Journal Article

The extent of enamel surface fractures. A quantitative comparison of thermally debonded ceramic and mechanically debonded metal brackets by energy dispersive micro- and image-analysis

U. Stratmann, K. Schaarschmidt, H. Wegener and U. Ehmer

in The European Journal of Orthodontics

Published on behalf of European Orthodontics Society

Volume 18, issue 6, pages 655-662
Published in print December 1996 | ISSN: 0141-5387
e-ISSN: 1460-2210 | DOI: http://dx.doi.org/10.1093/ejo/18.6.655
The extent of enamel surface fractures. A quantitative comparison of thermally debonded ceramic and mechanically debonded metal brackets by energy dispersive micro- and image-analysis

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This clinical study investigated the practical value of two methods for debonding brackets attached by the adhesive Concise to acid-etched enamel surfaces. Forty-two Ultratrimm Standard metal brackets and 42 Fascination ceramic brackets were collected from juvenile patients undergoing orthodontic treatment. All metal brackets were mechanically debonded by a conventional bracket removal plier, whereas the ceramic brackets were thermally debonded by a commercial Dentaurum ceramic debonding unit. All brackets were evaluated by scanning electron microscopy for the morphology of their adhesive fracture surfaces and for the occurrence of mineral-like particles attached to the adhesive fracture surfaces. These particles were analysed by an energy dispersive X-ray microprobe for their Ca/P ratios and by image analysis of scanning electron micrographs for measurement of their areas. The scanning electron micrographs showed 4 types of debonding fractures. The most frequent fracture was type 1 (between adhesive and bracket base) and type 2 (between adhesive and enamel surface). In the group of mechanically debonded metal brackets type 1 (38 per cent) and type 2 (45 per cent) showed a similar fequency, whereas thermally debonded ceramic brackets predominantly showed fracture type 1 (79 per cent) and only a minor percentage of type 2 (11 per cent). A statistical evaluation was applied to estimate the range of reproducibility of fracture types with a 95 per cent confidence interval (level of significance α=5 per cent). In both groups the microprobe analysis of fracture surfaces lying completely or partly between adhesive and enamel surface identified the mineral-like particles as enamel mineral. They occurred partly as single particles (range of thickness: 5–25 μm2, mean area: 3500 μm2) and partly as a coherent covering with a total area of 1.9–5.8 mm2.

It is concluded that the thermodebonding technique is superior to conventional mechanical debonding, because the frequent occurrence of fracture type 1 after thermodebonding affords a protection for the enamel surface, whereas mechanical debonding entails a comparatively high risk of enamel fractures.

Journal Article.  0 words. 

Subjects: Restorative Dentistry and Orthodontics

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