title: Cuspal Displacement Induced by Bulk Fill Resin Composite Polymerization: Biomechanical Evaluation Using Fiber Bragg Grating Sensors.
abstract: Polymerization shrinkage is a major concern to the clinical success of direct composite resin restorations. The aim of this study was to compare the effect of polymerization shrinkage strain of two resin composites on cuspal movement based on the use of fiber Bragg grating (FBG) sensors. Twenty standardized Class II cavities prepared in upper third molars were allocated into two groups (n = 10). Restorations involved the bulk fill placement of conventional microhybrid resin composite (Esthet•X® HD, Dentsply DeTrey) (Group 1) or flowable "low-shrinkage" resin composite (SDR™, Dentsply DeTrey) (Group 2). Two FBG sensors were used per restoration for real-time measurement of cuspal linear deformation and temperature variation. Group comparisons were determined using ANCOVA (α = 0.05) considering temperature as the covariate. A statistically significant correlation between cuspal deflection, time, and material was observed (p < 0.01). Cuspal deflection reached 8.8 μm (0.23%) and 7.8 μm (0.20%) in Groups 1 and 2, respectively. When used with bulk fill technique, flowable resin composite SDR™ induced significantly less cuspal deflection than the conventional resin composite Esthet•X® HD (p = 0.015) and presented a smoother curve slope during the polymerization. FBG sensors appear to be a valid tool for accurate real-time monitoring of cuspal deformation.
authors.affiliation: Faculty of Medicine, University of Coimbra, Avenida Bissaya Barreto, Blocos de Celas, 3000-075 Coimbra, Portugal.
authors.forename: Alexandra
authors.identifier: 0000-0001-6929-3807
authors.initials: A
authors.lastname: Vinagre
authors.affiliation: Faculty of Medicine, University of Coimbra, Avenida Bissaya Barreto, Blocos de Celas, 3000-075 Coimbra, Portugal.
authors.forename: João
authors.initials: J
authors.lastname: Ramos
authors.affiliation: Faculty of Medicine, University of Coimbra, Avenida Bissaya Barreto, Blocos de Celas, 3000-075 Coimbra, Portugal.
authors.forename: Sofia
authors.initials: S
authors.lastname: Alves
authors.affiliation: Faculty of Medicine, University of Coimbra, Avenida Bissaya Barreto, Blocos de Celas, 3000-075 Coimbra, Portugal.
authors.forename: Ana
authors.identifier: 0000-0003-4019-9379
authors.initials: A
authors.lastname: Messias
authors.affiliation: Instituto de Telecomunicações (IT), Campus Universitário de Santiago, 3810-193 Aveiro, Portugal.
authors.forename: Nélia
authors.identifier: 0000-0002-8176-7953
authors.initials: N
authors.lastname: Alberto
authors.affiliation: Instituto de Telecomunicações (IT), Campus Universitário de Santiago, 3810-193 Aveiro, Portugal.
authors.forename: Rogério
authors.initials: R
authors.lastname: Nogueira