December 1, 2013
by Jon B. Suzuki DDS, PhD, MBA; Diana Bronstein DDS, MS
Tooth extraction is one of the most widely performed dental procedures and tooth removal will generally result in alveolar bone loss, as well as structural and integral changes in the overlying soft tissue.2
A narrower and shorter knife edge ridge can be the expected sequelae of alveolar bone resorption10 and the process of resorption often results in the apex of the ridge being in a more lingual position.7 The process of ridge remodeling is further complicated if the buccal bone wall is lost11 as a result of inflammation, previous dental treatment or the extraction itself.
Sufficient alveolar bone volume and favorable architecture of the alveolar ridge are essential to obtain optimal functional and aesthetic prosthetic reconstructions. Therefore, knowledge of the healing process at the extraction site, including contour changes caused by bone resorption, is essential for treatment planning.8
Predictable regeneration requires both a high level of technical skill and a thorough understanding of underlying principles of wound healing. This article will attempt to answer the most prevalent questions regarding ridge preservation.
THE SEQUELAE OF EXTRACTION
Subsequent to removal of a tooth, the periodontium undergoes atrophy,2,3 with the complete loss of attachment apparatus including cementum, periodontal ligament fibers and bundle bone.4
Extraction of one or more teeth results not only in changes of the bony architecture, but also affects the overlying soft tissues of the ensuing ridge.2 Immediately following tooth extraction, there is absence of soft tissue covering the socket, and the socket defect is left to heal by secondary intention. Cell proliferation from the wound margins will increase soft tissue volume, and a soft tissue covering will seal the socket entrance at four to six weeks post extraction. The changes in the soft tissue contours are dependent on the corresponding changes in the external profile of the alveolar bone surrounding the extraction site.
Studies in the canine model5,6 have demonstrated that there are marked dimensional changes of the alveolar ridge in the first two to three months post-extraction, with the changes more pronounced on the buccal.6 Horizontal buccal bone resorption has been shown to reach as much as 56 percent while lingual bone resorption has been reported to be up to 30 percent;7 the overall reduction in width of the horizontal ridge has been reported to reach 50 percent.2
The greatest amount of bone loss in the horizontal dimension occurs mainly on the facial aspect of the ridge.8 There is also loss of vertical ridge height, which has been described to be most pronounced on the buccal aspect.19,20,5 This resorption process results in a narrower and shorter ridge21 and the effect of this resorptive pattern is the relocation of the ridge to a more palatal/lingual position. The defect resulting from the loss of a tooth may be complicated by previous bone loss due to periodontal disease, endodontic lesions, or a traumatic episode. The situation becomes even more compromised when the alveolus has lost walls or height.22 The size of the residual ridge is reduced most rapidly in the first six months, but bone resorption activity in the residual ridge continues throughout life at a slower rate. This results in the removal of large amounts of jaw structure.23 Morphologic changes in extraction sockets have been described by cephalometric measurements, study cast measurement, radiographic analysis and direct measurements of the ridge following surgical re-entry procedures.24
Two clinical cases of tooth extractions and sequelae are discussed in figures 1-12.
Although there are numerous strategies to reduce the amount of bone resorption, there is a “cost” associated with all of them. The use of a graft and barrier will limit the amount of facial and occlusal collapse in the treated area. When a graft material is inserted into the socket, it may have any of a number of effects. As a scaffold, it may enable osteoid deposition. If it is not resorbable in the time frame studied, there will be a limit on the amount of vital bone formed and available for osseointegration while remnants of the graft materials remain. If the grafting material resorbs and is converted to vital bone too quickly, the site may exhibit increased vertical and/or horizontal collapse of the alveolar socket. If the grafting material resorbs too slowly, the site may exhibit reduced amounts of vital bone formation. The practitioner performing the extraction must be aware of the biological interaction of the host environment with any graft and/or barrier inserted at the time of extraction. A cost/benefit analysis has to determine ideal regeneration and bone volume preservation synergistically with the patient situation. Continued research in this field will lead to improved biomaterials to act as bone replacement grafts and/or barriers. As more are developed and different techniques are studied, the process will be made simpler and more predictable.9 OH
Jon B. Suzuki DDS, PhD, MBA Professor, Temple University, School of Dentistry, Graduate Periodontology and Oral Implantology Department, Philadelphia, PA 19140, USA
Diana Bronstein DDS, MS Professor, Nova Southeastern University, College of Dental Medicine, Department of Periodontology, Ft. Lauderdale, FL 33328, USA.
Acknowledgments: Photos for case 1 and 2 taken by Ermal Lulaj, NSU HPD CDM NMB.
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