A comparative, scanning electron microscopic study of supragingival and subgingival calculus

Area of Science:

• Oral biology
• Microbiology
• Dental morphology

Background:

• Dental calculus, a mineralized bacterial plaque biofilm, forms on teeth.
• Understanding calculus morphology is crucial for effective plaque control and periodontal health.
• Differences in supragingival and subgingival calculus structure may influence their pathogenicity.

Purpose of the Study:

• To investigate the detailed morphology of supragingival and subgingival calculus using scanning electron microscopy.
• To compare the microbial composition and structural organization of the two types of dental calculus.
• To explore the initial stages of calculus formation and calcification.

Main Methods:

• Extraction of teeth with supragingival and subgingival calculus.
• Examination of oral, crevicular, and fracture surfaces using scanning electron microscopy (SEM).
• Treatment of calculus specimens with sodium hypochlorite to reveal subsurface structures.

Main Results:

• Both calculus types exhibited a heterogeneous core covered by a layer of microorganisms.
• Supragingival calculus had a filamentous microorganism covering oriented perpendicular to the calculus surface.
• Subgingival calculus showed a mixed microbial covering (cocci, rods, filaments) without a distinct orientation.
• Sodium hypochlorite treatment revealed channels within the calculus, supporting microbial involvement in calcification.

Conclusions:

• Dental calculus forms from a core of microorganisms, with distinct differences in surface microbial composition and organization between supragingival and subgingival types.
• The presence of channels after chemical treatment supports the hypothesis that calcification initiates between microorganisms within the calculus structure.
• SEM analysis provides valuable insights into the micro-morphology and formation process of dental calculus.