WO2011034781A2

WO2011034781A2 - Method of making dental implant model and articles

Info

Publication number: WO2011034781A2
Application number: PCT/US2010/048361
Authority: WO
Inventors: Roger K. Dawson; Ryan E. Johnson; Kevin W. Wenzel; Howard P. Wanless, Iii; William A. Goodwin
Original assignee: 3M Innovative Properties Company
Priority date: 2009-09-15
Filing date: 2010-09-10
Publication date: 2011-03-24
Also published as: WO2011034781A3

Abstract

The present invention pertains to methods of fabricating physical dental models, dental implant models, a method of seating a permanent restoration by use of a dental implant model, dental implant analog sleeves, and assemblies of dental implant analog sleeves and implant abutments.

Description

METHOD OF MAKING DENTAL IMPLANT MODEL AND ARTICLES

Background

As described for example in US 6,135,773; dental implants are becoming an increasingly popular means for restoring missing teeth in wholly or partially edentulous patients.

Dental implants are available in a variety of styles. One style is designed to install the implant substantially entirely within the patient's jawbone, accessible subgingivally at the crest of the jawbone. Another style of implant incorporates a transgingival section and is installed with that section extending through the gingiva overlying the site of the implant installation. This later style often referred to as a "single-stage" implant.

As described for example in U.S. Patent No. 6,135,773, regardless of the style, the process of fashioning a restoration often begins with the step of attaching an impression coping to the implant. After the coping is attached to the implant and a (e.g. silicone) impression is taken, this "negative" impression is removed from the patient's mouth and used to make a "positive" stone (e.g. gypsum) model of the patient's case.

As described for example in US 2008/0233537, in addition to the method that uses a (e.g. silicon) impression material to manually develop a stone model, systems exist that utilize scanning technology to assist in generating a prosthesis such as a permanent crown. A scanning device is used in one of at least three different approaches. First, a scanning device can scan the region in the patient's mouth where the prosthesis is to be placed without the need to use impression materials or to construct a mold. Second, the impression material that is removed from the healing abutment and surrounding area can be scanned to produce the permanent (e.g. crown) restoration. Third, a dentist (or a dental lab) can scan the stone model of the dental region that was formed from the impression material.

US2008/0153067 (abstract) describes a method of placing a dental implant analog in a physical model for use in creating a dental prosthesis is provided. The physical model, which is usually based on an impression of the patient's mouth or a scan of the patient's mouth, is prepared. The model is scanned. A three-dimensional computer model of the physical model is created and is used to develop the location of the dental implant. A robot then modifies the physical model to create an opening for the implant analog. The robot then places the implant analog within the opening at the location dictated by the three- dimensional computer model.

To avoid the use of (e.g. silicone) impression material, yet still construct a model, an image capture system such as an optical scanning device can also be used to image the patient's mouth and the three dimensional surface representation can be used to construct a model using subtractive processes such as milling, or additive processes such as stereolithography or three-dimension (e.g. wax) printing. (See for example

US2008/0015727).

Summary

The intraoral surfaces of a patient's mouth typically comprise natural teeth as well as various dental restorations such as filling, crowns and bridges. It is generally unproblematic for dental structures having exposed surfaces above the gum line to be scanned by a digital camera or other optical scanner.

However, in the case of a single-stage implant; a cover screw, healing abutment, or other temporary abutment typically extends through the gingivia overlying the site of the implant. Since these structures do not correspond to an implant abutment that receives a permanent (e.g. crown) restoration, it is difficult to make an accurate digital model (and then physical model from the digital model) from this scan of the patient's mouth.

The present invention concerns methods of fabricating physical dental models, dental implant models, a method of seating a permanent restoration by use of a dental implant model, dental implant analog sleeves, and assemblies of dental implant analog sleeves and implant abutments.

In one embodiment, a method of forming a dental implant model is described. The method comprises scanning at least a portion of a patient's mouth at a location of a dental implant to acquire a first digital surface representation. The method also comprises acquiring a second digital surface representation of at least the exterior surface of a dental implant analog sleeve. The method further comprises creating a three-dimensional digital model by modifying the first digital surface representation to remove (i.e. subtract) the second digital surface representation at the location of the dental implant thereby creating a void for receipt of the dental implant analog sleeve; and forming a physical model from the three-dimensional model.

The first digital surface representation (i.e. of at least a portion of a patient's mouth at a location of a dental implant) is preferably acquired by attaching a scannable (e.g. permanent) implant abutment to the dental implant and scanning the patient's mouth. Alternatively, the first digital surface representation may be acquired by attaching an orientation tool to the dental implant and scanning the patient's mouth.

In other embodiments, dental implant models or intermediates thereof are described. The intermediate model is a physical model of at least a portion of a patient's mouth at a location of a dental implant. The intermediate physical model further comprises a subgingival void having at least one mechanical orientation feature that mates with a cooperating orientation feature of a dental implant analog sleeve. The mating cooperating orientation feature preferably allows the sleeve to attach to the physical model in only one orientation. The physical intermediate model may be formed at a dental lab or rapid prototyping manufacturing center. The dental lab or a dental practitioner attaches the dental implant analog sleeve and/or attaches a permanent implant abutment to the sleeve. Further, the implant abutment preferably comprises at least one orientation feature that mechanically mates with or visually aligns with an orientation feature of the abutment when attached to the sleeve.

In preferred embodiments, the (i.e. same) dental implant abutment can serve the purpose of an orientation tool (also commonly referred to as a "scan locator") and a (e.g. permanent) implant abutment to be affixed to the implant that receives a permanent restoration. Further, this (i.e. same) dental implant abutment can be attached to a sleeve, and thereby also utilized in a physical dental model.

In yet another embodiment, a method of seating a permanent restoration is described comprising providing a physical model of at least a portion of a patient's mouth at a location of a dental implant. The physical model comprises a subgingival void having at least one mechanical orientation feature, a dental implant analog sleeve having a cooperating orientation feature mated with the mechanical orientation feature of the void, and a dental implant abutment attached to the sleeve. The method further comprises removing the dental implant abutment from the model and attaching the dental implant abutment to a patient's mouth. In yet another embodiment, a dental implant analog sleeve is described comprising a conical shaped base and an implant abutment-receiving end having a supragingival orientation feature suitable for aligning a dental implant abutment. The base of the sleeve is free of undercuts and free of horizontal recesses and protrusions having a depth greater than 0.1 mm

A set of dental implant analog sleeves is also described wherein the set comprises at least two dental implant analog sleeves having the same external geometry and the dental implant analog sleeves comprise different internal cavities that correspond in shape to different implant abutments.

In each of these embodiments, the dental implant analog sleeve and dental implant abutment may comprises one or more of various features as described herein, particularly orientation features for the purpose of properly aligning the analog sleeve to the void of the model and for aligning the implant abutment to the analog sleeve. Brief Description of the Drawings

Fig. 1 is a block diagram of a method of making a dental implant model;

Fig. 2 depicts a three dimensional scanning system;

Fig. 3 is an exploded view of an illustrative assembly of two-piece dental implant analog comprising a sleeve and an implant abutment;

Fig. 4 depicts a three-dimensional cross-sectional representation of the intraoral surfaces of an implant abutment attached to a dental implant;

Fig. 5 depicts the three-dimensional representation of Fig. 4 further comprising a subgingival void for receipt of a dental implant analog sleeve;

Fig. 6 depicts a stereo lithography apparatus;

Fig. 7 depicts a physical model of the three-dimensional representation of Fig. 4 and the sleeve inserted in the subgingival void;

Fig. 8 is an illustrative dental model comprising the sleeve and implant abutment of Fig. 3. Detailed Description

In the following description, the term "image" generally refers to a two- dimensional set of pixels forming a two-dimensional view of a subject within an image plane. The term "image set" generally refers to a set of related two dimensional images that might be resolved into three-dimensional data. The term "point cloud" generally refers to a three-dimensional set of points forming a three-dimensional view of the subject reconstructed from a number of two-dimensional views. In a three-dimensional image capture system, a number of such point clouds may also be registered and combined into an aggregate point cloud constructed from images captured by a moving camera. Thus it will be understood that pixels generally refer to two-dimensional data and points generally refer to three-dimensional data, unless another meaning is specifically indicated or clear from the context.

The terms "three-dimensional surface representation", "digital surface

representation", "three-dimensional surface map", and the like, as used herein, are intended to refer to any three-dimensional surface map of an object, such as a point cloud of surface data, a set of two-dimensional polygons, or any other data representing all or some of the surface of an object, as might be obtained through the capture and/or processing of three-dimensional scan data, unless a different meaning is explicitly provided or otherwise clear from the context. A "three-dimensional representation" may include any of the three-dimensional surface representations described above, as well as volumetric and other representations, unless a different meaning is explicitly provided or otherwise clear from the context.

In one embodiment, a method of forming a dental implant model is described. With reference to Fig. 1, the method comprises scanning at least a portion of a patient's mouth at a location of a dental implant to acquire a first digital surface representation thereof 103; acquiring a second digital surface representation of at least the exterior surface of a dental implant analog sleeve 106; and creating a three-dimensional digital model 110 such as by digitally modifying the first digital surface representation to substract the second digital surface representation thereby creating a void for receipt of the dental implant analog sleeve. The method further comprises forming a physical model from the three-dimensional model 111. The physical dental model is preferably fabricated by additive processes. Use of the method described herein can eliminate the use of traditional dental impression methods, wherein a (e.g. silicone) impression material is directly contacted with the intraoral surfaces of a patient's mouth to form a negative impression and then a (e.g. gypsum) stone model is cast from the negative impression.

Acquiring digital surface representation of intraoral structures is generally known. For example, US 7,698,014; incorporated herein by reference, describes a method of acquiring a digital surface representation of one or more intraoral surfaces and processing the digital surface representation to obtain a three-dimensional model.

As described in US 7,698,014, FIG. 2 shows an image capture system 200 that may include a scanner 202 that captures images from a surface 206 of a subject 204, such as a dental patient, and forwards the images to a computer 208, which may include a display 210 and one or more user input devices such as a mouse 212 or a keyboard 214. The scanner 202 may also include an input or output device 216 such as a control input (e.g., button, touchpad, thumbwheel, etc.) or a display (e.g., LCD or LED display) to provide status information.

The scanner 202 may include any camera or camera system suitable for capturing images from which a three-dimensional point cloud may be recovered. For example, the scanner 202 may employ a multi-aperture system as disclosed, for example, in U.S. Pat. Pub. No. 2004/0155975 to Hart et al. While Hart discloses one multi-aperture system, it will be appreciated that any multi-aperture system suitable for reconstructing a three- dimensional point cloud from a number of two-dimensional images may similarly be employed. In one multi-aperture embodiment, the scanner 202 may include a plurality of apertures including a center aperture positioned along a center optical axis of a lens and any associated imaging hardware. The scanner 202 may also, or instead, include a stereoscopic, triscopic or other multi-camera or other configuration in which a number of cameras or optical paths are maintained in fixed relation to one another to obtain two- dimensional images of an object from a number of slightly different perspectives. The scanner 202 may include suitable processing for deriving a three-dimensional point cloud from an image set or a number of image sets, or each two-dimensional image set may be transmitted to an external processor such as contained in the computer 208 described below. In other embodiments, the scanner 202 may employ structured light, laser scanning, direct ranging, or any other technology suitable for acquiring three-dimensional data, or two-dimensional data that can be resolved into three-dimensional data. In one embodiment, the scanner 202 is a handheld, freely positionable probe having at least one user input device 216, such as a button, lever, dial, thumb wheel, switch, or the like, for user control of the image capture system 200 such as starting and stopping scans. In an embodiment, the scanner 202 may be shaped and sized for dental scanning. More particularly, the scanner may be shaped and sized for intraoral scanning and data capture, such as by insertion into a mouth of an imaging subject and passing over an intraoral surface 206 at a suitable distance to acquire surface data from teeth, gums, and so forth. The scanner 202 may, through such a continuous acquisition process, capture a point cloud of surface data having sufficient spatial resolution and accuracy to prepare a dental model, either directly or through a variety of intermediate processing steps.

Although not shown in Fig. 2, it will be appreciated that a number of supplemental lighting systems may be usefully employed during image capture. For example, environmental illumination may be enhanced with one or more spotlights illuminating the subject 204 to speed image acquisition and improve depth of field (or spatial resolution depth). The scanner 202 may also, or instead, include a strobe, flash, or other light source to supplement illumination of the subject 204 during image acquisition.

The computer 208 may be, for example, a personal computer or other processing device. In one embodiment, the computer 208 includes a personal computer with a dual 2.8 GHz Opteron central processing unit, 2 gigabytes of random access memory, a TYAN Thunder K8WE motherboard, and a 250 gigabyte, 10,000 rpm hard drive. This system may be operated to capture approximately 1,500 points per image set in real time using the techniques described herein, and store an aggregated point cloud of over one million points. As used herein, the term "real time" means generally with no observable latency between processing and display. In a video-based scanning system, real time more specifically refers to processing within the time between frames of video data, which may vary according to specific video technologies between about fifteen frames per second and about thirty frames per second. More generally, processing capabilities of the computer 208 may vary according to the size of the subject 204, the speed of image acquisition, and the desired spatial resolution of three-dimensional points. The computer 208 may also include peripheral devices such as a keyboard 214, display 210, and mouse 212 for user interaction with the camera system 200. The display 210 may be a touch screen display capable of receiving user input through direct, physical interaction with the display 210. Communications between the computer 208 and the scanner 202 may use any suitable communications link including, for example, a wired connection or a wireless connection based upon, for example, IEEE 802.11 (also known as wireless Ethernet), BlueTooth, or any other suitable wireless standard using, e.g., a radio frequency, infrared, or other wireless communication medium. In medical imaging or other sensitive applications, wireless image transmission from the scanner 202 to the computer 208 may be secured. The computer 208 may generate control signals to the scanner 202 which, in addition to image acquisition commands, may include conventional camera controls such as focus or zoom.

In an example of general operation of a three-dimensional image capture system

200, the scanner 202 may acquire two-dimensional image sets at a video rate while the scanner 202 is passed over a surface of the subject. The two-dimensional image sets may be forwarded to the computer 208 for derivation of three-dimensional point clouds. The three-dimensional data for each newly acquired two-dimensional image set may be derived and fitted or "stitched" to existing three-dimensional data using a number of different techniques. Such a system employs camera motion estimation to avoid the need for independent tracking of the position of the scanner 202. One useful example of such a technique is described in commonly-owned U.S. Patent No. 7,605,817, incorporated herein by reference. However, it will be appreciated that this example is not limiting, and that the principles described herein may be applied to a wide range of three-dimensional image capture systems.

The display 210 may include any display suitable for video or other rate rendering at a level of detail corresponding to the acquired data. Suitable displays include cathode ray tube displays, liquid crystal displays, light emitting diode displays and the like. In some embodiments, the display may include a touch screen interface using, for example capacitive, resistive, or surface acoustic wave (also referred to as dispersive signal) touch screen technologies, or any other suitable technology for sensing physical interaction with the display 210.

The digital surface representation may be processed with one or more post- processing steps. This may include a variety of data enhancement processes, quality control processes, visual inspection, and so forth. Post-processing steps may be performed at a remote post-processing center or other computer facility capable of post-processing the imaging file, which may be, for example a dental laboratory. In some cases, this postprocessing may be performed by the image capture system 200. Post-processing may involve any number of clean-up steps, including the filling of holes, removing of outliers, etc.

Data enhancement may include, for example, smoothing, truncation, extrapolation, interpolation, and any other suitable processes for improving the quality of the digital surface representation or improving its suitability for an intended purpose. In addition, spatial resolution may be enhanced using various post-processing techniques. Other enhancements may include modifications to the data, such as forming the digital surface representation into a closed surface by virtually providing a base for each arch, or otherwise preparing the digital surface representation for subsequent fabrication steps.

The three-dimensional representation of a patient's intraoral surfaces at the location of a dental implant will vary depending of the type of dental implant procedure utilized. In the case of a single-stage implant; a cover screw, healing abutment, or a temporary abutment typically extend through the gingivia overlying the site of the implant. After the healing abutment has been in position for the appropriate length of time (i.e. after osseointegration), the retaining screw and healing abutment (or other temporary structure) is removed to expose the internal bore of the underlying implant (e.g. anchor). When a two-step dental implant method is employed, the method further comprises removing (healed) dental tissue above the tooth implant (e.g. anchor) such that the tooth implant (e.g. anchor) is exposed.

The first digital surface representation is typically acquired by attaching an appliance to the dental implant (e.g. anchor) 101. Such appliance generally conveys information about the position and orientation of the underlying dental implant. The appliance preferably comprises at least one orientation feature that is capable of being detected by the image capture system (e.g. by optically scanning). Such appliance may be an orientation tool (such as described in U.S. Patent No. 6,135,773), a mounting piece (such as described in and US2006/0019219), a healing abutment having scannable informational markers such as described in US2008/0153067, or the like. The appliance is preferably a (e.g. permanent) implant abutment having at least one orientation feature. For example, Fig. 4 depicts a three-dimensional cross-sectional representation of the intraoral surfaces of a patient's mouth at the location of a dental implant after attaching a scannable implant abutment 350 of Fig. 3 to the dental implant (e.g. anchor) 400.

The dental implant (e.g. anchor) 400 is generally a threaded cylindrical body which is implanted in a cylindrical bore made in the patient's jawbone (i.e., an endosseous implant) at the site of a edentulous ridge or tooth extraction socket. The dental implant (e.g. anchor) 400 also typically includes an internally-threaded cylindrical socket (e.g. having a hex-shape opening) in which to fasten a cover screw, healing cap, or implant abutments. Various implant systems are known, such as commercially available from Straumanns, 31, Astra tech, Zimmer, and Nobel. The width of the dental implant at the gingival aspect is typically slightly wider than the mating end of the implant abutment.

The abutment can typically attach to the dental implant (e.g. anchor) 400 in more than one orientation, such as in the case when the socket of the implant is a regular hexagon. It is preferred to attach the scannable implant abutment 350 of Fig. 3 to the dental implant (e.g. anchor) 400 such that the mechanical orientation feature is also highly visible to the dental practitioner. For example, if the abutment has a single orientation feature such as a single vertical flat, it is preferred to position the vertical flat such that it is not facing the adjacent teeth.

In some embodiments, the (e.g. permanent) implant abutment is a preformed (e.g. one piece) metal abutment having a base suitable for attachment to a tooth implant (e.g. anchor) and an opposing end suitable for receipt of a (e.g. permanent) restoration, such as a crown or bridge. Alternatively, the (e.g. permanent) implant abutment may comprise a preformed metal abutment that is an abutment interface having a base suitable for attachment to a tooth implant (e.g. anchor) and an opposing end suitable for receipt of a custom abutment such as ceramic custom abutment as can be prepared from Lava™ Zirconia available from 3M ESPE. A permanent restoration is then attached to the custom abutment. Unless specifically stated otherwise, the term "implant abutment" as used herein also encompasses implant abutment interfaces having an abutment as well.

A (i.e. temporary) surface treatment is generally applied to the intraoral (e.g. tooth) surfaces prior to three-dimensional scanning, such as described for example in

WO2009/089125; incorporated herein by reference. The surface treatment typically comprises a particulate opacifying agent, such as titanium dioxide, to reduce the specular reflectivity, translucency and the like of the intraoral surfaces. The particles typically create a micron-scale roughness contributing to diffuse, Lambertian surface reflection characteristics.

A variety of carriers may be employed to apply the surface treatment such as a mouthwash carrying sticky particles, or powders sprayed with air or other propellant. In some embodiments, the intraoral surface coating may include particles having a size ranging from about 15-30 microns. The surface treatment may also include an active light sensitive layer or particles that can be excited by proper illumination (e.g. induced fluorescence). In some embodiments, particles may be applied to form an incomplete coating of the surface such as less than 95% of the surface, less than 90% of the surface, less than 75 % of the surface, or less than 50%> of the surface.

The scan captures a three-dimensional representation of some or all of the dentition of a patient's intraoral surfaces at least at the location of a dental implant, i.e. typically the tooth structures directly adjacent to and those that will come in contact with the tooth- shaped surfaces of the restoration that will be affixed to the dental implant abutment.

When the appliance is a (i.e. specularly reflecting) preformed metal appliance that comprises orientation features, the opacifying (e.g. powdered) surface treatment can alter or mask the orientation features from being detected by the image capture system. To rectify this problem a preformed scannable implant abutment such as a preformed metal implant abutment having a permanently bonded opaque coating, such as described in patent application serial no. 61/242546, filed September 15, 2009, titled "DENTAL

IMPLANT ABUTMENTS AND METHODS OF USE"; incorporated herein by reference. Such scannable implant abutment (i.e. having at least one orientation feature) may be attached to the dental implant (e.g. anchor) after the opacifying surface treatment has been applied to the intra oral surfaces. In this embodiment, an orientation tool or mounting piece is not needed because the scannable implant abutment conveys information about the position and orientation of the axis of the underlying (osseointegrated) dental implant. Further, the (e.g. same) scannable implant abutment can attach to a sleeve in the physical model fabricated from the three-dimensional model. Further, this (e.g. same) scannable implant abutment can also receive a permanent restoration (e.g. crown or bridge). Hence, the (i.e. same) dental implant abutment can serve multiple purposes, thereby reducing the number of different parts needed during the processes of scanning a patient's mouth, generating a physical model, fabricating a restoration for the implant abutment, and seating such restoration in the patient's mouth.

With reference to Fig. 1, acquiring a second digital surface representation of at least the exterior surface of a dental implant analog sleeve 106 can be obtained by scanning a dental implant analog sleeve 104 in substantially the same manner as scanning a patient's intraoral surfaces. When the sleeve is a preformed metallic sleeve, the sleeve may also comprise a permanently bonded opaque coating (as in the case of the scannable implant abutment) to render the sleeve optically scannable. However, in preferred embodiments, the digital surface representation of the dental implant analog sleeve is incorporated into the software (e.g. used by the dental lab) to create the three-dimensional digital model. For example, the software may include the selection or entry of a particular dental implant (e.g. anchor) and the software then selects the proper sleeve having the correct internal cavity to simulate such dental implant.

The digital surface representations may be acquired by transmitting such information to a rapid fabrication facility such as a dental laboratory, an in-house dental laboratory at a dentist's office, or any other facility with machinery to fabricate physical models from digital models. In yet another embodiment, the digital surface

representations may be downloaded from an internet site.

With reference to Fig. 4, the patient's intraoral surface lacks a void that extends below the gumline at the location of the dental implant. However, such void is digitally created at the location of the implant by use of three-dimensional digital CAD software utilized for creation of the digital model. A three-dimensional digital model is created by modifying the digital surface representation of the patient's mouth to incorporate the digital surface representation of the exterior surface of the sleeve. Typically, the digital surface representation of the sleeve is selected (from the CAD software) 105 and superimposed at the location of the dental implant, as depicted in Fig. 5. The

superimposition is aligned to take into account the angularity and orientation feature(s) of the implant, as conveyed by the scannable implant abutment, orientation tool, or the like. For example, the digital surface representation of the sleeve is superimposed such that the orientation feature (e.g. vertical flat 315 of Fig. 3) of the sleeve is aligned with the digital surface representation of the orientation feature (e.g. 356 vertical flat of Fig. 3) of the scanned implant abutment, as will subsequently be explained in greater detail. The superimposed digital surface representation of the sleeve is then subtracted (by use of the software) from the digital surface representation of the patient's mouth, thereby creating a void for receipt of the dental implant analog sleeve.

Various CAD software is available that has three-dimensional subtraction capabilities. For example, creation of a "hole" is typically a standard CAD command. Further, several CAD program utilize Boolean union, intersection, and particularly subtraction operations via algorithms.

With reference to Fig. 1, the method comprises forming a physical model (i.e. directly) from the three-dimensional model of the patient's mouth and the implant analog sleeve, by use of a rapid prototyping system 111. Hence, the present invention is particularly useful for forming a (e.g. positive) model directly from the digital surface representation of the patient's mouth without the use of (e.g. silicone) impression materials.

Various rapid prototyping systems, such as described in US 7,698,014;

incorporated herein by reference have been described including subtractive processes such as milling, as well as additive processes such as stereo lithography and three-dimensional printing, or a combination thereof.

Milling is generally a subtractive technology in that material is subtracted from a block rather than added. Such milling blocks for physical model are typically comprised of relatively low cost material such as gypsum or a polymeric material. A milled physical model typically has a higher surface roughness than a cast (e.g. gypsum).

In addition a milling system may use a variety of cutting tools, and the milling system may include an automated tool changing capability to cut a single part with a variety of cutting tools. In milling a dental model, accuracy may be adjusted for different parts of the model. For example, the tops of teeth, or occlusal surfaces, may be cut more quickly and roughly with a ball mill and the prepared tooth and dental margin may be milled with a tool resulting in greater detail and accuracy. In general, milling systems offer the advantage of working directly with a finished material so that the final product is free from curing-related distortions or other artifacts. As a disadvantage, a high precision requires smaller cutting tools and correspondingly slower fabrication times.

Fig. 6 shows a stereo lithography apparatus ("SLA") that may be used with the systems and methods described herein. In general, the SLA 600 may include a laser 602, optics 604, a steering lens 606, an elevator 608, a platform 610, and a straight edge 612, within a vat 613 filled with a polymer. In operation, the laser 602 is steered across a surface of the polymer to cure a cross-section of the polymer, typically a photocurable liquid resin, after which the elevator 608 slightly lowers the platform 608 and another cross section is cured. The straight edge 612 may sweep the surface of the cured polymer between layers to smooth and normalize the surface prior to addition of a new layer. In other embodiments, the vat 613 may be slowly filled with liquid resin while an object is drawn, layer by layer, onto the top surface of the polymer. One useful commercial embodiment of an SLA apparatus is commercially available from 3D Systems under the trade designation iPro™ 8000.

Stereo lithography is well-suited for the high volume production of dental models and dies, because parts may be batched on machines for rapid production. When optimized, these parts may be used in lieu of plaster dental models and other dental objects. An SLA may be usefully employed for fabrication of dental models, arches and cast-able parts, as well as for other high-accuracy and/or high-throughput applications. In some embodiments an SLA may receive a digital surface representation directly from a clinician's intraoral scan, and manufacture a dental model corresponding to the patient's dentition with or without surrounding soft tissue. Where groups of related objects are manufactured, they may be physically interconnected during the SLA process so that a complete set or kit is readily handled after fabrication. Individual pieces of the kit may be separated and trimmed or finished as appropriate, such as by a qualified technician in a dental laboratory. In such embodiments, dental objects may be oriented so that the interconnecting frame or other mechanical infrastructure only contacts objects on non- critical surfaces. Thus, for example, connections might be avoided on opposing surfaces of a dental arch where fine detail is to be preserved.

Various types of three-dimensional printers exist. Some printers deposit a polymer in conjunction with a support material or a bonding agent. In some systems, the stage may move as well to control x-y motion of the print head relative to the platform and printed item. Models printed on such systems may require finishing steps, such as removal of wax supports and other cleaning processes. Three-dimensional printers are well suited to rapid fabrication of small parts such as wax patterns or wax-ups, as well as dies and other relatively small dental objects. One commercial system suitable for three-dimensional dental printing applications is the ProJet™ 3-D printers from 3D Systems.

With reference to Fig. 1, after the physical model intermediate has been formed comprising the suitably sized and shaped subgingival void, a dental implant analog sleeve is inserted into the void, (e.g. temporarily) attaching the sleeve to the physical model 112, such as depicted in Fig. 7. By virtue of fabricating the subgingival void of the physical model to have a mechanical orientation feature that mates with a cooperating orientation feature (e.g. flat 315 of Fig. 3) of the dental implant analog sleeve, the sleeve fits into the void in only one possible orientation.

The sleeve is designed to simulate the dental implant (e.g. anchor) and thus typically includes a (e.g. hex-shaped) internally-threaded cylindrical socket in which to fasten an implant abutment. Hence, the internal geometry of the socket of the sleeve is the same as the internal geometry of the dental implant.

An (e.g. permanent) implant abutment 350 is then (e.g. temporarily) attached to sleeve 310 of Fig. 3, such as depicted in Fig. 8. With reference to Fig. 3, the implant abutment 350 is attached to the sleeve such that the orientation feature (e.g. vertical flat 356) visually aligns with the orientation feature (e.g. flat 315 of Fig. 3) of the analog sleeve. Although, the mechanical orientation feature (e.g. flat 315 of Fig. 3) is not visible once the sleeve is inserted into the void of the fabricated physical model, the presence of such is known from a supragingival orientation feature (such as notch 370) of the sleeve.

With reference to Fig. 1, a permanent restoration, such as a crown or bridge, can be fabricated, as known in the art, and seated on the restorative -receiving (i.e. top) supragingival end of the implant abutment. When the implant abutment is an abutment interface, a (e.g. custom) abutment is first formed and then a permanent restorative is fabricated to (e.g. custom) fit the abutment.

The permanent (e.g. crown) restoration is preferably fabricated such that the restoration has a cavity having a cooperating mechanical feature to mate with the supragingival end of the implant abutment. For example, when the abutment comprises a vertical groove, the cavity of the restoration comprises a vertical protrusion that mates with such groove. Likewise, when the abutment comprises a vertical protrusion, the cavity of the restoration comprises a vertical groove that mates with such protrusion. Further, when the abutment comprises a vertical flat, the cavity of the restoration comprises a vertical flat that mates with such protrusion. When the permanent restoration is fabricated with a cooperating mating mechanical orientation feature, the inclusion of such insures proper placement of the restoration.

The mating orientation feature is preferably designed such that the restoration can be seated on the abutment in only one possible orientation. This can be accomplished when the abutment and restoration each comprise a single mechanical feature, such as a single mating vertical flat. Alternatively this can be accomplished by use of an abutment that comprises more that one vertical mechanical orientation features provided that these mechanical features are not evenly spaced about the circumference of the abutment. This results in the abutment having an asymmetrical cross-section. The asymmetry of the supragingival end of the abutment and restoration cavity permits these pieces to fit together in only one possible orientation. When the abutment is an abutment interface that receives a custom abutment, it is preferred that the custom abutment is designed to have an asymmetrical cross section. It is appreciated that the abutment may comprises other, relatively smaller mechanical features such as shallow groove anti-pull features that need not be replicated in the restoration to insure proper placement.

A variety of preformed restoratives are described. Temporary restorative (e.g. crowns) typically comprise a plastic; whereas permanent restorative generally comprise a ceramic material. The restoration may also comprise a malleable material such as described in US 7,674,850; incorporated herein by reference. When such restorative material is employed, the method generally comprises shaping at least a portion of the preformed restoration and hardening the restoration either prior to or after affixing the restoration to the supragingival end of the implant abutment.

The (e.g. permanent) restoration can be affixed to the implant abutment with a dental cement as known in the art. Typically, the cavity of the dental restoration is partially filled with a dental cement and then placed over the implant abutment such that the base of the dental article contacts the abutment platform (352 of FIG. 3). Suitable dental cements are commercially available from 3M ESPE under the trade designation "RelyX Unicem Self Adhesive Universal Resin Cement".

In some embodiments, the physical model is employed in a method of seating a permanent restoration. The method comprises (e.g. a dental lab or other facility) providing a physical model of at least a portion of a patient's mouth at a location of a dental implant. The physical model comprises a subgingival void, a dental implant analog sleeve attached to the void, and a dental implant abutment attached to the sleeve. The physical model may be provided preassembled or the physical model may be provided as separate pieces that are assembled at a dental office.

The method further comprises (e.g. a dental practitioner) removing the dental implant abutment from the model and attaching the dental implant abutment to a patient's mouth 116. In some embodiments, the dental implant abutment further comprises a permanent restoration (i.e. permanently attached to the dental implant abutment) prior to attaching to the patient's mouth 115. In other embodiments, the method further comprises attaching (e.g. cementing) a permanent restoration to the dental implant abutment after attaching the dental implant abutment to the patient's mouth.

The permanent restoration can be affixed to the implant abutment with a dental cement as known in the art. Typically, the cavity of the dental restoration is partially filled with a dental cement and then placed over the implant abutment such that the base of the dental article contacts the abutment platform (352 of Fig. 3). Suitable (e.g. temporary) cements are commercially available from 3M ESPE under the trade designation "RelyX Temp NE Temporary Cement".

The dental implant analog sleeve and implant abutment are typically preformed articles comprised of a metal such as palladium-silver alloy, stainless steel, aluminum, and most commonly titanium or a titanium alloy. The sleeve may alternatively be formed from a rigid thermoplastic or thermosetting material as well, such as an acrylic.

The dental implant analog sleeve and dental implant abutment useful for the methods described herein may have various designs.

With reference to Fig. 3, an exploded view of an illustrative assembly of a dental implant analog sleeve 310 and a (e.g. permanent) preformed implant abutment 350.

The implant abutment may take the form of an elongated tubular body generally comprising a base end 351 that is designed to mate with the gingival aspect of the implant (e.g. anchor) and an opposing supragingival end 353 that receives a permanent restoration. In the case of an implant abutment interface, the opposing end receives a (e.g. custom) abutment and then a permanent restoration.

The implant abutment may comprise a platform 352. Abutments that include a platform are commercially available from Nobel Biocare under the trade designation "Easy Abutment". Alternatively, the abutment may lack a platform. In such embodiment, the base of the dental article may rest directly on the implant anchor. Exemplary abutments that lack a platform are commercially available from Straumann ITI.

Implant abutments typically comprise one or more anti-rotation features as known in the art. For example, the base portion of the abutment that mates with the internal cavity of the sleeve (as well and the cavity of the sleeve) are typically hexagonal 355 in shape. Other anti-rotation features include for example a flat(s), groove(s), or

protrusion(s).

The implant analog sleeve 310 has sufficient structure such that it can be securely attached to the void of the physical model. In some embodiments, the height of the sleeve ranges from about 5 mm to about 15 mm. Typically, the sleeve extends into the model a depth about equal to the height of the supragingival (e.g. crown) structure. The walls of the sleeve about the cavity are of sufficient thickness (e.g. 0.5 - 2 mm) to protect the dental implant abutment from damage while being manipulated (e.g. by hand) during use of the physical model.

Although the sleeve may have various exterior shapes, the exterior geometry of the dental implant analog sleeve has substantially the same geometry as the void formed in the physical model from the digital surface representation of the dental implant analog sleeve.

The exterior geometry of the sleeve is preferably chosen to facilitate the fabrication of the void. The subgingival exterior surfaces of the sleeve as well as the void, are generally free of any other structural features that would detract from the fit between the exterior surface of the sleeve and the void. Hence, the subgingival exterior surfaces of the sleeve, as well as the void that receives such, are generally free of undercuts, as well as deep (e.g. horizontal) grooves or protrusions (e.g having a difference in depth of about 0.1 mm or greater). Lack of fit between the sleeve and void results in lack of accuracy and thus positional errors between the physical model fabricated from the three-dimensional model and the subsequently seated permanent restoration.

In some embodiments, the dental implant analog sleeve has a cylindrical or conical shape. As depicted in Fig. 3, in one design the dental implant analog sleeve has a substantially cylindrical upper portion and a slightly tapered lower portion, the lower portion being tapered at an angle of about 1°, 2°, 3° and preferably about 4°. The depicted implant analog sleeve comprises an internal cavity 340 capable of securely (e.g. temporarily) attaching with the gingival aspect of a dental implant abutment. In one embodiment, the abutment comprises a shoulder (not shown) within the cavity 354 for cooperation with a screw 370 to fasten the abutment to the implant anchor.

Although, the representative implant analog sleeve 310 of Fig. 3 has an internal cavity having a hexagonal cross-section, the internal cavity can be designed to attach to the base of most any implant abutment.

The sleeve preferably comprises one or more mechanical features that are amenable to proper orientation within the void. The sleeve preferably comprises at least one (e.g. mechanical) orientation feature such as a vertical groove, vertical protrusion, or (e.g. single) vertical flat 315. Such orientation feature can act as an anti-rotation feature to prevent rotation of the implant analog sleeve within the void. The void preferably comprises a cooperating (e.g. mechanical) orientation feature (e.g. single flat) that mates with the mechanical orientation feature of the sleeve. By mating with the corresponding (i.e. single) flat of the void, the sleeve can be inserted into the void in only one possible orientation. Hence, the orientation feature of the sleeve in combination with the orientation feature of the void insures proper placement of the sleeve in the void.

In some embodiments, the void is fabricated such that the exterior geometry of the sleeve precisely fits within the void (e.g. to a tolerance of no greater than about 25 microns). For example, when the exterior surface of the sleeve has shallow grooves, and the diameter of the sleeve is slightly greater near the top than near the base, and the void has the corresponding mating design, the sleeve may be attached by snapping the sleeve into the void. Alternatively, the tolerance can be slightly greater and the sleeve can be attached by other means such as by adhering the sleeve in the void. The void and sleeve may alternatively each be threaded such that the sleeve mechanically fastens within the void.

The sleeve preferably comprises orientation features that mechanically mate with or visually aligns with an orientation feature of the implant abutment.

As also depicted in Fig. 3, in one embodiment the sleeve may comprise a notch 370 or other orientation feature that visually aligns with a vertical flat 315 or other orientation feature of the (e.g. permanent) dental implant abutment. Although a regular hexagonal shaped abutment end can be inserted into the sleeve in six possible orientations, only one of such orientations results in the orientation feature (e.g. flat 315) of the abutment being aligned with the orientation feature (e.g. notch 370) of the sleeve.

The depicted notch has a rectangular shape (from either a top or side view) formed by removal of the collar at the intersection of the vertical flat 315 and collar 360. The notch may have other shapes such as a triangular or semi-circle. Alternatively, the sleeve may have a protrusion rather than a notch as an orientation feature to indicate the location of the subgingival orientation feature (e.g. vertical flat 356) of the sleeve. A protrusion may be preferred for sleeves that lack a collar. Finally, the sleeve may have etching or printed marking on the top and/or side of the collar or the sleeve as a visual orientation feature.

As depicted in Fig. 3, the sleeve may further comprise a collar 360 having a slightly larger circumference than the (e.g. cylindrical-shaped) base such that the lower surface of the collar contacts and rests upon a recessed lip at the perimeter of the void of the model. The presence of such lip, protrusion, or other mechanical feature about the opening of the internal cavity for receipt of the subgingival end of the abutment can aid in properly positioning the sleeve within the void.

As depicted in Fig. 3, the exterior surface of the sleeve may comprise (i.e.

horizontal) anti-pull feature such as shallow grooves 305 having a depth no greater than about 0.1 mm that hinder removal from the void. Other anti-pull features include for example shallow horizontal f at(s), horizontal groove(s), or horizontal protrusion(s). In the case of attachment with an adhesive, such shallow mechanical features or other surface roughening can increase the surface area, thereby improving the bond strength. Likewise, the implant abutment 350 may also comprises anti-pull features 357 that aid in retaining the permanently seated restoration.

In some embodiments, the digital surface representations of a variety of dental implant analog sleeves having different external geometries and/or dimensions are separately scanned or incorporated into the software for creating the three-dimensional model. In a preferred embodiment the exterior geometry of the dental implant analog sleeve is universal, i.e. a single exterior geometry would be suitable for a variety of implant abutments.

In some embodiments, the internal cavity may also be suitably (e.g. hex) shaped such that the cavity could accommodate more than one type of implant abutment

However, due to the variation in dimension and design among the dental implant abutment manufacturers and the desire for the implant abutment to precisely fit within the internal cavity of the sleeve, it is anticipated that a set of dental implant analog sleeves would be employed. The sleeve may be designed to accommodate various regular and wide neck abutments as well as synthetic temporary abutments such as available from Straumanns, 31, Astra tech, Zimmer, and Nobel. The set would comprise two or more dental implant analog sleeves having the same external geometry, yet comprise different internal cavities that correspond in shape to different implant abutments. Hence, with respect to the fabrication of the void and the fit between the void and the implant analog sleeve, the sleeve would be universal, yet each manufacturer may have a customized interior cavity of the sleeve to cooperate with a particular implant abutment design for the purpose of generating a model.

Claims

What is claimed is:

1. A method of forming a dental implant model comprising:

scanning at least a portion of a patient's mouth at a location of a dental implant to acquire a first digital surface representation;

acquiring a second digital surface representation of at least the exterior surface of a dental implant analog sleeve;

creating a three-dimensional digital model by modifying the first digital surface representation to subtract the second digital surface representation at the location of a dental implant thereby creating a subgingival void for receipt of the dental implant analog sleeve; and

forming a physical model from the three-dimensional model.

2. The method of claim 1 wherein the first digital surface representation is acquired by attaching a scannable implant abutment to the dental implant and scanning the patient's mouth.

3. The method of claim 1 wherein the first digital surface representation is acquired by attaching an orientation tool to the dental implant and scanning the patient's mouth.

4. The method of claim 2 wherein the scannable implant abutment comprises at least one orientation feature that mates with or visually aligns with an orientation feature of the sleeve.

5. The method of claim 4 wherein the three-dimensional model is created by

superimposing the second digital surface representation onto the first digital surface representation such that the orientation feature of the scannable implant abutment is digitally aligned with the orientation feature of the sleeve.

6. The method of claim 1 further comprising attaching the dental implant analog sleeve to the subgingival void of the physical model.

7. The method of claim 6 wherein the sleeve comprises at least one mechanical orientation feature that mates with a cooperating mechanical orientation feature of the void thereby allowing the sleeve to attach to the void in only one orientation.

8. The method of claim 6 wherein the sleeve comprises a collar that contacts a recessed lip at the perimeter of the void of the physical model.

9. The method of any of claims 6-8 wherein the sleeve has an internal cavity geometry that mates with an implant abutment.

10. The method of claim 8 further comprises attaching a dental implant abutment to the internal cavity of the sleeve.

11. The method of any of the previous claims wherein the dental implant abutment is a scannable preformed metal abutment comprising a permanently bonded opaque coating on at least supragingival surfaces.

12. The method of any of the preceding claims wherein the dental implant analog sleeve has a base that is free of undercuts and free of recesses and protrusions having a depth greater than 0.1 mm

13. The method of any of the preceding claims wherein the base of the dental implant analog sleeve has a tapered external geometry.

14. The method of any one of claims 10-13 further comprising attaching a permanent restoration to the dental implant abutment.

15. The method of any of the preceding claims wherein the digital surface representation of the sleeve is incorporated into software employed for creating the three-dimensional representation of the model.

16. The method of claim 15 wherein the software provides for the selection of at least two different three-dimensional representations of dental implant analog sleeves.

17. The method of claim 16 wherein the two different three-dimensional representations having the same external structure and different internal cavities that cooperate with different implant abutment external structures.

18. The method of any of the preceding claims wherein the model is formed using stereolithography or three-dimensional printing.

19. A dental implant model comprising:

a physical model of at least a portion of a patient's mouth at a location of a dental implant wherein the physical model comprises a subgingival void having at least one mechanical orientation feature that mates with a cooperating orientation feature of a dental implant analog sleeve.

20. The dental implant model of claim 19 further comprising the dental implant analog sleeve attached to the subgingival void of the physical model.

21. The dental implant model of claim 19 wherein the sleeve comprises a collar that contacts a recessed lip at the perimeter of the void of the physical model.

22. The dental implant model of claims 19-21 wherein the sleeve has an internal cavity geometry that mates with an implant abutment.

23. The dental implant model of claim 20 further comprising a dental implant abutment attached to the internal cavity of the sleeve.

24. The dental implant model of claim 23 wherein the dental implant abutment comprises at least one orientation feature that mates with or visually aligns with the orientation feature of the sleeve.

25. The dental implant model of claim 23 or 24 further comprising a permanent restoration affixed to the dental implant abutment.

26. The dental implant model of claim 19 wherein the physical model comprises hardened stereolithographic material or hardened three-dimensional printed material.

27. A method of seating a permanent restoration comprising:

providing a physical model of at least a portion of a patient's mouth at a location of a dental implant wherein the physical model comprises

a subgingival void having at least one mechanical orientation feature,

a dental implant analog sleeve having a cooperating orientation feature mated with the mechanical orientation feature of the void, and

a dental implant abutment that attaches to the sleeve;

removing the dental implant abutment from the model; and

attaching the dental implant abutment to a patient's mouth.

28. The method of claim 27 wherein the dental implant abutment comprises an orientation feature that mates with or visually aligns with an orientation feature of the sleeve.

29. The method of claim 27 or 28 wherein the dental implant abutment further comprises a permanent restoration prior to attaching to the patient's mouth.

30. The method of claim 27 or 28 further comprising attaching a permanent restoration to the dental implant abutment after attaching the dental implant abutment to the patient's mouth.

31. A dental implant analog sleeve comprising a conical shaped base and an implant abutment-receiving end having a supragingival orientation feature suitable for aligning a dental implant abutment wherein the base is free of undercuts and free of horizontal recesses and protrusions having a depth greater than 0.1 mm

32. The dental implant analog sleeve of claim 31 wherein the implant-abutment receiving end comprises a collar having a cross-section wider than the conical shaped base.

33. The dental implant analog sleeve of claim 31 wherein the supragingival orientation feature is a notch in the collar, an etched portion on the collar, a printed portion on the collar, or a combination thereof.

34. The dental implant analog sleeve of claim 31 wherein the sleeve further comprises a subgingival anti-rotation feature.

35. The dental implant analog sleeve of claim 34 wherein the anti-rotation feature is a vertical flat, vertical groove, or vertical protrusion aligned with the supragingival orientation feature.

36. The dental implant analog sleeve of claims 31 wherein the sleeve further comprises a subgingival anti-pull features.

37. An assembly comprising the dental implant analog sleeve of any of claims 31-36 and a dental implant abutment attached to the sleeve.

38. The assembly of claim 37 wherein the dental implant abutment comprises an orientation feature that mates with or visually aligns with an orientation feature of the sleeve.

39. A set of dental implant analog sleeves wherein the set comprises at least two dental implant analog sleeves having the same external geometry and the dental implant analog sleeves comprise different internal cavities that correspond in shape to different implant abutments.