Comparison of landmark positions between Cone-Beam Computed Tomogram (CBCT) and Adjusted 2D lateral cephalogram

Soo-Jung Son; Youn-Sic Chun; Minji Kim

doi:10.4047/jkap.2014.52.3.222

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Son, Chun, and Kim: Comparison of landmark positions between Cone-Beam Computed Tomogram (CBCT) and Adjusted 2D lateral cephalogram

Original Article

J Korean Acad Prosthodont 2014;52(3):222-232.

Published online: 9 February 2014

DOI: https://doi.org/10.4047/jkap.2014.52.3.222

Comparison of landmark positions between Cone-Beam Computed Tomogram (CBCT) and Adjusted 2D lateral cephalogram

Soo-Jung Son, Youn-Sic Chun, Minji Kim^∗

Graduate School of Clinical Dentistry, Ewha Womans University, Seoul, Republic of Korea

^∗Corresponding Author: Minji Kim Mokdong Hospital, Ewha Womans University 911-1, Mokdong, Yangcheon-gu, Seoul, 158-710, Republic of Korea +82 2 2650 5112: e-mail, minjikim@ewha.ac.kr

Received 20 June 201411 July 2014 Accepted 14 July 2014

This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/3.0/) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

Purpose

This study aims to investigate if 2D analysis method is applicable to analysis of CBCT by comparing measuring points of CBCT with those of Adjusted 2D Lateral Cephalogram (Adj-Ceph) with magnification adjusted to 100% and finding out at which landmarks the difference in position appear.

Materials and methods

CBCT data and Adj-Ceph (100% magnification) data from 50 adult patients have been extracted as research objects, and the horizontal (Y axis) and vertical (Z axis) coordinates of landmarks were compared. Landmarks have been categorized into 4 groups by the position and whether they are bilaterally overlapped. Paired t-test was used to compare differences between Adj-Ceph and CBCT.

Results

Significant difference was found at 11 landmarks including Group B (S, Ar, Ba, PNS), Group C (Po, Or, Hinge axis, Go) and Group D (U1RP, U6CP, L6CP) in the horizontal (Y) axis while all the landmarks in vertical (Z) axis showed significant difference (P<.05). As a result of landmark difference analysis, a meaningful difference with more than 1 mm at 13 landmarks were indentifed in the horizontal axis. In the vertical axis, significant difference over 1 mm was detected from every landmark except Sella.

Conclusion

Using the conventional lateral cephalometric measurements on CBCT is insufficient. A new 3D analysis or a modified 2D analysis adjusted on 19 landmarks of the vertical axis and 13 of the horizontal axis are needed when implementing CBCT diagnosis.

Keywords: CBCT, Adjusted lateral cephalogram, Landmark differences

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Fig. 1.

CBCT image of 3D and MPR (multiplanar projection reformat) for 3D landmark identification.

Fig. 2.

X, Y, Z axis of CBCT. N, (0,0,0); X axis, (-), right, (+), left; Y axis, (-), anterior, (+), posterior; Z axis, (-), upper, (+), lower.

Fig. 3.

Y (Horizontal), Z (Vertical) axis of adjusted 2D lateral cephalogram. N (0,0); Y axis, (-), anterior, (+) posterior; Z axis, (-), upper, (+), lower.

Fig. 4.

Classification of landmarks' position. Group A (Anterior landmark, marked ▲), ANS, A, B, Pog, Gn, Me; Group B (middle and posterior landmark, marked), S, Ar, Ba, PNS; Group C (R, L overlapped landmark, marked ★), Po, Or, Hinge axis, Go; Group D (Dental landmark, marked ■), U1CP, U1RP, U6CP, L1CP, L1RP, L6CP; red round, Nasion.

Fig. 5.

Horizontal difference between Adjusted Cephalogram and CBCT (values of Y axis) (mm).

Fig. 6.

Vertical difference between Adjusted Cephalogram and CBCT (values of Z axis) (mm).

Table 1.

Definition of landmarks

Landmark		2D Definition	3D Definition
Group A	ANS	Tip of the anterior nasal spine	Anterior nasal spine
	A	Deepest point between ANS, and the upper incisal alveolus	Deepest point on contour of maxillary alveolar process
	B	Deepest point between Pogonion, and the lower incisal alveolus	Deepest point on contour of mandibular alveolar process
	Pog	Most anterior point of the symphysis	Most prominent point of mentum
	Gn	Most inferior point of the mandible in the midline	Lowest point on mentum
	Me	Most inferior point on the symphyseal outline	Most inferior point of mandible in the midline
Group B	S	Center of Sella Turcica	Center of Sella Turcica
	Ar	Intersection of inferior cranial base surface and posterior surface of condyle	Predicted intersection of inferior cranial base surface and posterior surface of condyle
	Ba	Most inferior point of the Occipital bone	Anterior midpoint on foramen magnum
	PNS	Tip of the posterior nasal spine	Posterior nasal spine
Group C	Po	Most superior point of the external auditory meatus	(R, L) Most superior point of external auditory meatus
	Or	Most inferior point of the Orbital contour	(R, L) Most inferior point of the orbital contour
	Hinge Axis	Center of rotation of the condyle	Center of rotation of the condyle
	Go	Lowest posterior and most outword point of the mandible	(R, L) Lowest posterior and most outward point of the mandible
Group D	U1CP	Tip of the crown of the upper incisor	(R, L) Tip of the crown of the upper incisor
	U1RP	Tip of the root of the upper incisor	(R, L) Tip of the root of the upper incisor
	U6CP	Mesiobuccal cusp tip of the upper 1 ^st molar	Mesiobuccal cusp tip of the upper 1 ^st molar
	L1CP	Tip of the crown of the lower incisor	Tip of the crown of the lower incisor
	L1RP	Tip of the root of the lower incisor	Tip of the root of the lower incisor
	L6CP	Mesiobuccal cusp tip of the lower 1 ^st molar	Mesiobuccal cusp tip of the lower 1 ^st molar

Table 2.

Horizontal difference between Adjusted 2D Lateral Cephalogram and CBCT (values of Y axis)

Landmark		Adj-Ceph (N = 50) Mean ± SD (mm)	CBCT (N = 50) Mean ± SD (mm)	Mean ± SD of the difference between Adj-Ceph and CBCT (mm)	P value
Group A	ANS	-3.48 ± 4.50	-4.26 ± 2.88	0.78 ± 3.21	.094
	A	-0.12 ± 4.10	-0.89 ± 2.93	0.77 ± 2.56	.039^∗
	B	1.95 ± 9.54	0.98 ± 8.38	0.97 ± 3.91	.086
	Pog	0.61 ± 10.81	-0.19 ± 9.30	0.80 ± 4.43	.208
	Gn	3.14 ± 11.13	4.09 ± 9.55	1.34 ± 4.58	.044^∗
	Me	7.85 ± 10.73	6.58 ± 9.27	1.27 ± 4.57	.055
Group B	S	71.11 ± 4.10	65.01 ± 3.54	6.10 ± 1.53	<.001^∗∗
	Ar	86.79 ± 5.77	78.49 ± 5.01	8.30 ± 2.83	<.001^∗∗
	Ba	97.10 ± 6.48	87.93 ± 5.17	9.18 ± 3.19	<.001^∗∗
	PNS	47.85 ± 4.60	45.24 ± 3.52	2.61 ± 3.10	<.001^∗∗
	Po	97.16 ± 6.03	87.00 ± 5.05	10.16 ± 3.06	<.001^∗∗
Group C	Or	12.02 ± 3.07	9.22 ± 2.35	2.79 ± 2.49	<.001^∗∗
	Hinge Axis	82.38 ± 5.48	75.55 ± 4.75	6.83 ± 2.39	<.001^∗∗
	Go	76.69 ± 7.54	68.59 ± 6.46	8.10 ± 3.66	<.001^∗∗
Group D	U1CP	-7.87 ± 6.05	-6.99 ± 4.89	-0.88 ± 3.17	.055
	U1RP	4.60 ± 4.24	3.24 ± 3.49	1.50 ± 2.78	.001^∗∗
	U6CP	27.07 ± 5.91	21.52 ± 4.44	5.55 ± 4.11	<.001^∗∗
	L1CP	-6.45 ± 6.93	-6.03 ± 6.25	-0.42 ± 3.14	.346
	L1RP	3.79 ± 8.98	2.84 ± 7.87	0.94 ± 9.79	.498
	L6CP	21.24 ± 7.33	18.23 ± 6.72	3.01 ± 3.39	<.001^∗∗

^∗ P<.05,

^∗∗ P<.01.

(-) sign on Mean ± SD of Adjusted 2D Lateral Cephalogram and Mean ± SD of CBCT refers the given landmark is located anterior to the datum point (Nasion / Z axis).

(-) sign on Mean ± SD of Difference between Adjusted 2D Lateral Cephalogram and CBCT means Landmark on Adjusted Cephalogram is more anterior than CBCT.

Table 3.

Vertical difference between Adjusted 2D Lateral Cephalogram and CBCT (values of Z axis)

Landmark		Conventional Cephalogram (N = 50) Mean ± SD (mm)	CBCT (N = 50) Mean ± SD (mm)	Mean ± SD of the difference between Adj-Ceph and CBCT (mm)	P value
Group A	ANS	60.65 ± 4.56	55.24 ± 3.69	5.45 ± 1.99	<.001^∗∗
	A	68.93 ± 5.08	61.48 ± 4.36	7.40 ± 2.13	<.001^∗∗
	B	116.85 ± 8.02	107.01 ± 6.93	9.80 ± 3.36	<.001^∗∗
	Pog	130.15 ± 8.72	117.84 ± 7.28	12.33 ± 2.96	<.001^∗∗
	Gn	135.52 ± 8.51	122.39 ± 7.43	13.10 ± 2.72	<.001^∗∗
	Me	137.46 ± 8.78	124.56 ± 7.43	12.83 ± 2.80	<.001^∗∗
Group B	S	13.82 ± 3.64	11.75 ± 2.74	0.90 ± 2.99	<.001^∗∗
	Ar	48.89 ± 5.56	44.85 ± 3.78	2.63 ± 3.71	<.001^∗∗
	Ba	56.19 ± 6.50	51.41 ± 4.10	3.19 ± 4.10	<.001^∗∗
	PNS	61.80 ± 5.24	54.77 ± 3.90	6.23 ± 2.83	<.001^∗∗
Group C	Po	31.66 ± 2.79	29.32 ± 2.15	2.06 ± 2.67	<.001^∗∗
	Or	31.66 ± 2.79	29.24 ± 2.05	2.15 ± 2.25	<.001^∗∗
	Hinge Axis	42.71 ± 4.74	36.19 ± 2.81	4.48 ± 4.04	<.001^∗∗
	Go	100.42 ± 9.65	91.54 ± 7.84	8.00 ± 4.19	<.001^∗∗
Group D	U1CP	92.88 ± 5.99	84.55 ± 5.12	8.42 ± 2.19	<.001^∗∗
	U1RP	71.29 ± 5.11	64.21 ± 4.54	6.87 ± 2.16	<.001^∗∗
	U6CP	87.61 ± 6.02	79.87 ± 4.83	7.33 ± 2.57	<.001^∗∗
	L1CP	92.04 ± 6.01	83.56 ± 5.54	8.59 ± 1.96	<.001^∗∗
	L1RP	109.58 ± 6.99	100.84 ± 6.09	8.83 ± 2.51	<.001^∗∗
	L6CP	88.65 ± 6.20	81.41 ± 5.23	6.94 ± 2.38	<.001^∗∗

^∗ P<.05,

^∗∗ P<.01.

(+) sign on Mean ± SD of Difference between Adjusted 2D Lateral Cephalogram and CBCT means Landmark on Adjusted Cephalogram is more lower than CBCT.

Table 4.

The difference between conventional cephalogram and CBCT data of duplicated skull model

Landmark		Y axis Mean (mm)	Z axis Mean (mm)
Group A	ANS	-0.66	2.14
	A	-0.48	2.45
	B	-0.42	4.61
	Pog	-0.99	4.47
	Gn	-1.53	4.76
	Me	-0.69	5.37
Group B	S	2.12	-0.26
	Ba	2.36	0.78
	PNS	1.22	2.02
Group C	Po	2.54	0.46
	Or	0.94	0.79
	Hinge Axis	0.24	5.45
	Go	2.83	2.90
Group D	U1CP	2.60	2.60
	L1CP	2.87	2.87

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