Fungicidal effect of human lactoferrin against Candida albicans.

Human lactoferrin (LF) in its iron-free state (apo LF), killed Candida albicans in a time- and dose-dependent way. The lethal effect was stronger at pH 7.0 than at pH 5.5 and maximum inhibition at neutral pH was achieved in 25 min when the fungal cells were exposed to LF in 0.05 mM KCl at 37 degrees C. Fe(3+)-saturated LF had no fungicidal activity. Apo LF-mediated killing was also temperature-dependent with enhanced inhibition at higher temperatures (37 degrees, 42 degrees C). The presence of 1 mM D-glucose did not affect the candidacidal activity of apo LF but both phosphate and bicarbonate ions at physiological salivary concentrations completely blocked the anti-fungal effect. Therefore it seems unlikely that LF belongs to the major host defence factors against oral candidosis.

Saliva composition in Indian children with chronic protein-energy malnutrition.

The composition of paraffin-stimulated and unstimulated whole saliva was compared between two groups of 8-12-year-old Indian children-one group with severe to moderate chronic protein-energy malnutrition (PEM group) and an age- and sex-matched control group with normal protein status or mild PEM. The classification of PEM was based on anthropometric measurements compared with Indian standards. Stimulated saliva was analyzed for the following variables: electrolytes (Na+, K+, Ca2+, Cl-, and PO4(3-)), total protein, hexosamines, fucose, sialic acid, and amylase. Unstimulated saliva samples were analyzed for total protein, salivary and myeloperoxidase, thiocyanate, lactoferrin, lysozyme, a bacteria-agglutinating protein (BAGP), total IgG, total IgA, and specific anti-S. mutans IgA. The results show that the PEM group had a reduced secretion rate of stimulated but not unstimulated saliva. Further, the Ca2+ and Cl- concentrations in stimulated saliva were significantly lower in the PEM group compared with the control group, but the other electrolyte levels were similar. No differences were found in total protein concentration or glycoprotein bound carbohydrates in stimulated saliva between the two groups, but the quantity of total protein secreted per min was reduced by 20% in the PEM group. Significantly lower levels of lactoferrin, BAGP, and anti-S mutans IgA were found in unstimulated saliva from children in the PEM group, but significantly higher levels of total IgG. We conclude that children with severe or moderate PEM, who have reduced secretion rate, buffer capacity, lower Ca2+, and protein secretion in stimulated saliva, also have impaired immunological and agglutinating defense factors in unstimulated saliva.

Lysozyme enhances the inhibitory effects of the peroxidase system on glucose metabolism of Streptococcus mutans.

The combined effect of the salivary peroxidase system and lysozyme on the glucose uptake of Streptococcus mutans NCTC 10449 was investigated. The bacteria were grown to late-exponential phase, washed, re-suspended in buffer at pH6, and incubated with (1) 50 micrograms/mL lysozyme from human milk for 60 min; (2) 7-15 mumol/L hypothiocyanous acid/hypothiocyanite for 10 min; and (3) lysozyme for 60 min prior to addition of and incubation with hypothiocyanous acid/hypothiocyanite for 10 min. Glucose uptake was initiated by adding the bacterial suspensions to 10 mL of pre-warmed 50 mumol/L glucose containing 0.98 mumol/L D-(U-14C-)-glucose, and the mixture was incubated in a shaking water-bath at 37 degrees C. Samples were withdrawn at various time intervals, rapidly filtered through 0.45-microns membranes, washed with ice-chilled buffer, and the incorporated radioactivity determined. Lysozyme stimulated S. mutans glucose uptake slightly, but significantly inhibited S. rattus glucose metabolism. A 20-30% inhibition of radiolabeled glucose incorporation was observed with hypothiocyanous acid/hypothiocyanite alone. Incubation of the bacteria with lysozyme prior to addition of hypothiocyanous acid/hypothiocyanite containing peroxidase resulted in a total inhibition of the glucose uptake. In contrast, lysozyme in combination with hypothiocyanous acid/hypothiocyanite without peroxidase gave only a 30-50% inhibition. The addition of 5 mmol/L dithiothreitol after incubation with lysozyme and hypothiocyanous acid/hypothiocyanite eliminated the inhibition of the bacterial glucose uptake. The viability of S. mutans was not affected by treatment with any of the components used. Our results indicate that physiological concentrations of lysozyme and the salivary peroxidase system components have a synergistic effect which results in a significant inhibition of glucose metabolism by S. mutans.

Changes in whole saliva in patients with coeliac disease.

Many systemic diseases impair salivary flow rate and composition and therefore incite oral pathological processes. This study analyses the composition of whole saliva in patients with diagnosed coeliac disease (CD) and in healthy controls, and monitors possible changes in saliva composition after a short oral gluten challenge. Paraffin-stimulated whole saliva was collected from 128 CD patients and 55 healthy controls. In a separate study, paraffin-stimulated whole saliva samples were collected from 33 CD patients and 10 controls both before and 24 h after an oral mucosal and submucosal gluten challenge. No difference in saliva flow rate was observed, but total protein (P

Stimulated salivary flow rate and composition in asthmatic and non-asthmatic adults.

The number of decayed, missed and filled permanent teeth (DMFT), the degree of periodontal inflammation (Periodontal Status Index, PSI), stimulated salivary flow rate and the concentrations of total protein, lactoferrin, lysozyme, myeloperoxidase, salivary peroxidase, calcium, potassium, sodium and thiocyanate in whole saliva of 26 adult asthma patients were compared with those of 33 non-asthmatic controls. The saliva was also analysed for mutans streptococci, lactobacilli, total anaerobic flora and Candida spp. The mean PSI (p < 0.05; 95% confidence interval for the difference between means (95% CI) 2.47-25.30) was higher and the mean stimulated salivary flow rate (p < or = 0.05; 95% CI 0.57-0.55) was lower in the asthmatic group than in the control group. No differences were found between the groups in non-immune defense factors, except for myeloperoxidase. The myeloperoxidase concentrations were higher in asthmatics than in non-asthmatics (p < 0.05; 95% CI 4.4-134.0 ng/ml). No differences in microbial counts were found. It was concluded that stimulated salivary flow rates decrease while myeloperoxidase concentrations increase in adult asthmatic patients compared with non-asthmatic adults. The higher concentrations of myeloperoxidase are explained by a higher PSI in asthmatics.

Saliva flow rate, amylase activity, and protein and electrolyte concentrations in saliva after acute alcohol consumption.

OBJECTIVE: The aim of our study was to evaluate the effects of acute alcohol consumption on saliva secretion rate and selected salivary parameters in healthy nonalcoholic volunteers. STUDY DESIGN: Twenty-four volunteers (37.7 +/- 9.6 years, mean +/- SD) consumed 0.6 g or 0.7 g alcohol/kg of body weight (for women and men, respectively) in a soft drink. Saliva samples were collected, first (S0) before any alcohol was consumed, 45 minutes after consumption (S1) and, finally, 60 minutes after S1 (S2). Flow rates of both resting whole saliva and paraffin-stimulated (SWS) whole saliva were assessed. SWS was assessed for amylase, total protein, inorganic phosphate (PO4(3-)), sodium (Na+), potassium (K+), and calcium (Ca2+) content. RESULTS: SWS, but not resting whole saliva (in milliliters/minute), decreased significantly after consumption of alcohol. Amylase activity (P =.010) and the concentrations of Na+ (P =.000) and Ca2+ (P =.002) decreased significantly between S0 and S1. When SWS was analyzed for output, the total protein concentration (S0 to S1, P =.000; S0 to S2, P =.033) and amylase activity (S0 to S1, P =.000) decreased significantly. Further, the output of all the studied electrolytes decreased significantly as blood alcohol concentration increased. CONCLUSIONS: We conclude that acute alcohol consumption causes a decrease in SWS flow rate. The decrease in flow rate also results in impaired output of total protein and amylase, as well as in a decrease in the output of electrolytes.

Effects of the common cold and intranasal fluticasone propionate treatment on mucosal host defense assessed by human saliva.

OBJECTIVE: The purpose of this investigation was to study the effect of a potent topical steroid, fluticasone propionate, on patients with early signs and symptoms of the common cold. To characterize the mucosal inflammatory response, salivary defense factors and flow rate in these patients were analyzed. STUDY DESIGN: Forty patients with symptoms of the common cold were randomized into 2 groups to receive either high-dose fluticasone propionate (100 microg per nostril) or placebo 4 times daily for 6 days. Paraffin-stimulated whole saliva was collected on day 1 (before the onset of medication), day 7 (posttreatment), and day 21 (follow-up). RESULTS: Salivary flow rate, innate host defense factors, and total protein content were not affected by the common cold. IgA increased between day 7 and day 21 (P < or = .01; Student 2-tailed t test), and the relative proportions of salivary peroxidase and IgA increased on day 7 (P = .01) and day 21 (P= .05). In patients receiving fluticasone, saliva flow rate was lower on day 21 (P < or = .05) than on days 1 and 7. The innate salivary defense factors were not affected, but IgA increased both on day 7 (P < or = .001) and on day 21 (P < or = .001) in comparison with day 1. CONCLUSIONS: Of the oral mucosal defense factors, only IgA is activated during the common cold. Intranasally administrated fluticasone propionate does not have a suppressive effect on salivary antimicrobial capacity.

Salivary antimicrobial proteins and mutans streptococci in tonsillectomized children.

Whole saliva from 53 children who had been tonsillectomized when they were younger than 4 years old was analyzed for selected antimicrobial proteins and oral mutans streptococci 3-4 years after the operation. The results were compared with those from age- and gender-matched control children with no history of tonsillectomy. The salivary analyses comprised both immune (total IgA, IgG and IgM) and selected nonimmune (lactoferrin, myeloperoxidase, salivary peroxidase) antimicrobial proteins. Specific IgA and IgG antibodies against viral antigens (adeno-, cytomegalo-, respiratory syncytial- and Epstein-Barr-viruses) and against Streptococcus mutans cells were quantitated in both groups. The tonsillectomized children had statistically significantly higher concentrations of all immunoglobulin isotypes (P 0.001) as well as of lactoferrin (P less than 0.005), and myeloperoxidase (P less than 0.001) in saliva. However, no differences were found in the numbers of cariogenic mutans streptococci or in the total oral aerobic flora. In line with the streptococcal counts, no differences existed in anti-S. mutans IgA or IgG titers between the groups. Most antibodies against viruses, especially of IgG isotype, were significantly (P less than 0.001) higher in saliva of tonsillectomized children than in that of the controls. The results suggest that, within a long run, the humoral immune status of human saliva is not weakened by tonsillectomy. Also, mainly serum-derived antimicrobial proteins (myeloperoxidase, lactoferrin, IgG) exist in high concentrations in whole saliva after tonsillectomy.

Inhibition of Candida albicans by the Peroxidase/SCN-/H2O2 system.

Effects of the salivary peroxidase (SPO) system on the growth, glucose uptake and metabolic activities of oral bacteria are well documented but the effects on oral fungi are virtually unknown. Therefore, the viability of Candida albicans (ATCC 28366) exposed to the peroxidase/SCN-/H2O2 system was studied in sterilized saliva, in phosphate-buffered saline (PBS) and in potassium chloride. The growth of C. albicans in glucose-supplemented saliva was faster at pH 5.5 than at pH 7. The addition of the complete SPO (or lactoperoxidase) system to either sterilized saliva, KCl (50 microM) or PBS at pH 5.5 inhibited dose-dependently the viability of C. albicans in KCl, but no inhibition was found in PBS or saliva. Maximal inhibition was achieved in 2 h and with > 320 microM of peroxidase-generated HOSCN/OSCN-. However, physiological salivary concentrations of phosphate (> or = 1.0 mM) and PBS blocked the antifungal effect of HOSCN/OSCN-. The relative proportions of SCN- and H2O2 were critical to the antifungal effects. With 0.2 mM KSCN, a complete loss of viability was achieved, though the HOSCN/OSCN- concentrations did not exceed 100 microM. It is concluded that C. albicans is sensitive to HOSCN/OSCN- but salivary concentrations of phosphate block the antifungal effect of the peroxidase systems.

Effect of saliva composition on growth of Candida albicans and Torulopsis glabrata.

Candida albicans and Torulopsis glabrata are the most prevalent yeasts in humans. The majority harbor C. albicans in the oral cavity, but only a few develop oral candidiasis. We have sought a possible relationship between indigenous salivary constituents, including antimicrobial and nutritive factors, and the growth rate and/or viability of inoculated fungi in glucose-supplemented sterilized saliva. Stimulated whole saliva was collected from 30 healthy donors. Saliva samples were sterilized, supplemented with glucose and inoculated with C. albicans or T glabrata. After incubation of the inoculates for 20 h, the number of viable cells were counted. All saliva samples were analyzed for different indigenous salivary components and Candida before as well as after sterilization. Besides a 4% reduction in calcium (Ca2+) and thiocyanate (SCN-) concentrations, sterilization did not affect the concentrations of saliva electrolytes, but the proteins were significantly reduced (19-85%). Indigenous candidal carriage (n=19) correlated with neither the growth of inoculated fungi nor any of the analyzed components in saliva. The growth of C. albicans and T. glabrata was similar at pH 5 but, at pH 6, C. albicans had a remarkably slower growth rate than T. glabrata. Statistical analysis showed that the 5-h growth of C. albicans at pH 5 was associated with water and electrolyte secretion, whereas the growth after 20 h was associated with variations in protein-glycoprotein content. The growth of T. glabrata was not related to variations in the salivary variables analyzed.

Saliva and dental caries.

Caries is a unique multifactorial infectious disease. Our understanding of etiological factors, the progress of the disease, and the effectiveness of prophylactic procedures have led us to believe that we understand the disease. However, we still have too few answers to many questions: "Why can we not predict who will get the disease?" "Why do we not become immunized?" "How much saliva is enough?" or "Which salivary components are protective?" and "Which salivary components predispose for caries?" It is generally accepted, however, that saliva secretion and salivary components secreted in saliva are important for dental health. The final result, "caries to be or not to be", is a complex phenomenon involving internal defense factors, such as saliva, tooth surface morphology, general health, and nutritional and hormonal status, and a number of external factors-for example, diet, the microbial flora colonizing the teeth, oral hygiene, and fluoride availability. In this article, our aim is to focus on the effects of saliva and salivary constituents on cariogenic bacteria and the subsequent development of dental caries.

Effects of a lactoperoxidase system-containing toothpaste on levels of hypothiocyanite and bacteria in saliva.

Lactoperoxidase (LPO)/H2O2/SCN(-)-system-generated hypothiocyanite ions (OSCN-) and hypothiocyanous acid (HOSCN) are inhibitory against a number of oral bacteria, including mutans streptococci. A commercially available toothpaste (Biotene) comprises the complete LPO system. Generation of HOSCN/OSCN- by Biotene was studied in vitro both in sterilized and nonsterilized saliva of 10 healthy subjects. The HOSCN/OSCN- yield ranged from 100 to 300 microM with Biotene, while the salivary levels of HOSCN/OSCN- before the addition of Biotene were 30.1 +/- 25.1 microM. Two in vivo trials were carried out. In the first study, resting saliva was collected from 12 individuals before, immediately after, and 2, 5, 10 and 20 min after brushing with Biotene to evaluate the in vivo generation and decomposition of HOSCN/OSCN-. In the second study, 26 healthy individuals attended a 1-month crossover trial with Biotene and a control toothpaste, Vademecum (no LPO system), both containing F- and xylitol. The salivary counts of total streptococci, mutans streptococci (MS), lactobacilli and the total flora (TF), as well as the peroxidase, thiocyanate ion and HOSCN/OSCN- levels were determined before and after 2 and 4 weeks daily use of the toothpastes. Twice-a-day use of Biotene for 1 month resulted in an elevation of 'resting levels' of HOSCN/OSCN-. No such effect was found with the control toothpaste. No significant changes were found in the salivary levels of total streptococci, MS, lactobacilli or TF after 1-month use of either toothpaste. The results show the capability of the LPO-system-containing toothpaste to elevate the salivary levels of HOSCN/OSCN-, although no bactericidal effect was observed.

Effects of a lactoperoxidase-system-containing toothpaste on dental plaque and whole saliva in vivo.

The effects of a lactoperoxidase-system-containing toothpaste. Biotene, on saliva and dental plaque were studied. In a double-blind crossover study 20 healthy volunteers used an experimental (comprising the complete peroxidase system) or a placebo (without lactoperoxidase, KSCN, and glucose oxidase) toothpaste twice daily for 2 weeks separated by a 2-week washout period. At base lines and at the end of both test periods saliva and plaque samples were collected, and plaque pH changes were monitored. Saliva was analyzed for hypothiocyanite (HOSCN/OSCN-) and thiocyanate (SCN-) concentrations and salivary peroxidase activity. The amount of total streptococci, mutans streptococci, lactobacilli, and total anaerobic flora was determined both in saliva and in plaque samples. The accumulation and the acidogenicity of plaque were also quantitated. A 2-week daily use of Biotene had no effect on salivary flow rate, peroxidase activity, HOSCN/OSCN-, SCN-, or any of the monitored bacterial counts compared with the placebo toothpaste. The accumulation of dental plaque was not affected by the lactoperoxidase-system-containing toothpaste. The acidogenicity of plaque did not change significantly, nor did the two test dentifrices differ in their ability to inhibit the plaque pH drop caused by sucrose in subjects with normal salivary flow rate.

Healing of apical periodontitis after endodontic treatment: a comparison between a silicone-based and a zinc oxide-eugenol-based sealer.

AIM: To assess the treatment results up to 1 year after endodontic treatment of apical periodontitis using a silicone-based sealer in comparison with Grossman's sealer, and to compare the results at 3 months after treatment with the 12-month follow-up to assess the prognostic value of a 3-month control. METHODOLOGY: A total of 199 teeth were treated at three centres. The sealer was randomly chosen at the time of filling. Treatment results were evaluated clinically and radiographically 3 and 12 months after root-canal filling. The periapical status was evaluated using the periapical index (PAI). RESULTS AND CONCLUSIONS: Average PAI scores decreased from 3.43 at start to 2.21 at 12 months for Grossman's sealer and from 3.40 to 2.26 for the silicon-based material. No significant difference between the groups at start or any of the follow ups was seen. The 3-month control was adequate in establishing significant healing in both groups. The improvement of the periapical condition continued at the 12-month examination.

The effects of different (pseudo)halide substrates on peroxidase-mediated killing of Actinobacillus actinomycetemcomitans.

Actinobacillus actinomycetemcomitans is a Gram-negative bacterium which has an important role in localized juvenile and in progressive periodontitis. It is sensitive to killing by the myeloperoxidase (MP)-hydrogen peroxide (H2O2)-chloride system which is part of the innate host defense mediated by polymorphonuclear leukocytes. Since it has been recently suggested that thiocyanate, instead of chloride, could serve as a main substrate for MP as for lactoperoxidase (LP) and salivary peroxidase, we investigated in this study the effect of both LP and MP systems on A. actinomycetemcomitans with different (pseudo)halide substrates, thiocyanate, chloride and iodide. The concentrations of the substrates were physiological for oral fluids, as was the concentration range of H2O2. Both peroxidases produced end products with identical antibacterial activity with thiocyanate and iodide. The oxidation of iodide resulted in the highest antimicrobial efficiency followed by chloride and thiocyanate. Addition of thiocyanate into either MP-H2O2-chloride or MP/LP-H2O2-iodide system abolished the bactericidal activity of the oxidized halide. However, the chloride did not affect the bactericidality of the MP-H2O2-iodide system, but when all 3 (pseudo)halide substrates were present no antimicrobial effect was recorded. Our study shows that the presence of thiocyanate in physiological amounts is able to prevent the bactericidal activity of halide-peroxidase systems in low H2O2 concentrations. These results explain why thiocyanate-peroxidase systems of either innate origin (saliva, crevicular fluid) or introduced by commercial oral hygiene products are most probably ineffective against A. actinomycetemcomitans in vivo. Further studies of halide/thiocyanate ratio are needed to develop products which are also effective against oral anaerobes.

Effects of delmopinol on antimicrobial peroxidase systems and lysozyme in vitro and in human whole saliva.

Delmopinol is a new surface-active agent which can reduce plaque formation and gingivitis. This study was aimed to analyze whether delmopinol (0.0032-0.65 mM) interferes with the activity of two surface-active oral antimicrobial enzymes, salivary peroxidase and lysozyme. In addition to human whole saliva (pH 5.0 and 6.0), the experiments were done in 0.1 M phosphate buffer (pH 6.0) with purified lactoperoxidase (LPO) and myeloperoxidase (MPO). LPO and MPO were significantly inhibited in buffer by delmopinol concentrations > 6.5 mM and > or = 3.2 mM, respectively. No such inhibition was found for total peroxidase activity in mixed saliva. In vitro, delmopinol was found to desorb surface-bound peroxidases in an active form to the liquid phase. In further analyses, the possible effect of delmopinol on peroxidase-generated hypothiocyanite (HOSCN/OSCN-) was studied in saliva and buffer. No effect was found in buffer, but salivary HOSCN/OSCN- declined significantly with 6.5 mM delmopinol. This was obviously due to an enhanced decay of hypothiocyanite, rather than its reduced rate of formation. No delmopinol-related inhibition of lysozyme occurred in saliva or buffer. The results suggest that high concentration (6.4 mM -0.2%) of delmopinol may lower the concentrations of antimicrobial HOSCN/OSCN- in saliva but has no effect on human lysozyme.

Growth of xylitol-resistant versus xylitol-sensitive Streptococcus mutans strains in saliva.

Five Streptococcus mutans pairs (serotype c S. mutans 10449 and four clinical isolates of S. mutans: 123.1, LG1, OMFA, T10B) were used to find out if the xylitol-resistant (XR) natural mutants of the corresponding xylitol-sensitive (XS) S. mutans parental strains differ in their growth patterns in saliva. The isogenic X natural mutants of the parental S. mutans strains were selected after sequential cultivations in the presence of xylitol and glucose. The XR/XS strains pairs were grown in individual and pooled glucose-supplemented filter-sterilized salivas (one to five sequential cultivations). The two salivas used represented subjects with good or poor support of the growth of S. mutans in vivo. Protease and peptidase activities were determined from the saliva growth media and cell suspensions. Salivary protein profiles were analyzed using SDS-PAGE and native IEF before and after the cultivations. The growth properties of the XR/XS S. mutans pairs were similar in both individual and pooled salivas. Sequential cultivation of all strains did not show any differences in growth patterns. XS strains were inhibited by the presence of xylitol (2% w/v) in pooled saliva, as shown for other glucose-supplemented media. Protease and peptidase activities of the XR/XS S. mutans pairs were low and of similar magnitude. Also, the general hydrolytic properties of most XR/XS S. mutans pairs appeared similar as judged by the small growth-induced changes in salivary protein profiles. In conclusion, saliva, the source of nutrients for salivary microorganisms in vivo, favored neither the XR nor the XS strains of S. mutans.

Effects of oral hygiene products containing lactoperoxidase, lysozyme, and lactoferrin on the composition of whole saliva and on subjective oral symptoms in patients with xerostomia.

This study evaluates the effects of two oral hygiene products containing nonimmunoglobulin antimicrobial agents on whole saliva and on subjective oral symptoms in patients with xerostomia. Twenty patients used a lactoperoxidase-system-containing toothpaste (Biotene) combined with the use of a mouthrinse (Biotene), comprising also lysozyme and lactoferrin, for 4 weeks. Saliva samples were collected at base line, after 4 weeks' use of the products, and at the end of a 4-week washout period. Samples were analyzed for selected biochemical and microbiologic factors. The effects on subjective oral symptoms were also recorded. A 4-week daily use of toothpaste and mouthrinse relieved the symptoms of oral dryness in 16 patients. The levels of salivary hypothiocyanite, lysozyme, lactoferrin, or myeloperoxidase activity did not change, but there was a significant decrease in salivary pH (P < 0.05), total peroxidase activity (P < 0.05), and total protein content (P = 0.01). In patients with the lowest salivary flow rates (n = 5) a significant (P > or = 0.04) increase was detected in salivary hypothiocyanite concentrations. No major changes occurred in salivary microflora. The products relieved subjective oral symptoms in most xerostomic patients, but this was not necessarily related to the presence of antimicrobial agents.

Lysozyme and lactoperoxidase inhibit the adherence of Streptococcus mutans NCTC 10449 (serotype c) to saliva-treated hydroxyapatite in vitro.

Lysozyme, lactoperoxidase and salivary peroxidase inhibit the metabolism and growth of mutans streptococci, but any possible effects on the adherence of these bacteria are unknown. In this study the effects of lysozyme and lactoperoxidase on the adhesion of 3H-labelled Streptococcus mutans (NCTC 10449, serotype c strain) to saliva-coated hydroxyapatite were studied at pH 5.0 and 7.0. Human whole saliva was either lysozyme-depleted and centrifuged, or sterilized and dialysed to achieve no detectable lysozyme and peroxidase activities; this modified saliva was used to form experimental pellicles. The incorporation of lysozyme (50-200 micrograms/ml) to the pellicle caused a significant (p < 0.01) reduction in the adherence of S. mutans without any loss of bacterial viability. Pretreatment of either saliva-coated apatite or S. mutans cells with lysozyme did not change the results but lysozyme bound more readily to bacteria than to the experimental pellicles. Also, lactoperoxidase (10-200 micrograms/ml) reduced significantly (p < 0.001) the adherence of S. mutans but, in contrast to lysozyme, in a dose-dependent way. The strongest inhibition of adhesion was found when both saliva-coated apatite and bacteria were pretreated with lactoperoxidase. This enzyme bound to experimental pellicles in preference to streptococci. A non-specific protein control, albumin, did not block the inhibition by lysozyme or lactoperoxidase. The inhibition of adherence of a serotype c strain of S. mutans to saliva-coated hydroxyapatite is a novel antibacterial mechanism for both lysozyme and lactoperoxidase.