Periodontal regeneration refers to the restoration of supporting tissues of the teeth such as bone, cementum, and periodontal ligament to their original levels before damage from periodontal bacteria has occurred. The principle behind regenerative periodontal therapy is based on natural sequence of cellular activity in various living tissues. Let's consider this case scenario. An athlete injures himself while jogging, falls on the ground and breaks one of the bones in his foot. An orthopedic surgeon confirms the fracture with an x-ray and places a cast on the foot to stabilize the bone and promote healing. However, it will be at least 2-3 months before the injured athlete will be able to walk on his own. And here is another example. You accidentally cut yourself with a knife. After washing the area with water, you place a Band-Aid over the cut finger. A few days later you take the Band-Aid off, and the skin around the cut is almost completely healed. The reason that bone injury and skin injury heal differently has to do with their respective biological structures. Bone healing is a very slow process, it takes 2-3 weeks before bone starts producing new cells to fill in the injured area. On the other hand, skin or any other soft tissue starts producing new cells to repair itself 2-4 days after injury.

When periodontal (gum) disease develops, bacteria in the mouth penetrate deep below the gum line and start destroying supporting tissue of the teeth, which is bone. Destruction of the bone leads to the development of periodontal pockets, and if too much bone is lost, the teeth may need to be extracted. However, regenerative periodontal procedures could reverse some of the damage by rebuilding lost bone and other supporting tissues.  During this procedure, gums are  folded back and the area is thoroughly cleaned out to eliminate disease-causing bacteria. Isolation and protection of the clean bone area from overlying gum tissue will encourage body's natural ability to form new bone. Eliminating existing bacteria and regenerating bone and supporting tissues helps reduce pocket depth and repair damage caused by the progression of periodontal disease.

Over the last decade different modalities of regenerative treatment have been developed and applied clinically. The positive effects of bone grafts and bone substitutes on the outcome of periodontal regenerative procedures are well documented. Autografts, allografts, xenografts, and synthetic materials have been shown to improve attachment levels and promote bone fill. None of these materials is osteoinductive, meaning inducing new bone formation. Instead, these materials act as a scaffold to promote bone defect fill, - they are osteoconductive in their function. At the present time, periodontists favor the use of  human bone as a grafting material which has demonstrated clinical effectiveness (over 40 years of documented studies), functional periodontal repair, apparent bone defect fill, and reduction of pockets to manageable levels.

In addition to bone grafting material, in cases of severe bone loss the use of barrier membranes in regenerative procedures may enhance clinical success by offering better protection and containment of the bone substitute inside the defect and disallowing fast-growing gum tissue to get into the regenerative site and interfere with the process. The disadvantage of original barrier membranes was that they needed to be removed after first 6 weeks of post-surgical healing, therefore necessitating additional procedure. Introduction and improvement in clinical effectiveness of dissolving (resorbable) membranes has solved that problem. Most recommended and clinically proven to aid in regeneration membranes are collagen-based (Neomem and BioMend XT) and synthetic derivatives of poly-glycolic acid (Gore Adapt LT).  

Intense research is currently underway to identify and synthesize a variety of biologic modulators that may enhance wound healing and regeneration of lost tissues in periodontal therapy. In late 1990's the material called Emdogain was introduced to the periodontal market that claimed to eliminate the need for bone grafting and use of regenerative membranes and induce bone regeneration by stimulating tissue's own growth potential. Emdogain is a proteinacious gel that contains several amelogenins (proteins that participate in enamel formation and tissue differentiation in early stages of tooth development). Unfortunately, Emdogain did not turn out to be a panacea for bone regeneration around teeth, since in most procedures it was almost impossible to contain the flowing material in the area and the overlying gum ultimately collapsed into the defect preventing any bone formation. Emdogain may be added to a bone graft to enhance wound healing during regeneration and improve periodontal attachment gain and bone fill,  but has very little value if any if used alone.

Similarly to Emdogain, another combination material called PepGen P15 became commercially available in late 1990s. PepGen P15 consists of bovine bone and added synthesized protein P15 supposedly aiding in collagen cross-linking  and therefore ensuring better bond in the early stages of regeneration of the added bone graft to the surrounding bone and root structure. Unfortunately, studies that evaluated long-term regenerative effects of using PepGen P15 were not so glamorous. The material did not integrate or "fused" with the host bone even after 1 year after surgical procedure and did not show predictable bone fill as originally thought.

However, the most popular among periodontists bone grafting material consisting of processed sterilized human bone has undergone some modifications making it even more user-friendly and predictable to use. Currently,  there are three commercially available preparations containing human bone in the putty-like matrix, therefore ensuring predictable placement and containment of the material  inside the intrabony and/or root furcation defect. The three formulations are Dynagraft II and Dynagraft I putty and gel (GenSci Corporation), Grafton (Lifecore) and MTF Gel (MTF). MTF Gel and Dynagraft II putty contain the highest amount of bone by volume (over 90%). Dynagraft II is a preferred choice for bone grafting due to its excellent handling and predictable results in regenerative procedures around teeth and implants and ridge augmentation prior to implant placement. Dynagraft II fully integrates with the host bone since it contains human bone which is the most bio- compatible and clinically proven material for bone regeneration.

The best regenerative result around teeth is usually achieved by combining a bone graft (Dynagraft II putty) with the resorbable barrier membrane of choice (collagen based like Neomem and BioMendXT or PGA-based like Gore Adapt LT).

Pre-operative view of teeth 29-30		6-month post-surgical bone fill
Tooth #19 showing bone loss in furcation area		8-month post-surgical result showing bone fill of the furcation area

The next series of x-rays show pre- and post-surgical views of periodontal defects repaired with the combination of Dynagraft II bone graft and Emdogain gel.

Regeneration of supporting tooth structures is a huge step up in managing advanced periodontal disease and preventing tooth loss. Like other treatment options, it is not a panacea for all patients affected by periodontitis, but research gives us enough evidence to support the use of regenerative therapies in periodontics.