Immediate implants after extraction. A review of the current situation

PEÑARROCHA M, URIBE R, BALAGUER J. IMMEDIATE IMPLANTS AFTER EXTRACTION. A REVIEW OF THE CURRENT SITUATION MED ORAL 2004;9:234-42.

SUMMARY

Immediate implants are positioned in the course of surgical extraction of the tooth to be replaced. The percentage success of such procedures varies among authors from 92.7-98.0%. The main indication of immediate implantation is the replacement of teeth with pathologies not amenable to treatment. Its advantages with respect to delayed implantation include reduced post-extraction alveolar bone resorption, a shortening of the rehabilitation treatment time, and the avoidance of a second surgical intervention. The inconveniences in turn comprise a general requirement for membrane-guided bone regeneration techniques, with the associated risk of exposure and infection, and the need for mucogingival grafts to seal the socket space and/or cover the membranes.
The surgical requirements for immediate implantation include extraction with the least trauma possible, preservation of the extraction socket walls and thorough alveolar curettage to eliminate all pathological material. Primary stability is an essential requirement, and is achieved with an implant exceeding the alveolar apex by 3-5 mm, or by placing an implant of greater diameter than the remnant alveolus. Esthetic emergence in the anterior zone is achieved by 1-3 mm sub-crest implantation. Regarding guided regeneration of the alveolar bone, the literature lacks consensus on the use of membranes and the type of filler material required. While primary wound closure is desirable, some authors do not consider it to be of great relevance.

Key words: Dental implants, immediate implants.

INTRODUCTION

Immediate implants are defined as the placement of implants in the course of surgical extraction of the teeth to be replaced (1). The insertion of implants immediately after extraction is not new, and in the eighties the University of Tübingen advocated the procedure as the technique of choice for Tübingen and München ceramic implants (2). As a result of the success of the protocol designed by Brånemark and his team for their dental implant system, other procedures were largely relegated for many years. Initially, a healing period of 9-12 months was advised between tooth extraction and implant placement (3). Nevertheless, as a result of continued research, a number of the concepts contained in the Brånemark protocol and previously regarded as axiomatic - such as the submerged technique concept, delayed loading, machined titanium surface, etc. - have since been revised and improved upon even by the actual creators of the procedure.

Based on the time elapsed between extraction and implantation, the following classification has been established relating the receptor zone to the required therapeutic approach (1,4):

(a) Immediate implantation, when the remnant bone suffices to ensure primary stability of the implant, which is inserted in the course of surgical extraction of the tooth to be replaced (primary immediate implants).

(b) Recent implantation, when approximately 6-8 weeks have elapsed from extraction to implantation - a time during which the soft tissues heal, allowing adequate mucogingival covering of the alveolus (secondary immediate implants).

(c) Delayed implantation, when the receptor zone is not optimum for either immediate or recent implantation. Bone promotion is first carried out with bone grafts and/or barrier membranes, followed approximately 6 months later by implant positioning (delayed implants).

(d) Mature implantation, when over 9 months have elapsed from extraction to implantation. Mature bone is found in such situations.

EXPERIMENTAL AND CLINICAL STUDIES

Studies in dogs and primates have shown that implants positioned immediately after extraction can undergo osseointegration, with good surface bone adaptation and without clinically apparent mobility (5). Karabuda et al. (6), in a histological and morphometric study in canine mandibles, recorded 62.4% bone contact in hydroxyapatite-coated implants, versus 51.3% contact in titanium plasma-sprayed (TPS)-surface implants, after 8 weeks. Wilson et al. (7), in a histological study of a deceased patient, noted good osseointegration of immediate implants, as determined 6 months after implantation. Cornelini et al. (8) in turn carried out a clinical and histological study of a non-submerged immediate implant which 8 months after placement was found to cause discomfort requiring explantation. The corresponding histological evaluation revealed an important percentage of bone-implant contact. Block and Kent (9) confirmed good clinical results with immediate implants - posterior studies reflecting percentage successes of between 92.7% (10) and 98.0% (11). Grunder et al. (12) observed no significant differences in long-term success between immediate (92.4%) and delayed implants (94.7%). Mean bone resorption in immediate upper maxillary implants was found to be 0.8 mm yearly, versus 0.5 mm in the lower jaw. According to these authors, an increased failure rate was only obtained when immediate implantation was carried out after extracting teeth due to periodontal disease.

In contrast, according to Tolman and Keller (13), immediate implantation affords a lesser success rate when compared with implants positioned in mature bone. Nevertheless, in a study published by Schwart-Arad et al. (14) involving 380 implants, of which 31% were immediate, the cumulative survival rate after 5 years was seen to be 96% and 89.4% for immediate and non-immediate implantation, respectively.

INDICATIONS OF IMMEDIATE IMPLANTATION

Primary implantation is fundamentally indicated for replacing teeth with pathologies not amenable to treatment, such as caries or fractures. Immediate implants are also indicated simultaneous to the removal of impacted canines and temporal teeth (15,16).

Immediate implantation can be carried out on extracting teeth with chronic apical lesions which are not likely to improve with endodontic treatment and apical surgery (17). Novaes et al. (18), in a study in dogs, inserted immediate implants in locations with chronic periapical infection. These authors reported good results and pointed out that despite evident signs of periapical disease, implant placement is not contraindicated if pre- and postoperative antibiotic coverage is provided and adequate cleaning of the alveolar bed is ensured prior to implantation.

While immediate implantation can be indicated in parallel to the extraction of teeth with serious periodontal problems (17), Ibbott et al. reported a case involving an acute periodontal abscess associated with immediate implant placement, in a patient in the maintenance phase (19).

CONTRAINDICATIONS

The existence of an acute periapical inflammatory process constitutes an absolute contraindication to immediate implantation (20,21).

In the case of socket-implant diameter discrepancies in excess of 5 mm, which would leave most of the implant without bone contact, prior bone regeneration and delayed implantation may be considered (16).

ADVANTAGES

One of the advantages of immediate implantation is that post-extraction alveolar process resorption is reduced (22-24), thus affording improved functional and esthetic results (25,26).

Another advantage is represented by a shortening in treatment time, since with immediate placement it is not necessary to wait 6-9 months for healing and bone neoformation of the socket bed to take place. Patient acceptance of this advantage is good (27), and psychological stress is avoided by suppressing the need for repeat surgery for implantation (25).

Preservation of the vestibular cortical component allows precise implant placement, improves the prosthetic emergence profile, and moreover preserves the morphology of the peri-implant soft tissues (27) - thereby affording improved esthetic-prosthetic performance.

INCONVENIENCES

One inconvenience of immediate implant placement is the more frequent need for tissue regeneration and bone promoting techniques. The application of bone grafts and/or barrier membranes to the defect created by the socket-implant discrepancy contributes to increase the complexity and cost of treatment (28).

In general terms, the placement of membranes requires the raising of flaps to cover the latter - a circumstance that may lead to problems such as disappearance of the interdental papillae and the development of peri-implant mucositis over these non-keratinized displaced tissues. The possibility of membrane exposure and subjacent infection produces antiesthetic sequelae, and places implant viability at risk (29).

SURGICAL CONSIDERATIONS

The most common locations for immediate implant placement comprise the anterior sector (canines and incisors) and the premolar regions of both jaws. When the diameter of the root is less than that of the implant, the resulting primary stability is greater. This situation is observed when a periodontically compromised tooth is removed, presenting a bone support equivalent to les than one-third of the root (30).

The surgical criteria which apply to immediate implantation include the following:

Ensure that extraction is as least traumatic as possible, to maximize bone integrity. In teeth with multiple roots, dental sectioning is indicated, with individualized extraction of the roots. The socket walls are to be preserved during extraction, particularly the vestibular wall, the level of which should harmonized with that of the neighboring teeth, to ensure esthetic emergence of the prosthetic post.

Before positioning the immediate implant, careful curettage and alveolar cleaning is required to remove any trace of infected or inflamed tissue, together with remains of the periodontal ligament (31,32).

The implant must possess sufficient primary stability. This is generally ensured by exceeding the apex by 3-5 mm, or by using an implant of greater diameter than the socket (33,34).

-Implant placement

In anterior teeth, the ideal orientation of the implant axis does not usually correspond to that of the socket. Implant placement in the direction of the root would oblige vestibular emergence of the retention screw or the use of prosthetic additaments for the change in angle. The implant bed is to be prepared palatal, and osteodilators can be used to this effect. In the molar region of the upper jaw it is preferable to establish fixation in the palatal root, since the buccal counterparts are covered by a fine bone layer. In the posterior mandibular region, the inferior alveolar neurovascular bundle often lies very close to the apexes of the premolars and molars, and the roots of the latter tend to be large - thereby precluding adequate primary fixation of the implant. A common situation is implant placement in the inter-root septum, which causes the bone bed surrounding the implant to condition very precarious initial stability. This problem can be solved by using an implant of larger diameter (35), waiting for the alveolar space to fill with bone, and then performing delayed placement or positioning two implants to reconstruct a lower molar.

In some cases a vestibular crest defect or dehiscence occurs after implant positioning. If the bone defect is small (under 4 mm in length), it can be eliminated with bone filler material alone. In contrast, guided bone regeneration should be considered in the event of larger defects (29,36).

In order to achieve esthetic anterior sector emergence, the implants must be positioned below crest level. In this sense, Bascones and Frías (34) propose a distance of 2-3 mm, while Lazzara (37) and Lang et al. (28) refer a location between 1 and 3 mm apical to the alveolar crest level. Gelb (11) advocates a location 3 mm apical to the cementoenamel line of the adjacent teeth, while Becker et al. (33) prefer a position slightly inferior to the alveolar crest.

-Primary soft tissue closure

Following tooth extraction, a wound remains and primary socket closure is difficult. In this sense, while some authors consider immediate closure after implantation to be desirable (11,33), others are of the opinion that this is not a priority objective (37,38).

If a vestibular flap is used for primary socket closure, with two releasing vertical incisions and an incision upon the periosteum at the base of the flap, sufficient mobility can be achieved to displace and suture the flap on the extraction site. This technique offers good sealing but poses the inconvenience of reducing the width of the attached gingival tissue around the implant - thus adversely affecting the esthetic outcome and complicating patient-mediated care (29). Ladsberg (39) described immediate transgingival positioning of the implant after tooth extraction, covering the defect with a full thickness graft taken from the palatal region. This author also described a technique for socket sealing where after immediate implant placement the vacant spaces are filled with bone graft material, and the alveolar space is obturated by means of a graft containing epithelium and connective tissue. Despite the good results reported, the approach implies the inconvenience of creating a second surgical field, and healing is moreover slower.

Nemcovsky et al. (40) described another socket sealing method involving palatal rotation flaps in 61 immediate implants, associated to bovine bone grafts. For covering, these authors designed a palatal, full thickness pedicled rotation flap and a second partial thickness flap, with or without the application of a non-reabsorbable membrane. These three techniques achieved bone regeneration at the crest-implant interface in approximately 80% of cases.

Rosenquist (41) in turn employed a vestibular rotation flap. A horizontal flap measuring over 20 mm in length was raised from the vestibular mucosa, with a width equivalent to that of the extraction site, and rotating the flap to cover the socket.

According to Schwart-Arad et al. (14) and Chaushu et al. (42), the need for primary socket closure following immediate implant placement has not been confirmed. These authors have reported success with single anterior maxillary immediate implantation even in the absence of primary wound closure. Implants were placed in a single phase, achieving soft tissue closure around the healing post of the implant.

Vila and Marcet (43) proposed obviating incisions after extraction, to preserve the papillae in the anterior sector. They positioned transgingival implants with a soft tissue conformer, in a way similar to the approach proposed by Zets and Quereshy (44), who positioned delayed implants in a single phase using a tissue punch. This technique involved the use of a circular scalpel to minimize soft tissue disruption and optimize the esthetic results. The soft tissue above the implant site is extracted, and a transgingival healing post is used to close the wound - suturing the soft tissue around the implant.

In order to secure an increased marginal soft tissue profile, connective (45) or gingival tissue autografts (46) can be used, positioning the latter under the mucosal margins of the socket (47). Divi and Rojo (48) proposed an easy and interesting technique in secondary immediate implants where after waiting 3-11 weeks post-extraction of single-root teeth a palatalized crest incision is made, raising the neoformed tissue in the socket along with the flap and repositioning it over the vestibular cortical component of the implant zone.

-Guided bone regeneration

Studies in canine jaws (49) have used reabsorbable membranes to facilitate bone formation around immediate implants. Lazzara (37) was the first to use expanded polytetrafluoroethylene (PTFEe) after immediate implant placement, to prevent the formation of connective tissue and its contact with the implant. Barrier membranes can be used isolatedly or over bone graft material. It should be taken into account that premature membrane exposure, particularly when of a reabsorbable kind, can lead to complications such as infection, bone loss or implant failure - thus compromising the predictability of immediate implantation (14). In such cases it is therefore necessary to ensure stable tissue with sufficient thickness and offering good vascularization, sutured without tension, completely covering the membrane and totally sealing the defect from soft tissues (4).

The simultaneous use of membranes in immediate implantation is the subject of debate. Lazzara (37), Becker et al. (50), and Lang (28) advocate the use of occlusive membranes alone, without graft positioning, on the grounds that the stability of the immediate implant and clot, plus primary closure of the soft tissues, suffice to allow ossification, and that the use of membranes affords an increased amount and width of bone tissue.

In contrast, Schwartz and Chausu (31,32), and Henry et al. (51), reported no improved results on using membranes in immediate implants, and moreover indicated the possibility of complications such as infection. Kohal et al. (52) consider that the different graft materials do not differ in terms of the force required to extract the implant, while in contrast premature membrane exposure may complicate survival. Consensus is likewise lacking as regards the best filler material to be used with immediate implants. Authors such as Brugnami et al. (53) or Dealemans et al. (54) recommend the use of autografts instead of allografts, due to the absence of immune reactions associated with the former. In this sense, the general impression appears to be that autologous grafts are the best choice for osseoinductive purposes. Autologous bone can be obtained from the implant zone, the maxillary tuberosity, the retromolar region or the chin. These authors also coincide that demineralized bovine bone and hydroxyapatite particles as non-vital grafts possess no osteogenic activity - their main function being the maintenance of space. In contrast, morphogenetic protein and growth factors do possess osseoinductive potential, and can favor bone regeneration (55). All these materials can be used either alone or in combination with occlusive membranes, though histological evidence indicates that full bone regeneration of the space between the implant and the coronal portion of the alveolus can only be achieved when barrier membranes are employed (56).

-Implant loading

Regarding the timing of loading, Chaushu et al. (42) compared the immediate loading of 19 immediate implants with provisional acrylic crowns and 9 implants positioned over mature bone. The corresponding success rates were 82.4% for immediate restoration and 100% for non-immediate implantation, after an average of 13 months of follow-up. The authors referred a 20% failure risk with immediate loading of immediate implants.

CONCLUSIONS

(a) Immediate implantation affords a high success rate of between 92.7% (12) and 98.0% (13).

(b) When an extraction is indicated, immediate implants shorten the time to completion of rehabilitation while also reducing bone reabsorption of the residual alveolus and avoiding the need for a second surgical intervention.

(c) Chronic periapical pathology is no contraindication to immediate implantation, provided the procedure is carried out under adequate antibiotic coverage, with careful curettage of the bone bed.

(d) The insertion of immediate implants of between 3 and 5 mm in excess of the apex, and the use of an implant with a diameter greater than that of the extraction socket afford sufficient primary stability - the latter being an essential requirement for treatment success.

(e) Among the different guided bone regeneration techniques, no consensus exists among authors over the use or exclusion of membranes, their combination with graft material, and the type of filler material to be used. In the event of bone defects or implant-socket discrepancies of more than 5 mm, prior bone regeneration with delayed implantation is advised.

(f) While primary wound closure after immediate implant placement is widely believed to be desirable, some authors do not consider it to be of great relevance.

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