What is the corresponding medical diagnostic code and treatment code for dental procedure D3425 apico 1 root molar and D3426 additional root same tooth and D3430 retrograde filling per root

There is no specific medical code for these procedures as they are not typically covered by medical carriers. You may try 41899 and submit a breif narrative with the claim for possible payment.

As for a diagnostic code you would need to be specific as to the diagnosis...why is the provider doing an apicoectomy (i.e. gross caries, infection, ect.)

Keep in mind the diagnosis tells the carrier why a procedure is being provided (gives medical necessity)and the procedure tells the carrier what is being done.