Evaluation of esthetic brackets' resistance to torsional forces from the archwire.
BACKGROUND
The aim of this study was to evaluate the resistance to deformation or fracture of esthetic brackets produced by archwire torsion.


METHODS
Six types of maxillary right central incisor brackets were analyzed: traditional ceramic brackets (cer); ceramic brackets reinforced with a stainless steel slot (cer/ss); ceramic brackets reinforced with a gold slot (cer/gold); traditional polycarbonate brackets (poly); polycarbonate brackets reinforced with a stainless steel slot (poly/ss); and polycarbonate brackets reinforced with ceramic fillers and a stainless steel slot (poly/cer/ss). Stainless steel wire segments were used, and the testing instrument (Emic DL 10000, São José do Rio Preto, PR, Brazil) was moved at a rate of 1 inch per minute to generate the wire torsion.


RESULTS
The brackets showed deformation or fracture resistance values (gf x mm) in decreasing order as follows: cer/ss (3528.1 +/- 516.6), cer/gold (2858.7 +/- 611.6), cer (2424.0 +/- 352.1), poly/cer/ss (2279.5 +/- 174.5), poly/ss (2142.0 +/- 275.7), and poly (1463.6 +/- 193.3). The cer/ss ceramic brackets showed the greatest statistically significant (P <0.01) values of resistance to fracture, and the poly brackets had the lowest statistically significant (P <0.01) values of resistance to deformation. The cer brackets showed no significant differences (P >0.01) from the cer/gold, the poly/cer/ss, and the poly/ss brackets.


CONCLUSIONS
This suggested that the stainless steel slot might enhance resistance to deformation or fracture, although gold slots and ceramic fillers are ineffective for reinforcing esthetic brackets.
Nishio
Clarice
C
Department of Orthodontics, Universidade do Estado do Rio de Janeiro, Brazil. nishiocla@gmail.com
Mendes
Alvaro de Moraes
Ade M
Almeida
Marco Antonio de Oliveira
MA
Tanaka
Eiji
E
Tanne
Kazuo
K
Elias
Carlos Nelson
CN
D002516:Ceramics / Q000737:chemistry; D003722:Dental Alloys / Q000737:chemistry; D003764:Dental Materials / Q000737:chemistry; D004868:Equipment Failure; D004955:Esthetics, Dental; D006047:Gold Alloys / Q000737:chemistry; D006801:Humans; D008422:Materials Testing; D016382:Orthodontic Appliance Design; D016910:Orthodontic Brackets; D009969:Orthodontic Wires; D011076:Polycarboxylate Cement / Q000737:chemistry; D013193:Stainless Steel / Q000737:chemistry; D013314:Stress, Mechanical; D013499:Surface Properties; D054159:Torsion, Mechanical
D003722:Dental Alloys; D003764:Dental Materials; D006047:Gold Alloys; D011076:Polycarboxylate Cement; D013193:Stainless Steel; C005506:polycarbonate