Question

Which of the following parameters measures the percentage of incisor visibility relative to the clinical crown height?

• A. Smile Index
• B. Smile Arc
• C. Bolton’s Ratio
• D. Morley’s Ratio

Hint:

Incisor display percentage → Morley’s Ratio
Tooth size discrepancy → Bolton’s Ratio.

Answer 1

The Correct Option is D

Step 1: Understanding Incisor Display.
Incisor visibility plays a major role in smile aestheticsIt refers to the amount of maxillary incisor exposure during rest or smiling relative to the total clinical crown height
Step 2: Definition of Morley’s Ratio.
Morley’s Ratio specifically measures the percentage of maxillary incisor display relative to the clinical crown heightIt is commonly used in aesthetic smile analysis to evaluate incisal show and vertical tooth display
Step 3: Excluding Other Options.
Smile Index measures the ratio of smile width to smile height
Smile Arc describes the relationship between the curvature of the incisal edges and the lower lip
Bolton’s Ratio evaluates tooth size discrepancies between maxillary and mandibular teeth
Step 4: Conclusion.
Since Morley’s Ratio directly quantifies the percentage of incisor visibility relative to crown height, the correct answer is Morley’s Ratio