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OBJECTIVE: To measure the required clinical time and volume of occlusal adjustment when the maxillary cast in a virtual articulator is set using one of three methods: a face scan, average value alignment and digitization of a conventionally mounted articulator. MATERIALS AND METHODS: In this randomised, triple blind, crossover trial; 11 molars requiring a single crown restoration were enrolled. Three crowns were designed and milled for every participant molar. Each of the three crowns was fabricated with the participant’s casts virtually mounted utilizing a different virtual mounting method. An impression was taken of the crown in place prior to occlusal adjustment. Occlusal adjustment was then performed and timed. After the occlusal adjustment, an impression of the adjusted crown was taken. The pre-adjustment and post-adjustment impression were superimposed and volumetrically analyzed to determine the volume of occlusal adjustment performed. Kruskal-Wallis test was used to compare between the groups. RESULTS: No statistically significant difference in occlusal adjustment time or volume was found between crowns fabricated with different virtual mounting methods. CONCLUSIONS: A simplified approach in virtual articulator mounting appears to be justified in construction of single full coverage prosthesis. Added labor, time and cost of more elaborate virtual mounting methods seem to be counterproductive.

Objective To measure the required clinical time and volume of occlusal adjustment when the maxillary cast is positioned in a virtual articulator using one of three methods: digitization of a facebow-mounted mechanical articulator (group A), virtual Bonwill triangle (group B) or a 3D face scan (group F). Materials and methods In this randomized, triple-blind, crossover trial; 11 participants were enrolled. Every participant had one molar indicated for a single crown restoration. Three crowns were designed and milled for every participant molar totaling 33 crowns. Each of the three crowns was fabricated with the participant’s casts virtually mounted utilizing a different method. An impression was taken of the crown in place before occlusal adjustment. The occlusal adjustment was then performed and timed with the three crowns in the different groups. After the occlusal adjustment, an impression of the adjusted crown was taken. The pre-adjustment and post-adjustment impressions were digitally superimposed and the volume difference was measured. The Kruskal-Wallis test was used to compare the groups. Results Group A showed the shortest mean adjustment time (3:44.59 ± 3:39.07) followed by group F (4:30.09 ± 2:01.50) and group B (4:35.30 ± 2:32.33). The mean adjustment volume for group A was (28 ± 19.1 mm3) followed by group F (30.5 ± 18.8 mm3) and group B (40.6 ± 29.5 mm3). Different virtual mounting methods had no statistically significant effect on adjustment time (P-value = 0.538) or adjustment volume (P-value = 0.490). Conclusions A simplified approach in virtual articulator mounting appears to be justified in the construction of a single full-coverage prosthesis. Added labor, time and cost of more elaborate virtual mounting methods seem to be counterproductive.

Statement of the Problem: Alterations of pH in the oral cavity can lead to degradation of machinable esthetic materials that mimic the natural tooth appearance resulting in an esthetic failure. Hence, the stability of the optical and mechanical characteristics of these materials is essential for a long-term successful restoration.Aim of the Study: To evaluate the translucency, microhardness, and fracture toughness of two CAD/CAM materials (IPS e.max CAD and Vita Enamic) after immersion in two acidic beverages (Coffee and Coca-Cola).Materials and methods: A total of 36 samples were equally divided into two groups each (n=18) as follows, Group I: IPS e.max CAD and Group II: Vita Enamic. Each group was further subdivided into two subgroups (n=9) according to the acidic beverage used, either Coffee, or Coca-Cola. Samples were immersed in acidic beverage solutions for three weeks, after which all samples were subjected to measure the translucency parameter using a Reflective Spectrophotometer and then using Vickers Micro-Hardness Tester to measure surface microhardness and fracture toughness. Statistical analysis was performed using one-way analysis of variance followed by Tukey's posthoc test if showed significance. Student t-test was done between main groups, while Two-way ANOVA compared the effect of each factor.Results: There was a statistically significant difference between IPS e.max CAD and Vita Enamic regarding translucency. Significant difference in surface microhardness, and fracture toughness after immersion in two acidic beverage solutions was revealed.Conclusions: Acidic beverages can adversely affect the translucency of glass-ceramic and hybrid ceramic materials. Microhardness and fracture toughness of different CAD/CAM esthetic materials was negatively affected secondary to exposure to beverages with low pH values.