Aim:The aim of this study was (i) to evaluate the formation of air bubbles in the apical region of root canal (apical vapor lock) during syringe irrigation, using cone beam computed tomography (CBCT) and (ii) comparative evaluation of the elimination of an established vapor lock by EndoActivator, ultrasonics, and manual dynamic agitation (MDA), using CBCT. Materials and methods:A total of 60 extracted human singlerooted teeth were equally divided into three groups of 20 teeth each. The samples were decoronated 17 mm from the apex, cleaned, and shaped to size F4 Protaper using 3% sodium hypochlorite. Samples were irrigated with 3% sodium hypochlorite + cesium chloride radiopaque dye, and preoperative CBCT images were obtained. After formation of apical vapor lock in the scanned teeth, EndoActivator (group I), passive ultrasonic irrigation (group II), and MDA with K-file (group III) were performed and the teeth were again placed in CBCT scanner and results analyzed using the chi-square test. Results:The apical vapor lock was formed in all the samples. Out of the 20 teeth in each group, the apical vapor lock was eliminated in 18 samples of EndoActivator group (90%), 16 samples of ultrasonic group (80%), while it was eliminated in 10 samples by MDA (50%). Conclusion:It is concluded that (1) apical vapor lock is consistently formed during endodontic irrigation in closed canal systems and (2) sonic activation performs better than the ultrasonics and MDA in eliminating the apical vapor lock, with statistically significant difference between all the three groups (p < 0.05). Clinical significance:The results suggest that the apical vapor lock (dead water zone) is consistently formed during routine

Introduction. This in-vitro study aims to evaluate the effect of acidic environment and intracanal medicament on push out bond strength of Biodentine and Mineral Trioxide Aggregate Plus (MTA Plus) Method. Forty extracted single rooted teeth were sectioned below the cement-enamel junction. The root canals were instrumented using rotary files and then peeso reamer was used to obtain standardized root canal dimension. Specimens were randomly classified into following groups- Group 1: calcium hydroxide in the absence of acidic environment; Group 2: calcium hydroxide in the presence of acidic environment; Group 3: no intracanal medicament in the absence of acidic environment; Group 4: no intracanal medicament in the presence of acidic environment. Specimens were kept for 7 days at room temperature. Thereafter, specimens of each group were transversely sectioned into 1 mm thick slices and divided into 2 sub-groups according to the use of biodentine and MTA Plus. Using Universal Testing Machine, push out bond strength test was carried out and the data were analyzed statistically. Results. There was no statistically significant difference  in the bond strength of biodentine and MTA Plus (P>0.05). For both MTA Plus and biodentine, with or without calcium hydroxide, the push out bond strength was less in acidic environment and this difference was more pronounced without calcium hydroxide. In all the four groups, MTA plus showed comparable bond strength to biodentine. Conclusion. MTA Plus is a viable option for apexification. The push out bond strength of Biodentine and MTA Plus is impaired by acidic environment. Prior application of calcium hydroxide slightly increased the bond strength, though the difference was statistically  insignificant.  

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Objective:To determine the resistance failure value of nonprecious metal-ceramic restorations at the incisal edge with varying thickness under different application of load. Materials and methods:An Ivorian central incisor was prepared to receive metal-ceramic crown, which was further duplicated, invested, casted and 72 metal dies were fabricated in Co-Cr alloy. Metal dies were relieved with die spacer, lubricated and wax patterns were prepared for metal copings, which were further invested and casted and 72 metal copings were fabricated. The ceramic materials were used for the study viz. Vita/VMK, IPSd SIGN, and superporcelain. Ceramic built-up was carried out according to manufacturer instructions. Incisal ceramic built-up was carried out with increasing thickness from 2.00 to 2.5 and 3.00 mm.Results: A total of 72 samples, prepared for the study, were divided into two groups, i.e. group I (36 samples) and group II (36 samples), as per the direction of application of load. The samples were mounted on acrylic block (6 samples/block). A total 12 acrylic blocks were prepared. All the samples were tested using universal testing machine (MTS/USA). The load was applied with crosshead speed of 5 mm/min. Conclusion:Fracture resistance was found to be highest for the 2.00 mm and lowest for 3.00 mm incisal ceramic thickness samples regardless of the ceramic material in both groups. There was a gradual decrease in fracture resistance as the incisal ceramic thickness increased from 2.00 to 3.00 mm in all samples. Fracture resistance was marginally higher for incisal ceramic build-up of 3 mm thickness on group II metal copings than on group I copings. Fracture resistance was highest for IPSd SIGN followed by that of Vita/VMK-95 and superporcelain.Clinical significance: A 3.00 mm incisal ceramic thickness offered greater fracture resistance in comparison to lower values of incisal thickness; IPSd SIGN offered greatest fracture resistance followed by that of Vita/VMK-95 and superporcelain.

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