Ridge Crest Research Articles

Dimensional Stability of Light-Activated Urethane Dimethacrylate Denture Base Resins.

An accurate and dimensionally stable trial denture base is required for a successful denture. The aim of this in vitro study was to assess the dimensional stability of a light-activated urethane dimethacrylate (UDMA) visible light cure (VLC) denture base with three fabrication techniques and different curing cycles. Forty-five VLC denture base samples were divided evenly into three groups. Group A used a conventional fabrication technique with a curing cycle of 5 min. Group B used a modified fabrication technique with two 4-min curing cycles. Group C used a multi-step fabrication technique with three curing cycles (4 min, plus 4 min, plus 2 min). The samples were sectioned and observed under a stereomicroscope to measure the discrepancy between the sample and the master cast. The mean dimensional discrepancy (mm) at the molar region at mid-palate, after 24 h in Group A, B and C was 0.790 mm, 0.741 mm and 0.379 mm, respectively; at the right ridge crest, it was 0.567, 0.408 and 0.185, while at the left ridge crest it was 0.475, 0.331 and 0.125, respectively. Statistical analysis showed significantly different dimensional discrepancies among the groups at all three sites; right ridge crest (F = 93.54, p < 0.001), left ridge crest (F = 105.96, p < 0.001) and mid-palate (F = 125.53, p < 0.001). Within the limitations of this laboratory study, it can be concluded that the denture base using a multi-step fabrication technique with three curing cycles provides better adaptation than the conventional technique. The significance of the study is that clinicians should consider performing denture base fabrication using a multi-step technique to enhance adaptation and hence the stability of the dentures for patients.

MAPR: PMEL’s Miniature Autonomous Plume Recorder

The NOAA Vents program was established in 1983 at the Pacific Marine Environmental Laboratory (PMEL; Hammond et al., 2015), just six years after the discovery of hydrothermal vents and their unique chemosynthetic ecosystems (Corliss et al., 1979). Because seafloor hydrothermal venting contributes significantly to the transfer of heat and mass from the solid Earth to the ocean, the program’s mission was to systematically explore, discover, and characterize the environmental impacts of submarine volcanism and hydrothermal venting on ocean physical, chemical, and biological processes. The program initially focused on the mid-ocean spreading centers in PMEL’s “backyard” (i.e., the Gorda, Juan de Fuca, and Endeavour Ridges in the Northeast Pacific) where segment-scale surveys detected plumes in the water column above the ridge crest that led to the discovery of numerous individual vent fields (see Hammond et al., 2015, and references therein). New technologies and techniques were created and/or adapted to address the challenges of finding and studying these vents. Repeat visits to the Northeast Pacific sites documented spatial and temporal changes, stimulating the development of new hypotheses about their associated biogeochemical processes. However, testing how broadly applicable these hypotheses would be on a global scale required discovering new vent sites from a far wider range of geological settings, and global-scale exploration requires significant resources.

Management of Invasive Cervical Root Resorption with Biodentine: A Case Report

Abstract Invasive cervical resorption is a silent, yet aggressive resorption on the external surface of root that affects the cervical area below the epithelial attachment and above the ridge crest. Proper diagnosis and management of this condition determine the outcome of the treatment. Advancements in digital imaging modalities such as cone-beam computed tomography have enabled the clinician to diagnose and locate extent of pathological changes with great precision. Studies have reported that the use of 90% trichloroacetic acid (TCA) has got the ability to arrest the clastic activity. The commonly used materials to seal the resorptive defect are mineral trioxide aggregate and its modifications. This is a case report of surgical management of invasive cervical root resorption of mandibular canine using 90% TCA and the bioactive cement, Biodentine as restorative material to seal the defect.

Measurement and Analysis of Anatomical Structures Associated with the Implantation of Anterior Mental Foramen Based on CBCT

To evaluate the occurrence and morphological characteristics of related anatomical structures in the anterior mental foramen region and to verify the measurement consistency by cone beam CT (CBCT) and specimen measurement. Thirty-two mandibular specimens were selected to measure the relevant anatomical structures and to take CBCT images of the specimens for 3D reconstruction using NNT-Viewer. The studies included the occurrence and diameter of the mental foramen, accessory foramen, median lingual foramen, the distance from the lower margin of the foramen to the lower margin of the mandible, and the distance from the upper margin of the foramen to the crest of the alveolar ridge. Thirty-two specimens including a total of 59 central lingual foramens, with a 100% probability of occurrence. Four specimens were found to have an accessory mental foramen, of which 1 had bilateral accessory mental foramens. Compared with direct observation, there were differences in the number of central lingual foramens in 3 specimens. The mean distance between the upper mental foramen edge and the alveolus crest was 13.7 mm. There were statistically significant differences between the two methods in measuring the distance (mm) between the central lingual aperture and the alveolar crest (P<0.05). Except for the distance between the central lingual aperture and the alveolar crest (ICC=0.658), the ICC of the other study variables was above 0.85. The measurement results of the two methods showed a high degree of consistency. The measurement results of CBCT in this study showed a high degree of consistency with the measurement results from specimens, and the relevant anatomical structures of jaw bones could be analyzed using CBCT before the operation in the intermental foramen region.

Angular Dimensions of Retromolar Pad: An Observational Study

Background Retromolar pad RMP is at an incline and is relatively resistant to resorption as compared to mandibular residual alveolar ridge due to the attachments of muscles and dense cortical bone underlying it. The existing stock trays are usually flat and cause undue pressure in RMP region often requiring arbitrary modification of stock tray. This study was conducted to record the RMP incline and formulate a stock tray that will help in recording an accurate impression to achieve excellent seal stability and support in the denture base.Methods RMP inclines and the residual ridge crests were marked on 280 master casts using markers and the angle between them were recorded using a protractor kept at the level of eye. Results The angle of RMP with the crest of ridge recorded on right and the left sides ranged between 105deg- 175deg and 125deg-180deg respectively. A p value of 0.024 was obtained with paired sample t-test. The mean angle of left and right sides combined was 152.12 plusmn 13.10deg. After removal of outliers the lower limit was 135deg which can be incorporated in an impression tray to accommodate the critical incline of RMP.Conclusion The present study recorded an angle of 135deg between RMP and residual ridge which can be considered as the standard angle for stock trays. Incorporating an angle of 135deg would be adequate to accommodate higher angles up to 175deg. This enables creating a strong foundation for a good complete denture prosthesis in patients with extremely resorbed mandibular completely edentulous ridges.

Oligo-Miocene subduction-related volcanism of the Loyalty and Three Kings ridges, SW Pacific: a precursor to the Tonga-Kermadec arc

The SW Pacific region contains several ridges and basins that are inferred to represent pre-Quaternary volcanic arcs and back-arc basins. The geology of these features is less well characterized than that of the active Tonga-Kermadec and Vanuatu arcs. We report new major and trace element, and Pb, Hf, Sr and Nd isotope data for 27 lavas dredged from the Loyalty and Three Kings ridges during the 2015 VESPA cruise of R/V l'Atalante. Low-K basalts were dredged from the seabed deeper than 3300 m, and high-K to shoshonitic suites from shallower ridge crests at 2000–3300 m. The samples are mainly basalts, with lesser trachybasalts, basaltic andesites, trachyandesites andesites, dacites, and one granite (anhydrous SiO2 and K2O + Na2O range from ∼47 to 64 and 1.5 to 11 wt% respectively). Trace element patterns allow discrimination of three geochemical signatures, identified as i) depleted, ii) transitional and iii) enriched, based on their light to heavy rare earth element (REE) ratios (with La/Sm ranging from 0.4 to 8). Depleted and transitional samples are basalts, featuring REE concentrations similar to MORB, but with high field strength element and large ion lithophile element contents, typical of back-arc basin basalts. The most enriched samples are basaltic andesites, andesites, trachyandesites and trachytes with island arc magma trace element signatures. Pb isotope ranges are limited (208Pb/204Pb ∼38 to 39.8, 207Pb/204Pb ∼15.51 to 15.64 and 206Pb/∼17.9 to 20.1), while Hf isotopes display more diverse compositions (εHf ranging from +7.7 to +14). Both Nd (εNd = 2.8–9.3) and Sr (87Sr/86Sr = 0.7026–0.7048) isotopes are correlated with Hf data. Trace element and isotopic compositions can be explained in terms of mixing between three distinct geochemical endmembers in the mantle resembling DMM, HIMU and EM-2 sources. Our study confirms voluminous subduction-related magmatism on the Loyalty and Three Kings ridges, mostly of Late Oligocene – Early Miocene age. The issue of polarity of subduction to generate these rocks remains open, but the composition-space-time distribution of the igneous rocks can be explained in the context of SW Pacific geodynamics using a west-dipping Pacific slab model.

Assessment of location and anatomical characteristics of lingual foramen using cone beam computed tomography

Background/Aim. A lingual foramen (LF) is a small opening on the lingual surface of the mandible, most frequently located in the middle of the anterior part of the mandible, and shows significant variations in its location, size, and number. The aim of this study was to assess the location and anatomical characteristics of LF using cone beam computed tomography (CBCT). Methods. The research was designed as a retrospective study in which 99 CBCT scans were analyzed. The analysis covered the number of LF, their location concerning the teeth and the mandibular region itself, diameter, distance from the alveolar ridge crest, distance from the inferior border of the mandible, distance from the tooth apex, and position in relation to the tooth apex. Results. The average frequency of LF per patient was 2.4 ? 1.2. The largest number of LF were localized in the region of lower central incisors. Out of the total number of LF, 82.5% belonged to median LF, while 17.5% belonged to lateral LF. In 63.2% of cases, LF had a diameter of ? 1 mm, whereas, in 98.3% of cases, it was localized below the tooth apex. There was a statistically significant difference in the distance of LF from the alveolar ridge crest and the LF diameter in relation to gender (p = 0.019; p = 0.008). Conclusion. LF can be reliably localized and visualized using CBCT. It is recommended that CBCT scanning of the mandible be used while planning an oral surgical procedure and implant placement in order to prevent injuries of the neurovascular bundle, which passes through LF.

Yam Seep at Four-Way Closure Ridge: a prominent active gas seep system at the accretionary wedge SW offshore Taiwan

Hydroacoustic surveys at the accretionary wedge southwest of Taiwan reveal a confined active hydrocarbon seepage area of ~ 49,000 m2 in ~ 1350 m water depth on the northern crest of the Four-Way Closure Ridge, which we call Yam Seep. In this study, multibeam and side-scan sonar data acquired during surveys with an autonomous underwater vehicle during an expedition with R/V Ocean Researcher I in 2017 showed that the area is characterized by rough topography and high seafloor backscatter. Seafloor observations with a video sled and sediment sampling with gravity corers and the MeBo seafloor drill rig during an expedition with R/V SONNE in 2018 revealed that the area is almost entirely covered by intensely fractured methane-derived carbonates, which indicate that seepage has been ongoing for thousands of years. Hydroacoustic anomalies (‘flares’) in the water column indicated the presence of several gas bubble emission sites mostly at the center and eastern flank of the area in 2019. Drilling through massive carbonates in the northwestern part of Yam Seep induced free gas escape from a depth of ~ 5.1 m. This suggests the presence of gas hydrates in the subsurface as the seep area is located well within the gas hydrate stability zone. The inter-disciplinary investigations of the Yam Seep demonstrate that upward migration of light hydrocarbons and seafloor discharge has a considerable influence on the seabed properties.

Cyclic tidalites and seismites at a submarine hydrothermal system for a 2450 Ma banded iron formation, Hamersley Basin, Western Australia

The Hamersley Group in the Hamersley Basin, Western Australia, contains major deposits of banded iron formation of Neoarchean–Paleoproterozoic age (2629–2449 Ma). The 2450 Ma Weeli Wolli Formation near the top of the group includes banded iron formation with microbands (≤0.05–0.5 mm to rarely 1 mm thick) of chert and iron oxide lamina couplets that display distinctive cycles. Some adjacent, thin microbands have merged with compaction and the diagenetic removal of chert laminae, and maximum counts of cycle period by different studies is preferred, suggesting a period of ∼28 ± 2 microbands. Associated cyclic iron formation shows soft-sediment plastic deformation and brittle fracturing. Rare earth element geochemistry indicates that much of the iron in late Archean–early Paleoproterozoic banded iron formations was derived from submarine hydrothermal systems. Monitoring of hydrothermal vents on mid-ocean ridges and seamounts has identified tidal modulation of the discharge, temperature and dispersal of deep-sea hydrothermal plumes principally by semidiurnal variations in tidal loading and earth tides. Microearthquake swarms are associated with deep-sea hydrothermal systems at the crests of mid-ocean ridges, and tidal triggering of microearthquake activity is indicated for a hydrothermal system on the East Pacific Rise. The microband cycles in the Weeli Wolli Formation are interpreted as tidalites, comprising ∼28 ± 2 semidiurnal microbands per lunar (synodic) fortnightly cycle, related to the tidally modulated activity of a submarine hydrothermal system. The associated plastically deformed and brittle-fractured sediments are viewed as seismites resulting from microearthquakes also related to the hydrothermal system. The Weeli Wolli microband cycles and seismites may represent a rarely identified instance of iron-formation deposition near a submarine hydrothermal system. KEY POINTS Submarine hydrothermal venting was a major source of iron in late Archean–early Paleoproterozoic banded iron formations. Semidiurnal variations in tidal loading and earth tides commonly modulate present-day deep-sea hydrothermal activity, and microearthquake swarms are associated with deep-sea hydrothermal systems. Early Paleoproterozoic banded iron formation from the Hamersley Basin displays cycles with an estimated period of ∼28 ± 2 microbands and associated plastic deformation and brittle fracturing. The microband cycles are interpreted as tidalites comprising ∼28 ± 2 semidiurnal increments grouped in fortnightly cycles at a tidally modulated submarine hydrothermal system, and the deformed sediments as seismites caused by related microearthquake activity.

Mechanisms Driving the Dispersal of Hydrothermal Iron From the Northern Mid Atlantic Ridge

AbstractThe dispersal of dissolved iron (DFe) from hydrothermal vents is poorly constrained. Combining field observations and a modeling hierarchy, we find the dispersal of DFe from the Trans‐Atlantic‐Geotraverse vent site occurs predominantly in the colloidal phase and is controlled by multiple physical processes. Enhanced mixing near the seafloor and transport through fracture zones at fine‐scales interacts with the wider ocean circulation to drive predominant westward DFe dispersal away from the Mid‐Atlantic ridge at the 100 km scale. In contrast, diapycnal mixing predominantly drives northward DFe transport within the ridge axial valley. The observed DFe dispersal is not reproduced by the coarse resolution ocean models typically used to assess ocean iron cycling due to their omission of local topography and mixing. Unless biogeochemical models account for fine‐scale physics and colloidal Fe, they will inaccurately represent DFe dispersal from axial valley ridge systems, which make up half of the global ocean ridge crest.

Evaluation of the distribution characteristics of the mandibular lingual foramen and its potential risks during implant surgery using cone-beam computed tomography a cross-sectional, retrospective study.

The lingual foramen is a risk factor for implantation and other mandibular surgeries, but there are few systematic studies on the anatomical and distribution characteristics of the lingual foramen in the entire mandible. A retrospective study was performed using 405 CBCT images. The anatomical characteristics and symmetrical distribution of the mandibular lingual foramen were analyzed. All patients had at least one lingual foramina. According to the positional relationship between the mandibular lingual foramen and the root apex of tooth, the mandibular lingual foramen is divided into the upper lingual foramen and the lower lingual foramen. Upper lingual foramen were divided into three types according to its running direction, namely Type 1 (Enters the mandible and descend in the direction of the lower edge of the mandible), Type 2 (Enters the mandible and descends in the direction of the lower edge of the mandible with branches), and Type 3 (It enters the mandible and divides into two branches, one ascends toward the crest of the alveolar ridge, and the other descends toward the lower edge of the mandible). And their respective prevalence are 84.0% [95% Tolerance Limit (TL) 81.2%-86.8%], 9.9% [95% TL 7.6%-12.1%], and 6.1% [95% TL 4.3%-8.0%]. In addition, the 81.8% [95% TL 79.0%-84.7%] of the upper lingual foramen is distributed in the central incisor area. Lower lingual foramen were divided into three categories according to the running direction, namely Category 1 (Enters the mandible and ascends toward the buccal bone plate), Category 2 (Enters the mandible and descends toward the buccal bone plate), and Category 3 (Go straight into the mandible toward the buccal bone plate). And their respective prevalence are 29.6% [95% TL 26.4%-32.7%], 50.9% [95% TL 47.5%-54.4%] and 19.5% [95% TL 16.8%-22.3%]. The frequency of lower lingual foramen distributed anteriorly to the mental foramen is 55.8% [95% TL 52.3%-59.2%], mid-mental foramen is 21.4%[95% TL 18.5%-24.2%], and posterior to the mental foramen is 22.8% [95% TL 20.0%-25.8%]. Both the upper and lower lingual foramina should be evaluated in the anterior, middle, and posterior regions of the mental foramen before implant surgeries.

Clinical and radiographic outcomes of customized allogeneic bone block versus autogenous bone block for ridge augmentation: 6 Month results of a randomized controlled clinical trial.

To evaluate the efficacy of customized allogeneic bone block (CABB) for ridge augmentation compared with autogenous bone block. Patients (N=24) in need of ridge augmentation were randomly assigned to one of two treatment modalities: CABBs (CABB group) and autogenous bone blocks (ABB group). The primary outcome of the present study was the horizontal bone gain at 1 mm below the alveolar ridge crest (HBG1 ). Secondary outcomes were the bone gain at other levels, bone resorption rate, ridge width, operative time, postoperative pain score, and histological results. The data obtained from the current study were analysed using a generalized linear mixed effects model, two-sample t-test, or a Mann-Whitney U-test. Twenty-four patients completed a 6-month follow-up. One patient in the CABB group exhibited block exposure. The CABB group had significantly more horizontal bone gain (HBG1 ) and less horizontal bone resorption (HBRR1 ) at 1 mm below the alveolar ridge crest when compared with those in the ABB group (HBG1 : CABB group [4.29 ± 1.48 mm] and ABB group [1.12 ± 3.25 mm]; HBRR0 : CABB group [42.15 ± 14.03%] and ABB group [92.52 ± 55.78%], p < .05). In addition, a longer operative time was reported in the ABB group compared with the CABB group (p < .05). The histological observation indicated a new bone formation in both groups. The use of CABBs resulted in more horizontal bone gain and less horizontal bone resorption at 1 mm below the alveolar ridge crest at 6months post-surgery compared with ABBs while reducing the operative time in the treatment of ridge augmentation.

The spatiotemporal distribution of pollen traits related to dispersal and desiccation tolerance in Canarian laurel forest

AbstractQuestionsPollen traits (e.g., size, wall thickness, number of apertures) have been suggested to be relevant in terms of pollination mechanisms and the ability of the male gametophyte to withstand desiccation. We examined the spatiotemporal distribution of pollen traits related to dispersal (ornamentation and dispersal unit) and desiccation tolerance (wall thickness, presence of furrows and pores and pollen size). Specifically, we address two questions: how are the pollen traits distributed in relation to different levels of aridity? And, how did the pollen trait composition change with changing past environmental conditions?LocationLaurel forests of La Gomera and Tenerife (Canary Islands).MethodsWe used pollen rain from 19 forest plots on an elevational gradient of 1050 m and all laurel forest types (cold, dry, humid and ridge crest) to quantify pollen trait composition using community‐weighted means. In addition, we used fossil pollen to examine the composition of pollen traits over 9600 years in response to known intervals of regional past climate change.ResultsOur results demonstrated increased prevalence of desiccation tolerance‐related pollen traits over drier areas of the laurel forest distribution. We also found increased prevalence of rich pollen grain ornamentation in the core of the laurel forest distribution. Holocene pollen functional diversity increased during a trend towards drier conditions as did the proportion of pollen grains with apertures and thicker walls to indicate desiccation tolerance.ConclusionsOur study provides the first step towards understanding the role of pollen traits when quantifying the dynamics of different plant communities.

Transverse aeolian ridges in the landing area of the Tianwen-1 Zhurong rover on Utopia Planitia, Mars

The enigmatic transverse aeolian ridges (TARs), with distinct morphology and albedo, are among the key geological features investigated by China's Tianwen-1 Zhurong rover on southern Utopia Planitia, Mars. Their morphologies and morphometrics are investigated through high-resolution imaging science experiment (HiRISE) orthoimage and Digital Terrain Model (DTM) products. A total of 5089 TARs are identified, with barchan TARs being predominant (97.6%). Morphometric analysis shows these TARs to be small and symmetrical aeolian landforms, with an average crest–ridge lengths of 33.9 ± 20.5 m, profile widths of 9.4 ± 3.8 m, profile heights of 0.4 ± 0.4 m, profile-height-width ratios of 0.04 ± 0.02, and profile symmetry ratios of −0.01 ± 0.13. In-situ observations from the Navigation and Terrain Camera (NaTeCam) show the crests of the TARs to be dark and sharp, while the flanks are interlaced by dark and bright materials. Close-up Multispectral Camera (MSCam) images reveal the TARs to be coated by granules of ∼1.5 mm in diameter. Given the morphometric characteristics and the presence of coating granules, the TARs in the landing area could be categorized as megaripples. Buffered crater counting (BCC) technique-derived absolute model age (AMA) reveals the formation time, or the last active period of the TARs, could be as recent as 1 Ma in the Late Amazonian. The morphometrics and direction of the horns of the barchan TARs suggest the winds for the formation of TARs blew mostly from the north. During the spring-summer transition period (Ls: 50°–93°), the Mars Climate Station (MCS) had recorded local bimodal winds in the landing area, with the speed of the northerly wind in the afternoon being a little stronger than the speed of the southerly wind in the morning. These observations are consistent with the wind fields described in the Mars Climate Database (MCD), which imply the northerly winds during the northern winter season to be responsible for the net sediment transport to the south. Two TARs observed in-situ with secondary NW-SE trending crest-ridges indicate that forked TARs might form given sufficient time (i.e., in the order of millions of years) under modern wind conditions, i.e., the TARs may be currently reworked, if only extremely weakly.

From Long‐ to Short‐Term Inter‐Plate Coupling at the Subducted Carnegie Ridge Crest, Offshore Central Ecuador

AbstractWe investigate the relationship between the long‐term (Quaternary) interplate coupling and the short‐term geodetically derived interseismic coupling at the Central Ecuador subduction zone. At this nonaccretionary margin, the Cabo Pasado shelf promontory and coastal area are associated with two inter‐plate geodetically locked patches. The deepest patch ruptured co‐seismically during the Mw7.8‐2016 Pedernales earthquake, while the shallowest underwent dominantly after‐slip. Marine geophysical and chronostratigraphic data allow reconstructing the Quaternary tectonic evolution of the shelf promontory and substantiating variation of the long‐term inter‐plate coupling that led to the geodetically locked patches. Prior to ∼1.8 Ma, the outer‐wedge inter‐plate coupling was strong enough to activate trench‐subparallel strike‐slip faults. Then, between ∼1.8 and 0.79 Ma, shortening and uplift affected the shelf promontory, implying a locally increased inter‐plate coupling. After a short, post‐0.79 Ma period of subsidence, shortening and uplift resumed denoting a high inter‐plate coupling that endured up to the present. The synchronicity of the structural evolution of the shelf promontory with the subduction chronology of two reliefs of the Carnegie Ridge crest suggests that the locked patches are caused by a geometrical resistance to subduction that propagates landward causing permanent deformation. In 2016, the deepest subducted relief localized stress accumulation and high seismic slip, while the shallowest relief, which is associated with a weakened outer‐wedge, prevented updip rupture propagation. Thus, at nonaccretionary margins, active outer‐wedge strike‐slip faults might be considered a proxy of near‐trench coupling, and subducted relief a cause of plate coupling but an obstacle to the tsunami genesis when the relief is shallow.

Prevalence, Radiographic Features and Clinical Relevancy of Accessory Canals of the Canalis Sinuosus in Cypriot Population: A Retrospective Cone-Beam Computed Tomography (CBCT) Study.

Background and Objectives: This retrospective study aims to evaluate the prevalence, radiographic features, and clinical relevancy of the accessory canals (AC) of the canalis sinuosus (CS) in patients referred for implant surgery. Materials and Methods: Cone-beam computed tomography (CBCT) images of the patients were collected and ACs were evaluated. Age, sex, bilateral distribution, localization, diameter, distance to the buccal cortical plate, distance to the crest of the alveolar ridge, terminal ending localization, and the presence of tooth or implant were recorded. Ninety-one patients who were eligible for this study were enrolled. Results: A total of 188 ACs were found in 91 patients with 86 bilateral and 5 unilateral distributions. The mean age of the patients was 45.39. All ACs had a terminal ending at the palatal cortical border. All parameters showed a non-normal distribution; thus, the Mann–Whitney U test was preferred. Bilateral AC distribution (p = 0.761), AC distance to the crest of the alveolar ridge (p = 0.614), AC distance to the buccal cortical plate (p = 0.105), and AC diameter (p = 0.423) showed no significant difference between females and males. According to our study, a CS might be an anatomical structure rather than an anatomical variation, as all patients had at least one AC of the CS. It can be inferred that the detection of ACs will be achievable once clinicians are aware of these structures with continuous regular anatomy reworks and with small voxel-sized CBCT devices. Conclusion: This study was conducted to find the features and prevalence of the CS, and it was found that the CS is an anatomical structure rather than an anatomical variation. This argument is in line with the information on the CS in Gray’s Anatomy, 42nd Edition. Impaired healings and complications of the CS can be avoided if clinicians follow the American Academy of Oral and Maxillofacial Radiology guidelines regarding pre-operative implant examination. Otherwise, avertible complications may cause significant impairments in quality of life.

Contour Changes Following Implant Placement and Concomitant Soft Tissue Augmentation Applying a Volume-Stable Collagen Matrix.

The objective of this study was to assess volumetric and linear changes of buccal mucosal thickness at implant sites following soft tissue augmentation with a volume-stable collagen matrix (VCMX). Soft tissue augmentation using a VCMX was performed in 12 patients at the time of implant placement. Hydrocolloid impressions were taken prior to surgery and at 1 and 6 months postsurgery. Stone cast models were scanned, and stereolithography (STL) files from the three time points were uploaded to an image-analysis software. At all time points, linear and volumetric measurements of the contour changes up to 3 mm apical to the mucosal margin were performed and were analyzed statistically. At 1 mm apical to the mucosal margin, the change in soft tissue thickness between presurgery (T1) and 1 month (T2) amounted to 0.21 ± 1.22 mm, and the change between T1 and 6 months (T3) was 0.08 ± 1.47 mm. At 3 mm apical to the mucosal margin, the change in soft tissue thickness was 1.92 ± 1.70 mm between T1 and T2 and 0.31 ± 1.26 mm between T1 and T3. Contour (volumetric) changes revealed an increase of 0.58 ± 0.73 mm between T1 and T2 and an overall gain of 0.55 ± 0.73 mm between T1 and T3. Soft tissue augmentation with VCMX increased the ridge profile. The increase in ridge width was greater at 3 mm below the ridge crest than at 1 mm below the ridge crest. Remodeling processes during healing showed a decrease in the ridge contour between 1 and 6 months.

Influences of slope aspects on soil properties of Anatolian black pine forests in the semiarid region of Turkey

This study assessed the influences of slope aspect on soil physicochemical properties (soil quality indicators) on contiguous south-north facing slopes and hill plain (ridge crest) of the mid-mountain in Central Anatolia, having the same climate, vegetation and parent material. Anatolian black pine (Pinus nigra subsp. Pallasiana var. Pallasiana (Arnold)) was the dominant, and Cedar (Cedrus libani A. Richard), oak (Quercus sp.) were the co-dominant species in all aspects, whereas juniper (Juniperus sp.) was only recorded in north-facing forests. Some of the soil properties were determined on a grid with a 50 m sampling distance on the topsoil (0-15 cm depth). Accordingly, a total of 150 samples were taken from the three adjacent aspects. The data was analyzed using one-way ANOVA statistical methods. The investigated soil variables were soil organic matter (SOM), soil organic carbon (SOC), total nitrogen (TN), bulk density (BD), texture, lime (CaCO3), and pH. The showed that differences between SOC, BD and soil texture were statistically significant at 0.05 levels. Topographic aspect induced microclimatic differences were found to be important factors for the significant variations in SOC stocks. The resulting analyses showed no significant variation (p &lt; 0.05) across slope aspects for SOM, TN, lime, and pH. The differences may be attributed to topographic aspect induced microclimatic differences, which cause differences in the biotic soil component and organic matter trend and affect soil fertility. These results suggest that the slope aspect affects the soils of mountain forests through their direct influence on radiation, evaporation, biological activity, and soil moisture content.

Cosmogenic age constraints on rock avalanches in the Qinling Range associated with paleoearthquake activity, central China

Although it is generally assumed that understanding the trigger factor leading to the transition from a progressive rock failure toward sudden and rapid events is better to risk management, the ability to identify triggering factors responsible for prehistoric catastrophic rock avalanches is still debated. Here we describe two rock avalanches (Ganqiu and Shuiqiu) in the Cuihua Mountain area of the Qinling Range, China, providing new mapping of rock avalanche source areas and deposits and absolute age constraint from cosmogenic 10Be surface exposure dating. Results reveal that the Ganqiu rock avalanche is controlled by three sets of joints, causing the 380 m high ridge to collapse. Debris filled roughly the entire V-shaped valley and has a width ranging from 250 to 470 m, extending ~1260 m from the base of the cliff. The Shuiqiu rock avalanche was sourced near the summit of Cuihua Mountain from a cliff above 60° that is mainly controlled by inherited fault and joints. The rock mass fell ~250 m as a giant blocky stream across the width of the valley floor, with the deposit extending ~300 m from the base of the cliff. Both events caused the large-scale collapse of ridge crests and developed into high-mobility rock avalanches with long runout. Cosmogenic 10Be surface exposure dating from seven different parts of the deposits revealed nearly coincident ages for both rock avalanches, 10.0 ± 0.9 ka for the Ganqiu rock avalanche and 9.5 ± 1.2 ka for the Shuiqiu rock avalanche. Because this region was not affected by valley glaciation, rock avalanches triggering by paraglacial stress release can be excluded. Moreover, without clear evidence for specific climatic conditions in the Qinling area circa 9–10 ka, a climatic trigger for the Cuihua Mountain rock avalanches is equivocal. Instead, we find coincidence between the concurrent exposure ages and paleoseismic records from the nearby Qinling North Piedmont fault (QNF). This coincidence of ages, combined with the fact that the Mw 8.0 1556 CE Huaxian earthquake triggered numerous large rock falls in the Huashan Mountains at the eastern end of the Qinling Range, suggest that a large-magnitude earthquake centered in the middle-east section of QNF at ca. 8–11 ka may have triggered the Ganqiu and Shuiqiu rock avalanches.

Osteotomy combined with the trephine technique for invisible implant fracture: A case report

BACKGROUNDImplant fracture is one of the most serious mechanical complications of dental implants. Conventional treatment necessitates visibility of the apical portion of the fractured implant, whereas for deep and invisible implant fractures, the traditional trephine method has been ineffective. Surgical removal of the marginal bone to expose the fracture surface would be a time-consuming and extensively damaging procedure. Here, we propose a novel technique to address invisible implant fractures.CASE SUMMARYA 50-year-old woman was referred to our department with the chief complaint that her right mandibular implant tooth had fallen out 3 mo earlier. Cone-beam computed tomography examination showed an implant fracture with a fracture surface 5.1 mm below the crestal ridge. The patient was treated with osteotomy combined with the trephine technique to expose the surgical field and remove the implant. The invisible fractured implant was successfully removed, with minimal trauma. A modified Wafer technique-supported guided bone regeneration treatment was then administered to restore the buccal bone wall and preserve the bone mass. Six months later, fine regenerative bone and a wide alveolar crest in the edentulous area were observed, and a new implant was placed. Four months later, restoration was completed using a cemented ceramic prosthesis. Clinical and radiographic examinations 12 mo after loading fulfilled the success criteria. The patient reported no complaints and was satisfied.CONCLUSIONOsteotomy combined with the trephine technique can be effectively used to address deep and invisible implant fractures.