Objective:To observe the fluoride release rate of F-containing thermoplastic resina,trying to find a suitable concentration of fluoride in thermoplastic resina to prevent caries in base teeth of partial denture restorations.Methods:Na2(PO3)F-containing thermoplastic resina,respectively 0,10%,15%,20% and 25%(w/w)in concentration were cut into three 1 g blocks and immersed in 100,200 and 500 ml deionized water.These composite resins in 100 ml and 200 ml solutions were replaced every 1,2,3,6,9,16 days(every 7 days after that)until two months later,500 ml solution was reserved after 3,6,9 days every 7 days later until two months,2 ml of which were reserved every time.The fluoride release rates of these thermoplastic resina were tested by potentiometry.Results:All thermoplastic resina containing different concentrations of fluoride could release F-during the period of 65 days.Conclusion:When Na2(PO3)F is mixed in thermoplastic resina,it releases fluoride slowly.Thermoplastic resina containing 15% F-has higher release rates of fluoride.

OBJECTIVETo investigate the shear bond strength between veneering ceramic and zirconia core in different all-ceramic systems.

METHODSTwenty disk-shaped specimens with 8 mm in diameter and 3 mm in height for each zirconia system (Lava, Cercon, IPS e.max ZirCAD, Procera) were fabricated respectively and divided into four groups: Lava group, Cercon group, IPS e.max ZirCAD group, Procera group. For each group, 10 specimens were sintered with 1 mm corresponding veneering ceramic, while the other were sintered with 2 mm corresponding veneering ceramic respectively. The shear bond strength and fracture mode of specimens were observed and determined.

RESULTSThe values of shear bond strength for Lava, Cercon, IPS e.max ZirCAD and Procera were (13.82 +/- 3.71), (13.24 +/- 2.09), (6.37 +/- 4.15), (5.19 +/- 5.31) MPa in the group of 1 mm thicked veneering ceramics, respectively, while the values in the group of 2mm thicked veneering ceramics were (38.77 +/- 1.69), (21.67 +/- 3.34), (12.70 +/- 4.24), (9.94 +/- 6.67) MPa. The values of Lava and Cercon groups were significantly higher than that of IPS e.max ZirCAD and Procera groups (P < 0.05). And the values of 2 mm thicked veneering ceramic group were significantly higher than that in 1 mm thicked groups (P < 0.05). Adhesive fracture between core and veneering ceramics were observed in the fracture modes of most specimens.

CONCLUSIONThe shear bond strength of veneering ceramic to the zirconia framework are different from the zirconia system we chose, and the thickness of veneering ceramic has a great impact on its shear bond strength.

Ceramics ; Dental Bonding ; Dental Porcelain ; Dental Stress Analysis ; Dental Veneers ; Humans ; In Vitro Techniques ; Materials Testing ; Metal Ceramic Alloys ; Shear Strength ; Surface Properties ; Titanium ; Zirconium

OBJECTIVETo compare shear bond strength (SBS) between composite resin core (CRC) disposed with three different surface treatments and glass ionomer cement (GIC), so that to provide theoretical basis for luting of crowns to CRC.

METHODSAccording to three different surface treatments, thirty blocks of CRC were randomly and equally divided into three groups: Roughening with diamond grit bur(RDB), RDB plus etching with Gluma Etch 35 Gel (RDBE), RDB plus coating with Adper Single Bond2 adhensive (RDBA). All CRC were cemented with GIC. All specimens were preserved in 37 degrees C water for 24 h, then SBS tests for eight specimens in each group were performed using a universal testing machine at a constant crosshead speed of 0.5 mm x min(-1). The surface topography of one CRC of each group was observed using field emission scanning electron microscope (FE-SEM) at 100 amplification. The interface between CRC and GIC was observed using FE-SEM at 500 amplification. Then the nature of failure was also recorded using FE-SEM at 25 amplification and the data were analyzed with a Kruskal-Wallis H test.

RESULTSThe surface topography of each group and the interface between CRC and GIC observed using FE-SEM were significantly different, but significant differences on the nature of failure between groups were not found (P > 0.10). SBS of each group was (4.28 +/- 0.18) MPa for RDB, (4.65 +/- 0.17) MPa for RDBE, (2.39 +/- 0.21) MPa for RDBA, respectively (P < 0.01).

CONCLUSIONThe SBS between CRC and GIC is affected by the surface treatments of CRC.

Composite Resins ; Crowns ; Dental Bonding ; Glass Ionomer Cements ; Materials Testing ; Resin Cements ; Surface Properties

OBJECTIVETo study the influence of three different metal alloy surfaces treated with primer methacryloxy propyl trimethoxyl silane (gamma-MPS) coupling agent on the bond strength of Filtek Z350 resin.

METHODSTotal 36 specimens of nickel-chromium(Ni-Cr) alloy, pure titanium(Ti) and aurum-palladium(Au-Pd) alloy, each of 12 pieces produced by lost wax casting method, were divided into 6 groups. After treated with gamma-MPS on the bonding surface, experimental group samples were adhered to Filtek Z350 resin, then compared with the surface without gamma-MPS treatment. The tensile and shear strength of each group tested and the fracture sections were observed with scanning electron microscope (SEM).

RESULTSComparing the Ni-Cr alloy and pure Ti experimental group with them in control group, the shearing strength of the experimental group was higher, and the differences were significant (P < 0.001). The shearing strength of the experimental group and control group of Au-Pd alloy were not significant (P > 0.05). Comparing the experimental groups, the shearing strength of pure Ti was higher than Ni-Cr alloy, both were higher than Au-Pd alloy (P < 0.01). These entire specimens were adhesive fracture. Comparing with the control group, Ni-Cr alloy and pure Ti experimental group showed more resin juts in the fracture surface, while the Au-Pd alloy in experimental group showed less resin juts.

CONCLUSIONgamma-MPS can enhance the adhesion between metal and resin, but it is also related to the metal composition. gamma-MPS can significantly increase the bond strength of resin and Ti or Ni-Cr alloy, but not the case of Au-Pd alloy and resin.

Chromium Alloys ; Composite Resins ; Dental Alloys ; Dental Bonding ; Materials Testing ; Shear Strength ; Silanes ; Surface Properties ; Titanium