Immediate dental implants: when and how?

Thick gingival phenotype

Patients with thick gingival phenotype will be at reduced risk of marginal soft tissue recession. It is important to appreciate that the majority of the soft tissue in the anterior maxilla is found to be thin.¹¹

Thick buccal bone plate (thick bone morphotype)

This is difficult to assess, even with a cone beam CT scan (CBCT). The presence of a thick (>1 mm) buccal bone plate reduces the risk of resorption.¹² Thin buccal bone a tends to resorb in a corono-apical direction three times more than thick bone.¹³ In situations where a graft material is used with a thin buccal plate, the graft material will no longer be contained once the buccal bone plate resorbs post-extraction. This can result in loss of graft and soft tissue volume.

Intact buccal bone and absence of recession

There is a general consensus that severe buccal bony defects in the extraction site preclude using an immediate implant technique (Figure 3). The lack of a buccal bone wall is often associated with increased gingival recession.¹⁴ The greater the bone dehiscence, the greater the soft tissue recession will be. The labial plate can be palpated with a probe after an extraction.

Availability of adequate palatal and apical bone to acquire good primary stability of the implant

Anatomical structures, such as the nasal/sinus floor and inferior dental neuromuscular bundle, reduce available apical bone for primary stability. Approximately 5 mm of the osteotomy site should be intact to allow for good stability. This is usually bone apical to the tooth socket, but can involve the socket if the root was tapered.

When these key factors are absent, the clinician should consider a delayed approach.¹⁵ It is important to note that in some cases, the buccal bone plate will not be intact.¹⁶ Cooper and colleagues¹⁷ reported that 21% of sites planned to receive immediate implant placement were abandoned owing to the significant bone loss when teeth were extracted. This possibility should be explained to the patients at the outset.

Step 1: Flapless surgery

This approach has more predictable outcomes when compared with the open-flap technique (Figures 4,5,8–10). Flapless surgery is associated with less risk of buccal soft tissue recession⁵ owing to the maintenance of the blood supply that would otherwise be disrupted during periosteal elevation when a flap is raised. The authors advocate a flapless approach, when possible.

In some situations, a flap must be raised (Figure 6) to facilitate tooth extraction or a graft to repair minor bony defects. This can also facilitate the identification of any buccal plate perforation and aid implant angulation.

Step 2: Extraction

It is of paramount importance to avoid unnecessary trauma to the socket during the tooth removal, and minimize damage to the alveolus. This is to prevent the fracture and the loss of buccal and/or palatal plates or the undue compression on the walls, risking future necrosis. Difficult root morphology and curvatures can lead to traumatic dental extractions, which can preclude subsequent immediate implant placement.

The use of luxators and periotomes (Figure 6) to carefully loosen the tooth and sever the periodontal ligaments is helpful. These are to be used on the mesial, distal and palatal or lingual aspects of the root. Small labial plate fractures are less critical if the periosteum is intact. Should extraction forceps be used, maintaining apical force while carrying out rotational movements, particularly for upper central incisors, will reduce trauma to tooth sockets. Piezo-electric tips, which give superior control in terms of force and adaptability to the roots’ shape, could also be used for this purpose but can be time-consuming. The socket should be adequately curetted of any soft tissue if present. Another way of preserving the buccal cortical bone is the socket-shield technique, originally described by Hürzeler et al.¹⁸ This technique involves preserving the buccal aspect of the root while extracting the rest of it, followed by implant placement. The authors have not used this technique.

Step 3: Immediate implant placement

An increased primary stability is achieved by incorporating the palatal and lateral bone and using any bone available apical to the tooth socket. Ideally, this bone should be 4–5 mm long (Figures 7 and 8). If sufficient apical bone is unavailable, a delayed placement approach might be more appropriate. Implant placement directly in the extraction socket should avoid buccal plate perforation, which can lead to inferior primary stability and aesthetic outcomes.¹⁹ Therefore, the osteotomy in upper anterior teeth, for example, should be initiated by engaging the intact apical third of the palatal wall of the extraction socket. Drilling into the palatal tooth socket wall can be challenging, and the bur can slip unless firm guidance with a small round bur or a lance drill is used. Perforation of the palatal socket wall at about 120 degrees to the long axis of the socket should be followed by re-angulation to the desired osteotomy angulation.

A standard drilling sequence following the manufacturer's instructions should be followed. Optimal positioning and angulation of the drills can be facilitated by using tooth-borne surgical templates (Figure 4b) fabricated from the preextraction or diagnostic wax-up. Using the surgical guide will aid the positioning and alignment of the fixture to allow for a screw-retained restoration. Small departures from ideal placement can be managed at the prosthetic stages with some form of angle correction. Primary stability is a key factor in the success of immediate implants.

Maintaining a marginal gap of at least 2 mm between the coronal internal socket wall and the shoulder of the implant platform (Figures 4a and 8g) is recommended.²⁰ This will reduce the amount of buccal bone resorption that will inevitably take place following the tooth extraction. It is anticipated that this gap will eventually be filled with bone as part of bone healing and osseo-integration.²¹ The gap will also facilitate the formation of the blood clot and provide a provisional connective tissue matrix in most cases. This space is also important if bone substitutes are used, which will eventually transform into regenerated bone. Should the gap be less than 2 mm wide, the formation of the provisional matrix will be affected, resulting in less thickness of the regenerated buccal bone. Food impaction in the marginal gap should be avoided.

This can be prevented by a temporary replacement, such as a partial denture, bridge, provisional implant-supported crown or healing abutment. On occasion, a periodontal dressing could be used.

The shoulder, or fixture head, of the implant placed, should be 0.5–1-mm apical to the buccal bone crest (Figure 8g). The fixture head should be in the palatal side of the socket, as guided by the surgical template, and is often slightly subcrestal relative to the proximal and palatal bone crests. This is to compensate for the vertical buccal bone and soft tissue resorption that may take place.

Buccal soft tissues can be supported by a connective graft harvested from the palate and inserted into the internal aspect of the facial bone to support the soft tissue.²² This is to compensate the anticipated horizontal buccal bone resorption. Another technique described by Tarnow et al²³ is to use a very small particle bone substitute to graft the defect and coronal to the buccal bone crest into the soft tissue zone (dual zone technique), thereby, maintaining adequate soft tissue thickness. However, the authors have not used adjunctive soft or hard tissue grafting with acceptable results (Figures 4 and 8).

Step 4: Temporization following immediate implant placement

It is best to avoid subjecting the implant to any occlusal load while bone healing and osseo-integration take place. Hence, delayed loading with temporization of the extraction site using conventional methods, such as removable or fixed replacements, is advised. A partial denture or vacuumformed retainer that contains an acrylic/composite tooth replacement of the extracted tooth, should be trimmed adequately to avoid loading of the healing abutment. Another option is to provide an immediate provisional fixed resin-retained bridge (Figure 9d) or a provisional conventional bridge (Figure 6e). However, when treating patients with high aesthetic demands, these options might not be acceptable. Therefore, providing a provisional implant-supported restoration at the time of placement (type 1A protocol) might be required. This allows the peri-implant soft tissue to be shaped adequately around the implant²⁴ should it achieve sufficient primary stability (torque 25–40N). The occlusion should be arranged so the provisional implant crown is not loaded.

Step 5: Loading

Implant placement and the loading protocol should be planned prior to tooth extraction. Studies have suggested that minimal movement of the implant during the osseo-integration phase can be withstood without adversely affecting the healing process. These movements should be less than 50 microns.²⁵ Consequently, the restoration should be out of contact during the mandibular lateral excursive and protrusive movements to minimize the risk of osseo-integration failure.

Immediate and early loading (type 1A and type 1B)

Immediate loading of implants placed in fresh sockets showing good clinical outcomes have been reported²⁶ when disclusion of the provisional restoration during function is obtained. However, Chen et al²⁷ indicated a higher risk of gingival recession associated with immediate loading of immediate implants.

Delayed (conventional) loading (type 1C)

A systematic review conducted by Gallucci and colleagues²⁸ concluded that delayed loading of an immediate implant is the only validated approach compared to immediate and early loading approaches. Delayed loading is advised in situations where a flap needs to be raised (to facilitate tooth extraction or graft to repair the minor bony defect) is required. Moreover, a delayed loading protocol should be adopted when the primary stability of the implant is not optimal and when bone augmentation is undertaken. The authors favour a delayed loading protocol.

Step 6: Definitive restoration

Definitive restoration can be provided within 2–3 months in keeping with most standard protocols. The palatal position of the immediate implant facilitates the provision of a screw-retained implant-supported crown, which is the preferred type of restoration. This is especially true when peri-implant health is considered. Provisional restorations can help develop soft tissue contours, but in many cases, are not required. A definitive restoration made to the ideal contour will blanch the peri-implant tissues on insertion. So long as this blanching from pressure resolves during the appointment, the outcome will be good. Persistent blanching would require adjustment to the emergence profile. With careful treatment planning, multiple immediate implants can be placed and restored (Figure 10). The clinical outcome is in keeping with other treatment protocols if provided in this way (Figure 11).