Guilherme de Siqueira Ferreira Anzaloni Saavedra

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: To analyze the Knoop microhardness of samples made from Dima® Print Guide polymer (Kulzer – Brazil) after different disinfection methods. Material and Methods: A total of 15 samples of the Dima® Print Guide polymer (Kulzer – Brazil) were fabricated and divided into five groups with three samples in each group as follows: 1 - control group (C), in which the samples did not undergo any disinfection method; 2 - disinfected with 2% chlorhexidine (CHX); 3 - disinfected with peracetic acid (PA); 4 - disinfected with 70% alcohol (AL); and 5 - sterilized in an autoclave (AS). Three microindentations were made on the surface of each specimen using a 300 g load for a dwell time of 30 seconds, measured with a microhardness tester model HMV-G21DT (Shimadzu Corporation, Kyoto, Japan). Results: The microhardness results were submitted to one-way ANOVA, which showed statistically significant differences (p<0.001), followed by Tukey’s test. The mean and standard deviation of the samples by group were: C (33.26±1.49a); CHX (29.71±1.69a); AP (32.23±0.33a); AL (30.81±2.10a); and AS (25.46±1.18b) (p<0.05)). Conclusion: The samples sterilized in an autoclave showed a decrease in microhardness, while the other disinfection methods did not significantly alter the microhardness of the surgical guides. KEYWORDS Computer-assisted surgery; Disinfection; Hardness test; Sterilization; Three-dimensional printing.

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.

Objectives This study evaluated the effect of deep margin elevation (DME) and restorative materials (leucite-reinforced glass–ceramics [C] vs. indirect resin composite [R]) on the fatigue behavior and stress distribution of maxillary molars with 2-mm deep proximal margins restored with MOD inlay. Methods Fifty-two extracted human third molars were randomly assigned into four groups (n = 13): C; DME + C; R; and DME + R. Inlays were fabricated in CAD-CAM and bonded to all teeth. The fatigue behavior was assessed with the stepwise stress test (10,000 cycles/step; step = 50 N; 20 Hz; initial load = 200 N). Fatigue failure loads and the number of cycles were analyzed with 2-way ANOVA and Tukey’s test (p < 0.05) and Kaplan–Meier survival plots. The stress distribution was assessed with finite element analysis. The models were considered isotropic, linear, and homogeneous, and presented bonded contacts. A tripod axial load (400 N) was applied to the occlusal surface. The stress distribution was analyzed with the maximum principal stress criterion. Results For fatigue, there was no difference for DME factor (p > 0.05). For the material factor, the load and number of cycles for failure were statistically higher in the R groups (p < 0.05). The finite element analysis showed that resin composite inlays concentrated more stress in the tooth structure, while ceramic inlays concentrated more stress in the restoration. Non-reparable failures were more frequent in the resin composite inlays groups. Conclusions DME was not negative for fatigue and biomechanical behaviors. Resin composite inlays were more resistant to the fatigue test, although the failure mode was more aggressive. Clinical significance DME does not impair mechanical behavior. Resin composite inlays failed at higher loads but with a more aggressive failure mode.