Original study - ZZI 01/2013

Analysis of the precision of implant templates

F. Petschelt1, M. Millian1, T. Kraußeneck1

Aim: The aim of this study was to evaluate the precision of holes drilled in implant templates, which were analyzed with cone beam computed tomography (CBCT) using suitable planning software.

Material and methods: 40 templates that had been used clinically to enable successful treatment were studied. 17 of the analyzed templates were fabricated with the Med3D program (C. Hafner GmbH, Pforzheim) and 23 templates were made with the ExpertEase software of Dentsply Friadent GmbH. The Scanora Soredex was used for CBCT. Comparative measurements were made on a plaster model with silicone key using an individually fabricated appliance.
3 holes were drilled in each template by 3 different persons. The resulting data were compared to within less than a millimeter.

Results: Maximum deviations of 2.0 mm in the horizontal dimension and 1.0 mm in the vertical dimension were found. Much smaller deviations with more precise positions were found with the ExpertEase version compared with the Med3D-assisted procedure.

There were no significant differences in drilling precision between an experienced implantologist and a dental nurse without any practical experience on patients.

Conclusion: With observation of the basic principles of implantology and use of planning software for template-guided surgery, exact implant placement to within less than a millimeter is possible, even in the most demanding situations.

Keywords: Computer-aided implantology; CBCT; 3D navigation; implant templates; precision; drilling sleeves

Citation

Petschelt F, Millian M. Kraußeneck: Analysis of the Precision of Implant Templates. Z Zahnärztl Implantol 2013;29:58?69. DOI 10.3238/ZZI.2013.0058?0069

Introduction

Implant therapy always forms part of an overall restorative concept. Good preoperative planning is essential to meet the aesthetic and functional demands of implant-borne restorations [6, 8, 20].

Integration of implant-related diagnosis, planning and surgery in this overall concept should therefore be considered carefully, in accordance with DGZMK guidelines.

Radiographic imaging data are imported into the planning software and the implants are placed virtually. There is a wide choice of implant lengths and diameters from different manufacturers and these can be fitted to the bone [2, 7]. Suitable software enables the implant positions in the important anatomical structures to be analyzed and aligned in the axial, sagittal and horizontal dimensions. The usual tomographic views and three-dimensional reconstruction illustrate the planning results. The course of the inferior alveolar nerve, for example, is entered semi-automatically by the user so it can be shown realistically. The guide sleeves of the templates are calibrated so that the different drills can be passed precisely with the exchangeable sleeves [10, 11].

Various procedures for navigated three-dimensional implantology were defined at an early stage. Not least with the introduction of immediate restoration with immediate loading and with the major advances in digital volume tomography, the possibilities of the navigated three-dimensional technique have expanded greatly and are generally highly regarded. [9, 20] An X-ray template is indispensable for backward planning and therefore for well-founded and advanced implant planning [13]. The scan template is the key to success as initial illustration of the functional dental arches incorporating the achievable prosthetic rehabilitation is necessary in every software program to show the situation in the mouth. The software and its special functions can be used optimally only with an X-ray template produced in accordance with certain criteria.

When producing a template, a distinction is made between stereolithography and the model-based implant template, though this has no influence on the actual scan template [2, 5, 8, 11]. In nearly all systems, it must have a radiopaque section with a prosthetic component.

The Dentsply Friadent system, a development of the Simplant system (Materialise, Leuven, Belgium), enables the X-ray template to be produced by optical conversion of the site into the program [2, 16, 17].

The Med3D X-ray template, with the familiar Lego brick, is converted in the dental laboratory from the X-ray template to the subsequent operation template by a suitable calibration system.

With the systems we use, the decision to implant using navigation involves close collaboration with the planning center or laboratory. This provides an opportunity of achieving an optimal result through interdisciplinary collaboration.

Precision depends on the accuracy of transfer from the scan template to the operation template and this is the key to success.

There are several sources of error. Inaccuracy due to conversion of the CT data during production can impair the subsequent fit of the drilling template [14]. Despite precise radiographs, drill play can arise in the drill template sleeves. While these parameters have been investigated in different applications [2, 3, 5, 7, 10, 16, 17, 19, 20, 21], there are no known investigations of how accurate drilling through sleeves can be. This question is addressed in this study.

Intraoperative fixing of drilling templates depends on the residual dentition and the planned surgical procedure. Tooth-supported, mucosa-supported and bone-supported templates are possible [8, 11]. In the cases studies, tooth-supported templates, which are regarded as the most accurate, were used exclusively for analysis.

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