OBJECTIVE: The aim of the present study was to evaluate color changes and force degradation of orthodontic elastomeric ligatures in different stretching patterns during a 8-weeks period. METHODS: Two elastomers with the minimum and two with the maximum color changing, and gray elastomers of two brands (American Orthodontics and Ortho Technology) were selected according to an opinion poll with clinicians and color changes after 4 weeks of intraoral use were evaluated. These elastomers were mounted on special jigs fabricated using a CAD-CAM technique, underwent different stretching patterns and the force was measured in 0, 24 hours, 2, 4 and 8 weeks. During in vivo part of the study, force levels of elastomers were measured after 4 weeks on a material testing machine. Data were analyzed with four-way ANOVA and Tukey post hoc tests.RESULTS: All the elastomers showed color changing but the degree of color stability was significantly different. The mean force degradation was higher in 1-mm stretch groups. After 8 weeks, the average residual force of elastomers was 1.45 ± 0.18 N and the maximum force decay was seen in the elastomers that exhibited the maximum initial force.CONCLUSION: There is significant relationship between the stretching pattern and the amount of residual force of elastomers. Elastomers with higher initial forces exhibited higher percentages of force loss after 8 weeks. It seems that there is a relationship between initial color and color changing of elastomers.
STATEMENT OF THE PROBLEM:Examinations have an important role in evaluating students’ learning outcomes and their mastery of a subject. Passing or failing an examination can have far-reaching consequences for the students. Therefore, it is not surprising that international studies consistently show that dental students report examinations and grades among the highest ranking stressors in dental schools.PURPOSE:The aim of this research was to measure the levels of anxiety, self-perception of preparation and expectations for success using an objective structured clinical examination (OSCE), a written examination and a preclinical preparation test, and to examine the effects of the three predictive variables on the outcomes of assessments.MATERIALS AND METHODS:The present research is a cross-sectional study. The population under consideration was students of Kerman Dental School in 2013. Examination anxiety was measured with Spielberger's state anxiety inventory. Preparation for the assessment (I am fully prepared = 4, I am prepared = 3, I’m not prepared = 2, I’m not fully prepared = 1) and expectation to succeed (I am quite successful = 4, I am successful = 3, I’m not successful = 2, I’m not quite successful = 1) were quantified with Likert scale. The questionnaire was completed during an OSCE, a written examination, a preclinical crown and bridge preparation test and a nonexamination situation.RESULTS:The study population consisted of 138 4th, 5th, and 6th year Kerman dental students (65 males and 73 females). The results showed that all the assessment methods induced a significant increase in state anxiety compared to baseline levels with the highest anxiety levels reported during an OSCE (62.4 ± 8.1, P = 0.04) and a written examination (48.8 ± 9.2, P = 0.04). The preparation levels in females were significantly higher than those in males in OSCE (P = 0.03) and written (P = 0.04).CONCLUSION:State anxiety was high in all the three assessment methods. OSCE induced more anxiety than other assessment formats. However, anxiety was not predictive of performance outcomes in contrast to preparation and expectation to succeed, which were good predictors of the outcome scores. Also, this study showed that despite a better answer to the assessment of (I prepared myself well for the test), the students showed high levels of state anxiety.
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