Page 31 - Craniomaxillofacial Implant Surgery - Jeroen P.J. Dings

Reliability and accuracy of image-guided craniofacial implant planning
INTRODUCTION
Endosseous implants are established as a secure treatment in prosthetic rehabilitation
of craniofacial defects.1 Although osseointegration of craniofacial implants is 2 predictable, its success rate is mainly determined by primary implant stability.
Therefore, preoperative planning is essential for evaluation of the available bone
quantity and density to improve reliable treatment planning of craniofacial implants.2-12
Besides evaluating the available bone thickness, planning is also critical in determining
the spatial proximity of anatomical locations and avoiding vital structures.5,13-15
Obviously, a prerequisite for implant planning is the high geometric accuracy of the image data.16 Pre-surgical planning and image-guided surgical procedures, nowadays, are mainly based on three dimensional (3D) imaging acquired by medical multi- detector row computed tomography (MDCT) or cone beam computed tomography (CBCT).2,10,17,18 MDCT and CBCT are both feasible as high-resolution diagnostic imaging modalities for oral and maxillofacial procedures and implant planning.15,18-20
MDCT is still held as a reference standard in terms of geometric accuracy in maxillofacial surgery today.2,10,15 However, low-cost CBCT poses an alternative to traditional MDCT systems in providing images without superimposition and blurring. In addition, as compared to traditional MDCT, CBCT offers principal advantages, such as reduced radiation exposure, more rapid data acquisition and less disturbance from metallic artifacts, while still permitting reconstruction of the soft tissue profile. Therefore, CBCT is nowadays widely used for oral and maxillofacial procedures.4,5,8,10,14,15,20-31 However, disadvantages of CBCT include susceptibility to movement artifacts, lower image contrast, higher noise, limited field of view and inability to quantitatively measure tissue density in comparison to MDCT.11,24,32 These quantitative values expressing x-ray attenuation of a voxel relative to the attenuation of water are represented by Hounsfield units (HU) and are more accurate when voxel sizes are smaller and less material is averaged.4,29,32,33
A wide variety of engineering, medical and dental software packages are currently available.34 Cross-sectional images in multiplanar reconstructions of CBCT and MDCT image data enables linear measurements to be performed on bone surface size and cortical thicknesses.3,18 Literature comparing MDCT and CBCT shows moderate variability in image quality and high degree of dimensional accuracy of linear and
29