Abstract
Background: Very little is known about the effects of microbial composition of furcation defects. Limited results about the furcation microbiome reported higher levels of both overall microbiological counts and anaerobic counts for furcation areas compared with non-furcation after the debridement. Interestingly, it was also stated that the microbiological environment of furcation defects appeared different from non-furcation defects, with few periodontopathogenic species such as Porphyromonas and Treponema (including P. gingivalis and T. denticola), in particular advanced furcation involvements (FIs) seemed to experience progressive disease regardless of the presence or absence of well- known periodontal pathogens.Aim: To describe the furcation microbiological environment of subgingival dental plaque, comparing the level of aerobic, anaerobic, and facultative genera in furcation sites untreated, and treated with a surgical or non-surgical approach.
Materials and methods: A cross-sectional study with 57 participants, a single- centre randomized controlled clinical study with 20 participants and a multicentre randomised controlled clinical trial with 135 participants were designed to answer the research question. In the cross-sectional study, each participant contributed with a furcation defect, a matched non-furcation periodontal defect (NF) of similar probing pocket depth and a periodontally healthy site (HS). For the two RCTs, surgical and non-surgical periodontal treatment (NSPT) was provided on molars with advanced FI and a matched periodontally healthy molar was used as control. For all three projects, demographic, clinical parameters, and subgingival plaque samples were collected and analysed. Gingival crevicular fluid (GCF) was also collected in the cross-sectional study. Subgingival microbial composition was analysed sequencing the V3–V4 region of the 16S rRNA gene, and a multiplex bead immunoassay was carried out to estimate the level of 18 GCF biomarkers, associated with inflammation, connective tissue degradation and repair.
Results: For the cross-sectional study, 171 subgingival plaque and 84 GCF samples were included, while for each RCTs, 160 samples were analysed including test, control and healthy sites at the baseline and 4/6 months follow-up visit. Differences in richness, diversity, oxygen metabolism, microbial composition, GCF volume and biomarkers were observed when comparing different periodontal defects (FI and NF) with HS (p<0.05). Lower aerobic levels (p< 0.05) were detected in sites with untreated FI compared to NF and furcation sites treated with NSPT compared to surgically treated sites. IL-6, MMP-3, MMP- 8, BMP-2, SOST, EGF, and TIMP-1 levels were increased in untreated furcation defects compared with non-furcation periodontal sites, despite no difference in probing pocket depths (PPD). Specific bacteria as S. mutans, S. oralis, and S. gordonii showed significant increased levels in surgically treated sites compared to NSPT. A significant lower level of facultative (p<0.05), and a barely significant lower level of aerobic bacteria (p=0.05) was detected between Treatment A and Treatment B, 4 months after treatment, in the multicentre study. Interestingly 4 months after treatment, higher level of Cardiobacterium valvarum were detected in treatment B, and higher level of Fusobacterium periodonticum were detected in treatment A. No significant difference was detected in level of Streptococcus genera between Treatment B and HS after treatment.
Conclusion: The anatomical complexity of furcation defects with untreated periodontitis is characterized by a subgingival microbial composition with a reduced level of aerobic bacteria and an increase of several inflammatory, connective tissue degradation and repair markers compared with matched- periodontal defects in the same individual. Periodontal therapy using a non- surgical approached resulted in a less aerobic environment, while surgical treatments may interact with local anatomical factors selecting a unique microbiological profile characterised by higher level of aerobic bacteria, including streptococci species associated with root caries.
| Date of Award | 1 Oct 2024 |
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| Original language | English |
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| Supervisor | Luigi Nibali (Supervisor) & Mandeep Ghuman (Supervisor) |