Optimet multi-facet 3D Dental Scanner - Attainable ... · A multi facet scan test performed by the...
Transcript of Optimet multi-facet 3D Dental Scanner - Attainable ... · A multi facet scan test performed by the...
Optimet 3D Dental Multi-Facet Scanner
Attainable Accuracy for Dental Application Cases
Optimet Dental 3D Scanner
This paper presents an overview of the Optimet multi-facet Dental
Scanner used for 3D scanning of dental objects for CAD/CAM
procedures and the Scanner accuracy.
Optimet’s CAD/CAM Dental Scanner provides accurate 3-D scans
for an extensive range of dental objects and CAD/CAM products
including single to multi unit implant bridge cases, over-dentures,
individualized abutments, cast models (gypsum), wax-up’s and
impressions.
The Scanner, developed and manufactured by Optimet, is
marketed globally by Nobel Biocare under NobelProcera. The
Dental Scanner integrates Optimet’s patented conoscopic
holography (collinear) measurement technology combined with multi-facet optical technology
enabling accurate 3D scanning of undercuts, concavities and complex geometries, including undercut
coverage and double sided scans (360°).
In the Dental CAD/CAM application, accurate 3D measurements
provided by Optimet Dental Scanner are used for planning, design
and manufacturing of individualized dental restoration, including
crowns, bridges, single unit abutments and implant bridges and
frameworks. The design is performed by dedicated dental CAD
software based on 3D scan data of the cast models and impressions
representing the dental situation.
Optimet Multi-Facet 3D Dental Scanner
(Marketed by Nobel Biocare)
Multi-Facet scanning technology
Optimet collinear measurement technology
Conoscopic holography
Metrology definitions
Measurement Precision, Accuracy, Reproducibility and measurement Certainty (or Uncertainty) are
defined in different standards and publications (such as the German DIN). Dental objects under
measurement are characterized as free form geometries and surfaces. Relevant methods analyze the
accuracy as deviations of the 3D surface and dimension measurement from independent and accurate
dimensions (nominal values) of the object in defined coordinate system. The analysis provides the level
of certainty or uncertainty stipulated by statistical parameters based on the deviations distribution
(such as 2σ or 3σ) and related statistical tests.
Reproducibility analysis tests the ability of the Scanner to provide similar measurement results for the
same measure and under different and repeated measurement conditions.
Accuracy results on metrology objects
Optimet Dental Scanner accuracy was tested in several methods and
analyzed with “Geomagic Qualify 11” software, based on surface output
format (STL) of the scanner while additional tests were performed
based on the cloud of points output where specified.
The first object scanned and tested was a metal (brass) metrology cone
with undercuts and an edge radius of 0.150mm. The actual dimensions
of the metrology jig were certified by a CMM machine (with an
accuracy of 1µm).
The scans were performed by several Scanners in standard
environmental conditions and the results were compared to the solid
model file of the metrology jig.
The average deviations between scanned surface and the solid dimensions are within -5µm to +7µm
with Std. of 7µm. More than 95% of the surface (~2σ) is within ± 15µm from the nominal surfaces. The
results are typical for all object's area’s including the sharp margin/edge area. See the deviation map
and deviation distribution in the images herein.
Volumetric accuracy – multi spheres test
A volumetric accuracy test was performed by scanning a 3 spheres metrology jig with distances
between the spheres of 30mm, 40mm and 50mm (sphere
diameters of 19.5mm) and comparing the sphere center position
and distance with the nominal values. The metrology jig is
certified by a CMM machine (with 1µm accuracy).
Results of 40 measurement tests on 10
different Scanners show average deviations
of 7.9µ from the nominal dimensions (with
Std. of 5.26µm). The average deviations of
distances between the spheres were
6.67µm (30mm distance), 7.93µm (40mm
distance) and 9.10µm (50mm distance). The maximum deviation from the nominal distance values in
all tests (120 test scans by 10 different scanners) was 19µm.
Deviation map – metrology cone
Green color indicate deviations within
±15µ from nominal dimensions
Optimet Multi Facet Dental Scanner
3 spheres metrology jig measurement set-up
3 spheres jig
A multi facet scan test performed by the Dental Scanner on the metrology
sphere with a nominal radius of 19.5mm (tolerance of ±2µm) with average
deviations from a sphere surface of ±5µm with Std. of diameter of 6µm. The
actual measured radius is 19.062, 10µm from nominal value.
Accuracy in dental objects scans (free form)
Ten different Gypsum dies (anterior and posterior teeth) as well as a titanium die were scanned by
Optimet's Dental Scanner. The accuracy was analysed by comparing and calculating the deviations
between the scan results (surface) to accurate scans performed by a high accuracy industrial scanner
(having accuracies within ±4µm).
The average deviations of the scan results of the dies surface (on all the 10 test dies) were ±7µm with
Std. of 8µm (deviations are measured from the nominal values as scanned by the high accuracy
industrial scanner). 97.1% of the surface area of all dies was within ±15µm from nominal dimension
values. The deviation varied (according to the specific test die) between 95.5% – 98.5% of the scan
surface was within ± 15µm the different dies showed that on average
Reproducibility analysis performed by comparing scans of the dies by different Optimet scanners
showed accuracies with average deviations of -6.7µm / +5.8µm with a Std of 8.2µm (1σ = 15µm),
similar to the accuracy analysis above.
Deviation Maps - 3 dental test samples measured and compared to high accuracy industrial scans.
(green color represents surfaces deviations up to ±19µm deviations in scale).
An additional accuracy test was performed on a Titanium die (in a tooth shape) in height of 10mm with
edges in radiuses (simulating a sharp crown margin line) between 0.03mm - 0.1mm. The
scan was performed with no spray. Average deviations from the accurate nominal values
were within -9µm / +7µm. 93% of the surface area was within ±15µm of the nominal
surface (as measured by the high accuracy industrial scanner after deducting the
reference measurement uncertainty), including in the sharp margin area. See below for
a color deviation map and deviation distr ibution chart.
Deviation map – metrology sphere Green color indicate deviations within ±10µm
Comparative Profile along the Titanium die
Measurement Vs. solid
Deviation map – Ti die
Green color indicate deviations within ±15µm
From nominal values
Deviation distribution chart – Ti die
Accuracy results on Implant bridges
The design and manufacturing of Implant bridges require specifically very high accuracies. Special
algorithms embedded in the Dental Scanner software enable measurement of the implants accurate
position and inclination angle. This high accuracy 3D scan data enable design of the implant bridge
framework or bar as well as an over-denture in CAD/CAM procedures.
A comprehensive accuracy test performed included scans of
multiple implant bridge cases on cast models with 3-6 implants
(with distances of up to 45mm between implants). The implant
seats exact position (implant interface seat center) and angle was
extracted by the Dental Scanner software and then compared to
high precision measurements performed on a CMM measurement
system (accuracy within 1µm). The accuracy analysis on the exact
implant seats ZXY position and inclination angle (of the implant),
show deviations within ±5µm. Note that the most critical
parameters are the Z (height) and inclination angles (of the
implants).
Deviation colour maps (below) show two examples of the deviation analysis of the implant seat in
comparison to the nominal values (as measured by the CMM machine). In addition, the chart below
shows the accuracy in different test cases within ±4.5µm as well as the reproducibility of the test
results.
3D view of deviation map of implant bridge
seats including angulations.
Green color indicate deviations within ±4µm
Deviation map - implant bridge seats
Green color indicate deviations within ±4µm
Orange color represent ±6-8µm
Deviation chart - implant bridge seats scanning accuracies – multiple test cases result
Average deviations from nominal position within ±4.5µm
General Metrology Applications
The Multi Facet Scanner is capable of 3D scanning different objects with complicated geometries for
general metrology and reverse engineering applications. Optimet’s Conoscopic sensors have standard
interchangeable objective lenses from 16mm up to 250mm lens reaching accuracies up to sub-micron
range. The Scanner can be provided for metrology applications with lens objective from 25mm-100mm
allowing flexible resolutions and working ranges for different purposes.
3-D Multi facet measurement: a cutting tool and a plastic part measured by the multi facet scanner.
Measurements performed in one set-up and include holes and other geometries.
Summary
Dental and CAD/CAM procedures and tolerances should aim for reaching adequate clinical results in
planning, design and manufacturing of dental restorations. The accuracy results and analysis in this
paper represent the accuracies in digital data acquisition as part of the CAD/CAM process.
Optimet CAD/CAM Dental Scanner metrological accuracy and reproducibility were tested and analyzed
on different objects and cases. The accuracy results on dental die cases as well as verified metrology
jigs are within 15µm. Optimet’s Dental Scanner operational principle keeps the object being measured
in a Cartesian coordinate system (XY) with no angulations or rotation of the object during the
measurement. The volumetric accuracy as shown in the tests is therefore kept at the same level of
accuracy 15µm with no accuracy degradation in the scanning volume.
The accuracy results on multiple implant bridges cases (implants seats including height and
angulations) were within a range of 5µm with similar results in reproducibility tests.
References:
1. G.Y. Sirat; “Conoscopic holography”. Basis principles and physical basis” J. Opt. Soc. Am. )1992(
2. Redlich M, Weinstock T, Abed Y, Schneor R, Holdstein Y, Fischer A " A new system for scanning, measuring and analyzing
dental casts based on a 3D holographic sensor" Orthod Craniofac Res 2008;11:90–95
3. I Alvarez , J M Enguita , M Frade, J Marina and G Ojea "On-Line Metrology with Conoscopic Holography:
BeyondTriangulation" Sensors 2009, 9, 7021-7037
4. DIN 1319-1, Grundlagen der Messtechnik – Teil 1:Grundbegriffe Fundamentals of metrology – Part 1: Basic terminology
(German and English)
5. DIN 32877, Optoelectronic measurement of form, profile and distance, August 2000.
6. Eurolab, European Federation of National Associations of Measurement, Testing and Analytical Laboratories, Technical
Report No. 1/2006 August 2006.
7. International Organization of Standards "Guide to the Expression of Uncertainty in Measurement"- 1995.