Introduction

It had been clearly shown in both animal and clinical studies that the alveolar ridge remodeling took place soon after tooth extraction, which would particularly affect the shape of buccal lamella.1,2  The major drawback on implant-based rehabilitation was bone resorption. Several studies had suggested that osseointegration might be achieved through immediate implant placement,3  but this method could cause multiple biological responses in the extraction socket.4,5  The guided bone regeneration (GBR) was another widely used technique to preserve the alveolar ridge.6,7  However, the bone graft placed between the implants and labial bony plate may not compensate the buccal bundle bone loss.8  The question remains on how to prevent the bone loss during tooth implantation. Therefore, it is eager to demand desirable solution.

After tooth extraction, the remarkable alterations in the buccal bone plate were caused by periodontal ligament loss and the consecutive trauma.9  Intriguingly, it seemed bone resorption could be prevented by root retention. Hürzeler et al10  evaluated effects of retaining the buccal portion of the root in conjunction with immediate implant placement. Their results demonstrated that this technique could restrain the buccal bone resorption to a large degree. It also achieved significantly higher implant success rates compared with longitudinal data on immediate implant placement after complete root extraction.1116  In previous reports, only 1 root fragment exhibited signs of resorption, at the same time, the implant remained functional.15 

Notably, when implants were placed lingual to the tooth fragment, connective tissues could be observed in the gaps, which would affect implants and the coronal root fragments. On the other hand, placing implants in direct contact with tooth fragments could increase risk of displacing buccal root fragments or missing the buccal lamellar bone. Even with those concerns, it was evident that the socket-shield technique could maintain the healthy periodontium, gingival tissues, and original crestal bone height and contour. To further improve this method and reduce adverse effects, we attempted to keep the gaps and fill them with bone graft materials to minimize root resorption. This case report was targeted to evaluate the feasibility of this modified approach in a clinical practice setting.

Case Presentation

A female, aged 52 with noncontributory medical history, was admitted for an emergency evaluation in the Affiliated Hospital of Stomatology, Chongqing Medical University, considering the pain she experienced posttrauma in the maxillary anterior region. Clinical assessments revealed a horizontal fracture line in the cervical area on the right maxillary central incisor. Thinness of the buccal bundle bone was less than 1 mm.

Phase 1 periodontal therapy was performed prior to the implant procedure. After administration of local anesthesia and preoperative rinsing with .12% chlorhexidine, the osteotomy drills were used through the lingual dimension of the root. Among all the lingual, mesial, and distal aspects, a 15c scalpel blade was utilized in sharp dissection of the supracrestal fibers. Next, root tip forceps were used to atraumatically remove all root fragments, except the buccal portion of the root. Then, Bio-Oss particles (Geistlich Pharma AG, Wolhusen, Switzerland) were inserted into the jumping gap. Finally, modified healing abutments were connected.

This patient was prescribed amoxicillin, 1 g tid for 3 days and analgesics as prophylactically measured. In the meantime, mechanical oral hygiene was totally avoided. To facilitate soft tissue reforming, temporary crowns were constructed 6 months after surgery. Then, final prostheses were restored 3 months later. To evaluate the peri-implant soft tissues of the final prostheses, the pink esthetic score (PES)17  was employed. A total score of 12 or more was defined as perfect. In this case, the PES score was 13.

Discussion

Retention of roots has been widely accepted as a promising technique to maintain alveolar ridge contour and develop pontic sites for a long time. Based on this, the socket-shield technique was introduced by Hürzeler et al in 2010.10  Buccal aspects of the retained roots preserved a normal periodontal ligament attaching to the buccal bone plate. Meanwhile, tips of the implant threads were in direct contact with the root fragment. They were surrounded by newly formed cementum with no signs of fibrous tissues. Later on, socket-shield technique was adopted by several groups.1116  The only complication spotted in the patients was apical root resorption of a single retained root fragment.15 

In our study, by palatal placement of the implant, the dentin–implant interface was avoided, aligning with fibrous tissue sheath around the implant,18,19  and side effects of apical root resorption were significantly reduced. According to the literature, the score of the present case (13) was higher than previously reported,21,24  which normally ranged from 9.5–11.5.1723  The satisfactory result lived up to rigid criteria.

Before applying the socket-shield technique, we have to analyze the conditions of the failing teeth. Contraindications of this technique included infection, fracture, internal or external resorption, and perforation. Failing teeth with mobility or widened periodontal ligaments were also contraindicated as they may increase the risk of root fragment dislodgement.11,25 

Flapless surgery guaranteed the blood supply of the buccal plate of the ridge. Minimal surgical invasion preserved stability of the tooth fragment. Being sectioned horizontally, the crown of the tooth structure was left with about 1 mm cervical extension coronal to the buccal marginal bone. Besides the potential of buccal bone preservation, dentogingival fibers were also helpful to level off soft tissues.

Subsequently, the remaining root fragment was prepared using a high-speed diamond bur, with durable thickness (1.0 to 1.5 mm), occupying half of the full root length (4–6 mm length) at least 1-mm deep.

In the present case, the implant design was employed via a platform switch that had been found to minimize marginal bone loss.26  The tapered implant was underperformed with a biased palatal placement and lacked of facial teeth–implant contact. The 2-mm “labial gap” between tooth fragment and implant provided sufficient running room. This gap ensured the tooth socket was filled with a sufficient amount of bone materials.

After 6 months, we observed new bone formation between the implant and the tooth segments in cone beam computed tomography, which led to what we viewed as a delightful appearance of the gingival tissues.

Although the short follow-up period—just 6 months—is a limitation to our study, another limitation was lack of histologic analysis. We need a greater number of patients and long-term follow-up studies with histologic analysis to confirm this observation.

Overall, this technique is still under development and only recommended for experienced surgeons.

Abbreviations

    Abbreviations
     
  • GBR

    guided bone regeneration

  •  
  • PES

    pink esthetic score

Acknowledgment

Project Supported by Program for Innovation Team Building at Institutions of Higher Education in Chongqing in 2016 (NO. CXTDG201602006).

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Author notes

**

These authors contributed equally to this work.