Dental Implant Planning using Cone Beam CT imaging: a pictorial guide.

Transcription

1 Dental Implant Planning using Cone Beam CT imaging: a pictorial guide. Poster No.: C-1970 Congress: ECR 2015 Type: Educational Exhibit Authors: S. R. Rice, G. Price, S. Morley, T. Beale; London/UK Keywords: Education and training, Surgery, Structured reporting, Education, Cone beam CT, Ear / Nose / Throat DOI: /ecr2015/C-1970 Any information contained in this pdf file is automatically generated from digital material submitted to EPOS by third parties in the form of scientific presentations. References to any names, marks, products, or services of third parties or hypertext links to thirdparty sites or information are provided solely as a convenience to you and do not in any way constitute or imply ECR's endorsement, sponsorship or recommendation of the third party, information, product or service. ECR is not responsible for the content of these pages and does not make any representations regarding the content or accuracy of material in this file. As per copyright regulations, any unauthorised use of the material or parts thereof as well as commercial reproduction or multiple distribution by any traditional or electronically based reproduction/publication method ist strictly prohibited. You agree to defend, indemnify, and hold ECR harmless from and against any and all claims, damages, costs, and expenses, including attorneys' fees, arising from or related to your use of these pages. Please note: Links to movies, ppt slideshows and any other multimedia files are not available in the pdf version of presentations. Page 1 of 32

2 Learning objectives The purpose of this educational exhibit is: To understand the indications and advantages for CBCT in dental implant planning; To illustrate the appearances of normal anatomy and the key structures required for surgical planning; To explain the function and design of dental implants. Background The use of osseointergrated alveolar dental implants has revolutionised oral rehabilitation and is now commonly undertaken by non-specialists in general dental practice. Accurate radiological and surgical planning is vital for optimum implant placement. Imaging evaluation is essential to determine the appropriate number and type of implants to be placed, based on assessment of the alveolar ridge, proximity to adjacent structures and available space (Table 1 on page 3). Moreover, imaging now facilitates the production of stereolithographic guides to ensure implants are placed precisely at the desired location (Fig. 1 on page 4). Page 2 of 32

3 Fig. 1: Stereolithographic guide References: AEGIS Publications Cone beam computed tomography (CBCT - Fig. 2 on page 5) offers excellent spatial resolution down to 60 microns, reduced radiation dose and gives accurate cross-sectional 1 and 3D reconstruction of the dento-maxillofacial structures. It was first used in vascular imaging but was extended to dental imaging in the 1990s and is now extensively used, increasingly available at the point of care in the dental office. 2 Images for this section: Page 3 of 32

4 Table 1 Page 4 of 32

5 Fig. 1: Stereolithographic guide Page 5 of 32

6 Page 6 of 32

7 Fig. 2: CBCT unit (Accuitomo 170) Page 7 of 32

8 Findings and procedure details The protocol for implant planning using Cone Beam CT (CBCT) imaging includes the following: Field of View CBCT units allow the operator to visualise a minimum region of interest in the mesiodistal, bucco-lingual and superio-inferior dimensions, compatible with accurate implant placement planning. Units are now capable of capturing very small volumes (e.g. 3 cm 3 cm) thus markedly reducing the radiation dose (Table 2 on page 24). Dental Considerations Initial radiological assessment of CBCT imaging should include a comprehensive assessment of the dentition, if present. In particular, the radiologist should note the following: functional state of teeth adjacent to site of proposed alveolar implantation; presence of retained roots; angulation of adjacent roots; presence of occult disease e.g residual cysts or bone sequestration. Alveolar Considerations Alveolar ridge resorption is evident after tooth loss, most commonly presenting as reduction in ridge height and width. Alveolar ridge assessment is therefore essential as it predicts implant stability and success. CBCT enables the precise measurement of the alveolar dimensions in all planes. Normal alveolar dimensions are: Width >10mm Height >8mm An example of the normal alveolar anatomy is shown in Fig. 3 on page 19 Page 8 of 32

9 Fig. 3: Alveolar cross section maxilla demonstrating normal ridge height and width. References: Handelsman M. Surgical guidelines for dental implant placement. Br Dent J: 2006;201, Deficiency of the buccal cortex (cortical plate) after tooth extraction can present significant difficulty in implant reconstruction. The buccal cortical plate with a thickness <2 mm next to an implant has a higher risk of subsequent resorption. 4 Typically, implants require a minimum of 2mm bone between them and adjacent teeth (Fig. 4 on page 20) and 7mm of bone between implants (Fig. 5 on page 21). Page 9 of 32

10 Fig. 4: Space required for implant placement between teeth to enable normal soft tissue growth References: Faculty of Dental Surgery and Faculty of General Dental Practice UK, Royal College of Surgeons of England Page 10 of 32

11 Fig. 5: Space required between multiple implants and interocclusal space requirements for satisfactory occlusal restoration References: Faculty of Dental Surgery and Faculty of General Dental Practice UK, Royal College of Surgeons of England 5mm intraocclusal space is required for restoration of the implant superstructure (Fig. 5 on page 21). The optimal position for implant placement is in the occlusal plane, in the long-axis of the alveolar ridge (Fig. 6 on page 22). Most available implantplanning software systems enable the user to orientate implants in the CBCT images for assessment. Page 11 of 32

12 Fig. 6: Optimal implant position within the alveolar ridge References: Faculty of Dental Surgery and Faculty of General Dental Practice UK, Royal College of Surgeons of England Bone Considerations Implants should be fully covered by the bone. The quality and quantity of local bone influences implant stability and is one of the main factors influencing implant survival 5 rates. Following CBCT, the radiologist should assess both the cortical and medullary portion of the bone and classify against the Lekholm and Zarb classification system 6 Page 12 of 32

13 Fig. 8 References: Emam HA, Stevens MR. Concepts in Bone Reconstruction for Implant Rehabilitation. In A Textbook of Advanced Oral and Maxillofacial Surgery. Type I - principally cortical bone Type II - thick cortical bone with densely trabeculated medullary spaces Type III - thinner cortex with densely trabeculated medullary spaces Type IV - thin cortex with sparsely trabeculated medullary spaces Bone quality and quantity is usually much better in the mandible and this is reflected in slightly better clinical success rates for dental implants. Bone density is greatest in the anterior mandible, followed by the anterior maxilla then posterior mandible. The least compact bone is typically found in the posterior maxilla. Extensive bone atrophy usually requires surgical correction such as bone grafting or bone augmentation in order to allow for proper implant placement. Anatomical Considerations Careful assessment of the local anatomical structures is essential to avoid damage to adjacent structures. In particular, paying attention to the borders of the maxillary sinus and the path of the inferior dental canal and mental foramen. Maxilla: Maxillary antra, nasal floor, incisive canal: Page 13 of 32

14 Fig. 9: Coronal CBCT demonstrating left maxillary sinus References: University College Hospital - London/UK Page 14 of 32

15 Fig. 10: Coronal CBCT demonstrating right maxillary sinus and right nasal floor. References: University College Hospital - London/UK Page 15 of 32

16 Fig. 11: Axial CBCT demonstrating the incisive canal References: University College Hospital - London/UK Mandible: Inferior dental canal, mental foramen, lingual foramen, submandibular fossa, mylohyoid ridge Page 16 of 32

17 Fig. 12: Sagittal CBCT demonstrating left inferior dental canal. References: University College Hospital - London/UK Page 17 of 32

18 Fig. 13: Sagittal and coronal CBCT demonstrating the left mental foramen. References: University College Hospital - London/UK Extragnathic Pathology Even with small volume CBCT the field of view may include local structures including the temporomandibular joint (TMJ); sinus floor; vertebral bodies etc. When reporting CBCT the radiologist should note TMJ pathology, cysts, mucosal thickening, carotid artery calcification, and other pathology that may require treatment prior to implant placement. Design of dental implants Dental implants are made of pure titanium with a machine-roughened surface to promote osseointegration. They are most commonly cylindrical, with lengths varying from 6mm 18mm depending on the clinical case. In general, greater bone contact results in more long-term success. Page 18 of 32

19 Implants most commonly comprise of three components ( Fig. 7 on page 23 ): Fixture - a hollow screw that is placed into the bone; Abutment - components crewed into to the implant fixture to support the superstructure; Superstructure - may be an implant crown, bridge or overdenture, cemented or screwed to the abutment. Fig. 7: Components of a dental implant References: Faculty of Dental Surgery and Faculty of General Dental Practice UK, Royal College of Surgeons of England Images for this section: Page 19 of 32

20 Fig. 3: Alveolar cross section maxilla demonstrating normal ridge height and width. Page 20 of 32

21 Fig. 4: Space required for implant placement between teeth to enable normal soft tissue growth Page 21 of 32

22 Fig. 5: Space required between multiple implants and interocclusal space requirements for satisfactory occlusal restoration Page 22 of 32

23 Fig. 6: Optimal implant position within the alveolar ridge Page 23 of 32

24 Fig. 7: Components of a dental implant Table 2: Effective dose comparison Page 24 of 32

25 Fig. 8 Page 25 of 32

26 Fig. 9: Coronal CBCT demonstrating left maxillary sinus Page 26 of 32

27 Fig. 10: Coronal CBCT demonstrating right maxillary sinus and right nasal floor. Page 27 of 32

28 Fig. 11: Axial CBCT demonstrating the incisive canal Page 28 of 32

29 Fig. 12: Sagittal CBCT demonstrating left inferior dental canal. Page 29 of 32

30 Fig. 13: Sagittal and coronal CBCT demonstrating the left mental foramen. Page 30 of 32

31 Conclusion The international congress of oral implantologists recommends CBCT for the surgical planning for implant placement. 3 General radiologists receive little training in oral and maxillofacial imaging. The key aspects for assessing the dento-maxillary structures for suitability for dental implant placement are: Assessment of the remaining dentition Bone height and width measurement Bone quality measurement To determine the long axis of alveolar bone To identify and highlight normal anatomical landmarks To detect any underlying pathology Personal information Dr Scott Rice: UCL Centre for Medical Imaging, 3rd Floor East, 250 Euston Road, London NW1 2PG. scott.rice@ucl.ac.uk Dr Gemma Price: UCLH Foundation NHS Trust, 235 Euston Road, London NW1 2BU. Dr Simon Morley: UCLH Foundation NHS Trust, 235 Euston Road, London NW1 2BU. Dr Timothy Beale: UCLH Foundation NHS Trust, 235 Euston Road, London NW1 2BU References Page 31 of 32

32 Scarfe WC, Levin MD, Gane D, Farman AG. Use of Cone Beam Computed Tomography in Endodontics. International Journal of Dentistry Shah N, Bansal N, Logani A. Recent advances in imaging technologies in dentistry. World Journal of Radiology 2014;6(10): Bornstein MM, Scarfe WC, Vaughn VM, Jacobs R. Cone Beam Computed Tomography in Implant Dentistry: A Systematic Review Focusing on Guidelines, Indications, and Radiation Dose Risks. Int J Oral Maxillofac Implants 2014;29 (Suppl): Keys, F. D. (2004). Predictable S ingle-tooth Peri-implant Esthetics: Five Diagnostic Keys. Compendium, 25(11), 895. Friberg, B., Gröndahl, K., Lekholm, U., & Brånemark, P. I. (2000). Long# term Follow#up of Severely Atrophic Edentulous Mandibles Reconstructed with Short Branemark Implants. Clinical implant dentistry and related research, 2(4), Lekholm U, Zarb GA. In: Patient selection and preparation. Tissue integrated prostheses: osseointegration in clinical dentistry. Branemark PI, Zarb GA, Albrektsson T, editor. Chicago: Quintessence Publishing Company; pp Page 32 of 32