Western Society of Periodontics

Laboratory Studies

Volume Number 4, 1995

The periodontal ligament of teeth connected to osseointegrated implants. An experimental study in the beagle dog

The aim of this study was to analyze the periodontal tissues at immobilized teeth connected to osseointegrated implants. Ten beagle dogs were used. The mandibular second and third premolars and first molars were extracted, and healing was allowed for three months. Two Branemark fixtures were installed, and three months later the premolars were rigidly connected to osseointegrated implants but had no contact in occlusion. In group A, plaque control measures continued until the end of the after-abutment connection. After four months of periodontal tissue breakdown, apically positioned flap procedure was performed. Healing was allowed for two months. At the end of six months, radiographs were taken and biopsies harvested from all dogs. The results of measurements, made in histological sections, revealed that the splinting of mandibular premolars to osseointegrated implants failed to induce marked alterations in the gingiva and periodontal tissues of immobilized teeth. [E.L.H.]

Protective immunity to P. gingivalis

The aims of this study were to investigate immunity to P. gingivalis infection in the mouse abscess model, to measure the specific antibody response to this organism, and to determine serum antibody reactivity to individual mouse antigens. P. gingivalis was cultured anaerobically. The outer membrane (OM) antigen was prepared. Four groups of mice were primed with this OM protein, and the control group was injected with phosphate-buffered saline (PBS).Two weeks after injection the mice were challenged with live P. gingivalis, and the control with saline injections. Six mice from each group were sacrificed on 1, 3, 7, and 14 days after challenge, and blood samples were taken. Primary and secondary lesions were assessed. Microbiological assessment included black-pigmented colonies, PMN, ELISA test, and CD4 depletion (tested by injecting rat immunoglobulins).

All groups immunized with OM had significantly higher levels of specific antibody. Significantly more lesions were induced in the immunized mice when compared with the control. Microbial testing showed a downward trend in the number of black-pigmented colonies over the 14 days of post-challenge. No organisms were recovered on the blood agar plates. An increased number of PMNs were found in primary lesions of the immunized groups. There was less weight loss in the mice that were immunized when compared to the control. The control group showed changes in behavior, stiffness, and ruffled hair. The mice treated with anti-CD4 antibodies prior to immunization had significantly decreased levels of serum anti-P. gingivalis. Mice treated with saline or rat immunoglobulins prior to immunization with OM showed a faster healing pattern. Anti-CD4-treated mice had significantly larger lesions than mice treated with saline or rat immunoglobulins.

In conclusion, the effectiveness of immunization of mice with the OM of P. gingivalis was demonstrated. Smaller lesion sizes were noted in the mice immunized with higher amounts of OM. A number of OM antigens that could be involved in providing protective immunity to P. gingivalis infection also were identified. [c.c.]