John Bogle, D.M.D.
Gary Eggleston, D.D.S.
University of Minnesota
Department of Endodontics
Ridge Preservation Following Tooth Extraction in an Endodontic Office
In the United States alone, more than 24 million endodontic (root canal) procedures are performed annually. These cases are often associated with emergency clinical symptoms, which can originate from endodontically-induced apical periodontitis. Endodontic therapy (initial treatment, — i.e., retreatment — or surgical treatment) can be utilized to retain the patient’s natural dentition. However, in certain clinical situations teeth are compromised significantly and cannot be saved. Such situations include external root resorptive defects, incomplete crown fractures, vertical root fractures, inadequate crown/root ratio, extensive caries, and other clinical findings which place the long-term prognosis of the tooth in uncertain territory. In these scenarios, extraction with replacement utilizing implant therapy should be considered in the patient’s treatment plan. However, many of these compromised teeth are accompanied by cortical plate defects. In many cases, the severity of these defects can only be fully comprehended during surgical exploration. The assistance of the dental operating microscope and diagnostic and technical resources have positioned the endodontist in an ideal situation to assess the prognosis of potentially questionable teeth.
During an exploratory and often diagnostic surgical procedure, if the tooth is deemed non-restorable, the endodontist is in the optimal position to preserve the remaining ridge. By maintaining the ridge height and width at the time of tooth extraction,the patient may be best staged for implant therapy. Grafting materials may enhance regeneration of natural bone and maintain the original ridge architecture to improve the prognosis of implant integration at a future appointment.1
The goals of surgical procedures, including endodontic surgery, periodontal therapy, and extraction with graft placement, are to restore the tissues to their normal architecture. This type of healing has greater predictability when Guided Tissue Regeneration (GTR) procedures are utilized because the downward growth of epithelium is inhibited.2 As an osseous wound heals, different cells compete to populate the defect. If epithelial cells are not excluded, they can migrate into the bony defect and undermine bone cell repopulation. Furthermore, when a cortical plate defect is present, the overlying mucosa or gingival tissue will collapse into the extraction site and possibly lead to a defect that would require more extensive surgery to accept an implant. GTR procedures have a two-pronged approach for periodontal regeneration. First, by excluding epithelium cells of the PDL, cementum and alveolar bone are encouraged to fill the site. Second, the graft material serves as a bioactive space maintainer, acting as a bone-inducing scaffold for new bone cells to colonize. Regeneration of PDL and cementum are more applicable to endodontic and periodontal surgery, whereas regeneration of alveolar bone is the goal of tooth extraction with graft placement.
Various materials for grafting are available. When considering ridge preservation, both osseous bone replacement graft materials can be autogenous (host tissue), allograft (different individuals, same species), xenograft (different species), and alloplast (synthetic). Each of these materials has various benefits and risks associated with treatment (Table One). Grafting materials can also be classified according to their interaction with the bone tissue. The gold standard of grafting material is an autogenous graft due to its osteogenic properties. That is, these materials contain viable bone-forming cells within them. Other materials (allograft) are osteoinductive, which contain bioactive substances that induce bone-cell migration and bone formation. Osteoconductive materials do not contain bioactive substances, but function as scaffolds for new bone formation.
In order for GTF therapy to be effective, epithelial cells and connective tissue fibroblasts should be excluded from the post-surgical site to allow for repopulation of the natural osseous area.3 3 These principles apply for endodontic, periodontal, and ridge preservation surgeries. Various materials exist to accomplish the goal of tissue exclusion. Membranes can be composed of non-resorbable or resorbable materials. The most commonly used non-resorbable material is expanded polytetrafluoroethylene (GoreTex®).4
The benefits of most non-resorbable membranes are their biocompatibility and space maintenance capacity. However, these materials do require a second surgical procedure for removal. To avoid the need for additional surgical procedures, new membranes have been developed that are resorbable by the body. The dental market has seen an influx in the number and type of resorbable membranes used for GTR therapy. These can be composed of collagen, calcium sulfate, chitosan, polyurethane, polylactic acid, and others. Research has shown that resorbable membranes can achieve clinical results similar to non-resorbable membranes. Thus, by utilizing resorbable membranes, favorable results in regeneration can be achieved with minimal surgical intervention to prepare a site to receive an implant.
Extraction site preservation can take on many forms depending upon the clinical situation. Perhaps the two most important factors in ridge preservation are (1) maintaining the physical space, and (2) excluding the epithelium from the healing site. Currently, these objectives are best accomplished with the combination of a bone graft (to maintain space and induce bone formation) and a membrane (to exclude epithelium). A bone graft consisting of a mixture of demineralized freeze-dried bone allograft (DFDBA) and calcium sulfate (1:4 by volume mixed into a “paste” with sterile water) has a number of advantages. By using a demineralized bone graft, important growth factors are capable of being liberated from the matrix, therefore, possessing osteoinductive properties. Although DFDBA has the advantage of being osteoinductive, it does not have good longevity beyond a few weeks (limited osteoconductive properties). This disadvantage may be overcome by adding calcium sulfate (an alloplast with good osteoconductive properties), which will maintain space for new bone growth by preventing collapse of the overlying soft tissue. Additionally, the graft in the aforementioned DFDBA-calcium sulfate mixture is radiolucent when placed. In follow-up appointments, an increase in radiopacity of the graft site as the post-operative interval increases can be interpreted to be the host’s own new bone formation. A resorbable membrane is then placed over the edentulous area of the ridge much like a saddle is placed on a horse. Stabilization of the membrane is achieved by “tucking” it between the periosteum and the bone of the buccal and lingual cortical plates. Finally, horizontal mattress sutures (bioabsorbable) placed across the site will add stability to the graft and draw the wound edges closer.
Literature reviews have documented that epithelium grows well on collagen membranes, and it is encouraged to grow quickly across the membrane toward the opposing wound edge instead of downward into the defect.5 Meanwhile, the recommended bone graft, which has excellent osteoinductive and osteoconductive properties, is promoting new bone growth into the preserved site. Without complications, the preserved ridge can be ready to accept implant placement at four to six months following surgery.
Endodontists are often called upon for difficult diagnosis and treatment of dental disease. Occasionally, clinical situations arise during treatment which may require tooth extraction. In such cases, ridge preservation is a predictable, one-appointment procedure that will increase the patient’s options for tooth replacement should they desire an implant in the future.
1. Carmagnola D, Abati S, Celestino S, Chiapasco M, Bosshardt D, Lang NP. Oral Implants placed in bone defects treated with bio-oss, ostimpaste or PerioGlas: An experimental study in the rabbit tibiae. Clin Oral Implants Res 2008
2. Nyman S, Lindhe J, Karring T, Rylander H. New attachment following surgical treatment of human periodontal disease. J Clin Periodontol 1982 Jul;9(4):290-6.
3. Pecora G, Kim S, Celletti R, Davarpanah M. The guided tissue regeneration principle in endodontic surgery: One-year postoperative results of large periapical lesions. Int Endod J 1995 Jan;28(1):41-6.
4. Bashutski JD, Wang HL. Periodontal and endodontic regeneration. J Endod 2009 Mar;35(3):321-8.
5. Wolff LF, Mullally B. New clinical materials and techniques in guided tissue regeneration. Int Dent J 2000 Oct;50(5):235-44.