Is it possible for Thermage CPT to continue to cause indentations and hyperpigmentation 1.5 years after procedure?

Thanks for your question.  I have been doing Thermage since 2001 and have seen a "dent" only one time and it was in the early years of Thermage.  The dent was corrected with Sculptra.  I have never seen hyperpigmentation secondary to this proceedure, but it could occur if an area became too hot or if the tip were defective causing a superficial burn.  In my opinion, it is unlikely that these side effects would appear 18 months after treatment. Without photos it is difficult to determine a specific treatment, but IPL, KTP laser, microneedling, and peels plus dermaplaning may be reasonable treatments for the hyperpigmentation.  For the "dent" fillers such as Sculptra, hyaluronic acids, or Bellafill may be beneficial.  See an expert and all the best to you.