Introduction

Many patients visit the dental clinic for treatment, including patients with fractured or extracted teeth due to trauma, congenital tooth loss, and insufficient tooth amount due to caries. Above all, in the case of single tooth loss in the maxillary anterior region that does not require restoration of the adjacent remaining teeth, the difficulty of treatment is very high because restoration must be performed to achieve esthetic harmony with the adjacent teeth [1,2]. The advantages of single tooth implant restoration are that it decreases the risk of caries and root canal treatment, prosthesis fracture, and loss of adjacent teeth that traditional fixed partial prostheses, and reduces the degree of alveolar bone loss after tooth extraction [3]. However, as a disadvantage, there are local contraindications depending on whether the implant is placed or not, depending on the shape of the bone, the proper form of the prosthesis, and the mobility of the adjacent teeth [4,5]. The available bone depth should be able to be measured radiographically using a radiographic stent. It should be evaluated whether the labio-lingual width is sufficient to place the implant, and the maxillary anterior region should be carefully observed as concavities on the labial side. In addition, the amount of attached gingiva must be measured, and the degree of recession of the interdental papilla must be accurately identified to produce an esthetic prosthesis in order to achieve a successful prosthesis [6,7]. For this, alveolar bone augmentation should be performed if necessary, and stable maintenance of the transplanted bone is essential to ensure a successful prognosis in the future [8-10].

In this case, the esthetic implant was treated through guided bone regeneration (GBR) and connective tissue graft (CTG) at the same time as the removal of the residual root in the maxillary anterior region where alveolar bone was insufficient due to the progress of alveolar bone resorption.

Case Description

The patient in this case was a 22-year-old female patient who visited our dental hospital after a traumatic fracture of the left central incisor of the maxilla 9 years ago (Fig. 1). Patient had no mobility and caries activity of adjacent teeth, and planned to place a single tooth implant rather than a bridge restoration, considering the age and patient’s needs. After taking radiographic stent computerized tomography after oral examination and diagnosis, patient planned implant placement immediately after extraction of the remaining root, and required GBR and CTG due to the long period of loss (Fig. 2). The patient was fully informed about the treatment plan and procedure before treatment, and agreed to the entire treatment procedure.

After extraction of the residual root of the maxillary left central incisor, as a result of confirming that the buccal alveolar bone was thin, an implant fixture (TS III; Osstem, Seoul, Korea) was placed 2 mm below the residual bone after ridge expansion using osteotome. GBR was performed using a titanium mesh (SmartBuilder; Osstem), and primary CTG was performed after collecting connective tissue from the palatine side, and platelet rich fibrin was inserted (Fig. 3). Before the operation, the vestibular depth was not deep, and it became shallower due to the postoperative GBR. Since bone grafting was performed on the bone resorption area, artificial teeth were connected to adjacent teeth using G-fix (GC Co., Tokyo, Japan) to minimize irritation (Fig. 4). After about 6 months of osseointegration, the second surgery was performed, and after the titanium mesh was removed, a secondary CTG was performed on the buccal side (Fig. 5). After that, prosthetic restoration was performed after a two-month stabilization period.

Impression was made for provisional restoration, and the emergence profile was formed by measuring the upper right central incisor for symmetry and esthetics (Fig. 6). After connecting the temporary abutment, preparations were made along the established margins, and wax-up for provisional restorations was performed. After indexing the wax-up tooth us-ing a putty-type vinyl polysiloxane impression material (Exafine Putty Type; GC Co.), opaque resin was used so that the metal of the temporary abutment was not visible, and the provisional restoration was formed using bis-acryl resin (Luxatemp; DMG, Hamburg, Germany) (Fig. 7).

After rough shape formation using a margin trimmer, flowable composite resin (3M ESPE, St. Paul, MN, USA) was built up on the buccal side and a screw type provisional restoration was fabricated according to the emergence profile. The progressive provisional restoration was molded on the patient, and the gingiva was formed through the prosthesis correction process for about 2 months (Fig. 8). After proper gingival formation, preparation for final impression was carried out. The patient’s emergence profile was duplicated by removing the gingiva from the model and connecting the modified provisional restoration to form gingiva. After that, the impression copings were connected, and a customized coping was made using acrylic resin (Pattern Resin; GC Co.) to obtain final impressions (Fig. 9).

For the final prosthesis, a computer aided design/computer aided manufacturing customized zirconia-titanium connecting abutment (ZirPlus; Kuwotech, Gwangju, Korea) was used for the anterior esthetics, and the crown was made with an esthetic zirconia block (Zirmon TS; Kuwotech) (Fig. 10). The patient was satisfied with the size and shape (Fig. 11), and there was no gingival recession and bone resorption after 2 years followup period (Fig. 12).

Discussion

While the posterior implant mainly aims to restore the masticatory function through osseointegration, the maxillary anterior single tooth implant restoration aims to achieve harmony with the surrounding soft and hard tissues through osseointegration as well as aesthetic restoration. However, due to the limitations of implants compared to natural teeth, single anterior tooth implant restoration is one of the most difficult treatments [11].

Age and cost should be considered first to recover a single tooth implant in the maxillary anterior region. Age is generally postponed until at least 15 years for women and 18 years for men [12]. Rythén et al. [13] said that growth and development were over if there was no further growth through 6 months of follow-up observation. Brägger et al. [14] concluded that implant reconstruction is a better option financially in the long run from the perspective clinical management, as a result, the cost would also exceed the break-even point if the implant prosthesis could be maintained for about 7 years when comparing 3 unit bridges and other prostheses. In the case of the traditional fixed partial prosthesis, a loss of 2 to 32% was reported in 3 to 23 years, and in the case of the resin-adhesive fixed prosthesis, a loss of up to 54% was reported in 2 to 11 years. On the other hand, in the case of implant restoration, failures of up to 9% were reported during the observation period of 2 to 6.6 years [15]. Therefore, Priest [16] reported that implantretaining prostheses were the most suitable as a result of comparing various types of prostheses in repairing a single tooth.

The biological width of the implant is about 1 mm longer than that of a natural tooth, but the soft tissue healing ability is less than that of a natural tooth, so the labial gingival margin and interdental papilla around the implant prosthesis are more prone to soft tissue retraction by about 1 mm. In addition, the distribution of blood vessels and fibers in tissues around the implant is also less capable of maintaining soft tissue than in natural tooth. Therefore, the mesio-distal space is an important factor that greatly influence the long-term success rate of implant treatment [17]. If the width of the interdental bone between the implant and adjacent teeth is small, the resorption of marginal bone increases in the long term, so a width of at least 1.5 mm is required. In general, since the diameter of the implant fixture neck is larger than the diameter of the implant fixture body, it is a reality that the amount of interdental bone remains smaller.

Tarnow et al. [18] reported the amount of interdental papilla recovery for the distance from the natural tooth to the interdental bone and the adjacent contact point. On the contrary, it was possible to recover 100% within 5 mm, the recovery amount decreased significantly as the distance increased. Jemt [19] classified the index according to the amount of interdental papilla, and the average soft tissue height was 3.85 mm, and 12% were more than 5 mm. Therefore, it is necessary to make an appropriate provisional restoration to form the gingiva. When placing an implant, the emergence profile may vary depending on the location of the bucco-lingual restoration, and correction can be attempted through the abutment emergence profile molding. Steigmann et al. [20] stated that implants placed on the buccal side can thicken the soft tissue by concave the abutment, and the implants placed on the palatal side can convex and push the soft tissue toward to buccal side.

The placement location of implant can also be determined depending on whether the prosthesis is the cemented type or the screw retained type. In the case of screw retained type, it is recommended to implant the fixture slightly lingual position so that the screw hole is in the anterior tooth cingulum. For angle of the fixture in the maxillary anterior region, it is good to direct the fixture toward the incisal tip of the mandible. In the case of cemented type, it is better to place it slightly labial side at this time. And it is recommended to plant it to match the direction of the horizontal plane of the tooth. That is, the extension line of the fixture should pass through the incisal tip of the tooth to be restored [21]. In particular, in order to make an esthetic prosthesis, the greater the difference in width between the tooth and the implant, the deeper the fixture must be planted to make an aesthetic prosthesis. That is, as the width is similar, it may be planted closer to the cervical region. In general, it is recommended to place the fixture 2 to 4 mm below the cementoenamel junction of the adjacent teeth. The mesio-distal position of the fixture is affected by bone morphology, root proximity, accessibility, etc. It is better to place it in the middle of the prosthesis to be restored, that is, the deepest part of the cervical margin [11].

The provisional implant prosthesis should be able to be modified and reproducible before the restoration of the final prosthesis is restored. Soft tissue correction is possible on a provisional restoration, and Priest [16] proposed to correct the shape of the soft tissue by correcting the temporary prosthesis with four concepts. De Rouck et al. [22,23] formed the gingiva similarly to the adjacent teeth by correcting the soft tissue descending below the gingiva due to the provisional restoration with excessive buccal prosthesis molding. Regarding the period of the provisional restoration, Misch [24] said that soft tissue should be corrected for about 2 to 3 months, and Elian et al. [25] said that the provisional restoration should be used for about 2 months. It is clear that adjustments must be made to achieve the best results according to the patient’s condition and surrounding tissue.

In order to reproduce the appearance of the adjusted provisional restoration and the shape of the gingiva on the final restoration, a customized impression coping must be made to take a final impression. In this case, the metal abutment could be seen through due to the thin gingival margin, so a customized zirconia-titanium connection abutment was fabricated. It is reported that biocompatible and esthetic zirconia implant abutment can be used clinically in esthetic areas including anterior teeth [26,27].

In this case, despite the accompanying alveolar bone graft, it was difficult to completely regenerate the interdental papilla due to the long distance between the interdental bone and the adjacent contact point during the molding of the provisional restoration. The width and diameter of the adjacent teeth were similar, and the goal was to form the gingival level of the buccal side during provisional restoration correct for emergence profile. The final prosthesis was restored with zirconia, a biocompatible material. Monolithic zirconia for anterior restoration has improved the chipping problem of existing veneered zirconia restorations, and its transparency has been improved to increase esthetics [28]. In order to make the color similar to the adjacent teeth, only coloring and glazing were performed referring to the shade guide (Vitapan classical; VITA Zahnfabrik H. Rauter GmbH and Co., Bad Sackingen, Germany). When evaluating the final restoration in the patient’s mouth, the gingival zenith position evaluation showed a similar degree to the adjacent teeth, and the patient was also satisfied with the color and shape.

In the case of gingival recession and alveolar bone defects due to tooth loss for a long period of time in a single tooth defect in the maxillary anterior region, it is not easy to obtain esthetic results of a single implant prosthesis. In this case, an esthetic implant was treated through GBR and CTG at the same time as immediate implantation after extraction from the maxillary anterior region with alveolar bone resorption. During the provisional restoration period, the gingiva was made similar to the gingiva of the adjacent teeth through appropriate gingival correction and molding. We report that the patient was satisfied with the restoration of the lost area and consented to the entire treatment process.