Full Digital Workflow for Anterior Immediate Implants Using Custom Abutments

One of the most common treatment options for a failing anterior maxillary tooth is its extraction followed by immediate implant placement.^1,2  Such cases require careful surgical planning based on cone beam computerized tomographic (CBCT) images.³  In this context, image-guided implant surgery has been described and validated as a safe modality for single-tooth implants. Such type of surgery also can be performed within time-efficient digital workflows, in which intraoral scans are performed and combined with CBCT images, enabling the creation of a digital design of the desired implant crown.⁴  Virtual implant planning and surgical guide creation are then carried out based on the digitally designed crown, which in turn can also be 3-dimensional (3D) printed with polymethyl methacrylate materials or milled from ceramic materials.⁵ 

As described by a few recent clinical reports, full digital workflows also enable digital customization of implant abutments to match specific clinical situations.⁶  Immediate implants with custom abutments can also be immediately loaded with interim restorations, which are useful to test and confirm the desired crown design, esthetics, and soft tissue contours.^4,7  The same digital crown design can be used for both interim and definitive restorations.⁶  However, little is known on situations in which the patient is dissatisfied with the interim crown shape, and a new set of intraoral scans and stereolithographic images can be used for creating a new digital crown design, based on updated soft tissue contours and the patient preferences, to obtain a satisfactory definitive implant restoration.

Thus, the aim of this case report is to describe a full digital workflow for single immediate implant placement in the esthetic area using the same custom abutment for different interim and definitive restorations.

A male 54-year-old patient presented at the dental clinic of this study with a failing maxillary right central incisor. Both maxillary and mandibular arches, as well as the occlusion of the patient, were scanned using an intraoral scanner (Trios; 3Shape). Such initial intraoral scans were first imported to a computer-aided design (CAD) software (Dental Design Premium, 3Shape), in which the digital image of the original tooth to be extracted was removed from the dental arch in the scan. Then, a virtual custom abutment and a diagnostic virtual restoration were designed at the site of future extraction and immediate implant placement by using virtual wax-up tools in the same CAD software (Figure 1). The rationale of designing a custom abutment before an extraction and subsequent soft tissue healing is to offer improved conditions for the creation of an emergency profile (if needed, a new custom abutment could be designed after post-extraction soft tissue healing). All images obtained with the aforementioned procedure were saved in STL file format.

The patient also underwent CBCT (Orthophos XG 3D, Dentsply Sirona) with an appropriate imaging protocol (0.2-mm voxel, 120 kVp, 3 to 8 mA). A treatment plan for implant placement was then established by using intraoral and cross-sectional CBCT images. For this purpose, all STL files previously obtained were imported in an implant planning software (Implant Studio; 3Shape) to be superimposed with the CBCT data (Figure 2). In such software, we confirmed that the virtual wax-up was matching the shape of the extracted tooth, since it was visible in the initial CBCT scan superimposed. Virtual implant position was then established considering position of future implant-supported crown, retention type (screw-retained, which requires a position slightly palatal to the midcrest), emergency profile, and bone availability (also taking into consideration the location of the nasopalatine canal), striving to respect an axial load distribution. The same implant planning software was then used to generate the digital design of a tooth-supported surgical guide by using software tools for choosing drill sleeve size, the desired extension of tooth support, and then for automatic generating and exporting the digital shape of the surgical guide as a STL file.

The previously designed interim restoration and surgical guide were fabricated with poly (methyl methacrylate) resin by using a 3D printer (PROBO; Dio Co). The custom titanium abutment, in turn, was fabricated by using a milling machine (TRIONE; Dio).

After atraumatic extraction of the failing maxillary central incisor (Figure 3), we immediately placed the implant (UFII, 3.3 × 10 mm; Dio) by using the surgical guide (Figure 4). The remaining buccal gap was then filled with particulate xenograft (Bio-Oss; Geistlich, Figure 5). We tried the custom titanium abutment and the implant interim restoration. After confirming satisfactory adaptation, we removed them and luted the interim restoration with resin-based luting agent (RelyX Unicem; 3M ESPE) in the screw-retained abutment out of the oral cavity (Figure 6a and b). The rationale of using a resin-based luting agent was to offer stability and confidence for the patient. The interim restoration luted to the abutment was then connected on the implant body (Figure 7).

After a 6-month healing period, the patient reported dissatisfaction with the interim crown shape, and a new digital crown design was developed by intraoral scanning the same custom abutment alone and screwed to the implant fixture, without using any scan bodies. For this purpose and due to the resin cementation, we removed the interim restoration from the custom abutment using cylindrical drills and connected the custom abutment to the implant body to scan with the intraoral scanner (TRIOS; 3Shape, Figure 8). To start the new digital crown design, we used the mirroring functionality of the software (Implant Studio; 3Shape) to model the anatomical design of the corresponding tooth of the other side with satisfactory symmetry and esthetics. The new digital crown design was then adjusted according to the desired definitive crown shape. The definitive restoration was then produced with a minimum thickness of 1.2 mm by milling a monolithic lithium disilicate glass-ceramic block (IPS e.max CAD, Shade A3,5 LT – Low Translucence; Ivoclar Vivadent AG) and luted (Relyx U200 A3 opaque, 3M ESPE) to the custom abutment. The resulting one-piece restoration was then screwed to the implant to rehabilitate its site (Figure 9).

The full digital workflow presented herein involves the combination of intraoral and CBCT scans. As described in the literature, such combination requires a software interface to communicate STL files from intraoral scans and original digital communication in medicine (DICOM) files from CBCT.^8–11  In this context, the digital crown should be designed prior to implant surgical planning, and converted to a STL file. Accordingly, the surgical guide will also be based on the digital crown design, which allows for 3Dprinting or milling of implant restorations before implant placement.^12,13 

In contrast with the present article, other digital workflow methodologies have been described involving diagnostic casts or impression scanning.^14,15According to the aforementioned studies, the use of tabletop scanners has been reported as satisfactory for digital implant therapy. Similarly, the use of different intraoral scanning devices does not seem to affect precision and accuracy of the results, despite controversial results that have been reported for users with different degrees of experience and expertise.^16,17 

To our knowledge, only a few studies on full digital workflows have described the use of digitally designed custom abutments.^6,18  A recent study¹⁹  has found acceptable results for 3 different digital workflows using titanium and zirconia custom abutments, which support the present results. Another previous study⁶  has described the use of interim poly-methyl methacrylate custom abutments for soft tissue management around implants, also obtaining satisfactory results. In the present technique report, a second intraoral scan is performed after soft tissue management facilitated by the use of a 3D-printed interim implant restoration. The new STL file resulting from the second intraoral scan can be associated with the previous STL from the initial intraoral scan. The aforementioned images are used to design the definitive implant restoration. Since the custom abutment was also digitally designed as an STL file, no implant scan bodies are required for intraoral scanning.

Within the limitations of this case report, the present findings suggest that full digital workflows using custom titanium abutments and interim restorations are useful for anterior immediate implant cases.

Abbreviations

CAD:

computer-aided design

CBCT:

cone beam computerized tomography

DICOM:

digital communication in medicine

The authors declare they have no conflict of interest related to this study. No funding was available for this study.