[001] This application claims the benefit under 35 U.S.C. §1 19 of the filing date of Australian Patent Application No. 2014901246, filed April 7, 2014, hereby incorporated by reference in its entirety as if fully set forth herein.

Technical Field

[002] The present invention relates generally to medical processes and procedures and, in particular, to the formation of a guide for dental prosthetic procedures.

Background

[003] Since the 1950s, dentists have been developing methods to treat patients who have missing or extracted teeth. These methods typically involve some form of dental prosthetic, including the use of implanted foundations to carry artificial

replacements. Most of the techniques in the past required surgical treatments and resulted in substantial pain during the recovery stage.

[004] Such treatments often include frameworks, called sub-periosteal implants.

Some implants are made to sit under the gum and on the jawbones with projections above the gum to carry false teeth. Others require the opening of the gum to insert bladelike implants into the jaws to act as supports for porcelain bridges. Fig. 1 shows an X-ray image of such an implant in use.

[005] Since the mid-1980s hollow titanium screws 200, an example of which is shown in Fig. 2, have been used to carry various designs of artificial teeth 202. The screws 200 are surgically implanted in the jawbones 204 and left submerged under the gums 206 for a period of 6 months. The implanted screws 200 are then uncovered to carry a second, interlocking component, called an "abutment", or "stage 2 implant" (not visible in Fig. 2), which is shaped to carry the artificial tooth 202 and configured to mechanically secure the tooth 202 to the implant 200.

[006] The implants 200 are typically manufactured of titanium and range in length and diameter. Implants 200 can only be placed in regions where there is sufficient alveolar bone. A general rule of thumb is that a minimum of 10 mm length and 5 mm width of implantation is required, thereby establishing a minimum amount of alveolar bone required for surgical implantation.

[007] Patients who have had all teeth removed are known as edentulous patients, thereby exhibiting edentulism. Over time these patients generally experience an increase in bone resorption. Bone resorption is the process by which osteoclasts break down bone and release bone minerals, resulting in a transfer of calcium from bone fluid to the blood. As people get older, the rate of resorption tends to exceed the rate of bone replacement.

[008] The osteoclasts are multi-nucleated cells that contain numerous

mitochondria and lysosomes. These are the cells responsible for the resorption of bone. Osteoclasts are generally present on the outer layer of bone, just beneath the periosteum. Attachment of the osteoclast to the osteon begins the process. The osteoclast then induces an infolding of its cell membrane and secretes collagenase and other enzymes important in the resorption process. High levels of calcium, magnesium, phosphate and products of collagen will be released into the extracellular fluid as the osteoclasts tunnel into the mineralized bone.

[009] The mere presence of teeth, either natural or artificial, helps to minimise the rate of resorption.

[0010] If a minimum amount alveolar bone is not available to accommodate an implant, a bone graft is normally required before implants can be inserted. This typically adds an additional 3 - 6 months to the treatment process to allow for healing of the graft.

[001 1 ] In the early 1990's a technique called the AII-on-4™ was developed for edentulous patients. This technique applies a dental prosthesis with at least twelve teeth (a bridge) fixed in the jaw, based on only four titanium implants. The posterior implants are substantially angled at approximately 45 degrees to avoid compromising the sinus cavity in the upper jaw and the nerve canal in the (lower) jaw. A fixed standardized surgical guide is used to aid in placement of the implants.

[0012] In 2002-2003, a variation of the AII-on-4™ technique was introduced that utilized small diameter titanium implants, allowing very conservative, minimally invasive placement of the implants to stabilise loose complete dentures for patients. The implants are usually used in the lower jaw and to carry non-removable porcelain crowns and bridges. Due to the size and technique of placement, these implants are virtually painless and even if the jawbones have resorbed, the implants can be positioned in the anterior mandible where there is generally sufficient bone. The difference with utilizing the small implants of the AII-on-4™ technique is that the posterior implants are not angled. This simplifies drilling during the surgical implantation process.

[0013] Surgical guides are used during the surgical procedure of the AII-on-4™ technique to guide implant drilling and to provide for accurate placement according to a digital surgical treatment plan. Surgical guides are not normally utilised in regular implant placement for part dentate cases.

[0014] The use of surgical guides for such procedures has been found to simplify anatomic surgical management for improved accuracy of implant placement, reduce surgical time, and reduce the problems related to bone density and dimensions.

However, using surgical guides is complicated, expensive, and practitioners often find the guides do not fit the patient.

[0015] Surgical guides are currently fabricated via stereolithography / 3D printing.

Typical steps to the creation of a surgical guide involve:

1. Preparation of a radiographic guide;

2. Double Scan and Single Scan techniques;

3. Planning, generally assisted by software applications; and

4. Printing of the guide.

[0016] Preparation of the Radiographic Guide involves:

1. Take an impression of the arch (negative);

2. Pour up a (positive) plaster model;

3. Mark the placement of gutta percha radiological markers on the positive model for implant placement;

4. Undertake a suckdown on the model incorporating the markers with an acrylic film to form a (negative) radiographic guide; and

5. Trim the radiographic guide and check placement in patient's mouth.

[0017] Fig. 3 is a photo of an exemplary radiographic guide 300 with gutta percha markers 302. Once the radiographic guide 300 has been manufactured and appropriately trimmed, the patient then takes the radiographic guide to an imaging facility whereby the single or double scan technique takes place. [0018] The Single Scan Technique is utilised only in edentulous cases. The patient is scanned with the guide in situ. Only two of the planning software applications permit a single scan technique to be utilised.

[0019] With the Double Scan Technique, the radiographic guide is scanned in its correct orientation as though the radiographic guide was situated in the mouth. Once this scan is complete, the patient is scanned with the radiographic guide in situ. The scans produce two separate Digital Imaging and Communications in Medicine (DICOM) files which are imported into the planning software and superimposed upon each other.

[0020] Implant Planning is the preparation necessary to ensure that the implants to be utilised will be suitable for placement into the area of interest of the patient.

Planning involves the virtual placement and determination of the angulation of the implants using the scan images, determination of the abutment to be used, and the placement of the crown (restoration, artificial tooth) to the abutment.

[0021 ] Current software applications assist practitioners with virtual implant placement, by operating to assist with virtual placement of the restoration, being the visible part of the tooth, including a crown. Once the tooth is ideally placed, the software is operated to add the abutment, and then to add the implant to view the relationship to the bone. This provides for the practitioner generally sufficient information as to what is required to be done to attempt to maintain that ideal restoration position. Adjustments may then be necessary to the position of all three appliances contingent upon the amount of bone in the ideal location. Examples of currently available planning software applications are shown in the table of Fig. 4.

[0022] The cost of dental implant treatment varies depending upon on several factors. Generally however, the procedure is considered expensive. Most dental surgeons currently charge between AU$1 ,500 and AU$3,000 per tooth. Some people have been known to pay as much as $50,000 for a set of permanent dental implants. Planning is a significant contributor to those costs. Notwithstanding those costs, existing implant techniques are prone to error, often associated with surgical emplacement and arising from poor planning or encounters with unappreciated anatomical problems.

[0023] Particularly, for mandibular (lower jaw) implants in the vicinity of the mental foramen (MF), there must be sufficient alveolar bone above the mandibular canal, also called the inferior alveolar canal (IAC), which acts as the conduit for the neurovascular bundle carrying the inferior alveolar nerve (IAN). Failure to precisely locate the IAN and MF invites surgical insult by the drills and the implant itself. Such insult may cause irreparable damage to the nerve, often felt as a paresthesia (numbness) or dysesthesia (painful numbness) of the gum, lip and chin. This condition may persist for life and may be accompanied by unconscious drooling.

[0024] Whilst generally self-regulated, dentistry will ultimately face accreditation requirements, either from government authorities or health insurers. With this, the need to provide documentation for implant planning will become more prevalent, particularly to avert litigation from patients.

[0025] There is a need for a simple, user friendly and low cost dental prosthetic planning and implementation service.

SUMMARY

[0026] Presently disclosed is an integrated system for planning and

implementation of dental prosthetic surgery through surgical guide production that, in comparison to existing approaches, affords a cost effective and simple approach to planning, resulting in reduced surgical time and reduced risk to the patient and for the surgeon.

[0027] According to one aspect of the present disclosure there is provided a method of forming a guide for dental prosthetic surgery of a patient, said method being characterised by forming an impression of the patient using an impression tray and an impression material, and imaging the patient whilst both the impression and tray are in situ in the patient.

[0028] Typically the method comprises:

forming an impression of the patient using an impression tray and an impression material;

imaging the patient with the both impression and tray in situ in the patient to capture a plurality of images of a combination of the impression, the tray, and the patient; determining, from the images, optimal locations of structures for the prosthetic surgery;

milling by drilling at least one hole through the impression according to the optimal locations; and forming the guide by inserting a sleeve into each drilled hole of the milled impression, the sleeves with the impression thereby forming a guide by which drilling can be performed during the prosthetic surgery.

[0029] Most desirably the impression is retained in the tray and the milling comprises drilling holes through both the tray and impression at predetermined locations and at predetermined angles.

[0030] The imaging is preferably performed using a single scan of a cone beam computed tomography (CBCT) scanner after the impression material has set to form the impression. Desirably the impression is retained within the impression tray until at least after completion of the milling.

[0031 ] The impression tray advantageously comprises a body shaped for impression against a jaw of a patient, a plurality of reference points located about the body, and a matrix of markers distributed across the body. The reference points are desirably laterally spaced and the matrix of markers preferably comprise at least one of channels and ridges formed in generally horizontal surfaces of the tray. The determining can comprise registration of a plurality of image slices to identify the optimal locations relative to the impression and the tray. The registration most preferably comprises point registration of the reference points and surface registration performed using the matrix of markers.

[0032] According to another aspect, there is disclosed a dental impression tray, the tray comprising:

a body shaped for impression against a jaw of a patient:

a plurality of reference points located about the body; and

a matrix of markers distributed across at least one surface of the body.

[0033] Desirably the reference points are laterally spaced and are used for point registration of images captured using the tray, and the matrix of markers is used for surface registration of the images. Most preferably the reference points comprise generally vertically aligned tubular structures laterally spaced on an outside vertical surface of the tray, and the matrix of markers comprise at least one of channels and ridges formed in at least one horizontal surface of the tray. The reference points may comprise a matrix of holes in the at least one horizontal surface of the tray. [0034] Also disclosed is a method of dental treatment of a patient comprising: positioning at least a surgical guide, formed according to any of the methods described, in the patient;

drilling through the one or more sleeves of the surgical guide into the jaw of the patient;

removing the surgical guide from the patient; and

affixing a dental implant into the one or more drill holes in the jaw of the patient.

[0035] Advantageously the positioning comprises positioning the surgical guide in the tray in the patient and the drilling comprises drilling through both the tray and the guide into the jaw of the patient.

[0036] In a further aspect, disclosed is a system for dental prosthetic treatment of a patient, said system comprising:

a dental impression tray including a plurality of laterally spaced reference points and a matrix of markers, for forming an impression of the patient;

an imaging process configured to register a plurality of images captured of the dental impression tray and an impression in situ in the patient, the registration being performed using the reference points and the matrix of markers and forming a mapping between the tray, the impression material and anatomical structures of the patient required for the dental prosthetic treatment;

a user interface by which a user can specify, within the mapping, locations of prosthetic appliances required for the treatment;

a milling machine operable according to a milling instruction determined from the specified mapping to mill at least the impression to include at least one hole in the impression material to thereby form an surgical guide; and

a sleeve corresponding to each milled hole and inserted into each hole of the surgical guide to thereby form a completed surgical guide to be used to guide drilling of the patient during dental prosthetic surgery.

[0037] In the system:

the impression tray comprises a tray according to that mentioned above;

the imaging process comprises imaging using a 3D head and neck cone beam volumetric scan tomographic apparatus; and

the milling machine comprises a computer numerical controlled drill to drill one or more holes through both the tray and impression. [0038] Other aspects are also disclosed.

Brief Description of the Drawings

[0039] At least one embodiment of the present invention will now be described with reference to the drawings, in which:

[0040] Fig. 1 is an x-ray view of a traditional sub-periostal dental implant;

[0041 ] Fig. 2 illustrates a traditional implant with an attached artificial tooth;

[0042] Fig. 3 shows a radiographic guide;

[0043] Fig. 4 shows a table of prior art planning software products;

[0044] Fig. 5 is a schematic flow diagram of a method of dental surgical guide formation according to the present disclosure;

[0045] Figs. 6A to 6H are various views of upper and lower impression trays used for obtaining a dental impression according to the present disclosure;

[0046] Fig. 7 shows an example upper impression tray with an attached handle;

[0047] Fig. 8 shows the moulding of the impression with the tray of Fig. 7 inserted into an artificial mouth;

[0048] Fig. 9 is an x-ray point registration image of an exemplary tray and impression positioned within a jaw;

[0049] Fig. 10 is a plan view of the impression tray showing another example of the impression matrix;

[0050] Fig. 1 1 shows an implant guide with an embedded sleeve;

[0051 ] Figs. 12A and 12B form a schematic block diagram of a general purpose computer system upon which arrangements described can be practiced; and [0052] Figs. 13A to 13F are images representing the parts of the planning process for dental prosthetic surgery.

Detailed Description including Best Mode

[0053] Fig. 5 shows a method 500 for the formation of a dental surgical guide in which a dental impression obtained from the patient is used as to form a guide for the surgical implantation process. The method 500 is performed as a combination of manual steps and steps automated through the use of computing and associated systems to aid imaging and milling of the guide.

[0054] The method 500 starts 502 with an initial step 504 where a dental impression of the patient is obtained to make an exact replica of the patient's teeth, gingiva, and surrounding tissues in the mouth. The dental impression forms an imprint (i.e. a 'negative' mould) of those teeth and gums, which can be used to make a cast or 'positive' model of the patient's dentition.

[0055] In traditional dental impressions, alginate impression material is normally used which presents as a powder that, when mixed with water, forms a thick pasty material. A traditional dental impression tray is filled with the impression material and placed over the teeth, one arch at a time. The alginate impression material sets after 30 to 60 seconds in the patient's mouth. Cold water prolongs the setting time of alginate, while warm water shortens the set time considerably. Once the alginate impression material has set, it becomes solid. Where desired, a final study model may be formed by filling the set impression material with a stone mixture to obtain a positive cast of the patient's jaw.

[0056] Step 504 however makes use of a specially designed impression tray, as for example seen in Figs. 6A to 6H. Figs. 6A, 6B and 6C show respectively top perspective, bottom perspective and top plan views of an upper dental impression tray 600, whereas Figs. 6D - 6H show respectively top perspective, bottom perspective, rear elevation (inverted), bottom plan, and front elevation views of a lower dental impression tray 650. The upper tray 600 has a body 606 exhibiting a traditional curved shape suitable for impression against an upper jaw of a patient. The lower tray 600 has a body 608 exhibiting a traditional curved shape suitable for impression against a lower jaw of a patient. The trays 600 and 650 are preferably moulded or otherwise formed from a resilient and substantially inflexible plastics material, such as nylon or polypropylene. The trays 600 and 650 each include a number of holes 604, traditionally found with dental impression trays, through which the impression material may flow and which further operate to mechanically hold the impression in the tray 600/650 during and after setting.

[0057] The trays 600/650 differ from traditional impression trays through inclusion of a number of integrally formed references. Specifically the trays 600/650 each include laterally located reference points 602, best seen in each of Figs. 6A to 6H. The reference points 602, of which there are five (5) in each of the illustrated examples, are tubular structures mounted generally vertically to the exterior of the vertical wall of the tray 600/650 that follows the line of teeth. The reference points 502 permit the matching of points from the physical impression to a virtual impression, and between each slice of a single patient imaging scan.

[0058] The trays 600/650 also include references formed by a grid matrix of markers 610 formed on the flat, planar, generally horizontal outer surface 612 and flat, planar, generally horizontal inner surface 614 of the trays 600/650. The outer surface 612 (e.g. Figs. 6B and 6E) complements the inner surface 614 (e.g. Figs. 6A and 6D), against which the teeth are impressed. The matrix 610 is preferably moulded, etched or engraved to the surfaces 612 and 614 to provide a regular grid of references, specifically formed at intersections of the grid, generally arranged at 2mm spacings, and preferably at 1 mm spacings. Note that the illustrated grid matrix 610 is shown at a spacing somewhat larger than 2mm, for the purposes of clarity of these drawings.

[0059] In the specific examples illustrated, the matrix markers 610 formed on the outer surface 612 are formed as grooves or channels 610b in the body 606/608. These may be formed by moulding, cutting, etching or engraving. The matrix markers 610 formed on the inner surface 614 are seen as raised lines or ridges 610a and may be formed by moulding. In a specific form of manufacture, the matrix of markers 610 may be formed by pressing on the outer surface 612, to form the channels which deform the inner surface 614 to form the ridges. The depth/height of the markers 610a, 610b may be, for example, 0.5mm. The matrix markers 610 are construction in such a manner to be identifiable during scanning/imaging of the impression tray 600/650 (to be described).

[0060] Step 504 can be performed with a variety of suitable impression materials.

Preferably, a clear vinyl polysiloxane based impression material is used. An example of this is called Memosil 2, which is manufactured by Mitsubishi Chemicals, and distributed in Australia by Hereaus Dental. This material is selected as such is substantially more transparent to imaging with x-rays than the traditional alingate impression material discussed above. As seen in Fig. 7, to assist with handling and the positioning of the tray 600 in the patient's mouth, a removable handle 702 may be attached to the tray 600 via a front central reference point 602a. Fig. 7, being a photographic representation of the translucent impression tray 600, provides a view of the matrix of markers 610 which, in this specific example, includes a relatively coarse grid matrix formed by traverse ridges 710 and 712 at, for example, 5mm spacings, between which are formed a 5x5 matrix or array of holes 715, which may be laser drilled to a diameter of about 0.5mm. The holes 715 form additional reference points to the reference points 602 and the ridges 610, 710, 712.

[0061 ] For the remainder of this detailed description, unless otherwise indicated, reference will only be made to the (upper) tray 600, but it will be appreciated that the same operations may be performed using the lower tray 650. Step 504 is performed by selecting a tray 600 having size that is slightly larger than the arch of the patient. A cartridge of the two-part Memosil 2 material is loaded into an impression gun. The trigger of the impression gun squeezed and mixed Memosil 2 material is imparted into the tray. The amount used depends on the size of the tray. The Memosil 2 material has a working time of about 45 seconds, and a total setting time of 3 minutes 15 seconds from the start of mix. The tray 600 with the impression material is placed into the patient's mouth over the arch of interest (the upper arch for the tray 600, the lower arch for the tray 650) and held down for the setting time. This is depicted in Fig. 8 using a transparent model jaw structure. Once set, as seen in step 506, the tray 600 with the captive set impression may then be removed from the patient's mouth. As will be appreciated from Figs 6A to 6H, the reference points 602 are formed on the tray 600/650 and do not impact upon the impression. Similarly the matrix of markers 610b formed on the outside of the tray 600/650 and does not impact upon the impression, whereas the matrix of markers 610a formed on the inside of the tray 600/650 does impact upon the impression.

[0062] Where desired, prior to application of the impression material to the tray

600, the inside of the tray 600 may be painted with a radiographic material (gutta percha) to provide for greater contrast between the matrix 610 and impression.

[0063] According to step 508, the set impression, still residing within the tray 600, is then re-inserted into the patient who is then scanned with the impression tray 600 and the set material in situ. Such scanning is typically performed using a cone beam computed tomography (CNCT) scanner. Desirably this is done utilising a cone beam volumetric x-ray technique (CBVT), and preferably such scanning is performed using 3D Head & Neck Cone Beam Volumetric Scan Tomographic apparatus. A single volumetric scan is performed that captures a plurality of axial image slices of the combination of the tray 600, the impression and the jaw. The scanning is performed in situ to provide for accurate imaging alignment between the set impression material, the tray, and the anatomical structures of the jaw of the patient upon which restoration is to be performed.

[0064] In a variation of the procedure described above, the set impression and tray 600 may kept in the patient's mouth from the time of setting until such time as the scanning is complete. This may be appropriate where scanning is performed immediately after taking of the impression. Whilst this can ensure most exact alignment, removal and reinsertion of the tray with captive impression before scanning ensures that the set impression is appropriately sound and therefore sufficiently durable to withstand use and processing to follow.

[0065] As seen at step 512, the impression tray with the set impression contained therein are then set aside pending milling to form a surgical guide. Step 512 may include washing the assembly prior to storage.

[0066] The significant output of the scanning step 508 includes image files 510 of the slices of the single scan of the combination of the tray 600 and the impression in situ in the jaw of the patient. The image files 510 are provided to a planning module 520. The planning module 520 is preferably implemented in software as one or more application programs 1233 executable by a computing system, such as the system 1200 shown in Figs. 12A and 12B.

[0067] As seen in Fig. 12A, the computer system 1200 includes: a computer module 1201 ; input devices such as a keyboard 1202, a mouse pointer device 1203, a scanner 1226, and a cone beam computed tomography (CBCT) scanner 1227 (e.g. a CBVT scanner); and output devices including a printer 1215, a display device 1214, loudspeakers 1217, and a milling machine 1290. An external Modulator-Demodulator (Modem) transceiver device 1216 may be used by the computer module 1201 for communicating to and from a communications network 1220 via a connection 1221. The communications network 1220 may be a wide-area network (WAN), such as the Internet, a cellular telecommunications network, or a private WAN. Where the connection 1221 is a telephone line, the modem 1216 may be a traditional "dial-up" modem. Alternatively, where the connection 1221 is a high capacity (e.g., cable) connection, the modem 1216 may be a broadband modem. A wireless modem may also be used for wireless connection to the communications network 1220.

[0068] The computer module 1201 typically includes at least one processor unit 1205, and a memory unit 1206. For example, the memory unit 1206 may have semiconductor random access memory (RAM) and semiconductor read only memory (ROM). The computer module 1201 also includes an number of input/output (I/O) interfaces including: an audio-video interface 1207 that couples to the video display 1214, loudspeakers 1217 and microphone 1280; an I/O interface 1213 that couples to the keyboard 1202, mouse 1203, scanner 1226, CBVT scanner 1227 and optionally a joystick or other human interface device (not illustrated); and an interface 1208 for the external modem 1216, milling machine 1290 and printer 1215. In some implementations, the modem 1216 may be incorporated within the computer module 1201 , for example within the interface 1208. The computer module 1201 also has a local network interface 121 1 , which permits coupling of the computer system 1200 via a connection 1223 to a local- area communications network 1222, known as a Local Area Network (LAN). As illustrated in Fig. 12A, the local communications network 1222 may also couple to the wide network 1220 via a connection 1224, which would typically include a so-called "firewall" device or device of similar functionality. The local network interface 121 1 may comprise an Ethernet circuit card, a Bluetooth* wireless arrangement or an IEEE 802.1 1 wireless arrangement; however, numerous other types of interfaces may be practiced for the interface 121 1.

[0069] In some implementations, the CBVT scanner 1227 and/or the milling machine 1290 may be coupled to the computer 1201 via the networks 1220 or 1222, for example where third-parties offer those respective roles and services.

[0070] The I/O interfaces 1208 and 1213 may afford either or both of serial and parallel connectivity, the former typically being implemented according to the Universal Serial Bus (USB) standards and having corresponding USB connectors (not illustrated). Storage devices 1209 are provided and typically include a hard disk drive (HDD) 1210. Other storage devices such as a floppy disk drive and a magnetic tape drive (not illustrated) may also be used. An optical disk drive 1212 is typically provided to act as a non-volatile source of data. Portable memory devices, such optical disks (e.g., CD-ROM, DVD, Blu-ray Disc™), USB-RAM, portable, external hard drives, and floppy disks, for example, may be used as appropriate sources of data to the system 1200.

[0071 ] The components 1205 to 1213 of the computer module 1201 typically communicate via an interconnected bus 1204 and in a manner that results in a

conventional mode of operation of the computer system 1200 known to those in the relevant art. For example, the processor 1205 is coupled to the system bus 1204 using a connection 1218. Likewise, the memory 1206 and optical disk drive 1212 are coupled to the system bus 1204 by connections 1219. Examples of computers on which the described arrangements can be practised include IBM-PC's and compatibles, Sun Sparcstations, Apple Mac™ or a like computer systems.

[0072] The method of forming a dental implant guide may be implemented using the computer system 1200 wherein at least the planning processes of step 520, to be described, may be implemented as one or more software application programs 1233 executable within the computer system 1200. In particular, the planning steps are effected by instructions 1231 (see Fig. 12B) in the software 1233 that are carried out within the computer system 1200. The software instructions 1231 may be formed as one or more code modules, each for performing one or more particular tasks. The software may also be divided into two separate parts, in which a first part and the corresponding code modules performs specific data processing methods and a second part and the corresponding code modules manage a user interface between the first part and the user.

[0073] The software may be stored in a computer readable medium, including the storage devices described below, for example. The software is loaded into the computer system 1200 from the computer readable medium, and then executed by the computer system 1200. A computer readable medium having such software or computer program recorded on the computer readable medium is a computer program product. The use of the computer program product in the computer system 1200 preferably effects an advantageous apparatus for planning dental implant development.

[0074] The software 1233 is typically stored in the HDD 1210 or the

memory 1206. The software is loaded into the computer system 1200 from a computer readable medium, and executed by the computer system 1200. Thus, for example, the software 1233 may be stored on an optically readable disk storage medium (e.g., CD- ROM) 1225 that is read by the optical disk drive 1212. A computer readable medium having such software or computer program recorded on it is a computer program product. The use of the computer program product in the computer system 1200, particularly in concert with the CBVT scanner 1327, used in step 508, and the milling machine 1290 used in step 524 (to be described) effects an apparatus for forming a dental implant surgical guide.

[0075] In some instances, the application programs 1233 may be supplied to the user encoded on one or more CD-ROMs 1225 and read via the corresponding drive 1212, or alternatively may be read by the user from the networks 1220 or 1222. Still further, the software can also be loaded into the computer system 1200 from other computer readable media. Computer readable storage media refers to any non-transitory tangible storage medium that provides recorded instructions and/or data to the computer system 1200 for execution and/or processing. Examples of such storage media include floppy disks, magnetic tape, CD-ROM, DVD, Blu-ray™ Disc, a hard disk drive, a ROM or integrated circuit, USB memory, a magneto-optical disk, or a computer readable card such as a PCMCIA card and the like, whether or not such devices are internal or external of the computer module 1201. Examples of transitory or non-tangible computer readable transmission media that may also participate in the provision of software, application programs, instructions and/or data to the computer module 1201 include radio or infra-red transmission channels as well as a network connection to another computer or networked device, and the Internet or Intranets including e-mail transmissions and information recorded on Websites and the like.

[0076] The second part of the application programs 1233 and the corresponding code modules mentioned above may be executed to implement one or more graphical user interfaces (GUIs) to be rendered or otherwise represented upon the display 1214. Through manipulation of typically the keyboard 1202 and the mouse 1203, a user of the computer system 1200 and the application may manipulate the interface in a functionally adaptable manner to provide controlling commands and/or input to the applications associated with the GUI(s). Other forms of functionally adaptable user interfaces may also be implemented, such as an audio interface utilizing speech prompts output via the loudspeakers 1217 and user voice commands input via the microphone 1280.

[0077] Fig. 12B is a detailed schematic block diagram of the processor 1205 and a "memory" 1234. The memory 1234 represents a logical aggregation of all the memory modules (including the HDD 1209 and semiconductor memory 1206) that can be accessed by the computer module 1201 in Fig. 12A. [0078] When the computer module 1201 is initially powered up, a power-on self- test (POST) program 1250 executes. The POST program 1250 is typically stored in a ROM 1249 of the semiconductor memory 1206 of Fig. 12A. A hardware device such as the ROM 1249 storing software is sometimes referred to as firmware. The POST program 1250 examines hardware within the computer module 1201 to ensure proper functioning and typically checks the processor 1205, the memory 1234 (1209, 1206), and a basic input-output systems software (BIOS) module 1251 , also typically stored in the ROM 1249, for correct operation. Once the POST program 1250 has run successfully, the BIOS 1251 activates the hard disk drive 1210 of Fig. 12A. Activation of the hard disk drive 1210 causes a bootstrap loader program 1252 that is resident on the hard disk drive 1210 to execute via the processor 1205. This loads an operating system 1253 into the RAM memory 1206, upon which the operating system 1253 commences operation. The operating system 1253 is a system level application, executable by the

processor 1205, to fulfil various high level functions, including processor management, memory management, device management, storage management, software application interface, and generic user interface.

[0079] The operating system 1253 manages the memory 1234 (1209, 1206) to ensure that each process or application running on the computer module 1201 has sufficient memory in which to execute without colliding with memory allocated to another process. Furthermore, the different types of memory available in the system 1200 of Fig. 12A must be used properly so that each process can run effectively. Accordingly, the aggregated memory 1234 is not intended to illustrate how particular segments of memory are allocated (unless otherwise stated), but rather to provide a general view of the memory accessible by the computer system 1200 and how such is used.

[0080] As shown in Fig. 12B, the processor 1205 includes a number of functional modules including a control unit 1239, an arithmetic logic unit (ALU) 1240, and a local or internal memory 1248, sometimes called a cache memory. The cache memory 1248 typically includes a number of storage registers 1244 - 1246 in a register section. One or more internal busses 1241 functionally interconnect these functional modules. The processor 1205 typically also has one or more interfaces 1242 for communicating with external devices via the system bus 1204, using a connection 1218. The memory 1234 is coupled to the bus 1204 using a connection 1219. [0081 ] The application program 1233 includes a sequence of instructions 1231 that may include conditional branch and loop instructions. The program 1233 may also include data 1232 which is used in execution of the program 1233. The instructions 1231 and the data 1232 are stored in memory locations 1228, 1229, 1230

and 1235, 1236, 1237, respectively. Depending upon the relative size of the

instructions 1231 and the memory locations 1228-1230, a particular instruction may be stored in a single memory location as depicted by the instruction shown in the memory location 1230. Alternately, an instruction may be segmented into a number of parts each of which is stored in a separate memory location, as depicted by the instruction segments shown in the memory locations 1228 and 1229.

[0082] In general, the processor 1205 is given a set of instructions which are executed therein. The processor 1 105 waits for a subsequent input, to which the processor 1205 reacts to by executing another set of instructions. Each input may be provided from one or more of a number of sources, including data generated by one or more of the input devices 1202, 1203, data received from an external source across one of the networks 1220, 1202, data retrieved from one of the storage devices 1206, 1209 or data retrieved from a storage medium 1225 inserted into the corresponding reader 1212, all depicted in Fig. 12A. The execution of a set of the instructions may in some cases result in output of data. Execution may also involve storing data or variables to the memory 1234.

[0083] The planning processes 520 use input variables 1254, which are stored in the memory 1234 in corresponding memory locations 1255, 1256, 1257. The planning processes 520 produce output variables 1261 , which are stored in the memory 1234 in corresponding memory locations 1262, 1263, 1264. Intermediate variables 1258 may be stored in memory locations 1259, 1260, 1266 and 1267.

[0084] Referring to the processor 1205 of Fig. 12B, the

registers 1244, 1245, 1246, the arithmetic logic unit (ALU) 1240, and the control unit 1239 work together to perform sequences of micro-operations needed to perform "fetch, decode, and execute" cycles for every instruction in the instruction set making up the program 1233. Each fetch, decode, and execute cycle comprises:

a fetch operation, which fetches or reads an instruction 1231 from a memory location 1228, 1229, 1230;

a decode operation in which the control unit 1239 determines which instruction has been fetched; and

an execute operation in which the control unit 1239 and/or the ALU 1240 execute the instruction.

[0085] Thereafter, a further fetch, decode, and execute cycle for the next instruction may be executed. Similarly, a store cycle may be performed by which the control unit 1239 stores or writes a value to a memory location 1232.

[0086] Each step or sub-process in the planning step 520 is associated with one or more segments of the program 1233 and is performed by the register section 1244, 1245, 1247, the ALU 1240, and the control unit 1239 in the processor 1205 working together to perform the fetch, decode, and execute cycles for every instruction in the instruction set for the noted segments of the program 1233.

[0087] In a preferred implementation, the computer system 1200 operates as a server computer to which one or more client computers 1299 may couple via the networks 1220 and/or 1222 and with which dental practitioners and allied service providers may interact with the planning processes 520, as indicated by the input 522 in Fig. 5. For example, whilst Fig. 12A shows the CBVT scanner 1327 coupled directly to the computer module 1201 , such may couple via either of the networks 1220 or 1222, or the image files 510 may be provided by a third-party provider, for example via the client computer 1299. In addition to the image files 510, further input to the planning process 520 may include referral and reports for the referring dentist / doctor to review. The planning modules 520 are preferably integrated into or associated with a service provider communications suite.

[0088] The planning processes 520 utilises image registration 514 preferably formed using two image registration techniques - point registration 516 and surface registration 518. Image registration is the process of aligning two or more images of the same scene. This process involves designating one image of the image files 510 as a reference and applying geometric transformations to the other images of the image files 510 so that they align with the reference image.

[0089] Point Registration makes use of the 5 laterally located reference points 602 of the impression tray 600. These points 602, when scanned in the patient's mouth by the CBVT scanner 1327, appear as dense points 901 in the x-ray image, as seen for example in Fig. 9, showing single slice of a single scan of the combination of tray, impression and jaw 902 of the patient. Since the reference points 602 are tubular and vertically oriented, the dense points 901 will appear in each image slice of the captured scan, thereby providing accurate point registration amongst all slices. Step 516 implements a point- based method of registration performed on the basis of the relatively dense point sets, each from the respective image slice, being brought into correspondence, where these point sets constitute all, or a significant subset of, the available surface point samples. The point sets, which number at least two, but which typically number 5, are generally assumed to be relatively close to being aligned, and are registered by iteratively minimizing the sum of squared distances between mutually closest points between a (possibly transformed) surface SA, being a virtual reference surface in the software of the image registration module514, and a surface SB, being that represented by the slice being processed.

[0090] In addition to the points 602 used for point registration, the impression tray

600 includes the matrix of markers 610 within the surfaces of the tray 600. Those markers (channels 610b) are detected by the imaging, and for example can be seen, with some difficulty (due to size and resolution) in the image of Fig. 9. Nevertheless, since the markers (channels) 610b are formed in the tray 600, such provides for that surface of the tray 600 to have the corresponding imaged matrix surface registered in step 518 with a fixed virtual matrix corresponding to the tray 600 and stored within the software. Similarly, the ridges 610a may be detected from the imaging, and should be displaced from a surface registration of the channels 610b only by the thickness of the tray 600.

Computerised methods of surface registration are known in the art. Fig. 10 illustrates an exemplary tray 1000 with an alternate matrix of markers formed by a coarse transverse ridges 1002 and interspersed holes 1004.

[0091] The net result of the image registration step 514 is an accurate three- dimensional (3D) mapping between the slice images of the patient and the tray with impression. Significantly, the 3D mapping provides virtual representation of the patient's area of interest for accurate pre-location of anatomical structures of the jaw to permit accurate locating of restoration structures on the surgical guide, yet to be formed.

[0092] With the aligned/registered images, the dentist can log in to a personal account on the server 1201 and open the Implant planning link which is attached to the individual patient scan. The server 1201 may operate using appropriate viewing software, such as ActiveX, to assist in transportability of images and registrations thereof between a variety of computing platforms. [0093] The dentist will open the study of the particular patient and select an

Implant link application 532, representative of the service provider communications suite. Desirably a link ActiveX control and an Implant application 534 are then downloaded to and installed on the client computer 1299 at the same time automatically to avoid communication delays in the planning process. In some implementations, the implant link application may permanently reside upon the client computer 1299.

[0094] The process 520 then starts the implant application 534 when the patient study, including the images 510 and ancillary data, is completely downloaded to the client computer 1299. The implant application 534 can operate using command line

parameters, and for example with DICOMs: multi dicom + dicom dir files in the same folder.

[0095] With the processes 520, the dentist can identify the area of the patient they want to place an implant into, select the implant brand and type, and proceed to plan their surgical treatment through virtual emplacement of the implant onto one or more optimal locations for prosthetic surgery, as required, in the images captured using the CBVT scanner 1237. The optimal locations are typically those where there is sufficient room to accommodate a dental prosthesis such and an implant, and an associated abutment and crown, and that there is sufficient bone into which the implant can be successfully embedded. Such includes a determination of the appropriate angle of emplacement of the implant subject to bone availability. In this fashion for example, the implant 200 may be anchored into an angled hole in the jaw, whilst the abutment is used to change the angle of fastening and presentation of the crown such that the teeth properly align on completion of the restoration.

[0096] Figs. 13A to 13F provide exemplary screen capture images of implant planning using prior art GUI software, such as that of Fig. 4, useful for the implant application 534. Fig. 13A shows a GUI 1300 displaying a number of images obtained from the single scan discussed above and which represents a typical intermediate stage of the planning process. A panoramic view 1302 is shown upon which the user has inserted graphical objects 1304 and 1306 overlying the two nerve canals of the lower jaw. Also provided is an axial view 1308, a 3D model view 1310 and a number of cross- sectional views 1312, one of which is highlighted and provided as an enlarged view 1314, and which includes a graphic 1316 indicating the nerve canal 1304, complementing the relevant section of the panoramic view 1302. [0097] Fig. 13B shows a following stage 1320 of the planning process where a generic implant 1322 is virtually placed into the dental plan as seen in the panoramic view 1324, and in each of the cross-section 1326, axial view 1328 and model 1330. As seen, three indicator lines 1332 are provided in the panoramic view 1324 to show the centreline and bounds of an artificial tooth to be mounted to the implant.

[0098] Fig. 13C is a view of next stage where the GUI provides a menu 1340 of specific implants by which the user can select one 1342 of appropriate size and shape for virtual placement into the dental plan shown in the GUI.

[0099] Fig. 13D shows a following stage 1350 where the selected implant 1342 is inserted into the plan in place of the generic implant 1322. Note from the enlarged cross- sectional view 1352 that the selected implant is sized to be positioned with an appropriate clearance from the graphically indicated nerve 1354 and has a length to sit just proud of the jaw bone, but still within the gum of the jaw. These features are seen in greater detail in the further enlarged representation 1360 of Fig. 13E.

[00100] After acceptance of placement of the virtual implant into the correct position, the dentist can then lock the mapping file. The dentist can choose to continue to place additional implants by selecting an "Add Implant" process via a GUI of the implant application 534. The implant application 534 will tell the link application 532 that implant planning procedure is finished once the dentist selects a Finish button icon in the GUI (not illustrated), having identified all optimal positions for placement of implants. This activates the locking of the implant placement and exports the file from the client computer 1299 to a folder on the server 1201 .

[00101] Fig. 13F shows a completed plan for this particular patient having two virtually place implants 1342 and 1372 arranged to accept respective artificial teeth to replace the two missing natural teeth.

[00102] The imaging of Figs. 13A - 13F was captured with prior part approaches to show the basic planning stages. Where similar imaging included the images 510 captured according to the present disclosure, the imaging would further represent the lower jaw dental impression tray 650 and representation of the impression material. The imaging, particularly the axial views, would also represent the reference points 602 and the matrix of markers 610 thereby incorporating such references into the plan for accurate positioning of the implants appropriately referrable to the references 602, 610 to form the mapping file.

[00103] The milling step 524 of the method 500 is then performed. The planning file in the server 1201 is then exported to a controlling computer 525 of the milling machine 1290. The plan specified by the mapping file may then be checked and verified by relevant milling technicians and, if satisfactory, then the tray 600 with the captive impression is mounted in the milling machine 1290. The reference points 602 can then be manually identified by the technician by data entry at the milling machine 1290. This provides for alignment at the milling machine 1290 between the job and the plan that is input to the machine 1290 from the application 534.

[00104] The locked implant plan file is then imported into the milling computer 525 which then operates to align the matrix images obtained through the planning file through surface registration. This workflow includes feature detection, extraction, and matching, followed by transform estimation. This operates to ensure that the milling plan is actually correct and able to be matched to information determined from the milling machine 525 and thus able to be implemented by the machine 525.

[00105] The impression and tray is then mounted into the fixed jig utilising the lateral reference points 602. This preferably includes alignment of the aligned matrix images with at least the lateral reference points 602, and most preferably using the matrix 610 of the tray 600. The milling machine 1290 is activated and the impression guide is milled in accordance with the co-ordinates specified by the file. The milling specifically involves computer numerical control (CNC) drilling of guide holes through the tray 600 and the impression. The milling machine 525 is thus able to accurately position the drill bit to preferably within 0.5mm accuracy of the predetermined desired implant location and drill at a predetermined angle, within an accuracy of preferably 2 degrees so that the drilled hole forms a highly accurate guide for surgical drilling to be subsequently performed.

[00106] The milled guide (tray with impression) 526 is removed from the milling machine 1290. The tray may be optionally discarded as at step 532. Metal sleeves 1 102 are then inserted into the milled impression 526 to form a completed surgical guide 530. This is depicted in Fig. 1 1 which also shows a number of raised bumps (pimples) 1 104 representative of the impression material that seeped through the holes 604 before setting of the impression material. The metal sleeves 1 102 form appropriately angled guides through the completed surgical guide 530 that permit the surgeon to drill through the surgical guide 530 and into the patient's jaw at precise locations and corresponding precise angles, to thereby ensure subsequent correct and proper placement of implants 200 (Fig. 2) in the bone, and away from soft tissue, as planning intended.

[00107] In an alternative implementation, the tray is not discarded, and the sleeve(s) 1 102 are inserted through the tray 600 and captive impression to form the completed surgical guide 530. In some implementations, the milled impression may be removed from the tray 600 and the sleeve(s) 1 102 inserted into the milled impression, which can then be re-positioned or inserted back into the tray 600. This may be useful where the impression is thin and its strength may be questionable such that the tray 600 provides for mechanical support to prevent damage. The tray 600 may be retained in combination with the milled impression and the combination used as a surgical guide.

[00108] The completed surgical guide 530 is then sterilised, packed and able to be returned to the dentist ready for surgery.

[00109] At the time of surgery, the completed surgical guide 530 is inserted and positioned in the patient, and the embedded sleeves 1 102 are used for as guides for drilling into the bone, at a precise location(s) and at the corresponding correct angle. Once all drilling has taken place, implants 200 are then cemented drilled holes in the bone, each ready to receive an abutment and a corresponding artificial tooth or other prosthetic facility (such as a bridge).

[001 10] The arrangements presently disclosed, and particularly the in situ imaging of the impression and tray, provide a number of advantages, including:

(i) implant planning can be readily added to existing web based 3D CBVT communications and manipulation systems;

(ii) simple to use by the dentist;

(iii) offers the ability to section the arches in free form and box form and cut outside or inside of the box;

(iv) permits nerve marking to be able to be traced/manipulated from saggital / axial / coronal view;

(v) affords the ability to display opposite arch to view occlusion when implant in situ;

(vi) can show rendered view and transparent view with implant in situ;

(vii) provides for the virtual locating of abutments and virtual teeth; (viii) affords the ability to upload DICOM files from any CT or CBVT scanning apparatus;

(ix) affords the ability to compress DICOM files and download compressed DICOM files;

(x) ability to create virtual impression; and

(xi) ability to create an impression over the implant post placement (take negative) to generate a virtual guide - the virtual guide may then form an instruction for a 3D printer to construct a surgical guide.

[001 1 1] Coupled with the production of the completed implant guide 530, the system 1200 and method 500 are desirably used to generate an implant report including:

(i) display implant type and angulation, details of abutment;

(ii) a selection of images selected by the dentist;

(iii) uploads patient photographs and intra oral images where required;

(iv) the planning template is flexible and can grow dependant on dentist requirements and adjustments to the plan;

(v) through operation of the milling machine 1290, the ability for dentist to include their own logo (representative of a quality mark) on the implant guide;

(vi) ability to create PowerPoint™ presentation and PDF of the plan for technical and professional briefing of other parties in the supply and service chain; and

(vii) ability to create a chat room link for implant planning discussion between relevant providers.

[001 12] The arrangements presently disclosed also provide for distributed processing and interconnection of service providers. For example, numerous imaging centres may be coupled to the planning service 520 which similarly may couple to a number of providers of the milling service used at step 524. At each stage however, the responsible dentist may be involved with and interact as required with the operative service provider. A further advantage for the dentist is that, through the integrated automation and staged approach to implant guide manufacture, more accurate costing can be developed for each stage, thereby providing much greater cost certainty for each party, and notably dentist and patient.

Industrial Applicability [001 13] The arrangements specifically described are directly applicable to dental reconstruction industries however the principles of the methodology may be applied elsewhere.

[001 14] The foregoing describes only some embodiments of the present invention, and modifications and/or changes can be made thereto without departing from the scope and spirit of the invention, the embodiments being illustrative and not restrictive.

[001 15] (Australia Only) In the context of this specification, the word "comprising" means "including principally but not necessarily solely" or "having" or "including", and not "consisting only of. Variations of the word "comprising", such as "comprise" and

"comprises" have correspondingly varied meanings.