Background and Aim: To evaluate the bond strengths of FRC posts (Glassix "Nordin dental/Swiss" and Matchpost "RTD/ France") to root dentin after silanization. The null hypothesis tested was that silanization would produce greater bond strength.Materials and Methods: Roots of 40 human freshly extracted maxillary central incisors were endodontically treated and were divided into 4 group of each 10 (n=10.) They received the following treatments. Group 1: Glassix post + silane primer; Group 2: Glassix posts without silane primer; Group 3: Matchpost + silane primer;  Group 4: Matchpost without silane primer. The posts were cemented with panavia F2.0 dual cure resin cement. Each root was cut into 3 slices (2mm height) representing 1/3 coronal, middle, and apical portions respectively. After push-out  bond strength testing (at the cross head speed of  0.5 mm/min), the type of failure at the interface was determined. Results: Silanization of fiber posts had no effect on shear bond strengh (p>0.05). Without consideration of silanization, type of post had also no effect. (p>0.05). The apical third of the specimen had the greatest bond strength (p=0.001).Conclusion: Neither silanization of fiber post surfaces, nor the type of fiber post seem to have any statistically significant difference on shear bond strength of FRC posts to root canal dentin. Most of tested specimen had an adhesive failure mode at the interface of cement-dentin.

Statement of Problem: Mechanical strength and durability of dental composites are the main topics studied in this field of science today. This study examined fumed silica-based composite as a strong and durable restorative material through flexural and cycling test methods.Objectives: The purpose of this study was to evaluate the effect of silanization, ageing, cycling and hybridizing on mechanical properties of fumed silica-based resin composite.Materials and Methods: Composites were made of light-cured copolymer based on Bisphenol A glycolmethacrylate (Bis-GMA) and Triethylene glycoldimethacrylate (TEGDMA) at proportion of 50:50 which reinforced by fumed silica filler. For each composite sample, 5 specimen bars were made using Teflon mould (2 x 2 x 25 mm3). The samples with 12 wt% fumed silica (FS) were considered as a base line group. The samples were exposed to cyclic cold water (FS-CCW) and hot water (FS-CHW). The effect of silanization and adding more filler was studied together with samples containing 12 wt% (FS-S (12), 16 wt% (FS-S (16) and 20 wt% (FS-S (20) fumed silica filler. The filler was silanized with ( g-MPS). The degree of conversion was assessed with Fourier Transform Infra-Red spectroscopy. Flexural properties were evaluated with the Three-Point Bending test. Flexural data were analyzed with Excel software. Hardness was measured with an Atomic Force Microscope (AFM).Results: The degree of conversion of the resin reached 74% within 24 hrs. Salinization allowed more filler to be wetted by resin. Addition of silanized particles from sample FS-S (12) to sample FS-S (20) improved the mechanical strength. Hybridizing fumed silica with nano-silica (FS-N) had no significant effect on the strength, but nano-hardness improved greatly. Ageing and cycling had adverse effects on the strength of the sample FS. The flexural strength of FS-CHW was 72% less than FS sample.Conclusions: Sample FS-N with low diluent and filler percentage complied with the requirements of flexural strength was established by ISO 4049/2009 and may be cost benefit to be used as a dental composite for clinical application.

Background: This research studied mechanical properties of silica-based nanocomposite as a strong restorative material through flexural test method. Objectives: The purpose of this study was to evaluate the effect of weight fraction, silanization and filler size on the flexural properties of silica-based dental nanocomposite. Methods: The prepared composites were made of light-cured copolymer based on Bisphenol A glycolmethacrylate (Bis-GMA) and Triethylene glycoldimethacrylate (TEGDMA) at proportion of 50: 50 which reinforced by silica filler. The effect of silanization and weight fraction of the filler was studied with samples containing 10 wt% (n (10)), 20 wt% (n (20)) and 30 wt% (n (30)) nanosilica filler. Samples silanized with (-MPS) were also tested. Flexural properties were evaluated with Three-Point Bending test. Flexural strength of the nano SiO2 based composites were also compared to micro silica glass composites. Flexural data were analyzed with one-way analysis of the variance. Results: The sample with 10 wt% (n (10)) had equal strength as the sample with 30 wt% (n (30)) nanosilica filler. Modulus of the sample n (30) was higher than the other samples, but its toughness was significantly lower. Silanization had not expected positive effect on the flexural properties. Conclusions: Adding low amount of nanosilica improved mechanical properties of the resin composite. Silanization of the particles enhanced workability of the paste, but mechanical properties decreased significantly. Reduction in the size of the filler to nano scale caused better flexural strength in comparison to micro glass silica composites.

Objective: This study evaluated the effects of resin matrix composition and surface treatment on the bond strength of glass fiber-reinforced composite (FRC) posts to intraradicular dentin. Methods: Fifty-six extracted premolars were obtained. Post spaces were prepared for either epoxy resin-based posts (White Post DC) or Bis-GMA-based posts (Postec Plus) (n=28). The posts received different surface treatments (n=7): 70% ethanol (control), air abrasion and silanization, 35% H3PO4, and 24% H2O2. Posts were cemented and the samples were sectioned into cervical, middle, and apical thirds. The push-out bond strength of samples was compared between the groups using two-way ANOVA (α=0.05). Results: There was a significant difference in bond strength between the different treatment methods in all root sections (P < 0.05). The highest push-out bond strength in the cervical, middle, and apical sections was observed in subgroups treated with air abrasion and silanization, with a significant difference from other groups in most comparisons (P < 0.05). Epoxy resin and Bis-GMA posts had comparable bond strengths in the coronal and apical sections (P > 0.05). Additionally, their bond strengths were comparable in the middle section when the post surfaces were treated with air abrasion and silanization, or 35% H₃PO₄ (P > 0.05). Conclusions: Air abrasion and silanization could be suggested as the optimal surface treatment strategy to improve the bond strength of FRC posts to resin cement. Proper mechanical and chemical surface treatments might be more important than the resin matrix composition in determining the bond strength of FRC posts.