Dentistry – Apparatus – Having gauge or guide
Reexamination Certificate
1999-12-14
2001-10-02
Wilson, John J. (Department: 3732)
Dentistry
Apparatus
Having gauge or guide
Reexamination Certificate
active
06296483
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to the placing of dental implants intended for maintaining prosthesis.
2. Discussion of the Related Art
When a patient's dentition is greatly damaged, it may be envisaged to replace the missing teeth with dental prostheses. In a preferred placing method, the prostheses are anchored in the maxilla or in the mandible via one or several implants screwed in the involved jaw.
A difficulty is that, when a patient's dentition is greatly damaged, the osseous system of its jaws is also often in a poor condition. The locations where it is possible to place the implants are thus strongly limited and must be determined with great precision.
A conventional method of determining the implant position includes the following steps.
Step I
Taking a print of the jaw to be implanted by means of a printing material such as silicon, an alginate, a hydrocolloid, etc. and casting a plaster model based on this print.
Step II
Forming a transparent resin cradle, the aim of which is to bear an opaque radio mark that indicates in the mouth the location where the implant is desired to be placed in the bone. This cradle is shaped based on the plaster model. It is the negative reproduction of this model on which it must be able to intimately fit. The cradle surfaces that do not engage with the plaster model may have any shape. Based on an analysis of the teeth shape and of the patient's masticatory system, the surgeon generally determines a priori the locations where he estimates that it would be desirable to anchor the prosthesis and to place the implants.
Step III
The implant locations are materialized with are materializing cylinders or cones in a material visible by X-rays such as gutta-percha, arranged in the cradle with orientations corresponding to the estimated drilling axes. It must then be determined whether these estimated drilling axes, ideal from the prosthetic point of view, are compatible with the bone structure of the jaw.
Step IV
The patient puts the cradle in his mouth and is submitted to an X-ray scanner examination. The acquisition of the scanner cross-sections is gene rally performed in the axial plane (that is, parallel to the lower edges of the horizontal branch of the mandible). The radiologist is asked to provide cross-sections approximately crossing the desired implant position. For this purpose, the radiologist uses the opaque radio mark included in the cradle to indicate to the scanner software the desired implant location. The scanner software then calculates an image crossing this mark and perpendicular to the acquisition cross-section plane. Based on this calculated image, the dentist defines if he can put the implant in this location while respect to the different endo-osseous elements and the approximate trajectory. If he cannot put it in this location, he estimates the displacement to another position with respect to the mark included in the cradle. All these estimates are used to place, with no numerical parameters, the implant in the mouth.
Step V
The cradle is removed from the patient's mouth, after which, in some implementations, a drilling of the cradle is performed to be subsequently used as a guide for the jaw drilling at the location where the implant is desired to be inserted.
A problem that is raised in implementing such a method is due to the transfer of information relating to the optimal drilling axis obtained based on the scanner images to the drilling guide formed by the cradle. To be able to use the information provided by the scanner software and images, it is necessary to know the transformation linking the scanner imagery reference system to a reference system in which the cradle drilling is performed. It is also necessary to locate this cradle in the referential in which its drilling is performed.
It has already been provided to coat the outer surface of the cradle (step II hereabove) with a partially radio-opaque material to make this surface visible on the scanner images. Thus, the (three-dimensional) surface of the cradle can be located in the scanner referential, that is, a set of surface points can be acquired in scanner images (step IV hereabove). Once the cradle is removed from the patient's mouth, it is placed in a medium of optical or mechanical determination of a three-dimensional sensor. This sensor is used to locate the cradle surface in the drilling referential. The placing of the two surfaces (cradle surface acquired in the scanner referential and cradle surface located by the sensor) in correspondence enables one to determine the rigid transformation (transfer array) between the two referentials respectively linked to the scanner and to the sensor. The information relating to the position of the implant drilling axis, or the respective positions of the different drilling axes for different implants, can thus be transferred from the scanner images to the mechanical referential of the sensor in which a drilling robot is positioned.
Such a solution, described in French patent application NO. 2,705,027 however requires use of an optical or mechanical sensor to obtain this information transfer.
SUMMARY OF THE INVENTION
The present invention aims at providing a novel solution to transfer information relating to a drilling axis obtained in the scanner referential to a referential associated with the drilling guide, that is, with the cradle.
The present invention also aims at providing a solution that does not require use of an optical or mechanical three-dimensional sensor.
To achieve these objects, the present invention provides a cradle adapted for the placing of a dental implant including, in a protrusion of an external contour, at least two hollow rectilinear non-concurrent tubes emerging on either side of the protrusion and locatable by X-rays.
According to an embodiment of the present invention, the respective axes of the tubes inscribe in two parallel planes, perpendicular to a plane in which the cradle inscribes.
According to an embodiment of the present invention, the axes of the tubes form an angle included between 60 and 120°, preferably 90°.
The present invention also aims at a mechanical support for a cradle adapted for the placing of a dental implant, defining an open housing for receiving a protrusion of a cradle of the above type.
According to an embodiment of the present invention, this support includes at least two spaced apart plates protruding from a base, the two plates including, each, at least two openings and each opening being adapted to facing an end of a hollow tube.
According to an embodiment of the present invention, the support is associated with at least two rods adapted to being engaged, each through an opening of one of the plates into the tube facing the opening and into an opening of the other plate.
The present invention also aims at a system for transferring a simulated position of a dental implant from an X-ray scanner to a robot for drilling a cradle that has a complementary shape with respect to a dental casting, including at least one mechanical support; and means adapted for removably connecting in a reproducible position the cradle to the support, the cradle containing at least two rectilinear non-concurrent elements, visible with X-rays.
According to an embodiment of the present invention, the two rectilinear elements integrated to the cradle are part of the connection means between the cradle and the support.
According to an embodiment of the present invention, the system is adapted to implementing a dental implant positioning method including the steps of:
positioning at least two rectilinear non-concurrent elements visible with X-rays in an open housing of a first mechanical support;
forming a cradle based on a dental casting and on the mechanical support, to integrate said elements in the cradle;
placing the cradle, removed from the support, in the mouth, and performing scanner tomographic cross-sections of this cradle and of the corresponding jaw;
determining with a simulation software the o
Bumgarner Melba
Morris Duane
Plevy Arthur L.
Universite Joseph Fourier
Wilson John J.
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