Shield the socket: Procedure, case report and classification

The extraction of a tooth leads to a cascade of events which results in resorption of the alveolar bone around the socket. The buccal bone loss that occurs postextraction leads to vertical and horizontal bone loss. It requires complex hard and soft tissue reconstruction to achieve esthetically pleasing results in such cases. In the socket shield technique (SST) the root is bisected, and the buccal two third of the root is preserved in the socket so that the periodontium along with the bundle bone and the buccal bone remains intact. A classification of SST technique is proposed depending on the position of the shield in the socket. This classification is required so as to help in understanding the preparation design and the role of shield and in maximizing the usage of the shield to achieve best possible esthetics in immediate implant placement sites

INTRODUCTION
One of the major goals of prosthetic rehabilitation is to achieve and maintain the harmony between the pink and white zones especially in the esthetic areas. Atraumatic extraction of a tooth with immediate implant placement was found to result in the loss of buccal bone, both vertically and horizontally as well as flattening of the interproximal bony scallop resulting in a complicated rehabilitation.[1] The loss of supporting bone followed by the apical migration of soft tissue results in unesthetic black triangles between teeth. This presents a very challenging situation to a clinician in restoring the missing tooth with restoration having an acceptable esthetics, especially in the maxillary anterior region. Many preventive procedures such as ridge preservation techniques, and postridge collapse procedures, such as bone augmentation, soft tissue augmentation, or a combination of these, have been used in the past to compensate for this loss. On the other hand, the socket shield technique (SST) is used as a predictable therapy with minimum surgical intervention, less duration of total treatment, an optimum esthetic result.

The SST provides a promising treatment modality to manage these risks and preserve the postextraction tissues in esthetically challenging cases. The principle is to prepare the root of a tooth, which is indicated for extraction, in such a manner that the buccal/facial root section remains in place.

This technique is also known as partial extraction therapy,[4] root membrane technique,[5] and partial root retention. It aims at preserving the buccal two third of the root in socket so that the periodontium, along with the bundle bone and the buccal bone remains, intact. The buccal bone has bilateral blood supply from the gingiva above and the periodontium below. Once a tooth is extracted, buccal bone is deprived of the blood supply from socket side and this result in the loss of some buccal bone. The root section preserves the periodontal attachment apparatus that includes periodontal ligament (PDL), attachment fibers, vascularization, root cementum, bundle bone, and alveolar bone.[6] The root fragment remains vital and undamaged and prevents the expected postextraction socket remodeling and also supports the buccal/facial tissues

Procedure

The steps of the SST used for immediate implant placement are summarized as below

• Step 1: Cut the crown horizontally at the gingival level [Figure 1]

• Step 2: Bisect the root vertically in such a manner that palatal half is removed along with the apex

 

The length of the shield should be kept at two third of the root length. This step requires lot of practice, patience, and time. The buccal part is then reshaped such that the shield width is about 1.5–2 mm. The shield should be trimmed to the bone level. A bevel or S‑shaped profile on the inner side of the shield is given to accommodate the restorative components [Figure 2]. 

 

• Step 3: Placement of implant in correct three‑dimensional (3D) position

The optimum space between shield and implant is 1.5 mm or more. A bone graft is suggested if the gap is more than 3 mm. A provisional crown or a customized healing abutment given immediately after the implant placement will help in maintaining the soft tissue contours. The choice of prosthesis for the final restoration is a screw retained crown or a cement retained crown with restorative margin that can be easily accessed for cement clean up [Figure 3].

 

CASE REPORT
An adult female patient presented for the treatment of a fractured right central incisor [Figures 4 and 5]. The medical history was noncontributory. Implant placement with SST was chosen as treatment of choice. Following administration of local anesthesia, the tooth was sectioned at gingival level [Figure 6] and then divided into buccal and palatal parts using a long root resection bur [Figure 7]. This was intended to preserve the buccofacial half of the root intact and undamaged. Periotomes were used to sever the PDL [Figure 8], and palatal section of root was then carefully removed without traumatizing the buccal root section. The remaining root section was then shaped properly and reduced coronally to the level of the alveolar crest. The shaping of the section was done by thinning it both in apicocoronal and mesiodistal direction (using a long shanked, large, and round diamond bur). The extraction socket was then curetted to remove any granulation tissue, and buccal root shield was checked for immobility by applying a sharp probe to its surface. Once fully prepared, this root section is known as the socket shield or root membrane. The implant placement procedure was done as per the drilling sequence suggested by the implant manufacturer. The drilling was initiated using a lance drill to engage the palatal aspect of the root so that the buccal aspect would remain intact.

Following implant bed preparation, a tapered internal hex implant, 3.8 mm × 15 mm was placed in correct 3D position [Figures 9 and 10]. The implant so placed had mesial, distal, and palatal bony walls. On the buccal side, it had the remaining buccal portion of the root which had thin layer of dentine, followed by cementum PDL, and bundle bone in socket facial direction. After the implant placement, a screw retained temporary crown was fabricated, chairside as per routine protocol for immediate implant placement in the esthetic zone [Figures 11 13]. Following fabrication of the interim restoration, a meticulous occlusal check was performed to ensure nonfunctional loading. Postsurgical instructions included antibiotics and analgesic medication and chlorhexidine 0.12% oral rinse. The patient was also instructed to defer from tooth brushing or any mechanical trauma in the area for 2 weeks.

 

At 2 weeks, the patient was asked to return for a postoperative evaluation. Clinical and radiographic evaluation of the site was done after 3 months postoperatively. The routine clinical protocol was employed for the fabrication of the definitive restoration. Complete preservation of hard and soft tissue was noticed at the surgical site [Figure 14]. Zirconia abutments were used to fabricate the esthetically pleasing lithium disilicate crowns [Figures 15 17]. The patient was kept on follow up 3 months, 6 months, and yearly [Figure 18], thereafter.
 

DISCUSSION
The preservation of the entire attachment apparatus for complete preservation of the alveolar ridge makes SST, a promising procedure that helps to maintain the pink white esthetics. Before the procedure is actually done, a proper diagnosis should be made, and the site should be carefully evaluated. The patient may present with a complex and a mixed clinical scenarios such as two adjacent root stumps, root stumps adjacent to an edentulous site or implant. These sites present different challenges in front of the clinician and require a different treatment plan.

According to Salama et al., height of interdental papilla has limitations in vertical soft tissues height in addition to the proximal limitations. The vertical soft tissues height is different in different restorative scenarios [Table 1].[1] This table indicates that the adjacent natural tooth scenario has an advantage over the implant – natural teeth or implant implant combinations. In addition to this, Tarnow et al.[9] suggested that there should be minimum of 3 mm inter implant distance to have an ideal interdental papilla.

These studies provide a new dimension to the SSTs, wherein the shield can be prepared and modified in various clinical situations,[10] to preserve and maintain the hard and soft tissues, both horizontally and vertically.

Based on this, the authors propose a classification of various shapes of the shield to preserve soft and hard tissue contours and for the maintenance of the papillae

Classification
It is proposed that the classification of SST technique will help in understanding the clinical application of this technique depending on the position of the shield in socket. This classification is required so as to help in understanding the preparation design and role of shield, in treatment planning various clinical scenarios discussed above. 

Type I: Buccal shield
A case can be classified as buccal shield when the shield lies only in buccal part of the socket, (between proximal line angles of tooth). It is indicated in single edentulous site with both mesial and distal tooth present [Figure 19]


Type II: Full C buccal shield
A case can be classified as Full C Buccal shield when the shield lies in buccal part and the interproximal part on both sides of the socket.

This shield design is recommended for the following clinical scenarios:

• Existing implant on either side of the proposed site [Figure 20]
• Missing tooth on either side without an implant
• Having implant on one side and missing tooth on the other side.

Type III: Half C buccal shield
A case can be classified as half C buccal shield when the shield lies in buccal part and one of the interproximal part. This design is recommended when there is tooth on one side and implant or a missing tooth on the other side [Figure 21].

 Type IV: Interproximal shield
A case can be classified as interproximal shield when shield lies only in mesial or distal part of the socket. This design is indicated when there is buccal bone resorption requiring graft, and there is an adjacent side with missing tooth or an implant. Extraction of the complete tooth in such cases may lead to loss of the valuable interproximal bone [Figure 22].

Type V: Lingual‑palatal shield
A case can be classified as Lingual‑Palatal shield when the shield lies on the lingual or palatal side of the socket. This type of shield design has few indications but could be considered for maxillary molars [Figure 23].


Type VI: Multiple buccal shields
A case can be classified as multiple buccal shields when it has two or more shield in the socket. It is indicated in cases with a vertical root fracture. There is evidence to show bone deposition in between fractured roots which could assist in holding the two fragments in place [Figure 24].

Advantages of socket‑shield technique 

It is a minimally invasive surgical procedure, aimed at preserving a part of the root to help in maintaining hard and soft tissue contours. It minimizes the need of soft and hard tissue grafting procedures and hence shortens the overall treatment duration. Even in cases with adjacent implants, the interdental papilla can be preserved by preparing interdental socket shield. This is a highly promising technique in terms of maintaining pink and white esthetics and provides a solution for esthetically critical cases such as high lip line and maxillary anteriors. This technique not only preserves but also helps to maintain the hard and soft tissues, in future, as long as the shield is intact.

Limitations of the socket‑shield technique The clinician needs to be specially trained and need to have a high degree of clinical skills. The procedure requires a little more time and patience to avoid mobility in the shield. If the shield becomes mobile during surgery, it is removed and the conventional immediate implant placement or the grafting procedure is to be done. The case selection is very important for the success of the procedure. The technique is not recommended in mobile teeth, teeth which are out of the arch and teeth with large periapical lesions. The intactness of the shield plays an important role in the success of the treatment.

The classification discussed above is a suggestive hypothesis and needs to be confirmed by clinical studies to prove the safety as well as the claims that bone height and papilla will be maintained; applying such modifications of the original technique

CONCLUSION
The SST is gaining popularity among the clinicians across the world. The technique is very promising for the preservation of hard and soft tissues in cases of postextraction immediate implant placement. The proposed classification will enable clinicians to design the shield according to the clinical scenario and to achieve the best possible esthetics even in immediate implant cases.