Margin Failure Research Articles

Thoracoscopic anatomical sublobar resection for deep interlobar lung cancer with fused fissure.

The technical challenges associated with the removal of small nodules in challenging locations rather than peripheral locations remain unaddressed. We sought to illustrate the parenchymal-sparing surgical approach employed for deep interlobar lung cancer with fused fissures (DILCFFs). A retrospective review of 43 patients with cT1N0M0 DILCFFs from January 2013 through December 2022 was performed. Patients were grouped into the non-anatomical extended resection (NER): either a lobectomy or a (sub)segmentectomy for the predominant location with an extended wedge resection of a portion of an adjacent lobe, and the anatomical resection (AR): combined a lobectomy or a (sub)segmentectomy for the predominant location with a (sub)segmentectomy of an adjacent lobe. In total, 17 patients underwent NER, 26 with AR. There were more cases undergoing preoperative nodule localization in the NER group. The AR arm conferred a wider surgical margin (2.52 vs. 1.27 cm, P<0.001) and a higher proportion of margin to tumor size ratio ≥1 (73.1% vs. 35.3%, P=0.01) than the NER arm. A total of 10 types of interlobar vessels within fused fissures were identified with an overall incidence of 88.4% (38/43). No patients in both arms experienced severe morbidity. Five patients allocated to the NER arm experienced local recurrence at the surgical margin, in comparison with zero in the AR arm (29.4% vs. 0%, P=0.006). AR of partial of the adjacent lobe provides a wider surgical margin than that of NER in the removal of DILCFFs, potentially accounting for the lower incidence of margin failure.

Wearable devices for photodynamic therapy – A systematic review

Wearable devices for photodynamic therapy – A systematic review

There Are No Differences in Positive Surgical Margin Rates or Biochemical Failure-Free Survival among Patients Receiving Open, Laparoscopic, or Robotic Radical Prostatectomy: A Nationwide Cohort Study from the National Cancer Database.

Simple SummaryFew studies have evaluated oncologic outcomes in patients with prostate cancer (PC) receiving open, laparoscopic, or robotic radical prostatectomy (RP). To the best of our knowledge, this is the first and largest study to examine PSM and BFS rates in patients with PC undergoing open, laparoscopic, or robotic RP. After adjustment for confounders, no significant differences in PSM or BFS were noted among the patient groups.Purpose: To estimate the rates of positive surgical margin (PSM) and biochemical failure–free survival (BFS) among patients with prostate cancer (PC) receiving open, laparoscopic, or robotic radical prostatectomy (RP). Patients and Methods: The patients were men enrolled in the Taiwan Cancer Registry diagnosed as having PC without distant metastasis who received RP. After adjustment for confounders, logistic regression was used to model the risk of PSM following RP. After adjustment for confounders, Cox proportional regression was used to model the time from the index (i.e., surgical) date to biochemical recurrence. Results: The adjusted odds ratios (95% CIs) of PSM risk after propensity score adjustment for laparoscopic versus open, robotic versus open, and robotic versus laparoscopic RP 95% CIs were 1.25 (0.88 to 1.77; p = 0.2064), 1.16 (0.88 to 1.53; p = 0.2847), and 0.93 (0.70 to 1.24; p = 0.6185), respectively. The corresponding adjusted hazard ratios (95% CIs) of risk of biochemical failure after propensity score adjustment were 1.16 (0.93 to 1.47; p = 0.1940), 1.10 (0.83 to 1.47; p = 0.5085), and 0.95 (0.74 to 1.21; p = 0.6582). Conclusions: No significant differences in PSM or BFS were observed among patients receiving open, laparoscopic, or robotic RP.

Patterns Of Failure After Adjuvant Radiation For Meningioma, Radiologic Assessment To Inform Target Delineation And Treatment Planning

Adjuvant radiotherapy is increasingly used for intermediate and high-risk meningioma, and although short-term results from prospective trials demonstrate good rates of local control, long-term failures remain common. Moreover, the optimal expansions for postoperative radiotherapy target delineation for meningioma are unknown. We sought to elucidate the patterns of failure after adjuvant radiotherapy for meningioma to inform target delineation and treatment planning. Patients undergoing surgical resection for meningioma at a single institution were retrospectively reviewed for treatment with adjuvant radiation therapy, including external beam radiation therapy (EBRT), stereotactic radiosurgery (SRS), or brachytherapy. Patients treated with EBRT were evaluated for patterns of failure based on MRI review, and were classified as resection cavity, dural margin, osseous craniotomy tract, and intraparenchymal brain. Analysis was performed to evaluate factors associated with each failure type, and to identify the radiologic distance from the resection cavity margin to the furthest margin of each site of recurrent disease. From 1991 to 2015, 71 patients with 86 lesions were treated with adjuvant radiation therapy after resection of meningioma. The median follow-up was 4.2 years (IQR: 1.5-8.4 years). There were 14 (16%) grade 1, 49 (57%) grade II, and 23 (27%) grade III meningiomas, and gross total resection was achieved in 53 (61.6%) of cases. There were 22 local failures after EBRT, 16 (72.7%) were in-field, 11 (50%) were at the dural margin, 2 (9.1%) were along a craniotomy track, and 2 (9.1%) were intraparenchymal. In patients with dural marginal failure, the median distance from the edge of the resection cavity to the distal extent of the recurrence was 15 mm (IQR: 13-24 mm). Of the resection cavity recurrences, 5 (31.2%) occurred within 10 mm of the apex of the orbit or the cavernous sinus. The median MIB1 labeling index in meningioma with either intraparenchymal or craniotomy tract failure was 31.0%, compared to 11.3% (p = 0.018) in patients with infield or dural margin failure. Local failure along the dural margin after adjuvant radiation therapy for meningiomas occurred a median of 15 mm from the resection cavity. Failure along the craniotomy tract or parenchymal brain was uncommon, and was associated with a significantly higher MIB1, likely reflecting more aggressive tumor biology. These data may help to inform target delineation and margin expansion for patients receiving adjuvant radiotherapy for meningioma.

Comprehensive and Practical Way to Look at Far-End Crosstalk for Transmission Lines With Lossy Conductor and Dielectric

Far-end crosstalk (FEXT) noise is one of the major issues that limits signal integrity performance for high-speed digital products. It is important to estimate the crosstalk noise accurately to avoid noise margin failure or overdesigned transmission lines. Traditionally, analytical formulas for crosstalk noise are based on lossless and perfect impedance match assumptions, which provide limited guidance for a practical high-speed transmission line design. A phenomenon is observed that a lossy conductor increases the FEXT on coupled striplines. To provide a reasonable explanation, analytical and numerical investigations were performed using a modal analysis based approach. A new FEXT component due to the lossy conductor is proposed. Such FEXT component is important to a high-speed stripline design because it is a major contributor when all terminals are matched. To estimate the impact of loss on FEXT, a practical and fast estimation approach is proposed.

How turbidity current frequency and character varies down a fjord‐delta system: Combining direct monitoring, deposits and seismic data

AbstractSubmarine turbidity currents are one of the most important processes for moving sediment across our planet; they are hazardous to offshore infrastructure, deposit petroleum reservoirs worldwide, and may record tsunamigenic landslides. However, there are few studies that have monitored these submarine flows in action, and even fewer studies that have combined direct monitoring with longer‐term records from core and seismic data of deposits. This article provides one of the most complete studies yet of a turbidity current system. The aim here is to understand what controls changes in flow frequency and character along the turbidite system. The study area is a 12 km long delta‐fed fjord (Howe Sound) in British Columbia, Canada. Over 100 often powerful (up to 2 to 3 m sec−1) events occur each year in the highly‐active proximal channels, which extend for 1 to 2 km from the delta lip. About half of these events reach the lobes at the channel mouths. However, flow frequency decreases rapidly once these initially sand‐rich flows become unconfined, and only one to five flows run out across the mid‐slope each year. Many of these sand‐rich, channelized, delta‐sourced flows therefore dissipated over a few hundred metres, once unconfined, rather than eroding and igniting. Upflow migrating bedforms indicate that supercritical flow dominated in the proximal channels and lobes, and also across the unconfined mid‐slope. These supercritical flows deposited thick sand beds in proximal channels and lobes, but thinner and finer beds on the unconfined mid‐slope. The distal flat basin records far larger volume and more hazardous events that have a recurrence interval of ca 100 years. This study shows how sand‐rich delta‐fed flows dissipate rapidly once they become unconfined, that supercritical flows dominate in both confined and unconfined settings, and how a second type of more hazardous, and much less frequent event is linked to a different scale of margin failure.

Multimodality management of borderline resectable pancreatic adenocarcinoma.

Patients with borderline resectable pancreatic adenocarcinoma have primary tumors within the pancreas that involve the mesenteric vasculature to a limited degree. Their tumors are nonetheless at high-risk for a microscopically positive surgical resection margin and/or early treatment failure when pancreatectomy is performed de novo. The optimal treatment strategy for these patients has not been established; however, relatively favorable outcomes can be achieved with systemic chemotherapy and radiation therapy (RT) prior to intended resection. In this article, we discuss the modalities used to stage localized pancreatic cancer, the concept of borderline resectable pancreatic cancer (BRPC), the rationale for the use of preoperative therapy, and review recent publications, placing special emphasis on the necessity of appropriate patient selection and coordinating multimodality management to maximize outcomes.

C05: How we decrease the rate of positive surgical margin and biochemical failure during laparoscopic radical prostatectomy

C05: How we decrease the rate of positive surgical margin and biochemical failure during laparoscopic radical prostatectomy

Surgical Margins in Breast Conservation

Significant progress has been made in the diagnosis and treatment of breast cancer during the past 30 years. The increased availability of screening mammography has resulted in a higher percentage of woman being diagnosed with early stage disease allowing the option of breast conservation therapy to be more widely available. Long-term follow-up studies clearly demonstrate equivalent survival with breast conservation surgery (lumpectomy) and radiotherapy versus total mastectomy [1–3]. The importance of obtaining clear lumpectomy surgical margins has been well established in minimizing the risk of local recurrence [4]. Unfortunately there is a lack of uniform guidelines in terms of what constitutes an adequately clear lumpectomy margin. Substantial debate about bigger margins being better continues [5]. This has led to wide variations in lumpectomy margin reexcision rates from 15 to 47% [6]. These additional surgical procedures cause significant patient distress, utilize health care resources, and can adversely affect cosmesis. From the patient perspective, they may wonder why we did not get it right the first time. They want their cancer gone while maintaining a normal appearance. This special issue highlights the areas of controversy and demonstrates current best practices and emerging novel approaches towards optimal breast conservation approach. The goal is to improve our ability to provide breast-conserving approaches for breast cancer while avoiding multiple surgical procedures, minimizing recurrence risk while obtaining excellent cosmesis. We have chosen 6 of 16 submissions to be published in this special issue. Each paper was evaluated by at least two expert reviewers and revised according to review comments. P. Ananthakrishnan et al. provide an excellent comprehensive review article on all aspects involved in optimizing breast conservation. They include discussion of preoperative breast imaging, lesion localization, impact of tumor biology and systemic therapy, intraoperative lesion identification and margin assessment techniques, the role of margin ablation and oncoplastic techniques. They also discuss the promise of ductal anatomy mapping toward the goal of validating the “Sick lobe hypothesis” [7, 8] which may allow for more accurate identification of breast tissue to be targeted for excision. R. Emmadi and E. L. Wiley provide an excellent review from the pathology perspective of the different approaches to margin assessment. They explore issues of specimen processing, fixation, cutting techniques, and reporting. They well explain the reasons for the reporting variations between institutions and the need for standardization. J. L. Baker et al. present a scholarly review of our current understanding of the issue of atypical ductal hyperplasia (ADH) as it relates to surgical margins. They highlight the large interobserver variability among pathologists in differentiating ADH from low-grade ductal carcinoma in situ (DCIS). The issue of whether ADH is a precursor lesion to DCIS is explored. R. J. Rivera et al. report on a 21-site multicenter clinical trial evaluating the performance of the MarginProbe intraoperative device. This device is based on radiofrequency spectroscopy to assess adequacy of lumpectomy margins. They analyzed volume or resection and reexcision rates in the device group versus usual surgical standard of care (SOC). They demonstrate the reexcision rate of 14.1% in the device group versus 29.9% with SOC. Increased resection volume was 2.6% using the device. M. M. Chang et al. provide a comprehensive overview of oncoplastic breast reduction. This is a complete review of the techniques including indication, patient selection, practical pointers, and their experience including a low (3.3%) rate of margin failure. They stress the importance of a coordinated team approach between breast surgical oncology, plastic surgery, breast imaging, and radiation oncology. Lastly, G. H. T. Au et al. present an exciting research paper on margin assessment using a Quantum-Dot Molecular probe in a mouse model. This employs nanoparticle monoclonal antibodies with molecular imaging. Their concept has a potential advantage over optical imaging and radiofrequency spectroscopy in that it is not affected by tissue heterogeneity. It also can display and differentiate very small (100–200 cells) spots. Timeline of 30 minutes is practical for intraoperative use. This early work is an highly innovative approach to a practical issue. These papers present a great deal of important information and well explore the current state of the art, controversies and future directions towards the important goal of optimizing breast conservation with particular attention to margin issues.

Prediction and diagnosis of clinical outcomes affecting restoration margins

The longevity of dental restorations is largely dependent on the continuity at the interface between the restorative material and adjacent tooth structure (the restoration margin). Clinical decisions on restoration repair or replacement are usually based upon the weakest point along that margin interface. Physical properties of a restorative material, such as polymerisation shrinkage, water sorption, solubility, elastic modulus and shear strength, all have an effect on stress distribution and can significantly affect margin integrity. This review will focus on two aspects of margin deterioration in the oral environment: the in vitro testing of margin seal using emersion techniques to simulate the oral environment and to predict clinical margin failure and the relationship between clinically observable microleakage and secondary caries. The many variables associated with in vitro testing of marginal leakage and the interpretation of the data are presented in detail. The most recent studies of marginal leakage mirror earlier methodology and lack validity and reliability. The lack of standardised testing procedures makes it impossible to compare studies or to predict the clinical performance of adhesive materials. Continual repeated in vitro studies contribute little to the science in this area. Clinical evidence is cited to refute earlier conclusions that clinical microleakage (penetrating margin discoloration) leads to caries development and is an indication for restoration replacement. Margin defects, without visible evidence of soft dentin on the wall or base of the defect, should be monitored, repaired or resealed, in lieu of total restoration replacement.

The place of tubular concretions in hydrocarbon cold seep systems: Late Miocene Urenui Formation, Taranaki Basin, New Zealand

The late Miocene Urenui Formation cropping out on the eastern margin of Taranaki Basin, currently New Zealand's only commercially exploited hydrocarbon basin, is dominated by siliciclastic slope mudstone (5% carbonate) that locally includes a variety of tubular concretions (50–85% carbonate). Dominated by commonly large pipe and bulbous varieties, as much as 0.5 to more than 10 m (1.6 to 33 ft) long and 5 to 70 cm (2 to 28 in.) across, these concretions formed from the precipitation of fine-grained calcite or dolomite cement within siliciclastic mud in the shallow subsurface (likely 100 m burial). Most support a central conduit that may be empty or filled with sediment or multiple generations of post-shallow-burial carbonate cements. Depleted 13C values of the concretionary calcite cements (40 to 25 PDB) indicate that their carbon was sourced from oxidized methane. In contrast, enriched 13C values of the concretionary dolomite cements (10 to +11 PDB) indicate that their carbon was derived from methanogenic CO2 and/or extensive methane oxidation. The range of 18O values for the concretionary cement types (2 to +5 PDB) supports precipitation from fluids both depleted and enriched with respect to New Zealand Miocene marine waters, which are suggested to reflect episodes of gas hydrate formation and dissociation, respectively. The tubular carbonate concretions are interpreted to mark the subsea-floor pathways of focused methane infused upward fluid escape, and as such, they represent a part of the shallow subsurface plumbing system of a cold seep system developed on the continental margin bounding the Taranaki Basin in the late Miocene. This margin has been strongly influenced by periodic movements along the major Taranaki fault thrust system, which coincidentally directly underlies the Urenui concretion occurrences and was probably the most likely avenue for active fluid migration within the hydrocarbon seep system. The tubular concretions experienced periodic intervals of exhumation and burial caused by margin failure because of greater slope instability from injected fluids and resulted in conglomeratic channel-fill deposits within the Urenui Formation that include mass-transported tubular concretions.

Interglacial carbonates of the Cryogenian Umberatana Group, northern Flinders Ranges, South Australia

A detailed sedimentological and chronostratigraphic analysis of the Umberatana Group in the northern Adelaide Geosyncline has uncovered a depositional history involving the rapid progradation (at least 20 km) of a giant reef complex (up to 1.1 km relief) during mid-Cryogenian interglacial times. The reef complex, which occurs in the Balcanoona Formation, displays facies similar to Phanerozoic reefs. These include a basal forereef (slope) facies, overlain by a reef-margin facies (consisting of both stromatolitic and non-stromatolitic frameworks), and an upper backreef (platform) facies consisting of shallow-water peloidal and oolitic carbonate. The thickening of the reef complex in a basinward direction, and the distribution of the key facies are consistent with the progradation of the platform into deep water. Progradation was contemporaneous with deposition of the upper Tapley Hill Formation and had largely ceased after a major margin failure event. Following this event, reef growth continued for a short time before becoming extinct, possibly as a result of global climatic cooling and/or eustatic sea-level fall.

Liver Resection Using a Four-Prong Radiofrequency Transection Device

Multiple techniques are available for division of hepatic parenchyma. This is the largest United States report examining the use of the Habib 4X tissue coagulator (AngioDynamics, Queensbury, NY). The objective was to collect standard parameters associated with successful, benchmarked liver surgery outcomes using this new device, and in particular, examine the risk of margin failure. Ninety-four consecutive operations using the Habib 4X were analyzed with special attention to local failure at resection margin, blood loss/transfusion, and operative times. An institutional review board approved protocol allowed collection and analysis of demographic information and outcomes for intraoperative, perioperative, and long-term follow-up. Eighteen patients had biopsy only. Thirty-one had lobar resections and 46 had wedge or segmental resections. There were 30 primary hepatic and 46 metastatic tumor diagnoses. There were a total of 33 (43%) recurrences with a mean time to recurrence of 212 days (range 15-974). Of the 27 intrahepatic recurrences, four (15%) were at the margin. The OR time ranged from 115 to 642 minutes (average 283 min). The average recorded blood loss was 427 mL; 11 patients were transfused (average 0.43 units). The Habib 4X is a safe tool to use when evaluating the parameters of blood loss, transfusion, and margin recurrence.

Evaporites, petroleum exploration, and the Cenozoic evolution of the Libyan shelf margin, central North Africa

The Mediterranean margin of Libya can be divided into three physiographic provinces, the Pelagian Shelf, the Sirt Embayment, and Offshore Cyrenaica. The petroleum potential of the Pelagian Shelf has been investigated but the Sirt Embayment and Offshore Cyrenaica are almost unexplored. During 2004–2005, new 2D pre-stack time-migrated seismic data were acquired and used to examine the large-scale structural, depositional, and salt tectonic features of the Libyan shelf and slope. The data cover approximately 38,000 line kilometers in water depths ranging from under 50 to over 3000 m. Cenozoic strata along much of the Libyan margin have a demonstrable progradational character punctuated by surfaces of erosion and margin failure. Within the Sirt Embayment the most visible retrogradational surface becomes seismically coincident with the top of Messinian unconformity. This retrogradational surface extends for over 700 km along strike and cuts both sides of the Sirt Embayment. Over 5000 cubic kilometers of material are missing from above this surface. There are two ideas for how retrogradation occurred. One idea relates the retrogradation to margin erosion during the Messinian salinity crisis. The other idea suggests that a large part of the Libyan margin experienced a cataclysmic failure during the late Miocene. Some existing models for offshore Libya have interpreted a widespread layer of halite lying within the Messinian which thickens basinward. This interpretation was probably based on the fact seismic reflection continuity was lost over much of the Sirt Embayment on older data beneath the top Messinian unconformity. The loss of good reflection character adversely affected exploration efforts by obscuring deep structures. Recent seismic data and a current understanding of salt behavior do not support the interpretation of thick halite within the Messinian section. Regional observations do not indicate any mobile halite present in the Sirt Embayment. There is a relatively thin, high amplitude and high velocity layer of non-halite evaporites (mainly anhydrite) which caps the Messinian section. Where this high amplitude and high velocity layer is absent or eroded, seismic continuity within the Messinian interval is restored. Limited available well data support this interpretation. True mobile halite is interpreted to exist in offshore Libya only in the far west of the Pelagian Shelf near the Tunisian border. Beneath the Pelagian Shelf are a series of tight contractional folds that are interpreted to be salt cored. Basins adjacent to the folds display geometries characteristic of salt withdrawal. The fold crests formed bathymetric highs which served as nucleation sites for nummulitic shoal development. These shoals are the principal reservoirs of the Pelagian Shelf.

Comparative analysis of quality of service and memory usage for adaptive failure detectors in healthcare systems

Failure detection (FD) is an important issue for supporting dependability in distributed healthcare systems to guarantee continuous, safe, secure, and dependable operation, and often is an important performance bottleneck in the event of node failure. FD can be used to manage the health status of communication for delivering telemedicine services, and then to help distributed healthcare system reduce fatal accident rate and increase the reliability and safety of systems. Ensuring acceptable quality of service (QoS) is made difficult by the relative unpredictability of the network environment. In this paper, first, we compare QoS metrics of several adaptive FDs, discuss their properties and their relation, and then propose one optimization over the existing methods, called tuning adaptive margin failure detector (TAM FD), which significantly improves QoS, especially in the aggressive range and when the network is unstable. Second, we address the problem of most adaptive schemes, namely their need for a large window of samples. So we also analyze the impact of memory size on the performance of FDs, and then prove that the presented scheme is designed to use a fixed and very limited amount of memory for the distributed system. Our experimental results over several kinds of networks (Cluster, WiFi, LAN, Intercontinental WAN) show that the properties of the existing adaptive failure detectors, and demonstrate that the optimization is reasonable and acceptable. Furthermore, the extensive experimental results show what is the effect of memory size on the overall QoS of each adaptive failure detector. For our TAM FD, the effect of window size on their QoS is very small and can be negligible.

An open pilot study of ambulatory photodynamic therapy using a wearable low-irradiance organic light-emitting diode light source in the treatment of nonmelanoma skin cancer

Photodynamic therapy (PDT) is a popular treatment for nonmelanoma skin cancer with clearance rates of between 70% and 100%. Although reported to have a superior cosmetic outcome, the inconvenience of hospital visits and discomfort during therapy are considered drawbacks. To present an open pilot study of a low-irradiance, potentially disposable, lightweight, organic light-emitting diode (OLED), which is an area-emitting light source (2 cm diameter), suitable for ambulatory PDT. Twelve patients with Bowen's disease (eight) and superficial basal cell carcinoma (four) < 2 cm in diameter were recruited into the study following histological confirmation of the diagnosis. Two treatments (45-60 J cm(-2) red light, 550-750 nm, peak 620 nm, irradiance 5 mW cm(-2)) were administered 1 month apart following application of aminolaevulinic acid for 4 h. At the 12-month follow-up, seven of the 12 patients remained clear, with four of the nonresponders demonstrating peripheral margin failure. Patients were scored for pain during and immediately after treatment using the numerical rating scale (NRS; 1-10). All 12 subjects scored pain as < 2 using the NRS (median score 1). In contrast, a similar cohort of 50 consecutive patients from our routine PDT clinic (Aktilite inorganic LED source; 75 J cm(-2), irradiance 80 mW cm(-2)) scored a median of 6 on the NRS. Pain and inconvenience are practical barriers to the use of conventional PDT. This pilot study suggests that OLED-PDT is less painful than conventional PDT with the added advantage of being lightweight, and therefore has the potential for more convenient 'home PDT'. These results need to be validated in larger studies.

Influence of Margin Geometry on Failure of Brittle Coatings on Compliant Substrates: Relevance to Failure of Dental Crowns

This paper explores the so-called “margin failures” observed in loaded curved bi-layer structures. Hemispherical bi-layer model test specimens consisting of glass shells with varying margin geometry filled with epoxy resin, simulating brittle crowns on tooth dentine, are loaded with compliant indenters along the (convex) axis of symmetry. Using this unique setup, the influence of margin geometry on margin failure is examined. Nearly all previous studies have utilised hard spherical indenters of various radii, and examined crack initiation and evolution at the contact point. However, the modes of fracture observed in this traditional contact problem, surface cone cracking or flexure-induced radial cracking initiate close to or inside the (small) contact area, and thus not explain the margin failures commonly observed by dentists. Crack growth at the margins distant from the contact zone cannot be generated under indentation using hard spherical indenters. The use of a compliant (soft) indenter distributes the indentation force over a large contact area, generating a compressive zone underneath the contact, and effectively inhibiting the modes of fracture typically observed using hard indenters (radial and cone cracking). Consequently, significant tensile stresses at the support margin become dominant, and the focus shifts to fracture initiating at the support margins. In this study, cylindrical indenters composed of PTFE Teflon, with a modulus several orders of magnitude lower than the indented materials, are used to examine margin fracture in brittle crown like structures. The specific focus is the effect of margin geometry – Chamfered; Round; Shoulder margins are examined, and their influences on crack initiation and damage evolution are reported.

Experimental validation of a finite element model of light-activated polymerization shrinkage.

An important consideration in improving the longevity of dental resin composite restorations is how to minimize the stresses that develop between resin composites and the wall of the preparation as the resin shrinks during polymerization. If the stress is too great, failure of the bonded interface occurs and microleakage results, with possible margin failure, staining, and secondary caries. This present project was performed to validate a previously developed FEM approach for investigating polymerization shrinkage. Light-cured resin composite was condensed into a cylindrical cavity preparation, which contained a centrally located wire. A profilometer stylus was positioned on the end of the wire to detect the initial surface displacement as the wire moved with the superficial layer of composite resin. The plots of the experimentally derived data were compared to the data plot from the FEM. The initial segments of the experimental plots matched the calculated plot very closely in shape, thus validating the FEM approach.

Platform margin collapses and sequence stratigraphic organization of carbonate slopes: Cretaceous–Eocene, Gargano Promontory, southern Italy

We describe the sequence stratigraphic organization and the associated sedimentological characteristics of Cretaceous to Eocene slope and base‐of‐slope carbonate successions. The study area is located in the Gargano Promontory which belongs to the stable foreland of southern Italy. The succession consists of three superimposed depositional sequences separated by major unconformities. The upper two sequences are clear examples of sequence stratigraphic organization; in fact, they both start with huge megabreccia wedges (LST) followed upward by thin pelagic units (TST) and a thick package of calciturbidites and debrites that alternate with pelagic mudstone (HST). The Cretaceous highstand systems tract is clearly arranged in a number of coarsening‐upward cycles while the Eocene one which also comprises a toplap shallow water unit, is not.The Gargano stratigraphic palimpsest and the entire margin of the Apulia Platform show remarkable similarities with present‐day carbonate platform margins and slopes where irregular, convex‐bankward embayments suggest large‐scale failures. It is clear that classic sequence stratigraphic organization can result from simple platform dismantling, having no or little time relation with global sea‐level fluctuations. In fact, as the margin failure (LST) interrupts the carbonate production, a period of starvation (TST) along the entire slope and base‐of‐slope follows necessarily. Finally, when the margin once again becomes active and productive, sediment exportation starts again and the system begins to prograde (HST).

Creep-fatigue as a possible cause of dental amalgam margin failure.

Fracture of the margins is the most common cause of failure of dental amalgam restorations. Both corrosion and creep have been identified as possible contributors to this type of failure. The stresses that induce creep may arise from the continued setting expansion of the amalgam, the formation of corrosion products, mastication, or from the thermal expansion of the amalgam during ingestion of hot foods. The latter two are low-frequency cyclic stresses. The amalgams used in dentistry have fusion temperatures only about 40 degrees C above mouth temperature, and they experience grain boundary sliding during creep deformation. Since grain boundary sliding, low-frequency cyclic stresses, and a temperature near the fusion temperature of the alloy are prerequisites for so-called "creep-fatigue fracture", this type of fracture may contribute to amalgam margin failure. Amalgam made from seven different alloys was condensed into stainless steel dies. After being allowed to set for seven days, the specimens were thermally cycled between 4 degrees C and 50 degrees C for 500 and 1000 cycles. Amalgam margin integrity was evaluated by scanning electron microscopy both before and after each cycling period. The amount of margin fracture was calculated after 1000 cycles. Thermal cycling of amalgam restorations placed in stainless steel dies resulted in predominantly intergranular fracturing of the amalgam margins, indicating that creep-fatigue failure may be a significant contributor to in vivo margin fracturing.