IU Indianapolis ScholarWorks :: Browsing by Subject "Occlusion"

Browsing by Subject "Occlusion"

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Clinical non-effectiveness of clopidogrel use for peripheral artery disease in patients with CYP2C19 polymorphisms: A systematic review
(Springer, 2022) Huang, Shu; Yang, Seonkyeong; Ly, Shirly; Yoo, Ryan H.; Lo-Ciganic, Wei-Hsuan; Eadon, Michael T.; Schleyer, Titus; Whipple, Elizabeth; Nguyen, Khoa Anh; Medicine, School of Medicine
Purpose: To conduct a systematic review to identify studies that assessed the association between CYP2C19 polymorphisms and clinical outcomes in peripheral artery disease (PAD) patients who took clopidogrel. Methods: We systematically searched Ovid EMBASE, PubMed, and Web of Science from November 1997 (inception) to September 2020. We included observational studies evaluating how CYP2C19 polymorphism is associated with clopidogrel's effectiveness and safety among patients with PAD. We extracted relevant information details from eligible studies (e.g., study type, patient population, study outcomes). We used the Risk of Bias in Non-randomized Studies-of Interventions (ROBINS-I) Tool to assess the risk of bias for included observational studies. Results: The outcomes of interest were the effectiveness and safety of clopidogrel. The effectiveness outcomes included clinical ineffectiveness (e.g., restenosis). The safety outcomes included bleeding and death related to the use of clopidogrel. We identified four observational studies with a sample size ranging from 50 to 278. Outcomes and comparison groups of the studies varied. Three studies (75%) had an overall low risk of bias. All included studies demonstrated that carrying CYP2C19 loss of function (LOF) alleles was significantly associated with reduced clinical effectiveness and safety of clopidogrel. Conclusions: Our systematic review showed an association between CYP2C19 LOF alleles and reduced functions of clopidogrel. The use of CYP2C19 testing in PAD patients prescribed clopidogrel may help improve the clinical outcomes. However, based on the limited evidence, there is a need for randomized clinical trials in PAD patients to test both the effectiveness and safety outcomes of clopidogrel.
A critical evaluation of the T-Scan digital occlusion analysis system
(2023-07-12) Bawa, Devaansh; Katona, Thomas R.
Background: Universally used clinical armamentaria such as articulating paper, film, and silk, introduce an inter-dental material, thus leading to artefactual occlusal contact force measurements. Although the state-of-the-art high-tech T-Scan Novus similarly engages the dentition, the company promotes claims asserting T-Scan’s ability to provide reliable measurements of contact forces and their timing. Aims: A purpose of this study was to evaluate T-Scan’s capability to measure occlusal contact forces and their timing. Another purpose was to examine T-Scan’s data processing algorithm. Methods: The forces experienced by contacting crown-crown (control) and crown-sensor-crown (T-Scan) configurations with denture teeth were measured by a load cell. For statistical purposes, 21 occlusal relationships, in 0.05 mm incremental shifts of the lower member, were tested. The load cell-measured in-occlusal plane components (Fx and Fy) of the occlusal contact forces, for control and T-Scan, were isolated from the 5th chomp (of 7) during occlusion and disclusion when the bite force (Fz) was 15 N and 25 N. These Fx and Fy were used to calculate Flateral, the magnitude of the in-occlusal plane component of the occlusal contact force, Flateral. The effects on Flateral of bite force, occlusion/disclusion, and group (test/control) were analyzed using three-way repeated measures ANOVA. Results: The crown-crown Flateral forces are significantly (p<.001) larger than those of crown-sensor-crown. The presence of the sensor also alters the direction of Flateral. Additionally, the duration of a T-Scan chomp was about ½ seconds longer than control. Examination of the numerical algorithm reveals violations of basic engineering mechanics principles. Conclusion: The T-Scan system relies on engineering mechanics (statics) calculations that use artefactual occlusal contact force magnitude measurements, approximated artefactual contact point location measurements, and assumed occlusal contact force directions. As magnitude, location and direction comprise the essential defining parameters of a force vector, just one of the 3 deficiencies, by itself, is sufficient evidence to declare the impossibility of meaningful T-Scan analyses.
Critical flaws in the T-Scan digital occlusion analysis system
(2022-09-08) Katona, Thomas R.
Abstract The T-Scan digital occlusion analysis system has previously been criticized for its use of artefactual measurements. Far more than the traditional clinical occlusion detecting armamentaria (paper, film and silk), its crown-sensor-crown configured force measurements misrepresent the actual crown-crown contact forces. Yet another defect, thus far unaddressed, is the misapplication of basic Newtonian static equilibrium principles, presumably the basis of their (proprietary) numerical algorithm. The approach requires the complete characterization (magnitudes, directions and points of application (or the lines-of-action)) of the occlusal contact force vectors. Instead, because of inherent sensor limitations, their elaborate mechanics calculations rely on artefactual force magnitudes, assumed directions, and estimated contact locations. Thus, the seemingly impressive T-Scan analyses are, essentially, groundless.
The effects of antagonist size and shape on occlusal contact forces
(2022-08-26) Falasz, Adam G.; Katona, Thomas R.
Background: Occlusion is a biomechanical phenomenon wherein teeth experience loads (forces and moments) in three dimensions. These load profiles are complex and are often simplified in laboratory experiments and numerical models with the use of, for example, a spherical antagonist. Objective: The purpose of this study was to examine the effects of antagonist shape (denture tooth vs. steel spherical balls) and sphere size (2.9 vs. 5.9 mm diameter) on occlusal contact forces in paired 1st molar/1st molar and 1st molar/sphere systems. Methods: The occlusal forces experienced by in-vitro occluding two-element (tooth/tooth and tooth/spherical indenter) systems were measured. The occlusal relationship was altered by 0.05 mm incremental shifts of the lower member into 21 positions. Results: The data indicate that the peak magnitudes and/or directions of the in-occlusal plane force components acting on the tooth were significantly different (p values from <0.001 to 0.03) with the 3 loading protocols. Conclusion: Spherical indenters cannot replicate the mechanical environment produced by natural molar crowns. Thus, spheres should not be used in studies related to the loading of the tooth support structures (periodontal ligament, root and bone), and implant bodies and attachments.
An engineering model of the Stuart pantograph
(1993-12) Katona, Thomas R.; Garetto, Lawrence P.; Drum, Raymond K.
Mechanisms of Biliary Plastic Stent Occlusion and Efforts at Prevention
(The Korean Society of Gastrointestinal Endoscopy, 2016-03) Kwon, Chang-Il; Lehman, Glen A.; Department of Medicine, IU School of Medicine
Biliary stenting via endoscopic retrograde cholangiopancreatography has greatly improved the quality of patient care over the last 30 years. Plastic stent occlusion limits the life span of such stents. Attempts to improve plastic stent patency duration have mostly failed. Metal stents (self-expandable metal stents [SEMSs]) have therefore replaced plastic stents, especially for malignant biliary strictures. SEMS are at least 10 times more expensive than plastic stents. In this focused review, we will discuss basic mechanisms of plastic stent occlusion, along with a systematic summary of previous efforts and related studies to improve stent patency and potential new techniques to overcome existing limitations.
Predicting future occlusion or stenosis of lower extremity bypass grafts using artificial intelligence to simultaneously analyze all flow velocities collected in current and previous ultrasound examinations
(Elsevier, 2024-02-05) Luo, Xiao; Tahabi, Fattah Muhammad; Rollins, Dave M.; Sawchuk, Alan P.; Biostatistics and Health Data Science, Richard M. Fairbanks School of Public Health
Objective: Routine surveillance with duplex ultrasound (DUS) examination is recommended after femoral-popliteal and femoral-tibial-pedal vein bypass grafts with various intervals postoperatively. The presently used methodology to analyze bypass graft DUS examination does not use all the available data and has been shown to have a significant rate for missing impending bypass graft failure. The objective of this research is to investigate recurrent neural networks (RNNs) to predict future bypass graft occlusion or stenosis. Methods: This study includes DUS examinations of 663 patients who had bypass graft operations done between January 2009 and June 2022. Only examinations without missing values were included. We developed two RNNs (a bidirectional long short-term memory unit and a bidirectional gated recurrent unit) to predict bypass graft occlusion and stenosis based on peak systolic velocities collected in the 2 to 5 previous DUS examinations. We excluded the examinations with missing values and split our data into training and test sets. Then, we applied 10-fold cross-validation on training to optimize the hyperparameters and compared models using the test data. Results: The bidirectional long short-term memory unit model can gain an overall sensitivity of 0.939, specificity of 0.963, and area under the curve of 0.950 on the prediction of bypass graft occlusion, and an overall sensitivity of 0.915, specificity of 0.909, and area under the curve of 0.912 predicting the development of a future critical stenosis. The results on different bypass types show that the system performs differently on different types. The results on subcohorts based on gender, smoking status, and comorbidities show that the performance on current smokers is lower than the never smoker. Conclusions: We found that RNNs can gain good sensitivity, specificity, and accuracy for the detection of impending bypass graft occlusion or the future development of a critical bypass graft stenosis using all the available peak systolic velocity data in the present and previous bypass graft DUS examinations. Integrating clinical data, including demographics, social determinants, medication, and other risk factors, together with the DUS examination may result in further improvements. Clinical relevance: Detecting bypass graft failure before it occurs is important clinically to prevent amputations, salvage limbs, and save lives. Current methods evaluating screening duplex ultrasound examinations have a significant failure rate for detecting a bypass graft at risk for failure. Artificial intelligence using recurrent neural networks has the potential to improve the detection of at-risk bypass graft before they fail. Additionally, artificial intelligence is in the news and is being applied to many fields. Vascular surgeons need to know its potential to improve vascular outcomes.
A proposed mechanism for non-carious cervical lesions, root resorption and abutment screw loosening
(2022-01-13) Katona, Thomas R.; Eckert, George J.
Objectives The purpose of this paper is to present a mechanism for the shared etiologies of non-carious cervical lesions (NCCLs), orthodontics-associated root resorption and implant abutment screw loosening. These are persistent clinical problems with equivocal etiologies. Methods A matched pair of 1st molar denture teeth was set into occlusion within a testing apparatus. The weighted maxillary assembly, guided by slides, was cyclically lowered onto, and raised from, the mandibular tooth. The forces and moments on the mandibular tooth were continuously recorded by a load cell. The maxillary crown was rigidly fixed (ankylosed or implant supported). The mandibular tooth was rigidly fixed or supported by a PDL analogue. For statistics, 21 occlusal relationships were tested. Results The measurements confirmed earlier non- and counter-intuitive results. The directly relevant data were that the measured loads on the tooth, during the span of an individual chomp, are characterized by a wide range of magnitudes and directions. Moreover, these load profiles change with rigid vs. PDL support (p = 0.001), occlusal relationship (p < 0.001) and occlusion vs. disclusion (p = 0.002). Conclusion The demonstrated transient loads within the span of a single chomp produce complex mechanical environments. Thus, it is proposed that NCCLs, orthodontic root resorption and abutment screw loosening result from load component combinations, not from solitary occlusion forces as typically applied in experimental and numerical investigations. In principle, the loading combination concept applies to all phenomena that involve occlusal contacts, including occlusal trauma, implant loading, jaw fracture repairs, etc.
Responses to letter to the editor: "Does the presence of an occlusal indicator product affect the contact forces between full dentitions?"
(John Wiley & Sons, 2018-06) Mitchem, Jesse A.; Katona, Thomas R.; Moser, Elizabeth A. S.
The significance of loading profile on the occlusion mechanics of a viscoelastic periodontal ligament analogue-supported tooth
(2020-06) Thompson, James P.; Katona, Thomas R.; Eckert, George J.
Background: Benchtop studies of occlusal contact forces have used teeth that were rigidly attached or supported by readily available viscoelastic (VE) materials that served as periodontal ligament (PDL) substitutes. More recent specimens have incorporated a precisely dimensioned VE PDL-behavior matched analogue. Objectives: The objectives of this study were to evaluate a modified loading protocol (step function) that is more appropriate to VE support than the previously used ramp function. The occlusion manifestations of the time-dependent behaviors (creep and recovery) of the PDL analogue were examined using the revised protocol. Methods: A mandibular 1st molar denture tooth was set into a precision-machined root/socket assembly. The PDL substitute was then cured to tight dimensional tolerances. The matching rigidly fixed maxillary denture tooth was aligned into a Class I centric molar relationship in a testing apparatus. The weighted maxillary assembly was then cycled onto and off of the load cell-supported mandibular assembly. For statistical purposes, three loading schedules were tested in 21 0.05 mm shifted occlusal relationships. Rigid attachment served as control. Results: Statistical analyses were performed on the peak values of Flateral, the net in-occlusal plane force component of the occlusal contact forces. It was found that there were statistically significant differences between: chomp-to-chomp (p < .038), PDL vs. rigid (p < .001) and loading schedules (p < .044 for PDL only). Conclusion: The loading protocol affects outcomes, and the step functions maintained consistent timing with prescribable creep and recovery periods.

Browsing by Subject "Occlusion"

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