Effect of desensitizing agents on the resin bond strength to sound dentin.

This study aimed to evaluate the effect of dentin hypersensitivity treatments on immediate and long-term shear bond strength (SBS) of composite restorations. Ninety non-carious extracted human molars were cut to expose dentin, which was embedded in acrylic resin, and randomly divided into three groups (n = 30/group) according to surface treatment: 1) no treatment (C and C*; control); 2) silver diamine fluoride with potassium iodide (SDF/KI and SDF/KI*; Riva Star); and 3) nano-hydroxyapatite (nHAp and nHAp*; PrevDent). The specimens were etched through the etch-and-rinse technique, followed by universal adhesive application and resin composite cylinders (2.38 mm in diameter × 3.5 mm high). The SBS was tested immediately (24 h after the restoration) and after thermocycling (*) (5000 cycles, 5 °C to 55 °C) at a 0.5 mm/min crosshead speed using a universal testing machine. A stereomicroscope was used to evaluate the mode of failure, and representative scanning electron microscopy (SEM) images were also acquired. Data normality was verified, and two-way ANOVA and Tukey's post hoc tests were performed for multiple comparisons (α = 0.05). The control group presented the highest SBS (27.10 MPa), while SDF/KI* had the lowest values (6.87 MPa). nHAp-based desensitizer exhibited higher SBS than SDF/KI for both immediate (22.6 MPa) and thermocycled (19.03 MPa) conditions. No intragroup difference was evidenced between immediate and thermocycled samples for any group. Most specimens for the C and nHAp groups presented mixed failure, while the SDF/KI groups presented comparable adhesive and mixed failures. The SBS of adhesive restorations after the application of desensitizing agents is material dependent, where SDF/KI reduces SBS values below the acceptable minimum bond strength, while the nHAp application meets the minimally required bond strength.

Fatigue strength of 5Y-FSZ: glazing and polishing effects.

OBJECTIVE: The aim of this study was to evaluate the effect of four different finishing procedures on the fatigue strength of a fully stabilized zirconia (5Y-FSZ) material. MATERIALS AND METHODS: Disc-shaped specimens of a 5Y-FSZ (Katana UTML, Kuraray Noritake) were made (ISO 6872-2015), grinded with 600- and 1200-grit silicon carbide paper, sintered as recommended, and randomly assigned into four groups according to the finishing technique: C (control, as-sintered), P (polished with polishing rubbers), G (glaze application - powder/liquid technique), and PG (polished with polishing rubbers + glaze application - powder/liquid). Then fatigue strength (staircase method), X-ray diffraction (XRD), and scanning electron microscopy (SEM) analyses were performed. RESULTS: The C group presented the lowest fatigue strength, while the PG group presented the highest. The P and G groups presented intermediate behavior, presenting similar statistical results. XRD showed similar crystalline phase patterns for all groups. SEM images revealed some changes in the zirconia surface, with the P group presenting some scratches on the surface, while the scratches in the PG group were filled with the glaze material. CONCLUSION: None of the techniques analyzed in this study impaired the fatigue strength of fully stabilized zirconia. Importantly, the polishing rubbers combined with glaze application (PG group) improved its fatigue strength. CLINICAL RELEVANCE: The polishing rubbers followed by glaze application improve the fatigue strength in ultra-translucent zirconia.

Effect of microwave crystallization on the wear resistance of reinforced glass-ceramics.

This study compared the wear resistance of different reinforced glass-ceramics crystalized by conventional or microwave firing. The wear rate of three ceramics [one lithium disilicate ceramic (LD): IPS e.max CAD - Ivoclar Vivadent; and two zirconia reinforced lithium silicates: Suprinity - VITA Zahnfabrik (ZLS1) and Celtra Duo - Dentsply (ZLS2)] crystallized by conventional (c) or microwave (mw) firing protocols were collected according to the contact- [two-body (n = 20/gr)] and contact-free wear tests [three-body (n = 20/gr)]. After wear tests performed on ACTA wear machine, mean surface roughness (Ra) and Scanning Electron Microscopy (SEM) analyzes were performed to evaluate the surface alterations. The wear and roughness data (in µm) were evaluated using two-way ANOVA and Tukey post-hoc test (α = 0.05). Two-body wear test revealed that ZLS1 (1.30 ± 1.79)A showed higher wear rate than LD (0.79 ± 2.15)B and ZLS2 (0.85 ± 0.94)B, regardless the crystallization approach. For three-body test, conventional crystallization (0.62 ± 0.4)A showed higher wear rates than microwave (0.22 ± 0.71)B; while the type of ceramic was not significant. The crystallization protocol (p < 0.001) and ceramic material (p = 0.001) affected the surface roughness in the three-body; whereas the two-body test, only the crystallization protocol (p = 0.046). SEM analysis showed a similar and smother surface morphology for LD and ZLS2 compared to ZLS1. Conventional crystallization showed materials more prone to wear than the microwave, in the presence of food bolus. Therefore, the microwave crystallization can be suggested as an alternative to improve the evaluated glass-ceramics wear resistance.

Investigation on the relationship of dimensions of the maxillary sinus drainage system with the presence of sinusopathies: a cone beam computed tomography study.

OBJECTIVE: This study sought to assess the relationship between the dimensions of the maxillary sinus drainage system with the content of sinuses. DESIGN: Three-hundred cone beam computed tomography images were selected from a database (105 males and 195 females). The images were assessed by a single investigator, trained and calibrated, performing image analysis. The length of the infundibulum and the ostium height in both maxillary sinuses were measured. The data were analyzed using Minitab 16, using 5% as a critical p-value. RESULTS: A significant gender difference was also found for presence in the normal content of sinus for females and presence of antral pseudocyst for males (p < 0.05). Subjects with normal content in the maxillary sinus present lower ostium height values. There were statistically significant with presence of and higher ostium height values and antral pseudocyst (p < 0.01). CONCLUSION: The current study results demonstrated that some sinusopathies were significantly related to dimensions of maxillary sinus drainage.