Patent Description:
Edentulism, the condition of being toothless to some extent, may be treated by the implantation of a dental assembly. These assemblies require certain components to rest comfortably and securely in the patient's oral cavity. The implant fixture, also known as the dental implant or simply the implant, is the part of the dental assembly that becomes fused with the patient's jaw bone. The implant is available in both cylinder and screw-type varieties and is typically made from titanium or a titanium alloy. Implant abutments are screwed onto the implant and are positioned at and above the patient's gum line. Finally, a dental prosthesis is placed over the abutment and is designed to look and function like a natural tooth.

Alternatively, the prosthesis may be formed over the abutment outside of the patient's mouth, and the combined prosthesis and abutment may then be affixed to the implant with a fixation screw. To install the abutment and prosthesis onto the implant and to access the fixation screw during repair and maintenance of the dental assembly, the prosthesis must contain a screw access channel. In known dental assemblies, this screw access channel can often reside at the labial side of the tooth or on the biting surface, which is not desired as a matter of strength and aesthetics. Additionally, in known dental assemblies, this screw access channel must be of large enough diameter to allow the screw to traverse the channel. However, as the diameter of the channel increases, the strength of the prosthesis becomes more compromised. Also, a fixation screw that may pass through the screw access channel of the prosthesis increases the risk that the screw may become dislodged and lead to swallowing the prosthesis and/or the fixation screw.

Solutions to the problem of labial access to the fixation screw have been proposed. In one such dental assembly, the screw access channel resides on the lingual side of the prosthesis and is angled relative to the longitudinal axis of the implant. However, the screw access channel still requires a large enough diameter to allow the fixation screw to pass through the prosthesis. Additionally, this dental assembly contains a ceramic abutment affixed to a titanium implant, increasing the likelihood of crack propagation in the ceramic abutment during tightening of the fixation screw, which seats against the ceramic abutment.

<CIT> describes an interface element for dental prostheses, consisting of a cylindrical hollow body comprising: two different segments, namely a lower segment having a larger outside diameter and an upper segment having a smaller outside diameter, said segments being provided with external circular retaining grooves and an internal seat for the head of the screw that secures same to the implant; and a lower base. The interface element has a lateral cavity spanning the height of the upper segment, defining a lateral opening for the inclined entry of the screw and screwdriver, the height and width of said opening permitting an inclination of up to 30º, with respect to the axial axis of the cylindrical body and the lateral freedom of movement of the screwdriver by as much as 90º. Also provided are two flat regions in diametrically opposing points of the external surface of the larger-diameter lower segment of the circular body.

Therefore, there is a need for a dental assembly that addresses the present challenges and characteristics discussed above in regard to the screw access channel placement and the interface between the abutment and dental implant.

To these ends, a dental assembly is provided in accordance with appended claims <NUM> to <NUM> and a process for making the dental assembly of the appended claim <NUM> is provided in accordance with appended claims <NUM> to <NUM>.

An abutment is provided with a screw access hole and a slot in its sidewall adapted to allow a driver to access a screw in the screw access hole at an angle relative to a longitudinal axis of the screw. The abutment may include a screw seat and may be connected to an implant via a screw in the screw seat.

A dental assembly according to the invention includes the abutment and a screw within the screw access hole of the abutment. Additionally, the dental assembly may include an implant adapted for connection to the abutment via the screw. A prosthesis, which includes a driver access channel that has a diameter less than the outer diameter of the drive portion of the screw, is placed over the abutment.

A process according to the invention for making the dental assembly includes designing the dental assembly to include a screw access hole and the slot in the sidewall of an abutment of the dental assembly and manufacturing the dental assembly.

A method of attaching a prosthesis to a dental implant, the method not forming part of the claimed invention, may also be provided. The method includes assembling a fixation screw through a screw access hole of an abutment and then fabricating the prosthesis, which includes a driver access channel, over the abutment. The abutment may be aligned with the dental implant and a driver may be passed through the driver access channel and rotated to drive the fixation screw.

A method of detaching a prosthesis from a dental implant, the method not forming part of the claimed invention, may also be provided. The method includes inserting a driver into a driver access channel of the prosthesis, which is affixed to an abutment, and rotating the driver to disengage a fixation screw from the dental implant. The abutment and prosthesis are then removed from the dental implant.

The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and, together with a general description of the invention given above, and the detailed description given below serve to explain various aspects of the invention.

Although the invention will be described next in connection with certain embodiments, the invention is not limited to practice in any one specific type of dental assembly. In particular, those skilled in the art will recognize that the components of the embodiments of the invention described herein could be arranged in multiple different ways.

With reference now to the FIGS. , a dental assembly <NUM> is shown with an implant <NUM>, an abutment <NUM>, and a prosthesis <NUM>. In <FIG>, prosthesis <NUM> is shown with driver access channel <NUM> at an angle θ off the longitudinal access of fixation screw <NUM> and implant <NUM>, as best shown in <FIG> and <FIG>. A detailed view of the abutment <NUM> is shown in <FIG>. In the embodiment shown, the abutment may include an optional anti-rotation feature <NUM> at the apical region <NUM> of abutment <NUM> that interfaces with engaging features of the implant at its coronal end (not shown) to position the abutment <NUM> radially. Similarly, coronal region <NUM> of abutment <NUM> may include an optional anti-rotation feature <NUM> that interfaces with engaging features (not shown) of the prosthesis <NUM>. Also, in the embodiment shown, the coronal region <NUM> of the abutment <NUM> may include grooves to improve securing, e.g. cementing, of the prosthesis <NUM> to the abutment <NUM>.

Slot <NUM> in the sidewall <NUM> of abutment <NUM> allows a driver to access the fixation screw <NUM> at an angle. Such angular access allows for the placement of the driver access channel <NUM> on the lingual side of the prosthesis.

Abutment <NUM> also includes cavity <NUM> with a height <NUM> corresponding to the height <NUM> of the screw <NUM>. In this way, the screw <NUM> may move upwardly when being disengaged from the implant <NUM> while the prosthesis <NUM> remains attached to the abutment <NUM>. Therefore, the screw <NUM> need not ever be completely removed through the prosthesis <NUM>, and the risk of inadvertent swallowing of the screw <NUM> during removal of the prosthesis <NUM> is decreased. Stated differently, the screw <NUM> may disengage the implant <NUM>, but may also be contained within the cavity <NUM> of abutment <NUM>.

Referring still to <FIG>, the abutment <NUM> may be dual colored. The abutment <NUM> has an apical portion <NUM> configured to be positioned within a gingival region of a patient's mouth, and a coronal portion <NUM> configured to support the prosthesis <NUM>. The apical portion <NUM> may be a first color, generally gingival-colored, and the coronal portion <NUM> may a second color different from the first color, generally tooth-colored. Such a dual-colored abutment allows for a more aesthetically pleasing installation. However, such dual coloring is optional.

Although the embodiments discussed herein are drawn toward single-unit dental assemblies, it is also possible to adapt the present invention to multi-unit bridge dental assemblies. In such an embodiment, the anti-rotational features <NUM> of the abutment <NUM> are not engaged by the implant <NUM>. However, the cavity <NUM> of the coronal portion <NUM> of the abutment <NUM> is configured similarly to the cavity <NUM> of the single-unit dental assemblies.

As shown in <FIG> and <FIG>, a conventional ball-point hex driver <NUM> may be used to drive fixation screw <NUM> through the abutment <NUM> and into the implant <NUM>. The driver <NUM> passes through driver access channel <NUM>, which may be sized such that driver <NUM> fits therethrough but screw <NUM> does not. Through the use of a ball-point hex driver <NUM>, the user may change the angle θ of the driver <NUM> as driver <NUM> is rotated to insert or remove the screw <NUM>. Alternatively, the user may hold the angle θ steady throughout the insertion and removal procedure. However, in applications where it is desirable to make the screw <NUM> removable, the radius <NUM> of driver access channel <NUM> may be widened to allow the screw <NUM> to pass fully therethrough.

The dental assembly may be made through two main steps. First, conventional or digital processes may be used to design the dental assembly, which will be unique to each patient and application. Then, the dental assembly may be manufactured either via conventional manufacturing techniques modified to include the driver access channel <NUM> or through computer-aided manufacturing techniques.

Turning now to <FIG>, the prosthesis <NUM> may be formed by a modification to conventional methods. First, the dental professional makes an impression of the patient's oral cavity using conventional transfer techniques. Then, a stone model of the patient's jaw bone is created, including an implant analog <NUM> replicating the exact implant <NUM> orientation and height. Then the dental professional assembles abutment <NUM> onto implant analog <NUM> with screw <NUM>, ensuring that slot <NUM> in the sidewall <NUM> of abutment <NUM> is oriented at the desired position. A coping <NUM> is placed onto abutment <NUM>, again ensuring alignment of coping slot <NUM> in the sidewall <NUM> with abutment slot <NUM>. An access-channel plug <NUM> may be placed into slots <NUM>, <NUM> at the desired off-axis angle θ. The access-channel plug <NUM> will represent the driver access channel <NUM> within the completed prosthesis <NUM>. Acrylic wax may then be placed around the coping <NUM> and access channel plug <NUM>, and the plastic coping <NUM> may be modified as needed to create the desired prosthetic shape. Standard laboratory processes may be used to fabricate the prosthesis from the wax inverse negative thus formed. As a result, the formed prosthesis will contain a driver access channel <NUM> of the same diameter as the shaft <NUM> of access-channel plug <NUM>, and screw <NUM> will be contained within abutment <NUM> in such a manner that it may not pass through the driver access channel <NUM> and is contained within the cavity <NUM> of abutment <NUM>. Driver access channel <NUM> may thus have a generally elliptical shape with a long axis <NUM> and a short axis <NUM>, as best shown in <FIG>. The long axis <NUM> is configured to allow the driver <NUM> to move along the driver access channel <NUM> to contact the screw continuously during rotation of the driver <NUM>.

Alternatively, prosthesis <NUM> may be formed using a digital workflow procedure. First, the dental professional conducts an intra-oral or impression scan using digital impression techniques. The data thus generated are imported into software that determines implant or abutment height as well as the required orientation of the engaging features. This or other software may then be used to determine the correct linear, axial, and rotational location of the dental assembly components, including the desired location and orientation of the slot <NUM> of abutment <NUM>. Software also designs the prosthesis with an appropriate off-axis drive access channel. Finally, the prosthesis is fabricated following computer-aided manufacturing procedures.

An exemplary computer-aided manufacturing process using a 3SHAPE® CAD/CAM system is provided for further illustration. First, data obtained from either an intra-oral or impression scan of the patient's oral cavity are imported into the CAD system. Then, a computer model of the implant <NUM> and abutment <NUM>, the abutment <NUM> having a slot <NUM> in its sidewall <NUM>, is combined with a computer model of a prosthesis blank <NUM> in silico. The prosthesis blank <NUM> includes a scan adapter flat <NUM> that is aligned with the slot <NUM> in the sidewall <NUM> of the abutment <NUM>. The implant <NUM>, abutment <NUM>, and prosthesis blank <NUM> are placed within a visual depiction of the patient's oral cavity in the appropriate location, with the scan adapter flat <NUM> aligned in the desired direction of the off-axis driver access channel <NUM>. The angle of this off-axis driver access channel <NUM> may be modified, as desired, in silico. The design software can then be used to transform the prosthesis blank <NUM> into an appropriate prosthesis <NUM> that includes the off-axis driver access channel <NUM>.

Once the design of the dental assembly <NUM> is complete, the actual prosthesis <NUM> may be formed from a milling process using the data obtained from the CAD software. The milled prosthesis <NUM> may then be attached to an abutment <NUM> and implant <NUM> using cement, for example. It may be beneficial to insert an access channel plug <NUM> into the off-axis driver access channel <NUM> during the attachment of the prosthesis <NUM> to the abutment <NUM> to protect the screw <NUM> from the cement. Indeed, the access channel plug <NUM> may be used to align the prosthesis <NUM> by inserting the access channel plug <NUM> into the head <NUM> of the screw <NUM> and then passing the prosthesis <NUM> over the access channel plug <NUM> and onto the abutment <NUM>. Once the prosthesis <NUM> is formed and attached to the abutment <NUM> and implant <NUM>, the resulting dental assembly <NUM> may then be placed inside the patient's oral cavity.

Claim 1:
A dental assembly comprising
an abutment (<NUM>) with a longitudinal axis, a sidewall (<NUM>), and comprising a cavity (<NUM>) along the longitudinal axis and a slot (<NUM>) in the sidewall (<NUM>) adapted to allow a driver to access a screw (<NUM>) in the cavity at an angle relative to the longitudinal axis;
a prosthesis (<NUM>) having a driver access channel (<NUM>), the driver access channel (<NUM>) having an opening on at least one surface of the prosthesis, the prosthesis (<NUM>) placed over the abutment (<NUM>) with the prosthesis (<NUM>) attached to the abutment (<NUM>) using cement such that the driver access channel (<NUM>) of the prosthesis (<NUM>) and the slot (<NUM>) in the sidewall (<NUM>) of the abutment (<NUM>) overlap;
a screw (<NUM>) within the cavity of the abutment (<NUM>); and
an access channel plug (<NUM>) in the driver access channel (<NUM>) to protect the screw (<NUM>) from the cement.