ABSTRACT
Objective: Considering the use of triple antibiotic paste [TAP] for root canal treatment of open apex teeth, this study aimed to assess the effect of TAP and calcium hydroxide [CH] on bond strength of composite to dentin
Methods: This in-vitro study was conducted on 32 extracted human premolar teeth. After disinfection with 2% thymol solution, the enamel on the buccal surface of specimens was removed to expose a smooth dentin surface parallel to the long axis of the teeth with approximately 19mm2 surface areas. Specimens were divided into three groups of 11, 10 and 11 specimens. In group one, TAP, in group two CH and in group three, saline solution were applied to dentin surfaces for 14 days. After removal of medicaments, composite cylinders were bonded to the dentin surfaces using a bonding agent. Shear bond strength was measured in an Instron machine at a crosshead speed of 1mm/min. Data were analyzed using one-way ANOVA
Results: The highest mean bond strength belonged to the control group [14.4760 MPa] and the lowest belonged to the TAP group [11.5808 MPa]. The mean bond strength in CH group was less than that of the control and higher than that of the TAP group [11.7834 MPa]. However, the difference among the three groups was not statistically significant [p=0.327]
Conclusion: Use of medicaments such as CH and TAP has no effect on bond strength of composite to dentin
ABSTRACT
The aim of this in vitro study was to compare the effect of hand and rotary instruments on fracture strength of tooth roots. Thirty two teeth were randomly divided into two experimental groups of 15 each and one negative control group with two samples. In group 1, step-back technique with conventional stainless steel K-files was used, and in group 2, instrumentation was performed using rotary Ni-Ti Hero642. Samples in control group did not receive cleaning or shaping after access cavity preparation. After obturating each canal, tip of the spreader was locked within canal. The required force for root fracture was measured using Instron testing machine. Recorded data was statistically analyzed using t-test. The mean and standard deviation force required for vertical root fracture were 50.33 +/- 19.1 and 63.1 +/- 25.46 N for hand and rotary groups respectively. However, no significant difference was found between experimental groups. The results indicate that the manual technique did not lower fracture strength of obturated roots in comparison with the rotary preparation technique
ABSTRACT
Shear bond strength is one of the most important mechanical characteristics involved in clinical durability of tooth-colored restorations, which is directly related to polymerization shrinkage. This study evaluated the efficacy of two light-curing units [LED2 and QTH] and two types of dentin bonding agents [Excite and Clearfil SE bond] on composite resin shear bond strength to dentin. Forty caries-free sound human premolars were randomly divided into 4 groups of 10 after being disinfected with sodium hypochlorite. The occlusal surface of dentin in each specimen was exposed and flattened by a fissure bur; composite resin was bonded with Excite or Clearfil SE bonding agents and polymerized with QTH or LED2. Shear bond strength values of the specimens were tested in a Dartec universal testing machine. Data were analyzed by one-way ANOVA, two-way ANOVA and Dunkan test [? = 0.05]. Maximum shear bond strength values were recorded in composite restorations bonded with Clearfil SE bonding agent and polymerized by LED2; minimum values were recorded in composites restorations bonded with Excite and polymerized by QTH. Statistical analysis showed statistically significant differences between the experimental groups [p value = 0.03]. Under the limitations of this study, it can be concluded that two curing systems of LED2 and QTH are equally effective on shear bond strength of different bonding agents, whereas Clearfil SE bonding agent produces higher shear bond strength than Excite total-etch regardless of the type of light-curing unit