- Email: [email protected]
Digital bar prototype technique for full-arch rehabilitation on implants
Original Contributions
Clinical Dentistry Digital bar prototype technique for full-arch rehabilitation on implants Carlo Monaco, DDS, MSc, PhD; Antonio Arena, DDS, MSc, PhD; Giacomo Pallotti, DT; Adolfo di Fiore, DDS, PhD; Lorenzo Scheda, DDS ABSTRACT Background and Overview. The aim of the authors in this case report was to describe a new approach to using the digital bar prototype technique for complete digital full-arch implant rehabilitation. Two combinable structures were used during the same visit as prototypes to simultaneously test the implant locations and the prosthetic parameters. Then the structures were joined together to form the final prosthesis. Case Description. After the implant integration with the immediate provisional restoration, 3 sets of digital impressions were obtained to obtain a master digital model (MDM). A stereolithographic model with implant analogs was printed on the basis of the MDM. A titanium bar with implant connections and a functional resin structure were milled on the basis of the MDM and used as prototypes. To check the accuracy of the implant impression, the titanium prototype was tried in, and clinical and radiographic tests were performed. Then the resin prototype was slid into the positional prototype and fitted to the patient, and the esthetic and occlusal properties were evaluated and refined. Definitive restoration was obtained by luting the 2 prototypes together and finalizing the prosthesis with pink resin. Conclusions and Practical Implications. The prototypes allowed the clinician to simultaneously verify the accuracy of the digital impressions and test the prosthetic parameters in 1 visit. Moreover, they were used to create the final restoration. The digital bar prototype technique also allowed for the reduction of clinical and laboratory time in a full-arch rehabilitation on implants. Nevertheless, obtaining a full-arch impression in an edentulous arch can be challenging, and further studies are necessary to evaluate the long-term success of this technique. Key Words. Dental implants; restorative dentistry; fixed prosthetics; computer-aided design and computer-aided manufacturing. JADA 2019:150(6):549-555 https://doi.org/10.1016/j.adaj.2019.01.022
igital work flows are becoming increasingly relevant in everyday practice. Intraoral digital scanning devices, digital dental software, computer-aided design and computer-aided manufacturing (CAD-CAM) technology, and other tools such as cone-beam computed tomography (CBCT) give the clinician the opportunity to acquire patient data conveniently and plan and execute complex rehabilitation procedures.1-3 With the prosthetic-driven approach for complete arch rehabilitation, all phases of treatment can be projected and carried out on the basis of the planned outcome; thus, the method is feasible and favorable in terms of allowing prediction of the final prosthetic outcome.4,5 In the traditional work flow, full-arch implant rehabilitation requires several steps.6 Once the implants are integrated, an impression of the implants is made, and the master model cast with the inserted implant analog is poured. Before creating the final framework, the accuracy of the positions of the analogs within the model must be verified. This can be done using a prototype structure made of metal abutments linked with resin, first in the model and then clinically in the patient.7,8 In this way, the locations of the implants on the patient can be compared with the positions of the analogs in the model. Then, the clinician may proceed to the next phases, and the definitive framework can
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Figure 1. Initial clinical case.
be created. After that, prosthetic and functional parameters (esthetic appearance, occlusal relationship, occlusal vertical dimension [OVD]) can be evaluated in the patient using a wax-up technique that simulates the prosthetic teeth.6,9,10 As described by Monaco and colleagues,5 within the full digital work flow, once digital impressions are obtained and the digital master model is created, a metal prototype is milled to verify the implant impression accuracy. An additional resin prototype with milled implant connections is created on the basis of the virtual wax-up to test the essential prosthetic and functional parameters (occlusal relation, esthetic appearance, OVD). However, the locations of the implants and the prosthetic parameters cannot be checked simultaneously, and the prototypes are wasted after the clinical tests. Whichever work flow is chosen, the definitive framework generally is created by means of CAD-CAM milling, and then the technician may finalize it in different ways: by means of using artificial resin or composite teeth and pink resin materials, a ceramic material layered on a metal framework, or a zirconia restoration. The aim of this case report is to describe a full digital work flow in which metal and resin prototypes are designed to be combined so that the positional and prosthetic parameters are tested simultaneously. Moreover, the prototypes are produced with definitive materials so they can be combined to create the final restoration. CASE REPORT
ABBREVIATION KEY 3D: 3-dimensional. CBCT: Cone-beam computed tomography. FDP: Fixed dental prosthesis. MDM: Master digital model. OVD: Occlusal vertical dimension. SI1: First set of impressions. SI2: Second digital impression.
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Patient selection and surgical implant procedures We describe a clinical case of an 80-year-old woman with an inadequate mandibular ceramic fixed dental prosthesis (FDP) to illustrate the digital bar prototype technique (Figure 1). We obtained informed consent from the patient. We removed the old fixed dental prosthesis, extracted the hopeless teeth, and preserved the remaining teeth to support a full-arch provisional restoration. After 6 months, we obtained digital impressions (True Definition Scanner, 3M-ESPE) of the mandibular arch with and without the provisional restoration and performed cone-beam computed tomography. We combined the digital impressions of the mandibular arch (DWOS, Dental Wings) with the Digital Imaging and Communications in Medicine file of the cone-beam computed tomography and created a digital wax-up. We produced a stereolithographic model with implant analogs (Implant model, 3D Medical Print) and a surgical guide (Digital Drill Template, 3D Medical Print). In the stereolithographic model, we placed the implant analogs on the basis of the surgical plan and created an implant-supported, metal-reinforced provisional restoration. On the day of the surgery, we removed the teeth-supported provisional restoration and placed 4 implants (4.1 RC, Straumann) in the mandible according to a fully guided protocol. The surgical guide was supported by the teeth. At the end of the implant surgery, we extracted all the teeth (Figure 2A). We immediately screwed in the multibase abutments (SRA, Straumann) with torque of 25 newton centimeters. We secured the temporary abutments to the multibase abutments and relined the implant-supported screw-retained provisional restoration with resin on the patient (Figure 2B). Then we refined the provisional restoration on the stereolithographic model and, finally, immediately loaded it on the implants (Figure 2C). JADA 150(6)
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Figure 2. A. Try-in of the surgical guide supported by teeth. B. Four implants were inserted with the surgical guide, and temporary abutments were screwed to the implants. After the implant insertion, the teeth were extracted. C. The provisional restoration was relined and immediately loaded.
Digital impression and prototype fabrication (first visit) Four months after implant surgery (Figure 3A), we obtained 3 sets of digital impressions to provide information about the esthetic and functional parameters of the provisional restoration, the gingival architecture, the occlusal relationship, and the location of the implants using a fully digital approach. We obtained the first set of impressions (SI1) by means of scanning the provisional restoration screwed to the implants, the opposite arch, and the bite. In this way, the SI1 provided information about the esthetic parameters, the OVD, and the occlusal relationship. Then we removed the provisional restoration, screwed a standardized scanbody to the multibase abutments, and obtained the second digital impression (SI2) (Figure 3B). Finally, we scanned the provisional restoration in its entirety while outside of the mouth, including the pontic elements, to determine the shape of the transmucosal pathway over the implants and the architecture of the soft tissue surrounding the restoration. Then we merged the digital impressions (DWOS, Dental Wings) and obtained a master digital model (MDM). In this phase, we extrapolated implant locations from SI2 through automatic scanbody matching. Therefore, the MDM contained information about implant location, esthetic appearance, occlusal relation, OVD, and the gingival shape. On the basis of the MDM, we obtained a 3-dimensional (3D) print of a stereolithographic master model with implant analogs (Print@Dreve, Dreve). To verify the implant impression and the esthetic and functional parameters, we used CAD-CAM to mill a titanium positional prototype (CARES, Straumann) and a resin prototype (Milling Unit M1, Zirkonzahn). We designed the resin prototype with inferior slots that perfectly matched the titanium bar and obtained it by means of milling a disk of resin material (PMMA Multi Blank Z, Anaxdent). We designed the shapes of the teeth and the occlusal features of this prototype on the basis of the digital wax-up (Figure 4A, Figure 4B). Try-in of prototypes (second visit) We tested the titanium positional prototype while it was fitted to the patient through visual inspection, the finger pressure test, and periapical radiographs (Figure 5A). Then we mounted the JADA 150(6)
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Figure 3. A. The implants after healing period with multibase abutments secured to the fixtures. B. Scanbodies were secured to implants to obtain the second digital impression.
Figure 4. A. The positional and functional prototypes were designed on the master digital model. The anatomic shapes of the resin prototype were designed on the basis of the virtual wax-up. The wax-up was created starting from the previous fixed dental prosthesis. B. Apical view of the titanium positional prototype and the resin prototype. In the titanium positional prototype, the implant connections are integrated. The resin prototype has an inferior slot that matches the titanium prototype.
resin prototype and checked and adjusted the OVD, esthetic appearance, occlusal contacts, and guidance using articulation paper and a diamond bur (Figure 5B, Figure 5C). In case of discrepancies, the metal prototype could be sectioned, splinted with pattern resin, and then laser welded. If necessary, in the stereolithographic model the unfitting analogs could be extracted, secured to prototype, and refixed with resin. In case of section of the metal prototype, the resin prototype would be sectioned as well, rewelded with resin, and then refined by the technician. Definitive restoration (third visit) After the try-in procedures, we joined the resin prototype and the titanium positional prototype to create the full-arch restoration. We luted the prototypes together (Primer SR Connect, Ivoclar, on resin prototype; Clearfil Ceramic Primer Plus, Kuraray, on titanium prototype; Panavia V5, Kuraray, as luting agent) and finalized the restoration with pink resin (Lucitone Fas-Por, Dentsply Sirona) (Figure 6A). Then the full-arch implant restoration was delivered to the patient and screwed in (25 N cm torque) (Figure 6B). We checked the occlusal and lateral contacts with 12-micrometer articulation paper and obtained periapical radiographs (Figure 7). DISCUSSION In the conventional work flow, a full-arch implant rehabilitation requires several different steps, laboratory work, and multiple clinical appointments (and, therefore, involves high costs). After the implant impression is obtained, the master cast with implant analogs is obtained. This phase is technique sensitive because it involves manually securing the implant analogs to the impression copings, in addition to pouring operations.11 Before creating the final framework, a verification prototype is necessary to validate the positions of the analogs in the master model.7,8 If the implant 552
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Figure 5. A. Periapical radiographs of the titanium positional prototype secured to the implants. B. Clinical try-in of the combined prototypes. The resin prototype allows for testing of the prosthetic parameters; that is, the esthetic appearance, occlusal contacts and guidance, and occlusal vertical dimension. C. Occlusal check with articulation paper of the functional prototype inserted into the titanium positional prototype. The occlusal scheme of the prototype was duplicated from the previous fixed dental prosthesis.
Figure 6. A. Final restoration obtained by means of luting the prototypes and finalizing with pink resin on the stereolithographic model. B. Outcome of the final restoration.
locations in the patient do not match those of the analogs in the model, the master cast needs to be adjusted. In this case, nonfitting implants are extracted and refixed in the appropriate location12; only when the master cast with implant analogs is approved can the definitive framework be casted, refined, and tested while fitted to the patient. The final steps are the try-in procedures, performed with esthetic material, to verify the occlusal and esthetic parameters. The finalization procedures can then be executed. The digital bar prototype technique allows the clinician to execute a full-arch implant rehabilitation during 3 appointments. Digital impressions are obtained at the first appointment, and 3 sets of scans are obtained to register and digitally combine the essential parameters. The prototypes and the 3D-printed model are created directly on the basis of the same
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Digital impression and Digital master model
Positional prototype
Functional prototype
Stereolithographic master model with implant analogs 2nd visit
Clinical and radiographic tests Prototypes are combined and tried in the patient* Positional prototype is tried on the model†
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The prototypes are luted and finalized FINAL RESTORATION IS DELIVERED
Figure 7. Schematic representation of work flow of digital bar prototype technique * Clinical fitting tests are performed, and periapical radiographs are obtained. † Positional prototype is secured to the analogs in the stereolithographic model, and the fitting is evaluated. In case of nonpassive fitting, the nonfitting analogs are extracted, secured to the prototype, and refixed in the model with resin.
digital model. The creation of the milled prototypes and the printed model requires less time and is less expensive than the conventional method because it is a fully automated process. During the second appointment, the use of the 2 prototypes provides the clinician with the opportunity to check rapidly the accuracy of the impression, the suitability of the future restoration, and the adequacy of the 3D-printed model. The titanium prototype is tested while fitted to the patient, and then the functional resin prototype is mounted to verify the esthetic and occlusal parameters. Concurrently, the 3D-printed model is tested and, if a nonpassive fitting is present, it can be adjusted by removing the implant analog and refixing it with resin (or it can be reprinted). Because the positional prototype is composed of titanium alloy, it is not necessary to fabricate an additional metal framework for the definitive implant-supported restoration. Moreover, owing to the functional prototype, restorative teeth with appropriate occlusal and esthetic aspects are already in place. After the resin prototype is refined on the patient, it is luted on the titanium prototype and used in the final restoration. Thus, the laboratory phase of manual placement of artificial teeth over the framework while checking the occlusal relation on the articulator is no longer necessary. During the third appointment, the full-arch implant restoration is delivered. Digital scanning might be a reliable method in the full-arch implant impression.13-17 However, to our knowledge, no long-term clinical evidence is available yet. Moreover, obtaining a digital impression of an edentulous arch could be challenging, and there are more potential sources of error. The mobility of the mucosa, absence of teeth, and presence of saliva could impair the accuracy of the impression. In addition, during scanbody recognition via the dental software, incorrect extrapolation of the implant positions is possible. Finally, digitally combining the sets of scans might be difficult because the number of reference points in the edentulous arch is reduced. CONCLUSIONS The application of titanium and functional prototypes in our complete digital work flow confer 2 main advantages to the clinician: the ability to test efficiently the essential prosthetic parameters (that is, implant positions, occlusal contacts, esthetic parameters, and the OVD) and the opportunity to create a full-arch implant restoration in a rapid and replicable way. In addition, visit times and laboratory costs are reduced. However, obtaining a digital impression over an edentulous arch can be challenging, and further studies are required to evaluate the long-term success of this type of rehabilitation. n 554
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Dr. Monaco is an assistant professor, Division of Prosthodontics, Department of Biomedical and Neuromotor Science, Alma Mater Studiorum University of Bologna, Via S. Vitale 59, 40125 Bologna, Italy, e-mail [email protected]. Address correspondence to Dr. Monaco. Dr. Arena is a clinical instructor, Division of Prosthodontics, Department of Biomedical and Neuromotor Science, Alma Mater Studiorum University of Bologna, Bologna, Italy. Mr. Pallotti is a dental technician, Mignani Odontotecnica, Bologna, Italy.
1. Hultin M, Svensson KG, Trulsson M. Clinical advantages of computer-guided implant placement: a systematic review. Clin Oral Implants Res. 2012;23(6):124-135. 2. Tahmaseb A, Wismeijer D, Coucke W, Derksen W. Computer technology applications in surgical implant dentistry: a systematic review. Int J Oral Maxillofac Implants. 2014;29(suppl):25-42. 3. Joda T, Ferrari M, Gallucci GO, Wittneben J-G, Brägger U. Digital technology in fixed implant prosthodontics. Periodontol 2000. 2017;73(1):178-192. 4. Vercruyssen M, Laleman I, Jacobs R, Quirynen M. Computer-supported implant planning and guided surgery: a narrative review. Clin Oral Implants Res. 2015;26(11):69-76. 5. Monaco C, Ragazzini N, Scheda L, Evangelisti E. A fully digital approach to replicate functional and aesthetic parameters in implant-supported full-arch rehabilitation. J Prosthodont Res. 2018;62(3):383-385. 6. Treatment of edentulous mandible with fixed hybrid prosthesis. In: Drago C, ed. Implant Restorations: A Stepby-Step Guide. 2nd ed. Hoboken, NJ: Wiley-Blackwell; 2007:156-172.
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Dr. di Fiore is an adjunct professor, Department of Neuroscience, School of Dentistry, Division of Prosthodontics University of Padua, Padua, Italy. Dr. Scheda is a postgraduate student, Division of Prosthodontics, Department of Biomedical and Neuromotor Science, Alma Mater Studiorum University of Bologna, Bologna, Italy. Disclosure. None of the authors reported any disclosures. ORCID Number. Adolfo di Fiore: https://orcid.org/0000-0002-1766-2567.
7. Ercoli C, Geminiani A, Feng C, Lee H. The influence of verification jig on framework fit for nonsegmented fixed implant-supported complete denture. Clin Implant Dent Relat Res. 2012;14(1):e188-e195. 8. Papaspyridakos P, Kim Y-J, Finkelman M, ElRafie K, Weber H-P. Digital evaluation of three splinting materials used to fabricate verification jigs for full-arch implant prostheses: a comparative study. J Esthet Restor Dent. 2017;29(2):102-109. 9. Keerthi S, Proussaefs P, Lozada J. Clinical and laboratory steps for fabricating a complete-arch fixed prosthesis using CAD/CAM. Int J Periodontics Restorative Dent. 2015;35(4):473-480. 10. Mino T, Maekawa K, Ueda A, et al. In silico comparison of the reproducibility of full-arch implant provisional restorations to final restoration between a 3D Scan/ CAD/CAM technique and the conventional method. J Prosthodont Res. 2015;59(2):152-158. 11. Kim S, Nicholls JI, Han C-H, Lee K-W. Displacement of implant components from impressions to definitive casts. Int J Oral Maxillofac Implants. 2006;21(5):747-755.
12. Swallow ST. Technique for achieving a passive framework fit: a clinical case report. J Oral Implantol. 2004; 30(2):83-92. 13. Papaspyridakos P, Gallucci GO, Chen C-J, Hanssen S, Naert I, Vandenberghe B. Digital versus conventional implant impressions for edentulous patients: accuracy outcomes. Clin Oral Implants Res. 2016;27(4):465-472. 14. Vandeweghe S, Vervack V, Dierens M, De Bruyn H. Accuracy of digital impressions of multiple dental implants: an in vitro study. Clin Oral Implants Res. 2017; 28(6):648-653. 15. Amin S, Weber HP, Finkelman M, El Rafie K, Kudara Y, Papaspyridakos P. Digital vs. conventional fullarch implant impressions: a comparative study. Clin Oral Implants Res. 2017;28(11):1360-1367. 16. Pesce P, Pera F, Setti P, Menini M. Precision and accuracy of a digital impression scanner in full-arch implant rehabilitation. Int J Prosthodont. 2018;31(2):171-175. 17. Ahlholm P, Sipilä K, Vallittu P, Jakonen M, Kotiranta U. Digital versus conventional impressions in fixed prosthodontics: a review. J Prosthodont. 2018;27(1):35-41.
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Clinical Dentistry Digital bar prototype technique for full-arch rehabilitation on implants Carlo Monaco, DDS, MSc, PhD; Antonio Arena, DDS, MSc, PhD; Giacomo Pallotti, DT; Adolfo di Fiore, DDS, PhD; Lorenzo Scheda, DDS ABSTRACT Background and Overview. The aim of the authors in this case report was to describe a new approach to using the digital bar prototype technique for complete digital full-arch implant rehabilitation. Two combinable structures were used during the same visit as prototypes to simultaneously test the implant locations and the prosthetic parameters. Then the structures were joined together to form the final prosthesis. Case Description. After the implant integration with the immediate provisional restoration, 3 sets of digital impressions were obtained to obtain a master digital model (MDM). A stereolithographic model with implant analogs was printed on the basis of the MDM. A titanium bar with implant connections and a functional resin structure were milled on the basis of the MDM and used as prototypes. To check the accuracy of the implant impression, the titanium prototype was tried in, and clinical and radiographic tests were performed. Then the resin prototype was slid into the positional prototype and fitted to the patient, and the esthetic and occlusal properties were evaluated and refined. Definitive restoration was obtained by luting the 2 prototypes together and finalizing the prosthesis with pink resin. Conclusions and Practical Implications. The prototypes allowed the clinician to simultaneously verify the accuracy of the digital impressions and test the prosthetic parameters in 1 visit. Moreover, they were used to create the final restoration. The digital bar prototype technique also allowed for the reduction of clinical and laboratory time in a full-arch rehabilitation on implants. Nevertheless, obtaining a full-arch impression in an edentulous arch can be challenging, and further studies are necessary to evaluate the long-term success of this technique. Key Words. Dental implants; restorative dentistry; fixed prosthetics; computer-aided design and computer-aided manufacturing. JADA 2019:150(6):549-555 https://doi.org/10.1016/j.adaj.2019.01.022
igital work flows are becoming increasingly relevant in everyday practice. Intraoral digital scanning devices, digital dental software, computer-aided design and computer-aided manufacturing (CAD-CAM) technology, and other tools such as cone-beam computed tomography (CBCT) give the clinician the opportunity to acquire patient data conveniently and plan and execute complex rehabilitation procedures.1-3 With the prosthetic-driven approach for complete arch rehabilitation, all phases of treatment can be projected and carried out on the basis of the planned outcome; thus, the method is feasible and favorable in terms of allowing prediction of the final prosthetic outcome.4,5 In the traditional work flow, full-arch implant rehabilitation requires several steps.6 Once the implants are integrated, an impression of the implants is made, and the master model cast with the inserted implant analog is poured. Before creating the final framework, the accuracy of the positions of the analogs within the model must be verified. This can be done using a prototype structure made of metal abutments linked with resin, first in the model and then clinically in the patient.7,8 In this way, the locations of the implants on the patient can be compared with the positions of the analogs in the model. Then, the clinician may proceed to the next phases, and the definitive framework can
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Figure 1. Initial clinical case.
be created. After that, prosthetic and functional parameters (esthetic appearance, occlusal relationship, occlusal vertical dimension [OVD]) can be evaluated in the patient using a wax-up technique that simulates the prosthetic teeth.6,9,10 As described by Monaco and colleagues,5 within the full digital work flow, once digital impressions are obtained and the digital master model is created, a metal prototype is milled to verify the implant impression accuracy. An additional resin prototype with milled implant connections is created on the basis of the virtual wax-up to test the essential prosthetic and functional parameters (occlusal relation, esthetic appearance, OVD). However, the locations of the implants and the prosthetic parameters cannot be checked simultaneously, and the prototypes are wasted after the clinical tests. Whichever work flow is chosen, the definitive framework generally is created by means of CAD-CAM milling, and then the technician may finalize it in different ways: by means of using artificial resin or composite teeth and pink resin materials, a ceramic material layered on a metal framework, or a zirconia restoration. The aim of this case report is to describe a full digital work flow in which metal and resin prototypes are designed to be combined so that the positional and prosthetic parameters are tested simultaneously. Moreover, the prototypes are produced with definitive materials so they can be combined to create the final restoration. CASE REPORT
ABBREVIATION KEY 3D: 3-dimensional. CBCT: Cone-beam computed tomography. FDP: Fixed dental prosthesis. MDM: Master digital model. OVD: Occlusal vertical dimension. SI1: First set of impressions. SI2: Second digital impression.
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Patient selection and surgical implant procedures We describe a clinical case of an 80-year-old woman with an inadequate mandibular ceramic fixed dental prosthesis (FDP) to illustrate the digital bar prototype technique (Figure 1). We obtained informed consent from the patient. We removed the old fixed dental prosthesis, extracted the hopeless teeth, and preserved the remaining teeth to support a full-arch provisional restoration. After 6 months, we obtained digital impressions (True Definition Scanner, 3M-ESPE) of the mandibular arch with and without the provisional restoration and performed cone-beam computed tomography. We combined the digital impressions of the mandibular arch (DWOS, Dental Wings) with the Digital Imaging and Communications in Medicine file of the cone-beam computed tomography and created a digital wax-up. We produced a stereolithographic model with implant analogs (Implant model, 3D Medical Print) and a surgical guide (Digital Drill Template, 3D Medical Print). In the stereolithographic model, we placed the implant analogs on the basis of the surgical plan and created an implant-supported, metal-reinforced provisional restoration. On the day of the surgery, we removed the teeth-supported provisional restoration and placed 4 implants (4.1 RC, Straumann) in the mandible according to a fully guided protocol. The surgical guide was supported by the teeth. At the end of the implant surgery, we extracted all the teeth (Figure 2A). We immediately screwed in the multibase abutments (SRA, Straumann) with torque of 25 newton centimeters. We secured the temporary abutments to the multibase abutments and relined the implant-supported screw-retained provisional restoration with resin on the patient (Figure 2B). Then we refined the provisional restoration on the stereolithographic model and, finally, immediately loaded it on the implants (Figure 2C). JADA 150(6)
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Figure 2. A. Try-in of the surgical guide supported by teeth. B. Four implants were inserted with the surgical guide, and temporary abutments were screwed to the implants. After the implant insertion, the teeth were extracted. C. The provisional restoration was relined and immediately loaded.
Digital impression and prototype fabrication (first visit) Four months after implant surgery (Figure 3A), we obtained 3 sets of digital impressions to provide information about the esthetic and functional parameters of the provisional restoration, the gingival architecture, the occlusal relationship, and the location of the implants using a fully digital approach. We obtained the first set of impressions (SI1) by means of scanning the provisional restoration screwed to the implants, the opposite arch, and the bite. In this way, the SI1 provided information about the esthetic parameters, the OVD, and the occlusal relationship. Then we removed the provisional restoration, screwed a standardized scanbody to the multibase abutments, and obtained the second digital impression (SI2) (Figure 3B). Finally, we scanned the provisional restoration in its entirety while outside of the mouth, including the pontic elements, to determine the shape of the transmucosal pathway over the implants and the architecture of the soft tissue surrounding the restoration. Then we merged the digital impressions (DWOS, Dental Wings) and obtained a master digital model (MDM). In this phase, we extrapolated implant locations from SI2 through automatic scanbody matching. Therefore, the MDM contained information about implant location, esthetic appearance, occlusal relation, OVD, and the gingival shape. On the basis of the MDM, we obtained a 3-dimensional (3D) print of a stereolithographic master model with implant analogs (Print@Dreve, Dreve). To verify the implant impression and the esthetic and functional parameters, we used CAD-CAM to mill a titanium positional prototype (CARES, Straumann) and a resin prototype (Milling Unit M1, Zirkonzahn). We designed the resin prototype with inferior slots that perfectly matched the titanium bar and obtained it by means of milling a disk of resin material (PMMA Multi Blank Z, Anaxdent). We designed the shapes of the teeth and the occlusal features of this prototype on the basis of the digital wax-up (Figure 4A, Figure 4B). Try-in of prototypes (second visit) We tested the titanium positional prototype while it was fitted to the patient through visual inspection, the finger pressure test, and periapical radiographs (Figure 5A). Then we mounted the JADA 150(6)
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Figure 3. A. The implants after healing period with multibase abutments secured to the fixtures. B. Scanbodies were secured to implants to obtain the second digital impression.
Figure 4. A. The positional and functional prototypes were designed on the master digital model. The anatomic shapes of the resin prototype were designed on the basis of the virtual wax-up. The wax-up was created starting from the previous fixed dental prosthesis. B. Apical view of the titanium positional prototype and the resin prototype. In the titanium positional prototype, the implant connections are integrated. The resin prototype has an inferior slot that matches the titanium prototype.
resin prototype and checked and adjusted the OVD, esthetic appearance, occlusal contacts, and guidance using articulation paper and a diamond bur (Figure 5B, Figure 5C). In case of discrepancies, the metal prototype could be sectioned, splinted with pattern resin, and then laser welded. If necessary, in the stereolithographic model the unfitting analogs could be extracted, secured to prototype, and refixed with resin. In case of section of the metal prototype, the resin prototype would be sectioned as well, rewelded with resin, and then refined by the technician. Definitive restoration (third visit) After the try-in procedures, we joined the resin prototype and the titanium positional prototype to create the full-arch restoration. We luted the prototypes together (Primer SR Connect, Ivoclar, on resin prototype; Clearfil Ceramic Primer Plus, Kuraray, on titanium prototype; Panavia V5, Kuraray, as luting agent) and finalized the restoration with pink resin (Lucitone Fas-Por, Dentsply Sirona) (Figure 6A). Then the full-arch implant restoration was delivered to the patient and screwed in (25 N cm torque) (Figure 6B). We checked the occlusal and lateral contacts with 12-micrometer articulation paper and obtained periapical radiographs (Figure 7). DISCUSSION In the conventional work flow, a full-arch implant rehabilitation requires several different steps, laboratory work, and multiple clinical appointments (and, therefore, involves high costs). After the implant impression is obtained, the master cast with implant analogs is obtained. This phase is technique sensitive because it involves manually securing the implant analogs to the impression copings, in addition to pouring operations.11 Before creating the final framework, a verification prototype is necessary to validate the positions of the analogs in the master model.7,8 If the implant 552
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Figure 5. A. Periapical radiographs of the titanium positional prototype secured to the implants. B. Clinical try-in of the combined prototypes. The resin prototype allows for testing of the prosthetic parameters; that is, the esthetic appearance, occlusal contacts and guidance, and occlusal vertical dimension. C. Occlusal check with articulation paper of the functional prototype inserted into the titanium positional prototype. The occlusal scheme of the prototype was duplicated from the previous fixed dental prosthesis.
Figure 6. A. Final restoration obtained by means of luting the prototypes and finalizing with pink resin on the stereolithographic model. B. Outcome of the final restoration.
locations in the patient do not match those of the analogs in the model, the master cast needs to be adjusted. In this case, nonfitting implants are extracted and refixed in the appropriate location12; only when the master cast with implant analogs is approved can the definitive framework be casted, refined, and tested while fitted to the patient. The final steps are the try-in procedures, performed with esthetic material, to verify the occlusal and esthetic parameters. The finalization procedures can then be executed. The digital bar prototype technique allows the clinician to execute a full-arch implant rehabilitation during 3 appointments. Digital impressions are obtained at the first appointment, and 3 sets of scans are obtained to register and digitally combine the essential parameters. The prototypes and the 3D-printed model are created directly on the basis of the same
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Digital impression and Digital master model
Positional prototype
Functional prototype
Stereolithographic master model with implant analogs 2nd visit
Clinical and radiographic tests Prototypes are combined and tried in the patient* Positional prototype is tried on the model†
3rd visit
The prototypes are luted and finalized FINAL RESTORATION IS DELIVERED
Figure 7. Schematic representation of work flow of digital bar prototype technique * Clinical fitting tests are performed, and periapical radiographs are obtained. † Positional prototype is secured to the analogs in the stereolithographic model, and the fitting is evaluated. In case of nonpassive fitting, the nonfitting analogs are extracted, secured to the prototype, and refixed in the model with resin.
digital model. The creation of the milled prototypes and the printed model requires less time and is less expensive than the conventional method because it is a fully automated process. During the second appointment, the use of the 2 prototypes provides the clinician with the opportunity to check rapidly the accuracy of the impression, the suitability of the future restoration, and the adequacy of the 3D-printed model. The titanium prototype is tested while fitted to the patient, and then the functional resin prototype is mounted to verify the esthetic and occlusal parameters. Concurrently, the 3D-printed model is tested and, if a nonpassive fitting is present, it can be adjusted by removing the implant analog and refixing it with resin (or it can be reprinted). Because the positional prototype is composed of titanium alloy, it is not necessary to fabricate an additional metal framework for the definitive implant-supported restoration. Moreover, owing to the functional prototype, restorative teeth with appropriate occlusal and esthetic aspects are already in place. After the resin prototype is refined on the patient, it is luted on the titanium prototype and used in the final restoration. Thus, the laboratory phase of manual placement of artificial teeth over the framework while checking the occlusal relation on the articulator is no longer necessary. During the third appointment, the full-arch implant restoration is delivered. Digital scanning might be a reliable method in the full-arch implant impression.13-17 However, to our knowledge, no long-term clinical evidence is available yet. Moreover, obtaining a digital impression of an edentulous arch could be challenging, and there are more potential sources of error. The mobility of the mucosa, absence of teeth, and presence of saliva could impair the accuracy of the impression. In addition, during scanbody recognition via the dental software, incorrect extrapolation of the implant positions is possible. Finally, digitally combining the sets of scans might be difficult because the number of reference points in the edentulous arch is reduced. CONCLUSIONS The application of titanium and functional prototypes in our complete digital work flow confer 2 main advantages to the clinician: the ability to test efficiently the essential prosthetic parameters (that is, implant positions, occlusal contacts, esthetic parameters, and the OVD) and the opportunity to create a full-arch implant restoration in a rapid and replicable way. In addition, visit times and laboratory costs are reduced. However, obtaining a digital impression over an edentulous arch can be challenging, and further studies are required to evaluate the long-term success of this type of rehabilitation. n 554
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Dr. Monaco is an assistant professor, Division of Prosthodontics, Department of Biomedical and Neuromotor Science, Alma Mater Studiorum University of Bologna, Via S. Vitale 59, 40125 Bologna, Italy, e-mail [email protected]. Address correspondence to Dr. Monaco. Dr. Arena is a clinical instructor, Division of Prosthodontics, Department of Biomedical and Neuromotor Science, Alma Mater Studiorum University of Bologna, Bologna, Italy. Mr. Pallotti is a dental technician, Mignani Odontotecnica, Bologna, Italy.
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Dr. di Fiore is an adjunct professor, Department of Neuroscience, School of Dentistry, Division of Prosthodontics University of Padua, Padua, Italy. Dr. Scheda is a postgraduate student, Division of Prosthodontics, Department of Biomedical and Neuromotor Science, Alma Mater Studiorum University of Bologna, Bologna, Italy. Disclosure. None of the authors reported any disclosures. ORCID Number. Adolfo di Fiore: https://orcid.org/0000-0002-1766-2567.
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