Frequency of Color Vision Defect in Students of Mashhad Dental School and Evaluation of Related Factors

Introduction: In esthetic dentistry, color matching ability is one of the influencing factors in treatment. To achieve this goal, matching the color of restoration with natural teeth is essential. The objective of this study was to determine the frequency of color vision defect in students of Mashhad Dental School and evaluation of related factors.Materials & Methods: In this descriptive analytical study, 356 students of Mashhad Dental School were evaluated. Demographic data including age, gender, color vision defect in relatives, use of glasses and contact lenses, refractive errors (myopia, hypermetropia and astigmatism) were documented in the designed questionnaire. To determine the impaired color vision, Ishihara diagnostic test was used. Statistical analysis of SPSS version 19 was performed using Chi-Square and Logistic Regression tests at the significance level of 0.05%.Results: Color vision defect was found in 6% (12 persons) of male students while none of the females were affected. All affected persons were red-green color blind and strong deutan. There was a significant relationship between color vision deficiency and history of color vision defect in relatives (P= 0.03), so that 25% (3 persons) of affected persons had a positive family history of color vision defect. Conclusion: Considering the frequency of color vision defect in the present study as well as the importance of color matching in dental treatments and because most affected persons are unaware of this defect, color vision tests seem necessary

Effect of Polyvinyl Siloxane Viscosity on Accuracy of Dental Implant Impressions

Objectives: The aim of this study was to compare the accuracy of dental implant impressions obtained by a combination of different impression techniques and viscosities of polyvinyl siloxane (PVS). Materials and Methods: Four parallel fixtures were placed between mental foramina in a master model of lower dental arch. Three different viscosities (putty/light body, medium body/light body, and monophase: heavy body) and direct and indirect techniques (six groups) were used, and seven impressions were obtained from each group (n=42). To measure the accuracy of impressions, drift, horizontal, and vertical angles of the implants, as well as the hex rotation of the implants in casts were evaluated using a digitizer device (1μm accuracy), in comparison with master arch. Data were analyzed using five-factor two-way ANOVA and Tukey’s post-hoc test. Results: The accuracy of impressions was assessed and the results showed that direct technique was not significantly different from indirect technique (P>0.05). Also, there were no significant differences between the mentioned viscosities except for the horizontal angle (P=0.006). Conclusions: Viscosity of impression materials is of high significance for the accuracy of dental impressions.