Are flowable resin-based composites a reliable material for metal orthodontic bracket bonding?
OBJECTIVE
To compare the tensile bond strength (TBS) and adhesive remnant index (ARI) of three flowable resin-based composites and three orthodontic adhesive systems for metal bracket bonding.


METHODS
Sixty bovine incisors were randomly divided into six groups. Enamel surfaces were etched with 37 percent phosphoric acid for 30 seconds and stainless steel orthodontic brackets were bonded using either flowable resin-based composites (3M Flow, FL; Tetric Flow, TF; and Wave, WA) or orthodontic bonding systems (Transbond XT, TX; Concise Orthodontic, CO; Fill Magic Ortodôntico, FM). All specimens were thermal cycled and stored in distilled water at 37°C for 24 hours, after which they were subsequently tested for TBS using a universal testing machine. ARI scores were determined after the failure of brackets. TBS and ARI data were submitted to ANOVA, Tukey, and Kruskal-Wallis tests (p=0.05), respectively.


RESULTS
Rankings of the resin-based composites based on TBS means (MPa) were TX (6.4 ± 2.1), followed by CO (4.5 ± 2.7), FM (3.7 ± 1.2), FL (3.6 ± 1.2), TF (3.3 ± 1.2), and WA (2.4 ± 0.6). CO exhibited the lowest ARI mean score (0.9 ± 1.2) which was significantly different from the other five materials: TX (2.8 ± 0.42), FM (2.8 ± 0.42), FL (2.9 ± 0.32), TF (2.9 ± 0.32), and WA (3.0 ± 0.01). However, there were no statistically significant differences among the other groups with mean scores of 2.8-3.0. A score of 3.0 indicated that all the resin remained bonded to the tooth surface.


CONCLUSIONS
The flowable resin-based composites tested (Fl, TF, and WA) used to bond metal orthodontic brackets to bovine enamel had low mean TBS values but acceptable ARI mean scores.


CONCLUSIONS
Flowable composites may not be appropriate for bracket bonding, unless the teeth to be bonded are not subjected to higher orthodontic stresses, such as those without an antagonist.
Department of Dental Materials, School of Dentistry, University of São Paulo, Brazil. barbara@pick.com.br
Bárbara
B
Pick
Vinícius
V
Rosa
Tatiana Rocha
TR
Azeredo
Eduardo Augusto Mascarenhas
EA
Cruz Filho
Walter Gomes
WG
Miranda
D000134:Acid Etching, Dental; D000818:Animals; D017438:Bisphenol A-Glycidyl Methacrylate / Q000737:chemistry; D002417:Cattle; D003188:Composite Resins / Q000737:chemistry*; D003722:Dental Alloys / Q000737:chemistry*; D001840:Dental Bonding; D003743:Dental Enamel / Q000648:ultrastructure; D003799:Dental Stress Analysis / Q000295:instrumentation; D008422:Materials Testing; D016910:Orthodontic Brackets; D010756:Phosphoric Acids / Q000737:chemistry; D011897:Random Allocation; D019279:Resin Cements / Q000737:chemistry*; D013193:Stainless Steel / Q000737:chemistry*; D013314:Stress, Mechanical; D013499:Surface Properties; D013696:Temperature; D013718:Tensile Strength; D013997:Time Factors; D014783:Viscosity; D014867:Water / Q000737:chemistry
D003188:Composite Resins; D003722:Dental Alloys; C481898:Fill Magic; D010756:Phosphoric Acids; D019279:Resin Cements; C477790:Transbond XT; C111840:flowable hybrid composite; C452226:tetric flow composite resin; C471181:wave flowable composite; D014867:Water; D013193:Stainless Steel; D017438:Bisphenol A-Glycidyl Methacrylate; C030242:phosphoric acid