American Journal of Orthodontics and Dentofacial Orthopedics
Original ArticlesResidual monomer leaching from chemically cured and visible light-cured orthodontic adhesives
Section snippets
Materials and methods
Seven brands of alumina brackets and one stainless steel type were selected (Table I). Two types of orthodontic adhesives were used: a visible light-cured (Transbond, Unitek/3M, Dental Products Division, Monrovia, Calif.) and a two-paste chemically cured (Concise, Unitek/3M, Monrovia, Calif.). The bases of 10 upper incisor brackets of each brand were covered by a standardized amount (10 mg) of the visible light-cured adhesive and then were pressed against a yellowish background flat surface of
Results
Tables II and III present the mean values, the standard deviations, and the levels of statistically significant differences of residual TEGDMA and Bis-GMA monomer concentrations in the ethanol/water extracts of the orthodontic adhesives tested. Highly statistically significant differences were found among the bracket groups. The highest residual TEGDMA concentration was detected in the group of metallic brackets bonded to the chemically cured adhesive, whereas the highest Bis-GMA concentration
Discussion
The criteria for selection of the ethanol/water (75:25) solution as an immersion medium were based on the potential of this solution to increase the rate of monomer release from dental resin composites, inducing an accelerated aging effect and thus possibly simulating extreme conditions in the oral cavity.21 Although precise simulation of the oral environment is an almost impossible task, due to the multiplicity of factors involved in the degradation mechanism of resin composites,22, 23, 24 the
Conclusions
Under the conditions of this study, the following conclusions can be drawn:
- 1.
No statistically significant differences in the amount of released monomers were found among the ceramic bracket groups bonded to the visible light-cured adhesive and photopolymerized under direct or indirect irradiation.
- 2.
The polycarbonate base ceramic bracket demonstrated significantly higher amount of released monomers compared with ceramic brackets. Evidence of degradation of the polycarbonate base was detected.
- 3.
The
Acknowledgements
We express our appreciation to the manufacturers who contributed the brackets and the adhesives for this investigation.
References (27)
- et al.
Subcutaneous tissue response to composite resin in the dogs
Oral Surg Oral Med Oral Pathol
(1974) - et al.
In vitro studies of the carcinogenic potential of orthodontic bonding materials
Ecotoxicol Environ Safety
(1979) - et al.
Tissue reaction to orthodontic adhesives
Am J Orthod
(1982) - et al.
Long-term cytotoxicity of orthodontic direct-bonding adhesives
Am J Orthod Dentofac Orthop
(1988) Mutagenic potential of orthodontic bonding materials
Am J Orthod
(1981)- et al.
Analysis of aqueous extract from filled resins
J Dent
(1981) - et al.
Rate of elution of leachable components from composites
Dent Mater
(1990) Surface permeability and degradation of dental composites resulting from oral temperature changes
Dent Mater
(1989)- et al.
Studies of the haemolytic activity of bisphenol A diglycidyl methacrylate (Bis-GMA)
J Dent Res
(1978) - et al.
Binding of methyl methacrylate to bovine serum albumin
J Dent Res
(1980)