Introduction The aim of this study was to evaluate the effects of bleaching gel using 35% hydrogen peroxide (HP), associated with red carmine pigment (RC), in the 3:1 or 1:1 ratio, on fracture resistance and dentin microhardness of endodontically treated teeth. Materials and methods A total of 40 lower incisors were endodontically treated and divided into four groups (n = 10), according to the bleaching protocol: G1 (HP3), 35% HP + RC (3:1); G2 (HP1), 35% HP + RC (1:1); G3 (positive), 38% HP; and G4 (negative), unbleached. Four dental bleaching sessions were performed. The dental crowns were restored after the last session and submitted to the fracture resistance test. Totally, 60 specimens from the endodontically treated lower incisor crowns were prepared to evaluate the effects on dentin microhardness. The analysis was measured (in Knoop) prior to and after the last dental bleaching session using similar bleaching protocols. Results G2 presented the lowest fracture resistance (p < 0.05). The other groups were similar to each other (p > 0.05). No difference was observed in the reduction of dentin microhardness among the groups (p > 0.05). Conclusion A 1:1 ratio (bleaching gel:pigment) caused a significant fracture resistance reduction in relation to the other protocols. No effect on the dentin microhardness reduction was observed. Clinical significance The pigment addition to the bleaching agent accelerates the bleaching chemical reaction. However, no studies have evaluated the ideal proportion to optimize tooth bleaching. How to cite this article Galloza MOG, Jordão-Basso KCF, Bandeca MC, Costa SO, Borges AH, Tonetto MR, Tirintan FC, Keine KC, Kuga MC. Effects of the Ratio between Pigment and Bleaching Gel on the Fracture Resistance and Dentin Microhardness of endodontically treated Teeth. J Contemp Dent Pract 2017;18(11):1051-1055.
This study verified of remaining filling materials in flattened/oval-shaped root canals after use of several endodontic retreatment protocols. Material and methods: Seventy human mandibular incisors were selected. Sixty specimens received crown-apex preparation performed by ProTaper Next® system andwere filled with hybrid Tagger technique with gutta-percha and AH Plus®. Ten specimens were left unprepared (Control Group). The specimens were randomly distributed in six groups, according the different retreatment protocols: G1 – Clearsonic® + ProTaper Universal Retreatment® + Reciproc®; G2 – Reciproc®; G3 – Clearsonic® + ProTaper Universal Retreatment®; G4 – Clearsonic® + Reciproc®; G5 – Oscillatory EndoEze® + Manual files; G6 – ProTaper Universal Retreatment®. Presence of root canal filling material residual were evaluated using Scanning Electron Microscopy. The relative differences of remaining filling materials between the groups and root thirds were determined by Kolmogorov-Smirnov and Levene tests followed by Tukey post hoc test. The level of significance was set at α = 5%. Results: Regarding the presence residual, G1 (Clearsonic® + ProTaper Universal Retreatment® + Reciproc®), G2 (Reciproc®), G3(Clearsonic® + ProTaper Universal Retreatment®) and G6 (ProTaper Universal Retreatment®) protocols presented a lower amount (p<0.05). The highest values (p<0.05) of remaining filling materials were presented in the G5 (Oscillatory EndoEze® + Manual files) protocol. Intermediate values (p<0.05) were presented by G4 (Clearsonic® + Reciproc®) protocol. Conclusion: The endodontic retreatment protocols no showed effectiveness for complete removal of remaining sealing material from flattened/oval-shaped root canals.
Chemical and mechanical root canal preparation plays an essential role in reducing microbial burden. However, microorganisms present in areas not mechanically reachable by endodontic instruments. As an alternative to fix this problem, the laser can be applied.
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