Volumetric shrinkage and film thickness of cementation materials for veneers: An in vitro 3D microcomputed tomography analysis.
BACKGROUND
Few studies have investigated the volumetric polymerization shrinkage and film thickness of the different cementation techniques used to cement veneers.


OBJECTIVE
The purpose of this in vitro study was to evaluate the volumetric polymerization shrinkage (VS) and film thickness (FT) of various cementation techniques through 3-dimensional (3D) microcomputed tomography (μCT).


METHODS
Forty-eight artificial plastic maxillary central incisors with standard preparations for veneers were provided by a mannequin manufacturer (P-Oclusal) and used as testing models with the manufacturer's plastic veneers. They were divided into 8 groups (n=6): RelyX Veneer + Scotchbond Universal (RV+SBU); Variolink Esthetic LC+Adhese Universal (VE+ADU); Filtek Supreme Ultra Flowable + Scotchbond Universal (FF+SBU); IPS Empress Direct Flow + Adhese Universal (IEF+ADU); Filtek Supreme Ultra Universal + Scotchbond Universal (FS+SBU); IPS Empress Direct + Adhese Universal (IED+ADU); Preheated Filtek Supreme Ultra Universal + Scotchbond Universal (PHF+SBU); and Preheated IPS Empress Direct + Adhese Universal (PHI+ADU). Specimens were scanned before and after polymerization using a μCT apparatus (mCT 40; Scanco Medical AG), and the resulting files were imported and analyzed with 3D rendering software to calculate the VS and FT. Collected data from both the VS and FT were submitted to 1-way ANOVA (α=.05).


RESULTS
VE+ADU had the lowest volumetric shrinkage (1.03%), which was not significantly different from RV+SBU, FF+SBU or IEF+ADU (P>.05). The highest volumetric shrinkage was observed for FS+SBU (2.44%), which was not significantly different from RV+SBU, IED+ADU, PHF+SBU, or PHI+ADU (P>.05). Group RV+SBU did not differ statistically from the remaining groups (P>.05). Film thickness evaluation revealed the lowest values for RV+SBU, VE+ADU, FF+SBU, and IEF+ADU, with an average between groups of 0.17 mm; these groups were significantly different from FS+SBU, IED+ADU, PHF+SBU, and PHI+ADU (P>.05), with an average of 0.31 mm.


CONCLUSIONS
Both the VS and the FT of direct restorative composite resins were higher than those of veneer cements and flowable composite resins, whether preheated or not preheated.
Doctoral student, Department of Restorative Dentistry, State University of Campinas, Piracicaba, Brazil; Visiting Scholar, Department of Biomaterials and Biomimetics, New York University College of Dentistry, New York, NY; and Research Professor, Department of Biomaterials, University of Los Andes, Santiago, Chile. Electronic address: camisobral@hotmail.com.
Camila S
CS
Sampaio
PG International Program student, Department of Biomaterials and Biomimetics, New York University College of Dentistry, New York, NY; and Resident, Department of Advanced Education Program in Prosthodontics, New York University College of Dentistry, New York, NY.
João Malta
JM
Barbosa
Masters student, Department of Biomaterials and Biomimetics, New York University College of Dentistry, New York, NY.
Eduardo
E
Cáceres
Visiting Researcher, Department of Biomaterials and Biomimetics, New York University College of Dentistry, New York, NY.
Lindiane C
LC
Rigo
Associate Professor, Department of Biomaterials and Biomimetics, New York University College of Dentistry, New York, NY.
Paulo G
PG
Coelho
Professor, Department of Prosthodontics, University of São Paulo-Bauru College of Dentistry, Bauru, Brazil.
Estevam A
EA
Bonfante
Assistant Professor, Department of Biomaterials and Biomimetics, New York University College of Dentistry, New York, NY.
Ronaldo
R
Hirata
D001840:Dental Bonding / Q000379:methods; D003738:Dental Cements / Q000627:therapeutic use; D018772:Dental Marginal Adaptation; D003801:Dental Veneers; D006801:Humans; D021621:Imaging, Three-Dimensional; D066298:In Vitro Techniques; D058105:Polymerization; D011861:Radiography, Dental / Q000379:methods; D055114:X-Ray Microtomography / Q000379:methods
D003738:Dental Cements