Effect of Operator Experience on Ability to Place Sequential, 2-mm-thick Increments of Composite.

OBJECTIVE: To measure and compare the effect of operator experience in their ability to place composite in increments that are 2 mm thick. METHODS AND MATERIALS: Fifteen volunteers from each class of freshmen, sophomores, juniors, and senior dental students and 15 clinical faculty (total number of volunteers = 75) were asked to restore a Class I preparation that was 5 mm in diameter and 8 mm deep from the cusp tips using three increments of composite that were each to be 2 mm thick. Once completed, the models were sectioned, and the thickness of each increment was measured. A repeated-measures analysis of variance (pre-set α=0.05) was used to compare the mean increment thickness with respect to operator experience level and increment sequence number. In addition, the proportion of operators placing clinically acceptable increments (between 1.75 and 2.25 mm thick), as well as the proportions from each group who placed increments that either were thinner or thicker than this range, was determined using nonparametric analyses. RESULTS: Overall, there was an increasing trend for groups with a higher experience level to provide mean incremental thickness values close to 2 mm. However, the likelihood of placing an increment that was thicker or thinner than the manufacturer-recommended thickness was not significantly different. Regardless of the increment value, only about one-third of the increments placed fell within the desired range of 1.75 to 2.25 mm. CONCLUSIONS: Operator experience had no overwhelming significant influence on the ability to place increments of composite that were between 1.75 and 2.25 mm thick. An operator has only about one chance out of three to place a composite increment within this clinically acceptable range when using no external measurement system.

Effects of social relationships on survival for women with breast cancer: a prospective study.

In this study we examine the relationship between a woman's social contexts at the time of diagnosis and her chances of having survived breast cancer four years later. A cohort of 133 women were followed prospectively after initial diagnosis and treatment and data were obtained from a questionnaire mailed soon after diagnosis and from hospital charts. Using multivariate methods to examine predictors of survival, two clinical factors, pathologic nodal status and clinical stage of disease, were significantly associated with survival. In addition we found significant and independent effects on survival of: number of supportive friends, number of supportive persons, whether the woman worked, whether she was unmarried, the extent of contact with friends and the size of her social network. Thus, the woman's social context, particularly contexts of friendship and work outside the home, are statistically important for survival. Using existing literature, further data analyses and interviews with some survivors, we speculate on the ways in which social contexts may influence survival and suggest research methods suitable to this question.

Contraception with the cervical cap: effectiveness, safety, continuity of use, and user satisfaction.

With the growing interest in barrier contraceptive methods, the cervical cap has come back into use in North America. We examined the cap's effectiveness, safety, continuity of use, and user satisfaction among 617 women who were fitted at a family planning clinic in Toronto, Canada, between May 1981 and November 1983. Follow-up information was available for 516 of these women. Using a life table analysis with Bayesian adjustment, the probability of becoming pregnant after 12 months of use was 0.166 with a standard error of 0.022. There is evidence that after 1 year of use the caps deteriorate and that this deterioration may increase the risk of pregnancy. Many of the women in this study were very satisfied with the cervical cap; however, such problems as dislodgement, discomfort to user and partner, difficulty with insertion and removal, and unpleasant odour affected acceptability and continuity of use. It is likely that these problems could be alleviated by improving the quality of or changing the materials, modifying the design to improve the fit, and providing a greater range of sizes.