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Key Considerations for Implant Planning

Explore the factors influencing CBCT accuracy and radiation dosage optimization to ensure precise implant planning and patient safety.

Cone beam computed tomography (CBCT) offers numerous advantages, which include identification of pathology, vital anatomical structures, and assessing bone quality and quantity for implant planning. Three-dimensional (3D) CBCT generates a series of planar basis images that are reconstructed with special software to yield volumetric data sets of varying projections: axial, sagittal and coronal (Figures 1A through 1C).1 While considered quite accurate, various factors help determine the level of accuracy of CBCT images.2

FIGURES 1A through 1C. Two-dimensional cone beam computed tomography planes: axial (A), coronal (B), and sagittal (C).

A range of error exceeding 1 mm was usually noted while performing linear measurements of bone and anatomical structures. These errors can lead to clinical complications during surgical execution. Therefore, an agreed upon 2-mm safety zone is usually recommended when measuring how far the proposed implant is to vital anatomical structures. Other machine-dependent factors that can influence the accuracy of linear measurements include filtration, target-object and object-sensor distances, reconstruction algorithms used, and different head restraining devices.

For a CBCT machine to be considered a true advantage, it should have radiation dosages less than a spiral CT machine — preferably somewhere around the equivalent of two to 10 panoramic radiographs (or 20 to 100 μSv). However, reducing the radiation dosage too much may render some images diagnostically useless. Therefore, clinicians should aim for doses that are As Low As Diagnostically Acceptable being Indication-oriented and Patient-specific, otherwise known as ALADAIP.3

Some of the techniques to minimize radiation dosage are reducing scan time, the scan arc, or field of view (field of view; Figures 2A and 2B). All of these factors have no adverse effects in terms of the accuracy of linear measurements. However, when utilizing CBCT data for guided implant planning, clinicians should keep in mind that a field of view with sufficient points to be merged with the STL file is recommended.1

FIGURES 2A and 2B. Small field of view (A), and large field of view (B).

Another factor that plays a role in the resolution of CBCT images, but not necessarily the accuracy of linear measurements, is voxel size, which is usually predetermined by the type of CBCT machine. A voxel is the volume element, defined in 3D space. The dimensions consist of pixels and thickness of the slice. A voxel size of 0.3 to 0.4 mm is usually sufficient to provide necessary accuracy for implant treatment planning.1,4

References

  1. Fokas G, Vaughn VM, Scarfe WC, Bornstein MM. Accuracy of linear measurements on CBCT images related to presurgical implant treatment planning: a systematic review. Clin Oral Implants Res. 2018;29(Suppl 16):393–415.
  2. Tyndall DA, Price JB, Tetradis S, et al. Position statement of the American Academy of Oral and Maxillofacial Radiology on selection criteria for the use of radiology in dental implantology with emphasis on cone beam computed tomography. Oral Surg Oral Med Oral Pathol Oral Radiol. 2012;113:817–826.
  3. Jacobs R, Salmon B, Codari M, Hassan B, Bornstein MM. Cone beam computed tomography in implant dentistry: recommendations for clinical use. BMC Oral Health. 2018;18:88.
  4. Menezes CC, Janson G, da Silveira Massaro C, Cambiaghi L, Garib DG. Precision, reproducibility, and accuracy of bone crest level measurements of CBCT cross sections using different resolutions. Angle Orthod. 2016;86:535–542.

This information originally appeared in Alqallaf H, Su FY, Goel A, Lin WS. Utilizing a digital workflow for implant treatment planning. Decisions in Dentistry. 2021;7(5)12-14,16-17.

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