Designing a mandibular advancement device with topology optimization for a partially edentulous patient.

STATEMENT OF PROBLEM: Patients with partial tooth loss treated with implant-supported fixed partial dentures (FPDs) have difficulty using conventional mandibular advancement devices (MADs) because of the risk of side effects. Also, which design factors affect biomechanical stability when designing MADs with better stability is unclear. PURPOSE: The purpose of this finite element (FE) analysis study was to analyze the effect of the MAD design on biomechanical behavior and to propose a new design process for improving the stability of MADs. MATERIAL AND METHODS: Each 3D model consisted of the maxillofacial bones, teeth, and implant-supported FPDs located in the left tooth loss area from the first premolar to the second molar and a MAD. Three types of custom-made MADs were considered: a complete-coverage MAD covering natural tooth-like conventional MADs, a shortened MAD excluding the coverage on the implant-supported FPD, and a newly designed MAD without anterior coverage. For the new MAD design, topology optimization was conducted to reduce the stress exerted on the teeth and to improve retention of the MAD. The new MAD design was finished by excluding the coverage of the maxillary and mandibular central incisors based on the results of the topology optimization. A mandibular posterior restorative force for a protrusion amount of 40% was used as the loading condition. The principal stress and pressure of the cancellous bone and periodontal ligaments (PDLs) were identified. RESULTS: Considering the load concentration induced by the complete-coverage MAD, bone resorption risk and root resorption risk were observed at both ends of the mandibular teeth. The shortened MAD resulted in the highest stress concentration and pressure with the worst stability. However, in the case of the complete-coverage MAD, the pressure in the PDLs was reduced to the normal range, and the risk of root resorption was reduced. CONCLUSIONS: For patients with implant-supported FPDs, MAD designs with different extents of coverage had an influence on biomechanical behavior in terms of stress distribution in cancellous bone and PDLs. A MAD design without anterior coverage provided improved stability compared with complete-coverage or shortened designs. The presented method for MAD design, which combined FE analysis and topology optimization, could be effectively applied in the design of such improved MADs.

Markerless surgical robotic system for intracerebral hemorrhage surgery.

Conventional intracerebral hemorrhage (ICH) surgery uses a stereotactic frame to access an intracerebral hematoma. Using a stereotactic frame for ICH surgery requires a long preparation time. In order to resolve this problem, we propose a markerless surgical robotic system. This system uses weighted iterative closest point technology for surface registration, hand-eye calibration for needle insertion, and 3D surface scanning for registration. We need calibration to integrate the technologies: calibration of robot and needle coordinates and calibration of 3D surface scanning and needle coordinates. These calibrations are essential elements of the markerless surgical robotic system. This system has the advantages of being non-invasive, a short total operation time, and low radiation exposure compared to conventional ICH surgery.

Markerless registration for intracerebral hemorrhage surgical system using weighted Iterative Closest Point (ICP).

It is required to use a stereotactic frame on a patient's crainial surface to access an intracerebral hematoma in conventional ICH (Intracerebral Hemorrhage) removal surgery. Since ICH using a stereotactic frame is an invasive procedure and also takes a long time, we attempt to develop a robotic ICH removal procedure with a markerless registration system using an optical 3-D scanner. Preoperative planning is performed using a patient's CT (Computed Tomography) images, which include the patient's 3-D geometrical information on the hematoma and internal structures of brain. To register the preplanned data and the intraoperative patient's data, the patient's facial surface is scanned by an optical 3-D scanner on the bed in the operating room. The intraoperatively scanned facial surface is registered to the pose of the patient's preoperative facial surface. The conventional ICP (Iterative Closest Point) algorithm can be used for the registration. In this paper, we propose a weighted ICP in order to improve the accuracy of the registration results. We investigated facial regions that can be used as anatomical landmarks. The facial regions for the landmarks in the preoperative 3-D model are weighted for more accurate registration. We increase weights at the relatively undeformed facial regions, and decrease weights at the other regions. As a result, more accurate and robust registration can be achieved from the preoperative data even with local facial shape changes.

3D tracking of surgical instruments using a single camera for laparoscopic surgery simulation.

Most laparoscopic surgery simulation systems are expensive and complex. To overcome these problems, this study presents a novel three-dimensional tracking method for laparoscopic surgical instruments that uses only a single camera and fiducial markers. The proposed method does not require any mechanical parts to measure the three-dimensional positions/orientations of surgical instruments and the opening angle of graspers. We implemented simple and cost-effective hardware using the proposed method and successfully combined it with virtual simulation software for laparoscopic surgery.