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PubMed2006

Ontogenetic study of the supraorbital region in modern humans: a longitudinal test of the spatial model.

The structural significance of the hominid supraorbital torus and its morphological variation have always been a controversial topic in physical anthropology. Understanding the function of browridge variation in living and fossil human populations is relevant to questions of human evolution. This study utilizes radiograph images to evaluate the spatial model in modern humans during ontogeny. This structural model attributes variation in the supraorbital region to the positional relationship between the neurocranium and the orbits. The relationship between measurements of the antero-posterior supraorbital length and the factors specified in the spatial model were assessed by correlation and partial correlation analyses. Growth rates were also examined to study ontogenetic trajectories and infer aspects of developmental relationships between critical variables. Results agree with previous research supporting the existence of spatial influences between the neural and orbital-upper facial regions on browridge length during ontogeny.

Adolescent↗
PubMed2006

Statistical approaches to handle proportions as characters.

The handling of morphometric proportions as characters in phylogenetics is methodically hardly elaborated. Common approaches are either to search for statistically significant differences in "index"-values, usually quotients of measures, or to compare regression lines for logarithmic values. The former have their weakness in an insufficient consideration of allometric proportions, the latter in a lack of appropriate methods for testing statistical significance of differences. This contribution presents a methodical approach which considers both allometry and statistical significance. Moreover, not only significance, but also the size of mean differences, as compared to standard deviations, is calculated. If differences are too small, they do not allow to draw a clear distinction between compared groups, and therefore have a low quality as characters. At the beginning of the procedure a test for gradient differences between allometry lines is applied, and if no such are found, a second test for parallel shift between the two lines. If a difference is found, the extent of which exceeds a prearranged limit, it is accepted as a character difference suitable for phylogenetic reconstruction. This method was practically applied by Wiesemüller & Rothe (1999) in a phylogenetic investigation of New World monkeys (Platyrrhini, Primates).

Animals↗
PubMed2006

[Atrial flutter: an update].

Invasive electrophysiologic studies have changed the clinical outlook for patients with atrial flutter. Recognition of the reentrant circuit responsible for typical atrial flutter has led to the development of catheter ablation techniques that can prevent recurrence in >90% of cases. In addition, general understanding of atrial tachycardias has changed radically, such that ECG-based classifications are now obsolete. Atypical reentrant circuits associated with surgical scars or fibrotic areas in either atrium, which are indistinguishable from focal tachycardias on ECG, have been identified. These circuits also seem amenable to treatment by ablation. Recently, a new type of reentrant tachycardia that could be problematic in the future has emerged in patients who have undergone extensive left atrial ablation for the treatment of atrial fibrillation. These atypical circuits can be characterized using the mapping and entrainment techniques initially developed for typical flutter. In these cases, electroanatomical mapping, involving the construction of a virtual anatomical model of the atria, is extremely helpful. Despite the success of ablation, long-term prognosis is frequently overshadowed by the appearance of atrial fibrillation, which suggests that flutter and fibrillation share a common arrhythmogenic origin that is not modified by cavotricuspid isthmus ablation. In contrast with our clear electrophysiologic understanding of atrial flutter, little is known about the natural history of the condition because the literature has traditionally grouped patients with flutter and fibrillation together. Consequently, the complex relationship between the two arrhythmias has still to be clearly delineated. Primary prevention and preventing the development of atrial fibrillation after ablation remain outstanding clinical challenges.

Anisotropy↗
PubMed2006

Prosthetically directed implant placement using computer software to ensure precise placement and predictable prosthetic outcomes. Part 2: rapid-prototype medical modeling and stereolithographic drilling guides requiring bone exposure.

The purpose of this paper is to expand on part 1 of this series (published in the previous issue) regarding the emerging future of computer-guided implant dentistry. This article will introduce the concept of rapid-prototype medical modeling as well as describe the utilization and fabrication of computer-generated surgical drilling guides used during implant surgery. The placement of dental implants has traditionally been an intuitive process, whereby the surgeon relies on mental navigation to achieve optimal implant positioning. Through rapid-prototype medical modeling and the ste-reolithographic process, surgical drilling guides (eg, SurgiGuide) can be created. These guides are generated from a surgical implant plan created with a computer software system that incorporates all relevant prosthetic information from which the surgical plan is developed. The utilization of computer-generated planning and stereolithographically generated surgical drilling guides embraces the concept of collaborative accountability and supersedes traditional mental navigation on all levels of implant therapy.

Acrylic Resins↗
PubMed2006

Evaluation for the fully automatic inlay reconstruction by means of the biogeneric tooth model.

Length measurements and descriptive characterizations were previously the sole reference points for describing the morphology of the occlusal surface. For computerized methods in dentistry, this is not sufficient for producing a data record. So far, the literature has reported no solutions. With the aid of a tooth library containing three-dimensionally measured occlusal surfaces free of caries and abrasion, a mathematical model was produced to describe a certain type of tooth by reference to a few parameters, taking account of functional and biologically relevant structures. This biogeneric tooth model was tested on 27 different inlay situations. The results show that fully automatic reconstruction was possible in all cases. The deviations of the reconstructions from the original tooth surface were on average around 150 microm. Furthermore, the influence of different parameters on the mathematical model was examined. Here, combinations that guarantee the best possible reconstruction for many situations could be found. The visual evaluation and the metric comparison of the reconstructions among one another illustrate the great flexibility of the biogeneric tooth model. With the aid of the biogeneric tooth model, there is the possibility of reconstructing the occlusal surfaces of dental restorations by CAD/CAM processes fully automatically, taking account of morphological and functional criteria. Further studies are needed to show to what extent the inclusion of degree of abrasion, antagonist and adjacent teeth delivers the desired results in the whole spectrum of clinical cases.

Computer Graphics↗
PubMed2006

[The research advances of biomechanics of human knee joint ligaments].

Ligaments are the main parts which stabilize the knee joint. How to analog the ligaments in biomechanical model will affect the characteristics of the human knee dynamics and in the computation of the stress in ligaments between two bones. This symposium is aimed at the survey of the simplified method of the ligaments via mechanical parameters, and providing an exact method of constructing model.

Biomechanical Phenomena↗
PubMed2006

Control of cardiac hypertrophy and heart failure by histone acetylation/deacetylation.

The adult heart responds to acute and chronic stresses by a remodelling process that is accompanied by myocyte hypertrophy, impaired contractility, and pump failure, often culminating in sudden death. Pathological growth and remodelling of the adult heart is often associated with the reactivation of a fetal cardiac gene program that further weakens cardiac performance. Recent studies have revealed key roles for histone deacetylases (HDACs) in the control of pathological cardiac growth. Class II HDACs associate with the MEF2 transcription factor, and other factors, to maintain normal cardiac size and function. Stress signals lead to the phosphorylation of class II HDACs and their export from the nucleus to the cytoplasm, with consequent activation of genes involved in cardiac growth. HDAC knockout mice are hypersensitive to stress signalling and develop massively enlarged hearts in response to various pathological stress stimuli due to an inability to counteract pathological signalling to MEF2. Strategies for normalizing gene expression in the failing heart by regulating HDAC phosphorylation and function represent potentially powerful therapeutic approaches.

Acetylation↗
PubMed1991

Chemically distinct compartments of the thalamic VPM nucleus in monkeys relay principal and spinal trigeminal pathways to different layers of the somatosensory cortex.

The ventral posteromedial nucleus (VPM) of the monkey thalamus was investigated with combined immunocytochemical, histochemical, and connection-tracing techniques. Injections of anterogradely transported tracers were placed selectively in the caudal nucleus of the spinal trigeminal nuclear complex, and retrogradely transported horseradish peroxidase (HRP) or fluorescent dyes were placed on the surface or into the depths of defined parts of the trigeminal representation in the first somatic sensory area (SI) of the cerebral cortex. The results are correlated with those of the preceding paper (Rausell and Jones, 1991), which demonstrated the presence of 2 domains in the nucleus on the basis of different patterns of cytochrome oxidase (CO) staining and calcium-binding protein immunoreactivity. The cells of the CO-defined rod and matrix domains receive inputs from different components of the trigeminal afferent system and project to different layers of SI. The large- and medium-sized relay cells of the CO-rich rods, which are immunoreactive for parvalbumin, all project to middle layers of SI. The small relay cells of the weakly-stained CO-matrix, surrounding and intervening between the rods, are immunoreactive for 28-kDa calbindin and project to superficial layers (I and II) of SI. Anterograde tracing studies reveal that the rod domain in VPM is innervated by fibers arising in the contra- and ipsilateral principal trigeminal nucleus, while the matrix domain (and calbindin-positive domains in adjacent nuclei) are innervated by fibers arising in the caudal nucleus of the spinal trigeminal complex. These results demonstrate the modularity and parallel streaming of the functional components of the trigeminal part of the somatic sensory system and suggest that lemniscal and nonlemniscal elements of the system gain access by separate routes to different layers of the SI cortex.

Animals↗
PubMed2006

Presurgical implant-supported prosthesis: technique for cementation of a definitive prosthesis immediately after surgery.

A fixed prosthesis, supported by implants, was fabricated prior to surgery and cemented with passive fit immediately after placement of 14 implants in the mandible. The prosthesis was constructed before implant surgery on a plaster cast that precisely reproduced the patient's hard and soft tissues. The cast was built using a method that allowed the transfer of hard and soft tissue anatomy from computerized tomograms. A rigid surgical stent, cast in gold, was used to place the implants into prosthetically ideal positions under three-dimensional control. The prosthesis was placed immediately after implant placement, using an occlusion-driven method, which avoided the need for occlusal adjustments to the prosthesis.

Cementation↗
PubMed2006

Prosthetically directed implant placement using computer software to ensure precise placement and predictable prosthetic outcomes. Part 3: stereolithographic drilling guides that do not require bone exposure and the immediate delivery of teeth.

Previous publications have reviewed the concepts of implant diagnostics and computerized tomographic imaging used together to create an atmosphere of collaborative accountability. The use of SimPlant software in combination with stereolithographic medical modeling facilitates the fabrication of surgical drilling guides, which assist in precise placement of dental implants. In this article, the use of gradient density scanning appliances will be discussed. This type of scanning appliance allows tooth- or mucosa-supported surgical drilling guides to be fabricated and used for implant placement without bone exposure. The use of the SAFE System will be introduced, along with its application in simplifying the immediate-loading prosthesis concept, which can often bypass the need for traditional dental impressions.

Dental Implantation, Endosseous↗
PubMed2006

Steps, arches, and struts supporting the aortic leaflet of the mitral valve.

BACKGROUND AND AIM OF THE STUDY: The study aim was to re-examine the form and function of the cords exclusive to the aortic leaflet of the mitral valve. METHODS: The ventricular surface of the leaflet was exposed by a longitudinal incision between the coronary sinuses of the aorta. The cords exclusive to the leaflet, in between the so-called commissural cords on either side shared with the mural leaflet, were inspected visually in 75 human hearts obtained at autopsy. RESULTS: The cords were found to form two groups: (i) cords to the free edge, which support the gossamerthin free edge of the leaflet, and provide a low-pressure, bloodtight seal; and (ii) belly cords, which insert into the ventricular surface of the leaflet, usually forming graceful steps and arches between the lateral and medial groups of cordal support. Among these belly cords were found strut cords, which course perpendicular to the steps and arches. CONCLUSION: The so-called cords to the rough zone, better considered as belly cords, must be distinguished from cords supporting the free edge of the leaflet, as they have different forms and subserve a different function. The belly cords usually form steps, arches and struts, which facilitate the distribution of stress, whereas the cords supporting the free edge function to provide a blood-tight seal. An understanding of the pattern and variations in cordal support is necessary to appreciate the pathology, and to tailor restoration in the surgical repair of diseased valves.

Aorta↗
PubMed2007

Setting positive end-expiratory pressure during jet ventilation to replicate the mean airway pressure of oscillatory ventilation.

BACKGROUND: High-frequency ventilation can be delivered with either oscillatory ventilation (HFOV) or jet ventilation (HFJV). Traditional clinician biases may limit the range of function of these important ventilation modes. We hypothesized that (1) the jet ventilator can be an accurate monitor of mean airway pressure (P (aw)) during HFOV, and (2) a mathematical relationship can be used to determine the positive end-expiratory pressure (PEEP) setting required for HFJV to reproduce the P (aw) of HFOV. METHODS: In phase 1 of our experiment, we used a differential pressure pneumotachometer and a jet adapter in-line between an oscillator circuit and a pediatric lung model to measure P (aw), PEEP, and peak inspiratory pressure (PIP). Thirty-six HFOV setting combinations were studied, in random order. We analyzed the correlation between the pneumotachometer and HFJV measurements. In phase 2 we used the jet as the monitoring device during each of the same 36 combinations of HFOV settings, and recorded P (aw), PIP, and DeltaP. Then, for each combination of settings, the jet ventilator was placed in-line with a conventional ventilator and was set at the same rate and PIP as was monitored during HFOV. To determine the appropriate PEEP setting, we calculated the P (aw) contributed by the PIP, respiratory rate, and inspiratory time set for HFJV, and subtracted this from the goal P (aw). This value was the PEEP predicted for HFJV to match the HFOV P (aw). RESULTS: The correlation coefficient between the pneumotachometer and HFJV measurements was r = 0.99 (mean difference 0.62 +/- 0.30 cm H(2)O, p < 0.001). The predicted and actual PEEP required were highly correlated (r = 0.99, p < 0.001). The mean difference in these values is not statistically significantly different from zero (mean difference 0.25 +/- 1.02 cm H(2)O, p > 0.15). CONCLUSIONS: HFJV is an accurate monitor during HFOV. These measurements can be used to calculate the predicted PEEP necessary to match P (aw) on the 2 ventilators. Replicating the P (aw) with adequate PEEP on HFJV may help simplify transitioning between ventilators when clinically indicated.

Airway Resistance↗
PubMed2006

Linear ablation of left atrium for the treatment of atrial fibrillation guided by double Lasso catheters and three dimensional electroanatomical mapping.

BACKGROUND: Linear ablation of left atrium (LA) guided by three dimensional (3-D) electroanatomical mapping (Carto) has been used in many centres worldwide for the treatment of atrial fibrillation (AF) instead of pure anatomical approaches. There were little data about linear ablation of LA guided by Carto and double Lasso catheters in China. We report the results of linear ablation of LA guided by both Carto and double Lasso catheters. METHODS: After the anatomical model of LA and all pulmonary veins (PVs) had been established, circumferential ablations of the left pulmonary vein antrum and the right pulmonary vein antrum were performed with 2 circumferential mapping catheters (Lasso) placed within the ipsilateral superior and inferior PVs. The endpoint of ablation was abolishment or dissociation of the pulmonary vein potentials (PVPs). Oral amiodarone or propafenone was taken for at least 3 months by patients with persistent AF, permanent AF or those whose PVPs had not been isolated completely. The recurrence of atrial tachyarrhythmias was observed 3 months after the procedure. RESULTS: There were 106 patients (mean age, 51.4 +/- 9.9 years). Seventy-eight patients had paroxysmal AF, 12 persistent AF and 16 permanent AF. Onset of atrial fibrillation occurred in 52 patients during ablation procedure. Thirty-two patients restored to sinus rhythm eventually after the procedure. Abolishment or dissociation of PVPs was accomplished during the procedure in 94 patients (88.7%). The duration of procedure and exposure to X-ray were (213 +/- 45) minutes and (32.5 +/- 12.8) minutes, respectively. Among the 87 patients followed up for over 3 months, 62 were free of atrial tachyarrhythmias (including 8 patients who were still taking oral amiodarone). The success rate was 71.3% in the first procedure. Two patients had pericardial effusion treated by pericardial puncture and effusion drainage. No pulmonary vein stenosis, atrioesophageal fistula, stroke or procedural death occurred. CONCLUSIONS: Combination of double Lasso catheters with 3-D electroanatomical mapping to guide the linear ablation of left atrium procedure can confirm the isolation of PVPs.

Adult↗
PubMed1991

[Biomechanical data regarding the socket-neck orientation of hip endoprosthesis].

On the basis of clinico-statistical, roentgenologic, morphological and spectral studies it is possible to draw the conclusion that the cause of the structural deformation of the bone tissue around the endoprosthesis parts and an approach of their instability is in the mechanical interaction of bone and explant. Under the influence of the biomechanical forces the socket of the endoprosthesis gradually changes its position from 45-90 degrees to 25-30 degrees. The original 25-30 degree positioning of the socket significantly decreases the moment of forces that it is subjected to and, as a rule, there is no socket displacement observed. That is why this socket positioning in the process of operation is a preferable one. But the angles of necks of the Sivash endoprosthesis and its modifications are equal to 130 degrees +/- 3 degrees and when the socket is positioned at an angle 25-30 degrees there can occur limitation of the limb abduction, the socket loosening, the structure fretting and metallosis of tissues due to the setting of the neck against the end of the insert. It is expedient to change the angle of the endoprosthesis neck to 150 degrees +/- 3 degrees and some shortening of the neck.

Anthropometry↗
PubMed1991

[Computer-aided 3-dimensional reconstruction of the ossicular chains and their mechanic models].

This study was intended to reconstruct the human ossicular chains and their neighbouring structures by a image processing work station (IPWS). The reconstructed structures were placed in an X, Y, Z coordinate system and every point of the structures had its X, Y, Z values. This technique can reveal 3-D image of the biological structures in detail. It can also provide the quantitative measurement and the mechanic model of the ossicular chain. The mechanism of the ossicular chain in the conduction of sound was studied and discussed.

Acoustic Stimulation↗
PubMedDate not supplied

[The significance of zonography in X-ray diagnosis of midfacial fractures].

The possibilities offered by panoramic zonography (MT program) in the diagnosis of the midface are outlined. The imaging quality of various anatomical structures is demonstrated both on the anatomical model and in clinical use. The benefits and limitations of this procedure are discussed. Zonography is a reliable instrument adding to the range of basic diagnostic procedures in the midfacial region.

Facial Bones↗
PubMed1991

[3-dimensional model of the hip joint].

The main aim of this work was to build a three-dimensional theoretical pattern of the hip joint. It occurs as a generalization of the pattern of Pauwels, which was two dimensional. The equipment used is general mechanics plus an axiom we have added, which enables the calculation of the distribution of the surface pressures. Through theory, we find the experimental results of photo-elasticity. This pattern enables an analysis of the forces which act on the hip and their biomechanical role during gait. It leads to a better comprehension of the biomechanic failure, originating a pathology, and to a better choice in surgical correction. The calculation of the distribution of the surface pressures enables to understand the position of the acetabular rim. Our results contradict R. Bombelli's.

Biomechanical Phenomena↗