Subgingival Calculus — A Hidden Bacterial Reservoir
Hardened plaque locks bacteria against the root, out of reach of a toothbrush.
- ~80%: Calculus mineral content (calcium phosphate salts)
- ~10 days: Plaque to calculus (mineralization window)
- >4 mm: Pocket depth (periodontitis) (brush cannot reach)
- >700: Bacterial species in biofilm (subgingival plaque)
How calculus forms
Soft plaque mineralizes into hard calculus within days.
Why it matters
Rough calculus surface shelters bacteria from the immune system.
Calculus itself is not toxic — the living biofilm coating it is.
Clinical detection
Explorer probing and radiographs reveal deposits below the gumline.
Scaling — Breaking Calculus Free
A curette or ultrasonic tip fractures and lifts deposits off the root.
- 25–50 kHz: Ultrasonic frequency (piezoelectric tip)
- Pull stroke: Hand curette stroke (adapted to root contour)
- 70–80°: Working end angle (blade-to-tooth optimum)
- 30–45 min: Session time (quadrant) (typical SRP visit)
Instrument choice
Ultrasonic scalers vibrate deposits loose; curettes shear them off.
Tactile skill
Clinician feels for roughness through the instrument handle.
Thoroughness determines how much calculus is actually removed.
Irrigation
Water or antimicrobial rinse flushes debris from the pocket.
Root Planing — Smoothing the Cementum
Rough, endotoxin-laden cementum is planed to a hard smooth surface.
- <50 µm: Cementum removed (conservative planing)
- Superficial: Endotoxin depth (not deeply embedded)
- Glass-like: Root smoothness goal (to fingernail test)
- Sensitivity: Re-instrumentation risk (if over-planed)
Planing technique
Overlapping strokes shave the outer contaminated cementum layer.
Balance point
Enough cementum removed to smooth, not enough to weaken the root.
Smoothness matters more than removing large volumes of tooth structure.
Verification
A dental explorer glides without catching when planing is complete.
A Clean Root With No Retentive Niches
Smooth cementum gives bacteria nowhere to hide and recolonize.
- Minimal: Surface roughness (post-planing)
- >90%: Bacterial load drop (immediately after SRP)
- ~3 months: Recolonization window (without maintenance)
- Much lower: Plaque adhesion (on smooth cementum)
Why smoothness helps
Bacteria adhere far less readily to a polished root surface.
Immune access
A clean pocket lets host defenses reach the remaining flora.
Removing the reservoir, not sterilizing the mouth, is the real goal.
Maintenance need
Recall visits keep the reservoir from rebuilding over time.
Gingival Reattachment to the Cleaned Root
A new junctional epithelium seals the pocket against the smooth root.
- 1–2 weeks: Initial healing (epithelial closure)
- 1–3 mm: Pocket depth reduction (typical at reassessment)
- 4–6 weeks: Reassessment interval (post-SRP)
- Primary healing mode: Long junctional epithelium (vs. true reattachment)
Tissue response
Inflammation subsides and gingiva tightens against the tooth.
New attachment
Epithelial cells migrate to form a long junctional epithelium.
Healing narrows the pocket, cutting off bacteria from nutrients.
Long-term outcome
Good home care and recalls keep the reservoir from returning.