These tissue alterations, which include bone resorption, result in a widenedperiodontal ligamentspace and increased tooth mobility but no further loss of connective tissue attachment (c). If these teethare subjected to traumatizing forces of the jiggling type (b), pathologic and adaptive alterations occur within theperiodontal ligament space. Note the connective tissue infiltrate (shadowed areas) and thenoninflamed connective tissue between the alveolar bone and the apical portion of the infiltrate. Two mandibular premolars with supra- and subgingival plaque, advanced bone loss and periodontalpockets of a suprabony character (a). After occlusal adjustment (d) the width ofthe periodontal ligament is normalized and the teeth stabilized. These alterations result in a widened periodontal ligament space (c) and in an increased toothmobility but do not lead to further loss of connective tissue attachment. If suchpremolars are subjected to traumatizing forces of the jiggling type (b) a series of alterations occurs in the periodontalligament tissue. Two mandibular premolars are surrounded by a healthy periodontium with reduced height (a).Arrowheads indicates the apical extension of the junctional epithelium which coincideswith the apical border of the notch (N), prepared in the root surface prior to jiggling. This increase in tooth mobilityand the development of widened periodontal ligament space did not, however, result in apical downgrowth of thedentogingival epithelium (g). As a consequence,a widened periodontal ligament and increased tooth mobility resulted (f). The mandibular left fourth premolar (T) was exposed to jiggling forces (e). The dogs were subsequently placed on a plaque control program and 2 months later (Day 270) all experimentalteeth (the lower fourth premolars 4P and P4) were surrounded by a healthy periodontium with reducedheight (c and d). During surgery, a notch was prepared in the root at the level of thebone crest. When around 40-50% of the periodontal tissue support had been lost (b) the animals were treatedby scaling, root planing and pocket elimination. Dogs were allowed to accumulate plaque and calculus in the mandibular premolar regions over a 210-day period (a).The marginal gingiva is unaffected by trauma from occlusion because its blood supply is not affected, even when the vessels of the periodontal ligament are obliterated by excessive occlusal forces The question is whether a healthy periodontium with reduced height has a capacity similar to that of the normal periodontium to adapt to traumatizing occlusal forces (secondary occlusal trauma).After occlusaladjustment the width of the periodontal ligament becomes normalized (d) and the teeth are stabilized. The supraalveolar connective tissue isnot affected by the jiggling forces and there is no apical downgrowth of the dentogingival epithelium. When the effect of the force applied has been compensated for by the increased width of the periodontalligament space (c), the ligament tissue shows no sign of inflammation. As a result of bone resorptionthe periodontal ligament space gradually increases in size on both sides of the teeth as well as in the periapicalregion. The combined tension and pressure zones (encircled areas) are characterized by signs ofacute inflammation including collagen resorption, bone resorption and cementum resorption. Two mandibular premolars with normal periodontal tissues (a) are exposed to jiggling torces (e) as illustratedby the two arrows.“Teeth with occlusal discrepancies had significantly deeper initial probing depths, more mobility & poorer prognoses than teeth without discrepancies”.They termed this differentprogression of periodontal disease as an“altered pathway of destruction.” They termed thecombined effects of occlusal trauma and inflammationas “co-destructive factors” in periodontaldisease.Most studies of the effect of trauma from occlusion involving experimental animals have examined the primary type of trauma.Adaptive Capacity of the Periodontium to Occlusal Forces.
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