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Biomedical subjects

T Karring

Publications and source records attributed to T Karring.

At least 109 records · Page 6Linked to original sources
PubMed1982

The regenerative potential of the periodontal ligament. An experimental study in the monkey.

The aim of the present study was to examine if new cementum and new attachment may form during healing of a wound prepared in such a way that preference is given to periodontal ligament cells to repopulate the wound area adjacent to a root which has been surgically deprived of its periodontal ligament and cementum layer. The maxillary lateral incisors and mandibular canines in three monkeys were used for experimentation. Following elevation of a mucoperiosteal flap, the buccal and approximal alveolar bone was removed within an area extending from the mid-root level to a level 2 mm apical to the marginal bone crest. Following bone removal, the root surfaces were curetted in order to remove the cementum layer. Notches were prepared in the roots to demarcate the denuded root portion. Prior to repositioning of the tissue flap a millipore filter was placed over the treated area in order to prevent the gingival connective tissue from coming into contact with the root surface during healing. The animals were sacrificed 6 months after surgery. The jaws were removed and histological sections of the experimental teeth and surrounding periodontal tissues were produced. New cementum with inserting collagen fibers was observed on the curetted root surfaces. However, this result of healing did not consistently occur along the entire length of the curetted root portion. In the coronal part of the wound, healing was frequently characterized by connective tissue adhesion to the root surface without signs of cementum formation and fibrous attachment. The results of the experiment suggest that the periodontal ligament cells possess the ability to reestablish connective tissue attachment.

Alveolar Process↗
PubMed1982

New attachment following surgical treatment of human periodontal disease.

The present experiment was undertaken to test the hypothesis that new connective tissue attachment may form on a previously periodontitis involved root surface provided cells originating from the periodontal ligament are enabled to repopulate the root surface during healing. A mandibular incisor with advanced periodontal disease of long standing (the distance between the cemento-enamel junction and the alveolar bone crest was 9 mm) was subjected to periodontal surgery using a technique which during healing prevented the dentogingival epithelium and the gingival connective tissue from reaching contact with the curetted root surface. Preference was hereby given to the periodontal ligament cells to repopulate the previously diseased root surface. After 3 months of healing a block biopsy containing the incisor and surrounding tissue was sampled. The histological analysis revealed that new cementum with inserting principal fibers had formed on the previously diseased root surface. This new attachment extended in coronal direction to a level 5 mm coronal to the alveolar bone crest. This finding suggests that new attachment can be achieved by cells originating from the periodontal ligament and demonstrates that the concept that the periodontitis affected root surface is a major preventive factor for new attachment is invalid.

Connective Tissue↗
PubMed1982

Predominant cultivable microflora of human dental fissure plaque.

Plaque developed in 10 occlusal fissures from unerupted third molars during implantation for 200 to 270 days in lower molars of dental students was studied. To characterize the predominant cultivable flora, 592 isolates (51 to 67 from each fissure) were subcultured from anaerobic roll tubes. Twenty-eight of the isolates were lost. Streptococci constituted 8 to 86% (median, 45%) of the isolates, Streptococcus mutans constituted 0 to 86% (median, 25%) and S. sanguis constituted 0 to 15% (median, 1%). A few isolates of "S. mitior" and "S. milleri" were found, but no S. salivarius. Staphylococci made up 0 to 23% (median, 9%). Gram-positive rods constituted 6 to 59% (median, 35%). Of these, 0 to 46% (median, 18%) were Actinomyces naeslundii and A. viscosus, but no anaerobic actinomyces were isolated. Arachnia and propionibacteria made up small proportions, lactobacilli were isolated from two fissures, constituting 10 and 29%, and eubacteria were isolated from one fissure (27%). Gram-negative cocci made up 0 to 46% (media, 4%). Only two isolates of gram-negative rods were found, both facultative anaerobes. Although 8 of the 10 fissures had large proportions of S. mutans, lactobacilli, or both, no caries was found even with microradiography. The large individual variation probably reflects differences in initial colonization from saliva and in growth conditions in each fissure.

Bacteria↗
PubMed1981

Cell population kinetics in rat palatal epithelium treated with the carcinogen 4-nitroquinoline N-oxide (4NQO).

The carcinogen 4NQO was applied to the palates of rats for 2 weeks or 2 months. Eight weeks after termination of carcinogen application, animals were injected with colchicine and sacrificed at intervals of 3 h during a 24 h period. Histological sections were produced and the number of arrested metaphases counted in the palatal epithelium. The two groups had the same daily mitotic rate and exhibited a circadian rhythm in mitotic activity similar to that demonstrated in normal oral mucosa of nocturnal animals. Carcinogen was applied to the palates of other groups of rats for 2 weeks or 2 months. Animals treated with saline served as controls. At various time points during and after carcinogen treatment eight rats from each group were killed. Four of these animals were injected with colchicine prior to sacrifice and the number of arrested metaphases counted in the palatal epithelium. In the noncolchicinized rats all mitotic phases were counted. After cessation of carcinogen application the mitotic rates, the mitotic counts and the mitotic durations did not differ from those of control animals, indicating that the carcinogen had failed to induce irreversible changes in the cell population kinetics of the palatal epithelium.

4-Nitroquinoline-1-oxide↗
PubMed1981

Kielbone in new attachment attempts in Humans.

The purpose of this investigation was to evaluate, in humans, the use of Kielbone as a substitute for fresh autogenous bone in treating periodontal intrabony defects. A total of 92 intrabony defects were treated with a previously described new attachment procedure utilizing free mucosal grafts to cover the intrabony defects following bone grafting. Kielbone was placed in 46 of these defects, while the remaining 46 defects were treated with autogenous bone grafts. The results were evaluated after 6 months by periodontal probing and assessment of the bone level as seen on periodical, identical radiographs. No differences were observed between the amount of clinical gain of attachment obtained in defects treated with Kielbone and those treated with autogenous jaw bone. This indicates that in surgical procedures attempting to restore lost connective tissue attachment, Kielbone constitutes a suitable replacement for fresh autogenous bone. The results are discussed in th light of recent studies that challenge the beneficial effect of bone grafts in the treatment of intrabony defects.

Alveolar Process↗
PubMed1980

Healing following implantation of periodontitis affected roots into bone tissue.

The aim of the present experiment was to study whether new connective tissue attachment can occur to root surfaces which have been exposed to the oral environment and subsequently implanted into bone tissue. Twelve teeth in three beagle dogs were subjected to progressive periodontal breakdown to half the root length by placing cotton floss ligatures around the neck of the teeth. Following crown resection and root hemisection, the teeth were root filled and the roots thoroughly scaled and planed. Each root was extracted and implanted into bone cavities prepared in edentolous areas of the jaws in such a way that epithelial migration into the wound and bacterial infection were prevented during healing. Root implantation and sacrifice of the animals were scheduled to allow for observation periods of 1, 2 and 3 months. The results demonstrated that new connective tissue attachment did not occur to root surfaces which had been exposed to the oral environment, but healing was characterized by repair phenomena, i.e. mainly root resorption and ankylosis. In those areas of the roots where periodontal ligament tissue was preserved following tooth extraction, a functionally oriented attachment apparatus was reformed. The results indicate that in addition to apical migration of junctional epithelium and regrowth of subgingival plaque, the type of cells which repopulate the wound area may jeopardize new connective tissue attachment.

Animals↗
PubMed1980

Interproximal periodontal intrabony defects. Prevalence, localization and etiological factors.

The purpose of the present investigation was to study the distribution of interproximal periodontal intrabony defects as related to age, sex and localization, and to examine the relationship between some possible etiological factors and the occurrence of intrabony defects. A total of 209 adult patients presenting for dental treatment at the Royal Dental College in Arhus participated in this study. The patients were subjected to a questionnaire and were examined clinically and radiographically. All osseous defects in the radiographs were recorded but only those with a depth and width of a least 2 mm were considered periodontal intrabony defects. Only 18% of the participants had one or more periodontal intrabony defects but the prevalence was higher in older than in younger age groups. While periodontal intrabony defects occurred with the same frequency on the various tooth types, more defects were found on distal than on mesial surfaces. The presence of periodontal intrabony defects correlated with loss of attachment, increased tooth mobility, a wide interproximal space and open mesio-distal contact relationships between the teeth.

Adolescent↗
PubMed1980

Healing following implantation of periodontitis-affected roots into gingival connective tissue.

The aim of the present investigation was to examine if a new connective tissue attachment can be established on a previously periodontitis involved root surface, located in contract with gingival connective tissue during healing. A total of 28 teeth in one dog (beagle) and two monkeys (Macaca cynomolgus) were subjected to experimental periodontal tissue breakdown by placing cotton floss ligatures or orthodontic elastics around the teeth. The ligatures were left in situ until about 50% of the supporting tissues had been lost. Following resection of the crowns, the teeth were root filled and the exposed parts of the roots thoroughly scaled and planed. Each root was extracted and implanted into grooves prepared in edentulous areas of the jaws in such a way that the root was embedded to half its circumference in bone, leaving the remaining part to be covered by the gingival connective tissue of the repositioned flap of the recipient site. Root implantation and sacrifice of the animals were scheduled to allow for observation periods of 2 and 3 months of healing. An analysis of histologic specimens, obtained from biopsies of the recipient site tissues, disclosed that a new fibrous attachment failed to form on a previously "exposed" root surface located in contact with gingival connective tissue. In areas of the roots where the periodontal ligament tissue was preserved prior to transplantation, a fibrous reattachment occurred between the root and the adjacent gingival tissue. The results indicate that gingival connective tissue does not possess the ability to establish conditions which enable the formation of a new connective tissue attachment.

Alveolar Process↗
PubMed1977

Keratinizing potential of sulcular epithelium.

It has been shown that the connective tissue base determines the epithelial surface characteristics. Although there is no apparent difference between the connective tissues underlying the subcular and the surface gingival epithelium, the sulcular epithelium is not keratinized as is the gingival surface. The influence of the sulcular environment in determination of keratinization was explored in three adult Rhesus monkeys. Twenty-four intrasulcular mucoperiosteal flaps were elevated beyond the buccal mucogingival border, were turned inside out and sutured to leave the sulcular epithelium exposed on the surface. Short term speciments (1 hour to 7 days) were obtained from one monkey which received H3 thymidine 1 hour prior to sacrifice. Biopsies were obtained from the other two monkeys covering intervals of 1 week to 2 months. The findings indicate that the sulcular epithelium has potential for keratinization. The contact to the tooth appears to determine the lack of keratinization of the sulcular epithelium.

Animals↗
PubMed1976

Retardation of epithelial migration in new attachment attempts in intrabony defects in monkeys.

New attachment procedures were performed in 80 three-wall intrabony defects produced adjacent to incisors and canines in monkeys. Following a reverse bevel incision, mucoperiosteal flaps were raised on the buccal and lingual aspect of 40 intrabony defects. All soft tissue was removed from the defects and following transplantation of autogenous bone grafts, the tissue flaps were replaced and sutured. On the buccal and lingual aspect of another 40 intrabony defects a split flap procedure was performed. Granulation tissue was removed from the defects and following transplantation of autogenous bone grafts, the defects were covered with free palatal grafts. The animals were sacrificed to yield observation periods from 0 to 42 days. After decalcification of the specimens and embedding in paraffin, 8-mum serial sections were cut and stained. The epithelium on the full thickness flap seemed almost unaffected by the surgical procedure and had migrated between 0.2 mm and 2.0 mm along the root surface during the first week of healing. The epithelium on the transplants degenerated almost completely within the first week after surgery and epithelial migration along the root surface was not observed until after 10-12 days. These results indicate that the migration of epithelium during the postoperative phase of new attachment attempts can be retarded by covering the defects with free palatal grafts instead of full thickness flaps.

Animals↗
PubMed1976

The occlusal fissure of unerupted third molars as an experimental caries model in man.

The aim of the present investigation was to establish an experimental model for the study of fissure caries development under conditions as similar as possible to the in vivo situation. Twenty-one blocks (2 X 2 X 3 mm) constituting part of the occlusal fissure were made from unerupted human third molars, and implanted for 60 or 90 d in mandibular molars of students. One milliliter of a 50% sucrose solution was applied to the fissures twice a day. After removal, sections were examined microradiographically in polarized light and in the electron microscope. As a control, the morphology and enamel structure of fissures from 10 unerupted third molars were studied. After 90 d a subsurface, radiolucent caries-like lesion was observed in two specimens only. When examined in air in polarized light, however, all sections exhibited caries-like lesions symmetrically located around the fissures. The 60-d material showed similar lesions, but not as frequently as the 90-d specimens. In the experimental material processed for electron microscopy revealed that the fissure plaque mainly consisted of cocci and small rods. Most often the bacteria were separated from the enamel surface by a pellicle.

Dental Caries↗