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Healing Following Devitalization of Sites within the Periodontal Ligament by Ultralow Temperatures
Author(s) -
Tal Haim,
Stahl S. Sigmund
Publication year - 1986
Publication title -
journal of periodontology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.036
H-Index - 156
eISSN - 1943-3670
pISSN - 0022-3492
DOI - 10.1902/jop.1986.57.12.735
Subject(s) - periodontal fiber , medicine , dentistry
Healing of specific rat periodontal ligament (PDL) sites following freezing injury was monitored histologically to evaluate repair potentials of this tissue. Buccal alveolar plates supporting the first mandibular molar in 15 adult rats were surgically exposed. The coronal 3 mm of plate covering the buccal surface of the mesiobuccal root and underlying periodontal ligament and cementum were subjected to ultralow temperature using a gas expansion micro/cryoprobe, diameter 2 mm, cooled to ‐81°C for 5 seconds. Tissues were repositioned and sutured in layers. Animals were sacrificed at 1, 24 and 72 hours and at 2, 5 and 7 weeks following surgery and mandibles removed for histologic analysis. Microscopic evaluation of 24‐hour specimens showed loss of cellular vitality in the PDL, adjacent bone and cementum at experimental sites. Cellularity of the gingiva coronal to the crest, and of the PDL apical to the experimental zone, appeared to be within normal limits. Transition between experimental and nonexperimental sites was abrupt. After 72 hours cells from the PDL and gingiva appeared to migrate into and repopulate the noncellular PDL. Few capillaries surrounded by mesenchymal cells and limited polymorphonuclear neutrophil infiltration were observed within the injured PDL site. Marginal gingival inflammation was minimal. At 14 days, collagen lysis, resorption of alveolar bone and root resorption were evident. In the PDL space, nonfunctionally oriented, cellular connective tissue elements were abundant. At 5 and 7 weeks, root resorption was marked. At this time interval, Osteogenesis at seams of nonvital bone, repair cementum at sites of root resorption, and at times, ankylosis, were noted. Thus, cryosurgery devitalizes cells in predetermined areas in the PDL without causing significant morphologic changes in the periodontium. However, since healing following freezing injury may not be identical to that observed after standard surgery, the histologic sequences described in this study must be considered preliminary. On the other hand, freezing injury may be of value to further study PDL repair potential since this insult does not alter the gross morphology at the injured site.