الفهرس 
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Abstract
Dental caries is a multi-factorial disease. It affects all races, ages, and socioeconomic groups. In the domain of pediatric dentistry, early childhood caries (ECC) is a well-known challenge. Being cognizant of the possible contributing risk factors is absolutely imperative to fill the gaps in our knowledge and to create a complete model of caries etiology.
S.mutans has been known as the key player in the caries process, while the cariogenicity of C.albicans has been recently proposed. Scarce literature was available on salivary and dentinal carriage patterns of C.albicans among Egyptian children. Therefore, the present study aimed to examine the salivary and dentinal levels of S.mutans and C.albicans among a group of Egyptian children and to assess their association with dental caries experience. Moreover, in an attempt to explore one of the virulence attributes of C.albicans, the expression levels of C.albicans Sap1 and 2 were investigated.
The current study was an observational case-control study. Sixty Egyptian children were recruited from the Outpatient Clinic of the Pediatric Dentistry and Dental Public Health Department-Faculty of Dentistry-Ain Shams University. Eligible children were selected according to certain inclusion and exclusion criteria. The ethical aspects of the research, proposed by the ethical committee of Faculty of Dentistry- Ain Shams University, were fulfilled.
Questionnaire interview was conducted. The questionnaire aimed at gathering data about some of the risk factors of dental caries, such as; socio demographic factors, dietary habits, and tooth brushing frequency.
Caries experience was recorded using dmft index for children in the primary dentition stage (≥3 to 6 years old) and deft/DMFT indices for those in the mixed dentition stage (≥6 to12 years old). Upon dental examination, children were equally assigned into 4 groups based on the presence/absence of dental caries and their age.
Mothers of the participants received oral health education about dental caries in general and ECC in specific. Moreover, they were handed educational brochures on ECC. Proper oral hygiene practices were demonstrated and its importance was explained for the children as well as their mothers.
Whole saliva samples were collected from all the participants, while carious dentin samples were collected from caries active children. All the samples were plated on modified mitis salivarius agar media (MSA), anaerobically incubated at 37°C for 72 hours to isolate S.mutans, which was then identified by colonial morphology and biochemical testing. Similarly, all the samples were plated on sabouroud dextrose agar media (SDA) and aerobically incubated at 37°C for 72 hours to isolate C.albicans. Preliminary identification, based on colony morphology and Gram staining, was confirmed by conventional PCR using C.albicans-specific primers. Furthermore, the expression levels of C.albicans Sap1 and Sap2 was assessed using real time PCR.
Colonies of S.mutans and C.albicans were counted on each plate and then multiplied by the appropriate dilution factor to yield the colony-forming units per milliliter of the original sample.
Based on the questionnaire results, maternal education and employment were the most common risk factors associated with childhood caries. In terms of child-attributed factors, the most common risk factors were, on demand feeding, frequent snacking, frequent intake of sugary food and sweets, and infrequent tooth brushing.
The microbiological analysis revealed the presence of S.mutans in all saliva and dentin samples obtained from caries active children. The proportion of children that harbored salivary S.mutans was significantly higher in ECC group than in the age-matched, caries free group. The same holds true for salivary C.albicans. On the other hand, none of the pre-mentioned microbes scored significant differences regarding their detection frequency, between dental caries group and their age-matched control group. Comparing the microbial detection in saliva and dentin of both caries active groups, C.albicans showed significant higher detection frequency only in saliva of ECC children
Regarding the microbial count, salivary S.mutans levels were significantly higher in caries active groups compared to their age- matched control groups. As regards C.albicans, salivary C.albicans levels were significantly higher only in ECC group, compared to its age-matched control group.
In caries-active children, salivary and dentinal levels of S.mutans were associated with dmft and deft scores. C.albicans levels in saliva, but not in dentin, were associated with dmft scores. In children with dental caries, no association was found between C.albicans count, neither in saliva nor in dentin, and deft scores. Furthermore, there was no association between the microbial counts and DMFT scores.
Real time PCR analysis revealed that, the expression levels of C.albicans Sap1 were significantly higher in saliva samples of ECC children than those of caries free children in the respective control group. In contrast, the expression levels of Sap2 between the pre-mentioned groups showed no significant difference. Meanwhile, no significant difference was found between children with dental caries and their age-matched control regarding C.albicans Sap1 and 2 expression levels neither in saliva nor in dentin.
Moreover, comparing ECC children with dental caries children, the expression levels of salivary and dentinal C.albicans Sap1 and 2 showed no significant difference except for Sap2 in dentin, which was significantly higher in ECC group.