Asymptomatic Apical Abscess

Asymptomatic apical abscess (AAA), also referred to as suppurative apical periodontitis, is associated with a gradual egress of irritants from the root canal system into the periradicular tissues and formation of an exudate. The quantity of irritants, their potency, and their host resistance are all important factors in determining the quantity of exudate formation and the clinical signs and symptoms of the lesion. Asymptomatic apical abscess is associated with either a continuously or intermittently draining sinus tract. This is visually evident as a stoma on the oral mucosa or occasionally as a fistula on the skin of the face. The exudate can also drain through the gingival sulcus of the involved tooth, mimicking a periodontal lesion with a “pocket.” This is not a true periodontal pocket as there is not a complete detachment of connective tissue from the root surface. If left untreated, however, it can be covered with an epithelial lining and becomes a true periodontal pocket. An AAA is usually associated with little discomfort. If the sinus tract drainage becomes blocked, however, varying levels of pain and swelling will be experienced. Correspondingly, clinical examination of a tooth with this type of lesion reveals a range of sensitivity to percussion and palpation, depending on whether the tract is open, draining, or closed.

Vitality tests are negative on teeth with AAA because of the presence of necrotic pulps. Radiographic examination of these lesions shows the presence of bone loss at the apexes of the involved teeth. The sinus tract that leads away from this suppurative core to the surface may be partially lined with epithelium or the inner surface composed of inflamed connective tissue. The sinus tract, like the periradicular cyst, arises and persists because of irritants from the pulp. Similarly, these sinus tracts, whether lined or not, resolve following root canal treatment removing the etiology.

The healing of periradicular tissues after root canal treatment is often associated with formation and organization of a fibrin clot, granulation tissue formation and maturation, subsidence of inflammation, and, finally, restoration of normal architecture of the periodontal ligament. Since the inflammatory reactions are usually accompanied by microscopic and macroscopic resorption of the hard tissues, bone and cementum repair occurs as well.

Periradicular lesions repair from the periphery to the center. If the cortical plate is perforated by resorption, the healing process is partially periosteal in nature. If lesions have not involved the periosteum, the healing response will be endosteal, with formation of bony trabeculae extending inward from the walls of the lesion toward the root surface. On the periphery, osteoblasts appear and elaborate bone matrix (osteoid), which gradually mineralizes as it matures. If cementum or dentin has been resorbed by the inflammation, remodeling and repair are by secondary cementum.

The last to form is likely the fibrous component interposed between newly formed bone and the cemental root surface. These fibers have basically two orientations. One is a true periodontal ligament arrangement, whereas the other is an alignment of collagen parallel to the root surface.

Both orientations represent complete healing. The sequence of events post–endodontic treatment leading to complete repair of periradicular tissues, after inflammatory destruction of the periodontal ligament, bone, or cementum, has not been validated. Most information is based on repair of extraction sites or healing of bone cavities following periradicular curettage.

These may or may not be accurate as to patterns of nonsurgical apical repair. A blood clot forms following extraction or apicoectomy, which becomes organized into recognizable granulation tissue. This tissue contains endothelium-lined vascular spaces, vast numbers of fibroblasts, and associated collagen fibers. The granulation tissue is infiltrated by neutrophils, lymphocytes, and plasma cells. On the periphery of the granulation tissue, osteoblasts and osteoclasts abound. With maturation, the number of cells decreases, whereas collagen increases. Ultimately, mature bone forms from the periphery toward the center.

There is some evidence that at least some lesions may heal with formation of scar tissue. Although the frequency of healing by scar tissue is unknown, it is likely that it seldom occurs following root canal treatment, being much more common after periradicular surgery on maxillary anterior teeth.

Дата добавления: 2015-10-16