Tryggve Lie

Morphologic studies on dental plaque formation: Summary

The present summary and the following papers (I-VII) are submitted in partial fulfillment of the requirements for the degree of Doctor Odontologiae at the University of Bergen.I: Growth of dental plaque on hydroxyapatite splints. A method of studying early plaque morphology. J. Periodontal Res. 1974, 9, 135-146II: Pellicle formation on hydroxyapatite splints attached to the human dentition: Morphologic confirmation of the concept of adsorption. Arch. Oral Biol. 1975, 20, 739-742III: Scanning and transmission electron microscope study of pellicle morphogenesis. Scand. J. Dent. Res. 1977, 85, 217-231IV: Early dental plaque morphogenesis. A scanning electron microscope study using the hydroxyapatite splint model and a low-sucrose diet. J. Periodontal Res. 1977, 12, 73-89V: Ultrastructural study of early dental plaque formation. J. Periodontal Res. 1978, 13, 391-409VI: Dental plaque morphology as revealed by direct observation and by replicating techniques. Acta Odontol. Scand. 1978, 36, 279-288 Co-author: F....

Relative Production of IL-1β and TNFα by Mononuclear Cells After Exposure to Dental Implants

Interleukin-1 (also known as osteoclast activating factor, OAF) is a cytokine produced primarily by monocytes and macrophages and is thought to mediate many of the immunologic, metabolic, and endocrine alterations seen with microbial infection, tissue injury, inflammatory disease, and bone loss. Stimuli for IL-1 production include microorganisms, endotoxins (LPS), antigen-antibody complexes, clotting components, and other cytokines. The purpose of this study was to determine whether dental implants stimulated peripheral blood mononuclear cells (PBMCs) to produce IL-1β (OAF) as well as tumor necrosis factor (TNFα). This production may lead to bone loss or failure of an implant. Three duplicates of five different implants were incubated with 2 × 106 PBMCs/ ml in 20% autologous serum; the esterase positive PBMCs amounted to 14.5%. Measured by radioimmunoassay techniques and compared to controls, all of the implants except one caused significant in vitro generation of IL-1β and TNFα. The stimulation of IL1β/TNFα production by these materials suggests that they are not physiologically inert and that the IL-1β (OAF) production may contribute to a less favorable osseoadaptation. OAF has a physiologic (homeostatic) role in maintenance and alteration of osseous structures, but the level at which physiologic becomes pathologic is unknown. Although there were statistical differences between the cellular response to these implants, the clinical significance of the differences remains to be determined. J Periodontol 1992; 63:426-430.

Replica study of plaque formation on human tooth surfaces

Plaque formation on buccal tooth surfaces was studied by replica technique, consisting of impressions using low viscosity silicone impression materials and positive models produced in epoxy resins. Bacterial accumulation occurred near the cemento-enamel junction in 6-hr specimens, and subsequently expanded in a coronal direction. This development took place partly by extensions of single layers of bacteria, and partly by a pattern where the colonization was mostly restricted to vertical enamel cracks. Plaque accumulations were also frequently located in abrasion grooves and surface pits in the enamel, and prolific plaque areas were consistently surrounded by a monolayer of bacterial cells. Globular and hemispheric structures which occurred, especially on root surfaces immediately after cleaning, were probably artefacts caused by air bubbles or remaining moisture. In separate series of experiments it was demonstrated that improved reproduction of details from the plaque could be achieved by repeating the replicating procedure. The findings indicate that plaque formation starts by adsorption and proliferation of individual bacteria on tooth surfaces, and not by adsorption of aggregates of cells. Special attention should be directed against the problem of artefacts and moisture in replica studies of dental plaque.

Dental plaque morphology as revealed by direct observation and by replicating techniques

The ability of four elastomer impression materials to reproduce details of bacterial plaque structures was studied by comparing areas of the replica models with corresponding areas of the replicated plaque. Plaque was grown on hydroxyapatite splint segments for 48 hours and replica models were made from three different resins. One of the resins, a methacrylate material, was not suited for this purpose due to its content of spherical particles. The polysulfide and polyether impression materials reacted with the heat curing epoxy resin, and less satisfactory results were obtained with cold curing epoxy resin. Best results were obtained by a combined use of low viscosity silicone impression materials and cold or heat curing epoxy resins as model materials. However, a considerable loss of detail occurred in the replica models compared with observations of plaque directly on splint surfaces. Outlines of individual bacteria could sometimes be seen in the models, but generally several cells seemed to fuse, and appeared like small globular structures where cells and pellicle were difficult to distinguish. The bacterial colonization started near the gingival border of the surface, initiated by attachment of individual bacteria to the pellicle surface.

Periodontal awareness, health, and treatment need in dental school patients: I. Patient interviews

The present study aimed to evaluate the periodontal awareness and the amount of information and periodontal treatment received previously in a group of randomly selected patients scheduled for periodontal treatment in a dental school. A group of 124 patients were interviewed by a dental hygienist before the treatment started. Age, sex, and regularity of dental visits were used as predictors. Around 68% of the patients were not aware of the existing periodontal disease, and 74% had never received any information about the treatment possibilities. Ninety per cent claimed that they had never received any periodontal treatment at all. The modality of periodontal treatment and the extent to which the patients had been instructed in toothbrushing were almost equal in patients who visited the dentist yearly and in emergency patients.

Periodontal awareness, health, and treatment need in dental school patients: III. Treatment need

The need for periodontal treatment in a group of dental school patients was estimated by means of the periodontal treatment need system (PTNS). The findings were related to information about the regularity of dental visits, awareness of own disease, and periodontal treatment experience. All the patients required motivation and oral hygiene instruction (treatment need, class A). All their quadrants needed scaling or adjustment of subgingival restorations (treatment need, class B). As many as 71% of the patients and about 49% of the quadrants needed periodontal surgery (treatment need, class C). The mean periodontal treatment time per patient was 279 min (4 h 39 min). The middle age group (30-59 years) required more treatment time than the oldest group (greater than or equal to 60 years). This was probably due to more missing teeth in the oldest age group. There were no significant differences in treatment need between males and females. The regular dental visitors had a greater periodontal treatment need than the individuals visiting their dentist less frequently. This finding emphasizes the responsibility of the general practitioner in diagnosing and treating periodontal disease.