Effect of Streptococcus mutans on surface-topography, microhardness, and mechanical properties of contemporary resin composites

Abstract

Objective: Dental caries is the most prevalent disease globally, and Streptococcus mutans ( S. mutans) is a common associated oral bacteria. Additionally, S. mutans possess esterase activity capable of degrading resin composites (RC). However, the effect of degradation on the physical-mechanical properties of the RC has not been extensively studied. We evaluated the flexure strength (FS), the diametral tensile strength (DTS), the modulus of elasticity (ME), and the microhardness of three contemporary RC to establish if S. mutans could affect them. Methods: One hundred thirty-eight bar-shaped and 276 disc-shaped specimens were fabricated with Enamel Plus HRi, IPS Empress Direct, and Clearfil AP-X, and physical-mechanical testing was done after been incubated during 30 and 60 days in culture media with or without S. mutans. Also, a scanning electron microscope was used to identify surface changes. Results: None of the tested RC were affected in their mechanical properties (FS, ME, and DTS). However, Clearfil AP-X and Enamel Plus HRI showed eroded surfaces and a decreased microhardness after 30 and 60 days S. mutans incubation. IPS Empress Direct presented the lowest values in all the tests, but its physical-mechanical features and surface were not affected by bacteria’s exposure. Conclusions: Exposure to S. mutans could affect some contemporary RC; however, the effect seems superficial since its mechanical features were not affected.

Intraoral ageing of aligners and attachments: Adverse effects on clinical efficiency and release of biologically-active compounds

“… 43 In addition, bacterial esterase can also increase the shrinkage of methacrylate resin and reduce the mechanical properties of the material, such as hardness, bending strength, radial tensile strength and elastic modulus. 45 With an increase in the roughness of a resin attachment surface, adhesion of bacteria increases, and consequently the esterase that the bacteria produce enhanced biodegradation.…”

Biodegradation of Dental Resin-Based Composite—A Potential Factor Affecting the Bonding Effect: A Narrative Review

“…When the Bis-GMA-based resin was co-cultured with S. mutans , it was found that S. mutans considerably enhanced the surface roughness of the resin composite [ 38 ], and Bis-HPPP could be detected after 14 days [ 37 ]. In addition, bacterial esterase can also increase the shrinkage of methacrylate resin and reduce the mechanical properties of the material, such as microhardness, bending strength, radial tensile strength and elastic modulus [ 39 , 40 ]. When the surface of the resin becomes rough, the adhesion of bacteria increases.…”