Irreversible electroporation augments ß-glucan induced trained innate immunity for the treatment of pancreatic ductal adenocarcinoma.

BACKGROUND: Pancreatic cancer (PC) is a challenging diagnosis that is yet to benefit from the advancements in immuno-oncologic treatments. Irreversible electroporation (IRE), a non-thermal method of tumor ablation, is used in treatment of select patients with locally-advanced unresectable PC and has potentiated the effect of certain immunotherapies. Yeast-derived particulate ß-glucan induces trained innate immunity and successfully reduces murine PC tumor burden. This study tests the hypothesis that IRE may augment ß-glucan induced trained immunity in the treatment of PC. METHODS: ß-Glucan-trained pancreatic myeloid cells were evaluated ex vivo for trained responses and antitumor function after exposure to ablated and unablated tumor-conditioned media. ß-Glucan and IRE combination therapy was tested in an orthotopic murine PC model in wild-type and Rag-/- mice. Tumor immune phenotypes were assessed by flow cytometry. Effect of oral ß-glucan in the murine pancreas was evaluated and used in combination with IRE to treat PC. The peripheral blood of patients with PC taking oral ß-glucan after IRE was evaluated by mass cytometry. RESULTS: IRE-ablated tumor cells elicited a potent trained response ex vivo and augmented antitumor functionality. In vivo, ß-glucan in combination with IRE reduced local and distant tumor burden prolonging survival in a murine orthotopic PC model. This combination augmented immune cell infiltration to the PC tumor microenvironment and potentiated the trained response from tumor-infiltrating myeloid cells. The antitumor effect of this dual therapy occurred independent of the adaptive immune response. Further, orally administered ß-glucan was identified as an alternative route to induce trained immunity in the murine pancreas and prolonged PC survival in combination with IRE. ß-Glucan in vitro treatment also induced trained immunity in peripheral blood monocytes obtained from patients with treatment-naïve PC. Finally, orally administered ß-glucan was found to significantly alter the innate cell landscape within the peripheral blood of five patients with stage III locally-advanced PC who had undergone IRE. CONCLUSIONS: These data highlight a relevant and novel application of trained immunity within the setting of surgical ablation that may stand to benefit patients with PC.

Biomechanical Evaluation of a Mandibular Spanning Plate Technique Compared to Standard Plating Techniques to Treat Mandibular Symphyseal Fractures.

Purpose. The purpose of this study is to compare the biomechanical behavior of the spanning reconstruction plate compared to standard plating techniques for mandibular symphyseal fractures. Materials and Methods. Twenty-five human mandible replicas were used. Five unaltered synthetic mandibles were used as controls. Four experimental groups of different reconstruction techniques with five in each group were tested. Each synthetic mandible was subjected to a splaying force applied to the mandibular angle by a mechanical testing unit until the construct failed. Peak load and stiffness were recorded. The peak load and stiffness were analyzed using ANOVA and the Tukey test at a confidence level of 95% (P < 0.05). Results. The two parallel plates' group showed statistically significant lower values for peak load and stiffness compared to all other groups. No statistically significant difference was found for peak load and stiffness between the control (C) group, lag screw (LS) group, and the spanning plate (SP1) group. Conclusions. The spanning reconstruction plate technique for fixation of mandibular symphyseal fractures showed similar mechanical behavior to the lag screw technique when subjected to splaying forces between the mandibular gonial angles and may be considered as an alternative technique when increased reconstructive strength is needed.

Morphometric analysis of the location and activity of cytokines in the tissue implant response.

The objective of this investigation was to evaluate the location and activity of cytokines in the fibrous tissue surrounding tricalcium phosphate (TCP) implants loaded with androgenic hormones. Sixteen animals in four experimental groups (n = 4/group) were implanted with one TCP implant each: Group I (control), Group II (testosterone), Group III (dihydrotestosterone), and Group IV (androstenedione). At 90 days post-implantation, the fibrous tissue surrounding the implants were evaluated following staining with antibodies to IL-1ß, IL-2, IL-6, and TNF?. Data were collected on the presence and distribution of cytokines within the fibrous tissue surrounding all four groups. IL-1ß was primarily found intercellular and associated with fibroblasts and macrophages of Groups I-III. IL-2 was present in the extracellular matrix and was sporadically found on the surface of macrophages in Groups I-III. IL-6 was found primarily concentrated in the fibroblast and collagen rich portions of the fibrous tissue matrix in Groups I-III. TNF-? was present in the extracellular matrix of the fibrous tissue of all four groups and was strongly associated with fibroblast and macrophage rich areas. The results of this study confirm activity of cytokines on target cells and indicate their actions may vary in their effect within the fibrous tissue surrounding TCP implants loaded with androgens.

Human MCS5A1 candidate breast cancer susceptibility gene FBXO10 is induced by cellular stress and correlated with lens epithelium-derived growth factor (LEDGF).

Genetic variation and candidate genes associated with breast cancer susceptibility have been identified. Identifying molecular interactions between associated genetic variation and cellular proteins may help to better understand environmental risk. Human MCS5A1 breast cancer susceptibility associated SNP rs7042509 is located in F-box protein 10 (FBXO10). An orthologous Rattus norvegicus DNA-sequence that contains SNV ss262858675 is located in rat Mcs5a1, which is part of a mammary carcinoma susceptibility locus controlling tumor development in a non-mammary cell-autonomous manner via an immune cell-mediated mechanism. Higher Fbxo10 expression in T cells is associated with Mcs5a increased susceptibility alleles. A common DNA-protein complex bound human and rat sequences containing MCS5A1/Mcs5a1 rs7042509/ss262858675 in electrophoretic mobility shift assays (EMSAs). Lens epithelium-derived growth factor (LEDGF), a stress-response protein, was identified as a candidate to bind both human and rat sequences using DNA-pulldown and mass spectrometry. LEDGF binding was confirmed by LEDGF-antibody EMSA and chromatin immunoprecipitation (ChIP). Ectopic expression of LEDGF/p75 increased luciferase activities of co-transfected reporters containing both human and rat orthologs. Over-expressed LEDGF/p75 increased endogenous FBXO10 mRNA levels in Jurkat cells, a human T-cell line, implying LEDGF may be involved in increasing FBXO10 transcript levels. Oxidative and thermal stress of Jurkat cells increased FBXO10 and LEDGF expression, further supporting a hypothesis that LEDGF binds to a regulatory region of FBXO10 and increases expression during conditions favoring carcinogenesis. We conclude that FBXO10, a candidate breast cancer susceptibility associated gene, is induced by cellular stress and LEDGF may play a role in expression of this gene.

Preparation and characterization of novel elastin-like polypeptide-collagen composites.

Collagen-based biomaterials suffer from poor mechanical properties and rapid degradation. Elastin-like polypeptides (ELPs) possess good biocompatibility and have unique solution properties that allow them to coacervate above a critical temperature. The objective of this research was to prepare a series of freeze dried ELP-collagen composite scaffolds as a proof of concept. Combination of ELP and collagen has the potential to produce composite structures with varying strengths. Four different composite structures were prepared by varying the ratio of ELP to collagen. Increased ELP content in the scaffolds appears to have reduced the residual water content based on Fourier transformed infrared spectroscopy and differential scanning calorimetry. Scanning electron microscopy images of ELP-collagen composites showed a three-dimensional, open porous structure with the formation of characteristic aggregates of ELP. The mechanical testing experiments showed that the elastic modulus, tensile strength, and toughness of ELP-collagen scaffolds were significantly greater than neat collagen scaffolds. The improved mechanical properties were attributed to a homogeneous network structure with additional reinforcement coming from the ELP aggregates. Our study confirms that ELP-collagen composites with superior physical and mechanical properties compared to collagen scaffolds can be produced. Further optimization of design parameters will allow producing ELP-collagen composites for specific biomedical applications.

Rat Mcs1b is concordant to the genome-wide association-identified breast cancer risk locus at human 5q11.2 and MIER3 is a candidate cancer susceptibility gene.

Low-penetrance alleles associated with breast cancer risk have been identified in population-based studies. Most risk loci contain either no or multiple potential candidate genes. Rat mammary carcinoma susceptibility 1b (Mcs1b) is a quantitative trait locus on RN02 that confers decreased susceptibility when Copenhagen (COP)-resistant alleles are introgressed into a Wistar Furth (WF)-susceptible genome. Five WF.COP congenic lines containing COP RN02 segments were compared. One line developed an average of 3.4 ± 2.0 and 5.5 ± 3.6 mammary carcinomas per rat ± SD when females were Mcs1b-resistant homozygous and Mcs1b heterozygous, respectively. These phenotypes were significantly different from susceptible genotype littermates (7.8 ± 3.1 mean mammary carcinomas per rat ± SD, P = 0.0001 and P = 0.0413, respectively). All other congenic lines tested were susceptible. Thus, Mcs1b was narrowed to 1.8 Mb of RN02 between genetic markers ENSRNOSNP2740854 and g2UL2-27. Mammary gland-graft carcinoma susceptibility assays were used to determine that donor (P = 0.0019), but not recipient Mcs1b genotype (P = 0.9381), was associated with ectopic mammary carcinoma outcome. Rat Mcs1b contains sequence orthologous to human 5q11.2, a breast cancer susceptibility locus identified in multiple genome-wide association studies. Human/rat MAP3K1/Map3k1 and mesoderm induction early response (MIER; MIER3)/MIER3 are within these orthologous segments. We identified MIER3 as a candidate Mcs1b gene based on 4.5-fold higher mammary gland levels of MIER3 transcripts in susceptible compared with Mcs1b-resistant females. These data suggest that the human 5q11.2 breast cancer risk allele marked by rs889312 is mammary gland autonomous, and MIER3 is a candidate breast cancer susceptibility gene.

Histopathological and biomechanical parameters of repaired rat achilles tendons treated with and without mannose-6-phosphate.

Flexor tendon repairs are plagued by the formation of peripheral adhesions that limit motion. No current adjunct therapy is available to prevent this complication. Mannose-6-phosphate (M6P) is a natural sugar that has been shown to interact with the M6P/IGF-II receptor on fibroblasts. It is hypothesized that the addition of M6P to healing tendons would downregulate the production of unorganized scar collagen, allowing the tenocytes to guide tendon repair. Thirty-two (32) Sprague-Dawley rats underwent right Achilles tendon transection and suture repair. M6P was directly applied to the tendons of half of the rats prior to skin closure. Half of the animals in each treatment group were sacrificed after two weeks of healing, and the rest after four weeks. There were no post-operative complications (rupture, seroma, hematoma, infection). Histopathologic analysis was performed with H&E and elastin stains. Biomechanical analysis was performed to determine stress, strain, and elastic modulus. M6P was found to increase elastin production, decrease callus cross-sectional area, increase strain, and increase peak stress at failure. These changes were most evident at the two-week time point. The findings from this study support the continued investigation of M6P as an adjunct therapy to flexor tendon repair.

Neovascularization is influenced by androgenic hormones in the tissue implant response.

The objective of this investigation was to demonstrate the effect of androgens on the neovascularization of the fibrous tissue surrounding tricalcium phosphate (TCP) implants. Sixteen animals in four experimental groups (n = 4/group) were implanted with one TCP implant each. Group I animals were implanted with the sham TCP ceramic (Control). Group II animals received a testosterone-loaded ceramic. Group III animals were implanted with a dihydrotestosterone containing bioceramic. Group IV animals received the androstenedione filled bioceramic. At 90 days post-implantation, the fibrous tissue surrounding the implants were evaluated microscopically following staining with routine hematoxylin and eosin (H&E), Masson’s trichrome, and Papanicolaou stains. Using Image Pro (Media Cybernetics, Silver Spring, MD) digital analysis software, data were collected to compare the hormonal effects on the number (per high power field) and size of blood vessels (micrometers, µm) within the fibrous tissue surrounding all four groups. The presence of androgens greatly affected the angiogenic response within the fibrous tissue. All three hormones exhibited less neovascularization compared to the control. Though not as dramatic as androstenedione (3±0), both testosterone (12±1) and dihydrotestosterone (10±1) suppressed the number of blood vessels present in the fibrous tissue capsule compared to control (13±1). However, the circumference of the vessels was much larger for the testosterone (236µm ±8µm) and dihydrotestosterone (256µm±4µm) treated groups compared to the androstenedione (146µm ±7µm) or control (163µm±3µm) groups. The results of this study demonstrate androgens strongly vary in their effect on neovascularization by limiting the number of new vessels developed while contributing to the presence of larger vessels within the fibrous tissue surrounding TCP implants loaded with testosterone and dihydrotestosterone.

Effect of thermocycling on the flexural and impact strength of urethane-based and high-impact denture base resins.

OBJECTIVE: Mechanical properties of the acrylic resins used for denture fabrication may be influenced by water and temperature. Thus, the aim of this study was to evaluate the effect of thermocycling on the flexural and impact strength of a high-impact (Lucitone 199) and a urethane-based denture material (Eclipse). MATERIALS AND METHODS: Flexural strength (64 × 10 × 3.3 mm) and impact strength (60 × 6 × 4 mm) specimens were made following the manufacturers' instructions and assigned to two groups (n = 10): control (C) - not thermocycled - and T - thermocycled (5000 cycles between 5 and 55°C). Specimens were submitted to three-point bending and Charpy impact tests. RESULTS: Flexural strength (MPa) and impact strength (kJ/m(2)) data were analysed with two-way anova (p = 0.05). The flexural strength of material Eclipse (C, 136.5; T, 130.7) was significantly higher than that of resin Lucitone 550 (C, 99.4; T, 90.1). Material Eclipse exhibited significantly higher impact strength (C, 6.9; T, 5.3) than the resin Lucitone 550 (C, 3.5; T, 3.0). For both materials, a significant decrease in flexural and impact strengths was observed when the specimens were thermocycled. CONCLUSION: Flexural and impact strengths were higher for Eclipse than for Lucitone 550, in both groups. Thermocycling decreased the flexural and impact strengths of Eclipse and Lucitone 550.

Strength of a new method of achilles tendon repair in the rat - biomed 2011.

The rat Achilles tendon is frequently used as the model for tendon healing research. Several methods commonly employed in these studies may confound results. The Kessler method of suture repair requires immobilization of the operative extremity, which can be detrimental to healing. Determination of cross-sectional area of tendons by caliper measurement may lead to significant errors in normalization of biomechanical data for stress and elastic modulus. New methods of suture repair of rat Achilles tendons and micro-CT scanning of tendons are presented as preferable techniques for tendon healing studies in rats. Operations involved transection of the right Achilles tendon at the mid-portion and suture repair using a 4-strand, looped locking technique. Groups were: positive control (no injury or treatment); negative control (injury, suture repair, no healing); 2 week repair; and 4 week repair. The cross-sectional area of the tendons was significantly higher (p<0.05) in the repair groups compared to controls. Peak stress and elastic modulus of repair groups were significantly lower than positive control. Strain of repair groups was not significantly different from control. Four weeks after repair, tendons bore significantly higher peak loads than positive control tendons. Based on these results, further studies of adjunct therapy for tendon healing may be placed in the context of normal (repair groups), ideal (positive control), and worst case (negative control) healing. The methods presented for new a new surgical technique and cross-sectional area calculation are reliable for animal studies and increase the validity and applicability of biomechanical results.

Androgen administration and macrophage behavior in the tissue-implant response - biomed 2011.

Macrophages are a critical component in the biocompatibility and function of implantable ceramic materials used in drug delivery applications. As part of the chronic inflammatory response, these cells surround the implant, establishing the tissue-implant interface and produce cytokines critical for recruitment of other complementary cells involved in the response. The purpose of this study was to evaluate the effect of androgens on behavior of the macrophage by further quantifying their presence in the fibrous tissue capsule of calcium phosphate (TCP) ceramic drug delivery systems with respect to their cytokine activity and release profile of the implant. Sixteen animals in four experimental groups were implanted with one TCP bioceramic each. Group I animals were implanted with a sham TCP ceramic not containing a steroid hormone (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. The implants and fibrous tissue capsules were then extracted. Determination of macrophage populations and their behavior was conducted microscopically following H&E and IHC staining of antibodies to IL-1, IL-2, IL-6, and TNF- positive cells. All three of the hormones administered in this study, particularly androstenedione, significantly affect macrophage migration to the implant interface and surrounding fibrous tissue capsule when compared to the control group. In addition, these hormones limit the expression of cytokines severely limiting recruitment of other cells involved in the tissue-implant response.

Amino Acid coated uhmw-pe implants modify macrophage migration in the tissue-implant response - biomed 2011.

Polyethylene materials used in orthopedic applications are biocompatible and non-immunogenic with host tissues. Recent studies in our laboratory have demonstrated the need for further study of these devices in vivo to further elucidate methods to modulate the tissue-implant response. The purpose of this investigation was to determine macrophage behavior after implantation of ultra high molecular weight polyethylene (UHMW-PE) rinsed with saline (control) and coated with poly-L-lysine (PLL), arginine-glycine-aspartic acid (RGD), and arginine-glycine-glutamic acid (RGE) into 16 adult male rats intraperitoneally (I/P). Implants and surrounding tissue were harvested at 90 days post-implantation. The animals were euthanized; and the UHMW-PE implants and the fibrous tissue capsules surrounding them were harvested. Microscopic examination of routinely stained sections (5 microns, Hematoxylin & Eosin) of the fibrous tissue capsules revealed macrophage counts were highest in the saline coated group (9.75±0.86 cells/high power field). Amino acid coated implants resulted in decreased mean macrophage counts per high power field for RGD (3.51±0.45), RGE (2.86±0.06), and PLL (4.2±0.55) compared to saline and the differences were statistically significant (ANOVA, p < 0.05). These findings indicate macrophage behavior at the tissue-implant interface and in surrounding fibrous tissue can be reduced using various amino acid combination coatings. In addition, these results provide evidence that the intensity of the chronic inflammatory reaction to UHMW-PE can be reduced and controlled to some extent.

Microleakage evaluation of four self-etching adhesive systems.

This study sought to compare and rank the in vitro microleakage behavior of four self-etching adhesive systems to determine any differences in their marginal sealing ability. Using a coarse rounded diamond wheel, Class V cavities were prepared at the facial or lingual cementoenamel junction (CEJ) of 40 recently extracted human third molars. All preparations had incisal margins in enamel and gingival margins in dentin. Ten randomly selected teeth were restored with one of four different adhesive systems; all teeth received the same composite material. The teeth were stored in distilled water (37 degrees C) for four weeks, thermocycled between 4 degrees C and 58 degrees C for 100 cycles, treated with 45Ca radioisotope, sectioned, and placed on radiographic film to produce autoradiographs. The degree of microleakage was scored separately at the enamel (incisal) and dentin (gingival) margins, and the results were compared using nonparametric statistical methods. The analysis found statistically significant differences in the degree of microleakage between the materials used at both the dentin and enamel margins.

Loss and spontaneous recovery of forelimb evoked potentials in both the adult rat cuneate nucleus and somatosensory cortex following contusive cervical spinal cord injury.

Varying degrees of neurologic function spontaneously recovers in humans and animals during the days and months after spinal cord injury (SCI). For example, abolished upper limb somatosensory potentials (SSEPs) and cutaneous sensations can recover in persons post-contusive cervical SCI. To maximize recovery and the development/evaluation of repair strategies, a better understanding of the anatomical locations and physiological processes underlying spontaneous recovery after SCI is needed. As an initial step, the present study examined whether recovery of upper limb SSEPs after contusive cervical SCI was due to the integrity of some spared dorsal column primary afferents that terminate within the cuneate nucleus and not one of several alternate routes. C5-6 contusions were performed on male adult rats. Electrophysiological techniques were used in the same rat to determine forelimb evoked neuronal responses in both cortex (SSEPs) and the cuneate nucleus (terminal extracellular recordings). SSEPs were not evoked 2 days post-SCI but were found at 7 days and beyond, with an observed change in latencies between 7 and 14 days (suggestive of spared axon remyelination). Forelimb evoked activity in the cuneate nucleus at 15 but not 3 days post-injury occurred despite dorsal column damage throughout the cervical injury (as seen histologically). Neuroanatomical tracing (using 1% unconjugated cholera toxin B subunit) confirmed that upper limb primary afferent terminals remained within the cuneate nuclei. Taken together, these results indicate that neural transmission between dorsal column primary afferents and cuneate nuclei neurons is likely involved in the recovery of upper limb SSEPs after contusive cervical SCI.

Direct composite restorative materials.

Composite dental restorative materials have advanced considerably over the past 10 years. Although composites have not totally replaced amalgam, they have become a viable substitute in many situations. Problems still exist with polymerization contraction stress, large differences in the coefficient of thermal expansion (CTE) of composites compared with tooth structure, and with some technique sensitivity; however, new expanding resins, nanofiller technology, and improved bonding systems have the potential to reduce these problems. With increased patient demands for esthetic restorations, the use of direct filling composite materials will continue to grow. The one major caveat to this prediction is that clinicians must continue to use sound judgment on when, where, and how to use composite restoratives in their practices.

Microleakage of three conventional glass ionomers using 45Ca and methylene blue.

This study sought to compare the sealing ability of two conventional ionomers and a new intermediate/provisional ionomer formulation using sequential applications of two different tracer methodologies. Thirty freshly extracted (< 6 months) human third molars, stored in 0.1% sodium azide solution, were divided randomly into three experimental groups for preparation of simulated Class V caries at the cementoenamel junction of the facial surfaces. Three materials were used to restore the cavity preparations. After restoration, the teeth were thermocycled for 100 cycles (between 4.0 degrees C and 58 degrees C). To evaluate the microleakage of the materials and compare the tracer's ability to measure microleakage, the teeth were subjected to 45Ca and methylene blue. Treated teeth were bisected longitudinally through the restoration, then each sectioned tooth half was scored by three independent evaluators using a 0 to 4 scale, depending on the tracer penetration. The results showed that all of the materials investigated performed well and no statistical differences were found among the materials, the tracer used, or the margin evaluated.

Effect of microwave disinfection procedures on torsional bond strengths of two hard chairside denture reline materials.

PURPOSE: This study evaluated the potential effects of denture base resin water storage time and an effective denture disinfection method (microwave irradiation at 650 W for 6 minutes) on the torsional bond strength between two hard chairside reline resins (GC Reline and New Truliner) and one heat-polymerizing denture base acrylic resin (Lucitone 199). MATERIALS AND METHODS: Cylindrical (30 x 3.9 mm) denture base specimens (n= 160) were stored in water at 37 degrees C (2 or 30 days) before bonding. A section (3.0 mm) was removed from the center of the specimens, surfaces prepared, and the reline materials packed into the space. After polymerization, specimens were divided into four groups (n= 10): Group 1 (G1)--tests performed after bonding; Group 2 (G2)--specimens immersed in water (200 ml) and irradiated twice (650 W for 6 minutes); Group 3 (G3)--specimens irradiated daily until seven cycles of disinfection; Group 4 (G4)-specimens immersed in water (37 degrees C) for 7 days. Specimens were submitted to a torsional test (0.1 Nm/min), and the torsional strengths (MPa) and the mode of failure were recorded. Data from each reline material were analyzed by a two-way analysis of variance, followed by Neuman-Keuls test (p= 0.05). RESULTS: For both Lucitone 199 water storage periods, before bonding to GC Reline resin, the mean torsional strengths of G2 (2 days--138 MPa; 30 days--132 MPa), G3 (2 days--126 MPa; 30 days--130 MPa), and G4 (2 days--130 MPa; 30 days--137 MPa) were significantly higher (p < 0.05) than G1 (2 days--108 MPa; 30 days--115 MPa). Similar results were found for Lucitone 199 specimens bonded to New Truliner resin, with G1 specimens (2 days-73 MPa; 30 days--71 MPa) exhibiting significantly lower mean torsional bond strength (p < 0.05) than G2 (2 day--86 MPa; 30 days--90 MPa), G3 (2 days--82 MPa; 30 days--82 MPa), and G4 specimens (2 days--78 MPa; 30 days--79 MPa). The adhesion of both materials was not affected by water storage time of Lucitone 199 (p > 0.05). GC reline showed a mixed mode of failure (adhesive/cohesive) and New Truliner failed adhesively. CONCLUSIONS: Up to seven microwave disinfection cycles did not decrease the torsional bond strengths between the hard reline resins, GC Reline and New Truliner to the denture base resin Lucitone 199. The effect of additional disinfection cycles on reline material may be clinically significant and requires further study.

Mechanical strength repercussions of various fixative storage methods on bone.

This study compensates for the lack of literature on the actual effects that various fixative storage methods have on the mechanical strength characteristics of bone and attempts to identify the ideal fixative method for preservation of all tissues while maintaining in vivo bone strength. Researchers currently use a wide variety of storage methods that lessen the mechanical strength to varying degrees. Differences could introduce error into a great number of bone fracture studies if an inexact discrepancy in the mechanical properties of fixed bone does actually exist. Furthermore, such disparities could go on to pose clinical risks for patients. This study focuses on the mechanical strength testing of four different groups of rat femora that were retrieved at various times and subjected to differing storage procedures. The first, Group N, were fresh, new femora retrieved just days before testing. The second, Group F, were femora that have been fixed in a 10% formalin bath for just over a year prior to testing. The third, Group W, are femora that have also been fixed in 10% formalin for just over a year but were washed out just prior to testing. The fourth, Group P, were femora that were retrieved from rats that were perfused with formalin immediately following euthanasia. Mechanical strength tests on the four groups revealed that fixing bone in a 10% formalin bath significantly reduces the mechanical fracture strength properties of the bone regardless of whether the formalin is washed out prior to testing. Testing also revealed that bone from perfused animals behaves more similarly to fresh bones from non-perfused animals suggesting that the formalin did not entirely infiltrate the bone and permanently fix the material. These results could have profound implications on how studies equate the behavior of in vitro bone to in vivo bone which could manifest as clinical complications for patients.

Effect of microwave disinfection on the hardness and adhesion of two resilient liners.

STATEMENT OF PROBLEM: Microwave irradiation has been suggested for denture disinfection. However, the effect of this procedure on the hardness and bond strength between resilient liners and denture base acrylic resin is not known. PURPOSE: This study evaluated the effect of water storage time and microwave disinfection on the hardness and peel bond strength of 2 silicone resilient lining materials to a heat-polymerized acrylic resin. MATERIAL AND METHODS: Acrylic resin (Lucitone 199) specimens (75 x 10 x 3 mm) were stored in water at 37 degrees C (2 or 30 days) before bonding (n = 160). The resilient lining materials (GC Reline Extra Soft and Dentusil) were bonded to the denture base and divided into the following 4 groups (n = 10): Tests performed immediately after bonding (control); specimens immersed in water (200 mL) and irradiated twice, with 650 W for 6 minutes; specimens irradiated daily for 7 total cycles of disinfection; specimens immersed in water (37 degrees C) for 7 days. Specimens were submitted to a 180-degree peel test (at a crosshead speed of 10 mm/min) and the failure values (MPa) and mode of failure were recorded. Pretreatment and posttreatment hardness measurements (Shore A) of the resilient materials were also performed. Three-way analysis of variance, followed by the Tukey HSD test, was performed (alpha = .05). RESULTS: The analysis revealed that, for all conditions, the mean failure strengths of GC Reline Extra Soft (0.95-1.19 MPa) were significantly higher ( P < .001) than those of Dentusil (0.45-0.50 MPa). The adhesion of the liners was not adversely affected by water storage time of Lucitone 199 or microwave disinfection. All peel test failures were cohesive. There was a small but significant difference ( P < .001) between the pretreatment (34.33 Shore A) and posttreatment (38.69 Shore A) hardness measurements. CONCLUSION: Microwave disinfection did not compromise the hardness of either resilient liners or their adhesion to the denture base resin Lucitone 199.

An amino acid-modified and non-HEMA containing glass-ionomer cement.

It is known that unreacted 2-hydroxyethyl methacrylate (HEMA) in current resin modified glass ionomer cements (RMGICs) shows potential cytotoxicity to pulp and surrounding tissues. Elimination of HEMA could make RMGICs more attractive for dental applications. In this research, novel six acrylate and methacrylate derivatives of amino acids were synthesized, characterized and used for replace HEMA in RMGICs. The experimental RMGICs were formulated with vinyl-containing polymer, amino acid derivative, water, and commercial Fuji II LC glass. Among all the derivatives, methacryloyl beta-alanine (MBA) was selected for further formulations due to its relatively low solution viscosity and high CS. Effects of polymer content and powder/liquid, P/L, ratio were significant. The formulation with liquid composition of 50/25/25 (polymer/MBA/water) and P/L ratio of 2.7/1 was found the optimal. It appears that this novel non-HEMA-containing RMGIC system based on amino acid derivatives will be a better dental restorative because it demonstrated improved mechanical strengths and may eliminate potential cytotoxicity in current RMGICs caused by leached HEMA. The optimal MBA-modified GIC were 20% higher in CS, 70% higher in DTS and 93% higher in FS, compared to Fuji II LC.