ORTHODONTIC APPLIANCE |
|||||||
申请号 | EP05718894.8 | 申请日 | 2005-03-21 | 公开(公告)号 | EP1871276B1 | 公开(公告)日 | 2012-05-02 |
申请人 | DROR ORTHO-DESIGN LTD.; | 发明人 | NADAV, Orit; | ||||
摘要 | An orthodontic appliance and method are provided for moving one or more teeth to a desired set of positions. Each tooth that is to be moved is constrained to move along predetermined paths from an initial position to a final position, while being urged to do so by a suitable force inducing means, which provide a motive force for inducing movements in each individual tooth including translations and rotations. | ||||||
权利要求 | |||||||
说明书全文 | This invention relates generally to the field of orthodontic appliances. More specifically, the present invention relates to a method and appliance for orthodontic treatment in which individual teeth may be urged along predetermined paths of an alignment element that are based on a composite three dimensional numerical model of the patient's dentition. Many devices are known for aligning teeth, and include devices that are permanently fixed with respect to the teeth until treatment is completed, and removable devices that are designed to be worn part time or most of the time, day or night. The former are typically in the form of brackets that are bonded to individual teeth using a suitable adhesive, and a wire urges the teeth towards a final position to effect alignment. The latter are in the form of devices which fit in the intraoral cavity in a manner such as to urge teeth in a desired direction, and which are easily removable and refittable by the patient. The present invention is concerned with such removable devices. In a first stage for providing such removable devices, a physical plaster model of the patient's dentition is made. The procedure typically requires taking an impression of the teeth to form a negative mold of the teeth, into which a plaster material is poured and set to provide a positive model of the teeth. The positive model is typically dimensionally quite accurate, and faithfully duplicates the anatomy of the patient's intraoral cavity. Using such a model, which is typically referred to as a study model, the orthodontist is able to study the features of the patient's dentition and to devise a treatment plan to correct any malocclusion or other misalignment. For the purpose of devising such a plan, further models may be produced from the original negative mold, and these models, referred to as working models, may be used for customizing certain orthodontic appliances specific ally for the patient. For example, such a working model may be used for bending and positioning wires with respect to teeth, and then for welding the same in place or with respect to a stationary device. Typically, such appliances comprise an active element that actively generates corrective forces, and a passive element that is designed to remain stationary, serving as an anchor for the active element. Such active elements may comprise, for example, springs that generate orthodontic forces to the teeth or orthopedic forces to the malleable bony structures, and are positioned within a working model during fabrication of the appliance. Ideally, the springs are positioned such that each spring will eventually be in an unstressed state when the tooth it is urging has reached the position desired. This is thus to a great extent dependent upon the skill of the technician that is producing the appliance. When first installed in the intraoral cavity, the springs are each compressed by contact with the corresponding tooth that is intended to be moved by it, by an amount that is a function of the departure of the position of the tooth from the desired position. With the passage of time, each spring deflects its designated tooth, and at the same time releases the stored potential energy of the spring. In Other methods make use of a digital model of the dentition rather than a physical model. For example, in The invention provides an appliance in accordance with claim 1 below. In accordance with the present invention, an appliance is provided for moving one or more teeth to a desired set of positions. Each tooth that is to be moved is constrained to move along predetermined paths from an initial position to a final position, while being urged to do so by a suitable force inducing means. The force inducing means provide a motive force for inducing movements which include translations along and rotations about the three orthogonal axes of a Cartesian coordinate system. Of course any other reference coordinate system may be used. Thus, an orthodontic appliance for aligning one or a plurality of teeth in the intra oral cavity, comprising a corresponding one or plurality of guiding cells, the or each guiding cell being adapted to urge a particular tooth along a predetermined trajectory, wherein the or each said guiding cell comprises a force providing element for urging the corresponding tooth in a direction at least generally correlated with said trajectory, and a guiding structure adapted for guiding the tooth along said trajectory when acted upon by said force providing element. For each said guiding cell, the said guiding structure comprises a guiding element joined to an upstream end and a downstream end of the cell, and the downstream end preferably constitutes a part of said guiding structure. The guiding element is in a form that is complementary to a locus of said predetermined trajectory of at least a cusp of said tooth, and comprises a top segment adapted to abut said cusp as said tooth is urged along said trajectory, and side walls depending from said top segment guide the cusp of the tooth along said trajectory. Optionally, the appliance further comprises magnetic elements for providing a suitable magnetic field within said guiding cell. The magnetic elements typically comprise a pair of opposed magnets mounted to or integral with said guiding cell, and may be located one each on said upstream end and said downstream end. The force providing element may comprise at least one spring, typically a leaf spring, cantilevered from said upstream end and having an urging member at a free end thereof for abutting a face of said tooth. The spring is preferably adapted to provide a force at least in the general direction of said trajectory and also towards said top segment. Optionally, the spring is adapted for providing a substantially constant force at least until said tooth reaches said downstream end. Alternatively, the force providing element comprises a displaceable element, for example an extendable element, preferably an inflatable element, that is anchored at one end thereof to the upstream end, and comprises a pressure face or other abutment surface at the free end thereof to provide a force on the tooth when the extendable element is extended or inflated. The force provided by the extendable element may be controlled in any desired manner, for example to be constant, or pulsating in any desired frequency and amplitude, providing benefits to the teeth being treated. Alternatively, the displaceable element may comprise a pair of magnetic elements which provide the required motive force to the teeth. In one embodiment, the appliance made preferably from a suitable rigid or semi rigid material, for example an acrylic resin or the like, is in the form of a U-shaped tray adapted to fit over an arch of said intra oral cavity. The tray comprises one or a plurality of said guiding cells according to the number and dispositions of the teeth of said arch that require to be aligned with said appliance. At least one said guiding cell is adapted for urging a tooth in the lingual direction. Alternatively or additionally, at least one said guiding cell is adapted for urging a tooth in the buccal/labial direction. The tray may optionally further comprise static cells adapted for fitting over teeth that are not to be moved and for maintaining such teeth in their original positions as other teeth are aligned by said guiding cells. The guiding structure comprises an internal geometry that is derived from 3D numerical simulation of the movement of said tooth to a desired final position. In order to understand the invention and to see how it may be carried out in practice, a preferred embodiment will now be described, by way of nonlimiting example only, with reference to the accompanying drawings, in which:
In any given arch of an intra oral cavity, and referring to Referring to In a first embodiment of the present invention, and referring to Referring to The guiding cell 40 comprises guiding structure 70 and a force providing element or means 50. The guiding cell 40 has an opening 41 ( The cell 40 comprises an upstream end 42 substantially opposed to the first face 132, and that accommodates and aligns the force producing means 50 as required. The cell 40 further comprises a downstream end 44 having a shape complementary to the second face 134 of the tooth 100 that is opposed thereto, and oriented at the desired position corresponding to position 100'. Thus, when the tooth 100 is moved to position 100', the second face 134 is in engaging contact with downstream end 44. The guiding structure 70 comprises an alignment element or portion 46 joined at one end thereof to the upstream end 42, and at the other end thereof to the downstream end 44. As best illustrated in The ends 79 of the side walls 48 are typically joined in a smooth manner to the corresponding ends of the side walls of an adjacent cell. The cell 40 is preferably made from a dental-compatible material, and one that is rigid or semi-rigid, at least sufficiently rigid to ensure that the cell 40 does not itself deform under the action of force F or the reaction forces thereto with respect to the tooth 100. Suitable materials for cell 40 include, for example, acrylic resin or the like. Optionally, and as illustrated in In one variation of this embodiment, the force generating or providing means 50 is in the form of a mechanical spring 52, such as for example a leaf spring, cantilevered at one end thereof from the upstream end 42, and having a free end 55 comprising an urging member 56, as illustrated in In practice, it is usually sufficient to provide an approximation of the direction A, so that the force F provided by the spring is in a direction generally correlated with the desired trajectory. Continuous adjustment of the trajectory of the tooth 100 is provided by the alignment portion 46, which is shaped so as to maintain the cusp 160, and therefore the tooth 100, moving along the required direction. Thus, the pushing force F preferably comprises at least one component along the z-axis acting on the tooth 100 near to the gum line, and also another component acting along the x-direction and towards the alignment element 46 to maintain the tooth on track along the alignment element 46. In particular, once the tooth has reached position 100', but the orientation of the tooth 100 is not appropriate, continual urging by the spring 52 of the second face 134 against the downstream end 44 eventually seats the second face on the downstream end 44 to fully adopt the position 100', by further rotating the tooth 100 about axis q, for example. Thus, the spring 52 is designed to still provide a pushing force even after the tooth 100 arrives at the required position 100'. Alternatively, the spring 52 may be designed to become substantially unstressed by the time the tooth 100 arrives at the required position 100', and this may be the case when the direction A is fully calculated to achieve this final position. Optionally, a plurality of springs may be comprised in the cell 40. Preferably, the spring 52 is designed to provide a substantially constant force, in terms of magnitude and direction, at least until position 100' is reached by the tooth 100. Accordingly, the spring 52 comprises suitable characteristics such as high springback properties, resistance to permanent deformation, relatively constant force independent of the extension of the spring, and low modulus of elasticity. The spring 52 may be made from a suitable metal, for example, and may include nickel titanium alloys such as for example Nitinol. Preferably, the spring 52 is also adapted to permit the appliance 210 to be fitted and removed with respect to tooth 100 numerous times, and is thus ideal for use as a day time, and particularly a night time orthodontic appliance, particularly when the mouth is not being used for eating and drinking, or possibly for talking. Accordingly, the spring 52 may be in the form of an arc as illustrated in Alternatively, in another variation of this embodiment, and as illustrated in The inflatable means 152 may comprise, for example, a separate balloon or the like for each cell 40, and the balloons of adjacent cells 40 may optionally be interconnected. Optionally, and as illustrated in Preferably, the manifold 162 is disconnectable from the fluid supply 165 and comprises a suitable controllable valve 163. Thus, when the inflatable means 152 of each cell is appropriately inflated, providing the required force to each tooth 100, the fluid source 165 may be disconnected, which is thus more comfortable for the user, since the lines 160 are preferably mounted or integrally formed with respect to the appliance 210' in an unobtrusive manner. Optionally, when the user desires to remove the appliance 210', the valve 163 is opened, releasing the fluid pressure from the inflatable means, which then deflate accordingly. Alternatively, the appliance 210' may be reconnected to the fluid source 165, and the fluid drained thereinto from the inflatable means 152. The inflatable means 152 operated pneumatically or hydraulically, and may be inflated using any suitable fluid, preferably air or another suitable gas, or indeed a liquid such as for example water. The fluid supply 165 may comprise a source of pressurized fluid, and/or a suitable pump for pressurizing fluid in said lines 160. Pressurization and depressurization of the inflatable means 152 maybe controlled by a suitable electronic control unit (not shown) operated by the user. Optionally, the actual pressure provided to the inflatable means 152 may be controlled in any number of ways. In one mode of operation, the pressure to the inflatable means is kept constant while the user is wearing the appliance 210'. Thus, as the teeth 100 are moved and the inflatable means expand, the pressure initially would tend to drop, and thus the urging force on the teeth would also drop as well. By maintaining the pressure constant, the force on the teeth 100 is also kept constant. In another mode of operation, the pressure to the inflatable means is controlled such that the urging force to the teeth is terminated when the teeth arrive at their final positions 100'. In another mode of operation, the pressure to the inflatable means is varied as desired, for example in the form of periodic pulses, such as to provide a pulsating force to the teeth. The amplitude and frequency of the pulsations may be suitably controlled as desired, preferably by means of a suitable control unit (not shown) operatively connected to a pump (not shown). Such a pulsating force provides benefits to the teeth being treated. Optionally, it is also possible to provide a measure of the force F exerted on the teeth 100, the force being generally a function of the pressure provided to the inflatable means 152 when the contact area of the pressure face 156 is kept constant. This capability may be used to provide valuable data, which can be collated and used for various applications, including, for example, determining optimal conditions for forces to be applied to teeth. In practice, and as with the spring 52, it is usually sufficient to provide an approximation of the direction A, so that the force F provided by the inflatable means 152 is in a direction generally correlated with the desired trajectory. Continuous adjustment of the trajectory of the tooth 100 is provided by the alignment portion 46, which is shaped so as to maintain the cusp 160, and therefore the tooth 100, moving along the required direction. Thus, the pushing force F preferably comprises at least one component along the z-axis acting on the tooth 100 near to the gum line, and also another component acting along the x-direction and towards the alignment element 46 to maintain the tooth on track along the alignment element 46. In particular, once the tooth has reached position 100', but the orientation of the tooth 100 is not appropriate, continual urging by the inflatable means 152 of the second face 134 against the downstream end 44 eventually seats the second face on the downstream end 44 to fully adopt the position 100', by further rotating the tooth 100 about axis q, for example. Thus, the inflatable means 152 may be designed to still provide a pushing force even after the tooth 100 arrives at the required position 100', by increasing the pressure to effect greater expansion of the inflatable means 152. Alternatively, the inflatable means 152 may be designed to substantially cease urging the tooth 100 by the time the tooth 100 arrives at the required position 100', such as by, for example, limiting the pressure and thus the expansion of the expansion means and this may be the case when the direction A is fully calculated to achieve this final position. Preferably, the inflatable member 152 is designed to provide a substantially constant force, in terms of magnitude and direction, at least until position 100' is reached by the tooth 100. Accordingly, and referring to Furthermore, the upstream end 42 may be constructed so as to constrain the expansion of the inflatable means as much as possible in a desired direction, and thus may comprise the form illustrated in When the inflatable means 152 is in the deflated configuration, this permits the appliance 210' to be fitted and removed with respect to tooth 100 as desired, and is thus ideal for use as a day time, and particularly a night time orthodontic appliance, particularly when the mouth is not being used for eating and drinking, or possibly for talking. Alternatively, the inflatable means may be replaced by any other suitable expandable or displaceable means, mutatis mutandis, which is displaceable from a first position corresponding to the deflated configuration of the inflatable means 152, to an extended position, corresponding to the inflated configuration of the inflatable means 152. The expandable means may comprise, for example, a piston arrangement capable of being displaced as described, and thus the direction and force of the piston with respect to the tooth 100 may be controlled. The piston may be driven by means of a fluid such as air or another gas, or water or another liquid, and thus may be hydraulically or pneumatically operated. Alternatively, the piston may be actuated by mechanical means such as my means of a motor and screw jack mechanism, or by electrical means such as a solenoid or the like. Alternatively, the piston may be replaced by any other mechanism or arrangement that provides the required extended and retracted configurations. For example, an expandable means in the form of a displaceable element may comprise a magnetic element attached to the first face 132 of the tooth. A second magnetic element may then be provided in the cell 40, wherein the first and second magnetic elements have like polarities facing each other, providing a repulsive magnetic motive force that urges the tooth along its trajectory. Optionally, the second magnetic element is in the form of an electromagnet, the force and direction of which can be controlled to provide a constant force, a pulsating force, and so on. The tray 30 can held in a fixed relationship with the arch or interest in the intraoral cavity by virtue of the forces generated by force providing means of a plurality of cells 40, which act together to hold the tray 30 firmly against the teeth 100. Optionally, the jaw onto which the tray 30 is to be fitted may comprise a number of teeth that do not require to be moved, and thus the tray 30 may comprise a polymeric shell 295, corresponding to each such tooth, having a cavity that is shaped to receive and resiliently hold the static tooth. The shells 295 thus provide anchor points for the tray 30. Optionally, a base part (not shown) may be provided for holding the tray 30 relative to the intra oral cavity in a fixed relationship. The base part may be adapted to be seated or to fit under the palate or on the floor of the mouth between the base of the tongue and the gingival margin of the gum, depending on whether the appliance 210 is for use with respect to the upper or lower arch, respectively. Such a base part may act as an anchor point and provides a fixed datum, and may be formed as an acrylic mass having an external profile that is complementary to the part of the intraoral cavity in which it is adapted to be fitted during use of the appliance. In the cell 40 illustrated in The geometry of the cell 40, and in particular that of the alignment part 46 and the downstream end 44, is designed, and the cell 40 may be manufactured using such a design, as follows. Referring to In the next step 320, the data set DS1 is manipulated to provide a final tooth arrangement comprising a final digitized data set DS2, in which each tooth 100 is positioned in the desired position 100', for example as described in In the next step 330, and based on the initial data set DS1 and the final data set DS2, the 3D trajectory or path DSP between the initial and final positions of each tooth 100 is mapped and thus determined. The 3D path DSP may take the form of a surface enveloping the locus of positions of the 3D representation of each tooth 100 as this moves from the original position to the position 100'. This path can also be visualized as the path "tunneled" in 3D space by each tooth 100 separately as this moves to position 100' . Such a determination includes ensuring that this path will not adversely affect the disposition of the other teeth in the dentition. The final position 100' for each tooth is typically arrived at by the shortest path possible, consistent in also allowing the other teeth in the arch to move in an optimal manner. In step 325. a part of DS2, corresponding to the second face 134 and herein referred to as DS2P, provides the 3D data and thus the geometry for the downstream end 44 for each cell 40. In step 335 a part of the DSP data will correspond to the inner geometry of the alignment portion 46. The geometry of upstream end 42 may be constructed according to where the force providing means, such as spring 52 or the inflatable means 152, for example, is to be positioned, what type of spring or balloon is needed, and other factors and considerations may be taken into account, for each cell 40. A digitized representation DSU of the upstream end 42 may thus be created for each cell 40, step 315. The data sets DS2P, DSPP, DSU for each individual cell are then integrated to provide a dataset DSC representative of the internal surface of each cell 40. For teeth that do not require to be moved, the digital data corresponding thereto DSM in the original dataset DS1 will be substantially identical to that in the final digital dataset DS2, and data set DSM is obtained in step 340. In step 350, the datasets DSC for each cell 40 and the data sets DSM for the teeth that do not require to be moved (when such teeth are comprised in the arch) are combined to provide a data set DSCC that covers the internal geometry of the tray 30, step 360. The geometry of the external surface of each cell 40 is generally not of particular importance, other than it should be smooth and minimally interfere with the oral cavity. Typically, the cell 40 is of approximately uniform thickness. Thus, the outer shape of the tray 30 may be calculated by outwardly displacing the surface defmed by DSCC by a desired thickness, for example. It is also possible to provide the location of the force providing means, such as spring 52 or inflatable means 152, for example, within each cell 40 using the datasets created up to this point. For this purpose, a suitable program can be created that determines the direction and point of application of a force with respect to the tooth 100 such that will provide the required displacement to position 100'. It may be assumed that the direction of the force, as provided by force providing means , will be constant. Alternatively, the direction of this force may move as the force providing means such as a spring is extended or the inflatable means is inflated within the cell 40, and this may be compensated for using appropriate mathematical or numerical tools. According to the type of spring or inflatable means used, the program can then determine the anchoring point 51 of the spring within the cell 40. Thus, referring to The appliance 210 may then be manufactured using CNC machining methods, for example, in which the tray 30 may be produced either indirectly (e.g., by manufacturing the molds using CNC techniques) or directly by any suitable material removal operation applied to a suitable material. Alternatively, the tray 30 is fabricated using other methods. For example, the tray 30 may be fabricated using rapid prototyping techniques, for example based on a stereolithography machine, such as for example Model SLA-250/50 available from 3D System, Valencia, California. A liquid or non-hardened resin is hardened into a 3D form that can be separated from the non-hardened liquid or resin to form a positive model of the inner surface of each cell 40 and where appropriate also of shell 295, having received the 3D data set DSCC. A mold for the external surface of the tray 30 is produced in a similar manner to that described for the inner surface, mutatis mutandis, and injection techniques are used to provide the tray 30 from the inner and outer models thereof. Once the tray 30 is completed, the springs 52 can be mounted in each cell 40 using any suitable technique. Alternatively, the cells 40 may be formed integrally with force providing means, such as an integral spring 52 or an integral balloon or the like, when appropriate. Alternatively, the force providing means may be held temporarily in the positive model from which the tray 30 is fabricated, and the springs or inflatable means, or other expandable means, are anchored in the corresponding cells 40 as this is cast or formed with respect to the positive models. It should be noted that while the geometry of the downstream end 44 and the alignment portion 46, and of the entire inner surface of each cell 40, are advantageously determined using numerical/computer modeling methods and techniques as described, it is also possible to provide the required three dimensional geometries by techniques that are not computer based, for example including manual methods. While the creation of the appliance of the invention starting with the design thereof using numerical/computer methods is preferred over such manual methods, both methods are within the scope of the invention. Referring to Preferably, and as illustrated in As illustrated in the flowchart of |