Search

(1) Background: The long-term survival of an endodontically treated tooth depends on a successful root canal treatment as well as an adequate definitive coronal restoration. This study aimed to evaluate the strength of endodontically treated premolars with mesial–occlusal–distal (MOD) cavity preparation restored with different direct coronal restoration materials but from the same manufacturer against fracture. (2) Methods: sixty intact premolars were selected and placed into five groups (n = 12): G1—intact teeth, G2—endodontic treatment and unrestored MOD cavities, G3—endodontic treatment and MOD cavities restored with Tetric PowerFlow and Tetric EvoCeram, G4—endodontic treatment and MOD cavities restored with Multicore Flow and Tetric EvoCeram, and G5—endodontic treatment and MOD cavities restored with Multicore Flow. The specimens were subjected to an axial compression load at a speed of 1.6 mm/min and optically inspected before and after with a stereomicroscope. For each premolars group, the following data were recorded: the compression resistance, the compressive strength, and the maximum force supported. The microstructure of the samples after the compression test was analyzed using scanning electron microscopy (SEM). (3) Results: statistical analysis (ANOVA and Tukey test) showed that there was a statistically significant difference between G1 and the other groups. Even though there was no statistically significant difference between the restored groups, a better mechanical behavior was registered within the G3. (4) Conclusions: this in vitro study indicated that none of the materials used can lead to a higher or at least similar fracture resistance as the intact teeth. The coronal restoration only with nano-hybrid composites may lead to a higher therapeutic benefit for the fracture-susceptible premolars. [ABSTRACT FROM AUTHOR]

Short glass fibers are generally used in posterior dental restorations to enhance the mechanical properties and improve the material microstructure. Two resin-based composites (S0 and SF) were formulated and characterized to investigate the influence of zirconium in their characteristics and properties. The organic part of the investigated materials was the same (BisGMA, TEGDMA, and a photochemical polymerization system), and in the inorganic part, besides quart, glassA, and hydroxylapatite with Zn, sample S0 contained strontium glass with zirconium and sample SF contained fiber powder of chopped zirconium. The samples were characterized by the degree of conversion (DC), mechanical properties, water sorption (WS), scanning electron microscopy (SEM), atomic force microscopy (AFM) before and after the WS test, and antimicrobial properties. The results obtained were subjected to one-way ANOVA and Tukey's statistical tests. Both samples had a high DC. Regarding the mechanical properties, both samples were very similar, except DTS, which was higher for the composite without fibers. After 14 days, the WS value of the SF sample was lower than that of the S0 sample. Water caused significant changes in the topography of the SF sample, but thanks to its antimicrobial properties and the diffusion phenomenon, SF had a more pronounced antimicrobial effect. This study shows that the addition of appropriate amounts of Sr-Zr-glass powder gives the material in which it is added similar properties to material containing chopped zirconium glass fiber powder. According to the antimicrobial test results, resin composites containing experimental zirconia fillings can be considered in future in vitro clinical studies for posterior reconstructions with significantly improved mechanical properties. [ABSTRACT FROM AUTHOR]

The objective of this study was to compare the structure, morphology and enamel-composite and dentin-composite interface in the teeth of patients with chronic renal failure, predialysis and healthy patients, using two methods: atomic force microscopy (AFM) and scanning electron microscopy (SEM). Most of the tested enamel specimens showed a mixed type of failure. The AFM examination indicated a deep engraving for enamel and dentin in sick people compared to healthy people. The average value of the roughness (Ra) in enamel and dentin from healthy patients were significantly different (p <0.001) than from enamel and dentin in patients with renal failure. Regarding the SEM images, the dentin-composite material interface in teeth extracted from healthy patients, has uniformity, compared to the dentin-composite interface in teeth extracted from predialysis patients where a discontinuous hybrid layer with some gaps was identified. [ABSTRACT FROM AUTHOR]