Cariogenic biofilms can develop secondary caries within a week time in an undisturbed condition in vitro indicating high caries risk

Fahimeh Hayati, DDS,(a) Ayako Okada, DDS, PhD,(a),(b) Junji Tagami, DDS, PhD,(a),(c),(d) and Khairul Matin, BDS, PhD(a),(d)

(a)Cariology and Operative Dentistry, Department of Restorative Sciences, Graduate School, Tokyo Medical and Dental University, (b)Department of Translational Research, School of Dental Medicine, Tsurumi University, Yokohama, (c)Global Center of Excellence Program; International Research Center for Molecular Science in Tooth and Bone Diseases, Tokyo Medical and Dental University, and (d)Support Program for Improving Graduate School Education, Tokyo Medical and Dental University, Tokyo, Japan

Purpose: This in vitro study assessed the potency of cariogenic biofilms in developing secondary caries in human extracted teeth.
Materials and Methods: Cavities (3x2x2 mm3) were prepared in the blocks of mid-buccal human extracted molars. Cavities were filled with Clearfil AP-X composite with (SE-Bond) or without (No-bond) application of an adhesive. Biofilms were formed on both groups of specimens using three species of cariogenic bacteria inside an oral biofilm reactor for 20 hours and specimens were further incubated separately for 7 days or 30 days dividing into two groups. Developed secondary caries lesions were examined using fluorescence microscope and scanning electron microscope. Sizes of the lesions were measured by using image analysis software. Data were statistically analyzed by one-way ANOVA and Turkey’s HSD methods.
Results: The secondary caries were visible at resin-enamel interfaces in all cases including the 7-day specimens. Photomicrographs and data on image analysis clearly showed that the lesion size was smaller in SE-Bond sample compared to No-bond samples, which was statistically significant (p<0.05).
Conclusion: It is suggested that sucrose supplemented biofilms of mutans streptococci have the potency in developing secondary caries lesion within a week time indicating high caries risks in case plaque-biofilms left undisturbed in the oral cavity. (Int Chin J Dent 2009; 9: 61-68.)

Key Words: cariogenic biofilm, mutans streptococci, resin composite, secondary caries.