The Tissue Implant Response Surrounding Subcutaneous TCP, HA, And ALCAP Bioceramics.

The objective of this investigation was to quantify and further elucidate the tissue-implant response in the fibrous tissue surrounding tricalcium phosphate (TCP), hydroxyapatite (HA), and aluminum calcium phosphate (ALCAP) implants when implanted subcutaneously. Sixteen animals in four experimental groups (n = 4/group) were implanted with one implant each: Group I (control, TCP), Group II (HA), and Group III (ALCAP). At 90 days post-implantation, the fibrous tissue surrounding the implants was harvested. Sections of stained fibrous tissue were evaluated for the presence of macrophages, fibrocytes, neutrophils, vascularity and thickness for all three groups using semi-automated quantitative methods. The analysis indicated Group III demonstrated a significantly higher number of neutrophils but fewer macrophages and blood vessels per high power field and had a substantially thinner fibrous tissue capsule thickness compared to Groups I and II (alpha=0.05). Group II elicited a greater response of fibroblasts compared to Groups I and III suggesting HA may provide a slightly higher degree of stability to the implant. In total, these findings suggest both TCP and HA behave similarly in vivo when compared to ALCAP and may be better choices for subcutaneous soft-tissue application compared to ALCAP.

Neovascularization And Macrophage Behavior Under The Influence Of Androgens In The Tissue-Implant Response.

Macrophages and blood vessels are critical components in the biocompatibility and functionality of implantable ceramic materials used in drug delivery applications. The purpose of this study was to examine the correlation of macrophage and neovascularization by further defining their presence, relationship, and correlation in the fibrous tissue capsule of calcium phosphate (TCP) ceramic drug delivery systems. Sixteen animals in four experimental groups were implanted with one TCP bioceramic each. Group I animals were implanted with a TCP ceramic not containing a biologic (control group). Group II animals received the testosterone loaded TCP ceramic. Group III animals were implanted with the dihydrotestosterone loaded ceramic. Group IV animals received the androstenedione ceramic. At 90 days post-implantation, the animals were euthanized. Implants and fibrous tissue capsules were collected. Determination of macrophage populations and neovascularity was conducted microscopically following H&E staining and aided by ImagePro digital analysis software. Androgens have varying effects on vascularity and macrophage populations. Overall, macrophage counts were highly and significantly correlated with vascularity (p<0.05), particularly in Groups II, III, and IV. Correlations for Group I was not statistically significant. These findings suggest that presence of macrophages is be directly related to neovascularity, especially in the presence of exogenous androgens.

Characterization of chitosan films and effects on fibroblast cell attachment and proliferation.

Chitosan has been researched for implant and wound healing applications. However, there are inconsistencies in reports on the tissue and fibroblast responses to chitosan materials. These inconsistencies may be due to variations in chitosan material characteristics. The aim of this study was to correlate fibroblast responses with known chitosan material characteristics. To achieve this aim, chitosan was characterized for degree of deacetylation (DDA), molecular weight (MW), residual protein and ash contents, and then solution cast into films and characterized for hydrophilicity by water contact angle. The films were seeded with normal human dermal fibroblasts and the number of attached cells was evaluated for after 30 min. Cell proliferation was evaluated over 5 days. This study found no relationship between DDA, contact angle, cell attachment, and or proliferation. General trends were observed for increasing proliferation with increasing residual ash content and decreasing residual protein. These data indicate that chitosan characteristics other than DDA may be important to their biological performance.

Improved orthopaedic bone cement formulations based on rubber toughening.

Poly(methylmethacrylate) (PMMA) bone cements have been used for the fixation of hip and knee implants since the early 1960s. Aseptic loosening, related to fracture of the PMMA, continues to be the primary mode of failure for these prostheses. Failed prostheses must be replaced causing additional expense and patient trauma. Furthermore, the average lifetime of the revised prosthesis is significantly lower than that of a primary prosthesis. Recent work by Moseley and co-workers led to the development of a promising new rubber toughened cement. It is comprised of a matrix of the traditional PMMA with dispersed rubber particles to modify mechanical properties and, in particular, improve fracture toughness. The fracture toughness of the experimental material was 167% greater than the toughness of a nontoughened control; however, the elastic modulus and compressive strength were reduced. The reductions in properties should not pose a clinical problem based on results of the implant model reported by Moseley. More serious concerns were mixing and delivery problems and high residual monomer concentrations. The formulation and chemical/mechanical characterization of new toughened acrylic formulations that have residual monomer levels equivalent to Simplex and better mixing properties are reported.

Microleakage of two new combined primer/adhesive resin systems.

In vitro microleakage of two new combined primer/adhesive systems utilizing the all etch technique (enamel and dentin etch) with the hybrid composite resin TPH is reported. These new combined primer/adhesive systems were compared to the Optibond FL system, which consists of a separate primer and adhesive. Forty Class V preparations were cut on the facial surfaces at the cemento-enamel junction of bovine incisor teeth to a dimension of 2.0 mm x 3.0 mm x 2.0 mm with a 1.0 mm 45 degree incisal bevel. The enamel (incisal) and dentin (gingival) margins were scored separately. Results suggest that Prime & Bond provided an improvement in the gingival marginal seal over the other materials. There was no statistically significant difference in the sealing ability of the materials tested at the incisal margin.

Microleakage of new dentin bonding systems using human and bovine teeth.

The objective of this study was twofold: to evaluate the microleakage behavior of three dentin bonding systems and to determine if bovine teeth are comparable substrates to human teeth when studying the microleakage of various materials. The materials evaluated were Scotchbond Multi-Purpose Adhesive, Prisma Universal Bond 3, and All-Bond 2. All three bonding systems were used in combination with Prisma APH hybrid composite for comparison of microleakage behavior. Sixty class 5 preparations were cut at the cementoenamel junction for groups containing 30 human and 30 bovine teeth. A 1 mm 45 degree bevel was placed at the enamel margin. Teeth were grouped according to the dentin bonding system used and then restored according to the manufacturer's directions. After restoration, the teeth from each group were stored in distilled water at 37 degrees C for 3 days. The teeth were then thermocycled between 4 degrees C and 58 degrees C for 100 cycles and returned to distilled water at 37 degrees C for an additional 4 days. The teeth were then sealed with nail polish up to 1 mm from the margins of the restoration and placed in 45Ca isotope for 2 hours. The teeth were then sectioned and placed on x-ray film to produce autoradiographs. Microleakage was evaluated for the enamel and dentin margins separately using the following scale: 0 = no leakage, 1 = penetration of isotope to less than 1/2 the distance to the axial wall, 2 = penetration of isotope greater than 1/2 of the distance to the axial wall but short of the axial wall, and 3 = penetration of isotope to the axial wall or beyond. The materials were compared to each other using the Mann-Whitney U and Kruskal-Wallis tests. The gingival margins were compared to the incisal margins for all materials. No statistically significant differences in microleakage were revealed between the incisal and gingival location for human substrates, but there was statistically significant greater gingival microleakage for bovine substrates. All-Bond 2 leaked significantly more than Scotchbond Multi-Purpose for human substrates at the incisal margin. All-Bond 2 had significantly more microleakage than Prisma Universal Bond 3 at both dentin and enamel margins for the bovine substrate. There were no statistically significant differences in microleakage among the bonding systems for the human substrate. No statistically significant differences between the microleakage behavior of human and bovine substrates were found. These results support the use of bovine teeth for in vitro microleakage studies.

Microleakage and thermal properties of hybrid ionomer restoratives.

The objective of this study was to compare the microleakage and thermal properties of two recently introduced hybrid materials to those of a conventional glass-ionomer cement. Class V preparations were prepared at the cementoenamel junctions in freshly extracted bovine incisor and evaluated for microleakage with a 45Ca radioisotope method. Thermal properties were evaluated with thermal mechanical analysis and differential scanning calorimetry. The degree of microleakage and the coefficient of thermal expansion of the conventional glass-ionomer cement were found to be significantly less than those of either hybrid.

The effects of chewing frequency and duration of gum chewing on salivary flow rate and sucrose concentration.

On ten separate occasions, unstimulated saliva was collected from 12 adults and then eight samples of saliva over a 20-min period while chewing, in random order, 3 g of either Wrigley's Spearmint chewing-gum or gum-base at frequencies of 35, 50, 70, 90, or 130 chews/min. With both stimuli, flow rates peaked in the first minute of stimulation and then fell with time. A repeated-measures analysis of variance showed that for both the gum and the gum-base, flow rates were independent of chewing frequency, except during the first minute with the chewing-gum. The gum elicited a significantly higher flow rate over the first 4 min of chewing, while the base elicited a significantly higher flow rate over the 8-20-min period of chewing. The sucrose concentration in saliva was also independent of chewing frequency. The salivary sucrose concentration peaked during the second minute of chewing (mean +/- SE = 424.7 +/- 20.0 mM) and the concentration then fell progressively with time. However, sucrose was still being released into saliva during the 15-20 min period of chewing (12.6 +/- 0.8 mM). Gum-base which had been chewed without access to saliva was softer than unchewed base but showed no change in filler content or a reduction in the average molecular weight. The decrease in hardness of the chewed gum-base may have resulted from improved mixing of heterogeneous phases and increased dispersion of plasticizing agents.

Microleakage of a new dental adhesive comparing microfilled and hybrid resin composites.

The objective of this study was to evaluate the in vitro microleakage of a new adhesive system, Syntac. Class V preparations were cut at the cementoenamel junction in 20 extracted bovine incisors and 20 extracted human incisors. One group of 10 human and 10 bovine teeth was restored with Syntac and a microfilled posterior resin composite; the other group was restored with Syntac and a hybrid resin composite. Microleakage was evaluated at 1 week with a 45Ca radioisotope method. No statistically significant differences between human and bovine substrates were found with either resin composite. The Syntac/hybrid resin restorations leaked less than did the Syntac/microfilled resin restorations at the gingival (dentin) margin in the bovine teeth; however, this difference was not statistically significant.

Effect of heat-curing cycle and gypsum contamination on the bond strengths of composite bonded to a silane-treated alloy.

Silane-coated alloy specimens bonded to composite resin were tested for shear bond strengths and compared with an identical specimen group exposed to gypsum invested heat-processing conditions. The results indicate that the bond of composite resin to silane-coated alloy is not impaired by investing, boil-out, cleaning, packing, and curing during the process of securing artificial teeth to a partial denture framework. In a second part of this study, the alloy specimens were silane-coated and exposed to the gypsum invested heat-processing procedure before the composite resin was bonded to them. In addition, the specimens were exposed to one of three different cleaning agents (ethyl acetate, ethyl alcohol, and soap and water). Results in the second part of the study indicate that ethyl acetate is an effective cleaning agent to use when a silane-coated alloy surface previously exposed to gypsum processing is to be bonded to composite resin.

A one-appointment mouthstick appliance.

Quadriplegics rely on mouthstick appliances to perform a variety of tasks to establish more self-sufficiency. Present techniques to fabricate a quality mouthstick applicance requires professional expertise, time, and laboratory expense. A technique for providing an inexpensive, durable mouthstick appliance in one appointment is described.

Evaluation of a new dentinal bonding system.

The purpose of this study was to compare the in vitro microleakage of a new dentinal bonding system, not yet released in the United States, to the microleakage of two first-generation bonding agents. Simulated Class V cavities were prepared in freshly extracted bovine incisors and restored with the appropriate composite resin-bonding agent combination. Restorations were thermocycled and examined for microleakage at 24 hours and 60 days. Comparison of the materials revealed no statistically significant difference in microleakage scores at the gingival or incisal margins after 24 hours. However, the first-generation bonding agents exhibited significantly more microleakage at the gingival margin than did the new bonding system after 60 days. No significant increase in microleakage was measured at the incisal margin for any of the materials after 60 days. In contrast, all materials exhibited a significant increase in leakage at the gingival margin after 60 days. No correlation between microleakage and polymerization shrinkage or coefficients of thermal expansion of the composite resins could be established.

Method to measure the polymerization shrinkage of light-cured composites.

The polymerization shrinkage of light-cured dental composite resins has been reported to cause a marginal gap between the cavity wall and the restoration, leading to the premature and/or tensile stress failure of the composite restoration. This study measured the volumetric shrinkage of six light-cured posterior composites by measuring specific gravity differences between uncured and cured composite test specimens, using a modified version of ASTM method D792 "Specific Gravity and Density of Plastics by Displacement." The measured volumetric shrinkage ranged from 1.35% to 3.22%.

Shear strength of laboratory-processed composite resins bonded to a silane-coated nickel-chromium-beryllium alloy.

The shear bond strengths of three commercial laboratory curing composite resin veneers bonded to a nickel-chromium-beryllium alloy treated with the Silicoater system were evaluated. Two light-cured resins and one heat- and pressure-cured resin were evaluated. No statistically significant difference in bond strengths among the three resins was found. Microscopic analysis of the fracture surfaces indicated that all failures were complex and cohesive in nature within the resin and composite. On the basis of the shear bond strengths measured, any of the composite resin veneers tested appear to be clinically acceptable.

Shear bond strengths of prosthodontic adhesive systems to a nickel-chromium-beryllium alloy.

Panavia, a composite resin luting agent containing phosphate monomers, bonds chemically to air-abraded base metal alloys and is particularly suited for cementing resin-bonded retainers. Another adhesive methodology (Silicoater system) incorporates a pyrolytically applied silica layer to metal substrates to promote bonding of a resin adhesive. The object of this study was to compare prosthodontic adhesive systems that incorporated the Silicoater system and/or Panavia. The results showed that the surface treatment that provided significantly higher shear bond strengths was the Silicoater system and a layer of unfilled resin. A second test evaluated use of Panavia as a metal opaquing material beneath laboratory light-curing resins. Results showed that Panavia Opaque material was displaced peripherally during placement of overlying laboratory composite resin veneers. This resulted in an uneven intermediate layer of Panavia.

Strength of posterior composite repairs using different composite/bonding agent combinations.

Posterior composites are becoming a viable alternative to amalgam in selected cases. As the use of posterior composites increases, the necessity of repair of fractured, discolored, or worn restorations will increase. A number of studies have demonstrated that clinically acceptable repairs can be obtained for anterior composites. This study examined the bond strength of repairs made to aged posterior composite substrates when different bonding agent/composite pairs were used. Dentin bonding agent/composite pairs gave the highest bond strengths and were greater than the bond strength of resin to etched enamel. An enamel bonding agent/composite repair gave the lowest bond strengths, which were less than resin/etched enamel bond strengths.

Development of a custom-fit mouthstick appliance.

Quadriplegics rely on mouth-controlled devices to perform a variety of tasks and to establish some degree of self-sufficiency. The most functional mouthstick appliances have custom-fitted mouthpieces which are fabricated by dental professionals, and in some cases are cost-prohibitive. An inexpensive lightweight mouthstick which incorporates a new thermoplastic mouthpiece and can be custom-fitted by the user is described.