Esthetic Rehabilitation of Maxillary Anterior Teeth, Including an Immediate Provisionalization with an Implant-Supported Fixed Dental Prosthesis

This report describes the case of a patient who required rehabilitation of their maxillary anterior teeth following a traumatic injury through a physical altercation. The decision was made to extract the maxillary central incisors and maxillary right lateral incisor, perform immediate implantation on the maxillary right lateral incisor and left central incisor areas, and place a three-unit immediate provisional restoration. Predesigned virtual teeth enabled efficient fabrication of the immediate provisional restoration following the implant placement. After a sufficient healing period with periodic check-ups, final impressions were made using a digital approach, with meticulous care taken to preserve the gingival architecture around the sites of rehabilitation. Thus, the custom abutments and definitive restoration were placed without eliciting an uncomfortable feeling in the patient. Both esthetic and functional outcomes were satisfactory. Reduced soft tissue volume around the implant restoration was observed, primarily within the two months post-extraction/implantation, based on superimposition of the serial scan data. Soft tissue volume changes in the present case suggest the need for controlled clinical studies of three-dimensional changes of gingival contours after extraction and/or implantation.


Introduction
The application and development of digital technologies have extended the scope of implant dentistry [1,2]. Radical improvements in diagnostic imaging devices, as well as computer-aided design/computer-aided manufacturing (CAD/CAM) equipment, have enabled dentists to implement prosthetically-driven implant placement [3][4][5][6][7][8][9]. For many years, it has been recommended to perform a diagnostic wax-up procedure at the site of future implant placement, in order to achieve this "top-down" approach [10][11][12][13]. This procedure can now be completed by virtually arranging the teeth in implant-planning or CAD software [14,15]. Subsequent procedures following implant placement, such as making final impressions for implant prostheses, can also be performed by a digital approach with an intraoral scanner and a scan body [3,16].
Immediate placement of a fixed-type provisional crown following single-implant placement is regarded as a treatment option that is predictive of satisfactory outcomes, provided that the case selection is conducted appropriately [17][18][19]. This may benefit patients from an esthetic perspective, because it eliminates the edentulous stage. Moreover, when fabricated with an accurate three-dimensional (3D) position, the provisional crown can help to maintain the height of the 2 of 8 interproximal papillae [20,21]. Immediate provisionalization using one-piece implants was suggested as a treatment strategy to restore partially edentulous anterior teeth in the mandible or lateral teeth in the maxilla, [22,23]. However, there have been few reports regarding the immediate placement of a fixed-type provisional restoration after multi-implant placement in the maxillary anterior tooth region [24]. Bone grafting around the gap between the immediately placed implant and the surrounding bone has been suggested to preserve soft tissue contours and buccal plate thickness [25]. With advances in digital technology, reverse engineering software can provide a comprehensive visualization of dimensional changes that may have occurred after extraction.
This report describes the rehabilitation of an anterior tooth region with multiple implants-including an immediate provisionalization with an implant-supported fixed dental prosthesis in a fully digital workflow-and demonstrates three-dimensional changes in gingival tissues around the sites of rehabilitation over a one-year period.

Case Report
This study was conducted in accordance with the Declaration of Helsinki, and the protocol was approved by the Ethics Committee of Yonsei University Dental Hospital (2-2019-0006). An 18-year-old man requested rehabilitation of teeth that had experienced trauma on the maxillary arch after a physical altercation ( Figure 1). Although he had received emergency root canal treatments on the maxillary central incisors and maxillary right lateral incisor within a few days of this event (approximately one month before his visit to our clinic) to relieve pain, these teeth exhibited a poor prognosis. The diagnosis was a Class III crown/root fracture on the maxillary right central and lateral incisors, and a Class III crown fracture with a horizontal root fracture on the maxillary left central incisor. Hence, the decision was made to extract these three teeth, perform immediate implantation on the maxillary right lateral incisor and left central incisor areas, and place a three-unit immediate provisional restoration. papillae [20,21]. Immediate provisionalization using one-piece implants was suggested as a treatment strategy to restore partially edentulous anterior teeth in the mandible or lateral teeth in the maxilla, [22,23]. However, there have been few reports regarding the immediate placement of a fixed-type provisional restoration after multi-implant placement in the maxillary anterior tooth region [24]. Bone grafting around the gap between the immediately placed implant and the surrounding bone has been suggested to preserve soft tissue contours and buccal plate thickness [25]. With advances in digital technology, reverse engineering software can provide a comprehensive visualization of dimensional changes that may have occurred after extraction. This report describes the rehabilitation of an anterior tooth region with multiple implantsincluding an immediate provisionalization with an implant-supported fixed dental prosthesis in a fully digital workflow-and demonstrates three-dimensional changes in gingival tissues around the sites of rehabilitation over a one-year period.

Case Report
This study was conducted in accordance with the Declaration of Helsinki, and the protocol was approved by the Ethics Committee of Yonsei University Dental Hospital (2-2019-0006). An 18-yearold man requested rehabilitation of teeth that had experienced trauma on the maxillary arch after a physical altercation ( Figure 1). Although he had received emergency root canal treatments on the maxillary central incisors and maxillary right lateral incisor within a few days of this event (approximately one month before his visit to our clinic) to relieve pain, these teeth exhibited a poor prognosis. The diagnosis was a Class III crown/root fracture on the maxillary right central and lateral incisors, and a Class III crown fracture with a horizontal root fracture on the maxillary left central incisor. Hence, the decision was made to extract these three teeth, perform immediate implantation on the maxillary right lateral incisor and left central incisor areas, and place a three-unit immediate provisional restoration.  The maxillary and mandibular diagnostic casts obtained from the preliminary impressions were scanned with a tabletop scanner (Identica Blue, Medit Co., Seoul, Korea) ( Figure 2). The teeth that were to be extracted were removed from the maxillary diagnostic cast to arrange the virtual teeth within CAD software (Exocad DentalCAD version 2015.03, Exocad GmbH, Darmstadt, Germany). The maxillary and mandibular diagnostic casts obtained from the preliminary impressions were scanned with a tabletop scanner (Identica Blue, Medit Co., Seoul, Korea) ( Figure 2). The teeth that were to be extracted were removed from the maxillary diagnostic cast to arrange the virtual teeth within CAD software (Exocad DentalCAD version 2015.03, Exocad GmbH, Darmstadt, Germany). The virtual teeth were designed on the modified diagnostic cast to ensure that they exhibited no occlusal contacts with antagonists. Together with the remaining teeth on the same arch, the arranged virtual teeth were saved as a unit in a standard tessellation language (STL) file format. A cone-beam computed tomography scan was taken to design and fabricate a surgical guide. The guide was designed in the implant planning software (Implant Studio version 2.17.1.4, 3Shape, Copenhagen, Denmark) and fabricated using a 3D printer (Zenith U, Dentis, Daegu, Korea).
The virtual teeth were designed on the modified diagnostic cast to ensure that they exhibited no occlusal contacts with antagonists. Together with the remaining teeth on the same arch, the arranged virtual teeth were saved as a unit in a standard tessellation language (STL) file format. A cone-beam computed tomography scan was taken to design and fabricate a surgical guide. The guide was designed in the implant planning software (Implant Studio version 2.17.1.4, 3Shape, Copenhagen, Denmark) and fabricated using a 3D printer (Zenith U, Dentis, Daegu, Korea). Bone-level implants (Straumann BLT (Institut Straumann AG, Basel, Switzerland) 4.1 × 12 mm implant on right lateral incisor area and Straumann BL (Institut Straumann AG) 4.1 × 12 mm implant on left central incisor area) were placed using a flapless approach. Subsequently, the scan bodies (Geo Scanbody, GeoMedi, Uiwang-si, Korea) were connected to the implants and digital intraoral impressions were made using an intraoral scanner (Trios 3, 3Shape, Copenhagen, Denmark) ( Figure  3). The gaps between the implants and bony walls were filled with a deproteinized bovine bone mineral (Bio-Oss, Geistlich Pharma AG, Wolhusen, Switzerland). A bioresorbable collagen membrane (Bio-Gide, Geistlich Pharma AG) was then carefully applied to cover the graft material [26]. For the future pontic (right central incisor) area, a ridge preservation technique was performed using a demineralized bovine bone mineral with 10% collagen (Bio-Oss Collagen, Geistlich Pharma AG) without primary soft tissue closure [27,28]. Bone-level implants (Straumann BLT (Institut Straumann AG, Basel, Switzerland) 4.1 × 12 mm implant on right lateral incisor area and Straumann BL (Institut Straumann AG) 4.1 × 12 mm implant on left central incisor area) were placed using a flapless approach. Subsequently, the scan bodies (Geo Scanbody, GeoMedi, Uiwang-si, Korea) were connected to the implants and digital intraoral impressions were made using an intraoral scanner (Trios 3, 3Shape, Copenhagen, Denmark) ( Figure 3). The gaps between the implants and bony walls were filled with a deproteinized bovine bone mineral (Bio-Oss, Geistlich Pharma AG, Wolhusen, Switzerland). A bioresorbable collagen membrane (Bio-Gide, Geistlich Pharma AG) was then carefully applied to cover the graft material [26]. For the future pontic (right central incisor) area, a ridge preservation technique was performed using a demineralized bovine bone mineral with 10% collagen (Bio-Oss Collagen, Geistlich Pharma AG) without primary soft tissue closure [27,28].
The provisional restoration was prepared during the time the periodontist was performing these supplementary procedures. A new project file was created in the same CAD software and the digital intraoral impressions were imported. The initially predesigned virtual teeth and modified maxillary diagnostic cast assembly were then imported into the software and superimposed over the digital intraoral impressions. The arbitrarily arranged virtual teeth, which appeared on the project file as a default function of the software, fit onto the predesigned virtual teeth to automatically find their predetermined positions by employing a series of software functions (Video S1). Minor adjustments were made to finalize the design of the provisional restoration.
3). The gaps between the implants and bony walls were filled with a deproteinized bovine bone mineral (Bio-Oss, Geistlich Pharma AG, Wolhusen, Switzerland). A bioresorbable collagen membrane (Bio-Gide, Geistlich Pharma AG) was then carefully applied to cover the graft material [26]. For the future pontic (right central incisor) area, a ridge preservation technique was performed using a demineralized bovine bone mineral with 10% collagen (Bio-Oss Collagen, Geistlich Pharma AG) without primary soft tissue closure [27,28]. Two sets of provisional restorations from the same design were prepared; they were milled with a poly(methylmethacrylate) resin block (VIPI Block Trilux, Dental VIPI Ltda, São Paulo, Brazil) and bonded to the titanium link abutments (Geo Multibase Abutment, GeoMedi, Uiwang-si, Korea) with a resin cement (Multilink N, Ivoclar Vivadent, Schaan, Liechtenstein). One set of restorations was placed in the patient's mouth on the day of the implant surgery ( Figure 4). This immediate provisional restoration was sufficiently adjusted to provide relief above the ridge preservation area and allow interpapillary growth. Most importantly, occlusion was evaluated and adjusted in order to avoid contacts with antagonists, which inevitably compromised the esthetics to some extent. The provisional restoration was prepared during the time the periodontist was performing these supplementary procedures. A new project file was created in the same CAD software and the digital intraoral impressions were imported. The initially predesigned virtual teeth and modified maxillary diagnostic cast assembly were then imported into the software and superimposed over the digital intraoral impressions. The arbitrarily arranged virtual teeth, which appeared on the project file as a default function of the software, fit onto the predesigned virtual teeth to automatically find their predetermined positions by employing a series of software functions (Video S1). Minor adjustments were made to finalize the design of the provisional restoration.
Two sets of provisional restorations from the same design were prepared; they were milled with a poly(methylmethacrylate) resin block (VIPI Block Trilux, Dental VIPI Ltda, São Paulo, Brazil) and bonded to the titanium link abutments (Geo Multibase Abutment, GeoMedi, Uiwang-si, Korea) with a resin cement (Multilink N, Ivoclar Vivadent, Schaan, Liechtenstein). One set of restorations was placed in the patient's mouth on the day of the implant surgery ( Figure 4). This immediate provisional restoration was sufficiently adjusted to provide relief above the ridge preservation area and allow interpapillary growth. Most importantly, occlusion was evaluated and adjusted in order to avoid contacts with antagonists, which inevitably compromised the esthetics to some extent. The other set of provisional restorations was placed in the patient's oral cavity 2 months after the initial visit ( Figure 5). At this time, minor adjustments were conducted for the restoration, which resulted in better esthetic outcomes. Final impressions were made in the digital approach, with meticulous and specific emphasis on preserving the gingival architecture around the sites of rehabilitation. Custom abutments and the definitive porcelain-veneered zirconia fixed dental prosthesis were fabricated and placed in the patient's mouth ( Figure 6). Both esthetic and functional outcomes were satisfactory.  The other set of provisional restorations was placed in the patient's oral cavity 2 months after the initial visit ( Figure 5). At this time, minor adjustments were conducted for the restoration, which resulted in better esthetic outcomes. Final impressions were made in the digital approach, with meticulous and specific emphasis on preserving the gingival architecture around the sites of rehabilitation. Custom abutments and the definitive porcelain-veneered zirconia fixed dental prosthesis were fabricated and placed in the patient's mouth ( Figure 6). Both esthetic and functional outcomes were satisfactory. The provisional restoration was prepared during the time the periodontist was performing these supplementary procedures. A new project file was created in the same CAD software and the digital intraoral impressions were imported. The initially predesigned virtual teeth and modified maxillary diagnostic cast assembly were then imported into the software and superimposed over the digital intraoral impressions. The arbitrarily arranged virtual teeth, which appeared on the project file as a default function of the software, fit onto the predesigned virtual teeth to automatically find their predetermined positions by employing a series of software functions (Video S1). Minor adjustments were made to finalize the design of the provisional restoration.
Two sets of provisional restorations from the same design were prepared; they were milled with a poly(methylmethacrylate) resin block (VIPI Block Trilux, Dental VIPI Ltda, São Paulo, Brazil) and bonded to the titanium link abutments (Geo Multibase Abutment, GeoMedi, Uiwang-si, Korea) with a resin cement (Multilink N, Ivoclar Vivadent, Schaan, Liechtenstein). One set of restorations was placed in the patient's mouth on the day of the implant surgery ( Figure 4). This immediate provisional restoration was sufficiently adjusted to provide relief above the ridge preservation area and allow interpapillary growth. Most importantly, occlusion was evaluated and adjusted in order to avoid contacts with antagonists, which inevitably compromised the esthetics to some extent. The other set of provisional restorations was placed in the patient's oral cavity 2 months after the initial visit ( Figure 5). At this time, minor adjustments were conducted for the restoration, which resulted in better esthetic outcomes. Final impressions were made in the digital approach, with meticulous and specific emphasis on preserving the gingival architecture around the sites of rehabilitation. Custom abutments and the definitive porcelain-veneered zirconia fixed dental prosthesis were fabricated and placed in the patient's mouth ( Figure 6). Both esthetic and functional outcomes were satisfactory.  To record the dimensional changes around the rehabilitated areas, digital intraoral impressions were made five times: immediately after extraction, and at 2, 4, 6, and 12 months after the date on which the extraction and implantation were performed; these corresponded to specific time points, as shown in Table 1. Soft tissue dimensional changes around the sites of rehabilitation were visualized as color maps using the best-fit alignment function in the reverse engineering software (Geomagic Control X version 2018.0.1, 3D Systems, Cary, NC, USA) (Figure 7). To record the dimensional changes around the rehabilitated areas, digital intraoral impressions were made five times: immediately after extraction, and at 2, 4, 6, and 12 months after the date on which the extraction and implantation were performed; these corresponded to specific time points, as shown in Table 1. Soft tissue dimensional changes around the sites of rehabilitation were visualized as color maps using the best-fit alignment function in the reverse engineering software (Geomagic Control X version 2018.0.1, 3D Systems, Cary, NC, USA) (Figure 7).

Discussion
An appropriate future site for restoration was determined by performing diagnostic virtual tooth arrangements in the CAD software. These arrangements were reevaluated with respect to the relationship of the underlying alveolar bone in the implant planning software [15]. With regard to the immediate placement of provisional restorations, previous methods directly applied flowable composite resin onto the temporary abutment, or made impressions by using polyether or polyvinylsiloxane materials [29][30][31][32]. However, these methods may cause irritation to soft tissues and

Discussion
An appropriate future site for restoration was determined by performing diagnostic virtual tooth arrangements in the CAD software. These arrangements were reevaluated with respect to the relationship of the underlying alveolar bone in the implant planning software [15]. With regard to the immediate placement of provisional restorations, previous methods directly applied flowable composite resin onto the temporary abutment, or made impressions by using polyether or polyvinylsiloxane materials [29][30][31][32]. However, these methods may cause irritation to soft tissues and carry the risk of contamination because they involve manipulation around the surgical field.
In the present case, the immediate provisional restoration was produced without contact with conventional impression materials, which could minimize the risk of contamination. In addition, peri-implant soft tissues may have been less stimulated because the restoration was fabricated in a fully contoured form at a dental laboratory and did not require chairside relining.
Several techniques have been suggested to accurately transfer the peri-implant gingival tissue around the provisional restoration into the definitive cast [33][34][35][36][37][38][39]. In contrast to these physical methods, a digital approach was adopted in the present case. The intraoral impression was obtained first with the provisional restoration inserted state, followed by the trimming around the provisional restoration using a cutting tool in the software. Then, the peri-implant soft tissue impressions, with and without scan bodies, were added on to the previous digital intraoral impression. This procedure reduced the amount of time-dependent peri-implant tissue shrinkage [40]. The custom abutments and definitive restoration were placed without eliciting an uncomfortable feeling in the patient.
Considering the patient's young age, future residual adult growth-which occurs very slowly over decades-may cause infraocclusion of the implant restoration [41][42][43]. Hence, the patient was informed of the need for maintenance adjustments and the potential requirement for a new prosthesis in the future. Chair time was reduced because of the comprehensive teamwork and the use of predesigned virtual teeth data.
The labial gingival contours clearly indicated reduced volume after extraction over the 1-year follow-up period in the present case, although efforts to rehabilitate the soft tissue contours were accompanied by implant placement. The most significant reduction in soft tissue contours occurred during the first 2 months postoperation. Controlled clinical studies are necessary to elucidate both short-and long-term changes of gingival contours after extraction and/or implantation.

Conclusions
The present report described the satisfactory rehabilitation of an anterior tooth region with multiple implants on which a provisional restoration was placed immediately after the surgery. The provisional restoration was easily fabricated by utilizing predesigned virtual teeth data in the CAD software. Dimensional changes around the sites of rehabilitation were visualized with reverse engineering software over a 1-year period, from the time of implant placement to the time 6 months after placement of the definitive restoration.
Funding: This study was funded by the Yonsei University College of Dentistry (6-2018-0014).

Conflicts of Interest:
The authors declare no conflict of interest.