"Son left distessed"

I attended a paediatric appointment with my son at on Friday, 13th December. This appointment was the third he has had in recent months at the dental hospital following a referral from our usual dentist. The preceding appointments have gone well, and we have left understanding the recommended treatment plan and any procedures that were undertaken. However I was disappointed by the treatment he received last Friday which has left him very traumatised. He attended to have a filling. I had explained the procedure to him beforehand to prepare him as he gets very anxious. He coped well with the initial preparation and the injection. However we were then told that he had to have an ‘umbrella’ or covering over his tooth. I have since found out that this is known as a dental or rubber dam. It is not a method I am familiar with, and despite having many fillings myself, even as a child, this has never been used by my practitioners. The undergraduate dentist then tried unsuccessfully several times to place the dam in its correct position. She unintentionally hurt him in the process, which made him very upset. The supervising dentist then took over and was also unsuccessful in applying the dam. By now my son was very distressed and it was decided to clean the tooth without a dam and to just insert a temporary filling. The supervising dentist undertook the cleaning, but my son felt like he was choking and was distraught by the end, despite the supervising dentist rightly telling him that he had been very brave. My issue is that we were not adequately informed about the procedures involved in the filling. This led to much distress to my son as well as quite a bit of discomfort. I now have a child who is adamant that he will not be returning to the dental hospital to continue his treatment, and indeed does not want to see any dentist again. This is obviously concerning me as I know he needs further treatment, but I don’t want him to develop a real phobia of dentists from any further treatment. I really don’t know how we move forward from here, but I do know that better explanation to both of us initially would have helped the situation.