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    Effects of different cusp coverage restorations on the fracture resistance of endodontically treated maxillary premolars
    (MOSBY-ELSEVIER, 2016) Kalay, Tugba Serin; Yildirim, Tahsin; Ulker, Mustafa
    Statement of problem. Cusp coverage restorations for the restoration of endodontically treated teeth represent a conservative approach in terms of function and esthetics. However, limited scientific data are available regarding the optimum reduction design and thicknesses. Purpose. The purpose of this in vitro study was to evaluate the fracture resistance and fracture patterns of cusp coverage restorations with different cusp reduction designs and reduction thicknesses on endodontically treated maxillary premolars (ETMPs) with mesio-occluso-distal (MOD) cavities. Material and methods. One hundred sixty-five extracted intact human maxillary premolars were divided into 11 groups: G1-10 (test groups) and G11 (intact group). In the test groups, all of the teeth were restored with composite resin after canal treatments with MOD cavities. However, the cusps of the G1-9 teeth were reduced with combinations of different thicknesses (1.5, 2.5, and 3.5 mm) and designs (beveled, horizontal, and anatomic). The specimens were subjected to 105 cycles of 50 N mechanical loading. Next, the specimens were subjected to a compressive load at a crosshead speed of 0.5 mm/min until fracture. The fractured specimens were analyzed to determine the fracture pattern. Two-way ANOVA followed by the Fisher least significant difference (LSD) test was used to analyze the interaction between groups. Results. The fracture resistance values increased with increases in the cusp reductions. The fracture resistance values of the G6 (2.5 mm, anatomic) and G9 (3.5 mm, anatomic) groups were significantly greater than that of the MOD group. However, the G6, G8 (3.5 mm, horizontal), and G9 groups were comparable with G11. The highest restorable fracture rates were observed in G6 and G9 Conclusions. Cusp reduction design and thickness influenced the fracture resistance and fracture patterns of cusp coverage restorations of ETMPs with MOD cavities. The teeth restored with anatomic cusp reduction designs with reduction thicknesses of at least 2.5 mm exhibited greater fracture resistance and more frequent restorable fractures.
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    The evaluation of the influence of using MTA in teeth with post indication on the apical sealing ability
    (MOSBY-ELSEVIER, 2009) Yildirim, Tahsin; Tasdemir, Tamer; Orucoglu, Hasan
    Objectives. The aim of this study was to evaluate the influence of using MTA in teeth with post-core indication and to compare it with the immediate or delayed post space preparation on the integrity of apical seal in teeth filled with gutta-percha and sealer. Study design. Fifty-one single-rooted freshly extracted human maxillary incisor teeth were selected. The crowns of the teeth were removed to a length of 14 mm and canals were prepared by using K-files with the step-back technique. The teeth were randomly divided into 3 groups of 15 specimens each. Group A was filled with gutta-percha and sealer using lateral compaction, and post space was prepared immediately using a heated instrument. Specimens in Group B were filled with the same materials as Group A and post space was prepared after 1 week with Gates-Glidden drills. Group C was filled with MTA as an apical 5-mm filling. In all groups, materials were left in the root canals at the apical 5-mm level. The remaining 6 teeth were used as controls. The microleakage values of each group were measured after 1 month, using a computerized fluid filtration method. Results. The MTA (Group C) showed less microleakage than immediate and delayed post space preparation methods (Group A, B) in 1 month, and this difference was found to be statistically significant (P < .005). Additionally, no statistically significant difference was determined between Group A and Group B (P < .05). Conclusion. These results suggest that MTA can be used in the root canals as apical filling material in teeth with post-core indication. (Oral Surg Oral Med Oral Pathol Oral Radiol Endod 2009; 108: 471-474)
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    Long-term Evaluation of the Influence of Smear Layer on the Apical Sealing Ability of MTA
    (ELSEVIER SCIENCE INC, 2008) Yildirim, Tahsin; Orucoglu, Hasan; Cobankara, Funda Kont
    The aim of this in vitro study was to investigate the effect of the smear layer on apical microleakage in teeth obturated with mineral trioxide aggregate (MTA). Fifty single-rooted central maxillary teeth were used in this study. All teeth were instrumented to size 60 by using the step-back technique, The selected teeth were randomly divided into 2 groups (n = 20). In the first group (smear [+]), the teeth were irrigated with only NaOCl (5.25%). In the second group (smear [-]), the teeth were irrigated with ethylenediaminetetraacetic acid (EDTA) (17%) and NaOCl (5.25%) to remove the smear layer. The teeth were then filled with MTA. The computerized fluid filtration method was used for evaluation of apical microleakage. The quantitative apical leakage of each tooth was measured after 2, 30, and 180 days. Statistical analysis was done with the Mann-Whitney U and Wilcoxon signed ranks tests. At the end of this study there was no difference in 2 days between the groups, but removal of the smear layer caused significantly more apical microleakage than when the smear layer was left intact for 30 and 180 days (P < .005). Within the constraints of this study it can be concluded that the apical microleakage of MTA is less when the smear layer is present than when it is absent. (J Endod 2008;34:1537-1540)