Surface modification for enhanced silanation of zirconia ceramics

AbstractObjectiveThe overall goal of this research was to develop a practical method to chemically modify the surface of high strength dental ceramics (i.e. zirconia) to facilitate viable, robust adhesive bonding using commercially available silanes and resin cements.MethodsInvestigation focused on a novel approach to surface functionalize zirconia with a SixOy "seed" layer that would promote chemical bonding with traditional silanes. ProCAD and ZirCAD blocks were bonded to a dimensionally similar composite block using standard techniques designed for silica-containing materials (silane and resin cement). ZirCAD blocks were treated with SiCl4 by vapor deposition under two different conditions prior to bonding. Microtensile bars were prepared and subjected to tensile forces at a crosshead speed of 1mm/min scanning electron microscopy was used to analyze fracture surfaces and determine failure mode; either composite cohesive failure (partial or complete cohesive failure within composite) or adhesive failure (partial or complete adhesive failure).ResultsPeak stress values were analyzed using single-factor ANOVA (pxOy thick "seed" layer was similar in strength to the porcelain group (control). Analysis of failure modes indicated the above groups displayed higher percentages of in-composite failures. Other groups tested had lower strength values and displayed adhesive failure characteristics.ConclusionMechanical data support that utilizing a gas-phase chloro-silane pretreatment to deposit ultra-thin silica-like seed layers can improve adhesion to zirconia using traditional silanation and bonding techniques. This technology could have clinical impact on how high strength dental materials are used today

Effects of heat stress, dietary energy density and exogenous porcine somatotropin on tile growth performance of finishing pigs

This experiment was conducted to determine the interactive effects of environmental temperature porcine somatotropin (pST) and dietary energy density on the growth performance of finishing pigs. Forty-eight barrows were allotted randomly to four environmental chambers (EC) in a split plot design with two EClwhole plot (WP). Each EC (12 barrows/EC) represented one subplot (SP). The WP 24-h environmental cycles were: thermal neutral (TN), 8 h at 75°F and 50% relative humidity (RH)-1 h transition-14 h at 68°F and 60% RH-1 h transition; and heat stress (HS), 8 h at 95°F and 60% RH-1 h transition-14 h at 82°F and 80% RH-1 h transition. Each SP was a 2 x 3 factorial with two treatments (pigs were injected daily with either 4 mg pST (+) or placebo (-)) and three dietary energy densities (lA8, 1.60, and 1.71 Mcal ME/lb). Diets were formulated to contain 19.2% crude protein and at least 200% of NRC (1988) recommendations for essential nutrients. The study was conducted for 32 d. There were no interaction effects for ADG, average daily feed intake, d-14 respiration rate, or d-14 rectal temperature. Differences in respiration rate and rectal temperature were observed between the HS and TN environments (respiration rate 76 vs 28; rectal temperature, 103.8 vs lO1.8°F). There was an environment x pST interaction for feed efficiency (F/G). The F/G of barrows administered pST was similar in HS (2.23) and TN (2.29) environments. The F/G of placebo-treated barrows increased in HS (3.09) compared to the TN (2.80) environment. These results show that "the growth response of finishing pigs treated with pST is similar in the HS and TN environments

The effect of dietary energy density on growth performance of finishing swine treated with porcine somatotropin

A growth study (60 barrows averaging 125.4 lb) was conducted to evaluate the effect of dietary energy density on growth performance of finishing pigs treated with porcine somatotropin (pST). Barrows were blocked on weight and allotted randomly to pens (2 barrows/pen, 5 pens/treatment). Barrows were injected daily with 4 mg pST and fed six experimental diets with four energy densities (1.37, 1.48, 1.60, or 1.71 Meal ME/lb) and four lysinc:energy ratios (4.0, 3.7, 3.4, or 3.2 g lysine/Mcal ME). Diets were formulated to contain at least 200% of NRC (1988) recommendations for essential nutrients. Increasing dietary energy density and adjusting the lysine:energy ratio to maintain 3.4 g lysine/Mcal ME decreased average daily feed intake and improved feed efficiency, but did not affect average daily gain. Increasing dietary energy density without adjusting the lysine:energy ratio increased average daily gain, decreased average daily feed intake, and improved feed efficiency linearly. These results indicate that finishing pigs injected daily with 4 mg pST and consuming 30 g lysine per day require approximately 9 Meal ME per day to optimize growth performance and efficiency

The effect of dietary energy density and porcine somatotropin on apparent digestibility and retention of nutrients in finishing swine

Sixteen barrows were used in a metabolism study (avg wt of 101.2 lb) to evaluate the effect of dietary energy density and porcine somatotropin (pST) on apparent digestibility and retention of nutrients in finishing pigs. This study was designed as a split-plot with 4 mg pST/d or placebo injection as whole plot treatments and four dietary energy densities (1.37, 1.48, 1.60, and 1.71 Meal ME/lb) and period as the subplot treatments. Increasing dietary energy density increased apparent digestibility of dry matter, gross energy, and nitrogen, but had no effect on nitrogen retention. Porcine somatotropin administration had no effect on apparent digestibility of nutrients; however, percentage nitrogen retention was increased 42% compared to control pigs