Effects of aging on the tensile strength and surface condition of orthodontic aligners: a comparative study of five models.

Background/objective: The objective of this study is to determine the effect of aging on tensile strength and surface condition of orthodontic aligners on days 0, 1, 5, 7, 10, and 14.

Materials/methods: The total sample of 80 aligners included five brands (Accusmile®, Angel®, GRAPHY®, Invisalign® and Suresmile®) were placed in a thermocycler to imitate the temperature variations of the oral cavity and accelerate aging for 50, 250, 350, 500, and 700 cycles. The mechanical tensile properties (Young's modulus E, yield strength YS, maximum elastic stress MES, Ultimate Tensile Strength UTS, and maximum stress MS) were measured by Universal Testing Machine at a rate of 5 mm of deformation per minute for 4 minutes.

[Comparison of adhesive seal morphology between APC™ PLUS and APC™ Flash-Free Adhesive Coated brackets].

Introduction: Does the new adhesive-coated APC™ Flash-Free bracket from the 3M Unitek group simplify the bonding protocol without compromising precision?

Objectives: The aim of this study was to compare the morphology of the adhesive joint between the classic APC™ PLUS adhesive-coated brackets and APC™ Flash-Free brackets.

Materials And Methods: In vitro bonding of esthetic brackets in the CLARITY™ ADVANCED range was performed to compare the morphology of the excess flash between APC™ PLUS and APC™ Flash-Free brackets.

Results: No statistically significant difference was found concerning the morphology of the excess flash between APC™ PLUS and APC™ Flash-Free brackets.

[Is the shape memory effect a reality for 35° Copper Ni-Ti(®)? Study by means of differential scanning calorimetry].

Introduction: Copper-nickel-titanium alloys are supposed to deliver a shape memory effect: when they are brought to a low temperature phase and subjected to a plastic deformation, they should recover their initial shape by simple heating. Nickel-titanium alloys can display different crystallographic phases: martensite, austenite and an inconstant intermediate R-phase. The shape memory effect is generally associated with the transition from martensite to austenite but it could also accompany the transition from R-phase to austenite.

Torsional superelasticity of NiTi archwires.

Objective: To reproduce and compare the intraoral torsional behavior of 10 commonly used preformed upper NiTi 0.017 x 0.025 archwires in 0.

Influence of relative humidity on electrical properties of alpha-Al2O3 powders: resistivity and electrochemical impedance spectroscopy.

The influence of humidity on the electrical properties of alpha-Al2O3 powders has been investigated using adsorption isotherms, DC resistivity, and electrochemical impedance spectroscopy. Samples of two alpha-Al2O3 particle sizes were examined, both individually and mixed together. The results show that the grain-bed resistivity decreases with humidity, whereas the grain capacitance is almost constant.