Root canal treatment is widely regarded as one of the most effective methods for treating adult pulpitis and periapical diseases, and it is the preferred treatment in clinical practice. The primary goal is to eliminate infected material within the root canal system, including bacteria, residual pulp, and their metabolic byproducts, using both physical and chemical techniques. This promotes the healing of periapical tissue lesions and prevents reinfection of the periapical tissue.

The root canal treatment process is divided into four main steps. The first step is access opening, which involves creating a passage into the pulp tissue by drilling an opening on the occlusal surface of the tooth. This allows instruments, medications, and materials to reach the entire root canal system, enabling the thorough removal of microorganisms and infected tissue.

Following access opening, the next step is cleaning the root canal using specialized instruments and medications. Mechanical preparation is a crucial part of this process, typically performed with nickel-titanium files that shape and clean the infected surfaces of the root canal walls. However, mechanical preparation alone cannot completely remove all the infected material. To address this, root canal irrigation with disinfecting solutions is used during preparation to flush out any remaining bacteria and debris, ensuring a sterile environment inside the root canal.

The third step is root canal disinfection. Despite the use of mechanical shaping tools and chemical irrigation, the complex nature of the root canal system, including lateral canals, narrow areas, and apical ramifications, means that some regions may not be fully cleaned. At this stage, chemical agents such as calcium hydroxide or chlorhexidine are sealed inside the root canal to eliminate any remaining bacteria, completing the disinfection process.

Once the bacteria in the root canal system have been eradicated, the final step is root canal filling. The purpose of root canal filling is twofold: to entomb any remaining bacteria or infectious material and to tightly seal the entire root canal system. This ensures that no microorganisms from the oral cavity can re-enter the root canal and reach the periapical area, thereby preventing future periapical diseases.

In summary, root canal treatment consists of four key steps: access opening, canal preparation, canal disinfection, and canal filling. Each step is critical to ensuring the complete removal of infected material from the root canal system and preventing the recurrence of periapical lesions, thereby providing optimal treatment outcomes for patients.