Purpose: To investigate and compare the degree of Streptococcus mutans (SM) colonization before and after in vitro wear simulation on monolithic zirconia (MZ), lithium disilicate (LD), ceramo-metal (CM), and composite resin (CR) specimens.
Materials and methods: Sixteen circular discs (10 × 3 mm) were fabricated for each group (MZ, LD, CR, CM). Half of the samples from each group (n = 8) were subjected to a wear cycle (n = 32 in total). The wild-type SM bacteria was incubated, diluted, and cultured for growth on the specimens with polished (n = 32) and worn surfaces (n = 32). The number of bacteria was calculated from colony-forming units (CFU). ANOVA followed by Tukey honest significant difference test (α < .05) was used for statistics.
Results: SM adhesion on the polished surfaces of all the tested materials exhibited similar values (P = .215), with the number of SM being lowest for LD (21.87 ± 28.14) and highest for CM (90.62 ± 76.69). After the wear cycle, ANOVA indicated significant differences (P = .000) for the number of bacteria between pre- and postwear conditions of all groups. MZ (21,028 ± 1,507.98) and CM (13,025 ± 2,690.85) showed the highest and lowest numbers of SM colonies, respectively. According to t test, postwear SM adhesion to all materials (P = .000) was significantly higher. SM colonization on the worn surfaces of all the materials showed significant differences (P < .05), except for between LD and CR (P = .973).
Conclusion: Polished surfaces of evaluated materials showed similar SM colonization, which emphasizes the importance of following the minimum requirements of the polishing/glazing procedures. SM colonization on the material surfaces significantly increased after wear. MZ and CM possessed the highest and lowest SM colonizations, respectively.