Inappropriate Socket Shield Protocol as a Probable Cause of Peri-Implant Bone Resorption: A Case Report

Abstract

Alveolar ridge remodeling post-extraction is a well-documented process. Alveolar bone is in a continuous state of remodeling even after implant placement, and this leads to changes in the contour of the peri-implant tissues over the years. A vast number of procedures have been described in literature to address and correct this resorption including procedures like socket grafting, dual zone grafting, socket shield (partial extraction therapy) and many more. Socket shield (partial extraction therapy) is a relatively new procedure described in the literature. This technique aims to try and slow down this remodeling and maintain the peri-implant tissues in a state near normalcy. The aim of this article is to assess a case where the possible cause of buccal bone loss around an integrated implant was an inappropriately prepared socket shield. It is recommended that an evidence-based consensus be put forth on both case selection and execution to minimize inappropriate execution of this technique by the average clinician.

Introduction

In the current era of dentistry, clinicians placing dental implants are expected to deliver repetitive results with a high level of predictability. Consequently, some of the more conventional protocols for placement and restoration require frequent reappraisal. Of late, immediate implant placement after tooth extraction and provisionalization has gained immense popularity. This protocol obviously results in shorter treatment time and may aid in preserving the hard and soft tissues [1–4].

There are many evidence-based protocols to restore the deficient bone or gingival architecture, and these come under the term guided bone regeneration (GBR) [5].

Immediate extraction, implant placement and provisional restoration have been reported by some as a flapless procedure with predictable outcomes [6].

There are some attending disadvantages with this approach, such as residual infection in the socket [7, 8].

Socket shield technique has been reported by Hürzeler et al. [9], Chen and Pan [10], Kan and Rungcharassaeng [3] including many others.

In recent literature, the terms pontic shield and partial extraction therapy were coined to report the technique with indications and contraindications [11].

There are reports of osseointegrated dental implants, retrieved and examined under magnification showing mineralized compact bone matured with a Haversian system and without intervening connective tissue. With immediate implant placement gaining popularity, there are some pertinent questions that arise—would implants placed immediately after complete tooth extraction behave the same as those placed following the partial extraction therapy protocol when compared in the long run?

Of late, there are an increasing number of publications showcasing the root membrane or socket shield technique as an alternative route to maintaining the labial hard tissue [11]. Herein the operator leaves a sliver of the labial root thereby apparently leaving the buccal bone intact. The technique has been described and modified by many and has gained immense popularity in the hands of many clinicians with acceptable results.

Is it mandatory to graft the peri-implant space after partial extraction and immediate placement, if yes what would be the ideal biomaterial for this?

There have been many studies on these topics with some conflicting data. There are some authors that have reported excellent maintenance of peri-implant tissue following partial extraction therapy while some have reported a significant percentage of cases with complications.

There are case reports on modification of the shape of root shield left in place to influence papillary maintenance in addition to preservation of the labial hard and soft tissues [12].

Among other possible reasons for its rapid accession as a ‘go to’ technique for the esthetic zone, are economic benefits to the patient because biomaterials are seldom used to augment the peri-implant zone.

Though this has shown great results in the hands of experienced clinicians, relatively inexperienced clinicians need to take note of the fact that this is a highly technique sensitive protocol, and the outcome may vary if steps are not followed accurately as with any other technique. This case report showcases such a case, where an inappropriate socket shield protocol has probably led to peri-implant bone loss.

Case Report

Mr. X, a healthy 45-year-old male with no contributory history, reported to our facility with discomfort and slight tenderness over the labial gingiva adjacent to tooth 21 (left maxillary central incisor).

The patient reported that 3 years ago he had fractured the particular tooth for which he sought treatment and the dentist performed an extraction with immediate implant placement. He was informed of the alternative technique of socket shield, over conventional extraction, grafting and immediate or subsequent implant placement and had consented to the former (socket shield).

An immediate temporary restoration was placed over the implant which was changed to a definitive crown after 3–4 months. On examination the palatal surface revealed a screw access indicating that it was a screw retained restoration. There was no discharge from the labial gingiva or the sulcus. The implant crown did not exhibit any mobility. There was a probing depth of 4 mm at the labial sulcus.

He was prescribed broad spectrum antibiotics (co-amoxiclav 625 mg) twice daily for a period of 5 days.

A cone beam CT scan was obtained which showed the implant seemingly well integrated to the bone; it also showed a labial root sliver. No other important finding was noted (Fig. 1).

Fig. 1.

Cone beam scans showing the implant with the labial root sliver

After completion of the course of antibiotics, the patient reported with little respite from the tender swelling. A decision was made to explore the region with a papilla sparing flap for esthetic reasons. The screw retained crown was removed, and the labial aspect showed an exposed shield surface. On gentle assessment, this root sliver exhibited some mobility.

Upon flap reflection, it was observed that root sliver had lost all labial bone and was covered in granulation tissue. It exhibited mobility and was thus removed.

The root fragment that was originally retained as part of the socket shield protocol exhibited some part of the root apex (Fig. 2).

Fig. 2.

Root fragment showing part of retained apex

The implant had lost bone till the middle and apical 2/3rd of the implant on the labial aspect but was enveloped in bone on the mesial, distal and palatal aspects (Fig. 3).

Fig. 3.

Implant with bone loss till junction of middle and apical 3rd

All granulation tissue was carefully curetted out and the resultant defect left half the labial surface of the implant from the crest exposed.

The implant surface was debrided with a titanium microbrush (i-brush, Neo Biotech, Korea) and thereafter by alternate scrubbing with chlorhexidine and saline gauze pellets.

A mixture of autogenous (cortical shavings) and xenogenic bone (Bioss, Geistlich) was used to graft the defect. A resorbable collagen membrane (Memlok, Biohorizons) was used to cover the particulate biomaterial and secured using titanium tacks, and the gingival screw as a poncho (Fig. 4). Closure was done using 5,0 vicryl sutures (Ethicon, Johnson & Johnson). He was called for follow-up the next day (Fig. 5).

Fig. 4.

GBR with autograft, xenograft (Bioss, Geistlich) and resorbable collagen membrane (Memlok, Biohorizons)

Fig. 5.

Wound at Day 2

The patient’s old screw retained crown was inserted after 1 week of healing to support the labial and papillary soft tissues. The patient reported an uneventful healing phase. He was called for a follow-up visit after 1 month. The labial keratinized tissue may need to be augmented in future, and the patient was informed of the same.

Discussion

There are published cases where the partial extraction therapy has given stable results in immediate extraction placement cases, but the follow-up is relatively short when compared with the follow-up of other hard and soft tissue procedures in the esthetic zone to maintain peri-implant architecture.

This case brought to light some important facts, a notable feature is there is lack of a large-scale evidence-based consensus guideline for socket shield as a protocol of choice relative to the angulation of the dentoalveolar component as seen in the cone beam CT scans. In the absence of such a guideline, it is left to the discretion of the clinician to do a ‘socket shield procedure’ based on anecdotal advice. There may be difficulty in access to the apical aspect of the root (while sectioning) due to the near vertical positioning of the dentoalveolar segment, thereby increasing the chances of leaving behind the root apex. In such cases, the outcome may be compromised in the long run.

Gluckman et al. have commented in an editorial that it is not possible to maintain a 1.5 mm thickness of root sliver in all cases as reported by Han et al. [12].

A recent systematic review published on the socket shield showed a high risk of adverse effects for socket shield procedure [13] However, this review is based on available published literature till 2016, and it is warranted that a periodic assessment of evidence be done to guide the clinician regarding the specifications of this procedure.

Based on prior publications on socket shield, we were able to enlist the following aspects particular to this case:

1. The root sliver retained was larger than the recommended size as per prior published reports [11].

2. The retained fragment exhibited some part of the root apex.

3. The coronal part of the root sliver extended beyond the crest of bone by 1 mm. This is contrary to the procedure as described in the literature, where the recommended height of the root sliver should be at the level of the bone crest [14] .

4. These facts were not apparent in the scans, especially the partially retained root apex.

5. This could be due to the fact of radiographic burnout given the adjacent presence of highly radiopaque titanium implant.

6. The root had no labial bone over it but was covered in granulation tissue.

7. The clinical presentation of soft tissue at the labial surface of the implant and root sliver was misleading as it showed no evidence of the extensive granulation tissue that lays beneath.

Some protocols that are relatively more technique sensitive may require extensive practice before they can be executed to perfection in the mouth. Literature has numerous reports of esthetically acceptable results following partial extraction therapy as an alternate treatment modality to complete extraction and GBR [14, 15].

Though it remains a fact that clinical expertise requires practice and can only be bettered with an increasing number of cases being performed by any clinician but before putting to practice any new technique the operator should understand the protocols, pros and cons of the particular technique and at the same time be clinically adept in treating any complications that arise from the procedure in future.

Though there is clinical evidence to support the socket shield technique as such but that may not be sufficient to propel it to be used as a routine clinical option in every case of immediate extraction and implant placement [16]. If the proper clinical requirements are met and the technical handling of the operator is appropriate, these techniques could minimize buccal tissue resorption and make the procedure more patient friendly [17].

The loss of buccal hard tissue resulting from an inappropriately trimmed root membrane may be significant and would require further management and costs incurred by way of biomaterials to augment the same.

In a study by Mitsias et al. [14], only one patient in a series of 46 patients showed apical root resorption. This in turn leads to so-called ankylosis of the implant by deposition of trabecular bone in areas of resorption [13]. Davarpanah and Szmukler have also reported a case of resorption with this technique [18].

Specific protocols for radiographic control of cases treated with this technique have not been well established. Where a radiopaque implant superimposes the apical end of the retained root sliver, it is difficult to ascertain any detail on two-dimensional radiographs. In three-dimensional scans, the radiographic burnout due to juxtaposition of two materials with a huge difference in radiodensity lends another hurdle in providing any information about the root sliver and the surrounding tissues.

Of equal importance is a guideline being put to practice regarding the health of the root fragment being retained. There are many cases where the clinician encounters roots with old root canal sealers and filling materials that may have found their way into the dentinal tubules.

How prudent would it be to leave such a root fragment in close proximity to an immediately placed implant is a question we need to ask ourselves when selecting cases for socket shield.

Conclusion

Clinicians attempting partial extraction therapy and immediate implant placement should have sufficient experience and expertise in these protocols as a pre-requisite. Results observed from the work of clinicians experienced in the protocol may not necessarily be duplicated in the hands of operators with limited clinical exposure in the procedure. It is suggested that an evidence-based consensus protocol be put in place for case selection, which will enable clinicians to make objective decisions about opting for an optimal surgical protocol at the time of Type 1 (immediate) implant placement. It is also suggested that a large cohort RCT be done to assess the merits and technical protocols of the socket shield procedure more in detail.

Compliance with ethical standards

Conflicts of interest

The authors declare that they have no conflict of interest.