Scanning electron microscopy of dentin caries. Experimental in vitro studies with Streptococcus mutans

Area of Science:

• Oral microbiology
• Dental caries research
• Biomineralization

Background:

• Dental caries is a significant global health issue.
• Streptococcus mutans is a primary pathogen in human dentin caries.
• Understanding bacterial interaction with dentin is crucial for prevention and treatment.

Purpose of the Study:

• To investigate the mechanisms of Streptococcus mutans-induced dentin destruction.
• To analyze bacterial colonization and invasion of human dentin.
• To elucidate the role of bacterial metabolites in dentin caries.

Main Methods:

• In vitro culture of Streptococcus mutans (NCTC 10449) on sterile human dentin blocks.
• Incubation under controlled conditions (10% CO2, 37°C) for up to 288 hours.
• Scanning electron microscopy (SEM) for examining bacterial colonization and dentin structural changes.

Main Results:

• Slow colonization of dentin surfaces by S. mutans, nearing completion after 288 hours.
• Limited invasion of S. mutans into dentinal tubules, restricted to the superficial 5 microns.
• Acid metabolites from S. mutans caused lesions in dentin structures near bacterial colonies.
• Rapid destruction of peritubular dentin observed in rare cases of tubule invasion.

Conclusions:

• Carious destruction of dentin by S. mutans primarily occurs on colonized, exposed surfaces.
• Bacterial invasion into dentinal tubules plays a secondary role in deep dentin destruction.
• Diffusion of bacterial acid metabolites into tubules may contribute to deeper tissue damage.