Crest Region Research Articles

Optimal sites for mini-implant insertion into the infrazygomatic crest according to different craniofacial morphologies: A cross-sectional cone-beam computed tomography study

The infrazygomatic bone crest and other extraalveolar regions represent a viable option for the placement of temporary anchorage devices when distalizing the maxillary arch. This approach allows for the movement of the dentition without concern for potential collisions among dental structures. Nevertheless, it is of the utmost importance to conduct a thorough examination of the anatomy of this region before the placement of mini-implants to prevent potential injuries, such as maxillary sinus perforations. The objective of this study was to quantify the depth of the infrazygomatic crest and evaluate its correlations with age, gender, skeletal classification, and vertical pattern. The study sample of this cross-sectional, retrospective study consisted of 201 cone-beam computed tomography scans collected from patients treated at the master's program in orthodontics at the University of Valencia and at a private dental clinic. The cone-beam computed tomography scans were collected for 5 years, from January 2017 to May 2022. The total and intraalveolar lengths were defined and measured at 3 points: the distal roots of the maxillary second molars, the distal roots of the maxillary first molars, and the mesial roots of the maxillary first molars. These measurements were taken on both the right and left sides using the Carestream 3D Imaging System (Atlanta, Ga). The total length (TL) at the mesiobuccal level of the first molars was found to be significantly longer on both sides (P= 0.001). The intraalveolar length exhibited statistically significant differences between the right and left sides, with those of the left side exhibiting greater length (P<0.001). The normodivergent patterns demonstrated lower TL values than hypodivergent (P= 0.006) and hyperdivergent patterns (P= 0.033). A statistically significant inverse relationship was observed between the distance from the cementoenamel junction to the vestibular bone crest and the total and intraalveolar lengths in the studied regions. The TL was greatest in the region of the mesiobuccal root of the maxillary first molars, followed by the region of the distal root of the second molars, and finally, the region of the distobuccal root of the maxillary first molars. Patients with normodivergent patterns exhibited the lowest total infrazygomatic ridge height.

A new metric method for sex estimation using three-dimensional imaging of the nuchal crest.

In Walker's nonmetric method, the nuchal crest serves as the representative region for indicating sexual dimorphism in cranial bones. However, the accuracy of sex estimation using the nuchal crest is lower than that using other anatomical regions. Furthermore, because of the protruding processes and structurally challenging features characterized by uneven and rough surfaces, there is a lack of metric methods for sex estimation, making quantification challenging. In this study, we aimed to validate a derived metric method for sex estimation by reconstructing the nuchal crest region in three-dimensional (3D) images obtained from computed tomography scans of cranial bones and compare its accuracy with that of the nonmetric method. A total of 648 images were collected, with 100 randomly selected for use in the nonmetric method. We applied our metric method to the remaining 548 images. Our findings showed that the surface area of the nuchal crests was greater in male individuals than in female individuals. The nuchal crest surface area quantified by the metric method increased the accuracy of sex estimation by 48% compared with that by the nonmetric method. Our metric method for sex estimation, which quantifies the nuchal crest surface area using 3D images of the skull, led to a high sex estimation accuracy of 93%. Future studies should focus on proposing and quantifying new measurement methods for areas showing sexual characteristics in the skull that are difficult to measure, thereby enhancing the accuracy and reliability of sex estimation in human skeletal identification across various fields.

An in vitro study of a combined patient-specific device for safe and accurate insertion of infrazygomatic crest miniscrews.

To develop and assess the efficacy of a novel combined patient-specific device (CPSD) for the accurate and safe insertion of infrazygomatic crest miniscrews in orthodontic procedures. Twenty-eight miniscrews were placed in the infrazygomatic crest region of 28 cadaver maxillae using the direct manual method (n = 14) or the CPSD (n = 14) based on preset trajectories. The CPSD, designed based on the integration model, included a positioning guide, an insertion guide, and a depth-limiting groove. Deviations in the insertion site, tip location, insertion angle, and biting depth between the preset and real insertion trajectories were calculated to evaluate the accuracy of miniscrew insertion. Classification frequencies of root proximity, sinus penetration depth, and biting depth of the miniscrew after insertion were also calculated to evaluate the safety of miniscrew insertion. Regarding evaluation of accuracy, significant differences were observed in the deviation values of the insertion site, tip location, insertion angle, and biting depth between the CPSD and freehand groups (P = .001, P < .001, P < .001, P = .039, respectively). Regarding evaluation of safety, a significant difference was observed in the classification frequencies of root proximity between the two groups (P = .016). Compared with manual insertion, CPSD could be a preferred method for safe and accurate insertion of infrazygomatic crest miniscrews for orthodontists.

Measurement of Anterior Maxillary Alveolar Ridge Dimension and Assessment of Sagittal Root Position by Cone Beam Computerized Tomography (CBCT)

Maxillary anterior region is the implant site that may require the most rigorous pre-operative assessment as it will have a direct influence on aesthetic outcome and stability of the dental implant. In the present study, CBCT (cone beam computerized tomography) images were used to evaluate alveolar ridge dimension in the maxillary anterior region. This observational radiographic study was done at Nepal Medical College Teaching Hospital. The width of the alveolar bone was measured from the labial cortex to the palatal cortex of the maxillary anterior teeth in mm at the alveolar crest (L1), mid-root (L2), and apical root region (L3) for each tooth. Alveolar height was also measured from the alveolar crest to the floor of the nasal fossa. The Sagittal Root Position (SRP) of the maxillary anterior teeth was also assessed. Results showed that the maximum width of the alveolar bone was seen at L3 of canine and lateral incisor showed least width of alveolar bone width at L1. Maximum alveolar bone height was seen in canines. Males were seen to have increased width of the alveolar bone as compared to the females in all anterior teeth. The most frequent sagittal root position was class I which was seen in 270 (51.4%) of the total teeth examined, which was followed by class IV observed in 210 (40%) of the teeth examined. It could be concluded that for maxillary anterior region, additional regeneration therapy maybe required since class I is the most frequent SRP observed.

To evaluate the cortical bone thickness for ideal placement of infrazygomatic crest (IZC) and mandibular buccal shelf (MCS) bone screws in patients with different facial pattern using cone-beam computed tomography (CBCT)

This study aimed to measure the cortical bone thickness at different anatomical sites of InfraZygomatic Crest and Mandibular Buccal Shelf region for the ideal placement of IZC and MBS screws respectively in patients with different facial patterns using CBCT.Total participants were divided into 3 groups- GROUP A: horizontal growth pattern (FMA &amp;#60;22°); GROUP B: average growth pattern (FMA 22°-28°); GROUP C: vertical growth pattern(FMA &amp;#62;28°). Sixty CBCT images were taken into consideration. They were converted into standard DICOM format. Bone thickness were measured in the InfraZygomatic Crest (IZC) of the maxilla and in the Mandibular Buccal Shelf (MBS) region of the mandible using the Kodak CareStream CS 9300 Software.The results indicate that there was a highly statistical significant difference seen in the overall cortical bone thickness of IZC and MBS at various anatomical sites. The highest mean thickness was found to be at the MB70◦ maxillary 1st molar and distal root of the mandibular 1st molar. There was no difference in the bone thickness at the IZC region and at the MBS region seen between the horizontal and vertical facial patterns whereas the average facial patterns show the highest mean thickness but was not statistically significantThe study conducted on the Indian population yielded results demonstrating the possibly appropriate position for the IZC bonescrews and MBS bonescrews suggested that placing the IZC bonescrews at the mesiobuccal root of the maxillary 1st molar at an angulation of 70◦ and the MBS bonescrews at the distal root of the mandibular 1st molar at 11mm from the cementoenamel junction irrespective of the facial patterns could provide positive results.

Beta-arrestin 1 mediated Src activation via Src SH3 domain revealed by cryo-electron microscopy.

Beta-arrestins (βarrs) are key regulators and transducers of G-protein coupled receptor signaling; however, little is known of how βarrs communicate with their downstream effectors. Here, we use cryo-electron microscopy to elucidate how βarr1 recruits and activates non-receptor tyrosine kinase Src. βarr1 binds Src SH3 domain via two distinct sites: a polyproline site in the N-domain and a non-proline site in the central crest region. At both sites βarr1 interacts with the aromatic surface of SH3 which is critical for Src autoinhibition, suggesting that βarr1 activates Src by SH3 domain displacement. Binding of SH3 to the central crest region induces structural rearrangements in the β-strand V, finger, and middle loops of βarr1 and interferes with βarr1 coupling to the receptor core potentially impacting receptor desensitization and downstream signaling.

Falling film hydrodynamics of horizontal elliptical tube under column flow

Flow characteristics of falling film around a horizontal elliptical tube under column flow were numerically investigated with the volume of fluid method. The three-dimensional film thickness distributions for elliptical tubes with three ellipticities and two arrangements (the major axis oriented vertically and the major axis oriented horizontally) were captured. This investigation also considered the effects of spray Reynolds number and contact angle on film thickness distribution. A comparison between elliptical tube and circular tube was also performed under typical spray Reynolds number of 258 and tube spacing of 20 mm. The results show that the tube shape has a great influence on the film thickness and flow behaviors: The liquid film formed outside the elliptical tube with the major axis oriented vertically is thinner and more uniform than that of the circular tube. Conversely, the film on the elliptical tube with the major axis oriented horizontally is thicker and more non-uniform than that of the circular tube. The increasing of Reynolds number generally increases film thickness, particularly in the crest region. Under incompletely wetted condition, the increasing of ellipticity decreases the liquid film coverage rate around the tube. In addition, a correlation for predicting the film thickness around elliptical tubes was proposed.

Quasi‐Diurnal Lunar Tide O1 in Ionospheric Total Electron Content at Solar Minimum

AbstractFor the first time, characteristics of the geographical and seasonal distribution of the quasi‐diurnal lunar O1 tide were derived from a time series of ionospheric total electron content (TEC) maps provided by International Global Navigation Satellite System Service (IGS). The data analysis is focused on solar minimum in 2008 and 2009 where disturbing influences of geomagnetic and solar activity were minimal. We found that the magnitude of the O1 tide is as strong as the “dominant” semidiurnal lunar M2 tide. Relative amplitudes of 10% and larger are observed in some regions for the O1 component in TEC. The O1 component is particularly strong in northern hemispheric winter over the west coast of South America. There, two maxima occur which are northward and southward of the magnetic equator in the Equatorial Ionization Anomaly (EIA) crest regions. Following Yamazaki et al. (2017, https://doi.org/10.1002/2017ja024601), it might be assumed that a longitudinal anomaly of ionospheric conductivities in the Peruvian sector leads to a stronger modulation of the equatorial electrojet by the lunar tides. Electrodynamic lifting of plasma and transport to the EIA crests may explain the variations of the O1 component in TEC. Contrary to many studies, we find the O1 component (period 25.82 hr) more important than the M1 component (period 24.84 hr, a lunar day). We show that the geographical distribution of the O1 component is totally different from that of the M1 component which is smaller. The seasonal variation of O1 shows maximal amplitudes in northern hemispheric winter and minimal amplitudes in southern hemispheric winter.

Assessment of Bone Thickness at the Infra Zygomatic Crest Region for Various Orthodontic Miniscrew Implant (OMSI) Insertion Angles: A Cone-Beam Computed Tomographic Study.

To evaluate the infrazygomatic crest (IZC) bone and develop guidelines for the optimum placement of orthodontic miniscrew implants (OMSIs) along the distobuccal root of the permanent maxillary first molar. Bone thickness of the IZC region of 50 young adults (25 males and 25 females) aged 18-30 years were evaluated using cone-beam computed tomography images. The infrazygomatic bone thickness along the distobuccal root of the permanent maxillary first molar was assessed at various insertion angles (40° to 75° i.r.t the maxillary occlusal plane) with an increment of 5°. Student's t-test was used to compare the IZC bone thickness and height at the orthodontic miniscrew insertion site for males and females on the right and left sides. The bone thickness of the IZC region above the distobuccal root of the permanent maxillary first molar was estimated between 4.39±0.25 mm and 9.03±0.45 mm for insertion angles from 40° to 75° to the maxillary occlusal plane. The corresponding OMSI insertion heights were 17.71±0.61 mm to 13.69±0.75 mm, respectively, above the maxillary occlusal plane. There were statistically significant gender and side-wise variations in bone thickness at the IZC area and insertion height. The safe position for OMSI placement at the IZC was 13.69-16 mm from the maxillary occlusal plane with an insertion angle between 55° and 75°. These parameters provide the optimum placement of OMSIs along the distobuccal root of the permanent maxillary first molar.

Evaluation of bone thickness at infra-zygomatic crest region compared with cervical vertebrae maturation index.

Orthodontists should know variation in thickness of infrazygomatic crest region according to maturation status of patients. Therefore, it is of interest to evaluate the thickness of bone at infrazygomatic crest region and to correlate the thickness of bone with cervical vertebrae maturation index (CVMI) incorporating CBCT.A retrospective analysis of 120 patients' CBCT scans60 of them male and 60 female-was carried out. The thickness of the bone was determined at five locations. Using CBCT, the cervical vertebral maturation was created and the Hassel-Farmann index was used for analysis. A lone researcher conducted all of the measurements. Bone thickness of infrazygomatic arch at all five locations was found to increase as the maturation stage progressed from initiation stage to maturation stage. Then there was decrease in the bone thickness in completion stages compared to maturation stage. The thickness of bone at infrazygomatic arch is significantly correlated with CVM stages as determined by CBCT.

Diurnal and seasonal variation of GPS-TEC during a low solar activity period at EIA region (Bhopal)

The ionosphere near the equatorial ionization anomaly crest region in the Indian ionospheric sector was studied from May 2016 to April 2017, a solar minimum period. Total electron content (TEC) recorded using the multiple frequency GPS receivers at Bhopal (23.2° N, 77.4° E &amp; MLAT 14.2° N) is used for the study. The diurnal variation shows that the day minimum in TEC is attained around 06:00 hours LT, and the day maximum occurs at about 16:00 hours LT. A similar diurnal pattern was observed in all months across various seasons. During the period of study, it was observed that Seasonal variation of TEC was minimal in winter, whereas highest during equinox and summer months. The variation of TECmax with EEJ shows a positive correlation between the parameters for all the months. The highest correlation (0.8398) was observed in January 2017, while it was lowest (0.4004) in March 2017 and the results were compared with earlier observations, and a possible mechanism was discussed.

Ionospheric Channel Impulse Response Measurement System for NVIS Propagation Mode Over Java Island Based on Low‐Cost SDR Platform

AbstractThe development of a digital high‐frequency (HF) radio communication system requires an ionospheric channel model from the channel impulse response (CIR) measurement. Although the Watterson ionosphere channel model has been available and used for a long time, several CIR measurements have been conducted in all regions of the Earth in an attempt to validate or replace the Watterson channel model with a suitable model for their region. However, only a few CIR measurements were conducted in low‐latitude regions, especially over Indonesia. In this study, we develop the CIR measurement system for the near vertical incidence skywave (NVIS) propagation mode over Java Island based on the software defined radio platform to meet low‐cost and simple operation requirements. The specification of the system is based on the International Telecommunication Union ionospheric channel characteristic document and increased in order to be able to capture higher values. Results from a 1‐week campaign measurement period show the ability of the system to measure the root mean square of time delay within the range of 0.2–1.3 ms and the Doppler shift within the range of 0.7–1.1 Hz in the quiet conditions of the ionosphere. Further measurements will be conducted to obtain a comprehensive ionosphere CIR that is useful for designing the NVIS‐HF digital communication in Indonesia, which is located beneath the crest region of an equatorial ionospheric anomaly.

Bone turnover prediction in patients with chronic kidney disease (CKD) undergoing hemodialysis using shortened dynamic 18F-NaF PET/CT Ki–Patlak

This study investigated whether Ki–Patlak derived from a shortened scan time for dynamic 18F-NaF PET/CT in chronic kidney disease (CKD) patients undergoing hemodialysis can provide predictive accuracy comparable to that obtained from a longer scan. Twenty-seven patients on chronic hemodialysis, involving a total of 42 scans between December 2021 and August 2023 were recruited. Dynamic 18F-NaF PET/CT scans, lasting 60–90 min, were immediately acquired post-injection, covering the mid-twelfth thoracic vertebra to the pelvis region. Ki–Patlak analysis was performed on bone time–activity curves at 15, 30, 45, 60, and 90 min in the lumbar spine (L1–L4) and both anterior iliac crests. Spearman’s rank correlation (rs) and interclass correlation coefficient were used to assess the correlation and agreement of Ki–Patlak between shortened and standard scan times. Bone-specific alkaline phosphatase (BsAP) and tartrate-resistant acid phosphatase isoform 5b (TRAP5b) were tested for their correlation with individual Ki–Patlak. Strong correlations and good agreement were observed between Ki–Patlak values from shortened 30-min scans and longer 60–90-min scans in both lumbar spine (rs = 0.858, p < 0.001) and anterior iliac crest regions (rs = 0.850, p < 0.001). The correlation between BsAP and Ki–Patlak in the anterior iliac crests was weak and statistically insignificant. This finding suggests that a proposed shortened dynamic 18F-NaF PET/CT scan is effective in assessing bone metabolic flux in CKD patients undergoing hemodialysis, offering a non-invasive alternative approach for bone turnover prediction.

Exploring ionospheric plasma density trends in the Indian equatorial crest region under varying solar activity conditions

Long-term trends in the evolution of ionospheric plasma at Hyderabad (17.38∘N, 78.48∘E; 8.52∘N Magnetic Latitude), a near-equatorial anomaly (EIA) crest region of the Indian ionospheric sector, have been studied using 9 years of vertical Total Electron Content (TEC) data from 2004 to 2009 and 2011 to 2013 using global positioning satellites (GPS) measurements. The study examined the mean diurnal, monthly, seasonal, and yearly variations of TEC during geomagnetic quiet days in different seasons from 2004 to 2013. The findings reveal that the daytime TEC at the anomaly crest region exhibits semi-annual variations throughout the study period, while midnight TEC shows semi-annual variation only during the high solar activity years of 2011–2013. The winter anomaly was observed in 2004 and 2006. The study also assessed the performance of the International Reference Ionosphere (IRI) 2016 model in reproducing GPS TEC variability at the equatorial crest region. The diurnal and seasonal variation patterns in IRI-TEC show a good correlation with GPS TEC. However, the IRI 2016 model tends to overestimate TEC values during low solar activity conditions (2006–2009) but represents TEC variations reasonably well during high solar activity periods (2011–2013). Nevertheless, the IRI model fails to capture the wide plateau-like structure in the peak TEC, typically occurring between 1200–1600 IST at Hyderabad. Additionally, IRI-TEC consistently indicates very low TEC values during the early morning hours, whereas GPS-TEC measurements suggest a significant presence of plasma density. The study suggests a strong influence of the solar cycle on TEC variations at Hyderabad, evident from the positive correlation (R2= 0.71) with the F10.7 cm index. This characteristic is also well represented by the IRI 2016 model.

The Latitudinal and Longitudinal Variation of the Semidiurnal Lunar Tide in the Ionosphere During 2013

AbstractThe present paper studies the latitudinal and longitudinal variation of ionospheric semidiurnal lunar tide (M2) perturbations in 2013 with total electron content (TEC) data. Results show that the latitudinal distribution of M2 exhibits longitudinal difference. At 100 ∼ 120°E and 80 ∼ 100°W longitudes, the strongest M2 perturbations in the northern and southern hemispheres roundly appeared at about 10° ∼ 20°N and 15° ∼ 25°S magnetic latitude (MLAT), respectively, which supports previous suggestion that the M2 maximized in the EIA crest regions. Moreover, the latitude range of M2 at 80 ∼ 100°W longitudes was wider than that at 100 ∼ 120°E longitudes, especially for southern hemisphere (SH). The M2 maximized at 20° ∼ 30°N MLAT in the northern hemisphere (NH) and was absent in the SH at 50°W ∼ 20°E longitudes, which was distinctly different than those at other longitudes. This abnormal behavior of latitudinal distribution of M2 may be caused by the large magnetic declination angle at 50°W ∼ 20°E longitudes. Meanwhile, the longitudinal variation and hemispheric asymmetry of M2 amplitude are different between NH winter (SSW period) and other seasons. The M2 amplitudes were stronger disturbances in the NH and in the American longitudinal sector in NH winter. However, in other seasons, the M2 amplitude was largest in Asian sector, and the M2 amplitude in NH was larger than SH at 0° ∼ 130°E longitudes, which was contrast to these at 0° ∼ 110°W longitudes. These differences of M2 variation between NH winter and other seasons may be related to the differences of the combined effects of the geomagnetic configuration and background conditions of the atmosphere and ionosphere.

Comparison of different maxillary advancement protocols in patients with unilateral cleft lip and palate: a finite element analysis.

The aim of this study was to evaluate the stress distributions and possible amount of movement in the maxillofacial region resulting from different maxillary advancement protocols in patients with unilateral cleft lip and palate. A unilateral cleft lip and palate model (CLP model) with Goslon score 4 was created for finite element analysis. Three different protocols were compared: Group 1: usage of a face mask with elastics placed at a 30? angle to the occlusal plane over a conventional acrylic plate; Group 2: usage of a face mask with elastics placed at a 30? angle to the occlusal plane over miniplates placed in the infrazygomatic crest region; Group 3: usage of elastic from the menton plate placed in the mandible to the infrazygomatic plates in the maxilla. Dental effects were greater in the maxillary protraction protocol with a face mask over a conventional acrylic plate (Von Misses Stress Values; Group 1?=?cleft side:0.076, non-cleft side:0.077; Group 2?=?cleft side:0.004, non-cleft side: 0.003; Group 3?=?cleft side:0.0025; non-cleft side:0.0015), whereas skeletal effects were greater in maxillary protraction protocols with face mask using skeletal anchorage (Von Misses Stress Values; Group 1:0.008; Group 2:0.02; Group 3:0.0025). The maximum amount of counterclockwise rotation of the maxilla as a result of protraction was observed in traditional acrylic plate face mask protocol, and the minimum amount was observed by using elastics between infrazygomatic plates and menton plate. In individuals with unilateral cleft lip and palate with Goslon score 4, it was observed that the skeletally anchored face mask caused more skeletal impact and displacement than both the traditional acrylic plate face mask model and the pure skeletally supported maxillary protraction model. When planning maxillary protraction treatment in patients with cleft lip and palate, it should be considered that more movement in the sagittal plane might be expected on the cleft side than the non-cleft side, and miniplate and screws on the cleft side are exposed to more stress when using infrazygomatic plates as skeletal anchorage.

Statistical Analysis of Ionospheric Correlation for Shortwave System

AbstractStatistical analysis of the temporal and spatial variations in the ionosphere is necessary to improve the shortwave system. Based on the standardized Euclidean distance algorithm, multisource ionospheric assimilation data, International GNSS Service vertical total electron content data, and ionosonde data are used to statistically analyze the ionospheric correlation distance, and the variation of ionospheric correlation distances with local times, magnetic latitudes, and seasons are obtained. The statistical analysis results show that the zonal ionospheric correlation distance presents minima in the equatorial ionospheric anomaly crest regions. Additionally, the meridional correlation distance in middle magnetic latitudes is greater than that in other regions. The zonal ionospheric correlation distance presents obvious local‐time variability. The variation trends of the meridional and zonal correlation distance during spring and autumn are similar. The patterns of the ionospheric correlation range variation with local times, magnetic latitudes, and seasons can be used to select the optimal locations or spacing for ionosonde stations, shortwave multi‐station systems, and shortwave radio beacons.

Site selection of micro-implant anchorages in the infrazygomatic crest in adult orthodontic patients.

To determine the optimal placement of miniscrews, this study compared adult male and female patients in terms of cortical bone density, cortical bone thickness, and available bone width in the infrazygomatic crest region. The cone beam computed tomography imaging data of 200 patients (20-30 years old; 100 males and 100 females) were collected. The right maxillary posterior teeth in the sagittal plane were divided into six levels from proximal to distal, and three measurement sites were positioned at vertical distances of 8, 10, and 12 mm from the cementum. Cortical bone density, cortical bone thickness, and available bone width were measured in 18 measurement sites in the infrazygomatic crest and analyzed statistically. The highest cortical bone density, cortical bone thickness, and available bone width in the infrazygomatic crest in adult male and female patients were at the level of the interradicular space between the maxillary second premolar and maxillary first molar. The bone cortical density and thickness increased with vertical height, whereas the available bone width decreased with increasing vertical height. Differences were observed in cortical bone density, cortical bone thickness, and available bone width between adult male and female patients. The optimal implantation sites of the micro-implant anchorages in the infrazygomatic crest were at the level of the interradicular space between the maxillary second premolar and the maxillary first molar, and the vertical height of the optimal implantation site in males was appropriately higher than that in females.

Anatomical study on the posterior alveolar canal in maxillary tuberosity region using computed tomography

ObjectiveThis study aimed to identify the anatomical characteristics of the posterior alveolar canal (PAC) and related maxillary bone using computed tomography (CT). MethodsThe study included 40 Japanese cadavers (70 hemi-heads), comprising 23 males (41 hemi-heads) and 17 females (29 hemi-heads). Simple CT data of the maxillary bone region of the specimens were obtained and analyzed using a measurement software with reference to the Frankfurt horizontal (FH) plane to identify the PAC in the maxillary tuberosity region, alveolar crest (AC), and corner of the inferior crest of the zygomatic process (CICZP). The shortest distances between the PAC and the respective landmarks and the smallest width of the posterior wall of the maxillary sinus (WPWMS) at the PAC level were calculated and analyzed statistically. ResultsOf all specimens, the mean and SD of AC-PAC: 21.4 ± 3.32 mm, horizontal PAC-CICZP: 15.1 ± 2.89 mm, vertical PAC-CICZP: 5.70 ± 3.15 mm, WPWMS: 0.81 ± 0.31 mm, and the coefficients of variation ranged 15.5–55.3%. In the WPWMS, the mean value was statistically smaller in the female group (0.59 mm) than in the male group (0.96 mm) (p < 0.001). ConclusionsThe results showed certain tendencies in the distances between the PAC and the respective anatomical landmarks with large variations. The thickness of the posterior wall of the maxillary sinus was thinner in females than in males. However, it is < 1 mm in both sexes, and external forces caused by trauma or surgery may fracture the posterior wall of the maxillary sinus and damage the posterior superior alveolar artery regardless of sex.

Load Carrying Mechanism of Geocell Reinforced Embankment on Soft Soil

This paper investigates the influence of geocell reinforcement on the load carrying mechanism of embankments over soft soil. Using a geocell mattress beneath an embankment on soft soil, the size of the rupture zone in the foundation bed is found to have increased significantly, leading to increase in the mobilized shear resistance, and giving rise to enhanced bearing capacity. While the unreinforced embankment, owing to differential settlements, tends to crack and disintegrate, the geocell reinforced embankment continues to behave as a monolith up to a high surcharge pressure/fill height. The performance improvement tends to increase with increase in height of the geocell mattress. Strain variation in the geocell mattress indicates that its reinforcing efficacy is the largest at the central crest region of the embankment and decreases toward the toe. As the geocell mattress behaves as a semirigid slab, when it is present, the stress dispersion angle tends to increase significantly. Considering the stress dispersion zone as an equivalent rigid footing, the bearing capacity of unreinforced and geocell reinforced embankments are analyzed. The predicted bearing capacities are found to be in close agreement with the experimentally observed ones. Three-dimensional numerical analyses indicate that the pressure–settlement behavior of the embankments observed in the model tests is reproduced at large scale.