The main objective of the study was to recognize the effect of ceramic thickness and luting agent on the extent to which the restoration masks color variations that may be present in the underlying dental structure. Two pressable ceramics were used: Lithium disilicate reinforced (IPS e.max- Ivoclar Vivadent) and Leucite reinforced (Cergo- Dentsply). Fifteen ceramic discs were manufactured from each ceramic and divided into three groups, according to the thickness (0.5, 1, 1.5 mm). To simulate the color of a dark underlying dental structure, background discs, color C3, with 20 mm diameter, were made using resin composite. The ceramic discs with varying thicknesses were seated on the dark background of the resin composite with either resinous opaque cement or resinous cement. The color parameters were determined by the CIE Lab system of colors using a spectrophotometer and color differences (ΔE) were calculated. The results were then statistically analyzed, using ANOVA test and Tukey HSD test. The ΔE values of both ceramic systems were affected by both the luting agent and the ceramic thickness (P < 0.05). The use of an opaque luting agent resulted in an increase of the ΔE* values for all ceramics tested, regardless of the thickness. For the 1.5-mm thick veneers, higher values in the color parameters were obtained for both ceramic materials. The color masking ability of ceramics used for laminate veneers is significantly affected by the thickness of the ceramic and the shade of the luting agent used.

The venting and practice abutment techniques are suitable methods for reducing retained excess cement with optimal retention values.

Background and Objectives:This study was conducted to evaluate the retention of various prefabricated posts and to compare them with that of the conventional cast post.Materials and Methods:A sample of 60 freshly extracted single-rooted human mandibular first premolars were sectioned horizontally, 1 mm coronal to the cemento-enamel junction and randomly divided into four groups consisting of carbon fiber posts, glass fiber posts, stainless steel posts and cast metal posts. Cast metal post was the control group. Each group contained 15 specimen. The post space of 9 mm depth was prepared using specific drill supplied by the manufacturer. Resin patterns of the prepared post spaces were fabricated for 15 specimen and were cast in nickel chromium base metal alloy. All the posts were cemented with self-adhesive resin cement and mounted in acrylic cylinders. The teeth were subjected to tensile pull-out test using a universal testing machine. The force required to dislodge each post from the teeth was recorded. The data was analyzed using one-way analysis of variance and Bonferroni test.Results:The bond strength of all the prefabricated posts was significantly lower than the conventional cast post. Among the prefabricated posts highest bond strength was obtained for prefabricated stainless steel post and lowest for carbon fiber posts. There was no significant difference in the mean bond strength obtained for stainless steel and glass fiber post.Conclusion:Though no single prefabricated post could achieve results close to the control group, most retentive among the experimental group were the stainless steel posts. However, conditions where nonmetallic posts are indicated most preferred type of post can be the glass fiber posts.

No abstract