediction of mandibular growth rotation: assessment of the Skieller, Björk, and Linde-Hansen method.

The purpose of this investigation was to assess the method proposed by Skieller, Björk, and Linde-Hansen in 1984 to predict mandibular growth rotation. Our sample consisted of 40 randomly selected, untreated, adolescent subjects representative of the patient population generally encountered in orthodontic practice. The four independent variables identified in the Skieller study as having the highest predictive value (mandibular inclination, intermolar angle, shape of the lower border of the mandible, and inclination of the symphysis) were identified on initial lateral cephalograms. The proposed regression equations were applied and predicted mandibular rotations obtained. Final lateral cephalograms made 6 years after the initial profile radiographs were superimposed and actual mandibular rotation recorded. The observed and predicted rotations were compared and regression analyses performed to determine the amount of variability in observed values accounted for by the four variables individually and in combination. Only 5.6% of the variability in mandibular growth rotation could be accounted for using the four variables individually. Only 9% of the variability could be accounted for with a combination of the variables. In addition, we performed a Monte Carlo analysis, which mirrored the Skieller analysis but used random numbers instead of actual cephalometric data, to determine if the Skieller results may simply have capitalized on chance. Using the same forward stepwise selection procedure with a rejection level of P >.1, we found after 5000 simulations that a mean of 84% and a median of 94% of mandibular growth rotation variability could be accounted for using meaningless data in the Skieller analysis. This result was comparable to the Skieller value of 86%. In conclusion, information derived from pretreatment lateral cephalograms using the Skieller, Björk, and Linde-Hansen method does not permit clinically useful predictions to be made in a general population relative to the direction of future mandibular growth rotation.

Cephalometry↗
PubMed1998

Storage-phosphor computed radiography versus film radiography in the detection of pathologic periradicular bone loss in cadavers.

OBJECTIVES: The purpose of this study was to compare D-speed film, E-speed film, and the Soredex Digora system with respect to the detection of periradicular pathosis. STUDY DESIGN: Radiographic images of 100 cadaver jaws were made with E-speed film, D-speed film, and the Soredex Digora. Each set of 100 images was interpreted by four observers, with 30 days separating each of three viewing sessions from the next. The presence or absence of pathologic (inflammatory) periradicular bone resorption was determined by histologic examination of the samples. The observer performance was compared with the true histologic findings and evaluated with receiver operating characteristic and corrected receiver operating characteristic analysis. RESULTS: No statistically significant differences were found in diagnostic performance among the three radiographic techniques. In addition, no imaging technique was a good indicator of pathosis as determined by histologic analysis. CONCLUSION: Under the conditions of this study, it was determined that D-speed film, E-speed film, and the Soredex Digora were equivalent diagnostic imaging modalities with regard to the detection of pathologic periradicular bone resorption. No technique predictably indicated inflammatory resorption.

Alveolar Bone Loss↗
PubMed1996

Prevention of enamel demineralization during orthodontic treatment: an in vitro study using pit and fissure sealants.

Enamel demineralization during active orthodontic treatment remains a significant problem. The purpose of this in vitro study was to evaluate the efficacy of applying a light-cured unfilled resin, a conventional pit and fissure sealant, to the labial surface of teeth with previously placed orthodontic appliances to prevent demineralization. Orthodontic brackets were bonded to 40 extracted human teeth with a commercially available orthodontic adhesive. The exposed labial surfaces of 30 teeth (experimental group) were sealed with a clear, light-cured, unfilled resin. The remaining 10 teeth (control group) were left unsealed. Both groups were placed in a demineralization environment, and then all teeth were sectioned and examined under polarized light microscopy for the presence or absence of enamel demineralization. Every member of the control group exhibited demineralization of the entire exposed labial surface, whereas 80% of the sealed teeth exhibited no demineralization. Small, isolated areas of enamel loss were seen in six of the sealed teeth representing "breaks" in the sealant layer. The results of this study indicate that light-cured sealant treatment after orthodontic appliance placement significantly reduces enamel demineralization.

Bisphenol A-Glycidyl Methacrylate↗
PubMed1996

Fractal dimension in radiographic analysis of alveolar process bone.

OBJECTIVES: This in vitro study examined radiographic fractal dimension changes in alveolar process bone during simulated osteoporosis. STUDY DESIGN: Ten specimens of human maxillary alveolar process bone were progressively decalcified, and the percentage of calcium lost at each decalcification stage was quantified. Four radiographs of each specimen, together with an aluminum step-wedge, were exposed at 70 kVp at each stage. The test set of 560 radiographs was digitized, identical bony regions of interest were selected from the density-corrected images of each specimen, the regions were digitally filtered to reduce film-grain noise, and fractal dimension was computed on a line-to-line basis. Correlation analysis quantified the relationship between calcium loss and fractal dimension change. Analysis of variance and Duncan's multiple range test determined whether a difference existed in fractal dimension computed from images at x-ray beam angulations of -5, 0, and +5 degrees. RESULTS: A strong correlation (average r = -0.94, p < or = 0.0037) was found between generalized demineralization and decreasing fractal dimension. In every bone sample fractal dimension changed significantly (p < or = 0.0189) with angular change. CONCLUSIONS: Radiographic fractal dimension holds promise for detecting simulated osteoporosis in the maxilla under ideal conditions, but the sensitivity of fractal dimension to small x-ray beam angular change renders its clinical application questionable.

Alveolar Process↗
PubMed1996

Detection of simulated osteoporosis in maxillae using radiographic texture analysis.

An effective mass screening tool for detecting osteoporosis is currently lacking. Alveolar bone, routinely examined during periodic dental examinations, may provide a window into the status of systemic bone density. The primary objective of this investigation was to compare the performance of various textural features, computed from dental radiographs, in detecting early simulated osteoporosis of alveolar bone. Five specimens of human maxillary alveolar bone were progressively decalcified and the percentage calcium lost at each decalcification stage quantified. Two radiographs of each specimen, together with an aluminum stepwedge, were exposed at 70 kVp at each stage. The test set of 140 radiographs was digitized, identical bony regions of interest selected from the density-corrected images of each specimen, the regions digitally filtered to reduce film-grain noise, and textural features computed on a line-to-line basis. Correlation analysis identified a set of features whose changes consistently exhibited a moderate-to-strong linear association with bone mineral loss over a wide range of decalcification. Repeated measures analysis of variance was subsequently applied to this set to measure the minimal decalcification that could be detected by each feature under optimal conditions of x-ray beam angulation (0 degrees) and suboptimal conditions (+/- 5 degrees). The best performing features were mean intensity, gradient, Laws' texture energy measures, and fractal dimension which detected 5.7% bone decalcification at optimal beam angulation and 9.4-12.6% at suboptimal angulation.

Alveolar Process↗
PubMed1995

Intrusion anchorage potential of teeth versus rigid endosseous implants: a clinical and radiographic evaluation.

The purpose of this study was to compare the intrusion anchorage potential of teeth to osseointegrated titanium implants. Titanium implants were surgically placed unilaterally in a healed mandibular fourth premolar extraction site in eight adult mongrel dogs. The implants were surgically uncovered 3 months later and second stage abutments with soldered edgewise brackets secured. Edgewise brackets were also placed on the ipsilateral third premolars and on the contralateral third and fourth premolars. Segmental edgewise arch wires were placed between the implant and the third premolar and between the contralateral third and fourth premolars. Intrusion arch wire bends (v-bends) just mesial to the implant and the fourth premolar brackets were adjusted to apply a 50 to 60 gm intrusive force to the third premolars, bilaterally. Seven weeks later this force was increased to approximately 100 gm. Force levels were monitored biweekly for a total period of 16 weeks. Superimposition of initial and final periapical radiographs with bone markers demonstrated that for each dog the implant remained immobile and the third premolar on the implant anchor side was intruded in a curved path. On the contralateral side of the arch the dental anchor (fourth premolar) underwent an adverse reactive tip-back movement, and the third premolar was not intruded. We conclude that rigid endosseous implants are superior to dental anchorage for orthodontic intrusion of teeth and offer a potential means to intrude anterior teeth in adult patients with missing posterior teeth.

Animals↗
PubMed1995

Performance of filters for noise reduction in maxillary alveolar bone imaging.

Film-grain noise degrades image detail, hinders detection of subtle radiographic bone changes, and could thwart attempts to use dental radiographs of alveolar bone to detect osteoporosis. The purpose of this investigation was to quantify and compare the performance of various 1- and 2-D spatial and frequency domain filters in suppressing this noise. Estimates of noise-free bone profiles (scan lines) from each of five maxillary interdental areas were made by superimposing and averaging 16 identically exposed and digitized radiographs. The average mean absolute error and mean-squared error between the 80 initially noisy images and their respective noise-free profiles were calculated to provide an estimate of initial noise. Filter performance was measured as the change in these values after filtering the noisy images. Frequency domain analysis revealed that bone signal power spectra dominated at frequencies less than 2-3 cycles/mm and that some form of low-pass filtering would be applicable. The 2-D Butterworth low-pass filter provided the best performance, removing 57% of the film-grain noise when measured by mean absolute error, and over 80% when measured by mean-squared error. Surprisingly, the Lee, Lp mean, geometric mean, binomial, median, and simple neighborhood averaging filters offered comparable levels of performance.

Bone Density↗
PubMed1994

Detection of simulated osteoporosis in human anterior maxillary alveolar bone with digital subtraction.

The purpose of this in vitro study was to examine radiographic changes in human anterior maxillary alveolar bone during simulated osteoporosis (decalcification) and to determine the minimal amount of generalized decalcifications that can be detected under optimal radiographic conditions with the use of digital subtraction. Five samples of human anterior maxillary alveolus were progressively decalcified at timed intervals with 0.1 N hydrochloric acid solutions, and the percentage of calcium lost during each interval was quantified with calcium assays. Sets of four radiographs were exposed at 70 kVp initially and after each decalcification interval. The radiographs were digitized and digitally filtered, and bone profiles (scan lines) were generated between selected points on lead markers. To further reduce corrupting film-grain noise each set of four profiles were superimposed and averaged on a pixel-by-pixel basis. The averaged profile from each stage of decalcification was subtracted from the averaged initial profile on a pixel-by-pixel basis, and the mean profile intensity change for each decalcification stage calculated. Statistical analysis was performed with repeated measures analysis of variance. Results indicate that generalized decalcification less than or equal to 5.3% was detected in all samples of human anterior maxillae with the use of digital subtraction.

Alveolar Bone Loss↗
PubMed1994

Detection of simulated osteoporosis in dog alveolar bone with the use of digital subtraction.

The purpose of this in vitro study was to examine radiographic changes in dog alveolar bone during simulated osteoporosis (decalcification) and to determine the minimal amount of generalized bone loss that can be detected under optimal radiographic conditions with the use of digital subtraction. Five samples of dog maxillary alveolus were progressively decalcified at timed intervals with 0.1 N hydrochloric acid solutions. The percentage of calcium lost during each interval was quantified with calcium assays. Sets of four radiographs from each sample were exposed at 30 kVp and 50 kVp initially and after each decalcification interval. The radiographs were digitized and bone profiles (scan lines) were generated between images of lead markers. To suppress contaminating image noise each set of four profiles were superimposed and averaged on a pixel-by-pixel basis. The averaged profile from each stage of decalcification was subtracted from the averaged initial profile on a pixel-by-pixel basis, the mean profile intensity change for each decalcification stage calculated, and this mean change compared to the initial mean intensity to yield the percentage mean profile intensity change for each sample for each decalcification stage. Statistical analysis was performed with repeated measures analysis of variance. Results indicate that generalized decalcification of less than 7.5% was detected in all samples of dog maxillae with exposures of 30 kVp and that generalized decalcification of less than 19% was detected with exposure of 50 kVp.

Alveolar Bone Loss↗
PubMed1994

A three-dimensional system for planning orthognathic surgery. A case report.

Conventional records are often inadequate for planning correction of complex dentofacial deformities. A treatment planning system, consisting of computed tomographic-generated jaw models mounted on a special articulator, allows for presurgical decisions about the correctness of surgical movements or the need for alternative approaches.

Adolescent↗
PubMed1993

Maxillary alveolar bone imaging. Wiener filter design.

Optimal digital filter design is essential for noise suppression in the detection of subtle radiographic bony changes. The purpose of this study was to determine the signal (Ps) and noise (Pn) power spectra of sampled maxillary alveolar bone, to derive the optimal Wiener filter transfer function, H, from sets of Ps and Pn, and to quantify noise suppression through application of this filter. Sixteen standardized radiographs were made of five interproximal bony areas, each area from a separate dry human maxilla. The radiographs were digitized (0.02 mm/pixel resolution) and identical profiles (scan lines) generated between lead markers for each set of films. Ps was calculated from the averaged scan line of each set, Pn was calculated from the difference between the noisy images and the averaged scan line for each set, and an average maxillary H was calculated from the sets of Ps and Pn. Filtering of the 80 noisy sample radiographic profiles with H resulted in a 39% reduction in noise. Application of this digital filter should significantly improve detection of radiographic bony changes in the maxilla.

Alveolar Process↗
PubMed1993

Noise in D- and E-speed radiographic film.

The purpose of this investigation was to compare image noise in D- and E-speed radiographic film and to establish a basis for choosing a particular speed of film for study of trabecular changes in alveolar bone. Eleven D-speed and 11 E-speed radiographs were made at varying exposures and developed along with unexposed film of each type to produce uniform optical densities that range from approximately 0.05 to 2.5. Profiles (scan lines) were made of each film at a spatial resolution of 0.02 mm. Noise was quantified for each profile using three measures: the standard deviation of the profile pixel intensity, I(x), about the mean, I(x); the coefficient of variation of I(x) about I(x); and Wiener spectral analysis. Results indicate that the average magnitude of noise for D- and E-speed film over this range of optical densities exceeds 4% and 6%, respectively; the average noise content of E-speed film was 25% to 35% greater than D-speed; and noise energy of both films is concentrated at low spatial frequencies and low optical densities.

Alveolar Process↗
PubMed1993

Evaluation of strain at the terminal abutment site of a fixed mandibular implant prosthesis during cantilever loading.

PURPOSE: Cantilever lengths from 10 mm to 20 mm have been empirically recommended for Brånemark fixed mandibular implant prostheses. However, functional stresses generated within the framework and at the crestal bone associated with various cantilever lengths have not been well researched. The purpose of this investigation was to evaluate the strain generated within an implant-supported prosthesis and on a simulated bone surface during functional cantilever loading. MATERIALS AND METHODS: A symmetrical mandibular fixed-implant framework supported by six Nobelpharma 7.0 x 4.0-mm abutments and 15.0 x 4.0-mm fixtures was fabricated. The fixtures were embedded in a simulated bone matrix of polymethyl methacrylate resin. Fourteen different arrangements of active supporting abutments were tested during 15 lb unilateral static cantilever loading 7 mm, 14 mm and 20 mm distal to the terminal abutments. T-rosette strain gauges were placed immediately distal to the terminal abutment site on the right side of the framework and on the corresponding simulated bone surface. RESULTS: There was no difference in framework microstrain as abutment number and arrangement were varied. Microstrain distal to the terminal abutment increased significantly with increasing cantilever length. Distal abutment microstrain increased 213% (63 mu epsilon to 197 mu epsilon) when cantilever length was increased from 7 mm to 14 mm and an additional 55% (197 mu epsilon to 306 mu epsilon) when cantilever length was increased from 14 mm to 20 mm. Overall, microstrain increased 306% when cantilever length was increased from 7 mm to 20 mm. Microstrain on the framework was always tensile (positive). Microstrain at the simulated bone reached higher maximum levels than on the framework (-588 mu epsilon versus 314 mu epsilon) and was compressive in nature (negative). In contrast to framework microstrain, microstrain at the simulated bone site varied dramatically with changes in abutment arrangement. Strains observed at the simulated bone surface increased dramatically as the distance to the adjacent active abutment increased or as the anterior-posterior span of abutments decreased. Distal abutment microstrain also increased significantly at the bone site as cantilever length increased, however, percent increases were less (7 mm to 14 mm, 55%; 14 mm to 20 mm, 30%; 7 mm to 20 mm, 101%). CONCLUSIONS: The results of this study indicate that an optimum biomechanical environment should exist when cantilever spans exceeding 7 mm are planned regardless of the number of supporting abutments. Strain transmitted to the crestal bone can be decreased by maximizing the number and anterior-posterior spread of supporting fixtures while minimizing the distance between the distal abutment and its adjacent abutment.

Alveolar Process↗
PubMed1992

Quantitative features of digitized radiographic bone profiles.

The purpose of this investigation was to examine the use of four image features in describing digitized radiographic bony scan lines, or profiles. These features include the mean pixel intensity, I (x); pixel intensity variance, var I (x); mean absolute Fourier transform coefficient, magnitude of F(u); and mean spatial first moment of the absolute Fourier coefficients, M1. In an animal model I (x) and M1 differed significantly while magnitude of F(u) tended to differ significantly between digitized radiographic profiles of osteoporotic (n = 6) and control (n = 6) rabbit humeri. Case examples illustrating the application of this technique to digitized radiographs of human interproximal alveolar bone are presented.

Adult↗
PubMed1992

Comparison of digitized radiographic alveolar features between 20- and 70-year-old women. A preliminary study.

The purpose of this investigation was to determine whether a difference exists in four digital image features, extracted from standardized periapical radiographs of the maxillary alveolar bone, between younger and older women. These features included mean pixel intensity, I(x); pixel intensity variance, var I(x); mean absolute Fourier transform coefficient, magnitude of F(u); and mean spatial first moment of the absolute Fourier coefficients, M1. The interproximal bone between the maxillary canine and lateral incisor was analyzed in two groups of 10 younger and older women with mean ages of 24 and 74 years, respectively. I(x) was significantly less in the 70-year-old group than in the 20-year-old group (p = 0.01), as were magnitude of F(u) (p less than 0.05) and M1 (p less than 0.01). Var I(x) tended to be significantly less in the 70-year-old group (p = 0.06). We conclude that in women a measurable diminution in the magnitude of these four bony features comes with age.

Adult↗
PubMed1992

Periodontal force: a potential cause of relapse.

Relapse of aligned mandibular anterior teeth and the progressive collapse of the mandibular arch is a significant problem for orthodontists. However, identification of a specific cause of such relapse has proved elusive. The transseptal fiber system is thought to stabilize teeth against separating forces. It is hypothesized that this fiber system may actually maintain the contacts of approximating teeth in a state of compression, the long-term result of which could be contact slippage and collapse of the arch. The interproximal force (IPF) at the mandibular first molar-second premolar contact was investigated on the basis of previous studies with this representative contact. The IPF was measured in 10 subjects at six different widths of contact separation. By means of graphic plotting techniques, the IPF at zero separation was calculated to estimate the contact force when the molar and premolar were actually touching. The mean IPF at zero separation was found to be 36.7g (SE = 6.6g), and a t test confirmed the hypothesis that a state of compression between contacts exists (p less than 0.0001). After chewing, the mean IPF at zero separation was 57.2g (SE = 9.1g), and a paired t test revealed an increase in contact compression had resulted (p less than 0.01). It was concluded that the periodontium exerts a continuous force on the mandibular dentition and that this force acts to maintain the contacts of approximating teeth in a state of compression. This force is increased after occlusal loading and may help to explain long-term crowding of the mandibular anterior teeth, physiologic drifting of teeth, and maintenance of posterior dental contacts after interproximal wear.

Bite Force↗