Dental plans do not offer a comprehensive coverage for all kinds of dental treatments, especially when the policies are purchased through employers.
In general, the exclusions can be in the form of restrictions on the number of visits to the dentists, dental providers and types of treatment.
Hence, there is a need for you to obtain supplemental insurance to cover high dental cost.
Below is the step by step approach for your kind reference.
Step 1:

• Gather all the information about your existing dental plan.
  Find out exactly what kind of coverage it provides and list down the types of coverage which are not included in your policy.
  Make sure you don't buy insurance for the coverage you already have.
  

Step 2:

• Find out more information about supplemental dental insurance from internet or other sources.
  You can either obtain information online or contact a few local insurance agents to assist you.
  

Step 3:

• Gather all the information about different types of supplemental insurance options.
  Make thorough comparisons on the premiums, benefits offered and the exclusion clauses.
  

Step 4:

• Shortlist the companies that provide supplemental plans you want.
  Consider the background of the insurance companies to make sure they are reliable.
  

Step 5:

• If you are not very sure about those packages, you can refer to credit and labor unions.
  They also provide good supplemental dental coverage to their members.
  

Step 6:

• Select the best option that suits your needs and budget most.
  

Last but not the least; an important reminder here is DO NOT CANCEL your existing dental policy even you have signed up for the supplemental plan.
This plan is just a secondary plan that makes your oral healthcare more completed.