Denta l Extract ion s and P re s e r v a t i o n of Sp a c e f o r I m p l a n t Pl a c e m e n t i n M o l a r Sites Michael S. Block, DMD KEYWORDS  Dental implants  Extraction sites  Mandibular molars

KEY POINTS

INTRODUCTION The clinician is often asked to remove a tooth and place an implant into the site. The implant must be placed with appropriate stability to allow for integration to occur, which requires bone presence. Bone is also necessary to allow for ideal implant positioning within the alveolus for functional and esthetic concerns. The purpose of this article is to discuss the changes in socket dimensions over time and how to promote space maintenance, with an algorithm for treatment based on evidence.

SOCKET HEALING Socket healing approximates 40 days, beginning with clot formation and culminating in a bonefilled socket with a connective and epithelial tissue covering.1,2 An extraction site may heal with bone formation to preserve the original dimensions of the bone. Unfortunately, bone resorption is common after tooth extraction. The use of graft material may be necessary to provide ideal bone for

implant placement and reconstruction of the patient with an esthetic and functional restoration. Bone resorption usually is greater in the horizontal plane than in the vertical plane.3,4 Horizontal bone loss may be enhanced by thin facial cortical bone over the roots or bone loss from extension of local infection, such as caries or periodontal disease. Ideal placement of a dental implant centers the implant over the crest in a line connecting the fossae of the adjacent posterior teeth, or for anterior teeth, palatal to the emergence profile of the planned restoration. Unless the horizontal bone dimension is reconstructed or preserved after tooth extraction, implant placement is compromised, and in the esthetic zone, flattening of the ridge will occur, which results in a compromised restoration appearance. In the posterior mandible, these changes may be less dramatic, presumably because of the thickness of the buccal bone. The thin bundle bone, which was/is adjacent to the tooth roots, lies within the corpus of thick buccal cortical bone, and thus its remodeling may not result in rapid loss of ridge width.

Private Practice, 110 Veterans Memorial Boulevard, #112, Metairie, LA 70005, USA E-mail address: [email protected] Oral Maxillofacial Surg Clin N Am - (2015) -–http://dx.doi.org/10.1016/j.coms.2015.04.001 1042-3699/15/$ – see front matter Ó 2015 Elsevier Inc. All rights reserved.

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 The algorithm for implant placement, either immediately after tooth removal or delayed, works well with excellent long-term crestal bone width maintenance.  Clinicians can use tissue health as 1 factor to form their treatment strategy for the timing of implant placement into molar sites.  Bone resorption is common after tooth extraction; the use of graft material may be necessary to provide ideal bone for implant placement and reconstruction of the patient with an esthetic and functional restoration.

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Block With regard to the esthetic zone of the maxilla, which includes the premolars, canines, and incisors, patients often present with teeth in need of extraction. Reasons for extraction of a singlerooted maxillary tooth in an adult include internal or external resorption after trauma, a breakdown of post and cores that were placed because of trauma, caries, root canal failure, and periodontal disease. Traditional protocols for restoring these sites rely on bone deposition to fill the extraction site before the implant is placed.5,6 Hard and soft tissue grafting often is necessary to provide an ideal functional and esthetic restoration. Grafts compensate for the bone resorption that accompanies the natural healing process in an extraction socket.7–10 When implants are placed 8–16 weeks after tooth extraction, the clinician must compensate for the loss of labial bone that occurs during the early phase of extraction site healing.3,11,12 To prevent the need for hard or soft tissue grafting when implant placement is delayed, it is recommended to place an osteoconductive graft material within the extraction site to promote bone fill, to limit labial bone collapse, and to maintain bone for optimal implant placement.13

TREATMENT PLANNING When a patient presents with a molar tooth in need of removal, 3 situations are common:

1. The tooth is nonrestorable but has intact surrounding bone and relatively healthy gingiva, with minimal pain (Fig. 1). 2. The tooth is nonrestorable and has intact surrounding bone. However, the tooth is acutely painful and may have purulent exudate and nonhealthy gingiva. 3. The tooth is nonrestorable but has lost a portion of the buccal bone (Fig. 2). Preoperative imaging can determine the presence of the surrounding bone, the presence of interceptal bone, and the location of the inferior alveolar nerve canal in relation to the tooth. Sufficient space is necessary for placement of an implant of sufficient length to maintain a single molar implant tooth. The molar tooth has roots that diverge and are separated by an isthmus of bone. The thickness of the bone between the roots may not be sufficient by itself for immediate implant placement. The labial and lingual cortical bone plates narrow in the apical regions and can be engaged to stabilize an implant in the molar site. The bone surrounding the molar tooth may be completely intact, or chronic infection may have caused large areas of bone loss, which if not grafted, result in inadequate bone available for implant placement. If the treatment plan includes placement of an implant into a posterior tooth site, cone-beam cross-sections

Fig. 1. (A) This patient required removal of a lower right first molar. The tooth was in cross bite. (B) A sulcular incision was made with vertical release sparing the papilla and a flap developed. The tooth was removed. (C) The implant was placed on the lingual aspect of the extraction site to correct the cross bite. The initial drill was placed without regard to interceptal bone, since the implant position needed to be different than the tooth’s position due to the cross bite tendency. Allograft was placed into the defects from the root sockets. (D) A postoperative radiograph shows good implant positioning.

Dental Extractions and Preservation of Space

Fig. 2. (A) This patient’s mandibular first molar requires extraction. The patient had been using antibiotics and chlorhexidine rinses preoperatively to reduce the bacterial flora around this tooth as much as possible. (B) An incision is made around the labial surface of the tooth and linked with 2 vertical extensions. The vertical releasing incisions are made within the site of the first molar, with care taken to avoid raising the attached tissues on the adjacent teeth. A full-thickness exposure is performed, exposing the lateral aspect of the tooth and the extensive bone loss. (C) The tooth is removed along with a small amount of granulation tissue. The area is irrigated thoroughly. Note the intact lingual plate of bone and the loss of the labial plate to the root apices. This defect has intact mesial and distal walls, as well as the lingual plate; therefore, this can be characterized as a 3-wall defect. (D) A graft of human mineralized bone is placed into the defect to reconstruct both the height and the width of the socket. After compaction of the graft material, the area is closed primarily. Primary closure was achieved with advancement of the keratinized gingiva, previously on the labial aspect of the tooth, and was sutured to the lingual aspect of the ridge. Chromic sutures are used in the vertical releasing incisions. To advance the flap, the periosteum was scored to provide mobilization of the flap, allowing tension-free closure. (E) 4 months later, the ridge has healed and is ready for implant placement. (F) This is the final crown 2 years after implant placement showing an excellent tissue response. (G) The 2 year radiograph showing excellent bone healing around the implant.

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Block can be used to determine the amount of bone available or determine that there has been significant bone loss that prevents primary stability of the implant at time of tooth removal.14 The technique described next has proved useful for grafting of the posterior molar site. After reviewing the image from a cone beam scanner, and the physical examination of the patient, a decision can be made for treatment.

ANATOMIC CONFIGURATIONS AFTER TOOTH EXTRACTION After a tooth has been extracted, the resultant defect in the bone may have several anatomic configurations that directly influence implant placement. This section discusses 10 findings that may be seen after tooth extraction. Each finding may be isolated or may be among several morphologic observations (Box 1).

Loss of All Facial Bone to the Apex of the Tooth If the bone on the facial aspect of the socket is not present, the clinician should graft the socket and delay implant placement. Primary implant stability at the time of placement is compromised by the loss of bone. A mobile implant at the time of placement does not reliably integrate. These sites need to be reconstructed with bone before implant placement.

pathology associated with the tooth, the preferred treatment is to graft the socket and place the implant 4 months after grafting.

Loss of Less Than 3 mm of Facial Bone at the Crest This is a common situation when a tooth has extensive caries or a fracture. Crestal resorption may be limited to 3 mm from the planned gingival margin or the cemento-enamel junction (cej) of the adjacent tooth. In this situation, the implant can be placed at the level of the bone. This places the implant 3 mm from the gingival margin, which is the preferred location. There is usually no need to graft the buccal bone in this situation unless it is very thin.

Lack of Bone Inferior to the Apex of the Socket, with Extreme Proximity of Adjacent Vital Structures, Such as the Inferior Alveolar Canal or Mental Foramen These extraction sites may need grafting prior to implant placement to ensure implant stability is achieved only.

Lack of Lingual Bone This is an uncommon finding, because lingual bone is the last to resorb after tooth loss. If the lingual bone is not present, a graft is necessary before placement of an implant.

Loss of a Portion (3–6 mm) of the Facial Bone

Concavity Within the Extraction Site When Removing an Ankylosed Deciduous Molar

In this situation, a graft is necessary to restore the facial portion of the missing bone. If the surgeon is unsure of the result in these cases and 50% of the facial bone has been lost as a result of the

This finding is seen in younger individuals and is associated with congenitally missing teeth and retention of the deciduous teeth. The buccal bone may be normal in shape, with a concavity

Box 1 Anatomic configurations after tooth extraction 1. Loss of all labial bone to the apex of the tooth 2. Loss of a portion (3–6 mm) of the labial bone 3. Loss of

Dental Extractions and Preservation of Space for Implant Placement in Molar Sites.

The clinician is often asked to remove a tooth and place an implant into the site. The implant must be placed with appropriate stability to allow for ...
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