Evaluation of surface roughness of the bracket slot floor--a 3D perspective study

An important constituent of an orthodontic appliance is orthodontic brackets. It is either the bracket or the archwire that slides through the bracket slot, during sliding mechanics. Overcoming the friction between the two surfaces demands an important consideration in an appliance design. The present study investigated the surface roughness of four different commercially available stainless steel brackets.

All tests were carried out to analyse quantitatively the morphological surface of the bracket slot floor with the help of scanning electron microscope (SEM) machine and to qualitatively analyse the average surface roughness (Sa) of the bracket slot floor with the help of a three-dimensional (3D) non-contact optical surface profilometer machine.

The SEM microphotographs were evaluated with the help of visual analogue scale, the surface roughness for group A = 0-very rough surface, group C = 1--rough surface, group B = 2--smooth surface, and group D = 3-very smooth surface. Surface roughness evaluation with the 3D non-contact optical surface profilometer machine was highest for group A, followed by group C, group B and group D. Groups B and D provided smooth surface roughness; however, group D had the very smooth surface with values 0.74 and 0.75 for mesial and distal slots, respectively.

Evaluation of surface roughness of the bracket slot floor with both SEM and profilometer machine led to the conclusion that the average surface roughness was highest for group A, followed by group C, group B and group D.