Evaluation of the Prevalence Rate and Related Risk Factors of Ridge Preservation

Background:

The alveolar process is a tooth-dependent tissue that develops in conjunction with the eruption of the teeth. The tooth is anchored to the jaws via the bundle bone into which the periodontal ligament fibers invest. Subsequent to the removal of the tooth, the alveolar process will undergo atrophy. The dynamics and magnitude of these changes have been investigated in the dog model as well as in humans. Most of the resorption occurs during the first 3 months of healing, although dimensional changes can be observed up to 1 year after tooth extraction, resulting in approximately 50% reduction of the bucco-lingual dimension of the alveolar ridge, mainly due to the resorption of the bundle bone plate. Some studies showed that significant loss of tissue contour occurs during the first month after tooth extraction, averaging 3~5mm in width at 6 months. As a result, a residual ridge is often inadequate for ideal implant placement, which creating a clinical challenge for the placement of a dental implant in an ideal position. However, placement of a dental implant in an ideal three-dimensional position is critical in achieving a predictable functional and esthetic restoration.

Therefore, the timing of implant placement in extraction sockets can influence the surgery operability and treatment period of time. The classifications of timing of implant placement in extraction sockets as following: Type I: immediate implant placement: implant placement immediately following tooth extraction and as part of the same surgical procedure. Type II: early implant placement: surgery after complete soft tissue coverage of the socket (typically 4~8 weeks).Type III: early implant placement: implant surgery after substantial clinical and/or radiographic bone fill of the socket (typically 12~16 weeks). Type IV: late implant placement: surgery at healed site (typically more than 16 weeks). Considering of technique sensitivity and treatment time consuming, early implant placement is the most acceptable clinically. However, different treatment strategies may be applied because of the vary amounts of resorption after tooth extraction.

Some of the extraction sockets will heal completely and the implant can be placed in an ideal position 3 months after tooth extraction. Others may require adjunctive surgical procedures (like guided bone regeneration, GBR) during the implant surgery. In some cases, with severe bone resorption after tooth extraction, staged approach for implant placement is recommended due to lack of sufficient bone volume, which is the most time consuming and expensive treatment method.

In order to avoid this situation, some surgical procedures have been described to prevent alveolar ridge collapsing after tooth extraction, including regenerative techniques for socket preservation and immediate implant placement after tooth extraction. The socket preservation technique has been widely tested in controlled and uncontrolled studies with various materials and clinical approaches. However, this may require longer treatment period compare to early implant placement protocol and so far, there is no study revealed how often and when does socket preservation need to prevent the residual ridge deformity in our daily clinical practice.