WO2011034780A1

WO2011034780A1 - Dental implant abutments and methods of use

Info

Publication number: WO2011034780A1
Application number: PCT/US2010/048358
Authority: WO
Inventors: 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

Abstract

The present invention concerns methods of fabricating a permanent restoration for a dental implant and dental implant abutment articles.

Description

DENTAL IMPLANT ABUTMENTS AND METHODS OF USE

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.

After the dental implant has been in position for the appropriate length of time (i.e. after osseointegration), a permanent implant abutment having a permanent restoration (e.g. crown or bridge) is attached to the underlying implant (e.g. anchor). The permanent implant abutment can be a preformed one piece metal article 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 permanent implant abutment can have a two piece design including an "abutment interface", i.e. a preformed metal article 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 a ceramic custom abutment as can be prepared from Lava™ Zirconia available from 3M ESPE.

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.

Summary

In one embodiment, a method of making a dental restoration is described. The method comprises attaching a dental implant abutment to a dental implant in a patient's mouth; scanning at least a portion of the patient's mouth comprising the dental implant abutment to acquire a digital surface representation; creating a three-dimensional digital model from the digital surface representation; and forming a restoration from the three- dimensional digital model.

The dental implant abutment has been adapted to be suitable for use as an orientation tool, also known as a "scan locator". To serve this purpose, the supragingival end of the dental implant abutment is optically scannable and comprises at least one orientation feature. The same dental implant abutment is also suitable for use as a permanent or temporary abutment that receives a dental restoration. 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, fabricating a restoration for the implant abutment, and seating such restoration in the patient's mouth.

Also described are dental implant abutment articles. In one embodiment, a dental implant abutment is described comprising a gingival end for mating with a dental implant and a supragingival end for mating with a dental restoration. The supragingival end is optically scannable and comprises at least one orientation feature.

In another embodiment, a dental implant abutment is described comprising a gingival end for mating with a dental implant and a supragingival end for mating with a dental restoration wherein the dental implant abutment comprises a metal base article comprising an opaque polymeric coating on at least the surpagingival end. The inclusion of the opaque polymeric coating can improve the aesthetic appearance of the (e.g. crown or bridge) restoration attached to the abutment. When such dental implant abutment is also employed as a scan locator in the method described herein, the dental abutment article further comprises at least one (e.g. optically scannable) supragingival orientation feature.

In each of these embodiments, the optically scannable orientation feature may comprise digital information, at least one visual feature, at least one mechanical feature, or a combination thereof. The optically scannable orientation feature is preferably a (e.g. single) mechanical feature such as a vertical groove, protrusion, or flat, that mates with a cooperating orientation feature of a custom abutment or dental restoration, such as a crown or bridge.

Brief Description of the Drawings

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

Fig. 2 depicts a three dimensional scanning system;

FIG. 3 is an illustrative dental 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 is a graph of the total reflection of a metal dental implant abutment in comparison to an abutment comprising a permanently bonded opaque coating;

Fig. 6 is an optical micrograph of an illustrative dental implant abutment;

Fig. 7 is an optical micrograph of another illustrative dental implant abutment.

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.

The term "implant abutment" refers to a preformed (e.g. one piece) metal article having a base suitable for attachment to a tooth implant (e.g. anchor) and an opposing end suitable for receipt of a permanent restoration, such as a crown or bridge. In some embodiments, the implant abutment 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 (e.g. 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. In one embodiment, a method of making a dental restoration is described. With reference to Fig. 1, the method comprises attaching a dental implant abutment to a dental implant in a patient's mouth 101; scanning at least a portion of the patient's mouth at a location of the dental implant abutment to acquire a digital surface representation 103; creating a three-dimensional digital model from the digital surface representation 110; and fabricating a restoration from the three-dimensional digital model 114. The dental implant abutment has been adapted to be suitable for use as an orientation tool, also known as a "scan locator". To serve this purpose, the supragingival end of the dental implant is optically scannable and comprises at least one orientation feature.

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 postprocessing 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 acquired by attaching a dental implant abutment to the dental implant (e.g. anchor) 101. The implant abutment conveys information about the position and orientation of the underlying dental implant. The implant abutment comprises at least one orientation feature that is capable of being detected by the image capture system (e.g. by optically scanning). 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 an 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-shaped 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.

Dental abutments and abutment interfaces are preformed articles comprised of a metal such as palladium-silver alloy, stainless steel, aluminum, and most commonly titanium or a titanium alloy. However, as illustrated in the forthcoming examples, the reflection properties of such metal surfaces are problematic to optical scanning.

Specular reflection is the mirror-like reflection of light from a surface, in which light from a single incoming direction (a ray) is reflected into a single outgoing direction. Such behavior is described by the law of reflection, which states that the direction of incoming light (the incident ray), and the direction of outgoing light reflected (the reflected ray) make the same angle with respect to the surface normal, thus the angle of incidence equals the angle of reflection. This is in contrast to diffuse reflection, where incoming light is reflected in a broad range of directions. When a surface exhibits Lambertian reflectance, light falling on it is scattered such that the apparent brightness of the surface to an observer is the same regardless of the observer's angle of view. The surface luminance is considered isotropic. Not all rough surfaces are perfect Lambertian reflectors, but this is often a good approximation when the characteristics of the surface are unknown. In computer graphics, Lambertian reflection is often used as a model for diffuse reflection. The effect this has from the viewer's perspective is that rotating or scaling the object does not change the apparent brightness of its surface.

One way to increase the diffuse reflection in favor of specular reflection and thereby increase the total reflection of a metal implant abutment is to apply the same opacifying (e.g. powdered) surface treatment as is typically applied to the patent's oral surfaces. However, for embodiments wherein the implant abutment comprises an orientation feature (such as a visual marking), the opacifying (e.g. powdered) surface treatment can alter or mask the orientation feature(s) from being detected by the image capture system.

To address this problem, the abutment is preferably a preformed metal abutment wherein at least the supragingival end is optically scannable without application of a (i.e. temporary) surface treatment. In preferred embodiments, the supragingival end of the dental implant abutment, i.e. the portion underlying the subsequently seated restoration (e.g. crown or bridge), is rendered optically scannable by inclusion of a permanently bonded coating that increases the total reflection of the abutment. A permanently bonded opaque coating can also mask the appearance of the preformed metal abutment, thereby improving the aesthetic appearance of the subsequently seated (e.g. crown or bridge) restoration.

With reference to Fig. 5, the coating can increase the total reflection of the metal abutment such that the total reflection is at least 25%, 30%, 40%, 45%, 50%, or 55% at the wavelength(s) of light utilized by the scanner. In some embodiments, the scanner employs blue light having a wavelength ranging from about 450 nm to 495 nm. In one

embodiment, a predominant amount of the light emitted form the scanner has a

wavelength of about 465 nm. In other embodiment, the scanner employs a red light, having wavelengths ranging from 620 to 750 nm. In other embodiments, the scanner employs white light, emitting wavelength of light that span the entire visible light spectrum, i.e. from about 380 nm to 750 nm.

In some embodiments, the coating also increases the roughness of the coated abutment. For example, the scannable (e.g. supragingival) surface of the abutment may have a surface roughness, Ra, of at least 3 and more preferably at least 4, 5, or 6. In some embodiments, the surface roughness is at least 10, 15, or 20. The surface roughness of the uncoated abutment may be about 1 for a metal abutment that has not been subjected to surface roughening. A sandblasted metal abutment may have a surface roughness of about 2 to 3.

It is appreciated that the target roughness and total reflection properties may vary to some extent depending on the type or even brand of scanner. 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.

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.

It is surmised that since the implant abutment being scanned is identical to the implant abutment that receives the restoration, a permanent restoration can be fabricated without making a physical model. However, if desired, one could also make a physical model of the patient's mouth at the location of the dental implant, as known in the art, to verify the fit. For example, with reference to Fig. 1, a dental model could be made by traditional dental impression techniques such as by covering the dental implant abutment with an impression coping 120, forming a negative (e.g. silicone) impression of the patient's mouth 121 (that comprises the impression copings cured therein), and forming a positive (e.g. stone) model from the negative impression 122. One could scan the resulting stone model, as described in the art. If a physical model is desired, it is preferably formed by use of a (e.g. additive) rapid prototyping 111 as described in copending Provisional Patent Application Serial No. 61/242543, filed September 15, 2009; incorporated herein by reference.

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". Various coatings have been described in the art that are suitable for coating metal dental articles. For example, U.S. Patent No. 5,454,716 describes an orthodontic arch wire coated with an opaque coating. Such coatings are also suitable for increasing the total reflection of the metal implant abutment. Such coatings generally comprise a polymeric binder and at least one opaque filler and/or pigment.

Suitable polymeric materials include thermoplastic, thermosetting, and

polymerizable materials such as acrylics, epoxies, liquid crystal polymers, acetals, nylons, polysulfones, polyamides, polyimides, polyacetates, phenolics, polyesters, and amino type resins such as melamine formaldehyde, and urea formaldehyde. Polymerizable materials that crosslink upon heat or radiation curing are generally preferred.

Particularly preferred resins include monomeric and polymeric acrylates and in particular methacrylates which are ultraviolet, electron beam, or heat curable. In the case of polymerizable dental compositions, the long-chained monomers of U.S. Pat. No.

3,066,112 on the basis of bisphenol -A and glycidyl methacrylate, or their derivatives obtained by adding isocyanates, are often used in particular. The acrylic acid or methacrylic acid esters of mono or preferably polyhydric alcohols, for example triethylene glycol dimethacrylate and the like, are also particularly suitable. The diacrylic and dimethacrylic acid esters of bishydroxymethyltricyclo-[5.2.1.0.sup.2.6 ]-decane named in DE-A-2 816 823 are also particularly suitable. The reaction products from diisocyanates and hydroxyalkyl(meth)acrylates, as described for example in DE-A-2 312 559, can also be used. Mixtures of monomers or unsaturated polymers made therefrom can of course also be used. The fillers typically have an average particle size of < 50 microns and more typically less than < 25 microns, and more typically less than 10 microns. In some embodiments, the fillers have a primary particle size of less than 5, 4, 3, 2, or 1 micron. Inorganic fillers can be for example quartz, ground glasses powder (e.g. which contain strontium, barium or lanthanum), and silica. For better incorporation in the polymer matrix, it is of advantage to hydrophobize the inorganic fillers. Customary

hydrophobization agents are organosilanes such as trimethoxymethacryloyloxypropyl silane. The quantity of silane used is customarily 0.5 to 10 wt.-%, relative to inorganic fillers, and preferably 2 to 5 wt.-%. The filler is typcially present in the polymeric coating at a concentration of at least 10%, 15% or 20% up to 40%, 50%, or 60% by weight. The particle size of the filler is small for embodiments wherein the coating is quite thin. .

In preferred embodiments, the kind and amount of filler and/or pigment is chosen such that a tooth-colored coating is achieved. When the supragingival surfaces of the implant abutment are metal, the underlying metal can change the appearance of the (e.g. crown) restorative affixed to such supragingival surface.

In some embodiments, the kind and amount of filler and/or pigment renders the supragingival surface sufficiently opaque or tooth colored.

In other embodiments, the polymeric coatings can be made by using a mixture of titanium dioxide and iron oxide pigments. The titanium dioxide and iron oxide pigments can be used in varying amounts depending on the shade of tooth enamel desired to be reproduced. For example, about 20 wt-% to about 40 wt-% titanium dioxide, and about 0.01 wt-%) to about 0.10 wt-% iron oxide, based on the total weight of the polymeric coating material, give a natural tooth enamel appearance to the coating. Additional pigments or colorants can be optionally added to the starting coating powders to color- match the polymeric coating to a desired tooth color.

At least the supragingival surfaces of the metal abutment are covered by the coating at least at a thickness such that the exposed surfaces of the abutment (e.g. when in the patient's mouth) are optically scanneable. For rendering the metal abutment scannable alone, the coating may be applied at thickness of as little as 10 microns.

In preferred embodiments, especially for implant abutments for anterior teeth, the coating is of sufficient thickness to opacify at least the supragingival surfaces of the metal implant abutment. Since some restoratives, such as temporary crowns prepared from plastic materials, have some transparency, the underlying metal abutment can alter the color of such restoratives. Hence, opacifying the supragingival portion of the preformed metal abutment can improve the aesthetics of the restorative.

In this embodiment, the (e.g. polymeric) coating typically has a thickness of at least about 25 micrometers, and more preferably a thickness of least about 50

micrometers. The (e.g. polymeric) coating typically has a thickness of no more than about 100 micrometers thick, and more typically a thickness of no more than about 75 micrometer. In another embodiment, the polymeric coating is a powder coating. A

conventional powder coating techniques, typically includes electrostatic spraying processes, followed by thermally treating the powder to melt the powder coating and bond the resulting molten material to the crown surface. Such powder coating techniques are well known to one of skill in the art.

Powder coatings typically have an average particle size (i.e., the largest dimension of a particle, such as the diameter of a spherical powder) of at least about 20 microns, and more preferably at least about 40 microns. The average particle size is typically no more than about 100 microns, and more preferably no more than about 60 microns.

One suitable powder coating that comprises a polyester/epoxy hybrid compositions as described in U.S. 7,008,229; incorporated herein be reference. Such powder coating preferably includes about 20 percent by weight (wt-%) to about 40 wt-% polyester, and about 20 wt-% to about 40 wt-% epoxy, based on the total weight of the coating powder.

In another embodiment, at least the supragingival surfaces of the implant abutment comprises a ceramic coating. For example, US 2009/0092943 describes a coated implant prepared by depositing in electrophoresis at least one ceramic layer one a body potion of an implant and sintering the ceramic layer using optical radiation.

An organo-metallic coupling agent may be either precoated onto at least the supragingival surfaces of the metal abutment or added to the polymeric coating to improve adhesion between the metal implant abutment and the polymeric coating. Various organo- metallic coupling agents are known such as described in U.S. Patent No. 5,454,716.

Prior to coating, at least the supragingival surfaces of the implant abutment can be prepared to remove oil or other surface contaminants by vapor degreasing, alkaline cleaning, acetone cleaning, or ultra-sonic cleaning, for example. Surface oxides may be removed and surface activation can be accomplished by acid treatment or abrasive (e.g. sand) blasting, for example.

Acid treatment and abrasive blasting typically roughen the surface. Such roughening can also favor diffuse reflection in favor of specular reflection. However, such surface roughening alone is inadequate to render the supragingival surface scanneable. Surface roughening can also improve adhesion of the implant abutment with a cemented restorative, such as a crown. For this reason, surface roughening is generally preferred. With reference to FIG. 3, an exploded view of an illustrative preformed implant abutment (e.g. interface) 350, the implant abutment may take the form of an elongated tubular body generally comprising a (e.g. hex shaped) base end 355 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. 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 (e.g. anchor).

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 implant (e.g. anchor) are typically hexagonal 355 in shape. Other anti-rotation features include for example vertical flat(s), vertical groove(s), or vertical protrusion(s).

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.

For embodiments wherein the dental implant abutment is also suitable for use as a "scan locator" the supragingival end of the implant abutment comprises at least one orientation feature. The orientation feature may comprise digital information, at least one visual feature, at least one mechanical feature, or a combination thereof. The orientation feature preferably comprises a (e.g. single) mechanical feature such as a vertical groove, vertical protrusion, vertical flat (e.g. 356 of FIG. 3), or a combination thereof.

In another embodiment, the abutment comprises more that one (e.g. 2, 3, or 4) vertical groove, vertical protrusion, vertical flat (e.g. 356 of FIG. 3), or a combination thereof. However, these features are not evenly spaced about the circumference of the abutment. This results in the abutment having an asymmetrical cross-section. In this embodiment, the orientation feature is the asymmetry of the supragingival end of the abutment, rather than the presence of a single mechanical feature.

The exterior geometry of the abutment and mechanical orientation feature are preferably chosen to facilitate intraoral scanning and the fabrication of the subsequently seated restoration. The supragingival exterior surfaces of the abutment, are generally free of any structural features that would detract from the fit between the exterior surface of the abutment and the restorative. Hence, the supragingival exterior surfaces of the abutment, as well as the restoration 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).

In one embodiment, the dental implant abutment comprises a mechanical orientation feature and the restoration comprises a cooperating mechanical orientation feature that mates with the mechanical orientation feature of the dental implant abutment. Similarly, an impression coping, rather than a restoration may have a cooperation mechanical component that mates with the mechanical orientation feature of the dental implant abutment. Hence, in these embodiments, the mechanical feature insures that the restoration and/or impression coping are properly placed with respect to rotation.

As depicted in FIG. 3, the supragingival end of the implant abutment may comprise anti-pull feature such as shallow grooves 305 that hinder removal of the restoration from the abutment. In some embodiments, such anti-pull features have a depth no greater than about 0.1 mm. Other anti-pull features include for example shallow horizontal flat(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.

Examples

Example 1

A prototype dental implant abutment interface was fabricated to the final shape from CP Titanium Grade 5 (purity specification: max . IO C, .5 Fe, .015 H, 0.05 N, and .50 O, Perryman Co., Houston, PA). An optical micrograph of the dental implant abutment having a length of about 7 mm is depicted in Fig. 6.

The uncoated interface was sandblasted at 2 bars of pressure with 50 um aluminum oxide using a Vaniman Sandstorm XL (Vaniman Co., Fallbrook, CA), the nozzle being positioned ½" from the interface.

The sandblasted interface was coated per manufacturer's instructions with Sinfony™ Indirect Lab Composite (Part #49000, 3M ESPE, St. Paul, MN). First, the Opaquer Liquid (Item No. 049860) was applied and light cured (3M LED curing light, Part #XL 3000, 3M ESPE, St. Paul, MN). Next the opaque powder (shade A2, Item No. 049610) was mixed with the opaque liquid in a 1 : 1 ratio with the addition of one drop of the Activating Liquid (Item No. 049870). The opaque mixture was applied to the treated surface of the interface with a brush and light cured. The surface of the coated interface was lightly sandblasted as described above, but using 1 bar of pressure at 6" nozzle distance for a sufficient time to remove the gloss (by visual inspection), being careful not to sandblast through the coating.

Example 2 (coated without sandblasting)

A prototype implant interface was prepared according to the method of Example 1 , omitting the final, light sandblasting of the coated and cured interface.

Example 3 (coated without sandblasting)

Example 2 was repeated except that coating was vacuum cured to render a more uniform coating.

Control A (sandblasted w/o coating) The prototype implant interface with no coating was sandblasted as described in Example 1.

Control B (no coating, no sandblasting)

Control B was a prototype implant interface with no coating or sandblasting, having a somewhat glossy surface after the fabrication process.

Optical Scanning Testing

The coated implant abutment prepared in Examples 1-2 were scanned according to manufacturer's instructions in a Lava COS (Chairside Oral Scanner, 3M ESPE, St. Paul, MN), producing an acceptable image. Attempts to scan Control A and B resulted in an error message.

The coated interface prepared in Examples 1-3, Control A and Control B were also scanned according to manufacturer's instructions in a Lava Scan ST scanner with Lava Design 4.2 software (3M ESPE, St. Paul, MN) using an exposure setting of 35.

Examples 1-3 produced an acceptable image, while Control A and B produced error messages.

Surface Roughness

The surface roughness was measured on each of the flats of each of the abutments of Examples 1-3 and Control A and Control B. Topographic data was obtained from the nominally flat regions using the Keyence VK-9710 color 3D laser scanning confocal microscope with 20x/0.46 objective and VK Viewer observation software. Measurements were take use the VK Analyzer shape and particle analysis software program. The surface roughness measurement analysis was executed according to JIS B0601 :2001 (ISO

4287: 1997) with the measurement areas set to the entire image file. Surface curvature was removed from the topography prior to the roughness parameters Ra (arithmetic mean of absolute values). Ra was tabulated based on three measurements of each abutment sample as follows: Surface Roughness

The results show that Examples 1-3, each having a coating, had a higher surface roughness than the milled titanium implant abutment (Control B) and sandblasted titanium implant abutment (Control A).

Total Reflection

The UV- Visible reflectance spectroscopy of Example 3 (coated with Sinfony™ and vacuum cured) and Control A (sandblasted titanium) were measured as follows.

Total Reflectance (TR) measurements were made on a Perkin Elmer Lambda 900

Spectrophotometer fitted with a PELA 1000 Integrating Sphere Accessory. This sphere is 150 mm (6 inches) in diameter and complies with ASTM methods E903, D1003, E308, et al. as published in "ASTM Standards on Color and Appearance Measurement", Third Edition, ASTM, 1991. A Perkin Elmer quartz optics small spot accessory was used in tandem with the PELA 1000 iris to focus and mask the beam to a size of about 1.2 mm diameter on the white plate at the back sample position of the sphere. After zeroing the instrument, the sample to be measured was suspended in the focal plane centered in the beam. The beam illuminated ca. half the diameter of the sample and the back enclosure served as a light trap behind the sample. The software-controlled internal reference beam attenuator was set at 10 percent. Duplicate measurements were made for the samples - one on a flat and one on a threaded area. Samples were aligned for each measurement. The results are depicted in Fig. 3. The results show that coated abutment has substantially lower total reflectance. Pull Test = Adhesion Testing of Coated Abutment (Pull Test)

Prototype sandblasted titanium abutments were prepared as described in Example 1 , except the horizontal groove anti-pull features were omitted in order to evaluate the effect of the coating alone on adhesion. An optical micrograph of the dental implant abutment having a length of about 7 mm is depicted in Fig. 7.

Titanium abutments were coated as described in Example 3. Uncoated titanium abutments were used as control samples. Lava Zirconia custom abutments were manufactured to a size and shape for mating with the titanium abutments as described in EP1992302A1. A Lava Scan ST, Lava Form CNC Milling System, and Lava Therm Furnace were used to form the abutment from a Lava Frame Zirconia Mill Blank. Onto each coated or control abutment, a Lava Zirconia custom abutment was cemented using RelyX Unicem Self Adhesive Universal Resin Cement (3M ESPE, St. Paul, MN) per manufacturer's instructions. The cemented assemblies were autoclaved by holding for 10 minutes at 135 deg. C. The autoclaved samples were further prepared for Instron testing (Model 5500R, Instron Corp., Canton, Mass.) by attaching each to an implant analog (TERMINOLOGY AGAIN) using a screw. The implant analog was clamped in the jaws of the Instron. A custom steel plate having a circular hole was used to encircle the base of the zirconia abutment near the titanium abutment, to avoid crushing the ceramic abutment in the jaws. The steel plate was gripped in the pulling jaws of the Instron and the jaws were pulled apart at a crosshead speed of 0.5mm/min.

The force required to pull the zirconia abutment from the coated or control samples was: Coated samples (n = 7): 49.49 kg, std. deviation of 14.92 kg

Uncoated control samples (n = 3): 54.81 kg, std. deviation of 15.73 kg

Claims

What is claimed is:

1. A method of making a dental restoration comprising:

attaching a dental implant abutment to a dental implant in a patient's mouth wherein the dental implant abutment comprises a gingival end for mating with a dental implant and a supragingival end for mating with a dental restoration; wherein at least the supragingival end is optically scannable and comprises at least one orientation feature;

scanning at least a portion of the patient's mouth comprising the dental implant abutment to acquire a digital surface representation;

creating a three-dimensional digital model from the digital surface representation; and forming a restoration from the three-dimensional digital model.

2. The method of claim 1 wherein at least the supragingival portion of the dental implant abutment has a total reflection of least 30 at a wavelength emitted during scanning.

3. The method of claim 1 wherein at least the supragingival portion of the dental implant abutment has a surface roughnessof at least 3.

4. The method of claim 1 wherein the restoration is a preformed crown or bridge.

5. The method of claim 4 wherein the method further comprises affixing the restoration to the supragingival end.

6. The method of claim 1 wherein the orientation feature comprises digital information, at least one visual feature, at least one mechanical feature, or a combination thereof.

7. The method of claim 6 wherein the orientation feature comprises a single mechanical feature.

8. The method of claim 6 or 7 wherein the mechanical feature is a vertical groove, vertical protusion, vertical flat, or a combination thereof.

9. The method of claim 6 or 7 wherein the supragingival end of the implant abutment has an asymmetrical cross-section.

10. The method of claims 7-9 wherein the restoration comprises a cavity having a cooperating mechanical feature to mate with the supragingival end of the implant abutment.

11. The method of any one of claims 4-10 wherein the restoration comprises a malleable material and the method further comprises shaping at least a portion of the restoration and hardening the restoration either prior to or after affixing the restoration to the

supragingival end.

12. The method of any one of claims 4-10 wherein the restoration comprises a preformed plastic or ceramic material and the preformed crown or bridge is cemented to the supragingival portion of the dental implant.

13. The method of claim 1 wherein the method further comprises making a physical dental model.

14. The method of claim 10 with the method comprises covering the dental implant abutment with an impression coping, forming a negative impression of the patient's mouth comprising the impression coping, and forming a positive model from the negative impression.

15. The method of claim 13 wherein the method further comprises scanning the positive stone model.

16. A dental implant abutment comprising a gingival end for mating with a dental implant and a supragingival end for mating with a dental restoration wherein the supragingival end is optically scannable and comprises at least one orientation feature.

17. The dental implant abutment of claim 16 wherein at least the supragingival portion of the dental implant abutment has a total reflection of at least than 30 at a wavelength of visible light.

18. The dental implant abutment of claim 16 or 17 wherein at least the supragingival portion of the dental implant abutment has a surface roughness of at least 3.

19. The dental implant abutment of any one of claims 16-18 wherein the orientation feature comprises digital information, at least one visual feature, at least one mechanical feature, or a combination thereof.

20. The dental implant abutment of claim 19 wherein the orientation feature comprises a single mechanical feature selected from a horizontal groove, horizontal protusion, horizontal flat, or a combination thereof.

21. The dental implant abutment of claim 19 wherein the supragingival end has an asymmetrical cross-section.

22. The dental implant abutment of any one of claims 16-21 wherein the dental implant comprises a metal base article and a coating permanently bonded on at least the surpagingival end.

23. The dental implant abutment of claim 22 wherein the coating comprises a polymeric binder and a filler or pigment.

24. A dental implant abutment comprising a gingival end for mating with a dental implant and a supragingival end for mating with a dental restoration wherein the dental implant abutment comprises a metal abutment and a permanently bonded opaque tooth-colored polymeric coating on at least the surpagingival end.

25. The dental implant abutment of claim 24 wherein the article comprises at least one supragingival orientation feature.

26. The dental implant abutment of claim 25 wherein the orientation feature comprises a single mechanical feature.

27. The dental implant abutment of claim 26 wherein the mechanical feature is a horizontal groove, protusion, flat, or a combination thereof.

28. The dental article dental implant abutment of any of the previous claims wherein the dental implant abutment comprises a dental implant abutment interface and a custom abutment.