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Parkinson's disease (PD) affects one to two out of every 1,000 individuals. PD, being age-related, is affecting a percentage of those over and around the sixth decade. Lewy bodies containing α-synuclein and a reduction in dopaminergic neurons in the substantia nigra, which impairs the region's capacity to promote voluntary movements, are the main neuropathological findings. The three main symptoms of PD are stiffness, bradykinesia, and tremor. Treatment of edentulous conditions in patients with PD becomes a challenge due to decreased neuromuscular coordination and decreased mobility. This case report outlines a 64-year-old male patient with complete edentulism suffering from PD. Complete denture fabrication was done using the concepts of the neutral zone and denture characterization. Significantly, it not only improves the stability of the dentures but also establishes good denture aesthetics.

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A flabby ridge is a hyperplastic and movable soft tissue that affects both maxillary and mandibular ridges most commonly the maxillary anterior region. This tissue that supports the denture is dynamic and can be dislodged by masticatory pressures, which affects denture stability and causes a loss of peripheral seal. The mobile tissue may be distorted as a result of forces applied during the impression-making process. For dental practitioners, fabricating dentures on a flabby ridge might be a Herculean endeavor because the dentures may not be stable and may not yield satisfactory outcomes. When treating such patients, practitioners should use extra caution. While treating such circumstances, adjustments to standard impression processes can be helpful. There are several ways to address flabby ridges, such as implant therapy, balanced occlusal load distribution, surgical management, and unique impression techniques. In this case report, a patient with a flabby ridge is treated prosthodontically via an alternative impression approach.

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The ill-fitting and unstable complete denture prosthesis is the most commonly faced problem by patients with compromised resorbed ridge. The retention, support, and stability of dentures are compromised in severely resorbed ridges, leading to difficulty in mastication and swallowing. The flabby tissue can be managed by using appropriate mucostatic impression techniques, and severely resorbed ridges can be managed by the coordination of a complete denture prosthesis with the neuromuscular function using a neutral zone for the arrangement of artificial teeth. This case report presents a combination of the Hobkirk technique and the neutral zone concept for the rehabilitation of the flabby tissue and severely resorbed alveolar ridge.

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Background: This study aimed to assess the effectiveness of surgery in the management of vertical compensatory head posture in patients with congenital nystagmus (CN) inherited in an X-linked manner in a Chinese family and determine the molecular pathogenesis of this disease. Methods: We studied 18 members belonging to four generations in a family with congenital nystagmus. Parks shift of neutral zone surgeries were performed on 7 patients with vertical compensatory head posture from the family. In addition, head posture, visual acuity, and stereopsis of the 7 patients were evaluated before and 2-years after the displacement surgeries. Gene alternations of the disease were researched by sequencing a candidate gene (FRMD7). From each generation of the family, one patient (including the proband) and one normal control were sampled for Sanger sequencing. Results: Over a median follow-up period of 2 years, the anomalous head posture, visual acuity, and stereopsis significantly improved postoperatively (P < 0.05). Sanger sequencing revealed that a variant c.586G > T (p.D196Y) in exon 7 of FRMD7 was co-segregated with the disease in this family. Conclusions: Parks shift of neutral zone surgeries relieved the vertical compensatory head posture and improved visual acuity and stereopsis in the primary position of CN patients. In this study, it was concluded that a missense mutation in exon 7 (c.586G > 7, p.D196Y) in FRMD7 was possibly responsible for the disease in this family.

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Tooth loss and subsequent complete denture rehabilitation can profoundly affect a patient's psychological and social well-being. Dentures play an important role in helping individuals regain a sense of normalcy as well as facilitating communication in today's appearance-conscious society. However, common issues with dentures include discomfort while chewing and dissatisfaction with esthetics and speech. Prosthetic rehabilitation for complete denture patients should aim not just at replacing missing teeth but at fully restoring masticatory functions and appearance. This article outlines a simple, economical, and esthetically pleasing approach to rehabilitating patients with complete dentures, particularly those with resorbed ridges and with difficulty in phonetics. The focus is on comprehensively restoring the patient's orofacial complex.

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Postural assessments of the lumbar spine lack valuable information about its properties. The purpose of this study was to assess neutral zone (NZ) characteristics via in vivo lumbar spine passive stiffness and relate NZ characteristics to standing lumbar lordosis. A comparison was made between those that develop low back pain during prolonged standing (pain developers) and those that do not (nonpain developers). Twenty-two participants with known pain status stood on level ground, and median lumbar lordosis angle was calculated. Participants were then placed in a near-frictionless jig to characterize their passive stiffness curve and location of their NZ. Overall, both pain developers and nonpain developers stood with a lumbar lordosis angle that was more extended than their NZ boundary. Pain developers stood slightly more extended (in comparison to nonpain developers) and had a lower moment corresponding to the location of their extension NZ boundary. Overall, in comparison to nonpain developers, pain developers displayed a lower moment corresponding to the location of their extension NZ boundary which could correspond to greater laxity in the lumbar spine. This may indicate why pain developers have a tendency to stand further beyond their NZ with greater muscle co-contraction.

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Whether the heat and cold tolerance of endotherms evolve independently or correlatively remains unresolved. Both physiological trade-offs and natural selection can contribute to a coevolutionary pattern of heat and cold tolerance in endotherms. Using a published database, we tested the correlation between upper and lower thermal limits across endothermic species with multi-response generalized linear mixed models incorporating phylogenies. We found a positive correlation between upper and lower thermal limits, which suggested a coevolutionary pattern of heat and cold tolerance. Specifically, this relationship between heat and cold tolerance is phylogenetically constrained for tropical endotherms but not for temperate endotherms. The correlated evolution between heat and cold tolerance may have a significant influence on endotherms' evolution and ecology and needs to be further investigated.

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BACKGROUND: Analyse and discuss the immediate stability of the cervical spine after anterior cervical discectomy and fusion using a door-shaped titanium plate and compare it with the traditional titanium plate, to provide biomechanical evidence for the rationality and effectiveness of the door-shaped titanium plate in clinical applications. METHODS: Ten adult goat C4/5 vertebral bodies were obtained, and models were prepared using denture base resin. Biomechanical experiments were performed on the specimens before internal fixation. MTS was used to conduct non-destructive biomechanical loading tests in six directions, including flexion, extension, left-right bending, and left-right torsion, recording the range of motion (ROM) and neutral zone (NZ) of each specimen. The specimens were then randomly divided into two groups: the study group was fixed with a door-shaped titanium plate, and the control group was fixed with a traditional titanium plate. ROM and NZ in each direction were measured again. After measurements, both groups were subjected to 0.5 Hz torsion loading with a torque of 2 N m for a total of 3000 cycles, followed by measuring ROM and NZ in six directions once more. RESULTS: Compared to before fixation, ROM and NZ in both groups significantly decreased in all six directions after fixation, with statistical significance (P < 0.05); after fixation, the study group showed slightly lower values for various mechanical reference parameters compared to the control group, with no statistical significance (P > 0.05); after 3000 torsional loads, both internal fixation groups showed increased ROM and NZ compared to after fixation but to a lower extent, and no screw or titanium plate loosening was observed. Compared to before fixation, the differences were still statistically significant (P < 0.05), with the study group having slightly lower ROM and NZ values in all directions compared to the control group, with no statistical significance (P > 0.05). CONCLUSION: The door-shaped titanium plate exhibits mechanical properties similar to the traditional titanium plate in all directions, and its smaller size and simpler surgical operation can be used for anterior cervical endoscopic surgery, reducing surgical trauma. It is clinically feasible and deserves further research and promotion.

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In vivo lumbar passive stiffness is often used to assess time-dependent changes in lumbar tissues and to define the neutral zone. We tested the hypothesis that flexing the hips would alter tension in hip and spine musculature, leading to a more extended passive stiffness curve (i.e., right-shifted), without changes in lumbar stiffness. Twenty participants underwent side-lying passive testing with the lower limbs positioned in Stand, Kneel, and Sit representative postures. Moment-angle curves were constructed from the lumbar angles and the moment at L4/5 and partitioned into three zones. Partially supporting our hypothesis, lumbar stiffness within the low and transition stiffness zones was similar between the Stand and Sit. Contrary to our hypothesis, lumbar angles were significantly larger in the Sit compared to the Stand and Kneel postures at the first and second breakpoints, with average differences of 9.3° or 27.2% of passive range of motion (%PassRoM) in flexion and 5.6° or 16.6 %PassRoM in extension. Increased flexion in the Sit may be linked to increased posterior pelvic tilt and associated lower lumbar vertebrae flexion. Investigators must ensure consistent pelvis and hip positioning when measuring lumbar stiffness. Additionally, the adaptability of the neutral zone to pelvis posture, particularly between standing and sitting, should be considered in ergonomic applications.

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Body temperature regulation under changes in ambient temperature involves adjustments in heat production and heat exchange rates between the animal and the environment. One mechanism involves the modulation of the surface temperature of specific areas of the body through vasomotor adjustment. In homeotherms, this thermoregulatory adjustment is essential for the maintenance of body temperature over a moderate temperature range, known as the thermal neutral zone (TNZ). The bill of the toco toucan (Ramphastos toco) has been described as a highly efficient thermal window and hypothesized to assist in the thermal homeostasis of this bird. Herein, we directly evaluated the contribution of heat exchange through the bill of the toco toucan and role of the bill in the delimitation of the TNZ. To do this, we measured metabolic rate (MR), via oxygen consumption, over a range of ambient temperatures from 0 to 35°C. MR measurements were made in birds with the bill intact and with the bill insulated. The limits of the TNZ did not differ between treatments, ranging from 10.8 to 25.0°C. The MR differed among treatments only at elevated temperatures (30 and 35°C), reaching 0.92±0.11 ml O2 g-1 h-1 (mean±s.d.) for the intact group and 1.13±0.13 ml O2 g-1 h-1 for the insulated group. These results indicate that although heat dissipation through the bill does not contribute significantly to widening of the TNZ, it may well be critically important in assisting body temperature regulation at higher temperatures extending above the upper limit of the TNZ.

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Purpose: Management of Anderson and D'Alonzo type II odontoid fractures continues to be controversial despite extensive research and increasing prevalence. To the authors' knowledge, the three odontoid ligaments, the alar ligament, the vertical portion of the cruciate ligament, and the transverse ligament, have not been biomechanically examined in type II odontoid fracture in spite of their potential significance in management. Therefore, this study aims to explore the intersegmental rotations of the craniovertebral junction following Anderson and D'Alonzo type II odontoid fracture and various combinations of ligament ruptures. Methods: A validated C0-C7 cervical spine finite element model was employed to address the research objectives. The model was subjected to flexion-extension, lateral bending, and axial rotation under eight distinct injury conditions apart from the intact state. Prescribed rotations were applied to the top of the cranium while the C7 inferior surface was fixed. Rotation-moment data were retrieved from the model. Results: Type II odontoid fracture caused mixed forms of instability considering flexion-extension. In lateral bending, the fracture alone did not have a significant effect, whereas the disruption of ligaments led to moderate rotation increments. Notably, in axial rotation, the fracture was the most crucial factor for stability. Conclusions: Overall, type II odontoid fracture was found to be the main destabilizing element. Nonetheless, the vertical cruciate and the transverse ligament played a modest role in stabilization. The alar ligament provided minimal or no stability. Furthermore, instances were observed where both the vertical cruciate and the transverse ligament were necessary to prevent more instability.

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Disfigurement of the face has a significant impact not only on the appearance and function but also on the psychological well-being of an individual. Due to tooth loss, various psychological problems can occur. Dentures can help patients regain a sense of normalcy and also boost their confidence to live in society. Complete denture restores phonetics, esthetics, and mastication. A 63-year-old male patient reported to the Department of Prosthodontics with the chief complaint of total loss of teeth and wanted to get treated for the same. The purpose of this article is to describe changes in impression techniques, dental material, methodologies in teeth setting, and novel approaches to enhance the esthetics to optimize the results in a final complete denture. To reestablish the patient's masticatory, apparatus steps of complete denture fabrication were revisited accompanied by the modern application of innovative techniques with the base of historical concept.

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The vast majority of previous experimental studies on the thoracic spine were performed without the entire rib cage, while significant contributive aspects regarding stability and motion behavior were shown in several other studies. The aim of this literature review was to pool and increase evidence on the effect of the rib cage on human thoracic spinal biomechanical characteristics by collating and interrelating previous experimental findings in order to support interpretations of in vitro and in silico studies disregarding the rib cage to create comparability and reproducibility for all studies including the rib cage and provide combined comparative data for future biomechanical studies on the thoracic spine. After a systematic literature search corresponding to PRISMA guidelines, eleven studies were included and quantitatively evaluated in this review. The combined data exhibited that the rib cage increases the thoracic spinal stability in all motion planes, primarily in axial rotation and predominantly in the upper thorax half, reducing thoracic spinal range of motion, neutral zone, and intradiscal pressure, while increasing thoracic spinal neutral and elastic zone stiffness, compression resistance, and, in a neutral position, the intradiscal pressure. In particular, the costosternal connection was found to be the primary stabilizer and an essential determinant for the kinematics of the overall thoracic spine, while the costotransverse and costovertebral joints predominantly reinforce the stability of the single thoracic spinal segments but do not alter thoracic spinal kinematics. Neutral zone and neutral zone stiffness were more affected by rib cage removal than the range of motion and elastic zone stiffness, thus also representing the essential parameters for destabilization of the thoracic spine. As a result, the rib cage and thoracic spine form a biomechanical entity that should not be separated. Therefore, usage of entire human non-degenerated thoracic spine and rib cage specimens together with pure moment application and sagittal curvature determination is recommended for future in vitro testing in order to ensure comparability, reproducibility, and quasi-physiological validity.

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BACKGROUND CONTEXT: Intervertebral disc degeneration represents one of multiple potential trigger factors for reduced passive spinal mobility and back pain. The effects of age-related degenerative intervertebral disc changes on spinal flexibility were however mainly investigated for the lumbar spine in the past, while intervertebral disc degeneration is also highly prevalent in the thoracic spine. PURPOSE: To evaluate the effect of the degeneration grade on the range of motion and neutral zone of the thoracic spine. STUDY DESIGN: Experimental study including combined radiological grading of intervertebral disc degeneration and biomechanical testing of 95 human thoracic functional spinal units (min. n=4 per level from T1-T2 to T11-T12) from 33 donors (15 female / 18 male, mean age 56 years, age range 37-80 years). METHODS: Degeneration grades of the intervertebral discs were assessed using the validated x-ray grading scheme of Liebsch et al. (0=no, 1=mild, 2=moderate, 3=severe degeneration). Motion segments were loaded with pure moments in flexion/extension, lateral bending, and axial rotation to determine range of motion and neutral zone at 5 Nm. RESULTS: All tested specimens exhibited degeneration grades between zero and two. Range of motion significantly decreased for grades one and two compared with grade zero in any motion direction (p<.05), showing the strongest decrease in extension comparing grade two with grade zero (-42%), while no significant differences were detected between grades one and two. Similar trends were found for the neutral zone with the strongest decrease in extension also comparing grade two with grade zero (-47%). Donor age did not significantly affect the range of motion, whereas the range of motion was significantly reduced in specimens from male donors due to the significantly higher degeneration grade in this study. CONCLUSIONS: Even mild intervertebral disc degeneration reduces the range of motion and neutral zone of the thoracic spine in any motion plane, whereas progressing degeneration does not further affect its flexibility. This is in contrast to the lumbar spine, where a more gradual decrease of flexibility was found in prior studies, which might be explained by differences between thoracic and lumbar intervertebral disc morphologies. CLINICAL SIGNIFICANCE: Thoracic intervertebral disc degeneration should be considered as one of multiple potential causal factors in patients showing reduced passive mobility and middle back pain.

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BACKGROUND: Today, the use of virtual reality (VR) technology as an educational tool in dental education has expanded considerably. This study was aimed to evaluate the effectiveness of using VR technology in teaching neutral zone and teeth arrangement. METHODS: This randomized trial was conducted at Kermanshah University of Medical Sciences, Iran in 2019. The study sample consisted of 50 six-year dental students who were randomly divided into experimental (n = 25) and control (n = 25) groups. Students' performance in both groups was assessed using tests. A questionnaire was used to assess the usability of VR technology and students' satisfaction with it. RESULTS: All faculty members confirmed the usability of VR technology in dental education. The majority of students (76%) were highly satisfied with the use of this technology in their learning process. The mean score of students was significantly higher in the experimental group (16.92 ± 1.12) than in the control group (16.14 ± 1.18). CONCLUSION: In general, it can be argued that VR technology is useful and effective in the teaching-learning process. Therefore, its use in medical and dental schools can play an effective role in creating a dynamic, attractive, and successful learning environment.

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Lack of adequate retention, support, and stability in the complete denture can be attributed to a poor fit or incorrect shape of the polished surfaces. This article presents a case using the neutral zone technique effectively with the fabrication of computer-aided design and computer-aided manufacturing (CAD-CAM) record bases in an edentulous patient with severely resorbed alveolar ridges and discusses the overall treatment steps and clinical implications of this technique. A stable neutral zone and an accurate jaw relation were recorded using CAD-CAM record bases and stability of complete denture was optimized by arranging denture teeth and reforming polishing surfaces in the neutral zone. A new complete denture was fabricated for a patient with atrophic alveolar ridges by a technique utilizing the neutral zone with CAD-CAM record bases.

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PURPOSE: To present a clinical rationale for the effectiveness of denture space recording methods for the prosthetic treatment of edentulous patients through a review of the literature. STUDY SELECTION: A total of 3167 studies were extracted from a search of four terms, namely denture space, neutral zone technique, flange technique, and piezography using PubMed and J-STAGE databases. A total of 57 documents that matched the inclusion and exclusion criteria were selected. RESULTS: From the extracted articles, the clinical application of denture space recording methods was found to be effective in edentulous patients with severe ridge resorption. The relationship between the labiolingual and buccolingual pressure in patients with neuromuscular problems or with mandibular or lingual defects differs from those without it, so a stable prosthesis can be easily fabricated by locating the neutral zone using denture space recording methods. CONCLUSION: The literature on denture space recording methods suggests that its application on challenging cases of edentulous patients is useful in providing prostheses with improved retention and stability.

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Neutral zone (NZ) is an important biomechanical parameter when evaluating spinal instability following destabilizing and restabilizing events, with particular relevance for implant efficacy testing. It remains unclear what NZ calculation methods are most sensitive at capturing NZ changes across treatment conditions and a direct comparison is needed. The purpose of this study was to determine the most sensitive method at quantifying instability in human spines. Six cadaveric lumbar motion segments were subjected to a repeated measures implant testing schema of four sequential conditions: (1) Intact, (2) injury by herniation, (3) device implantation, (4) long-term cyclic fatigue loading. NZ was expected to increase after destabilization (steps 2 & 4) and decrease after restabilization (step 3). NZ methods compared in this study were: trilinear (TL), double sigmoid (DS), zero load (ZL), stiffness threshold (ST), and extrapolated elastic zone (EEZ). TL, ZL, and EEZ identified statistically significant NZ differences after each condition in flexion/extension and lateral bending. The ZL method also captured differences in axial rotation. All methods identified expected NZ changes after destabilization and restabilization, except DS in axial rotation. The TL, ZL, and EEZ methods were the most sensitive methods with this human cadaveric dataset. Future investigations comparing methods with additional datasets will clarify outcome generalizability and determine what curve profiles are most suitable for DS and ST methods. Understanding the applicability of NZ methods can enhance rigor and reliability of spinal instability measurements when quantifying the efficacy of novel implants and permits insight into clinically relevant biomechanical changes.

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To date, no in vitro studies have been conducted to explore lumbar soft tissue injury potential and altered mechanical properties from exposure to impact forces. After a motor vehicle collision (MVC), the cause of reported acute onset low back pain is difficult to associate with potential soft tissue strain injury sites including the facet joint and innervated facet joint capsule ligament (FJC). Thus, the purpose of this investigation was to quantify intervertebral anterior-posterior (AP) translation and facet joint capsule strain under varying postures and impact severities. Seventy-two porcine spinal units were exposed to three levels of impact severity (4 g, 8 g, 11 g), and posture (Neutral, Flexion, Extension). Impacts were applied using a custom-built impact track that replicated parameters experienced in low to moderate speed rear-end MVCs. Flexion-extension and anterior-posterior shear neutral zone testing were completed prior to impact. AP intervertebral translation and the strain tensor of the facet capsule ligament were measured during impacts. A significant main effect of collision severity was observed for peak AP intervertebral translation (4 g-2.8 ±0.53 mm; 8 g-6.4 ±2.9 mm; 11 g-8.3 ±0.45 mm) and peak FJC shear strain (2.37% strain change from 4 g to 11 g impact severity). Despite observed main effects of impact severity, no influence of posture was observed. This lack of influence of posture and small FJC strain magnitudes suggest that the FJC does not appear to undergo injurious or permanent mechanical changes in response to low-to-moderate MVC impact scenarios.

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