This study evaluated the effect of substrate core materials and occlusal contact patterns on the fatigue mechanical behavior and stress distribution of single-unit ceramic crowns. One hundred and twenty monolithic crowns were fabricated from zirconia (YZ - IPS e.max ZirCAD, Ivoclar), lithium disilicate (LD - IPS e.max CAD, Ivoclar) and polymer infiltrated ceramic network (PICN - Enamic, Vita Zahnfabrik). The crowns were allocated considering two factors: 'substrate' (epoxy resin or cast Ni-Cr metal core) and 'occlusal contact pattern' (contact at the cusp ridges or cusp tips). The substrate models were design, milled and scanned to plan the restorations in a digital workflow. The crowns were milled, bonded to the substrates, and subjected to an accelerated fatigue test (100 N; 10,000 cycles/step; 20 Hz step-size: 100 N up to 1600 N, and after, 200 N until failure or survival at 2,800N; immersed in water). Statistical analyses were performed using two-way ANOVA, Tukey's post-hoc test, and Kaplan-Meier survival analysis (α = 0.05) considering fatigue failure load and cycles for fatigue failure (FFL/CFF). Fractographic and finite element analysis (FEA) were carried out. The results indicate that the 'substrate' factor did not influence the mechanical behavior of YZ and LD monolithic crowns (p > 0.05). However, PICN crowns bonded to epoxy resin exhibited statistically superior results for FFL and CFF (p < 0.05) compared to Ni-Cr cores. Regarding the 'occlusal contact pattern' factor, YZ and LD exhibited higher mean FFL and CFF when associated with cusp tip contact compared to cusp ridge contact (p < 0.05), except for YZ bonded to the epoxy resin substrate (p > 0.05). No differences were detected for the 'occlusal contact' factor in PICN crowns (p > 0.05). The predominant failure was Hertzian cone cracks, regardless of the restorative material. Stress measurements showed higher stress peaks at the cusp ridges. The core material did not alter the fatigue mechanical behavior of YZ or LD crowns. However, the incidence of cusp ridge contacts in YZ or LD crown increases the risk of failure. Conversely, when using PICN crowns, a core with a more similar elastic modulus enhances mechanical behavior compared to a stiffer core, and no influence on the occlusal pattern was observed.

It is uncertain whether the interchangeable use of two adhesive systems would yield comparable shear bond strength (SBS) for both Polyetheretherketone (PEEK) and Polyetherketoneketone (PEKK); investigating this was the main objective of this study. Milled PEEK (Bredent, Senden, Germany) and PEKK (Pekkton Ivory, AnaxDent, Stuttgart, Germany) blocks were prepared with standardized roughness (0.20 μm) and randomly assigned into two groups (n = 72): with and without aluminum oxide air abrasion (AquaCare Twin, Medivance Instruments, London, UK). Two adhesive systems (Visio.link, Bredent, Senden, Germany, or PEKKBond, AnaxDent, Stuttgart, Germany) were randomly applied (n = 36). Flowable gingival composite (AnaxGum Gingiva, AnaxDent, Stuttgart, Germany) was bonded, and the samples were stored in water (37 °C, 24 h). SBS was measured (MPa) and data were analyzed using three-way ANOVA, followed by Tukey’s test (α = 0.05). All main effects and interactions were significant (p < 0.05), except for polymer (p = 0.163) and the triple interaction (p = 0.601). In the PEEK group, Visiolink showed higher SBS (p < 0.001), regardless of prior air abrasion. For the PEKK group, PEKKBond significantly increased SBS values (p < 0.001) for both pre-treatment groups. Previous air abrasion only significantly increased the SBS of controls without adhesive. This study highlights the importance of material-specific adhesive selection, rather than interchangeable use, for optimal results. The bond strength of PEEK and PEKK is influenced by the adhesive system applied. Moreover, PEKK consistently demonstrated higher SBS values in comparison to PEEK, even without the need for pre-treatment or adhesive conditioning. This characteristic renders PEKK a preferred choice for the fabrication of adhesive restorations.

Objective: The aim of the study was to report the aplicability of intraoral scanning while rubber dam isolation is in place. Material and Methods: Female patient, 50 years old, required restorative procedures on teeth 35 and 37. An intraoral scan was initially performed on both arches. Isolation was carried out from 33 to 37, tooth preparation and immediate dentin sealing were carried out. A new scan with the rubber dam in place was performed and a CAD/CAM lithium disilicate hybrid block was digitally designed, milled, crystallized and cemented under the tooth surface with the rubber dam still in position. After completing this stage, the rubber dam was removed, the occlusion was verified, presenting excellent aesthetic and functional results. Results: The absolute isolation process used in the present study works as an excellent device for gingival retraction. Conclusion: The absolute isolation can be recommended in clinical activities of intraoral scanning favoring the quality of the final result of treatments. KEYWORDS CAD/CAM; Denture precision attachment; Digital technology; Mouth rehabilitation; Rubber dams.