Effect of intraoral aging on the setting status of resin composite and glass ionomer orthodontic adhesives.
BACKGROUND
The aim of this study was to assess the effect of intraoral aging on the setting status of a resin composite and a glass ionomer adhesive, relative to control specimens stored in water.


METHODS
Metallic brackets were bonded with resin composite orthodontic adhesive (Transbond XT; 3M Unitek, Monrovia, Calif) or a glass ionomer cement (Fuji I; GC, Tokyo, Japan) to recently extracted premolars and kept in water for 6 months. The same materials were also bonded to the premolars of orthodontic patients. After 6 months, the teeth were carefully extracted, with the brackets intact on their buccal surfaces. All teeth were embedded in epoxy resin and sectioned buccolingually. Fourier transform infrared microscopy and Raman microscopy were used for the estimation of the degree of cure in the composite and the salt yield in the glass ionomer adhesives.


RESULTS
The control samples of the composite showed significantly lower degrees of cure than did the retrieved specimens (52.40% ± 3.21% vs 57.62% ± 1.32% by Fourier transform infrared microscopy, and 61.40% ± 2.61% vs 67.40% ± 3.44% by Raman microscopy). Raman microscopy significantly overestimated the degree of cure and failed to provide reliable information for the salt yield in the glass ionomer cement. Fourier transform infrared microscopy showed increased, but no statistically significant difference in, aluminum-carboxylate salts in the retrieved specimens.


CONCLUSIONS
Enhanced oxidation of residual carbon-carbon bonds in the composite and slightly increased dissolution of the weaker calcium-salt phase in the glass ionomer cement were the main differences in the intraorally aged specimens in comparison with the specimens stored in water.
Postgraduate student, Department of Orthodontics, School of Dentistry, University of Athens, Athens, Greece.
Anna
A
Iliadi
Attending dental physician, Department of Orthodontics and Paediatric Dentistry, Center of Dental Medicine, University of Zurich, Zurich, Switzerland.
Stefan
S
Baumgartner
Professor and director of orthodontics, Dubai School of Dental Medicine, Dubai, United Arab Emirates; professor, Department of Orthodontics, School of Dentistry, Aristotle University of Thessaloniki, Thessaloniki, Greece.
Athanasios E
AE
Athanasiou
Professor and director, Department of Orthodontics and Paediatric Dentistry, Center of Dental Medicine, University of Zurich, Zurich, Switzerland. Electronic address: theodore.eliades@zzm.uzh.ch.
Theodore
T
Eliades
Professor and head, Department of Dental Biomaterials, School of Dentistry, University of Athens, Athens, Greece.
George
G
Eliades
D000293:Adolescent; D000328:Adult; D017607:Aluminum Compounds / Q000737:chemistry; D017610:Calcium Compounds / Q000737:chemistry; D002244:Carbon / Q000737:chemistry; D002264:Carboxylic Acids / Q000737:chemistry; D003188:Composite Resins / Q000737:chemistry*; D003722:Dental Alloys / Q000737:chemistry; D005260:Female; D005899:Glass Ionomer Cements / Q000737:chemistry*; D006801:Humans; D008297:Male; D009055:Mouth / Q000502:physiology*; D016910:Orthodontic Brackets; D010084:Oxidation-Reduction; D058105:Polymerization; D019279:Resin Cements / Q000737:chemistry*; D017550:Spectroscopy, Fourier Transform Infrared; D013059:Spectrum Analysis, Raman; D013696:Temperature; D013997:Time Factors; D014867:Water / Q000737:chemistry; D055815:Young Adult
D017607:Aluminum Compounds; D017610:Calcium Compounds; D002264:Carboxylic Acids; D003188:Composite Resins; D003722:Dental Alloys; D005899:Glass Ionomer Cements; D019279:Resin Cements; C477790:Transbond XT; D014867:Water; C084541:Fuji glass-ionomer lining cement; D002244:Carbon