Biomedical subjects
Publications and source records attributed to K N May.
Four proprietary composite resins cured with ultraviolet light were inserted into Class I and II cavity preparations. The restorations were evaluated over a 3-year period for color match, interfacial staining, secondary caries, loss of anatomic form, marginal adaptation, and surface texture. The percent of restorations exhibiting no generalized loss of anatomic form ranged from 47% to 93%.
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Acquisition of psychomotor skills is one of the most important educational tasks in dental education; yet, there has been little systematic research in this area. This investigation compared a traditional method of teaching psychomotor skills with an experimental method. The investigation was conducted in a preclinical restorative dentistry laboratory course. Eighty-eight freshman students were randomly assigned to an experimental (n = 44) or control group (n = 44); instructors (n = 4) were randomly assigned to each group. The control group was taught using the traditional method used at the University of North Carolina School of Dentistry at Chapel Hill; the experimental group was taught using a guided systematic approach that relied on detailed checklists and exhaustive faculty feedback. Dependent variables measured were quality of performance on laboratory practical examinations, time required to complete practical examinations, and time required to complete the course. Results suggest that this experimental approach has promise for psychomotor skill teaching and learning in dentistry.
The student evaluation system in a preclinical technique course serves several important functions. This paper describes an evaluation system that has been used for three years. Designed to evaluate student performance in the cognitive, psychomotor, and affective domains, the system maximizes characteristics of formative evaluation and uses multiple forms of assessment to evaluate competency. Further, specific provisions have been made to ensure timely and detailed feedback and opportunities for remediation. Over the past three years, student and faculty review of this system has been positive.
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Total and anaerobic counts were ascertained on boneless, cooked, cubed, frozen chicken meat. We determined survival of aerobes and anaerobes in the natural flora after the meat was freeze-dehydrated and rehydrated at room temperature for 30 min and at 50, 85, and 100 C for 10 min. Total and anaerobic counts of bacteria in the rehydrated meat were established during storage of samples at 4, 22, and 37 C-until a spoilage odor was detected. Samples were also inoculated with Clostridium sporogenes and were dried and rehydrated at 100 C and stored at 37 C. Approximately 21% of the aerobes and 37% of the anaerobes survived drying and rehydration at room temperature. Many genera of aerobes, anaerobes, and facultative anaerobes survived drying and rehydration at 50 C; only sporeformers survived rehydration at 85 or 100 C. Low-temperature (4 C) storage of rehydrated meat produced ample shelf life (over 20 days), whereas storage at the higher temperature resulted in a shelf life of less than 30 hr. Approximately 81% of the C. sporogenes cells survived rehydration at 100 C and grew to over 10(7) cells within 40 hr. Our study presents additional data for adequate microbiological control in processing of freeze-dehydrated meat. Also, it points out the natural selection for sporeformers at high temperature of rehydration, stressing the need for consumer education in product handling for safety purposes.
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Previous studies have shown that different phosphoric acid-based etchants do not penetrate intertubular dentin to the same depth. The purpose of this study was to determine the effect of different phosphoric acid-based conditioners on dentin shear bond strengths of three one-bottle bonding systems and to evaluate the corresponding interfacial ultramorphology. The null hypothesis to be tested was that no correlation could be established between the depth of intertubular demineralization and dentin shear bond strengths. The labial surface of 90 bovine incisors was polished to expose middle dentin. The specimens were randomly assigned to three one-bottle adhesive systems (n = 30): OptiBond SOLO, Permaquick PQ1, and Single Bond. For each adhesive system the specimens were divided into three subgroups of different silica-thickened etching gels (n = 10): 37.5% phosphoric acid gel (Kerr Gel Etchant), 35% phosphoric acid gel (Ultraetch), and 35% phosphoric acid gel (Scotchbond Etching Gel). After 24 hours in water at 37 degrees C, the specimens were thermocycled for 500 cycles in baths kept at 5 degrees C and 55 degrees C and the shear bond strengths measured. The data were analyzed with one-way and two-way ANOVA. Further, the adhesives were applied to 800 microns-thick bovine dentin disks (two per subgroup), which were restored with a low-viscosity composite resin. Six small dentin/resin sticks with a cross-section of 1.0 mm x 1.0 mm were obtained from each bonded disk. They were then decalcified in a buffered solution of EDTA, fixed, stained, and sectioned in 90 nanometer-thick slices to observe under the Transmission Electron Microscope (TEM). The mean shear bond strengths were not statistically different at a confidence level of 95%. When the means were pooled for dentin adhesive and for etching gel, the number of cohesive failures was greater for Permaquick PQ1 and for Ultraetch, respectively. Pearson's correlation coefficient showed no correlation between hybrid layer thickness and bond strengths. The ultramorphological observation showed that all materials penetrated the dentin and formed a hybrid layer, regardless of the etching gel used.
UNLABELLED: This study compared the diagnostic accuracy of bitewing images for detection of simulated recurrent caries using the following imaging modalities: Ektaspeed Plus film and different digital imaging system technologies comprised of a charge-coupled device (CCD) based digital imaging unit, a photo-stimulable phosphor (PSP) based unit and contrast- and brightness-enhanced PSP images. STUDY DESIGN: Twenty-four extracted posterior teeth with MOD inlay preparations were secured in models simulating a natural arrangement of teeth. Lesions were created in proximal boxes using dental burs of varying sizes. Defects were filled with wax and plaster and preparations were restored with composite or amalgam. RESULTS: Averages of receiver operating curve areas (Az) revealed diagnostic performances of Az = 0.74 for film, Az = 0.80 for CCD, Az = 0.73 for unenhanced PSP and Az = 0.64 for enhanced PSP. The differences between these means were significant (MANOVA p < 0.0001). Unenhanced PSP produced significantly poorer performance than other modalities. CCD performance was not significantly better than enhanced PSP. Lesions under radiopaque composite restorations were easier to detect, followed by those under amalgam and radiolucent composites across imaging modalities and lesion locations. Based on lesion location, those located at the buccal point angle were easiest to detect, followed by those at mid-gingival floor and lingual-point angle sites. CONCLUSIONS: Contrast and brightness-enhanced digital images enabled better signal detection and a comparable performance with film for detection of artificially induced recurrent caries.
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