Biomaterial Database

SEM analysis of marginal expansion and gap formation in Class II composite restorations. 1997

B M Thonemann, and M Federlin, and G Schmalz, and K A Hiller

Dental School, University of Regensburg, Germany. birger.thonemann@klinik.uni-regensburg.de

OBJECTIVE Morphological changes in terms of marginal expansion have been observed at the dentin-composite interface of resin composite restorations with the scanning electron microscope (SEM), which could not be described with the criteria conventionally used for quantitative marginal analysis. The purpose of the present study was to elucidate the influence of marginal expansion upon marginal integrity and clarify the cause of these morphological changes. METHODS A total of 22 extracted human molars were restored with Class II resin composite restorations, with and without the use of a dentin bonding agent. The cervical restoration margin was located below the cemento-enamel-junction (CEJ). The marginal adaptation at the dentin- and enamel-composite interfaces was evaluated and measured on replicas using quantitative SEM analysis after different storage periods. The chemical composition of the marginal expansion was determined qualitatively by EDX (Energy Dispersive X-Ray) analysis using original tooth samples. The results obtained from quantitative SEM analysis were statistically analyzed by applying the Mann-Whitney U-test and the error rates method. RESULTS Significantly less marginal expansion occurred at the enamel interface than at the dentin-composite interface (p < or = 0.01). Within the dentin, less marginal expansion was observed with the use of a dentin bonding agent than without a dentin bonding agent (p < or = 0.05). At 1 y, a significant (p < or = 0.05) decrease in marginal expansion was observed in both groups. EDX analysis revealed that the chemical composition of the marginal expansion is comparable to the resin composite, since peaks for silicon, barium and ytterbium could be found at these sites. CONCLUSIONS In Class II resin composite restorations below the CEJ, partial disruption of the adhesive bond may occur initially when curing the restoration. Water sorption causes gap reduction by hygroscopic expansion, seen in the SEM as a volume increase. Thus, the observed morphological changes can be regarded as an early sign of insufficient adhesion between composite and dentin at sites where disruption of the bond occurred initially, whether or not a dentin bonding agent was used.

UI	MeSH Term	Description	Entries
D008855	Microscopy, Electron, Scanning	Microscopy in which the object is examined directly by an electron beam scanning the specimen point-by-point. The image is constructed by detecting the products of specimen interactions that are projected above the plane of the sample, such as backscattered electrons. Although SCANNING TRANSMISSION ELECTRON MICROSCOPY also scans the specimen point by point with the electron beam, the image is constructed by detecting the electrons, or their interaction products that are transmitted through the sample plane, so that is a form of TRANSMISSION ELECTRON MICROSCOPY.	Scanning Electron Microscopy,Electron Scanning Microscopy,Electron Microscopies, Scanning,Electron Microscopy, Scanning,Electron Scanning Microscopies,Microscopies, Electron Scanning,Microscopies, Scanning Electron,Microscopy, Electron Scanning,Microscopy, Scanning Electron,Scanning Electron Microscopies,Scanning Microscopies, Electron,Scanning Microscopy, Electron
D003188	Composite Resins	Synthetic resins, containing an inert filler, that are widely used in dentistry.	Composite Resin,Resin, Composite,Resins, Composite
D003793	Dental Restoration, Permanent	A restoration designed to remain in service for not less than 20 to 30 years, usually made of gold casting, cohesive gold, or amalgam. (Jablonski, Dictionary of Dentistry, 1992)	Dental Fillings, Permanent,Dental Filling, Permanent,Dental Permanent Filling,Dental Permanent Fillings,Dental Restorations, Permanent,Filling, Dental Permanent,Filling, Permanent Dental,Fillings, Dental Permanent,Fillings, Permanent Dental,Permanent Dental Filling,Permanent Dental Fillings,Permanent Dental Restoration,Permanent Dental Restorations,Permanent Filling, Dental,Permanent Fillings, Dental,Restoration, Permanent Dental,Restorations, Permanent Dental
D003804	Dentin	The hard portion of the tooth surrounding the pulp, covered by enamel on the crown and cementum on the root, which is harder and denser than bone but softer than enamel, and is thus readily abraded when left unprotected. (From Jablonski, Dictionary of Dentistry, 1992)	Dentine,Dentines,Dentins
D006801	Humans	Members of the species Homo sapiens.	Homo sapiens,Man (Taxonomy),Human,Man, Modern,Modern Man
D000179	Acrylates	Derivatives of acrylic acid (the structural formula CH2
D017220	Dentin-Bonding Agents	Cements that act through infiltration and polymerization within the dentinal matrix and are used for dental restoration. They can be adhesive resins themselves, adhesion-promoting monomers, or polymerization initiators that act in concert with other agents to form a dentin-bonding system.	Dentin Bonding Agent,Dentin-Bonding Agent,Bonding Agents, Dentin,Agent, Dentin Bonding,Agent, Dentin-Bonding,Agents, Dentin Bonding,Agents, Dentin-Bonding,Bonding Agent, Dentin,Dentin Bonding Agents
D018709	Statistics, Nonparametric	A class of statistical methods applicable to a large set of probability distributions used to test for correlation, location, independence, etc. In most nonparametric statistical tests, the original scores or observations are replaced by another variable containing less information. An important class of nonparametric tests employs the ordinal properties of the data. Another class of tests uses information about whether an observation is above or below some fixed value such as the median, and a third class is based on the frequency of the occurrence of runs in the data. (From McGraw-Hill Dictionary of Scientific and Technical Terms, 4th ed, p1284; Corsini, Concise Encyclopedia of Psychology, 1987, p764-5)	Kolmogorov-Smirnov Test,Kruskal-Wallis H Statistic,Mann-Whitney U Test,Rank-Sum Tests,Spearman Rank Correlation Coefficient,Wilcox Test,Wilcoxon Rank Test,Non-Parametric Statistics,Nonparametric Statistics,Statistics, Non-Parametric,Kolmogorov Smirnov Test,Mann Whitney U Test,Non Parametric Statistics,Rank Sum Tests,Rank Test, Wilcoxon,Rank-Sum Test,Statistics, Non Parametric,Test, Kolmogorov-Smirnov,Test, Mann-Whitney U,Test, Rank-Sum,Test, Wilcox,Test, Wilcoxon Rank,Tests, Rank-Sum,U Test, Mann-Whitney
D018772	Dental Marginal Adaptation	The degree of approximation or fit of filling material or dental prosthetic to the tooth surface. A close marginal adaptation and seal at the interface is important for successful dental restorations.	Adaptation, Marginal, Dental,Marginal Adaptation, Dental,Dental Internal Adaptation,Dental Internal Fit,Adaptation, Dental Internal,Adaptation, Dental Marginal,Adaptations, Dental Internal,Adaptations, Dental Marginal,Dental Internal Adaptations,Dental Internal Fits,Dental Marginal Adaptations,Fit, Dental Internal,Fits, Dental Internal,Internal Adaptation, Dental,Internal Adaptations, Dental,Internal Fit, Dental,Internal Fits, Dental,Marginal Adaptations, Dental
D019279	Resin Cements	Dental cements composed either of polymethyl methacrylate or dimethacrylate, produced by mixing an acrylic monomer liquid with acrylic polymers and mineral fillers. The cement is insoluble in water and is thus resistant to fluids in the mouth, but is also irritating to the dental pulp. It is used chiefly as a luting agent for fabricated and temporary restorations. (Jablonski's Dictionary of Dentistry, 1992, p159)	Resin Cement,Cement, Resin,Cements, Resin