Introduction

To the uninitiated, a maxillary incisor site may seem the ideal spot for placement of an immediate implant (IIP), but nothing could be further from reality. Assuming that a flapless, minimally traumatic extraction has been achieved without damage to the universally thin buccal plate of bone, the site chosen for initiation of the implant osteotomy will depend on the existing sagittal root socket position. The socket apex is rarely appropriate as the initiation site, the majority of situations requiring initiation into some point along the dense, palatal socket wall. As discussed in Chapter 1 of this book, based on cone beam computed tomography (CBCT) scans from 150 patients, Gluckman et al. [1] published a useful classification of sagittal/radial root positions to assist in choosing the appropriate initiation point. Their class I root positions (root located centrally in its socket) would be ideal, as osteotomies could begin through the root socket apex (Figure 7.1), but this scenario rarely (around 6% of cases) presents. The great majority (≥ 75%) of radial/sagittal tooth root positions are class II (root apices inclined facially with either a thick or thin cortical bone plate; Figure 7.2). Class II‐A sockets having thicker buccal bone make them better candidates for IIP than class II‐B (buccal bone < 1 mm in thickness) [2]. The risk with IIP would be creating a fenestration in the thin buccal bone apically, particularly if there is a buccal concavity, in trying to set up the situation for a screw‐retained crown. Such a fenestration could lead to unfavorable buccal soft tissue recession and compromised esthetics [3, 4].

Having established whether an IIP is feasible based on where osteotomy preparation should begin, the next difficulty is always that the dense palatal cortical socket wall will usually favor unwanted buccal drift of the surgical burs, especially with freehand implant placement surgery [5]. Even computer‐assisted implant placement using surgical guides with metal bur sleeves cannot totally eliminate this drift because of the need for bur‐to‐metal sleeve tolerance requirements [6]. If this bur drift is significant, the implant osteotomy may very well not end up in the ideal anatomic, prosthetically driven, three‐dimensional (3D) position with an inadequate buccal gap or “jumping distance” (> 2 mm from the implant platform to the inner aspect of the buccal plate of bone) for the grafting needed to thicken the buccal bone ensuring long‐term soft and hard tissue stability [4, 7]. Bur drift also increases risk for fenestration of a thin buccal plate [8], especially if there is a buccal ridge concavity (Figure 7.3). While a small fenestration might not impede achievement of implant primary stability, it could easily trigger sufficient bone remodeling to impact final esthetic outcomes negatively including excessive remodeling of the facial bone and significant gingival recession.

The Concept of Anatomically Guided Implant Placement

Rodriguez‐Tizcareno and Bravo‐Flores [9] were among the first to suggest that more accurate 3D positioning of immediate implants could be achieved with the assistance of anatomical guidance by beginning osteotomy development before rather than after tooth extraction. Others [10] confirmed benefits for this approach with immediate molar implants, making it a current widely accepted molar IIP protocol [11]. Some sort of guidance is also needed for IIPs in the esthetic zone, and the usual approach has been to use surgical guides, which give better outcomes than freehand implant placement [12]. Taking the cue from the usefulness of anatomical guidance at molar sites, we recently published a proof‐of‐principal report and suggested protocol for anatomically guided development of osteotomies at maxillary incisor sites [13], with the rationale that this could greatly limit buccal bur drift. The suggested procedural steps included:

1. Preoperative radiographic assessment with periapical radiographs and CBCT to determine the existing radial root position and ensure appropriate case selection.
2. Inclusion criteria:
   1. healthy, non‐smoking or minimal cigarette smoking subjects practicing good oral hygiene with a maxillary central or lateral incisor indicated for extraction
   2. thick gingival biotype and intact buccal socket wall; thinner tissues may require augmentation using autogenous connective tissue grafts or alternatives.
3. Preparing a matrix impression of the existing or restored tooth crown to assist in immediate temporization (Figure 7.4).
4. Decoronating the tooth at the level of the cementoenamel junction (CEJ) and marking the osteotomy entry point in the former cingulum with a round bur and depth of 2 mm.
5. Beginning the osteotomy through the established entry point with an initial penetration or Lindeman bur and further developing it with a 2 mm twist bur.
6. Taking a check periapical radiograph to verify the desired bur direction.
7. Continuing the osteotomy development with the twist bur to a depth sufficient to engage at least 2 mm of bone apically followed by a further check radiograph.
8. Removing the remaining root fragment maintaining a flapless approach and minimal trauma.
9. Enlarging the osteotomy to the desired width (slightly undersized osteotomies preferred); consideration should be given to using an appropriate osseodensification bur in a counterclockwise direction to ensure good implant stability.
10. Placing the implant and ensuring adequate primary stability (≥ 35 Ncm).
11. Grafting the buccal peri‐implant gap with a mineralized allograft or xenograft.
12. Temporizing the implant using the original or modified crown using the prepared matrix as a guide.
13. Ensuring the temporary is out of occlusion and supports the original soft tissue profile.

As indicated, if the original crown of the condemned tooth is not fully intact but restorable, it should be rebuilt with a flowable composite resin to approximate the tooth’s original normal shape and size. Afterwards during temporization, the putty matrix (Figure 12.4) will assist in placing the crown such that it will support and maintain the original soft tissue contours and provide some early non‐occlusal loading as an osteogenic stimulus. This early loading also will accelerate achievement of secondary implant stability measured in Implant Stability Quotient values [14] and help to minimize subsequent marginal bone loss [15]. Alternatively, customized, screw‐retained temporary crowns [16] or customized healing abutments [17–19] can be used with the same goals.

The first and proof of principle, anatomically guided case performed was for a maxillary lateral incisor replacement in a healthy 53‐year‐old non‐smoking male patient (Figure 7.5a,b). The tooth crown first was rebuilt with flowable composite to allow fabrication of the required putty matrix. Then, to ensure that the extraction would indeed be atraumatic and that all four socket walls remained intact, the restored tooth was extracted with minimal trauma using a flapless approach. This allowed the crown to be sectioned from the root extraorally near the CEJ using a high‐speed carbide bur. The same bur was then used to establish an osteotomy entry point (3 mm wide × 3.5 mm deep) into the cingulum of the tooth after which the root was reinserted into its socket (Figure 7.5c). While bracing the reinserted root buccally with a periosteal elevator, the osteotomy was initiated by drilling into the prepared cingulum insertion point with a new precision bur (Figure 7.5d). Once the intended path of this bur was established, it was replaced by a 2‐mm diameter pilot bur (Figure 7.5e), widening the osteotomy using a pumping motion to avoid binding with the root surface and to approximately two‐thirds the root length, at which point a check radiograph was obtained (Figure 7.5f). Having this confirmation of the osteotomy direction, drilling was continued with the same bur through the remaining root length and into apical bone, with the intention of placing the planned implant at a final depth of 2 mm subcrestally. The root was then removed again for final osteotomy drilling to depth with a 3.5‐mm diameter implant bur and the implant inserted (Figure 7.5g,h). Insertion torque was recorded as greater than 35 Ncm.

Peripheral venous blood had been collected from the patient just before surgery to be able to prepare the liquid phase of platelet‐rich fibrin for use in making “sticky bone” [20] from mineralized ground cortical allograft. This converted the particulate graft into a malleable paste rich in growth factors (Figure 12.5i). After placing the implant, the buccal gap was packed with this prepared graft extending supracrestally to help in supporting the soft tissues buccally (Figure 7.5j). A temporary snap abutment was trimmed and inserted into the implant to receive the original crown as the transitional restoration (Figure 7.5k). Teflon tape was placed in the screw access hole and over the graft material to allow finalization of the temporary in the mouth (Figure 7.5l). Luxatemp^® (Zenith/DMG) then was injected around the abutment and into the hollowed‐out crown, which was then seated within the putty matrix and allowed to set in the mouth (Figure 7.5m). The matrix and provisional restoration were removed for customization extraorally, including contouring with flowable light‐cured composite resin on the abutment interface with the provisional. The crown then was adjusted in the mouth and inserted with hand tightening of the retention screw (Figure 7.5n). Further adjustment ensured no occlusal contact in excursive movements. The post‐operative radiograph is seen in Figure 7.5o while Figure 7.5p shows the soft tissue healing at 3 weeks. Figure 7.5q shows the radiographic status of the restored implant after 4 months in function while Figures 7.5r,s document the radiographic and clinical status 14 months later.

A periapical radiograph of a lateral incisor in a second patient treated with the original protocol is shown in Figure 7.6a. The patient was a 21‐year‐old man who had suffered earlier trauma to his maxillary anterior teeth, three of which had required endodontic treatments. The left lateral also needed to have a full crown supported by a post/core, which subsequently was dislodged. After the tooth was determined to be no longer restorable, CBCT images (Figures 7.6b,c) suggested a thin, but intact, buccal plate with a class III radial root position. The root was extracted and then reinserted to allow initiation of the osteotomy through the cingulum (Figure 7.6d). Subsequently, after re‐extracting the root and completing the osteotomy, a 3.5‐mm diameter by 13‐mm long ^® implant was inserted with initial torque of 35 Ncm, and the existing crown used as a transitional restoration (Figure 7.6e). A graft of “sticky” bone allograft was used to graft the buccal gap as with case one. A periapical radiograph was taken subsequently, at the time of final prosthesis insertion (Figure 7.6f).

After these two cases had been completed successfully, the protocol was modified slightly to include osteotomy initiation and site development up to the pilot drill before the condemned root was removed. A sample patient treated with this modified protocol is shown in Figure 7.7a,b. The condemned tooth was again an endodontically treated maxillary left lateral incisor. The gingival tissue labially was thick and adequately keratinized and the local ridge anatomy appeared satisfactory for immediate implant placement. The initial radiograph suggested that the tooth had been restored after the endo treatment using a carbon fiber post (Figure 7.7c). After some slight luxation, osteotomy preparation proceeded as usual before extracting the root. The osteotomy entry point in the cingulum region was created with a #701 FG carbide surgical bur. The same bur, rather than the more delicate precision bur, was then used to initialize the osteotomy to a depth of 5–6 mm to make it easier to complete it with a 2‐mm twist drill. Once the twist drill had reached the approximate length of the root, a periapical radiograph was taken to verify its orientation mesiodistally (Figure 7.7d), which showed that the presence of the carbon fiber post had resulted in significant deviation of the bur. Therefore, the decision was made to extract the root before proceeding. A side‐cutting Lindemann bur was then used to reorient the pilot osteotomy more distally before continuing with a 3.0‐mm diameter Densah^® bur (Versah Corporation, Jackson, MI) in counterclockwise direction to complete the drilling and ensure adequate initial stabilization for a 3.5‐mm diameter by 13‐mm NobelReplace^® (Nobel Biocare, Zurich, Switzerland) implant. This led to a favorable final implant position (Figure 7.7e). Before removing this last bur, however, the buccal gap was densely packed with “sticky bone allograft” [20]. The grafting was extended crestally beyond the osteotomy to help in supporting the peri‐implant soft tissues, as recommended by Chu et al. [21], and this was covered with a concentrated growth factor [20] compressed clot as a poncho before inserting the patient’s original crown as temporization (Figure 7.7f). The clinical and radiographic situations after final implant restoration are seen in Figure 7.7g,h. The immediate transitionalization and the dual zone grafting resulted in maintenance of peri‐implant soft tissues [21].

A fourth patient came as an emergency with a loose crown at his maxillary left central incisor, as shown in the panoramic radiograph in Figure 7.8a and periapical in Figure 7.8b. After removing the crown, extensive recurrent caries were found, and the tooth was diagnosed as non‐restorable. To keep the tooth, esthetically unfavorable crown lengthening would have been necessary (Figure 7.8c). The loose crown was removed, and the osteotomy begun through the tooth root using the same approach as in case three initial use of a #701 FG carbide bur to a depth of around 6 mm followed by the 2‐mm twist drill to full depth (Figure 7.8d), subsequent gentle removal of the tooth root, and finalizing the osteotomy with a 4.0 mm‐diameter Densah bur operated in counterclockwise direction to complete the drilling for a 4.3‐mm diameter by 13 mm Nobel Replace implant (Figure 7.8e). Before removing this last bur, the buccal gap was densely packed with “sticky bone allograft” extended crestally beyond the osteotomy to help in supporting the peri‐implant soft tissues. Initial stability was recorded as greater than 35 Ncm and the original crown was modified to provide an immediate temporary without occlusal contact and free of excursive contacts (Figures 7.8f,g). Finally, Figures 7.8h–j show the clinical and radiographic status 2 years following placement of the definitive restoration.

A final case is included as the clinician was able to obtain a follow‐up CBCT. The patient was a 32‐year‐old man who presented with his maxillary left lateral incisor crown missing after its fracture (Figure 7.9a). An osteotomy was developed using the cingulum region as the initial entry point (Figure 7.9b), and a check radiograph was taken to establish the implant orientation after using the pilot drill (Figure 7.9c). Following implant insertion/gap grafting, the site was left without a transitional restoration (Figure 7.9d). A CBCT obtained 6 months later (Figure 7.9e) showed excellent implant positioning and favorable retention of buccal bone. The clinical status of the final treatment outcome after 2 years in function is shown in Figure 7.9f.

Discussion and Conclusions

Experts agree that placement of immediate implants at maxillary incisor sites is challenging as it requires perfect prosthetically driven, 3D osteotomy creation to ensure a stable, esthetically pleasing, long‐term outcome without significant facial soft tissue recession. In most situations following tooth extraction, this requires initiation of the osteotomy into some point along the palatal socket wall, and a major risk here is bur drift facially, even when computer assistance is used. [6] An anatomically guided drilling approach can minimize this risk by initiating the osteotomy while the tooth root remains in situ (Figure 7.10). Ideally, treatment planning should include preoperative CBCT assessment of the planned IIP site. In the examples presented, drilling was through an entry point in the cingulum area of the decoronated incisors and following the coronoapical root orientation. As the sagittal/radial root orientations of the majority (around 80%) of maxillary incisors are classes I or II after Gluckman et al. [1], this approach seems likely to be suitable in most intended maxillary incisor IIP sites, meaning that the final prosthetic restorations can be screw retained.