Patent Application
20220117709
The present invention relates to one or more new teeth for production of a denture as well as a denture comprising the teeth. Novel techniques for positioning and fixing teeth into a denture plate are described.
Dentures are prosthetic devices constructed to replace missing teeth. Complete dentures replace all of the teeth in the upper and/or the lower jaw, whereas partial dentures only replace some of the teeth in the jaw concerned. For example, partial dentures may replace one or more front teeth and/or one or more of the posterior teeth. Generally, they are supported by the surrounding soft and hard tissues of the oral cavity. Complete dentures can also be implant supported, whereby the denture attaches to one or more dental implants fitted into the alveolar bone of the mandible or maxilla (lower or upper jaw). Conventional dentures are removable as and when required.
In natural human dentition, the tooth distribution in each quadrant of the mouth consists of three front teeth, and four or five posterior teeth including two pre-molars and two or three molars. When constructing a complete denture, either three or more typically four posterior teeth are used in each quadrant. When constructing a partial denture, the number of teeth used depends on factors such as the number of remaining natural teeth and the space available. The third molar tooth is not always present in the natural human dentition, and is not usually included in dentures.
Dentures should be retentive, comfortable and provide support for the cheeks and lips. They should allow effective mastication, acceptable aesthetics, clear phonetics, and contribute to the wearer's confidence and self-esteem.
The construction of complete dentures involves a number of clinical and laboratory stages.
In traditional denture construction, impressions of one or both jaws are first taken by the clinician. These are commonly referred to as primary impressions.
Into these impressions, technicians at a dental laboratory pour a material, such as plaster, to form a model representing the shape and contours of the soft and hard tissue area of the jaws concerned as well as any remaining natural teeth. Once solidified, this forms a model of the upper and/or lower jaws of the individual patient. The dental technician may make custom made special trays with which the clinician takes secondary impressions for greater accuracy and if so the dental technician will pour second models. Alternatively the models in either case may be made by digital means including 3D printing.
The dental technician then constructs on the models of the upper and lower jaw a bite rim/block out of wax, positioned to replicate the position of the missing teeth and including the extant teeth. These are made of solid wax with the extant teeth in the plaster to approximate or record approximately the correct dimensions but without any anatomical modelling. They are then sent to the clinician to make various adjustments so as to give information to the technician about facial height, anterior tooth position, lip support, occlusal plane etc., and to mark various anatomical landmarks. These are then returned to the dental laboratory, where the dental technician mounts the models and bite rims on an articulator (an articulator is a hinged metal piece of equipment used to represent the movements of the jaws in the dental laboratory) together with a model of the teeth in the opposing arch if these are still extant.
The dental technician then models in wax the plate that will form the denture itself and teeth are added to it in the functionally and aesthetically correct positions. This wax model with teeth is referred to as a denture try-in. The clinician checks the try-in in the patient's mouth against either the denture or the try-in of the opposing arch or the existing teeth in the opposing arch, with regard to the appearance, phonetics, and function. Adjustments are made by the clinician where necessary.
Once the try-in has been returned to the dental laboratory, the dental technician then finishes any modelling work on the try-in that may be needed in order to get a true representation of the finished denture. The technician then takes the wax denture with teeth attached and invests it into plaster contained in a metal flask, taking care to put a separator film between the two halves of the flask in order that it may be opened when set. Once set, the dental technician opens the two halves of the flask and, using boiling water, removes the wax from the flask leaving the teeth embedded into one half. The teeth remain in the flask where they are held in position by the plaster and there is hollow space corresponding to where the wax has been removed. An acrylate dough is then packed into the hollow space in the flask, and it is closed tight in a conventional manner and heated to cure the acrylate dough forming the denture plate material. Once cured, the plaster is broken away and the denture is cleaned and polished before sending back to the clinician to fit into the patient's mouth.
In recent years, modern technology has been utilised so that one or more of the stages of the traditional denture production method is implemented digitally, in order to reduce the overall method time.
For example, once an impression of a patient's mouth or patient's jaw is taken, it can be scanned and recorded in a digital form for example on a device such as a computer in the dental laboratory. In some cases, the impression may be scanned directly at the chairside and the data transmitted electronically to the dental laboratory. Alternatively, a model may be produced from this impression and may be scanned and recorded in a digital form for example on a device such as a computer either in the laboratory or directly at the chairside. The components of the denture are then positioned digitally, by inputting additional information including measurements of the anatomical features and dimensions of the patient's mouth into a device such as a computer, and using specialist software to design the denture electronically. Such a method avoids the laborious steps of physically setting up the teeth and also enables different occlusal schemes to the tried out virtually using the software.
The denture plate is then milled out of wax or other material, leaving space for precisely fitting teeth to be inserted into the wax to form the try-in. As an alternative, both the denture plate and teeth can be milled together out of wax or other material. This is then sent to a clinician for checking in the patient's mouth, following which the try-in can be invested into plaster contained in a metal flask, as in the traditional manner described above.
In an alternative shorter method, the step of producing and fitting a try-in is completely omitted. In either case the denture is produced directly from the digital design by milling the finished denture plate from prepolymerised plastic or 3D printing, leaving space for the individual teeth to be fixed in with an adhesive, such as an acrylic adhesive material. Alternatively, both the individual teeth themselves as well as the denture plate are produced by milling or 3D printing, and the teeth and base are fixed together using adhesive. As an alternative, both the denture plate and teeth can be milled together out of tooth coloured acrylic or 3D printed using tooth coloured material and the denture plate itself can be stained or painted pink.
In addition to the traditional methods of taking impressions of the contours of the mouth using impression material, methods have also been developed to take digital impressions of a patient's jaw, so that physical models are not even required. Together with these methods for taking impressions of the mouth additional information including recording the occlusal plane, the lip line, the position of the front teeth, other measurements of the anatomical features and dimensions of the patient's mouth must be input into the computer.
However the procedures to carry this out can be very laborious. For instance, Dentca Inc. in U.S. Pat. No. 8,998,615 claims a method of obtaining a gum impression of a patient's mouth and measuring jaw relations, a dental impression tray assembly including a lower tray and an upper tray to fabricate a denture, is used. The lower tray includes a first piece and a pair of second pieces and the upper tray includes a third piece and fourth piece. The method includes inserting the lower tray loaded with an impression material into the mouth to take an impression; taking out the lower tray from the mouth and cutting the impression material along a borderline between the first piece and the pair of second pieces; separating the first piece from the pair of second pieces; attaching an intra-oral tracer to the first piece and inserting the first piece, to which the intra-oral tracer is attached, and the third piece into the mouth to measure the jaw relations.
The try-in or finished denture may be designed and produced with the aid of computer design software as outlined in the steps above.
For any of the above methods which involve the separate production of the denture plate and teeth and adhesive bonding together of the components, the individual teeth need to be fixed into pre-milled or 3D printed spaces in the milled acrylic or 3D printed denture plate. This positioning of the teeth is susceptible to twisting and/or rotation within the spaces, so that the exact position of the individual teeth in the final denture may not be correct, leading to problems in terms of occlusion or appearance.
In addition, the step of positioning the teeth together in the denture plate is quite difficult to achieve in practice since it is difficult to ensure the angles of entry into the denture plate are correct for all of the teeth when placed together.
Furthermore, the shape of known prosthetic teeth have surfaces which meet at angles which are not correct for inserting into pre-prepared spaces in a denture plate since this was never the objective when the teeth were first designed.
Therefore, there remains a need for improved prosthetic teeth which can be accurately and more easily properly positioned in a denture, as well as a method for establishing correct alignment of prosthetic teeth in a denture.
In first aspect, the invention provides a prosthetic tooth for a denture wherein the tooth comprises a lingual or palatal surface, an opposing vesibular surface, opposing proximal surfaces, an incisal or occlusal surface and an opposing apical surface, wherein a pocket or slot is defined in the apical surface.
Preferably, the apical surface is curved. In this regard, the apical surface extends from the lingual or palatal surface to the vesibular surface of the tooth and is preferably concave.
Preferably, the tooth has proximal surfaces at opposing sides of the tooth and the pocket or slot is positioned substantially equally between the proximal surfaces of the tooth.
Preferably, the pocket or slot has an open end facing the apical surface of the tooth. Preferably, the pocket or slot has an opposing planar end defined in the tooth. Preferably, the end of the pocket or slot defined in the tooth is substantially parallel with the incisal or occlusal surface of the tooth.
Preferably, the planar end of the pocket or slot defined in the tooth defines a polygon. Preferably, the polygon is substantially rectangular or trapezoid. Alternatively, the polygon is another shape, for example a triangle, pentagon, cross or a star.
Preferably, the pocket or slot has a width equal to about one third of the distance between the proximal surfaces of the tooth.
Preferably, the pocket or slot has a length substantially perpendicular to its width and the length of the pocket or slot is preferably greater than its width.
Preferably, the pocket or slot has a longitudinal axis parallel to its length extending from adjacent the vestibular surface of the tooth to adjacent the lingual or palatal surface (ie from front to back of the tooth).
In one embodiment, the pocket or slot is defined in only the apical surface of the tooth.
In another embodiment, the pocket or slot extends through the lingual or palatal surface of the tooth.
In another embodiment, the pocket or slot extends only partially through the lingual or palatal surface of the tooth. According to this embodiment, the pocket or slot has a more than one depth.
Advantageously, the presence of the pocket or slot makes it easier to determine whether the tooth is positioned correctly when the tooth is aligned with a denture plate and assists with determining whether the tooth has twisted or tilted.
In addition, the invention provides the advantage that the revised design of the teeth reduces the bulk of teeth so that removing excess tooth is less often going to be necessary. This reduces the time required for shaping the teeth and reduces waste material.
A further advantage is that the strength of the bond between teeth of the invention and a denture base is improved.
In a second aspect, the invention provides a set of teeth comprising a plurality of teeth according to the invention.
Preferably, the set of teeth comprises one or more upper and/or lower teeth. Preferably, the set of teeth comprises one or more of central, lateral, cuspid, first cuspid, second cuspid, first molar and second molar teeth. Preferably, the set of teeth comprises anterior and/or posterior teeth. Preferably, the set of teeth comprises anterior, pre-molar and molar teeth.
Preferably, the set of teeth comprises all of central, lateral, cuspid, first bicuspid, second bicuspid, first molar and second molar teeth.
In a further aspect, the invention provides a method for manufacturing a tooth of the invention which comprises the step of moulding a tooth having a pocket or slot defined therein. Alternatively, the method comprises the steps of moulding a tooth and milling a pocket or slot into the moulded tooth. Alternatively, the method comprises the steps of three dimensional printing a tooth having a pocket or slot defined therein, or three dimensional printing a tooth and milling a pocket or slot in the tooth. Alternatively, the method comprises the steps of milling a tooth having a pocket or slot defined therein.
In a further aspect, the invention provides a denture comprising a denture plate and one or more teeth of the invention.
In a further aspect, the invention provides a method for correctly positioning teeth in a denture which comprises providing one or more teeth of the invention and a denture plate and aligning the teeth with the denture plate.
The invention will now be described with reference to the accompanying drawings, in which:
The following definitions shall apply throughout the specification and the appended claims.
The singular forms “a,” “an,” and “the” include plural reference unless the context clearly dictates otherwise.
Within the context of the present specification, the term “comprises” is taken to mean “includes” or “contains”, i.e. other integers or features may be present, whereas the term “consists of” is taken to mean “consists exclusively of”.
Within the present specification, the term “about” means plus or minus 20%; more preferably plus or minus 10%; even more preferably plus or minus 5%; most preferably plus or minus 2%.
Within the present specification, the term “denture” means a prosthetic device constructed to replace missing teeth; a denture consists of a denture plate that is supported by the soft and hard tissues of the oral cavity, and artificial denture teeth that restore aesthetics and function for a patient.
Within the present specification, the term “slot” means a depression, indent or groove defined in a tooth. A slot is a depression with a uniform cross-section along its length and generally longer than it is wide or deep. A “pocket” is a depression, indent or groove that does not meet the criteria to be considered a slot.
Within the present specification, the term “apical” refers to the direction towards the root(s) or apex(es) of a tooth (the apices), as opposed to coronal, which refers to the direction towards the crown of a tooth.
Within the present specification, the term “lingual” refers to the side of a tooth which in situ would be adjacent to (or the direction towards) the tongue, as opposed to vestibular which refers to the side of a tooth adjacent to (or the direction towards) the inside of the cheek or lips.
Within the present specification, the term “palatal” refers to the side of a tooth which in situ would be adjacent to (or the direction towards) the palate, as opposed to vestibular which refers to the side of a tooth adjacent to the inside of the cheek or lips.
Within the present specification, the term “vestibular” refers to the side of a tooth which in situ would be adjacent to (or the direction towards) the inside of the cheeks or lips, as opposed to lingual or palatal, which refer to the side of a tooth adjacent to (or the direction towards) the tongue or palate, respectively.
Within the present specification, the term “proximal” refers to the surfaces of teeth that which in situ would be adjacent to another tooth.
Within the present specification, the term “incisal surface” refers to the biting surface of the anterior teeth ie the teeth toward the front of the mouth.
Within the present specification, the term “occlusal surface” refers to biting surfaces of the posterior teeth ie the teeth towards the back of the mouth.
Unless defined otherwise, all technical and scientific terms used herein have the same meanings as commonly understood by one of ordinary skill in the art.
Embodiments have been described herein in a concise way. It should be appreciated that features of these embodiments may be variously separated or combined within the invention.
In a method for production of a denture, the teeth of the denture are inserted into a previously manufactured denture plate so that they may be positioned as a block into pre-milled or three dimensionally printed spaces in the denture plate thus avoiding the problem of individual teeth twisting or rotating within the spaces. However, this is difficult to achieve.
To assist in positioning the teeth correctly, with reference to
The tooth (1) has proximal surfaces (4,5) at opposing sides of the tooth (1) and the pocket or slot (8) is positioned substantially equally between the proximal surfaces (4,5) of the tooth (1).
The pocket or slot (8) has an open end (9) facing a curved apical surface (7) of the tooth (1) and an opposing planar end (10) defined in the tooth (1) which is substantially rectangular or trapezoid. The end (10) of the pocket or slot (8) defined in the tooth (1) is substantially parallel with the incisal or occlusal surface (6) of the tooth (1).
The pocket or slot (8) has a width equal to about one third of the distance between the proximal surfaces (4,5) of the tooth (1) and a length substantially perpendicular to its width, wherein in one embodiment, the length of the slot (8) is greater than its width.
The pocket or slot (8) has a longitudinal axis parallel to its length extending from adjacent the vestibular surface (3) of the tooth (1) to adjacent the lingual or palatal surface (2) (i.e. from front to back of the tooth (1)).
In a first embodiment shown in
In second and third embodiments shown in
As shown in
A denture of the invention comprises a denture plate and one or more teeth (1) of the invention.
The tooth (1) of the invention is manufactured by a method which includes the step of moulding the tooth (1) and a pocket or slot (7) is defined therein. Alternatively, the method comprises the steps of moulding a tooth (1) and milling a pocket or slot (7) into the moulded tooth (1). Alternatively, the method comprises the steps of three dimensional printing a tooth (1) having a pocket or slot (7) defined therein, or three dimensional printing a tooth (1) and milling a pocket or slot (7) in the tooth. Alternatively, the method comprises the steps of milling a tooth (1) having a pocket or slot (7) defined therein.
Although the present invention has been described with respect to a presently preferred embodiment, the present invention should not be limited to the embodiment, and it will be appreciated by those skilled in the art that various modifications may be made without departing from the spirit and scope of the present invention.
| Number | Date | Country | Kind |
|---|---|---|---|
| 1902213.6 | Feb 2019 | GB | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/GB2020/050367 | 2/17/2020 | WO | 00 |
