Dynamic Occlusion Research Articles

Effect of preoperative transcatheter arterial chemoembolization on the perioperative outcome of patients with hepatocellular carcinoma

To explore the surgical risk, perioperative outcome and the response of patients with hepatocellular carcinoma (HCC) after preoperative transcatheter arterial chemoembolization (TACE). A retrospective case-matched study was conducted to compare the characteristics and corresponding measures of patients in the preoperative TACE group and the control group without TACE. A total of 105 patients (82 patients with selective and dynamic region-specific vascular occlusion to perform hepatectomy for patients with complex hepatocellular carcinoma) was included in this study, in which 35 patients underwent TACE therapy, and a 1:2 matched control group of 70 subjects. The patients of preoperative TACE therapy group had a higher level of γ-glutamyl transpeptidase before operation (119.52±98.83) U/L vs. (67.39±61.25) U/L (P=0.040). The operation time was longer in the TACE group than that in the control group but with a non-significant difference (232.60±95.43) min vs. (218.70±75.13) min (P=0.052). The postoperative recovery of liver function and severe complications in the preoperative TACE group were similar to that in the control group (P>0.05). There were no massive hemorrhage, biliary fistula and 30-d death neither in the treatment group and matched control group. Preoperative TACE therapy has certain negative effect on liver function. It is preferable to use selective and dynamic region-specific vascular occlusion technique during hepatectomy and combine with reasonable perioperative treatment for this group of patients, that can ensure safety of patients and promote their rapid recovery.

Video Object Classification System with Shadow Removal using Gaussian Mixture Model

Classification is the process of assigning a class to a group of objects. Moving objects classification can be difficult a task in the presence of dynamic factors like occlusion clutters and shadows. This paper developed a classifier for moving images (video stream) by using a modified adaptive background mixture model method. This system removes shadows and correctly classifies moving objects as human, human group and vehicles. Background Mixture Model is common technique used in Computer Vision, Video object classification is not an exception, many background models have been designed to address different problems ranging from slow start and shadow removal; this paper presents a method which models each pixel as a mixture of Gaussians and using a Maximum A Posteriori approximation to update the model, this paper also introduces a two level shadow removal technique which suppressed shadows in colour and texture consistencies in the classified objects so that the system will not mis- classify moving shadows as objects. This work overcome the problem of slow learning in busy environment and can classify more than one object in view of the camera

Anesthetic Management for Laser Excision of Ball-Valving Laryngeal Masses

A 47-year-old obese woman with GERD and COPD presents for CO2-laser excision of bilateral vocal fold masses. She had a history of progressive hoarseness and difficulty in breathing. Nasopharyngeal laryngoscopy revealed large, mobile, bilateral vocal cord polyps that demonstrated dynamic occlusion of the glottis. We describe the airway and anesthetic management of this patient with a topicalized C-MAC video laryngoscopic intubation using a 4.5 mm Xomed Laser Shield II endotracheal tube. We examine the challenges of anesthetic management unique to the combined circumstances of a ball-valve lesion and the need for a narrow-bore laser compatible endotracheal tube.

Don’t Believe What You See in Mouth, Listen To Condyles-A Systemic Review

Centric relation, static and dynamic occlusion are less talked about than its actual importance in dentistry. Their relevance to different disciplines of odontology (general dentistry, conservative dentistry, orthodontics, prosthodontics, dental technicians) has been well documented. Numerous articles in scientific literature regarding the importance and necessity of interdisciplinary teamwork in dentistry to correct problems associated with occlusion has been documented. The centric occlusion and centric relation (CO CR) discrepancy is multifactorial with a degree of psychogenic influence varying throughout an individual’s life with phases of symptoms affecting the quality of life. The current review highlights role of various disciplines in rectifying problems relating to discrepancy in centric occlusion and centric relation.1

Bow hunter’s syndrome secondary to bilateral dynamic vertebral artery compression

Bow hunter’s syndrome is a condition in which vertebrobasilar insufficiency is resultant from head rotation, clinically manifested by presyncopal sensation, syncope, dizziness, and nausea. It is usually diagnosed clinically, with supporting vascular imaging demonstrating an occluded or at the very least compromised unilateral vertebral artery, while the dominant vertebral artery remains patent in the neutral position. Dynamic imaging is utilized to confirm the rotational compression of the dominant vertebral artery. We present the rare case of a patient with typical Bow hunter’s symptoms, bilaterally patent vertebral arteries on neutral imaging, and bilateral compromise with head rotation. Our patient underwent posterior decompression of the culprit atlanto-axial transverse foramen and subaxial cervical fusion, with resolution of his symptoms. Our patient exemplifies the possibility of bilateral dynamic vertebral artery occlusion. We show that Bow hunter’s syndrome cannot be ruled out in the setting of bilaterally patent vertebral arteries on neutral imaging and that severe cervical spondylosis should impart further clinical suspicion of this unusual phenomenon.

Reconstructing cultural behavior from dental wear studies: Is para-facets analysis approach scientifically valid?

It is common knowledge, that in archaic populations teeth were used as tools, this behavior can be studied by evaluating attrition patterns. Parafacets were defined as nonmasticatory wear areas that have no antagonist matching wear facets. The presence of the parafacets led to far-reaching conclusions regarding cultural interactions between Near Eastern Neanderthals and anatomically modern humans. This study was aimed to examine the identification of parafacets in some of the Qafzeh specimens. Based on findings of our research we suggest that the attrition facets mistakenly considered as parafacets are in fact the result of the static and dynamic occlusion. Therefore the observations induce much less dramatic interpretation. We here propose several guidelines that would be beneficial in that they aim to evaluate the parafacets with heightened accuracy.

Noninvasive Restoration of Severe Erosion by Means of CAD/CAM Indirect Composite Occlusal Restorations: A Technical Note

The use of new materials and computer-aided design/computer-aided manufacturing techniques can help dental practitioners efficiently treat dental erosion in a predictable manner. If the vertical dimension of occlusion has to be increased, the static and dynamic occlusion need to be reorganized. This article presents and documents a practical, digital approach to such treatment and discusses possible merits as they relate to treatment time, ease of treatment, and predictability.

The Application of Esophageal Pressure Measurement in Patients with Respiratory Failure

This report summarizes current physiological and technical knowledge on esophageal pressure (Pes) measurements in patients receiving mechanical ventilation. The respiratory changes in Pes are representative of changes in pleural pressure. The difference between airway pressure (Paw) and Pes is a valid estimate of transpulmonary pressure. Pes helps determine what fraction of Paw is applied to overcome lung and chest wall elastance. Pes is usually measured via a catheter with an air-filled thin-walled latex balloon inserted nasally or orally. To validate Pes measurement, a dynamic occlusion test measures the ratio of change in Pes to change in Paw during inspiratory efforts against a closed airway. A ratio close to unity indicates that the system provides a valid measurement. Provided transpulmonary pressure is the lung-distending pressure, and that chest wall elastance may vary among individuals, a physiologically based ventilator strategy should take the transpulmonary pressure into account. For monitoring purposes, clinicians rely mostly on Paw and flow waveforms. However, these measurements may mask profound patient-ventilator asynchrony and do not allow respiratory muscle effort assessment. Pes also permits the measurement of transmural vascular pressures during both passive and active breathing. Pes measurements have enhanced our understanding of the pathophysiology of acute lung injury, patient-ventilator interaction, and weaning failure. The use of Pes for positive end-expiratory pressure titration may help improve oxygenation and compliance. Pes measurements make it feasible to individualize the level of muscle effort during mechanical ventilation and weaning. The time is now right to apply the knowledge obtained with Pes to improve the management of critically ill and ventilator-dependent patients.

Spontaneous atraumatic vertebral artery occlusion due to physiological cervical extension

Vertebral artery (VA) occlusion is a serious and potentially life-threatening occurrence. Bow hunter's syndrome, a mechanical occlusion of the VA due to physiological head rotation, has been well described in the medical literature. However, mechanical VA compression due to routine flexion or extension of the neck has not been previously reported. The authors present the unique case of a woman without any history of trauma who had multiple posterior fossa strokes and was found to have dynamic occlusion of her right VA visualized via cerebral angiogram upon extension of her neck. This occlusion was attributed to instability at the occipitocervical junction in a patient with a previously unknown congenital fusion of both the occiput to C-1 and C-2 to C-3. An occiput to C-3 fusion was performed to stabilize her cervical spine and minimize the dynamic vascular compression. A postoperative angiogram showed no evidence of restricted flow with flexion or extension of the neck. This case emphasizes the importance of considering symptoms of vertebrobasilar insufficiency as a result of physiological head movement. The authors also review the literature on VA compression resulting from physiological head movement as well as strategies for clinical diagnosis and treatment.

The role of virtual articulator in prosthetic and restorative dentistry.

Virtual reality is a computer based technology linked with the future of dentistry and dental practice. The virtual articulator is one such application in prosthetic and restorative dentistry based on virtual reality that will significantly reduce the limitations of the mechanical articulator, and by simulation of real patient data, allow analyses with regard to static and dynamic occlusion as well as to jaw relation. It is the purpose of this article to present the concepts and strategies for a future replacement of the mechanical articulator by a virtual one. Also, a brief note on virtual reality haptic system has been highlighted along with newly developed touch enabled virtual articulator.

The aperture capture illusion: Misperceived forms in dynamic occlusion displays.

Visual illusions can reveal unconscious representations and processes at work in perception. Here we report a robust illusion that involves the misperception of moving, partially occluded objects. When a dynamically occluded object is seen through 2 misaligned apertures, the object appears misaligned in the direction of the apertures, creating the Aperture Capture Illusion. Specifically, when part of a dynamically occluded object disappears behind an occluding surface and then another part of the object comes into view immediately afterward, the 2 parts appear misaligned in the direction of the offset of the apertures through which they were seen. This illusion can be nulled: Separating the 2 object parts to increase the time interval between their appearance produced the percept of alignment. The ability to null the illusion in this manner demonstrates that dynamically occluded regions of moving objects continue to persist in perceptual awareness but, we argue, are perceived to move at a slower velocity than visible regions. We report 7 experiments establishing the existence of the illusion and ruling out several classes of explanation for it. We interpret the illusion and the ability to nullify it within the context of Palmer, Kellman, and Shipley's (2006) theory of spatiotemporal object formation.

ИсследованИе дИнамИческой окклюзИИ у пацИентов с заболеванИямИ пародонта

ИсследованИе дИнамИческой окклюзИИ у пацИентов с заболеванИямИ пародонта

R1 Hepatectomy With Exposure of Tumor Surface for Centrally Located Hepatocellular Carcinoma

Hepatectomy with exposure of tumor surface (a special type of R1 resection) provides a chance of cure for selected patients with centrally located hepatocellular carcinoma (HCC) that is adherent to or compresses major vessels. However, the operative indications, safety, and patient outcomes are not well defined. We performed hepatectomy for removal of complex centrally located HCC using a selective and dynamic region-specific vascular occlusion technique. Between May 2006 and March 2012, a total of 118 patients underwent resection with exposure of tumor surface (exposure group) and 169 underwent conventional hepatectomy (without exposure of the tumor and vascular surface). The short- and long-term outcomes of patients were evaluated and compared. The postoperative recovery of liver function was comparable between the two groups. Bile leakage occurred in five patients, all in the exposure group. The 1-, 3-, and 5-year recurrence-free survival rates were 74.4, 45.6, and 30.1 % in the exposure group and 80.9, 57.2, and 31.7 % in the control group (p = 0.041). Corresponding overall survival rates were 92.3, 70.3, and 44.9 % in the exposure group and 97.8, 81.4, and 53.1 % in the control group (p = 0.094). Hepatectomy with exposure of tumor surface is technically demanding, but can be performed safely. It is also associated with a risk of tumor recurrence. Multidisciplinary combined therapy would be the solution and can contribute to improve overall survival.

Parallel and adaptive visibility sampling for rendering dynamic scenes with spatially varying reflectance

Fast rendering of dynamic scenes with natural illumination, all-frequency shadows and spatially varying reflections is important but challenging. One main difficulty brought by moving objects is that the runtime visibility update of dynamic occlusion is usually time-consuming and slow. In this paper, we present a new visibility sampling technique and show that efficient all-frequency rendering of dynamic scenes can be achieved by sampling visibility of dynamic objects in an adaptive and parallel way. First, we propose a two-level adaptive sampling scheme to distribute sample points spatially and compute visibility maps angularly on each sample point. Then, we present a parallel hemispherical distance transform to convert these visibility maps into spherical signed distance fields. Finally, using such a distance-based visibility representation, we integrate our visibility sampling algorithm in the all-frequency rendering framework for scenes with spatially varying BRDFs. With an entire GPU-based implementation, our algorithm enables interactive all-frequency rendering of moderate dynamic scenes with environment lighting and spatially varying reflectance.

Depth perception from dynamic occlusion in motion parallax: Roles of expansion-compression versus accretion-deletion

Motion parallax, or differential retinal image motion from observer movement, provides important information for depth perception. We previously measured the contribution of shear motion parallax to depth, which is only composed of relative motion information. Here, we examine the roles of relative motion and accretion-deletion information in dynamic occlusion motion parallax. Observers performed two-alternative forced choice depth-ordering tasks in response to low spatial frequency patterns of horizontal random dot motion that were synchronized to the observer's head movements. We examined conditions that isolated or combined expansion-compression and accretion-deletion across a range of simulated relative depths. At small depths, expansion-compression provided reliable depth perception while accretion-deletion had a minor contribution: When the two were in conflict, the perceived depth was dominated by expansion-compression. At larger depths in the cue-conflict experiment, accretion-deletion determined the depth-ordering performance. Accretion-deletion in isolation did not yield any percept of depth even though, in theory, it provided sufficient information for depth ordering. Thus, accretion-deletion can substantially enhance depth perception at larger depths but only in the presence of relative motion. The results indicate that expansion-compression contributes to depth from motion parallax across a broad range of depths whereas accretion-deletion contributes primarily at larger depths.

The clinical application of NAT/NFR occlusal concept

Many concept of occlusion have been introduced in the past, but there isn't any generally accepted unified theory since a single occlusion theory cannot represent the natural perfection, especially considering the difference in clinical experience, the dynamic occlusion, and individual diversity in mastication pattern. NAT(Naturgemasse Aufwachstechnik)/NFR((Natur Funktionsgerechte Rekonstruktion) occlusion is not just a theory on occlusion, but a clinical occlusion that can be practically applied to clinical practice by providing dynamic occlusion adjusted to the individual mastication pattern and biomechanics. This report aims to provide a guide to a clinically biomechanical occlusion through the teamwork of both the dentist and the lab technician by introducing the NAT occlusion through following: reviewing the concept of occlusion in terms of morphology, its correlation with NAT/NFR occlusion, reviewing the limitation of conventional occlusion theories, and introducing the clinical application of NAT/NFR.

T-scan III 시스템을 이용한 하악 측방운동 시 교합접촉 양상의 분석

이 논문의 목적은 시간에 따른 교합의 변화를 측정할 수 있는 T-scan system을 이용하여 젊은 성인 남성(33명)정상교합에서의 하악골 측방운동 시 교합접촉 양상을 분석하는 것이다. 정해진 하악 위치에서의 교합접촉이 아닌, 기능적 범위 내에서 비작업측 교합이개 시점에서의 교합접촉 양상을 분류하고 분류된 군 간에 교합이개 시간, 측방유도 시 견치가 담당하는 교합력의 비율, 측방운동 시 가해지는 교합력 등을 비교하였다. 연구 결과 기존의 분류와는 다른 측방접촉들이 존재하였고 군기능 유도가 우세하게 나타났다. 교합이개 시간, 측방유도 시 견치가 담당하는 교합력의 비율, 측방운동 시 가해지는 교합력 등에서 군 간의 유의한 차이를 나타내었다. T-scan system은 교합접촉 양상을 분류하고 교합력, 교합이개 시간, 견치가 담당하는 교합력 비율 등의 항목을 비교 분석하는데 있어서 유용한 도구이다. The objective of this study was to analyze occlusal contact pattern of 33 young adult males with normal occlusion during lateral excursion using T-scan III system which can measure the dynamic occlusion. Occlusal contact patterns were examined and categorized in non-working side disclusion point(more functionally acceptable position) not canine-to-canine position. Disclusion time, occlusal force, and occlusal force distribution ratio of upper canine at disclusion point during lateral excursion movement was also measured and compared among the groups divided according to contact patterns. The results showed that group function was clearly more dominant than canine guidance and other occlusal contact patterns different with existing patterns were found. There were significantly difference between groups in variables of T-scan measurement. T-scan III system is effective tools to analyze and evaluate occlusal contact patterns, disclusion time, occlusal force, and occlusal force distribution ratio of upper canine at disclusion point.

Bilateral mechanical rotational vertebral artery occlusion

Rotational vertebral artery occlusion, or bow hunter's stroke, is reversible, positional symptomatic vertebrobasilar ischemia. The typical mechanism of action is obstruction of a dominant vertebral artery with contralateral head rotation in the setting of baseline ipsilateral vertebral artery stenosis or occlusion. Here we present a rare case of mechanical occlusion of bilateral patent vertebral arteries manifesting as near syncope with rightward head rotation. Diagnostic cerebral angiography showed dynamic right C5 vertebral occlusion and left C2 vertebral occlusion. The patient underwent right C4/5 transverse process decompression. Postoperative angiogram showed patent flow through the right vertebral artery in neutral position and with head turn with resultant resolution of symptoms.

History of materials used for recording static and dynamic occlusal contact marks: a literature review.

In the discipline of prosthetic dentistry it is important not only to examine the occlusion, but to be able to record, store, and transfer the information. Over the years many occlusion testing materials have been used. It has been suggested the clinical recording and transfer of information using waxes and other occlusion recording materials have disadvantages relating to inaccuracy and problems of manipulation. Therefore, there has been introduction of many new systems for recording occlusion contacts to overcome such problems. The correct physiological recovery of occlusion posses as much a challenge as ever for every dentist and technician. Even the smallest high spots measuring just a few microns can cause dysfunctions like temporo-mandibular pain. Occlusal proportions are being constantly changed with every procedure. Therefore, an understanding of the synergy of the teeth in static and dynamic occlusion forms the basis of good dentistry. The purpose of this review article is to give and overview of the various materials and methods that have been used to record occlusal contact marks. Key words:Occlusal contact marks, Occlusion indicators, Occlusion test materials, Occlusion recording materials.

An unusual case of pediatric bow hunter′s stroke

Background:Bow Hunter's syndrome/stroke is defined as symptomatic, vertebrobasilar insufficiency provoked by physiologic head rotation. It is a diagnostically challenging cause of posterior circulation stroke in children. While there have been prior reports of this rare disorder, we describe an exceptional case of pediatric Bow Hunter's stroke resulting from a near complete occlusion the right vertebral artery (VA) secondary to an anomalous spur emanating from the right occipital condyle. Surgical and endovascular options and approaches are also detailed herein.Case Description:A 16-year-old male presented with multiple posterior circulation ischemic strokes. A dynamic computerized tomography angiogram performed with the patient's head in a rotated position revealed a near complete occlusion of the V3 segment of the right VA from a bone spur arising from his occipital condyle. The spur caused a focal dissection of the distal right VA with associated thrombus. He was initially managed with a cervical collar, antiplatelet therapy with aspirin 81 mg and anticoagulation with coumadin (INR goal 2-3) for 3 months. Despite the management plan, he had a subsequent thromboembolic event and a right VA sacrifice with coil embolization was then performed. At the 3-month follow-up, the patient was doing well with no reports of any subsequent strokes.Conclusion:We report the first reported pediatric case of Bow Hunter's stroke due to dynamic right VA occlusion from an occipital condylar bone spur. The vascular compression from this spur led to a right VA dissection and thrombus formation and ultimately caused multiple posterior circulation thromboembolic strokes. Endovascular treatment options including vessel sacrifice should be considered in cases that have failed maximal medical management.