Not all composite fillings are created equal.
This tooth has become painful. Most likely reason being failed bond between the filling and the tooth (brown stained lined surrounding the filling). This allows bacteria to go in that fissure and irritate the tooth nerve. Following proper isolation and bonding techniques increases chances for a longer-lasting restoration.
Disclaimer: All above photographs  are of Dr. Andrew Yegorovykh's  patient and treatment. Photographs are for informational purposes only because individual treatment results will vary from patient to patient. Some patients may not be candidates for treatment. It is important for a prospective candidate to engage in detailed discussions with a dentist about treatment options, realistic outcomes, possible complications, costs, informed consent.