Crestal module design optimization of dental implants: finite element analysis and in vivo studies

The aim of this study was to evaluate the biomechanical behavior of Bone Level dental implants with four different neck designs in contact with cortical bone. Numerical simulations were performed using a Finite Element Method (FEM) based-model. In order to verify the FEM model, the in silico results were compared with the results obtained from histological analysis performed in an in vivo study with New Zealand rabbits. FEM was performed using a computerized 3D model of Bone Level dental implants inserted in the lower jaw bone with an applied axial load of 100 N. The analysis was performed using four different implant neck designs: even surfaced, screwed, three-ring design and four-ring design. Interface are of bone growth was evaluated by analyzing the Bone-Implant-Contact (BIC) parameter obtained from in vivo histological process and analyzed by Scanning Electron Microscopy (SEM). Bone Level implants were inserted in the rabbit tibia, placing two implants per tibia. The BIC was evaluated after three and six weeks of implantation. FEM studies showed that the three-ring design presented lower values of stress distribution compared to the other studied designs. The lower levels of mechanical stress were then correlated with the in vivo studies, showing that the three-ring design presented the highest BIC value after 3 and 6 weeks of implantation. In silico and in vivo results both concluded that the implants with three-ring neck design presented the best biomechanical and histological behavior in terms of new bone formation, enhanced mechanical stability and optimum osseointegration.

Control of stem cell response and bone growth on biomaterials by fully non-peptidic integrin selective ligands

Integrin selective peptidomimetics tune stem cell behavior in vitro and improve bone formation in rat calvarial defects.

Unravelling the effect of macro and microscopic design of dental implants on osseointegration: a randomised clinical study in minipigs

Several dental implants are commercially available and new prototype design are constantly being fabricated. Nevertheless, it is still unclear what parameters of the design affect most the osseointegration of dental implants. The purpose of this study is to assess the effects of the microscopic and macroscopic design of dental implants in the osseointegration by comparing three macroscopic designs (Straumann tissue level (STD), essential cone (ECD) and prototype design (PD)) and six surface treatments. A total of 96 implants were placed in 12 minipigs. The implant stability quotient (ISQ), was assessed at the time of implantation, as well as at 2, 4 and 8 weeks. Histomorphometric and statistical analyses were conducted at the different sacrifice times, being 2, 4 and 8 weeks, to analyse the bone to implant contact (BIC), the bone area density (BAT) and the density of bone outside the thread region (ROI). The macroscopic design results showed higher ISQ values for the ECD, whereas the histomorphometric analysis showed higher ossoeintegration values for the STD. Regarding the microscopic design, both Sandblasted plus acid etching (hydrochloric/sulphuric acid) in a nitrogen atmosphere (SLActive) and Shot-blasted or bombarded with alumina particles and posterior alkaline immersion and thermal treatment (ContacTi) showed superior results in terms of osseointegration and reduced the osseointegration times from 8 weeks to 4 weeks compared to the other analysed surfaces. In conclusion, each of the macroscopic and microscopic designs need to be taken into account when designing novel dental implants to enhance the osseointegration process.

Advanced biomatrix designs for regenerative therapy of periodontal tissues

Periodontitis is an inflammatory disease that causes loss of the tooth-supporting apparatus, including periodontal ligament, cementum, and alveolar bone. A broad range of treatment options is currently available to restore the structure and function of the periodontal tissues. A regenerative approach, among others, is now considered the most promising paradigm for this purpose, harnessing the unique properties of stem cells. How to make full use of the body's innate regenerative capacity is thus a key issue. While stem cells and bioactive factors are essential components in the regenerative processes, matrices play pivotal roles in recapitulating stem cell functions and potentiating therapeutic actions of bioactive molecules. Moreover, the positions of appropriate bioactive matrices relative to the injury site may stimulate the innate regenerative stem cell populations, removing the need to deliver cells that have been manipulated outside of the body. In this topical review, we update views on advanced designs of biomatrices-including mimicking of the native extracellular matrix, providing mechanical stimulation, activating cell-driven matrices, and delivering bioactive factors in a controllable manner-which are ultimately useful for the regenerative therapy of periodontal tissues.

Therapeutic bioactive microcarriers: co-delivery of growth factors and stem cells for bone tissue engineering

Novel microcarriers made of sol-gel-derived bioactive glasses were developed for delivering therapeutic molecules effectively while cultivating stem cells for bone tissue engineering. Silica sols with varying concentration of Ca (0-30 mol.%) were formulated into microspheres ranging from 200 to 300 μm under optimized conditions. A highly mesoporous structure was created, with mesopore sizes of 2.5-6.3 nm and specific surface areas of 420-710 m(2)g(-1), which was highly dependent on the Ca concentration. Therapeutic molecules could be effectively loaded within the mesoporous microcarriers during microsphere formulation. Cytochrome C (cyt C), used as a model protein for the release study, was released in a highly sustainable manner, with an almost zero-order kinetics over a period of months; the amount released was ~2% at 9 days, and 15% at 40 days. A slight increase in the release rate was observed in the microcarrier containing Ca, which was related to the dissolution rate and pore size. The presence of Ca accelerated the formation of hydroxyapatite on the surface of the microcarriers. Cells cultured on the bioactive microcarriers were well adhered and distributed, and proliferated actively, confirming the three-dimensional substrate role of the microcarriers. An in vivo study performed in a rat subcutaneous model demonstrated the satisfactory biocompatibility of the prepared microspheres. As a therapeutic target molecule, basic fibroblast growth factor (bFGF) was incorporated into the microcarriers. A slow release pattern similar to that of cyt C was observed for bFGF. Cells adhered and proliferated to significantly higher levels on the bFGF-loaded microcarriers, demonstrating the effective role of bFGF in cell proliferative potential. It is believed that the developed mesoporous bioactive glass microspheres represent a new class of therapeutic cell delivery carrier, potentially useful in the sustainable delivery of therapeutic molecules such as growth factors, as well as in the support of stem cell proliferation and osteogenesis for bone tissue engineering.

Micro- and nanostructured hydroxyapatite-collagen microcarriers for bone tissue-engineering applications

Novel hydroxyapatite (HA)-collagen microcarriers (MCs) with different micro/nanostructures were developed for bone tissue-engineering applications. The MCs were fabricated via calcium phosphate cement (CPC) emulsion in oil. Collagen incorporation in the liquid phase of the CPC resulted in higher MC sphericity. The MCs consisted of a porous network of entangled hydroxyapatite crystals, formed as a result of the CPC setting reaction. The addition of collagen to the MCs, even in an amount as small as 0.8 wt%, resulted in an improved interaction with osteoblast-like Saos-2 cells. The micro/nanostructure and the surface texture of the MCs were further tailored by modifying the initial particle size of the CPC. A synergistic effect between the presence of collagen and the nanosized HA crystals was found, resulting in significantly enhanced alkaline phosphatase activity on the collagen-containing nanosized HA MCs.

Cell response to collagen-calcium phosphate cement scaffolds investigated for nonviral gene delivery

Collagen-hydroxyapatite (HA) scaffolds for the non-viral delivery of a plasmid encoding the osteoinductive protein bone morphogenetic protein (BMP)-7 were developed. The collagen-HA was obtained by the combination of calcium phosphate cement in a collagen template. The effect on cell behavior of increasing amounts of HA in the scaffolds was evaluated. Collagen-HA scaffolds containing 13, 23 or 83 wt% HA were prepared. Cell proliferation was reduced in the 83% HA scaffold after 1 day compared to 13 and 23% HA, but by 14 days the number of cells in 83% HA considerably increased. Alkaline phosphatase (ALP) activity was 8 times higher for the 83% HA scaffolds. BMP-7 plasmid was incorporated into the 83% HA scaffold. The transfection was low, although significant levels of BMP7 were expressed, associated with an increase in cell proliferation.

Intrinsic porosity of calcium phosphate cements and its significance for drug delivery and tissue engineering applications

One key point in the field of tissue engineering and drug delivery is to provide materials with an adequate porosity. Many events, including nutrient and waste exchange in scaffolds for tissue engineering, as well as the drug-loading capacity and control of the release rate in drug delivery systems, are controlled by the size, shape and distribution of the pores in the material. Calcium phosphate cements (CPCs) possess an intrinsic porosity that is highly suited for these applications, and this porosity can be controlled by modifying some processing parameters. The objective of this work was to characterize and control the intrinsic porosity of alpha-tricalcium phosphate (alpha-TCP) cements, and to investigate its role against adsorption of bovine serum albumin (BSA). Cements with different percentages of open porosity (35-55%) were prepared by modifying the liquid-to-powder ratio. In addition, two different TCP particles were used to yield cements with specific surface areas of approximately 20 and approximately 37m(2)g(-1). Mercury porosimetry analysis on the set cements showed in most cases a bimodal pore size distribution which varied with the processing parameters and affected differently the adsorption and penetration of BSA. The peak occurring at larger pore dimensions controlled the penetration of BSA and was ascribed to the voids generated in between crystal aggregates, while the peak appearing at lower pore sizes was believed to be due to the intercrystallite voids within aggregates. It was found that, at the concentrations studied, the high intrinsic porosity in CPC does not ensure protein penetration unless there is an adequate pore size distribution.

Liposuction and diabetes type 2 development risk reduction in the obese patient

Obesity is a disabling disease which has gained greater attention worldwide and particularly in the United States. It significantly increases the risk for other diseases such as insulin independent diabetes mellitus also known as diabetes type 2. The most common surgical procedure for obesity is liposuction. It is traditionally performed either as small-volume liposuction or large-volume liposuction, the majority being small-volume liposuction procedures. Large-volume and small-volume liposuction have been clinically shown to improve insulin sensitivity in obese patients thus reducing their risk of developing type 2 diabetes. In this paper, evidence is presented to support the hypothesis that liposuction disrupts the pathway that brings about insulin insensitivity in the obese patient. It is proposed that using liposuction in the overall treatment of obesity could lead to an improvement in insulin sensitivity and thus greatly improve the quality of life of the obese patient.

Health and welfare benefit litigation under ERISA

Denial of health benefits may result in devastating financial problems for the consumer. Given the complexities of the system, more and more employees turn to attorneys for help. Litigation and the resultant costs, in turn, further exacerbate the cost of providing benefits to employees and the burden to the employer. The law governing employer-paid health care and benefit plans is a blend of third party beneficiary contract law, trust law and administrative law. This article provides an overview of the federal litigation resulting from a third party payer's denial of coverage.

What is the optimal frequency of cycling in automated peritoneal dialysis?

OBJECTIVE

The recent increase in the use of automated peritoneal dialysis (APD) has led to concerns about the adequacy of clearances delivered by this modality. Few clinical studies looking at the effects of varying the individual components of the APD prescription on delivered clearance have been done, and most published data are derived from computer modeling. Most controversial is the optimal frequency of exchanges per APD session. Many centers prescribe 4 to 6 cycles per night but it is unclear if this is optimal. The purpose of this study was to address at what point the beneficial effect of more frequent cycles is outweighed by the concomitant increase in the proportion of the total cycling time spent draining and filling.

METHODS

A comparison was made between the urea and creatinine clearances (CCrs) achieved by 4 different APD prescriptions, used for 7 days each, in 18 patients. The prescriptions were for 9 hours each and were all based on 2-L dwell volumes, but differed in the frequency of exchanges. They were 5 x 2 L, 7 x 2 L, and 9 x 2 L, as well as a 50% tidal peritoneal dialysis (TPD) prescription using 14 L. Ultrafiltration, dwell time, glucose absorption, sodium and potassium removal, protein excretion, and relative cost were also compared. Clearances due to day dwells and residual renal function were not included in the calculation.

RESULTS

Mean urea clearances were 7.5, 8.6, 9.1, and 8.3 L/night for the four prescriptions respectively. Urea clearance with 9 x 2 L was significantly greater than with the other three prescriptions (p < 0 0.05). Urea clearance with 7 x 2 L and TPD were superior to 5 x 2 L (p < 0.05). Mean CCr was 5.1, 6.1, 6.4, and 5.6 L/night, respectively. Compared to 5 x 2-L, the 7 x 2-L, 9 x 2-L, and TPD prescriptions achieved greater CCr (p < 0.05). Taking both urea and CCr into account, 9 x 2 L was the optimal prescription in 12 of the 18 patients. Ultrafiltration and sodium and potassium removals were all significantly greater with the higher frequency prescriptions.

CONCLUSION

The 5 x 2-L prescription significantly underutilizes the potential of APD to deliver high clearances, and 7 x 2 L is a consistently superior prescription if 2-L dwells are being used. Although more costly, 9 x 2 L should be considered if higher clearances are required.

High creatinine excretion ratio predicts a good outcome in peritoneal dialysis patients

The creatinine excretion (CrEx) ratio was first described as a method for detecting noncompliance in peritoneal dialysis (PD) patients. However, a high CrEx ratio is not specific for noncompliance and may also be found in compliant patients with a relatively greater lean body mass (LBM). A cohort of 44 PD patients was followed up for a mean of 13 +/- 8 months after measurement of baseline CrEx ratio to investigate whether greater values were predictive of good or poor clinical outcomes. During this follow-up, 11 patients died, 12 patients transferred to hemodialysis, 4 patients underwent transplantation, 1 patient recovered renal function, and 16 patients continued on PD. The mean CrEx ratio in all patients was 1.14 +/- 0.32. It did not differ between men and women (1.15 versus 1.13, respectively; P = 0.76) but showed a trend toward being less in patients with diabetes (1.03 versus 1.19; P = 0. 19). The mean weekly Kt/V, weekly creatinine clearance, normalized protein equivalent of nitrogen appearance, and serum albumin values were 2.18 +/- 0.57, 73.57 +/- 33.75 L/1.73 m(2), 0.80 +/- 0.22 g/kg/d, and 3.22 +/- 0.59 g/dL, respectively. Technique failure (P < 0.001) and death (P < 0.05) were significantly more common in patients with a CrEx ratio less than 1 compared with those with a CrEx ratio greater than 1. On Cox regression analysis, the CrEx ratio was the only significant predictor of technique failure and was also an independent predictor of death. High CrEx ratio is a predictor of good, rather than poor, outcome in PD patients, perhaps because it is primarily an index of nutrition. This further weakens the argument that it is a reliable or useful marker of noncompliance.

High creatinine excretion ratio predicts a good outcome in peritoneal dialysis patients

The creatinine excretion (CrEx) ratio was first described as a method for detecting noncompliance in peritoneal dialysis (PD) patients. However, a high CrEx ratio is not specific for noncompliance and may also be found in compliant patients with a relatively greater lean body mass (LBM). A cohort of 44 PD patients was followed up for a mean of 13 +/- 8 months after measurement of baseline CrEx ratio to investigate whether greater values were predictive of good or poor clinical outcomes. During this follow-up, 11 patients died, 12 patients transferred to hemodialysis, 4 patients underwent transplantation, 1 patient recovered renal function, and 16 patients continued on PD. The mean CrEx ratio in all patients was 1.14 +/- 0.32. It did not differ between men and women (1.15 versus 1.13, respectively; P = 0.76) but showed a trend toward being less in patients with diabetes (1.03 versus 1.19; P = 0. 19). The mean weekly Kt/V, weekly creatinine clearance, normalized protein equivalent of nitrogen appearance, and serum albumin values were 2.18 +/- 0.57, 73.57 +/- 33.75 L/1.73 m(2), 0.80 +/- 0.22 g/kg/d, and 3.22 +/- 0.59 g/dL, respectively. Technique failure (P < 0.001) and death (P < 0.05) were significantly more common in patients with a CrEx ratio less than 1 compared with those with a CrEx ratio greater than 1. On Cox regression analysis, the CrEx ratio was the only significant predictor of technique failure and was also an independent predictor of death. High CrEx ratio is a predictor of good, rather than poor, outcome in PD patients, perhaps because it is primarily an index of nutrition. This further weakens the argument that it is a reliable or useful marker of noncompliance.

Polyarteritis nodosa presenting as massive upper gastrointestinal hemorrhage

We report the first case of massive upper gastrointestinal hemorrhage as the initial presentation of polyarteritis nodosa (PAN), which is an uncommon form of systemic necrotizing vasculitis that may involve many organ systems and could affect any age group. Abdominal pain is the most common sign of gastrointestinal involvement. Gastrointestinal bleeding occurs less frequently in approximately 6% of cases. Reported cases of gastrointestinal hemorrhage have been in the form of coffee ground emesis, melena, or hematochezia. Such bleeding complications have resulted from ischemic ulceration or perforation of the small or large intestine. However, we are unaware of previous reports showing massive hematemesis to be the initial presentation of PAN.

Machine learning for a dynamic manufacturing environment

Within the semiconductor wafer manufacturing process, tight quality control is of utmost importance. This is due to such factors as the highly competitive nature of the business [2] and the complex nature of the process itself. Therefore, it is imperative that processing problems are recognized and corrected as quickly as possible. To accomplish this, a Parametric Test facility exists where a critical quality check is performed on the wafers. This is accomplished by measuring a number of electrical parameters at existing test sites on the wafer. Each measurement must fall within an acceptable range of values for its associated parameter to pass the critical check. If test results indicate that a parameter is outside of its acceptable range, the wafer may fail the quality check and be scrapped. If this happens an expert must examine all the parametric data associated with that wafer and attempt to determine the reason for failure and where in the manufacturing process the problem may have occurred.

Characterization of the ATP-dependent binding of wheat germ protein synthesis initiation factors eIF-(iso)4F and eIF-4A to mRNA

The ATP-dependent binding of wheat germ protein synthesis initiation factors eIF-(iso)4F and eIF-4A to an oligoribonucleotide has been investigated by direct fluorescence titration techniques. In addition, the effect of ATP on the interaction between another cap-binding initiation factor, eIF-4F, and eIF-4A was studied using the same methods. Comparison of the equilibrium association constants (K(eq)) indicate that 1) hydrolyzable ATP affects the affinity of eIF-(iso)4F for eIF-4A, regardless of whether or not mRNA was previously bound to the eIF-(iso)4F; in contrast, ATP had no effect on the eIF-(iso)4F/oligoribonucleotide interaction; 2) in the presence of ATP, the binding of the binary eIF-(iso)4F.eIF-4A complex to the oligoribonucleotide is of similar affinity as the binding of the oligoribonucleotide to the eIF-(iso)4F alone; the stoichiometry of this ternary eIF-(iso)4F.eIF-4A.mRNA complex was found to be 1:1:1; and 3) a similar ATP effect is observed for the eIF-4F/eIF-4A interaction as for the eIF-(iso)4F.eIF-4A complex.

Angiotensin II binding sites in the hamster brain: localization and subtype distribution

This study was designed to characterize the distribution of angiotensin II (AII) binding sites in the hamster brain. Brain sections were incubated with [125I][sar1,ile8]-angiotensin II in the absence and presence of angiotensin II receptor subtype selective compounds, losartan (AT1 subtype) and PD123177 (AT2 subtype). Binding was quantified by densitometric analysis of autoradiograms and localized by comparison with adjacent thionein stained sections. The distribution of AII binding sites was similar to that found in the rat, with some exceptions. [125I][sar1,ile8]-angiotensin II binding was not evident in the subthalamic nucleus and thalamic regions, inferior olive, suprachiasmatic nucleus, and piriform cortex of the hamster, regions of prominent binding in the rat brain. However, intense binding was observed in the interpeduncular nucleus and the medial habenula of the hamster, nuclei void of binding in the rat brain. Competition with receptor subtype selective compounds revealed a similar AII receptor subtype profile in brain regions where binding is evident in both species. One notable exception is the medial geniculate nucleus, predominately AT1 binding sites in the hamster but AT2 in the rat. Generally, the AII binding site distribution in the hamster brain parallels that of the other species studied, particularly in brain regions associated with cardiovascular and dipsogenic functions. Functional correlates for AII binding sites have not been elucidated in the majority of brain regions and species mismatches might provide clues in this regard.

Malignant fibrous histiocytoma of the gingiva. A clinicopathological study

A case is reported of malignant fibrous histiocytoma (MFH) of the gingiva. The 65-year-old female presented with a fast-growing mass originating from the left lower gingiva. The tumor measured 15 cm in diameter, occupying the entire oral cavity, protruding outside, and causing a mechanical airway obstruction. It appeared to respond to a 1000 rad single dose of preoperative radiation but recurred soon after composite resection with mandibulectomy, even though surgical margins were reportedly free from microscopic invasion. The patient expired from massive lung metastasis in spite of appreciable local response from treatment. This supports the thesis that MFH is a malignant disease and behaves like any soft-tissue sarcoma, which must be treated aggressively by a combined modality of surgery, radiation, and perhaps chemotherapy.

Vascular calcification presenting as necrosis of penis in patient with chronic renal failure

An unusual presentation of metastatic calcification as gangrene of the penis is reported in a patient with chronic renal failure on maintenance hemodialysis. Calcification of the vessels of the penis was documented radiographically and pathologically. Recognition of the possible occurrence of this complication becomes of great importance in younger patients on dialysis or with kidney transplants.

Contractile proteins (actin, myosin) and tubulin are revealed within DNA-containing nucleocytoplasm in mature spermatozoa of Libinia emarginata L

The localization of DNA and the distribution of the cytoskeletal proteins actin, myosin and tubulin in spermatozoa of Libinia emarginata L. were the aims of this study. DAPI, a highly reactive DNA-binding agent, revealed fluorescent staining within nucleocytoplasmic compartments around the acrosome and in the radial processes extending from the central region of the spermatozoa. The sites of DAPI-DNA staining corresponded to the position of the branched chromatin fibers revealed by electron microscopy. Antisera to myosin, actin, and tubulin revealed staining at different nucleocytoplasmic sites and in radial processes of the spermatozoa. Myosin was present at the base of each of three radial extensions, whereas actin appeared throughout the nucleocytoplasmic compartment and in the radial extensions. Actin fluorescence corresponded to the 6 nm thick filaments visualized by electron microscopy forming the core of the radial processes. Although tubulin was observed throughout the cell and within radial processes by immunofluorescence staining, intact microtubules were not revealed by electron microscopy. However, SDS PAGE comparisons between Libinia sperm extracts and dogfish brain showed small amounts of protein that comigrate with alpha and beta tubulin. These results demonstrate the existence of contractile proteins (myosin, actin) and tubulin within the DNA-containing nucleocytoplasmic compartments of Libinia sperm.

Hypofibrinogenemia-dysfibrinogenemia and von Willebrand's disease in the same family

Two Puerto Rican families were studied. One family included a number of members with dysfibrinogenemia occasionally associated with hypofibrinogenemia. The second family had members with von Willebrand's disease. The two diseases merged in the proband's immediate family; the affected members of this family exhibited a mild bleeding disorder. Others in the two families had no obvious bleeding tendency.