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Table of Contents   
ORIGINAL RESEARCH  
Year : 2020  |  Volume : 31  |  Issue : 2  |  Page : 175-179
Cone beam computed tomographic–Based retrospective study on newark population for the assessment of distance between incisive canal and maxillary central incisors: Clinical implications


1 Department of Comprehensive Dentistry, Division of Oral and Maxillofacial Radiology, Thee University of Texas Health Science Center San Antonio, Texas, USA
2 Department of Oral and Maxillofacial Radiology, Rutgers School of Dental Medicine, Newark, NJ, USA
3 Department of Orthodontics, Rutgers School of Dental Medicine, Newark, NJ, USA
4 Department of Oral Medicine, Robert Schattner Center, University of Pennsylvania School of Dental Medicine, Philadelphia, PA, USA

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Date of Submission29-Jan-2019
Date of Decision12-May-2019
Date of Acceptance04-Sep-2019
Date of Web Publication19-May-2020
 

   Abstract 


Aims: To calculate the relative distance between the incisive canal and maxillary central incisors using cone beam computed tomography (CBCT) and utilize the results in treatment planning in a clinical setting. Methods and Materials: A retrospective study was conducted on CBCT taken for other purposes in the Oral and Maxillofacial Radiology Department. All the quantitative measurements were performed between the incisive canal and both maxillary central incisors using CBCT on 61 subjects. The anterior-posterior measurements were taken on both sides and the average of both values was considered for the statistical analysis. All the linear measurements were performed on the axial plane at three different vertical reference points located on the sagittal plane. Statistical Analysis: The interexaminer reliability was tested by interclass correlation coefficient using two-way mixed and absolute agreement model. The comparison of linear measurement among each level was done by “Repeated measure ANOVA” and contrast method was used for pair-wise comparison when repeated measure analysis of variance (ANOVA) was significant. Results: The average anterior-posterior distance between the maxillary central incisor roots and the incisive canal measured was approximately 5–6 mm. The incisive canal width increases from the root apex level of maxillary central incisors (P3) to the oral opening level of the incisive canal (P1). Conclusions: The results of our study could be helpful in a clinical setting requires significant retraction of maxillary incisors or implant placement in maxillary anterior region.

Keywords: Cone beam CT, incisive canal, maxillary central incisors, retraction

How to cite this article:
Khurana S, Parasher P, Mukherjee P, Mupparapu M, Lotlikar PP, Creanga AG. Cone beam computed tomographic–Based retrospective study on newark population for the assessment of distance between incisive canal and maxillary central incisors: Clinical implications. Indian J Dent Res 2020;31:175-9

How to cite this URL:
Khurana S, Parasher P, Mukherjee P, Mupparapu M, Lotlikar PP, Creanga AG. Cone beam computed tomographic–Based retrospective study on newark population for the assessment of distance between incisive canal and maxillary central incisors: Clinical implications. Indian J Dent Res [serial online] 2020 [cited 2020 Jul 10];31:175-9. Available from: http://www.ijdr.in/text.asp?2020/31/2/175/284590



   Introduction Top


Maxillary anterior teeth play an important role in esthetics, phonetics, and mastication.[1],[2] Because of the esthetic and functional significance, it is important to evaluate their position in three-dimensional planes before initiating orthodontic treatment. The anatomical structures that limit orthodontic tooth movement are periodontal apparatus, the pressure exerted by lips, cheeks, and tongue on the teeth, muscles, and connective tissue component of TMJ, contours of the integuments of the face, and the buccal and palatal cortical plates.[3],[4] The concept of “envelope of discrepancy” given by Proffit and Ackerman explains the changes possible with different types of orthodontic treatment such as camouflage orthodontic treatment, functional appliance therapy using growth modification, and surgical orthodontics.[5] These changes in all the planes are not uniform. The potential of changes is more in retraction and extrusion than protraction and intrusion.[6],[7],[8] According to the literature, the maximum amount of ~7 mm of change is possible by retraction of maxillary anteriors.[5] With the emerging trends of utilizing cone beam computed tomography (CBCT) in orthodontic diagnosis, it is now possible to identify structures which were not clearly visible earlier on two-dimensional radiographs. One such structure is the incisive canal on palatal aspect of maxillary incisors.

The incisive canal is present in the midline palatal to maxillary incisors [Figure 1]a and b]. The nasopalatine nerve and terminal branches of nasopalatine artery pass through the incisive canal and innervates the palatal aspect of six anterior maxillary teeth (canine to canine).[9] Exclusion criteria: 1) History of orthodontic treatment which can lead to bias in sample collection due to change in upper incisor to SN angle and upper incisor to NA angle. Due to the morphological variation of incisive canal anatomy, it is difficult to locate its exact location in association with maxillary incisor teeth. The uncertainty to locate the canal can cause root resorption postorthodontic retraction of anterior maxillary teeth.[10] Other complications include nonosseointegration of the implant and implant-related nerve injuries during or after implant placement.[11],[12] Although many authors[13],[14],[15] have well documented the morphology and approximation of the incisive canal to maxillary incisors, the purpose of this study was to generate data on a different population group with a mean age of 31 ± 3.04 years.
Figure 1: (a) 3D reconstruction and (b) Sagittal volume rendered images outlining the incisive canal

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   Subjects and Methods Top


The cross-sectional study was done in the Department of Oral and Maxillofacial Radiology, with the approval of Institutional Review Board. The large CBCT volume (16 × 13 cm) was extracted from the department's database. All the CBCT volumes were already acquired for some other purpose on iCAT 17-19 (Imaging Science International, Hatfield, PA) using 18.54 mA, 120 kV, a scanning time of 8.9 s, image acquisition at 0.3-mm voxel size. The CBCT volumes were viewed as multiplanar reformatted images at a reconstructed slice thickness of 1.5 mm. The following inclusion and exclusion criteria were used to retrospectively extract the data.

Inclusion criteria: 1) Large CBCT volume (16 × 13 cm) showing Glabella as the upper limit and Menton as the lower limit of the scan. 2) The patient age should be equal to greater than 18. 3) The scans were selected irrespective of gender. 4) Normal overjet and overbite with class I molar relationship. 5) The upper incisor to SN (sella-nasion) angle should be 103 ± 6°. 6) The upper incisor to NA (nasion to point A) angle should be 22 ± 6°.

Exclusion criteria: 1) History of previous orthodontic treatment. 2) Presence of any tooth or bone anomalies in the maxillary midline region. 3) Trauma to maxillary central incisors. 4) Any trauma to the maxillofacial region which could change the occlusal relationship between arches and mislead the occlusion categorization and 5) Any CBCT volumes that are not of diagnostic quality.

Any CBCT volumes that are not of diagnostic quality. A total number of 1,020 CBCT volumes were examined by two investigators taken between January 2010 and October 2017. In total, 61 CBCT volume that met our study criteria were included in this study. This study utilized Steiner's cephalometric analysis to evaluate the skeletal relationship. All the CBCT volumes were de-identified before performing any measurements.

Measurements on CBCT slices

After collecting all the data, all the images were saved in DICOM format and measurements were done in InVivo Dental imaging software (version 5.4.4, Anatomage, San Jose, CA). Before performing any measurement, all the images were realigned parallel to Frankfort-horizontal (FH) plane in the sagittal plane. All the linear measurements were done following Choa et al.[13] method at three different vertical reference points located on the sagittal plane[Figure 2]: 1) the palatal opening of the incisive canal (opening level, P1), (2) midlevel between the opening level and the root apex of the maxillary central incisors (midlevel, P2), and (3) the root apex of the maxillary central incisors (root apex level, P3).
Figure 2: Multiplanar reformatted-sagittal slice at the level of incisive foramen/nasopalatine canal showing three different vertical reference points. P1: The palatal opening of the incisive canal (opening level). P2: Midlevel between the opening level and the root apex of the maxillary central incisors. P3: The root apex of the maxillary central incisors (root apex level)

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At all the three different levels, landmarks were defined and measurements were performed as follows: Rm, the most medial point of the maxillary central incisor roots; Rp, the most posterior point of the maxillary central incisor roots; Cl, the most lateral point of the incisive canal; Rm-Rm, inter-root distance; Rp-Rp, posterior inter root distance; and Cl-Cl, canal width [Figure 3]a and b]; Ca, the most anterior point of the incisive canal; Cat, the tangent line through Ca; Rm-Cat, the distance from Rm to Cat; Rm-Canal, the distance from Rm to the anterior border of the incisive canal; and Cl-Root, the distance from Cl to the posterior border of the maxillary central incisor root [Figure 4]. The anteroposterior measurements were taken on both sides and the average of both values was considered for the statistical analysis.
Figure 3: (a) Diagrammatic representation (b) axial slice of CBCT showing. Rm: The most medial point of the maxillary central incisor roots. Rp: The most posterior point of the maxillary central incisor roots. Cl: The most lateral point of the incisive canal. Rm-Rm: Inter root distance; Rp-Rp: Posterior inter root distance; Cl-Cl: Canal width

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Figure 4: Diagrammatic representation showing. Ca: The most anterior point of the incisive canal. Cat: The tangent line through Ca. Rm-Cat: The distance from Rm to Cat. Rm-Canal: The distance from Rm to the anterior border of the incisive canal. Cl-Root: The distance from Cl to the posterior border of the maxillary central incisor root

Click here to view



   Results Top


The mean age of our sample set was 31 ± 3.04 and the measurements were not separately done on male or female.

Measurements to determine incisive canal width (CI-CI) and inter-root distance (Rm-Rm, Rp-Rp) of the maxillary central incisors at P1, P2, and P3 level

The incisive canal width (Cl-Cl) was determined 3.9 ± 0.60, 3.7 ± 0.66, and 3.2 ± 0.72 at P1, P2, and P3 levels, respectively. There was a statistically significant difference in canal width among all three levels (P-value <0.05). The canal width was smaller at P3 level than at P2 level and P1 level. Inter-root distance (Rm-Rm) was 2.7 ± 0.46, 3.5 ± 0.55, and 7.1 ± 0.54 mm at P1, P2, and P3 levels, respectively (P-value <0.05). Inter-root distance significantly increased from P1 to P3 levels. Posterior inter-root distance (Rp-Rp) was 7.4 ± 0.47, 7.3 ± 0.46, and 7.1 ± 0.54 mm at P1, P2, and P3 levels, respectively. Because of the taper of the root anatomy, at the apex, there was no point difference between Rm and Rp. Hence, Rm-Rm and Rp-Rp were the same at the P3 level. The inter-root distance (Rp-Rp) was significantly decreased from P1 to P2 level (P < 0.05) [Table 1] and [Graph 1].
Table 1: The width of the incisive canal and the distance between maxillary central incisor roots at P1, P2, and P3 levels

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Measurements to determine the proximity of the anterior border of the incisive canal to the maxillary central incisor root at P1, P2, and P3 level

The CI-root and Rm-Canal were not measured at P3 level, because the most posterior point of the root apex at P3 (Rp/RM) was away from the median plane and not in the line with the lateral border of the incisive canal (C1). It was not possible to draw a straight line from Rm/Rp to CI, and hence, linear measurement was not done. CI-root was 5.0 ± 0.60 mm, and 4.9 ± 0.66 mm at P1 and P2 levels, respectively. The measurement of Rm-Canal was 5.4 ± 0.66 at P1 and 5.3 ± 0.70 at P2 level. Rm- Cat was 5.3 ± 1.68, 5.2 ± 1.64, and 5.0 ± 1.95 at P1, P2, and P3 levels, respectively. The measurements of CI-root, Rm-Canal, and Rm-Cat did not show any statistically significant difference at different vertical levels [Table 2], [Graph 2].
Table 2: Distance between anterior border of the incisive canal (at three different levels) and maxillary central incisor roots

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The interclass correlation coefficient using two-way mixed and absolute agreement model showed very strong (range for different measurements 0.994–0.999) inter-observer relation between all measurements done at P1, P2, and P3 levels.


   Discussion Top


In this study, we found a mean anterior-posterior distance between maxillary central incisors and the incisive canal was 5–6 mm, which is in accordance with Choa et al.[13] study. The distance cannot be considered as the standard for maximum retraction for all the individuals because our results are slightly lesser than the literature.[11] The literature described the maximum anterior retraction possible is 7 mm.[5] The patients in which inter-root distance of maxillary central incisors is larger than the width of the incisive canal are at lower risk of canal perforation, and hence, maximum retraction possible could be more than 5–6 mm. The inter-root distance is well appreciated on axial slices of CBCT at different root levels. The measurements can be performed on CBCT before initiating any orthodontic treatment. The use of CBCT in orthodontic diagnosis could help prevent the complications of root resorption that may occur due to direct contact of maxillary incisor roots with the incisive canal.[10],[13]

With the advent of CBCT, pre- and postorthodontic treatment 3D superimposition of CBCT images is possible to appreciate changes of the position of the incisive canal. Chung et al.[10] in their article superimposed pre- and post-treatment CBCT by automatic voxel-by-voxel registration at the cranial base. They did not notice any change in the surrounding alveolar bone, the position of the central incisors in contact or approximation with the incisive canal, or the incisive canal itself.

The incisive foramen is an anatomic limiting factor for the implant placement as well. The results of our study should be taken into consideration before immediate implant placement. The incisive canal shows morphological and related dimensional variations.[14],[16],[17],[18],[19] Because of the morphological variation, the CBCT-guided diagnosis should be performed to evaluate the position of incisive canal foramen and its approximation with the maxillary incisor root. According to Kraut and Boyden[20] analysis in 4% of the cases, the size of the incisive canal did not allow implant placement. The incisive canal deflation and neurovascular bundle lateralization procedures can be performed to prevent nerve injury if the incisive foramen is in close contact with maxillary incisor roots.[20]

The gender morphological variations of the incisive canal are well documented in the literature.[14],[16],[19] In this study, we did not take separate measurements for males and females.

According to the study of Choa et al.,[13] there is no gender variation in any of the measurement. In Mraiwa et al.,[4] Güncü et al.,[14] and Bornstein et al.[19] study, the male showed larger mean canal diameter as compared with female. Further studies are needed on a larger sample size and measurements needed to be done separately on male and female groups. It would be important before performing orthodontic retraction. It would also be interesting to quantify these measurements in growing patients at different time points since orthodontic treatment is routinely performed in children and adolescents.

In this study, CBCT and InVivo software were used to analyze the incisive foramen and its approximation with maxillary incisor roots. The images were acquired at 300-micron voxel and large FOV was used. Although 300-micron resolutions are adequate, less than 100-micron resolutions are preferred. The authors recommend using smaller voxel size and small or medium FOV to improve the resolution of the image for measurements. The orthodontist and implantologist should consider CBCT for better diagnosis and treatment planning.


   Conclusions Top


  1. The results of our study could be clinically helpful to treatment plan orthodontic cases that require significant retraction of maxillary incisors. Authors recommend a pretreatment CBCT in cases that require maximum anterior retraction in the maxilla.
  2. The incisive canal is an important landmark that should be considered prior to placement of dental implants.


Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.



 
   References Top

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Güncü GN, Yıldırım YD, Yılmaz HG, Galindo-Moreno P, Velasco-Torres M, Al-Hezaimi K, et al. Is there a gender difference in anatomic features of incisive canal and maxillary environmental bone? Clin Oral Implants Res 2013;24:1023-6.  Back to cited text no. 14
    
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Matsumura T, Ishida Y, Kawabe A, Ono T. Quantitative analysis of the relationship between maxillary incisors and the incisive canal by cone-beam computed tomography in an adult Japanese population. Prog Orthod 2017;18:1-6.  Back to cited text no. 15
    
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Correspondence Address:
Dr. Priti P Lotlikar
Rutgers School of Dental Medicine, Department of Oral and Maxillofacial Radiology, 110 Bergen Street, Newark, NJ 07101-1709
USA
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/ijdr.IJDR_88_19

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