Effect of preheating and precooling on the flexural strength and modulus of elasticity of nanohybrid and silorane-based composite

Statement of the Problem: Composite resin may be used in different temperatures; it is crucial to determine the effect of temperature on mechanical properties of nanohybrid and silorane-based composite

Purpose: This in vitro study compared the flexural strength and modulus of elasticity of nanohybrid and silorane-based resin composite, at 4[degree]C, room temperature [25[degree]C], and 45[degree]C

Materials and Method: In this experimental study, 60 specimens were prepared in a metal split mold [2×2×25mm]. Two different resin composites, Filtek Z250 XT [3M/ ESPE] and Filtek P90 [3M/ESPE], were evaluated. The material were inserted into split molds at room temperature, 4[degree]C or 45[degree]C and cured with LED [1200 mW/cm2] for 20 seconds in four points [n=10]. Then, a three-point bending test was performed using a universal testing machine at a crosshead speed of 0.5 mm/min for measuring the flexural strength and flexural modulus of samples. The data were analyzed by the two-way ANOVA and Tukey test [p< 0.05]

Results: The mean highest flexural strength was observed at 45[degree]C, showing statistically significant difference with flexural strength at 4[degree]C [p= 0.0001] and 25[degree]C [p= 0.003] regardless of the type of resin composite. The flexural modulus at 45[degree]C was highest, showing the statistically significant difference with flexural modulus at 4[degree]C [p= 0.0001] and 25[degree]C [p= 0.002]. The flexural modulus was statistically different between nanohybrid and silorane-based resin composite [p= 0.01] in 25[degree]C and 45[degree]C, but there were no statistically significant differences between flexural strength of Filtek Z250 XT and Filtek P90 regardless of the temperatures [p= 0.062]. Conclusion: Preheating the resin composite at 45[degree]C improves flexural strength and modulus of nanohybrid and silorane-based resin composite. However, flexural strength and modulus of the tested materials were not affected by precooling. The flexural modulus of nanohybrid resin composite was significantly higher than siloranebased resin composite in 25[degree]C and 45[degree]C temperatures

Fracture resistance of endodontically treated maxillary premolars restored by silorane-based composite with or without fiber or nano-ionomer

PURPOSE: This in vitro study investigated the fracture resistance of endodontically treated premolars restored using silorane- or methacrylate-based composite along with or without fiber or nano-ionomer base. MATERIALS AND METHODS: Ninety-six intact maxillary premolars were randomly divided into eight groups (n = 12). G1 (negative control) was the intact teeth. In Groups 2-8, root canal treatment with mesio-occlusodistal preparation was performed. G2 (positive control) was kept unrestored. The other groups were restored using composite resin as follows: G3, methacrylate-based composite (Z250); G4, methacrylate composite (Z250) with polyethylene fiber; G5 and G6, silorane-based composite (Filtek P90) without and with the fiber, respectively; G7 and G8, methacrylate- and silorane-based composite with nano-ionomer base, respectively. After aging period and thermocycling for 1000 cycles, fracture strength was tested and fracture patterns were inspected. The results were analyzed using ANOVA and Tukey HSD tests (alpha=0.05). RESULTS: Mean fracture resistance for the eight groups (in Newton) were G1: 1200 +/- 169a, G2: 360 +/- 93b, G3: 632 +/- 196c, G4: 692 +/- 195c, G5: 917 +/- 159d, G6: 1013 +/- 125ad, G7: 959 +/- 148d, G8: 947 +/- 105d (different superscript letters revealed significant difference among groups). Most of the fractures in all the groups were restorable, except Group 3. CONCLUSION: Silorane-based composite revealed significantly higher strength of the restored premolars compared to that of methacrylate one. Fiber insertion demonstrated no additional effect on the strength of both composite restorations; however, it increased the prevalence of restorable fracture of methacrylate-based composite restored teeth. Using nano-ionomer base under methacrylate-based composite had a positive effect on fracture resistance and pattern. Only fiber-reinforced silorane composite restoration resulted in a strength similar to that of the intact teeth.

Serum level of galectin-3 in patients with oral squamous cell carcinoma

Galectin-3, a member of the family of beta-galactoside-binding animal lectins, has been implicated in tumor invasion and metastasis. Using an ELISA kit, we assessed the circulating levels of galectin-3 in sera from 40 oral squamous cell carcinoma [OSCC] patients and from 43 healthy controls. Serum galectin-3 levels in OSCC patients were significantly higher [5.1 +/- 2.5 ng/ml] when compared with healthy controls [2.6 +/- 3.07 ng/ml, P<0.0005]. There was no apparent correlation between serum galectin-3 concentration and clinico-pathological features such as stage, tumor size, nodal status, distant metastasis and histological grade. This result suggests that, in addition to other tests, measurement of serum galectin-3 concentrations can be utilized as an adjuvant test for establishing a diagnosis of OSCC