Vertical Fractures Research Articles

Numerical study on the effects of fracture on density-driven flows in CO2 sequestration

In this study, CO2 transport in density-driven flows within an ideal model of a fractured porous medium, which contains a single or two intersecting fractures, is investigated numerically. The study employs a multi-scale modeling in which the flow in the matrix is modeled by Darcy's law, while the flow in the fracture is modeled by the Navier–Stokes equations. Our study shows that a horizontal fracture minimally impacts CO2 distribution, and depending on its length, slightly reduces dissolved CO2 during sequestration by 1.5%–2.5%. Vertical fractures play a crucial role in redirecting CO2 movement within the matrix, guiding it toward the fractures and altering its original pathway. Notably, the observed oscillations of CO2-rich water between the interfaces of the vertical fracture highlight the flow consistency with the pore scale. The domain-scale circulation induced by the vertical fracture leads to a rapid increase in flux and dissolved CO2 mass, but early convection shuts down. The results demonstrate that a longer vertical fracture leads to earlier shut down of convection and a potential decrease in storage of over 11%. The flow behaviors observed in inclined fractures are akin to those in vertical fractures, as they disrupt the fingerlike structure of CO2 around the fracture, form the circulation around the fracture, and are accompanied by vortices at the top. Additionally, intersecting fractures can lead to dynamic interactions between the fractures, with high-angle fractures dominating mixing flow. Different fracture angle combinations minimally affect dissolution mass.

A letter to editor addressing a methodological concern: A critical analysis of papers included in a systematic review on vertical root fractures

A letter to editor addressing a methodological concern: A critical analysis of papers included in a systematic review on vertical root fractures

Characteristics of proppant transport and placement within rough hydraulic fractures

A three-dimensional reconstruction of rough fracture surfaces of hydraulically fractured rock outcrops is carried out by casting process, a large-scale experimental setup for visualizing rough fractures is built to perform proppant transport experiments. The typical characteristics of proppant transport and placement in rough fractures and its intrinsic mechanisms are investigated, and the influences of fracture inclination, fracture width and fracturing fluid viscosity on proppant transport and placement in rough fractures are analyzed. The results show that the rough fractures cause variations in the shape of the flow channel and the fluid flow pattern, resulting in the bridging buildup during proppant transport to form unfilled zone, the emergence of multiple complex flow patterns such as channeling, reverse flow and bypassing of sand-carrying fluid, and the influence on the stability of the sand dune. The proppant has a higher placement rate in inclined rough fractures, with a maximum increase of 22.16 percentage points in the experiments compared to vertical fractures, but exhibits poor stability of the sand dune. Reduced fracture width aggravates the bridging of proppant and induces higher pumping pressure. Increasing the viscosity of the fracturing fluid can weaken the proppant bridging phenomenon caused by the rough fractures.

Investigation of the mechanical properties and propagation of cracks in prosthetic teeth composed of porcelain and dental ceramics using cohesive meshing under quasi-static loading conditions

With the significant progress in dental science and the reliance of dental researchers on understanding the mechanical properties and behaviors of teeth and materials used for tooth replacement, there is an increasing demand for study and research in this sector. Composite samples, dental porcelains, and materials used in 3D printers have gained significance as substitutes for human teeth. Therefore, it is crucial to conduct research and analyze these materials' physical and mechanical characteristics compared to human teeth. Tooth damage and fracture may arise from various causes, such as falls, sports-related incidents, or traffic accidents. Tooth fractures may vary in severity, ranging from mild fractures that include chipping of the tooth's surface layers, known as enamel and dentin, to more serious ones, such as diagonal, vertical, or horizontal fractures extending into the root of the tooth.

Separation of fast and slow shear waves and prediction of fracture parameters based on non-orthogonal assumptions

SUMMARY Natural fractures play a significant role in oil and gas reservoirs. Accurate predictions of fracture parameters are vital in reservoir prediction and oil and gas development. The birefringent phenomenon of shear waves in fractured media makes shear wave splitting (SWS) analysis an important tool in formulating fracture predictions. The traditional SWS analysis method is based on an orthogonal assumption of fast and slow shear waves. However, in an orthotropic medium composed of a background vertical transversely isotropic medium and a set of vertical fractures, fast and slow shear waves are not necessarily orthogonal. This causes the traditional SWS analysis method to fail. To solve this problem, we proposed an SWS analysis algorithm with a non-orthogonal assumption of fast and slow shear waves in this study. First, we introduced a parameter (difference angle) to characterize the angle between slow shear waves and the normal polarization directions of the fast shear waves. Subsequently, based on the traditional two-parameter scanning algorithm, a parameter was added to facilitate three-parameter scanning. In addition, we derived an expression for the two-parameter scanning objective function using the non-orthogonal assumption. Two-parameter scanning can accurately extract fast and slow wave time delay data, but it cannot determine an accurate fast shear wave polarization direction. Therefore, we optimized the three-parameter scanning algorithm as follows: first, we used two-parameter scanning to obtain the fast and slow wave time delays and then performed further scanning to determine the polarization direction of the fast shear wave and difference angle. The optimization algorithm significantly improved the computational efficiency. Subsequently, we tested the accuracy of this method using synthetic single-trace and three-component vertical seismic profile data. We demonstrated the implementation process of the three-parameter scanning method using actual data, separated fast and slow shear waves, and predicted fracture parameters. The final fracture parameters were verified.

Generalized Analytical Well-Test Solutions for Vertically Fractured Wells in Commingled Reservoirs

Abstract Layered zones with vertical fracture are often found in analyzing well-test data of deep/ultra-deep reservoirs and tight reservoirs. Analyzing and modeling the well-test data in a computation-accurate and easy-program manner have been a challenge for these problems due to the lack of suitable solutions. This work thus presents the generalized analytical well-test solutions for vertically fractured wells in infinite and bounded commingled reservoirs with computation accuracy and functional simplicity. These solutions are derived based on the early-time approximate solution of the infinite/finite-conductivity fracture model, Laplace and Fourier cosine transformation, pressure superposition principle, and Duhamel principle. Subsequently, model validation is carried out by comparing the pressure and derivative results with those of commercial saphir software. The results show that the average absolute percent deviation between the presented analytical solutions and saphir for three kinds of outer boundaries is ∼2% for pressure results and ∼4% for pressure derivative results. Finally, a field case in Xinjiang oilfield is interpreted, indicating that the proposed analytical well-test solutions are feasible to interpret the parameters of commingled reservoirs.

Coronal vertical fracture of vertebral body following minimally invasive lateral lumbar interbody fusion: risk factor analysis in consecutive case series.

To investigate the incidence and risk factors of coronal vertical vertebral body fracture (CV-VBF) during lateral lumbar interbody fusion (LLIF) for degenerative lumbar disease. Clinical data, including age, sex, body mass index, and bone mineral density, were reviewed. Radiological assessments, such as facet joint arthrosis, intervertebral disc motion, index disc height, and cage profiles, were conducted. Posterior instrumentation was performed using either a single or staged procedure after LLIF. Demographic and surgical data were compared between patients with and without VBF. Out of 273 patients (552 levels), 7 (2.6%) experienced CV-VBF. Among the 552 levels, VBF occured in 7 levels (1.3%). All VBF cases developed intraoperatively during LLIF, with no instances caused by cage subsidence during the follow-up period. Sagittal motion in segments adjacent to VBF was smaller than in others (4.6° ± 2.6° versus 6.5° ± 3.9°, P = 0.031). The average grade of facet arthrosis was 2.5 ± 0.7, indicating severe facet arthrosis. All fractures developed due to oblique placement of a trial or cage into the index disc space, leading to a nutcracker effect. These factors were not related to bone quality. CV-VBF after LLIF occurred in 2.6% of patients, accounting for 1.3% of all LLIF levels. A potential risk factor for VBF involves the nutcracker-impinging effect due to the oblique placement of a cage. Thorough preoperative evaluations and surgical procedures are needed to avoid VBF when considering LLIF in patients with less mobile spine.

Relationship between Natural Fracture and Structural Style and its Implication for Tight Gas Enrichment: A Case Study of Deep Ahe Formation in the Dibei‐Tuzi Area, Kuqa Depression

AbstractThe deep Lower Jurassic Ahe Formation (J1a) in the Dibei‐Tuzi area of the Kuqa Depression has not been extensively explored because of the complex distribution of fractures. A study was conducted to investigate the relationship between the natural fracture distribution and structural style. The J1a fractures in this area were mainly high‐angle shear fractures. A backward thrust structure (BTS) is favorable for gas migration and accumulation, probably because natural fractures are more developed in the middle and upper parts of a thick competent layer. The opposing thrust structure (OTS) was strongly compressed, and the natural fractures in the middle and lower parts of the thick competent layer around the fault were more intense. The vertical fracture distribution in the thick competent layers of an imbricate‐thrust structure (ITS) differs from that of BTS and OTS. The intensity of the fractures in the ITS anticline is similar to that in the BTS. Fracture density in monoclinic strata in a ITS is controlled by faulting. Overall, the structural style controls the configuration of faults and anticlines, and the stress on the competent layers, which significantly affects deep gas reservoir fractures. The enrichment of deep tight sandstone gas is likely controlled by two closely spaced faults and a fault‐related anticline.

Fracture Height Quantification from Vertical and Horizontal Section Fiber Measurements: A Comprehensive Study Using LF-DAS Measurements from HFTS-2 Data Set

Summary Understanding fracture height growth is critical for optimizing hydraulic fracture treatments and field development. In recent years, low-frequency distributed acoustic sensing (LF-DAS) has become a popular tool for monitoring strain changes during hydraulic fracturing. While LF-DAS data from vertical monitoring wells (VMWs) can be used to determine fracture height, measurements from the vertical section of horizontal wells may have the potential to capture fracture height growth. The objectives of this study are (1) to apply three methods—(a) using the vertical section of horizontal fiber measurements, (b) using the vertical fiber measurements, and (c) using the horizontal section of horizontal fiber measurements—to determine the fracture height using the Hydraulic Fracturing Test Site 2 (HFTS-2) data set and (2) to demonstrate the reliability of using LF-DAS measurements from the vertical section of horizontal fibers for fracture height determination. In an effort to determine the fracture height from the HFTS-2 data set using the three methods, we demonstrate the reliability of the height prediction using strain measurements in the vertical section of the horizontal monitoring well (VS-HMW). First, we analyze the measurements from the vertical section of the horizontal fiber (B3H) during the stimulation of the heel-most stages of the horizontal wells (B1H, B2H, and B4H). Second, we analyze the measurements from the VMW (B5PH) during the stimulations of B1H, B2H, and B4H. Third, we use a geomechanical inversion algorithm to obtain height estimates from the horizontal section of the LF-DAS measurements at B3H during B1H, B2H, and B4H stimulations. The fracture height is determined based on the transition of the extension-compression zone in the LF-DAS measurements from the vertical sections. The height estimates obtained using the three methods are compared and found to be consistent in the six well pairs we analyzed. The LF-DAS measurements from the vertical well B5PH provide a complete height profile, while measurements from the vertical section capture fracture growth from the upper tip of the fracture to the landing depth of the horizontal well. The fracture height estimates obtained from our inversion algorithm represent the average height value of all fracture hits at the chosen stage. This study demonstrates the potential to determine fracture height growth using LF-DAS measurements in the vertical section of a horizontal well, thus avoiding the cost associated with drilling VMWs to obtain fracture heights.

Prediction of thermal front movement in geothermal reservoirs containing distributed natural fractures

When designing a reinjection scheme for geothermal development, one needs to predict the flow and thermal behavior between the recharge and discharge wells. Premature thermal front breakthrough is of great concern and is often observed in real fields. However, prediction methods based on homogeneous media are prone to overly optimistic estimates. In this study, geothermal reservoirs with vertical fractures which are discretely distributed in the permeable rock are considered, and the streamline simulation is developed and applied to evaluate the thermal front movement, represented by the characteristic times tD*. With 1000 simulation results for stochastically generated natural fracture systems, regression models are developed for the expected values of tD* with minimal information requirements on fracture parameters. In general, the fracture orientation θf has a stronger negative correlation with tD* than the total fracture length Σf. The intensity of natural fractures has opposing effects (delay or advance) on tD* depending on θf, and taking this effect into account improves the quality of the regression model. In addition, when the pressure difference between the doublet wells is available, the model accuracy is further improved by incorporating pressure data into the regression. The prediction models are of practical use for understanding the thermal behavior and designing a reinjection scheme in fractured geothermal reservoirs.

Does Magnetic Resonance Imaging Predict Neurological Deficit in Patients with Traumatic Lower Lumbar Fractures?

A retrospective cohort study. This study aimed to understand the role of magnetic resonance imaging (MRI) in predicting neurological deficits in traumatic lower lumbar fractures (LLFs; L3-L5). Despite studies on the radiological risk factors for neurological deficits in thoracolumbar fractures, very few have focused on LLFs. Moreover, the potential utility of MRI in LLFs has not been evaluated. In total, 108 patients who underwent surgery for traumatic LLFs between January 2010 and January 2020 were reviewed to obtain their demographic details, injury level, and neurology status at the time of presentation (American Spinal Injury Association [ASIA] grade). Preoperative computed tomography scans were used to measure parameters such as anterior vertebral body height, posterior vertebral body height, loss of vertebral body height, local kyphosis, retropulsion of fracture fragment, interpedicular distance, canal compromise, sagittal transverse ratio, and presence of vertical lamina fracture. MRI was used to measure the canal encroachment ratio (CER), cross-sectional area of the thecal sac (CSAT), and presence of an epidural hematoma. Of the 108 patients, 9 (8.3%) had ASIA A, 4 (3.7%) had ASIA B, 17 (15.7%) had ASIA C, 21 (19.4%) had ASIA D, and 57 (52.9%) had ASIA E neurology upon admission. The Thoracolumbar Injury Classification and Severity score (p =0.000), CER (p =0.050), and CSAT (p =0.019) were found to be independently associated with neurological deficits on the multivariate analysis. The receiver operating characteristic curves showed that only CER (area under the curve [AUC], 0.926; 95% confidence interval [CI], 0.860-0.968) and CSAT (AUC, 0.963; 95% CI, 0.908-0.990) had good discriminatory ability, with the optimal cutoff of 50% and 65.3 mm2, respectively. Based on the results, the optimal cutoff values of CER >50% and CSAT >65.3 mm2 can predict the incidence of neurological deficits in LLFs.

Results of numerical modeling of the effect of vertical fractures on electrical logging data

Based on the results of numerical modeling, the effect of vertical drilling-induced fractures on the data of galvanic electrical logging methods is considered. Geoelectric models represent a space with different resistivity values, a well and axisymmetric fractures filled with drilling fluid. The effect of fractures limited in radial depth on galvanic logging data leads to a change in signals similar to the change opposite the formation with a penetration zone located within the fracture interval. Based on the on gradient probes and focused logging data, a model of both a formation with an invaded zone and an impermeable formation with a vertical resistivity less than the horizontal one is selected. Thin vertical fractures do not affect the signals of induction probes, which may be a sign of their presence.

(132) Vertical Fracture of the Penis: A Rare Entity

Abstract Introduction Penile fracture is not an uncommon occurrence. It is a serious injury involving the rupture of the tunica albuginea in the erect state of the penis. While most cases are transverse fractures occurring during coitus, we present a rare case of a “vertical” penile fracture, the second reported in English literature. Objective To document a rare case of penile fracture i.e. a vertical penile fracture and its management. Methods A 33-year-old man presented to the emergency room of the hospital past midnight. He experienced sharp excruciating pain while attempting to penetrate vagina in a rear entry position. He gave a history of popping sound followed by detumescence, and increasing swelling of penis with discoloration and curvature. The pain continued though reduced in severity over time. The patient was evaluated under the guidance of consultant urologist (Author 2). Magnetic resonance imaging reported suspected vertical tear in tunica albugenia and also suspected urethral injury. Results Emergency surgery revealed a vertical long tunica albugenia tear along with corpora spongiosal tear and intact urethral mucosa. The tunica albugenia tear was primarily repaired. Good erectile function was reported by the patient, and normal sexual activity resumed after 6 weeks. Conclusions This case report emphasizes the need for clinicians to be aware of and consider this uncommon entity, “Vertical Tunica Albugenia tear” while managing penile fractures. The utilization of MRI imaging of the penis can provide valuable insights into the pattern and extent of the injury, aiding in appropriate management decision. Surgical intervention within 6–8 hours of the injury offers excellent result and preserves sexual function without complications. Disclosure No.

Fracturing and Dome‐Shaped Surface Displacements Above Laccolith Intrusions: Insights From Discrete Element Method Modeling

AbstractInflation of viscous magma intrusions in Earth's shallow crust often induces strain and fracturing within heterogeneous host rocks and dome‐shaped ground deformation. Most geodetic models nevertheless consider homogeneous, isotropic, and linear‐elastic media wherein stress patterns indicate the potential for failure, but without simulating actual fracturing. We present a two‐dimensional Discrete Element Method (DEM) application to simulate magma recharge in a pre‐existing laccolith intrusion. In DEM models, fractures can propagate during simulations. We systematically investigate the effect of the host rock toughness (resistance to fracturing), stiffness (resistance to deformation) and the intrusion depth, on intrusion‐induced stress, strain, displacement and spatial fracture distribution. Our results show that the spatial fracture distribution varies between two end‐members: (a) for high stiffness or low toughness host rock or a shallow intrusion: extensive cracking, multiple vertical surface fractures propagating downward and two inward‐dipping highly cracked shear zones that connect the intrusion tip with the surface; and (b) for low stiffness or high toughness host rock or a deeper intrusion: limited cracking, one central vertical fracture initiated at the surface, and two inward‐dipping fractures at the intrusion tips. Abrupt increases in surface displacement magnitude occur in response to fracturing, even at constant magma injection rates. Our modeling application provides a novel approach to considering host rock mechanical strength and fracturing during viscous magma intrusion and associated dome‐shaped ground deformation, with important implications for interpreting geodetic signals at active volcanoes and the exploitation of geothermal reservoirs and mineral deposits.

Rainfall–Mining Coupling Effects on Slope Failure Mechanism and Evolution Process: A Case Study of Open-Pit to Underground Mining

This research examines how rainfall and mining affect the slope damage resulting from the transition from open-pit mining to underground mining. Using an unmanned aerial vehicle (UAV), the Huangniu slope of the Dexing Copper Mine was fully characterized, and experiments were conducted on rock samples from appropriate sites. First, the mechanical properties of the samples were measured. Then, the parameters of the similarity simulation experiments were derived based on the similarity theory. Subsequently, the rainfall, rock slope, data acquisition, and monitoring systems were designed. Finally, the rock mass failure with different slope angles was analyzed, and the deformation and damage patterns under the coupling effect were obtained. The results show that rainfall increases pore water pressure and moisture content. Rainfall and slope-slip water have more of an impact on the open-pit platform. The pore water pressure values on the upper rock mass rise faster than inside it. In the open-pit mining stage, the rock mass shifts slightly to the upper left. In the room mining stage, vertical fractures and goaf sinking occur. The fractures above the mine form a semi-ellipse. In the pillar mining stage, overlying rock displacement is evident and fractures persist. In the continuous pillar mining stage, the overlying rock collapses. The 65° slope model was the most damaged, while the 55° slope model was the least damaged. The results also suggest that the UAV guides sample selection.

Integrated geophysical approach for detection and size-geometry characterization of a multiscale karst system in carbonate units, semiarid Brazil

Abstract The karstification of carbonate rocks creates 3D maze voids that are normally controlled by fracture networks and sedimentary bedding. The spatial distribution and density of karst systems are usually complex and difficult to predict, demanding multidisciplinary studies at different scales of investigation to determine the spatial distribution and density of karst features and their possible links with cave systems controlled by the regional structural setting. The present study integrates geophysical datasets (gravity, electrical resistivity tomography - ERT, and ground penetrating radar - GPR) with a digital elevation model to investigate a karst system in the Irecê basin, a semiarid region of Brazil. Morphostructural lineaments reveal a NNW-SSE- and E-W-oriented structural setting of the crystalline basement, which is imprinted on the internal basin architecture, and surface drainage network. Negative gravity anomalies and high-gradient gravity zones indicate the main karstic zone, where karst landforms are concentrated. In addition, 2.5D gravity modeling provides the internal basin geometry, demonstrating that the karst system has evolved in the thickest sector of the basin. ERT profiles delineate the underground passages that connect dolines at depth. Finally, GPR data image shallow subsurface ghost-rock karstification that spread out from the surface to depth and that took advantage of vertical fractures and slightly arched bedding planes. Our results point out the role of the fracture corridors in channelizing hydrodynamic energy at a sufficiently high level to create caves by the total removal of dissolved material, whereas in the surrounding areas under low hydrodynamic conditions, overall shallow ghost-rock karstification took place, creating residual weathered rocks (alterites).

Analysis of Dynamic Evolution of Surrounding Rock Movement and Stress-Fracture in the Upward and Repeated Mining of Close-Distance Coal Seams

The distribution of mining-induced stress and the resulting rock fractures are two crucial factors affecting mineral extraction in protective layer mining. This research establishes a correlation between the vertical fracture aperture and the second derivative of the rock layer’s subsidence curve equation. The article explores the span requirement for a simply supported beam to fracture. This condition is relevant to understanding the dynamic evolution of rock movement and stress fractures during repeated mining of close-distance coal seams. Our study investigates alterations in rock stress and fractures resulting from repeated upward mining of coal seams, using the nearby coal seam cluster in Jincheng Mine as a case study. The research findings indicate that during the mining of the upper coal seam, the roof experiences significant but brief periodic loading intervals, as well as severe and moderate periodic loading. As mining progresses to the lower coal seam, pressure relief of the upper coal seam gradually increases in both degree and range. In the upper coal seam, the vertical stress distribution follows a sequence of “V,” “U,” and “W” forms. The upper coal seam undergoes five stages of expansion deformation: compression, expansion, increased expansion, decreased expansion, and stable expansion.

Exploring the geological structure of a large-scale landslide using semi-airborne TEM in the Karst area of southwest China

Abstract The karst strata in the southwestern mountainous areas of China are extensively developed, creating a fragile geological environment. Landslide geological disasters occur frequently in these areas due to high annual rainfall, concentrated time periods, and frequent human engineering activities. Conventional ground geophysical methods face challenges in complex terrains, making it difficult to quickly and reliably obtain underground structures in landslide-prone areas. The semi-airborne transient electromagnetic method (SATEM) combines ground-based transmission and airborne reception of electromagnetic responses. This method, characterized by large emission magnetic moment and rapid data collection in the air, offers advantages in detecting deep geological structures in complex terrain areas. This article presents the application of a newly developed loop source SATEM system, integrated with multi-rotor unmanned aerial vehicles (UAVs), to conduct deep geological structure detection experiments on a large-scale landslide. The inversion results clearly depict the spatial distribution of the Feixianguan Formation and Longtan Formation, as well as vertical fractures developed in the strata due to underground coal mining. The detection test demonstrates the applicability of the SATEM method in detecting underground structures in Karst Plateau special landform areas, providing a new detection approach for similar regions.

Injection Temperature Impacts on Reservoir Response during CO2 Storage

Summary Sustained injection of industrial-scale volumes of cold CO2 into warmer subsurface rock will result in extensive cooling which can alter rock mass mechanical behavior and fluid migration characteristics. Advanced simulation tools are available to assess and characterize such phenomena; however, the effective use of these tools requires appropriate injection temperatures and rock thermophysical parameters (in addition to geomechanical and hydraulic properties). The primary objective of this study was to demonstrate the sensitivity of injection-induced tensile fracturing and fault reactivation to injection temperature and reservoir thermophysical properties during CO2 injection operations. This was achieved by (1) compiling and reviewing thermophysical parameter data available for formations in the province of Alberta, Canada, and CO2 injection temperature records for CO2 injection projects in western Canada and (2) using a 3D, physics-based, fully integrated hydraulic fracturing and reservoir simulation numerical model to examine the geomechanical response of several potential CO2 reservoirs in the Alberta Basin as a function of injection temperature, thermal conductivity (TC), and coefficient of linear thermal expansion (CLTE) values. The simulation results indicate that reducing the fluid injection temperature from 15°C (assumed in previous work) to 2°C (conservative value selected based on temperature data reviewed in this work) could trigger extensive vertical (20–130 m high, 100–600 m long) tensile fractures with rapid fracture initiation and full vertical growth within short periods (weeks to months) and continued horizontal length increase. When low values for thermophysical properties are used, the results show that thermally-induced tensile fracturing is unlikely, whereas the use of high values results in extensive tensile fracturing in all simulations. A similar conclusion was reached for the thermally-induced reactivation (unclamping) of proximal, critically-stressed faults. Notably, slip is predicted for all simulations where high thermophysical property values are used. This confirms that accurate determination of minimum fluid injection temperature and thermophysical parameters is important for containment risk assessment for commercial-scale CO2 storage projects. Another significant outcome of this work is the observation that most thermophysical parameters in the available data were measured using experimental conditions and/or temperature paths that are not representative of CO2 injection projects. As such, the development and validation of best practice approaches for accurate assessment of these parameters seem necessary.

Cracked Teeth and Vertical Root Fractures in Pandemic Crisis - Retrospective Study.

Dental fatigue fractures are the result of occlusal overloads occurring because of increased intensity of occlusal forces or decreased resistance of dental hard tissues to habitual occlusal forces. In the COVID-19 pandemic, occlusal stress has increased significantly, and so has the number of dental fractures. The study has the aim to determine if the number of cases of dental fatigue fractures during the pandemic crisis was higher than in the immediately preceding period. The retrospective study was carried out in a private dental clinic, selecting from the case series presented during March 2019-March 2021 the cases of dental fatigue fractures presented for diagnosis and treatment. The data collected from the patients included the reason for the presentation, the dental and medical history, and results from dental examination and radiological data. The statistical analysis was carried out with Microsoft Excel and SPSS software. The study included 644 patients, 430 women and 214 men, with ages between 25 and 85 years (61±7.4 years). From a total of 2581 visits, 1534 visits were made to 383 patients between March 2019 and March 2020, and 1047 visits were made to 261 patients between March 2020 and March 2021, the number of visits decreasing by 31.75% during the pandemic. During the pandemic, the number of fractured teeth tripled, increasing from 0.53% to 1.53% (p=0.009). The most affected teeth were the maxillary premolars and the permanent first molar, both mandibular and maxillary. In most cases, the indication for treatment was extraction. The Sars-Cov2 virus pandemic crisis has significantly increased the number of teeth with dental fatigue fractures presented to the dental office for diagnosis and treatment.