Maxillary Central Incisor– Incisive Canal Relationship: A Cone Beam Computed Tomography Study Joseph Y.K. Kan, DDS, MS Professor, Department of Restorative Dentistry, Loma Linda University School of Dentistry, Loma Linda, California, USA. Kitichai Rungcharassaeng, DDS, MS Associate Professor, Department of Orthodontics and Dentofacial Orthopedics, Loma Linda University School of Dentistry, Loma Linda, California, USA. Phillip Roe, DDS, MS Assistant Professor, Department of Restorative Dentistry, Loma Linda University School of Dentistry, Loma Linda, California, USA. Juan Mesquida, DDS Private Practice, Marlow, United Kingdom. Pakawat Chatriyanuyoke, DDS, MS Assistant Professor, Department of Restorative Dentistry, Loma Linda University School of Dentistry, Loma Linda, California, USA. Joseph M. Caruso, DDS, MS, MPH Professor and Chair, Department of Orthodontics and Dentofacial Orthopedics, Loma Linda University School of Dentistry, Loma Linda, California, USA. Correspondence to: Dr Joseph Kan Center for Prosthodontics and Implant Dentistry, Loma Linda University School of Dentistry, 11092 Anderson St, Loma Linda, CA 92350. Email: [email protected] 180 THE AMERICAN JOURNAL OF ESTHETIC DENTISTRY © 2012 BY QUINTESSENCE PUBLISHING CO, INC. PRINTING OF THIS DOCUMENT IS RESTRICTED TO PERSONAL USE ONLY. NO PART MAY BE REPRODUCED OR TRANSMITTED IN ANY FORM WITHOUT WRITTEN PERMISSION FROM THE PUBLISHER. The purpose of this study was to determine the maxillary central incisor–incisive canal (CI-IC) relationship by comparing the visibility of the incisive canal on the two-dimensional sagittal images of the central incisors acquired from two cone beam computed tomography (CBCT) reconstruction modalities. A retrospective review of CBCT images from 60 patients (30 men and 30 women) with a mean age of 57.9 years (range: 19 to 83 years) was conducted. The CBCT images were evaluated using the manufacturer’s recommended method (MRM) and a modified method (MM). The CI-IC relationship was classified as invisible, partially visible, or completely visible. The frequency distribution of the CI-IC relationships of the 60 samples indicated that the visibility of the incisive canal is significantly greater at all locations when using the MRM compared to the MM and on the right central incisor versus the left central incisor. Evaluation of the CI-IC relationship using the proposed method may allow the clinician to better determine whether additional surgical procedures are necessary when planning immediate implant placement and provisionalization at the maxillary central incisor positions. (Am J Esthet Dent 2012;2:180–187.) he success of immediate implant placement and provisionalization is greatly Tdependent on the initial implant stability.1,2 Initial stability for immediate im- plant placement in the anterior maxilla requires the implant to engage 4 to 5 mm of bone apical to the root tip socket and palatal bone.3,4 However, when a failing maxillary central incisor is to be replaced, the proximity of the incisive canal can become a limiting factor5,6 that precludes immediate implant placement. There- fore, it is imperative that the central incisor–incisive canal (CI-IC) relationship is accurately identified during diagnosis and treatment planning. Due to its accuracy7–11 and relatively low effective dose of ionizing radiation,12 the use of cone beam computed tomography (CBCT) during treatment planning for implant placement has increased. Because the diagnostic features of CBCT can be customized, it is important that the data are properly reconstructed to provide an accurate diagnosis. The purpose of this study was to determine the CI-IC relationship by compar- ing the visibility of the incisive canal on two-dimensional (2D) sagittal images of the central incisors acquired from two CBCT reconstruction modalities. The clini- cal implications are also discussed. 181 VOLUME 2 • NUMBER 3 • FALL 2012 © 2012 BY QUINTESSENCE PUBLISHING CO, INC. PRINTING OF THIS DOCUMENT IS RESTRICTED TO PERSONAL USE ONLY. NO PART MAY BE REPRODUCED OR TRANSMITTED IN ANY FORM WITHOUT WRITTEN PERMISSION FROM THE PUBLISHER. KAN ET AL MATERIALS AND METHODS Communications in Medicine) file and opened using a proprietary software Patient selection viewer (i-CAT Vision, Imaging Sciences International). This retrospective study was approved In the axial view, an open polygon by the Institutional Review Board of was created using 11 mapping points. Loma Linda University and was con- From this radiographic mapping, a pan- ducted at the Center for Prosthodontics oramic view and a series of 2D cross- and Implant Dentistry, Loma Linda Uni- sectional images were created along versity School of Dentistry, Loma Linda, the open polygon. The reconstructed California. Treatment records and CBCT 2D cross-sectional (sagittal) images of images of patients who received treat- the maxillary central incisors were used ment from May 2006 to November 2009 to evaluate the CI-IC relationship. In this were reviewed. To be included in this study, two reconstruction modalities study, the patients must (1) be at least were used: 18 years of age, (2) have both central incisors, (3) have stable posterior oc- 1. Manufacturer’s recommended meth- clusal support, and (4) show no clinical od (MRM): Nine mapping points or radiographic evidence of alterations were evenly distributed on the alveo- to the anterior maxilla (surgical altera- lar housings or, in their absence, on tion and/or trauma). the residual ridge, following its con- tour in a curvilinear fashion (Figs 1a Data reconstruction and and 1b). image acquisition 2. Modified method (MM): Five anterior mapping points were adjusted to All CBCT scans were performed us- create a line tangential to the ante- ing the i-CAT system (Classic i-CAT, rior maxillary arch form at the midline Imaging Sciences International). Fol- and parallel to the facial surface of lowing the primary reconstruction, the the central incisors (Figs 2a and 2b). volumetric data were opened using the 2D orthogonal multiplanar reformatting Data collection viewer for the secondary reconstruc- tion. The image was rotated so that the The visibility of the incisive canal on palatal plane (the line joining the an- nine reconstructed 2D sagittal images terior and posterior nasal spines) was of each maxillary central incisor (mid- parallel to the horizontal and vertical dle of the tooth [Mid] and 0.8, 1.6, and reference lines in the sagittal and axial 2.4 mm mesial [M] and distal [D] to views, respectively. In the coronal view, Mid) using both CBCT modalities were the image was rotated so that the verti- recorded and compared. The visibility cal line bisecting the facial structures of the incisive canal was classified as was perpendicular to the horizontal invisible, partially visible, or completely reference line. The data were exported visible. Descriptive statistics were used as a DICOM (Digital Imaging and to analyze the data. 182 THE AMERICAN JOURNAL OF ESTHETIC DENTISTRY © 2012 BY QUINTESSENCE PUBLISHING CO, INC. PRINTING OF THIS DOCUMENT IS RESTRICTED TO PERSONAL USE ONLY. NO PART MAY BE REPRODUCED OR TRANSMITTED IN ANY FORM WITHOUT WRITTEN PERMISSION FROM THE PUBLISHER. KAN ET AL Axial slice position: 66.40 b Figs 1a and 1b (a) Axial view with the open polygon tool bisecting the alveolar process; (b) sagittal view a of the failing tooth using the MRM. Axial slice position: 66.40 b Figs 2a and 2b (a) Axial view with the open polygon tool parallel to the facial surface of the maxillary central incisors; (b) sagittal view of a the failing tooth using the MM. 183 VOLUME 2 • NUMBER 3 • FALL 2012 © 2012 BY QUINTESSENCE PUBLISHING CO, INC. PRINTING OF THIS DOCUMENT IS RESTRICTED TO PERSONAL USE ONLY. NO PART MAY BE REPRODUCED OR TRANSMITTED IN ANY FORM WITHOUT WRITTEN PERMISSION FROM THE PUBLISHER. KAN ET AL IV IV PV PV CV CV 100 100 1.7 1.7 6.7 16.7 16.7 20.0 23.3 28.4 30.0 30.0 40.0 75 53.4 75 35.0 46.7 35.0 33.3 76.7 36.7 38.3 85.0 91.7 50 50 50.0 38.3 78.3 68.3 41.6 58.3 25 48.3 38.3 25 50.0 33.3 40.0 20.0 21.7 11.7 20.0 8.3 6.6 11.7 0 3.3 3.3 1.7 0 2.4D 1.6D 0.8D Mid 0.8M 1.6M 2.4M 2.4D 1.6D 0.8D Mid 0.8M 1.6M 2.4M Fig 3 Percentage distribution of incisive canal Fig 4 Percentage distribution of incisive canal visibility on the maxillary right central incisor visibility on the maxillary left central incisor sagittal images using the MRM. IV = invisible; sagittal images using the MRM. IV = invisible; PV = partially visible; CV = completely visible. PV = partially visible; CV = completely visible. IV IV PV PV CV CV 100 100 3.3 8.3 1.7 11.7 10.0 1.7 6.7 31.7 33.3 25.0 75 51.7 75 38.3 40.0 75.0 50 50 100 100 100 100 96.7 91.7 36.7 90.0 73.3 66.7 35.0 25 48.3 25 55.0 30.0 20.0 13.3 0 5.0 0 2.4D 1.6D 0.8D Mid 0.8M 1.6M 2.4M 2.4D 1.6D 0.8D Mid 0.8M 1.6M 2.4M Fig 5 Percentage distribution of incisive canal Fig 6 Percentage distribution of incisive canal visibility on the maxillary right central incisor visibility on the maxillary left central incisor sagittal images using the MM. IV = invisible; sagittal images using the MM. IV = invisible; PV = partially visible; CV = completely visible. PV = partially visible; CV = completely visible. RESULTS sagittal images are presented in Figs 3 to 6. The visibility of the incisive canal A total of 60 patients (30 men and was significantly greater at all locations 30 women) with a mean age of 57.9 (2.4 mm D to 2.4 mm M) when using years (range: 19 to 83 years) were in- the MRM (Figs 3 and 4) as opposed to cluded in this study.