Assessment of antero-posterior skeletal relationships in adult Korean patients in the natural head position and centric relation

Jang-Hoon Ahn; Kwang-Hak Bae; Young-Ju Park; Ryoon-Ki Hong; Joeng-Hun Nam; Mi-Ja Kim

doi:10.4041/kjod.2010.40.6.421

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Assessment of antero-posterior skeletal relationships in adult Korean patients in the natural head position and centric relation

Original Article

Korean J Orthod 2010;40(6):421-431.

Published online: 19 January 2010

DOI: https://doi.org/10.4041/kjod.2010.40.6.421

Assessment of antero-posterior skeletal relationships in adult Korean patients in the natural head position and centric relation

Jang-Hoon Ahn, DDS, MSD, PhD^a, Kwang-Hak Bae, DDS, MSD, PhD^b, Young-Ju Park, DDS, MSD, PhD^c, Ryoon-Ki Hong, DDS, PhD^d, Joeng-Hun Nam, DDS, MSD, PhD^e, Mi-Ja Kim, DDS, MSD, PhD^f

^aAssociate Professor, Department of Orthodontics, Kangnam Sacred Heart Hospital, Hallym University

^bAssistant Professor, Department of Preventive Dentistry, School of Dentistry, Seoul National University

^cProfessor, Department of Oral and Maxillofacial Surgery, Kangnam Sacred Heart Hospital, Hallym University

^dChairman, Department of Orthodontics, Chong-A Dental Hospital

^eAssistant Professor, Department of Oral and Maxillofacial Surgery, Kangnam Sacred Heart Hospital, Hallym University

^eAssistant Professor, Department of Orthodontics, Hangang Sacred Heart Hospital, Hallym University

Corresponding author: Mi-Ja Kim. Department of Orthodontics, Hangang Sacred Heart Hospital, Hallym University, 94-200 Yeongdeungpo-dong, Yeongdeungpo-gu, Seoul 150-719, Korea. ＋82 2 2639 5580; e-mail, aurora0@hanmail.net.

Received 10 February 2010 Revised 11 June 2010 Accepted 14 June 2010

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

Objective:

This study aimed to verify the intra-individual reproducibility of the natural head position (NHP) in adult Korean patients in the centric relation (CR) position and to prove the inter-individual variability of the Frankfurt horizontal (FH) plane and sella-nasion (SN) line compared to the true horizontal line (THL). In addition, the study aimed to investigate the correlations between linear measurements from A-point and B-point to the nasion true vertical line (NTVL) and angular measurements from A-point and B-point to the SN line.

Methods:

Two lateral cephalograms were taken of 116 subjects (23 males, 93 females) with CR wax bites in a NHP at a one-week interval.

Results:

Method errors of three variables and intraclass correlation coefficients of six parameters proved the intra-individual reproducibility of NHP (p ＜ 0.001). The angle of the FH to the THL was not significantly different from 0° (p ＞ 0.05), but it was clinically variable (SD 3.89°) on the inter-individual level. Conversely, the angle of the SN line to the THL was significantly different from 7° (p ＜ 0.05). Very low correlation was found between the linear measurements and angular measurements of A-point and B-point (p ＜ 0.01).

Conclusions:

The NTVL could be a useful reference line for assessing the antero-posterior position of the maxilla and mandibleof Korean adult patients in NHP and CR.

Keywords: Natural head position, Centric relation, Frankfurt horizontal plane, Sella-nasion line, Nasion true vertical line

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Fig 1.

Registration of the centric relation wax bite. A, Guiding the mandible using the tripoding method; B, centric relation wax bite (anterior and posterior portion).

Fig 2.

Registration in the natural head position and lateral cephalogram. A, Subjects looked into their eyes in the mirror (orthoposition); B, standing position with arms and chin relaxed.

Fig 3.

Reference points used in this study.

Fig 4.

Reference planes used in this study. 1, Nasion true vertical line (NTVL) passing through the nasion point perpendicular to the floor; 2, E-line, tip of nose-soft tissue pogonion; 3, cervical vertebrae tangent-plane the posterior tangent to the odontoid process through cv4ip; 4, odontoid process tangent plane, the posterior tangent to the odontoid process through cv2ip; 5, palatal plane, ANS-PNS; 6, true horizontal line passing through nasion point perpendicular to the NTVL; 7, sella-nasion plane; 8, Frankfurt horizontal plane, porion-orbitale.

Fig 5.

Angular measurements. A, 1, Nasion true vertical line (NTVL) to palatal plane; 2, NTVL to E-Line; 3, NTVL to cervical vertebrae tangent; 4, NTVL to sella-nasion (SN); 5, true horizontal line (THL) to odontoid process tangent (OPT); 6, SN to OPT. B, 1, THL to Frankfurt horizontal plane; 2, THL to SN.

Fig 6.

Linear measurements. A, 1, Nasion true vertical line (NTVL to A-point); 2, NTVL to B-point. B, 1, Sella nasion A-point (SNA) angle; 2, sella nasion B-point (SNB) angle.

Table 1.

Digitizing method errors (n = 15)

Variables	Degrees
SN/NTVL	0.22
SN/OPT	0.52
OPT/THL	0.46

NTVL,Nasiontrueverticalline;OPT,odontoidprocess tangent;SN,sella-nasion;THL,truehorizontalline.

Table 2.

Positioning method errors (n = 116)

Variables	This study (n=116)	Huggare³³ (n=33)	Solow & Tallgren¹⁹ (n=120)
SN/NTVL	1.06	1.60	1.43
SN/OPT	1.28	1.35	1.43
OPT/THL	0.77	2.10	1.95

Dateareindegrees.NTVL,Nasiontrueverticalline; OPT,odontoidprocesstangent;SN,sella-nasion;THL, truehorizontalline.

Table 3.

Reproducibility of natural head position (NHP by intraclass correlation coefficients (n = 116)

Variables	Average of raters(α)	p-value
NTVL/E-line	0.9925	<0.001
NTVL/palatalplane	0.6102	<0.001
NTVL/CVT	0.9883	<0.001
NTVL/SN	0.9703	<0.001
SN/OPT	0.9815	<0.001
NTVL/OPT	0.9917	<0.001

Table 4.

Differences in Frankfurt horizontal line (FHL) to true horizontal line (THL) and SN to true horizontal line compared to norms (n = 116)

Variables	N	Mean	SD	Min	Max	p-value
THL/FH	116	−0.16	3.89	−12.43	7.65	<0.05
THL/SN	116	9.73	4.60	−2.11	17.50	<0.05

Norms:THL/FH=0

^o ,THL/SN=7

^o .SD,Standarddeviation;Min,minimum;Max,maximum.

Table 5.

Correlations between linear measurements of A-point to nasion true vertical line (NTVL) and sella-naison (SN)-A angles, and linear measurements of B-point to NTVL and SN-B angles using Pearson correlation coefficients (n = 116)

	NTVLA	NTVLB	NTVLA1	NTVLB1	NTVLA2	NTVLB2
SNA	0.094
SNB		0.314^∗
SNA1			0.328^∗
SNB1				0.314^∗
SNA2					0.309^∗
SNB2						0.287^∗

AandB,MeanofT1andT2data;A1andB1,T1data;A2andB2,T2data.

^∗ p <0.01.

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