Introduction

Clinical use of immediate dental implants by experienced implant surgeons has become an acceptable approach in replacing condemned teeth, although it may increase risk of failure compared with standard delayed implant procedures [1]. Immediate implantation has the advantages of requiring fewer surgeries, an increased ability to place the implant in its ideal three‐dimensional position, and the likelihood of having a positive psychological impact on the patient [2]. However, most reports on immediate implant placements (IIPs) are from studies in sites other than anterior mandible [3]. A recent exception is the 2023 report by Pedrinaci et al. [4] Their work was based on 186 implants (delayed or immediate placements of incisors and canines only) used in anterior mandibles in a total of 108 patients followed for a mean of 5.48 years (range 0.1–11.34 years). Implants were either single or multiple and were restored with fixed partial implant‐supported restorations. The cumulative implant survival rate at 11.34 years was 90.9%, although IIP (odds ratio, OR, 2.75; p = 0.08) and immediate implant loading (OR 8.8; p = 0.02) showed higher risk of failure than late implant placement or loading. Also of interest was that implants placed using static, computer‐assisted surgical guides showed less risk of failure compared with freehand implant placement (OR 0.18; 95% confidence interval, CI, 0.02–1.37; p = 0.09). Reasons for early failures could have been compromised bone quantity and quality attributed to factors such as previous periodontal disease or traumatic tooth extraction resulting in insufficient initial implant stability, as well as factors such as inadequate width of keratinized tissue, insufficient gingival thickness around the implant collar [5], poor patient compliance, or improper prosthesis design.

Lateral incisors (45.1%) or canines (37.1%) in mandible were more frequent implant sites than central incisors (17.8%). Screw‐retained restorations were used in 38.2%, while 48.0% had cemented restorations, with no mention of retention type for 29 implants (15.6%). A total of 128 (68.8%) implants had diameters ≤ 3.3 mm while 42 (22.6%) had diameters ≥ 4.1 mm. Most of the 17 failures occurred early, but 3 were later (≥ 3 years post‐implantation). Males accounted for 79.6% of the failures, while moderate cigarette smoking (< 10 per day) appeared not to be a factor, supporting very old data that mandibular anterior appears to have the lowest implant failure risk for smokers compared with other sites such as posterior maxilla [6]. Not unexpectedly, 15 of the 17 failures happened in patients with a history of periodontitis.

The challenges of using immediate dental implants in anterior mandibles are related to local anatomy, including the risk of serious bleeding by damage to anterior lingual arterial anastomoses from the sublingual, submental, and incisive arteries. This plexus of blood supply is located in close proximity to the lingual cortical plate of the mandibular anterior area [7]. A potential emergency includes developing a hematoma that leads to airway obstruction as result of lingual plate perforation and arterial damage during implant osteotomy preparation [7]. All preventive measures must be taken to prevent such a complication.

Damage to the mental foramina, including their anterior nerve loops, is also a risk (see Chapter 2). An anterior loop is often present where the inferior mandibular nerve extends superiorly and/or inferiorly before terminating at the mental foramen, with a reported prevalence of 10.4–94%. It can be unilateral or bilateral with no side predominance, and its average length is 0.89–7.61 mm, with males having longer anterior loops than the females [8].

Lingual concavities are present in canine sites and at premolars, the latter enabling attachment for mylohyoid muscle and housing the sublingual glands. However, the risk of lingual plate perforation is low here [9], although possibly higher at second premolar sites where 23% of jaws have undercut (U‐shaped) borders. Because the lingual concavity in the premolar region houses the sublingual gland, there have been reports of “plunging ranula” (i.e. damage to the ducts of the glands with rapidly increasing size due to leakage of saliva) in the floor of mouth, developing within 2 days to 1 week and extending into the neck [10, 11]. Timely referral to an oral maxillofacial surgeon is most likely necessary with diagnosis requiring magnetic resonance imaging and/or computed tomography [11]. Dental implant removal may or may not be necessary, but since the swelling will not subside on its own, surgical removal of the affected sublingual gland could be required.

In contrast, the incisor–canine regions often show the presence of buccal concavities. According to Chan et al. [12], 77% of mandibular canines show this configuration. No specific percentage of buccal plate perforations in anterior mandible could be found in the literature, but it certainly occurs, and is more frequent than lingual plate perforation. The risk of unfavorable deviations in implant site angulation with buccal plate perforation can occur with freehand osteotomy preparation, but is reduced using surgical guides [9]. One way to minimize unintentional changes in implant angulation at mandibular premolar sites can be to prepare the osteotomy through the root before extraction [13], as was also recently reported for maxillary incisors [14] (see also Chapter 7).

As is the case in anterior maxilla, thin buccal plates can be a problem for IIPs in anterior mandible, making contour bone augmentation at the time of implant placement a common necessity [15]. Cone beam computed tomography studies have documented the average buccal plate thickness of 60% of anterior mandibular teeth to be less than 1 mm (0.95 mm) in the coronal one‐third but increasing more apically to 1–3 mm (Figure 4.1a) [16]. Mandibular premolars also follow similar osseous patterns, but buccal plate thickness in mandible is known to increase from anterior to posterior regions [17] (Figure 4.1b).

Average alveolar socket dimensions likewise are often unfavorable, particularly in the mesiodistal dimension. The smallest mesiodistal dimensions occur at incisor sites (Table 4.1), often making immediate implants impossible to place. If, for example, both central incisors need to go, likely the only option is to place one implant with a cantilever, remembering that should two adjacent implants be used in this situation, an inter‐implant distance between two implants needs to be 3 mm. Alternatively, every effort should be made to retain questionable mandibular incisors for as long as possible, with frequent periodontal maintenance and splinting, either with wire or, if feasible, by a cast gold alloy lingual apron. In regard to both buccolingual and mesiodistal dimensions of the incisors, implant diameter becomes a crucial parameter given that a buccal gap of ≥ 2 mm should be left between the buccal of the implant platform and the endosseous side of the buccal cortical plate, and that distances of at least 1.5 mm ideally need to be left between each implant and its adjacent tooth/teeth.

Esthetic and soft tissue complications can be issues with immediate implants placed in anterior mandible although less so than in the maxillary esthetic zone. Improperly positioned IIPs can disrupt overall esthetic harmony and soft tissue integrity. Uneven gingival contours and loss of interdental papillae with the formation of “black triangles” can be associated with incorrect crown contours. In addition, the distance from the crest of bone to the contact point of each implant placed next to a natural tooth should be 5 mm or less to achieve appropriate papilla fill [19].

Soft tissues deficiencies are common in anterior mandible and may require soft tissue grafting either before or after implant placement to increase keratinized tissue and peri‐implant soft tissue thickness and promote long‐term implant health (Figure 4.2) [5, 20].

Hof et al. [21] reported esthetic outcomes of 43 anterior mandibular single‐tooth implants in 15 women and 28 men using esthetic indices (pink esthetic score [PES], papilla index, subjective esthetic score [SES]), as well as patient satisfaction using visual analog scale ratings. Restoration of the implants was either by single crowns or tulip‐shaped double crowns, with added pink acrylic on single implants to replace two adjacent incisors. Clinical and radiological parameters (implant and crown dimensions, pocket depth, bleeding on probing, plaque, keratinized mucosa, marginal bone level, and distance to adjacent [21] teeth) were tested for influence. PES (pink esthetic score) was based on seven variables including mesial papilla, distal papilla, level of soft tissue margin, soft‐tissue contour, alveolar process deficiency, soft‐tissue color, and soft‐tissue texture with scores of 0, 1, or 2; 0 represented the poorest and 2 the best outcome. A perfect objective score was 14 points [22]. Papilla height was assessed using the papilla index: 0 meaning no papilla present, 1 being less than a half papilla height present, and 2 being over half of the papilla height being present, 3 denoting total papilla formation, and finally 4 indicating hyperplastic papillae [23]. The SES was used to classify mid‐facial gingival recession, with 1 being recession of ≤ 0.5 mm or less, 2 as mid‐facial recession between 0.5 and 1 mm, 3 showing the recession to be 1–1.5 mm and 4 assessed as mid‐facial recession > 1.5 mm [24]. PES of 10–14 were recorded in only 42% of implants, while the median papilla index was 2. SES scores varied with minimal recession at 51% and greatest at 23% of cases. Overall, incisor single crowns achieved superior esthetics to tulip‐shaped crowns.

An alternative way to replace two mandibular incisors with a single implant is simply to add a cantilever. Nelluri et al. [25] presented 3‐year findings of this approach in 30 patients each missing two adjacent mandibular incisors reporting survival of 95%. The biggest issue was screw loosening in 81% of the restorations as an early complication only. In another more recent 2023 study, Kolerman and colleagues [26] presented retrospective outcomes of 75 anterior mandible IIPs placed, together with guided bone regeneration (GBR) in 42 patients, since buccal bone was compromised in all cases (< 1 mm) often with dehiscences or fenestrations. Single crowns were used in only 21.4% (9/42) of sites, with the remaining 78.6% being restored with fixed partial bridges including single implants with single cantilevers.

Patients were enrolled in personalized maintenance programs including evaluation by the same periodontist and scheduled scaling/prophylaxis by dental hygienists every 3–6 months, and had been followed for anywhere from 3 to 8 years (mean of 6.95 ± 1.78 years). Implants were evaluated for esthetics, marginal bone loss, and biologic and prosthetic complications. For implants that had passed 8 years in function, the survival rate was 100%. However, smokers (≤ 10 cigarettes/day) had greater marginal bone loss than non‐smokers by that time (2.98 mm vs. 1.23 mm, respectively, p = 0.016). At 3 years, only 13.3% of the implants had mesial papillae, 36.0% had distal papillae, and 16.0% had visible abutment exposure, but this would have been affected by the reduced bone height of the adjacent periodontally compromised teeth. It could also have been impacted by the fact that implant‐to‐tooth distances had been < 2 mm (mean 1.37 ± 0.81 mm; range 0.3–4.6 mm) for 24% of the sites.

Most importantly, and despite the regular follow‐ups, peri‐implantitis (bleeding and/or suppuration on gentle probing, probing pocket depths of ≥ 6 mm, and crestal bone loss ≥ 3 [27]) was seen in 20.7% (6 of 29) of patients whose implants had reached 8 years in function. Peri‐implant mucositis was seen in 13 patients (45%). All the prostheses had been cement‐retained, which may have contributed to these unfavorable outcomes. More likely the reason was that all 42 patients originally had a history of serious or very serious periodontitis [28] (stage 3 or 4 [29]), with bone loss exceeding two‐thirds of the root length in anterior mandible. Interestingly, in a 2020 systematic review of peri‐implantitis occurrence, Song et al. [30] found that the condition was more often diagnosed in anterior as opposed to posterior mandible.

Sample Cases

Sample Case Two

This patient required the removal of his right mandibular central and lateral incisors, but given space limitations, the proper solution was felt to be placement of a single implant in the central incisor socket (Figure 4.4a–d), later to carry a cantilever for the adjacent lateral incisor. The buccal gap and buccal undercut were grafted with hard tissue substitute and the soft tissues repositioned.

Patient three wished to have his four mandibular incisor teeth replaced with an implant‐supported fixed prosthesis. (Figure 4.5a,b) Implants were inserted towards the lingual in both lateral incisor sockets, taking care to leave adequately sized buccal gaps for hard tissue grafting. Thereafter, using a vestibular incision subperiosteal tunnel access (VISTA) approach, soft tissue tunneling under the periosteum was done to create a space for buccal bone augmentation (Figure 4.5c). A collagen membrane was teased into the developed tunnel (Figure 4.5d) and bone substitute biomaterial packed into the space between the barrier and underlying buccal bone (Figure 4.5e), with the purpose of eliminating the buccal concavity in the region and avoid future thinning of the buccal plate, and the VISTA incision sutured to contain the graft material (Figure 4.5f). A radiograph of the outcome 1 year after final restoration is shown in Figure 4.5g. A clinical image of the outcome 1 year after final restoration is shown in Figure 4.5h.

A fourth example is that of a 65‐year‐old male patient wishing to have full mouth reconstruction due to extensive occlusal wear and loss of vertical dimension (Figure 4.6a). He had previously received a single implant and crown to replace his mandibular right central incisor (Figure 4.6b). The treatment plan included removal of the remaining mandibular incisors and these teeth were extracted without raising a mucoperiosteal flap (Figure 4.6c). Osteotomies were prepared at both lateral incisor sites (Figure 4.6d) and two narrow‐diameter bone‐level implants successfully inserted (Figure 4.6e). The clinical view of the final full‐mouth restorations at the time of delivery is depicted in Figure 4.6f. All three implants were splinted to support a four‐unit fixed prosthesis, given the patient’s known parafunctional habits. A radiograph taken at the 2‐year post‐restoration follow‐up is presented in Figure 4.6g.

Figure 4.7a shows a case where all six mandibular teeth had failed, with significant destruction of their alveolar housings. Knowing that bone reconstruction would be needed, flaps were raised to expose and extract the six teeth (Figure 4.7b). Three implants were inserted in the sockets of the left central incisor, the left and right cuspids placing them subcrestal and as far towards the lingual as feasible (Figure 4.7c). A collagen membrane was fitted under the lingual flap (Figure 4.7d). The gaps remaining were overfilled with particulate bone substitute as was the buccal aspect, (Figure 4.7e), and covered with a collagen membrane (Figure 4.7f), before achieving passive closure of the flaps (Figure 4.7g). The final restoration is depicted radiographically and clinically in Figure 4.7h,i.

The final case that we have included is that of a patient with a non‐restorable mandibular left second bicuspid. The tooth was removed with minimal trauma, a single implant installed, and a soft tissue graft from the patient’s palate inserted and stabilized under the thin buccal marginal soft tissues (Figure 4.8a–f).

Conclusions

Most reports on the use of IIPs are from studies where the implants are placed in sites other than anterior mandible so that there is minimal useful published information on this treatment. However, it is well recognized that there are significant challenges using immediate dental implants in anterior mandible, related to local anatomy including thin buccal socket walls, narrow buccolingual and mesiodistal socket widths, and the presence of both buccal and lingual concavities. Narrow diameter implants often are needed to be able to leave suitably sized buccal gaps for hard tissue grafting.

Major risks include damage to local vasculature with subgingival hematomas and life‐threatening emergencies. Damage to the mental nerves and anterior nerve loops is also a risk. As in anterior maxilla, while it may seem to the inexperienced implant surgeon that placement of immediate implants in anterior mandible is a straightforward procedure, this is definitely not the case. If all four mandibular incisors require extraction at one time, it is inappropriate to attempt to place an implant for each tooth because of serious space limitations.