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Third-molar impaction diagnostic with cone-beam computerized tomography
International Congress Series 1281 (2005) 1196 – 1199
www.ics-elsevier.com
Third-molar impaction diagnostic with cone-beam computerized tomography Reyes EncisoT, Robert A. Danforth, Emanuel S. Alexandroni, Ahmed Memon, James Mah University of Southern California, School of Dentistry, Los Angeles, USA
Abstract. Precise three-dimensional localization of impacted third molars as it relates to the inferior dental canal (IDC) is critical to their clinical management and highly influences surgical outcomes. Recently introduced dental 3D volumetric imaging systems coupled with semi-automatic modelling techniques allows 3D visualization of the IDC and the third molar. In this study, the spatial relationship of impacted third molars is described using imaging data obtained from various 3D volumetric imaging systems (NewTom 9000, Morita Accuitomo and Hitachi Mercuray). D 2005 CARS & Elsevier B.V. All rights reserved. Keywords: Third molar; Impacted; Diagnosis; CT; Inferior dental canal
1. Introduction The risks from potential treatment complications and resultant patient morbidity associated with complex impacted bwisdom teethQ are well known [1]. There is particular concern for inferior alveolar nerve damage during the surgery due to an unfavorable tooth nerve relationship. Nerve damage in such situations has been reported to range from 0.4% to 5.5% with permanent damage reported from 0.3% to 0.9% [1,2]. Further contributing to this problem are the limitations of traditional two-dimensional radiographs [3,4]. To improve risk assessment evaluation, use of three-dimensional imaging has been advocated [5]. Despite 3D images produced in multiple planes, the viewer is still required to organize numerous flat images into a bmental modelQ of the proposed surgical site. The objective of this study was to create a virtual image model of a proposed surgical site for a mandibular third molar using data from a 3D cone-beam volumetric imaging T Corresponding author. Tel.: +1 213 821 6730; fax: +1 213 740 5715. E-mail address: [email protected] (R. Enciso). 0531-5131/ D 2005 CARS & Elsevier B.V. All rights reserved. doi:10.1016/j.ics.2005.03.149
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device. Development of an accurate virtual model would seem a valuable asset for improving risk assessment evaluation. 2. Materials and methods In this section we will review the imaging devices, the subject’s characteristics and the methods. 2.1. Devices The three maxillofacial volumetric imaging systems used in the course of this research were the NewTom 9000 (QR SRL, Via Silvestrini 20, 37135 Verona, Italy), the Hitachi MercuRay (Hitachi Medical Systems America, Inc., 1959 Summit Commerce Park, Twinsburg, OH 44087) and the 3DX Accuitomo (J. Morita USA Inc., 9 Mason, Irvine, CA 92618). The main differences are summarized in a previous publication [6]. NewTom 9000 and Accuitomo have 8-bit sensors with 256 grayscale, compared to 3DX Accuitomo with 12bit sensors (4096 grayvalues). The 3DX produces lower radiation effective dose (0.0074 mSv) compared to the NewTom 9000 (0.04–0.05 mSv). There is no available data for the Hitachi device. The imaging area is substantially smaller for the 3DX (3.0 4.0 cm) compared to the NewTom 9000 (13 13 cm). The Hitachi can run in three modes: D mode is 5.12 cm, P mode is 11.7 cm and C mode is 15.0 cm on height. 2.2. Software Amira 3.1 (Mercury Computer Systems Inc., 199 Riverneck Rd., Chelmsford, MA 01824) is an advanced three-dimensional visualization software suite. DICOM CT data can be loaded and used to perform automatic and interactive segmentation followed by the creation of 3D meshes to visualize three-dimensional anatomical landmarks. 2.3. Subjects Prior to extraction surgery four patients were referred for a cone-beam CT of the mandible. One patient was imaged with the NewTom 9000 at the Redmond Imaging Center (University of Southern California, Los Angeles, CA); one was imaged with the
Fig. 1. NewTom 9000. Three-dimensional models of the third molar and the inferior dental canal show that the IDC passes in between the roots.
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R. Enciso et al. / International Congress Series 1281 (2005) 1196–1199
Fig. 2. Hitachi. Three-dimensional models of the third molar and the inferior dental canal show that the IDC is lingual to the roots of the third molar.
3DX Accuitomo at Newhall Dental Imaging (Newhall, CA) and two were imaged with the Hitachi MercuRay at Advanced Dental Imaging (Las Vegas, NV). 2.4. Methods The reconstructed stacks of axial CT images were exported to DICOM format and then imported in Amira software. After contrast enhancement, the mandibular canal and the third molar were manually segmented using Amira’s label field function (between 10 and 20 min per site depending on the complexity of the case). Thereafter, the software allows for creation of a mesh or 3D model of each object using the SurfaceGen function, which can then be rendered from any point of view and with any color of choice. Furthermore, the segmented mandibular canal and third molar can be visualized within the context of the mandible using Amira’s Voltex function. The alpha value/opacity of the mandible can be adjusted and the overall model can be rotated in virtual space, allowing anatomic visualization from various angles. Amira also allows users to make measurements on the model, permitting an accurate measurement of a tooth’s proximity to the mandibular canal. 3. Results and discussion Each of the four patients in our study was imaged with one of the devices described in Section 2.1. Using methods described in Section 2.4, the proposed surgical site was
Fig. 3. Hitachi. The 3D models show the unerupted third molar is lingual to the canal.
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Fig. 4. Accuitomo. The rough 3D model shows the IDC is in proximity to the third molar.
segmented and modelled with results shown in Fig. 1 (NewTom 9000), Figs. 2 and 3 (Hitachi), and Fig. 4 (Accuitomo). The 3D model of the tooth and the canal were created and the surgeon could visualize in three dimensions the tooth nerve relationship. This research project does not allow one to conclude which of the volumetric imaging devices is better suited for imaging of a third-molar impaction. 4. Conclusions An interactive virtual model of a proposed third molar surgical site was developed including the third molar and the inferior dental canal. Anatomical accuracy, benefit for risk assessment and cost effectiveness of developing the model require further investigation. References [1] E. Valmaseda-Castellon, et al., Inferior alveolar nerve damage after lower third molar surgical extraction: a prospective study of 1117 surgical extractions, Oral Surg. Oral Med. Oral Pathol. Oral Radiol. Endo. 92 (2001) 377 – 383. [2] F.A. Carmichael, D.A. McGowan, Incidence of nerve damage following third molar removal: a West of Scotland Oral Surgery Research Group study, Br. J. Oral Maxillofac. Surg. 30 (1992) 78 – 82. [3] G.W. Bell, et al., The accuracy of dental panoramic tomographs in determining the root morphology of mandibular third molar teeth before surgery, Oral Surg. Oral Med. Oral Pathol. Oral Radiol. Endo. 95 (2003) 119 – 125. [4] N.A. Drage, T.R. Renton, Inferior alveolar nerve injury related to mandibular third molar surgery: an unusual case presentation, Oral Surg. Oral Med. Oral Pathol. Oral Radiol. Endo. 93 (2002) 359 – 361. [5] H. Maegawa, et al., Preoperative assessment of the relationship between the mandibular third molar and the mandibular canal by axial computed tomography with coronal and sagitta reconstruction, Oral Surg. Oral Med. Oral Pathol. Oral Radiol. Endo. 96 (2003) 639 – 646. [6] R.A. Danforth, J. Peck, P. Hall, Cone beam volume tomography: an imaging option for diagnosis of complex mandibular third molar anatomical relationships, J. Calif. Dent. Assoc. 31 (2003) 847 – 852.
www.ics-elsevier.com
Third-molar impaction diagnostic with cone-beam computerized tomography Reyes EncisoT, Robert A. Danforth, Emanuel S. Alexandroni, Ahmed Memon, James Mah University of Southern California, School of Dentistry, Los Angeles, USA
Abstract. Precise three-dimensional localization of impacted third molars as it relates to the inferior dental canal (IDC) is critical to their clinical management and highly influences surgical outcomes. Recently introduced dental 3D volumetric imaging systems coupled with semi-automatic modelling techniques allows 3D visualization of the IDC and the third molar. In this study, the spatial relationship of impacted third molars is described using imaging data obtained from various 3D volumetric imaging systems (NewTom 9000, Morita Accuitomo and Hitachi Mercuray). D 2005 CARS & Elsevier B.V. All rights reserved. Keywords: Third molar; Impacted; Diagnosis; CT; Inferior dental canal
1. Introduction The risks from potential treatment complications and resultant patient morbidity associated with complex impacted bwisdom teethQ are well known [1]. There is particular concern for inferior alveolar nerve damage during the surgery due to an unfavorable tooth nerve relationship. Nerve damage in such situations has been reported to range from 0.4% to 5.5% with permanent damage reported from 0.3% to 0.9% [1,2]. Further contributing to this problem are the limitations of traditional two-dimensional radiographs [3,4]. To improve risk assessment evaluation, use of three-dimensional imaging has been advocated [5]. Despite 3D images produced in multiple planes, the viewer is still required to organize numerous flat images into a bmental modelQ of the proposed surgical site. The objective of this study was to create a virtual image model of a proposed surgical site for a mandibular third molar using data from a 3D cone-beam volumetric imaging T Corresponding author. Tel.: +1 213 821 6730; fax: +1 213 740 5715. E-mail address: [email protected] (R. Enciso). 0531-5131/ D 2005 CARS & Elsevier B.V. All rights reserved. doi:10.1016/j.ics.2005.03.149
R. Enciso et al. / International Congress Series 1281 (2005) 1196–1199
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device. Development of an accurate virtual model would seem a valuable asset for improving risk assessment evaluation. 2. Materials and methods In this section we will review the imaging devices, the subject’s characteristics and the methods. 2.1. Devices The three maxillofacial volumetric imaging systems used in the course of this research were the NewTom 9000 (QR SRL, Via Silvestrini 20, 37135 Verona, Italy), the Hitachi MercuRay (Hitachi Medical Systems America, Inc., 1959 Summit Commerce Park, Twinsburg, OH 44087) and the 3DX Accuitomo (J. Morita USA Inc., 9 Mason, Irvine, CA 92618). The main differences are summarized in a previous publication [6]. NewTom 9000 and Accuitomo have 8-bit sensors with 256 grayscale, compared to 3DX Accuitomo with 12bit sensors (4096 grayvalues). The 3DX produces lower radiation effective dose (0.0074 mSv) compared to the NewTom 9000 (0.04–0.05 mSv). There is no available data for the Hitachi device. The imaging area is substantially smaller for the 3DX (3.0 4.0 cm) compared to the NewTom 9000 (13 13 cm). The Hitachi can run in three modes: D mode is 5.12 cm, P mode is 11.7 cm and C mode is 15.0 cm on height. 2.2. Software Amira 3.1 (Mercury Computer Systems Inc., 199 Riverneck Rd., Chelmsford, MA 01824) is an advanced three-dimensional visualization software suite. DICOM CT data can be loaded and used to perform automatic and interactive segmentation followed by the creation of 3D meshes to visualize three-dimensional anatomical landmarks. 2.3. Subjects Prior to extraction surgery four patients were referred for a cone-beam CT of the mandible. One patient was imaged with the NewTom 9000 at the Redmond Imaging Center (University of Southern California, Los Angeles, CA); one was imaged with the
Fig. 1. NewTom 9000. Three-dimensional models of the third molar and the inferior dental canal show that the IDC passes in between the roots.
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Fig. 2. Hitachi. Three-dimensional models of the third molar and the inferior dental canal show that the IDC is lingual to the roots of the third molar.
3DX Accuitomo at Newhall Dental Imaging (Newhall, CA) and two were imaged with the Hitachi MercuRay at Advanced Dental Imaging (Las Vegas, NV). 2.4. Methods The reconstructed stacks of axial CT images were exported to DICOM format and then imported in Amira software. After contrast enhancement, the mandibular canal and the third molar were manually segmented using Amira’s label field function (between 10 and 20 min per site depending on the complexity of the case). Thereafter, the software allows for creation of a mesh or 3D model of each object using the SurfaceGen function, which can then be rendered from any point of view and with any color of choice. Furthermore, the segmented mandibular canal and third molar can be visualized within the context of the mandible using Amira’s Voltex function. The alpha value/opacity of the mandible can be adjusted and the overall model can be rotated in virtual space, allowing anatomic visualization from various angles. Amira also allows users to make measurements on the model, permitting an accurate measurement of a tooth’s proximity to the mandibular canal. 3. Results and discussion Each of the four patients in our study was imaged with one of the devices described in Section 2.1. Using methods described in Section 2.4, the proposed surgical site was
Fig. 3. Hitachi. The 3D models show the unerupted third molar is lingual to the canal.
R. Enciso et al. / International Congress Series 1281 (2005) 1196–1199
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Fig. 4. Accuitomo. The rough 3D model shows the IDC is in proximity to the third molar.
segmented and modelled with results shown in Fig. 1 (NewTom 9000), Figs. 2 and 3 (Hitachi), and Fig. 4 (Accuitomo). The 3D model of the tooth and the canal were created and the surgeon could visualize in three dimensions the tooth nerve relationship. This research project does not allow one to conclude which of the volumetric imaging devices is better suited for imaging of a third-molar impaction. 4. Conclusions An interactive virtual model of a proposed third molar surgical site was developed including the third molar and the inferior dental canal. Anatomical accuracy, benefit for risk assessment and cost effectiveness of developing the model require further investigation. References [1] E. Valmaseda-Castellon, et al., Inferior alveolar nerve damage after lower third molar surgical extraction: a prospective study of 1117 surgical extractions, Oral Surg. Oral Med. Oral Pathol. Oral Radiol. Endo. 92 (2001) 377 – 383. [2] F.A. Carmichael, D.A. McGowan, Incidence of nerve damage following third molar removal: a West of Scotland Oral Surgery Research Group study, Br. J. Oral Maxillofac. Surg. 30 (1992) 78 – 82. [3] G.W. Bell, et al., The accuracy of dental panoramic tomographs in determining the root morphology of mandibular third molar teeth before surgery, Oral Surg. Oral Med. Oral Pathol. Oral Radiol. Endo. 95 (2003) 119 – 125. [4] N.A. Drage, T.R. Renton, Inferior alveolar nerve injury related to mandibular third molar surgery: an unusual case presentation, Oral Surg. Oral Med. Oral Pathol. Oral Radiol. Endo. 93 (2002) 359 – 361. [5] H. Maegawa, et al., Preoperative assessment of the relationship between the mandibular third molar and the mandibular canal by axial computed tomography with coronal and sagitta reconstruction, Oral Surg. Oral Med. Oral Pathol. Oral Radiol. Endo. 96 (2003) 639 – 646. [6] R.A. Danforth, J. Peck, P. Hall, Cone beam volume tomography: an imaging option for diagnosis of complex mandibular third molar anatomical relationships, J. Calif. Dent. Assoc. 31 (2003) 847 – 852.