Effect of Different Implant-Abutment Mismatches on Stress Distribution: A 3-Dimensional Finite Element Study.

Platform-switching reduces peri-implant marginal bone loss (MBL). The aim of this study was to compare the effect of platform-switching on stress within crestal bone using different implant-abutment mismatches (0.65 and 1 mm) under 2 different vertical loads (30 N vs 200 N) for implants placed in posterior jaw sites. Three-dimensional modeling software was used for an implant with a diameter of 4.5 mm and length of 13 mm. Molars were modeled using computerized tomography images of bone density in human maxilla (D3 bone) and mandible (D2 bone). Collected data were analyzed using CATIA software. In posterior mandible, stress of 30 N force with platform mismatches of 0.65 or 1 mm were 2.920 and 2.440 MPa respectively. Using 200 N force, values increased to 19.44 and 16.30 MPa. In posterior maxilla and 30 N force, stresses with mismatches of 0.65 and 1 mm were 3.77 and 3.18 MPa, respectively, increasing to 25.14 and 20.17 MPa with 200 N force. The effect can be predicted to be greatest as the mismatch increases with implants placed into lower quality bone (posterior maxilla with D3 quality).

Comparison of Osteoblastic Differentiation of Human Periodontal Ligament Stem Cells through Application of Two ß-tricalcium Phosphate Products: An in vitro Study.

Statement of the Problem: Osteoblastic differentiation of periodontal ligament stem cells (PLSCs) is essential for alveolar bone regeneration. Purpose: The purpose of this study was to compare the potential of two ß-tricalcium phosphate (ßTCP) products to induce osteoblastic differentiation of human PLSCs. Materials and Method: In this in vitro study, human PLSCs were cultured in mediums supplemented with Guidor Easy-Graft [ßTCP+polylactide-co-glycolide (PLCG)+n-methyl-2-pyrrolidone (NMP)] [Sunstar Company, Swiss] or Sorbone [ßTCP] [Meta Company, South Korea] as two alloplasts experimental groups, mesenchymal cells differentiated into osteoblasts without alloplast as positive control group, and mesenchymal cells without osteoblastic induction as negative control group. Osteoblastic differentiation was evaluated using Alizarine Red staining and spectrophotometry to assay calcium deposits and real-time polymerase chain reaction to examine expression of alkaline phosphatase (ALP) and osteopontin (OPN) antigens on day 21. Data were analyzed by using SPSS 22 software and one-way ANOVA and Bonferoni tests (p< 0.05). Results: Spectrophotometry confirmed that calcium deposits were higher in Guidor Easy-Graft group compared to Sorbone group (p< 0.001) and higher in two experimental groups than controls (p< 0.05). According to real-time polymerase chain reaction, level of ALP expression was higher in Sorbone than Guidor and the levels of Guidor, positive control and negative control were equal; OPN levels of the positive control were more than the other groups. OPN levels of Sobone, Guidor and negative control were the same. Conclusion: These findings indicated that Guidor Easy-Graft and Sorbone enhanced differentiation of human PLSCs to osteoblasts, and could be employed as appropriate bone-graft materials.

Differentiation of Bone Marrow Stem Cells in Presence of Human and Xenogeneic Acellular Dermal Matrix and Collagen Membrane: an in vitro Study.

Statement of the Problem: Predictable bone regeneration is an objective in implant and periodontal treatments and barrier membranes may play a significant role in osteogenic reconstruction and differentiation. Purpose: We compared the osteoblastic differentiation level of bone marrow stem cells in the vicinity of different barrier membranes. Materials and Method: In this experimental in vitro study, human collagen membrane (HCM; Regen), xenogeneic collagen membrane (XCM; Jason), human acellular dermal matrix (HADM; Regen), and xenogeneic acellular dermal matrix (XADM) were used in 4 groups. No membranes were used in the control group (5th group). Bone marrow stem cells with 150,000 cells/well density were added to the culture medium. Cellular differentiation was assessed through real-time quantitative reverse transcription polymerase chain reaction (QRT-PCR) for alkaline phosphatase (ALP) and osteopontin (OPN) gene expression, and Alizarin Red staining after 21 days. Data were analyzed using Kruskal- Wallis and Mann-Whitney statistical tests on SPSS 20 software (p Value< 0.05). Results: ALP gene expression was significantly higher in HCM group compared to other four groups (p< 0.009) followed by XADM, control, HADM and XCM groups, respectively (p< 0.001). OPN gene expression was significantly more prominent in HCM group compared to other groups (p< 0.01) followed by XADM group in which OPN gene was expressed significantly more than XCM group. OPN gene expression was not significantly different in HADM and control groups (p= 0.52). Light absorption rate was higher in HCM group compared with other groups (p< 0.012). Light absorption rate was not significantly different among HADM, XADM, and control groups (p> 0.05), though it was higher in XCM group (p= 0.009). Conclusion: Bone marrow stem cells show different levels of differentiation in the vicinity of different membranes. Generally, cell differentiation was more prominent in the vicinity of human collagen membrane.

Cellular Behaviors of Periodontal Ligament Stem Cells in the Presence of Bone Grafting Biomaterials, In-Vitro Study.

Periodontal regeneration through the employment of bone substitutes has become a feasible strategy in animal and clinical studies. In this regard, we aimed to compare the periodontal ligament stem cell behavior in the vicinity of various bone grafting substitutes. Three types of popular bone substitutes, including allografts (Regen), xenografts (Cerabone), and alloplasts (Osteon) were studied in this experimental survey. The cellular attachment was assessed after four hours using the MTS assay and SEM imaging. In addition, cellular proliferation was investigated after 1, 3, 5, and 7 days through MTS assay. Osteogenesis was studied after 21 days of cell culture in a differentiation medium (DM+) and a normal medium (DM-), by employing real-time PCR and alizarin red staining. The highest cellular attachment was seen in the xenograft group with a significant difference in comparison to the other grafting materials. Despite the relatively low primary attachment of cells to allografts, the allograft group showed the highest total proliferation rate, while the lowest proliferation capacity was found in the alloplast group. Osteogenesis fount to be accelerated mostly by xenografts in both mediums (DM+ and DM-) after 3 weeks, while alloplasts showed the lowest osteogenesis. This study revealed that the type of bone substitutes used in regenerative treatments can affect cellular behavior and as a whole allografts and xenografts showed better results.

In Vitro Study of the Recruitment and Expansion of Mesenchymal Stem Cells at the Interface of a Cu-Doped PCL-Bioglass Scaffold.

Developing new barrier membranes with improved biomechanical characteristics has acquired much interest owing to their crucial role in the field of periodontal tissue regeneration. In this regard, we enriched the electrospun polycaprolactone (PCL)/gelatin (Gel) membranes by adding bioglass (BG) or Cu-doped bioglass (CuBG) and examined their cellular adhesion and proliferation potential in the presence of alveolar bone marrow-derived mesenchymal stem cells (aBMSCs). The membranes were fabricated and characterized using mechanical strength, SEM, FTIR, EDX, and ICP assay. Besides, aBMSCs were isolated, characterized, and seeded with a density of 35,000 cells in each experimental group. Next, the cellular morphology, cell adhesion capacity, proliferation rate, and membrane antibacterial activity were assessed. The results displayed a significant improvement in the wettability, pore size, and Young's modulus of the PCL membrane following the incorporation of gelatin and CuBG particles. Moreover, all scaffolds exhibited reasonable biocompatibility and bioactivity in physiological conditions. Although the PCL/Gel/CuBG membrane revealed the lowest primary cell attachment, cells were grown properly and reached the confluent state after seven days. In conclusion, we found a reasonable level of attachment and proliferation of aBMSCs on all modified membranes. Meanwhile, a trace amount of Cu provided superiority for PCL/Gel/CuBG in periodontal tissue regeneration.

The Diagnosis and Treatment of a Rare Maxillary Plasmacytoma: a Case Report.

The jaw plasmacytoma is a very rare condition, which its diagnosis is difficult in clinical routine. Up to now, less than 60 cases of jaw plasmacytoma have been reported in the literature. In the present case report, we reported a rare case of jaw plasmacytoma in a 42-year-old female, which was misdiagnosed with dental granuloma and abscess. The diagnosis of plasmacytoma was done by immunohistochemistry (IHC) evaluation following a cone beam computed tomography (CBCT) assessment. The patient was treated with radiotherapy and is disease free after 2 years.

Development of reduction scenarios for criteria air pollutants emission in Tehran Traffic Sector, Iran.

Transport-related pollution as the main source of air pollution must be reduced in Tehran mega-city. The performance of various developed scenarios including BAU (Business As Usual) as baseline scenario, ECV (Elimination of carburetor equipped Vehicle), NEM (New Energy Motorcycles), HES (Higher Emission Standard), VCR (Vehicle Catalyst Replacement), FQE (Fuel Quality Enhancement), DPF (Diesel Particulate Filter) and TSA (Total Scenarios Aggregation) are evaluated by International Vehicle Model up to 2028. In the short term, the ECV, VCR, and FQE scenarios provided high performance in CO, VOCs and NOx emissions control. Also FQE has an excellent effect on SOx emission reduction (86%) and DPF on PM emissions (20%). In the mid-term, the VCR, ECV, and FQE scenarios were presented desirable mean emission reduction on CO, VOCs, and NOx. Moreover, NOx emission reduction of DPF scenario is the most common (14%). Again FQE scenario proves to have great effect on SOx emission reduction in mid-term (86%), DPF and HES scenarios on PM (DPF: 49% and HES: 17%). Finally for the long term, VCR, ECV, FQE, and NEM scenarios were shown good performance in emission control on CO, VOCs and NOx. For SOx only FQE has a good effect in all time periods (FQE: 86%) and DPF and HES scenarios have the best effect on PM emission reduction respectively (DPF: 51% and HES: 27%) compared with BAU scenario. However, DPF scenario increases 12% SOx emission in long-term (2028). It can be generally concluded that VCR and ECV scenarios would achieve a significant reduction on gaseous pollutants emission except for SOx in general and FQE scenarios have desirable performance for all gaseous pollutants in the short term and also for SOx and VOCs in long term. In addition, the DPF and HES would be desirable scenario for emission control on PM in Tehran Traffic Sector.

Comparison of ADM and Connective Tissue Graft as the Membrane in Class II Furcation Defect Regeneration: A Randomized Clinical Trial.

Background and aims. Furcally-involved teeth present unique challenges to the success of periodontal therapy and influence treatment outcomes. This study aimed to assess to compare use of ADM and connective tissue membrane in class II furcation defect regeneration. Materials and methods. 10 patient with 2 bilaterally class II furcation defects in first and/or second maxilla or man-dibular molar without interproximal furcation involvement, were selected. Four weeks after initial phase of treatment, before and thorough the surgery pocket depth (PD), clinical attachment level to stent (CAL-S), free gingival margin to stent(FGM-S) , crestal bone to stent (Crest-S), horizontal defect depth to stent (HDD-S) and vertical defect depth to stent (VDD-S) and crestal bone to defect depth measured from stent margin. Thereafter, one side randomly treated using connective tissue and DFDBA (study group) and opposite side received ADM and DFDBA (control group). After 6 months, soft and hard tissue parameters measured again in re-entry. Results. Both groups presented improvements after therapies (P & 0.05). No inter-group differences were seen in PD re-duction (P = 0.275), CAL gain (P = 0.156), free gingival margin (P = 0.146), crest of the bone (P = 0.248), reduction in horizontal defects depth (P = 0.139) and reduction in vertical defects depth (P = 0.149). Conclusion. Both treatments modalities have potential of regeneration without any adverse effect on healing process. Connective tissue grafts did not have significant higher bone fill compared to that of ADM.

Efficacy of Connective Tissue with and without Periosteum in Regeneration of Intrabony Defects.

Background and aims. Connective tissue grafts with and without periosteum is used in regenerative treatments of bone and has demonstrated successful outcomes in previous investigations. The aim of present study was to evaluate the effectiveness of connective tissue graft with and without periosteum in regeneration of intrabony defects. Materials and methods. In this single-blind randomized split-mouth clinical trial, 15 pairs of intrabony defects in 15 patients with moderate to advanced periodontitis were treated by periosteal connective tissue graft + ABBM (test group) or non-periosteal connective tissue graft + ABBM (control group). Probing pocket depth, clinical attachment level, free gingival margin position, bone crestal position, crest defect depth and defect depth to stent were measured at baseline and after six months by surgical re-entry. Data was analyzed by Student's t-test and paired t-tests (α=0.05). Results. Changes in clinical parameters after 6 months in the test and control groups were as follows: mean of PPD reduction: 3.1±0.6 (P<0.0001); 2.5±1.0 mm (P<0.0001), CAL gain: 2.3±0.9 (P<0.0001); 2.2±1.0 mm (P<0.0001), bone fill: 2.2±0.7 mm (P<0.0001); 2.2±0.7 mm (P<0.0001), respectively. No significant differences in the position of free gingival margin were observed during 6 months compared to baseline in both groups. Conclusion. Combinations of periosteal connective tissue graft + ABBM and non-periosteal connective tissue graft + ABBM were similarly effective in treating intrabony defects without any favor for any group. Connective tissue and perio-steum can be equally effective in regeneration of intrabony defects.

Blood flow vectoring control in aortic arch using full and partial clamps.

BACKGROUND: Early diagnosis and treatment of aneurysm plays an important role in reducing the mortality risk of rupture. The aneurysm is a complex phenomenon and caused by different reasons, such as arteriosclerosis and heredity. In addition, pressure and Wall Shear Stress are two known factors influencing the establishment of an aneurysm. The aim of this study is to investigate the effect of using a full or partial clamp to control the blood flow streamlines and hence the location of stress concentration in a clean configuration of aorta. The main question is how to control the stresses distribution in order to reduce the possibility of aneurysm growth with less negative effects on the other sides. METHODS AND RESULTS: A simple form of aortic arch with three branches is considered to simulate the effect of changing blood flow streamlines directions. A parameter study has been performed on the main characteristics of clamp, i.e. size, location, and the percentage of coverage. The Shear Stress Transport model is employed to simulate steady-state Newtonian blood flow when the Reynolds number is about 6500. Simulations are conducted using the commercial CFD solver ANSYS Fluent. The obtained results show that the location of clamp is more effective than the size. It is also found that increasing the depth of clamp has a negative impact on mean velocity field and hence on stress concentration. CONCLUSION: The present results demonstrate that the Blood Flow Vectoring Control (BFVC) can change the main form of flow streamlines and consequently the distributions of pressure and Wall Shear Stress. A partial clamp leads to better results.

Relationship between osteoporosis and periodontal disease: review of the literature.

OBJECTIVE: Osteoporosis is a skeletal disease characterized by reduction in bone mass and micro architectural changes in the bone, which leads to increased bone fragility. The gold standard for the diagnosis of osteoporosis is the measurement of bone mineral density (BMD) by dual energy x-ray absorptiometry (DXA). Periodontal disease is a chronic destructive disease which can occur in adults, young people and children. Periodontal pathogens cause inflammation of the gingiva which is called gingivitis. When periodontal tissue destruction and alveolar bone loss happen, it is called periodontitis. Since both osteoporosis and periodontal diseases are bone destructive diseases, it has been hypothesized that osteoporosis could be a risk factor for the progression of periodontal disease. The aim of this study is to review the articles assessing the relationship between osteoporosis and periodontitis MATERIALS AND METHODS: In this review, articles were selected from PubMed between January of 1998 and June 2010. Amongst 508 articles identified from the electronic search, 17 articles were selected for a full-text reading based on the inclusion and exclusion criteria. RESULTS: Among the 17 studies focused on, 11 studies showed a positive relation between osteoporosis and periodontal disease and the six remaining studies found no significant relation between osteoporosis and periodontal disease. CONCLUSION: These data indicate a greater propensity to lose alveolar bone in subjects with osteoporosis, especially in subjects with preexisting periodontitis. This would indicate that osteoporosis or low systemic BMD should be considered a risk factor for periodontal disease progression.

Evaluation of a new solid boundary implementation in the lattice Boltzmann method for porous media considering permeability and apparent slip.

The accuracy of solid wall treatment in the lattice Boltzmann method (LBM) simulation of porous structures affects different hydraulic parameters including integral properties, such as permeability, or local phenomena, such as apparent slip. Based on an analysis of the advantages and disadvantages of the current methods, a new technique is introduced for exact boundary extraction from binary representation. Using this technique, the LBM model can simultaneously benefit from the advantages of existing approaches, i.e. the real micro-/nanostructure obtained with X-ray computed tomography, and a reduction in the resolution requirement. To evaluate the technique, permeability and slip length on the solid walls are investigated for a porous gas diffusion layer. The results show acceptable accuracy improvement balanced with computational costs.