U.S. patent application number 14/540524 was filed with the patent office on 2015-03-12 for impression scanning for manufacturing of dental restorations.
This patent application is currently assigned to 3Shape A/S. The applicant listed for this patent is 3Shape A/S. Invention is credited to Tais CLAUSEN, Nikolaj DEICHMANN, Rune FISKER, Brieuc GILLES.
Application Number | 20150073577 14/540524 |
Document ID | / |
Family ID | 37735093 |
Filed Date | 2015-03-12 |
United States Patent
Application |
20150073577 |
Kind Code |
A1 |
FISKER; Rune ; et
al. |
March 12, 2015 |
IMPRESSION SCANNING FOR MANUFACTURING OF DENTAL RESTORATIONS
Abstract
A method of obtaining orientation and localization of at least
one dental implant includes the following steps: (a) obtaining an
impression comprising at least one fixated impression abutment
corresponding to the at least one dental implant(s) and/or
obtaining an impression comprising at least one fixated impression
abutment corresponding to the at least one dental implant(s) on
which is mounted a scan implant/analog (b) obtaining pre-determined
information of the shape of the impression abutment and/or scan
implant/analog, (c) scanning at least a part of the impression,
wherein the part includes the at least one impression abutment
and/or scan implant/analog thereby obtaining scan data, (d)
determining the orientation and localization of the dental implant
based on the pre-determined information and the scan data.
Inventors: |
FISKER; Rune; (Virum,
DK) ; DEICHMANN; Nikolaj; (Kobenhavn, DK) ;
CLAUSEN; Tais; (Kobenhavn, DK) ; GILLES; Brieuc;
(Vanlose, DK) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
3Shape A/S |
Copenhagen K |
|
DK |
|
|
Assignee: |
3Shape A/S
Copenhagen K
DK
|
Family ID: |
37735093 |
Appl. No.: |
14/540524 |
Filed: |
November 13, 2014 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
12095154 |
Oct 13, 2008 |
8932058 |
|
|
PCT/DK2006/000678 |
Nov 30, 2006 |
|
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14540524 |
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Current U.S.
Class: |
700/98 |
Current CPC
Class: |
A61B 5/0037 20130101;
A61B 5/055 20130101; G06F 30/00 20200101; B33Y 50/02 20141201; A61C
9/0053 20130101; A61B 6/506 20130101; A61C 9/002 20130101; A61C
19/04 20130101; B29C 64/386 20170801; A61C 9/0006 20130101; A61C
9/00 20130101; A61B 6/14 20130101; A61C 13/34 20130101 |
Class at
Publication: |
700/98 |
International
Class: |
A61C 13/34 20060101
A61C013/34; B29C 67/00 20060101 B29C067/00; A61B 5/055 20060101
A61B005/055; G06F 17/50 20060101 G06F017/50; A61C 9/00 20060101
A61C009/00; A61B 6/14 20060101 A61B006/14 |
Foreign Application Data
Date |
Code |
Application Number |
Nov 30, 2005 |
DK |
PA200501693 |
Feb 23, 2006 |
DK |
PA200600259 |
Claims
1. (canceled)
2. A method of manufacturing a dental model of at least a part of a
jaw, the method comprising: obtaining a three-dimensional model of
at least the said part of the jaw by either impression scanning,
in-the mouth scanning, CT, MR or x-ray scans, scanning of a
positive model or a combination thereof, manufacturing a dental
model from the obtained three-dimensional model, and including at
least one implant analog in the dental model.
3. The method of claim 2, wherein the implant analog is included by
adding a virtual slot to the obtained three-dimensional model and
mounting said implant analog in the resulting slot of the
manufactured dental model.
4. The method of claim 2, wherein the implant analog is included by
manufacturing the implant analog as an integrated part of the
manufacturing process.
5. The method of claim 2, comprising inverting the surface
orientation of the three-dimensional model prior to
manufacturing.
6. The method of claim 2, comprising attaching the surface of the
three-dimensional model to a CAD base prior to manufacturing.
7. The method of claim 2, comprising obtaining a virtual solid
model from the three-dimensional model prior to manufacturing.
8. The method of claim 7, comprising including at least one
articulator interface into the virtual solid model.
9. The method of claim 7, comprising adding a model of a
pre-manufactured interface/base in the virtual solid model.
10. The method claim 8, comprising sectioning the three-dimensional
and/or virtual solid model prior to manufacturing.
11. The method of claim 10, wherein means for positioning
subsections of the sectioned model are included in at least one
subsection obtained by sectioning.
12. The method of claim 11, wherein said sectioning and positioning
means allows for the removal and reinsertion of parts of the
produced dental model.
13. The method of claim 12, wherein the parts of the produced
dental model comprise a model of a preparation.
14. The method of claim 2, wherein both the Maxilla and Mandible
models are manufactured.
15. The method of claim 2, wherein said implant analog is included
in the design process.
16. The method claim 2, wherein said implant analog manufactured by
same process as the dental model.
17. The method of claim 2 wherein the position and orientation of
said implant is found by scanning the impression and/or positive
model of a healing abutment.
18. The method of claim 17, wherein the position and orientation of
said implant is found by aligning the data from said scanning with
pre-determined information of the healing abutment.
19. The method of claim 18, wherein the pre-determined information
of the healing abutment comprises a CAD model of the healing
abutment.
20. The method of claims 17, wherein said healing abutment
comprises one or more marks allowing for the identification of one
or more characteristics of said healing abutment and or implant to
which said healing abutment is/were connected.
21. The method of claim 2, wherein the dental model is manufactured
by rapid prototyping equipment.
22. The method of claim 2, wherein the jaw is an upper jaw and/or a
lower jaw.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] The present application is a continuation of U.S. Ser. No.
12/095,154, which is a national stage application of
PCT/DK2006/000678, filed on Nov. 30, 2006, and which claims the
priority of Danish patent application PA 2006 01693, filed on Nov.
30, 2005 and Danish patent application PA 2006 00259, filed on Feb.
23, 2006. The entire contents of PCT/DK2006/000678, Danish patent
application PA 2006 01693, and Danish patent application PA 2006
00259 are incorporated herein by reference.
[0002] The present invention relates to a system and a method for
creating a three-dimensional model of the teeth and bite by
scanning and aligning dental impressions.
[0003] All patent and non-patent references cited in the
application, or in the present application, are also hereby
incorporated by reference in their entirety.
BACKGROUND
[0004] The present invention is related to the field of
manufacturing of dental restorations such as crowns, bridges,
abutments and implants. When a patient requires a dental
restoration the dentist will prepare the teeth e.g. a damage tooth
is grinded down to make a preparation where the crown is glued
onto. An alternative treatment is to insert implants (titanium
screws) into the jaw of the patient and mount crowns or bridges on
the implants. After preparing the teeth or inserting an implant the
dentist normally makes an impression of the upper jaw, the lower
jaw and a bite registration or a single impression in a
double-sided tray (also known as triple trays).
[0005] The impressions are sent to the dental technicians who
actually manufacture the restorations e.g. the bridge. The first
step to manufacture the restoration is traditionally to cast the
upper and lower dental models from impressions of the upper and the
lower jaw, respectively. FIG. 1a and FIG. 8 shows a dental model
and a impression, respectively. The models are usually made of
gypsum and often aligned in a dental articulator using the bite
registration. The articulator simulates the real bite and chewing
motion. The dental technician builds up the dental restoration
inside the articulator to ensure a nice visual appearance and bite
functionality. A proper alignment of the cast in the articulator is
crucial for the final restoration.
[0006] CAD technology for manufacturing dental restoration is
rapidly expanding improving quality, reducing cost and facilitating
the possibility to manufacture in attractive materials otherwise
not available. The first step in the CAD manufacturing process is
to create a 3-dimensional model of the patient's teeth. This is
traditionally done by 3D scanning one or both of the dental gypsum
models. The 3-dimensional replicas of the teeth are imported into a
CAD program, where the entire dental restoration or a bridge
substructure is designed. The final restoration 3D design is then
manufactured e.g. using a milling machine, 3D printer, rapid
prototyping manufacturing or other manufacturing equipment.
Accuracy requirements for the dental restorations are very high
otherwise the dental restoration will not be visual appealing, fit
onto the teeth, could cause pain or cause infections.
[0007] In an ideal 3D scanner and dental CAD/CAM solution the
dental laboratory or dentist would not need to make a gypsum model
from the impression but rather scan the impression directly. This
would make the handling easier and less costly. Also the
restoration would be more accurate as the impression geometry is
more accurate than a sectioned gypsum copy of this. Even if an
impression scan could be done with CT or MR scanning equipment such
scanners are prohibitively expensive and do not provide the
required accuracy. Optical scanners such as laser or white light 3D
scanners are on the contrary less costly and provide a higher
accuracy and detail level. The problem with optical surface
scanners is that these typically cannot efficiently scan the narrow
cavities of a dental impression. Typically the scans would lack
data or be less accurate in the deep narrow parts of the
impression.
[0008] An alternative to impression scanners is direct in-the-mouth
scanners. However impression scans have a clear number of
advantages compared to in-the-mouth scanners including no mandatory
equipment investment at dentist clinic, virtually no training for
impression taking, shorter chair time, a physical model can always
be poured in case of scanning problems or used as physical
reference, low accuracy for in the mouth scanners, no powdering of
the patient mouth necessary, and significantly reduced difficulties
in capturing the antagonist and larger areas and contrary to
in-the-mouth scan the impression has the margin line clearly
visible.
SUMMARY
[0009] If an impression is scanned instead of a gypsum model the
traditional dental model might not be made at the laboratory. If a
traditional dental model would still be needed by the dental
laboratory or dentist to check or modify the fit and design of the
manufactured restoration such a model could still be provided from
the impression scan by inverting the data and adding a virtual base
or other features and then manufacturing this model with suitable
3D manufacturing equipment.
[0010] The present invention provides a solution for scanning the
impressions directly thereby avoiding the time consuming and costly
need for creating the gypsum cast, still obtaining the required
accuracy of the final restoration. Accordingly, the invention
relates to a method for obtaining an accurate three-dimensional
computer model of a dental impression, said method comprising the
steps of:
[0011] 1) scanning at least a part of an upper jaw impression
and/or a lower jaw impression, obtaining an impression scan,
[0012] 2) evaluating the quality of the impression scan, and
[0013] 3) if the quality does not allow for an accurate
three-dimensional model of the dental impression, then
[0014] filling one or more cavities of the dental impression with
filling material to obtain a model of said cavities, and scanning
said model to obtain a model scan, and
[0015] aligning and combining said model scan and impression scan
thereby obtaining a three-dimensional model, and/or
[0016] rescanning one or more areas of interest of the dental
impression, and
[0017] aligning and combining said area of interest scan and
impression scan thereby obtaining a three-dimensional model,
or,
[0018] 4) if the quality does allow for an accurate
three-dimensional model of the dental impression, then
[0019] use the impression scan to obtain a three-dimensional
model,
[0020] thereby obtaining an accurate three-dimensional model of the
dental impression.
[0021] In another aspect the invention relates to method for
obtaining a three-dimensional model of a dental impression, wherein
the alignment of the scans to obtain a correct bite is provided.
Accordingly, the invention further relates to A method for
obtaining a three-dimensional model of a dental impression, said
method comprising the steps of:
[0022] scanning the upper jaw impression and the lower jaw
impression of a double sided impression obtaining a scan of the
double sided impression,
[0023] aligning the upper jaw impression scan and the lower jaw
impression scan of the double sided impression,
[0024] thereby obtaining a three-dimensional model of the dental
impression.
[0025] It is clear that the two methods may be combined so that the
scanning of the single sided impression may be conducted by the
method for obtaining an accurate three-dimensional computer model
of the single sided dental impression.
[0026] In a third aspect the invention relates to a method of
evaluating the quality of an impression and/or a preparation,
comprising the following steps:
[0027] a. obtaining a three-dimensional computer model of said
impression and/or preparation to be evaluated,
[0028] b. evaluating the said impression and/or preparation based
on the three-dimensional model.
[0029] By such an evaluation significant cost and/or strain may be
saved by allowing fast feedback while the patient is still at the
dentist office. It is clear that especially in combination with the
other aspects of the invention such evaluation may provide valuable
information to the dentist.
[0030] In a fourth aspect the invention relates to a method of
obtaining a three-dimensional model comprising at least one tooth
and neighbouring tissue(s) comprising the following steps:
[0031] a. scanning at least a part of an upper jaw impression
and/or a lower jaw impression and/or a double-sided impression,
obtaining an impression scan,
[0032] b. using at least one impression scan to obtain a
three-dimensional pre-model, aligning said three-dimensional
pre-model with at least a part of a CT and/or MR and/or X-ray scan
obtaining a new three-dimensional model. In this aspect the
invention is particularly suitable for designing drill guides.
[0033] In a fifth aspect of the invention relates to a method of
manufacturing at least one part of a tooth crown comprising the
following steps:
[0034] a. obtaining a three-dimensional model by scanning at least
part of a dental impression comprising information about the site
in which the crown is to be located,
[0035] b. performing a CAD design of the at least one part of a
tooth crown in and/or relative to said three-dimensional model
obtaining a computerized model of the at least one part of a tooth
crown,
[0036] c. manufacturing said full or complete crown from at least
part of the obtained computerized model.
[0037] In this way at least a part of the work performed manually
today may be performed by the way of electronically guided
manufacturing equipment providing the potential for lower cost and
higher accuracy.
[0038] In a sixth aspect the invention relates to a method of
obtaining orientation and localization of at least one dental
implant comprising the following steps:
[0039] a. obtaining an impression comprising at least one fixated
impression abutment corresponding to said at least one dental
implant(s) and/or
[0040] obtaining an impression comprising at least one fixated
impression abutment corresponding to said at least one dental
implant(s) on which is mounted a scan implant/analog and/or
[0041] a positive model of at least a part of an upper jaw and/or a
lower jaw comprising at least one model implant/analog, with
orientation and localization corresponding to the orientation and
localization of the dental implant(s), and/or
[0042] a positive model of at least a part of an upper jaw and/or a
lower jaw comprising at least one model implant/analog, with
orientation and localization corresponding to the orientation and
localization of the dental implant(s) on which is mounted a
scanning abutment,
[0043] b. obtaining pre-determined information of the shape of the
impression abutment and/or scan implant/analog and/or model
implant/analog and/or scanning abutment,
[0044] c. scanning at least a part of said impression, wherein said
part comprises the at least one impression abutment and/or scan
implant/analog thereby obtaining scan data, and/or
[0045] scanning at least a part of said positive model wherein said
part comprises at least one model implant/analog and/or scan
abutment, thereby obtaining scan data,
[0046] determining the orientation and localization of the dental
implant based on said pre-determined information and said scan
data. This aspect of the invention enables CAD design, such as of a
prosthetic tooth connected to said implant as this requires the
exact location orientation of the implant.
[0047] In a seventh aspect the invention relates to a method of
manufacturing a dental model of at least a part of an upper jaw
and/or a lower jaw comprising the steps of:
[0048] obtaining a three-dimensional model of at least the said
part of the upper jaw and/or a lower jaw by either impression
scanning, in-the mouth scanning, CT, MR or x-ray scans, scanning of
a positive model or a combination thereof, manufacturing a dental
model from the obtained three-dimensional model. Such a method of
manufacturing dental models from a obtained data may enable easier
storage of dental models in that only the data is stores and a
physical model may be produced if needed. Such models may also be
utilized to omit the necessity to ship impressions and/or models
between sites such as place of manufacturing abutments and a place
of handling models and/or scanning.
[0049] In an eighth aspect the invention relates to a computer
program product including a computer readable medium, said computer
readable medium having a computer program stored thereon, said
program comprising instructions for conducting the steps of the
other aspects of the invention.
[0050] In a ninth aspect the invention relates to a system for
producing a three-dimensional computer model and/or at least one
part of a tooth crown/bridge, said system including computer
readable memory having one or more computer instructions stored
thereon, said instructions comprising instructions for conducting
the steps of the other aspects of the invention.
[0051] In a tenth aspect the invention relates to a tray suitable
for obtaining a single or double sided dental impression
characterized in that said tray further comprises fixture means
suitable for holding the tray in a three-dimensional scanner. By
this aspect the need for additional fixation means in the scanner
may be omitted and scanning process may by significantly
simplified.
[0052] In a eleventh aspect the invention relates to a tray
suitable for obtaining a double sided dental impression
characterized in that said tray is mechanically stable by
reinforcements by at least one of the following materials metal,
steel, and fibre-composite. With such a reinforced tray it may be
possible to omit the need for single sided impressions.
[0053] Furthermore, invention relates to a method for obtaining an
accurate three-dimensional computer model of a dental impression,
wherein the impression is scanned using one sensor, i.e. camera and
light source, having an angle A between the light source and the
camera, and afterward regions of interest are rescanned using
another sensor, wherein for said other sensor there is an angle B
between the light source and the camera, and said angle B is
smaller than said angle A. Thereby it is possible to scan deeper
cavities than it will be using only one scanner having the angle A.
The invention may further comprise a step of determining the angle
B based on the impression scan, before the rescan-step is
performed. Preferable the angle B is less than 95% of angle A, less
than 90% of angle A, less than 85% of angle A, less than 80% of
angle A, less than 70% of angle A, less than 60% of angle A, less
than 50% of angle A, less than 40% of angle A, less than 30% of
angle A, less than 20% of angle A, less than 10% of angle A, less
than 5% of angle A.
[0054] Finally, the invention relates to a method for obtaining an
accurate three-dimensional computer model of a dental impression,
said method comprising the steps of:
[0055] 1) scanning at least a part of an upper jaw impression
and/or a lower jaw impression using a three-dimensional sensor
having an angle A between the light source and the camera,
obtaining an impression scan,
[0056] 2) evaluating the quality of the impression scan, and
[0057] 3) if the quality does not allow for an accurate
three-dimensional model of the dental impression, then
[0058] selecting another three-dimensional sensor having an angle B
between the light source and the camera, wherein the angle B is
smaller than the angle A,
[0059] rescanning one or more areas of interest of the dental
impression using said selected sensor, and
[0060] aligning and combining said area of interest scan and
impression scan thereby obtaining a three-dimensional model,
or,
[0061] 4) if the quality does allow for an accurate
three-dimensional model of the dental impression, then
[0062] use the impression scan to obtain a three-dimensional
model,
[0063] thereby obtaining an accurate three-dimensional model of the
dental impression.
DESCRIPTION OF DRAWINGS
[0064] FIG. 1a: Dental gypsum model
[0065] FIG. 1b: 3D scan of single side impression
[0066] FIG. 2: 3D scan of upper part of double side impression
[0067] FIG. 3: 3D scan of lower part of double side impression
[0068] FIG. 4: Representative parts for alignment
[0069] FIG. 5: Superimposed alignment of FIG. 4
[0070] FIG. 6: Representative parts for alignment
[0071] FIG. 7: Superimposed alignment of FIG. 6
[0072] FIG. 8 shows an impression of teeth
[0073] FIG. 9a shows a scan of the impression from FIG. 8 having
good quality.
[0074] FIG. 9b shows the inverted scan of the scan of FIG. 9a.
[0075] FIG. 9c shows example of alignment of scan of a single tooth
(from FIG. 11b) with the inverted scan of FIG. 9b.
[0076] FIG. 9d shows the aligned bridge after first alignment done
in FIG. 9c.
[0077] FIG. 10a shows a scan of the impression from FIG. 8 having a
poor quality with little accuracy due to noise 1001 and holes
1000.
[0078] FIG. 10b shows the inverted scan of the scan of FIG. 10a
showing the result of the noise and the holes.
[0079] FIG. 10c shows example of alignment of scan of a single
tooth (from FIG. 11 b) with the inverted scan of FIG. 10b.
[0080] FIG. 10d shows the aligned bridge after first alignment done
in FIG. 10c.
[0081] FIG. 10e shows the final aligned bridge after all
alignments.
[0082] FIG. 11a shows dies of impression cavities from three
different teeth.
[0083] FIG. 11b shows scan of the dies of FIG. 11a.
[0084] FIG. 12 Traditional transfer of implant position and
orientation from patient mouth to dental model.
[0085] FIG. 13 Scan analog mounted in impression abutment to obtain
position and orientation of implant.
[0086] FIG. 14 Impression scan of Encoded Healing Abutment
(EHA)
[0087] FIG. 15 Turning the impression (negative) to model
(positive) by rotation and cutting away superfluous surface.
[0088] FIG. 16 Virtually model created model from impression scan
with virtual base, trimming, sectioning, pinning and articulator
interface.
[0089] FIG. 17 Virtually created model with pins for
positioning
[0090] FIG. 18 Virtually created model with more advanced
sectioning and positioning means.
[0091] FIG. 19 3D printed model mounted in articulator.
DEFINITIONS
[0092] Dental impression: a negative impression of the teeth
preferably made in a tray.
[0093] Dental model: a positive replica of the teeth made from the
dental impression.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0094] The objective of the invention is an improved scanning and
alignment method for scanning dental impressions used as input for
CAD manufacturing of dental restorations avoiding the costly and
time consuming manufacturing of dental gypsum models. Impression
scanning will also improve quality since the traditional casting
process and dental model segmentation introduces errors.
Furthermore, impression scanning will not increase chair time for
patients at the dentist, there is no mandatory entry cost for the
dentist, no education of the dentist is required and the overall
manufacturing time is reduced thereby improving patient
satisfaction and potentially avoiding temporary restorations.
Accurate Three-Dimensional Model
[0095] The scanning of dental impressions by optical 3D scanners is
very challenging mostly due to a lack of visibility in cavities. A
traditional 3D scan will thus result in a lack of coverage, i.e.
the 3D scan may have holes or missing areas that have not been
scanned. The present invention provides a solution to that problem.
As described above, one solution may be to rescan, optionally using
a different scanner and/or a different scanner setting, one or more
regions of interest of the impression, to provide a scan having a
better quality, such as fewer holes, or no holes in the region of
interest. Thus the term scan "quality" means quality in relation to
coverage and accuracy of the scan. Insufficient coverage might be
automatically detected by triangulation of the surface and then
locating the holes on the surface. A good quality requires no holes
or only very few holes in the regions of interest. If any holes are
accepted, the position of such holes may not interfere with the
production of an accurate three-dimensional model. In practice this
means that holes must not be in the preparation area. The
preparation area can be located based on manual selection or
preferably automatically detected e.g. using feature detection.
Examples of critical holes 1000 in the preparation area are shown
in FIG. 10.
[0096] Furthermore, noise may lead to less accurate scans. Noise is
a particular dominant problem when scanning into cavities like
impressions, since the cavities creates significant amount of
tracking and half occlusion noise. Half occlusion noise is
described in details in Curless and Levoy (1995). Lack of accuracy
due to noise 1001 is shown in FIG. 10. Half occlusion noise and
coverage is the main limitation for practical use of impression
scanning and determining whether a scan points is a noise point or
a true point is very critical for the final quality of the dental
restoration. Hence it is very critical to determine noise and
coverage problems automatically. Noise points might be
automatically detected using point quality derived from the laser
tracking, surface orientation at capture, multiple cameras views,
local surface statistics, surface curvature, shape statistics or
reverse ray-tracing.
[0097] By the term "accurate three-dimensional model" is meant a
model that possess such accuracy that it may be used directly for
producing the dental restoration.
[0098] Another important quality evaluation that instantly can be
derived from the scan is the quality of the impression and
preparation, respectively. In fact low quality impressions and poor
preparations created by the dentist are two of the largest quality
issues for the final restoration. However the quality of the
impression and preparation can be evaluated based on the scan e.g.
by under cut detection, air bubble detection, noise level,
impression material evaluation, shape evaluation or geometrical
measurements. The result of the evaluation can be shown visually on
the 3D scan to guide the dentist to improve the impression or
preparation.
[0099] Particular if the scan is performed directly in the dentist
clinic then an impression and preparation quality evaluation might
potentially lead to taking a new impression or improving the
preparation. Preferably, a fast scanner, such as the 3Shape D250
scanner, is employed so that the evaluation may be performed while
the patient is waiting. This could significantly improve
restoration quality and/or reduce patient discomfort and cost by
eliminating the delay and effort involved in a second consultation
to retake an impression.
[0100] Other types of quality influencing the final result of the
restoration might also be evaluated.
[0101] The quality evaluations described might also be performed on
other types of scans of the mouth region such as traditional 3D
scans of gypsum models, directly in the mouth scans, CT, MR or
x-ray scans.
[0102] Scanning into cavities like a dental impression is a
challenging problem using a price competitive structured light
scanner. The problem originates from the fundamental construction
with a light source projection a pattern onto the object where one
or more sensors acquire images of the projected pattern. To perform
the 3D reconstruction an angle of typically 20-30 degrees between
light source and sensor is required. The required angle and the
fact that the sensor and laser need to see the same point on the
surface at the same time to make a 3D reconstruction strongly
limits the scanners ability to scan cavities. To achieve the
optimal result the actual viewpoint becomes crucial. Scanners with
at least 3 axis, such as the 3Shape D200, D250 or D300 scanner, can
reorient the object in 3D and hence change the relative viewpoint.
Adaptively changing the view point and scanning sequence to match
the individual object can be applied to obtain coverage in
difficult dental impressions as described in WO 2006/007855.
[0103] In one embodiment the quality of the impression scan is
improved by selecting or automatically detecting one or more
regions or interest and rescan such regions of interest. The
rescanning may be conducted using a scanner and/or scanner setting
optimised to the specific region of interest.
[0104] Missing areas can be rescanned by detecting these in the
initial 3D dataset and then calculating the optimal mechanical
positioning of the impression or the 3D sensor with regards to
their relative position in order to cover the missing areas in an
additional automatic scanning session. The optimization function
takes into consideration the exact position of the detected hole
and also the surrounding impression geometry that might occlude the
view of the light source and/or cameras.
[0105] The rescan could also be performed by utilizing an
additional 3D sensor (camera and light source) or one or more extra
cameras in the scanner. Such additional sensor should have a
smaller angle between light source and camera and would thus be
able to look into cavities with a higher debt to width ratio. In
such embodiment a camera and light source combination with a higher
angle between light source and camera could be used to make a first
scan and then an additional camera or light source with a lower
angle with respect to the light source/camera could be used to
cover the deepest areas of the cavities.
[0106] The rescanning may also be conducted after having cut the
impression to improve visibility. If the required cuts destroy
areas with needed information then the scans before and after
cutting can be aligned and combined to form a complete 3D model.
Typically the uncut scan will include the margin line area, which
will then be cut away to create visibility into the deep cavities
corresponding to leaving the impression of the top of the teeth
remaining. However, the model may be cut one or more time to
achieve accurate scanning. The model is scanned prior to each cut
and the corresponding three-dimensional models may then be aligned
either sequentially of simultaneously.
[0107] In another embodiment the problem of scanning into the
cavities is solved by making a model of the cavity(ies) by filling
a filling material into the cavity. Then the model of the
cavity(ies) may be scanned, and the scan(s) aligned and combined
with the impression scan. In one embodiment at least two cavities
are filled, such as at least three cavities. The cavities may be
neighbouring cavities or cavities separated by one or more
un-filled cavities.
[0108] The process is illustrated in FIGS. 10a and 10b where 2
preparations are lacking coverage 1000 and one preparation has
noise issues 1001 create quality problems. The models for 3
problematic preparations are then poured as separate gypsum models
1100 using the impression. These 3 "positive" models are then
scanned 1200 without quality issues and the scans are aligned and
merged 1103 into the corresponding preparations 1102 in the
impression. The alignment might be performed by selecting
corresponding points 1104 on the two scans followed by an ICP
alignment (Best and McKay, 1992). In yet another embodiment the
problem of scanning into cavities is solved by combining rescanning
of regions of interest and model scanning. In some embodiments it
is preferred to provide models in that the models may be prepared
manually and for example clearly include lines delining the tooth,
so that the scan also includes the distinct lines.
[0109] The visual properties of the impression material are also
very important for the scan quality. This is in particular true for
a deep or thin tooth where inter reflections can create image
tracking software problems and significant noise. Problems with
half occlusion noise at the edge of occlusion can also create
significant scanning artefacts, which might be removed by a reverse
ray-tracing algorithm.
[0110] The aligned scan are combined, e.g. by replacing the
impression scan parts with corresponding parts of the model scan or
region of interest scan or both and merging the common surface of
the scans. The alignment of the scans may be conducted as described
below in relation to the three-dimensional model including bite
information.
[0111] The method according to the invention may further include a
step of pre-scanning the impression before the impression scan is
conducted. By the information obtained from the pre-scan it is
possible to adjust the scanner settings and scan sequence incl.
motions for making more accurate impression scans or regions of
interest scans.
[0112] Depending on the restoration to be made based on the
accurate three-dimensional model the whole impression scan may be
used to provide the model, or only a region of the impression scan
may be used. Therefore, in one embodiment a region of the
impression scan is defined before alignment, and in a further
embodiment alignment is conducted only for said defined region. In
one example the alignment is performed for at least two teeth, such
as at least three teeth.
[0113] In general the reflectivity of the impression material
should be as little as possible. In one embodiment the impression
material is coated before scanning, such as coated with a
non-reflective coating thereby improving the scanning quality. In
another embodiment the impression itself is made from a material
having a little or no reflective characteristics.
[0114] Alignment of upper jaw scan and lower jaw scan may be
conducted by any suitable method. In one embodiment the alignment
is conducted using CT-scans or MR-scans of the jaws. One advantage
may be that such scans also include information of jaw and nerves.
In another embodiment the alignment of upper jaw scan and lower jaw
scan is conducted using a double-sided impression scan, for example
as described below.
[0115] Of course CT-scans and MR-scans may be used for other
alignment purposes if necessary. CT or MR scans might also be
combined and/or aligned with impression scans, e.g. for design of
drill guides for implants or simply to provide an improved
three-dimensional model.
Three-Dimensional Model Including Bite Information
[0116] The basis for the scan is at least two dental impressions.
One impression is a double sided impression that captures the
upper, the lower jaw and the bite in one impression. Unfortunately
the double trays may lack physical stability creating lower quality
impressions and is not accepted by many dentists. To compensate for
this problem at least one single side impression is also created,
thereby mapping only the upper or lower jaw. The single sided
impression is created in a traditional tray with very high physical
stability providing high quality impression.
[0117] The possible quality problem with the double sided
impressions can be solved by aligning and combining scans of the
double sided impressions with one or two single sided impression
scans. The accuracy requirement at the prepared teeth area is 20
microns where as the bite and the antagonist teeth only requires
50-100 microns. By applying the single sided scan at the prepared
area and the double sided scan for the bite and antagonist teeth
the accuracy demand will be fulfilled. Optionally an additional
single sided scan is made of the antagonist side.
[0118] The following scans need to be created in any order:
[0119] 1. 3D scan 100 of single side impression prepared for the
restoration, see FIG. 1a (optionally)
[0120] 2. 3D scan 200 of upper side of double sided impression, see
FIG. 2
[0121] 3. 3D scan 300 of lower side of double sided impression, see
FIG. 3
[0122] 4. 3D scan of single side impression at antagonist side
(optionally)
[0123] Note the prepared teeth 101, the normal unprepared
neighbouring teeth 201 and the antagonist teeth 301.
[0124] The next step after scanning is to perform a region-based
alignment of the single impression scans 100 with the corresponding
double sided scan 200. Unfortunately non-common data originating
from the fact that the two impressions often differ outside the
preparation line significantly complicates the alignment process.
This is especially true because the operator will need to cut back
the impression to create visibility for scanning deep teeth. In one
embodiment of the invention a region 400 is defined where common
high quality exists. The definition of the region can e.g. be
performed by an operator or automatically by the computer. During
the alignment process only the data in the regions are used. The
alignment can be performed e.g. using the ICP algorithm (Best &
McKay, 1992). The superimposed result of the alignment is shown in
FIG. 5.
[0125] The alignment of the two double side impression scans
requires a tray that facilitates scanning of common data such as
vertical sides 600 of the tray and special alignment features e.g.
a T-shape 601, dots or vertical lines. When common data exists the
two scans can be aligned using a standard alignment algorithm such
as ICP. The initialisation for the alignment can e.g. be done by
the computer or by the user selecting two corresponding points 602.
The superimposed result of the alignment is shown in FIG. 7. The
tray might be designed such that it fits directly into the scanner
for easy handling. Furthermore, the tray may include a fixturing
system for connecting directly to the scanner. The tray or
impression might also include a horizontal eye line to be aligned
with the eyes of the patient so that visual appearances of
prosthetic tooth/teeth may be aligned with over facial features of
the patient during the design. Obviously, such a tray may
preferably be combined with any of the methods and systems
described.
[0126] In another embodiment of the invention the double sided tray
can be placed in a scanning fixture, which is included in the two
scans. Only the fixture then needs to contain common data and
alignment features. The impression may be turned automatically.
[0127] Finally the aligned scans are combined, e.g. by replacing
the double sided scan with the corresponding part of the single
sided scan and merging the common surface of the two double side
scans.
[0128] Optionally a single sided scan can also be performed on the
antagonist side and aligned and combined with the existing data in
a similar procedure.
[0129] The development of double sided trays with improved
properties such as physical stability and proper bite mapping may
potentially make the single sided impression superfluous. In one
embodiment, the double sided tray obtains increased stability by
reinforcement, such as a metal, steel, and/or fibre-composite
reinforcement. Obviously, such a tray may preferably be combined
with the features of the tray described above and any of these
trays are preferred when obtaining impressions in relation to any
the methods and systems described in this document.
[0130] Although the text relating to three-dimensional models
including bite information relates to scan of dental impressions,
it is clear for the person skilled in the art that the same method
and system may be used for scanning a dental model.
[0131] As described above, the single sided scans may be performed
by the method for obtaining an accurate three-dimensional model of
the dental impression.
[0132] In another aspect the invention relates to a computer
program product including a computer readable medium, said computer
readable medium having a computer program stored thereon, said
program for producing a three-dimensional model of a dental
impression comprising program code for conducting the steps of the
method as defined above.
[0133] In a further aspect the invention relates to a system for
producing a three-dimensional model, said system including computer
readable memory having one or more computer instructions stored
thereon, said instructions comprising Instructions for conducting
the steps of the method as defined above.
Manufacturing of a Crown
[0134] Impression scanning becomes particular interesting in
combination with CAD design of the full anatomical crowns followed
by the manufacturing of the complete crown, both referred to as
tooth crown. With such an approach there is no need for a model to
complete the design and manufacturing. However, if the impression
scan is only used for coping design then a model is still required
to complete the design. The full crown might be designed with a
suitable manufacturing process such as separating the designed
crown into two or more layers where the inside layer corresponds to
the coping and the outside layers is the ceramic. The coping can be
manufactured using known equipment such as milling, machines, 3D
wax printers or sintering machines. The outer layer might be
manufactured by first manufacturing a copy in wax, plastic,
polymers or other material that can melt e.g. using milling
machines or 3D printers. This wax copy is then mounted on the
coping and over pressing technologies such as Ivoclars Impress can
be used to create the ceramic layer.
Implants
[0135] In another embodiment of the invention the dental
restoration is implants 1200, which are typically titanium or
zirconia "screws" that are inserted into the gingival 1201 and jaw
bone. To perform the CAD design of the crown or bridge fitting on
the implant it is required to locate the exact position and
orientation of the implant from the impression scan.
[0136] Traditionally the position and orientation of the implant
1200 is transferred from the mouth of the patient to the dental
model by the use of impression abutments 1202. In practice the
transfer is performed by mounting impression abutments on the
implants. A dental impression 1203 is then taken where the
impression abutments are fixated in the impression material 1204
and the abutments are released form the implant. The impression
1203 including impression abutments 1202 is removed from the
patient mouth. Then model implants/analogs 1205 are mounted on the
impression abutments and the model 1206 is poured from the
impression--typically in gypsum. The last step is to remove the
impression 1203 and impression abutments 1202 when the model is
hardened. In one embodiment of the invention the position and
orientation of the implant is obtained by scanning the poured
positive model wherein scanning abutments are mounted to facilitate
easy determination of the position and orientation of the model
implants/analogs, and thereby the position and orientation of the
implants, from the scanning data. One method of determining said
orientation and position from data obtained from the scanning
abutment is to overlay the corresponding model data with CAD data
of the shape of the scanning abutment. Here the scanning abutment
may be identical to or different from the impression abutment.
[0137] In another embodiment of the invention the position and
orientation of the implant is determined directly from the
impression by scanning the impression abutment 1202 mounted in the
impression 1203 and then use the knowledge of its 3D shape and
dimensions e.g. CAD model. In practice the position and orientation
might be obtained by features extraction or alignment a CAD of the
impression abutment to the corresponding part of the scan.
[0138] Unfortunately the impression abutment is often covered by
impression material or hardly surface above the impression. In yet
another embodiment of the invention it is possible to mount a scan
analog 1300 on the impression abutment. This analog is then scanned
as a part of the impression scan and the known shape and dimensions
can be applied to derive the corresponding implant position and
orientation, e.g. using alignment of the CAD model or feature
extraction. This operation can be performed for one or more
implants combined or in an iterative procedure.
[0139] The prior art (U.S. Pat. No. 6,790,040) describes an
alternative method based on encoded healing abutments (EHA) used to
determine both the implant type and it's position and orientation
from a scan.
[0140] In another embodiment of the invention it is for some cases
also possible to scan an impression, or the positive poured model,
of the implant directly and derive the position and orientation in
a similar way as above.
[0141] In yet another embodiment, any of the above methods may be
improved by including data from in-the mouth scanning.
[0142] Furthermore, it may also be possible to manufacture
customized healing abutments based on the methods described
above.
Manufacturing of the Model
[0143] If the dental laboratory or dentist would still need a
traditional dental model e.g. to check or modify the fit and design
of the manufactured restoration such model could still be
manufactured from the impression scan. A traditional sectioned
gypsum model is shown in FIG. 1A. The actually model manufacturing
from the scan could be performed using classic manufacturing
equipment or more suitable rapid prototype equipment such as
milling machines or 3D printers. The model might be manufactured in
any proper material such as plastic, polymers, wax, gypsum or
ceramics.
[0144] The manufacturing equipment normally requires a solid
3D/watertight model to be created, see traditional model in FIG.
1A. Recall the impression scan 100 only contains a surface and not
a solid model. To create an attractive model for the dental lab and
dentist one or more of the following virtual steps need to be
performed on the scan:
[0145] Inverting the surface from negative to positive
[0146] Cutting away extra surface (material)
[0147] Creating a virtual base
[0148] Trimming
[0149] Sectioning
[0150] Pinning or other positioning means
[0151] Add articulator interface
[0152] Add other structures e.g. implant/analog interface
[0153] For achieving acceptance of the impression scanning
technology it is very important to be able to manufacture models
with similar performance as the gypsum models used in the dental
labs today, e.g. a model where the teeth are on a base and the
preparations are trimmed 1A00, sectioned 1A01 and pinned.
[0154] To transform the scan from an impression scan 1500
(negative) to a model 1501 (positive) the surface orientation need
to be inverted. Preferably the scan should also be rotated, see
FIG. 15. Typically the next step will then be to cut away part of
the scan surface (material) that is not needed. The cutting can be
performed by a splice based cutting tool 1502, triangle selections
or other selection/cutting tools.
[0155] To create a basic solid model the cut scan surface can be
attached or connected to a virtual base. The virtual base can be
created by combining the scan surface with a base model e.g. by
combing a CAD base with the scan surface by the creation of a
connecting surface between the two surfaces. A variant of the
process is illustrated in FIG. 16 where the cut scan surface 1600
is combined with a base 1601 that is created by vertically
extending cut surface into a common surface, in this case a plane.
The process is also shown in FIGS. 9a to 9b and 10a to 10b. This
may be perceived as forming a new base consisting of the material
which is not positioned between two surfaces from the original
scan.
[0156] For restoration purposes both the Maxilla (upper) and
Mandible (lower) models need to be created. Recall the relative
physical correct position is already known from the previous
alignment.
[0157] An important extension to the virtual base is to add an
articulator interface 1605 to the solid model such the manufactured
models can be inserted and articulated in standard articulators.
Optimal results would be obtained by using calibrated articulators.
To minimise the manufacturing model cost it might be advantageous
to insert a pre-manufactured interface 1606 between the model and
the articulator.
[0158] As mentioned, the step of attaching a base is primarily
carried out so that the cut scan surface will be a part of a solid
shape which is required for a physical representation such as a
manufactured model. Accordingly, one may subsequently cut part or
all of the base from the solid shape either virtually or post
manufacturing.
[0159] The trimming of the preparation is traditionally performed
to remove the gingival and create accessibility to the margin line
area for the crown design. Note for the traditional trimming of the
preparation there is no information available that is not present
in the impression. Hence the trimming can be performed virtually
1202 even improving the quality due to the controlled environment.
The virtual trimming might be performed by selecting the area that
is to be trimmed away on the model. One way to perform this
selection is by placing a curve such as a spline on the surface
part corresponding to the margin line. The trimming might then be
performed by removing the surface outside of the margin line and
making an artificial surface 1701, 1802 connecting the margin line
to the rest of the model 1802 and/or preparation 1701. In many
situations it is preferred to also manufacture a tooth crown and/or
a prosthetic tooth, bridge or the like from the same model forming
the basis for manufacturing the model. In this way booth may be
manufactured from the three-dimensional model and the interaction
may be physically investigated.
[0160] The sectioning of the model 1A01 typically into the
individual preparations are performed to enable the dental
technicians to easily access and work on the crowns, see FIG. 1a.
An integrated part of the sectioning is the positing system so that
the individual sections can be removed from the model and inserted
back into the model preserving the original position. Typically the
positioning means are pins attached to the sections and accurately
fitting into the base. Other examples include screws, bolts, bores
including or excluding threads, and push buttons. Preferably,
positioning means are included in any of the sections resulting
from the sectioning described below.
[0161] The virtual sectioning 1603 can replicate the classical
sawed sectioning by the use of plane cuts as illustrated in FIG.
16. The pins 1700 can then be added and corresponding holes 1604
created using Boolean addition and subtract of CAD models. However
the virtual approach enables the opportunity to create more
advanced and optionally integrated sectioning and positioning means
1800 e.g. using Boolean functions. Due to the flexibility of the
CAD design process almost any shape can be applied for sectioning
and positioning such as cylindrical, triangles, spheres, cones 1800
or a combination of these 1800. Handles 1801 for easy removal and
positioning can also be created e.g. using Boolean functions.
[0162] An example of a manufactured model 1900 mounted in a
standard articulator 1901 is shown in FIG. 19. The model is
manufactured using 3D printing.
[0163] Additional structures for dental items might also be added.
This structure can be the full or partial dental item or interfaces
to the dental item. One important example is printing the
implant/analog directly as a part of the model, such that the
designed structures e.g. customised abutment or super structure can
be mounted directly on the model. For difficult implant structures
or due to material requirements it might be preferable to add an
interface for the implant/analog, such as a slot, so that the
implant/analog can be mounted in the manufactured model afterwards.
Examples on other dental items are attachments, locking systems
other crown/bridge design support structures.
[0164] Although the text is relating to scans of dental
impressions, it is clear for the person skilled in the art that the
same methods and systems may be used for other types of scans of
the mouth region such as traditional 3D scans of gypsum models,
directly in the mouth scans, CT, MR or x-ray scans. Besides the
manufacturing of parts or complete tooth crowns it may also be
possible to manufacture customized healing abutments based on the
methods described above.
* * * * *