Dentistry – Apparatus – Work support
Reexamination Certificate
2001-07-26
2003-05-06
Wilson, John J. (Department: 3732)
Dentistry
Apparatus
Work support
C433S058000
Reexamination Certificate
active
06558161
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a dental articulator used for completely reproducing human jaw movement, especially articulation, in producing dental prostheses for defective or missing teeth.
2. Description of the Prior Art
Reproduction of mandibular movement is indispensable to production of dental prostheses for enabling good mastication. Interocclusal movement shows highly noticeable differences among individuals. Thus, a dental articulator capable of completely reproducing the mandibular movement of the jaw of each individual is desired, and accordingly, there have been so far proposed a variety of dental articulators for this purpose.
As one of the dental articulators, there is an arcon-type full-adjustable articulator. The arcon type denotes a structure, which is provided at its mandible portion with a condylar sphere similarly to a living subject, and at its maxilla portion with condyle path regulation. The full-adjustable articulator comprises a regulating mechanism having a function of detecting mandibular movement in a form of three-dimensional movement of the jaw to effect three-dimensional regulation for the entire movement.
In Japanese Patent No. 2866084 (Japanese Patent Application Publication No. HEI 11-028217), the inventors of the present invention disclosed an arcon-type “completely reproducible articulator” capable of perfect reproduction of mandibular movement. The articulator disclosed in this Japanese publication will be discussed, upon explaining an ordinary technique in relation to the articulator.
First, terminology for describing an occlusion will be briefly defined. In dentistry, the front, side and plane in a general sense are expressed in terms of “frontal plane”, “sagittal plane” and “occlusal plane”, respectively. In general, the side toward which mandibular movement is directed is termed the “working side”, and the opposite side is termed the “balancing side” or “non-working side”. Of the maxilla and mandible, which constitute the jaw, the mandible is movable and restrained in movement via configuration of the glenoid fossae accommodating right and left “condyle heads”. The mandible moves in five directions, i.e. protrusive, lateral (leftward), lateral (rightward), posterior and vertical directions. A center of a condylar point is termed “condylar point”, a line connecting centers of right and left condyle heads is termed “condylar axis”, and locus along which the condylar point moves along the glenoid fossae is termed “condyle path”.
The conventional full-adjustable articulators also have various types of contrivances for reproducing the mandibular movement, which are common in principle.
First, jaw movement to be reproduced is fulfilled by the mandibular movement made in the five directions as touched upon above. However, all five-directional mandibular movements, may be practically ruled out of the movements of the conventional articulators. That is, movement of the condylar points in the protrusive, leftward and rightward directions will suffice for reproducing the jaw movement. With respect to the lateral movement of the jaws, when the mandible moves rightward, the right condyle head works as the working side and the left condyle head works as the balancing side. The reverse is also true when the mandible moves Leftward. Thus, the jaw movement to be reproduced must vary according to the movement of each condyle head, which is performed in different manner in moving the mandible rightward or leftward.
That is to say, the jaw movement at the time of the protrusive motion of the condyle heads and the lateral motions of the right and left condyle heads when the respective condyle heads work as the working side or balancing side may be accurately reproduced. In other words, it may be required to reproduce only the protrusive movements of the right and left condyle heads and the lateral movements of the condyle head (working condyle head) and condyle head (balancing condyle head).
There has been a method for reproducing movement of the condyle heads noted above, in which a three-dimensional reproduction of the movement is effected by combining movements of the jaw in an internal-external, upward-downward and anteroposterior directions. With a dental articulator, jaw movement has been recognized by bringing a plate member called a “regulation plate” in touch with the condyle heads so as to permit the condyle heads to move along the regulation plate, and varying an angle (gradient) of the regulation plate to derive a direction in which the regulation plate moves relative to condyle heads. Hence, internal-external, upward-downward and anteroposterior regulation plates are provided for each condyle head in order to regulate movements of the condyle head, so that the condyle heads are guided in composite directions in which the regulation plates are regulated.
In a common articulator, a vertical regulation plate is called a “sagittal condylar path inclination plate”, a mesio-lateral regulation plate is called a “Bennett plate”, and an anteroposterior regulation plate is called a “rear wall”.
Next, a regulating method will be described in detail. At the time of protrusive movement of a jaw, both condyle heads move in an anterior-downward direction during the protrusive movement, thereby to be restrained in a vertical direction. During lateral movement of the jaw, the working condyle head moves slightly, but the balancing condyle head largely moves inwardly in an anterior-downward direction. Consequently, the balancing condyle head is restrained in vertical and lateral directions, and simultaneously, the working condyle head is restrained in vertical and anteroposterior directions, while being thrust outwardly.
What does matter at this point is usage of vertical regulation for reproducing three sets of vertical components of the protrusive movement, right lateral movement and left lateral movement. To be specific, the sagittal condylar path inclination plate used for vertical regulation corresponds to these movements made in three directions, but the vertical components of the movements in the three directions varies relative to each other with the direction in which the jaw moves. Thus, in a case that the mandible is regulated in its right lateral movement and successively in its left lateral movement, the right condyle head first works as the working condyle and successively as the balancing condyle. At that time, it is necessary to readjust an angle of the sagittal condylar path inclination plate. Therefore, work required for the regulation disadvantageously requires much time and labor and proves to be troublesome.
To overcome the unfavorable problems described above, there has been adopted a method in which a rotary inclination mechanism called a “Fischer slide” is attached to the sagittal condylar path inclination plate.
FIG. 15
shows a conventional articulator adopting a method using a “Fischer slide”. As shown in
FIG. 15
, one sagittal condylar path inclination plate
522
is provided with an inclination rotatable about an intercondylar axis (A) and an inclination (of the Fischer slide) rotatable about a sagittal condylar path inclination axis (C), thereby to possess two inclination angles, so that the sagittal condylar path inclination plate
522
can be restrained in two directions of vertical movement with one regulation plate. However, this conventional method capable of reproducing only two of the movements made in three directions required for vertical regulation could not completely reproduce the desired mandibular movement. In
FIG. 15
, reference numeral
513
denotes the condyle head,
521
denotes the Bennett plate (angular regulation plate rotatable about the axis B), and
523
denotes the rear wall (angular regulation plate rotatable about the axis R).
To overcome the disadvantage suffered by the conventional articulator, the inventor of this invention proposed in Japanese Patent No. 2866084 an improved articulator capable of completely reproducing the mandibular movement.
To be m
Wenderoth , Lind & Ponack, L.L.P.
Wilson John J.
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