Deionized water can substitute common bleaching agents for nonvital tooth bleaching when treated with non-thermal atmospheric plasma.

The bleaching efficacy of common bleaching agents and deionized water treated with non-thermal atmospheric pressure plasma in the pulp chamber for nonvital tooth bleaching was evaluated. A total of 120 extracted human maxillary first incisors were stained using human blood. Teeth were randomly divided into eight groups (n = 15). In the first four groups, teeth were bleached using 35% hydrogen peroxide gel, 37% carbamide peroxide gel, 2:1 (w/v) sodium perborate paste, and deionized water for 30 min. In the remaining groups, bleaching agents were treated with non-thermal atmospheric plasma for 5 min inside the pulp chamber. Overall color changes (∆E) were determined using Commission Internationale de L'Eclairage Lab Colour System. The plasma-assisted tooth bleaching has not increased tooth temperature beyond 37°C. Bleaching efficacies of bleaching agents were significantly improved when treated with non-thermal atmospheric plasma compared to their application (P < 0.05). A remarkable bleaching effect was obtained when bleaching agents were substituted with water and when treated with non-thermal atmospheric plasma. Non-thermal atmospheric plasma treatment could be a novel tool for activation of bleaching agents in the pulp chamber for nonvital tooth bleaching procedure. Moreover, water could be used as a novel bleaching agent when treated with the non-thermal atmospheric plasma to eliminate possible risks which might arise from peroxide-containing agents.

The effect of ultrasonically activated irrigation and laser based root canal irrigation methods on debris removal.

PURPOSE: To test the efficacy of debris removal of 5 in vitro irrigation protocols: conventional irrigation, irrigation activated by ultrasound, Er:YAG laser with photon-induced photoacoustic streaming (PIPS) tip, and 2 diode laser techniques. METHODS: The root canals of 75 extracted human canine teeth were enlarged and bisected longitudinally. Standardized grooves were prepared 2-6 mm from the root apex and filled with 0.5 mm of dentine debris. The teeth were reassembled and irrigated using 1 of the following techniques (n = 15/technique): (1) conventional irrigation, (2) diode laser irrigation - tip placed 2 mm from working length, (3) diode laser irrigation - tip placed at root canal orifice, (4) Er:YAG laser - PIPS, and (5) ultrasonically activated irrigation. The root segments were disassembled, and the amount of remaining debris was evaluated by 3 examiners under a stereomicroscope at ×20 magnification using a 4-grade scoring system. The data were statistically analyzed using Kruskal-Wallis and Dunn's multiple comparison tests, with a 95% confidence level (p = 0.05). Cohen's kappa test was used to evaluate inter-observer and intra-observer agreement. RESULTS: Ultrasonically activated irrigation removed significantly more dentinal debris than conventional irrigation (p = 0.016), but there were no significant differences between the other groups. CONCLUSIONS: Ultrasonically activated irrigation was more effective than conventional irrigation in the removal of apically placed dentine debris.

Microleakage of 4 post-luting cements evaluated by the computerized fluid filtration method.

PURPOSE: The aim of this study was to evaluate the microleakage of 4 fiber post-luting systems using the computerized fluid filtration method. METHODS: 60 extracted human mandibular permanent premolar teeth were used for the study. The teeth were instrumented with Hedstroem files up to size 60, post spaces were prepared and then Unicore fiber posts were cemented using 4 luting systems. Group1: Duolink, Group 2: Resinomer, Group 3: Fuji Plus, Group 4: Multilink Sprint, Group 5: Positive Control, and Group 6: Negative Control. The samples were stored in distilled water for 2 weeks and then microleakage was evaluated. Data were analyzed with 1 way-ANOVA and Dunett T3 tests (P<.05). Groups 2 and 3 significantly exhibited higher microleakage values than groups 1 and 4 (P<.05). RESULTS: Resin cements used with total etch-bonding systems demonstrated lower microleakage values than the other cements. CONCLUSIONS: Reduction of steps in dentin conditioning of resin luting cements may have a promoting effect on microleakage.

Comparative micro-computed tomography evaluation of apical root canal transportation with the use of ProTaper, RaCe and Safesider systems in human teeth.

The aim of this study was to compare apical centring ability of nickel titanium (NiTi) ProTaper, RaCe and mainly stainless steel Safesider systems using micro-computed tomography. Thirty freshly extracted mandibular molars with two separate mesial canals and separate foramina were used for the study. Mesial roots were embedded in acrylic resin and instrumented with the ProTaper, RaCe or Safesider systems. Root canal transportation and centring ability of the instruments were evaluated using superimposed micro-computed tomography images of the apical 4 mm of the roots taken at 1 mm intervals. One-way analysis of variance and post hoc Tukey's tests were performed to compare apical transportations. Significant differences were observed between groups at the apical 1, 2 and 3 mm levels (P < 0.05). The reciprocating Safesider system transported root canals significantly more than the other two NiTi systems in the apical 1 mm level (P = 0.001) and more than RaCe system in the apical 2 mm level (P = 0.003). The ProTaper instruments caused more apical root canal transportation than did RaCe instruments at apical 3 mm (P = 0.045). NiTi instrumentation systems showed better centring ability than the mainly stainless steel Safesider system because of the flexible structure of the NiTi alloy.

Evaluation of the apical adaptation performance of various root canal instruments.

OBJECTIVE: The aim of this study was to evaluate the apical root canal adaptation performance of various root canal instruments. MATERIALS AND METHODS: A total of 40 freshly extracted single-rooted mandibular incisors were used in this study. Coroner parts of all teeth were removed from cemento-enamel junction and root canal of each tooth was explored with a size 8 K-file until the tip of the file was just visible at the apex. Working lengths (WLs) were determined as 1 mm short of these measurements. ProTaper, K-file, profile and hedstroem files were inserted into the root canals of 10 teeth to the WL following the flaring of the coronal and middle thirds. Instruments were fixed in the root canals with acrylic resin. The apical 1 mm of each root tip was ground on wet sandpaper to expose the canal and the instrument at the WL and the apical region of each tooth was examined under stereomicroscope. The stereoscopic images of the teeth were digitized and analyzed with software in order to determine the differences between the areas of root canals and file tips. Result data were analyzed using the one-way analysis of variance test (P = 0.05). RESULTS: There were no significant differences between apical file/root canal areas of the evaluated instruments (P > 0.05). CONCLUSIONS: None of the evaluated instruments performed a perfect adaptation with the apical root canal surface at the WL in mandibular incisors. Therefore, total removal of the debris from the apical canal surface may not be achieved when these filing instruments are used.

The efficacy of an experimental single solution versus alternate use of multiple irrigants on root dentin microhardness.

OBJECTIVES: This study was carried-out to evaluate and compare the efficacy of various irrigants when used singly or in combination on the microhardness of root canal dentin. STUDY DESIGN: A total of 50 root-halves were randomly divided into 5 groups immediately after the initial baseline microhardness measurements and treated with: Group-1; 7.5%Ethylenediaminetetraaceticacid (EDTA) + 2.5%sodium hypochlorite (NaOCl), Group-2; 7.5%ethyleneglycol-bis[b-aminoethylether]-N,N,N0,N0-tetraaceticacid (EGTA) + 2.5%NaOCl, Group-3; 7.5%trans1,2diaminocyclohexane NNN',N'tetraaceticacid (CDTA) + 2.5% NaOCl, Group-4; 7.5%EDTA + 2.5% Ethylenediamine (EDA), and Group-5; 1/1 (v/v) EDTA-EDA mixture + 1/1 (v/v) EDTA-EDA mixture. Fifty mL of each solution was used for 1 minute. The reference and post-treatment microhardness values were measured with a Vickers indenter under 80-gram load, 15-second dwell time. Data were analyzed by two-way ANOVA and Bonferroni tests (p=0.05). RESULTS: All solutions decreased microhardness of dentin (p< 0.05). There was statistically significant difference between each group, except Group-1 and 4, after 1st solution application. While Group-2 resulted in a greater reduction of dentin hardness, Group-5 caused the least change in microhardness values, after 1st solution application (p< 0.05). No statistical difference was observed between Groups 1-4, after 2nd solution application. However, Group-5 showed a significant difference compared with all other groups, after 2nd solution application (p< 0.05). CONCLUSIONS: Under the experimental conditions, all tested solutions reduced the microhardness of the root canal dentin. EGTA was the most efficient chelating agent. EDTA-EDA single mixture has led to least change on the microhardness of root dentin. Key words:Microhardness, CDTA, EDTA, EGTA, Ethylenediamine.

The effect of three different sealers on the radiopacity of root fillings in simulated canals.

OBJECTIVE: The aim of this study was to investigate the effect of 3 root canal sealers on radiopacity of root fillings in simulated canals by means of direct digital radiography. STUDY DESIGN: Thirty simulated root canals in transparent acrylic blocks were prepared with a 4% tapered, size 25 instrument. A single 4% tapered, size 25 gutta-percha cone was inserted into each canal. Standardized images of the blocks with an aluminum step-wedge were obtained by using Digora storage phosphor plates. Then, 3 root canal sealers (Roeko, Diaket, Pulpdent) were mixed according to the manufacturers' instructions. The gutta-percha cones were completely coated with one of the sealers and placed in the identical canal to the full working length. The images of the blocks were reobtained after sealer application. The mean gray values (MGVs) of root fillings were measured with or without the sealer at 3 different levels (1 mm, 6 mm, and 11 mm from apex) by using the Image Tool program. Each MGV measurement was then converted to its aluminum equivalent by means of the step-wedge values. A paired t test was used for statistical analysis. RESULTS: RoekoSeal caused a significant decrease in the radiopacity of the root fillings at the 1-mm level (P < 0.01). Diaket and Pulp Canal Sealer (PCS) increased the radiopacity of the fillings at all levels significantly (P < 0.01) except 6- and 11-mm levels of the Diaket specimens (P > 0.05). CONCLUSION: The type and the thickness of root canal sealers can influence the radiopacity of the root fillings.