PROSTHODONTIC PROTOCOL
Crown-to-Root Ratio
Restorability & Stability Assessment
Clinically
Symmetrical
Symmetrical
MM
MM
Measurements should be taken from the crest of the alveolar bone.
STABILITY COEFFICIENT
1:2.0
IDEAL STABILITY
1:2 (Optimum)
1:1 (Minimum)
2:1 (Fail)
The Clinical Logic of C/R Ratios
The **Crown-to-Root ratio** is a key prognostic factor in dentistry. It compares the portion of the tooth above the alveolar bone to the portion embedded within it. A poor ratio acts as a lever, increasing the risk of mobility and eventual tooth loss under occlusal loading.
What is the "Minimum" ratio for a bridge?
Classically, a **1:1 ratio** is considered the absolute minimum for a tooth to serve as an abutment for a fixed bridge, though 1:1.5 is clinically preferred.
Does crown lengthening improve the ratio?
No. Crown lengthening actually **worsens** the Crown-to-Root ratio because it removes bone to expose more tooth structure, increasing the lever arm.
Clinically Reviewed By:
Dr. Nikhil Mahajan, PT