The present invention relates to an arrangement and a method for fabricating custom implant abutments, such as dental implant abutments used for dental restorations.

It is previously known to implant titanium screws, so-called fixtures, in the jaw bone of a more or less toothless person. There are different dental implant systems on the market today which are based on such biocompatible screw elements. There are also different methods for attaching a dental prosthesis/superstructure to the implant, either directly to the implant screw itself, or indirectly by means of a

spacer/abutment applied onto the implant screw. The dental prosthesis is then applied for instance by cementing or by means of separate securing screws. One example of a dental prosthesis in the form of a bridge restoration is illustrated in US 6,319,000 Bl.

The increased accessibility for dental implant solutions for more patients has resulted in a clear dominance for single-teeth implant supported replacements today. Actually, such replacements are estimated to represent more than 70% of all implant reconstructions worldwide today.

It is therefore natural that the demand for customized single abutment solutions rapidly is increasing from both clinicians and patients because they offer superior aesthetics and comfort due to the fact that they are tailored to the specific patient. An arrangement for fabricating a customized single abutment generally comprises a device for scanning a model of the dental abutment, control means for the scanning device, online server and manufacturing facilities.

Systems for manufacturing individually and accurately designed dental products are commercially available on the market. Reference is made for instance to the PROCERA CAD/CAM system, but there are also several others on the market today.

The PROCERA CAD/CAM system is a patient adapted/tailor made custom-abutment solution developed by the pioneer in this field, Matts Andersson Sweden. The system has been used since the 90 h in dental laboratories and the use has also been increased within dental practises. Then an in-house CAD/CAM system enables the dentist to create a finished dental product in as little as a couple of hours instead of using a remote dental laboratory. A typical CAD/CAM system includes scanning of the custom object in the form of a denture model or the like by means of a digital 3D scanner. An image (scan) is taken of the object and the image, the digital impression, is drawn into a computer. Together with any additional restorative design made by the dentist this virtual data is then sent to a milling machine for making the dental product.

Initially the CAD/CAM system was used as the optimal solution for cement retained prosthesis and therefore offered to a premium price strategy. All components in the treatment are industrially manufactured in proven biocompatible dental bulk materials which guarantees a pores-free biocompability material with optimal precision and mechanical function.

However, maintaining a long-term problem free reconstruction for the patient year after year requires regular maintenance and follow-up why the demand for retrievable screw -retained abutment solutions, with the possibility to provide an optimal position and angle the screw- access channel entrance, has shown to be the ultimate solution. In case of a screw-retained abutment the securing screw is applied through a screw channel in the abutment in such a way that the screw channel has a first mouth through which the screw should be inserted and a screw member seat with a second mouth, for providing support to the head of the securing screw during fixation of the abutment to a dental implant. A

communication is then obtained between the first mouth and the second mouth. A special screw driver having a rotatable handle portion and flexible and/or bendable shaft portion could be used for fixing the securing screw. Angled screw channels in the prosthesis itself are previously known, see for instance EP 2053985.

The rapid growth of customized abutments is mainly driven by dental laboratories and milling centres that has invested in a dental CNC milling solution offering customized abutments manufactured from pre-milled blanks. Some even mills the entire custom abutment from a solid block/disc that is an extreme costly and time-consuming solution. There are various pre-mill blank designs and holding systems on the market. However, actual commercial available systems, such as Medentika, ,ΝΤ-Trading, DESS Abutments,

Straumann and others, are limited to mill custom abutments with fixed straight screw- channels. The most frequent used systems (type Medentika, DESS Abutments, Straumann) can even not mill the custom abutment to 100%. The remaining part of the pre-mill blank connected to the screw entrance access end has to be removed manually resulting in an imprecise final product compared to the original CAM production file.

Specifically, in US 2012/0214133 Al Jung it is presented a system and a method for fabricating custom implant abutments using an implant abutment connector to secure a partial blank with respect to a milling tool of a CNC milling machine. In Fig. 7 in this publication it is illustrated a partial blank 106 secured to the connector 54 and it is evident from this figure that the system is limited to mill custom abutments with fixed straight screw-channels only, see bore 116.

In US 2016/0193020 Al Medentika GmbH it is presented a similar holding device for an abutment blank system representing a most frequent used solution of commercial available pre-mill blanks with integrated straight screw-access channel attached to the holding device that fits actual dental or industrial 4- and 5-axic CNC milling machines. According to the solution used by Medentika the pre-mill blank is attached in the screw entrance end of the pre-mill blank which makes it impossible to fully mill the custom abutment. The remaining part of the pre-mill block, after the milling process, has to be removed manually.

The advantage of such a solution is a simple pre-mill blank design and holding system compatible with all implant brands and platforms that is commercialized by several manufacturers of dental implants and implant components. However, a disadvantage of the system is the fact that there is no complete milling process due to the need for manual removal of remaining pre-mill blank part resulting in a final abutment shape that is imprecise and that differs from the original CAM production file. Furthermore, there is no possibility for milling individual screw-access angles due to the fixation system and integrated straight screw-access channel.

In German Offenlegungsschrift DE 10 2012 102 059 Al NT-Trading GmbH & Co. KG it is illustrated another similar prior art system of commercial available pre-mill blanks with integrated straight screw-access channel attached to the pre-mill blanks holder system in both ends of the pre-mill blank. The advantage of this system is the possibility to mill the entire final abutment shape in one step. However, the disadvantage of this system is the complicated pre-mill blank holder system that requires individual adapters/holders for each implant brand and platform. And again, there is no possibility for milling individual screw-access angles due to the fixation system and integrated straight screw-access channel. This is true for instance from Fig. 2 in the above German Offenlegungsschrift DE 10 2012 102 059 Al which illustrates the holder system with fixation in both ends of the pre-mill blanks 50 with integrated straight screw-access channel.

It is true that leading implant manufacturers and dental milling centres with industrial equipments, such as Nobel Biocare, Straumann, Anthogyr, Heraeus and others, have recently started to offer also angled screw channels as an option to their CAD/CAM manufacturing reconstructive solutions. However in this case big and expensive machines are required that are working directly with the basic material from a solid block/bar/disc (not pre-mill blanks) which means a complicated and expensive machine investment affordable only by big industrial and milling centres. This also means that this is a feature that normally is charged extra due to the complicated manufacturing procedure involved. It is therefore an object of the present invention to provide a new designed pre-mill blank and a pre-mill blank holder system that offers the possibility to fabricate affordable custom abutments also in different dental materials with straight or individual angled screw-access channels in one step using existing commercialised 5-axis dental or industrial CNC-milling machines. This should then make the invention largely applicable compared to said complicated and expensive machines for providing angled screw channels for the custom abutments.

According to the invention the new arrangement comprises a pre-mill blank from where the shape of the custom abutment is milled and a multiple pre-mill blank holder device for fixation of a number of pre-mill blanks for milling the outer individual custom abutment shape as well as an access channel for a prosthetic screw by a CNC milling machine, and wherein said pre-mill blank and pre-mill blanks holder device is arranged to fabricate in one single milling step a straight or individual angled screw-access channel for the prosthetic securing/fixation screw. Specifically, the pre-mill blank according to the invention comprises a solid body without any pre-milled screw access channel, an interface geometry compatible with implant

manufacturers implant platform designs and a holder foot for fixing/attaching the pre-mill blank to the pre-mill blanks holder device, and the pre-mill blanks holder device according to the invention is adapted to any CNC milling machine and comprises means for attaching a plurality of pre-mill blanks to the holder device in order to mill the abutments in one and the same milling process.

According to a preferred embodiment of the invention said means for attaching the pre-mill blank to the pre-mill blank holder device comprises a holder foot.

According to a further preferred embodiment of the invention each pre-mill blanks holder foot is secured to the holder device by means of fixation screws for securing stability and precision during the milling procedure.

According to another preferred embodiment of the invention the pre-mill blanks holder device or platform having means for attaching a plurality of pre-mill blanks on both sides of the holder platform in order to mill as many custom abutments as possible during one and the same milling process.

According to a further preferred embodiment of the invention the pre-mill blank top has a spherical design in order to facilitate the entrance of the milling tool for angled screw channels.

An example of the invention will now be described in more detail with reference to the enclosed drawings, in which:

FIG. 1 illustrates a dental implant screw having a custom abutment with a straight as well as an angled screw channel,

FIG. 2 is a side view of a pre-mill blank according to the invention, FIG. 3 is a perspective view of the pre-mill blank showing the special designed holder foot for securing the pre-mill blank to the holder platform,

FIG. 4 illustrates a pre-mill blanks holder according to the invention in cylindrical design and without any pre-mill blanks mounted,

FIG. 5 illustrates the pre-mill blanks holder with a number of pre-mill blanks mounted on both sides of the holder, FIG. 6 is a side view illustrating more in detail the pre-mill blanks mounted on both sides of the holder,

FIG. 7 illustrates more in detail the securing means of the holder and calibration means, FIG. 8 illustrates the first step to mill a traditional straight screw-access hole from the top in the pre-mill blank,

FIG. 9 illustrates the corresponding milling of an individual angled screw-access hole, FIG. 10 illustrates the milling of the customized outer design and the drilling of the straight screw-access hole from the opposite side of the blanks holder,

FIG. 11 illustrates the corresponding milling in case of an angled screw-access hole, FIG. 12 illustrates a step in which the final milled custom abutment is detached from the pre- mill blank fixation platform foot, and

FIG. 13 illustrates a final custom abutment milled in one step and with an individually positioned screw-access channel according to the invention.

Figure 1 illustrates a conventional dental implant screw 1 to be anchored into the jaw bone by means of conventional technique which is not described here. There are different dental implant systems on the market today which are based on such biocompatible screw elements. A spacer/abutment 2 is attached to the implant screw 1 by means of a prosthetic screw 3. The abutment 2 comprises a main body having an outer individual shape 4 for receiving a crown or other dental prosthesis, a base portion 5 having an interface/connection geometry compatible with the implant screw in question and an access channel for the prosthetic screw 3. In the figure it is illustrated a straight access channel 6 having a longitudinal axis in line with the longitudinal axis of the implant screw as well as an angled access channel 6

As mentioned in the introductory portion of our specification there is recently an increasing demand for such customised single abutment solutions due to the fact that they are tailored to the specific patient. In said US 2016/0193020 Al Medentika GmbH it is illustrated a prior art system for fabricating custom abutments with straight screw-access channels. The abutments are fabricated from pre-mill blanks attached to a holding device that fits actual dental or industrial 4- and 5-axic CNC milling machines. According to this prior art solution the pre-mill blank is attached in the screw entrance end of the pre-mill blank which makes it impossible to fully mill the custom abutment. The remaining part of the pre-mill block, after the milling process, has to be removed manually.

As also mentioned in the introductory portion of our specification the advantage of such a solution is a simple pre-mill blank design and holding system compatible with all implant brands and platforms that is commercialized by several manufacturers of dental implants and implant components. However, a disadvantage of the system is the fact that there is no complete milling process due to the need for manual removal of remaining pre-mill blank part resulting in a final abutment shape that is imprecise and that differs from the original CAM production file. An important feature of our invention is the design of the pre-mill blank and how the pre-mill blank is attached to the holder device or platform making it possible to mill the outer individual custom abutment shape and straight or angled screw-access channels of choice in one step from both sides of the pre-mill blank holder device. According to our invention a special designed pre-mill blank 7 without screw-access channels is used, see figures 2 and 3. The pre-mill blank can be produced in any dental materials used for milling custom abutments, but most frequent used are dental metals like Titanium and Cobalt Chrome, but also composite/plastic materials like PMMA and PEEK materials can be used. As illustrated in figure 2 the pre-mill blank comprises a solid, cylindrical main body 8 from where the outer shape of the individualized custom-made abutment is milled. The pre- mill blank body can be offered in different sizes in order to limit the volume of material to be milled away. The top portion 9 of the pre-mill blank 7 has a spherical design in order to facilitate the milling of angled screw-access channels, see below.

The pre-mill blank 7 further comprises a protruding portion having an implant platform interface/connection part 10 compatible with any implant manufacturers platform designs and a base portion 11 for securing the pre-mill blank 7 to the special designed pre-mill blanks holder device 12 illustrated in figure 4. The base portion 11 is formed as a cylindrical, disc- shaped holder foot. The holder foot 11 has three screw-holes 13 used for fixing/securing the pre-mill blank 7 to the holder platform 12. The holder foot 11 also has an indexing or positioning hole or marking 14, which will be explained more in detail in connection with figure 7. The special designed holder device or platform 12 for the pre-mill blanks is illustrated in figures 4 and 5. It can be adapted to any CNC-machine manufacturers holder system requirements. A majority of the pre-mill blanks holder system used on the market are cylindrical but can also be squared or use a bar-system attached to the milling machine. In our preferred embodiment the holder platform is cylindrical, disc- shaped, and having means for attaching a plurality of pre-mill blanks 7 to the holder platform in order to mill the abutments in one and the same milling process. Specifically, the pre-mill blanks 7 are fixed to the pre- mill holder using three fixation screws in order to secure necessary stability and precision during the CNC-milling procedure. Several pre-mill blanks can be mounted on both sides of the pre-mill holder platform 12 in order to mill as many custom-abutments as possible during one and the same milling process.

In the example illustrated in figures 4 and 5 the holder device is designed with ten seats or positions 15 for attaching the pre-mill blanks 7. The seats are distributed and positioned on both sides of the holder close to the outer peripheral part of the holder. Each seat 15 is formed as a circular recess corresponding to the cylindrical pre-mill blank holder foot 11 to provide a specific position for each pre-mill blank 7 and the three fixation screws for each pre-mill blank then secures stability and precision during the milling procedure . Figure 5 illustrates a multiple pre-mill blank holder with ten pre-mill blanks mounted in the seats on both sides of the holder, i.e. five pre-mill blanks on each side of the holder. Each seat is provided with three screw holes 13' for the securing screws and a central access hole 13" used for the drilling procedure from the opposite side of the pre-mill blanks holder as illustrated in figures 10 and 11 below. The holder 12 also has a central seat 16 for a calibration blank 17. The calibration blank 17 secures the exact three-dimensional positioning of the mounted pre-mill blanks for the CNC- machine. The upper portion of the calibration blank design can be adapted to the machine- manufacturers or CAM-software suppliers requirements while the securing part comprises a holder foot adapted to the central seat 16 like the pre-mill blanks.

The holder 12 also has a point or marker 18 close to each seat 15 which together with said indexing or positioning hole or marking 14 secures the exact rotational indexing/position of the pre-mill blank in relation to the implant interface rotational index. Figure 6 illustrates how the pre-mill blanks 7 are mounted on both sides of the holder device 12, and also the calibration blank 17 mounted in the central seat 16 on the upper side of the holder.

Figure 7 illustrates more in detail the seats 15 on the upper side of the holder and also the calibration and positioning means in the form of calibration blank 17, point or marker 18 and holder foot marking 14.

As an example of the present invention the following steps can be used for fabricating a custom abutment according to the invention.

Step 1. Milling of the screw-access entrance hole and screw seating in straight or angled position.

The special designed pre-mill blank 7 without pre-milled screw-access hole offers the possibility to mill a traditional straight 19 or an individual angled screw-access hole 20. The milling is performed using a conventional dental or industrial 5-axis CNC milling machine with a milling tool 21 schematically illustrated in figures 8 and 9. The first step after the pre- mill blanks have been fixed by the three fixation screws on the holder is to mill the screw- entrance hole and screw- seating from the top. In order to facilitate the entrance of the milling tool 21 for angled screw-channels the pre-mill blank top portion 9 has been designed spherical.

It should be understood that for a desired custom abutment shape according to figure 8 the straight screw-access channel 19 provides an optimal screw-access entrance positioning, while a straight screw-access channel provides a non-optimal screw-access entrance positioning for a specific abutment shape according to figure 9. In that case instead an angled screw-access channel provides the optimal screw-access entrance positioning. The angled screw-access channel 20 might have an angle a between 0° and 90°. Principally there is no restriction on the angle depending on the milling procedure. However, there is a practical limit on the angle depending on the prosthetic screws and screw driver to be used for securing the custom abutment. This means that the screw access channel might have an angle a of approximately up to 30°.

Step 2. Milling of the outer customized abutment shape

The outer individual abutment shape is milled according to traditional CNC milling procedure for custom abutments, which is illustrated in figures 10 and 11 for the abutments with straight and angled screw-access channels, respectively.

Step 3. Drilling of the hole for fixation screw from the opposite side of the pre-mill blanks holder. The final screw hole for the fixation screw is drilled from the opposite side of the pre-mill blanks holder as illustrated in figures 10 and 11.

Step 4. Cutting of final custom abutment from the pre-mill blank fixation platform foot. The final milled custom abutment is detached from the pre-mill blank fixation platform foot with a slitting saw 22 as illustrated in figure 12.

Figure 13 illustrates the final custom abutment milled in one step and with an individually positioned screw-access angle/entrance according to the invention. The invention is not limited to the above example but can be varied within the scope of the following claims. Specifically, it should be understood that instead of a cylindrical holder device as described here any other outer design of the holder, such as squared holder or a holder shaped as a bar, could be used depending on the milling machine. It should also be understood that the design and number of seats for the pre-mill blanks on the holder device an example only and can be varied within the scope of the invention.