Distal Ridge Research Articles

Mapping Origins of Tendons on the Medial Epicondyle to Improve Treatment of Medial Epicondylitis: Anatomical Study

Medial epicondylitis is a tendinosis found commonly in throwing and golfing athletes. Although there are choices for nonsurgical treatments, when these fail, surgical intervention can be considered. When surgical treatment is performed, the objective is to debride the diseased tissue from the epicondyle. The purpose of this study was to clarify the locations and size of the common flexor tendons and medial collateral ligament (MCL) relative to each other and to the posterior ridge of the medial epicondyle. The common flexor tendons and MCL were dissected and reflected their origin on the medial epicondyle in six cadaver elbows. Measurements were taken from the posterior and distal ridges of the medial epicondyle with respect to the humerus. Each origin was also measured for its height and width. The flexor carpi ulnaris origin starts at a mean of 4.2 mm from the posterior ridge of the medial epicondyle and extends anteriorly an average of 4.8 mm. The flexor carpi radialis starts at a mean of 4.2 mm from the posterior ridge and extends anteriorly an average of 7.4 mm. The pronator teres begins at a mean of 4.6 mm from the posterior ridge and extends an average of 5.7 mm anteriorly. The MCL starts at an average of 10.4 mm from the posterior ridge and extends 5.2 mm anteriorly. The measurements found have allowed the creation of a map of the specific common flexor tendon origins and their sizes on the medial epicondyle, as well as their position relative to the MCL. A surgeon may debride 1 cm anteriorly from the posterior ridge of the medial epicondyle to safely address the affected tissues and ensure the safety and integrity of the MCL.

A lateral extra-articular tenodesis without additional hardware: Surgical technique and biomechanical comparison with an anatomic anterolateral ligament reconstruction in the augmentation of anterior cruciate ligament reconstruction

BackgroundThe aims of this study were to describe a lateral extra-articular tenodesis (LET) using no additional hardware and compare the tibiofemoral kinematics of anterior cruciate ligament (ACL) reconstruction augmented with either the LET or a standard anatomic anterolateral ligament (ALL) reconstruction using intra-tunnel fixation. MethodsTen cadaveric knees were mounted on a robotic testing system and underwent a kinematic assessment of anterior tibial translation and internal tibial rotation under a simulated pivot-shift in the following states: ACL-intact, ACL-sectioned, ACL-sectioned/anterolateral complex (ALC)-sectioned, ACL-reconstructed/ALC-sectioned, ACL-reconstructed/ALL-reconstructed, and ACL-reconstructed/LET. For the LET, an iliotibial autograft was passed under the fibular collateral ligament and secured to the femur with the pull sutures of the ACL reconstruction femoral cortical suspensory fixation device, positioned at the distal ridge of Kaplan’s fibers. ResultsAnterior tibial translation was restored to normal by ACL reconstruction without meaningful benefit of augmentation with LET or ALL. ACL reconstruction restored internal tibial rotation close to normal between 0° and 30°, but increased internal tibial rotation persisted between 45° and 90°. Augmentation of ACL reconstruction with the LET reduced internal rotation close to normal between 45° and 90°, whereas increased internal rotation persisted after ALL reconstruction. ConclusionACL reconstruction and LET are complementary in controlling tibiofemoral kinematics of knees with a combined ACL and ALC injury: ACL reconstruction restored native tibiofemoral kinematics except for internal rotation at flexion greater than 30°. The increased internal rotation at flexion greater than 30° was restored to normal with an LET, but not with an ALL reconstruction.

Nubian Levallois Technology During MIS 5: Refitted Lithic Sequences and OSL Ages of Dimona South, Israel, and Their Broader Implications

The site of Dimona South is a knapping locality in the Negev desert of Israel, situated at the raw material source. A test excavation followed by a salvage excavation conducted during 2020 revealed a partly buried archaeological layer that was exposed over an area of ~ 40 m2 and yielded a well-preserved lithic assemblage. Optically stimulated luminescence (OSL) ages of sediments within and above the archaeological layer fall within MIS 5. With a lithic assemblage dominated by Nubian Levallois technology, this site provides a rare opportunity for analysis of a well-dated, in situ Nubian assemblage. A refitting study in combination with an attribute analysis of the whole assemblage allowed the reconstruction of the Nubian reduction sequence. Our analyses indicate that a specifically pre-planned Nubian point production system existed at the site. It is characterized by the early preparation of an acute distal ridge and its careful maintenance throughout the reduction process until the cores were exhausted. These characteristics stand out from most Levantine Middle Paleolithic assemblages.The discovery of Dimona South allows us to revisit some of the technological issues at the heart of debates about Levallois Nubian technology that could not be addressed from analyses of partial surface assemblages. These new data from a secure and dated context are crucial to the inter-site and regional technological comparisons, informing our views of the Nubian technology and its role in the Middle Paleolithic world of eastern Africa, Arabia and the Levant.

Evaluation of marginal bone loss in implant supported over-dentures

Aim: The purpose of the present research was to assess the marginal bone loss due to stresses encountered in implant supported over-dentures. Methodology: Tridimensional models were built from the images of a computerized tomography of a mandible and 3D laser digitalization of implants, abutments, mucosa, and complete denture. The geometric models of implants and abutments were mounted at the canine region to build reference model 1 - absence of bone resorption. To build the test models the mandible geometric solid was modified to simulate 2-mm vertical bone loss surrounding the implants (model 2) and resorption of the distal ridge (model 3). Finite elements models were generated, and a 100 N static load was applied at the first molar region of each model to compare the von Mises stress distributions in selected points. Results: Von Mises stresses increased on the bone surrounding implants and on the prosthetic components in the model with 2-mm vertical bone loss. The combination of 2-mm vertical bone loss and resorption of the distal ridge did not increase the stresses compared with the model with only bone loss surrounding implants.

Chlorine-36 Surface Exposure Dating of Late Holocene Moraines and Glacial Mass Balance Modeling, Monte Sierra Nevada, South-Central Chilean Andes (38°S)

The development of robust chronologies of Neoglaciation from individual glaciers throughout the high-altitude Andes can provide fundamental knowledge of influences such as regional temperature and precipitation variability, and aid in predicting future changes in the Andean climate system. However, records of Late Holocene glaciation from the Central Chilean Andes are sparse, and often poorly constrained. Here, we present 36Cl surface exposure ages, dendrochronologic constraints, and glacial mass balance modeling simulations of Late Holocene glacier fluctuations in the Central-South Chilean Andes. A series of concentric moraine ridges were identified on Monte Sierra Nevada (38°S), where exposure dating of basaltic boulders was used to establish a chronology of ice recession. We infer that moraine abandonment of the most distal ridge in the valley commenced by ∼4.2 ka, and was followed by glacier margin retreat to an up-valley position. Exposure ages of the oldest Late Holocene boulders (∼2.5–0.8 ka) along the marginal extents of the moraine complex indicate fluctuations of the glacier terminus prior to ∼0.65 ka. A final expansion of the ice margin reoccupied the position of the 4.2 ka moraine, with abatement from the outermost composite moraine occurring by ∼0.70 ka, as constrained by tree-ring data from live Araucaria araucana trees. Finally, a series of nested moraines dating to ∼0.45–0.30 ka, formed from a pulsed ice recession during the latest Holocene when the lower reaches of the glacial snout was most likely debris mantled. A distributed temperature index model combined with a glacier flow model was used to quantify an envelope of possible climatic conditions of Late Holocene glaciation. The glacial modeling results suggest conditions were ∼1.5°C colder and 20% wetter during peak Neoglaciation relative to modern conditions. These records also suggest a near-coeval record of Late Holocene climate variability between the middle and high southern latitudes. Furthermore, this study presents some of the youngest 36Cl exposure ages reported for moraines in the Andes, further supporting this method as a valuable geochronologic tool for assessing Late Holocene landscape development.

Morphology and paleohydrology of intracrater alluvial fans north of Hellas Basin, Mars

Alluvial fans and sinuous ridges are both important records of the history of fluvial activity on Mars, and they often occur together. We present observations of alluvial fans, many of which exhibit inverted relief, in five craters in the region north of Hellas basin. The observed fans ranged in size from ~10 to 820 km2. We identified three primary fan surface morphology classes (chute, degraded, and Inverted) as well as many instances where the morphology transitions from proximal chutes (or, rarely, a cratered degraded surface) to distal ridges corresponding to increasing thermal inertia. Clear superposition relationships at contacts between adjacent fans are rarely observed, suggesting interfingered deposits and concurrent fan development across the region. Localized factors appear to influence fan development as there is no systematic trend in the azimuth range of fan location, size of fan or catchment, as well as the degree of crater filling. Water and sediment availability may be controlled by lithology differences and weather patterns. Many of the fans had a mismatch between catchment and fan volume, corresponding to significant amounts of erosion perhaps due to windblown stripping of fine sediment. However, several notable fans exhibited volumes greater than their corresponding catchments. This may reflect uncertainty in the accuracy of the estimated paleosurface, or it may indicate sediment contributions to the fan from outside the mapped catchment. Ridges, inferred to be the resistant remnants of fluvially transported deposits, were used to estimate flow magnitude in fan construction with computed discharges of 60–400 m3/s and corresponding supply rate runoff values ~1–20 mm/h. Acknowledging that width-derived discharge values may overestimate flow conditions due to the likelihood of amalgamated channel deposits, this quantification provides important climate constraints.The upper range of runoff values and discharge rates are quite high, and would require either intense rain storms to generate immediate runoff, or longer-term snow accumulation and subsequent melt-runoff, potentially enhanced by rain-on-snow events. Minimum continuous formation time scales of less than a century are computed, but are incompatible with fan morphology (e.g., superposition relationships, embedded craters) and mechanisms to sustain flows. More realistic lower-limit fan construction times, accounting for modeled precipitation rates from the literature, are tens to hundreds of thousands of years. Fans were active in multiple events spanning the Hesperian to Amazonian periods, requiring transient climate conditions to support the fan aggradation.

Intraoral scanner-based monitoring of tooth wear in young adults: 12-month results

ObjectivesTo investigate tooth wear in young adults, intraoral scanning was used for digital monitoring of the mandibular first molar over 12 months. A possible influence of aetiological factors obtained by a questionnaire on tooth wear was investigated.Materials and methodsA total of 109 participants (mean age at the start of the study: 21.0 ± 2.2 years) were included in this clinical study. At baseline (T0), an intraoral scan (Trios 3, 3Shape) of the study tooth (FDI # 36 or #46) was conducted. After a mean observation period of 373 ± 19 days, a second intraoral scan (T1, n = 94) of the same tooth as at T0 was performed and standard tessellation language datasets were superimposed with 3D analysis software (GOM Inspect). The occlusal surface of the study tooth was divided into 7 areas (5 cusps, 2 ridges) and maximum vertical substance loss was measured between T0 and T1 (n = 91). Three types of tooth wear were defined: cupping (C), facet (F) and combined cupping-facet (CF). Furthermore, a questionnaire on aetiological factors, such as dietary behaviour, was filled out at T0. Data were analysed with non-parametric tests (p < 0.05).ResultsOnly one study tooth exhibited no tooth wear at T0, whereas 3 teeth showed C, 47 teeth F and 40 teeth CF. A progression of vertical substance loss for all three types was shown. Most affected were the mesiobuccal cusps (43, 38/47 µm; median, 95%CI) followed by distobuccal (36, 33/39 µm), mesiolingual (35, 26/40 µm), distolingual (34, 27/36 µm) and distal (31, 25/34 µm). On mesial and distal ridges, only F was detected with the lowest vertical substance loss of all areas (mesial ridge: 0, 0/0 µm; distal ridge: 0, 0/0 µm). An association between aetiological factors and loss values could not be shown.ConclusionsAll study teeth showed clear signs of wear, and after only 1 year, further substance loss was detectable. This result is of significance for young adults.Clinical relevanceSince data of young adults regarding tooth wear are scarce, the results give a first idea of the amount of vertical loss per year and its relation to aetiological factors such as dietary behaviour. Therefore, further studies over a longer observation period are highly recommended.

Accessory cusp expression at the enamel-dentine junction of hominin mandibular molars.

Studies of hominin dental morphology frequently consider accessory cusps on the lower molars, in particular those on the distal margin of the tooth (C6 or distal accessory cusp) and the lingual margin of the tooth (C7 or lingual accessory cusp). They are often utilized in studies of hominin systematics, where their presence or absence is assessed at the outer enamel surface (OES). However, studies of the enamel-dentine junction (EDJ) suggest these traits may be more variable in development, morphology and position than previously thought. Building on these studies, we outline a scoring procedure for the EDJ expression of these accessory cusps that considers the relationship between these accessory cusps and the surrounding primary cusps. We apply this scoring system to a sample of Plio-Pleistocene hominin mandibular molars of Paranthropus robustus, Paranthropus boisei, Australopithecus afarensis, Australopithecus africanus, Homo sp., Homo habilis and Homo erectus from Africa and Asia (n = 132). We find that there are taxon-specific patterns in accessory cusp expression at the EDJ that are consistent with previous findings at the OES. For example, P. robustus M1s and M2s very often have a distal accessory cusp but no lingual accessory cusp, while H. habilis M1s and M2s show the opposite pattern. The EDJ also reveals a number of complicating factors; some apparent accessory cusps at the enamel surface are represented at the EDJ only by shouldering on the ridges associated with the main cusps, while other accessory cusps appear to have little or no EDJ expression at all. We also discuss the presence of double and triple accessory cusps, including the presence of a double lingual accessory cusp on the distal ridge of the metaconid in the type specimen of H. habilis (OH 7–M1) that is not clear at the OES due to occlusal wear. Overall, our observations, as well as our understanding of the developmental underpinnings of cusp patterning, suggest that we should be cautious in our comparisons of accessory cusps for taxonomic interpretations.

Transverse Ridge of Premolars and Oblique Ridge of Maxillary Molars are in Divine Golden Ratio

In premolars and molars, transverse ridge (TR) and oblique ridge (OR) play major roles in providing strength and stability to the cusps in particular and tooth as a whole. Hence, they could be divided at the central groove or the transverse groove in a divine golden ratio. Twenty pairs of maxillary and mandibular casts were retrieved from the Department of Orthodontics. The lengths of buccal triangular ridge (BTR), lingual triangular ridge (LTR) and TR of maxillary and mandibular first and second premolars were measured. Similarly, lengths of distal cuspal ridge of mesiopalatal cusp, triangular ridge of distobuccal cusp (DBTR) and OR of the maxillary first and second molars were measured using a brass wire and a Vernier caliper. The TR:BTR, BTR:LTR, OR:distal ridge of mesiopalatal cusp (MPDR), and MPDR:DBTR ratios were calculated to find out the possibility of golden ratio. Transverse ridges of the premolars and OR of the maxillary first and second molars were divided at the central groove in a divine golden ratio. The mean TR/BTR ratio for maxillary first premolar was 1.61 ± 0.007, whereas the mean BTR/LTR ratio was 1.63 ± 0.02. The mean TR/BTR ratio for maxillary second premolar was 1.61 ± 0.01, whereas the mean BTR/LTR ratio was 1.62 ± 0.04. The TR/BTR and BTR/LTR ratios for mandibular first premolar were 1.6 ± 0.008 and 1.64 ± 0.02, respectively. Similarly, the mean TR/BTR ratio for mandibular second premolar was 1.61 ± 0.01, whereas the mean BTR/LTR ratio was 1.63 ± 0.02. The ORs of maxillary first molar ridge and TR of maxillary and mandibular premolars are divided into two parts at transverse and central grooves, respectively, in a divine ratio. The ORs of maxillary first molar ridge and TR of maxillary and mandibular premolars are divided into two parts at transverse and central grooves, respectively, in a divine ratio. This signifies the strength and stability of the occlusal table in the posterior teeth, as the golden ratio is the mark of functional excellence. Golden ratio should be taken into consideration while restoration or fabrication of the posterior teeth.

Spore morphology and its systematic implication in Pteris (Pteridaceae).

Pteris (Pteridaceae) spores are usually trilete and can be distinguished by the perine ornamentation. The systematic value of spore morphology in Pteris is unclear, especially based on the renewed infrageneric classification of Pteris. In the present study, we used scanning electron microscopy (SEM) to understand spore characters in 57 Pteris species, one Onychium species, and two Astrolepis species; 40 species are reported here for the first time. The observed spore characters combined with published spore data, totaling 100 species from 16 sections of Pteris, were mapped onto a reconstructed phylogenetic tree. Seven characters (five proposed in previous studies), including an equatorial flange, laesural ridges, proximal ridges, distal ridges, tubercula on distal faces, coarse reticula on distal faces, and a row of extervermiculi between the distal face and equatorial flange, were analyzed to investigate spore morphology evolution in Pteris. However, the results showed no synapomorphies with other genera in Pteridaceae. Most of the characters were found to have arisen independently several times in different lineages or were even frequently reversed. Equatorial flanges and tubercula on distal faces are plesiomorphies and present in most Pteris species. Overall, the application of spore morphology in section circumscription is limited. Thus, we suggest combining spore morphology with leaf characters for Pteris infrageneric classification.

Influence of Access Cavity Preparation and Remaining Tooth Substance on Fracture Strength of Endodontically Treated Teeth

IntroductionThe purpose of this study was to assess the impact of access cavity preparation and the remaining tooth substance on the fracture strength of endodontically treated teeth. MethodsOne hundred sound mandibular first and second molar teeth were selected and divided into 1 control and 9 test groups (n = 10/group) as follows: control group, intact teeth; group 1, teeth prepared with traditional endodontic access cavity (TEC); group 2, teeth prepared with conservative endodontic access cavity (CEC); group 3, teeth prepared with truss endodontic access cavity (TREC); group 4, TEC + 3 residual walls; group 5, CEC + 3 residual walls; group 6, TREC + 3 residual walls; group 7, TEC + 2 residual walls; group 8, CEC + 2 residual walls; and group 9, TREC + 2 residual walls. After access cavity preparation, all test teeth were endodontically treated and restored. The specimens were then loaded to fracture in a universal loading machine (Triaxial Tester T400 Digital; Controls srl, Cernusco, Italy), and fracture values were recorded in newtons. The data were analyzed with 2-way analysis of variance and Tukey post hoc analysis for multiple comparisons (P < .05). ResultsIntact teeth were more resistant to fracture than the teeth in all the test groups. No statistically significant differences were found between the 3 tested access cavities (P > .05). Significant differences were observed between the different number of residual walls (P < .05). ConclusionsTRECs do not increase the fracture strength of endodontically treated teeth in comparison with CECs and TECs. Moreover, the loss of mesial and distal ridges reduced the fracture strength of teeth significantly.

Effect of Implant Position and Edentulous Span Length on Stresses Around Implants Assisting Claspless Distal Extension Partial Overdentures: An In Vitro Study.

The aim of this in vitro study was to evaluate the effect of implant position and edentulous span length on stresses around implants assisting claspless distal extension partial overdentures. Four bilateral mandibular distal extension acrylic models were constructed. Two implants were inserted in the distal extension ridges parallel to each other and perpendicular to the ridges. Based on the implant position, models were categorized into two groups: Group I, mesial implants position and Group II, distal implant position. Each group was subdivided into 2 subgroups according to the length of edentulous span: Subgroup a, long span and Subgroup b, short span. Four claspless partial overdentures were fabricated on the models and retained to the implants with ball-and-socket attachments. Three strain gauges were cemented to the acrylic resin at buccal, lingual, and distal sides of each implant. Static unilateral vertical load of 60N was applied in the central fossae of the first molar, and peri-implant stresses were measured on loading and nonloading sides. Distal implant placements recorded significantly higher peri-implant stresses than did mesial implant placements. Long saddle recorded significantly higher stresses than did short saddle. The greatest peri-implant stresses were recorded with distal placement and long saddle at the loading side. At loading and nonloading sides, the mesial placement with a short saddle recorded the lowest strain. For mandibular distal extension partial overdentures, a mesially placed implant combined with short saddle may be preferable to a distally placed implant combined with long saddle, as the former was associated with reduced peri-implant stresses.

Are the posterior bracket placement patterns reliable?

Objective: Investigate the marginal ridges leveling accuracy of Alexander and Viazis bracket placement methods.Methods: Eighty pairs of dental casts were selected, with complete permanent dentition, without occlusal wear or restorations. A linking line between mesial and distal ridges of posterior teeth was done to measure the occlusal thirds with digital caliper. The means, obtained from 3 different examiners, were compared with the values of Alexander and Viazis’ equations through One-way ANOVA with α=0.05.Results: The second premolar placement value (x) suggested by the authors showed no difference in comparison to the occlusal third size of the sample teeth (p&gt;0.05), however for the first premolars, a significant difference was found (p&lt;0.001). The value adopted for positioning on the first permanent molars (x-0.5mm) is consistent with the size of the occlusal third of these teeth (p=0.0531). A significant difference was also found for the second permanent molars bracket positioning between the predefined value (x-1mm) and the sample (p&lt;0.001).Conclusions: The vertical positioning values proposed by Alexander and Viazis for placement of second premolars and first permanent molars do contribute to the leveling of marginal ridges, which cannot be applied for the values recommended for the first premolars and second permanent molars.

Are the posterior bracket placement patterns reliable?

Objective: Investigate the marginal ridges leveling accuracy of Alexander and Viazis bracket placement methods.Methods: Eighty pairs of dental casts were selected, with complete permanent dentition, without occlusal wear or restorations. A linking line between mesial and distal ridges of posterior teeth was done to measure the occlusal thirds with digital caliper. The means, obtained from 3 different examiners, were compared with the values of Alexander and Viazis’ equations through One-way ANOVA with α=0.05.Results: The second premolar placement value (x) suggested by the authors showed no difference in comparison to the occlusal third size of the sample teeth (p&gt;0.05), however for the first premolars, a significant difference was found (p&lt;0.001). The value adopted for positioning on the first permanent molars (x-0.5mm) is consistent with the size of the occlusal third of these teeth (p=0.0531). A significant difference was also found for the second permanent molars bracket positioning between the predefined value (x-1mm) and the sample (p&lt;0.001).Conclusions: The vertical positioning values proposed by Alexander and Viazis for placement of second premolars and first permanent molars do contribute to the leveling of marginal ridges, which cannot be applied for the values recommended for the first premolars and second permanent molars.

火星衝突クレーターの特異なエジェクタ地形と劣化過程

Mars has fascinated us in terms of discovering vital activities and examining planetary surface evolutions. Recent explorations detected subsurface ice and methane, which reveal the importance of investigating ancient environments and their evolution. Impact craters and their ejecta morphologies are natural probes for obtaining knowledge on ancient surface and subsurface environments, because detailed morphologies of impact craters and their ejecta are sensitive to impact conditions and degradation processes. Martian enigmatic ejecta morphologies and their currently-proposed origins are summarized, and some degradation processes effective on Martian craters are introduced. Ejecta of Martian impact craters are different from those of lunar or Mercurian impact craters. They possess clear distal ridges and cliffs, and are diverted by preexisting obstacles, while edges of lunar or Mercurian ejecta are ambiguous. Their unique morphologies suggest that the ejecta are emplaced by radial ground-hugging flows generated at the time of the impact. Processes and agents of the fluidization draw attention, because the atmosphere and/or subsurface volatiles are suggested for its formation. Degradation processes on Mars vary, and include superimposed impacts, viscous relaxation, mass movements, lava infilling, fluvial incision, gully formation, lacustrine erosion and deposition, ice-related processes, and airfall deposition. Due to high ancient erosion rates, degraded crater morphologies also provide useful information on the ancient environment.

Three- to nine-year survival estimates and fracture mechanisms of zirconia- and alumina-based restorations using standardized criteria to distinguish the severity of ceramic fractures.

The aims of this study were set as follows: 1. To provide verifiable criteria to categorize the ceramic fractures into non-critical (i.e., amenable to polishing) or critical (i.e., in need of replacement) 2. To establish the corresponding survival rates for alumina and zirconia restorations 3. To establish the mechanism of fracture using fractography Fifty-eight patients restored with 115 alumina-/zirconia-based crowns and 26 zirconia-based fixed dental prostheses (FDPs) were included. Ceramic fractures were classified into four types and further subclassified into "critical" or "non-critical." Kaplan-Meier survival estimates were calculated for "critical fractures only" and "all fractures." Intra-oral replicas were taken for fractographic analyses. Kaplan-Meier survival estimates for "critical fractures only" and "all fractures" were respectively: Alumina single crowns: 90.9 and 68.3 % after 9.5 years (mean 5.71 ± 2.6 years). Zirconia single crowns: 89.4 and 80.9 % after 6.3 years (mean 3.88 ± 1.2 years). Zirconia FDPs: 68.6 % (critical fractures) and 24.6 % (all fractures) after 7.2 and 4.6 years respectively (FDP mean observation time 3.02 ± 1.4 years). No core/framework fractures were detected. Survival estimates varied significantly depending on whether "all" fractures were considered as failures or only those deemed as "critical". For all restorations, fractographic analyses of failed veneering ceramics systematically demonstrated heavy occlusal wear at the failure origin. Therefore, the relief of local contact pressures on unsupported ceramic is recommended. Occlusal contacts on mesial or distal ridges should systematically be eliminated. A classification standard for ceramic fractures into four categories with subtypes "critical" and "non-critical" provides a differentiated view of the survival of ceramic restorations.

Morphological Variation of the Baculum in Coyotes (Canis latrans)

Bacula are penile bones present in many species of mammals. There is great variation in the shape of this bone among the different species where it is present. Within most species there is not much variability in its shape. A small sample of coyote bacula previously described variations in their shape including curvatures and the presence or absence of dorsal ridges. This study expands the sample size to include 100 bacula and I describe the morphological variation that includes lateral curvature, profile shape, distal tip bend and dorsal ridge of these bones.

A formation mechanism for concentric ridges in ejecta surrounding impact craters in a layer of fine glass beads

Ejecta patterns are experimentally examined around craters formed in a layer of glass beads by vertical impacts at low velocities. The diameters of the constituent glass beads of three different targets range 53–63μm, 90–106μm, and 355–500μm. The impact velocities and ambient pressures range from a few to 240ms−1 and from 500Pa to the atmospheric pressure, respectively. Various ejecta patterns are observed around craters and are classified into two major classes based on whether they have concentric ridges or not. We propose a possible formation model for the ridges in which the wake created by a projectile as it passes through the atmosphere causes the crater rim to collapse: The model can explain the observation that the degree of collapse of the resultant crater rim depends on the impact velocity and ambient pressure. Using the ratio between the hydrodynamic drag of the airflow induced by the wake and the gravitational force of the degraded part of the rim, we calculate the critical conditions of the impact velocity and ambient pressure necessary for the wake to erode the rim. The conditions turn out to be roughly consistent with the boundary between the two morphological classes. As a result, it is possible that the projectile wake triggers the collapse of the crater rim, leading to a ground-hugging flow that settles to form the distal ridge observed in this study. This mechanism may play a role in producing ejecta morphologies on planetary bodies with atmosphere.

An Anatomical Study of the Watershed Line on the Volar, Distal Aspect of the Radius: Implications for Plate Placement and Avoidance of Tendon Ruptures

The watershed line is a useful surgical landmark for positioning a volar locking plate. Implants placed on or distal to it can impinge on flexor tendons and cause injury. However, the details of the anatomy of this line are unclear. We studied macroscopically and histologically the structures of the volar aspect of the distal radius. We studied 20 distal forearm regions of 10 cadavers (5 males and 5 females; mean age, 79 y [range, 56-88 y]) to clarify the details of the watershed line. In 16 specimens, we investigated the macroscopic appearance of the volar aspect of the radius and the relationships among the bone, the volarradiocarpal ligaments, and the pronator quadratus. Histological analyses were performed in 4 specimens of 2 cadavers to examine the morphology of the margin of the bony structures. In the medial half of the distal volar radius, 2 lines were identified by direct macroscopic visualization; one was the proximal line that corresponded to the distal ridge of the pronator fossa, and the other was the distal line, which was more prominent. A medial bony prominence was situated on the distal line. In the lateral half, the distal and proximal lines of the medial half merged to form a single line. A lateral prominence was situated on this line. The watershed line might not be a distinct line, and it corresponds to the distal margin of the pronator fossa in the lateral half of the volar radius and to a hypothetical line between the distal and proximal lines in the medial half. The medial and lateral bony prominences on the volar radius should be key structures for accurate plate placement to avoid flexor tendon injury. The present study suggests bony landmarks for positioning a volar locking plate.

황해 중동부 경기만의 후기 제4기 순차층서 연구

황해 경기만은 제4기에 반복된 해침과 해퇴로 4개의 해침-해퇴 퇴적체(DS-1, DS-2, DS-3, DS-4)를 형성하였다. 본 연구는 황해 경기만 퇴적체의 형성을 6개 퇴적단계로 나누어 설명한다. A 단계는 MIS-6 저해수면 시기로서 큰 규모의 해수면 하강으로 인해 대부분의 지역이 대기에 노출되고 광범위한 하도 침식 및 풍화작용의 영향을 받았다. 이어지는 B 단계는 MIS-5e 까지 빠른 해수면 상승과정에서 MIS-5 시퀀스의 하부 해침퇴적체가 형성되었고, 다음에 이어지는 MIS-5d부터 MIS-4 저해수면 시기까지의 C 단계에서는 MIS-5 시퀀스의 상부인 해퇴퇴적체가 만들어졌다. 다음의 D 단계는 MIS-4 저해수면 시기부터 MIS-3c 고해수면 시기까지로 하도 침식 및 하도 충전 구조로 이루어진 MIS-3 해침 퇴적체가 형성되었다. 다음의 E 단계에서는 LGM 시기까지 계속적인 해수면 하강이 있었고 외해쪽에서는 천해 기원의 MIS-3 해퇴퇴적체가 만들어진 반면에, 내륙쪽에서는 노출된 환경에서 하도 충전 퇴적체나 범람원 퇴적체가 형성되었다. 마지막 단계인 F 단계는 황해 전체적으로 홀로세 해침이 발생하였고, 이 시기에 외해쪽에서는 대륙붕 사질 퇴적체와 조석사주 퇴적체가 형성되어 고해수면 시기인 현재까지 퇴적이 일어나고 있다. The Yellow Sea has sensitively responded to high-amplitude sea-level fluctuations during the late Quaternary. The repeated inundation and exposure have produced distinct transgression-regression successions with extensive exposure surfaces in Kyeonggi Bay. The late Quaternary strata consist of four seismic stratigraphic units, considered as depositional sequences (DS-1, DS-2, DS-3, and DS-4). DS-1 was interpreted as ridge-forming sediments of tidal-flat and estuarine channel-fill facies, formed during the Holocene highstand. DS-2 consists of shallow-marine facies in offshore area, which was formed during the regression of Marine Isotope Stage (MIS)-3 period. DS-3 comprises the lower transgressive facies and the upper highstand tidal-flat facies in proximal ridges and forced regression facies in distal ridges and offshore area. The lowermost DS-4 rests on acoustic basement rocks, considered as the shallow-marine and shelf deposits formed before the MIS-6 lowstand. This study suggests six depositional stages. During the first stage-A, MIS-6 lowstand, the Yellow Sea shelf was subaerially exposed with intensive fluvial incision and weathering. The subsequent rapid and high amplitude rise of sea level in stage-B until the MIS-5e highstand produced transgressive deposits in the lowermost part of the MIS-5 sequence, and the successive regression during the MIS-5d to -5a and the MIS-4 lowstand formed the upperpart of the MIS-5 sequence in stage-C. During the stage-D, from the MIS-4 lowstand to MIS-3c highstand period, the transgressive MIS-3 sequence formed in a subtidal environment characterized by repetitive fluvial incision and channel-fill deposition in exposed area. The subsequent sea-level fall culminating the last glacial maximum (Stage-E) made shallow-marine regressive deposits of MIS-3 sequence in offshore distal area, whereas it formed fluvial channel-fills and floodplain deposits in the proximal area. After the last glacial maximum, the overall Yellow Sea shelf was inundated by the Holocene transgression and highstand (Stage-F), forming the Holocene transgressive shelf sands and tidal ridges.