Extent Of Extrusion Research Articles

Analysis of Deformations of the Tunnel Excavation Face via Simplified Calculation Methods

The stability of the excavation face during the excavation of a tunnel is necessary to safeguard the lives of workers and to guarantee regular and rapid progress of the works. In this paper, the stability conditions of the tunnelling face were analysed using simplified numerical calculation methods (one-step approach) and analytical methods, in order to evaluate the extrusion of the tunnelling face as a representative quantity of the mechanical behaviour of the rock ahead of it. A comparison between the numerical method and the hemispherical method was illustrated, which was able to demonstrate how the latter can be used with high reliability in this type of study. An extensive parametric analysis of the typical conditions encountered in the excavation of tunnels in weak rock made it possible to determine the extent of the face extrusion and the effect on it of the main considered geometric and geomechanical parameters. Thanks to the comparison of the extrusion values obtained from the calculation with the limit value indicated by the scientific literature, it is possible to arrive at a rapid assessment on the stability of the face. A specific study on the role of the pressure applied to the face on the extent of the extrusion then made it possible to understand how to proceed to define the intensity of the main stabilisation systems (TBM thrust and longitudinal fiberglass bolts) to avoid the risk of collapse of the excavation face.

WEIGHT BEARING 3-D JOINT SPACE WIDTH DISTRIBUTION AT THE KNEE VARIES ACCORDING TO LOCATION AND EXTENT OF MENISCAL EXTRUSION: A MOST INVESTIGATION

Quantitative 3-D measurement of joint space width (JSW) from weight bearing computed tomography (WBCT) allows analysis of knee tibiofemoral compartments in a loaded stance without subregional constraints on analysis. The relationship between 3-D JSW distribution and meniscal extrusion is yet to be established. To demonstrate topographic variations in 3-D JSW distribution at the knee derived from WBCT imaging data according to meniscal extrusion location and extent. WBCT knee imaging was acquired at the 144-month visit of the Multicenter Osteoarthritis Study (MOST). A subset of individuals had medial and lateral meniscal extrusion grading according to the MRI Osteoarthritis Knee Score to identify medial extrusion of the medial meniscus (MMmed), anterior extrusion of the medial meniscus (MMant), anterior extrusion of the lateral meniscus (LMant), and lateral extrusion of the lateral meniscus (LMlat). The extent of extrusion was graded as 0: <2 mm; 1: 2 to 2.9 mm, 2: 3 to 4.9 mm; and 3: >5 mm. After semi-automatic segmentation of 663 baseline knees, joint space mapping was performed to create 3-D JSW maps for each knee registered to a template surface. Statistical parametric mapping (SPM) was performed using a general linear model to test the dependence of 3-D JSW distribution on each of meniscal extrusion type in turn. SPM results were plotted on the canonical joint surface, with unmasked regions demonstrating the topographic difference in JSW for each increment in extrusion score. 568 knees from 330 participants had meniscal extrusion grading available. Participants (178 female) had mean ± SD age 62.0 ± 9.3 years, body mass 82.2 ± 17.4 kg, height 170 ± 9.5 cm, and BMI 28.3 ± 4.8 kg/m2. Analysed knees were bilateral for 238 participants and unilateral for 92 participants. For MMmed (cohort score range 0-3), the central-to-posterior medial compartment had significantly lower JSW by up to 0.4 mm for each increment in meniscal extrusion grade. Both MMmed and MMant (score range 0-3) were associated with a small region of similarly significantly lower JSW along the medial margin of the lateral compartment, but also with significantly greater JSW at the anterior medial compartment of up to 0.6 mm per grade. The posterior medial joint space was significantly narrower (up to 3 mm) comparing knees with LMant scores of 0 vs 1. This same magnitude of narrowed JSW was detected along the periphery of the lateral joint space comparing grades in the lateral tibiofemoral compartment, but this was not statistically significant. LMlat (score range 0-2) was associated with a trend for greater reduction in JSW in the central lateral compartment of up to 0.5 mm per grade, but this was not statistically significant. Direction of meniscal extrusion is represented by the black arrowhead in the figure. Both medial and anterior extrusion of the medial meniscus are associated with significant reduction in JSW at the medial margin of the lateral joint space and widening of the anterior margin, likely from a posteromedial shift of the femoral condyles with respect to the tibia. Medial extrusion of the medial meniscus is also associated with narrowed JSW in the central to posterior medial joint space, likely as a direct effect of the loss of meniscal hoop tension. Anterior (but not lateral) extrusion of the lateral meniscus is associated with significantly lower JSW in the posterior medial joint space. These findings confirm that the extent and location of meniscal extrusion are key factors in weight bearing 3-D JSW distribution.

Comparison of calcium hydroxide extrusion with syringe versus spiral filler delivery: A pilot study.

This study aimed to evaluate Ca(OH)2 extrusion in relation to delivery technique, apical size and depth of placement. Plastic blocks had j-shaped canals shaped to apical sizes #35 and #45 (n = 32 each). Amounts of calcium hydroxide extrusion was determined relative to apical taper, depth of insertion and whether syringe or spiral filler at 500 rpm was used. Blocks were immersed in pH-sensitive gel and observed for colour change. Extent of extrusion was expressed in mm2 . Extrusion occurred in 48/64 of the samples. At 3 mm from the canal terminus, the device affected the frequency of extrusion, with syringe placement causing extrusion significantly (P < 0.01) more frequently, irrespective of apical size. Extrusion was significantly greater at 2 mm short of the canal terminus (median 27.44 mm2 ) compared to 3 mm (median 19.69 mm2 ). Under in-vitro conditions, a spiral filler at 500 rpm, 3 mm short of the apex, minimised extrusion of Ca(OH)2 from root canals.

Surgical extrusion of a maxillary premolar after orthodontic extrusion: a retrospective study.

ObjectivesCrown-root fracture and cervical caries in maxillary premolars constitute a challenge in cases of subgingival placement of restoration margins. Surgical extrusion has been practiced successfully in permanent anterior teeth. The aim of the present retrospective study was to assess the clinical outcome of surgical extrusion after orthodontic extrusion in maxillary premolars.Materials and MethodsTwenty-one single, tapered root maxillary premolars with subgingival crown-root fracture or caries were included. Presurgical orthodontic extrusion was performed on all teeth to prevent root resorption. Extent of extrusion and rotation was determined based on crown/root ratio. The postoperative splinting period was 7 to 14 days. Clinical and radiographic examination was performed at an interval of 1, 2, and 3 months.ResultsAfter the mean follow-up of 41.9±15.2 months, failure was observed as increased mobility in 3 of 21 cases. No significant difference was observed in the outcome of surgical extrusion based on tooth type, age, sex, 180° rotation, or time for extraction. Furthermore, marginal bone loss was not observed.ConclusionSurgical extrusion of maxillary premolars can be a possible therapeutic option in cases of subgingival crown-root fracture.

Free sugar content, in vitro starch digestibility and predicted glycemic index of ready-to-eat breakfast cereals commonly consumed in Turkey: An evaluation of nutritional quality

Breakfast cereal products are produced using the extrusion technique, which improves their digestion and absorption in the small intestine. However, this technique may cause an increase in the glycemic index of a food. Although high carbohydrate-rich foods are consumed in Turkey, there is not enough information about their GIs. The purpose of this study was to determine the free sugar content, in vitro starch digestibility, and predicted GI of different types of breakfast cereals commonly consumed in Turkey and evaluate their nutritional quality. The hydrolysis index of breakfast cereals ranged from 78.1 to 114.9, whereas the GI ranged from 82.6 to 102.8. The GI of 6 out of 12 breakfast cereal products was higher than that of white bread. Free sugar content, rapidly available glucose, and resistant starch amounts were significantly related to the increase and decrease of GIs in breakfast cereals, but there was no significant relationship between rapidly and slowly digestible starches. This may be related to the free sugar content in the samples and the extent of extrusion used for the samples. When the breakfast cereal groups were evaluated, overall, the GIs of samples containing oats were lower than those containing rice and corn.

Relationship Between Preoperative Extrusion of the Medial Meniscus and Surgical Outcomes After Partial Meniscectomy

Background: No previous study has examined arthritic change after meniscectomy with regard to extrusion of the medial meniscus. Purpose: (1) To determine the factors related to preoperative meniscal extrusion; (2) to investigate the relationship between medial meniscal extrusion and postoperative outcomes of partial meniscectomy, and to identify a cutoff point of meniscal extrusion that contributes to arthritic change after partial meniscectomy in nonosteoarthritic knees. Study Design: Cohort study; Level of evidence, 3. Methods: A total of 208 patients who underwent partial meniscectomy of the medial meniscus between January 2000 and September 2006 were retrospectively reviewed. The extent of extrusion and severity of degeneration of the medial meniscus as shown on preoperative MRI were evaluated. The minimum follow-up duration was 7 years. Clinical function was assessed with the Lysholm knee scoring scale, the International Knee Documentation Committee (IKDC) subjective knee evaluation form, and the Tapper and Hoover grading system. Radiological evaluation was conducted by use of the IKDC radiographic assessment scale. Regression analysis was performed to identify factors affecting preoperative extrusion of the medial meniscus and factors influencing follow-up results after partial meniscectomy. Receiver operating characteristic curve was used to identify a cutoff point for the extent of meniscal extrusion that was associated with arthritic change. Results: The mean ± SD preoperative Lysholm knee score was 65.0 ± 6.3 and the mean IKDC subjective score was 60.1 ± 7.5. The mean follow-up functional scores were 93.2 ± 5.1 (P < .001) for the Lysholm knee score and 89.0 ± 6.2 for the IKDC subjective score (P < .001). Preoperative extent of meniscal degeneration (P < .001) and preoperative pattern of meniscal tear (P < .001) were related to preoperative meniscal extrusion. Preoperative extrusion of the meniscus showed a tendency to increase as the extent of intrameniscal degeneration increased, and the medial meniscus was extruded more in patients with horizontal, horizontal flap, and complex tears. The preoperative extent of meniscal extrusion had a statistically significant correlation with follow-up Lysholm knee score (coefficient = −0.10, P = .002), IKDC subjective score (coefficient = −0.09, P = .007), Tapper and Hoover grade (odds ratio = 1.05, P < .001), and IKDC radiographic grade (odds ratio = 1.13, P < .001) at the mean follow-up period of 88.6 months. The cutoff point for the relative value of preoperative meniscal extrusion associated with arthritic change was 34.6% (sensitivity = 69.3%; specificity = 82.7%; accuracy = 77.9%). Conclusion: The preoperative extent of intrameniscal degeneration and the preoperative patterns of meniscal tear including horizontal, horizontal flap, and complex tears were associated with preoperative extrusion of the medial meniscus. The preoperative extrusion of the medial meniscus was negatively correlated with outcomes of partial meniscectomy. The preoperative extent of meniscal extrusion can be used as a predictive factor for osteoarthritis in partial meniscectomy.

Meniscal Extrusion in the Knee: Should only 3 mm Extrusion be Considered Significant? An Assessment by MRI and Arthroscopy.

Aim. The aim of this study was to assess whether significant meniscal extrusion of more than 3 mm or of even lesser degrees of extrusion could be considered significant. We also aimed to determine the morphology of tears that are most likely to be associated with significant extrusion.Study design and material. The study was done retrospectively on a group of 202 patients (157 males and 45 females) who had been seen in our hospital between 2007 and 2011 with meniscal tears (in one knee only) diagnosed by MRI and confirmed on arthroscopy. Extrusion of 3 mm or more (usually considered significant) was seen in 102 cases and less than 3 mm in 100. Extrusion was measured on the coronal MR images rather than on saggital images because of ease and reproducibility. The tears were confirmed by arthroscopy and correlated with the extent of extrusion on MRI.Results: Out of the total of 202 cases, 102 cases (50.5%) had extrusion of 3 mm or more on MRI. Of these, the medial meniscal posterior horn tears accounted for 63 cases (64.26%), 21 cases were medial meniscal body tears (21.42%), five medial meniscal root tears (5.1%), nine lateral meniscal body tears (9.18%) and four lateral meniscal posterior horn tears(4.08%). Forty-four cases had extrusion of 3-4 mm, 26 had extrusion of 4-5mm, 17 cases had extrusion of 5-6mm, ten had extrusion of 6-7mm and five had extrusion of 7 mm or more. One hundred cases fell in the < 3mm extrusion category, of which 80 (39.6%) were in the 2-3 mm extrusion group and 20 (9.9%) in the 1-2 mm extrusion group. They comprised of 61 cases of medial meniscal posterior horn tears, 23 cases of medial meniscal body tears, six medial meniscal root tears, eight lateral meniscal body tears and two lateral meniscal posterior horn tears. The highest proportion of meniscal tears was seen in the 2-3 mm category comprising nearly 40% of the entire study group. The majority of tears were medial meniscal posterior horn tears.Conclusion: Menisci that extruded 2-3 mm from the tibial margin formed a major proportion of menisci treated for tears by repair or menisectomy. We should consider extrusion of more than 2mm as significant. Most tears had extrusion of 2-4 mm.

Comparison of medial and lateral meniscal transplantation with regard to extrusion of the allograft, and its correlation with clinical outcome

We compared extrusion of the allograft after medial and lateral meniscal allograft transplantation and examined the correlation between the extent of extrusion and the clinical outcome. A total of 73 lateral and 26 medial meniscus allografts were evaluated by MRI at a mean of 32 months (24 to 59) in 99 patients (67 men, 32 women) with a mean age of 35 years (21 to 52). The absolute values and the proportional widths of extruded menisci as a percentage were measured in coronal images that showed maximum extrusion. Functional assessments were performed using Lysholm scores. The mean extrusion was 4.7mm (1.8 to 7.7) for lateral menisci and 2.9 mm (1.2 to 6.5) for medial menisci (p < 0.001), and the mean percentage extrusions were 52.0% (23.8% to 81.8%) and 31.2% (11.6% to 63.4%), respectively (p < 0.001). Mean Lysholm scores increased significantly from 49.0 (10to 83) pre-operatively to 86.6 (33 to 99) at final follow-up for lateral menisci (p = 0.001) and from 50.9 (15 to 88) to 88.3 (32 to 100) for medial menisci (p < 0.001). The final mean Lysholm scores were similar in the two groups (p = 0.312). Furthermore, Lysholm scores were not found to be correlated with degree of extrusion (p = 0.242). Thus, transplanted lateral menisci extrude more significantly than transplanted medial menisci. However, the clinical outcome after meniscal transplantation was not found to be adversely affected by extrusion of the allograft.

Apical Extrusion of Sodium Hypochlorite Using Different Root Canal Irrigation Systems

Introduction Root canal irrigation carries a risk of extrusion of irrigant into the periapical tissues. The objective of this study was to compare different irrigation systems in matched pairs of teeth prepared to an apical size of 35.06 and 50.06 by measuring the frequency and extent of apical extrusion of sodium hypochlorite (NaOCl) into a simulated periapical environment. The null hypothesis was tested that there is no difference between systems. Methods Bilaterally matched pairs (n = 10) of single-canal extracted human anterior teeth were instrumented to an apical size of either 35.06 or 50.06. Teeth were embedded in a gel containing the pH-sensitive dye M-cresol purple that changes from yellow at pH 7.4 to purple at pH 9. Root canals were irrigated with 6% NaOCl (pH 11) by using EndoActivator (EA), EndoVac (EV), Rispi-Sonic/MicroMega 1500 (MM), passive ultrasonic irrigation (PUI), and syringe irrigation with a slot-tipped needle (SN), so that each tooth underwent all irrigation procedures in a randomized crossover design. Apical extrusion was evaluated by image analyses. Results The frequency of extrusion was less in teeth with apical preparation size 35.06 (36%) compared with 50.06 (60%) ( P = .014) and was dependent on the irrigation system in 35.06 ( P = .039) but not 50.06 groups. In the 35.06 group the frequency of extrusion was less for EV than for MM and SN (both P = .029). The extent of extrusion was less for MM compared with PUI ( P = .024) and SN ( P = .046) in the 35.06 group and greater for SN compared with all other systems in the 50.06 group ( P < .05). The null hypothesis was rejected. Conclusions The frequency of apical extrusion of NaOCl was dependent on the type of root canal irrigation system and apical preparation size. The extent of extrusion depended on the irrigation system, with syringe and slotted-needle irrigation resulting in the greatest extent of extrusion.

Medial meniscus extrusion on knee MRI: is extent associated with severity of degeneration or type of tear?

The meniscus is considered "extruded" when it extends beyond the tibial margin. We hypothesize that severe degeneration, large radial tears, complex tears, and tears involving the meniscal root would alter meniscal stability and cause more substantial extrusion. The knee MRI database at Thomas Jefferson University Hospital was searched for reports describing meniscal extrusion; MR images were reviewed retrospectively. On mid coronal images, extrusion of the medial meniscus was quantified in millimeters. A separate, independent review of the meniscus evaluated degeneration severity and tear (type and extent). Radial tears were divided into those involving more (large) or less (small) than 50% of the meniscal width. Tears that involved the "root" at the tibial spine were recorded. Chi-square analysis compared these findings with extrusion extent, divided into minor (</= 3 mm) and major (> 3 mm) extrusion. One hundred five knees were reviewed (12 men and 93 women; age range, 34-83 years; mean age, 56 years). Distribution of medial meniscus extrusion was 2 mm (n = 17), 3 mm (n = 17), 4 mm (n = 27), 5 mm (n = 14), 6 mm (n = 16), and 7-10 mm (n = 14). Mild, moderate, or marked degeneration was seen in 47%, 26%, and 27% with minor extrusion, respectively, and in 17%, 41%, and 42% with major extrusion, respectively (p = 0.003). Tears were seen in 59% (20/34) with minor extrusion versus 89% (63/71) with major extrusion (p = 0.001). Tears involved one third, two thirds, or all of the meniscus in 75%, 25%, or 0%, respectively, with minor extrusion and 46%, 40%, or 14% with major extrusion, respectively (p = 0.014). Longitudinal (nonradial) and horizontal tears were not associated with extent of extrusion (p = 1.0). Oblique tears were significantly associated with minor extrusion (minor, 26% [9/34]; major, 4% [3/71]; p = 0.003). Radial tears were seen in 9% (3/34) with minor extrusion versus 21% (15/71) with major extrusion (p = 0.20). All three radial tears with minor extrusion were small; conversely, 87% (13/15) of radial tears with major extrusion were large (p = 0.019). Complex tears were seen in 18% (6/34) with minor extrusion versus 59% (42/71) with major extrusion (p < 0.001). Tears involving the meniscal root were seen in 3% (1/34) with minor extrusion and 42% (30/71) with major extrusion (p < 0.001). Substantial medial meniscus extrusion (> 3 mm) is associated with severe meniscal degeneration, extensive tear, complex tear, large radial tear, and tear involving the meniscal root.

Micromechanics of an Extrusion in High-Cycle Fatigue With Creep

Extrusions and intrusions often are sites of fatigue cracks. The extent of extrusions is important in fatigue crack initiation. Metals often are subject to fatigue loadings at elevated temperatures. At temperatures below one half of the melting temperature slip is the main mechanism of inelastic deformation. In this study, an aluminum polycrystal loaded in this temperature range is considered. A most favorably oriented crystal located at a free surface of a f.c.c. polycrystal subject to creep under cyclic tension and compression of high-cycle fatigue is considered. An extrusion in this crystal is shown to be produced by a positive slip in one thin slice “P” and a negative slip in a closely located slice “Q”. An initial tensile strain εααI in the thin slice “R” sandwiched between P and Q causes a positive initial shear stress ταβI in P and a negative one in Q. It is shown that the extrusion growth causes a tensile strain in R, which can activate a second slip system giving a creep strain with a tensor component εαα. It has the same effect as the initial strain εααI in causing this difference in shear stresses in P and Q and gives much additional extrusion growth. The extent of intrusion and extrusion is important in this study of crack initiation.

Intraalveolar transplantation: (I) The use of autologous bone transplants in the periapical region

Intraalveolar transplantation of teeth with unfavourable cervical root fractures were performed in 15 patients. The roots were surgically extruded on an average 4.5 mm, and autologous bone transplants were placed above the apical part to support the root. Temporary endodontic therapy was carried out before the transplantation in 10 patients and 3 weeks after transplantation in 2 patients. 3 of the teeth had old root fillings. Postoperative controls were made weekly during the first month, after 3 months, 6 months, 1 and 2 years. The roots had become stable in most cases after 3 weeks. The mobility grade was dependent on the extent of extrusion. Radiographic controls showed formation of a normal periodontal space around the roots after 3 months, but also minor root resorption in the most apical part in 10 of the cases. The resorption was, however, not progressive in nature and was limited to the apical part. Remodelling of the marginal bone contour around the transplanted roots was evident in 11 patients. Periapical destructions were found in 3 patients at the 2-year control. Crown therapy was carried out with due attention to the special prosthetic problems associated with preparation of small remaining root fragments with unfavourable crown/root ratio.