Objective The aim of this in vitro study was to evaluate the effects of substrate colors, different levels of ceramic thickness and translucency, and cement shades on the color difference from a reference color of lithium‐disilicate crowns. Materials and Methods A premolar tooth preparation was made on a study model for 1.0 and 1.5 mm thick full‐ceramic crowns. Digital impressions were taken (3Shape TRIOS) and crowns designed in a CAD program (DentalDesigner). Shade A1 crowns were milled (Everest, Kavo) from high‐translucency (HT) and low‐translucency IPS e.max (Ivoclar Vivadent) blocks. Twelve substrates were made of different colors and materials (Natural Die Material, Co‐Cr, zirconia, and gold‐colored alloy). Three different shades of try‐in pastes were used to simulate the effect of cements (Variolink Esthetic try‐in paste; Ivoclar). Shade measurement was done three times for each crown by a spectrophotometer (VITA Easyshade Advance); averages were compared to a reference crown (A1, HT, 1.5 mm, ND2 abutment, neutral try‐in paste) with ΔE00 (CIEDE2000, according to the CIE latest standard) calculated. Results All the examined parameters influenced the ΔE00 of the crowns. The weakest effect was exerted by the try‐in paste. Conclusions All examined parameters influenced the final color of e.max CAD lithium‐disilicate ceramic crowns. Clinical Significance Matching the shade of ceramic crowns to the natural tooth color is a great challenge in dentistry. To meet patients' increasing esthetical expectations, CAD/CAM methods are very popular for full‐ceramic crowns. However, several factors such as the shade of the abutment, luting cement color, ceramic thickness, and translucency may influence the final color. Our objective was to measure the optical effect of these factors on the final shade of CAD/CAM lithium‐disilicate ceramic crowns.

Background The objective of this research was to investigate the change in dimensional stability of 3D printed dental model construction types with time. By comparing the models to each other, we sought to find the most suitable building technique based on causing the least deformation of the 3D printed model with time.Methods Four dental casts were printed at an angle of 0°, polymerizing every 50 µm using UV light with a wavelength of 405 nm. The four types of models were as follows: 2.5 mm wall thickness hollow (2,5 mm.H), 2 mm wall thickness hollow (2 mm.H), 2 mm wall thickness hollow with stabilization bars (2 mm.B), and 2 mm wall thickness with hollow with gypsum base (2 mm.G). Casts were digitized with a laboratory scanner (3Shape E3 Red E Scanner) after printing, to create the reference Standard Tessellation Language (STL) files. All models were stored under constant conditions (25°C and 50% humidity) and scanned again after 1 day and 1, 2 and 10 weeks. These scan data were compared to the reference STL file and were analysed by comparing the deformation in a surface fitting software (Geomagic Control X, 3D Systems). The results were statistically evaluated using paired Student’s t tests with the SPSS 23.0 software program. The significance level was set at p < 0.05.Results There were significant differences in dimensional stability after 10 weeks between the 2.5 mm.H(18,45 µm ± 7,661) and 2 mm.B(11,49 µm ± 2,648), p < 0.05; the 2 mm.H(13,81 µm ± 3,18) and 2 mm.G(21,57 µm ± 1,897) p < 0.0001; and the 2 mm.B(11,49 µm ± 2,648) and 2 mm.G(21,57 µm ± 1,897) p < 0.0001 casts. The results suggest that the 2 mm.B casts experienced the least deformation.Conclusions For of all casts, the deformation stayed within the clinical acceptance range, but there were significant differences between the different building structures. Of this four structures, the 2 mm cast with a stabilization bar (2 mm.B) showed the best results.

The aim of this case report is to explain the clinical and laboratory procedures for fabricating ultra-thin lithium-disilicate pressed veneers using a mixed analog/ digital workflow. Summary: Four ultra-thin pressed lithium-disilicate veneers were produced for maxillary fractured incisors with the help of virtual smile design, digital wax-up and intraoral mock-up. With initial photos from the patient, the smile design could be performed considering the patient's individual face form. An intraoral scan was taken for the digital wax-up, which was guided by the contour line of smile design on the face photo. A printed model and template were manufactured for the mock-up. After a guided minimally invasive preparation and digital impression, the final veneers were designed as an exact copy of the mock-up. Wax pattern was designed on computer and fabricated by milling machine. Finally, lithiumdisilicate veneers were pressed, individualized and cemented using an adhesive technique. Key learning points: 1. digital workflow is convenient for a predictable procedure making ultra-thin lithium-disilicate pressed veneers. 2. the virtual smile designdigital wax-up-intraoral mock-up scheme presents an opportunity for effective communication with the patient and laboratory. 3. smile design software recommends an ideal smile curve for the patient with the help of definitive points and reference lines on the face. 4. guided preparation through mock-up preserves the greatest amount of enamel structure, which is important with regards to adhesive cementation. 5. when pressing lithium-disilicate veneers, a mixed analog/digital workflow using CAD and a milled wax pattern results in better physical properties and marginal fit than fully digitally milled veneers.