Periodontal Region Research Articles

A study of the reformation of severed gingival fibers in aging mice using 3H-proline autoradiography.

The present study monitored the healing responses at sites of attached but severed gingival fibers by following matrix production and turnover using 3H‐proline in mice of different ages. Fifty‐six BNL short‐lived mice of mixed sex to 78‐week‐old were used. A vertical gingival incision was made at the mesial papilla of the right maxillary first molar to the alveolar bone crest severing the gingival fibers. The left side was used as a control. Periodontal regions adjacent to the incision and some distance from the incision were studied. All mice were given a s.q. dose of 2μCi of 3H‐proline/gm. b. wt. and killed from 1 to 90 days later. Autoradiographs were prepared from routinely processed histologic sections for grain counting. The control crestal region exhibited the greatest matrical turnover of all sites tested regardless of age. With increasing age, however, the rates of uptake and turnover were significantly reduced in all regions. Post‐injury, additional peaks of activity occurred in young mice. In old mice, the injured cemental side exhibited significant uptake and prolonged matrical turnover. It was concluded that the matrix on the injured corium side was the most stable, while the cemental region was the least stable. Aging did not impede the tissue response to injury but increased the long term response.

Effects of rotational jaw growth on the occlusion and profile

S tudies using cephalograms employ a method of tracing skeletal structures on a radiograph exposed at one time point, tracing these structures again on a second radiograph exposed at a second time point, superimposing the two tracings on some central reference point, and connecting presumed identical landmarks with a straight line .6p 6 This technique produces a self-fulfilling conclusion that the face and jaws grow downward and forward from beneath the cranium in a linear, translatory fashion. This perspective has influenced orthodontists to expect that the dental occlusion will also be carried in a similar, straight-line, downward and forward manner. Interest in vertical facial growth lead BjSrk,lv * Bjiirk and Palling,s Bjork and Skieller,4 e)degaard,*l-I2 Schudy,13-15 and Isaacson and associatess-lo in recent years to focus more attention on nonlinear jaw growth or jaw rotation. Jaw rotation was not recognized by early workers using cephalograms because of surface remodeling bone changes masking rotational effects as they occurred. This phenomenon of bone remodeling in jaws during normal growth has been carefully documented by BjSrk and Skieller,4 using metallic implants, and Enlow and Hunter,s using histologic techniques. Tooth movement also masked changes in dissimilar jaw growth by compensatory movements at the periodontal regions causing the occlusion to remain apparently in nearly constant relations.4 A recent report focused on a mechanism whereby vertical condylar growth can be converted into changes in anteroposterior jaw relationslo This mechanism explains how vertical condylar growth can, under specific conditions, result in significant anteroposterior dental and profile changes. According to this report, the long-held and widely reported concept of linear downward and forward facial growth is the exception rather than the rule. This report noted that, in order for translatory mandibular growth to occur, vertical

Regeneration of Periodontal and Transseptal Fibers After Autografts in Rhesus Monkeys : A Qualitative Approach

Autografts were performed on rhesus monkeys. After standard endodontic procedures and reimplantation the monkeys were killed at one week intervals. Elastic, reticulin, collagen, and oxytalan fibers were studied histologically in the periodontal ligament and transseptal regions. Ankylosis and fiber degeneration may be related to the quality of the regenarted fibers and the lack of functional stimulation during fiber regeneration.

Cellular dynamics in root formation of teeth in rhesus monkeys.

The cellular kinetics around the developing root apex of rhesus monkey teeth were studied using tritiated thymidine. Labeled cells of the epithelial diaphragm did not show migration into the periodontal ligament to become cell rests of Malassez. The periodontal region adjacent to the root apex was a zone of active proliferation of connective tissue cells.

The development of the periodontal membrane in the rat incisor

Rats from 1 day before birth to 14 days after birth were used to study the development of the periodontal membrane of the incisor teeth. The first appearance of a definitive periodontal membrane was observed during the day following birth with the proliferation of fibroblasts, the breakdown of Hertwig's sheath and the formation of bundles of fibres, some attached to the alveolar bone and some to the tooth. On subsequent days these bundles elongated towards the middle of the periodontal region and here joined the follicular fibres to form the intermediate plexus. At the same time the process of development gradually extended further along the root towards the basal end. Fibres were at first argyrophil but changed into mature collagen within a few days. Development in the incisor is fundamentally similar to that in the rat molar and also resembles the development of a facial suture.

The effect of total-body irradiation on the oral tissues of the Syrian hamster

Characteristic lesions produced in the oral cavity of the Syrian hamster after total-body irradiation are described. These lesions consist of areas of necrosis localized preferably in the periodontal region and progressing to involve the oral mucosa, the neighboring soft tissues, and the alveolar bone margin. The threshold dose for the production of oral lesions in the experiments was 700 r; they appeared earlier and had a more severe evolution when the radiation dose was increased. In the surviving animals the oral lesions healed with retractile scars. Irradiated animals fed a soft, pappy diet seemed to have more severe lesions.