OBJECTIVES: The aim of this in-vitro study is to evaluate the effect of different zirconia surface pretreatments, different cement types and the effect of accelerated aging on the adherence of bonding cements to zirconia. MATERIALS AND METHODS: 64 zirconia 3Y-TZP tapered rings were pressed from TZ-3YSB-E zirconia powder, pre-treated with different surface treatments, then cemented to titanium abutment pins using 8 different cements: Maxcem Elite chroma (Kerr), TheraCem (Bisco), RelyX Unicem2 (3M ESPE), Multilink Automix (Ivoclar Vivadent), Panavia SA Cement Plus (Kuraray), Ceramir C&B (Doxa), CemEZ Universal (Zest Dental), and Bifix SE (VOCO). The partitally sintered zirconia specimens were divided according to design of experment (DOE). Zirconia surface treatments: 1) control group with no surface treatment, 2) airborne particle abrasion of fully sintered zirconia ring (FS-APA50), 3) airborne particle abrasion of partially sintered zirconia (PS-APA50), 4) tribochemical silica coating of fully sintered zirconia (FS-CoJet30), 5) tribochemical silica coating of partial sintered zirconia (PS-CoJet30), and 6) nano-structured alumina coating of fully sintered zirconia (NanoAl). Zirconia rings were subjected to post-treatment:1) control 24h incubation after cementing proceedure, and 2) accelerated aging . The pull-out axial tensile retention load was tested using an Instron Model 5566A. Multi factorial linear regression model (JMP Pro 15) was used for data analysis (α=0.05). RESULTS: The retention force (N) of zirconia rings to titanium abutment pins was evaluated using a pull-out test. Four key factors were investigated in this study: zirconia surface pre-treatment, cement type, post-treatment and firing effect. There was a significant effect of zirconia surface pre-treatment on retention force (nano-structured alumina coating ≥ tribochemical abrasion = airborne-particle abrasion ≥ control). There was a significant effect of cement type on retention force [Multilink AM ≥ (Cem EZ = TheraCem = Panivia SA = RelyX Unicem2 = BiFix) ≥ Ceramir CB = Maxcem Elite]. There is a significant difference in retention strength to zirconia among post-treatment effect, with accelerated aging groups achieving slightly higher bond strength than 24h water storage groups. CONCLUSIONS: Significant different retention loads were found among tested groups. Nano-structured alumina coating surface pre-treatment has significantly higher bond strength than other treatments. Some cement systems with functional monomer had significant higher bond strengths.

The objective of this study is to develop a fast curing phenolic formaldehyde (PF) and polymeric diphenyl methane isocyanate (MDI) based hybrid resin system for wood products applications. Various formulas of PF resins were synthesized with different formaldehyde to phenol ratio, sodium hydroxide to phenol and isocyanate group (-NCO) to hydroxyl group (-OH) molar ratios. The shear bonding strength property was used to evaluate and optimize the formulations by appropriate sample preparation. The optimized resins were characterized by rheometer, Fourier transform infrared spectroscopy (FTIR) and other methods. In order to eliminate the influence of hydroxyl groups from water in the PF resin, a frozen dried method was applied to remove the water while keeping PF resin in liquid state. Acetone was used to disperse the hybrid co-polymer to improve the mobility of the mixture of frozen dried PF resins and MDI. An unexpected phenomenon was observed when the two resins were mixed in acetone and a sharp reaction occurred. This led to an assumption that acetone promoted the curing of hybrid resin. The effect of acetone on the curing behavior of hybrid resin was studied by differential scanning calorimetry (DSC), confocal laser scanning microscope (CLSM) and other techniques. It was confirmed that acetone promoted the curing of the co-polymer system. The gel time of hybrid resin with acetone decreases sharply compared to that of pure phenolic resin and original hybrid resin. Acetone also helped the hybrid resin to have better penetration behavior by improving the mobility and this also resulted in less variation of the strength distribution. Finally, lap shear samples were prepared at room temperature curing commercial polyurethane (PU), phenol-resorcinolormaldehyde resin (PRF) and laboratory made hybrid resins based on PF and MDI to compare the shear strength of different resins under different application conditions. The strength reduction of frozen dried PF with acetone/MDI is the lowest in humidity, temperature and humidity-temperature conditions. With just humidity condition, its shear strength reduction is significantly lower than that of any other resins including the solid wood control.

Indiana University-Purdue University Indianapolis (IUPUI) / Clinical evidence suggests that the use of liners in posterior composite restorations may increase the frequency of restoration fractures. Materials that have been used as liner materials for resin composite (RC) restoration include conventional glass ionomers, resin-modified glass ionomers (RMGI), and flowable composites. The aim of this study was to compare the flexural strength of a monolayer of resin composite with that of a bilayer of resin composite and liner. Four types of RC beams were tested: a monolayer control that is an un-lined RC (Tetric EvoCeram, Ivoclar Vivadent) and three “bilayer” specimens that consisted of this same RC lined with one of three liners. The three liners used included two RMGI cements (Vitrebond LC liner; 3M ESPE and, GC Fuji Lining LC; GC America) and a flowable resin composite (Tetric EvoFlow, Ivoclar Vivadent). Each group was tested after water storage for 24 h and 30 d. Altogether, eight, 12-specimen groups were fabricated and tested. Methods: A 25 x 2 x 2 mm mold was completely filled with the RC to form the control beams. To form the bilayer beams, this mold was filled with 0.5 mm of the liner and then with 1.5 mm of the RC. Specimens were stored in 37oC distilled for either 24 h or 30 d. Immediately prior to testing, the 30-day groups were also thermocycled 2500 times, between water baths at 7 oC and 48oC with a 30-s dwell time and a 10-s transit time. Flexural strength was determined using a three-point–bending device. A twoway analysis of variance (ANOVA) with interactions was used to investigate how liner group (or no liner) and storage time affected strength. Results: The interaction between liner type and storage time was significant (p = 0.0128). The un-lined RC (the monolayer beam) was significantly stronger after 24 h than after 30 d in water (p = 0.0098). Water storage between 24 h and 30 d did not change the flexural strength of any of the bilayer (lined) beams (p > 0.05). After storage for 24 h and also for storage for 30 d, both un-lined RC and RC lined with the flowable RC exhibited significantly higher flexural strength (p = 0.0001) than the bilayer beams lined with either RMGI liners.

Indiana University-Purdue University Indianapolis (IUPUI) / Cementing of indirect restorations with resin cements generally requires the pre-treatment of dentin with an adhesive. When dual-cured or chemical-cured resin cements are used with these single-step adhesives, incompatibility issues exist. This has resulted in manufacturers making chemical changes in their products. Kerr Dental markets a new resin cement, Nexus Third generation (NX3), which utilizes a proprietary redox system different from the second generation of composite luting agent (NX2). The aim of this study was to evaluate microtensile bond strength and mode of failure of NX3 and NX2 with two different adhesive systems (total-etch and self-etch) after 1 week and after 3 months of storage. Methods: Sixty-four non-carious teeth were sectioned to expose the dentin using a low-speed saw. Dentin surfaces were ground with 320-grit SiC paper. The adhesives Optibond Solo Plus (SOL), and Optibond All In One (AIO) were applied, and resin cements (NX2, NX3) were used to lute 4-mm composite discs to the treated dentin surfaces. Microtensile bond strength was determined at 1 week (IM) and after 3 months (3MON) of storage using a universal testing machine (MTS). All specimens were examined under the stereomicroscope to determine the mode of failure. Random specimens from each failure group were examined using scanning electron microscopy. Statistical Analysis: Comparisons between the treatment combinations for differences in microtensile bond strength were performed using Weibull-distribution survival analysis. Comparisons between the treatment combinations for differences in the failure mode were performed using Fisher’s Exact tests. The group NX3 SOL IM (30.5 MPa) had significantly higher bond strength than NX3 SOL 3MON (13.4 MPa); NX3 AIO IM (11.3MPa); NX3 AIO 3MON (8.2 MPa; NX2 AIO 3MON (5.8 MPa); NX2 SOL IM (6.3 MPa), and NX2 SOL 3MON (3.2 MPa). The group NX2 AIO IM (19.3 MPa) was not significantly different from NX3 SOL IM. The group NX2 SOL 3MON and group NX2 SOL IM had a significantly higher percentage of teeth with mixed failure than all of the other groups. None of the other groups had significantly different failure mode. The group NX3 SOL IM had 90-percent beam survival beyond 17 MPa, and NX2 AIO IM had 50 percent of beams surviving beyond 17 MPa, a better performance. For all the other groups, more than 50 percent of beams failed below 17 MPa. Results show high evidence of degradation for all groups considered in this investigation. The use of these types of cement adhesive combinations in clinical situations should be used with this understanding.

Latex polymers serve as binders in a wide range of architectural paints and coatings. A latex is an aqueous colloidal dispersion of polymer particles that when dried above the polymer’s film formation temperature coalesces into a dry polymer film (Dragnevski, Routh, Murray, & Donald, 2010). The other main components of paint include associative thickeners, surfactants, pigments and fillers with the thickener being the primary area of focus for this study. The relatively simple system of latex, associative thickener and surfactant has been studied extensively. These studies have shown the mechanism of thickening for the associative thickener, and surfactant effects on both latex and thickener; however, there are few studies conducted for a fully-formulated system. The introduction of pigments, fillers, coalescing aids, functional amines, and other additives greatly increases the difficulty of research in this area. The addition of many additives ultimately affects the stability and physical properties of the end-product. Phase separation of the paints, also called syneresis, is a major concern of paint formulators because paints need to be as stable when left sitting in a paint-can for an extended period of time. The goal of this project is to essentially probe the areas of phase separation for some hydrophobically modified ethoxylated urethane (HEUR) thickened paint systems that are very similar to commercially used paint formulations. The probing of these phase separated regions includes the careful preparation of each paint sample, physical property testing, as well as new experimental development in the area of syneresis, rheology, followed by statistical analysis of data. Dispersion phase diagrams (DPDs) were first reported by Kostansek (2003) in a simple system of HEUR thickener, surfactant, and latex. They are a plot of the three possible dispersion states for an associative thickened system. These states include bridging flocculation which occurs at low levels of HEUR in which 50% or less of the latex particle surface is covered by the associative thickener. The second state is a good dispersion, which does not show any signs of flocculation. The third state is a mode of flocculation called depletion flocculation that occurs when the particle surfaces of the system are covered mostly with surfactant. The free associative polymer in the system is excluded from the free space in between particles, and the latex particles form aggregates (Otsubo, 1995). The three dispersion phases are then plotted with wt% HEUR on the continuous phase versus wt% surfactant on the continuous phase. The ideal end product for this project would be to use various combinations of latex, surfactant, and associative thickeners (ATs) to create multiple DPDs, which then could be used to troubleshoot formulations and samples in which flocculation is present. Each formulation was made using a thickening package of two non-ionic HEURs: a low-shear and high-shear thickener. Surfactant additions were made after the HEUR in small incremental amounts. Each DPD would consist of one surfactant, the previously stated combination of HEURs, and an all-acrylic latex. Three different surfactants were used in the study: two non-ionic surfactants, and an anionic surfactant. The first non-ionic surfactant was not studied in full as the other two surfactants due to time constraints. Two different all-acrylic latexes were used which varied in the particle size. The first latex studied, Acrylic-A, has an average particle size of 105 nm, and the second latex was Acrylic-B with 150 nm particle size. The TiO2 used in each DPD was surface treated and used in powder form. By the end of the project, 4 full-scale DPDs were made with the following combinations: Acrylic-A and a non-ionic surfactant, Acrylic-A and an anionic surfactant, Acrylic-B and a non-ionic surfactant, and Acrylic-B and an anionic surfactant. From these DPDs the mechanistic interactions of various components of the system could be made. The DPDs could also be used to troubleshoot problematic paints and even hypothesize new formulations.

No description available.

No description available.

SonicFillTM is a new composite resin and delivery system designed to provide rapid filling of cavity preparations by decreasing viscosity through application of sonic energy. However, it may produce unwanted air voids in the final restoration due to the short filling time. Air voids compromise long-term performance by providing weak foci, discontinuity at cavosurface margins and at internal cavity walls, and potential crack propagation. This study assessed the locations, sizes, and numbers of voids in SonicFill restorations compared with traditional composite resin restorations in a set of extracted molars with mesio-occlusal-distal (MOD) cavity preparations. Fifty noncarious intact extracted third molars were collected randomly from a large collection of discarded anonymous tooth specimens. Standardized MOD cavity preparations were cut, and teeth were assigned randomly to one of two groups (n = 25). The first group was restored with SonicFill composite in two steps. The second group was restored with Herculite UltraTM using an multiple increment layering technique (1-2 mm per layer). Cross-sectional images of the filling were taken by digital microscope. A total of 196 voids were found in the 50 specimens: 97 in SonicFill restorations and 99 in conventional restorations. Mean number of voids in SonicFill restorations was 3.88 versus 3.96 for conventional restorations. Mean percentage of void area in SonicFill restorations was 0.588% versus 0.508% for conventional restorations. Unpaired t tests for these differences indicated no statistically significant differences (p =.931 and p =.629, respectively). One-way ANOVA tests for mean void count and mean void area percentage differences by three location zones for conventional and SonicFill restorations also indicated no significant differences among the groups. The bulk-fill SonicFill system does not result in increased or decreased numbers or ii area of voids within Class II MOD restorations compared with a conventional composite resin layering system. / Oral Biology

In this investigation, a comprehensive Vacuum Assisted Resin Transfer Molding (VARTM) process simulation model was developed and verified. The model incorporates resin flow through the preform, compaction and relaxation of the preform, and viscosity and cure kinetics of the resin. The computer model can be used to analyze the resin flow details, track the thickness change of the preform, predict the total infiltration time and final fiber volume fraction of the parts, and determine whether the resin could completely infiltrate and uniformly wet out the preform. Flow of resin through the preform is modeled as flow through porous media. Darcy's law combined with the continuity equation for an incompressible Newtonian fluid forms the basis of the flow model. During the infiltration process, it is well accepted that the total pressure is shared by the resin pressure and the pressure supported by the fiber network. With the progression of the resin, the net pressure applied to the preform decreases as a result of increasing local resin pressure. This leads to the springback of the preform, and is called the springback mechanism. On the other side, the lubrication effect of the resin causes the rearrangement of the fiber network and an increase in the preform compaction. This is called the wetting compaction mechanism. The thickness change of the preform is determined by the relative magnitude of the springback and wetting deformation mechanisms. In the compaction model, the transverse equilibrium equation is used to calculate the net compaction pressure applied to the preform, and the compaction test results are fitted to give the compressive constitutive law of the preform. The Finite Element/Control Volume (FE/CV) method is adopted to find the flow front location and the fluid pressure. The code features the ability of simultaneous integration of 1-D, 2-D and 3-D element types in a single simulation, and thus enables efficient modeling of the flow in complex mold geometries. VARTM of two flat composite panels was conducted to verify the simulation model. The composite panels were fabricated using the SAERTEX multi-axial warp knit carbon fiber fabric and SI-ZG-5A epoxy resin. Panel 1 contained one stack of the carbon fabric, and Panel 2 contained four stacks of the fabric. The parameters verified included the flow front location and preform thickness change. For Panel 1, the flow front locations were accurately predicted while the predicted resin infiltration was much slower than measured for Panel 2. The disagreement is attributed to the permeability model used in the simulation, which failed to consider the interface flow in the unstitched preform containing more than one stack of the fabric under very low compaction force. The predicted transverse displacements agree well with the experimental measurement qualitatively, but not quantitatively. The reasons for the differences were discussed, and further investigations are recommended to develop a more accurate compaction model. The simulation code was also used to investigate the VARTM of a new form of sandwich structure with through-the-thickness reinforcements, which is being considered for use in primary aircraft structure. The infiltration of three foam core sandwich preforms with different stitch densities was studied. The objective of the study was to determine whether the preforms could be completely infiltrated and how the stitch density affects the infiltration process. The visualization experiments were conducted to verify the simulation. The model accurately predicted the resin infiltration patterns. The calculated filling times underpredicted experimental times by 4 to 14%. The model revealed the resin flow details and found that increasing the stitch spacing shortens the total filling time, but increases the nonuniformity of the flow front shape. Extreme nonuniformity of the flow front shape could result in the formation of the voids. / Ph. D.

Polymer-coated controlled-release fertilizers (PCFs) are the most widely used class of fertilizers in the production of container-grown nursery plants. Nutrient release from PCFs is primarily influenced by temperature. The objective of this study was to determine the influences of temperature and time on the nutrient release patterns of three PCFs (each with a rated longevity of 8-9 months), each using a different coating technology: Osmocote Plus™ 15N-3.93P-9.96K, Polyon™ 18N-2.62P-9.96K, and Nutricote™ 18N-2.62P-6.64K. The first three experiments investigated the effects of time on long-term nutrient release. In Expt. 1, each of the three PCFs were placed in flasks of distilled water maintained at 40°C for 22 weeks. Fertilizer solutions were poured off at bi-weekly intervals and measured for electrical conductivity (EC) and NO3-N, NH4-N, P, K, Fe, Mn, Cu, and Zn concentrations. Overall, nutrient release for the three PCFs was higher and more variable in the first eight weeks than later in the experiment. Polyon's™ macronutrient release was generally more gradual than that of the other products. Micronutrient release patterns varied substantially between fertilizers and nutrients. In Expt. 2, pine bark (PB)-filled containers were amended with the three PCFs and irrigated regularly in a greenhouse. PCFs were removed from containers when Osmocote Plus'™ NO₃-N supply was ~66% expended and analyzed for EC, NO₃-N, NH₄-N, and P concentration. Except for P, the percentage of each nutrient remaining was roughly comparable to those remaining at the corresponding stage of Expt. 1, suggesting that PCF nutrient release behavior in the laboratory method is comparable with nutrient release behavior in PB in the greenhouse. At the end of Expts. 1 and 2, Osmocote Plus™ had expended a higher percentage of its nutrients than the other fertilizers. In Expt. 3, substrate solutions were collected weekly from PB-filled containers (same treatments as in Expt. 2) and EC was determined. The substrate solution EC of Osmocote Plus™-fertilized PB began to decline sooner than that of the other fertilizers. Overall, these three experiments led to the conclusion that Osmocote Plus™ nutrient release declines more quickly than does Polyon™ or Nutricote™, while Polyon™ has the most gradual nutrient release pattern. The objective of the second set of experiments was to determine the effects of temperature on short-term nutrient release. In Expt. 4, 14 g of each PCF was maintained at 40°C until ~33% of the NO3-N content in Osmocote Plus™ was expended. Each fertilizer was then placed in a sand column and leached with distilled water at ~100 mL/h. Columns were then incrementally subjected to a simulated diurnal container temperature change from 20°C to 40°C and back to 20°C over a period of 20 h. Leachate was collected hourly and measured for soluble salts and NO₃-N and NH₄-N concentrations. For all fertilizers, nutrient release increased and decreased with the respective increase and decrease in temperature. Nutrient release patterns of the three fertilizers were significantly different, with Osmocote Plus™ showing the greatest overall change in nutrient release between 20°C and 40°C and Nutricote™ the least. In Expt. 5, PCFs were placed in flasks of distilled water in constant temperature baths. Initially, fertilizers were held at 40°C for three days and then at temperatures of 22, 28, 34, or 40°C for two weeks. Fertilizer solutions were poured off after the first and second weeks. Only solutions from the second week were analyzed for soluble salts and NO₃-N, NH₄-N, P, and K concentrations. For Osmocote Plus™ and Polyon™, there was a 29% to 86% (depending on the nutrient measured) mean increase in nutrient release between 22°C and 40°C, whereas for Nutricote™ there was a 345% to 364% (depending on the nutrient measured) mean increase. The overall mean increases in nutrient release in Expt. 4 were between 1032% and 4023%, whereas the mean increases in Expt. 5 were between 29% and 364%. In summary, the second set of experiments found that PCF nutrient release was highly sensitive to diurnal temperature changes. / Master of Science