Asunto(s)

Asunto(s)

Asunto(s)

Asunto(s)

Asunto(s)

RESUMEN

This study evaluated the accuracy of occlusal contacts relative to the mode in which casts are mounted. Specifically, the direct effect on occlusal contacts was assessed with respect to: (a) the type of mounting stone used; (b) the amount of material used relative to the distance between the mounting plate and the cast base; and (c) the presence or absence of a restriction of the articulator's vertical opening. A 3 x 2 x 2 factorial analysis of variance and a Dunn's Multiple Comparison Procedure (P < .05) showed that one of the three mounting stones was statistically significantly less accurate in reproducing occlusal contacts when a distance of 19 mm existed between the cast and the articulator, regardless of the existance of articulator restriction.

Asunto(s)

RESUMEN

While several investigations assessing applications of contemporary motor learning theory to preclinic laboratory instruction have been successful, they provide only indirect and incomplete validation of theoretical constructs. This study's purpose was to further evaluate the validity of salient constructs through the use of a validation technique called verbal self-reporting, and to describe applications for dental education. Subjects were videotaped completing a preparation. Later, the tape was replayed and a structured interview used to stimulate recall of mental processes that occurred during the preparation. Transcribed self-reports were classified by two calibrated raters into categories corresponding to the constructs of interest. Results confirm many of the constructs' characteristics. Subjects reported that they a) defined the desired outcome in detail before beginning production; b) defined performance strategies that would be useful for different aspects of the preparation; c) constantly generated knowledge of results during the course of production in order to directly assess the adequacy of the product; and d) generated knowledge of performance as an indirect assessment of product acceptability especially when visual access was impeded. These results support previous applications of the theory to dentistry and have important implications for the improvement of instruction in preclinic laboratory courses.

Asunto(s)

RESUMEN

Previous investigations have revealed commercial alginate impression material to be contaminated with viable microorganisms. Some manufacturers are now producing alginate materials that contain antimicrobial agents. The purpose of this study was to test and compare two antimicrobial and four control brands without antimicrobial agents of commercial dental alginate impression material for the presence of viable microorganisms. Forty-eight or 96 measured samples of each brand were taken from previously unopened containers using a sterile technique. The samples were placed on chocolate agar plates and in thioglycolate broth tubes and were incubated along with appropriate parallel controls. After incubation, colonies were enumerated, gram-stained, and identified using standard microbiologic methods. The two antimicrobial brands contained viable organisms in 12.5% of the samples incubated on agar media and also contained such organisms from 0% to 16.7% of the samples incubated in thioglycolate media. The four control brands contained viable organisms in from 29.2% to 100% of the samples incubated on agar media and also contained these organisms in from 25% to 79.2% of the samples incubated in thioglycolate media. There was a statistically significant difference (p less than 0.05) in contamination frequencies among some brands. Contamination frequencies of the top and middle portions of the containers did not differ significantly. The concentration of organisms in contaminated samples was 2.8 colony-formed units (CFUs) per gram for the antimicrobial alginates, and from 9 to 161.1 CFUs per gram for the control brands.(ABSTRACT TRUNCATED AT 250 WORDS)

Asunto(s)

RESUMEN

The purpose of this study was to test the adherence strength of oxides to some silver-free high-palladium alloys, and to compare the results to values obtained from Au-Pd and Ni-Cr metals. The results showed that the adherence strengths of the oxides were greater than the reported cohesive strength of opaque porcelain. This would indicate that the oxides formed on the alloys examined in this study are sufficiently adherent to their substrates to produce adequate porcelain bonds.

Asunto(s)

Asunto(s)

Asunto(s)

RESUMEN

The purpose of this study was to describe the prevalence of decayed, missing, and filled teeth among federal male prisoners (aged 21-75) in the US Penitentiary. Leavenworth, Kansas, and to assess the impact of age, race, number of years incarcerated, and number of visits to the prison dentist on these parameters of oral health. Inmates (n = 191) were randomly selected and represented 16.4 percent of the prison population (N = 1,161). Two calibrated examiners collected caries and tooth loss data using NIDR criteria. No radiographs were taken. Results showed a mean DMFT of 12.9 for inmates aged 20-34, 16.4 for inmates aged 35- 44, and 22.1 for inmates aged 45 and older. Whites had significantly fewer decayed teeth (P less than .05) than black inmates for ages 20-34. The number of missing teeth increased significantly (P less than .01) with inmate age. Proportion edentulous (both arches) was 5.2 percent for ages 35 to 44, 17.3 percent for ages 45-54, and 45.5 percent for ages 55 to 75. Cross tabulations and chi-square analyses showed that inmates incarcerated less than two years had a significantly (P less than .001) lower utilization rate of dental services, and that inmates who made greater use of available dental services had fewer decayed teeth than those with lower utilization rates.

Asunto(s)

RESUMEN

Preclinical technique curricula seldom provide training in those prerequisite skills that may facilitate performance in a large class of procedures. Instead, students typically progress from simple to increasingly difficult preparations and it is assumed that positive transfer occurs between them. Another strategy that may provide greater benefits is the leadup activity, which closely simulates the criterion tasks, but eliminates one or more complexities thought to interfere with prerequisite skill acquisition. This investigation evaluated the effectiveness of such a training program on performance in all projects of a freshman operative laboratory course. Twenty-six student volunteers participated in an eight-hour program that was largely self-instructional. Their performance was compared to that of a randomly selected control group with replacement at each observation. Raters were calibrated and blind to group affiliation of completed preparations. Analyses of covariance with PAT as the covariate indicated that the experimental group statistically significantly outperformed the control group on all but one preparation. It is concluded that the implementation of leadup activities at least for a freshman operative technique laboratory may be warranted.

Asunto(s)

RESUMEN

This article reviews one theory of motor performance that was derived from a large body of research findings. The validity of any theory depends on the extent to which it can generate testable hypotheses. Based on a number of applied investigations in the preclinical setting, several predictions developed from this theory have been supported. These, as well as other, potential applications are discussed and a model of preclinical instruction derived from the theory is presented.

Asunto(s)

RESUMEN

Various investigations have reported the presence of cytotoxic lymphocyte activity in inflammatory periodontal disease. The collective evidence indicates that the inflammatory infiltrates of gingivitis and periodontitis should feature a major component of large granular lymphocytes (NK-cells) possessing cytotoxic potential. Thus, the purpose of this study was to determine and compare, by use of immunohistochemical methods, the numbers of NK-cells in biopsies of clinically healthy gingiva, chronic gingivitis and chronic adult periodontitis and their relationship, if any, to the T- and B-lymphocyte populations. Gingival biopsies were obtained from 8 patients in each of three disease groups selected on the basis of predetermined clinical criteria. Using the avidin-biotin immunoperoxidase technique, four consecutive serial sections from each biopsy specimen were stained with a panel of antihuman monoclonal antibodies for T-lymphocytes (UCHL-1) B-lymphocytes (CD-45R), and NK-cells (Leu-7 and Leu-11b). Analyses of variance yielded a statistically significant main effect for each cell immunophenotype. The Newman-Keuls Sequential Range Test showed statistically significant differences for all but two mean comparisons (p less than 0.01). The comparisons for UCHL-1 and Leu-7 between chronic gingivitis and periodontitis specimens did not demonstrate significance. Although T- and B-lymphocyte populations increased approximately 20 x progressing from healthy to gingivitis to periodontitis specimens, the NK-cell population showed only a 3 x increase which represented 19%, 6.6% and 7% of the total of all positively stained lymphocytes across biopsy groups.

Asunto(s)

RESUMEN

Knowledge of results (KR) for subtasks is an important type of error information for students, since it is related to a particular sequence of movements. Students' attempts to correct movement errors may be hindered when the KR provided by different instructors is not consistent. This investigation evaluated the effectiveness of a training program designed to improve interrater agreement and reliability of assessments for subtasks. The training consisted of discussions of five case studies, and subsequent group grading of prepared teeth. A comparison of pre- and posttraining data suggests that interrater agreement for subtasks can be significantly improved, thereby providing students with more consistent KR.

Asunto(s)

RESUMEN

Knowledge of the desired outcome of a series of movements is a critical component of motor performance, since it is used to develop the appropriate motor program and to form a basis for understanding terminal extrinsic feedback and formulating subjective reinforcement. In dentistry, information about the desired outcome is almost always disseminated in a lecture and laboratory manual, and a demonstration often is provided. However, mastery by students usually is not given the importance it deserves. The purpose of this study was to evaluate an instructional strategy designed to increase the students' knowledge of the desired outcome by determining whether such knowledge had an effect on dental motor performance. Two intact groups of first-year dental students were randomly assigned to a control or experimental treatment. The control treatment included conventional written and oral descriptions of criteria and methods for completing the occlusal (n = 93) and mesio-occlusal (n = 99) amalgam preparations. The experimental treatment directed the students' attention to critical features of tooth anatomy, and the preparation and methods for assessing performance. Results indicated statistically significant differences (p less than .05) in favor of the experimental group for both performance and degree of agreement with the instructor's evaluation of the mesio-occlusal amalgam only.

Asunto(s)

RESUMEN

In preclinical dentistry, precise terminal knowledge of results (KR) typically is provided by an instructor when the student has completed all or a portion of a preparation. A contemporary model of psychomotor learning implies that performance can be improved if continual precise KR also is available. This investigation compared a traditional instructional format that provided instructor-generated terminal KR with one that also trained students to generate continual KR using two sections of an operative laboratory (n = 55 each). The dependent variable was student performance on occlusal and mesio-occlusal amalgam preparations. Students in the experimental group significantly outperformed those in the control group on both preparations.

Asunto(s)

RESUMEN

Many investigators have reported attempts to develop reliable laboratory and clinic evaluation systems. However, few studies, regardless of level of success, have used an analytic procedure to identify those components of the evaluation system that, if refined further, could improve reliability. This paper described the development of an evaluation system for two preclinical laboratory courses. Reliability estimates of 0.80, 0.74, and 0.68 were obtained for three different evaluation instruments used in conjunction with the evaluation system. An analytic technique for identifying components contributing to, and detracting from, the reliability of the evaluation system is also described. Further refinements based on this analysis are discussed.

Asunto(s)