Dental caries is one of the most prevalent human infectious diseases affecting life style and genetic factors. The skewed distribution of caries in the Western populations and its weak association with traditional life style factors,
Mucins are vital components of the mucous layers covering the epithelial surfaces of the human body. In the oral cavity, mucins are secreted by submandibular and sublingual glands, and various minor salivary glands, but not by the parotid glands. Mucins constitute the third most abundant group of proteins in saliva and form various complexes with other salivary proteins, thereby modulating their activities. Two structurally distinct mucins have been identified in human saliva: high-molecular weight (MG1) and the low-molecular weight (MG2) mucins [2].
The human
The exploitation of mucin molecules for diagnostics is gaining increasing interest in a variety of disease conditions [3]. A recent study has suggested that genetic polymorphisms, which can alter mucin gene expression, have been associated with mucinrelated diseases [5]. While no studies have been performed on the MG2 polymorphism for dental caries, the potential of these molecules about dental caries cannot be ignored and will likely be subjected to further exploration.
To date, the relationship between the
The study included 24 dental students with caries aged between 18 to 23 years (mean age 20.2 ± 1.2) and 20 dental students without caries aged between 19 to 26 years (mean age 21.95 ± 2.2). Forty-four healthy dentistry students were enrolled in this study, 24 of them (aged between 18 to23 years, mean age 20.2 ± 1.2) were classified to have carries [decayed, missing, filled-teeth (DMFT)=5.6] according to the World Health Organization (WHO) criteria, and 20 of them (aged between 19 to 26, mean age 21.95 ± 2.2) were caries- free (DMFT=0). Inclusion criteria for subjects with caries and without caries were as follows; no oral complains, good oral hygiene, absence of smoking and drinking habits, no systemic diseases, no drug abuse. Exclusion criteria was unwillingness to participate in the study. The subjects signed an informed consent form to participate in this study.
One experienced dentist examined all subjects for their adherence to inclusion criteria. The WHO criteria were used for DMFT [6]. The oral hygiene and gingival status were assessed using the simplified oral hygiene index (OHI-S) and gingival index (GI) [7]. A structured questionnaire was used to collect data on oral hygiene habits (frequency of tooth brushing, use of dental floss), professional counseling on oral health and hygiene, and the presence of gingival bleeding. All subjects had good oral health and had regular dental care.
Fasting unstimulated whole saliva samples were collected at the same time of day (between 08:30 and 11:00 am) for a 1-week period by the same researcher in all cases. Before saliva collection, the mouth was rinsed with distilled water. Subsequently, saliva was allowed to accumulate on the floor of the mouth and the subjects were instructed to spit into the test tubes. During the saliva collection, the participants stayed in a relaxed position with their heads bent forward. Each saliva collection period was 10 minutes long. Immediately after collection, saliva volume was measured and then salivary flow rate calculated as mL/min. Saliva samples were stored at –20 °C until used.
The temperature of the saliva samples was raised from –24 °C to 4 °C and kept for an hour. After thawing, they were centrifuged and supernatants were used for salivary analysis. Total protein level was determined by the method of Lowry
The Marmara University Ethics Committee approved the study protocol, and written informed consent was obtained from all participants. DNA was extracted from peripheral blood cells by using High Pure polymerase chain reaction (PCR) Template Preparation Kit (Roche Diagnostics Deutschland GmbH, Mannheim, Germany) according to the manufacturer’s instructions. Isolated DNA samples were kept at –20 °C if not studied on the same day. The
The significance in the statistical analyses between groups was assessed using the χ2 test [Statistical Package for the Social Sciences (SPSS) 10.0 for Windows; SPSS Inc., Chicago, IL, USA]. Relationships yielding
Simplified oral hygiene index and GI were not significantly different between the two groups. Salivary pH, flow rate, buffering capacity and total protein levels were also not significantly different between the young adults with caries (DMFT = 5.62) and without caries (DMFT = 0) (p >0.05). Table 1 lists the values of these markers.
Mean levels of all parameters, and
Parameters | Group With No Caries ( | Group With Caries ( | |
---|---|---|---|
Simplified oral hygiene index | 0.14 ± 0.008 | 0.15 ± 0.011 | 0.605 |
Gingival index | 0.017 ± 0.008 | 0.02 ± 0.009 | 0.507 |
pH | 7.02 ± 0.41 | 7.17 ± 0.35 | 0.292 |
Salivary flow rate (mL/min.) | 0.48 ± 0.22 | 0.52 ± 0.24 | 0.577 |
Salivary buffering capacity | 1.63 ± 0.32 | 1.50 ± 0.29 | 0.174 |
Salivary total protein (mg/dL) | 131.00 ± 48.00 | 132.00 ± 49.00 | 0.871 |
Results are presented as mean ± SD (standard deviation).
No new variants were observed in 44 subjects in the N-terminal coding region of the
Mucins coat the gastrointestinal, genito-urinal and respiratory tracts, as well as the oral cavity. In the oral cavity, they have a variety of functions such as lubricating and protecting the oral cavity and providing a nonspecific immune defense [10].
In our cohort, OHI-S, GI, salivary pH, flow rate, buffering capacity and total protein levels were not significantly different between the two groups. These parameters have important effects on oral hygiene, and also for dental caries. But in our study cohort, all of these parameters did not affect dental caries formation.
Low-molecular weight mucin contains 377 amino acids. The first 20 of these are located in the N-terminal domain and are very hydrophobic. It contains a central part, made of six tandem repeats of 23 amino acids that are rich in proline and hydroxylated amino acids, and having approximately 90-100 O-linked chains. A histatin-like domain with a leucine-zipper segment, followed by a moderately glycosylated region, constitute the N-terminal domain; a heavily glycosylated domain, and a second leucine-zipper segment for the C-terminal extremity. The distal regions of MUC7 do not exhibit any cysteine-rich domains, only two cysteine residues are present towards its N-terminal end. So far, MG2 has no sequence homology with any other mucins. The N-terminal region of the protein binds
Low-molecular weight mucin has been reported to interact with several strains of streptococci by promoting their agglutination [13]. The N-terminal region of MG2 has a broad-spectrum fungicidal and bactericidal activity
It was shown that a 20 kDa MG2 fragment, containing the N-terminal region, was present in the saliva and suggested that cleavage of MG2
In conclusion, the SNP detected in this study may be a specific polymorphism effecting the Turkish population. Further studies with a larger number of individuals are necessary in order to clarify our findings.