# Patent

## Title
Method for selecting implant components

## Abstract

Methods of selecting or designing an implant to be used in a patient are provided. A CT scan of a patient's mouth is performed. A 3D CAD model of the patient's mouth is created utilizing data generated by the CT scan. Properties of the patient's mouth are determined based upon CT scan data and assigned to the 3D CAD model. A desired location for an implant is selected. A FEA simulation is performed on the 3D CAD model to choose an implant or to design an implant that optimizes a selected variable.

## Background
RELATED APPLICATIONS
This application is a continuation of U.S. application Ser. No. 13/530,708, filed Jun. 22, 2012, now U.S. Pat. No. 9,089,380, which is a continuation of U.S. application Ser. No. 12/151,261, filed on May 5, 2008, now U.S. Pat. No. 8,206,153, which claims priority from U.S. Provisional Application No. 60/930,812, filed May 18, 2007. All of these applications are hereby incorporated by reference in their entirety.


FIELD OF INVENTION
The present invention relates generally to implant systems for implants placed in bone. More particularly, the present invention relates to restoration components for dental implant systems and a computer model for selecting or developing an implant by optimizing at least one variable utilizing finite element analysis.
BACKGROUND OF THE INVENTION
The dental restoration of a partially or wholly edentulous patient with artificial dentition is typically done in two stages. In the first stage, an incision is made through the gingiva to expose the underlying bone. An artificial tooth root, usually a dental implant, is placed in the jawbone for integration. The dental implant generally includes a threaded bore to receive a retaining screw holding mating components therein. During the first stage, the gum tissue overlying the implant is sutured and heals as the osseointegration process continues.
Once the osseointegration process is complete, the second stage is initiated. Here, the gum tissue is re-opened to expose the end of the dental implant. A healing component or healing abutment is fastened to the exposed end of the dental implant to allow the gum tissue to heal therearound. Preferably, the gum tissue heals such that the aperture that remains generally approximates the size and contour of the aperture that existed around the natural tooth that is being replaced. To accomplish this, the healing abutment attached to the exposed end of the dental implant has the same general contour as the gingival portion of the natural tooth being replaced.
During the typical second stage of dental restoration, the healing abutment is removed and an impression coping is fitted onto the exposed end of the implant. This allows an impression of the specific region of the patient's mouth to be taken so that an artificial tooth is accurately constructed. Thus, in typical dental implant systems, the healing component and the impression coping are two physically separate components. Preferably, the impression coping has the same gingival dimensions as the healing component so that there is no gap between the impression coping and the wall of the gum tissue defining the aperture. Otherwise, a less than accurate impression of the condition of the patient's mouth is made. The impression coping may be a “pick-up” type impression coping or a “transfer” type impression coping, both known in the art. After these processes, a dental laboratory creates a prosthesis to be permanently secured to the dental implant from the impression that was made.
More recently, single stage restoration have become more common, where an implant is placed in the patients mouth and a prosthesis is placed on this implant during the same procedure. Such a procedure typically reduces the number of visits a patient must make to a clinician, however, additional complications may occur in a patient during single stage restoration if an implant lacks proper initial stability. One way to help predict initial implant stability involves using finite element analysis (“FEA”) to attempt to predict effects of placing the implant into bone. These effects may include stress levels within the implant, stress levels in bone surrounding the implant, initial implant stability, torque required to seat an implant and many other factors. However, a real-time FEA simulation of the placement of an implant into bone has not been performed to date. Rather FEA simulations have only focused on the implant after it has already been placed into bone. Thus, a need exists for a method to accurately predict effects of placing an implant into bone.
SUMMARY OF THE INVENTION
According to one process, a method of selecting an implant to be used in a patient is provided that performs a CT scan of a patient's mouth. The method creates a 3D CAD model of the patient's mouth utilizing data generated by the CT scan. Properties of the patient's mouth are determined based upon data generated by the CT scan. The determined properties of the patient's mouth are assigned to the 3D CAD model. The method selects a desired location for the implant. The implant to be placed into the patient is selected. The method performs an FEA simulation of the selected implant being installed in the patient's mouth with the 3D CAD model. The method confirms the implant chosen by the act of selecting is clinically appropriate based upon the results of the FEA simulation of the 3D CAD model.
According to another process, a method of selecting an implant to be used in a patient is provided that performs a CT scan of the patient's mouth. A 3D CAD model of the patient's mouth is created utilizing data generated by the CT scan. The method determines properties of the patient's mouth based upon data generated by the CT scan. The determined properties of the patient's mouth are assigned to the 3D CAD model. The method selects a desired location for the implant. At least one variable to be optimized by a FEA simulation is assigned. The method performs an FEA simulation on the 3D CAD model to optimize the assigned variable. The method choosing the implant from a plurality of implants to use in the patient based upon results from the act of performing the FEA simulation.
According to a further process a method of designing an implant to be used in a patient is provided that performs a CT scan of the patient's mouth. The method creates a 3D CAD model of the patient's mouth utilizing data generated by the CT scan. Properties of the patient's mouth are determined based upon data generated by the CT scan. The determined properties of the patient's mouth are assigned to the 3D CAD model. The method selects a desired location for the implant. At least one variable to be optimized by a FEA simulation is assigned. The method performs a FEA simulation on the 3D CAD model to optimize the assigned variable. The implant to use in the patient is designed based upon results from the act of performing the FEA simulation.
According to yet another process, a method of verifying a FEA simulation used to select an implant is provided that creates a 3D CAD model of an actual calibration sample. Properties of the actual calibration sample are assigned to the 3D CAD model. The method performs an FEA simulation of placing the implant into the calibration sample on the 3D CAD model to generate FEA simulation data. An actual implant is placed into the actual calibration sample. The method collects measured data during the placement of the actual implant into the actual calibration sample. The measured data gathered during the act of collecting measured data is compared with the FEA simulation data generated by the act of performing the FEA simulation. The method ascertains whether the FEA simulation data accurately predicts the measured data. The method modifies FEA simulation variables if the act of ascertaining determines the FEA simulation does not accurately predict the measured data.
According to yet a further process, a method of selecting an implant to be used in a patient performs a CT scan of a region of the patient's body to contain the implant. A 3D CAD model of the region of the patient's body is created utilizing data generated by the CT scan. Properties of the region of the patient's body are determined based upon data generated by the CT scan. The method assigns the determined properties of the region of the patient's body to the 3D CAD model. A desired location for the implant is selected. The method selects the implant to be placed into the patient. An FEA simulation is performed of the selected implant being installed in the region of the patient's body with the 3D CAD model. The method confirms the implant chosen by the act of selecting is clinically appropriate based upon the results of the FEA simulation of the 3D CAD model.



BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a block diagram of a method according to one process for selecting a dental implant by utilizing a Finite Element Analysis (“FEA”) simulation;
FIG. 2 is a block diagram of a method according to another process for selecting a dental implant by utilizing a FEA simulation;
FIG. 3 is a block diagram of a method according to a further process for designing a dental implant by utilizing a FEA simulation;
FIG. 4 is a block diagram of a method according to one process for verifying a FEA simulation.



While the invention is susceptible to various modifications and alternative forms, specific embodiments thereof have been shown by way of example in the drawings and will herein be described in detail. It should be understood, however, that it is not intended to limit the invention to the particular forms disclosed but, on the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the invention as defined by the appended claims.
DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS
As shown in FIG. 1 a method 10 is shown to determine initial implant stability. As shown in block 12, a CT scan is performed on a patient. It is contemplated that various types of CT scans may be performed, such as Concentric CT scans or Cone-Beam CT scans. The CT scan produces data that may be used in forming a 3D CAD model of a patient's mouth within a CAD system as depicted in block 14. The CT scan allows a determination to be made regarding the type of bone found in the patient's mandible or maxilla where the implant is to be placed.
For example, the CT scan allows a practitioner to determine that Type I bone is present, a bone type that has almost all cortical bone tissue. Similarly, the CT scan may reveal that Type II, Type III, or Type IV bone is present at additional different planned implant locations. The various bone types have properties associated therewith, such as Type I bone being harder than Type IV bone. An implant being placed in Type I bone requires additional torque to seat the implant than an implant being placed in Type IV bone.
It is additionally contemplated that other technologies than CT scanning may be utilized to generate data used to form the 3D CAD model, such as ultrasonic scanning, MRI, or other scanning techniques.
Once the type, or types, of bone that implants will be placed in is determined, material properties for the bone may be assigned to the 3D CAD model of the patient's mouth, as shown in block 16.
The 3D CAD model of the patient's mouth allows a practitioner to determine locations to place the implants to be utilized, and also allows the practitioner to select particular implants to use on the patient. First, by analyzing the patient's particular anatomical structure, the practitioner determines desired locations for implants at block 18. Based on the patient's anatomical structure at the desired locations, a practitioner selects an implant to be placed within the patient at block 20. As the general ranges for material properties for Type I-Type IV bone are known, the 3D CAD model of the bones of the patient are assigned material properties at block 22. The assigning of material properties may be performed automatically by software based on the results of the CT scan, or a practitioner may analyze the CT scan and assign material properties to the 3D CAD model of the patient based on what is shown on the CT scan. Based on output from CT scan, such as the number of Hounsfield's units obtained from the CT scan, a bone type may be obtained.
The CAD system contains a library of dental implants and other restorative components that a practitioner may choose from when developing a treatment plan for a patient. As shown at block 24, the practitioner selects a proposed implant to use within a first implant site of the patient within the CAD system. The CAD system contains a library of dental implants, so that 3D models exist of the various implants that a practitioner may select. The selection of a proposed implant also causes the CAD system to create an osteotomy for the selected implant at the first implant site of the 3D CAD model.
As depicted in block 26, once the practitioner has selected a proposed implant, a finite element analysis (“FEA”) simulation is performed. The FEA simulation may evaluate placing the implant into a patient's bone, the implant and bone immediately after placement of the implant, and further may analyze the implant and bone after oseointegration occurs. Thus, the FEA simulation analyzes the characteristics and conditions of the implant and the bone as the implant is being placed into the bone, not just following the placement of the implant.
The FEA simulation of the implant placement analyzes the torque necessary to seat the implant into the bone. Based on the bone type present in the area around the implant site, as well as the characteristics of the implant and characteristic of the osteotomy, the amount of torque required to drive the implant into the bone is determined using the FEA simulation. After the simulation has determined the torque required to seat the implant within the bone, initial implant stability is analyzed. Knowing the amount of torque required to seat the implant is important, as using more torque than required to obtain a needed level of initial implant stability can generate more friction between the implant and the bone, which generates heat that can damage bone cells near the implant.
Initial implant stability is a measure of the stiffness of the connection between the bone and the dental implant, prior to osseointegration occurring. Initial implant stability can be used to determine how likely it is that the implant may loosen prior to osseointegration occurring. The higher the initial implant stability, the less likely the implant is to come loose. Factors that may influence initial implant stability, and that can be accounted for in the FEA simulation, include implant geometry, such as the thread design and implant size, bone type, and osteotomy properties, such as osteotomy geometry, whether the osteotomy has a counter sink, and whether the osteotomy is tapped.
Further, the FEA simulation may be used to calculate a resonant frequency of the implant and bone assembly, at the time of implantation. A resonant frequency analysis (“RFA”) allows a practitioner to track the osseointegration of the implant. As the implant is integrated into the bone, the resonant frequency changes, indicating to the practitioner how osseointegration is progressing.
The FEA simulation further may be used to analyze the stress and strain generated as the implant is placed in to the osteotomy. This analysis can be used to evaluate the stress and strain at the interface of the bone and the implant, as well as the stress and strain within the patient's bone. Thus, the FEA simulation allows a practitioner to determine the potential stress and strain that will exist within the patient as the implant is placed into the bone.
Thus, the FEA simulation allows a practitioner to evaluate many factors of a selected implant in a 3D virtual environment, prior to performing any surgical procedures on a patient. Thus, a practitioner may select an implant, virtually place the implant into the 3D model of the patient's bone, and perform an FEA simulation on the implant and the bone as the implant is being placed into the 3D model of the patient's bone.
From the FEA simulation, a practitioner may determine, as shown in block 28, whether the selected implant offers necessary initial implant stability without requiring too high a level of torque being needed to place the implant into the patient's bone and without placing too much stress or strain on the bone. If the practitioner determines that the FEA simulation indicates that the selected implant meets the patient's clinical needs and offers appropriate initial implant stability without producing too much stress or strain within the bone or at the bone and implant interface, the practitioner has verified that an acceptable implant has been selected.
If the selected implant is determined to not meet the patient's clinical needs, the practitioner selects a different implant, and repeats the process as shown in blocks 20-28 until an acceptable implant is found.
Once an acceptable implant is found, as shown in block 30, it is determined if there are any additional implant locations that need to be analyzed. If there are additional implant locations, the practitioner repeats the process shown in blocks 18-28 until there are no additional implant locations.
Once every desired implant location has been analyzed and an appropriate implant for each proposed location found, the FEA simulation may be ended.
It is contemplated that the FEA simulation may allow one or more of the properties to be optimized. For example, initial implant stability may be optimized, such that the selected implant allows immediate loading in a manner that will be less likely to cause the implant to come loose prior to osseointegration. Similarly, an implant may be selected that maximizes the initial implant stability relative to a given maximum torque required to install an implant.
Turning now to FIG. 2, a method 100 is shown that depicts a similar method to the method 10 depicted in FIG. 1, expect the method 100 of FIG. 2 uses software to optimize the implant selection based on a selected criteria or criterion.
As shown in block 112, a CT scan is performed on a patient that is used in block 114 to create a 3D CAD model of the patient's mouth. Based on the CT scan, properties of the patient's bone may be determined, as shown in block 116. It is contemplated that the properties of the patient's bone may be determined by selecting the types of bone in a patient's mouth, and assigning properties to regions of the 3D CAD model based upon typical material properties for that type of bone as shown in block 118. Alternatively, the CT scan may be used to determine bone density such that a magnitude of bone density is assigned various regions within the 3D CAD model based upon the CT scan.
Once the 3D CAD model has been assigned properties based upon the CT scan, the practitioner determines the desired locations for implant placement, as shown at block 120. Next, as shown in block 122, the practitioner determines at least one variable to optimize utilizing a FEA simulation. The variable to be optimized may be, for example, the initial implant stability, the amount of torque to install an implant, an acceptable amount of stress and strain within the bone around the implant, some other variable, or some combination of variables. An example of a combination of variables would be to optimize the initial implant stability for a low torque level required to seat an implant.
After the variable, or variables, to be optimized is selected, a FEA simulation of implant placement is performed at block 124. The FEA simulation may evaluate a plurality of implants contained in a library of the 3D CAD system. The FEA simulation produces a result at block 126 that informs a practitioner of the implant that optimizes the result for the variable, or variables, the practitioner had selected. For example, if a practitioner had chosen to maximize initial implant stability while minimizing placement torque, the FEA simulation would be performed on a variety of implants, and the FEA simulation would inform the practitioner of the particular implant that best meets the selected criterion. Once the implant for a first desired location has been selected, it is determined at block 128 if there are any additional implants required by the patient. If additional implants are required, the method returns to step 120 for the next implant. If there are no additional implants, the FEA simulation is ended, as shown in block 130.
It is contemplated according to another method that the practitioner may constrain the results given by the FEA simulation as shown in FIG. 2. For example, the practitioner may specify a diameter for the implant, and then the FEA simulation will be limited to optimizing the criterion selected only for implants of the chosen diameter. Additional examples of variable constraints the practitioner may place on the FEA simulation include, but are not limited to, implant length, implant thread design, osteotomy profile, whether the osteotomy has a countersink, and whether the osteotomy is tapped.
As shown in FIG. 3, a further method 200 is shown in which a custom patient specific implant is designed based upon an FEA simulation. Similar to the methods previously described, a CT scan of a patient's mouth is taken at block 212. From the CT scan, a 3D CAD model of the patient's mouth is created, as depicted at block 214. As depicted at block 216, properties of the patient's bone are determined from the CT scan, such as bone type, or bone density. Once the properties of the patient's mouth are determined, the properties are assigned to 3D CAD model of the patient's mouth at block 218.
At block 220 of FIG. 3, the practitioner then selects desired locations for at least one implant. The practitioner at block 222 selects at least one variable to optimize using an FEA simulation, such as, for example, creating a high level of initial implant stability with a low level of torque required to seat the implant.
An FEA simulation is performed on the 3D CAD model to determine implant-design variables at step 224. Based upon the implant-design variables determined by the FEA simulation, a custom implant is designed for the patient that optimizes the at least one variable previously selected by the practitioner, as shown at block 226. A 3D CAD model of the custom implant is created at block 228 that may be used to machine a custom implant. The method determines at block 230 if there is an additional implant required by the patient. If there is, the method returns to block 220 if not, the FEA simulation is ended as shown at block 232.
It is contemplated according to some processes that a limited number of implant design variables may be modified to create a custom implant for a patient. Implant variables that may be modified include, but are not limited to, implant diameter, implant length, implant material, implant surface preparation, and implant thread design including thread type, thread width, diameter, and the thread pitch.
While an FEA simulation is a valuable tool for selecting or designing a proper implant for a patient, the FEA simulation must be verified by comparing an FEA simulation with measured data collected when placing an implant into a sample, as shown by method 300 in FIG. 4. FIG. 4 illustrates the manner in which the FEA modeling analysis is verified.
As shown at block 310, a CT scan is performed on a calibration sample. Actual material properties of the calibration sample are known. Data generated by the CT scan of the calibration sample is used to form a 3D CAD model of the calibration sample at block 312. Next, properties of the calibration sample are determined at block 314 and assigned to the 3D CAD model at block 316. A desired location for placing the implant within the calibration sample is selected at block 318. Block 320 depicts a FEA simulation being performed on the 3D CAD model.
As shown at block 322, an actual implant is placed into the calibration sample. The implant is placed into the calibration sample using a test fixture that measures data during the placement of the implant into the calibration sample as shown at block 324. Examples of data that may be collected include the torque required to place the implant, the stress and strain levels of the implant, and the stress and strain level of the calibration sample near the implant. Once the measured data is obtained, the FEA simulation results are compared to the measured data, as shown at block 326. Next it is determined whether the FEA simulation result compares favorably with the measured data, as shown in block 328. If the FEA simulation does not accurately predict the measured data, FEA simulation variables are adjusted at block 330. Non-limiting examples of variables that may be adjusted include material properties, such as the modulus of elasticity of the bone, the yield strength of the bone or implant, shear strength of the bone or implant, mechanical properties, failure criteria, such as why the implant or bone failed, and failure response, such as what happened to the bone after failure. After adjusting the FEA simulation variables, the FEA simulation is performed again using the adjusted variables as shown at block 332. The adjusted FEA simulation results are then again compared with the measured data, and this process repeats until the FEA simulation results closely track the measured data. Once the FEA simulation is determined to accurately predict the measured data, the FEA simulation is considered to be properly calibrated, as shown at block 334.
Once the method 300 depicted in FIG. 4 is completed, one of the previous analysis methods shown in FIGS. 1-3 may be performed with confidence that the FEA simulation model produces results that accurately predict the forces and stresses present during the placement of the implant.
While the above methods have been described using CT scanning to generate data to form a 3D CAD model, it is contemplated that other methods may be used to gather this data. For example, an X-ray may be used in place of CT scan.
While the above embodiments have related to dental implants, it is contemplated that the above described methods may be utilized on other regions of a patient's body with other types of non-dental implants, such as orthopedic implants.
While particular embodiments and applications of the present invention have been illustrated and described, it is to be understood that the invention is not limited to the precise construction and compositions disclosed herein and that various modifications, changes, and variations may be apparent from the foregoing descriptions without departing from the spirit and scope of the invention as defined in the appended claims.

## Claims

1. A method for placing an implant in a patient comprising:
performing a CT scan of an anatomical area of a patient;
creating a 3D CAD model of the anatomical area utilizing data generated by the CT scan;
determining properties of the anatomical area based upon data generated by the CT scan;
assigning the determined properties of the anatomical area to the 3D CAD model;
selecting a desired location for the implant and an implant to be placed into the anatomical area;
assigning at least one variable to be optimized by a FEA simulation;
performing an FEA simulation in real-time of placing the implant into the anatomical area on the 3D CAD model to optimize the assigned variable;
determining a necessary transient torque to seat the selected implant into the anatomical area based on the determined properties of the anatomical area, the selected implant and the desired location via the real-time FEA simulation; and
choosing a protocol to seat the selected implant based upon results from performing the FEA simulation and the necessary transient torque.

2. The method of claim 1, wherein determining properties determines the properties of the bone present in the anatomical area.

3. The method of claim 1, wherein determining properties determines a magnitude of bone density of the anatomical area.

4. The method of claim 1, wherein assigning the at least one variable to optimize assigns initial implant stability relative to the necessary transient torque to seat the implant in the bone as the variable to optimize.

5. The method of claim 1, wherein assigning the at least one variable to optimize assigns a maximum stress level not to be surpassed in the bone surrounding the implant.

6. The method of claim 1, wherein performing an FEA simulation occurs on a plurality of possible implants contained in a library of the 3D CAD system to optimize the assigned variable.

7. The method of claim 1, wherein the anatomical area is a patient's mouth and the implant is a dental implant.

8. The method of claim 1, further comprising designing an osteotomy for the anatomical area based on the determined properties of the anatomical area, the selected implant and the desired location via the real-time FEA simulation.

9. The method of claim 1, wherein performing the FEA simulation includes a simulating a plurality of possible protocols each including an osteotomy, wherein the associated geometries for the osteotomies are stored in a library of the 3D CAD system to optimize the assigned variable.

10. A method for selecting a clinically appropriate implant to be used in an anatomical area of a patient including a bone, the method comprising:
storing a CT scan of the anatomical area;
creating a 3D CAD model of the anatomical area utilizing data generated by the CT scan;
determining properties of the anatomical area based upon data generated by the CT scan assign the determined properties of the anatomical area to the 3D CAD model;
accepting a selection of a desired location for the implant and an implant to be placed into the anatomical area;
performing a real-time FEA simulation of placing the selected implant in the anatomical area with the 3D CAD model; and
determining a necessary transient torque to seat the selected implant into the anatomical area based on the determined properties of the anatomical area, the selected implant and the desired location via the real-time FEA simulation.

11. The method of claim 10, wherein the properties of the anatomical area includes properties of the bone present in the anatomical area.

12. The method of claim 10, wherein the properties of the anatomical area includes a magnitude of bone density of the anatomical area.

13. The method of claim 10, wherein the selection of an implant is made from a CAD library having a plurality of 3D CAD models of implants.

14. The method of claim 10, wherein the anatomical area is a patient's mouth and the implant is a dental implant.

15. The method of claim 10, further comprising a CT scanner operable to generate the CT scan of the anatomical area.

16. The method of claim 10, further comprising optimizing at least one variable by the FEA simulation.

17. The method of claim 16, wherein the at least one variable is the initial implant stability relative to the necessary transient torque to seat the implant in the bone.

18. The method of claim 16, wherein the at least one variable is the maximum stress level not to be surpassed in the bone surrounding the implant.