Lutz Ritter

Accuracy of cone beam computed tomography in assessing peri‐implant bone defect regeneration: a histologically controlled study in dogs

OBJECTIVE To assess the accuracy of cone-beam computed tomography (CBCT) in terms of buccal bone-wall configuration and peri-implant bone defect regeneration after guided bone regeneration (GBR). MATERIAL AND METHODS Titanium implants were inserted into standardized box-shaped defects in the mandible of 12 foxhounds. Defects of one side were augmented following the principle of GBR, while the other side was left untreated. Radiological evaluation was performed using CBCT and compared with histomorphometrical measurements of the respective site serving as a validation method. RESULTS Non-augmented control sites providing a horizontal bone width (BW) of<0.5 mm revealed a significantly lower accuracy between the radiological and the histological evaluation of the buccal defect depth (1.93 ± 1.59 mm) compared with the group providing a BW of >0.5 mm (0.7 ± 0.7 mm) (P<0.05, Mann-Whitney U-test). In GBR-treated defects, the subgroup <0.5 mm (1.49 ± 1.29 mm) revealed a significantly higher difference between CBCT and histology compared with >0.5 mm (0.82 ± 1.07) (P>0.05, Mann-Whitney U-test). However, a radiological discrimination between original bone, integrated and non-integrated bone substitute material was not reliable. Additionally, it was found that a minimum buccal BW of 0.5 mm was necessary for the detection of bone in radiology. CONCLUSION The evaluation of peri-implant bone defect regeneration by means of CBCT is not accurate for sites providing a BW of <0.5 mm. Moreover, a safe assessment of the success of the GBR technique is not possible after the application of a radiopaque bone substitute material.

Computer-aided manufacturing technologies for guided implant placement.

Implant treatment increasingly focuses on the reduction of treatment time and postoperative impairment. The improvement of 3D dental diagnosis by ConeBeam computed tomography allows detailed preparation for the surgical placement of dental implants under prosthetic considerations. While the first generation of implant planning software used high-contrast multislice computed tomography, software that has been specifically designed for ConeBeam computed tomography is now available. Implant placement can be performed using surgical guides or under the control of optical tracking systems. Surgical guides are more commonly used in private office owing to their availability. The accuracy for both techniques is clinically acceptable for achieving implant placement in critical anatomical indications. When using prefabricated superstructures and in flapless surgery, special abutments or an adjusted workflow are still necessary to compensate misfits of between 150 and 600 µm. The proposition to ensure proper implant placement by dentists with limited surgical experience through the use of surgical guides is unlikely to be successful, because there is also a specific learning curve for guided implant placement. Current and future development will continue to decrease the classical laboratory-technician work and will integrate the fabrication of superstructures with virtual treatment planning from the start.

Efficient Point-Based Isosurface Exploration Using the Span-Triangle

We introduce a novel span-triangle data structure, based on the span-space representation for isosurfaces. It stores all necessary cell information for dynamic manipulation of the isovalue in an efficient way. We have found that using our data structure in combination with point-based techniques, implemented on graphics hardware, effects in real-time rendering and exploration. Our extraction algorithm utilizes an incremental and progressive update scheme, enabling smooth interaction without significant latency. Moreover, the corresponding visualization pipeline is capable of processing large data sets by utilizing all three levels of memory: disk, system and graphics. We address practical usability in actual medical applications, achieving a new level of interactivity.

Nerves - level sets for interactive 3D segmentation of nerve channels

In this paper, we present a novel method for 3D segmentation of the nerve channels in the human mandible that contain the nervus alveolaris inferior. The technique utilizes geodesic active surfaces that are implemented with level sets. The method consists of two steps: (i) After defining two points, which denote the entry and exit of the nerve channel, a connecting path of minimal action inside the channel is calculated. This calculation is driven by the gray values in proximity to the two defined points inside the channel, (ii) Using this path as an initial configuration, an active surface evolves until the inner borders of the channel are reached. Since this initial configuration is located very close to the borders of the channel, a propagation term is not necessary in this model.

JULIUS - An Extendable Software Framework for Surgical Planning and Image-Guided Navigation

In this paper we introduce the extendable and cross-platform software framework JULIUS, which will become public available by the end of this year. JULIUS consists of three conceptual layers and provides diverse assistance for medical visualization, surgical planning and image-guided navigation. The system features a modular and portable design and combines both pre-operative planning and intra-operative assistance within one single environment.

Extendable application framework for medical visualization and surgical planning

This paper introduces an extendable cross-platform software framework Julius for medical visualization and surgical planning, consisting of two conceptual layers: the Julius Software Development Kit (JSDK) and the Julius Graphical User Interface (JGUI). The JSDK can be used stand-alone to speed up development of research tools. While the JGUI acts like a front end for the JSDK and offers easy handling combined with time-saving functionality to increase performance and productivity. Julius features a modular, cross-platform design and comes with a full set of components, like semi-automatic segmentation, registration, visualization and navigation.

An open software framework for medical applications

In this paper we introduce the extendible and cross-platform software framework Julius. Julius combines both pre-operative planning and intraoperative assistance within one single environment. In this paper we discuss three aspects of Julius: the medical data processing, the visualization pipeline and the interaction. Each aspect provides interfaces that allow to extend the application with own algorithms and to build complex applications. We believe that this approach facilitates the development of image guided navigation and simulation procedures for computer-aided-surgery.

JULIUS - An Extendable Application Framework for Medical Visualization and Surgical Planning

In this paper we introduce the extendable cross-platform software framework Julius for medical visualization and surgical planning, consisting of two conceptual layers: the Julius Software Development Kit (JSDK) and its front-end the Julius Graphical User Interface (JGUI). Julius features a modular, platform-independent design and includes a full set of components, like semi-automatic segmentation, registration, visualization and navigation.

Comparison of different autografts for aural cartilage in aesthetic rhinoplasty: is the tragal cartilage graft a viable alternative?

Auricular cartilage is an important source of grafts for various reconstructive procedures such as aesthetic rhinoplasty. The purpose of this investigation was to compare tragal cartilage with auricular cartilage harvested from the concha and scapha, and describe its clinical viability, indications, and morbidity in rhinoplasty. A total of 150 augmentation rhinoplasties with a total of 170 grafts were included. The donor sites were tragus (n=136), concha (n=26), and scapha (n=8). The time needed to harvest the grafts, the donor site morbidity, and the indications for operation were recorded. The anthropometric changes to 4 auricular variables after the cartilage had been harvested were analysed and compared with those on the opposite side in 48 patients using Students paired t-test. Intraobserver reliability was assessed using Pearsons intraclass correlation. The mean (SD) harvesting time was 27 (8) min for the concha, 4.5 (1.4) min for the tragus, and 5.7 (1.6) min for the scapha. The largest graft was taken from the concha (28×19 mm), followed by the tragus (20×12 mm), and the scapha (18×6 mm). The grafts were placed at the following sites: tip grafts (n=123), columella struts (n=80), shield (n=20), rim (n=17), and dorsal onlay (n=15). Harvesting tragal cartilage is safe, simple, fast, and has a low morbidity, but it can affect the patients ability to wear earphones. Tragal cartilage is a good alternative for nasal reconstruction if a graft of no longer than 20 mm is required.