An in-vitro study of plaque sedimentation and wear between self-ligating and conventional brackets

OBJECTIVES: Different systems were studied aiming a reduction of the friction particularly in vitro. A significant inferior effort was performed study the strict interaction between bracket type and hygiene protocols in order to reduce plaque accumulation and appliance wear for the entire duration of an orthodontic treatment. This qualitative study aims to evaluate the variation of plaque sediments (amount of accumulation and consistency) and wear in relation to brackets typology, through the scanning electron microscopy (SEM).

MATERIALS AND METHODS: Forty brackets of canines and premolars (Group A: 20 conventional brackets, Group B: 20 self-ligating brackets) where collected from a patient sample for rebracketing purpose. The two Groups of brackets removed from patient’s were immersed in fixative containing 4 per cent formaldehyde and 1 per cent glutaraldehyde in phosphate buffer for 24 hours, followed by 0.1 M phosphate buffer for 12 hours. The specimens were treated and sent to SEM examination (Philips SEM 515, Eindhoven, Netherlands and Carl Zeiss SUPRA 25, Oberkochen, Germany) operated at an accelerating voltage of 15 kV. Magnification ranging from 21.2x to 110x. Plaque composition was assessed using SEM visualizing bacteria as cocci, rods and filaments according to their morphological characteristics with particular attention to formations and aggregations. Bracket wear was evaluated at the slot base, mesial and distal margin of the slot base, lateral slot surface, lateral slot angle, self-ligating bracket clip and bracket wings.

RESULTS: The SEM analysis showed a larger amount of plaque in the negative profiles of conventional brackets, on the area that touches the tooth, under the perimeter of the steel ligation and in the slot where the arch wire is positioned. In self-ligating brackets it was observed a reduced presence of mature plaque. Overall, the self-ligating brackets appeared cleaner than conventional, even though the two types of brackets have plaque accumulations in different areas.
Self-ligating brackets presented less wear in particular in the lateral surfaces of the slots.

CONCLUSIONS: This qualitative study, within its limitations, highlighted a significant lower plaque accumulation and brackets’ wearing in self-ligating typology with respect to traditional ones.

CLINICAL SIGNIFICANCE: This study show that self-ligating brackets have a lower plaque accumulation and wearing traditional orthodontic brackets.

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