Orientation of craniofacial planes to gravity horizontal plane

1
Orientation of craniofacial planes to gravity
horizontal plane

• Petricevic N, Celebic A, Krajnovic M,
  Knezovic-Zlataric D, Baucic-Božic M.
• Department of Prosthodontics, School of Dental
  Medicine, University of Zagreb, Croatia

INTRODUCTION To proceed clinical and laboratory
procedures out of patients mouth, it is
necessary to precisely register and orientate
patients casts in the articulator. However, the
occlusal plane is evaluated with respect to
anatomic relationships, which is then transferred
to the articulator (1). Orientation planes for
mounting casts in various articulators are
thought to be parallel with real horizontal plane
(gravity horizontal plane). The face-bow usually
aligns the soft-tissue Frankfort horizontal (FHP)
plane parallel to the ground with the idea that
these two planes are parallel in normal erect
posture with a head and shoulders in relaxed
natural position (2). However, according to some
authors, inclination of the FHP differs
significantly from the true horizontal in natural
head position (NHP) (36).
AIM OF THE STUDY The aim of the present study
was to assess the inclination of occlusal plane
and craniofacial planes to the real gravity
horizontal plane (GHP).
MATERIALS AND METHODS Fifty six dental students
with complete natural dentition and Angle Class I
participated. Upper margin of an adhesive tape
was placed in the line of the Frankfort plane
(left tragus left orbitale). Left profiles and
an-face photographs (Figure 1) with a subject in
a natural head position (6,7) and clenching on a
Fox plane (FoxP) (Candulor AG, Wangen,
Switzerland) were obtained from a distance of 1.5
m. A plumb line was pending from the ceiling to
identify gravity vector (true vertical).
Perpendicular line to a true vertical line (plumb
line) was drawn on digital photographs (true
horizontal). Inclinations between Frankfort
horizontal plane (FHP) and the true horizontal
(GHP), between Camper's line (CP) and true
horizontal (GHP), and inclination between the Fox
plane (FoxP) and the true horizontal (GHP) were
measured on the left profile photographs.
Inclination between bipupilar line (BP) and the
true horizontal (GHP), as well as inclination
between the Fox plane (FoxP) and the true
horizontal (GHP) were measured on the an face
photographs. ISSA computer program was used for
direct angular measurements on digital images
(VAMS, Zagreb, Croatia). Statistical analysis
(descriptives, t test) was made using SPSS 12 for
Windows. Craniofacial planes that were
downward-orientated (head flexed) on the
left-profile photographs and were
counter-clockwise on frontal photographs were
defined to have a positive angle to the true
(gravity) horizontal plane (GHP). Craniofacial
planes that were upward-orientated on the
left-profile photographs and were clockwise on
the frontal photographs were defined to have a
negative angle to GHP.
B) Frontal view
A) Lateral view
Figure 1. Subject in a natural head position
clenching a Fox plane. True vertical is
represented by a plumb line.
Table 1. Mean angles, standard deviations and the
significance of the differences between
craniofacial planes and gravity horizontal plane,
between Fox plane and gravity horizontal plane
RESULTS No significant differences were found
between male and female subjects (pgt0.05). Mean
angles and standard deviations between planes and
GHP are presented in the Table 1, as well as the
significance of the differences between the
planes and GHP. It was supposed that the planes
should be parallel, i.e. that the degree between
them should be zero. Therefore, the test value
was zero and one-sample t test was used for
comparison. In frontal view bipupilar plane
was almost parallel to GHP (-0.25 degrees) and no
significant difference was observed (t 0.96
P0.39, NS). Occlusal plane in frontal view
(FoxP) was also almost parallel (-0.53 degrees)
to GHP, and no significant difference was
observed (t -1.571 P0.129, NS). In lateral
view, FoxP (cclusal plane) was almost parallel to
GHP (1.42 degrees), and the difference was not
statistically significant (t 1.9 Plt0.061). FHP
was not parallel to GHP (difference was
statistically significant (t -11.62 Plt0.001)),
neither was CP (difference was statistically
significant (t 5.39 Plt0.001)). FHP was
upward-orientated (-10.33 degrees) and CP was
downward-orientated to GHP (5.384 degrees).
Angle (degrees) x SD t p
FHPGHP (left profile) -10.330 6.65 -11.624 lt0.01
CP-GHP (left profile) 5.384 7.69 5.389 lt0.01
FoxP-GHP (left profile) 1.42 4.81 1.511 0.132 NS
BP-GHP (frontal photograph) -0.25 1.94 -0.966 0.339 NS
FoxP-GHP (frontal photograph) -0.53 1.1 -1.571 0.129 NS
downward-orientated to GHP -
upward-orientated to GHP counter-clockwise
to GHP - clockwise to GHP NS Not significant
at 95 probability level lt0.01 Significant
at 99 probability level
DISCUSSION In frontal view the orientation of
the bipupilar plane and the occlusal plane was
about horizontal in a natural head position.
Parallelism to bipupilar plane is suitable
landmark for reconstruction of the occlusal
plane. In lateral view, not only that planes of
orientation, such as Frankfort horizontal plane
and Campers line, are not parallel to gravity
horizontal plane during natural head position,
but are not parallel to the occlusal plane, as
well. Absence of parallelism with Campers plane
makes this landmark unreliable for establishing
the occlusal plane, because occlusal plane
parallel to Campers plane would be too high
posteriorly on mandibular dentures, which would
cause problems with denture stability and food
accumulation in buccal sulci. Results of this
study might be compare with other authors
(6,7,8-12). The results indicate that with the
head in a natural position, the occlusal plane is
almost parallel to GHP. It would be impulsively
to assume that the position of a head is
determined by the position of occlusal plane and
further study on this matter should be organized
CONCLUSIONS 1) In frontal view, parallelism with
bipupilar plane is a suitable landmark for
reconstruction of the occlusal plane. 2) Occlusal
plane is almost parallel to gravity horizontal
plane in a natural head position. 3) Frankfort
horizontal plane and Campers plane are not
parallel to gravity horizontal plane in a natural
head position. 4) Campers plane is not a
suitable landmark for occlusal plane
reconstruction
REFERENCES Academy of Prosthodontics. Glossary
of Prosthodontic Terms, Electronic version, 6th
Ed. Editorial Council of the J Prosthet Dent
1994. Leitao P, Nanda RS. Relationship of natural
head position to craniofacial morphology. Am J
Orthod Dentofacial Orthop 2000117406. Ferrario
VF, Sforza C, Miani A Jr, Tartaglia G.
Craniofacial morphometry by photographic
evaluations. Am J Orthod Dentofac Orthop
1993103327-37. Ferrario VF, Sforza C, Tartaglia
G, Barbini E, Michielon G. New television
technique for natural head and body posture
analysis. J Craniomandib Pract 19951324755. Pit
chford JH. A reevalutation of the axis-orbital
plane and the use of orbitale in a facebow
transfer record. J Prosthet Dent
19916634955. Ciancaglini R, Colombo-Bolla G,
Gherlone EF, Radelli G. Orientation of
craniofacial planes and temporomandibular
disorder in young adults with normal occlusion. J
Oral Rehabil 200330878-886. Ferrario VF, Sforza
C, Serrao G, Ciusa V. A direct in vivo
measurement of the three-dimensional orientation
of the occlusal plane and of the sagittal
discrepancy of the jaws. Clin Orthod Res
2000315-22. Koller MM, Merlini L, Spandre G,
Palla S. A comparative study of two methods for
the orientation of the occlusal plane and the
determination of the vertical dimension of
occlusion in edentulous patients. J Oral Rehabil
199219413-25. Nissan J, Barnea E, Zeltzer C,
Cardash HS. Relationship between occlusal plane
determinants and craniofacial structures. J Oral
Rehabil 200330587-91. Karkazis HC, Polyzois GL.
A study of the occlusal plane orientation in
complete denture construction. J Oral Rehabil.
198714399-404. Karkazis HC, Polyzois GL.
Cephalometrically predicted occlusal plane
implications in removable prosthodontics. J
Prosthet Dent 199165258-64. Ercoli C, Graser
GN, Tallents RH, Galindo D. Face-bow record
without a third point of reference theoretical
considerations and an alternative technique. J
Prosthet Dent 199982237-41.