A Second Opinion, With the Useful Questions
Make a second opinion useful: bring the proposed plan, identify your uncertainty, and compare the reasons behind each recommendation.

Name the question first
A large treatment plan can leave you unsure what you are being asked to decide. Before booking another opinion, write down the uncertainty: whether a tooth can be repaired, why a procedure is recommended, how urgent it is, or whether a different option fits your priorities.
The ODA says you can seek a second opinion and should expect that the additional examination and consultation may have a fee. Ask about that cost when booking. Request the proposed treatment plan and arrange relevant records so the second dentist has useful background.[1]
Compare explanations
Bring the same questions to both conversations. What finding supports the recommendation? What alternatives were considered? What would change the recommendation? Ask each dentist to explain their reasoning in language you understand, including the limits of what can be predicted.
A different recommendation does not, on its own, tell you which plan is better. It gives you something specific to discuss. Keep notes on the benefits, risks, maintenance and timing of each option. If the original concern is urgent, ask how quickly a decision is needed while you arrange the consultation.