Good morning sir Previously they used to fill with silver amalgam giving base beneath Visit near by dentist they will remove e and clean the fractured restoration then refill with composite material which is tooth coloured restoration And since ur complaining of pain get an x ray done to check the Pulpal involvement, if it's too close then you will have to go for root canal treatment depending on x ray

That white material is known as a base. Go to a dentist. He/she will remove the old filling including base and do a new filling. There is nothing to worry about.