October 1, 2013
by Avi Shelemay, DDS, MSc (Perio), FRCD(C)
Dental implants are the preferred method for replacing missing teeth in most circumstances. They offer high predictability, which is backed by many long-term studies. Very often the discussion on tooth replacement starts when patients learn that they will be losing one or more teeth. What they often don’t realize is that the extraction procedure becomes an essential part of a treatment leading to implant placement and resulting with the delivery of the final prosthesis. If the extraction is not performed in a carful and planned manner often in conjunction with “ridge preservation maneuvers” the implant recipient site will be deficient reducing the chances of success and resulting in surgical difficulties. Incorporating the extraction of a tooth as an integral part of the implant surgery offers an opportunity for more predictable and improved outcome. It has been well documented that the ridge follows a predictable pattern of resorption following the extraction of a tooth. The centre of the ridge shifts towards the lingual/palatal (Lam, 1960,1 Atwood, 1973,2 Cawood and Howell, 19883) as the thin buccal bone resorbs. The magnitude of bone loss has been estimated at 40-60 percent during the first 3 years following tooth loss. Then it continues to decrease by 0.25-0.5 percent per year (Ashman and Rosenlicht, 19934). The cause for ridge resorption is thought to be related to loss of blood supply secondary to loss of the periodontal ligament with its rich vascularity and its role of maintaining of the tooth supporting alveolus. In addition, disuse atrophy may also contribute to loss of volume of the alveolus. Infections, preexisting root fractures and traumatic extractions can be additional contributing factors.
When patients present for dental implant treatment with an existing edentulous ridge, we follow a systematic analysis of the ridge. The primary objective is to determine whether the existing bone volume is sufficient for implant placement in a favourable prosthetic position. If the ridge proves to be deficient then we plan for a ridge augmentation procedure(s). The secondary objective is to assess the soft tissue at the implant recipient site, particularly in the aesthetic zone. We may have to plan a soft tissue augmentation procedure as well, to be able to fulfill the aesthetic expectations for the case.
We prefer to incorporate the extraction of the tooth into the continuum of implant surgery to avoid the need for augmentation procedure of the result of an unfavorable post-extraction alveolar ridge. Elian et. al. 20075 proposed a simplified classification system for extraction sockets (Fig.1). Type I refers to a situation where there is no bone or soft tissue loss around the tooth. Type II involves buccal bone loss, but no soft tissue loss. Type III involves both soft tissue and bone loss on the buccal.
Type I extraction sites where both the soft and hard tissue are intact lend themselves to simultaneous extraction and immediate insertion of the implants. One might caution the operator that such protocol is technique sensitive, often requiring “blind” preparation of the site. Hence the margin for error is smaller. Therefore staging treatment in type I extraction sites is often preferred by practitioners as being more “controlled” and more predictable. Ridge preservation techniques (erroneously called at times “socket preservation techniques”) involve bone grafting in preparation for delayed implant placement. The rationale for bone grafting has been long documented (Lekovic, 19986, Iasella, 20037), and it is to preserve bone volume for proper implant positioning as well as for soft tissue support (Figs. 2-5, Figs. 6-15, Figs. 23-32).
Type II extraction sites have compromised bony housing due to loss of the buccal plate of bone. The buccal bone is typically very thin thus making it prone to resorption secondary to infection or compromised blood supply. An example would be a vertical root fracture extending bucco-lingually. Clinically, type II scenario will present with deep probing depth at the mid-buccal site, alerting the clinician that the buccal plate of bone has been compromised. Type II extraction sites are best managed with a staged approach. Bone grafting such extraction sites requires the use of a membrane to contain the bone grafting material, as well as provide a barrier for the exclusion of soft tissue growth in to the grafted site. Type II extraction sites are still more favorable than grafting a healed extraction site, since the grafting procedure takes place within the partially retained alveolar housing. The mesial and distal aspects of the extraction socket help contain the graft as well as provide bony walls for osteogenic cells. Type II extraction sites are also characterized by intact soft tissue envelope. This is of tremendous importance since the success of any bone grafting procedure depends on our ability to manipulate the soft tissue in order to obtain and maintain tension-free primary closure over the grafted site. Many procedures exist, ranging from flap advancement for primary closure, or the use of specialized non-resorbable PTFE (Polytetrafluoroethylene) membranes that remain exposed graft material. PTFE membranes in such applications must be removed 3 to 4 weeks following the extraction. Once removed, new keratinized gingiva is present underneath the membrane and over the bone graft (Figs. 6-15, Figs. 16-22).
Type III extraction sites are the most complex to treat, and will always require a staged approach with bone and soft tissue augmentation. Often, it is advantageous to stage the extraction and bone grafting procedure. Waiting 6-8 weeks following the extraction would allow the soft tissue to heal over the extraction site. The additional soft tissue facilitates flap closure over the bone graft at the second surgical procedure (Figs. 23-32, tooth 26). Additional soft tissue augmentation can be carried out either simultaneously with the bone graft, at the time of implant placement, or during both procedures. It is obvious that management of type III extraction sites is lengthier and requires secondary bone augmentation either as a separate procedure or simultaneously with implant placement.
Regardless of the clinical situation, the bony and soft tissue foundations for dental implants should be evaluated prior to the removal of teeth. Management strategy should be discussed with the patient before treatment begins in addition to discussions concerning realistic expectations from the treatment. Each step during treatment should be regarded as part of a continuum. When multiple practitioners are involved in treatment of a patient, each should be kept informed with regards to treatment decisions as well as treatment progress. Resorption of the residual ridge begins once the tooth is extracted, and it is in the best interest of our patients that we have a management strategy in place in order to facilitate dental implant therapy.OH
Dr. Shelemay maintains a private practice in Ottawa limited to periodontics and implant surgery. Dr. Shelemay is a Fellow of the Royal College of Dentists of Canada in Periodontology. He obtained his DDS from the University of Toronto in 1996, and subsequently completed a one year internship at Mount Sinai Hosptial. Dr. Shelemy completed his MSc degree and specialty training in Periodontology at the University of Toronto in 2002. Dr. Shelemay can be reached at email@example.com.
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