Introduction
Extraction of the tooth sets up a cascade of reactions in the surrounding alveolar bone in an attempt to heal the socket. This is generally associated with some degree of loss in the alveolar bone dimensions. Residual ridge resorption is a continuous process and occurs most rapidly in the first six months of extractions. Estimated dimensional loss of alveolar bone has been accounted to 29-63% horizontally and 11-22% vertically after 6 months following tooth extraction.1
The loss of the supporting alveolar bone and subsequent apical migration of the overlying gingival tissue result in interdental spaces between the teeth. These spaces contribute to an unaesthetic appearance owing to the presence of the so-called ‘black triangles’.2 The condition is especially of concern when present in the maxillary anterior region as it affects the esthetics of the patient. The intervention of the resorption process can be done by rehabilitating the edentulous ridges with dental implants. Furthermore, if rehabilitation of the lost tooth is to be done by means of dental implants, it is crucial to maintain an adequate amount of supporting alveolar bone and vascularity around the tooth socket to prevent inadvertent failure of the implant.3
To prevent the collapse of the cortical plates and maintain the dimension of the alveolar ridge, various strategies have been devised over the years. Ridge preservation techniques, hard and/or soft tissue augmentation procedures, socket preservation, and immediate implant placement have been used in the past to compensate for this loss. 4 Although varied degrees of success have been reported, these procedures have failed to demonstrate optimal preservation of the alveolar socket. 5
Partial Extraction Therapy (PET) is one such procedure that provides optimum esthetics with minimum surgical interventions and requires shorter treatment times. PET collectively involves root submergence, Socket-shield technique (SST), Proximal socket-shield technique, and Pontic shield technique. 6 The present review aims to provide a comprehensive overview of the various aspects related to SST in implant dentistry such as its indications, procedure, advantages, and limitations. The review holds an objective to elucidate the complexities related to SST in a simplified manner to the clinicians aiding them to understand the concept better.
The Socket Shield Technique
The SST, first proposed by Hurzeler et al., involves the preservation of the root of a tooth with intact buccal bone, preserving the periodontium and bundle bone.4, 5, 7 Thus, it is also known as Partial root retention or root membrane technique. With the preservation of a portion of the tooth root, the loss of PDL is avoided, thereby reducing the remodeling and resorption of hard and soft tissue associated with tooth extraction.8 The indications and contra-indications of the SST are listed in Table 1.
Table 1
Indicationsand contra-indications of the socket shield technique
Classification
Kumar PR and Kher proposed the classification for various types of socket shields that can be employed to preserve the soft and hard tissue and to maintain the height of the interdental papilla (Table 2).9 The classification provides an understanding of the preparation design and treatment planning. (Figure 1)
Table 2
Classification of the socket shields and their specific indications
Surgical procedure
The SST technique involves several sequential tooth preparatory and implant placement steps. Initially, the tooth is decoronated under local anesthesia with a high-speed handpiece under coolant using diamond rotary instruments at the gingival level.10, 11 The root is then sectioned vertically in a mesiodistal direction. Intraoral periapical radiographs or alternatively, Gates Glidden drills may be used to determine the length of the root. The palatal sections of the root are mobilized within the socket with the aid of peritome/microelevators following which it is removed by microforceps.
A concave structure is prepared on the facial part of the root with the rotary instruments. Additionally, the socket shield is reduced to approximately half the thickness from the canal to facial limits.4, 11 Curettage of the apical portion of the socket is performed to eliminate debris or pathological tissues present within the socket. The roots are then reduced coronally using large diamond burs up to the level of the alveolar crest. An internal beveled chamfer is created to accommodate the S-shaped prosthesis emergence.10 Implant osteotomy should be prepared apical and palatal to the fully prepared socket and the Implant is placed according to conventional protocol. To compensate for the jumping distance, graft material can be used if the space is larger. 12
The overall procedure for SST is depicted inFigure 2
An interim crown can be placed if adequate implant stability is achieved (ISO > 70), or a custom trans gingival abutment is attached if ISO < 60. The interim crown should have minimal or no contact in maximum intercuspation or excursive movements. 10
Advantages and Limitations
The SST offers numerous advantages over the conventional surgical techniques for preservation of alveolar bone width comparatively to which it is less invasive. 13, 14 Conventional bone and soft tissue augmentation procedures require a donor site. The need for a donor graft is eliminated in SST, and this eliminates the complications associated with a second surgical site.4 Although some preparatory procedures are required, the overall duration of treatment time is reduced because of the preservation of the socket dimensions. The technique provides optimal esthetic results by effectively preserving the soft and hard tissue contours. The preservation of the interdental papilla by an interdental socket shield further enhances the esthetic results for the patient.13, 14
While there are various advantages for which clinicians may opt for SST, some of its inherent limitations must be borne in mind. The SST procedure is technique-sensitive and thus, requires a high degree of clinical and technical expertise. 4 Additionally, there is a requirement for absolute immobilization of the socket shield when they are adapted to the socket walls. It is imperative to remove the shield in case it moves during the surgical procedure for any reason. 9
The ‘Jumping’ Distance
According to Han CH et al., 72.6% bone-to-implant contact was present when the SST was used to preserve the buccal bone plate with healthy periodontal tissue. 15 The authors observed that all implants survived one-year post-placement with very few complications. It is recommended that there should be at least 1.5mm of space between the shield and the implant. Should the distance between the bone and implant increase to more than 3 mm, bone grafting procedures are warranted. This distance of 3mm, is thus, referred to as “Jumping Distance”. 16 (Figure 3) It has been suggested to fill in the gap between the implant and the buccal portion of the root with particulate grafting material.11
On the contrary, Siormpas and Mitsias were of the view that grafting is not required to fill in the gaps between the implant and the socket shield as the method inherently preserves the PDL and associated vasculature. 17 Placing an implant immediately post-extraction into the sockets with an intact buccal wall can achieve adequate healing and osseointegration without the aid of any flap, graft material, or membrane despite the presence of a large gap.18
Hurzeler et al utilized heterologous graft material in cases where the jumping distance was 2 mm or more. 19 Other authors have suggested that grafting must be performed only if the distance is greater than 1mm. 16, 20
The gap between the dental implant and buccal shield when filled with PRF has exhibited prompt osteogenesis and an osteoconductive environment while providing an anti-infectious state. The growth factors from the PRF, such as platelet-derived growth factor and vascular endothelial growth factor promote bone regeneration and microvascular formation in the newly regenerated bone.21, 22 PRF also acts as an anti-inflammatory medium during the bone-healing period. 18
Conclusion
The SST provides favorable results in preserving the alveolar ridge immediately post-extraction and providing optimal esthetic outcomes. The technique is less invasive eliminating the need for a second surgical donor site and thus, more favorable to the patients. The present review would serve to provide the clinicians with necessary information relevant to the SST in an easy-to-comprehend manner.
