Changes in the Microflora and Humoral Immune Response Following Periodontal Therapy

Darby, Ivan B (1999) Changes in the Microflora and Humoral Immune Response Following Periodontal Therapy. PhD thesis, University of Glasgow.

Abstract

This thesis investigated the changes in the microflora and humoral immune response with periodontal therapy. Scaling and root planing (SRP) has been shown to reduce the microbial load and produce clinical improvement. Generally, culture techniques have been used to analyse the microflora in periodontitis, but this technique is now recognised as having many errors and limitations. Polymerase chain reaction is a very sensitive and accurate technique for detecting bacteria and was used in these studies to investigate the flora in adult periodontitis (AP) and generalised early-onset periodontitis (GEOP) subjects before and after SRP. In addition, the effect of SRP on the systemic and local humoral immune response in AP patients was assessed. The antibody response is thought to be protective and the response of the humoral immune system to SRP may reflect this. The relationship between the microflora and humoral immune response was also determined. Antibody serostatus has been shown to have a relationship with baseline clinical parameters and affect the magnitude of both the clinical and humoral immune response to SRP. Serostatus was assessed and its effect on other parameters investigated in AP patients. Checkerboard DNA-DNA hybridisation is a relatively new technique with which to determine the content of periodontal plaque samples, but, although it has been shown to be more sensitive than culture, it has not been compared to other microbial assays such as PCR. Another aspect of this thesis was to compare PCR and the Checkerboard technique for microbial analysis. Smoking has been shown to be a risk factor for periodontal disease, and smoker patients tend to have greater periodontal destruction levels and respond less well to periodontal therapy. The effect of smoking on the AP and GEOP patients was also investigated, and in the AP patients, the humoral immune response between smokers and non-smokers was compared. Fifty seven untreated patients, 33 AP and 24 GEOP, were recruited for this study. Clinical parameters were recorded and GCF and plaque samples taken before and after SRP. There were 10 AP smokers and 12 GEOP smokers. In addition, venous blood was collected from AP subjects before and after therapy. Plaque samples were analysed for the presence of P. gingivalis, P. intermedia, B. forsythus, A. actinomycetemcomitans and T. denticola using both PCR and Checkerboard. GCF and serum samples were analysed by ELISA for antibody titres and serum antibody avidity to these organisms. Comparison of AP and GEOP subjects at baseline showed that GEOP subjects have lower BOP and GCF volume, which may have resulted from the greater proportion of smokers in this group. GEOP subjects also had deeper pocketing and higher prevalences of B. forsythus and A. actinomycetemcomitans. The higher prevalence of these bacteria may be due to the deeper pocketing but also suggests a role for these organisms in GEOP. SRP produced significant clinical improvement and the reductions in PD and AL were in keeping with previously published data. However SRP produced few significant changes in the micro flora in AP subjects and this probably reflects the sensitivity of PCR. GEOP subjects had significant reductions in the flora in response to SRP which mirrored the greater reduction in pocket depth (PD) seen in these patients compared to AP subjects. Bleeding on probing (BOP), suppuration (Supp) and bacterial prevalences were related to pocket depth in AP subjects and the magnitude of the reduction of PD related to initial PD in both AP and GEOP subjects. Post-SRP, B. forsythus and T. denticola were associated with deep pockets in AP and P. intermedia in GEOP patients. In AP subjects the presence of P. gingivalis, P. intermedia, B. forsythus, and T. denticola were interrelated and, in GEOP, T. denticola was always detected with B. forsythus. The comparison of PCR and Checkerboard showed roughly 60% agreement and the higher bacterial prevalences using PCR reflected the lower detection limit of this technique. However, a number of technical problems prevented optimal analysis by Checkerboard. Using Checkerboard to analyse microbial prevalence before and after SRP produced a higher number of significant reductions in the flora compared to PCR suggesting that the sensitivity of PCR masked the reductions in bacterial load. SRP produced little change in systemic and local antibody titres and also antibody avidity, in contrast to previous reports. The results suggest that the poor immune response may have been a factor in the onset of disease. (Abstract shortened by ProQuest.).

• Item Type: Thesis (PhD)
• Qualification Level: Doctoral
• Additional Information: Adviser: D F Kinane
• Keywords: Dentistry, Immunology
• Date of Award: 1999
• Depositing User: Enlighten Team
• Unique ID: glathesis:1999-74909
• Copyright: Copyright of this thesis is held by the author.
• Date Deposited: 27 Sep 2019 15:14
• Last Modified: 27 Sep 2019 15:14
• URI: https://theses.gla.ac.uk/id/eprint/74909