Diurnal variation of salivary anaerobes correlates severe dental caries in children

Salivary secretion has diurnal fluctuations and the saliva amount affects oral bacterial activity. In this study, the time dependence of number of anaerobic bacteria in saliva such as Streptococcus mutans (S. mutans) was investigated and examined its impact on caries severity. This study was conducted at university hospital in Japan. Twenty subjects (2–10 years old) with the primary dentition were asked to collect whole saliva every 1 hour after the supper while awake at home. Eighteen subjects delivered the collected saliva, which was cultured for S. mutans and total anaerobes in trypticase-yeast extract-cysteine sucrose-bacitracin (TYCSB) medium and the Gifu anaerobic medium (GAM), respectively. The numbers of severe dental caries were also analyzed from medical records. A positive correlation was found between the number of colonies in GAM medium and the saliva collection time of the day. No significant correlation was observed between the number of colonies in TYCSB medium and the collection time. The patients were grouped based on whether or not they had experienced pulp treatment. The number of colonies of S. mutans and anaerobic bacteria were increased in the later hours of only the experienced group. The number of oral anaerobic bacteria of children fluctuated in time-dependent manner after dinner to bedtime, and was higher late in the night. Children with severe dental caries had increased S. mutans as the night progressed, whereas children without them did not.

Dental caries; Circadian rhythms; Salivary anaerobes; Streptococcus mutans

[1] Roenneberg T, Allebrandt K, Merrow M, Vetter C. Social jetlag and obesity. Current Biology. 2012; 22: 939–943.

[2] Seppä L, Pöllänen L, Hausen H. Streptococcus mutans counts obtained by a dip-slide method in relation to caries frequency, sucrose intake and flow rate of saliva. Caries Research. 1988; 22: 226–229.

[3] Sarkar A, Kuehl MN, Alman AC, Burkhardt BR. Linking the oral microbiome and salivary cytokine abundance to circadian oscillations. Scientific Reports. 2021; 11: 2658.

[4] Reppert SM, Weaver DR. Coordination of circadian timing in mammals. Nature. 2002; 418: 935–941.

[5] Honma S. Development of the mammalian circadian clock. European Journal of Neuroscience. 2020; 51: 182–193.

[6] Furukawa M, Kawamoto T, Noshiro M, Honda KK, Sakai M, Fujimoto K, et al. Clock gene expression in the submandibular glands. Journal of Dental Research. 2005; 84: 1193–1197.

[7] Vujovic N, Davidson AJ, Menaker M. Sympathetic input modulates, but does not determine, phase of peripheral circadian oscillators. American Journal of Physiology. Regulatory, Integrative and Comparative Physiology. 2008; 295: R355–R360.

[8] Nirvani M, Khuu C, Utheim TP, Hollingen HS, Amundsen SF, Sand LP, et al. Circadian rhythms and gene expression during mouse molar tooth development. Acta Odontologica Scandinavica. 2017; 75: 144–153.

[9] Xie B, Yuan H, Zou X, Lu M, Zhang Y, Xu D, et al. p75NTR promotes tooth rhythmic mineralization via upregulation of BMAL1/CLOCK. Frontiers in Cell and Developmental Biology. 2023; 11: 1283878.

[10] Di T, Guo M, Xu J, Feng C, Du Y, Wang L, et al. Circadian clock genes REV-ERBα regulates the secretion of IL-1β in deciduous tooth pulp stem cells by regulating autophagy in the process of physiological root resorption of deciduous teeth. Developmental Biology. 2024; 510: 8–16.

[11] Shigeyoshi Y, Taguchi K, Yamamoto S, Takekida S, Yan L, Tei H, et al. Light-induced resetting of a mammalian circadian clock is associated with rapid induction of the mPer1 transcript. Cell. 1997; 91: 1043–1053.

[12] Honma K, Hashimoto S, Nakao M, Honma S. Period and phase adjustments of human circadian rhythms in the real world. Journal of Biological Rhythms. 2003; 18: 261–270.

[13] Rosier BT, Marsh PD, Mira A. Resilience of the oral microbiota in health: mechanisms that prevent dysbiosis. Journal of Dental Research. 2018; 97: 371–380.

[14] Khan SY, Schroth RJ, Cruz de Jesus V, Lee VHK, Rothney J, Dong CS, et al. A systematic review of caries risk in children <6 years of age. International Journal of Paediatric Dentistry. 2024; 34: 410–431.

[15] Sandy LPA, Helmyati S, Amalia R. Nutritional factors associated with early childhood caries: a systematic review and meta-analysis. The Saudi Dental Journal. 2024; 36: 413–419.

[16] ElSalhy M, Honkala S, Soderling E, Varghese A, Honkala E. Relationship between daily habits, Streptococcus mutans, and caries among schoolboys. Journal of Dentistry. 2013; 41: 1000–1006.

[17] American Academy of Pediatric Dentistry. Caries-risk assessment and management for infants, children, and adolescents. The Reference Manual of Pediatric Dentistry (pp. 301–307). Chicago, Ill.: American Academy of Pediatric Dentistry. 2023.

[18] Nishide S, Yoshihara T, Hongou H, Kanehira T, Yawaka Y. Daily life habits associated with eveningness lead to a higher prevalence of dental caries in children. Journal of Dental Sciences. 2019; 14: 302–308.

[19] Thibodeau EA, O’Sullivan DM, Tinanoff N. Mutans streptococci and caries prevalence in preschool children. Community Dentistry and Oral Epidemiology. 1993; 21: 288–291.

[20] Weinberger SJ, Wright GZ. Correlating Streptococcus mutans with dental caries in young children using a clinically applicable microbiological method. Caries Research. 1989; 23: 385–388.

[21] Rosier BT, Takahashi N, Zaura E, Krom BP, MartÍnez-Espinosa RM, van Breda SGJ, et al. The importance of nitrate reduction for oral health. Journal of Dental Research. 2022; 101: 887–897.

[22] Van Palenstein Helderman WH, Ijsseldijk M, Huis in ’t Veld JH. A selective medium for the two major subgroups of the bacterium Streptococcus mutans isolated from human dental plaque and saliva. Archives of Oral Biology. 1983; 28: 599–603.

[23] Alqaderi H, Tavares M, Al-Mulla F, Al-Ozairi E, Goodson JM. Late bedtime and dental caries incidence in Kuwaiti children: a longitudinal multilevel analysis. Community Dentistry and Oral Epidemiology. 2020; 48: 181–187.

[24] Sardana D, Galland B, Wheeler BJ, Yiu CKY, Ekambaram M. Effect of sleep on development of early childhood caries: a systematic review. European Archives of Paediatric Dentistry. 2023; 24: 1–14.

[25] Thaiss CA, Levy M, Korem T, Dohnalová L, Shapiro H, Jaitin DA, et al. Microbiota diurnal rhythmicity programs host transcriptome oscillations. Cell. 2016; 167: 1495–1510.e12.

[26] Chellappa SL, Engen PA, Naqib A, Qian J, Vujovic N, Rahman N, et al. Proof-of-principle demonstration of endogenous circadian system and circadian misalignment effects on human oral microbiota. The FASEB Journal. 2022; 36: e22043.

[27] Yamazaki S, Numano R, Abe M, Hida A, Takahashi R, Ueda M, et al. Resetting central and peripheral circadian oscillators in transgenic rats. Science. 2000; 288: 682–685.

[28] Nishide SY, Honma S, Nakajima Y, Ikeda M, Baba K, Ohmiya Y, et al. New reporter system for Per1 and Bmal1 expressions revealed self-sustained circadian rhythms in peripheral tissues. Genes Cells. 2006; 11: 1173–1182.

[29] Nishide S, Honma S, Honma K. The circadian pacemaker in the cultured suprachiasmatic nucleus from pup mice is highly sensitive to external perturbation. European Journal of Neuroscience. 2008; 27: 2686–2690.

[30] Nishide S, Hashimoto K, Nishio T, Honma K, Honma S. Organ-specific development characterizes circadian clock gene Per2 expression in rats. American Journal of Physiology-Regulatory, Integrative and Comparative Physiology. 2014; 306: R67–R74.

[31] Yoshihara T, Otsuki Y, Yamazaki A, Honma S, Yamasaki Y, Honma K. Maternal deprivation in neonatal rats alters the expression of circadian system under light–dark cycles and restricted daily feeding in adulthood. Physiology & Behavior. 2005; 85: 646–654.