As clinical studies conducted to explore the safety and efficacy of new procedures are considered an important focus in endodontic research , the aim of this controlled clinical study was to compare a laser-assisted endodontic treatment using an erbium , chromium : yttrium-scandium-gallium-garnet ( Er , Cr : YSGG ) laser and radial firing tips ( RFT ) versus the conventional use of @ % sodium hypochlorite and interim calcium hydroxide paste , in teeth with chronic apical periodontitis .