Excessive Bleeding

Excessive bleeding during dental implant surgery is fortunately rare, but can present as a result of poor surgical technique, vascular anomalies, genetics, systemic conditions affecting blood clotting, renal or liver disease, or the use of medications that interfere with hemostasis. The lingual aspect of the mandibular anterior is an area rich in arterial anastomoses from the sublingual artery, submental artery, and the incisive artery. This plexus of blood supply is located in close proximity to the lingual cortical plate of the mandibular anterior [9]. A potential emergency includes a hematoma leading to airway obstruction as result of lingual plate perforation during implant osteotomy preparation [10, 11], which can be life threatening [12, 13]. Therefore, all preventive measures must be taken to prevent such a complication.

Buccal or Lingual Plate Perforations

The prevalence of buccal plate perforation (BPP) in the maxillary esthetic zone is relatively high, happening during site drilling at any tooth in the zone. Lateral incisor sites often have significant buccal concavities apically. The preferred approach for IIP placement is flapless so that BPP can happen particularly if carefully designed surgical guides are not employed to avoid inadvertent buccal bur drift with unwanted changes in osteotomy angulation. At maxillary bicuspid sites, the risk of buccal plate fenestrations can be reduced by positioning osteotomies slightly palatal and angling them marginally towards the buccal. A surgical guide created using a primary, pretreatment wax‐up (real or virtual) of the desired prosthesis will significantly reduce risk of complications [14].

A case where buccal plate issues came into play in anterior maxilla is shown in Figure 13.1. The patient presented with a non‐restorable maxillary left central incisor (Figure 13.1a). After flapless extraction and during freehand osteotomy site drilling, the bur drifted buccally, making the clinician wary of buccal bone damage. Consequently, a flap was raised and revealed paper‐thin buccal bone apically (Figure 13.1b). Recognizing that this would likely result in an apical fenestration during postoperative remodeling, the clinician correctly elected to augment the buccal plate with particulate bone allograft (Figure 13.1c) covered with a resorbable collagen membrane and primary soft tissue closure. The site healed non‐eventfully and at the time of re‐entry showed successful restoration of buccal bone contour (Figure 13.1d).

The series of CBCT images in Figure 13.2 shows another incidence where freehand osteotomy drilling resulted in a major BPP. The implant had to be removed and the osteotomy redirected followed by buccal augmentation bone grafting.

In anterior mandible, both BPPs and lingual plate perforations (LPPs) [15] are possible due to local anatomy (see also Chapter 2). CBCT analyses have identified four anatomical configurations of anterior mandible: convex (C‐type), parallel (P‐type), undercut (U‐type) and crescent‐shaped (S‐type), where there is a buccal rather than a lingual concavity [16] (Figure 13.3). It has been reported that 77.4% of mandibular canine sites have the S‐type configuration, making BPPs common here. In contrast, 13.1% had the C‐type morphology, and U‐type was rarest, hovering close to 0%. Owing to the low prevalence of U‐type morphology, it was reported that mandibular canine sites have a 0.7% risk of LPP [16]. The predominant ridge morphology in the mandibular bicuspid region is P‐type at 58–70%, but U‐type also is seen at second bicuspid sites (23.3%). The reason for a lingual concavity here is to accommodate the sublingual gland, and there have been reports of plunging ranula as a complication after implant placement in this region following lingual plate perforation [17]. This presents as painless swelling in the sublingual space occurring within 2 days to 1 week after implant placement. Timely referral to an oral maxillofacial surgeon will be necessary if the practitioner is not equipped to manage the situation. Magnetic resonance imaging and computed tomography may be required to make the diagnosis [18]. Dental implant removal itself will not alleviate the situation. Far more mandibular second bicuspid than first bicuspid sites are U‐type (16.7% vs. 0–2%). Nevertheless, LPPs are low here, at about 4.1%.

Another issue is that the average buccal plate thickness in anterior mandible is less than 1 mm in the coronal one‐third [19]. The crestal buccolingual ridge width in anterior mandible is narrow, making the choice of implant diameter a key decision in avoiding buccal bone dehiscences [20]. Narrow mesiodistal socket widths and interproximal bone widths in anterior mandible also make the choice of number of implants highly important, to be able to maintain adequate inter‐implant distances of 3 mm or more.

Buccal plate perforations are more frequent at mandibular first bicuspid than second bicuspid sites. In the example shown (Figure 13.4), an IIP was planned for replacement of the mandibular right first bicuspid where there often is an apical buccal concavity. After flapless extraction and during osteotomy drilling, a buccal apical fenestration was suspected, making elevation of a flap necessary (Figure 13.4a). As an aside, the fenestration might have been avoided if osseodensification burs had been used to gently expand the apical bone buccally [21]. In the case shown, after implant insertion, the fenestration was grafted with particulate bone allograft and covered with a collagen barrier membrane secured with tacks (Figure 13.4b), which allowed submerged healing. Three more implants were installed in healed sites during the same surgery to allow restitution of the quadrant (Figure 13.4c).

In addition to local anatomy, surgical technique can increase risk of perforations in IIP placement. Average freehand deviation in osteotomy angulation has been estimated at 6.8 degrees and greater than with guided surgery (3–4%). If either a buccal or lingual plate perforation occurs due to bur deviation during site preparation, removal and redirecting the osteotomy bur may be indicated, unless adequate IIP primary stability cannot be achieved in which case implant removal and socket grafting with early (4–8 weeks) or delayed implant placement are better options.

Implant Misalignments and Malpositioning

Implant misalignments refer to deviations from intended angulations, depth and/or 3D prosthetically driven positioning of the osteotomy relative to adjacent teeth, implants, or anatomical structures. While less common among experienced clinicians, misalignments and malpositioning can still occur, particularly under challenging anatomical and/or stressful intraoperative conditions. Options for correcting minor misalignments may include IIP removal and modification of the osteotomy or if not feasible, later use of angled prosthetic abutments. More serious malpositioning may require abortion of the procedure, with removal of the implant together with socket preservation grafting and delayed implant placement [22, 23]. If a patient presents with a malpositioned but integrated implant in the esthetic zone as in the example provided (Figure 13.5a, b), whether or not to keep the implant should depend upon: (i) having a reasonable restorative plan; (ii) the presence or absence of crestal bone resorption with exposure of implant threads; and (iii) whether the implant had been placed in adequate depth [24].

If an inappropriate diameter is chosen for an IIP, there may be no, or a minimal, buccal gap left for hard tissue grafting, leading to loss of buccal bone and exposure of implant surface. Sometimes, to avoid implant removal, the exposed implant surface can be thoroughly debrided and covered with a soft tissue graft (Figure 13.6) [25], provided that the patient has excellent daily homecare and attends regularly for monitoring and maintenance therapy.

Errors in depth of implant placement can also lead to unfavorable esthetic outcomes. There is no doubt that placing implants subcrestal has benefits including helping to minimize the impact of physiologic remodeling of crestal bone [27]. However, it is possible to place IIPs too deep, making it difficult to achieve esthetic harmony between the final implant crown and its neighbors. Figure 13.7a displays a case where IIP was inappropriate, resulting in the implant being too deep. As can be seen in a pretreatment panoramic film, the patient’s maxillary right lateral and central and left central incisors had suffered severe attachment loss. The right central clearly needed to be sacrificed as it had virtually no bony support remaining. Extraction could have been accompanied by GBR, possibly with the aid of autologous platelet‐rich preparations [28] in attempts to create sufficient bone to receive a delayed implant [29]. However, the clinician mistakenly went for an IIP. This resulted in a markedly overseated implant, the location of which had further compromised the adjacent lateral incisor (Figure 13.7b). In the end, the crown inserted needed to excessively long and inappropriately large, leading to a restoration of inappropriate proportions and in no way in harmony with the other teeth (Figure 13.7c).

An example of a more subtle but still inappropriate depth of IIP placement is shown in Figure 13.8a. The patient presented with an existing implant replacing her left central incisor. Her right central needed replacement and it was decided to opt for the IIP route. However, the height of the crestal bone at this site was noticeably lower than that of the existing implant. As a result, the two implants ended up at significantly different depths, making it necessary to use a longer crown with a pink acrylic collar for the new implant (Figure 13.8b).

Overseating with significant consequences is shown in Figure 13.9. The clinician made the error of trying to place an IIP at a mandibular first bicuspid site with very low bone density and in placement the implant fell into a large marrow space.

Another serious error with IIP placement is placing implants too close to one another. For the patient depicted in the panoramic radiograph of Figure 13.10a, the plan was to extract all four mandibular incisors with replacement using IIPs and a fixed prosthesis. Unfortunately, the teeth had suffered significant buccal bone loss impacting an already narrow alveolar ridge. An appropriate but challenging approach could have been to place narrow diameter (3.3 mm) implants at the two lateral incisor sites along with significant buccal hard tissue augmentation grafting (GBR). The clinician made the common error of using more implants than needed replacing both the right central and lateral incisors. These teeth had been too close to one another to receive implants in both of their sockets, the clinician not remembering that adjacent implants need to be separated by at least 3 mm mesiodistally to preserve and/or increase the existing interproximal bone [30]. The required buccal hard tissue augmentation also was not done, and as a result, the two adjacent implants suffered severe bone loss with subsequent peri‐implantitis (Figure 13.10b) and treatment failure.

Damage to Vital Structures

Damage to the mental nerve is a recognized complication associated with IIP placement in mandibular anterior and premolar areas [31], and risk increases with anatomical variations such as the presence of an anterior loop in the mental foramen [31, 32]. Nerve damage can also occur from stretching during the use of surgical instruments or excessive pressure due to postoperative inflammation. Manifestations can include altered sensation, pain, and/or numbness in the affected area. The incidence of mental nerve damage varies, with rates reported between 0.4% and 8.6%, or even higher [33]. Another anatomic feature in the mandibular interforaminal region is the lingual foramen, which is situated in the midline of the mandible, at the level of, or superior to, the mental spines [34]. Some authors hold that there is nerve as well as vascular tissue existing from this foramen, the nerve tissue possibly arising from the mylohyoid nerves.