Degree of conversion of bis-acrylic based provisional crown and fixed partial denture materials / 대한치과보철학회지

STATEMENT OF PROBLEM: The degree of conversion may influence the ultimate mechanical and physical properties of provisional crown and fixed partial denture materials. The high levels of the unreacted residual monomer may cause deleterious effect on the properties. PURPOSE: The purpose of this study was to measure the degree of conversion of bis-acrylic based provisional crown and fixed partial denture materials by using an infrared spectroscopic method. MATERIAL AND METHODS: Chemically activated three bis-acrylic based provisional crown and fixed partial denture materials, LuxaTemp [DMG, Hamburg, Germany], fast set TemPhase [Kerr, Orange, CA, USA] and Protemp 3 Garant [3M-ESPE, St Paul, MN, USA], were investigated by Fourier transform infrared spectrometry (FTIR). The FTIR spectra of the materials tested were immediately obtained after mixing. The specimens were stored under dry conditions and at 23 degrees C for 24 hours, and then the spectra of the materials were also obtained. The degree of conversion (percent) was calculated from the spectrum of the absorbance between the aliphatic double bond at 1637 cm-1 and the aromatic double bond at 1608 cm-1 using the baseline method. The data were statistically analyzed using one-way ANOVA and the multiple comparison Scheffe test at the significance level of 0.05. RESULTS: The mean value and standard deviation of the degree of conversion were 52.5 percent +/- 1.1 percent, 50.3 percent +/- 0.8 percent, and 42.3 percent +/- 4.9 percent for LuxaTemp, Protemp 3 Garant and fast set TemPhase, respectively. There was no significant difference between LuxaTemp and Protemp 3 Garant, whereas there was a statistically difference between Protemp 3 Garant and fast set TemPhase, and LuxaTemp and fast set TemPhase (P < .05). CONCLUSION: The degree of conversion of fast set TemPhase was significantly lower than those of the others. The degree of conversion may be correlated with the rate of polymerization.

Effect of water on HEMA conversion by FT-IR spectroscopy

The use of HEMA as a biocompatible material in dentin bonding systems and its potential for clinical applications has been well established. Excess water can affect conversion of bonding resins. The aim of this study was to survey the effect of water on the degree of conversion of HEMA by Fourier Transform Infra-red Spectroscopy [FT-IR]. In this experimental study, distilled water was added in amounts of 0, 0.05, 0.1, 0.2, and 0.4 ml to 1 ml of curable HEMA solution. Six repetitions per water ratio were made and investigated. Each sample was polymerized for 60 seconds. Degree of conversion was obtained from the absorbance IR-Spectrum of the materials before and after polymerization by FT-IR spectroscopy. One way ANOVA and Tukey-HSD were carried out to compare and detect any differences among groups. Statistical analysis indicates highly significant difference between pairs of groups at level [P<0.001]. The results showed a trend of decreasing in HEMA conversion with increasing water. Degree of conversion changes significantly within the 0.05 ml to 0.2 ml water range. However, degree of conversion did not change after reaching 0.02 ml and before 0.05. Degree of conversion of HEMA decreased by increasing water. The most dramatic effect of water on the polymerization process occurs within a range which exists under clinical conditions. The reason that the degree of conversion did not show significant result before 0.05 ml may be related to the hydrophilic nature of HEMA

Tuberculous meningitis and hydrocephalus treated successfully with a combination of immunomodulation and cerebrospinal fluid diversion

The management of tuberculous meningitis with hydrocephalus is complex with most centres advocating ventriculoperitoneal shunting only in the presence of raised CSF pressure. This article reports a case of tuberculous meningitis with hydrocephalus treated with a combination of early surgical and immunomodulatory therapy in addition to conventional steroids and antituberculous agents. This case demonstrates that during the early phase of tuberculous meningitis with hydrocephalus, a combined multi-disciplinary approach will help prevent neuronal injury due to progressive ventricular enlargement and inflammation

Microstructure and mechanical property of a new IPS-Empress 2 dental glass-ceramic / 中华口腔医学杂志

<p><b>OBJECTIVE</b>To investigate the microstructure and mechanical properties of a new IPS-Empress 2 dental glass-ceramic.</p><p><b>METHODS</b>AFM, SEM and XRD were used to analyze the microstructure and crystal phase of IPS-Empress 2 glass-ceramic. The flexural strength and fracture toughness were tested using 3-point bending method and indentation method respectively.</p><p><b>RESULTS</b>IPS-Empress 2 glass-ceramic mainly consisted of lithium disilicate crystal, lithium phosphate and glass matrix, which formed a continuous interlocking structure. The crystal phases were not changed before and after hot-pressed treatment. AFM showed nucleating agent particles of different sizes distributed on the highly polished ceramic surface. The strength and fracture toughness were 300 MPa and 3.1 MPam(1/2).</p><p><b>CONCLUSION</b>The high strength and fracture toughness of IPS-Empress 2 glass ceramic are attributed to the fine lithium disilicate crystalline, interlocking microstructure and crack deflection.</p>