From your history it sounds like you have occlusal problems. If your tooth chipped while you were eating something it was probably interfering with the lower teeth on chewing and too much pressure was being put on the tooth. I am assuming you have good oral hygiene in which case the failure of your subsequent crowns can also be attributed to this. The constant added pressure on the tooth will have caused it to weaken over the years and this is why you are now left with a root and a metal peg. To check whether your existing crown is getting too much pressure you need to place you index finger on the front face of the crown and tap your back teeth together. If you feel any movement of the tooth that is crowned is interfering with your bite. This moving sensation is called ‘ fremitus’. If this is the case then this crown will also fail and eventually the root will fracture and you will be faced with needing an implant.

I have a feeling that the crown is getting too much pressure. My reasons are as follows;

1) Your gum is receding. This has absolutely nothing whatsoever to do with tooth brushing techniques. When too much or the wrong types of pressure are put on teeth the gums can migrate upwards and recede because of the trauma. The gums are attached to the teeth and the extra pressure is thought to cause the tooth to flex around the junction of the enamel and root. It is good to use circular motions when tooth brushing but it will never grow back or reshape favourably.

2) The tooth seems to be getting darker. This can happen to teeth when continually traumatised. Having a metal peg in place doesn’t help situation.

3) You have experienced continual failure of that tooth and any restoration that has been placed on it.

You can definately get this problem resolved by finding a privatedentist that knows what he/ she is doing. White pegs can be used now and the new crown can be made of porcelain only and fabricated so that it is the correct position in your jaw