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.
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 frequency, 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 alpha = 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 microns, mean area: 3500 microns2) 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.
Stratmann
U
U
Institute of Anatomy, University of Münster, Germany.
Schaarschmidt
K
K
Wegener
H
H
Ehmer
U
U
D000134:Acid Etching, Dental; D000269:Adhesives / Q000737:chemistry; D000293:Adolescent; D017438:Bisphenol A-Glycidyl Methacrylate / Q000737:chemistry; D002118:Calcium / Q000032:analysis / Q000737:chemistry; D002516:Ceramics / Q000737:chemistry; D002648:Child; D016001:Confidence Intervals; D003722:Dental Alloys / Q000737:chemistry; D017005:Dental Debonding / Q000009:adverse effects / Q000295:instrumentation / Q000379:methods*; D003743:Dental Enamel / Q000293:injuries / Q000648:ultrastructure*; D004577:Electron Probe Microanalysis; D006358:Hot Temperature; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008855:Microscopy, Electron, Scanning; D016910:Orthodontic Brackets; D010758:Phosphorus / Q000032:analysis / Q000737:chemistry; D015203:Reproducibility of Results; D013499:Surface Properties; D014082:Tooth Fractures / Q000209:etiology / Q000473:pathology
D000269:Adhesives; D003722:Dental Alloys; D010758:Phosphorus; D017438:Bisphenol A-Glycidyl Methacrylate; D002118:Calcium