Adaptation Mechanisms of Streptococcus mutans to Stresses Induced by Resin Composite Biodegradation By-products
Bibliographic record
Abstract
Resin composites are currently the most popular dental restorative materials. While providing several beneficial properties such as superior esthetics and excellent adhesive strength to dentin and enamel, resin composites undergo biological breakdown in the oral cavity that results in secondary/recurrent caries and reduced restoration longevity compared to amalgam. The breakdown of the resin-dentin interface by salivary and bacterial esterases generates biodegradation by-products (BBPs) including triethylene glycol (TEG) and bis-hydroxy-propoxy-phenyl-propane (BisHPPP). This chemical degradation contributes to gap formation between the restoration and the tooth, providing a path for microleakage of cariogenic microorganisms such as Streptococcus mutans, potentially resulting in recurrent/secondary caries, which is a major cause for resin composite restorations replacement. To test the hypothesis that BBPs activate signaling pathways that are involved in Streptococcus mutans pathogenicity and understand the molecular pathways that regulate the BBPsâ effects on cariogenic bacteria, this thesis quantitatively and mechanistically studied the effect of TEG or BisHPPP at clinically-relevant concentrations on the virulence properties of S. mutans UA159 in a relevant in vitro model. Quantitative real-time polymerase chain reaction showed up-regulation of seven dominant virulence-associated genes i.e. gtfB, gtfC, gbpB, comCDE and atpH, more significantly in biofilm vs. planktonic cells, only at cariogenic pH (5.5). Exposure of the constructed knock-out and complemented strains of S. mutans for the key regulatory genes, vicK and comC, to BBPs suggested these signalling pathways as potential mechanisms for up-regulation of the virulence-associated genes. S. mutans biofilm proteome analysis after exposure to TEG/BisHPPP confirmed activation of specific bacterial adaptation mechanisms such as biofilm formation and adhesion, acid tolerance, optimization of phosphotransferase system and stress-response pathways in response to BBPs. Microarray data were consistent with the proteomics findings for BisHPPP. Furthermore, both BBPs increased glucosyltransferases enzyme activity, involved in synthesizing exopolysaccharide glucan associated with the formation of cariogenic biofilms. This thesis provides significant insight into the adaptive response of S. mutans to the dental biomaterial-derived degradation products and elucidates the potential molecular mechanisms that could contribute in pathogenesis of secondary caries in resin composite restorations. It also provides a rationale for development of dental restorative materials that are more biostable and biocompatible.
Fetched live from OpenAlex and de-inverted. Abstracts are not stored in this database: the inverted indexes are 8.6 GB of the frame’s 9.3 GB of text, and the host has 13 GB free.
How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".