The aims of this study were to compare two pretreatment methods of a fiber post and to evaluate the effect of heat treatment to applied silane on the push-out bond strength for different levels of root. In this in vitro study, 40 glass fiber posts were divided into five groups (n=8) according to the kind of surface treatment applied. They were then inserted into extracted and endodontically treated human canines using a self-etch resin cement (Panavia F2.0, Kuraray, Japan). Group HF+S = hydrofluoric acid (HF) etching and silane (S) application; group HF+S+WP = HF etching and heat-treated silane application and warmed posts (WP); group H2O2+S = hydrogen peroxide etching and silane application; group H2O2+S+WP = hydrogen peroxide and heat-treated-silane application and warmed post; and group C, the control group, received no pretreatment. After completion of thermal cycling (1000 cycles, 5-55°C), all specimens were cut horizontally to obtain three sections. Each section was subjected to a push-out test, and the test results were analyzed using two-way analysis of variance, post-hoc Tukey honestly significant difference test, and a paired sample t-test (α=0.05). It was found that bond strength was not statistically influenced by the kind of etching material used (p=0.224), but was significantly affected by heat treatment of applied silane (p<0.001). The interaction between these two factors was not statistically significant (p=0.142). Group HF+S+WP showed the highest bond strength (12.56±1.73 MPa) (p<0.05). Scanning electron microscopy revealed the effect of the different treatments on the surface characteristics of posts. In the four pretreated groups, the bond strength decreased significantly from the coronal to the apical root canal sections (p≤0.05). The results of this study show that the use of heat-treated silane significantly enhances the push-out bond strength of the fiber posts to root. HF acid etching with heat-treated silane application led to the highest bond strength.

Simvastatin is a hypocholestrolemic drug that is insoluble in water. Its low water solubility rate limits the pharmacological effects. The aim of this study was to improve the dissolution rate of simvastatin using spherical crystallization method. The drug was dissolved in boiling dichloromethane as the good solvent. This solution was added to 5°C water as the non-solvent. After sedimentation, isopropyl acetate was added as the bridging solvent. At the end the crystals were collected and dried for 12 h in a 50°C oven. The FTIR and DSC results showed no change in the drug after crystallization process. XRPD studies showed the sharp peaks are present in the diffractograms of spherical crystals with minor reduction in height of the peaks. The particle size of spherical aggregates was about 37 μm and the dissolution efficiency of simvastatin up to 60 min increased to about 2-fold in phosphate buffer solution containing 0.5% sodium dodecyl sulfate (pH 7) using the rotating paddle method. Spherical crystals showed enhanced solubility than untreated powder possibly due to partial conversion to amorphous form. Their dissolution rate at 60 min was still 4-fold of untreated powder when stored at 25°C and 84% relative humidity for one month.