PURPOSEVeneering porcelain might be delaminated from underlying zirconia-based ceramics. The aim of this study was the evaluation of the effect of different surface treatments and type of zirconia (white or colored) on shear bond strength (SBS) of zirconia core and its veneering porcelain.MATERIALS AND METHODSEighty zirconia disks (40 white and 40 colored; 10 mm in diameter and 4 mm thick) were treated with three different mechanical surface conditioning methods (Sandblasting with 110 µm Al2O3 particle, grinding, sandblasting and liner application). One group had received no treatment. These disks were veneered with 3 mm thick and 5 mm diameter Cercon Ceram Kiss porcelain and SBS test was conducted (cross-head speed = 1 mm/min). Two and one way ANOVA, Tukey's HSD Past hoc, and T-test were selected to analyzed the data (α=0.05).RESULTSIn this study, the factor of different types of zirconia ceramics (P=.462) had no significant effect on SBS, but the factors of different surface modification techniques (P=.005) and interaction effect (P=.018) had a significant effect on SBS. Within colored zirconia group, there were no significant differences in mean SBS among the four surface treatment subgroups (P=0.183). Within white zirconia group, "Ground group" exhibited a significantly lower SBS value than "as milled" or control (P=0.001) and liner (P=.05) groups.CONCLUSIONType of zirconia did not have any effect on bond strength between zirconia core and veneer ceramic. Surface treatment had different effects on the SBS of the different zirconia types and grinding dramatically decreased the SBS of white zirconia-porcelain.

With the caution of small sample size, the results of this study provide evidence that use of BO can improve food avoidance and physical disability aspects of patient satisfaction with complete dentures.

PURPOSEPost surface conditioning is necessary to expose the glass fibers to enable bonding between fiber post and resin cement. The purpose of the present study was to evaluate the effect of different surface conditioning on tensile bond strength (TBS) of a glass fiber reinforced post to resin cement.MATERIALS AND METHODSIn this in vitro study, 40 extracted single canal central incisors were endodontically treated and post spaces were prepared. The teeth were divided into four groups according to the methods of post surface treatment (n=10): 1) Silanization after etching with 20% H2O2, 2) Silanization after airborne-particle abrasion, 3) Silanization, and 4) No conditioning (Control). Adhesive resin cement (Panavia F 2.0) was used for cementation of the fiber posts to the root canal dentin. Three slices of 3 mm thick were obtained from each root. A universal testing machine was used with a cross-head speed of 1 mm/minute for performing the push-out tests. Two-way ANOVA and Tukey post hoc tests were used for analyzing data (α=0.05).RESULTSIt is revealed that different surface treatments and root dentin regions had significant effects on TBS, but the interaction between surface treatments and root canal regions had no significant effect on TBS. There was significant difference among H2O2 + Silane Group and other three groups.CONCLUSIONThere were significant differences among the mean TBS values of different surface treatments. Application of hydrogen peroxide before silanization increased the bond strength between resin cements and fiber posts. The mean TBS mean values was significantly greater in the coronal region of root canal than the middle and apical thirds.

Objective:The aim of this study was to investigate the influence of implant crown splinting and the use of angulated abutment on stress distribution in implant body and surrounding bone by three-dimensional finite element analysis.Materials and Methods:For this study, three models with two implants at the site of mandibular right second premolar and first molar were designed (1): Both implants, parallel to adjacent teeth, with straight abutments (2): Anterior implant with 15 mesial angulations and posterior implant were placed parallel to adjacent tooth, (3): Both implants with 15 mesial angulations and parallel to each other with 15° angulated abutments. Restorations were modeled in two shapes (splinted and nonsplinted). Loading in tripod manner as each point 50 N and totally 300 N was applied. Stress distribution in relation to splinting or nonsplinting restorations and angulations was done with ABAQUS6.13.Results:Splinting the restorations in all situations, led to lower stresses in all implant bodies, cortical bone and spongy bone except for the spongy bone around angulated first molar. Angulated implant in nonsplinted restoration cause lower stresses in implant body and bone but in splinted models more stresses were seen in implant body in comparison with straight abutment (model 2). Stresses in nonsplinted and splinted restorations in cortical bone of angulated molar region were more than what was observed in straight molar implant (model 3).Conclusion:Implant restorations splinting lead to a better distribution of stresses in implant bodies and bone in comparison with nonsplinted restorations, especially when the load is applied off center to implant body. Angulations of implant can reduce stresses when the application of the load is in the same direction as the implant angulation.

No abstract

The most frequent occlusal configuration was the "+4" form; thus, there is a high evolutionary trend in Iranian mandibular second molars.

PURPOSEDebonding of a composite resin core of the fiber post often occurs at the interface between these two materials. The aim of this study was to evaluate the effects of different surface treatment methods on bond strength between fiber posts and composite core.MATERIALS AND METHODSSixty-four fiber posts were picked in two groups (Hetco and Exacto). Each group was further divided into four subgroups using different surface treatments: 1) silanization; 2) sandblasting; 3) Treatment with 24% H2O2, and 4) no treatment (control group). A cylindrical plexiglass matrix was placed around the post and filled with the core resin composite. Specimens were stored in 5000 thermal cycles between 5℃ and 55℃. Tensile bond strength (TBS) test and evaluation using stereomicroscope were performed on the specimen and the data were analyzed using two-way ANOVA, Post Hoc Scheffe tests and Fisher's Exact Test (α=.05).RESULTSThere was a significant difference between the effect of different surface treatments on TBS (P<.001) but different brands of post (P=.743) and interaction between the brand of post and surface treatment (P=.922) had no significant effect on TBS. Both silanization and sandblasting improved the bonding strength of fiber posts to composite resin core, but there were not any significant differences between these groups and control group.CONCLUSIONThere was not any significant difference between two brands of fiber posts that had been used in this study. Although silanization and sandblasting can improve the TBS, there was not any significant differences between surface treatments used.

Aim: Remnants of provisional cement on the internal surface of cast restorations can have an adverse effect on the performance of the definitive luting agent. The purpose of this study was to evaluate the effect of eugenolcontaining temporary cement removal by an ultrasonic or an organic solvent on the retentive strength of metallic rings cemented to amalgam cores using zinc phosphate cement. Methods and Materials:A total of 36 cylindrical amalgam cores measuring 5.9×6 mm were made by condensing amalgam in brass molds for use in this in vitro study. Thirty-six cylindrical spaces measuring 6×6 o mm were machined in the center of cast rods of Rexillium III alloy to create simulated retainers. The amalgam cores were divided into two groups and provisionally cemented in these cylindrical spaces (retainers) using zinc oxide-eugenol cement. After separation of the cores from the retainers, one group was cleaned with an ultrasonic cleaning device with water and the other group was cleaned with Solitine organic solvent. All specimens were then cemented with zinc phosphate cement and the samples were stored at 100% humidity in a 37°C water bath after which they were tested with a DARTEK testing machine at a 0.02 cm/minute cross head speed. The data were analyzed using the Independent t-test. Results:The statistical analysis revealed a significant difference between the two groups (p<0.0005) with the ultrasonic group having significantly higher separation forces than the Solitine group. Ramin Mosharraf, DDS, MS; Bahram Soleimani, PhD;Mehdi Sanaee-Nasab, DDS Abstract © Seer Publishing Conclusion: Specimens treated with the ultrasonic cleaner showed a higher mean separation force (282.2 MPa) than the solvent group (439.5 MPa).Clinical Significance: Despite the convenience of using an organic solvent for cleaning the internal surface of cast restorations, the ultrasonic cleaning method is more effective for removing zinc-oxide temporary cement.