This study aimed to compare the effects of different irrigants on root dentine microhardness, erosion and smear layer removal. A total of 72 root dentine slices were divided into six groups, according to the final irrigants used: Group 1: 17% ethylenediamine tetra-acetic acid (EDTA) + 2.5% NaOCl, Group 2: 7% maleic acid (MA) + 2.5% sodium hypochloride (NaOCl), Group 3: 1.3% NaOCl + mixture of tetracycline, acid and detergent (MTAD), Group 4: Smear Clear + 2.5% NaOCl, Group 5: 5% NaOCl, Group 6: saline. Vickers microhardness values were measured before and after treatment. In total, 42 root-halves were prepared for scanning electron microscope to evaluate the amount of smear and erosion in the coronal, middle and apical thirds. Data were analysed using two-way anova, Duncan and two-proportion z-tests. Maleic acid showed the greatest reduction in dentine microhardness (P < 0.05), followed by EDTA and MTAD. EDTA, maleic acid, MTAD and Smear Clear removed smear layer efficiently in the coronal and middle thirds of root canal. However, in the apical region, maleic acid showed more efficient removal of the smear layer than the other irrigants (P < 0.05).

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This study aimed to evaluate Root ZX accuracy with different NaOCl concentrations and to observe effects of the alginate model when NaOCl was used in the canal during electronic measurements. Fifty extracted single-rooted, single-canal human teeth were used in five experimental groups. NaOCl concentrations of 5.25%, 2.65%, 1.00%, and 0.50%, respectively, were injected into the root canals of teeth in four groups and distilled water in control group 5. After measuring root lengths with Root ZX, the files were locked in place. There were no statistically significant differences among all the groups (p > 0.95) when evaluating the distance of the file tips and apical constriction or for the distance from file tip to apical foramen. Root ZX could be used in root canal length measurements with various NaOCl concentrations. Designation of apical constriction needs more care. The alginate model could be used for in vitro electronic measurements with various NaOCl concentrations.

The aim of this study was to evaluate the effect of different post-space treatments on the push-out bond strength and failure modes of glass fibre posts. Forty mandibular premolar roots were cut and endodontically treated. Post spaces were prepared and roots were divided into four groups. In group 1 distilled water irrigation (control), in group 2 2.25% NaOCl irrigation, in group 3 2.25% NaOCl + 17% EDTA irrigation were done and in group 4 diode laser was applied to the prepared post spaces. Scanning electron microscope (SEM) analysis was made for each group. Fibre posts were then luted with resin cement. Each root was prepared for push-out test. Data were statistically analysed with anova (P = 0.05). After push-out test, the failure modes were observed but not statistically analysed. There were statistically significant differences between Group 3 and Group 2 in both regions (P < 0.05), also in the middle region of Group 4 and Group 2 (P < 0.05). Cervical root segments showed higher bond strengths than middle ones in all groups (P < 0.05). The highest bond strength values were obtained from NaOCl/EDTA and the lowest bond strength values were obtained from NaOCl for both regions.

The aim of the study was to compare the fracture resistance of maxillary premolars with one remaining cavity wall restored using different post systems. Forty-eight maxillary premolars were endodontically treated and randomly assigned to four groups for postcore restoration. The first three test groups were restored with polyethylene woven fiber posts, custom-made glass fiber-reinforced composite posts, and titanium posts respectively. In the control Group 4, standardized cavities (3.5×1.5 mm) were prepared in the palatal canal entrance and filled with a resin composite. All the specimens were then restored with a resin composite crown seated on the post. Load was applied with a stainless steel ball (1 mm/min), and the failure modes of all specimens were evaluated. There were no significant differences in fracture resistance and failure mode among the different restorative materials (p>0.05). Within the limitations of this in vitro study, it was concluded that the presence and type of post did not influence the fracture load and failure mode of maxillary premolar teeth with one remaining cavity wall.

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The objective of the study was to observe the morphological changes on root canal dentin after Er:YAG laser and Nd:YAG laser treatment. Twenty-one teeth biomechanically prepared were divided into three groups with seven teeth of each. Group A was unlased as a control. In group B, Er:YAG laser and in group C, Nd:YAG laser was applied to the root canal dentin. The roots were split longitudinally and examined using a scanning electron microscopy for the evaluation of debris, smear layer, and recrystallization. There was no statistically significant difference between the groups. This study indicates that laser beam is not effective in removing debris and smear layer.

Kıvanç BH, Alaç am T, Ulusoy Ö _ IA, Genç Ö , Gö rgü l G. Aim To compare the fracture resistance of thin-walled roots after restoration with different types of post systems.Methodology One hundred and sixty-five decoronated maxillary central incisors were root filled and randomly assigned to three groups with respect to the remaining dentine thickness of root (1.0 mm, 1.5 mm, 2.0 mm). Each group was randomly divided into five equal subgroups. The subgroups were restored with one of the following post systems: polyethylene woven fibre (R), composite resin cured by light-transmitting post + glass fibre post (L), electrical glass fibre post (E), composite corono-radicular restoration (C) and cast metal post (M). Standard cores were constructed using composite resin in the first four groups. The samples were subjected to a gradually increasing force (1 mm min). The force required to fracture was recorded. The data was analysed with anova and Tukey test (P = 0.05). Results The cast metal post group had the highest fracture strength (P < 0.001). There was no significant difference in fracture resistance between the other four groups. Fracture resistance was affected largely by the remaining dentine thickness in fibre post groups; however, the difference was not significant. On the contrary in the cast metal post group load failure was inversely influenced by axio-proximal dimension of dentine walls. Conclusion The cast post group had a higher fracture strength than resin groups. The force required to fracture the roots was similar for all fibre post systems and for all dentine thicknesses.