Three-dimensional analysis of dual-arch impression trays.

OBJECTIVE: The objective of this investigation was to measure and compare the dimensions of casts made using four types of impression trays and two impression materials to the dimensions of the original master model. This study differed from previous studies by using three-dimensional measurement. METHOD AND MATERIALS: Vinyl polysiloxane and polyether impressions were made of two crown preparations of ivorine teeth cemented into an acrylic master model. Two grooves were placed into each of the preparations. In addition, six points were placed on each occlusal surface and six were placed on each finish line. Impressions were poured with a Type IV dental stone at 48 hours. A three-dimensional measuring system was used to determine coordinates of 32 points on the master model and resulting casts. Inter- and intratooth dimensions were calculated from the measured coordinates. RESULTS: The accuracy and precision of the impression techniques were assessed using analysis of variance (ANOVA) and Dunnett's t test. The ANOVA and Dunnett's t test indicated that only the custom tray did not detect any inaccuracies and was as reproducible as the master model. CONCLUSION: This study suggests that the custom tray technique is most accurate, even though all other techniques evaluated apparently produce clinically acceptable results.

A multimedia patient simulation for teaching and assessing endodontic diagnosis.

Teaching and assessing diagnostic skills are difficult due to relatively small numbers of total clinical experiences and a shortage of clinical faculty. Patient simulations could help teach and assess diagnosis by displaying a well-defined diagnostic task, then providing informative feedback and opportunities for repetition and correction of errors. This report describes the development and initial evaluation of SimEndo I, a multimedia patient simulation program that could be used for teaching or assessing endodontic diagnosis. Students interact with a graphical interface that has four pull-down menus and related submenus. In response to student requests, the program presents patient information. Scoring is based on diagnosis of each case by endodontists. Pilot testing with seventy-four junior dental students identified numerous needed improvements to the user interface program. A multi-school field test of the interface program using three patient cases addressed three research questions: 1) How did the field test students evaluate SimEndo I? Overall mean evaluation was 8.1 on a 0 to 10 scale; 2) How many cases are needed to generate a reproducible diagnostic proficiency score for an individual student using the Rimoldi scoring procedure? Mean diagnostic proficiency scores by case ranged from .27 to .40 on a 0 to 1 scale; five cases would produce a score with a 0.80 reliability coefficient; and 3) Did students accurately diagnose each case? Mean correct diagnosis scores by case ranged from .54 to .78 on a 0 to 1 scale. We conclude that multimedia patient simulations offer a promising alternative for teaching and assessing student diagnostic skills.