Navigated implantology
The navigated implantology is a prosthetic-surgical auxiliary procedure in the oral and maxillofacial surgery as well as in dentistry , which is used in the planning and in the operative procedure for the placing of dental implants in the jawbone . The term 3D-planned and template-guided implantology is used as another German-language designation for this procedure. In English-speaking countries, the terms navigated implantology, navigated surgery, guided-surgery, guided-implantology, computer-assist implantology or computer-assist surgery are used . It is one of the computer-assisted surgery procedures .
The principle of the navigated implantation of dental implants means that the implant position is strictly based on the ideal position of the planned denture (so-called backward planning). The aim is to position the dental implant as precisely as possible. This assumes the following conditions:
- An ideal shape and position of the teeth to be replaced ( wax-up ) based on the respective patient case .
- A radiologically visible copy of the wax-up in the form of a scan template or a digitally created tooth shape at the desired implant position.
- A preoperative, three-dimensional representation of the anatomy of the operating theater in the form of a 3D X-ray image, with the planned prosthetic restoration displayed.
- The virtual planning of an optimal implant position in relation to the desired tooth shape and position.
- Transfer of the virtually planned implant position to the operating theater using a guide template.
Indications and Limitations
The indications and restrictions on use for a navigated implantation are set out in the guidelines of the European Association of Osseointegration (EAO) and, for the German-speaking area, in the S2-K guideline of the German Society for Dentistry, Oral and Maxillofacial Medicine (DGZMK). Most of the indications relate to an expansion of the diagnostic possibilities for three-dimensional representation of the jawbones and their neighboring structures in order to enable an improved assessment of the surgical area, especially in the case of a small amount of bone or its unclear representation in conventional imaging techniques. The so-called ALARA principle (As Low As Reasonably Achievable) must be observed with regard to every X-ray examination . Thus, the imaging method should be selected and carried out with the lowest possible radiation dose for the respective problem with sufficient imaging quality. The decision for 3D planning and navigated implantation should be made against the background that the benefits of a 3D image for the patient outweigh the expected additional exposure to ionizing radiation. The necessity of using the navigated implantation depends on the individual patient situation, but also on the surgeon's experience.
Clinical and dental technical procedure
Wax model
The shape of the teeth to be replaced produced by the dental technician at the beginning of the therapy as a wax model or as a digitally created shape in a CAD program is referred to as a wax-up. It is the most important part of prosthetic-guided implant planning. The presentation of the desired treatment result before the start of the therapy enables the dentist , oral surgeon or oral surgeon to assess the possibilities and limitations of the treatment case and to discuss them with the patient. The decisions about the number and position of the implants required are made based on the desired shape of the subsequent tooth replacement. The question of whether additional measures have to be carried out to improve the implant site ( bone structure , augmentations) can also be answered reliably and predictably using a wax model.
3D image display
Carrying out a navigated implantation of dental implants requires the ability to display three-dimensional images in the form of a computed tomogram (CT) or digital volume tomography (DVT).
Due to the significantly lower cost structure of DVT technology compared to CT systems, DVT has become more widespread in surgical and implantological practices. Furthermore, planning software is required that enables preoperative virtual implant positioning.
Planning software
Most software versions display the CT or DVT images in three dimensions in all views and cross-sections. The implants can now be placed in the ideal position in relation to the existing jawbone and the planned restoration. The stored implant databases enable the type, diameter and length of these to be freely selected. During and after placing the implants, all views can be rotated freely and viewed from all angles. A tool that is common to almost all systems is the display and marking function of the courses of the mandibular nerve . Some programs also enable the integration of optical surface data (scanned models or optical impressions) into the 3D X-ray data.
Scan template and 3D imaging
The scan template is used to determine the bony supply at the planned implantation site, as well as to assess distances to sensitive neighboring structures such as nerve or vascular courses in the 3D X-ray. It is made from plastic containing barium sulfate , analogous to the shape of the wax-up . In all cases, it is important that the template is safely and stable intra-oral support. The remaining teeth or, in the case of complete toothlessness, additional supports in the form of temporary implants are suitable for support. In any case, the support should be chosen so that an unintentional change of position can be excluded as safely as possible. In addition to the classic production of the guide template from cold polymerizate or a deep-drawn splint on a plaster model , CAD / CAM-based systems can also be used. With these systems, the wax-up is digitized or can be digitally designed directly in the software in the Surface Tesselation Language (STL) file format (digital wax-up).
The guide template is then produced using the so-called rapid prototyping (RPP) process. The type of RPP production varies between the individual systems.
Reference markings (plug-in modules containing barium sulfate, radio-opaque glass spheres, etc.) are also included in most of the scan templates so that referencing can be carried out later in the software.
Virtual implant positioning
The data set ( DICOM data) obtained through the 3D recording is read into the planning software. After the DICOM data record has been processed (removal of artifacts ), the reference bodies shown in the recording are first aligned with the corresponding reference bodies in the planning software. The planned implants can then be optimally positioned taking into account the anatomical conditions of the patient and the desired prosthetic restoration.
Manufacture of the guide template
The transfer of the virtual implant position into a guide template for the implant drill can be done in various ways. As a rule, most systems use so-called positioners. The scan template is mounted on a swiveling drilling table, which can change its angle of inclination in relation to the drilling and positioning aid for the guide sleeves. Analogous to the previously generated coordinate system, the corresponding values are set on the positioner for each implant and the guide sleeve for each implant is first drilled and then glued. Alternatively, the drilling template can also be produced entirely using the CAD / CAM process. Corresponding stencils are produced either in the stereolithography process or in a 3D printer .
Template-guided implantation
The implant may under certain favorable conditions, even without the exposure of the jaw bone ( ger .: flapless ) be carried out. After the guide template has been positioned, the holes for the dental implants are made in the same way as the previously planned position specified in the drilling template. The implant form drills are aligned by the guide sleeves during the drilling process. In addition to the bores in the implant bed, the implant can also be inserted through the guide sleeves, provided the implant system used allows this.
Accuracy of 3D planned systems
From a medical point of view, the navigated insertion (introduction) of a dental implant should enable greater accuracy in the positioning of the artificial tooth root. Most of the currently available scientifically collected data on the deviations between the planned and achieved implant position are in-vitro studies (laboratory studies) on models or human specimens (body parts). Or they are investigations into systems in which the position of the rotating instrument in the operating site (operating theater) is simultaneously tracked through an optical recording option during the procedure in the form of radiological monitoring (so-called tracking or dynamic systems). The accuracy can be mapped with the deviation between the planned and the achieved implant position in 3D-planned systems. For this purpose, the following spatial deviations are defined:
- Horizontal deviations at the point of entry of the drilling into the implant site
- Horizontal deviations at the apex of the drill or the implant
- Vertical deviations of the achieved implant position
- Deviations in the axis of the implant or the drill
In a review of the international literature, the following mean values for template-guided systems are given for two of the above-mentioned deviation parameters: Horizontal deviations of 1.12 mm (max. 4.5 mm) at the entry point and 1.2 mm (max. 7.1 mm) at the apex. For the vertical deviations 0.23 mm (max. 1.43 mm) and deviations in the angulation of 4.0 ° (max. 20.43 °) are given. More recent studies that examined the accuracy of guide templates made from cold-curing polymers came to the result that mean deviations of 0.3 to 0.9 mm occurred at the implant shoulder and 0.5–0.9 mm at the apex. Mean deviations in angulation were 2.1 ° to 4 °.
Individual evidence
- ↑ S. Harder: 3D-planned template-guided implantology. In: the young dentist. 3, 2012, pp. 10-19, doi : 10.1007 / s13279-012-0189-3 .
- ↑ D. Harris, K. Horner et al. a .: EAO guidelines for the use of diagnostic imaging in implant dentistry 2011. A consensus workshop organized by the European Association for Osseointegration at the Medical University of Warsaw. In: Clinical oral implants research. Volume 23, Number 11, November 2012, pp. 1243-1253, ISSN 1600-0501 . doi : 10.1111 / j.1600-0501.2012.02441.x . PMID 22432473 .
- ↑ a b S2k guideline: Indications for implantological 3D X-ray diagnostics and navigation-assisted implantology ( memento of the original from September 23, 2015 in the Internet Archive ) Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice. German Society for Dentistry, Oral and Maxillofacial Medicine (DGZMK). Retrieved October 19, 2014.
- ^ RE Jung, D. Schneider u. a .: Computer technology applications in surgical implant dentistry: a systematic review. In: The International journal of oral & maxillofacial implants. Volume 24 Suppl, 2009, pp. 92-109, ISSN 0882-2786 . PMID 19885437 . (Review).
- ↑ HJ Nickenig, M. Wichmann u. a .: Evaluation of the difference in accuracy between implant placement by virtual planning data and surgical guide templates versus the conventional free-hand method - a combined in vivo - in vitro technique using cone-beam CT (Part II). In: Journal of Cranio-Maxillo-Facial Surgery . Volume 38, Number 7, October 2010, pp. 488-493. doi : 10.1016 / j.jcms.2009.10.023 . PMID 19939691 .
- ↑ A. Behneke, M. Burwinkel u. a .: Accuracy assessment of cone beam computed tomography-derived laboratory-based surgical templates on partially edentulous patients. In: Clinical oral implants research. Volume 23, Number 2, February 2012, pp. 137-143, ISSN 1600-0501 . doi : 10.1111 / j.1600-0501.2011.02176.x . PMID 21443593 .
