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Positional symmetry of porion and external auditory meatus in facial asymmetry.

Choi JW, Jung SY, Kim HJ, Lee SH - Maxillofac Plast Reconstr Surg (2015)

Bottom Line: Their right and left side distance discrepancies were calculated and statistically compared.EAM was located 10.3 mm below and 2.3 mm anterior to Po in group I.  The vertical distances from Po to EAM of both sides were significantly different in group II-B (p = 0.001), while other groups were not.Interside discrepancy of the vertical distances from EAM to Mx in group II-B also showed the significant differences, as compared with those from Po to Mx and from Orb to Mx.

View Article: PubMed Central - PubMed

Affiliation: Department of Oral and Maxillofacial Surgery, College of Dentistry, Yonsei University, 50 Yonsei-ro, Seodaemun-gu 120-752 Seoul, Korea.

ABSTRACT

Background: The porion (Po) is used to construct the Frankfort horizontal (FH) plane for cephalometrics, and the external auditory meatus (EAM) is to transfer and mount the dental model with facebow. The classical assumption is that EAM represents Po by the parallel positioning. However, we are sometimes questioning about the possible positional disparity between Po and EAM, when the occlusal cant or facial midline is different from our clinical understandings. The purpose of this study was to evaluate the positional parallelism of Po and EAM in facial asymmetries, and also to investigate their relationship with the maxillary occlusal cant.

Methods: The 67 subjects were classified into three groups. Group I had normal subjects with facial symmetry (1.05 ± 0.52 mm of average chin deviation) with minimal occlusal cant (<1.5 mm). Asymmetry group II-A had no maxillary occlusal cant (average 0.60 ± 0.36), while asymmetry group II-B had occlusal cant (average 3.72 ± 1.47). The distances of bilateral Po, EAM, and mesiobuccal cusp tips of the maxillary first molars (Mx) from the horizontal orbital plane (Orb) and the coronal plane were measured on the three-dimensional computed tomographic images. Their right and left side distance discrepancies were calculated and statistically compared.

Results: EAM was located 10.3 mm below and 2.3 mm anterior to Po in group I.  The vertical distances from Po to EAM of both sides were significantly different in group II-B (p = 0.001), while other groups were not. Interside discrepancy of the vertical distances from EAM to Mx in group II-B also showed the significant differences, as compared with those from Po to Mx and from Orb to Mx.

Conclusions: The subjects with facial asymmetry and prominent maxillary occlusal cant tend to have the symmetric position of Po but asymmetric EAM. Some caution or other measures will be helpful for them to be used during the clinical procedures.

No MeSH data available.


Related in: MedlinePlus

Measurements of vertical distances from Po to Orb/EAM to Orb to indicate the asymmetrical locations of bilateral EAM in facial asymmetry subjects with remarkable maxillary occlusal cant. a Frontal view. b Lateral view. c Lateral oblique view of asymmetric locations of bilateral EAM. MSP midsagittal plane, Orb orbital plane, Po porion, EAM external auditory meatus)
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Fig3: Measurements of vertical distances from Po to Orb/EAM to Orb to indicate the asymmetrical locations of bilateral EAM in facial asymmetry subjects with remarkable maxillary occlusal cant. a Frontal view. b Lateral view. c Lateral oblique view of asymmetric locations of bilateral EAM. MSP midsagittal plane, Orb orbital plane, Po porion, EAM external auditory meatus)

Mentions: The vertical distances from Po to Orb (Po-Orb) and from EAM to Orb (EAM-Orb) were measured on both sides to obtain the vertical distances of Po and EAM (Fig. 3). The horizontal distances from Po and EAM to Fro (Fro-Po and Fro-EAM) on both sides were also measured for horizontal (anteroposterior) locations of Po and EAM. The vertical and horizontal distances between Po and EAM were measured on the right and left side.Fig. 3


Positional symmetry of porion and external auditory meatus in facial asymmetry.

Choi JW, Jung SY, Kim HJ, Lee SH - Maxillofac Plast Reconstr Surg (2015)

Measurements of vertical distances from Po to Orb/EAM to Orb to indicate the asymmetrical locations of bilateral EAM in facial asymmetry subjects with remarkable maxillary occlusal cant. a Frontal view. b Lateral view. c Lateral oblique view of asymmetric locations of bilateral EAM. MSP midsagittal plane, Orb orbital plane, Po porion, EAM external auditory meatus)
© Copyright Policy - OpenAccess
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4591197&req=5

Fig3: Measurements of vertical distances from Po to Orb/EAM to Orb to indicate the asymmetrical locations of bilateral EAM in facial asymmetry subjects with remarkable maxillary occlusal cant. a Frontal view. b Lateral view. c Lateral oblique view of asymmetric locations of bilateral EAM. MSP midsagittal plane, Orb orbital plane, Po porion, EAM external auditory meatus)
Mentions: The vertical distances from Po to Orb (Po-Orb) and from EAM to Orb (EAM-Orb) were measured on both sides to obtain the vertical distances of Po and EAM (Fig. 3). The horizontal distances from Po and EAM to Fro (Fro-Po and Fro-EAM) on both sides were also measured for horizontal (anteroposterior) locations of Po and EAM. The vertical and horizontal distances between Po and EAM were measured on the right and left side.Fig. 3

Bottom Line: Their right and left side distance discrepancies were calculated and statistically compared.EAM was located 10.3 mm below and 2.3 mm anterior to Po in group I.  The vertical distances from Po to EAM of both sides were significantly different in group II-B (p = 0.001), while other groups were not.Interside discrepancy of the vertical distances from EAM to Mx in group II-B also showed the significant differences, as compared with those from Po to Mx and from Orb to Mx.

View Article: PubMed Central - PubMed

Affiliation: Department of Oral and Maxillofacial Surgery, College of Dentistry, Yonsei University, 50 Yonsei-ro, Seodaemun-gu 120-752 Seoul, Korea.

ABSTRACT

Background: The porion (Po) is used to construct the Frankfort horizontal (FH) plane for cephalometrics, and the external auditory meatus (EAM) is to transfer and mount the dental model with facebow. The classical assumption is that EAM represents Po by the parallel positioning. However, we are sometimes questioning about the possible positional disparity between Po and EAM, when the occlusal cant or facial midline is different from our clinical understandings. The purpose of this study was to evaluate the positional parallelism of Po and EAM in facial asymmetries, and also to investigate their relationship with the maxillary occlusal cant.

Methods: The 67 subjects were classified into three groups. Group I had normal subjects with facial symmetry (1.05 ± 0.52 mm of average chin deviation) with minimal occlusal cant (<1.5 mm). Asymmetry group II-A had no maxillary occlusal cant (average 0.60 ± 0.36), while asymmetry group II-B had occlusal cant (average 3.72 ± 1.47). The distances of bilateral Po, EAM, and mesiobuccal cusp tips of the maxillary first molars (Mx) from the horizontal orbital plane (Orb) and the coronal plane were measured on the three-dimensional computed tomographic images. Their right and left side distance discrepancies were calculated and statistically compared.

Results: EAM was located 10.3 mm below and 2.3 mm anterior to Po in group I.  The vertical distances from Po to EAM of both sides were significantly different in group II-B (p = 0.001), while other groups were not. Interside discrepancy of the vertical distances from EAM to Mx in group II-B also showed the significant differences, as compared with those from Po to Mx and from Orb to Mx.

Conclusions: The subjects with facial asymmetry and prominent maxillary occlusal cant tend to have the symmetric position of Po but asymmetric EAM. Some caution or other measures will be helpful for them to be used during the clinical procedures.

No MeSH data available.


Related in: MedlinePlus