Alveolar Bone Structure and Periodontal Defects

Alveolar Bone Structure and Loss

• Alveolar bone surrounds and supports teeth, with facial and lingual cortical plates enclosing cancellous bone.
• Alveolar crest margins run parallel to the cementoenamel junction (CEJ) at a consistent 1-2mm distance.
• Normal alveolar bone morphology is scalloped with a knife-edge appearance.
• Tooth form, embrasure width, CEJ position, and tooth arch position affect alveolar bone housing.

Introduction to Osseous Defects

• Osseous defects in periodontal disease result from alveolar bone destruction.
• Normal alveolar bone height is maintained at the CEJ by a balance between osteoblast formation and osteoclast resorption.
• This balance is influenced by local and systemic factors.

Mechanisms of Bone Formation and Destruction

• Osteoblasts synthesize bone matrix, which calcifies.
• Periodontal disease-related bone destruction is caused by local and systemic factors.

Local Factors in Bone Destruction

• Chronic gingival inflammation is the most common cause of bone destruction in periodontal disease.
• Trauma from occlusion can cause bone destruction, even in the absence of inflammation.
• A combination of both chronic inflammation and occlusal trauma can also be a causative factor.

Role of Chronic Gingival Inflammation

• Chronic gingival inflammation is the primary cause of periodontal bone loss.
• Transition from gingivitis to periodontitis involves changes in bacterial plaque composition or host resistance.
• Pathogenic bacteria and inflammatory cells within the lesion contribute to its destructive and progressive nature, evidenced by a transition from T-lymphocytes to B-lymphocytes.

Pathways of Inflammation Spread

• Inflammation spreads interproximally and facially/lingually into periodontal tissue.

Changes in Bone Due to Inflammation

• Gingival inflammation leads to changes in bone marrow spaces, including leukocyte presence and fluid exudates.
• Proliferating fibroblasts and blood vessels appear in response to inflammation.
• Osteoclast and mononuclear cell increases occur.
• Bone trabeculae thin, and marrow spaces enlarge.
• Bone height decreases as a result of the above.

Bone Loss from Traumatic Occlusion

• Trauma from occlusion is another cause of bone destruction in periodontal disease.
• This can occur independently of or in conjunction with inflammation.

Bone Destruction from Systemic Factors

• Immune deficiencies, osteoporosis, and smoking are systemic factors contributing to bone destruction.
• Generalized skeletal disturbances like hyperparathyroidism, leukemia, and histocytosis X can also cause periodontal bone loss.

Radius of Action

• Locally produced bone resorption factors exert their effect primarily in close proximity to the bone surface (1.5-2.5mm).
• Bacterial plaque within this area primarily causes bone loss.

Bone Destruction Patterns in Periodontal Disease

• Horizontal bone loss, vertical/angular defects, osseous craters, bulbous bony contours, reversed architecture, ledges, and furcation involvement are common.

Horizontal Bone Loss

• Horizontal bone loss is the most common pattern of bone loss in periodontal disease.
• The bone height reduces, but margins remain perpendicular to the tooth surface.
• It is associated with suprabony pockets.

Vertical/Angular Defects

• Vertical defects create troughs in the bone along the root.
• Angular defects are accompanied by infrabony pockets.
• Angular defects are classified by the number of osseous walls. (one, two, or three walled).

Osseous Craters

• Osseous craters are concavities in the interdental bone crest, bounded by facial and lingual walls.
• They commonly appear on mandibular bone (higher proportion) as compared to maxillary.

Reversed Architecture

• Reversed architecture defects result from loss of interdental bone, including facial and lingual plates, without accompanying loss of radicular bone.
• Maxillary location is more common.

Bulbous Bony Contours

• Bulbous bony contours are enlargements from exostoses, adaptation to function, or buttressing bone formation.
• They are more common in the maxilla than the mandible.

Ledges

• Ledges are plateau-like margins of bone, resulting from resorption of thickened bony plates.

Furcation Involvement

• Furcation involvement occurs when periodontal disease invades the bifurcations or trifurcations of multirooted teeth.
• Mandibular molars are the most affected.

Types of Osseous Surgery

• Osseous surgery types are classified based on the relative positioning of interdental and radicular bone (positive, negative, or flat).

Diagnosis of Osseous Defects

• Clinical examination (transgingival probing), radiographs (not precise for bone wall evaluation), and surgical exposure (precise bone evaluation) are methods for diagnosing osseous defects.

Conclusion

• Periodontal disease bone loss patterns vary, even in the same person, and can differ between areas.
• Regenerative periodontal surgery, using bone grafts, bioactive molecules, and membranes, can treat vertical bone loss.
• Horizontal bone loss and osseous craters typically require flap surgery combined with osseous surgery.