Human lactoferrin protects against Streptococcus mutans-induced caries in mice.

OBJECTIVES: The objective of this study is to evaluate the importance of human lactoferrin (hLF) in an experimental caries induced by Streptococcus mutans in a lactoferrin-knockout (LFKO(-/-)) mouse model compared with C576J/BL wild-type (WT) mice. MATERIALS AND METHODS: The WT and LFKO(-/-) mice were infected with S. mutans (1 × 10(8) cells) and/or sham infection. Furthermore, the effect of hLF administration was evaluated in LFKO(-/-) mice infected with S. mutans. Mice were assessed for colonization, salivary pH, and caries development. RESULTS: The results showed that the lactoferrin-knockout infected (LFKO(-/-) I) mice had significantly higher colonization with S. mutans (P = 0.02), lower salivary pH (P = 0.01), and more carious lesions (P = 0.01) when compared to wild-type infected (WTI) mice. In addition, the administration of hLF did not show any evidence of S. mutans colonization as well as carious lesions (P = 0.001) in LFKO(-/-) I mice when compared to untreated LFKO(-/-) I mice. CONCLUSION: These results show that endogenous LF protects against S. mutans-induced caries and that exogenous hLF can exert a protective effect against caries development.

Oral lactoferrin protects against experimental candidiasis in mice.

AIMS: To determine the role of human lactoferrin (hLF) in protecting the oral cavities of mice against Candida albicans infection in lactoferrin knockout (LFKO(-/-)) mice was compared to wild-type (WT) mice. We also aim to determine the protective role of hLF in LFKO(-/-) mice. METHODS AND RESULTS: Antibiotic-treated immunosuppressed mice were inoculated with C. albicans (or sham infection) by oral swab and evaluated for the severity of infection after 7 days of infection. To determine the protective role of hLF, we added 0·3% solution of hLF to the drinking water given to some of the mice. CFU count, scoring of lesions and microscopic observations were carried out to determine the severity of infection. LFKO(-/-) I mice showed a 2 log (P = 0·001) higher CFUs of C. albicans in the oral cavity compared to the WT mice infected with C. albicans (WTI). LFKO(-/-) I mice given hLF had a 3 log (P = 0·001) reduction in CFUs in the oral cavity compared to untreated LFKO(-/-) I mice. The severity of infection, observed by light microscopy, revealed that the tongue of the LFKO(-/-) I mice showed more white patches compared to WTI and LFKO(-/-) I + hLF mice. Scanning electron microscopic observations revealed that more filiform papillae were destroyed in LFKO(-/-) I mice when compared to WTI or LFKO(-/-) I + hLF mice. CONCLUSIONS: Human LF is important in protecting mice from oral C. albicans infection. Administered hLF may be used to prevent C. albicans infection. SIGNIFICANCE AND IMPACT OF THE STUDY: Human LF, a multifunctional iron-binding glycoprotein can be used as a therapeutic active ingredient in oral healthcare products against C. albicans.

An overview of children's oral health-related quality of life assessment: from scale development to measuring outcomes.

The objectives of this paper are to present an overview of children's oral health-related quality of life and include specific applications for using quality of life assessment in dental research. The process of developing pediatric oral health- related quality of life measures, in particular the Child Oral Health Impact Profile, is outlined. Examples of children's oral health-related quality of life measurement in caries research are also provided. Quality of life outcomes are presented and discussed in the context of caries research. Lastly, the relevance of measuring clinically meaningful difference in the context of measuring outcomes research is highlighted with recommendations for future research.

The effect of distance and tooth structure on laser fluorescence caries detection.

The DIAGNOdent, a device used in caries detection, uses a laser to excite fluorescence from pigments in carious tooth structure. In clinical use assessing occlusal surfaces, distance and tooth structure may separate the instrument's tip from the fluorescent source.The aim of this in vitro study was to examine the effect of distance and tooth structure on laser fluorescence (LF) readings.In one set of experiments, a porphyrin pigmentin oil suspension was used as a LF signal source. Thin slices of enamel and dentin were obtained from extracted molars. Pigment-induced LF readings were obtained when these slices were placed between the porphyrin pigment and the LF instrument's tip. The effect of either demineralized or intact tooth tissue on pigment-induced LF readings was assessed.In other experiments on extracted molars with small occlusal caries, LF readings were taken from pit/fissure sites before and after removal of the occlusal surface.LF readings are proportional to pigment con-centration and inversely proportional to the distance between the suspension and the instrument's tip. Enamel, demineralized enamel,dentin, and demineralized dentin all caused significant reductions in LF signal, all readings being taken with the same tip-pigment distance. Demineralized enamel (white with intact surface) caused the most reduction.After sectioning of carious teeth, there was a significant increase in LF readings.The results of this study indicate that distance and the presence of tooth structure between the carious lesion and the instrument's tip reduce LF readings. These results indicate that anatomic factors interfere with the LF device's ability to assess occlusal caries. DIAGNOdent readings should not be relied on when making diagnostic decisions.

Characterization of dentine structure in three dimensions using FIB-SEM.

All biological tissues are three dimensional and contain structures that span a range of length scales from nanometres through to hundreds of millimetres. These are not ideally suited to current three-dimensional characterization techniques such as X-ray or transmission electron tomography. Such detailed morphological analysis is critical to understanding the structural features relevant to tissue function and designing therapeutic strategies intended to address structural deficiencies encountered in pathological states. We show that use of focused ion beam milling combined with scanning electron microscopy can provide three-dimensional information at nanometre resolution from biologically relevant volumes of material, in this case dentine.

Clinical anti-microbial efficacy of a new zinc citrate dentifrice.

This crossover design clinical study compared the anti-microbial effects of a new 1% zinc citrate dentifrice with a control formulation. Thirty adults completed a washout phase and baseline samples of dental plaque, buccal mucosa, tongue, saliva, and plaque collected to enumerate anaerobes and streptococci. Subjects were randomly assigned a test dentifrice to use for the next 13 days. Oral samples similar to the baseline were collected on day 14 prior to oral hygiene for microbial analysis. The subject then placed a custom intra-oral stent with hydroxyapatite (HA) squares and brushed their teeth with their assigned dentifrice. Oral samples and HA squares were collected 5 h later for microbial analyses. This completed the study with one test dentifrice. The entire study was repeated with the alternate dentifrice after a second washout phase. Whereas baseline samples demonstrated no significant differences in microbial parameters between the two treatment groups (p > 0.05), subjects provided the zinc citrate dentifrice demonstrated 24-52% reductions in anaerobic bacteria and streptococci on day 14 versus the control paste (p < 0.05). In the 5-h post-brushing samples, subjects provided the zinc citrate toothpaste demonstrated 27-49% reductions for anaerobic bacteria and streptococci (p < 0.05). Additionally, in situ microbial biofilm formation on HA disks was significantly inhibited amongst the zinc citrate group (p < 0.05). Significant reductions in anaerobic bacteria and streptococci were observed amongst all intra-oral locations along with in situ biofilm formation after use of the zinc citrate dentifrice.

Mechanotransducers in rat pulpal afferents.

The hydrodynamic theory suggests that pain associated with stimulation of a sensitive tooth ultimately involves mechanotransduction as a consequence of fluid movement within exposed dentinal tubules. To determine whether putative mechanotransducers could underlie mechanotransduction in pulpal afferents, we used a single-cell PCR approach to screen retrogradely labeled pulpal afferents. The presence of mRNA encoding BNC-1, ASIC3, TRPV4, TRPA1, the alpha, beta, and gamma subunits of ENaC, and the two pore K+ channels (TREK1, TREK2) and TRAAK were screened in pulpal neurons from rats with and without pulpal inflammation. ASIC3, TRPA1, TREK1, and TREK2 were present in approximately 67%, 64%, 14%, and 10% of pulpal neurons, respectively. There was no detectable influence of inflammation on the proportion of neurons expressing these mechanotransducers. Given that the majority of pulpal afferents express ASIC3 and TRPA1, our results raise the possibility that these channels may be novel targets for the treatment of dentin sensitivity.

Discovering new treatments for sensitive teeth: the long path from biology to therapy.

Tooth sensitivity is a common dental pain condition where sufferers experience brief episodes of sharp well-localized pain when their teeth are subjected innocuous stimuli such as cold, air-currents and probing with a metallic instrument. In this review, we will make no attempt to describe all the treatments that have been developed to treat tooth sensitivity. We will review the basic anatomic and physiological mechanisms responsible for sensitivity. The insights into the dental lesions responsible for tooth sensitivity, as well as the physiological processes linking stimuli and pain generation have suggested several treatments and preventive strategies. Unfortunately, many tooth sensitivity treatments fail to perform better than placebos in clinical trials that seek to assess the effect of agents on pain symptoms. In the case of the most commonly used self-applied desensitizing agent, potassium salts, the mechanism of action established by laboratory and animal models may not apply to clinical use. Thus results obtained with laboratory and animal models must be applied with care to clinical use. Clinical literature suggests that tooth sensitivity is the symptomatic manifestation of significant dental problems, such as wear and other forms of non-carious tooth structure loss. These conditions are increasing in frequency as people age, retaining their natural teeth longer. They are frequently the consequences of aggressive oral hygiene practices and diets rich in acids. Treatments directed at the underlying causes rather than the symptoms of tooth sensitivity would hinder the development of these lesions and provide researchers with objective targets for assessing therapeutic efficacy.

Assessing the Appearance and Fluorescence of Resin-Infiltrated White Spot Lesions With Caries Detection Devices.

OBJECTIVE: This in vitro study examined the effectiveness of caries detector devices in assessing the ability of resin infiltration (RI) (Icon, DMG-Hamburg, Hamburg, Germany) to improve the optical properties of enamel white spot lesions (WSLs). METHODS AND MATERIALS: Ten caries-free third molars were used. Photographs, a subjective visual assessment of the photographs, fluorescent camera (FC) images using the Spectra (Air Techniques, Melville, NY, USA), and laser fluorescent (LF) readings using the DIAGNOdent (KaVo, Biberach, Germany) were obtained from each tooth's buccal surface. Specimens were coated with nail polish leaving a rectangular window on the buccal surface and placed in pH 4.5 lactic acid gel for two weeks to create a WSL. The WSLs were analyzed by the same methods. RI was applied to half of each WSL; final photographs were then taken, and caries detector assessments were conducted. FC images were converted to grayscale, and the fluorescent image's brightness intensity was measured using ImageJ. Data were analyzed with analysis of variance and Tukey-Kramer honestly significant difference test. Significance was set at α=0.05. RESULTS: Subjective assessment of the photographs showed that RI improved the appearance of the WSLs so that they resembled intact enamel. Mean FC-brightness intensities for intact, demineralized, and demineralized RI-treated areas were 159.6 ± 9.2, 123.4 ± 7.2, and 160.9 ± 11.5, respectively. There were no significant differences in fluorescent intensity between the intact and RI areas ( p=0.58). The demineralized areas had significantly lower fluorescent intensity than both the RI-treated and intact areas ( p<0.001). LF values did not differ significantly between intact, demineralized, or RI-treated areas. CONCLUSIONS: This study demonstrates the ability of RI to restore artificial WSLs to the esthetics and fluorescence of intact enamel. The FC can be used to assess the optical properties of WSLs and the impact of RI on these properties.

Decreasing intradental nerve activity in the cat with potassium and divalent cations.

Nerve activity was recorded from deep dentinal cavities in the canine teeth to assess the possible influence of potassium and divalent cations in decreasing this activity in hypersensitive teeth. The decreased activity after the topical application of 0.756 mol/l KCl to the cavity was primarily due to the cation. KCl elicited a biphasic response from intradental nerves, an initial transient excitatory response followed by a prolonged inhibitory period. During the inhibitory period 3 mol/l NaCl, an effective excitatory stimulus, failed to evoke intradental nerve activity. However, with time the response to 3 mol/l NaCl eventually recovered to its previous control level. Close, intra-arterial injection of KCl showed the same biphasic response and time-course of intradental nerve activity as with topical application. Therefore, whether KCl was applied topically or injected its effectiveness in altering the nerve activity was similar. Pretreatment of the dentinal cavity with CaCl2, MgCl2 or SrCl2 greatly reduced the response of intradental nerves to KCl. Therefore these divalent cations seem to have a depressant action on pulpal nerve fibres. The mechanism of action of KCl seems to be an alteration of K+ concentration immediately surrounding the intradental nerves which presumably depolarizes the nerve fibre membrane and elicits an initial firing of action potentials. Because of the persisting high levels of extracellular potassium a sustained depolarized state occurs that results in an inactivation of the action potential. Divalent cations appear to depress the excitability of the nerve cell membrane without altering membrane potential. Such ionic agents could be used in conjunction with KCl as a possible treatment for hypersensitive teeth.

Comparison of pulpal blood flow in dog canine teeth determined by the laser Doppler and the 133xenon washout methods.

Pulpal blood flow measurements by laser Doppler flowmetry were compared with those made simultaneously and on the same teeth by the 133Xe washout method. Pulpal method flow in the resting state was 82.4 ml/min per 100 g as calculated from the fast component of the 133Xe washout, whereas laser Doppler flowmetry recorded 263 mV. The close intra-arterial (i.a.) injection of the vasoconstrictor norepinephrine (10(-2)-10(-1) micrograms/kg) caused a reduction of pulpal blood flow by 20.2% with the 133Xe washout and by 9.7% with the laser Doppler flowmetry in 6 observations in 4 dogs. The laser Doppler flowmetry measurements of these norepinephrine-induced changes correlated significantly with changes measured by the 133Xe washout method as analysed by linear regression (p = 0.004).

Comparison of the effects of intra-arterial and locally applied vasoactive agents on pulpal blood flow in dog canine teeth determined by laser Doppler velocimetry.

The vasoactive agents norepinephrine, 5-hydroxytryptamine, isoproterenol and bradykinin, at concentrations which changed local arterial pressure without changing systemic arterial pressure significantly, were injected intra-arterially (i.a.) into the maxillary artery or applied directly in a deep dentinal cavity on the buccal surface of canine teeth. The probe of a laser Doppler velocimeter was placed in the cavity to monitor pulpal blood flow. Bolus i.a. injections of the vasoconstrictors norepinephrine and 5-hydroxytryptamine produced a statistically significant (p less than 0.05) reduction in pulpal blood flow, 21.1 +/- 3.7 and 30.7 +/- 15.2%, and the local arterial pressure from the lateral nasal artery increased with norepinephrine but decreased with 5-hydroxytryptamine. The i.a. injections of the vasodilators isoproterenol and bradykinin were found to decrease both local arterial pressure and pulpal blood flow, 17.7 +/- 6.0 and 22.7 +/- 4.2%, respectively (p less than 0.05). However, local application of isoproterenol and bradykinin caused a biphasic response: an increase in pulpal blood flow, 8.6 +/- 1.6 and 9.4 +/- 1.1% (p less than 0.05), followed by a decrease, 19.1 +/- 11.9 and 5.3 +/- 2.1% (p greater than 0.005). Local application of norepinephrine and 5-hydroxytryptamine caused a decrease in pulpal blood flow, 23.7 +/- 5.2% (p less than 0.05) and 9.3 +/- 5.2% (p less than 0.05), respectively. These findings were in accordance with those from other reliable methods, such as injections of radioisotope-labelled 15 microns microspheres and the 133Xe washout technique, making laser Doppler flowmetry a reliable alternative. In addition, the biphasic response to the locally applied vasodilators and the reduction of pulpal blood flow after i.a. injection of vasodilators suggest that regulation of pulpal blood flow is determined by the combined effects of the low compliance environment and the stealing of perfusion to the pulp by the neighbouring tissues.

Hypersensitive teeth. Experimental studies of dentinal desensitizing agents.

The effect of dentinal desensitizing agents on nerve activity was tested. Effective agents such as KNO3 reduce dentinal sensory nerve activity. This effect is due to the depolarizing action of the K+ ion.

Lactoferrin knockout mice demonstrates greater susceptibility to Aggregatibacter actinomycetemcomitans-induced periodontal disease.

BACKGROUND: Among the innate defense mechanisms in the oral cavity, lactoferrin (LF) is a vital antimicrobial that can modify the host response against periodontopathogens. Aggregatibacter actinomycetemcomitans is the main periodontopathogen of localized aggressive periodontitis. The aim of this study is to evaluate the role of LF during A. actinomycetemcomitans-induced periodontitis. METHODS: Differences in the expression levels of cytokines, chemokines, chemokine receptors, and bone loss markers between wild-type (WT) and LF knockout mice (LFKO(-/-)) were evaluated by real time-PCR. Serum IgG and LF levels were quantified by ELISA. Alveolar bone loss among the groups was estimated by measuring the distance from cemento-enamel junction (CEJ) to the alveolar bone crest (ABC) at 20 molar sites. RESULTS: Oral infection with A. actinomycetemcomitans increased LF levels in periodontal tissue (P = 0.01) and saliva (P = 0.0004) of wild-type infected (WTI) mice compared to wild-type control mice. Pro-inflammatory cytokines such as interferon-γ, tumor necrosis factor-α, interleukin (IL)-1ß, IL-6, and IL-12 were increased in the infected LF knockout (LFKO(-/-)I) mice compared to the WTI mice, whereas the anti-inflammatory cytokines IL-4 and IL-10 were decreased. Chemokines and chemokine receptors showed different expression patterns between WTI and LFKO(-/-)I mice. The LFKO(-/-)I mice developed increased bone loss (P = 0.002), in conjunction with increased expression of receptor activator of nuclear factor-κB ligand and decrease in osteoprotegerin, compared to WTI mice. CONCLUSIONS: These results demonstrate that the infected LFKO(-/-) mice were more susceptible to A. actinomycetemcomitans-induced alveolar bone loss, with different patterns of immune responses compared to those of WTI mice.

Activity of antimicrobial peptide mimetics in the oral cavity: I. Activity against biofilms of Candida albicans.

Naturally occurring antimicrobial peptides hold promise as therapeutic agents against oral pathogens such as Candida albicans but numerous difficulties have slowed their development. Synthetic, non-peptidic analogs that mimic the properties of these peptides have many advantages and exhibit potent, selective antimicrobial activity. Several series of mimetics (with molecular weight < 1000) were developed and screened against oral Candida strains as a proof-of-principle for their antifungal properties. One phenylalkyne and several arylamide compounds with reduced mammalian cytotoxicities were found to be active against C. albicans. These compounds demonstrated rapid fungicidal activity in liquid culture even in the presence of saliva, and demonstrated synergy with standard antifungal agents. When assayed against biofilms grown on denture acrylic, the compounds exhibited potent fungicidal activity as measured by metabolic and fluorescent viability assays. Repeated passages in sub-minimum inhibitory concentration levels did not lead to resistant Candida, in contrast to fluconazole. Our results demonstrate the proof-of principle for the use of these compounds as anti-Candida agents, and their further testing is warranted as novel anti-Candida therapies.

Tooth sensitivity: mechanisms and management.

Tooth sensitivity is a common complaint encountered in clinical practice. Exposed superficial dentin is free of nerve endings, yet sensitive. Experimental evidence indicates that stimuli, such as probing the dentin surface and air blasts, induce fluid movements in the dentinal tubules and these fluid movements, in turn, activate the intradental nerves. The condition of the dentin surface is critically important in allowing this process. In addition, the internal environment of the pulp may influence nerve excitability. Therapies for tooth sensitivity include both agents that obstruct the dentinal tubules and agents that can decrease the excitability of the intradental nerves. The exact treatment used depends on the etiology of the individual's problem and the extent of dentinal tissue damage.