Improvement of the efficacy of endodontic solvents by ultrasonic agitation

Abstract

[Excerpt] The success rates of endodontic treatment can reach levels from 86% to 98% (Abitbol et al., 2003). However, apical periodontitis may still persist or develop after treatment due to various factors, namely coronal leakage, caries or fractures, thus enabling reinfection by microorganisms of the oral cavity or proliferation of microorganisms in persisting endodontic infections (Siqueira, 2001, Correia-Sousa et al., 2015, Melo et al., 2017).

Endodontic retreatment aims to reduce the bacterial load to a level that enables periapical healing. Nevertheless, its outcome is poor – about 70.9–83% (Torabinejad et al., 2009, Ng et al., 2011). The cleanliness of root canals cannot be accurately assessed through conventional periapical radiography or magnifying devices, but residual gutta-percha is systematically found in micro-CT scans after retreatment (Oltra et al., 2017). Chloroform and xylene have been widely used as endodontic solvents but concerns about their toxicity and potential carcinogenic effect led to seeking alternatives (Tamse et al., 1986, Metzger et al., 2000, Vajrabhaya et al., 2004, Magalhaes et al., 2007). Essential oils, like eucalyptol or orange oil, are one of the most common alternative groups of solvents used to enhance the dissolution or softening of gutta-percha. However, although they are considered less toxic, they are also reported as less powerful (Zaccaro Scelza et al., 2006, Faria-Junior et al., 2011, Martos et al., 2011). Studies show that, despite all the currently available technology, it is still not possible to achieve the complete removal of the potentially infected filling materials, which prevents total debridement and effective bacteria control (Alves et al., 2016, Keles et al., 2016, Rossi-Fedele and Ahmed, 2017). Although solvents have been indicated to prevent complications, such as ledges or perforations, in retreatment procedures, the literature reports that their use may hinder the cleaning of the root canal (Horvath et al., 2009). Retreatment can be carried out with or without solvents, but professionals often prefer to remove gutta-percha mainly with instrumentation, even though this may be a longer and less predictable procedure (Sae-Lim et al., 2000, Khalilak et al., 2013). Thus, endodontic solvents have almost fallen out of use. A new insight on endodontic retreatment seems to be necessary. [...]