ABSTRACT
The present comparative study aimed to evaluate the surface corrosion and fracture resistance of two commercially available nickel-titanium (NiTi)-based archwires, as induced by a combination of fluoride, pH, and thermocycling. One hundred and ten rectangular section NiTi-based archwires were used, 55 of each of the following: thermally activated Thermaloy® and super-elastic NeoSentalloy® 100 g. Each of these was divided into five equal subgroups. One of these five subgroups did not undergo any treatment and served as the control, while the other four were subjected to 30 days of incubation at 37°C under fluoridated artificial saliva (FS) at 1500 ppm fluoride treatment alone (two subgroups) or combined with a session of thermocycling (FS + Th) treatment at the end of incubation (two subgroups). Within each of the Thermaloy® and NeoSentalloy® groups, the FS and FS + Th treatments were performed under two different pH conditions: 5.5 and 3.5 (each with one subgroup per treatment). Analysis of the surface topography and tensile properties by means of scanning electron microscopy (a single sample per subgroup), atomic force microscopy, and a universal testing machine for ultimate tensile strength were carried out once in each of the control subgroups or immediately after the treatments in the other subgroups for 10 of the archwires. Non-parametric tests were used in the data analysis. Significant effects in terms of surface corrosion, but not fracture resistance, were seen mainly for the Thermaloy® group at the lowest pH, with no effects of Th irrespective of the group or pH condition. Different NiTi-based archwires can have different corrosion resistance, even though the effects of surface corrosion and fracture resistance appear not to be significant in clinical situations, especially considering that thermocycling had no effect on these parameters.
Subject(s)
Cariostatic Agents/chemistry , Dental Alloys/chemistry , Fluorides/chemistry , Nickel/chemistry , Orthodontic Wires , Titanium/chemistry , Corrosion , Dental Stress Analysis/instrumentation , Humans , Hydrogen-Ion Concentration , Imaging, Three-Dimensional/methods , Materials Testing , Microscopy, Atomic Force/methods , Microscopy, Electron, Scanning , Saliva, Artificial/chemistry , Stress, Mechanical , Surface Properties , Temperature , Tensile StrengthABSTRACT
Luting of fiber posts to intra-radicular dentin represents the worst-case scenario in terms of control of polymerization shrinkage. This study tested the hypothesis that filler content of resin cements does not influence luting of fiber posts to intra-radicular dentin, by assaying polymerization stress, push-out bond strength, and nanoleakage expression. The polymerization stress of experimental cements containing 10%, 30%, 50%, or 70% in filler content was investigated. Post spaces were prepared in endodontically treated teeth, and fiber posts were cemented with the experimental cements. A push-out test was performed, and interfacial nanoleakage expression was analyzed. Results showed that luting cements with higher filler content were related to increased polymerization stress (p < 0.05), decreased push-out bond strength (p < 0.05), and increased interfacial nanoleakage expression (p < 0.05). Conversely, lower-stress luting materials increased bonding of fiber posts to intra-radicular dentin. Further in vivo studies are needed to investigate the long-term clinical performance of these materials.
Subject(s)
Cementation/methods , Dental Bonding , Post and Core Technique/instrumentation , Resin Cements/chemistry , Adhesiveness , Aluminum Compounds/chemistry , Dental Leakage/classification , Dental Prosthesis Design , Dental Pulp Cavity/ultrastructure , Dentin/ultrastructure , Dentin-Bonding Agents/chemistry , Fluorides/chemistry , Humans , Materials Testing , Methacrylates/chemistry , Particle Size , Polymers/chemistry , Polyurethanes/chemistry , Silicon Compounds/chemistry , Silicon Dioxide/chemistry , Stress, Mechanical , Surface Properties , Tooth, Nonvital/pathologyABSTRACT
OBJECTIVES: This study examined the effect of chlorhexidine (CHX) content on degree of conversion (DC) and E-modulus of experimental adhesive blends. The hypothesis tested was that increasing concentrations of CHX result in decreased DC and E-modulus in relation to adhesive hydrophilicity. METHODS: Experimental adhesive blends with increasing hydrophilicity R2 (70% bisGMA, 28.75% TEGDMA); R3 (70% BisGMA, 28.75% HEMA); R4 (40% BisGMA, 30% TCDM, 28.75% TEGDMA); R5 (40% BisGMA, 30% BisMP, 28.75% HEMA) and different CHX concentrations (1 and 5%) were analyzed. 5% CHX could not be dissolved in R2. A differential scanning calorimeter was used to measure the DC of resin blends. Photopolymerized disks of the experimental comonomer mixtures (n=10/gp) were used to measure the E-modulus of each specimen using a biaxial flexure test. Data were analyzed with two-way ANOVA (resin type and CHX concentration) and Tukey's post hoc test. RESULTS: The addition of 1% CHX did not significantly alter the DC of R2 and R3. Significant decrease in R3 DC values was observed when 5% CHX was added. CHX significantly increased the DC of R4 and R5. 1% CHX reduced the E-modulus of all resins (p<0.05) except for R2, in which the E-modulus was significantly increased (p<0.05). 5% CHX significantly reduced the E-modulus of resins R3 to R5 (p<0.05). SIGNIFICANCE: In conclusion, increasing concentrations of CHX dissolved in resin blends had little adverse effect on DC but decreased the E-modulus 27-48% compared to controls. Solvation of CHX in ethanol prior to incorporation of CHX into R2 may permit higher CHX concentrations without lower polymer stiffness.
Subject(s)
Anti-Infective Agents, Local/chemistry , Chlorhexidine/chemistry , Resin Cements/chemistry , Bisphenol A-Glycidyl Methacrylate/chemistry , Calorimetry, Differential Scanning , Composite Resins/chemistry , Elastic Modulus , Humans , Materials Testing , Methacrylates/chemistry , Pliability , Polyethylene Glycols/chemistry , Polymers/chemistry , Polymethacrylic Acids/chemistry , Solubility , WettabilityABSTRACT
This study aimed to compare two different implant surface treatments of the implant system Bi-Implant (Plan 1 Health): one surface sandblasted with hydroxyapatite (HA) (Osseogrip(R)) and one machined surface. Histomorphologic and histomorphometric evaluations of the bone healing at the interface between a titanium implant and bone were performed using a light microscopic technique. Twenty-four commercially pure titanium implants with a smooth surface and 24 implants with a sandblasted surface were inserted in the tibias of 12 rabbits. The 12 rabbits were divided into three groups, each consisting of four animals, were sacrificed at 4 weeks (I group), 8 weeks (II group) and 12 weeks (III group) after the insertion of the bio-material. The results emphasized that in the sections examined with the light microscope, the bone was in intimate contact with the implant surface and the bone surrounding the implants was mostly lamellar. After 4 weeks, mature bone tightly surround-ing some areas of the implant perimeter was observed. The implant with the Osseogrip(R) surface showed an average percentage of bone-implant contact (%BIC) equal to 33%, while the one with the machined surface showed a %BIC equal to 17%. After 8 weeks, a progressive increase in mineralized bone surrounding the implant surface was detected, making the results of the machined surface superposable to the Osseogrip(R) surface results (48 and 44%). After 12 weeks, the implants with the machined surface exhibited close contact with the bone tissue corresponding to 62% of their perimeter, while for the implants with the Os-seogrip(R) surface the surface contact was 67% of the implant surface. The morphometric evaluation of %BIC at the three time points evidenced an increase in bone-titanium contact over time on both machined and Osseogrip(R) surfaces. Moreover, implants with rough surfaces demonstrated better behavior than the implants with the machined surface when taking into account the earlier osteointegration (4 weeks) of the peri-implantar tissues.
