Biomechanical performance of resin composite on dental tissue restoration: A finite element analysis.

This study investigates the biomechanical performance of various dental materials when filled in different cavity designs and their effects on surrounding dental tissues. Finite element models of three infected teeth with different cavity designs, Class I (occlusal), Class II mesial-occlusal (MO), and Class II mesio-occluso-distal (MOD) were constructed. These cavities were filled with amalgam, composites (Young's moduli of 10, 14, 18, 22, and 26 GPa), and glass carbomer cement (GCC). An occlusal load of 600 N was distributed on the top surface of the teeth to carry out simulations. The findings revealed that von Mises stress was higher in GCC material, with cavity Class I (46.01 MPa in the enamel, 23.61 MPa in the dentin), and for cavity Class II MO von Mises stress was 43.64 MPa, 39.18 MPa in enamel and dentin respectively, while in case of cavity Class II MOD von Mises stress was 44.67 MPa in enamel, 27.5 in the dentin. The results showed that higher stresses were generated in the non-restored tooth compared to the restored one, and increasing Young's modulus of restorative composite material decreases stresses in enamel and dentin. The use of composite material showed excellent performance which can be a good viable option for restorative material compared to other restorative materials.

Biomechanical analysis of printable functionally graded material (FGM) dental implants for different bone densities.

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 µÎµ) in low-density (0.7-0.8 g/cm3) bone, however, FGM implants produced optimal strain (990-1280 µÎµ) in the high-density bone (0.9-1 g/cm3) 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.

Journal Club is a way forward to adopt Evidence Based Practice among dental House Officers.

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.

Comparing Oral Health-related Quality of Life (OHIP-14) and Masticatory Efficiency with Complete Denture Treatment.

OBJECTIVE: To measure impact of oral health in complete denture wearers and its effects on masticatory efficiency with new complete dentures over the period of three months. STUDY DESIGN: Experimental study design. PLACE AND DURATION OF STUDY: Department of Prosthodontics, Bahria University Medical and Dental College, Karachi, Pakistan from September 2019 to December-2019. METHODOLOGY: Oral health impact profile (OHIP) was used to measure the oral health impact; and chewing gum method was used to measure the masticatory efficiency in this study. All participants were old denture wearers having the experience of at least 3 years and requiring new set of complete dentures. A total of 31 patients were asked to chew the gum from the routine site of mastication for 20 seconds. The weight reduction corresponded to the masticatory efficiency. The OHIP-14 score and masticatory efficiency was recorded at baseline and after three months of complete denture treatment. The data was analysed on SPSS version 23. RESULTS: The average values of masticatory efficiency were significantly reduced from median (IQR) value 1.20 (1.20-1.30) to 0.90 (0.70-0.90), respectively (p <0.001). There was a moderate positive correlation for physical pain and disability (0.407 and 0.455) at baseline and strong positive correlation (0.771 and 0.825) after 3 months of complete denture treatment with p-value <0.001 on OHIP-14 scale. CONCLUSION: Statistically significant improvement was observed in both quality of life and masticatory efficiency after 3 months of treatment with conventional complete dentures. Masticatory efficiency was highly correlated with all subscales of OHIP-14 after treatment. Key Words: Complete denture treatment, Masticatory efficiency, Oral health impact profile-14 (OHIP-14).

Safety of returning patients immediately to their originating hospitals after primary percutaneous coronary intervention.

INTRODUCTION: The objective of this study was to evaluate the safety and feasibility of the immediate return of patients with ST-elevation myocardial infarction (STEMI) to their originating hospitals after primary percutaneous coronary intervention (PPCI). METHODS: This was a prospective study, conducted between January 2014 and December 2017. All patients with STEMI who were transferred for PPCI and returned back to their referring hospitals (RB group) were included and compared to the onsite STEMI population (OS group). Patient's demographics, PPCI data, bleeding and adverse cardiovascular events (ACEs) occurring during transfer, hospital stay, and at 1-month follow-up were recorded. RESULTS: A total of 156 patients in the OS group were compared against 350 patients in the RB group. We found that first medical contact to balloon time and onset of symptoms to balloon time were significantly longer in the RB group than in the OS group [110 ± 67 min vs. 46 ± 35 min (p < 0.0001) and 366 ± 300 min vs. 312 ± 120 min (p = 0.04)], respectively. There were no differences between the RB and OS groups in in-hospital ACEs: 0.3% versus 0% (p = 0.8) for death, 0.3% versus 0.6% (p = 0.79) for reinfarction, 0.6% versus 2% (p = 0.72) for bleeding, and no reported cases of repeat revascularization; and 30-day ACEs: 0.3% versus 0.6% (p = 0.82) for death, 0.3% versus 1.2% (p = 0.68) for reinfarction, 0.6% versus 2% (p = 0.74) for bleeding, and 1.1% versus 1.2% (p = 0.9) for repeat revascularization. CONCLUSION: The immediate return of patients with noncomplicated STEMI after PPCI to their referring hospitals is safe and feasible, and can be used as part of an effective reperfusion strategy.

A novel design, analysis and 3D printing of Ti-6Al-4V alloy bio-inspired porous femoral stem.

The current study is proposing a design envelope for porous Ti-6Al-4V alloy femoral stems to survive under fatigue loads. Numerical computational analysis of these stems with a body-centered-cube (BCC) structure is conducted in ABAQUS. Femoral stems without shell and with various outer dense shell thicknesses (0.5, 1.0, 1.5, and 2 mm) and inner cores (porosities of 90, 77, 63, 47, 30, and 18%) are analyzed. A design space (envelope) is derived by using stem stiffnesses close to that of the femur bone, maximum fatigue stresses of 0.3σys in the porous part, and endurance limits of the dense part of the stems. The Soderberg approach is successfully employed to compute the factor of safety Nf > 1.1. Fully porous stems without dense shells are concluded to fail under fatigue load. It is thus safe to use the porous stems with a shell thickness of 1.5 and 2 mm for all porosities (18-90%), 1 mm shell with 18 and 30% porosities, and 0.5 mm shell with 18% porosity. The reduction in stress shielding was achieved by 28%. Porous stems incorporated BCC structures with dense shells and beads were successfully printed.

A comprehensive analysis of bio-inspired design of femoral stem on primary and secondary stabilities using mechanoregulatory algorithm.

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.

Influence of functionally graded pores on bone ingrowth in cementless hip prosthesis: a finite element study using mechano-regulatory algorithm.

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 [Formula: see text]m 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 [Formula: see text]m 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 [Formula: see text]m 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.

Hepatic estrogen receptor α is critical for regulation of gluconeogenesis and lipid metabolism in males.

Impaired estrogens action is associated with features of the metabolic syndrome in animal models and humans. We sought to determine whether disruption of hepatic estrogens action in adult male mice could recapitulate aspects of the metabolic syndrome to understand the mechanistic basis for the phenotype. We found 17ß-estradiol (E2) inhibited hepatic gluconeogenic genes such as phosphoenolpyruvate carboxykinase 1 (Pck-1) and glucose 6-phosphatase (G6Pase) and this effect was absent in mice lacking liver estrogen receptor α (Esr1) (LERKO mice). Male LERKO mice displayed elevated hepatic gluconeogenic activity and fasting hyperglycemia. We also observed increased liver lipid deposits and triglyceride levels in male LERKO mice, resulting from increased hepatic lipogenesis as reflected by increased mRNA levels of fatty acid synthase (Fas) and acetyl-CoA carboxylase (Acc1). ChIP assay demonstrated estradiol (E2) induced ESR1 binding to Pck-1, G6Pase, Fas and Acc1 promoters. Metabolic phenotyping demonstrated both basal metabolic rate and feeding were lower for the LERKO mice as compared to Controls. Furthermore, the respiratory exchange rate was significantly lower in LERKO mice than in Controls, suggesting an increase in lipid oxidation. Our data indicate that hepatic E2/ESR1 signaling plays a key role in the maintenance of gluconeogenesis and lipid metabolism in males.

2,3-Dihydro-1H-pyrrolizin-1-one.

There are two nearly identical mol-ecules in the asymmetric unit of the title compound, C(7)H(7)NO. The mol-ecules are nearly planar (r.m.s. deviations of 0.025 and 0.017 Å) and oriented at a dihedral angle of 28.98 (3)°. The two mol-ecules are linked by a C-H⋯O hydrogen bond. In the crystal, weak inter-molecular C-H⋯O hydrogen bonds link the mol-ecules into zigzag chains along the c axis.

Custom made alar stents for nostril stenosis: a 24-month evaluation.

Nostril stenosis is an uncommon deformity and its aetiology is variable. The shape alteration and nostril asymmetry may have negative aesthetic and functional effects on nostril stenosis patients. Five patients were included in this study and followed up for 24 months; four of these had congenital nostril stenosis and one had an acquired deformity. Alar stent dilators were constructed from measured diameter of the affected nostril/s. The congenital nostril stenosis patients initially received a customised chairside soft nasal dilator (CCSND), which were later replaced with a customised laboratory rigid nasal dilators (CLRND). Treatment outcomes were evaluated using a questionnaire and a visual analogue scale to assess improvements in nostril breathing, comfort, appearance and satisfaction of the treatment provided by both types of dilators. There was improvement in nostril diameter with an average expansion of 7mm and this was stable at the desired diameter. The overall number of stents used to expand the tissues to the desired dimension ranged from 3 to 8 stents. Alar stent therapy is a conservative method to expand nostril tissues and has successfully maintained the nostril diameter for both acquired and congenital stenosis. This improvement in all parameters and the patients' satisfaction would make the custom-made nostril dilator in particular the CLRND a satisfactory treatment modality for congenital and acquired nostril stenosis.