I looked in the M-W dictionary

"Dear" has the following definitions (if in doubt, check a dictionary first)

1. obsolete : noble

2. : highly valued : precious <a dear friend> —often used in a salutation <dear Sir>

3. : affectionate, fond

4. : high or exorbitant in price : expensive <eggs are very dear just now>

5. : heartfelt <our dearest prayers>

So you might also translate it to 尊敬的，尊貴的，and similar terms?