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Biomedical subjects

D Hatcher

Publications and source records attributed to D Hatcher.

17 recordsLinked to original sources
PubMed2003

Current status and future needs in craniofacial imaging.

Imaging is a keystone in understanding and delivery of craniofacial health care. Recent developments in imaging have brought forth many diverse technologies and approaches. This review provides the current status of methods in craniofacial imaging and discusses future needs and directions. New developments in three-dimensional dental and skeletal imaging, as well as three-dimensional facial image acquisition and animation of jaw movement and facial expression are reviewed. Visualization and convergence of the data from these technologies for construction of patient-specific models is described. Insights on how these technologies and approaches could impact research, education as well as the future of craniofacial health care will be discussed.

Computer Simulation↗
PubMed2003

Measurement of mechanical strain on mandibular surface with mastication robot: influence of muscle loading direction and magnitude.

OBJECTIVES: To investigate the mechanical effects of mastication on the mandible, we developed computational controlled mastication robot system with human dry skull and analyzed the strain distribution on the mandibular bone surface. DESIGN: In the mastication robot, the mandible was suspended by eight wires, which simulated masticatory muscles. A non-linear spring damper generated viscoelastic properties, and tension sensors for simulation of jaw reflection to avoid unusual biting force were applied as a biological feedback mechanism. By using this robot system, various patterns of muscle loading (change of wire direction and magnitude) were performed. RESULTS: From the results, significant differences in the amount of principal strain and its distribution were demonstrated in each condition (ANOVA, post hoc test, and p < 0.05). The value of maximum principal strain ranged from 79.66 x 10(-6) [at anterior border of ramus (Buccal side), 128 N] to -1.42 x 10(-6) [at foramen mentale (Buccal side), 32 N]. CONCLUSION: These results suggested that the muscle loading generated the mechanical strain on the mandibular bone surface and it was affected by the changes in loading direction and magnitude.

Analysis of Variance↗
PubMed2003

Micro X-ray computed tomography analysis for the evaluation of asymmetrical condylar growth in the rat.

OBJECTIVES: To investigate the influence of forced lateral bite on mandibular growth, micro X-ray computed tomography (CT) was used for the purpose evaluating condylar cartilage and cancellous bone formation in 10 male Wister rats (3 weeks of age). SETTINGS AND SAMPLE POPULATION: The rats were divided into two groups--experimental and control. In experimental group, an inclined crown was cemented onto the maxillary incisors to produce 2.5 mm shift toward the left side during mastication. Right-left differences in whole mandibular length, mandibular height, condylar size, trabecular structure of the condylar head and three-dimensional (3-D) finite element analysis were assessed using 3-D images reconstructed from micro X-ray CT scans when the mice had reached 21 weeks. MEASUREMENTS AND RESULTS: Asymmetrical growth was found in the experimental group, in which the left condylar head became thicker and shorter than the right condylar head during development. When comparing the left and right condyles of the experimental animals, histomorphometric analysis from micro X-ray CT showed that the bone volume (BV) of the cancellous bone, the surface area of the cancellous bone (BS), the BS/BV ratio, the BV fraction (BV/TV), and the trabecular thickness and trabecular number were less for the right condyle than for the left condyle. CONCLUSIONS: These findings suggested that artificial changes in the mastication do influence the growth of condylar head, condylar bone trabecular structure, and mineralization.

Animals↗
PubMed2003

A three-dimensional evaluation of the upper airway in adolescents.

The link between the facial growth and airway function has been a subject of controversy in orthodontics for many years. This study investigates how well lateral cephalometric headfilms depict three-dimensional upper airway structures. Subjects are 11 normal adolescent children, ages 7-16 years old. Airway information over the same anatomic area in the nasopharynx is compared between lateral cephalometric headfilms and three-dimensional cone beam computed tomography (CT) scans. Intra-subject proportion of airway volume to area shows moderate variability. CT airway volume shows more variability than corresponding headfilm airway area.

Adolescent↗
PubMed2001

Cortical bone mineral density in asymmetrical mandibles: a three-dimensional quantitative computed tomography study.

The three-dimensional distribution (3D) of the highest mineralized cortical bone was evaluated in 32 subjects between the ages of 8 and 30 years with asymmetrical mandibles using quantitative computed tomography (QCT). The geometrical distribution of the highest mineralized areas (> 1250 mg/cm3) representative of mandibular cortical bone was determined by 3D reconstruction of the images. The length of the mandible on each side was determined by defining a new linear measurement from the centre of the 3D reconstructed condyle to the midline of the symphysis as identified from a submental view. The cross-sectional areas of the masseter and medial pterygoid muscles were assessed from bilateral axial views through the middle of the muscles parallel to the Frankfort-Horizontal plane. Comparison between the lengths of the two mandibular sides (right-left = mm) indicated a range of asymmetries with an equal number of subjects with the left and right mandible longer. Comparison of the area of highest mineralized cortical bone between the right and left sides (R/L) to the ratio of the mandibular length (R/L) showed a high correlation coefficient (r = 0.629) suggesting that the shortest mandibular side had more highly mineralized bone. A comparison of the area of highest mineralized cortical bone between the right and left sides (R/L) to the ratio of cross-sectional areas of the muscles showed the highest correlation coefficient (r = 0.724) with the ipsilateral masseter muscle. These findings indicate that asymmetrical mandibles are associated with asymmetrical distributions of the highest mineralized cortical bone and that this is age dependent.

Adolescent↗
PubMed2000

Magnetic resonance imaging of the temporomandibular joint: interobserver agreement in subjective classification of disk status.

OBJECTIVES: To determine interobserver agreement in interpretation of magnetic resonance images of the temporomandibular joint by independent observers and to evaluate interobserver agreement within each subjectively assigned category. STUDY DESIGN: Sixty magnetic resonance images of adolescent temporomandibular joints were randomly drawn for evaluation by 4 observers who had not previously worked together. All observers independently classified disk position on sagittal magnetic resonance images according to written classification criteria consisting of 6 categories. RESULTS: Kappa statistics of agreement show moderate agreement among all observers for both medial (95% CI, 0.486-0.622) and lateral (95% CI, 0.450-0.566) components of the joint. Disk displacement without reduction was the category with the greatest agreement among all observers (kappa = 0.914). CONCLUSION: Moderate to substantial observer agreement across all defined categories of disk status may be achieved among a number of observers when standardized classification criteria are used. Interobserver agreement is, however, not uniform across all categories of disk position described.

Adolescent↗
PubMed1999

Craniofacial imaging in orthodontics: historical perspective, current status, and future developments.

Rapid and substantial advances in imaging methods and technology have not always been expediently or adequately communicated to the practicing orthodontist. In this review we highlight contemporary imaging techniques and innovations in imaging that, in the future, are likely to greatly improve the depiction of craniofacial structures for use in diagnosis and treatment planning. In order to provide an appropriate background for this topic, we first discuss the evolution of craniofacial imaging in orthodontics and review the limitations of current methods, including the two-dimensional representation of three-dimensional anatomy, depiction as a patchwork of site-specific images, associated geometric errors, and images that have a limited point of view and are static in space and time. Three-dimensional computed tomography can be considered a partial solution to these limitations, but imaging costs, radiation exposure, and lack of soft tissue representation may make it unacceptable for routine orthodontics. A more complete solution might be achieved through digital processing of contemporary imaging technologies that would extend their capabilities, overcome many of their limitations, and result in an increase in the amount of relevant information obtained. Digital processes are currently being developed that create accurate multidimensional models that integrate form and function. These models will be interactive, linked to knowledge databases, and will provide the clinician with answers to pertinent questions. These advances in imaging are likely to enhance the accuracy and reliability of orthodontic diagnosis and treatment planning, and will be of importance in both clinical practice and research.

Cephalometry↗
PubMed1999

Magnetic resonance imaging and clinical assessment of temporomandibular joint pathology in ankylosing spondylitis.

OBJECTIVE: To evaluate temporomandibular joint (TMJ) articular disc position and osseous degenerative changes using magnetic resonance imaging (MRI) as well as clinical symptoms of temporomandibular disorders in patients with ankylosing spondylitis (AS). METHODS: A sample of 43 patients with AS (38 males, age 45.9+/-10.7 years) and 16 controls (all male, age 41.3+/-6.3 years) were studied. All subjects completed a self-administered questionnaire and underwent clinical examination and MRI survey. Recorded variables included disease characteristics, subjective neck and TMJ disorder symptoms, and axial mobility measurements. MRI variables included TMJ disc position and severity of osseous degenerative change. RESULTS: TMJ disorder symptoms of headache duration and frequency, TMJ pain duration and frequency, and painful jaw movement were more frequent in patients with AS (p < 0.05). Significant differences were also observed in MRI indices for disc displacement (AS, 0.89; controls, 0.36; p = 0.005) and degenerative changes (AS, 0.55; controls, 0.06; p = 0.01). A total of 50 (62%) joints in the AS group had disc displacement compared to 11 (34%) joints in the controls. A total of 16 (20%) joints in the AS group had degenerative change compared to 2 (6%) joints in the controls. CONCLUSION: TMJ internal derangement, degenerative changes, and subjective pain complaints are frequent in patients with AS. Physicians should be aware of potential TMJ involvement in these patients, which may require specific assessment and therapy.

Facial Pain↗
PubMed1998

Social and demographic characteristics of young and mature aged nursing students in Australian universities.

This national study compares the social and demographic characteristics of direct and delay entry students in a control group of 1551 students in higher education programmes in 1987 and 1990 with the national study group of 2295 students sampled in 1995. Using a specially constructed socioeconomic variable for comparison the analyses demonstrated a significant difference in the socioeconomic level of the household for the younger aged group but not for the mature aged group. There was also a significant difference between males and females in their age of entry patterns. Furthermore, there was a significant difference in the location of school attended for most of their secondary education for the younger aged group but not for the mature aged group. For both groups there was a significant difference in the number of siblings, the level of education attained by the mother and the income received by the mother in the households of the control and study groups. Logit analysis revealed that there was a significant interaction between the household variables: socioeconomic status, number of siblings, and income received by the mother of the respondents in the control and study groups for the younger age group but not for the mature age group. This interaction for the younger age group, plus the finding that nursing students were more likely to delay their Higher Education Contribution Scheme (HECS) payment than other university students suggests that politicians need to take great care in any changes to current HECS payments as such changes could upset the delicate social balance that has been achieved in nursing recruitment in Australia.

Adolescent↗
PubMed1998

Interobserver reliability in quantitative MRI assessment of temporomandibular joint disk status.

OBJECTIVE: The purpose of this study was to investigate interobserver reliability of a new technique for quantification of magnetic resonance images of temporomandibular joint disk status. STUDY DESIGN: Sixty magnetic resonance images of adolescent temporomandibular joints were randomly drawn for analysis. Four experienced observers traced the articular disk and osseous structures on sagittal magnetic resonance slice images. Quantitative measurements of disk length and disk displacement were recorded for each slice of 57 joints traced by each observer through use of a new quantification technique. Intraclass correlation coefficients were computed to assess interobserver agreement in the tracing of joint structures. RESULTS: The calculated intraclass correlation coefficient was 0.681 for disk length and 0.830 for disk displacement. In addition, the mean variability among observers was 1.041 mm for measurement of disk length and 0.972 mm for measurement of disk displacement. CONCLUSIONS: Interobserver agreement is high when the new quantification technique is used to interpret magnetic resonance images.

Adolescent↗
PubMed1998

Quantitative assessment of temporomandibular joint disk status.

The purpose of this study was to quantify temporomandibular joint disk-slice information produced by magnetic resonance imaging by means of a stepwise discriminant analysis. One hundred ninety-four adolescents consented to magnetic resonance imaging evaluation of their temporomandibular joints. Sagittal magnetic resonance imaging slices of each joint were assigned to one of six subjective categories of disk position by an experienced maxillofacial radiologist. Standardized reference planes transferred to each magnetic resonance image from corresponding lateral cephalometric radiographics facilitated the measurement of disk length and disk displacement and the computation of ratio values of these measurements. Discriminant analysis revealed that all three quantitative variables were descriptive and discriminant for grouping slice data into pre-established subjective categories. Cross-validation and misclassification error calculations showed a 69.3% agreement between subjective and discriminant classification. Therefore quantification of disk displacement can be used in place of subjective evaluation. In addition, discriminant analysis disclosed a reduction in disk length associated with increased severity of disk displacement.

Adolescent↗
PubMed1998

Mechanical performance of clinically available, neonatal, high-frequency, oscillatory-type ventilators.

OBJECTIVE: To perform a functional evaluation of five different high-frequency, oscillatory-type ventilators that are currently being marketed for neonatal high-frequency oscillation. DESIGN: Observational animal study. SETTING: Laboratory. SUBJECTS: New Zealand White male rabbits. INTERVENTIONS: Oscillator waveforms and delivered volumes were measured plethysmographically for the following ventilators: the SensorMedics 3100 A; the Dräger Baby Log 8000; the Metran Humming V; the Infant Star; and the Infant Star 950. The independent variables which were adjusted included frequency (5 to 15 Hz), amplitude (25% to 100%), mean airway pressure (5 to 25 cm H2O) and lung injury. MEASUREMENTS AND MAIN RESULTS: At 15 Hz, the volume delivered at the 100% amplitude setting varied from 2.1 to 8.8 mL. Generally, the delivered volume decreased with increasing frequency, and with increased percentage of amplitude. Volume delivery was relatively unaffected by mean airway pressure but decreased with lung injury. Waveforms ranged from pure sinusoidal to a complex square wave. The handling of inspiration/expiration time ratios was ventilator specific. The SensorMedics inspiration/ expiration ratio is user selected over a range from 1:2.3 (30% inspiratory time) to 1:1 (50% inspiratory time) and once selected it is consistent over its entire range of operating frequencies. The Drager ratio is machine determined and varied from 1:2.5 at 5 Hz to 1:1 at 15 Hz. Inspiratory time of the Infant Star is machine set at 18 msecs such that the inspiration/expiration ratio is 1:10.1 at 5 Hz and 1:2.7 at 15 Hz. The Humming V has a fixed inspiration/expiration ratio of 1:1. The relationship of the mean airway pressure displayed on the ventilator to the alveolar occlusion pressure varied considerably among devices. The displayed mean pressure could either overestimate (SensorMedics at 33% inspiratory time or Infant Star), approximate (Humming V), or underestimate (Dräger) the mean lung distending pressure measured during a brief occlusion maneuver. CONCLUSIONS: The findings demonstrate large variations in machine performance. The ventilators also differed profoundly in complexity of operation and versatility as neonatal ventilators.

Animals↗
PubMed1997

Total quality management in accredited New South Wales hospitals: a public/private comparison.

Analysis of data collected in a 1994-95 survey of accredited New South Wales hospitals examined the adoption of key elements of total quality management practice in the public and private sectors. In a number of areas of practice widely considered to be central to a hospital's total quality management efforts, there was no statistically significant difference between the two sectors. Where differences existed, total quality management practices more likely to be adopted by public hospitals were limited in their scope and likely to be explained by structural peculiarities. In contrast, private hospitals were more likely to adopt practices more critical to the successful implementation of total quality management.

Accreditation↗
PubMed1996

The social and gender composition of nursing students in Australia: a comparison between 1987-1990 and 1995 recruits.

This national study compares the social and gender characteristics of an earlier group of 1551 students in higher-education programs in 1987 and 1990 with the national study group of 2295 students sampled in 1995. Using a specially constructed socio-economic variable for comparison, the analyses demonstrated a significant difference in the socio-economic level of the household for the female but not the male group. There was a significant difference in the proportion of males entering nursing between the earlier and latter groups. Further, in the latter group, these males were more likely to enter nursing programs directly from school. Members of the female group in the latter sample were more likely to have attended a school in a less populated area, come from households with a reduced family size, have mothers who were earning an income and have mothers who had achieved a higher level of education than was found in the earlier group. Logic analysis revealed that there was a significant interaction between the household variables, socio-economic status, number of siblings and income received by the mother of the respondents in the early and latter groups for females but not for males. This interaction for the female group, plus the finding that members of the latter group were more likely than other university students to defer their Higher Education Contribution Scheme (HECS) payments, suggests that if politicians were to make changes to the HECS it may affect the delicate social balance currently achieved in nursing recruitment in Australia.

Australia↗
PubMed1996

Total quality management practices in the NSW hospital system--an overview.

A two-phase descriptive study involving a questionnaire survey was undertaken during 1994 and 1995 to evaluate the extent of implementation of total quality management practices in New South Wales hospitals accredited by the Australian Council on Healthcare Standards. A survey response rate of 72 per cent was attained. Results indicated that most hospitals were aware of and consciously implemented aspects of the total quality management philosophy in some way. There is little evidence that whole systems have embraced the total quality management approach as a fully integrated endeavour.

Community-Institutional Relations↗
PubMed1995

Magnetic resonance spectroscopy of the human masseter muscle in nonbruxing and bruxing subjects.

The masseter muscles of six nonbruxing subjects (five men, one woman) and six bruxing subjects (four men, two women) were assessed during chewing by nuclear magnetic resonance spectroscopy (31P-NMR). The NMR spectra were collected on a GE Sigma 1.5T whole body magnet with a double-tuned 31P/1H surface coil. Two-minute trials of rest/chewing/rest were completed three times. Averaged spectra of inorganic phosphate, phosphocreatine, and three adenosine 5' triphosphate peaks were collected in each trial. Bruxing subjects had a lower concentration of total phosphate and phosphocreatine than nonbruxing (control) subjects at rest. Bruxing subjects increased their inorganic phosphate during chewing significantly less than control subjects. The pH levels during rest and during chewing were similar in both controls and bruxers. These preliminary results suggest that bruxing subjects exhibit an altered phosphate metabolism during rest and exhibit a different phosphate metabolism pattern during chewing as compared to nonbruxing subjects.

Adenosine Triphosphate↗