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Biomedical subjects

S C White

Publications and source records attributed to S C White.

At least 73 records · Page 4Linked to original sources
PubMed1989

A subjective study of dental diagnostic utility comparing xeroradiography and film radiography.

This study determined the perceived strengths and weaknesses of xeroradiography, D-speed film, and E-speed film for intraoral radiography. Results indicated that xeroradiography was preferred for the imaging of structures useful in periodontics and endodontics whereas film demonstrated a low level of image artifacts and was judged to be better for the imaging requirements of routine restorative dentistry. D-speed film was rated higher than E-speed film. These subjective assessments are similar to previously reported pilot studies but differ from previously published objective studies, which showed no significant difference between the three imaging techniques. Although there are substantial subjective differences between xeroradiography, D-speed film radiography, and E-speed film radiography, all the techniques provide more than the threshold level of necessary diagnostic information and all techniques portray adequate information for evaluation of common abnormalities encountered in the oral cavity.

Dental Restoration, Permanent↗
PubMed1989

Computer-aided differential diagnosis of oral radiographic lesions.

A program called ORAD was designed using Bayes' theorem to evaluate the radiographic and clinical features of patients with intrabony lesions in order to assist in their identification. Ninety-eight jaw lesions were described by their prevalence and their distribution by age, sex, race, presence of pain, number, size and location of lesions, association with teeth, expansion, locularity, borders, contents and impact on adjacent teeth. The user follows a menu of 16 questions in order to characterize a specific lesion. The program output is a list of the lesions in order of their estimated probability. In addition, an estimate of the extent of match between the lesion in question and the typical appearance of each lesion in the knowledge base is calculated. Preliminary trials indicate that ORAD is useful in assisting clinicians in formulating a differential diagnosis.

Diagnosis, Computer-Assisted↗
PubMed1988

Prior exposure to medical and dental x-rays related to tumors of the parotid gland.

Findings from this population-based study in Los Angeles County suggest, for the first time, that tumors of the parotid gland are related to prior exposure to diagnostic medical and dental radiography. Responses to interviews with 408 patients with a parotid tumor (269 benign tumors and 139 malignant tumors) were compared to responses of 408 neighborhood controls. Cumulative exposure of the parotid gland from diagnostic radiography was associated with a dose-related increase in risk of malignant tumors (P for trend less than .05; relative risk for exposure to greater than or equal to 50 rad = 3.4; 95% confidence interval = 1.02-11.46). Benign tumors showed a weaker positive association, and exposure before age 20 to a major diagnostic examination (full-mouth or panoramic dental radiography or medical radiography to the head) increased risk (relative risk = 1.8; confidence interval = 1.13-2.91). This study also confirmed the association of malignant tumors with prior radiation treatment to the head or neck; 28% of these tumors are attributable to exposure of the parotid gland from diagnostic and therapeutic radiation.

Adult↗
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↗
PubMed1988

A clinical comparison of xeroradiography and film radiography for the detection of proximal caries.

Xeroradiographs and conventional film radiographs (D- and E-speed) were compared in a clinical study with the use of 1 complete-mouth radiographs for (1) the presence of interproximal caries and (2) the determination of the depth of interproximal caries with the use of 200 tooth surfaces. In addition, an analysis of correct classification rates making a comparison of the same techniques was conducted. The results with the use of ROC analysis indicated that when a comparison was made of xeroradiography and D- and E-speed film, all techniques were equally useful. A broad range of observer ROC area values was found, indicating that diagnostic performance varies greatly with observer. The results of the diagnostic decisions made on carious surfaces versus noncarious surfaces indicated that all techniques tested were similar: 90% correct for noncarious surfaces and 77% correct for carious surfaces.

Dental Caries↗
PubMed1988

A clinical comparison between xeroradiography and film radiography for the detection of recurrent caries.

Xeroradiographs and conventional film radiographs (D- and E-speed) were compared in a clinical study with the use of one-half complete-mouth radiographs for the detection of recurrent dental caries in 200 teeth. The results indicated that film was the most useful in identification of noncarious restored teeth (91% correct versus 79% correct for xeroradiography); however, xeroradiography was better than film for detection of recurrent caries (67% versus 53%). With ROC analysis, both film and xeroradiography were equally useful, having the same ROC value of 0.78. At rates of 67% and 53% for detection of the presence of recurrent caries, neither imaging system can overcome basic geometric limitations of superimposition of metallic restorations. Thus, there is the continued need for careful clinical assessesment of existing restorations for the presence of recurrent caries.

Dental Caries↗
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↗
PubMed1987

Caries detection with xeroradiographs: the influence of observer experience.

This study evaluated whether the degree of experience of dentists with xeroradiography influenced their performance in interpreting proximal surface dental caries on xeroradiographs. The performance of ten dentists with a minimum of 1.5 years of experience with xeroradiography was compared with that of dentists inexperienced with xeroradiographs. These data, collected in a clinical environment, were compared with those collected in a controlled laboratory environment by dentists inexperienced in interpretation of xeroradiographs. It was found that lack of experience in viewing xeroradiographs does not compromise interpretation of these images. Furthermore, both high- and low-contrast xeroradiographs were found to be slightly more useful than conventional radiographs for the detection of proximal surface caries. In general, observers who had optimal viewing conditions performed better than those in a clinical environment.

Clinical Competence↗
PubMed1986

The Aerospace Medical Research Laboratory: a leader in the development of life support.

The progress in the development of life support for the crewman parallels the changing flight envelope of the airplane and spacecraft. A constant in this history is man. In spite of elaborate attempts to refine the selection of the crew, the basic lists of requirements has not changed. Only the urgency and the need for providing the entire list of requirements have been seen. Generally, progress in the flight envelope has demanded more reliable and often more complex provisions to support the crew. The debate as to how this should be done has often centered on the argument about having man wear or carry the life support elements versus integration of these provisions into the vehicle. This debate initiated the concept of risks/benefits, a debate that has now reached all aspects of man's endeavors, including his medical care. This paper will discuss the major milestones of providing life support, some of the key contributors (a role that General Armstrong played in a great way), and how this has provided the base for the next steps in aviation and space operations.

Aerospace Medicine↗
PubMed1985

Treatment of systemic mycoses with ketoconazole: in vitro susceptibilities of clinical isolates of systemic and pathogenic fungi to ketoconazole.

Ketoconazole was tested in vitro in three different media against 69 isolates of pathogenic fungi by using a macro-broth dilution procedure. The dimorphic systemic pathogens were highly susceptible, with most isolates of Blastomyces dermatitidis and Histoplasma capsulatum being inhibited and killed by concentrations less than or equal to 0.39 micrograms of ketoconazole/ml. Most isolates of Coccidioides immitis were also inhibited or killed by 0.39 micrograms of ketoconazole/ml; however, several were not killed by 100 micrograms/ml. Isolates of Cryptococcus neoformans and Sporothrix schenckii appeared to be less susceptible, with many isolates being resistant to less than or equal to 1.56 micrograms of ketoconazole/ml. There were 19 isolates of B. dermatitidis, C. immitis, and H. capsulatum recovered from 12 patients either during or following treatment with ketoconazole. Evidence for selection of secondary resistance to ketoconazole in these isolates was not observed. Results of these in vitro studies correlated poorly with the clinical responses to ketoconazole observed in the patients from whom the isolates were recovered.

Blastomyces↗
PubMed1985

A dental x-ray validation study. Comparison of information from patient interviews and dental charts.

Information was collected from dentists of a subset of participants in a case-control interview study conducted in Los Angeles County, California, in August 1980-August 1981 to evaluate the relationship of dental x-rays to tumors of the parotid gland. Complete dental charts were available from 142 dentists of 84 cases and from 130 dentists of 79 controls. Analysis of data from these interview-chart comparisons indicates that recall appears to be unbiased since the measures of agreement between interview and dental chart data are similar for cases and controls. The authors further conclude that interview data alone may be used for case-control comparisons of dental x-ray exposure and would, because of unbiased misclassification, tend to underestimate the relative risks.

Adult↗
PubMed1984

Patient-selection criteria for panoramic radiography.

The purpose of this study was to determine whether selection criteria could be developed for the use of panoramic radiographs in the treatment planning of patients seeking dental care. A total of 1,424 patients were included in this 10-month study. Clinicians were asked to indicate what signs or symptoms caused them to order a panoramic radiograph. After the radiograph was taken, the referring clinician was asked to indicate the extent that the panoramic radiograph influenced the patient's care. The panoramic examination was found to be most productive in dentulous patients when no other radiographs were ordered and least productive in dentulous patients who had already had a full-mouth set of radiographs. Considering all patients, it is possible to reduce the number of panoramic examinations by 73% while missing 6% of the findings that influence patient treatment. The most important selection criteria for the panoramic examination are whether the radiograph was ordered for a "general screening examination" (a negative predictor) and whether the radiograph was ordered for any specific examination (a positive predictor).

Adult↗