Inhibitory and preventive effects of Lactobacillus plantarum FB-T9 on dental caries in rats

Figures & data

Figure 1. Experimental design for evaluating the induction of dental caries in SPF rats

Figure 2. The inhibition effect of L. plantarum FB-T9 on S. mutans. (A and B) L. plantarum FB-T9 on TSA and 1/2 TSA plates; (C and D) S. mutans on TSA and 1/2TSA plates. Competition between FB-T9 and S. mutans: (E, G, I) on TSA plates; (F, H, J) on 1/2 TSA plates; (E and F) S. mutans and L. plantarum FB-T9 were inoculated on the plates at the same time; (G and H) L. plantarum FB-T9 was first inoculated on the plates; (I and J) S. mutans was first inoculated on the plates

Figure 3. Biomass of S. mutans mediated by L. plantarum FB-T9 at different stages. C₁₂, biofilm of negative control at 12 h. C₂₄, biofilm of negative control at 24 h. C₄₈, biofilm of negative control at 48 h. *P < 0.05 when compared with the control treatment and compared between groups

Figure 4. CLSM of S. mutans biofilm on glass coverslips. Addition of FB-T9 bacterial suspension at 0 h (A and B), 6 h (C and D), 12 h (E and F), 24 h (H and L) and 48 h (J and N) respectively. (G and K) S. mutans biofilm after incubation for 24 h with medium alone. (I and M) S. mutans biofilm after incubation for 48 h with medium alone. And A, C, E, G, H, I, J are corresponding 3D graphs

Figure 5. Total bacterial area of biofilm and biofilm viability after intervention by L. plantarum FB-T9 at different stages. The left axis corresponded to the histogram, showing the bacterial area of biofilm (×10⁴ μm²). Biofilm mediated by FB-T9 at 0 h, 6 h, 12 h was compared to the 12 h negative control, while biofilm mediated by FB-T9 at 24 h and 48 h were compared to the 24 h and 48 h negative control, respectively. The dashed line indicated the biofilm viability of three controls, and the solid line indicated the biofilm viability after treatment at different stages. C₁₂, biofilm of negative control at 12 h. C₂₄, biofilm of negative control at 24 h. C₄₈, biofilm of negative control at 48 h. The assay was performed three times and data are expressed as mean ± standard error of the mean. *P < 0.05 when compared with the control treatment and compared between groups

Table 1. S. mutans counts from rat dental samples at different periods

	Caries-free group (CFU/mL)	Caries group(×10^5CFU/mL)	Intervention group(×10^5CFU/mL)
Sampling times	C3	C	T1	T2	T3
1	<30^Aa	2.56 ± 0.7^Ba	3.37 ± 0.8^Bb	3.20 ± 2.2^Bb	1.23 ± 0.36^Bb
2	<30^Aa	1.89 ± 0.8^Ba	0.10 ± 0.0^Ca	0.04 ± 0.0^Ca	0.06 ± 0.0^Ca
3	<30^Aa	1.40 ± 0.7^Ba	0.20 ± 0.0^Ca	0.03 ± 0.0^Ca	0.15 ± 0.0^Ca

A, B and C indicated the difference in the number of S. mutans in the oral cavity of rats in each row.

a, b and c showed the difference of the number of S. mutans in the oral cavity of rats sampled three times in each group.

Data are presented as the mean with the standard error of the mean in parentheses following the statistical analyses of all pairs using the Tukey–Kramer multiple comparison test (n = 8).

Figure 6. S. mutans & lactobacilli count from rat dental samples at different periods in prevention groups. (A) S. mutans counts; (B) lactobacilli counts; Data are expressed as mean ± standard error of the mean (n = 8)

Table 2. Number of linear units assigned to each molar

	Mandible			Maxillary
Caries site	1st	2nd	3rd*	1st	2nd	3rd*
Buccal	6	4	4	6	4	3
Lingual	6	4	4	6	4	3
Sulcal	7	5	2	5	3	2
Proximal	1	2**	1	1	2**	1

*1st, 2nd and 3rd denote the first, second and third molars, respectively;

**The second molar contains a near-middle and a far-middle neighbourhood.

Table 3. Effect of different groups on caries development (incidence and severity) in rats

Group	Number	Caries level
		E	Ds	Dm
Caries group	C3	47.6 ± 0.7	28.6 ± 1.0	15.3 ± 1.3
Intervention group	T1	34.8 ± 1.4*	24.7 ± 1.3*	14.7 ± 0.9
	T2	23.9 ± 1.0*	14.4 ± 0.9*	8.6 ± 0.8*
	T3	40.7 ± 1.3	27.6 ± 1.1	13.5 ± 0.7
Prevention group	P1	28.0 ± 0.8*	10.6 ± 0.7*	–
	P2	14.7 ± 0.9*	8.0 ± 0.6*	–
	P3	30.7 ± 1.5*	14.5 ± 0.8*	–

Data are expressed as mean ± standard error of the mean (n = 8). E, enamel caries; Ds, dentin exposed; Dm, three-fourths of the dentin affected. * P < 0.05.