Evaluation of Static Friction of Polycrystalline Ceramic Brackets after Conditioning with Different Powers of Er:YAG Laser

Abstract

This research aimed to reduce the friction between the wire and brackets by Er:YAG laser. To measure the friction between the wires and brackets in 0° and 10° of wire angulations, 40 polycrystalline ceramic brackets (Hubit, South Korea) were divided into 8 study groups and irradiated by 100, 200, and 300 mj/s of Er:YAG laser power. Two groups of brackets were not irradiated. The friction between the wires and brackets was measured with universal testing machine (SANTAM) with a segment of .019 × .025 SS wire pulled out of the slot of bracket. ANOVA and t-test were used for analyzing the results. To evaluate the effect of the laser on surface morphology of the bracket, SEM evaluations were carried out. The mean frictional resistances between the brackets and wires with 0° of angulation by increasing the laser power decreased compared with control group, but, in 10° of angulation, the friction increased regardless of the laser power and was comparable to the friction of nonirradiated brackets. Furthermore, with each laser power, frictional resistance of brackets in 10° of angulation was significantly higher than 0° of angulation. These results were explained by SEM images too.

Effect of CO2 laser power intensity on the surface morphology and friction behavior of alumina ceramic brackets

“…When the resulting peaks and troughs reach a uniform distribution on the bracket surface, they could reduce frictional resistance (Table ) by decreasing the surface contact area between the brackets and SS archwires, which can be achieved by laser irradiation with intensities above 70 J/cm 2 . Sliding the wires over these peaks results in a smaller contact area, which requires less force to overcome the frictional resistance to their movements (Arash et al, ).…”

“…The results of this study indicate that increasing laser intensity leads to a larger number of peaks. When these peaks produce uniform pillars, a wire can slide across them owing to less contact with the Al 2 O 3 ceramic bracket surface (Arash et al, ). However, low laser intensities create an uneven surface, with the different heights of peaks and troughs resisting wire movement (as confirmed by SEM and AFM analyses of the surface morphology for different groups of brackets).…”

“…A universal testing machine (UTM) was used to measure the friction between the wires and the brackets. To ensure zero angles of the wires when moving through the bracket slots, a special setup was built and attached to the lower stable plate of the UTM, so that the slot was kept precisely parallel to the edge of this plate (Arash, Anoush, Rabiee, Rahmatei, & Tavanafar, ; Arash et al, ). The machine used a straight line static traction test to simulate sliding of wires in the bracket (Figure ).…”

“…Higher power settings of the CO 2 laser and higher energy intensity of the excimer laser improved the hardness and smoothness of ceramic surfaces compared to conventionally glazed ceramics (Abdallah, Hammouda, Kamal, Abouelatta, & El‐Salam, ). Previous attempts were successful in reducing the frictional resistance between orthodontic ceramic brackets and wires at 0° angulations’ using Er:YAG irradiation (Arash, Javanmard, Eftekhari, Rahmati‐Kamel, & Bahadoram, ). To the best of our knowledge, no other study has investigated effect of CO 2 laser on ceramic brackets’ frictional behavior and surface morphology.…”

“…Arash, Anoush, Rabiee, Rahmatei, & Tavanafar, 2015a;Arash et al, 2015b). The machine used a straight line static traction test to simulate sliding of wires in the bracket(Figure 2).…”