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Aims: The study aims to assess the effect of Arabic Qahwa (AQ) on the color parameters of lithium disilicate glass ceramic (LDGC), IPS e.max computer-aided design (CAD), and multilayered zirconia CAD/ computer-aided manufacturing (CAM) ceramic materials after immersion in AQ and also, to measure the biaxial fracture strength and fracture modes of the tested materials., Materials and Methods: Sixty circular specimens were milled from LDGC and zirconia. Before AQ immersion, the color parameters of the specimens L, a, and b were measured and recorded using a spectrophotometer on white, black, and gray background and analyzed after AQ staining and aging for 14 days. Biaxial compressive forces and fracture types were recorded. The collected data were analyzed with SPSS for descriptive statistics, one-way analysis of variance, and post hoc tests., Results: The overall TP values were 16.79 and 15.85 for LDGC and zirconia, respectively. The recorded Δ E * values were 2.63 and 2.99 for LDGC and zirconia, which have no remarkable difference. The TP values after AQ staining were slightly lesser. Subgroup analysis revealed considerable differences in TP values among zirconia specimens under both backgrounds, whereas substantial differences in Δ E * values were observed between LDGC and zirconia under white background only. Lithium disilicate glass ceramic (LDGC) had higher biaxial fracture forces than zirconia. Reparable, semi-reparable, and non-reparable fractures comprised 60, 30, and 10% of the overall fracture modes, respectively, with significant differences between and within groups ( p = 0.034)., Conclusion: AQ staining had a marked effect on the TP and Δ E * values of the tested CAD/CAM materials, but the values were within clinically acceptable levels. The optical properties were dependent on the material. Lithium disilicate glass ceramic (LDGC) had higher biaxial fracture forces than zirconia. Reparable fracture was the dominant type among the examined materials., Clinical Significance: Glazed surface for any CAD/CAM ceramic prostheses is highly recommended. Both tested materials are strongly recommended to be used for AQ consumers.

Aim and Objective: To evaluate the effect of cervical margin relocation (CMR) for crowns designed using CAD/CAM technology and fabricated from lithium disilicate (e.max, CAD) before and after aging; and to compare the fracture forces and failure type of the tested crowns., Materials and Methods: Mesio-occluso-distal(MOD) cavities 1 mm above the cementoenamel junction(CEJ) were prepared on 40 maxillary first premolars. The teeth were divided into four groups. In group A, all cervical margins (CM) were located 1 mm above the CEJ. However, in both mesial and distal proximal boxes of groups B, C, and D, in addition to the MOD cavities, the CMs were extended 2 mm on both sides below the CEJ apically to simulate the CMR technique. In group B, the mesial and distal proximal boxes were filled with flowable composite, while for group C and group D, specimens were filled with composite resin fillings. To simulate the CMR technique, the cavities were filled with composite layers of 3 mm in two increments. Using the CAD/CAM system, 40 standard crowns were prepared on premolars, then cemented using a dual-curing adhesive cement. Assessments of the marginal integrity of interfaces of the proximal boxes of the cemented crowned teeth were recorded. Statistical differences between groups were analyzed using the ANOVA and Bonferroni's posthoc test., Results: The first null hypothesis was accepted since no statistically significant differences were found in marginal integrity before and after aging ( p >0.05), while the second was partially rejected since different fractured force values were recorded and a significant difference was detected between group D and group B. The third hypothesis was rejected because the catastrophic fracture rate was the highest among the four groups., Conclusion: The implementation of CMR before and after aging had a good effect on the marginal integrity of CM relocation. The CMR technique with resin luting cement of lithium disilicate crowns is effective and recommended for the restoration in deep proximal boxes of premolars or posterior teeth., Clinical Significance: CAD/CAM-generated e. max all-ceramic crowns with composite as the CMR enable the reconstruction of severely destroyed teeth irrespective of the position of the cavity margins.