Accommodate the patient on a dental chair, in an upright position, looking straight ahead. Don't lie on the back.
Completely assemble the Postural Face-Bow with the goniometers, knob with level leaving it loose.
Insert the sphere of the rod in the spoon, load the top and bottom of the spoon with wax or a similar substance, insert it into the bow, insert the facial centring cross with the knob always loose.
Place it in the patient's mouth resting yourself delicately on the cheek.
Position it perfectly on the median line and make the patient bite.
Adjust the whole bow until the bubble level is centred.
Recheck the alignment of the median line.
In this position, block the joint of the spoon with self-polymerising resin directly in the mouth or externally after having very carefully removed the whole bow and spoon (without any movement).
Once the polymerisation has taken place, reposition the bow and make it slide forward or back, bring the centre of the goniometer ruler in collimation of the condylar point if previously established, or match the tragus of the patient, to the tragus of the goniometric ruler, the arbitrary condylar axis is obtained, 12mm outside - 8mm down Tragus-Cantus (Slavicek)
Lightly tighten the knob; the L measurement is imprinted on the handle due to the needlepoint on the screw of the knob.
Read in transparency the angle on the orbital point that can be used as a condylar eminence, now under study, and the two measurements between the horizontal point and the condylar point. Measure right H and left H.
Pull the bow, including the spoon, from the patient.
Pull out the rod and spoon, which are now a single body. After having loosened the knob write in the space provided the measurements with an indelible pen highlighting the point, or points in case of condylar longitudinal asymmetries left imprinted with the tightening of the knob.
Modern dental practice tends to focus on the postural occlusion-structural relationship of the body. The posture of the head or Natural Head Position (NHP) can be defined as the orientation, in respect to the terrestrial vertical (straight line to the centre of the earth mass) or true vertical, of the vertical passage to the barycentre of the head. The postural balance is individual and is the result of information sent to the body by gravity interceptors, the otoliths of the vestibular apparatus and the visual field.
The force of gravity is the suitable stimulus for the gravity inceptors positioned in the body and the otoliths of the vestibular apparatus, which process the Subjective Horizontal Posture (SHP) together. The positioning of the patient in the visual field enables the Subjective Visual Vertical (SVV) to be established. Since, the organs needed to establish the orientation in the environment are located in the head, the eyes and the vestibular apparatus, it follows that the NHP is the obvious expression of the synergic postural balance, corresponding to the SHP and the SVV.
Anthropometrical studies have shown that the occlusal plane in the NHP of healthy people with correct occlusion is on average aligned at the true horizontal. This shows the importance of transferring the exact orientation of the occlusal plane of the mouth on an Articulator. This transfer enables the operator to avoid any spatial designing errors to occur in the rehabilitation, thus preventing irritating pins to enter into the Balance System of the patient triggered by occlusal contacts. The Postural Face-Bow (PFB) enables the spatial position of the maxillary arch, the dimensions, height and depth of the maxillary occlusal plane from the patient's condyle to be transferred onto the Articulator.
A facial bow without eartips was patented for this purpose. This facial bow consists of a disposable registration spoon that joins itself with the solid rod to the facial-bow by means of a circular joint. This joint allows a three-way orientation of the occlusal plane space. A cylindrical plane placed on the facial bow enables the posture of the patient to be registered. When the bow matches the bubble level and the bubble is stable, it is certain that the occlusal plane of the jaw is simultaneously aligned to the sagittal, frontal and horizontal planes.
The analysis of the models with the Postural Face-Bow enables the jaw in reference to the true horizontal plane to be correctly examined. The first picture shows a normal patient, the second a patient with a flexed occlusal plane and the last a patient with an extended occlusal plane.
It is therefore evident that we can immediately check for any collapses or extrusions of the occlusal plane using the Postural Face-Bow. These photos are part of a more detailed study on the use of the Postural Face-Bow carried out at the University of Milan in 2000.
Preliminary clinical experiences with the use of the Postural Face-Bow: the dental technician's point of view
Claudio M. Riva. Dental technician with private practice, Monza (MI), Italy
The facial bow was introduced into the clinical practice approximately one hundred years ago to reveal accurately and reproduce the position of the upper jaw bone in respect to the cranial structure, transferring the relationship between the occlusal floor and a reference position of the condyle-meniscal complex called terminal hinge axis (THA) onto an articulator. In the traditional facial bows two planes are used for this purpose: 1) the occlusal plane, revealed by means of a spoon placed under the teeth of the jaw bow, 2) a reference plane generally determined by three intracranial points, two back points that represent the temporo-mandibular articulations and one front point, for example the orbital point. One of the planes normally used for this purpose is the Frankfurt plane (FP) that is used in a horizontal position during the transfer procedure. Nevertheless, it was demonstrated that the FP in subjects with normal posture was extended. As a result of this incorrect interpretation an exaggerated slope of the occlusal plane is obtained, incorrectly lowering the front teeth. In other words, the occlusal plane is not mounted on the articulator with the occlusal plane in same position as the patient has in his/her normal life, or in NHP (natural head position). It follows that the aesthetic evaluation in the laboratory is distorted, since the dental technician does not have the patient in front of him. Secondly, due to the frequent asymmetrical positioning of the intracranial landmark points used, positioning errors occur of the occlusal plane in respect to the condylar complex of the articulator. This is expressed as a rotation around the x, y, and z axes. These positioning errors are reflected in premature contacts that must then be removed at the chair. A Postural Facial-Bow using the extra-cranial landmark points can eliminate some of these errors. In fact, the true horizontal plane is used as a reference, making it then coincide with the plane of the articulator's upper jaw. As a result, the procedure of transfer is free from any cranial-facial asymmetries.
C, LAFAS, Dipartimento di Anatomia Umana, Universitа di Milano, Italy
The Face-Bow, ever since its inception, has been regarded as a necessary tool in dentistry for comprehensive treatment planning and diagnosis. Two posterior landmarks (e.g. the left and right extemal auditory meati) and a third anterior reference point (e.g. orbitale), are used to identify a plane representing the cranium: one of the most common reference planes is the Frankfort plane, which is assumed lo be horizontal when the patient is in the natural head position. In this study, the 3D orientation of the occlusal plane in the natural head position and its relationship to the palatal plane were quantified by using a Postural Face-Bow.
Materials and methods
The 3D position of the occlusal plane in the natural head position was assessed with a Postural Face-Bow for 22 subjects (age 20-32 years) with a complete dentition in both arches. An alginate impression of the maxillary arch was made for each subject and cast in dental stone. The maxillary arch was then mounted on a methyl methacrilate articulator in the natural head position with use of the Postural Face-Bow. The 3D inclination on the sagittal plane of the plane of occlusion and the palatal plane were measured by using a computerized digitizer.
The plane of occlusion was roughly parallel lo the true horizontal in all subjects, with a mean inclination of 2.14°, standard deviation 1.08'. The difference between the plane of occlusion and the palate yielded a positive value (mean 1.51°, sd 0.35) in 10 subjects, and a negative one (mean -2.47°, sd 0.64) in the remaining 12 subjects.
The plane of occlusion seems to be roughly parallel (±2° range) to the palatal plane and to the true horizontal. The Postural Face-Bow can be a helpful aid in recording the true spatial orientation of master models in the articulator.