Effect of an experimental 4% titanium tetrafluoride varnish on dental erosion by a soft drink

Objectives: This in vitro study assessed the effect of an experimental 4%TiF4 varnish on enamel erosion.Methods: Sixty bovine enamel blocks were randomly allocated to each type of varnish:Duraphat((R)) -D (NaF, 2.26%F), Duofluorid((R))-F(NaF, 2.71% F), TiF4-T(2.45%F) and no-fluoride-P. After application of the varnishes, the blocks were subjected to six sequential pH cycles (cola drink for 10 min and artificial saliva for 50 min, each) per day, during 4 days. After the pH cycles, the blocks were maintained in artificial saliva for 18 h. Enamel alterations were determined in the 2nd and 4th days, using profilometry (wear) and microhardness (%SMHC) tests. Data were tested using ANOVA and Tukey's tests (p < 0.05).Results: the mean %SMHC (+/- S.D.) at the 2nd and 4th day was, respectively, D (-77.26 +/- 5.04(a) and -88.59 +/- 5.11(A)), F (-76.79 +/- 7.82(a) and -88.78 +/- 6.10(A)), T(-88.28 +/- 3.19(b) and -92.04 +/- 2.54(A,B)) and P (-87.96 +/- 2.23(b) and -94.15 +/- 1.14(B)). The mean wear (mu m +/- S.D.) at the 2nd and 4th day was, respectively, D (3.16 +/- 0.32(a) and 7.56 +/- 0.90(A)), F(3.35 +/- 0.78(a,b) and 7.92 +/- 0.98(A)), T (3.81 +/- 0.43(b) and 7.69 +/- 0.76(A)) and P (3.43 +/- 1.13(a,b) and 7.31 +/- 0.53(A)).Conclusions: the NaF varnishes reduced the softening, but had no effect on the reduction of the wear. The TiF4 varnish was not able to reduce the softening and wear. (C) 2007 Elsevier Ltd. All rights reserved.

The use of ultrasound for cleaning the surface of stainless steel and nickel-titanium endodontic instruments

Aim the aim of this study was to evaluate the efficacy of ultrasound in cleaning the surface of stainless steel and Ni-Ti endodontic instruments.Methodology Twenty nickel-titanium instruments (10 Quantec files and 10 Nitiflex) and 20 stainless steel K-files (10 Maillefer-Dentsply and 10 Moyco Union Broach) were removed from their original packages and evaluated using a scanning electron microscope. Scores were given for the presence of residues on the surface or the instruments. The instruments were then cleaned in an ultrasonic bath containing only distilled water or detergent solution for 15 min, and re-evaluated, using scanning electron microscopy.Results Before cleaning, a greater amount of metallic debris was observed on the nickel-titanium Quantec instruments (P < 0.05), when compared to those made of stainless steel. Statistical analysis showed that the use of ultrasound was effective for cleaning the instruments, regardless of the irrigating solution or the instruments type (P < 0.05).Conclusions the use of ultrasound proved to be an efficient method for the removal of metallic particles from the surface of stainless steel and Ni-Ti endodontic instruments.

Evaluation of shear bond strength at the interface of two porcelains and pure titanium injected into the casting mold at three different temperatures

Statement of problem. Titanium has physical and mechanical properties, which have led to its increased use in dental prostheses despite casting difficulties due to high melting point and formation of oxide layers which affect the metal-ceramic bond strength.Purpose. This in vitro study evaluated the shear bond strength of the interface of 2 dental porcelains and pure titanium injected into a mold at 3 different temperatures.Material and methods. Using commercially pure (cp) titanium bars (Titanium, Grade I) melted at 1668degreesC and cast at mold temperatures of 430degreesC, 700degreesC or 900degreesC, 60 specimens were machined to 4 x 4 mm, with a base of 5 x 1 mm. The 4-mm surfaces were airborne-particle abraded with 100 mum aluminum oxide before applying and firing the bonding agent and evaluating the 2 porcelains (Triceram/Triline ti and Vita Titankeramik). Ten specimens were prepared for each temperature and porcelain combination Shear bond testing was performed in a universal testing machine, with a 500-kg load cell and crosshead speed of 0.5 mm/min. The specimens were loaded until failure. The interfaces of representative fractured specimens of each temperature were examined with a scanning electron microscope (SEM) and energy dispersive spectrometer (EDS). Data for shear bond strength (MPa) were statistically analyzed by 2-way ANOVA and the Tukey test (alpha = .05).Results. The results showed significant differences for the metal/porcelain interaction effect (P = .0464). There were no significant differences for the 2 porcelains (P = .4250). The Tukey test showed a significant difference between the pair cp Ti 430degreesC Triceram and cp Ti 900degreesC Triceram, with respective mean values and SDs of 59.74 +/- 11.62 and 34.03 +/- 10.35 MPa.Conclusion. Triceram porcelain showed a bond strength decrease with an increase in the mold temperature for casting titanium. The highest bond strength for Vita porcelain and the best metal-ceramic interface observed with the SEM were found with the mold temperature of 700degreesC.

Electrochemical stability of anodic titanium oxide films grown at potentials higher than 3 V in a simulated physiological solution

The cathodic behaviour of oxides formed on titanium electrodes in physiological solutions at potentials between 3 and 5 V (vs. SCE) was studied by cyclic voltammetry. In case of anodic polarization at potentials higher than 3 V (vs. SCE), a cathodic peak at similar to 0.4 V (vs. SCE) appears in the cathodic scan, which could be due to the reduction of unstable peroxides. The results show that this peak depends on the anodic potential and the oxidation time. This behaviour supposedly is due to the formation of unstable titanium peroxides like TiO3 during anodization. Based on repetitive oxidation-reduction processes can be concluded that the created amount of TiO3 inside of the TiO2 surface layer seems to be constant. (c) 2006 Elsevier Ltd. All rights reserved.

Titanium and zirconium complexes containing sterically hindered hydrotris(pyrazolyl)borate ligands: synthesis, structural characterization, and ethylene polymerization studies

The synthesis, characterization and ethylene polymerization behavior of a set of Tp'MCl3 complexes (4, M = Ti, Tp' HB(3-neopentyl-pyrazolyl)(3)(-) (Tp(NP)); 5, M = Ti, Tp'= HB(3-tert-butyl-pyrazolyl)(3)(-) (Tp(tBu)); 6, M = Ti, Tp' = HB(3-phenyl-pyrazolyl)(3)(-) (Tp(Ph)); 7, M = Zr, Tp' = HB(3-phenyl-pyrazolyl)(3)(-) (Tp(ph)); 8, M = Zr, Tp' = HB(3-tert-butyl-pyrazolyl)(3)(-) (Tp(tBu))) is described. Treatment of these tris(pyrazolyl)borate Group IV compounds with methylalumoxane (MAO) generates active catalysts for ethylene polymerization. For the polymerization reactions performed in toluene at 60 degreesC and 3 atm of ethylene pressure, the activities varied between 1.3 and 5.1 X 10(3) g of PE/mol[M](.)h. The highest activity is reached using more sterically open catalyst precursor 4. The viscosity-average molecular weights ((M-v) over bar) of the PE's produced with these catalyst precursors varying from 3.57 to 20.23 x 10(5) gmol(-1) with melting temperatures in the range of 127-134 degreesC. Further polymerization studies employing 7 varying Al/Zr molar ratio and temperature of polymerization showed that the activity as well as the polymer properties are dependent on these parameters. In that case, higher activity was attained at 60 degreesC. The viscosity-average molecular weights of the polyethylene's decreases with increasing AI/Zr molar ratio. (C) 2003 Elsevier B.V. All rights reserved.

Effect of 17 beta-estradiol and alendronate on the removal torque of osseointegrated titanium implants in ovariectomized rats

Background: This study investigated the influence of estrogen deficiency and its treatment with estrogen and alendronate on the removal torque of osseointegrated titanium implants.Methods: Fifty-eight female Wistar rats received a titanium implant in the tibia metaphysis. After 60 days, which was needed for implant osseointegration, the animals were randomly divided into five groups: control (CTLE; N = 10), sham surgery (SHAM; N = 12), ovariectomy (OVX; N = 12), ovariectomy followed by hormone replacement (EST; N = 12), and ovariectomy followed by treatment with alendronate (ALE; N = 12). The CTLE group was sacrificed to confirm osseointegration, whereas the remaining groups were submitted to sham surgery or ovariectomy according to their designations. After 90 days, these animals were also sacrificed. Densitometry of femur and lumbar vertebrae was performed by dual-energy x-ray absorptiometry (DXA) to confirm systemic impairment of the animals. All implants were subjected to removal torque.Results: Densitometric analysis of the femur and lumbar vertebrae confirmed a systemic impairment of the animals, disclosing lower values of bone mineral density for OVX. Analysis of the removal torque of the implants showed statistically lower values (P <0.05) for the OVX group in relation to the other groups. However, the group treated with alendronate (ALE group) presented significantly higher torque values compared to the others.Conclusion: According to this study, estrogen deficiency was observed to have a negative influence on the removal torque of osseointegrated implants, whereas treatment with alendronate