Development of an ultra-miniaturized inertial measurement unit for jaw movement analysis during free chewing

Problem statement: Jaw movement analysis, as a clinical aid, can provide an objective basis for understanding and diagnosing jaw musculoskeletal disorders. Therefore, the use and development of devices for quantitatively measuring and analyzing jaw movement have become more common and popular in the clinic. Many types of jaw tracking devices have been developed, but most of them are still not handy and easy to be used. Approach: To improve the handiness and utility of the jaw movement analysis devices, we developed a simple to be used jaw tracking prototype by using a new ultra-miniaturized Inertial Measurement Unit (IMU) named WB-3. The WB-3 IMU was composed by 3-axis gyroscope, 3-axis accelerometer and 3-aixs magnetometer, which can not only measure the acceleration and angular speed of jaw movement, but also can measure mouth opening angle. The IMU's extremely reduced weight and size allowed it to be easily adhered to mandible during normal tests without physical restriction to the subjects. A preliminary experiment for jaw movement analysis during free chewing of three types of food with different shapes and hardness was evaluated. A group of 15 healthy subjects aged from 21-36 years old kindly participated in the experiment. Results: The parameters of chewing time, chewing frequency, power spectrum density of jaw's angular speed and acceleration, cumulative distribution function of jaw's acceleration and mouth opening angle were presented. The experimental results clearly showed that the subjects used less chewing time, less chewing frequency, less acceleration cumulative distribution and energy to eat soft food; higher values were found in the case of hard food and there was no significant difference in mouth opening angle while eating these three foods. Conclusion: Our jaw movement analysis prototype using IMU WB-3 was proved to be a valid and handy method for jaw movement and pattern analysis which may be used clinically as an assistant system for dental therapy. © 2010 Science Publications

악관절의 해부학적 구조에 기반한 하악 움직임 경로의 생성

학위논문 (석사)-- 서울대학교 대학원 : 공과대학 컴퓨터공학부, 2019. 2. 김명수.We introduce a new approach to the generation of mandible trajectories that can avoid collision between mandibular condyle and maxilla. This is used for analyzing occlusion and the development virtual articulator simulation technique to naturally move mandible following input from a user. Mandible movement has 6 degrees of freedom. However, articular disk, ligament, and muscle near temporomandibular joint constrain the condyle movement. As a result, Mandibular condyle moves from inside of mandibular fossa to below of articular tubercle through a specific trajectory. Therefore, we propose an effective condyle trajectory modeling method based on these features of the anatomical structure of a temporomandibular joint to show accurate mandible movement. By utilizing Bezier surfaces approximating components of both sides of temporomandibular joints, it constrains movable space of both condyles and expresses sequential mandible movement according to the location of those condyles. Mandible can be easily manipulated by simple user interface like virtual articulator, and it can present various movements such as protrusion, retrusion, and lateral movement. Also, the additional interface presents a space which is generated by one point of mandible located through all kinds of movements.본 논문에서는 환자의 치아 교합을 파악하기 위해 두개골 모델을 사용하여 하악 과두(mandibular condyle)의 충돌을 회피하면서 자연스럽게 움직이는 하악의 이동 경로를 생성하고, 사용자의 입력에 따라 하악 동작을 제어하는 가상 교합기 시뮬레이션 기법을 제시한다. 하악의 움직임은 한정된 공간에서 6-자유도(6-DOF)를 가지는 것으로 보이지만, 악관절(temporo-mandibular joint) 부근의 관절 원판(articular disk), 인대, 근육 등에 의해 하악 과두의 움직임이 크게 제한되어 있기 때문에 하악 과두는 상악의 관절 융기(articular tubercle)를 따라 일정한 경로 범위 이내에서만 움직인다. 이러한 악관절 해부학적 구조에 따라, 일반적인 과두의 움직임 경로를 효과적으로 모델링하고 하악의 움직임을 정확하게 나타내는 새로운 시뮬레이션 방법을 제안한다. 악관절 부근을 근사한 베지에 곡면을 이용하여 양측 과두의 움직임을 제한하고, 이에 따라 연속적으로 변화하는 하악의 위치와 방향을 구한다. 가상 교합기와 같이 간단한 사용자 인터페이스를 통해 과두의 움직임을 쉽게 조작할 수 있으며, 경로의 선택에 따라 전방 운동(protrusion), 후방 운동(retrusion), 측방 운동(lateral movement) 등을 다양하게 나타낼 수 있다. 이외에도, 생성된 경로에 따라 환자의 하악이 움직일 수 있는 공간을 나타내는 인터페이스를 제시한다.제 1 장 서론 1 1.1 연구의 배경 및 목적 1 1.2 관련 연구 3 1.3 논문의 구성 5 제 2 장 본론 6 2.1 예비지식 6 2.1.1 베지에 곡선과 베지에 곡면 6 2.1.2 사원수 7 2.2 하악의 움직임 9 2.3 교합기 13 2.4 과두의 움직임 경로 모델링 14 2.4.1 과두 경로 후보 14 2.4.2 접번축 위상과 하악 위치 결정 15 2.4.3 인터페이스 정의 16 2.4.4 과두 경로 후보 수정 16 2.5 시스템 구성 18 2.6 시뮬레이션 결과 20 2.6.1 전방 운동 20 2.6.2 측방 운동 22 2.6.3 하악 이동 가능 범위 시각화 23 제 3 장 결론 26 참고문헌 31 Abstract 32 감사의 글 34Maste

Visualization of mandibular movement relative to the maxilla during mastication in mice: integration of kinematic analysis and reconstruction of a three-dimensional model of the maxillofacial structure

Background: Mastication is one of the most fundamental functions for the conservation of human life. To clarify the pathogenetic mechanism of various oral dysfunctions, the demand for devices for evaluating stomatognathic function has been increasing. The aim of the present study was to develop a system to reconstruct and visualize 3-dimensional (3D) mandibular movements relative to the maxilla, including dynamic transition of occlusal contacts between the upper and lower dentitions during mastication in mice.Methods: First, mandibular movements with six degrees of freedom were measured using a motion capture system comprising two high-speed cameras and four reflective markers. Second, 3D models of maxillofacial structure were reconstructed from micro-computed tomography images. Movement trajectories of anatomical landmark points on the mandible were then reproduced by integrating the kinematic data of mandibular movements with the anatomical data of maxillofacial structures. Lastly, 3D surface images of the upper dentition with the surrounding maxillofacial structures were transferred to each of the motion capture images to reproduce mandibular movements relative to the maxilla. We also performed electromyography (EMG) of masticatory muscles associated with mandibular movements.Results: The developed system could reproduce the 3D movement trajectories of arbitrary points on the mandible, such as incisor, molars and condylar points with high accuracy and could visualize dynamic transitions of occlusal contacts between upper and lower teeth associated with mandibular movements.Conclusions: The proposed system has potential to elucidate the mechanisms underlying motor coordination of masticatory muscles and to clarify their roles during mastication by taking advantage of the capability to record EMG data synchronously with mandibular movements. Such insights will enhance our understanding of the pathogenesis and diagnosis of oral motor disorders by allowing comparisons between normal mice and genetically modified mice with oral behavioral dysfunctions