Unprepared root canal surface areas: causes, clinical implications, and therapeutic strategies

Abstract

Chemomechanical preparation is intended to clean, disinfect, and shape the root canal. This step is of utmost importance during treatment of infected teeth with apical periodontitis, because treatment outcome depends on how effectively the clinician eliminates bacteria, their products, and necrotic tissue that would serve as substrate for bacterial regrowth. Nonetheless, curvatures and complex internal anatomical variations of the root canal system can pose a high degree of difficulty in reaching these goals. In infected teeth, bacteria may persist not only in difficult-to-reach areas such as isthmuses, ramifications, dentinal tubules, and recesses from C-shaped or oval/flattened canals, but also in areas of the main canal wall that remain untouched by instruments. If bacteria withstand chemomechanical procedures, there is an augmented risk for post-treatment apical periodontitis. This article discloses the reasons why some areas remain unprepared by instruments and discusses strategies to circumvent this issue and enhance infection control during endodontic treatment/retreatment of teeth with apical periodontitis.

Efficacy of reciprocating and ultrasonic activation of 6% sodium hypochlorite in the reduction of microbial content and virulence factors in teeth with primary endodontic infection

“…Several instrumentation systems have been developed to achieve maximum disinfection of the root canal (Marinho et al , Tomson & Simon ). Despite the development of instrument systems with new thermal treatment, design and kinematics, disinfection of the root canal continues to be extremely challenging, probably due to the presence of lateral canals, isthmuses, apical deltas, curvatures, and dentinal tubules (Marinho et al , , Siqueira et al ).…”

“…Therefore, auxiliary procedures have been proposed to optimize the antimicrobial effect of chemical‐mechanical preparation within infected root canals, including a final irrigation protocol using irrigant activation. These protocols include several techniques such as manual dynamic activation (Virdee et al ), passive ultrasonic irrigation (Plotino et al , van der Sluis et al ), sonic irrigation (Karade et al , Zeng et al ), apical negative pressure irrigation (Gu et al , Tomson & Simon ), reciprocating activation (Kato et al ), laser activation with photon‐induced photo‐acoustic streaming (PIPS) (Arslan et al ), and irrigant activation using either XP‐endo finisher (FKG Dentaire, La Chaux de Fonds, Switzerland), self‐adjusting file system (SAF; ReDent Nova, Ra'anana, Israel), TRUShape (Dentsply Sirona, Ballaigues, Switzerland) or XP‐endo shaper (FKG Dentaire) (Siqueira et al ). In the literature, there is no consensus on the best irrigation protocol necessary for effective activation of the irrigant and the removal of smear layer and debris from the root canal (Rodrigues et al , Nakamura et al ).…”

The effect of ozone therapy in root canal disinfection: a systematic review

“…Root canal preparation enlarges the main root canal promoting mechanical removal of infected dentine and simultaneously favours the penetration of irrigants through the canals, enhancing the decontamination process (Estrela et al ). However, a significant percentage of the root canal surface remains untouched, regardless of the instruments used for mechanical preparation (Siqueira Jr et al ). Such unreached areas may protect micro‐organisms from root canal disinfecting protocols (Gomes & Herrera ).…”

“…Sodium hypochlorite (NaOCl) is the most commonly used root canal irrigant; it has an effective antimicrobial activity, a broad bacterial range, and creates a significant reduction in endotoxins levels (Zehnder , Fidalgo et al , Neelakantan et al ). However, several studies have demonstrated that complete bacterial elimination cannot be achieved consistently with any of the current disinfection protocols (Siqueira Jr et al , Silva et al ). Therefore, efforts have been made to develop novel techniques to provide additional disinfection for the root canal system, such as passive ultrasonic irrigation (PUI) (Dioguardi et al ), photodynamic therapy (PDT) (Eslami ), continuous irrigating techniques (Dioguardi et al , Silva et al ) and apical positive and negative pressure irrigation methods (Dioguardi et al , Eslami , Silva et al ).…”

The effects of different 650 nm laser diode irradiation times on the viability and proliferation of human periodontal ligament fibroblast cells

“…2 Unsuccessful conventional root canal treatment is usually due to complex root canal anatomy rendering the removal of all healthy pulp tissue and bacterial residue difficult. 3 Since damage to the periodontal ligament limits its regenerative ability, root canal treatment and laser therapy can improve the prognosis of the lesion healing process. 4 Progenitor cells are identified in periodontal structures including periodontal ligaments.…”