A Micro-computed Tomography Analysis of Marginal and Internal Fit of Endocrowns Fabricated from Three CAD/CAM Materials

OBJECTIVE

To assess the marginal and internal misfit of endocrowns fabricated from a resin matrix ceramic (CS), a partially crystallized (EMC), and a fully crystallized (ILS) lithium disilicate glass-ceramic.

METHODS AND MATERIALS

Thirty human premolar teeth restored with endocrowns were investigated. Three CAD/CAM materials were used (n=10 per group): CS, EMC, and ILS. Two-dimensional (2D) analysis of marginal and internal misfit was performed on micro-computed tomography scans before and after adhesive bonding. Further, three-dimensional (3D) analysis was performed to determine the total internal volume discrepancy. Surface roughness of the fitting surfaces of endocrowns was characterized using optical profilometry and scanning electron microscopy.

RESULTS

Adhesive bonding did not significantly affect marginal or internal misfit (p≥0.093). Differences in marginal misfit among the experimental groups were not statistically significant (p≥0.221). However, differences in 2D internal misfit were statistically significant; the CS group exhibited the largest internal misfit (p=0.001), while no significant difference was found between other groups (p=0.123). The largest discrepancies were observed at the pulpal floor and cervical region of all investigated specimens. No statistically significant difference was found in 3D misfit between ILS and EMC groups (p=0.711); however both exhibited statistically lower 3D misfit values compared to the CS group (p≤0.037). ILS endocrowns exhibited the smoothest and most homogenous fitting surface profile (p<0.001). However, there was no significant correlation between 2D internal misfit and the surface roughness (p≥0.082).

CONCLUSIONS

The choice of CAD/CAM material may influence the fitting accuracy of endocrowns. The investigated lithium disilicate glass-ceramics conferred superior internal fit for endocrowns compared to resin matrix ceramic.

Increased Handpiece Speeds without Air Coolant: Aerosols and Thermal Impact

This study assessed the impact of increased speed of high-speed contra-angle handpieces (HSCAHs) on the aerosolization of a severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) surrogate virus and any concomitant thermal impact on dental pulp. A bacteriophage phantom-head model was used for bioaerosol detection. Crown preparations were performed with an NSK Z95L Contra-Angle 1:5 (HSCAH-A) and a Bien Air Contra-Angle 1:5 Nova Micro Series (HSCAH-B) at speeds of 60,000, 100,000, and 200,000 revolutions per minute (rpm), with no air coolant. Bioaerosol dispersal was measured with Φ6-bacteriophage settle plates, air sampling, and particle counters. Heating of the internal walls of the pulp chambers during crown preparation was assessed with an infrared camera with HSCAH-A and HSCAH-B at 200,000 rpm (water flows ≈15 mL min^-1 and ≈30 mL min^-1) and an air-turbine control (≈23.5 mL min^-1) and correlated with remaining tissue thickness measurements. Minimal bacteriophage was detected on settle or air samples with no notable differences observed between handpieces or speeds (P > 0.05). At all speeds, maximum settled aerosol and average air detection was 1.00 plaque-forming units (pfu) and 0.08 pfu/m³, respectively. Irrespective of water flow rate or handpiece, both maximum temperature (41.5°C) and temperature difference (5.5°C) thresholds for pulpal health were exceeded more frequently with reduced tissue thickness. Moderate and strong negative correlations were observed based on Pearson's correlation coefficient, between remaining dentine thickness and either differential (r = -0.588) or maximum temperature (r = -0.629) measurements, respectively. Overall, HSCAH-B generated more thermal energy and exceeded more temperature thresholds compared to HSCAH-A. HSCAHs without air coolant operating at speeds of 200,000 rpm did not increase bioaerosolization in the dental surgery. Thermal risk is variable, dependent on handpiece design and remaining dentine thickness.

Mapping Ligand Interactions of Bromodomains BRD4 and ATAD2 with FragLites and PepLites─Halogenated Probes of Druglike and Peptide-like Molecular Interactions

The development of ligands for biological targets is critically dependent on the identification of sites on proteins that bind molecules with high affinity. A set of compounds, called FragLites, can identify such sites, along with the interactions required to gain affinity, by X-ray crystallography. We demonstrate the utility of FragLites in mapping the binding sites of bromodomain proteins BRD4 and ATAD2 and demonstrate that FragLite mapping is comparable to a full fragment screen in identifying ligand binding sites and key interactions. We extend the FragLite set with analogous compounds derived from amino acids (termed PepLites) that mimic the interactions of peptides. The output of the FragLite maps is shown to enable the development of ligands with leadlike potency. This work establishes the use of FragLite and PepLite screening at an early stage in ligand discovery allowing the rapid assessment of tractability of protein targets and informing downstream hit-finding.

Discriminative SKP2 Interactions with CDK-Cyclin Complexes Support a Cyclin A-Specific Role in p27KIP1 Degradation

The SCFSKP2 ubiquitin ligase relieves G1 checkpoint control of CDK-cyclin complexes by promoting p27KIP1 degradation. We describe reconstitution of stable complexes containing SKP1-SKP2 and CDK1-cyclin B or CDK2-cyclin A/E, mediated by the CDK regulatory subunit CKS1. We further show that a direct interaction between a SKP2 N-terminal motif and cyclin A can stabilize SKP1-SKP2-CDK2-cyclin A complexes in the absence of CKS1. We identify the SKP2 binding site on cyclin A and demonstrate the site is not present in cyclin B or cyclin E. This site is distinct from but overlapping with features that mediate binding of p27KIP1 and other G1 cyclin regulators to cyclin A. We propose that the capacity of SKP2 to engage with CDK2-cyclin A by more than one structural mechanism provides a way to fine tune the degradation of p27KIP1 and distinguishes cyclin A from other G1 cyclins to ensure orderly cell cycle progression.

FragLites-Minimal, Halogenated Fragments Displaying Pharmacophore Doublets. An Efficient Approach to Druggability Assessment and Hit Generation

Identifying ligand binding sites on proteins is a critical step in target-based drug discovery. Current approaches to this require resource-intensive screening of large libraries of lead-like or fragment molecules. Here, we describe an efficient and effective experimental approach to mapping interaction sites using a set of halogenated compounds expressing paired hydrogen-bonding motifs, termed FragLites. The FragLites identify productive drug-like interactions, which are identified sensitively and unambiguously by X-ray crystallography, exploiting the anomalous scattering of the halogen substituent. This mapping of protein interaction surfaces provides an assessment of druggability and can identify efficient start points for the de novo design of hit molecules incorporating the interacting motifs. The approach is illustrated by mapping cyclin-dependent kinase 2, which successfully identifies orthosteric and allosteric sites. The hits were rapidly elaborated to develop efficient lead-like molecules. Hence, the approach provides a new method of identifying ligand sites, assessing tractability and discovering new leads.

Structural insights into the functional diversity of the CDK-cyclin family

Since their characterization as conserved modules that regulate progression through the eukaryotic cell cycle, cyclin-dependent protein kinases (CDKs) in higher eukaryotic cells are now also emerging as significant regulators of transcription, metabolism and cell differentiation. The cyclins, though originally characterized as CDK partners, also have CDK-independent roles that include the regulation of DNA damage repair and transcriptional programmes that direct cell differentiation, apoptosis and metabolic flux. This review compares the structures of the members of the CDK and cyclin families determined by X-ray crystallography, and considers what mechanistic insights they provide to guide functional studies and distinguish CDK- and cyclin-specific activities. Aberrant CDK activity is a hallmark of a number of diseases, and structural studies can provide important insights to identify novel routes to therapy.

The Effects of Colored Pigments on the Translucency of Experimental Dental Resin Composites

OBJECTIVE

Colored pigments are incorporated into dental resin composites to produce clinically acceptable shades for restorative materials but studies on their effects on translucency are rare. The aim of this study was to examine the effects of the addition of different colored pigments on the translucency of experimental dental resin composites.

MATERIALS AND METHODS

12 types of experimental dental resin composites containing different concentrations of red and yellow iron oxide pigments were formulated and light-cured. Total and diffuse translucency as well as CIE L*a*b* values were measured and the color differences were calculated.

RESULTS

There was a statistically significant difference in the translucency values between the composites with no pigments and the composites with increasing concentrations of the pigments (p<0.05). The translucency decreased as the concentration of the pigments increased. However at pigment concentrations greater than 0.02%, the translucency of the composites reached a plateau and ceased to be influenced by the addition of the pigments (p⟨0.05). All color differences were in the range of 3.62-16.00 ΔE*ab unit.

CONCLUSIONS

The pigments used in this study can influence the translucency of the experimental resin composites and should be considered as an important factor by clinicians to achieve optimal esthetic restorative outcome.

Differences in the Conformational Energy Landscape of CDK1 and CDK2 Suggest a Mechanism for Achieving Selective CDK Inhibition

Dysregulation of the cell cycle characterizes many cancer subtypes, providing a rationale for developing cyclin-dependent kinase (CDK) inhibitors. Potent CDK2 inhibitors might target certain cancers in which CCNE1 is amplified. However, current CDK2 inhibitors also inhibit CDK1, generating a toxicity liability. We have used biophysical measurements and X-ray crystallography to investigate the ATP-competitive inhibitor binding properties of cyclin-free and cyclin-bound CDK1 and CDK2. We show that these kinases can readily be distinguished by such inhibitors when cyclin-free, but not when cyclin-bound. The basis for this discrimination is unclear from either inspection or molecular dynamics simulation of ligand-bound CDKs, but is reflected in the contacts made between the kinase N- and C-lobes. We conclude that there is a subtle but profound difference between the conformational energy landscapes of cyclin-free CDK1 and CDK2. The unusual properties of CDK1 might be exploited to differentiate CDK1 from other CDKs in future cancer therapeutic design.

Recent Respiratory and Enteric Adenovirus Infection in Children in the Manchester Area

Seventy-three group B adenoviruses (29 type 3 and 44 type 7) identified in a recent community outbreak were analysed with restriction endonucleases. Considerable genetic heterogeneity was identified, particularly amongst the type 3 isolates, but this genome variation could not be correlated with either clinical or epidemiological findings. Group F adenoviruses were found in 132 (4.1%) of 3202 stool specimens from children with gastroenteritis and, after rotaviruses, they were the most common viruses identified. Unlike rotaviruses, these enteric adenoviruses were endemic throughout the 3–year study period and the greatest proportion of infections (47.6%) were found in babies under 6 months old.

Wound Discharge After Pharmacological Thromboprophylaxis in Lower Limb Arthroplasty

BACKGROUND

The benefits vs risk of pharmacological prophylaxis for thromboembolic disease in orthopedic patients remain controversial. Pharmacological thromboprophylaxis regimes are commonly used in this patient group. Few studies specifically examine wound complications attributable to this therapy. In this prospective trial, we investigated the effect of various regimens on postoperative wounds.

METHODS

A prospective, observational, multicenter study involving patients undergoing elective hip or knee arthroplasty was undertaken. Patients were divided into 3 groups depending on thromboprophylaxis: no anticoagulation, aspirin, or low molecular weight heparin (LMWH) (enoxaparin). Surgical wounds were evaluated for each regime using the Southampton Wound Assessment Score.

RESULTS

Over a 12-month period, 327 patients were enrolled with a mean age of 68.1 years (±11.2 years). There were 105 patients in the no anticoagulation group (32.1%), 97 patients in the aspirin group (29.7%), and 125 patients in the LMWH group (38.2%). Wound scores were evaluated for evidence and amount of discharge. The use of LMWH conferred a 4.92 times greater risk and aspirin a 3.64 times greater risk of wound discharge than no pharmacological thromboprophylaxis (P < .0001). There were no significant differences in the incidence of deep vein thrombosis or pulmonary embolus between groups either as an inpatient or postdischarge.

CONCLUSION

There is a significant increase in the risk of wound discharge when aspirin or LMWH is used in arthroplasty patients. As potential complications of wound problems are significant, a more balanced view of risk vs benefit needs to be taken when prescribing thromboprophylaxis for this patient group.

Fitness Profiles of Elite Adolescent Irish Rugby Union Players

Wood, DJ, Coughlan, GF, and Delahunt, E. Fitness profiles of elite adolescent Irish rugby union players. J Strength Cond Res 32(1): 105-112, 2018-Rugby unions throughout the world are implementing player development models to prepare young players to meet the demands of professional rugby union. An example of this is the Irish Rugby Football Union Long Term Player Development model. The purpose of this study was to provide normative data relating to the physical fitness of elite adolescent Irish rugby union players and determine the differences in the physical capacities between players in the forward and back units as well as to provide descriptive data for the position categorizations within these units for this unique population. Players in the forward unit were significantly taller and heavier than players in the back unit (1.85 ± 0.06 m and 96.88 ± 9.00 kg vs. 1.79 ± 0.05 m and 81.97 ± 7.09 kg, respectively). Forwards (38.37 ± 4.00 cm) had a significantly lower countermovement jump height than backs (41.31 ± 4.44 cm). Forwards had a significantly lower triple hop for the distance score on their right (5.78 ± 0.52 m) and left (5.78 ± 0.55 m) legs compared with backs (6.26 ± 0.42 m and 6.33 ± 0.45 m, respectively). Forwards (1.85 ± 0.07 seconds) had a significantly higher 10-m sprint time than backs (1.77 ± 0.06 seconds). Furthermore, forwards (675.90 ± 82.46 m) had a significantly lower 150-m shuttle test score than backs (711.71 ± 27.46 m). The results of this study provide normative data for players who currently possess underage international potential and could be used by strength and conditioning coaches to guide the selection of players through talent identification processes.

The introduction of digital dental technology into BDS curricula

The aim of this study was to determine the degree to which digital dental technologies have been introduced into the curricula of UK dental schools. A survey was carried out of all the UK dental schools that teach undergraduate dental students. The survey contained six questions and was designed to determine if digital dental technology techniques or systems were being taught in the curricula, what these techniques were, and whether the school dental laboratories supported these techniques. Sixteen schools were surveyed and 11 replied: a response rate of 69%. Forty-five percent of the schools that replied did not teach digital dental technology in their curriculum. Of the 55% of schools who did teach digital dental technology, 50% gave lectures or demonstrations while the other 50% allowed practical involvement by the student. Two thirds of these stated that not all the students participated in practical usage. Seventy-three percent of the schools that replied had dental laboratories using some, but not all the digital dental technology techniques listed. Eighty percent of the schools that were not teaching digital dental technology said it was because it was not included in the curriculum, and 20% stated it was due to a lack of technical expertise or support.

Knee joint preservation with combined neutralising high tibial osteotomy (HTO) and Matrix-induced Autologous Chondrocyte Implantation (MACI) in younger patients with medial knee osteoarthritis: a case series with prospective clinical and MRI follow-up over 5 years

PURPOSE

There is no ideal treatment for younger patients with medial knee osteoarthritis (OA) and varus malalignment. We have investigated the first case series of combined neutralising high tibial osteotomy (HTO) and Matrix-induced Autologous Chondrocyte Implantation (MACI) with MRI. Treatment goals were clinical improvement and delay of arthroplasty.

METHODS

Between 2002 and 2005 18 patients (Mean age 47 years) underwent surgery. Exclusion criteria were lateral compartment and advanced patellofemoral OA. The Knee Injury and Osteoarthritis Outcome Score (KOOS), six minute walk test (6MWT) and a validated MRI score were outcome measures.

RESULTS

There were significant improvements (p<0.05) in all five KOOS domains. Four were significantly maintained to 5 years. The domain "symptoms" and results in the 6MWT dropped off at 5 years. MRI results were first significantly improved (24/12) but declined at 60 months. Good quality infill was found in 33% patients at the study endpoint (n=5/15). Histological investigation of one knee demonstrated full-thickness hyaline-like cartilage (20/12). After 2 early failures and one graft detachment graft fixation was changed (Smart nails instead of sutures in 14 cases). Graft hypertrophy requiring a chondroplasty occurred once. There were no other major complications. Specific minor complications included patellar tendinitis (n=8).

CONCLUSIONS

This combined procedure provides a safe treatment option for younger patients with medial knee OA and varus alignment with significant clinical improvement at 5 years. However, overall graft survival and cartilage infill were poor. Larger studies are needed to statistically verify predictors for longer term cartilage repair in these patients.

Nested PCR-SSCP assay for the detection of p53 mutations in paraffin wax embedded bone tumours: improvement of sensitivity and fidelity

DNA extraction and PCR amplification from paraffin wax embedded bone tumour specimens present several difficulties, firstly, because of the abundant matrix they contain and, secondly, because decalcification often causes degradation of DNA. In this report, comparative studies were carried out to determine the most efficient method for DNA extraction and PCR amplification from such specimens. The results indicated that nested PCR produced appropriate strong reaction products with minimal background contamination. A method for DNA extraction from paraffin wax embedded bone tissue and a nested PCR-SSCP technique have been developed for use in such diagnostic specimens.

Malignant fibrous histiocytoma complicating nephrogenic systemic fibrosis post liver transplantation

A 46-year-old man with cirrhosis secondary to hepatitis C virus infection and alcohol underwent orthotopic liver transplantation, which required urgent re-grafting because of biliary sepsis from necrosis of the left liver lobe. Recovery was complicated by renal failure and nephrogenic systemic fibrosis (probably related to intravenous gadolinium exposure). He subsequently developed a malignant fibrous histiocytoma. We present this case highlighting the occurrence of two rare conditions in the same patient following liver transplantation. We believe this is the first case of its kind to be reported.

Nanoparticles for dentine tubule infiltration: an in vitro study

Nanosized particles of hydroxyapatite were produced by a hydrothermal synthesis technique. Reaction time and starting pH were varied in order to produce a range of particle dimensions and morphologies. The particles were suspended in alcohol and used for in-vitro trials of dentinal tubule infiltration in etched sections of clinically extracted human molars. Particles were of rod-like morphology, and decreased in aspect ratio as the starting pH was raised. Particles prepared at pH 12 had a mean length of approximately 70 nm and diameter of approximately 30 nm. These showed the most promising infiltration results, with up to 90% of the tubules being fully or partially occluded. Comparisons were made with commercially-available 40 nm spherical silica particles. Information on the depth of infiltration was obtained from sections of dentine prepared using focussed ion beam milling (FIB-SEM).

Indirect selective laser sintering of apatite—wollostonite glass—ceramic

This paper develops an indirect selective laser sintering (SLS) processing route for apatite—wollastonite (A—W) glass—ceramic, and shows that the processing route, which can create porous three-dimensional products suitable for bone implants or scaffolds, does not affect the excellent mechanical and biological properties of the glass—ceramic. ‘Green parts’ with fine integrity and well-defined shape have been produced from glass particles of single-size range or mixed-size ranges with acrylic binder in various ratios by weight. A subsequent heat treatment process has been developed to optimize the crystallization process, and an infiltration process has been explored to enhance mechanical strength. Three-point bending test results show flexural strengths of up to 102 MPa, dependent on porosity, and simulated body fluid (SBF) tests show that the laser sintered porous A—W has comparable biological properties to that of conventionally produced A—W.

Traditional vs accelerated approaches to post-operative rehabilitation following matrix-induced autologous chondrocyte implantation (MACI): comparison of clinical, biomechanical and radiographic outcomes

OBJECTIVE

To determine the effectiveness of 'accelerated' compared to 'traditional' post-operative load bearing rehabilitation protocols following matrix-induced autologous chondrocyte implantation (MACI).

METHOD

A randomized controlled study design was used to investigate clinical, biomechanical and radiographic assessment at 3 months post-surgery in 62 patients following MACI to the medial or lateral femoral condyle. Both rehabilitation interventions sought to protect the implant for an initial period, then incrementally increase load bearing. Under the 'accelerated' protocol, patients reached full weight bearing at 8 weeks post-surgery, compared to 11 weeks for the 'traditional' group.

RESULTS

Patients in the 'accelerated' group achieved greater 6 min walk distances and daily activity levels as measured by accelerometry (P<0.05) compared to the 'traditional' group. Furthermore, the 'accelerated' group reported significantly better improvement in knee pain at 12 weeks as indicated by the Knee Injury and Osteoarthritis Outcome Score (P<0.05), and regardless of the rehabilitation protocol employed, no patient suffered any adverse effect to the implant as assessed by magnetic resonance imaging at 3 months. Comparison of each rehabilitation group with an unaffected control group revealed a significant difference in peak knee adduction and flexion moments for the traditional group (P<0.05). However, there was no difference for accelerated patients (P>0.05), which may demonstrate a faster return to knee loading patterns typically observed in unaffected subjects.

CONCLUSION

The 'accelerated' load bearing approach that reduced the length of time spent ambulating on crutches resulted in reduced knee pain, improved function, no graft complications and may speed up the recovery of normal gait function. Patient follow-up to at least 24 months would be required to observe longer-term graft outcomes.

Total knee replacement with and without patellar resurfacing: a prospective, randomised trial using the profix total knee system

We have examined the differences in clinical outcome of total knee replacement (TKR) with and without patellar resurfacing in a prospective, randomised study of 181 osteoarthritic knees in 142 patients using the Profix total knee system which has a femoral component with features considered to be anatomical and a domed patellar implant. The procedures were carried out between February 1998 and November 2002. A total of 159 TKRs in 142 patients were available for review at a mean of four years (3 to 7). The patients and the clinical evaluator were blinded in this prospective study. Evaluation was undertaken annually by an independent observer using the knee pain scale and the Knee Society clinical rating system. Specific evaluation of anterior knee pain, stair-climbing and rising from a seated to a standing position was also undertaken. No benefit was shown of TKR with patellar resurfacing over that without resurfacing with respect to any of the measured outcomes. In 22 of 73 knees (30.1%) with and 18 of 86 knees (20.9%) without patellar resurfacing there was some degree of anterior knee pain (p = 0.183). No revisions related to the patellofemoral joint were performed in either group. Only one TKR in each group underwent a re-operation related to the patellofemoral joint. A significant association between knee flexion contracture and anterior knee pain was observed in those knees with patellar resurfacing (p = 0.006).

Inhibition of biofilms associated with dentures and toothbrushes by tetrasodium EDTA

AIMS

We examined the efficacy of tetrasodium EDTA in eradicating biofilms derived from salivary inocula or pure cultures of Candida albicans on discs of polymethyl methacrylate (PMMA) denture base or on toothbrushes that had been used normally for 4-8 weeks. Its efficiency in virus neutralization was also determined.

METHODS AND RESULTS

Overnight (16 h) treatment with 4% (w/v) tetrasodium EDTA solution reduced salivary and C. albicans biofilm viable counts by > or =99%. Biofilm removal was confirmed using confocal laser scanning microscopy. Presence/absence of sucrose during biofilm formation had no effect on killing efficacy. Prolonged treatment of PMMA with tetrasodium EDTA did not influence subsequent formation of C. albicans biofilms or affect surface roughness of the PMMA, but it reduced subsequent biofilm formation from a salivary inoculum. Infectivities of herpes simplex virus and polio virus suspensions were reduced by >99.99% by treatment for 1 and 2 h, respectively.

CONCLUSIONS

Tetrasodium EDTA solution efficiently disinfected toothbrushes and PMMA discs, with the detachment of biofilms, and rapidly neutralized both nonenveloped and enveloped viruses.

SIGNIFICANCE AND IMPACT OF THE STUDY

Dentures and toothbrushes become contaminated by bacterial biofilms and by viruses. There is a need for disinfection methods that are rapidly effective, cost-effective, nontoxic and easily implemented. These studies indicate that tetrasodium EDTA solution has disinfection applications in the oral care field.

Evidence that human cartilage and chondrocytes do not express calcitonin receptor

OBJECTIVE

Calcitonin (CT) has been recently shown to exhibit direct protective effects on articular cartilage against joint degenerative disease. It has been proposed that CT might act via the CT receptor (CTR) to activate the cyclic AMP (cAMP) pathway and protect type II collagen degradation. In this study, we investigated the existence of CTR in human articular cartilage and chondrocytes, and examined the potential pharmacological effects and transduction pathway of salmon CT (sCT) in human chondrocytes.

METHODS

Five human articular cartilage samples were examined for the expression of the CTR by polymerase chain reaction (PCR), immunostaining and Western blot analysis. cAMP levels in human chondrocyte stimulated with sCT were assessed by ELISA. The effect of sCT on the gene expression profiles, including aggrecan, type II collagen, MMP-1, MMP-3 and MMP-13, of human chondrocytes was also examined by relative quantitative Real-time PCR.

RESULTS

We failed to detect the CTR at both the transcriptional and protein levels in human chondrocytes and cartilage tissue by PCR, immunostaining and Western blotting. cAMP levels were significantly elevated in human chondrocytes by forskolin (100muM) to more than 10-fold (P<0.001), however, were not induced by sCT (10(-7)M, 10(-8)M, 10(-9)M). Real-time PCR analysis demonstrated that sCT slightly reduced the gene expression of MMPs, although this effect was not statistically significant.

CONCLUSION

In contrary to previous reports, our data indicate that human cartilage and chondrocytes do not express CTR. Furthermore, sCT does not appear to have direct effects on human chondrocytes. We propose that the chondroprotective effect of CT observed in vivo may be indirect via its impact on subchondral bone resorptive activity of osteoclasts.

Effect of flexion/extension splintage post total knee arthroplasty on blood loss and range of motion -- a randomised controlled trial

Previous published research has shown promising results with flexion splinting post total knee arthroplasty. Before instituting this practice, we conducted a randomised controlled trial to confirm any benefits over splinting in extension. Five patients were recruited into the trial. 5 were excluded. The flexion group consisted of 49 patients who had their knee placed in 70 degrees of flexion over an inactive CPM machine for 24 h post operation. The extension group consisted of 46 patients who were splinted in full extension for the first 24 h post operation. We assessed post-operative day 1 drain volume, haemoglobin and haematocrit, blood transfusions, duration of inpatient stay, range of motion and complications within 6 weeks of surgery. There was no significant difference between the two groups among any of the outcomes measured. As such, we have been unable to demonstrate any benefit with splintage in flexion post total knee arthroplasty and have not adopted it as part of our post-operative management.

The effect of 24h non-stop hydrogen peroxide concentration on bovine enamel and dentine mineral content and microhardness

OBJECTIVES

Tooth bleaching agents may adversely affect tooth structure. The aim of this study was to investigate the effect of hydrogen peroxide concentration on mineral loss and microhardness of bovine teeth.

METHODS

Twenty-six freshly extracted intact bovine incisor teeth were stored in distilled water. Five teeth were sectioned and four samples (2 mm x 2 mm x 1.5 mm) each of enamel and dentine were obtained from each tooth. The samples of enamel and dentine were divided into four groups and immersed in either 0%, 3%, 10% or 30% (w/v) hydrogen peroxide solutions for 24h at 37 degrees C. Samples from the solutions were taken for ion release analysis using inductively coupled plasma mass spectrometry. The remaining 21 teeth were mounted in epoxy resin and the upper surface of the specimens were ground and polished to expose the enamel and dentine for microhardness measurements. These specimens were randomly divided into three equal groups and Vickers microhardness values were recorded on the enamel and dentine surfaces of each group before and after bleaching.

RESULTS

The differences in ion release concentration after treatment with 0% (control) and each of 3%, 10% and 30% hydrogen peroxide (w/v) were statistically significant (p<0.025). The release of calcium and phosphorous ions increased with increasing hydrogen peroxide concentrations. A significant reduction (p<0.05) in Vickers microhardness values for enamel was recorded after bleaching.

CONCLUSIONS

Ion release from both enamel and dentine increased with increasing hydrogen peroxide concentration. Microhardness of enamel decreased significantly with bleaching.

Ursodeoxycholic acid modulates histone acetylation and induces differentiation and senescence

Agents that can modulate colonic environment and control dysregulated signaling are being evaluated for their chemopreventive potential in colon cancer. Ursodeoxycholate (UDCA) has shown chemopreventive potential in preclinical and animal models of colon cancer, but the mechanism behind it remains unknown. Here biological effects of UDCA were examined to understand mechanism behind its chemoprevention in colon cancer. Our data suggests that UDCA can suppress growth in a wide variety of cancer cell lines and can induce low level of apoptosis in colon cancer cells. We also found that UDCA treatment induces alteration in morphology, increased cell size, upregulation of cytokeratin 8, 18 and 19 and E-cadherin, cytokeratin remodeling and accumulation of lipid droplets, suggesting that UDCA induces differentiation in colon carcinoma cells. Our results also suggest significant differences in UDCA and sodium butyrate induced functional differentiation. We also report for the first time that UDCA can induce senescence in colon cancer cells as assessed by flattened, spread out and vacuolated morphology as well as by senescence marker beta-galactosidase staining. We also found that UDCA inhibits the telomerase activity. Surprisingly, we found that UDCA is not a histone deacytylase inhibitor but instead induces hypoacetylation of histones unlike hyperacetylation induced by sodium butyrate. Our results also suggest that, although UDCA induced senescence is p53, p21 and Rb independent, HDAC6 appears to be important in UDCA induced senescence. In summary, our data shows that UDCA modulates chromatin by inducing histone hypoacetylation and induces differentiation and senescence in colon cancer cells.

Iontophoresed segmental allografts in revision arthroplasty for infection

Revision arthroplasty after infection can often be complicated by both extensive bone loss and a relatively high rate of re-infection. Using allograft to address the bone loss in such patients is controversial because of the perceived risk of bacterial infection from the use of avascular graft material. We describe 12 two-stage revisions for infection in which segmental allografts were loaded with antibiotics using iontophoresis, a technique using an electrical potential to drive ionised antibiotics into cortical bone.

Iontophoresis produced high levels of antibiotic in the allograft, which eluted into the surrounding tissues. We postulate that this offers protection from infection in the high-risk peri-operative period. None of the 12 patients who had two-stage revision with iontophoresed allografts had further infection after a mean period of 47 months (14 to 78).

Bone allograft non-union is related to excessive osteoclastic bone resorption: a sheep model study

Using a sheep femoral allograft model we have investigated the cellular and molecular mechanisms associated with non-union of bone allografts. Histomorphometric analysis revealed that allograft non-unions featured both marked increases in osteoclast (OC) numbers and total eroded bone surface as compared to allografts which had undergone direct union. Three distinct cellular layers lying adjacent to the allograft bone surface were identified in all non-union cases. The outer or fibroblastic layer contained an abundance of fibroblasts and connective tissue. Circumscribing this layer was a band of synovial-like cells consisting mainly of large spindle-shaped mononuclear cells mixed with scattered round-shaped mononuclear cells. The third layer, which was directly juxtaposed to the allograft bone surface, consisted predominantly of multinuclear OCs which were positively identified by calcitonin receptor immunohistochemistry. Interestingly, in-situ hybridisation revealed that surrounding synovial-like cells in non-union allografts, expressed abundant gene transcripts for receptor activator NF-kappaB ligand (RANKL), a membrane bound factor critical for both the induction of OC activity and osteoclastogenesis. We propose that excessive bone resorption by host OCs contributes, at least partially, to the failure of bone allografts. The production of RANKL by synovial-like fibroblasts may be the driving force responsible for the elevated generation and activation of OCs. Based on such evidence novel therapeutic strategies for the treatment of non-union bone allografts using anti-bone resorbing agents may be devised.

Iontophoresis of antibiotics into segmental allografts

Iontophoresis is a novel technique which may be used to facilitate the movement of antibiotics into the substance of bone using an electrical potential applied externally. We have examined the rate of early infection in allografts following application of this technique in clinical practice. A total of 31 patients undergoing revision arthroplasty or surgery for limb salvage received 34 iontophoresed sequential allografts, of which 26 survived for a minimum of two years. The mean serum antibiotic levels after operation were low (gentamicin 0.37 mg/l (0.2 to 0.5); flucloxacillin 1 mg/l (0 to 1) and the levels in the drains were high (gentamicin 40 mg/l (2.5 to 131); flucloxacillin 17 mg/l (1 to 43). There were no early deep infections. Two late infections were presumed to be haemotogenous; 28 of the 34 allografts were retained. In 12 patients with pre-existing proven infection further infection has not occurred at a mean follow-up of 51 months (24 to 82).

Polio vaccine: The first 50 years and beyond

A conference on "Polio vaccine: the first 50 years and beyond" was held in Toronto, Canada, June 2005. The purpose of the conference was to bring together regulators, manufacturers, academics and public health authorities to celebrate the accomplishments of the past 50 years, to consider the challenges of achieving and sustaining polio eradication and to review standardization and regulatory issues around existing and new polio vaccines. In the final session of the conference the following summary of the meeting was presented.

Indirect selective laser sintering of an apatite-mullite glass-ceramic for potential use in bone replacement applications

The feasibility of using indirect selective laser sintering (SLS) to produce parts from glass-ceramic materials for bone replacement applications has been investigated. A castable glass based on the system SiO2 Al2O3 P2O5 CaO CaF2 that crystallizes to a glass-ceramic with apatite and mullite phases was produced, blended with an acrylic binder, and processed by SLS. Green parts with good structural integrity were produced using a wide range of processing conditions, allowing both monolayer and multilayer components to be constructed. Following SLS the parts were post-processed to remove the binder and to crystallize fully the material, evolving the apatite and mullite phases. The parts were heated to 1200O C using a number of different time-temperature profiles, following which the processed material was analysed by differential thermal analysis, X-ray diffraction, and scanning electron microscopy, and tested for flexural strength. An increase in strength was achieved by infiltrating the brown parts with a resorbable phosphate glass, although this altered the crystal phases present in the material.

Processing of an apatite-mullite glass-ceramic and an hydroxyapatite/phosphate glass composite by selective laser sintering

The work presented details the results of an investigation into the feasibility of using Selective Laser Sintering (SLS) to directly produce customised bioceramic implants. The materials used were bioactive in nature and included a glass-ceramic and a combination of hydroxyapatite and phosphate glass. The glass-ceramic was selected from the range of apatite-mullite materials in the SiO2.Al2O3.CaO.CaF2.P2O5 series, due to their potentially suitable biological and mechanical properties. The hydroxyapatite and phosphate glass combination was chosen to allow an alternative production approach to be investigated. The viability of using both these materials with the SLS process was assessed and the process route and resulting material properties characterised using a variety of techniques including Differential Thermal Analysis (DTA), X-ray Diffraction (XRD) and Scanning Electron Microscopy (SEM). The results obtained indicate that it was possible to produce multiple layer components from both materials using the SLS process. The glass-ceramic materials could only be processed at very low scan speeds and powers, yielding relatively brittle components. It was though possible to produce parts from the hydroxyapatite and phosphate glass combination across a much wider range of parameters, producing parts which had a greater potential for possible implant production.

Fluorapatite-mullite glass sputter coated Ti6Al4V for biomedical applications

A number of bioactive ceramics have been researched since the development of Bioglass in the 1970's. Fluorapatite mullite has been developed from the dental glass-ceramics used for more general hard tissue replacement. Being brittle in nature, glass-ceramics are currently used mainly as coatings. This paper shows that fluorapatite glass LG112 can be used as a sputtered glass coating on roughened surfaces of Ti6Al4V for possible future use for medical implants. An AFM was used to measure the roughness of the surface before and after coating to determine the change in the topography due to the coating process as this greatly affects cell attachment. The sputter coating partially filled in the artificially roughened surface, changing the prepared topography. Osteoblasts have been successfully grown on the surface of these coatings, showing biocompatibility with bone tissue and therefore potential use in hard tissue repair.

Microleakage of glass-ionomer cement placed in association with non-setting calcium hydroxide

The purpose of this investigation was to determine whether non-setting calcium hydroxide [Ca (OH)2] cement placed in the root canal system of premolar teeth would affect the subsequent microleakage of a glass-ionomer restoration (GIC). Following selection, 62 human premolar teeth extracted for orthodontic reasons were accessed and root canals prepared according to a standardized procedure. The specimens were then allocated randomly into two major groups each of 30 teeth. Two other teeth were used as a positive and a negative control. The control group was restored with glass-ionomer cement following drying of the canal and placement of a cotton wool pledget. The test group had all canals dressed with non-setting Ca(OH)2 and then was subdivided, one set (n = 22) being restored following conditioning of the access cavity margins, the other (n = 8) having the margins cleaned with a hand excavator. Samples were assessed for microleakage using a two-point scoring system (leakage or no leakage) in conjunction with a clearing technique using AgNO3. Using Fisher's exact test, a statistically significant difference was found between the control and test groups (P < 0.05) but there was no significant difference between the excavated and conditioned cavities (P=0.55). It is concluded that contamination of access cavity margins with Ca(OH)2 during medication of a root canal interferes with the bond of GIC, resulting in increased microleakage in vitro.

Molecular characterisation of chondrocytes in autologous chondrocyte implantation

Autologous chondrocyte implantation (ACI) relies on the use of cultured cells. However, the biosynthetic profile of cultured chondrocytes is shown to be altered during in vitro expansion. The purpose of this study therefore, was to examine the cellular phenotype of chondrocytes cultured for ACI and to determine the apoptotic index of cells implanted into patients. Using electron microscopy, immunohistochemistry, RT-PCR and flow cytometry analyses, we have investigated protein and gene expression of several chondrocyte-specific, or associated markers in cultured cells used for implantation in patients. They included S-100, type I and II collagen, aggrecan, transforming growth factor beta, glucocorticoid receptor alpha and beta and vitamin D3 receptor. We have also examined the apoptotic index of chondrocytes. Our results demonstrated that cultured cells for ACI display the characteristics of chondrocytes. These cells are round in shape, contain numerous small surface processes of cytoplasmic membrane and have an accumulation of glycogen within the cytoplasm. They express S-100, aggrecan TGF-beta, glucocorticoid receptor alpha and vitamin D3 receptor as evidenced by either immunohistochemistry or RT-PCR, however, there is variation in the expression of type I, type II collagen glucocorticoid receptor beta between cases. Chondrocyte used for implantation has relatively low level of apoptosis (<11%). In conclusion, although there was variation in the level of expression of these genetic markers, our data indicate that cultured cells used for ACI were of chondrocytic lineage cells and have low level of apoptotic cells.

Hard and soft tissue augmentation in implant therapy using acellular dermal matrix

The use of acellular dermal matrix to correct soft and hard tissue defects involving implants is described through three case reports. Correction of a ridge deformity caused by a root fracture, submerging of an existing implant and correction of recession defects around adjacent teeth, and ridge preservation for implant placement are presented. The use of acellular dermal matrix prevented the need for a second surgical site for donor material and the possible attendant postoperative complications. It also enhanced patient comfort and satisfaction with the procedure. All three cases demonstrated excellent functional and esthetic results for both the patients and professionals involved in the therapy.

Equity of access to adult hospice inpatient care within north-west England

There is a growing debate about the question of equity of access to hospice and palliative care services. Even countries with relatively well developed palliative care systems are considered to have problems of access and inequity of provision. Despite these concerns, we still lack a relevant evidence base to serve as a guide to action. We present an analysis of access to adult hospice inpatient provision in the north-west region of England that employs Geographical Information Systems (GIS). Measures of the possible demand for, and supply of, hospice inpatient services are used to determine the potential accessibility of cancer patients, assessed at the level of small areas (electoral wards). Further, the use of deprivation scores permits an analysis of the equity of access to adult inpatient hospice care, leading to the identification of areas where additional service provision may be warranted. Our research is subject to a number of caveats--it is limited to inpatient hospice provision and does not include other kinds of inpatient and community-based palliative care services. Likewise, we recognise that not everyone with cancer will require palliative care and also that palliative care needs exist among those with nonmalignant conditions. Nevertheless, our methodology is one that can also be applied more generally.

Pre-surgery knee joint loading patterns during walking predict the presence and severity of anterior knee pain after total knee arthroplasty

This study tested if abnormal sagittal knee joint loading patterns after total knee arthroplasty (TKA) were present pre-surgery, and if patterns with higher external knee flexion moments were related to the presence and severity of post-surgery anterior knee pain. Gait analysis and clinical evaluation were performed on 34 patients (41 arthroplasties) both before and 12-18 months after TKA, and on 20 healthy age-matched controls at matched velocities. The majority of knees with abnormal flexor or extensor sagittal knee joint loading patterns post-surgery (18 of 26, 69%) also displayed these patterns pre-surgery. Knee joint loading in the early mid-stance phase of walking prior to surgery was identified by stepwise regression as a significant predictor of the presence (exp(beta)=2.9, CI: 1.2-6.8, p=0.017) and severity of post-surgery anterior knee pain (R2=0.314, p=0.019). Therefore, the frequency and severity of anterior knee pain after TKA can be partially explained by retained pre-surgery gait patterns that had higher external flexion moments in the early mid-stance phase, which place higher forces on the patellofemoral joint.

New vaccine technologies

New vaccine development for potential use in human medicine is buoyant. New science (genomics and proteomics) is presenting major new opportunities. New approaches (DNA vaccines, new combination vaccines, new formulations, novel delivery routes, new adjuvants) are being vigorously explored. New needs (defence vaccines) are being identified. One common element in all these varied areas is that pre-clinical evaluation of a candidate new vaccine is a pre-requisite before initiation of clinical trials in humans. Laboratory evaluation also usually continues during the clinical phase of vaccine development. Pre-clinical and laboratory evaluations often involve animals. Data from these studies are used to support an application for marketing authorisation. Regulatory Authorities use precedent to help assess these applications. Where no precedent exists the Regulatory Authorities apply risk-benefit analyses based on the perceived risks of a new product or process. These perceived risks are constantly reviewed as experience is gained. The World Health Organisation facilitates the development of scientific consensus on issues that have an impact on the quality and safety of biological medicines, including vaccines. New vaccine technologies often present new challenges for the safety and efficacy evaluation of candidate preparations. Animal models are usually very important in this process. The number of new vaccine candidates seems set to increase in the short-term.

The scientific basis for stopping polio immunisation--issues and challenges

Eradication of polio is in sight. Once this is finally achieved there is general agreement that the world should move from the current policy of universal childhood immunisation, mostly with the oral poliovirus vaccine (OPV), to no immunisation. The challenge ahead is to build consensus on how and when this is achieved. The major area of scientific uncertainty is whether OPV-derived strains excreted by vaccinees will establish chains of transmission in communities, especially in settings of poor hygiene, when population immunity levels begin to fall after immunisation ceases. Evidence from several sources suggests that this may not occur. Most convincing are studies that show polioviruses are not detected beyond three months after mass OPV campaigns in at least two countries that only use OPV in this way. However it is clear that there are significant gaps in our knowledge. These include the transmissibility of OPV-derived strains under certain ecological settings, the potential for persistently infected individuals to re-seed viruses into a community, and the molecular basis of transmissibility. Research in these areas is underway and will help develop and refine strategies for stopping polio immunisation. The potential risks and benefits of ceasing polio immunisation are such that the best available science is required to reach an informed decision.

Risks of reintroduction of polio after eradication: the vaccine origin of an outbreak of type 3 poliomyelitis

Sabin live-attenuated strains, which have proved to be the most effective tools for poliovirus eradication, could also be the source of reintroduction of polio epidemics after global eradication of wild poliomyelitis is achieved. There are still considerable gaps in our knowledge about the persistence of vaccine-derived viruses in the population and the mechanisms involved in poliovirus transmissibility, both of which are essential factors in assessing the risks posed by such strains and in designing effective strategies for the cessation of polio immunisation. In this report, we have examined virological and epidemiological aspects of an epidemic of poliomyelitis in 1968 in Poland that was shown to be associated with the use of the USOL-D-bac live-attenuated vaccine strain. Possible causes of the origin and progress of the outbreak included the pattern of virus excretion from vaccinees, mutations identified in epidemic viruses and the unique vaccination policies in Poland during the years preceding the epidemic.

The determination of freeway space using two different methods

The aim of this study was to determine the average freeway space of dentate subjects and relate this to recommended ranges for edentulous patients, also to see if any differences were observed between two different methods of measuring freeway space. The freeway space of 72 dentate subjects was measured, first using a Willis gauge, and secondly using a pair of sprung dividers. The intra- and interoperator variability was evaluated as was the reproducibility of the accuracy of both techniques. The mean freeway space using the Willis gauge was 3.3 mm, for both intra and inter operator variability, and with the sprung dividers 3.1 and 2.9 mm, respectively, with no significant difference being seen between any combination of results (P > 0.05). Individual measurements within the two measuring methods being assessed showed significant differences (P < 0.05). The mean measurements of freeway space in dentate subjects found in this study were within the recommended 2-4 mm range, however, 15% of the subjects in the study had freeway space measurements outside this range. This study would suggest that the range for freeway space measurement could more realistically be 2-7 mm.