Bone augmentation (Proceedings)

The success of bone augmentation in periodontal therapy has advanced at an accelerated rate in the past few years. Successful bone regeneration in periodontal pocket formation is an expected reality.

Obligate symptoms of periodontitis are inflammation, true periodontal pocket formation and bone resorption. These symptoms occur in varying degrees, with varying degrees of bone loss.

Pocket formation advances with the severity of periodontal disease. Pocket formation advances from pocket formation with attachment loss and proliferating pocket epithelium with beginning crestal bone loss to vertical or horizontal bone loss that extends beyond the alveolar crest.

There are basically two types of bone loss seen in advanced periodontal disease. Vertical and horizontal.

Vertical bone loss is seen in Infrabony pocket formation. The depth of the pocket is apical to the crestal height of bone. Horizontal bone loss has virtually no pocket formation with a uniform lowering of crestal bone.

Infrabony pocket (infra-alveolar vertical bone loss) exhibit various forms in relation to the infected bone The osseous defects are classified as: Three -wall bony defect, bordered by three osseous surfaces and one tooth surface: Two-wall bony defect, bordered by two osseous walls and two tooth surfaces: One wall bony defect, bordered by two tooth surfaces and one osseous wall: Combined bony defect (cup), bordered by several surfaces of tooth and several of bone. Successful bone fill is greatest with three wall pockets followed by two walls, then one wall and cup.

Bone augmentation materials are classified as osseous conductive and osseous inductive.

Osseous inductive bone or bony substitutes take part in the formation of new bone, whereas osseous conductive materials provide a scaffold or trellis for bony regeneration without taking part of bone formation itself.

Osseous inductive material in the past has generally been autogeous bone transplants. That is bone harvested from the host and implanted into the prepared bony defects. This results in very successful bone augmentation. However host bone is not always attainable, hence the use of new augmentation materials has been developed.

Most osseous conductive materials have been forms of ceramics, glass, or hydroxyapatite serving as scaffolding mechanisms for bone growth. The use of demineralized, freeze-dried or radiated bovine and human bone is still a widely used osseous conductive agent with some claims of osseous induction results.

Bone Morphogenic Proteins (BMPs) are one of the advancements in bone augmentation. They are combined with demineralized bone allographs producing increases in cementum and bone. BMPs produce multiple effects by acting as mitogens on undifferentiated Mesenchymal cells and osteoblast precursors. They induce the expression of the osteoblast phenotype increasing alkaline phosphate activity in bone cells.

There seems to be an endless variety of new osseous conductive materials currently available. The following products and their application and efficacy are some of the recommended materials, but not the only material available for Veterinary periodontal therapy.

Emdogain, (Biora Rapport): Has been promoted for use in Veterinary Dentistry within the past four years. Emdogain is an enamel matrix protein harvested from porcine primary dentition. It has shown the ability to increase levels of Transforming Factor-Beta 1 and Platelet derived growth factor.

The new Emdogain Gel provides better handling qualities than the original form. It is best used in combination with other conductive agents such as demineralized freeze-dried bone allograph material. After a full thickness flap is raised, all granulomatous tissue is removed from the three walls and or two wall pockets, the root surfaces thoroughly root planed and treated with EDTA. The Emdogain Gel cocktail, (Emdogain and demineralized freeze dried bone) is applied to the defect and tightly sutured. Added and more effective increases in bone are obtained when placed as a cocktail under a resorbent-guided tissue membrane

Consil, (Nutrimax Laboratories Inc.) Consil is by far the most widely used osseous conductive material by Veterinarians. Consil is a type of glass bead material similar to other polymers for osseous conduction only. Its efficacy is virtually the same as other osseous conductive materials.

HTR-polymer, (Bioplant Inc.) a biocompatible polymer in bead form which forms a non-resorbent radiopaque pours matrix scaffolding for osseous conduction. It is delivered into a prepared bony defect through a straight barrel syringe. The gingival flap must be tightly sutured to prevent loss of the HTR beads. Like Consil, it is an effective osseous conductive material. However all conductive materials do not provide the effective bony fill that is often needed.

OsteoGraf/N, (CertaMed Dental) A natural anorganic bovine mineral that restores through cell mediation. It is a Xenograph that is suitable for both human and animal osseous conduction. It is one of the better osseous conductive materials that seem to outperform most polymers.

AllGro, (CertaMed Dental) Demineralized Freeze-Dried Bone Allograph, (DFDBA). This is the only DFDBA that is routinely assayed for osteo-inductive activity. Demineralized Freeze-dried bone has been characterized as near osteo conductive by many clinicians. However this product seems to be more effective that the osteo-conductive polymers currently used by veterinarians.

PepGen-P-15: This product is the current state of the art augmentation material. A composite of Type -1 collagen in particulate form. The particulate form can be difficult to deliver to the surgical sites, however the putty form, (sodium alginate) of PepGen- P-15 shows excellent biocompatibility and handling properties. This product combines a synthetic cell binding peptide with anorganic bovine biomineral resulting in the first and only tissue-engineered bone replacement graft to mimic both the inorganic and organic components of autogenous bone biopolymer.

In multi center trials PepGen P-15 demonstrated positive results. ABM/P-15 bovine derived hydroxyapatite matrix (ABM/ P-15 i.e. PepGen- P-15) has shown superior results to demineralized bone powder. Histological confirmation of the entopic cellular differentiation of ABM/ P-15 and the eventual phenotypic expression of the undifferentiated Mesenchymal cells in to bone producing osteocytes were histologically confirmed.

A study was conducted at the research division of Mayo clinic utilizing ten beagle dogs. Four sites per dog and four bone substitute materials were used. Human freeze-dried dematerialized bone (H-FDDB), Dog derived freeze-dried demineralized bone (D-FDDB), OsteoGraf/N-300 and OsteoGraf/N-300 with PepGen P-15. The 14 day evaluation reveled the defects containing H-FDDB and D-FDDB had little to no volume in all ten dogs The defects containing N-300 maintained the initial volume, but were palpable and mobile in all ten dogs The defects containing PepGen- P-15 maintained their volume and showed palpable sings of ossification. Thirty days histological evaluation showed the defects containing PepGen P-15 demonstrated cellular differentiation consistent with entopic osteoinduction.

This product is the result of research conducted by Dr. Rajendra Bhatnagar, University of San Francisco bioengineering. He disrobes the transformation of a different type of gingival fibroblasts into bone. This mimics the use of stem cell research. CertaMed purchased the results of his research. The result was the development of PepGen -P-15 that works by transforming gingival fibroblasts into bone.

Veterinary Periodontics has benefited from human periodontal therapy, but also has been limited by an understanding of the limits and effects of the most commonly used bone augmentation products for Veterinarians.

Since limited time is often seen in clinical Veterinary Dentistry, the clinician should employ the most efficient augmentation material to avoid retreatment, lost time, and inferior results

References on request