Can pulpal floor debonding be detected from occlusal surface displacement in composite restorations?

João Batista Novaes Jr; Elissa Talma; Estevam Barbosa Las Casas; Wondwosen Aregawi; Lauren Wickham Kolstad; Sue Mantell; Yan Wang; Alex Fok

doi:10.1016/j.dental.2017.11.019

Can pulpal floor debonding be detected from occlusal surface displacement in composite restorations?

Dent Mater. 2018 Jan;34(1):161-169. doi: 10.1016/j.dental.2017.11.019. Epub 2017 Dec 6.

Authors

João Batista Novaes Jr¹, Elissa Talma², Estevam Barbosa Las Casas², Wondwosen Aregawi³, Lauren Wickham Kolstad⁴, Sue Mantell⁵, Yan Wang⁶, Alex Fok⁷

Affiliations

¹ Department of Clinical, Pathology and Surgery, School of Dentistry, University of Minas Gerais, Belo Horizonte, Brazil; Biomechanical Engineering Group, Department of Structures, School of Engineer, University of Minas Gerais, Belo Horizonte, Brazil. Electronic address: novaes@ufmg.br.
² Biomechanical Engineering Group, Department of Structures, School of Engineer, University of Minas Gerais, Belo Horizonte, Brazil.
³ Minnesota Dental Research Center for Biomaterials and Biomechanics, School of Dentistry, University of Minnesota, Minneapolis, MN, USA.
⁴ Minnesota Dental Research Center for Biomaterials and Biomechanics, School of Dentistry, University of Minnesota, Minneapolis, MN, USA; Department of Mechanical Engineering, University of Minnesota, Minneapolis, MN, USA.
⁵ Department of Mechanical Engineering, University of Minnesota, Minneapolis, MN, USA.
⁶ Department of Prosthodontics, Guanghua School of Stomatology, Sun Yat-sen University, Guangzhou, China.
⁷ Minnesota Dental Research Center for Biomaterials and Biomechanics, School of Dentistry, University of Minnesota, Minneapolis, MN, USA. Electronic address: alexfok@umn.edu.

PMID: 29199007
DOI: 10.1016/j.dental.2017.11.019

Abstract

Objectives: Polymerization shrinkage of resin composite restorations can cause debonding at the tooth-restoration interface. Theory based on the mechanics of materials predicts that debonding at the pulpal floor would half the shrinkage displacement at the occlusal surface. The aim of this study is to test this theory and to examine the possibility of detecting subsurface resin composite restoration debonding by measuring the superficial shrinkage displacements.

Methods: A commercial dental resin composite with linear shrinkage strain of 0.8% was used to restore 2 groups of 5 model Class-II cavities (8-mm long, 4-mm wide and 4-mm deep) in aluminum blocks (8-mm thick, 10-mm wide and 14-mm tall). Group I had the restorations bonded to all cavity surfaces, while Group II had the restorations not bonded to the cavity floor to simulate debonding. One of the proximal surfaces of each specimen was sprayed with fine carbon powder to allow surface displacement measurement by Digital Image Correlation. Images of the speckled surface were taken before and after cure for displacement calculation. The experiment was simulated using finite element analysis (FEA) for comparison.

Results: Group I showed a maximum occlusal displacement of 34.7±6.7μm and a center of contraction (COC) near the pulpal floor. Group II had a COC coinciding with the geometric center and showed a maximum occlusal displacement of 17.4±3.8μm. The difference between the two groups was statistically significant (p-value=0.0007). Similar results were obtained by FEA. The theoretical shrinkage displacement was 44.6 and 22.3μm for Group I and II, respectively. The lower experimental displacements were probably caused by slumping of the resin composite before cure and deformation of the adhesive layer.

Significance: The results confirmed that the occlusal shrinkage displacement of a resin composite restoration was reduced significantly by pulpal floor debonding. Recent in vitro studies seem to indicate that this reduction in shrinkage displacement could be detected by using the most accurate intraoral scanners currently available. Thus, subject to clinical validation, the occlusal displacement of a resin composite restoration may be used to assess its interfacial integrity.

Keywords: Debonding; Dental restoration; Intraoral scanner; Polymerization shrinkage; Resin composite.

Publication types

Research Support, Non-U.S. Gov't

MeSH terms

Acrylic Resins / chemistry*
Composite Resins / chemistry*
Dental Cavity Preparation
Dental Cements
Dental Marginal Adaptation
Dental Restoration Failure*
Dental Restoration, Permanent / methods*
Elastic Modulus
Finite Element Analysis
Image Processing, Computer-Assisted
Light-Curing of Dental Adhesives
Materials Testing
Polymerization
Polyurethanes / chemistry*
Surface Properties

Substances

Acrylic Resins
Adper single bond 2
Composite Dental Resin
Composite Resins
Dental Cements
Polyurethanes