crack in tooth enamel

I had large Amalgam fillng that started to detriorate, causing metalic taste in my mouth. I replaced ith with composite by a IAOMT dentist.
I had pain when I eat seeds like sesame seeds, or pomgranate seeds. the dentist said that tooth has crack in the enamel. he sealed it by applying more composite.
the dentist said it can heal in 4 weeks. if not then a crown needed.

I would like to know how can I encourage that crack to heal? is there any possiblity to heal it?