What is the main factor that causes reversible pulpitis to progress into irreversible pulpitis?

Explanation

The transition from reversible to irreversible pulpitis occurs mainly due to the invasion of microorganisms into the pulp tissue, which triggers an inflammatory response that the pulp cannot recover from. While factors like vascular constriction, weakened host immunity, and increased microbial virulence can influence the process, the primary cause is bacterial infiltration.