Introduction

While successful placement of single‐tooth immediate implants in the esthetic zone can be learned by a clinician already experienced with traditional delayed implant procedures, placement of multiple immediate implants in the anterior maxilla generally requires greater knowledge and experience, and is sometimes best managed as a team approach between experienced specialists with a clear understanding of the treatment complexity [1]. The costs are significant, and therefore satisfying patients’ esthetic expectations will define the success of the rehabilitation.

It goes without saying that cone beam computed tomography (CBCT) is essential in planning and executing multiple immediate implant placement (MIIP) treatments, which will ideally include immediate non‐occlusal loading using transitional naturally contoured fixed prostheses with good marginal integrity to help in maintaining the extracted tooth soft tissue profiles [2]. Maintenance or enhancement of soft tissue contours including interdental papillae and interdental bone contours must be a priority. Digital planning of the preferred implant sites and number of implants should be done with the patient’s CBCT files and an implant planning software. At the very least, a tooth‐supported, computer‐based static surgical guide should be prepared to replicate the implant positions planned with the software and help guide the surgical burs in developing suitable osteotomies. Otherwise, making significant changes in osteotomy direction relative to the socket profiles for immediate implant placement (IIP) can be a daunting task. A virtual or actual “wax‐up” should be prepared well in advance to allow the patient to accept the future restoration before undertaking treatment. A full assessment beforehand also should be made of the soft tissue phenotype including the existing width of keratinized tissue as well as the vertical thickness of the supracrestal soft tissue (keratinized tissue height from bone crest to the coronal point of the junctional epithelium), which has been termed the “supracrestal tissue attachment” (STA) [3]. The STA should be thicker by ≥ 1 mm than the biologic width around natural teeth [4], or if not, it should be thickened as part of the treatment. Ultimately, an adequately thick gingival phenotype (STA) will be at least as beneficial as the post‐treatment buccal bone thickness in maintaining successful long‐term esthetics [5, 6]. One group of investigators has calculated that the threshold for STA thickness that would limit crestal bone loss is almost 3 mm (i.e. 2.88 mm) [7]. This thickness is important to maintain soft tissue stability at the crown margins and mask any grayish discoloration that might arise from the underlying metal if titanium abutments are used.

The choice of implant type, length, and diameter appropriate for each failed tooth meant to be replaced with an implant should be determined in advance based on individual socket dimensions determined in the CBCT images, recognizing that for any implant placed a buccal gap of ≥ 2 mm, depending on the thickness of existing buccal plate, must be left for hard tissue grafting to minimize post‐treatment resorption. Tapered implants with aggressive threads (e.g. NobelActive^®, Nobel Biocare Services AG, Zurich, Switzerland) are often recommended to improve initial implant stability [8]. Alternatively, standard implants can be placed using osseodensification burs [9] with the same goal in mind. The appropriate implant depth of placement will be dependent on the implant type chosen. For example, if “bone level” (this terminology is deceptive) implants with internal conical connections are planned, they should be inserted subcrestal (i.e. not at bone level) by approximately 2 mm (or even deeper in the esthetic zone) as this will automatically thicken the STA by approximately the same amount and help to limit or eliminate the risk of crestal bone loss later [10]. If an implant with a hexagonal connection is planned, it likely will experience some micro‐movements under function, and therefore should be placed more or less epicrestal and a plan made to add a connective tissue graft or an allogeneic substitute to thicken the STA.

The plan should include which tooth sockets will or will not receive implants. While one implant per tooth to allow individual (non‐splinted) crowns might be considered, for example if socket shielding is employed [11], the associated costs and certain biological concerns could be prohibitive, making fixed prostheses with fewer implants perhaps in combination with partial extraction therapy for pontic sites [12], an alternate approach. If possible, with the exception of two maxillary central incisors (Figure 3.3.1), placing two implants side by side in the esthetic zone should be avoided as great difficulty will subsequently arise in reforming adequate inter‐implant papillae. When an implant is positioned next to a natural tooth, implant‐tooth papilla reformation will benefit from the height of the tooth’s periodontium. However, when two implants are placed side by side, the height of the inter‐implant crestal bone will end up being much more apical and therefore unable to foster reformation of normal, esthetically pleasing papillae [13]. In most cases, only 2, 3, or 4 mm of soft tissue height (average 3.4 mm) can be expected to form over the inter‐implant bone crest even where the implants were placed 3 mm apart to preserve bone as much as possible. Therefore, rather than placing two implants adjacent to each other, a more appropriate option would be to have an ovate pontic between them, and to thicken its underlying soft tissue with soft tissue grafting to help in simulating papillary formation. This would certainly be appropriate to replace maxillary lateral incisors since these sites very often have deep buccal concavities [14] adding the risk of buccal plate perforation during osteotomy preparation.

The importance of anticipating and planning in advance for possible complications in the treatment plan cannot be stressed enough. This will help to minimize stress for the surgeon as possible solutions for arising complications will have already been considered. It is well recognized that the greater the stress arising during a procedure, the harder it is for the clinician to focus on what really matters in dealing with complications [15].

One key goal in placing multiple immediate implants in anterior maxilla is to retain or regenerate as far as possible the original alveolar boney housing and soft tissue contours of the condemned teeth, recognizing that as soon as teeth are removed bone resorption and with it, soft tissue changes will begin [16]. Therefore, if fixed prostheses are planned, leaving one or more extraction sockets without implants, efforts to minimize alveolar shrinkage at these sites must be included in the plan. One way to do this can be to do socket preservation grafting with mineralized, slowly resorbing particulate bone substitute materials [17]. Another approach can be to do partial extraction therapy [18] maintaining and submerging tooth roots or employing “socket shielding” (i.e. leaving only a thin shell of the original tooth buccally and/or inter‐proximally and packing the remaining socket with hard tissue substitute to maintain ridge volume. A 2021 literature review and meta‐analysis suggested no differences in implant failure between socket‐shield and conventional techniques for IIP placement in the esthetic zone. However, a lower marginal bone loss and higher pink esthetic scores were found for the socket‐shield technique [19].

Case Selection

Unless the clinician and patient are prepared for major alveolar reconstruction, only those patients who are losing teeth due to advanced caries, endodontic lesions, root fracture, root resorption, cemental tears, or horizontal crown fracture at or below the gingival margin should be considered for MIIP. Teeth being lost due to well‐established periodontal disease likely should not be considered for MIIP treatment. Kolerman et al. [20] reported retrospective data for a group 39 patients in whom 118 MIIPs had been “immediately” (24–72 hours after implantation) restored with transitional prostheses. After functioning for a mean of 32.2 ± 18 months, implant survival was 100%. However, marginal bone loss was higher where extractions were due to periodontitis compared with those due to caries (e.g. mean mesial loss of 1.37 mm vs. 1.01 mm, p = 0.001). There was also a higher ratio of recessions and missing papillae in those patients with periodontitis. It should be noted, however, that the treatments were done between 2005 and 2012 when there was much still to be learned about protocols for placing multiple immediate implants. For example, full mucoperiosteal flaps were raised rather than currently preferred flapless approaches.

As a general rules three‐dimensional correct positioning is very important, in particular in cases where multiple implants are planned. In addition, where freehand surgery is planned, parallel placement of fixtures using paralleling devices or pins is essential (Figure 3.3.2).

Another important caution in cases of freehand multiple immediate maxillary anterior implants is to avoid placing implants in embrasure areas, which will have major detrimental impact on esthetics and ability to practice adequate daily hygiene (Figure 3.3.3).

Another reason to avoid placing implants for all the missing teeth is that mesiodistal socket dimensions may be inadequate to maintain the crucial minimum distance of 1.5 mm between implant shoulders and approximating teeth [21]. This distance is necessary to maintain bone and sufficient blood supply to support papilla preservation between implant and tooth. In the bucc‐palatal dimension, the effort should always be made to place implants of appropriate diameter towards the palatal socket wall to: (i) leave the important buccal gap of 2–3 mm (depending on the existing thickness of buccal cortex) for hard tissue grafting; and (ii) permit the placement of screw‐retained restorations. It should be noted, however, that the latter aim is now less crucial following the introduction of abutments with angulated screw access channels (e.g. angulated screw channel solutions, Nobel Biocare) [22] and implants themselves with a comparable feature (e.g. Co‐Axis^®, Southern Dental Implants, Irene, South Africa) [23] (see also Chapter 12). As already stated, should it be necessary to have two adjacent implants in the rehabilitation, there needs to be a minimum distance of 3 mm between them to preserve the inter‐implant bone, although platform switching is useful here if slightly less than 3 mm is available [24]. Apicocoronally, leaving a distance of 5 mm between future contact points and inter‐proximal bone crests will best replicate good papillary regeneration [25]. Should bicuspid sites be involved, implants placed here should have a slight buccal inclination to ensure good emergence profiles.

Further Sample Cases

Figure 3.3.4a depicts a case where an anterior three‐unit conventional bridge had failed and the approach taken was to place two IIPs to replace the bridge. After sectioning the bridge, flapless extractions of the two abutment teeth were successfully done and two implants placed with parallelism (Figure 3.3.4b).

Sample case three was a patient who presented with remnants of only five remaining natural teeth and wanted a full arch rehabilitation. The five teeth each received an IIP, together with three others healed edentulous sites (Figure 3.3.5).

The next example is of a patient whose previous conventional fixed prostheses in both arches needed replacement (Figure 3.3.6a). Because of the extensive existing bone defects, full flaps were required for proper assessment and management (Figure 3.3.6b). In total, eight implants were placed, including three immediate implants. There was a very large bone defect in the right posterior and the “shell technique” was used to allow effective hard tissue grafting [26] (Figure 3.3.6c, d). The grafted sites then were covered with resorbable collagen membranes secured with sutures anchored to the apical periosteum (Figure 3.3.6e), and the flaps repositioned with tension‐free suturing (Figure 3.3.6f). Ultimately, the patient received a hybrid fixed prosthesis to complete the rehabilitation of his maxilla (Figure 3.3.6g, h).

The final case presented here is that of a 50‐year‐old man who required removal of his remaining maxillary teeth, in this case due to advanced cervical caries. After raising conservative buccal and palatal full thickness flaps, the digitally planned and designed foundation portion of a stackable surgical guide was secured to the maxilla with bicortical screws (Figure 3.3.7a). All remaining teeth were decoronated and the planned pontic sites prepped for root submergence [18] in a concave subcrestal manner using large round carbide and diamond burs with a straight shank (Figure 3.3.7b).

Next, the teeth planned for replacement with immediate implants were prepared using the socket‐shield technique [12], retaining a 1–1.5 mm thick fragment of the buccal root and periodontal ligament attachment at the level of the alveolar crest. The goal here was to retain the “bundle bone” and periodontal ligament attachment buccally to minimize resorption of the buccal plate.

After preparation of the shields and pontic sites, the secondary layer of the stackable guide was secured to the foundation base (Figure 3.3.7c), and a combination of traditional and osseodensification burs [27] were used to develop the osteotomies at the socket‐shield‐retained extraction sites (Figure 3.3.7d). Implants then were placed in their predetermined positions followed by their connection to multi‐unit abutments and temporary cylinders (Figure 3.3.7e), and the prepared full arch, printed, scalloped prosthesis luted to the cylinders with flowable resin material (Figure 3.3.7f). The scalloped interim prosthesis was designed to develop during soft tissue healing (Figure 3.3.7g,h) the subcritical and critical contours of the future gingival margins (Figure 3.3.7i) [28] for the final prosthesis (Figure 3.3.7j; see also Chapter 10).

Conclusions

Placement of multiple immediate implants in anterior maxilla generally requires substantial knowledge and experience, and often is best managed as a team approach between specialists. At the very least, a tooth‐supported, computer‐based, static surgical guide should be prepared to replicate the implant positions that were treatment planned with computer software helping to guide development of the osteotomies. A virtual or actual “wax‐up” should be prepared well in advance to allow the patient to accept the future restoration before undertaking treatment. One key goal in placing multiple immediate implants in anterior maxilla is to retain or regenerate as far as possible the original alveolar boney housing and soft tissue contours of the condemned teeth. MIIP treatments will ideally include meticulous preparation of splinted, transitional prostheses, with good marginal integrity to support and maintain soft tissue profiles and carefully loaded with appropriate occlusal adjustments so as to minimize off‐axis loading during initial site healing.