Al-Rafidain Dental Journal

Aim: To evaluate the effect of beverages (Distilled water ,Artificial orange, Zamzam water, Natural orange, Cola, coffee, and Tea) on the color stability of the highly impact resin. Materials and methods: Total samples of this research were (48) samples of highly impact resin were prepared 30 * 20 * 1.5 mm (length, width and thickness). Six samples were immersed in each type of beverage. The last six sample (control) without any type of beverage (after control group and other beverage groups were evaluated after (3 hours, 9 hrs, 18 hrs, 36.5 hrs, and 73 hrs) immersion time intervals by using (CIE L* a* b* ) system. the results of this research were analyzed statistically by ANOVA and Duncan’s multiple range test. Results : There was no significant difference among beverages at immersion time intervals (3 hrs, 9 hrs, 18 hrs, and 73 hrs) except at (36.5 hrs) there was a significant difference, also the results showed that there was no significant difference among immersion time intervals for different types of bever-ages. Conclusions: among beverages coffee and tea showed unaccepted value of ΔE at all immersion time intervals except at (9 hrs) while cola showed an accepted values of ΔE except at (3 hrs) of immer-sion where ΔE value was unaccepted.

Introduction: Early orthodontic treatment is recommended since the morphologic pattern of the prognathic face associated with excessive forward mandibular growth is most likely established early in life. The chin cup is the preferred orthopedic appliance for growing children with mandibular prognathism and a normal maxilla. Aims Of Study: Evaluation of the stress and displacements in the mandible from various chin cup force vectors, using three-dimensional finite element model. Materials And Methods: Three-dimensional model of the mandible was modeled and analyzed. Chin cup with 800 g force was applied on the pogonion of the mandible. The direction of the loading vectors were 150, 200, 250, 300, 350, 400 and 900 relative to x axis, then, the mechanical responses in terms of displacement and Von Mises stresses are evaluated. Results: The highest stress levels observed in the condylar, posterior ramus regions and inferior sigmoid notch, and increased as the force vector was transferred away from the condyle. The mandible was displaced in downward and backward direction with the vector passing below and through the condyle (with angles 150, 200 and 250) forward and upward displacement was recorded as the force vector move away from the condyle (within 300, 350, 400 and 900). Conclusions: With the limitations of modeling, boundary conditions, and solution assumptions, chin cup applied in various directions produce different force vectors, which induce different stress and displacements. The force vector is an important determinant of the orthopedic effects of the chin cup and therefore should be carefully considered.