Search

Graphical abstract Abstract Traditionally, high stiffness hip prostheses are associated with aseptic loosening. Hence, the effects of stiffness, coating length, and interference press fit on load sharing and micro-movements are investigated for a better understanding from a mechanical perspective. A simplified 3D model of the femur and prostheses composed of cobalt chrome (CoCr), titanium (Ti), and glass/polypropylene (Twintex [0] 2nT) composite are constructed. Three interference fits corresponding to 5, 25, and 50 µm are used with half, three-quarter, and full lengths of coating that are used to assemble the prostheses with bones to investigate micro-movements at the bone-prosthesis interfaces, interfacial failure, and stress transfer to the bone. The reaction forces of body weight and muscular forces in the femur are used to simulate the FE model. The results indicate that the CoCr and Ti prostheses exhibit low micro-movements at the proximal end and high micro-movements at the distal end and vice versa for the Twintex [0] 2nT composite prosthesis. Uniformity of stress transfer to the bone along the prosthesis efficiently increases with increases in the coating lengths and interference press fits for all the cases. A fully coated length of Twintex [0] 2nT composite prosthesis with a 50-µm interference press fit provides the most efficient load sharing and stress transfer to the bone and micro-movements at the bone–prosthesis interface. [ABSTRACT FROM AUTHOR]

Titanium porous cellular microstructures are commonly used in bone mimetic implants. The orientations of the internal strut architectures of these microstructures affect the mechanical performance under various loads; however, poor architectural designs may result in their failure. Three-dimensional (3D) finite element models of cubic, diamond, and body-centered cubic (BCC) geometries were constructed with 1 – 4 numbers of unit cells and 4–10-mm unit cell size. Mechanical testing of the finite models of the cubic, diamond, and BCC structures with porosities of 20–90% was performed under compression, bending, and torsional loads. The BCC structure showed moderate and relatively isotropic mechanical properties compared with those of the diamond and cubic structures. A design space for a BCC porous structure with a porosity of 40–65% was estimated to model a complete porous stem to mimic the bone properties. Furthermore, the stems with the determined porous mechanical properties of the BCC microstructures with 20–90% porosities were tested under physiological loading conditions. It was found that a porosity of 47.3% of the BCC structure exhibits the closest stiffness (469 N/mm) to an intact bone (422 N/mm). This was predicted by our suggested design space of the porosity. [ABSTRACT FROM AUTHOR]

Cementless hip prostheses with porous outer coating are commonly used to repair the proximally damaged femurs. It has been demonstrated that stability of prosthesis is also highly dependent on the bone ingrowth into the porous texture. Bone ingrowth is influenced by the mechanical environment produced in the callus. In this study, bone ingrowth into the porous structure was predicted by using a mechano-regulatory model. Homogenously distributed pores (200 and 800 μm in diameter) and functionally graded pores along the length of the prosthesis were introduced as a porous coating. Bone ingrowth was simulated using 25 and 12 μm micromovements. Load control simulations were carried out instead of traditionally used displacement control. Spatial and temporal distributions of tissues were predicted in all cases. Functionally graded pore decreasing models gave the most homogenous bone distribution, the highest bone ingrowth (98%) with highest average Young’s modulus of all tissue phenotypes approximately 4.1 GPa. Besides this, the volume of the initial callus increased to 8.33% in functionally graded pores as compared to the 200 μm pore size models which increased the bone volume. These findings indicate that functionally graded porous surface promote bone ingrowth efficiently which can be considered to design of surface texture of hip prosthesis. [ABSTRACT FROM AUTHOR]

Conventional dense titanium (Ti) implants cause stress shielding, aseptic loosening and implant failure. This study investigates the effects of porous dental implants (63% porous and 77% porous) with different neck angles (straight, 10° and 15°) on the healthy and osteoporotic bone under different loading conditions (axial load and buccolingual load). Simulation results showed that in cortical bone, the von Mises stresses are greater in the case of 77% porous Ti implant A (straight) as compared to implant B and C (10°, 15° angled neck). Overall, in the case of the osteoporotic bone, the strains are higher than the healthy bone. [ABSTRACT FROM AUTHOR]

Radial bone shaft fractures are commonly treated with bone plates. Flexible bone plates made of fiber-reinforced polymer composites have advantages over complications, such as stress shielding, corrosion, harmful ions, X-ray artifacts, resulting from metallic bone plates. Postoperative rehabilitation exercise is an important factor influencing the healing outcomes of radial bone fractures. A finite element model of radial shaft fracture was treated with Twintex [0] 2nT composite bone plate and six stainless steel bicortical screws. Axial compression (10 N), bending moment (0.1 Nm), and torsion (0.1 Nm) as single, combined, and alternative loads (10% loads of daily activities) were used in the finite element study. A mechano-regulation algorithm based on deviatoric strain was used to predict the healing of bone fractures. The healing performance and bending stiffness were evaluated and compared to estimate the healing status of bone fractures. The best exercise mode, which gave the highest healing performance (68%) and bending stiffness (89%), was suggested. These results can be successfully utilized for the design of healing devices for the rehabilitation of fractured bones. [ABSTRACT FROM AUTHOR]

Energy is a crucial factor and a capital of a country's resources leading indicator. World's energy focus is shifting towards alternate renewable, cheap and environment-friendly resources that can provide long-term sustainability for survival. Due to the fossil fuels depletion and their ever-growing cost, the need to shift focus towards renewable energy resources has increased a lot. To overcome the above-said problems, there is a need to look for a feasible and robust solution for thermal applications in remote areas. Biomass gasification proved to be one of the most efficient and clean waste-to-energy conversion processes in contrast to direct combustion of agricultural waste. Other than controlled burning of biomass, it can be subjected for different purposes like a thermal, synthesis of ethanol, engine running, and for fuel cell applications. An excessive amount of impurities like char, ash, tar, and particulate matter are making these syngas non-feasible for thermal or engine applications. To overcome the above-stated problem, a downdraft gasifier with cyclone separator and hybrid biomass filter was fabricated using locally available materials in the workshop of the Dept. of Farm Machinery and Power at the University of Agriculture, Faisalabad. Uniform distribution of 2.54-5.08 cm2 sizes of feedstock was used for gasification. Air was used as a gasifying agent. The reactor capacity was 0.19 m3. The values of performance parameters for wood waste and corncobs were recorded as fuel consumption rate (0.002195, 0.002323) kg-s-1, the volume of gas produced (24.56, 26.33) m3, operating time (5480, 5164) s, cleaning unit efficiency (81.79, 79.9) % and gas yield (2.04, 2.19) m³-kg-1. [ABSTRACT FROM AUTHOR]

By analyzing the impact energy effects, impact resistance of CFRP composite plate is investigated using LS DYNA. For accurate simulations, a finite element model is developed and validated through comparison of time-force curves and damage profiles from simulations and experiments. Numerical simulations are performed to find the safe, critically safe, and failure energies for four different conditions: constant velocity, constant mass, constant energy, and different energies. Results show that for constant velocity, constant mass, and different energy conditions, the composite plates fail at 77.492 J, 74.649 J, and 75.990 J, respectively, and no failure was observed for constant energy conditions. [ABSTRACT FROM AUTHOR]

OBJECTIVES: To find an association of dental anxiety with age, education status, previous dental experience and reason for visiting dentist in Bahria Dental University Hospital, Karachi and to assess the MDAS score of male and female patients visited to dental OPD. METHODOLOGY: All those patients who were reported to oral medicine OPD, between the age group of 18-65 years were included. The patients with neuro-psychological and depressive symptoms for less than six weeks and had bereavement in the last six weeks were excluded from the study. Total 550 MDAS (modified dental anxiety scale) questionnaires were distributed from which 512 questionnaires were completed and entered on SPSS version 23 for data analysis. P value < 0.05 was considered as statistically significant. RESULTS: The prevalence of anxiety was found to be 31(6.1%). The mean MDAS score was 10.53+5.25. In this study; 18-30 and 31-45 years of patients were equally anxious (35%); on the other hand intermediate/graduate patients were found to be more (64.5%) anxious as compare to other educational levels. Patients having positive experience (93.5%) of past dental treatment were more anxious. Upon MDAS responses; majority of participants (n=29-5.7%) were extremely anxious during local anesthesia. Male participants were found to be very anxious then female participants. CONCLUSION: Dental anxiety was associated with educational status and visited to dentists for RCT. MDAS score was found more in male patients as compare to female patients. The dental procedures in which injection or anesthesia was used made the patients more anxious according to MDAS score.

Metallic implants with high Young's moduli are used to treat long-bone fractures; however, they cause stress shielding and prevent bones from attaining their original strength. Thus, flexible composite implants have been designed to enhance tissue development without stress shielding. Herein, 3D-printed composite bone plates with different Young's moduli were designed, and their effects on 3D models of long-bone fractures were analysed. A biphasic mechano-regulation algorithm, coupled with cell diffusion and tissue phenotype activities, was developed using a Python script to analyse bone-healing patterns for 112 days after surgery. A composite bone plate (Young's modulus, 40 GPa) showed the best healing performance (100%), compared with a stainless-steel bone plate (70%). Further, cell and tissue development using bone plates with different Young's moduli under different loading conditions are presented. [Display omitted] [ABSTRACT FROM AUTHOR]

OBJECTIVE: To assess unreported cases of needle stick injuries (NSIs) and to find association between awareness, attitude, practices with unreported odds of NSIs. It was hypothesized that more than 50% NSIs are unreported. METHODOLOGY: It was cross sectional study design executed in Karachi among the dental care providers from July - September 2018. The calculated sample size was 281 which was augmented as 396. Total 312 questionnaires were completely filled. The data was analyzed on SPSS version 23. Association between categorical variable were assessed by Chi square/ Fischer exact test. RESULTS: Total n=195(62.5%) subjects experienced NSIs during clinical practice; from which n=110(56.4%) were unreported and n=85(43.5%) were reported cases in individual’s working setup. Majority of the subjects were aware of the harms of NSIs but not reporting the cases in clinical settings. From the to tal sample (n=231-74%) were aware of the needle safety device but (n=139-60%) were not reporting the incidence at p-value of 0.043-graph-1. Total (n=294-92%) participants were in favor of the need of strong reporting system of NSIs. On the other hand; majority of the study participants were practicing the preventive measures against NSIs but more than 50% were not reporting the NSIs; there was significant difference found for wearing gloves for disposing contamination and bent needle before dispose but not reporting the NSIs at p-value of 0.012 and 0.003 respectively CONCLUSION: It was inferred that more than 50% needle stick injury cases were unreported among dental personnel despite of having sufficient awareness, attitude and practices towards safe clinical practice.

PurposeDeletion of Glutathione S-Transferase Theta 1 (GSTT1) encoding gene is implicated in breast cancer susceptibility, clinical outcomes, and survival. Contradictory results have been reported in different studies. The present investigation based on a representative Pakistani population evaluated the GSTT1-absent genotype in breast cancer risk and prognosis.MethodsA prospective study comprising case-control analysis and case series analysis components was designed. Peripheral blood samples were collected from enrolled participants. After DNA extraction, GSTT1 genotyping was carried out by a multiplex PCR with β-globin as an amplification control. Association evaluation of GSTT1 genotypes with breast cancer risk, specific tumor characteristics, and survival were the primary endpoints.ResultsA total of 264 participants were enrolled in the molecular investigation (3 institutions). The study included 121 primary breast cancer patients as cases and 143 age-matched female subjects, with no history of any cancer, as controls. A significant genetic association between GSTT1-absent genotype and breast cancer susceptibility (p-value: 0.03; OR: 2.13; 95% CI: 1.08-4.29) was reported. The case-series analysis showed lack of association of GSTT1 genotypes with menopause (p-value: 0.86), tumor stage (p-value: 0.12), grade (p-value: 0.32), and size (p-value: 0.07). The survival analysis revealed that GSTT1-absent genotype cases had a statistically significant shorter overall survival (OS) than those with the GSTT1-present genotype cases (mean OS: 23 months vs 33 months). The HR (95% CI) for OS in patients carrying GSTT1-absent genotype was 8.13 (2.91-22.96) when compared with the GSTT1-present genotype.ConclusionsThe present study is the first report of an independent significant genetic association between GSTT1-absent genotype and breast cancer susceptibility in a Pakistani population. It is also the foremost report of the association of this genotype with OS in breast cancer cases. Upon further validation, GSTT1 variation may serve as a marker for devising better population-specific strategies. The information may have translational implications in the screening and treatment of breast cancers.

• Fatigue study of biodegradable magnesium wire–polylactic acid (Mg/PLA) composites. • Simulated body fluid conditions used, accelerating pitting corrosion. • Mg/PLA composites implants found safe under physiological loading conditions. • Experiment coupled Finite Element Analysis of bone healing used. • Fatigue life can further be improved by using non-degradable material near holes. This study investigated the fatigue life of biodegradable magnesium wire–polylactic acid (Mg/PLA) composite implants during the initial patient rehabilitation period under physiological loads through experimental and finite element methods. Under a simulated body fluid condition, the fatigue life was observed to be completely affected by material degradation, which accelerated the pitting corrosion of the composite bone plate. The mechanical behaviour of Mg/PLA composite bone plate was investigated under physiological loading conditions for the case of a tibial fracture with a 3 mm gap. A three-point bending fatigue test setup was employed to validate the fatigue characteristics of composite specimens. Finally, to alleviate the generated stress and enhance the fatigue resistance of fully biodegradable composites, a hybrid composite bone plate is proposed. At the screw section, the hybrid composite is partly composed of a comparatively more fatigue-safe non-degradable glass–polypropylene composite, which improves the healing performance of the fractured tibia. [ABSTRACT FROM AUTHOR]

The coated porous section of stem surface is initially filled with callus that undergoes osseointegration process, which develops a bond between stem and bone, lessens the micromotions and transfers stresses to the bone, proximally. This phenomenon attributes to primary and secondary stabilities of the stems that exhibit trade-off the stem stiffness. This study attempts to ascertain the influence of stem stiffness on peri-prosthetic bone formation and stress shielding when in silico models of solid CoCr alloy and Ti alloy stems, and porous Ti stems (53.8 GPa and 31.5 GPa Young's moduli) were implanted. A tissue differentiation predictive mechanoregulation algorithm was employed to estimate the evolutionary bond between bone and stem interfaces with 0.5-mm- and 1-mm-thick calluses. The results revealed that the high stiffness stems yielded higher stress shielding and lower micromotions than that of low stiffness stems. Contrarily, bone formation around solid Ti alloy stem and porous Ti 53.8 GPa stem was augmented in 0.5-mm- and 1-mm-thick calluses, respectively. All designs of stems exhibited different rates of bone formation, diverse initial micromotions and stress shielding; however, long-term bone formation was coherent with different stress shielding. Therefore, contemplating the secondary stability of the stems, low stiffness stem (Ti 53.8 GPa) gave superior biomechanical performance than that of high stiffness stems. [ABSTRACT FROM AUTHOR]

The present study was carried out to evaluate the antidiabetic activity of Vinca rosea methanolic whole plant extracts in alloxan induced diabetic rats for 14 days. The methanolic whole plant extract at high dose (500 mg/kg) exhibited significant anti-hyperglycemic activity than whole plant extract at low dose (300 mg/kg) in diabetic rats. The methanolic extracts also showed improvement in parameters like body weight and lipid profile as well as regeneration of β-cells of pancreas in diabetic rats. Histopathological studies reinforce the healing of pancreas, by methanolic Vinca rosea extracts, as a possible mechanism of their antidiabetic activity.

The long-term success of a dental implant is related to the material and design of the implant, and bone density. Conventional implants cause stress-shielding due to a mismatch between the implant and bone stiffness. Functionally graded porous materials and designs are a great choice for the design of implants to control the local stiffness at a certain location to meet the biomechanical requirements. The purpose of this study is to analyze five designs of axial and radial functionally graded materials (FGM) implants besides the conventional implant and conical and cylindrical shapes that were simulated with five different bone densities. The results showed that strain in bone increased with a decrease in cancellous bone density. The shape of the implant did not play an important role in strain/stress distribution. Conventional implants showed optimal strain (1000-2240 με) in low-density (0.7-0.8 g/cm 3 ) bone, however, FGM implants produced optimal strain (990-1280 με) in the high-density bone (0.9-1 g/cm 3 ) as compared to conventional implants. The proposed designs of FGM implants have the potential to address the complications of conventional implants in high-density bone., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022 Elsevier Ltd. All rights reserved.)

Objectives: To identify the improvement in knowledge, presentation skills, critical skills and self-directed learning process during Journal Club platform amidst dental house officers of 2018, 2019 and 2020 after completing one year house job training at Bahria dental College Karachi., Methods: This cross-sectional study was conducted from Dec- 2018 till Dec-2020. The six items were asked about perception of change for evidence-based process of (knowledge, cognitive, affective and participant domains) after completion of house job training by each cohort. The responses were noted on three point likert scale as agree, neutral and disagree. Total 150 questionnaires were distributed in three cohorts. The SPSS version 23 was used. P-value < 0.05 was considered as statistically significant., Results: Total n=145 house officers had completed the proforma with response rate of 96.65%. The mean age was 24.45 ± SD 0.63 among three groups. There were n=20(14%) males and n=125(86%) females. There was improvement found for knowledge acquisition about relevant literature search among all three groups. Regarding knowledge acquisition of bio-statistics; majority of subjects n=26 (52%) in 2020 group had reported no change and in 2019 cohort n=23(48%) were agreed. Majority n=21(44%) of house officers had reported no change when asked as JC helped in critical thinking in year 2019., Conclusion: Knowledge acquisition about relevant literature search, presentation and confidence skills were improved but no significant changes were found in knowledge of biostatistics and critical thinking skills. JC is a convincing platform to learn evidence-based process amid dental house officers., Competing Interests: Conflict of Interest: None., (Copyright: © Pakistan Journal of Medical Sciences.)