- Email: [email protected]
Single-arch digital removable complete denture: A workflow that starts from the intraoral scan
DENTAL TECHNIQUE
Single-arch digital removable complete denture: A workflow that starts from the intraoral scan Lucio Lo Russo, DDS, PhDa and Angelo Salamini, Engb Technological developments ABSTRACT in computer-aided design and The production of removable dentures from intraoral scans has been problematic. In addition, the computer-aided manufacture digital design and fabrication of a single-arch denture cannot be routinely managed. (CAD-CAM) technologies have The workflow presented provides a proof of concept that an optical intraoral scan of the edentulous allowed the complete digitalimaxilla is feasible and that a functional single-arch maxillary denture can be designed and fabrization of design and manufaccated using a digital protocol. (J Prosthet Dent 2017;-:---) ture of removable dentures.1 Such a digital approach has numerous advantages2 and The authors are unaware of intraoral scans used to is being increasingly used in daily workflows.3 Current produce removable dentures. Indeed, scanning edenCAD-CAM denture systems start by digitizing imprestulous jaws has not been recommended8 because of 4 sions or definitive casts with a laboratory scanner. problems in obtaining accurate scans of soft tissues. Nonetheless, intraoral digital scans are possible, and Complete-arch conventional impressions have been clinicians could benefit from a fully digital approach to reported to have significantly greater precision and the production of removable dentures. The absence of a trueness than digital impressions.9 However, the physical impression improves patient comfort, eliminates average amount of such differences in trueness (38.2 potential allergies to impression materials, and avoids errors related to the distortion of impression materials and changes in the gypsum cast; storage of the physical impressions and gypsum cast is also unnecessary.5 Intraoral scans allow the development of a truly mucostatic impression of the edentulous arch,6 especially beneficial with sharp, thin, flat, or flabby residual ridges. According to the mucostatic concept, denture retention is not achieved by the peripheral seal but depends on surface tension created by the intimate contact of the denture base with underlying tissues. Consequently, border molding is not mandatory and the precise definition of vestibular depth and width is not as stringent as with the functional impression technique.7 This might permit shorter denture flanges without affecting retention. Nonetheless, excessive underextension of the denture Figure 1. Preoperative conditions. Intraoral scan of maxilla. To complete flanges is not desirable because it may reduce secondary this scan about 800 images were used, as indicated by on-screen image counter in Trios software. retention and stability and impair lip and cheek support.
a
Associate Professor of Oral Diseases, Department of Clinical and Experimental Medicine, School of Dentistry, University of Foggia, Foggia, Italy. Co-founder, Sintesi Sud Srl, Ariano Irpino (AV), Italy.
b
THE JOURNAL OF PROSTHETIC DENTISTRY
1
2
Volume
-
Issue
-
Figure 2. Occlusal records. A, Design of baseplate for occlusion rim. B, Occlusion rim made with wax mounted on baseplate obtained with 3-dimensional printing, adapted to patient in order to register information for teeth arrangement, as well as maxillo-mandibular relation.
Figure 3. Alignment of digital casts to occlusal rim. A, Accuracy of alignment: cross-section on sagittal and frontal plane. B, Frontal view of aligned casts.
mm) and precision (19.9 mm)9 may not be clinically relevant for the fabrication of removable dentures. The present technique has been used to make an intraoral scan of an edentulous maxilla and then design and fabricate a functional single-arch maxillary denture in a completely digital workflow. In the mandibular arch of the patient described, the first and the second left and right premolars, the first left and right molar, and the right second molar were present, and the patient wore a removable acrylic resin partial denture. TECHNIQUE 1. Scan the edentulous arch and the antagonist. Use the 3Shape Trios 3 color (3Shape) intraoral scanner and a U-shaped retractor to retract and stabilize buccal mobile tissues, avoiding their overextension. Process and export scans (Fig. 1) with Trios software. Use either Trios direct connection to export to a desktop or the 3Shape Communicate system. Also use Trios 3 for the other scans.
THE JOURNAL OF PROSTHETIC DENTISTRY
2. Create digital casts with the specific workflow in the 3Shape Dental System software (DS; 3Shape). Also use DS for all the other steps in the design process. 3. Design the baseplate for the occlusion rim (OR) and make a rapid prototype of it. Use the workflow for individual impression trays, setting the space for the material to zero so that the baseplate is completely adapted to the mucosa (Fig. 2A). Add some mechanical retention for the wax rim to the baseplate. Transfer the standard tessellation language (STL) file of the designed baseplate to the software application of the 3D printer (M200; Zortrax) and then print with a 0.09-mm thickness of the material (Z-Ultrat; Zortrax). 4. Add wax (Bite Wax Rims; Henry Schein, Inc) to the baseplate for the definitive OR. 5. Record the vertical dimension, occlusal plane, lip support, maxillary incisor length, and midline by adapting the OR on the patient. Lo Russo and Salamini
-
2017
3
Figure 5. Production phase. A, Denture base milled. B, Intaglio surface of milled denture base.
Figure 4. Denture design. A, Teeth selected from available libraries and position modified according to desired occlusal concept and information integrated in occlusion rim. B, Occlusion evaluated and modified in virtual articulator: digitally calculated dynamic occlusion. C, Finalizing design of both teeth and denture base.
6. Make the facebow and jaw relation records. Use Arcus Digma II (KaVo Dental GmbH) to record settings for the virtual articulator and centric relation. Guide the patient into centric relation,10 following the manufacturer’s instructions, and register it in the OR previously heated in warm water (Fig. 2B). 7. Scan the OR (Fig. 2B). Lo Russo and Salamini
8. Align digital casts to the OR. In a new order (‘order’ is how the design process is referred to in DS), set to design a ‘provisional’ positioned anywhere on the cast and import digital casts and the scan of the OR as a ‘pre-preparation scan.’ Align the ‘prepreparation scan’ (the OR) to both digital casts using the 3-point method. Evaluate results of the alignment on cross-sections (Fig. 3A). Once finished, STL files of aligned digital casts are available in the ‘order’ folder. 9. Design the denture. Use a workaround (at the time this paper was written, no workflow for single-arch denture was available in DS): create a new ‘order,’ set tooth design as ‘temporaries on prepared models’ and the denture base design as gingiva on a ‘phantom coping’ (a coping positioned anywhere on the cast just to have access to tools for designing gingiva). Import in the ‘order’ aligned digital casts and the scan of the OR as a ‘prepreparation scan,’ and proceed with the design workflow (Fig. 4). 10. Design the denture flange extensions on the digital casts by an analysis of anatomic landmarks in order to have complete coverage of load-bearing areas
THE JOURNAL OF PROSTHETIC DENTISTRY
4
Volume
13.
14.
15.
16.
-
Issue
-
definitive denture. Reopen the ‘order’ and adjust the design based on desired modifications or use the scan of the adapted trial denture, imported in the ‘order,’ as a guide for more precision. Prepare the final STL file of the denture base. Subtract the teeth from the denture base using reverse-engineering software (Netfabb; Autodesk Inc), to create tooth sockets in the base. Mill the denture base and the teeth. Use STL files of both the denture base and teeth in a CAM software (hyperDENT; FOLLOW-ME! Technology Group) to create the corresponding projects in a 25-mm-high poly(methylmethacrylate) blank (Smile Cam Total Prosthesis; Pressing Dental srl) and in a multilayer poly(methylmethacrylate) copolymer blank (Smile Cam; Pressing Dental srl), respectively. Then, generate the corresponding output for the specific milling machine (DWX-51D; Roland) (Fig. 5) (Supplemental Video 1). Bond teeth to the milled base with a fast polymerizing acrylic resin (Jet Repair; Lang Dental Mfg Co, Inc), following the manufacturer’s instructions. Deliver the definitive denture to the patient (Fig. 6) (Supplemental Video 2).
DISCUSSION
Figure 6. Denture delivery. A, Definitive denture ready to be delivered. B, Intraoral dynamic occlusion. Note adherence to CAD project in Fig. 4B. C, Patient with definitive denture.
and provide adequate support for lips and cheeks. At the end of the design process, STL files of the denture base and teeth are created. 11. Make a rapid prototype of the trial denture. Use procedure and settings detailed in step 3. Then, cover the trial denture flange with a thin layer of pink wax (Tenasyle; Kemdent). 12. Clinically assess the trial denture. At this stage, changes, if required, can be incorporated into the
THE JOURNAL OF PROSTHETIC DENTISTRY
The definitive maxillary denture obtained with the presented workflow was rated by the patient as good for both function and retention. No complication has been observed so far after 7 months of denture usage. The clinical effectiveness of the described digital denture is the result of accuracy, integration, and fine-tuning of multiple steps, starting from intraoral scanning, proceeding with the denture design, and ending with milling. The use of open digital technologies3 provided the opportunity to take control of each aspect of the workflow, remove potential limitations of using systeminherent devices, and apply a customized approach to solve specific and open issues. With the current workflow, at least 2 visits are required to deliver the denture provided that the patient can wait approximately 80 minutes for the OR to be built, and the clinical session for the trial denture evaluation is omitted. The provision of the maxillary denture took less than 60 minutes of chairside time, an average of 90 minutes of laboratory time, 135 minutes to mill the denture base before manual polishing, and about 2 hours to mill teeth. In the near future, the design process will be simplified and no workaround will be necessary, because a new specific workflow for single-arch removable dentures has been announced by 3Shape. The technique described is promising, but clinical long-term validation is necessary. In addition, progress for technological developments in the field of digitizing Lo Russo and Salamini
-
2017
anatomic information and registration of maxillomandibular relation is expected. REFERENCES 1. Bilgin M, Baytaroglu E, Erdem A, Dilber E. A review of computer-aided design/computer-aided manufacture techniques for removable denture fabrication. Eur J Dent 2016;10:286-91. 2. Kattadiyil MT, AlHelal A. An update on computer-engineered complete dentures: A systematic review on clinical outcomes. J Prosthet Dent 2017;117: 478-85. 3. Lo Russo L, Salamini A. Removable complete digital dentures: A workflow that integrates open technologies. J Prosthet Dent 2017. accepted Jun 22. 4. Steinmassl PA, Klaunzer F, Steinmassl O, Dumfahrt H, Grunert I. Evaluation of currently available CAD/CAM denture systems. Int J Prosthodont 2017;30: 116-22. 5. Quaas S, Rudolph H, Luthardt RG. Direct mechanical data acquisition of dental impressions for the manufacturing of CAD/CAM restorations. J Dent 2007;35:903-8.
Lo Russo and Salamini
5
6. Page HL. Mucostatics. Ticonium Contacts 1946;4:7. 7. Rao S, Chowdhary R, Mahoorkar S. A systematic review of impression technique for conventional complete denture. J Indian Prosthodont Soc 2010;10:105-11. 8. Patzelt SB, Vonau S, Stampf S, Att W. Assessing the feasibility and accuracy of digitizing edentulous jaws. J Am Dent Assoc 2013;144:914-20. 9. Ender A, Mehl A. Accuracy of complete-arch dental impressions: A new method of measuring trueness and precision. J Prosthet Dent 2013;109:121-8. 10. Sojka A, Huber J, Kaczmarek E, Hedzelek W. Evaluation of mandibular movement functions using instrumental ultrasound system. J Prosthodont 2017;26:123-8. Corresponding author: Prof. Lucio Lo Russo Via Serro D’Annunzio, 55 83050 Vallesaccarda (AV) ITALY Email: [email protected] Copyright © 2017 by the Editorial Council for The Journal of Prosthetic Dentistry.
THE JOURNAL OF PROSTHETIC DENTISTRY
Single-arch digital removable complete denture: A workflow that starts from the intraoral scan Lucio Lo Russo, DDS, PhDa and Angelo Salamini, Engb Technological developments ABSTRACT in computer-aided design and The production of removable dentures from intraoral scans has been problematic. In addition, the computer-aided manufacture digital design and fabrication of a single-arch denture cannot be routinely managed. (CAD-CAM) technologies have The workflow presented provides a proof of concept that an optical intraoral scan of the edentulous allowed the complete digitalimaxilla is feasible and that a functional single-arch maxillary denture can be designed and fabrization of design and manufaccated using a digital protocol. (J Prosthet Dent 2017;-:---) ture of removable dentures.1 Such a digital approach has numerous advantages2 and The authors are unaware of intraoral scans used to is being increasingly used in daily workflows.3 Current produce removable dentures. Indeed, scanning edenCAD-CAM denture systems start by digitizing imprestulous jaws has not been recommended8 because of 4 sions or definitive casts with a laboratory scanner. problems in obtaining accurate scans of soft tissues. Nonetheless, intraoral digital scans are possible, and Complete-arch conventional impressions have been clinicians could benefit from a fully digital approach to reported to have significantly greater precision and the production of removable dentures. The absence of a trueness than digital impressions.9 However, the physical impression improves patient comfort, eliminates average amount of such differences in trueness (38.2 potential allergies to impression materials, and avoids errors related to the distortion of impression materials and changes in the gypsum cast; storage of the physical impressions and gypsum cast is also unnecessary.5 Intraoral scans allow the development of a truly mucostatic impression of the edentulous arch,6 especially beneficial with sharp, thin, flat, or flabby residual ridges. According to the mucostatic concept, denture retention is not achieved by the peripheral seal but depends on surface tension created by the intimate contact of the denture base with underlying tissues. Consequently, border molding is not mandatory and the precise definition of vestibular depth and width is not as stringent as with the functional impression technique.7 This might permit shorter denture flanges without affecting retention. Nonetheless, excessive underextension of the denture Figure 1. Preoperative conditions. Intraoral scan of maxilla. To complete flanges is not desirable because it may reduce secondary this scan about 800 images were used, as indicated by on-screen image counter in Trios software. retention and stability and impair lip and cheek support.
a
Associate Professor of Oral Diseases, Department of Clinical and Experimental Medicine, School of Dentistry, University of Foggia, Foggia, Italy. Co-founder, Sintesi Sud Srl, Ariano Irpino (AV), Italy.
b
THE JOURNAL OF PROSTHETIC DENTISTRY
1
2
Volume
-
Issue
-
Figure 2. Occlusal records. A, Design of baseplate for occlusion rim. B, Occlusion rim made with wax mounted on baseplate obtained with 3-dimensional printing, adapted to patient in order to register information for teeth arrangement, as well as maxillo-mandibular relation.
Figure 3. Alignment of digital casts to occlusal rim. A, Accuracy of alignment: cross-section on sagittal and frontal plane. B, Frontal view of aligned casts.
mm) and precision (19.9 mm)9 may not be clinically relevant for the fabrication of removable dentures. The present technique has been used to make an intraoral scan of an edentulous maxilla and then design and fabricate a functional single-arch maxillary denture in a completely digital workflow. In the mandibular arch of the patient described, the first and the second left and right premolars, the first left and right molar, and the right second molar were present, and the patient wore a removable acrylic resin partial denture. TECHNIQUE 1. Scan the edentulous arch and the antagonist. Use the 3Shape Trios 3 color (3Shape) intraoral scanner and a U-shaped retractor to retract and stabilize buccal mobile tissues, avoiding their overextension. Process and export scans (Fig. 1) with Trios software. Use either Trios direct connection to export to a desktop or the 3Shape Communicate system. Also use Trios 3 for the other scans.
THE JOURNAL OF PROSTHETIC DENTISTRY
2. Create digital casts with the specific workflow in the 3Shape Dental System software (DS; 3Shape). Also use DS for all the other steps in the design process. 3. Design the baseplate for the occlusion rim (OR) and make a rapid prototype of it. Use the workflow for individual impression trays, setting the space for the material to zero so that the baseplate is completely adapted to the mucosa (Fig. 2A). Add some mechanical retention for the wax rim to the baseplate. Transfer the standard tessellation language (STL) file of the designed baseplate to the software application of the 3D printer (M200; Zortrax) and then print with a 0.09-mm thickness of the material (Z-Ultrat; Zortrax). 4. Add wax (Bite Wax Rims; Henry Schein, Inc) to the baseplate for the definitive OR. 5. Record the vertical dimension, occlusal plane, lip support, maxillary incisor length, and midline by adapting the OR on the patient. Lo Russo and Salamini
-
2017
3
Figure 5. Production phase. A, Denture base milled. B, Intaglio surface of milled denture base.
Figure 4. Denture design. A, Teeth selected from available libraries and position modified according to desired occlusal concept and information integrated in occlusion rim. B, Occlusion evaluated and modified in virtual articulator: digitally calculated dynamic occlusion. C, Finalizing design of both teeth and denture base.
6. Make the facebow and jaw relation records. Use Arcus Digma II (KaVo Dental GmbH) to record settings for the virtual articulator and centric relation. Guide the patient into centric relation,10 following the manufacturer’s instructions, and register it in the OR previously heated in warm water (Fig. 2B). 7. Scan the OR (Fig. 2B). Lo Russo and Salamini
8. Align digital casts to the OR. In a new order (‘order’ is how the design process is referred to in DS), set to design a ‘provisional’ positioned anywhere on the cast and import digital casts and the scan of the OR as a ‘pre-preparation scan.’ Align the ‘prepreparation scan’ (the OR) to both digital casts using the 3-point method. Evaluate results of the alignment on cross-sections (Fig. 3A). Once finished, STL files of aligned digital casts are available in the ‘order’ folder. 9. Design the denture. Use a workaround (at the time this paper was written, no workflow for single-arch denture was available in DS): create a new ‘order,’ set tooth design as ‘temporaries on prepared models’ and the denture base design as gingiva on a ‘phantom coping’ (a coping positioned anywhere on the cast just to have access to tools for designing gingiva). Import in the ‘order’ aligned digital casts and the scan of the OR as a ‘prepreparation scan,’ and proceed with the design workflow (Fig. 4). 10. Design the denture flange extensions on the digital casts by an analysis of anatomic landmarks in order to have complete coverage of load-bearing areas
THE JOURNAL OF PROSTHETIC DENTISTRY
4
Volume
13.
14.
15.
16.
-
Issue
-
definitive denture. Reopen the ‘order’ and adjust the design based on desired modifications or use the scan of the adapted trial denture, imported in the ‘order,’ as a guide for more precision. Prepare the final STL file of the denture base. Subtract the teeth from the denture base using reverse-engineering software (Netfabb; Autodesk Inc), to create tooth sockets in the base. Mill the denture base and the teeth. Use STL files of both the denture base and teeth in a CAM software (hyperDENT; FOLLOW-ME! Technology Group) to create the corresponding projects in a 25-mm-high poly(methylmethacrylate) blank (Smile Cam Total Prosthesis; Pressing Dental srl) and in a multilayer poly(methylmethacrylate) copolymer blank (Smile Cam; Pressing Dental srl), respectively. Then, generate the corresponding output for the specific milling machine (DWX-51D; Roland) (Fig. 5) (Supplemental Video 1). Bond teeth to the milled base with a fast polymerizing acrylic resin (Jet Repair; Lang Dental Mfg Co, Inc), following the manufacturer’s instructions. Deliver the definitive denture to the patient (Fig. 6) (Supplemental Video 2).
DISCUSSION
Figure 6. Denture delivery. A, Definitive denture ready to be delivered. B, Intraoral dynamic occlusion. Note adherence to CAD project in Fig. 4B. C, Patient with definitive denture.
and provide adequate support for lips and cheeks. At the end of the design process, STL files of the denture base and teeth are created. 11. Make a rapid prototype of the trial denture. Use procedure and settings detailed in step 3. Then, cover the trial denture flange with a thin layer of pink wax (Tenasyle; Kemdent). 12. Clinically assess the trial denture. At this stage, changes, if required, can be incorporated into the
THE JOURNAL OF PROSTHETIC DENTISTRY
The definitive maxillary denture obtained with the presented workflow was rated by the patient as good for both function and retention. No complication has been observed so far after 7 months of denture usage. The clinical effectiveness of the described digital denture is the result of accuracy, integration, and fine-tuning of multiple steps, starting from intraoral scanning, proceeding with the denture design, and ending with milling. The use of open digital technologies3 provided the opportunity to take control of each aspect of the workflow, remove potential limitations of using systeminherent devices, and apply a customized approach to solve specific and open issues. With the current workflow, at least 2 visits are required to deliver the denture provided that the patient can wait approximately 80 minutes for the OR to be built, and the clinical session for the trial denture evaluation is omitted. The provision of the maxillary denture took less than 60 minutes of chairside time, an average of 90 minutes of laboratory time, 135 minutes to mill the denture base before manual polishing, and about 2 hours to mill teeth. In the near future, the design process will be simplified and no workaround will be necessary, because a new specific workflow for single-arch removable dentures has been announced by 3Shape. The technique described is promising, but clinical long-term validation is necessary. In addition, progress for technological developments in the field of digitizing Lo Russo and Salamini
-
2017
anatomic information and registration of maxillomandibular relation is expected. REFERENCES 1. Bilgin M, Baytaroglu E, Erdem A, Dilber E. A review of computer-aided design/computer-aided manufacture techniques for removable denture fabrication. Eur J Dent 2016;10:286-91. 2. Kattadiyil MT, AlHelal A. An update on computer-engineered complete dentures: A systematic review on clinical outcomes. J Prosthet Dent 2017;117: 478-85. 3. Lo Russo L, Salamini A. Removable complete digital dentures: A workflow that integrates open technologies. J Prosthet Dent 2017. accepted Jun 22. 4. Steinmassl PA, Klaunzer F, Steinmassl O, Dumfahrt H, Grunert I. Evaluation of currently available CAD/CAM denture systems. Int J Prosthodont 2017;30: 116-22. 5. Quaas S, Rudolph H, Luthardt RG. Direct mechanical data acquisition of dental impressions for the manufacturing of CAD/CAM restorations. J Dent 2007;35:903-8.
Lo Russo and Salamini
5
6. Page HL. Mucostatics. Ticonium Contacts 1946;4:7. 7. Rao S, Chowdhary R, Mahoorkar S. A systematic review of impression technique for conventional complete denture. J Indian Prosthodont Soc 2010;10:105-11. 8. Patzelt SB, Vonau S, Stampf S, Att W. Assessing the feasibility and accuracy of digitizing edentulous jaws. J Am Dent Assoc 2013;144:914-20. 9. Ender A, Mehl A. Accuracy of complete-arch dental impressions: A new method of measuring trueness and precision. J Prosthet Dent 2013;109:121-8. 10. Sojka A, Huber J, Kaczmarek E, Hedzelek W. Evaluation of mandibular movement functions using instrumental ultrasound system. J Prosthodont 2017;26:123-8. Corresponding author: Prof. Lucio Lo Russo Via Serro D’Annunzio, 55 83050 Vallesaccarda (AV) ITALY Email: [email protected] Copyright © 2017 by the Editorial Council for The Journal of Prosthetic Dentistry.
THE JOURNAL OF PROSTHETIC DENTISTRY