Evaluation of torsional strength and torque presentation of coated rectangular stainless steel archwires, an in vitro study.

OBJECTIVES: An in vitro experimental study was performed to evaluate the torsional strength and torque released by esthetic coated archwires. MATERIALS AND METHODS: A total of 52 coated (study group) and 52 stainless steel (control group) rectangular archwires from two manufacturers (brand I: Gestenco International AB, Gothenburg, Sweden and brand II: Ortho Technology, Lutz, FL, USA) in two sizes (0.019â€¯× 0.025 and 0.017â€¯× 0.0250-inch) were evaluated. The straight parts on both ends of each preformed archwire were cut in 30 mm segments. A specially designed experimental device was attached to the universal testing machine (Model Z020, Zwick Roell, Ulm, Germany) to measure torsional strength and to calculate the clinically significant torque interval. The groups were compared based on their brand, presence of coating and size using three-way analysis of variance (ANOVA) test at a significance level of 5%. RESULTS: The results revealed that coating of the wires of brand 1 resulted in a significant reduction of torsional strength in both wire sizes (P-value = 0.0001). For the wires of brand 2, coating of the 0.017â€¯× 0.025-in wire resulted in a significant reduction in torsional strength. However, for the 0.019â€¯× 0.025 in wire size, the presence of coating significantly increased the torsional strength (P-value = 0.0001). Coating did not affect the measured clinical torque interval of the analyzed wires when a torque between 5 and 20 Nmm was applied (P-value = 0.062). CONCLUSIONS: Mechanical behavior of coated archwires depends mainly on the thickness of their inner core alloy. Reduction in the diameter of the inner alloy resulted in reduced torsional strength. Despite lower mean torsional strength, in the settings of this study, coated and conventional wires demonstrated comparable torque angles if loaded in the typical range of activation.

Comparison of the Bony Changes of TMJ in Patients With and Without TMD Complaints Using CBCT.

STATEMENT OF THE PROBLEM: Temporomandibular joint disorders (TMD) may show a poor correlation between their clinical findings and radiological characteristics. PURPOSE: The aim of this study was to assess the osseous alterations of temporomandibular joint (TMJ) in symptomatic and asymptomatic subjects by employing cone beam computed tomography (CBCT) images. MATERIALS AND METHOD: In this study, CBCT images of 120 temporomandibular joints in 30 patients with TMJ disorder and 30 age- and sex-matched individuals without TMJ complaints were evaluated. Osteoarticular derangements of the joint were assessed by two experienced examiners. Data was statistically analyzed with SPSS software using chi-square test (p <0.05). RESULTS: Out of 120 CBCT images (60 in each group), at least one osseous change was observed in 90% and 86.7% joints in symptomatic and asymptomatic subjects, respectively. There were no significant differences between symptomatic and asymptomatic subjects regarding frequency of osteoarticular changes including flattening (73.3% vs. 75%), irregularity (36.7% vs. 48.3%), sclerosis (20% vs. 8.3%), cyst (3.3% vs. 3.3%), erosion (13.3% vs. 21.7%), hypoplasia (3.3% vs. 5%), ankylosis (1.7% vs. Zero), osteophyte (43.3% vs. 40%), decrease joint space (3.3% vs. 3.3%), and increase joint space (5% vs. 5%). (p> 0.05). CONCLUSION: By employing CBCT as a modern diagnostic imaging tool, findings of this study revealed that the frequency of various temporomandibular joint alterations on CBCT images is comparable in patients with and without TMD complaints, suggesting that some people with TMJ structural damage may not display clinical manifestations. Moreover, CBCT imaging might not be necessary for TMD patients and more attention should be given to clinical examination.

Effect of Finishing Time on Microleakage at the Composite-Repair Interface.

BACKGROUND: Repair is a conservative treatment of defective composite restoration. Sealing the repair interface is a critical factor to achieve successful repaired restorations. OBJECTIVE: The aim of this study was to evaluatethe effect of three finishing times on the microleakage at the composite-repair interface. METHOD: Eighty composite specimens (Z250) were made and aged for eight weeks in water. They were randomly divided into four groups. In the control group, repairing was done with no surface treatment and using bonding agent. In groups 2 to 4, the specimens were repaired following roughening, etching and use of Adper Single Bond, and finished immediately, after 20 minutes and after 24 hours, respectively. After thermocycling, the microleakage at the repair interface was assessed using dye-penetration technique. The results were analyzed using Kruskal-Wallis and Mann-Whitney tests (α=0.05). RESULTS: There was a significant difference among the four groups (P<0.001). The control group with the highest leakage showed a significant difference with the other groups (P<0.05). Immediate finishing showed a significantly higher leakage compared to 20-minute and 24-hour delayed finishing time (P<0.001). The two latter groups had no difference. CONCLUSION: Immediate finishing of the repaired restorations negatively affect the sealing at the repair interface, while 20-minute and 24-hour delayed finishing had no adverse effect on the interface sealing.