Intracanal Medication

J.F. Siqueira Jr., DDS, MSc, PhD (*) PostGraduate Program in Endodontics, Faculty of Dentistry, Estácio de Sá University,

Av. Alfredo Baltazar da Silveira, 580/cobertura, Recreio, Rio de Janeiro, RJ 22790-710, Brazil e-mail: jf_siqueira@yahoo.com

I.N. Rôças, DDS, MSc, PhD PostGraduate Program in Endodontics and Molecular Microbiology Laboratory,

Faculty of Dentistry, Estácio de Sá University, Av. Alfredo Baltazar da Silveira, 580/cobertura, Recreio, Rio de Janeiro, RJ 22790-710, Brazil e-mail: isabela.siqueira@estacio.br

The Infectious Problem

In a nutshell, clinicians face basically two conditions that require endodontic treatment: uninfected and infected root canals. The former are represented by teeth with vital pulps, which usually need root canal treatment because of irreversible pulpitis. The latter include teeth with necrotic pulps and usually associated with primary apical periodontitis and root canal-treated teeth that require retreatment because of posttreatment apical periodontitis. In teeth with irreversible pulpitis, infection is generally restricted to the area of exposure or the coronal pulp, with the radicular pulp being inflamed or not, but not infected [1, 2]. In these cases, root canal treatment should be completed as soon as possible, with asepsis as the key element to

Fig. 16.1 Biofilm is the main form that bacteria are found in endodontic infections. (a) Bacterial biofilm covering the entire perimeter of the canal in cross section. (b) Higher magnification showing the biofilm attached to the canal walls. An accumulation of polymorphonuclear

neutrophils can be seen close to the biofilm. These defense cells are usually ineffective in eliminating the endodontic biofilm (Taylor’s modified Brown & Brenn staining, courtesy of Dr. Domenico Ricucci)

influence a successful outcome [3]. It seems consensual that treatment of uninfected teeth should be accomplished in a single visit, provided time, professional skills, and equipment are favorable.

Infected root canals are a completely different problem. Intraradicular infection is the primary cause of both primary and posttreatment apical periodontitis [4–7]. In infected cases, endodontic procedures need to focus not only on asepsis but also on eliminating bacteria from the canal system [8–10]. An optimal outcome of the endodontic treatment will depend on how effective the clinician is in accomplishing these goals.

The success rate of the endodontic treatment of teeth with apical periodontitis is 10–25 % lower than vital teeth or necrotic teeth with no detectable disease [11–17]. Nonetheless, the outcome of treatment of infected teeth filled in the absence of detectable cultivable bacteria (negative culture) is very high and matches that of vital teeth [18]. One can thereby infer that for treatment of infected teeth (necrotic and retreatment cases) to reach a success rate comparable to that of uninfected teeth (vital cases), bacteriologic conditions within the root canals should be similar. This means that maximal bacterial reduction must be achieved in infected teeth before filling.

Bacteria colonizing the infected root canal associated with either primary or posttreatment apical

periodontitis are usually organized in biofilm structures attached to the dentinal walls (Fig. 16.1) [6, 7, 19–23]. In addition to the main root canal, bacterial biofilms can be disclosed in anatomical variations including apical ramifications, lateral canals, and isthmuses [2, 24–26]. Biofilms adhered to the apical root surface (extraradicular biofilms) have also been described in some teeth evincing posttreatment apical periodontitis [27–29]. Bacteria that invade and colonize dentinal tubules are a challenge to disinfection procedures and may affect the treatment outcome [20, 30, 31].

The main steps of endodontic treatment involved with infection control are represented by chemomechanical preparation and intracanal medication. Chemomechanical preparation is of paramount importance for root canal disinfection, since instruments and irrigants act primarily in the main canal, which is the most voluminous area of the system and consequently harbors the largest bacterial density. Bacterial elimination from the root canal is carried out by means of the mechanical action of instruments and irrigation as well as the chemical (antibacterial) action of the irrigant solutions. Although substantial amounts of bacteria are eliminated by chemomechanical preparation, studies have demonstrated that 40–60 % of the root canals still present detectable levels of bacteria after instrumentation