Evaluation of physical properties of a nanocomposite after aging, bleaching and staining.
OBJECTIVE
The objective of the in vitro study was to assess the effect accelerated artificial aging, bleaching agents and coffee staining on the color, gloss, roughness and microhardness of a nanocomposite.


METHODS
120 (7 × 2 mm) were prepared and randomly divided into 2 groups (n = 60) depending on the aging. Each group was further subdivided into 6 subgroups (n = 10) according to the bleaching and staining as follows: 10% carbamide peroxide (10% CP), 10% CP + staining, 35% hydrogen peroxide (35% HP), 35% HP + staining, without bleaching treatment (WB) and WB + staining. Scanning electron microscopy was performed for qualitative analysis of the resin surface. Data were submitted to 3-way analysis of variance (ANOVA) and Tukey's test for multiple comparisons. As for ∆E, multiple comparisons were performed by using Tukey's and Dunnett's tests (α = 0.05).


RESULTS
The bleaching reduced significantly the microhardness of the nanocomposite in without aging groups. All physical properties were found to be negatively changed after the aging process, with bleaching treatment with 10% CP increasing significantly the roughness and loss of gloss compared to the 35% HP. Staining reduced microhardness of both with and without aging nanocomposite as well as the color of the former (E&gt;25), a significantly different result compared to controls.


CONCLUSIONS
The bleaching reduced the microhardness of the nanocomposite, whereas the aging process changed all the properties studied. The bleaching favored extrinsic staining of the with aging nanocomposite.
Restorative Dentistry Department, Piracicaba Dental School, State University of Campinas - FOP/Unicamp, Piracicaba, SP - Brazil.
Thayla H N
TH
Gouveia
Restorative Dentistry Department, Piracicaba Dental School, State University of Campinas - FOP/Unicamp, Piracicaba, SP - Brazil.
Juliana C
JC
Públio
Social Dentistry/Statistics Department, Piracicaba Dental School, State University of Campinas - FOP/Unicamp, Piracicaba, SP - Brazil.
Gláucia M B
GM
Ambrosano
Restorative Dentistry Department, Piracicaba Dental School, State University of Campinas - FOP/Unicamp, Piracicaba, SP - Brazil.
Luís A M S
LA
Paulillo
Restorative Dentistry Department, Piracicaba Dental School, State University of Campinas - FOP/Unicamp, Piracicaba, SP - Brazil.
Flávio H B
FH
Aguiar
Restorative Dentistry Department, Piracicaba Dental School, State University of Campinas - FOP/Unicamp, Piracicaba, SP - Brazil.
Débora A N L
DA
Lima
D000077463:Carbamide Peroxide; D003069:Coffee / Q000737:chemistry*; D006861:Hydrogen Peroxide / Q000737:chemistry*; D053761:Nanocomposites / Q000737:chemistry* / Q000648:ultrastructure; D010545:Peroxides / Q000737:chemistry*; D013499:Surface Properties; D013997:Time Factors; D014508:Urea / Q000031:analogs & derivatives* / Q000737:chemistry
D003069:Coffee; D010545:Peroxides; D000077463:Carbamide Peroxide; D014508:Urea; D006861:Hydrogen Peroxide