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

• Ahn JH
• Bae KH
• Park YJ
• Hong RK
• Nam JH
• Kim MJ

• KMID: 1459544
• DOI: http://doi.org/10.4041/kjod.2010.40.6.421

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 0degrees (p > 0.05), but it was clinically variable (SD 3.89degrees) on the inter-individual level. Conversely, the angle of the SN line to the THL was significantly different from 7degrees (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.

Keyword

Natural head position; Centric relation; Frankfurt horizontal plane; Sella-nasion line; Nasion true vertical line

MeSH Terms

Adult
Bites and Stings
Centric Relation
Head
Humans
Male
Maxilla

Figure

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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).

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  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.

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  Fig 3. Reference points used in this study.

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  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.

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