Management of a Complication With Partial Extraction Therapy: A Clinical Case Letter and Clinical Recommendations

The socket shield technique (SST), introduced by Hürzeler, is an approach to minimize or eliminate the postextraction resorption of the labial cortical plate.¹  The intentional retention of a buccal root fragment, followed by immediate implant placement, has been reported to support and prevent the collapse of the buccal bone plate, thereby supporting the soft tissues.^1,2  This minimally invasive surgical procedure (1) maintains hard- and soft-tissue contours, (2) reduces the number of surgical and prosthetic interventions, and (3) shortens the overall treatment duration with superior esthetic results.^3–6  This technique also reduces the need for biomaterials required for additional hard- and soft-tissue grafting versus the use of an early or delayed implant placement protocol used for similar cases.²  The SST, also known as partial extraction therapy (PET), has now been documented for more than a decade, with an implant survival rate of 96.5%. The technique is also supported by emerging clinical data.^7,8 

This technique of implant placement, although clinically challenging, has demonstrated successful clinical outcomes in the existing literature.^9,10  However, some clinical studies with PET have demonstrated several types of complications commonly related to (1) infection due to the retained root fragment, (2) bone loss, (3) failure of osseointegration, (4) mobility and migration, and (5) exposure of the shield. Crestal/buccal bone loss accounts for 78.78% of all complications followed by exposure of the shield (15.15%) and deep pockets (3.03%).^9,10  A recent review by Gharpure and Bhatavadekar¹¹  on the current evidence on the SST discusses the various complications and outcomes of PET. However, in clinical scenarios, in which the risk of implant failure with the use of PET is considered high, socket preservation techniques should be considered.¹²  Bone augmentation and/or connective tissue grafts have been successfully used to compensate for (or prevent) horizontal bone loss when conventional protocols are followed for immediate placement of implants in extraction sockets.

This case report demonstrates a soft-tissue complication encountered with the SST due to bone loss and its management using an autogenous connective tissue graft.

A 49-year-old woman with a 2-month history of controlled diabetes mellitus reported to the implantology department with a fractured restoration of her upper left lateral incisor. The tooth had undergone endodontic treatment 20 years earlier and was restored with a porcelain fused to metal crown. Clinical and radiographic examination of the site demonstrated a noncarious, endodontically treated and periodontally healthy root piece in relation to No. 10 upper left lateral incisor (Figure 1). There was generalized spacing between the anterior teeth and an anterior open bite. A thin gingival biotype was observed. On exaggerated smiling, a high smile line with acceptable gingival zeniths at adjacent teeth was noted. A sagittal section of the cone-beam computerized tomography (CBCT) scan showed the root piece in close juxtaposition to a very thin labial bone cortex, classified as Class I sagittal root position, based on Kan's classification^13,14  (Figure 2).

An immediate implant placement was planned in conjunction with the SST. A screw-retained final restoration would require the implant be placed with its shoulder positioned toward the palate, thus running a risk of dehiscence of the labial plate at the apex of the implant. Therefore, a cement-retained crown was planned for the definitive restoration. Using the International Team for Implantology's SAC (straightforward, advanced, complex) assessment tool, the case was classified as “complex.”¹⁵ 

The surgical phase began with the segmentation of the root piece corono-apically using a long shank bur (Komet Dental, Rock Hill, SC). The apex of the root and the palatal segment of the root were completely removed, followed by coronal and apical sectioning of the labial (buccal) segment. The coronal labial root segment was left intact as a shield for buccal wall preservation and was reduced to the level of crestal bone¹⁰  (Figure 3). A Biohorizons tapered internal 3.8 × 15 mm 3.5 platform implant (Biohorizons Implant Systems, Inc, Birmingham, Ala) was placed. The implant stability quotient (ISQ buccal 60, mesial 54, distal 57, palatal 60) was assessed using the Osstell ISQ instrument (Osstell, A WGH Company, Gothenburg, Sweden). A low-profile gingiva former was connected to the implant, and the gap between the implant and the labial tooth fragment was grafted with small-particle xenograft (Cerabone, Biotiss Biomaterials, Zossen, Germany).

An acrylic partial denture was fabricated before surgery and delivered as a provisional restoration, taking care to ensure it did not touch the gingiva former. After 4 months, an implant-supported provisional restoration was inserted. Two weeks later, a soft-tissue defect was noticed on the midfacial contour of the provisional crown. The defect resulted in exposure of the metal abutment (Figure 4).

To improve the soft-tissue volume and esthetics, a connective tissue autograft was planned to treat the gingival recession that had occurred. Following administration of local anesthesia (2% lidocaine with 1:80 000 epinephrine; Lignospan Special, Septodont, Maharshtra, India), a modified Langer and Langer technique described by Bruno in 1994 was used to correct the defect (Figure 5a–c).¹⁶  Using a microsurgical knife (BLT15S Lance tip 15 degree), a partial-thickness horizontal incision at the base of the papilla was made at the cementoenamel junction level of adjacent teeth mesially and distally. Each horizontal incision was connected with a sulcular incision. These incisions were extended mesiodistally and apically to prepare a large flap for proper access and mobilization of the flap. The interdental papillae were deepithelized. A subepithelial connective tissue graft was harvested from the palate using the Langer and Langer technique.¹⁷  The connective tissue graft was then placed on the recipient bed and stabilized with the help of sling sutures (suture 4-0 Nylon PS-2 Ethilon black 18″ monofilament; Ethicon Inc, J&J Company, Cincinnati, Ohio). The flap was then advanced coronally and secured with interrupted sutures. The patient was advised to (1) not brush on the surgical site for 2 weeks, (2) gently clean the area twice daily using 0.2% chlorhexidine for 2 weeks, (3) take the prescribed Augmentin Duo 625 mg antibiotic (500 mg amoxicillin + 125 mg clavulanic acid; GlaxoSmithKline Pharmaceuticals Ltd, Maharashtra, India) twice a day for 5 days, and (4) take the nonsteroidal anti-inflammatory drug (Enzoflam, diclofenac 50 mg + paracetamol 325 mg + serratiopeptidase 15 mg; Alkem Laboratories Ltd, Mumbai, India) twice a day for 5 days. Suture removal was done after 10 days, and the patient was advised to resume brushing using a soft toothbrush. Follow-ups were performed on a weekly and then monthly basis up to 6 months to check for graft acceptance and coverage of the recession defect.

After 6 months, the final restoration, a cement-retained zirconia crown (Lava premium high-translucency all-zirconia crown; 3M, St Paul, Minn) was fabricated and inserted (Figure 6). The patient was followed up at regular intervals. One- and 2-year follow-up showed stable, well-healed, and healthy peri-implant soft tissue (Figures 7 and 8).

Peri-implant soft-tissue biotype and contour are key determinants in the long-term success and esthetic outcome with dental implants.^18,19  Soft-tissue thickness greater than 2 mm is required around dental implants to ensure good soft-tissue health and masking of restorative components.²⁰ 

Implants with less than 2 mm of soft-tissue thickness are significantly more susceptible to recession and greater marginal bone loss over time.^18,21  Soft-tissue defects around implants occur most commonly due to improper implant position, inappropriate contour of the abutment, larger than required implant diameter, and a thin gingival biotype.²²  Patients with thin biotypes have an increased incidence of gingival recession.¹⁶  Likewise, in cases where PET has been performed, loss of buccal hard tissue due to improper trimming of the root fragment and increased bone resorption has been reported. This leads to inadequate support for soft tissue, which therefore requires correction through augmentation.^23,24 

In a systematic review by Lee and coworkers,²⁵  1.07 mm of horizontal bone loss and 0.78 mm vertical bone loss has been reported after the conventional immediate placement of implants. Bäumer et al²⁶  reported an average midfacial recession of 0.33 ± 0.23 mm around immediately placed implants with SST. A prospective case series study on the SST by Hinze et al²⁷  reported a mean change of 0.17 ± 0.67 mm in the gingival margin, with 8 patients showing gingival recession around implants.²⁷  The findings in this case report are greater than in those reported studies.

Soft-tissue grafting aids in maintaining keratinized mucosa with reduced marginal bone loss over time.²⁸  Defects such as soft-tissue recession around implant restorations can be corrected using connective tissue grafts with a coronally repositioned flap.^29–31  The subepithelial connective tissue graft has a high predictability rate, provides superior esthetic results, and is also capable of achieving increased keratinized tissue width.³²  In 93% of cases, connective tissue grafting achieved a final soft-tissue thickness of ≥2.5 mm.³³  A review by Lin et al³⁴  stated that no difference was found between immediate and staged soft-tissue augmentation around implants when keratinized tissue width and midbuccal marginal recession was assessed.³⁴ 

The failures in SST are known to occur due to resorption of the root fragment or presence of an infection. This is usually followed by bone loss and soft-tissue recession and even implant surface exposure. Gluckman et al¹⁰  recommended that the residual root fragment be trimmed down to the osseous crest prior to implant placement. On the contrary, Siormpas and coworkers recommended that the root fragment be kept 1 mm above the osseous crest.^10,35  In the present case, with the labially inclined root piece and lack of bone in the crestal 1 mm of the root, the soft tissue was vulnerable to recession once the root was sectioned and the residual fragment was trimmed down to the bone crest. Such a recession was seen approximately 5 months after the implant surgery. A similar complication and principles of management have recently been reported by Zuhr et al,³⁶  who also treated a soft-tissue defect in a partial extraction situation using a connective tissue graft. They stated that the long-term failures in the SST protocol are manageable.³⁶  Assessment of anatomy, identifying possible risk factors and complications with this technique, are essential for its successful application in today's implant therapy.

Based on the outcomes of this case report and the current literature on SST, the authors provide the following clinical recommendations:

1. PET is a complex clinical procedure and must be attempted only by experienced clinicians with advanced training in surgical and restorative implantology, especially related to management of potential complications.^26,24 

2. In cases in which the root is positioned very closely along the labial cortical plate, PET may be considered as one of the treatment modalities, in order to eliminate/minimize labial bone loss and reduce the need for future augmentation procedures that may be required with early or delayed implant placement.^14,24 

3. Bone sounding must be performed without fail, prior to the root sectioning and trimming procedure. If the labial bone crest on the tooth to be extracted is more apical than that of the adjacent teeth, one must consider not trimming the root fragment to the bone crest so that the soft issue does not lose support and undergo recession.³⁷  In these cases, the root fragment sliver, if subgingival, must be reduced in height only to the point of being level with the bone crest of the adjacent teeth. The authors have encountered situations in which there is a midfacial bone loss and the root fragment needed to be trimmed down to the bone level (due to caries or fracture), but they have always used a concomitant soft-tissue graft as part of the partial extraction treatment protocol in such cases.³⁷ 

4. In implant placement with SST with thin gingival biotype, a connective tissue gingival graft at the same time of implant placement can minimize or eliminate potential soft-tissue complications in the future.^38,39 

The SST can be considered as a very promising treatment protocol, owing to its conservative approach and considerable reduction in treatment time and cost for complex esthetic cases. However, one must remember that there are risks associated with the procedure that can lead to numerous complications; therefore, clinical expertise and precise case selection are instrumental in determining its clinical success.¹¹