The problem with just wanting the prior dentist to cover the cost of fixing the mistake is that the cost of litigating the case could far exceed any recovery.
You need a medical report indicating how, specifically, the work deviated below the average standard of care and how, precisely that deviation caused injury. This is an abbreviation of the legal standard applicable in such cases. The dental care practitioner who writes this report will need to be compensated and also you'll have court costs.
As a practical matter, see if your current dentist will write such a letter. Then send it to the old dentist with a demand for the cost of treatment.
This answer is provided for informational purposes only. True legal advice can only be provided in an office consultation by an attorney in your jurisdiction with experience in the area in which your concern lies.
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