The effect of ethanol on surface of semi-interpenetrating polymer network (IPN) polymer matrix of glass-fibre reinforced composite

Aim of the study:The aim of this laboratory study was to evaluate the effect of ethanol treatment on the surfaceroughness (Sa), nano-mechanical properties (NMP) and surface characterization of dentalfiber reinforcedcomposite (FRC) with semi-interpenetrating polymer network (IPN).Materials and methods:A total of 240 FRC specimens with bisphenol A-glycidyl methacrylate - triethyleneglycoldimethacrylate–Poly (methylmetahcrylate) (bis-GMA-TEGDMA-PMMA) IPN matrix system were light cured for40 s and divided into 2 groups (L and LH). The group LH was further post-cured by heat at 95 °C for 25 min. Thespecimens were exposed to 99.9%, 70% and 40% for 15, 30, 60 and 120 s respectively. The treated specimenswere evaluated for Sausing non-contact profilometer. NMP were determined using nanoindentation techniqueand chemical characterization was assessed by Fourier Transform-Infrared (FTIR) spectroscopic analyses.Scanning electron microscopic (SEM) images were made to evaluate the surface topographical changes.Results:Both the L and LH group showed changes in the Saand NMP after being treated by different con-centrations of ethanol and at different time interval. The highest Sawas observed with L-group (0.733μm)treated with 99.9% ethanol for 120 s. Specimens in LH-group treated with 99.9% ethanol for 120 s (1.91 GPa)demonstrated increased nano-hardness, and group treated with 40% ethanol for 120 s demonstrated increasedYoung's modulus of elasticity (22.90 GPa). FTIR analyses revealed changes in the intensity and bandwidth inboth the L and LH groups.Conclusion:The present study demonstrated that both light-cured and heat post-cured FRC were prone forethanol induced alteration in the surface roughness (Sa), nano-mechanical properties (NMP) and chemicalcharacterization. The interphase between the glassfibers and the organic matrix was affected by ethanol. Thechanges were considerably less in magnitude in the heat post-cured FRC specimens.</p

The effect of mechanical and chemical polishing techniques on the surface roughness of heat-polymerized and visible light-polymerized acrylic denture base resins

Objective: The purpose of this study was to compare the effects of mechanical polishing (MP) and chemical polishing (CP) on the average surface roughness (Ra) of heat-cured (HC) and light-cured (LC) denture base acrylic resins. Methods: A total of 120 specimens (30 × 15 × 3 mm) were prepared from one HC and one LC acrylic resin. To remove nodules and gross surface irregularities, all specimens were finished with a lathe-mounted small acrylic bur and 360-grit sandpaper. Ten finished specimens of each acrylic resin were randomly assigned to each of six polishing techniques: Resilit High-luster Polishing Liquid (RHPL), Universal Polishing Paste, Abraso-star K50, pumice, Jet Seal Liquid, or Acrypoint. MP was performed with an automatic polishing machine for 2 min, under 50 rpm and 500 g of load. CP was performed by immersing the HC and LC specimens in preheated methyl methacrylate at 75 ± 1 °C for 10 s. The surface roughness of the acrylic resin specimens was measured with a contact profilometer. The Ra values were analyzed by two-way analysis of variance, post hoc Scheffe's test, and paired t-test (p ⩽ 0.05). Polished and tested acrylic resin surfaces were evaluated by scanning electron microscopy. Results: MP was more effective than CP. The smoothest surface was obtained with the use of the RHPL on the LC (0.05 ± 0.01 μm) or HC (0.07 ± 0.01 μm) acrylic resin. Two-way ANOVA showed a statistically significant difference between MP and CP. Conclusions: MP produced the smoothest surface of denture base acrylic resin. The mean surface roughness values after MP and CP were not influenced by the type of acrylic resin. Keywords: Surface roughness, Mechanical polishing, Chemical polishing, Contact profilometer, Acrylic resi

Surface dissolution and transesterification of thermoset dimethacrylate polymer by dimethacrylate adhesive resin and organic catalyst-alcohol solution

Objectives: To evaluate transesterification based dissolution of dimethacrylate and epoxy polymers, the former containing ester groups. Polymer substrates were treated with an adhesive resin (Stick™ Resin) and an organic catalyst-alcohol solution (ethylene glycol and triazabicyclodecene). The surface was chemically and nanomechanically analyzed with Fourier Transform-Infrared (FTIR) spectroscopy, surface profile peak (Rp) and nanohardness and modulus of elasticity.Methods: A total of 100 specimens each of light-cured dimethacrylate polymer and heat-cured diepoxy polymer were prepared. 20 specimens were randomly selected and used as control group (0s). The remaining specimens were randomly divided into 40 each for treatment with an Stick™ resin and ethylene glycol+triazabicyclodecene. Within each group the 40 specimens were randomly subdivided into 20 each for treatment at 5min and 24h, with 10 specimens for FTIR and nanohardness and modulus of elasticity, and the other 10 for SEM and surface Rp analyses.Results: Dimethacrylate polymer showed a reduction in the nanohardness and modulus of elasticity, Rp values and SEM also showed significant topographical changes after being treated with either Stick™ resin or ethylene glycol+triazabicyclodecene, whereas epoxy resin substrate did not. FTIR analyses affirmed changes in the intensity of ester groups.Significance: Ester group containing dimethacrylate polymer showed a reduction in NMP within 5min of exposure to the treatment agents with softening by solution ethylene glycol+triazabicyclodecene associated to the reduction of ester groups in the polymer structure by transesterification. Epoxy polymer without ester groups was not affected by surface softening with treatment agents. Adhesive resin caused surface swelling.</p

The effect of ethanol on surface of semi-interpenetrating polymer network (IPN) polymer matrix of glass-fibre reinforced composite

Aim of the study: The aim of this laboratory study was to evaluate the effect of ethanol treatment on the surface roughness (Sa), nano-mechanical properties (NMP) and surface characterization of dental fiber reinforced composite (FRC) with semi-interpenetrating polymer network (IPN).Materials and methods: A total of 240 FRC specimens with bisphenol A-glycidyl methacrylate - triethyleneglycol dimethacrylate - Poly (methylmetahcrylate) (bis-GMA-TEGDMA-PMMA) IPN matrix system were light cured for 40 s and divided into 2 groups (L and LH). The group LH was further post-cured by heat at 95 °C for 25 min. The specimens were exposed to 99.9%, 70% and 40% for 15, 30, 60 and 120 s respectively. The treated specimens were evaluated for Sa using non-contact profilometer. NMP were determined using nanoindentation technique and chemical characterization was assessed by Fourier Transform-Infrared (FTIR) spectroscopic analyses. Scanning electron microscopic (SEM) images were made to evaluate the surface topographical changes.Results: Both the L and LH group showed changes in the Sa and NMP after being treated by different concentrations of ethanol and at different time interval. The highest Sa was observed with L-group (0.733 μm) treated with 99.9% ethanol for 120 s. Specimens in LH-group treated with 99.9% ethanol for 120 s (1.91 GPa) demonstrated increased nano-hardness, and group treated with 40% ethanol for 120 s demonstrated increased Young's modulus of elasticity (22.90 GPa). FTIR analyses revealed changes in the intensity and bandwidth in both the L and LH groups.Conclusion: The present study demonstrated that both light-cured and heat post-cured FRC were prone for ethanol induced alteration in the surface roughness (Sa), nano-mechanical properties (NMP) and chemical characterization. The interphase between the glass fibers and the organic matrix was affected by ethanol. The changes were considerably less in magnitude in the heat post-cured FRC specimens.</p