title: Correlation between polymerization stress and interfacial integrity of composites restorations assessed by different in vitro tests.
abstract: OBJECTIVE
  to correlate polymerization stress data obtained under two compliance conditions with those from different interfacial quality tests.
  
  
  METHODS
  Six commercial composites were tested (Filtek Z250/3M ESPE, Heliomolar/Ivoclar Vivadent, Aelite LS Posterior/Bisco, Filtek Supreme/3M ESPE, ELS/Saremco and Venus Diamond/Heraeus Kulzer). Bond strength (BS) was evaluated by push-out test on slices of bovine dentin (2-mm thick) with tapered cavities. For microleakage (ML) and gap analysis, cylindrical cavities in bovine incisors (4-mm diameter and 1.5-mm height) were restored and epoxy replicas of the cavo-surface margins were prepared for analysis under scanning electron microscopy (200×). The same specimens were submitted to a microleakage protocol using AgNO3 as tracer. After sectioned twice perpendicularly, ML was determined under a stereomicroscope (60×). Polymerization stress (PS, n=5) was determined by the insertion of the composite (h=1.5mm) between poly(methyl methacrylate), PMMA, or glass rods (Ø=4 mm) attached to a universal testing machine. Data were analyzed using Kruskal-Wallis (ML and gaps), and ANOVA/Tukey (BS and PS, α=5%). Pearson's correlation test was used to verify correlations between stress and interfacial quality.
  
  
  RESULTS
  BS varied from 4.7 to 7.9 MPa. Average ML data ranged from 0.34 to 0.89 mm. Maximum ML varied from 0.61 to 1.34 mm. Gap incidence varied from 13 to 47%. PS ranged from 2.5 to 4.4 MPa in PMMA, and between 2.1 and 8.2 in glass. Statistically significant correlations were observed between stress and interfacial quality, except between BS and PS in glass. These correlations were stronger when PMMA was used as bonding substrate.
  
  
  CONCLUSIONS
  PS data obtained using a high compliance testing system showed a stronger correlation with "in vitro" interfacial integrity results, compared to data from a low compliance system.
authors.affiliation: Universidade de Santo Amaro, São Paulo, SP, Brazil; Universidade de São Paulo, São Paulo, SP, Brazil. Electronic address: eticiacidreiraboaro@gmail.com.
authors.forename: Letícia Cristina Cidreira
authors.initials: LC
authors.lastname: Boaro
authors.affiliation: Universidade de São Paulo, São Paulo, SP, Brazil.
authors.forename: Nívea Regina
authors.initials: NR
authors.lastname: Fróes-Salgado
authors.affiliation: Universidade de São Paulo, São Paulo, SP, Brazil.
authors.forename: Vinicius Edwardo Souza
authors.initials: VE
authors.lastname: Gajewski
authors.affiliation: Universidade Federal de Uberlândia, Uberlândia, MG, Brazil.
authors.forename: Aline A
authors.initials: AA
authors.lastname: Bicalho
authors.affiliation: Universidade Federal de Uberlândia, Uberlândia, MG, Brazil.
authors.forename: Andrea Dolores Correa M
authors.initials: AD
authors.lastname: Valdivia
authors.affiliation: Universidade Federal de Uberlândia, Uberlândia, MG, Brazil.
authors.forename: Carlos José
authors.initials: CJ
authors.lastname: Soares
authors.affiliation: Universidade de São Paulo, São Paulo, SP, Brazil.
authors.forename: Walter Gomes
authors.initials: WG
authors.lastname: Miranda Júnior
authors.affiliation: Universidade de São Paulo, São Paulo, SP, Brazil.
authors.forename: Roberto Ruggiero
authors.initials: RR
authors.lastname: Braga
mesh_terms: D000818:Animals; D002417:Cattle; D001840:Dental Bonding; D003763:Dental Leakage; D003799:Dental Stress Analysis; D066298:In Vitro Techniques; D058105:Polymerization
keywords: Bond strength; Composites; Marginal gap; Polymerization stress