Journal List > Korean J Orthod > v.40(6) > 1043649

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

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.

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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).
kjod-40-421f1.tif
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.
kjod-40-421f2.tif
Fig 3.
Reference points used in this study.
kjod-40-421f3.tif
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.
kjod-40-421f4.tif
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.
kjod-40-421f5.tif
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.
kjod-40-421f6.tif
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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