Computer methods for automating preoperative dental implant planning: Implant positioning and size assignment

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Abstract

The paper presents computer-aided methods that allocate a dental implant and suggest its size, during the pre-operative planning stage, in conformance with introduced optimization criteria and established clinical requirements. Based on computed tomography data of the jaw and prosthesis anatomy, single tooth cases are planned for the best-suited implant insertion at a user-defined region. An optimum implantation axis line is produced and cylindrical implants of various candidate sizes are then automatically positioned, while their occlusal end is leveled to bone ridge, and evaluated. Radial safety margins are used for the assessment of the implant safety distance from neighboring anatomical structures and bone quantity and quality are estimated and taken into consideration. A case study demonstrates the concept and allows for its discussion.

Introduction

In recent years, computer-aided methods have been introduced as supportive tools for diagnosis, operation planning and treatment in implant dentistry. Based on computed tomography (CT), their aim is to support preoperative planning towards a safer and more predictable treatment outcome.

Transfer of the dental implant planning on the computer screen offers significant advantages such as enhanced visualization capabilities of the anatomical case, accurate measurements, data processing for optimum implant allocation and size selection and, as well as, an inclusive documentation of the patient treatment. Increased user interaction and responsibility for the evaluation of the results are still, nevertheless, present in these systems.

This paper presents a computer-aided methodology that aims to a systematic dental implant planning approach based on appropriately processed CT-data. Patient anatomy, as it is represented by voxels of specific coordinates and intensity in CT images, is analyzed and the obtained results are evaluated towards an objective implant planning control. The rational allocation of a dental implant within a subject-specific anatomical site is addressed. Through a limited user input, an implantation axis with best possible position and orientation complying with established medical criteria is at a first stage suggested. Implants of various possible sizes are then automatically positioned and aligned to this axis and the thus produced alternative problem solutions are evaluated and classified. The produced implant planning schemes, for the dentist to make the final decision, are classified in terms of the derived bone volume and quality indexes at the implant site.

A case study demonstrates concept and method and allows for its discussion.

Section snippets

Background

The limitations of conventional pre-implant treatment planning, which is based among other data on 2D radiographs, have been over-passed, to a certain extent, by computer software systems and tools. Main contribution of the latter towards an optimum end result is the interactive visualization of multi-planar two-dimensional sections of the relevant anatomy including axial, cross-sectional and user-defined panoramic images, extended by 3D rendered representations of CT data [1], [2], [3]. Within

Method design considerations

Prosthetic dental treatment planning associated with implants is a complicated process, where many parameters have to be carefully assessed in order that the patient is properly treated. In addition to clinical issues, main factors that need to be accounted for, involve the geometry of the anatomic structures in contact or adjacent to the implant and the quality of the recipient bone mass [20], [21]. The placement of the prosthetic superstructure requires also particular consideration for a

Method implementation

Present method development stage provides for the assessment of mandible cases where every single tooth site is treated separately. Free splinted completed crowns are considered for restoration. CT images that contain patient-specific jaw anatomy and the provisional prosthesis morphology constitute the initial data. Matlab (MathWorks, Natick, MA) computing language is used for the method implementation and Mimics (Materialise, Leuven, Belgium) for the 3D visualization. An overview of the method

Case study and discussion

The studied instances for three posterior teeth in the patient mandible, at position nos. 36, 35 and 34 are presented and discussed. The patient wore a radio-opaque template of the pursued aesthetical and functional restorative result and was CT scanned. DICOM images were acquired with a resolution of 512 × 512, slice thickness 0.5 mm and pixel size 0.32 mm.

For each instance the axial range of prosthesis and mandibular bone images was at first selected. An axial plane inside the bone was in

Conclusions

The paper has presented a semi-automatic computer-aided methodology for the planning of dental implant therapy in single tooth cases of posterior mandible. For a given region of interest with regard to the pursued prosthetic outcome, an optimum orientation, position and size of a cylindrical implant are derived. The quality of the patient anatomic CT-data, such as the absence of serious artefacts, the geometrical consistence of the scanned radio-opaque template with that of the pursued

Acknowledgement

This research is supported by the General Secretariat for Research and Technology of Greece (GSRT, www.gsrt.gr) within the frame of the RTD program PENED.

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