SUMMARYAim: This study compared the fracture resistance of endodontically-treated mandibular molars with mesio-occluso-distal (MOD) cavities restored using different restoration techniques. Methodology: Sixty sound extracted mandibular molars were randomly assigned to six groups (n=10). Group 1 did not receive any preparation.The teeth in Groups 2-6 received root canal treatment and a MOD cavity preparation. The teeth in Group 2 were kept unrestored. Group 3 was restored conventionally with amalgam. Group 4 was restored with a dentin bonding system (DBS, Clearfil SE Bond) and resin composite (CR) (Clearfil Photoposterior). Group 5 was restored with indirect hybrid ceramic inlay material (Estenia). In Group 6, polyethylene ribbon fiber (Ribbond) was inserted into cavities in a buccalto-lingual direction and the teeth were then restored with DBS and CR. After finishing and polishing, the specimens, except for Group 2, were loaded to failure by a chewing simulation device ( To restore endodontically-treated molars, the use of indirect hybrid inlay restorations may be recommended due to their more favorable fracture failure modes compared with amalgam, resin composite and fiber-reinforced resin composite restoration techniques and their greater fracture resistance compared with amalgam restorations. . There were statistically significant differences between the groups annotated with different letters. Thus, Group 1 (intact teeth) had the greatest fracture resistance and Group 2 (non-restored teeth) the poorest. No statistically significant differences were found between Groups 3 (amalgam), 4 (resin composite) and 6 (polyethylene ribbon fiber reinforced composite) (p>0.05). Group 5 (indirect hybrid ceramic inlay) had greater fracture resistance than Group 3 (p<0.05). Conclusions: Within the limitations of this study, although all of the restoration groups were stronger than the prepared-only group, none of the restoration techniques tested was able to completely restore the fracture resistance lost from MOD cavity preparation. However, use of indirect hybrid inlay restorations in these teeth may be recommended, because this restoration technique indicated more favorable fracture failure modes than other restoration techniques used in this study and particularly greater fracture strength than amalgam restorations. The promising result of indirect hybrid inlay restorations may need to be confirmed by long-term clinical studies.

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Objective: The aim of this in vitro study was to investigate the possible interactions between photon-induced photoacoustic streaming (PIPSÔ)-activated oxidizing agents and 2% chlorhexidine digluconate. Background data: There is no information about the safety of laser-activated oxidizing agents in combination usage with chlorhexidine gluconate. Materials and methods: Groups were designed as follows G1: 98% para-chloroaniline (PCA); G2: 2% chlorhexidine (CHX); G3: 5.25% sodium hypochlorite (NaOCl) +2% CHX; G4: 5.25% NaOCl (30 sec PIPS activated) +2% CHX; G5: 5.25% NaOCl (60 sec PIPS activated) +2% CHX; G6: 3.5% chlorine dioxide (ClO 2 ) + 2% CHX; G7: 3.5% (ClO 2 ) (30 sec PIPS activated) +2% CHX; G8: 3.5% (ClO 2 ) (60 sec PIPS activated) +2% CHX. The laser-irrigation protocol was performed with an erbium:yttrium-aluminum-garnet laser with a wavelength of 2940 nm equipped with a 140 mm long endodontic fiber tip (PIPS) using 10 mJ at 15 Hz (0.15 W), per pulse operating outputs. Groups were analyzed with proton nuclear magnetic resonance spectroscopy, using PCA as an internal standard. Results: No free PCA was formed in any groups of mixtures or after PIPS activation. Conclusions: Mixing of 3.5% ClO 2 and 2% CHX does not form bulky precipitates, unlike the mixture NaOCl + CHX. PIPS activation does not cause changes in reactions of oxidizing agents.

Objectives This study assessed the antibacterial activity of both separate and combined uses of 5.25% sodium hypochlorite (NaOCl), 2% chlorhexidine (CHX), 17% ethylenediaminetetraacetic acid (EDTA), 3% hydrogen peroxide (H 2 O 2 ), MTAD, SmearClear (SC) and 13.8% chlorine dioxide (ClO 2 ) irrigation solutions against Enterococcus faecalis. Materials and Methods Two hundred eighty single rooted human premolars were randomly grouped into 26 test and 2 control (negative and positive) groups and were incubated for 24 h with E. faecalis , except for the negative control group. The tested solutions were as follow: NaOCl; CHX; ClO 2 ; MTAD; SC; EDTA; H 2 O 2 ; NaOCl + CHX; NaOCl + MTAD; SC + NaOCl; EDTA + NaOCl; H 2 O 2 + NaOCl; ClO 2 + CHX; CHX + MTAD; SC + CHX; EDTA + CHX; CHX + H 2 O 2 ; ClO 2 + MTAD; SC + ClO 2 ; EDTA + ClO 2 ; ClO 2 + H 2 O 2 ; SC+MTAD; EDTA+MTAD; MTAD + H 2 O 2 ; SC + H 2 O 2; and EDTA + H 2 O 2. Optic density values were recorded at 0, 6, 12, 18, 24, 30, 36, 42 and 48 h and bacterial growth curve created for each solution. Results The CHX, MTAD and ClO 2 showed a high potential for the elimination of E. faecalis, both alone and in all combinations. The EDTA, H 2 O 2 , H 2 O 2 + EDTA, H 2 O 2 + NaOCl and SC + NaOCl groups showed less antibacterial activity than the other groups. The SC + CHX group showed the best antibacterial effect against E. faecalis . Conclusion The SC + CHX combination can be recommended as the most effective irrigation regimen against E. faecalis in persistent endodontic infections.