Generating Classes of 3D Virtual Mandibles for AR-Based Medical Simulation

Simulation and modeling represent promising tools for several application domains from engineering to forensic science and medicine. Advances in 3D imaging technology convey paradigms such as Augmented and Mixed Reality (AR/MR) inside promising simulation tools for the training industry. Motivated by the requirement for superimposing anatomically correct 3D models on a Human Patient Simulator (HPS) and visualizing them in an AR environment, the purpose of this research effort is to derive method for scaling a source human mandible to a target human mandible. Results show that, given a distance between two same landmarks on two different mandibles, a relative scaling factor may be computed. Using this scaling factor, results show that a 3D virtual mandible model can be made morphometrically equivalent to a real target-specific mandible within a 1.30 millimeter average error bound. The virtual mandible may be further used as a reference target for registering other anatomical ! models, such as the lungs, on the HPS. Such registration will be made possible by physical constraints among the mandible and the spinal column in the horizontal normal rest position

Robots and tools for remodeling bone

The field of robotic surgery has progressed from small teams of researchers repurposing industrial robots, to a competitive and highly innovative subsection of the medical device industry. Surgical robots allow surgeons to perform tasks with greater ease, accuracy, or safety, and fall under one of four levels of autonomy; active, semi-active, passive, and remote manipulator. The increased accuracy afforded by surgical robots has allowed for cementless hip arthroplasty, improved postoperative alignment following knee arthroplasty, and reduced duration of intraoperative fluoroscopy among other benefits. Cutting of bone has historically used tools such as hand saws and drills, with other elaborate cutting tools now used routinely to remodel bone. Improvements in cutting accuracy and additional options for safety and monitoring during surgery give robotic surgeries some advantages over conventional techniques. This article aims to provide an overview of current robots and tools with a common target tissue of bone, proposes a new process for defining the level of autonomy for a surgical robot, and examines future directions in robotic surgery

The development of bite force resistance and cranial form in Neanderthals and modern humans

The general aim of the thesis is to understand how biting mechanics interact with cranial form to impact post-natal craniofacial ontogeny in modern humans and Neander-thals. To this end, CT scans of ontogenetic samples of 12 Neanderthal and 63 modern human crania were collected and a series of reconstructions of Neanderthal crania were carried out. Geometric morphometric and multivariate regression approaches were used to create a craniofacial growth model for each species. Using these two models, 3D virtual crania representing the mean adult, juvenile, and infant were extracted in each species. These 6 mean crania were then converted into finite element models and used to conduct two biting simulations: at the right second premolar or second deciduous molar (RP2/RdM2) and right first incisor (RI1), applying the same muscle forces for all models because these are unknown especially for Neanderthals. This study compared modes and magnitudes of deformation, and the distribution and magnitude of tensile and compres-sive strains between the mean infant, juvenile, and adult models within each species and between the two species at each age stage.The morphometric analyses indicate that cranial ontogenetic trajectories differ be-tween modern humans and Neanderthals. The finite element analyses (FEA) in both bit-ing simulations indicate that, within each species, the mean infant juvenile and adult mod-els deform differently. Further, in both biting simulations, the highest strains are localised over similar regions of the cranium; over the anterior maxilla, orbits, and anterior subna-sal surface. Modern humans and Neanderthals deform differently and show differences in the development of biting forces during RI1 and RP2/RdM2 biting simulations at each stage. These findings confirm that modern human and Neanderthal crania have divergent postnatal developmental trajectories and manifest differences in the resistance of masti-catory system loadings throughout life. Differences in modes of deformation and so, strain distributions are considered in light of known differences in craniofacial bone growth remodeling between Neanderthals and modern humans. The findings show some correspondence with the remodeling maps for both species, particularly during RP2/RdM2 biting simulations. They do not falsify the hypothesis that facial remodeling differences arise because of differences in load resistance, and so, in the strain environment during post-natal development. As such, how differences among adult crania arise through post-natal interactions between form and functional loadings merits further investigation through more detailed analyses of a wider range of loading scenarios

Evaluation of diagnostic accuracy of digital models

AIM OF THE STUDY: The aim of the study is to evaluate the accuracy of non powdered digital impression by comparing mesio-distal width measurements and Bolton ratio, length of tooth, inter-canine and inter-molar width obtained through intraoral digital impression and compare it with conventional models. MATERIALS AND METHODS: Based on the inclusion criteria All 9 patients were studied using 2 different methods and measurements were made. Group A (study group)- the patient's dentition was scanned with the intraoral (IOS)scanner (iTero/ Cadent; invasalign, carlstad New Jersy). Group B (control group)- maxillary and mandibular impressions were taken Using poly vinyl siloxane (PVS) material orthodontic study models was poured using orthocal without any dimensional change of the impression. Digital Vernier caliper (Aero space, Resolution 0.01mm) was used to measure the mesio-distal width of individual teeth and the data was used to find bolton tooth ratio. Intraoral scanned model was measured using Dolphin 11.8 and both the groups were compared. RESULTS: Statistical analysis were performed using statistical package for social sciences software (SPSS version 22.0). Normality of the entered data was checked statistically using Shapiro-wilk test and data comparison was done, using Independent sample t test and it was used to compare statistical significance of obtained result. CONCLUSION: It was concluded that iTero (study group) models are capable of capturing tooth size accurately along with dolphin version (11.8) as compared with manual measurement on conventional plaster model

Virtual Morphology and Evolutionary Morphometrics in the new millenium.

EDITED VOLUME; abstract N/

Finite Element Analysis and Its Applications in Dentistry

Finite Element Analysis or Finite Element Method is based on the principle of dividing a structure into a finite number of small elements. It is a sophisticated engineering tool, which has been used extensively in design optimization and structural analysis first originated in the aerospace industry to study stress in complex airframe structures. This method is a way of getting a numerical solution to a specific problem, used to analyze stresses and strains in complex mechanical systems. It enables the mathematical conversion and analysis of mechanical properties of a geometric object with wide range of applications in dental and oral health science. It is useful for specifying predominantly the mechanical aspects of biomaterials and human tissues that cannot be measured in vivo. It has various advantages, can be compared with studies on real models, and the tests are repeatable, with accuracy and without ethical concerns