ACCURACY VERIFICATION OF ALIGNER CAD PROCESS · 2009. 1. 16. · Introduction Invisible removable...
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Introduction Invisible removable orthodontics has been in use for over 60 years. However, in the past this was accomplished by manual process of moving teeth on the stone model toward idealized orthodontic position. Thereafter, the very basic vacuum suck-down machines were used followed by manual cutting of the excess aligner material to fabricate the clear aligners. This process was extremely cumbersome as it utilized manual labor at each phase of aligner fabrication. In the past decade several companies began automating the process of aligner fabrication using computer aided design (CAD) which allows digital tooth movement. Once the digital file is moved into the first of multiple phases of tooth movement, this digital file is printed using rapid prototype 3D printers followed by computer aided manufacturing (CAM). Therefore, rather than using a modified stone model, this 3D printed model is now used in order to vacuum a polymer sheet, most often polycarbonate or a variation thereof, to fabricate the final aligner. Thereafter, the excess material which once was cut off one at a time by manual labor is a memory of the past. The technology now allows CAM process using milling machines controlled by software programs to cut the aligner excess at the gingival margin, referred to as a tool path. The advanced automation allowed enhanced esthetics and ease of application by the clinician thereby increasing the popularity of clear removable orthodontics. Although this automation has streamlined the process of aligner fabrication, attention must be given to the accuracy of the CAD/CAM process. The purpose of this study was to assess the accuracy verification process of the computer aided design (CAD) software utilized to move teeth on the digital file, Results (cont) References 1.Profit, W.R.: Equilibrium theory revisited: factors influencing position of the teeth. Angle Orthod. 48: 175-186, 1978. 2.Weinstein, S., et al.: On an equilibrium theory of tooth position. Angle orthod. 33: 1-26, 1963. 3.Baumrind, S.: A reconsideration of the propriety of the “pressure-tension” hypothesis. Am. J. Orthod. 55: 12-22, 1969. 4.E. W. H. Ng. Localized sequential use of resilient lining to generate orthodontic force in thermoformed active removable appliances. Journal of Orthodontics, December 2005;32(4), 235-240 5. Laura J. Barbagallo. A Novel Pressure Film Approach for Determining the Force Imparted by Clear Removable Thermoplastic Appliances. Annals of Biomedical Engineering , February 2008; 36(2) : 335-341 6. Kim TW . Clear aligner: an efficient, esthetic, and comfortable option for an adult patient. 7.Bolton WA : Disharmony in tooth size and its relation to the analysis and treatment of malocclusion . Angle Orthod 1958 ; 28: 113- 30 . Acknowledgement We would like to take this opportunity to thank Dr. Patrick Turley, former Professor and Chairman UCLA Orthodontics, NuBrace Inc allowing us to test accuracy verification of OrthoMove CAD software, Dr. Joseph Matyas, recently passed, but his contributions to literature always evident and both Dr. Dan Nathanson, former Associate Dean Boston U and Norm Weinstock, Pres of Zahn Dental, for their trust and confidence in the technology. Results Discussion 1.This study demonstrated that the teeth movement performed by OrthoMove Computer Aided Design (CAD) software were extremely accurate when comparative engineer overlap analysis was performed 3M, an independent company using their own accuracy verification testing analysis. 2.Notice that the color coded table (Fig 3, 4) is reflective of 0.2mm tooth movement for the lateral incisors and 0.6mm for the central incisors: Consistent with the tooth movement performed by OrthoMove. 3.The degree of accuracy was to the 1/100mm variance. 4.Figure 5, 6 demonstrate photoelastic stress analysis. The findings show an increased stress to the centrals with 0.6mm movement as compared to the laterals with 0.2mm tooth movement. Further, findings demonstrated minimal stress / movement to the other teeth which had no movement. 5.Photoelastic findings were consistent with the overlap engineer analysis all of which support the accuracy of the OrthoMove CAD software. 6.Clinician should consider using the medium thickness laminated aligner (0.50mm) as it allows for similar stress patterns as the thicker aligner (0.75mm), but may allow for less supereruption. Conclusion 1.Results indicate that tooth movement in the range of 0.2mm to 0.6mm are able to be performed effectively and with appropriate fit. 2.Further, results indicate that the movements performed by OrthoMove CAD software are accurate to the 100 th mm degree of accuracy as per an independent source of testing conducted by 3M. 3.Photoelastic results demonstrated greater stress concentration to the central incisors as compared to the lateral incisors consistent with the tooth movement performed by OrthoMove. 4.The clinical implications of this study are that the accuracy verification of OrthoMove CAD software used to orthodontically move teeth based on clinician’ s request will allow extremely accurate movements toward idealized tooth positions. ACCURACY VERIFICATION OF ALIGNER CAD PROCESS A. Caputo, T. Kalili, T. Tong. V. Cheng, K. Ruiz, T. Darie Biomaterials Science, UCLA School of Dentistry Material and Method 1. Photoelastic model of dentulous adult maxilla was fabricated using different teeth and bone simulants to represent “patient.” 2.PVS impression of the model was sent to 3M for CT scan. 3.Teeth were moved on the digital file in a lingual direction using OrthoMove CAD software per online clinician lab instructions with the following specifications per Figure #1: a. Maxillary lateral incisors 0.2mm. b. Maxillary central incisors 0.6mm. Three completely different disciplines of scientific approach were utilized to analysis and test for accuracy verification: 1.OrthoMove CAD software accuracy verification: a. OrthoMove performed the above referenced lingual tooth movements (centrals by 0.6mm and laterals by 0.2mm) on the original scan of the photoelastic model referred to as altered file. b. Altered file was sent to 3M for accuracy verification using digital overlap comparative analysis. This process entails overlying the altered file over the original file and assessing degree of change to the teeth followed by a readout of the difference. 2.OrthoProofUSA a subsidiary of 3M: 1. PVS impression was taken of the photoelastic model and sent for CT scan “original file.” 2. Original scan was sent to NuBrace which made the requested tooth movements and sent back the “altered file” to OrthoProofUSA. 3. OrthoProofUSA performed an engineering overlap comparative analysis to for accuracy verification of the tooth movements performed by NuBrace. 4. The results of the engineering analysis is referenced in Figure SCALE 0.1 = 0.1mm tooth movement Figure 3 – Above is a CT scan of the photoelastic model post tooth movement. 3M performed engineer comparative analysis to assess accuracy verification. This is determined by placing the orthodontically altered digital file performed by OrthoMove CAD software over the original un altered digital file of the photoelastic model. The difference is indicated by the color scale depending on degree of tooth movement. Hence, lingual movement of centrals by 0.6mm and laterals by 0.2mm using OrthoMove reverse modeling software. Figure 2. Above is 3D Comparison Results of the Engineer Overlap Comparative Analysis for accuracy verification of specific tooth movement performed by OrthoMove. Percentage Deviation is based the amount of tooth movement performed by OrthoMove and the variance based on the engineer comparative results with an accuracy verification to the 100 th mm. Figure 1. OrthoMove computer aided design (CAD) software used to digitally move teeth toward idealized position. Desired teeth were selected on the digital file. Each click by OrthoMove allows for 0.1mm of tooth movement. Central incisors were lingually moved by 0.6mm and lateral incisors were lingually moved by 0.2mm. Notice that the degree of movement by OrthoMove are consistent with the results of the engineering comparative analysis indicated on the color coded bar to the left. and the greater the number of fringes denotes greater intensity of stress. Figure 5. Above is the photoelastic model with no aligner. Notice that there are no stress associated with any of the teeth and the model is stress free prior to testing. Stress is visualized as areas demonstrated by rainbow like banners with different colors reflective of various intensity. The closer the fringes are to one another the higher the concentration of stress Figure 6. THIN ALIGNER 0.25mm Above is the photoelastic model with the thin aligner inserted. Notice that the stress distribution in both number of fringes and proximity of fringes are less around the centrals and laterals, area of tooth movement. Figure 4. Above are various views of the engineer overlap comparative analysis performed by OrthoProofUSA to assess accuracy verification of OrthoMove CAD software. Image courtesy of OrthoProofUSA a subsidiary of 3M. Notice that for every movement a compensation of that given movement has been allocated on the opposing side reflective with the colors on the opposing side of each tooth that has been moved. The degree of space allocation is indicated by the color chart. For example: The central incisors have moved in a lingual direction by 0.6mm as reflective by the color on the facial aspect of the centrals. In order to for the orthodontic aligner to allow this amount of movement in the lingual direction, compensatory space must be created to allow tooth movement in that direction by the aligner. Therefore, OrthoMove creates a Sagittal cut within the plane of the tooth and increases the thickness of the tooth in the direction of desired movement in order to allow space for tooth to move in that direction. Hence, the central incisors possess an orange color on the facial and blue on the lingual. Cross over to the color chart indicates a movement of +0.6mm and -0.6mm on the lingual to allow for room in the opposing direction.
Transcript of ACCURACY VERIFICATION OF ALIGNER CAD PROCESS · 2009. 1. 16. · Introduction Invisible removable...
IntroductionInvisible removable orthodontics has been in use for over 60 years. However, in the past this wasaccomplished by manual process of moving teeth on the stone model toward idealizedorthodontic position. Thereafter, the very basic vacuum suck-down machines were used followedby manual cutting of the excess aligner material to fabricate the clear aligners. This process wasextremely cumbersome as it utilized manual labor at each phase of aligner fabrication. In thepast decade several companies began automating the process of aligner fabrication usingcomputer aided design (CAD) which allows digital tooth movement. Once the digital file is movedinto the first of multiple phases of tooth movement, this digital file is printed using rapid prototype3D printers followed by computer aided manufacturing (CAM).
Therefore, rather than using a modified stone model, this 3D printed model is now used in orderto vacuum a polymer sheet, most often polycarbonate or a variation thereof, to fabricate the finalaligner. Thereafter, the excess material which once was cut off one at a time by manual labor is amemory of the past. The technology now allows CAM process using milling machines controlledby software programs to cut the aligner excess at the gingival margin, referred to as a tool path.The advanced automation allowed enhanced esthetics and ease of application by the clinicianthereby increasing the popularity of clear removable orthodontics. Although this automation hasstreamlined the process of aligner fabrication, attention must be given to the accuracy of theCAD/CAM process. The purpose of this study was to assess the accuracy verification process ofthe computer aided design (CAD) software utilized to move teeth on the digital file,
Results (cont)
References1.Profit, W.R.: Equilibrium theory revisited: factors influencing position of the teeth.
Angle Orthod. 48: 175-186, 1978.2.Weinstein, S., et al.: On an equilibrium theory of tooth position. Angle orthod. 33:
1-26, 1963.3.Baumrind, S.: A reconsideration of the propriety of the “pressure-tension”
hypothesis. Am. J. Orthod. 55: 12-22, 1969.4.E. W. H. Ng. Localized sequential use of resilient lining to generate orthodontic
force in thermoformed active removable appliances. Journal of Orthodontics,December 2005;32(4), 235-240
5. Laura J. Barbagallo. A Novel Pressure Film Approach for Determining the ForceImparted by Clear Removable Thermoplastic Appliances. Annals of BiomedicalEngineering, February 2008; 36(2) : 335-341
6. Kim TW. Clear aligner: an efficient, esthetic, and comfortable option for an adultpatient.
7.Bolton WA : Disharmony in tooth size and its relation to the analysis andtreatment of malocclusion . Angle Orthod 1958 ; 28: 113- 30 .
AcknowledgementWe would like to take this opportunity to thank Dr. Patrick Turley, former Professorand Chairman UCLA Orthodontics, NuBrace Inc allowing us to test accuracyverification of OrthoMove CAD software, Dr. Joseph Matyas, recently passed, buthis contributions to literature always evident and both Dr. Dan Nathanson, formerAssociate Dean Boston U and Norm Weinstock, Pres of Zahn Dental, for their trustand confidence in the technology.
Results Discussion1.This study demonstra ted that the teeth movement performed byOr thoMove Computer Aided Design (CAD) sof tware were extremelyaccurate when comparative engineer overlap analysis was performed 3M,an independent company using their own accuracy verification testinganalysis.2.Notice that the color coded table (Fig 3, 4) is reflective of 0.2mm toothmovement for the lateral incisors and 0.6mm for the central incisors:Consistent wi th the tooth movement performed by OrthoMove.3.The degree of accuracy was to the 1/100mm variance.4.Figure 5, 6 demonstrate photoelastic stress analysis. The findings showan increased stress to the centrals with 0.6mm movement as compared tothe laterals with 0.2mm tooth movement. Further, findings demonstratedminimal stress / movement to the other teeth which had no movement.5.Photoelastic findings were consistent with the overlap engineer analysisall of which support the accuracy of the OrthoMove CAD software.6.Clinician should consider using the medium thickness laminated aligner(0.50mm) as it al lows for similar stress patterns as the thicker aligner(0.75mm), but may allow for less supereruption.
Conclusion1.Results indicate that tooth movement in the range of 0.2mm to 0.6mm areable to be performed effectively and with appropriate fit.2.Further, results indicate that the movements performed by OrthoMoveCAD software are accurate to the 100th mm degree of accuracy as per anindependent source of testing conducted by 3M.3.Photoelastic results demonstrated greater stress concentration to thecentral incisors as compared to the lateral incisors consistent with the toothmovement performed by OrthoMove.4.The clinical implications of this study are that the accuracy verification ofOrthoMove CAD software used to orthodontically move teeth based onclinician’s request will allow extremely accurate movements towardidealized tooth positions.
ACCURACY VERIFICATION OF ALIGNER CAD PROCESSA. Caputo, T. Kalili, T. Tong. V. Cheng, K. Ruiz, T. Darie
Biomaterials Science, UCLA School of Dentistry
Material and Method1. Photoelastic model of dentulous adult maxilla was fabricated using different teeth and bonesimulants to represent “patient.”2.PVS impression of the model was sent to 3M for CT scan.3.Teeth were moved on the digital file in a lingual direction using OrthoMove CAD software peronline clinician lab instructions with the following specifications per Figure #1:
a. Maxillary lateral incisors 0.2mm.b. Maxillary central incisors 0.6mm.
Three completely different disciplines of scientific approach were utilized to analysis and test foraccuracy verification:
1.OrthoMove CAD software accuracy verification:a. OrthoMove performed the above referenced lingual tooth movements (centrals by
0.6mm and laterals by 0.2mm) on the original scan of the photoelastic model referredto as altered file.
b. Altered file was sent to 3M for accuracy verification using digital overlap comparativeanalysis. This process entails overlying the altered file over the original file andassessing degree of change to the teeth followed by a readout of the difference.
2.OrthoProofUSA a subsidiary of 3M:1. PVS impression was taken of the photoelastic model and sent for CT scan “original file.”2. Original scan was sent to NuBrace which made the requested tooth movements and sent
back the “altered file” to OrthoProofUSA.3. OrthoProofUSA performed an engineering overlap comparative analysis to for accuracy
verification of the tooth movements performed by NuBrace.4. The results of the engineering analysis is referenced in Figure
SCALE0.1 = 0.1mm tooth movement
Figure 3 – Above is a CT scan of the photoelastic model post tooth movement.3M performed engineer comparative analysis to assess accuracy verification.This is determined by placing the orthodontically altered digital file performed byOr thoMove CAD sof tware over the original un altered digital fi le of thephotoelastic model. The difference is indicated by the color scale depending ondegree of tooth movement. Hence, lingual movement of centrals by 0.6mm andlaterals by 0.2mm using OrthoMove reverse modeling software.
Figure 2. Above is 3D Comparison Results of the Engineer OverlapComparative Analysis for accuracy verification of specific tooth movementperformed by OrthoMove. Percentage Deviation is based the amount of toothmovement performed by OrthoMove and the variance based on the engineercomparative results with an accuracy verification to the 100th mm.
Figure 1. OrthoMove computer aided design (CAD) software used to digitally move teeth toward idealizedposition. Desired teeth were selected on the digital file. Each click by OrthoMove allows for 0.1mm of toothmovement. Central incisors were lingually moved by 0.6mm and lateral incisors were lingually moved by0.2mm. Notice that the degree of movement by OrthoMove are consistent with the results of theengineering comparative analysis indicated on the color coded bar to the left.
and the greater the number of fringes denotes greater intensity of stress. Figure 5.Above is the photoelastic model with no aligner. Notice that there are nostress associated with any of the teeth and the model is stress free prior totesting. Stress is visualized as areas demonstrated by rainbow like bannerswith different colors reflective of various intensity. The closer the fringes areto one another the higher the concentration of stress
Figure 6. THIN ALIGNER 0.25mmAbove is the photoelastic model with the thin aligner inserted. Notice that the stressdistribution in both number of fringes and proximity of fringes are less around thecentrals and laterals, area of tooth movement.
Figure 4. Above are various views of the engineer overlap comparative analysisperformed by OrthoProofUSA to assess accuracy verification of OrthoMoveCAD software. Image courtesy of OrthoProofUSA a subsidiary of 3M. Noticethat for every movement a compensation of that given movement has beenallocated on the opposing side reflective with the colors on the opposing side ofeach tooth that has been moved. The degree of space allocation is indicated bythe color char t. For example: The central incisors have moved in a lingualdirection by 0.6mm as reflective by the color on the facial aspect of the centrals.In order to for the orthodontic aligner to allow this amount of movement in thelingual direction, compensatory space must be created to allow tooth movementin that direction by the aligner. Therefore, OrthoMove creates a Sagittal cutwithin the plane of the tooth and increases the thickness of the tooth in thedirection of desired movement in order to allow space for tooth to move in thatdirection. Hence, the central incisors possess an orange color on the facial andblue on the lingual. Cross over to the color chart indicates a movement of+0.6mm and -0.6mm on the lingual to allow for room in the opposing direction.
