Comparison of digital scanning and polyvinyl siloxane impression techniques by dental students: instructional efficiency and attitudes towards technology.

INTRODUCTION: With increasing use of digital scanning with restorative procedures in the dental office, it becomes necessary that educational institutions adopt instructional methodology for introducing this technology together with conventional impression techniques. OBJECTIVE: To compare the time differences between instructing dental students on digital scanning (DS) (LAVA C.O.S. digital impression system) and a conventional impression technique (CI) (polyvinyl siloxane), and to compare students' attitudes and beliefs towards both techniques. MATERIALS AND METHODS: Volunteer sophomore dental students (n = 25) with no prior experience in clinical impressions were recruited and IRB consent obtained. Participants responded to a pre-and post-exposure questionnaire. Participants were instructed on the use of both DS and CI for a single tooth full coverage crown restoration using a consecutive sequence of video lecture, investigator-led demonstration and independent impression exercise. The time necessary for each step (minutes) was recorded. Statistical significance was calculated using dependent t-tests (time measurements) and 2-sample Mann-Whitney (questionnaire responses). RESULTS: The time spent teaching students was greater for DS than CI for video lecture (15.95 and 10.07 min, P = 0.0000), demonstration time (9.06 and 4.70 min, P = 0.0000) and impression time (18.17 and 8.59 min, P = 0.0000). Prior to the instruction and practice, students considered themselves more familiar with CI (3.96) than DS (1.96) (P = 0.0000). After the instruction and practice, participants reported CI technique proved significantly easier than expected (pre-instruction: 3.52 and post-instruction: 4.08, P = 0.002). However, overall participants' perception of ease of use for DS was not influenced by this instruction and practice experience (pre-instruction: 3.84 and post-instruction: 3.56, P = 0.106). Despite the results, 96% of participants expressed an expectation that DS will become their predominant impression technique during their careers. CONCLUSIONS: Dental students with no clinical experience have high expectations for digital scanning, and despite their initial difficulty, expect it to become their primary impression technique during their professional futures. The instructional time necessary for introducing DS into the curriculum is significantly greater than CI in both classroom (lecture) and clinical simulation settings (investigator-led demonstration).

Is cerebral control of plasma [Na] a major determinant for systemic sodium balance?

To evaluate the role of volume expansion for prandial/postprandial natriuresis, we first determined spontaneous daily NaCl, H2O, and diet turnover and Evans blue and inulin spaces in male Wistar rats on various high-salt diets. Second, we measured the time course of Na and water clearance in chloralose/ketamine anesthetized rats over 270 minutes after a single intragastric Na load (0, 290.4, or 581 micromol/100 g body weight). Finally, similar measurements were made during and after a local [NaCl] increase in the left carotid artery supplying the brain for 60 minutes. Daily NaCl, H2O, and diet intake per rat was 2 to 74 mmol, 13 to 223 ml, and 1.5 to 33 g, respectively. Only inulin space and plasma [Na] correlated with daily Na uptake (X; regressions Y = 0.02X + 15.13, N = 99, r2 = 0.0716, P = 0.02; and Y = 141.7 + 0.1005X, N = 179, r2 = 0.104, P < 0.0001, respectively). Under chloralose/ketamine anesthesia, 86% to 102% of the total (i.v. plus i.g.) Na load and some 50% of the unilaterally administered intracarotid Na were excreted. Chloralose/ketamine anesthesia is thus suitable for studies on Na balance mechanisms. Plasma [Na] is under cerebral control. Because of its immediate onset, this mechanism might be the principal determinant of prandial and postprandial natriuresis and hence for the systemic Na balance.

Chloralose/ketamine anaesthesia preserves a form of postprandial sodium chloride balance in Wistar rats.

Studies on the mechanisms underlying Na balance in anaesthetized rats are complicated by the fact that the most frequently used barbiturate anaesthetics attenuate or abolish this phenomenon. In the present study we show that a combination of nonbarbiturate anaesthetics: chloralose (140 mg/kg i.v.) and ketamine (30 mg/kg i.m. ), preserve the ability of rats to excrete intragastrically applied NaCl loads dose dependently. Thus rats anaesthetized with this regime excreted 86-102% of in- tragastrically applied NaCl whereas rats anaesthetized with thiobutabarbitone sodium (Inactin) excreted only 20-28%. We conclude that chloralose/ketamine anaesthesia is suitable for studies on Na balance mechanisms.