One-appointment endodontic therapy -Biological considerations.

By Lin LM, Lin J, Rosenberg PA.

Date: 12/2008
Journal: JADA


Purpose:  to review the existing literature regarding the biological aspects of endodontics that must be evaluated when performing one- appointment endodontic therapy for asymptomatic teeth with apical periodontitis. Biological considerations:

•Satisfactory root canal disinfection in one visit is necessary as intracanal medication cannot be used.

The clinician relies on:

1.Adequate working length control,

2.Mechanical instrumentation,

3.Antimicrobial irrigation and removal of the smear layer to eliminate intracanal bacteria.

4.Achieve a bacteria-tight seal with obturating materials to prevent reinfection.

Working length control:

•In teeth with apical periodontitis the bacteria may extend to the apical few mm of the root canals. Leaving critical numbers of bacteria could result in persistent inflammation after RCT. (Nair 1990)

•1-mm shortening in WL increased incidence of failures by 14% in teeth with apical periodontitis. (Chugal 2003)

•Both EAL and RG measurements should be used to obtain the best estimation of WL.

Mechanical instrumentation and antimicrobial irrigation:

•Repeated irrigation with copious amounts of irrigation is the most effective way to reduce intracanal bacterial level.

•The available evidence indicates no significant difference in antibacterial activity between 0.5 percent and 2.0 percent sodium hypochlorite in vivo. (Zehnder, 2006)

•Instrumentation the root canals to #40, (58%) of cultures were –ve. (Sjögren, 1997). instrumentation #35 to #60, (67%) of cultures were -ve. (Peters, 2002).

•A systematic review indicated that the larger the apical root canal preparation, the higher the percentage of bacteria that is eliminated from the infected root canals. (Baugh, 2005)

•Because of the complexity of the root canal anatomy, complete root canal disinfection may be impossible to achieve in teeth with apical periodontitis regardless of the number of dental visits.

•Contemporary instruments and irrigation alone could not remove biofilms in inaccessible areas of the canal system in one-visit treatment, because of anatomical complexity. (88% +ve). (Nair et al 2005).

•However, the presence of bacteria in root canal system, especially in an incompletely obturated canal system, is the central factor determining the ultimate outcome of endodontic therapy.

Smear layer removal:

•The smear layer can prevent penetration of irrigants into the dentinal tubules to kill microorganisms.

Root canal obturation:

•Its goal is to completely seal the root canal system preventing bacterial microleakage and protecting the periradicular tissues from developing disease.


  • Teeth appropriate for one- appointment endodontic therapy should be free of clinical signs and/or symptoms, such as pain, swelling or draining sinus tract.
  • The root canal anatomy should permit a sufficiently large apical root canal preparation that enables the dentist to remove intracanal bacteria effectively and deliver irrigant apically without causing perforation or transportation.
  • Regardless of the number of appointments, effective bacteriologic control of the root canal system is critical in endodontic therapy.

Clinical significance:   

Based on a systematic literature review, one-appointment endodontic therapy may be feasible in selected cases of apical periodontitis in asymptomatic teeth.