Evaluation and comparison of three-dimensional finite element analysis of stress distribution in immediately placed and loaded conventional and customized three-dimensional printed dental implants.

Aim: The aim of this study was to evaluate and compare the stress distribution patterns in immediately placed and loaded conventional and customized three-dimensional (3D) printed dental implants by 3D finite element analysis. Materials and Methods: Twelve 3D finite element models [Group A-3 models; Group B-9 models] with 72 test conditions which were modeled and compared from customized 3D printed dental implants [Group A] and 3 commercially available implant systems [Group B] (Straumann, Ankylos, and Astratech) using "SolidWorks". All models were embedded in extraction socket models of the maxillary central incisor (CI) and Canine (C), Mandibular 1st Premolar. An occlusal loading by axial and nonaxial force of 100 N and 150 N at 30° and 45° was applied on the abutment using the "ANSYS" Suite. Customized 3D printed dental implant (Group A) for maxilla (Max.) CI, Max. C, and mandibular 1st premolar (PM) socket model was compared with three commercial available dental implant systems (Group B) for Max. CI, Max. C, and mandible (Mand.) 1st PM socket model to understand the stress distribution patterns. Results: With increasing oblique loads, von Mises stresses were reduced for the customized group as compared to conventional implants. Increased axial loads caused proportionate increase in the stresses for both groups, yet remained under the physiologic limits in all test conditions. Higher stresses were observed in cortical bone than in cancellous bone at bone-implant contact in general. Marked reduction in von Mises stress was observed at the boundary between compact and cancellous bone. Customized 3D printed implants performed better for oblique loads and comparable for axial load stress distribution in comparison to conventional implant systems in Max. CI and C, Mand. 1st PM. Conclusion: Thus, customized 3D printed implants appear a promising alternative for immediately placed immediately loaded protocols, with additional benefits in specific clinical situations.

Three dimensional changes of maxillary arch in Unilateral cleft lip and palate patients following comprehensive orthodontic treatment on digital study models.

OBJECTIVE: To compare the effects of comprehensive orthodontic treatment on palatal area, volume, inter-canine and inter-molar width in patients with Unilateral Cleft Lip and Palate (UCLP) using scanned models of the maxillary arch. DESIGN: Retrospective cohort study. SETTING: Tertiary setting. PATIENTS: Two hundred and ten plaster study models of 70 patients with Unilateral Cleft Lip and Palate (Study group SG) and Control Group (n = 70) were scanned using Maestro 3D Dental scanner. The study groupwas further divided into subgroups; Subgroup I: treated with orthodontic treatment only (non-surgical), Subgroup II: patientsmanaged with combined orthodontics and orthognathic surgery (either maxillary advancement or maxillary distraction), Subgroup A: age >14 years and Subgroup B: age <14 years. INTERVENTIONS: Comprehensive orthodontic and Orthosurgical treatment. MAIN OUTCOME MEASURES: Pre- and post-treatment scanned maxillary models of the study group were compared for palatal area and volumeand intercanine and intermolar width. The palatal dimensions of post-treatment scanned models were also compared to that of the control group. RESULTS: The Palatal area and volume, intercanine and intermolar width were significantly higher in the post-treatment as compared to pre-treatment study models (P < 0.01). The measurements ofthe maxillary arch were significantly higher in the control group compared to the post-treatment measurements of the study group. The increase in palatal area and volume was greater in Subgroup I and A compared to Subgroup II and B patients, respectively. CONCLUSION: The 3-Dimensional palatal dimensions in UCLP group improved after orthodontic treatment but were still not comparable to the normal subjects. The patients with age >14 years showed more improvement in the maxillary arch.

Ergonomics evaluation of lawn mower operator's working posture using JACK software and kinect interface.

BACKGROUND: Nowadays, real-time motion tracking devices are widely used for ergonomic assessment of several manual quotidian activities. The real-time tracking of human activities makes it easier to observe the exposure of work-related musculoskeletal disorders (WMSDs) in the human body. OBJECTIVE: This study aims to determine the suitability of a real-time motion tracking device (Kinect v1 interfaced with a commercial ergonomic assessment software, JACK) for real-time ergonomic evaluation of the strenuous operation of the manual lawn mower. METHOD: The lawn mower operators perform various strenuous activities while operating the manual lawn mower for long intervals of time, which causes WMSDs in the entire body of the operators. These working operators' activities have been captured using Kinect v1 interfaced with JACK, to address the ergonomic issues responsible for the whole-body WMSDs. The forces acting on the lower back, Rapid Upper Limb Assessment score and static strength have been predicted using JACK. RESULTS: This study proves the exposure of the operators towards the whole-body WMSDs while operating the manual lawn mower. CONCLUSION: The findings provide a quick and straightforward approach for performing the real-time ergonomic evaluation of any operation, which can help the industrial staff estimate the risk of level WMSDs.

Finite element study on the influence of pore size and structure on stress shielding effect of additive manufactured spinal cage.

The stress shielding effect occurs when the orthopedic implant reduces the load delivered to the bone, causing inefficient stress transfer to the host bone. The usage of porous additive manufactured (AM) cages reduces the stress shielding effect and promotes bone ingrowth also. The purpose of this work is to study the stress and deformation on porous hybrid spinal cages under different loading conditions using Finite Element Analysis (FEA). The spinal cages consisting of three porous structures with pore sizes ranging from 0.4 to 0.6 mm were investigated for stress shielding and fatigue strength. The results showed a significant reduction in stress shielding for the studied designs and conclude that the pore size has a greater significant effect on stress shielding than the porous structure in spinal cages.

Changes in condylar position after orthognathic surgery and its correlation with temporomandibular symptoms (TMD)- a prospective study.

The aim of the study was to assess the changes in the condylar position after orthognathic surgery (OGS) and its effect on temporomandibular disorders (TMD). A total of 37 dentofacial deformity patients included in the study who had undergone OGS were divided into three groups: Group I, Le Fort I maxillary advancement; Group II, bilateral sagittal split osteotomy (BSSO) mandibular advancement ± Le Fort I; and Group III, BSSO mandibular setback ± Le Fort I. Patients were evaluated clinically using Diagnostic Criteria for TMD and by radiography preoperatively and 6 months postoperatively. The positional changes in condyle were correlated with signs and symptoms of TMD. A total of 37 patients in three groups (Group I, 8 patients; Group II, 10 patients; and Group III, 19 patients) were evaluated. Overall, condyles had anterio-medio-inferior movement with 7 of 8 patients in Group I, 6 of 10 patients in Group II and 13 of 19 patients in Group III having ≤2 mm displacement. In angular changes, inward-anterio-medial movement was observed with 6 of 8 patients in Group I; about 5 of 10 patients, and 10 of 19 patients in Group II and III respectively had ≤5° change. Intragroup and intergroup comparisons showed insignificant changes in TMD and linear/angular movement (p ≥ 0.05). Pearson correlation coefficient was found to be nonsignificant on the radiographic and clinical comparison (p ≥ 0.05). Intrarater reliability (Kappa value) was found to be 0.83, confirming the results. Within the limitations of the study it seems that there are minimal linear and angular changes in condyle after orthognathic surgery that were not responsible for the development of temporomandibular disorders in the postoperative course.

Vibration Exposure and Transmissibility on Dentist's Anatomy: A Study of Micro Motors and Air-Turbines.

The use of dental hand pieces endanger dentists to vibration exposure as they are subjected to very high amplitude and vibration frequency. This paper has envisaged a comparative analysis of vibration amplitudes and transmissibility during idling and drilling with micro motor (MM) and air-turbine (AT) hand pieces. The study aims to identify the mean difference in vibration amplitudes during idling, explore different grasp forces while drilling with irrigant injection by the dentist, and various vibration transmission of these hand pieces. The study utilized 22 separate frequency resonances on two new and eight used MMs and two new and eight used ATs of different brands by observing the investigator at 16 different dentist clinics. The study adopted a descriptive research design with non-probability sampling techniques for selecting dentists and hand pieces. Statistical methods like Levene Test of Homogeneity, Welch ANOVA, independent t-test, and Games-Howell test were utilized with SPSS version 22 and MS-Excel. The results reveal that vibration amplitudes and vibration transmissibility when measured at position 2 are higher than in another position 1. Vibrations during idling for used MMs are more than AT hand pieces, and the used MM (MUD) and used AT (AUA) hand pieces differ due to their obsolescence and over-usage. Vibration amplitudes increase every time with the tightening of grasping of the hand piece. Vibration amplitudes for each grasping style of MM hand piece differ from all other grasping styles of AT hand pieces. Routine exposure to consistent vibrations has ill physical, mental, and psychological effects on dentists. The used hand pieces more hazardous as compared to newer ones. The study suggests that these hand pieces must be replaced periodically, sufficient to break between two operations, especially after every hand piece usage. Hence, the present research work can be further extended by creating some control groups among dentists and then studying the vibration amplitude exposure of various dental hand pieces and subsequent transmissibility to their body parts.

Variations in Electrocortical Activity due to Surgical Incision in Anaesthetized Cardiac Patients: Electroencephalogram-Based Quantitative Analysis.

This study examines the alterations in scalp recorded cortical activity due to surgical incision in anaesthetized cardiac patients using electroencephalogram (EEG) patterns. The primary aim was to compare the changes in electrocortical activity after surgical incision. The secondary aim was to compare the changes in time, frequency, and wavelet domain parameters after loss of consciousness (LoC) and after intubation. Real-time EEG data were recorded from 19 patients undergoing cardiac surgery and signals were quantified with time, frequency, and wavelet domain parameters. An increase in hjorth activity, hjorth complexity, rms value, total band power, relative delta band power, standard deviation and maxima of approximation coefficients (a 5), minima of detail coefficients (d 5, d 4, and d 3) and decrease in hjorth mobility; approximate entropy; relative theta, alpha, and beta band power; specentropy; median, spectral edge, and mean frequency; mean of detail coefficients (d 4); standard deviation of detail coefficients (d 5, d 4, and d 3); maxima of detail coefficients (d 5); and minima of approximation coefficients (a 5) were observed during LoC. Decrease in hjorth activity; hjorth mobility; rms value; total band power; relative theta band power; median frequency; standard deviation of coefficients (a 5, d 5, d 4, and d 3); and maxima of coefficients (a 5, d 5, d 4, and d 3) and increase in hjorth complexity; mean of detail coefficients (d 5); and minima of coefficients (a 5, d 5, d 4, and d 3) were observed after intubation. Significant decrease in hjorth activity; hjorth mobility; total band power; relative alpha band power; specentropy; median and mean frequency; standard deviation and maxima of detail coefficients (d 5, d 4, and d 3) and increase in rms value; relative delta band power; mean of coefficients (a 5 and d 5); and minima of coefficients (d 5, d 4, and d 3) were observed due to surgical incision. It can be concluded that different spectral and temporal parameters of EEG signals are highly sensitive to induction, intubation, and surgical incision which are potentially informative for measuring the depth of anaesthesia or efficacy of anaesthetic agents.

Proposed solution for dorsal internal carotid artery aneurysms: Suggestion of a novel new clip design.

Dorsal internal carotid artery (ICA) aneurysms are notorious for their high morbidity and mortality. They have an extremely fragile wall and have a high chance of rupture and clip slippage during the intraoperative and postoperative period. Strategies proposed to mitigate these problems encompass including part of the normal ICA wall in addition to neck of aneurysm in clip blades, as well as the use of encircling materials (silicon, cellulose, Weck's clip) over a clip. The Achilles' heel of the problem is to take an appropriate thickness of the normal ICA in clip blades. Too less or too much of this can spell disaster. This is easier said than done during an actual surgical procedure. So, in this difficult situation, is there any better method of clipping? We propose a fenestrated clip in which the clip blades are placed just at the beginning of fenestration and at right angles to the clip. This occludes the aneurysm taking part of the normal ICA wall in the clip blades. The fenestration hugs the ICA and prevents clip slippage. This has been explained with appropriate figures in the two and three-dimensional format. There cannot be a single stop solution for a complex disease like dorsal ICA aneurysm. The present proposed design is an attempt to provide a better clipping chance in these difficult aneurysms. Future work on this design can prove its usefulness.

"Soft that molds the hard:" Geometric morphometry of lateral atlantoaxial joints focusing on the role of cartilage in changing the contour of bony articular surfaces.

PURPOSE: The existing literature on lateral atlantoaxial joints is predominantly on bony facets and is unable to explain various C1-2 motions observed. Geometric morphometry of facets would help us in understanding the role of cartilages in C1-2 biomechanics/kinematics. OBJECTIVE: Anthropometric measurements (bone and cartilage) of the atlantoaxial joint and to assess the role of cartilages in joint biomechanics. MATERIALS AND METHODS: The authors studied 10 cadaveric atlantoaxial lateral joints with the articular cartilage in situ and after removing it, using three-dimensional laser scanner. The data were compared using geometric morphometry with emphasis on surface contours of articulating surfaces. RESULTS: The bony inferior articular facet of atlas is concave in both sagittal and coronal plane. The bony superior articular facet of axis is convex in sagittal plane and is concave (laterally) and convex medially in the coronal plane. The bony articulating surfaces were nonconcordant. The articular cartilages of both C1 and C2 are biconvex in both planes and are thicker than the concavities of bony articulating surfaces. CONCLUSION: The biconvex structure of cartilage converts the surface morphology of C1-C2 bony facets from concave on concavo-convex to convex on convex. This reduces the contact point making the six degrees of freedom of motion possible and also makes the joint gyroscopic.

Musculoskeletal-based finite element analysis of femur after total hip replacement.

This article evaluates the effect of stress variation on adult femur following total hip replacement using musculoskeletal-based finite element analysis. The aim was to study the changes in stress distribution in the femur after total hip replacement by providing simulated in vivo loading and boundary conditions. The loading and boundary conditions were generated using a musculoskeletal modelling software 'AnyBody' and were applied on femur model, generated from the computed tomography (CT) scan data for standing posture of male patient. The results showed considerable variation in stress distribution pattern in the femur before and after total hip replacement, the metallic implant taking major loads of human body and transferring very less loads to the femur.