CASE 1 - FRACTURED TOOTH
If a piece of the tooth is fractured, the best way to restore the case is, quite frankly, by glueing the fractured piece back. In case the fragment was lost, porcelain would be the material that mimics better the biomechanics and optical appearance of the missing bit.
Having said this, porcelain is a difficult material to work with, making the rehabilitation complex and costly. A good alternative can be achieved with composite. Despite some limitations in shine and stability, one can achieve satisfactory results with this technique.