Bone Loss and Patterns of Bone Destruction

by

Dr. Marcel Hallare

BONE DESTRUCTION CAUSED BY EXTENSION OF GINGIVAL INFLAMMATION

The most common cause of bone destruction in periodontal disease is the extension of inflammation from the marginal gingiva into the supporting periodontal tissue

The inflammatory invasion of the bone surface and the initial bone loss that follows marks the transition from gingivitis to periodontitis

The transition from gingivitis to periodontitis is associated with changes in the composition of bacterial plaque

In advance stages of disease, the number of motile organisms and spirochetes increase whereas the number of coccoid rods and straight rods decrease

Radius of action – From the focal point, a range of

effectiveness of about 1.5 to 2.5 mm within which bacterial plaque can induce loss of bone

Rate of bone loss– 0.1 mm a year is within normal limits

Period of Destruction– Destruction occurs in an episodic,

intermittent fashion, with periods of inactivity or quiescence

– Destruction results in loss of collagen and alveolar bone with deepening of the periodontal pocket

Mechanism of Bone Destruction– Factors involved in bone destruction in

periodontal disease are bacterial and host mediated

– Bacterial plaque products induce the differentiation of bone progenitor cells into osteoclasts and stimulate gingival cells to release mediators that have the same effect act as direct

– Plaque products and inflammatory mediators can also act directly on osteoblasts or their progenitors, inhibiting their action and reducing their number

– Nonsteroidal anti-inflammatory drugs such as ibuprofen inhibit prostaglandin E2 production, slowing bone loss

Bone Formation in Periodontal Disease– Areas of bone formation are also found

immediately adjacent to sites of active bone resorption and along trabecular surfaces at a distance from the inflammation in an apparent effort to reinforce the remaining bone (buttressing bone formation)

– The response of alveolar bone to inflammation includes bone formation and resorption

– Bone loss in periodontal disease is not simply a destructive process but results from the predominance of resorption over formation

– New bone formation retards the rate of bone loss, compensating in some degree for the bone destroyed by inflammation

– These periods of remission and exacerbation appear to coincide with the quiescence or exacerbation of gingival inflammation manifested by changes in the extent of bleeding, amount of exudates, and composition of bacterial plaque

– The presence of bone formation in response to inflammation even in active periodontal disease has a hearing on the outcome of treatment

– The basic aim of periodontal therapy is the elimination of inflammation to remove the stimulus for bone resorption and therefore allow the inherent constructive tendencies to predominate

BONE DESTRUCTION CAUSED BY TRAUMA FROM OCCLUSION

In the absence of inflammation, the changes caused by trauma from occlusion vary from increased compression and tension of the periodontal ligament and increased osteoclasis of alveolar bone to necrosis of periodontal ligament and bone and resorption of bone and tooth structure– Primary traumatic occlusion

In the presence of inflammation, trauma from occlusion aggravates the bone destruction caused by the inflammation and causes bizarre bone patterns– Secondary traumatic occlusion

BONE DESTRUCTION CAUSED BY SYSTEMIC DISORDERS

Osteoporosis is a physiologic condition of postmenopausal women, resulting in loss of bone mineral content and structural bone changes

BONE DESTRUCTION PATTERNS IN PERIODONTAL DISEASE

Periodontal disease alters the morphologic features of bone in addition to reducing bone height

Horizontal Bone Loss

– Is the most common pattern of bone loss in periodontal disease

– Bone is reduced in height, but the bone margin remains roughly perpendicular to the tooth surface

– The interdental septa and facial and lingual plates are affected

Vertical or Angular Defects

– These defects occur in an oblique direction, leaving a hollowed-out trough in the bone along the root

– The base of the defect is located apical to the surrounding bone

– Vertical defects increase in age– The three-walled vertical defect was originally

called an infrabony defect– The one-wall vertical defect is also called a

hemiseptum

Osseous Craters

– They are concavities in the crest of the interdental bone confined within the facial and lingual walls

Bulbous Bone Craters

– They are bony enlargements caused by Exostoses, adaptation to function, or buttressing bone formation

– Found more frequently in the maxilla than in the mandible

Reverse Architecture

– Defects are produced by loss of interdental bone, including facial plates, lingual plates, or both without concomitant loss of radicular bone

– Common in the maxilla

Ledges

– They are plateau-like bone margins caused by resorption of thickened plates

Furcation Involvement

– Refers to the invasion of the bifurcation and trifurcation of multirooted teeth by periodontal disease

Grade I - is incipient bone lossGrade II - is partial bone loss (cul-de-sac)Grade III - is total bone loss with through-

and-through opening of the furcationGrade IV - is similar to Grade III with gingival

recession exposing the furcation to view