Proteins in Whole Saliva during the First Year of Infancy

Salivary Protein and Electrolyte Profiles during Primary Teeth Eruption: A Cross-Sectional Study

This study aimed to assess the qualitative changes in the saliva during the process of primary teeth eruption. This cross-sectional study was conducted on 147 children from 2 to 48 months, of which 49 were in group A (no erupted primary teeth), 53 were in group B (at least one active erupting primary tooth), and 45 were in group C (eruption of all 20 primary teeth was completed). Salivary proteins were evaluated by sodium dodecyl sulfate electrophoresis with polyacrylamide gel, while the concentrations of salivary sodium, potassium, chloride, and calcium ions were evaluated by ion selective electrodes. The data were analyzed using ANOVA and Bonferroni tests (alpha = 0.05). The concentration of proteins with molecular weights of 20-30 KDa was significantly higher in group A, and it gradually decreased with age. The concentration of proteins with molecular weights of 50-60 KDa in group B was significantly lower than those of groups A and C. The calcium ion concentration in group A was significantly higher than that of the other groups. The concentration of potassium ions was minimal in group C. The proteins and electrolyte profiles of the subjects' saliva changed in the process of primary tooth eruption. The highest concentrations of proteins such as statherin, histatin, P-B peptide, and cystatin and the lowest concentrations of proteins such as amylase were present in group B.

NMR-Based Metabolomics Demonstrates a Metabolic Change during Early Developmental Stages from Healthy Infants to Young Children

The present study aims to identify the salivary metabolic profile of healthy infants and young children, and to correlate this with age, salivary gland maturation, and dentition. Forty-eight children were selected after clinical evaluation in which all intraoral structures were examined. Total unstimulated saliva was collected, and salivary metabolites were analyzed by 1H Nuclear Magnetic Resonance (NMR) at 25 °C. Partial least squares discriminant analysis (PLS-DA), orthogonal PLS-DA (O-PLS-DA), and univariate analysis were used, adopting a 95% confidence interval. The study showed a distinct salivary metabolomic profile related to age and developmental phase. The saliva of children in the pre-eruption teeth period showed a different metabolite profile than that of children after the eruption. However, more evident changes were observed in the saliva profile of children older than 30 months. Alanine, choline, ethanol, lactate, and sugar region were found in higher levels in the saliva of patients before 30 months old. Acetate, N-acetyl sugar, butyrate, caproate, creatinine, leucine, phenylalanine, propionate, valine, succinate, and valerate were found to be more abundant in the saliva of children after 30 months old. The saliva profile is a result of changes in age and dental eruption, and these findings can be useful for monitoring the physiological changes that occur in infancy.

Analysis of salivary proteomic biomarkers for the surveillance of changes in high-risk status of early childhood caries

Background

Early childhood caries is an urgent public health concern. The aim of this study was to investigate salivary proteomic biomarkers for the surveillance of changes in the high-risk status of early childhood caries. The process involves the screening of specific salivary peptides that were differentially expressed only under dynamic changes in individual caries status.

Methods

Stimulated whole saliva samples were collected from 28 kindergarten children aged 3–4 years in Beijing at baseline and 3 months and 6 months after baseline. A total of 68 samples were collected. In terms of their caries status and progress during the observation period, participants were divided into 3 groups; 7 in the non-caries recurrence group, 6 in the caries recurrence group, and 15 in the healthy control group. Salivary peptides that exhibited no significant differences in cross-sectional comparisons between different groups of caries status but only expressed differentially along with dynamic changes of individual caries were screened using the technique of magnetic beads combined with matrix-assisted laser desorption-ionization time-of-flight mass spectrometry (MALDI-TOF MS). The technique of liquid chromatography-electrospray ionization-tandem mass spectrometry (LC-ESI-MS/MS) was employed to identify the proteins from which these peptides were derived.

Results

We found two salivary peptides differentially expressed only under dynamic changes in individual caries status in the above comparisons; mass-to-charge ratio (m/z) values of the two peptides were 1045.9 and 2517.6, respectively (P < 0.05). Principal component analysis (PCA) and the decision tree model based on these two peptides showed an acceptable distinguishing ability for changes in the high-risk status of early childhood caries. The source proteins of the two peptides with m/z values of 1045.9 and 2517.6 were identified as submandibular gland androgen regulatory protein 3B (SMR-3B) and mucin-7, respectively.

Conclusions

Two proteins in children’s saliva, namely SMR-3B and mucin-7, have the potentiality to serve as candidate biomarkers for dynamic surveillance of changes in high-risk status of early childhood caries.

Estimation of salivary proteins in early childhood caries before and after treatment using gel electrophoresis

BACKGROUND

Saliva being an important biological fluid of our body contains both specific and nonspecific protective factors which form an integral part of our immune system. Salivary proteins play a substantial role in protecting humans against infection. Their level in oral cavity is subject to constant variations which is dependent on various factors.

PURPOSE

The purpose of the study was to compare the levels of salivary proline-rich proteins (PRPs), glycoproteins, amylase bands, and salivary pH in children with early childhood caries before and after treatment using gel electrophoresis.

MATERIALS AND METHODS

The whole salivary pH, mean protein concentrations, and electrophoretic profiles of the salivary proteins were measured using sodium dodecylsulfate-polyacrylamide gel electrophoresis in both pre- and posttreatment groups. Statistical analysis was done using Statistical Package for Social Sciences (SPSS) version 15.0 software. Chi-square test and independent t-test were used to further compare the results.

RESULTS

The results were statistically significant in all the groups. There was variation in pre- and posttreatment values seen.

CONCLUSION

Salivary proteins (glycoproteins, PRPs, and amylase) establish an imperative defense mechanism as antimicrobial agents.

In vitro models of gut digestion across childhood: current developments, challenges and future trends

The human digestion is a multi-step and multi-compartment process essential for human health, at the heart of many issues raised by academics, the medical world and industrials from the food, nutrition and pharma fields. In the first years of life, major dietary changes occur and are concomitant with an evolution of the whole child digestive tract anatomy and physiology, including colonization of gut microbiota. All these phenomena are influenced by child exposure to environmental compounds, such as drugs (especially antibiotics) and food pollutants, but also childhood infections. Due to obvious ethical, regulatory and technical limitations, in vivo approaches in animal and human are more and more restricted to favor complementary in vitro approaches. This review summarizes current knowledge on the evolution of child gut physiology from birth to 3 years old regarding physicochemical, mechanical and microbial parameters. Then, all the available in vitro models of the child digestive tract are described, ranging from the simplest static mono-compartmental systems to the most sophisticated dynamic and multi-compartmental models, and mimicking from the oral phase to the colon compartment. Lastly, we detail the main applications of child gut models in nutritional, pharmaceutical and microbiological studies and discuss the limitations and challenges facing this field of research.

Inhibition of Influenza A Virus by Human Infant Saliva

Innate antiviral factors in saliva play a role in protection against respiratory infections. We tested the anti-influenza virus activities of saliva samples taken from human infants, 1–12 months old, with no history of prior exposure to influenza. In contrast to the inhibitory activity we observed in mouse and ferret saliva, the activity of human infant saliva was complex, with both sialic acid-dependent and independent components, the proportion of which differed between individuals. Taken as a whole, we showed that the major anti-influenza activity of infant saliva is acquired over the first year of life and is associated with sialic acid-containing molecules. The activity of sialic acid-independent inhibitors was lower overall, more variable between individuals, and less dependent on age. The results show that the saliva of very young infants can provide a degree of protection against influenza, which may be critical in the absence of adaptive immunity.

Group A Streptococcus-Mediated Host Cell Signaling

In the past decade, the field of the cellular microbiology of group A Streptococcus (S. pyogenes) infection has made tremendous advances and touched upon several important aspects of pathogenesis, including receptor biology, invasive and evasive phenomena, inflammasome activation, strain-specific autophagic bacterial killing, and virulence factor-mediated programmed cell death. The noteworthy aspect of S. pyogenes-mediated cell signaling is the recognition of the role of M protein in a variety of signaling events, starting with the targeting of specific receptors on the cell surface and on through the induction and evasion of NETosis, inflammasome, and autophagy/xenophagy to pyroptosis and apoptosis. Variations in reports on S. pyogenes-mediated signaling events highlight the complex mechanism of pathogenesis and underscore the importance of the host cell and S. pyogenes strain specificity, as well as in vitro/in vivo experimental parameters. The severity of S. pyogenes infection is, therefore, dependent on the virulence gene expression repertoire in the host environment and on host-specific dynamic signaling events in response to infection. Commonly known as an extracellular pathogen, S. pyogenes finds host macrophages as safe havens wherein it survives and even multiplies. The fact that endothelial cells are inherently deficient in autophagic machinery compared to epithelial cells and macrophages underscores the invasive nature of S. pyogenes and its ability to cause severe systemic diseases. S. pyogenes is still one of the top 10 causes of infectious mortality. Understanding the orchestration of dynamic host signaling networks will provide a better understanding of the increasingly complex mechanism of S. pyogenes diseases and novel ways of therapeutically intervening to thwart severe and often fatal infections.

MUC7 Level As A New Saliva Risk Factor For Dental Caries In Adult Patients

Purpose: Data currently available indicate the significance of salivary mucins MUC5B and MUC7 in the protection of teeth against caries. Our study aimed to determine the relationship between dental caries in adults and levels of MUC5B and MUC7. Methods: The studies were conducted on 45 adult subjects selected on the basis of dental examination and calculation of the DMFT (Decayed, Missing, and Filled Teeth) index. Among these patients, two research groups were distinguished: group 1 included 19 caries-free subjects (DMFT = 0); and group 2 included 26 patients with severe caries (DMFT > 13.9). Samples of whole unstimulated saliva were collected and centrifuged. MUC5B and MUC7 content in saliva supernatant were estimated using an enzyme-linked immunosorbent sandwich assay (ELISA). Analysis of the obtained data receiver operating characteristic (ROC) curves was employed to define relationships between the contents of the studied mucins and the detected dental caries. Results: In subjects from group 1, the mean level of MUC5B amounted to 0.63 ± 0.35 ng/ml and this was significantly higher than the concentration of mucin in patients of group 2, which amounted to 0.38 ± 0.32 ng/ml (p = 0.023). The mean level of MUC7 amounted to 5.47 ± 1.18 ng/ml and this was significantly higher than the level of the mucin in group 2, which was 1.39 ± 0.86 ng/ml (p< 0.0001). In parallel, a relationship was detected between levels of the examined mucins and manifestation of dental caries. For MUC7, the optimal cut-off value was obtained (i.e. corresponding to 100% sensitivity and specificity), amounting to 2.5 ng/ml for the detection of dental caries risk. Conclusions: Development of dental caries is linked to reduced concentrations of MUC5B and MUC7. The level of MUC7 may represent a significant parameter clinically suitable for evaluation of disease risk.

In Vitro Identification of Histatin 5 Salivary Complexes

With recent progress in the analysis of the salivary proteome, the number of salivary proteins identified has increased dramatically. However, the physiological functions of many of the newly discovered proteins remain unclear. Closely related to the study of a protein’s function is the identification of its interaction partners. Although in saliva some proteins may act primarily as single monomeric units, a significant percentage of all salivary proteins, if not the majority, appear to act in complexes with partners to execute their diverse functions. Coimmunoprecipitation (Co-IP) and pull-down assays were used to identify the heterotypic complexes between histatin 5, a potent natural antifungal protein, and other salivary proteins in saliva. Classical protein–protein interaction methods in combination with high-throughput mass spectrometric techniques were carried out. Co-IP using protein G magnetic Sepharose TM beads suspension was able to capture salivary complexes formed between histatin 5 and its salivary protein partners. Pull-down assay was used to confirm histatin 5 protein partners. A total of 52 different proteins were identified to interact with histatin 5. The present study used proteomic approaches in conjunction with classical biochemical methods to investigate protein–protein interaction in human saliva. Our study demonstrated that when histatin 5 is complexed with salivary amylase, one of the 52 proteins identified as a histatin 5 partner, the antifungal activity of histatin 5 is reduced. We expected that our proteomic approach could serve as a basis for future studies on the mechanism and structural-characterization of those salivary protein interactions to understand their clinical significance.

Salivary protein profiles are linked to bitter taste acceptance in infants

Based on recent studies in adult subjects, saliva composition is increasingly considered as a physiological factor contributing to taste sensitivity or acceptance. In order to evaluate a possible link between salivary protein composition and taste acceptance in infants, 73 infants participated longitudinally in taste acceptance tests and donated saliva at the age at 3 and 6 months. Intake ratios, reflecting acceptance of a taste solution relative to water were calculated for the five basic tastes. Salivary proteins were separated by one-dimensional electrophoresis and bands were semi-quantified by image analysis. Partial least square (PLS) regression analyses were performed for each taste at both ages to explain intake ratios by band intensities. Bitterness acceptance in the younger infants was unique in the sense that salivary protein profiles could partly predict bitter taste acceptance. At that age, infants were on average indifferent to the 0.18-M urea solution, but great variability in acceptance was observed. The six bands considered as the best predictors for bitterness acceptance were identified by MALDI-TOF mass spectrometry. Higher abundance of bands containing secretory component, zinc-α-2-glycoprotein and carbonic anhydrase 6 was associated to a lower bitterness acceptance, while higher abundance of bands containing lactoperoxidase, prolactin-inducible protein and S-type cystatins was associated to a higher bitterness acceptance. In a second stage, S-type cystatin abundance was measured by Western blotting in order to tentatively confirm this particular finding in an independent group of 22 infants. Although not reaching statistical significance, probably due to a relatively small sample size, it was again observed that cystatin abundance was higher in infants accepting more readily the bitter solution over water.

CONCLUSION

saliva protein composition may contribute to bitter taste acceptance in the younger infants.

Characterization and in vitro properties of oral lactobacilli in breastfed infants

Background

Lactobacillus species can contribute positively to general and oral health and are frequently acquired by breastfeeding in infancy. The present study aimed to identify oral lactobacilli in breast and formula-fed 4 month-old infants and to evaluate potential probiotic properties of the dominant Lactobacillus species detected. Saliva and oral swab samples were collected from 133 infants who were enrolled in a longitudinal study (n=240) examining the effect of a new infant formula on child growth and development. Saliva was cultured and Lactobacillus isolates were identified from 16S rRNA gene sequences. Five L. gasseri isolates that differed in 16S rRNA sequence were tested for their ability to inhibit growth of selected oral bacteria and for adhesion to oral tissues. Oral swab samples were analyzed by qPCR for Lactobacillus gasseri.

Results

43 (32.3%) infants were breastfed and 90 (67.7%) were formula-fed with either a standard formula (43 out of 90) or formula supplemented with a milk fat globule membrane (MFGM) fraction (47 out of 90). Lactobacilli were cultured from saliva of 34.1% breastfed infants, but only in 4.7% of the standard and 9.3% of the MFGM supplemented formula-fed infants. L. gasseri was the most prevalent (88% of Lactobacillus positive infants) of six Lactobacillus species detected. L. gasseri isolates inhibited Streptococcus mutans binding to saliva-coated hydroxyapatite, and inhibited growth of S. mutans, Streptococcus sobrinus, Actinomyces naeslundii, Actinomyces oris, Candida albicans and Fusobacterium nucleatum in a concentration dependent fashion. L. gasseri isolates bound to parotid and submandibular saliva, salivary gp340 and MUC7, and purified MFGM, and adhered to epithelial cells. L. gasseri was detected by qPCR in 29.7% of the oral swabs. Breastfed infants had significantly higher mean DNA levels of L. gasseri (2.14 pg/uL) than infants fed the standard (0.363 pg/uL) or MFGM (0.697 pg/uL) formula.

Conclusions

Lactobacilli colonized the oral cavity of breastfed infants significantly more frequently than formula-fed infants. The dominant Lactobacillus was L. gasseri, which was detected at higher levels in breastfed than formula-fed infants and displayed probiotic traits in vitro.

Age- and sex-associated differences in the glycopatterns of human salivary glycoproteins and their roles against influenza A virus

Recent studies have elucidated that expression of certain glycoproteins in human saliva is increased or decreased according to age; meanwhile, human saliva may inhibit viral infection and prevent viral transmission. However, little is known about the age- and sex-associated differences in the glycopatterns of human salivary glycoproteins and their significant roles against influenza A virus (IVA). Here, we investigate the glycopatterns of human salivary glycoproteins with 180 healthy saliva samples divided into six age/sex groups using lectin microarrays and fabricate saliva microarrays to validate the terminal carbohydrate moieties of glycoproteins in individual saliva samples. Furthermore, we assess the inhibiting and neutralizing activity of saliva against two strains of influenza A (H9N2) virus. We find that seven lectins (e.g., MAL-II and SNA) show significant age differences in both females and males, and seven lectins (e.g., WFA and STL) show significant sex differences in children, adults and elderly people. Interestingly, we observe that elderly individuals have strongest resistance to IVA partly by presenting more terminal α2-3/6-linked sialic acid residues in their saliva, which bind with the influenza viral hemagglutinations. We conclude that age- and sex-associated differences in the glycopatterns of human salivary glycoproteins may provide pivotal information to help understand some age related diseases and physiological phenomena.

The scientific exploration of saliva in the post-proteomic era: from database back to basic function

The proteome of human saliva can be considered as being essentially completed. Diagnostic markers for a number of diseases have been identified among salivary proteins and peptides, taking advantage of saliva as an easy-to-obtain biological fluid. Yet, the majority of disease markers identified so far are serum components and not intrinsic proteins produced by the salivary glands. Furthermore, despite the fact that saliva is essential for protecting the oral integuments and dentition, little progress has been made in finding risk predictors in the salivary proteome for dental caries or periodontal disease. Since salivary proteins, and in particular the attached glycans, play an important role in interactions with the microbial world, the salivary glycoproteome and other post-translational modifications of salivary proteins need to be studied. Risk markers for microbial diseases, including dental caries, are likely to be discovered among the highly glycosylated major protein species in saliva. This review will attempt to raise new ideas and also point to under-researched areas that may hold promise for future applicability in oral diagnostics and prediction of oral disease.

Human infant saliva peptidome is modified with age and diet transition

In order to describe developmental changes in human salivary peptidome, whole saliva was obtained from 98 infants followed longitudinally at 3 and 6months of age. Data on teeth eruption and diet at the age of 6months were also recorded. Salivary peptide extracts were characterised by label-free MALDI-MS. Peptides differentially expressed between the two ages, and those significantly affected by teeth eruption or introduction of solid foods were identified by MALDI TOF-TOF and LC ESI MS-MS. Out of 81 peaks retained for statistical analysis, 26 were overexpressed at the age of 6months. Exposure to solid foods had a more pronounced effect on profiles (overexpression of nine peaks) than teeth eruption (overexpression of one peak). Differential peaks corresponded to fragments of acidic and basic PRPs, statherin and histatin. Comparison with existing knowledge on adult saliva peptidome revealed that proteolytic processing of salivary proteins is qualitatively quite comparable in infants and in adults. However, age and diet are modulators of salivary peptidome in human infants.

An assessment of the cariogenicity of commonly used infant milk formulae using microbiological and biochemical methods

Dental caries is an important dental public health problem and is the most prevalent oral disease among children in the world. The present study was undertaken to evaluate and comparatively assess the change in plaque and salivary pH after ingestion of various commercially available infant milk formulae, and also to evaluate and comparatively assess plaque and salivary samples for change in colony-forming units of Streptococcus mutans caused due to their ingestion. 36 children in the age group of 1-2 years were fed with infant milk formulae three times a day for 21 days and results quantified. The present study revealed a highly significant increase in the levels of colony-forming units of Streptococcus mutans in both the plaque and salivary samples when assessed at baseline and after a period of 21 days, with the t value being 11.92 for the plaque samples and 11.66 for the salivary samples. It was also observed that all the test samples produced significantly lower plaque pH values than pre-feed pH. Based upon this study, further evaluation of the cariogenicity of infant milk formulae is recommended.

Quantitation of SPLUNC1 in saliva with an xMAP particle-based antibody capture and detection immunoassay

The short palate lung and nasal epithelial clone 1 (SPLUNC1) protein may be differentially expressed in oral infections, oral inflammatory disorders, or oral malignancies and may be involved in innate immune responses in the oral cavity. However, the actual concentration of SPLUNC1 in saliva has not previously been determined. In this study, we determined the concentrations of SPLUNC1 in saliva using a particle-based antibody capture and detection immunoassay. A commercial goat anti-rhSPLUNC1 polyclonal antibody (AF1897) was linked to fluorescent polystyrene microspheres and used as the capture antibody. A commercial mouse IgG2b anti-rhSPLUNC1 monoclonal antibody (MAB1897) was biotinylated and used as the detection antibody. Western blot and 2-dimensional fluorescence difference gel electrophoresis (2-D DIGE) analysis of immunoprecipitated rhSPLUNC1 and SPLUNC1 from saliva were used to show that the capture AF1897 and detection MAB1897 antibodies both recognized SPLUNC1. Protein concentrations in saliva from 20 subjects ranged from 0.9 to 23.9mg/ml; SPLUNC1 concentrations ranged from 34.7ng/ml to 13.8μg/ml; and SPLUNC concentrations normalized per mg of total salivary protein ranged from 4.7ng/ml to 5.3μg/ml. These results show that SPLUNC1 is detected in saliva in a variety of concentrations. This immunoassay may prove to be useful in determining the concentration of SPLUNC1 in saliva for assessing its role in the pathogenesis of oral infections, oral inflammatory disorders, or oral malignancies.

Resemblance of salivary protein profiles between children with early childhood caries and caries-free controls

Although prolonged bottle feeding with a carbohydrate-rich content is commonly agreed to be the main etiologic factor for early childhood caries (ECC), in recent years additional endogenous factors, including the composition of saliva, have been suspected as predisposing factors in children for the development of this aggressive form of dental caries. As a basis for investigating the putative involvement of salivary proteins in the etiology of ECC, a qualitative comparison of major salivary protein profiles between children with ECC and caries-free controls was performed. Saliva was collected from 30 children with ECC and, after separation by sodium dodecyl sulphate-polyacrylamide gel electrophoresis, was compared with saliva from 20 caries-free controls for the general composition of proteins by means of silver staining, glycoprotein staining, and lectin blotting. Gels and blots were analysed using densitometry, and the protein-banding patterns resulting from the individuals' samples were compared by image analysis for the presence or absence of protein bands. Dendrograms obtained after comparison of all samples showed a high degree of similarity for the experimental groups. In summary, the results attest a uniform expression of the major protein components in children's saliva, regardless of the clinical manifestation of ECC, and thus pave the way for further detailed investigations of more subtle differences in the salivary proteome.

Identification of glycoprotein receptors within the human salivary proteome for the lectin-like BabA and SabA adhesins of Helicobacter pylori by fluorescence-based 2-D bacterial overlay

Because gastric infection by Helicobacter pylori takes place via the oral route, possible interactions of this bacterium with human salivary proteins could occur. By using modified 1- and 2-D bacterial overlay, binding of H. pylori adhesins BabA and SabA to the whole range of salivary proteins was explored. Bound salivary receptor molecules were identified by MALDI-MS and by comparison to previously established proteome maps of whole and glandular salivas. By use of adhesin-deficient mutants, binding of H. pylori to MUC7 and gp-340 could be linked to the SabA and BabA adhesins, respectively, whereas binding to MUC5B was associated with both adhesins. Binding of H. pylori to the proline-rich glycoprotein was newly detected and assigned to BabA adhesin whereas the SabA adhesin was found to mediate binding to newly detected receptor molecules, including carbonic anhydrase VI, secretory component, heavy chain of secretory IgA1, parotid secretory protein and zinc-alpha(2)-glycoprotein. Some of these salivary glycoproteins are known to act as scavenger molecules or are involved in innate immunity whereas others might come to modify the pathogenetic properties of this organism. In general, this 2-D bacterial overlay technique represents a useful supplement in adhesion studies of bacteria with complex protein mixtures.

Antibacterial effect of ozone on cariogenic bacterial species

OBJECTIVE

The aim was to evaluate the antibacterial effect of ozone on cariogenic bacterial species with and without the presence of saliva and a possible effect on the salivary proteins.

METHODS

Suspensions of Actinomyces naeslundii (ACTCC 12104(T)), Lactobacilli casei (N CTC 151) and Streptococcus mutans (NCTC 10449), in salt buffer or in saliva, were exposed to ozone gas delivered by the ozone generator Healozone 2130C. Aliquots of the suspensions were taken after 10, 30 and 60s ozone exposures and cultivated on agar plates. Initial number of bacteria per ml was 8.0 x 10(7) (SD 2.2 x 10(7)) (A. naeslundii), 1.0 x 10(8) (SD 3.1 x 10(6)) (L. casei) and 1.0 x 10(8) (SD 7.0 x 10(5)) (S. mutans), respectively. The proteins were separated by SDS electrophoresis and visualized by silver staining.

RESULTS

In salt buffer 92%, 73% and 64% of the initial numbers of A. naeslundii, S. mutans and L. casei, respectively, were killed already after 10s ozone exposure, while approximately 99.9% of the bacteria were dead after a 60s exposure. After 10 and 30s, but not after 60s exposure to ozone, S. mutans and L. casei were less efficiently killed in saliva compared to the salt buffer. Various saliva proteins were degraded by ozone after a 60s exposure.

CONCLUSIONS

The cariogenic species S. mutans, L. casei and A. naeslundii were almost eliminated following 60s of ozone treatment. This killing was reduced in the presence of saliva although increasing the ozone application time to 60s overcame these reductants in saliva. Detection of altered salivary proteins indicates that saliva components constitute additional targets for ozone.

Tensile strength and durability of bovine dentin

This study investigated the effects of thermal cycling on the tensile strength of dentin. Bovine dentin were divided into 10 groups, which were then subjected to various conditions: intact after preparation, thereby serving as a control; heating in boiling water for 45 minutes; 10,000 thermal cycles in water; 10,000 thermal cycles in PBS; storage in water at 5, 23, or 55 degrees C for two weeks; and storage in PBS at 5, 23, or 55 degrees C for two weeks. Subsequently, bovine dentin were trimmed into dumbbell-shaped specimens and the tensile test performed in distilled water at 37 degrees C. Mean tensile strengths were compared statistically by one-way ANOVA and Fisher's PLTD test (p<0.05). Fracture surfaces were observed by scanning electron microscopy, and reliability of the results was analyzed with Weibull distribution. Tensile strength did not significantly change after thermal cycling or storage in water and PBS at all temperatures tested (71.2-77.0 MPa) but decreased after treatment with boiling water (65.5 MPa).

Ontogeny of salivary epidermal growth factor and necrotizing enterocolitis

OBJECTIVE

To examine the ontogeny of salivary epidermal growth factor (sEGF) in premature infants and to determine the relation of sEGF to the development of necrotizing enterocolitis (NEC).

STUDY DESIGN

Salivary EGF was prospectively measured in 327 infants with gestational ages from 23 weeks to term. Infants of < or = 32 weeks' gestation (n = 261) were followed with weekly sEGF measurements through 3 weeks of life. Multivariable regression analyses were used to determine variables significantly related to sEGF levels and to identify predictors of NEC.

RESULTS

Over the first 3 weeks of life, sEGF increased across gestational age and postnatal age categories. In multivariable models, gestational age was a significant predictor of sEGF levels (P < .009). In a cohort of 27 infants who had NEC, gestational age, race, and changes in sEGF levels between weeks of life 1 and 2 were predictive of the development of NEC. These infants had lower sEGF at week 1 and greater increases from week 1 to week 2 compared with infants without NEC.

CONCLUSIONS

There is a positive relation between sEGF levels and gestational age. Patterns of sEGF levels over the first 2 weeks of life were significantly related to development of NEC in very low birth weight infants.