A study on the bacterial adhesion of Streptococcus mutans in various dental ceramics: In vitro study

Abstract

Streptococcus mutans (S. mutans) has been identified as a major etiologic agent of human dental caries and forms a significant proportion of oral streptococci in carious lesions. This study investigates the correlation of surface properties (effect of contact angle [CA] and free surface energy) on three restorative materials (zirconia, nickel–chromium–molybdenum alloy and composites) used in dental prosthetics with bacterial adhesion to S. mutans. Ten samples of each material (zirconia, nickel–chromium–molybdenum alloy and composites) of 8 mm diameter and 2.5 mm thickness were used. Aqueous CA measurements, free surface energy and bacterial adhesion to the sample surfaces were performed. Bacterial adhesion is determined by planting samples in the blood agar cultures and using an electron microscope (scanning electron microscopy [SEM]). The highest values of bacterial adhesion are found in composites, followed by the metal alloy, while the lowest values are observed in zirconia. Measurements show that zirconia has 17 bacteria; Ni–Cr–Mo alloy has 65, while the composite has 80 bacteria. The composites showed the highest degree of bacterial adhesion, compared to the other investigated materials, which correlates with the free surface energy of the samples (24.31 mJ/m2 for zirconia, 31.78 mJ/m2 for Ni–Cr–Mo alloy and 48.82 mJ/m2 for the composite).

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“…An increase in SFE usually results in increased adhesion of bacteria. 43,44 The application of BOA resulted in a slight (by $1 mN/m) increase in SFE and a significant ($ 78%) reduction in the number of adhered bacterial cells. This indicated that BOA affected bacteria directly by the contact-killing mechanism and not passively via changes in thermodynamic properties and reduced adhesion.…”

“…It was reported before that the adhesion of bacteria is related to surface free energy. An increase in SFE usually results in increased adhesion of bacteria 43,44 . The application of BOA resulted in a slight (by ~1 mN/m) increase in SFE and a significant (~ 78%) reduction in the number of adhered bacterial cells.…”

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“…Kim et al 13) reported that the potential of gold alloys with higher surface energies facilitated greater adhesion of early colonized bacteria (S. oralis, S. sanguinis, and S. gordonii) compared to that on zirconia, alumina-toughened zirconia, and titanium surfaces. Bislimi et al 32) found that the surface energies of different materials (zirconia, metal alloys, and CRs) correlated with their susceptibility to S. mutans adhesion. The surface energy is also affected by the surface roughness.…”