Aesthetic colour performance of plastic and ceramic brackets -- an in vitro study

To evaluate the aesthetic colour performance (colour blending) of plastic and ceramic brackets by determining the colour changes of shade guide tabs before and after bracket placement.

In vitro, laboratory study.

Four plastic and four ceramic brackets were investigated (n=5). Brackets were placed on the labial surface of the A1 and A4 tabs of a Vitapan classic shade guide. The colours of the areas corresponding to the central and inferior areas of the brackets were measured before and after bracket placement according to the CIELAB colour scale with a spectroradiometer. Changes in colour (ΔE*(ab)) and colour coordinates (ΔL*, Δa*, Δb* and ΔC*(ab)) of the tabs after bracket placement were calculated.

Colour changes in the central and inferior areas were in the ranges of 5·6-11·1 and 4·3-12·3 ΔE*(ab) units, respectively. Changes in colour and colour coordinates were influenced by shade tab colour and bracket brand (P<0·05). Compared to A1 tab, ΔE*(ab), Δa*, Δb* and ΔC*(ab) values on A4 tab were significantly higher (P<0·01). The hybrid polymer bracket and glass reinforced plastic bracket induced the smallest colour changes in the central and inferior areas.

All the investigated aesthetic brackets induced clinically unacceptable (ΔE*(ab)>5·5) or perceptible (ΔE*(ab)>2·6) colour changes when placed on the shade tabs. Aesthetic colour performance of brackets on the less chromatic and lighter tab was better than that on the more chromatic and dark tab. High translucency of bracket alone did not lead to better aesthetic colour performance.