Regeneration of Dental Hard Tissue

The process of generation and regeneration of dental hard tissues is one that has been under extensive study. Two such techniques that are currently being investigated are distraction osteogenesis and guided tissue regeneration. Both methods mentioned above offer a means to regenerate bone, however the method of regeneration is different.

Distraction osteogenesis is a procedure that utilizes alveolar osteotomies and extra-oral devices to separate and expand bone. After a planned osteotomy is performed. Distraction osteogenesis offers many advantages over conventional osteotomies. One large advantage is that distraction osteogenesis can expand bone up to a length of 20 mm or more without the need for additional grafting. Distraction can also be performed in three dimensions which offers the surgeon more options for reconstruction. Unlike a traditional osteotomy, distraction can be used to increase ramus height, has less relapse and a lower incidence of nerve damage.

Currently, there are two types of distraction devices available. For smaller areas of bone regeneration, an intra-oral device is used. This is advantageous to the patient as it allows for bone regeneration with minimal hardware implantation. For larger bone defects, the use of an extra-oral distraction device is mandatory. These devices are often times placed under general anesthesia and are used to regenerate large portions of missing bone lost due to congenital defects, trauma, cancer, or infection.

Guided tissue regeneration (GTR) is a surgical procedure that aims to regenerate the periodontal tissues when the disease is advanced and could overcome some of the limitations of conventional therapy. It consists of placing barriers of different types to cover bone and periodontal ligaments after conventional bone grafting surgery. This membrane separates the bone from the gingival epithelium.

As a result of excluding the epithelium and connective tissue, the wound will not apically migrate. In addition, periodontal ligament and bone cells will be more apt to repopulate the area. Numerous studies (by authors such as Lindhe, Karring, and Gottlow) have been performed documenting the success of GTR showing histological evidence of periodontal regeneration even in cases of horizontal bone loss.

One area of particular interest concerning GTR is that of enamel matrix proteins. Enamel matrix proteins are secreted by Hertwig's epithelial root sheath during tooth development and induce acellular cementum formation. The use of enamel matrix proteins may enhance periodontal regeneration by promoting differentiation of cells required for the synthesis of the periodontal ligament, bone and cementum.

One enamel matrix protein which has gained recent popularity is that obtained from developing porcine teeth (Emdogain). Emdogain is a viscous gel which is applied to the root surface before closure of periodontal flaps. In a histological study of ten defects, Yukna and Mellonig report evidences of regeneration in 3 specimens and long junctional epithelium in 4 specimens without ankylosis. Although Emdogain has gained popularity among periodontists and oral surgeons, long term follow up studies are not conclusive.