Question

An 8-year-old patient has a combined mesiodistal width of 19.5 mm for the four mandibular incisorsUsing the Tanaka-Johnston analysis, what is the predicted width of the unerupted mandibular canine and premolars on one side?

• A. 20.5 mm
• B. 20.25 mm
• C. 20.75 mm
• D. 20 mm

Hint:

For Tanaka–Johnston analysis: Mandibular arch = (Sum of lower incisors ÷ 2) + 10.5 Maxillary arch = (Sum of lower incisors ÷ 2) + 11

Answer 1

The Correct Option is B

Step 1: Understanding Tanaka–Johnston Analysis.
Tanaka–Johnston analysis is a mixed dentition space analysis method used to predict the combined mesiodistal width of unerupted canines and premolarsIt uses the measured width of the four mandibular incisors to estimate the size of unerupted teeth
For the mandibular arch, the formula is:
\[ \text{Predicted width (one side)} = \frac{\text{Sum of four mandibular incisors}}{2} + 10.5 \]
Step 2: Substitute the Given Value.
Sum of four mandibular incisors = 19.5 mm
\[ = \frac{19.5}{2} + 10.5 \]
\[ = 9.75 + 10.5 \]
\[ = 20.25 \text{ mm} \]
Step 3: Conclusion.
The predicted combined width of the unerupted mandibular canine and premolars on one side is 20.25 mm