This study compared the push-out bond strength of mineral trioxide aggregate (MTA) and a new endodontic cement (NEC) as root-end filling materials in root-end cavities prepared by ultrasonic technique (US) or Er,Cr:YSGG laser (L). Eighty single-rooted extracted human teeth were endodontically treated, apicectomised and randomly divided into four following groups (n = 20): US/MTA, US/NEC, L/MTA and L/NEC. In US/MTA and US/NEC groups, root-end cavities were prepared with ultrasonic retrotip and filled with MTA and NEC, respectively. In L/MTA and L/NEC groups, root-end cavities were prepared using Er,Cr:YSGG laser and filled with MTA and NEC, respectively. Each root was cut apically to create a 2 mm-thick root slice for measurement of bond strength using a universal testing machine. Then, all slices were examined to determine the mode of bond failure. Data were analysed using two-way anova. Root-end filling materials showed significantly higher bond strength in root-end cavities prepared using ultrasonic technique (US/MTA and US/NEC) (P < 0.001). The bond strengths of MTA and NEC did not differ significantly. The failure modes were mainly adhesive for MTA, but cohesive for NEC. In conclusion, bond strengths of MTA and NEC to root-end cavities were comparable and higher in ultrasonically prepared cavities.

Background and Aim: Compressive strength of acrylic resin base is an effective factor on durability of a prosthesis. The purpose of this in vitro study was to compare the compressive strength of three different types of heat-cure acrylic resins. Materials and Methods: In this in vitro experimental study, 60 acrylic samples were fabricated from Acropars, Acrosun, and Meliodent acrylic resins (n=20 from each). The specimens were placed in a universal testing machine, and force was applied until their fracture. The load at fracture was recorded as the compressive strength. Data were analyzed using one-way ANOVA followed by the Tukey's test. Results: The mean compressive strength was 80.6 ± 6.9, 85.6 ± 6.9, and 71.9 ± 5.3 MPa for Acropars, Acrosun, and Meliodent, respectively. The compressive strength of Acrosun was significantly higher than that of other groups (P=0.047). Conclusion:In general, the results showed that the highest and the lowest compressive strength values were related to Acrosun and Meliodent, respectively. These results indicated the optimal compressive strength of Iranian acrylic resins.

Objectives: The aim of this study was to assess the shear bond strength (SBS) of zirconia ceramic to composite resin with various surface treatments following pressure changes. Materials and Methods: Totally, 135 zirconia blocks were prepared by computer-aided design/computer-aided manufacturing technology. The samples were divided into 9 groups (n=15). Three surface treatments including sandblasting, tribo-chemical preparation, and laser application were used. For each method, 45 samples were considered and tested under different pressure conditions. Z-Prime Plus primer was used for bonding of all samples to composite cylinders. All specimens were stored in water for 24 h, underwent thermocycling, and were then placed in a pressure chamber under normal-, high-, and low-pressure conditions. Then, the SBS test was performed for each sample. Data were analyzed by two-way and one-way ANOVA (α=0.05). Results: The SBS was significantly higher in sandblasting and tribochemical preparation compared with laser irradiation (P<0.05). There was no statistically significant difference in SBS of sandblasting and tribochemical preparation methods (P>0.05). Sandblasting, tribochemical preparation, and laser methods did not show a significant difference in SBS at different pressures (P>0.05). Conclusion: Sandblasting and tribochemical preparation yielded a higher SBS than laser. Different pressures had no effect on SBS, irrespective of surface preparation method.

A BSTRACT Objectives: This study aims to evaluate the accuracy of digital impression making based on trueness and precision measurements of dental implants placed in maxillofacial lesions to produce Maxillofacial prosthesis substructures. Methods: Two intra-oral scanners (Trios 3 and CS 3700) and one Desktop scanner (open technology) were examined in this study. A Model of a patient with a lesion in the ear region was created as a reference. The reference model was scanned by each scanner 10 times. Standard Tessellation Language files were provided from each scanner and were examined in terms of Trueness and Precision aspects. Results: In Distance 1, in the one-way analysis of variance test, there was a significant difference between the three scanners. The Trios group has less deviation than the Open Technology group ( P = 0.015) compared with the CareStream (CS) group that showed more deviation ( P < 0.000). There is a statistically significant difference in distance 2 among scanners. The Trios group showed more deviation as compared with the Open Technology group ( P < 0.000). While this deviation is not statistically significant compared with the CS group ( P = 0.0907). Open Technology Group compared with the CS group also has less deviation in distance 2, which has been statistically significant ( P < 0.000). The preparation of a precise model of maxillofacial lesions is still difficult for some Intraoral scanners. Conclusion: There were significant statistical differences in Trueness and Precision among scanners. Used scanners can be applied as an alternative to conventional impression methods.