Role of saliva in caries models

Role of Fluoride in Dentistry: A Narrative Review

Fluoride has performed a central role in the growth over the last fifty years. This report examines the present state of knowledge about fluoride's involvement in preventing dental caries. In recent years, our knowledge of the development of dental caries and the manner of operation of fluoride has been shifted. Dental caries is a constant procedure for enamel demineralization and remineralization, and fluoride plays an important part in this action by acting at the plaque-enamel contact. Fluoride's major method of action is now recognized as posteruptive. Fluoride's post-eruptive activity has led to the development of novel fluoride delivery systems. The importance of various fluoride delivery techniques on a population and societal level is discussed, along with suggestions.

Effects of different remineralizing agents on color stability and surface characteristics of the teeth following vital bleaching

The aim of the study was to investigate the effects of various remineralizing agents on the color stability and surface characteristics of the teeth after vital bleaching. The extracted 96 human incisors were used for the study. Initially, the samples were randomly divided into two groups and exposed to in-office and at-home bleaching agents. Then, the groups were divided into six subgroups (n = 8), including the control group did not undergo remineralization after bleaching, according to five remineralizing agents (Gelato APF Gel, Remin Pro, Tooth Mousse, MI Paste Plus, Curodont Protect). Surface roughness was assessed at baseline, after bleaching and remineralization procedures. Color measurements of the samples were obtained at baseline, after bleaching and then after immersion in the staining solution following remineralization process. Scanning electron microscopy and atomic force microscopy (AFM) analyzes were carried out in order to examine the morphological changes on the surface of the enamel. The independent t-test, paired-samples t-test, and one-way ANOVA was used to compare the data and post-hoc LSD test to compare the difference among the study groups (α = .05). Surface roughness increased following in-office and at-home bleaching in all groups, and reduced after application of remineralizing agents in all groups. Significant differences were found among the groups with respect to changes in surface roughness and color values following treatment with remineralizing agents (p <.05). AFM analyses revealed increased surface roughness after bleaching and a reduction of rough surfaces following treatment with remineralizing agents. Remineralizing agents can be used to reduce postbleaching increase in surface roughness and to maintain color stability after bleaching.

The role of salivary contents and modern technologies in the remineralization of dental enamel: a narrative review

Human enamel once formed cannot be biologically repaired or replaced. Saliva has a significant role in remineralization of dental enamel. It not only has a buffering capacity to neutralize the oral cavity’s low pH generated after acidic encounters, but also acts as a carrier of essential ions, such as fluoride, calcium and phosphate, which have a positive role in enamel’s remineralization. This review discusses how salivary contents, like proteins and enzymes, have a natural role in enamel’s mineralization. In addition, the presence of ions, such as fluoride, calcium and phosphate, in saliva further enhances its capability to remineralize the demineralized enamel surface. The review further examines modern innovative technologies, based on biomimetic regeneration systems, including dentin phosphoproteins, aspartate-serine-serine, recombinant porcine amelogenin, leucine-rich amelogenin peptide and nano-hydroxyapatite, that promote enamel remineralization. Fluoride boosters like calcium phosphates, polyphosphates, and certain natural products can also play an important role in enamel remineralization.

The role of salivary contents and modern technologies in the remineralization of dental enamel: a narrative review

Human enamel once formed cannot be biologically repaired or replaced. Saliva has a significant role in remineralization of dental enamel. It not only has a buffering capacity to neutralize the oral cavity's low pH generated after acidic encounters, but also acts as a carrier of essential ions, such as fluoride, calcium and phosphate, which have a positive role in enamel's remineralization. This review discusses how salivary contents, like proteins and enzymes, have a natural role in enamel's mineralization. In addition, the presence of ions, such as fluoride, calcium and phosphate, in saliva further enhances its capability to remineralize the demineralized enamel surface. The review further examines modern innovative technologies, based on biomimetic regeneration systems, including dentin phosphoproteins, aspartate-serine-serine, recombinant porcine amelogenin, leucine-rich amelogenin peptide and nano-hydroxyapatite, that promote enamel remineralization. Fluoride boosters like calcium phosphates, polyphosphates, and certain natural products can also play an important role in enamel remineralization.

Salivary flow rate, pH and buffering capacity in patients undergoing fixed orthodontic treatment - A prospective study

Background

Human saliva has got many important functions like lubrication of the oral tissues, making oral functions like speech, mastication and deglutition possible and also protecting teeth and oral mucosal surfaces in different ways. Dental Caries is one of the common complications in patients undergoing orthodontic treatment. Subjects with impaired saliva flow rate often show high caries incidence. A low flow rate combined with a low or moderate buffer effect clearly indicates poor salivary resistance against microbial attack.

Aim

To investigate the changes in stimulated and unstimulated salivary flow rate, pH and buffer capacity in patients undergoing therapy with fixed orthodontic appliances.

Materials and Methods

Salivary flow rate, pH and buffering capacity of 20 patients who underwent fixed orthodontic treatment at Department of Orthodontics, Ragas Dental College and Hospital, Chennai were examined using GC saliva check buffer kit. The procedure was carried out during the initiation of orthodontic treatment and subsequently, one month and six months after the placement of appliance.

Results

Results showed there was a significant increase in the salivary flow rate one month and six months after placement of fixed appliance while pH and buffering capacity showed no significant changes.

Conclusion

Salivary flow rate increases significantly during fixed orthodontic treatment. Salivary pH and buffering capacity showed no significant changes suggesting that they are not sole factors for demineralization in orthodontic patients.

Changes in white spot lesions following post-orthodontic weekly application of 1.25 per cent fluoride gel over 6 months-a randomized placebo-controlled clinical trial. Part II: clinical data evaluation

Background

White spot lesions (WSL) frequently occur as side-effect of multibracket appliance treatment. The clinical effects of local fluoridation on post-orthodontic WSL and oral health development are however inconclusive.

Objective

In vivo monitoring of clinical WSL and oral health changes in response to weekly 1.25 per cent fluoride gel application after multibracket appliance treatment.

Trial design

Randomized, single-centre, double-blind, parallel-group, placebo-controlled study.

Participants

Patients with not less than 1 WSL (modified score 1 or 2) on not less than 1 upper front teeth after debonding.

Interventions

Professional fluoride/placebo gel application during weeks 1-2; self-administered home application (weeks 3-24).

Outcomes

Clinical evaluation of WSL index, lesion activity, plaque index, gingival bleeding index, and decayed, missing, and filled teeth index as well as saliva buffer capacity and stimulated salivary flow rate (T0-T5).

Randomization

Random assignment to test (n = 23) or placebo group (n = 23) using a sequentially numbered list (random allocation sequence generated for 50 subjects in 25 blocks of 2 subjects each).

Recruitment

The clinical study duration lasted from March 2011 to September 2013.

Blinding

Unblinding was performed after complete data evaluation.

Numbers analysed

Intention-to-treat analysis set comprised 39 participants (test: n = 21, placebo: n = 18).

Outcome

No clinical parameter except stimulated salivary flow rate (fluoride group: 1.1ml/min, placebo group: 0.74ml/min; P = 0.022) showed a statistically significant group difference after 24 weeks.

Harms

Several adverse events occurred similarly frequent in both groups; none was classified as possibly related to the study product.

Limitations

The number of dropouts was higher than expected and the socio-economic status was not assessed. Furthermore, the unknown level of compliance during the home application phase must be considered as limitation.

Conclusion

Based on the results of this study, no clinical effect of post-orthodontic high-dose fluoride treatment on WSL and oral health changes could be detected.

Registration

The study was registered with ClinicalTrials.gov (Identifier: NCT01329731).

Protocol

The protocol wasn't published before trial commencement.

Vibrational algorithms for quantitative crystallographic analyses of hydroxyapatite-based biomaterials: II, application to decayed human teeth

A systematic investigation, based on highly spectrally resolved Raman spectroscopy, was undertaken to research the efficacy of vibrational assessments in locating chemical and crystallographic fingerprints for the characterization of dental caries and the early detection of non-cavitated carious lesions. Raman results published by other authors have indicated possible approaches for this method. However, they conspicuously lacked physical insight at the molecular scale and, thus, the rigor necessary to prove the efficacy of this spectroscopy method. After solving basic physical challenges in a companion paper, we apply them here in the form of newly developed Raman algorithms for practical dental research. Relevant differences in mineral crystallite (average) orientation and texture distribution were revealed for diseased enamel at different stages compared with healthy mineralized enamel. Clear spectroscopy features could be directly translated in terms of a rigorous and quantitative classification of crystallography and chemical characteristics of diseased enamel structures. The Raman procedure enabled us to trace back otherwise invisible characteristics in early caries, in the translucent zone (i.e., the advancing front of the disease) and in the body of lesion of cavitated caries.

Mandibular incisal edge demineralization and caries associated with Twin Block appliance design

Demineralization and caries are well documented and unwanted complications of orthodontic therapy. These are most commonly reported in relation to fixed appliance therapy. Five cases are presented of patients undergoing Twin Block appliance therapy with the appliances incorporating lower labial segment capping, illustrating a pattern of demineralization and caries of the incisal tips of the mandibular labial segment, influenced by the incisal capping and the frequent intake of carbonated soft drinks.

Matrix metalloproteinases: potential therapeutic target for diabetic neuropathic pain

INTRODUCTION

MMPs are zinc-dependent endopeptidases that play a key role in the remodeling of extracellular matrix (ECM). Various pathogenic mediators trigger abnormal MMP activity that leads to ECM abnormality. Hyperglycemia is one of the strong stimuli among oxidative stress and inflammation that upregulate MMP expression in the central and peripheral nervous system. MMP-mediated ECM abnormality hypersensitizes peripheral as well as central nerves that precipitate neuropathic pain in diabetic patients.

AREAS COVERED

Molecular mechanisms associated with MMP-mediated diabetic neuropathic pain have been discussed. Various endogenous, natural and synthetic MMP inhibitors are also explored.

EXPERT OPINION

In diabetes, hyperglycemia activates MMPs that along with the other pathogenic mediators cause neuronal injury and precipitates neuropathic pain. Thus, MMPs play a crucial role in the development of neuropathic pain among diabetics. However, MMPs are not only responsible for deleterious ECM abnormalities but are also required for beneficial remodeling of ECM under normal physiological conditions. Therefore, highly selective and specific inhibitors must be designed and explored for their clinical potential for treatment/prevention of diabetic neuropathic pain.

Effect of fixed orthodontic appliances on salivary properties

BACKGROUND

So far, a few studies have tried to investigate the relationship between the placement of fixed orthodontic appliances and the change of nonmicrobial salivary properties, mostly with conflicting outcomes and short-term assessment (up to 6 months from bracket placement). The purpose of this study was to evaluate the salivary flow rate, pH and buffer capacity prior to the beginning of therapy and after 1 year from bracket placement using a simple and commercially available chairside saliva check kit.

METHODS

The study population consisted of 20 healthy patients (mean age, 16.5±4 years) scheduled for fixed orthodontic treatment. Salivary samples were taken just before bracket bonding (T0; baseline assessment) and after 1 year of treatment (T1; half-treatment assessment) using the GC Saliva-Check Kit (GC Corp., Leuven, Belgium).

RESULTS

No statistically significant difference was detected between T0 and T1 for the salivary parameters examined in the present study.

CONCLUSIONS

Under the conditions of this study, the placement of fixed orthodontic appliances did not change the salivary pH, buffer capacity and flow rate after 1 year of treatment if compared with the baseline assessment.

Regulation of recombination between gtfB/gtfC genes in Streptococcus mutans by recombinase A

Streptococcus mutans produces 3 types of glucosyltransferases (GTFs), whose cooperative action is essential for cellular adhesion. The recombinase A (RecA) protein is required for homologous recombination. In our previous study, we isolated several strains with a smooth colony morphology and low GTF activity, characteristics speculated to be derived from the GTF fusions. The purpose of the present study was to investigate the mechanism of those fusions. S. mutans strain MT8148 was grown in the presence of recombinant RecA (rRecA) protein, after which smooth colonies were isolated. The biological functions and sequences of the gtfB and gtfC genes of this as well as other clinical strains were determined. The sucrose-dependent adherence rates of those strains were reduced as compared to that of MT8148. Determination of the sequences of the gtfB and gtfC genes showed that an approximately 3500 bp region was deleted from the area between them. Furthermore, expression of the recA gene was elevated in those strains as compared to MT8148. These results suggest that RecA has an important role in fusions of gtfB and gtfC genes, leading to alteration of colony morphology and reduction in sucrose-dependent adhesion.

An in vivo investigation of salivary properties, enamel hypomineralisation, and carious lesion severity in a group of Iraqi schoolchildren

BACKGROUND

Hypomineralised enamel is a prevalent, congenital defect vulnerable to deteriorate post-eruptively particularly in the presence of an unfavourable oral environment.

AIMS

To assess the influence of salivary characteristics on the clinical presentation of hypomineralisation lesions diagnosed in first permanent and second primary molars and to evaluate caries severity in relation to the defect's clinical presentation.

DESIGN

Recruitment consisted of 445 seven- to nine-year-old participants, of whom 152 were diagnosed as having molar hypomineralisation (MH); the remaining unaffected subjects (N = 293) were considered their controls for saliva analysis. Dental caries status was assessed in 300 subjects of saliva sub-sample, equally divided as MH-affected and non-affected children. The International Caries Detection and Assessment System was used for caries detection. Salivary flow rates, viscosity, pH, and buffering capacity were determined.

RESULTS

Molar hypomineralisation-affected children have significantly higher mean caries scores compared to the non-affected group. Dentinal carious lesions were ten times more frequent in teeth with post-eruptive breakdown (PEB) than with teeth with opacities only. Low salivary flow rates (LSFR), moderately viscous saliva, and low pH were significantly more common in the affected group. LSFR and moderate and highly acidic saliva were more likely associated with PEB.

CONCLUSION

Demarcated hypomineralised enamel is a dynamic defect highly influenced by individual characteristics of the oral environment.

Postoperative prognostic predictors of pancreatic ductal adenocarcinoma: clinical analysis and immunoprofile on tissue microarrays

BACKGROUND

Most pancreatic ductal adenocarcinomas (PDACs) metastasize even after curative resection. Our goal was to investigate the important factors affecting metastasis and overall survival (OS).

METHODS

We studied 88 PDACs with R0 resection and evaluated immunohistochemical markers on tissue microarrays to assess the expression levels of the following: EGFR, amphiregulin, VEGF, p-c-met, MMP2, MMP7, MMP9, CXCR3, and CXCR4.

RESULTS

The median OS in patients who had positive versus negative expression of AREG and MMP9 were 25 versus 16 months and 24 versus 13 months, respectively (P = 0.03, P = 0.006). However, the median OS in patients with positive versus negative expression of MMP2 was 22 versus 37 months (P = 0.04). Immunoprofiles also revealed that patients with positive expression of p-c-met or VEGF had significantly shorter distant metastasis-free survival. Adjuvant treatment, postoperative decrease of CA 19-9, angiolymphatic invasion, AREG, and MMP2 were independent prognostic factors affecting OS in multivariate analysis.

CONCLUSIONS

Immunoprofiles revealed the groups with unfavorable tumor biology: negative expression of AREG and positive expression of MMP2. Also, high immunoreactivity of p-c-met or VEGF seemed to be associated with early distant organ metastasis in R0 resected PDACs; however, they still need to be further investigated. These results may give us useful insights in understanding the tumor biology and the patterns of PDAC dissemination.

Nanotechnology in Dental Sciences: Moving towards a Finer Way of Doing Dentistry

Nanotechnologies are predicted to revolutionize: (a) the control over materials properties at ultrafine scales; and (b) the sensitivity of tools and devices applied in various scientific and technological fields. In this short review, we argue that dentistry will be no exception to this trend. Here, we present a dynamic view of dental tissues, an adoption of which may lead to finer, more effective and minimally invasive reparation approaches. By doing so, we aim at providing insights into some of the breakthroughs relevant to understanding the genesis of dental tissues at the nanostructural level or generating dental materials with nanoscale critical boundaries. The lineage of the progress of dental science, including the projected path along the presumed nanotechnological direction of research and clinical application is mentioned too. We conclude by claiming that dentistry should follow the trend of probing matter at nanoscale that currently dominates both materials and biological sciences in order to improve on the research strategies and clinical techniques that have traditionally rested on mechanistic assumptions.

Diagnostic applications of saliva in dentistry

Background: The use of saliva to identify individuals with disease and to follow the progress of the affected individual has attracted the attention of numerous investigators. Its noninvasive method of collection, simplicity, and cost effectiveness make it a useful tool not only to the general practitioner but also to the pediatric dentist.

Aim: The aim of this paper is to provide the clinician with a comprehensive review of the diagnostic uses of saliva in dentistry.

Oral and salivary changes in patients with end stage renal disease (ESRD): a two year follow-up study

OBJECTIVES

To compare oral health, salivary flow rate, xerostomia and thirst in end stage renal disease (ESRD) patients remaining on dialysis treatment and after renal transplantation.

DESIGN

Longitudinal observation.

SETTING

ESRD patients recruited from dialysis centres in Amsterdam, The Hague and Utrecht, The Netherlands.

METHOD

At baseline and after two years, salivary flow rates, xerostomia and thirst were determined in 43 ESRD patients. The number of decayed missing filled teeth/surfaces (DMFT/DMFS) was recorded, and periodontal status assessed.

RESULTS

After renal transplantation (n = 20), the salivary flow rate increased significantly from UWS = 0.30 +/- 0.21 ml/min to 0.44 +/- 0.29 ml/min (p <0.001) and the level of xerostomia and thirst decreased. After two years, the percentage of bleeding on probing in dialysis patients (n = 23) decreased from 29.5 +/- 25.4% to 10.3 +/- 12.3%, (p <0.05). No differences in DMFT and DMFS were observed between dialysis and renal transplant patients.

CONCLUSIONS

DMFT, dental plaque, gingival bleeding and periodontal indices did not change remarkably after two years, comparing dialysis and renal transplant patients. Renal transplantation enhances salivary flow and decreases symptoms of xerostomia and thirst, and hence enhances the potential to improve the quality of life of affected individuals.

Inflammation-responsive transcription factors SAF-1 and c-Jun/c-Fos promote canine MMP-1 gene expression

Matrix metalloproteinase-1 (MMP-1) has been implicated in the pathogenesis of osteoarthritis (OA) due to its ability to degrade extracellular matrix component of the joint cartilage tissue that cushions the bone from frictional damage. Canine hip dysplasia, a developmental orthopedic disease which results in arthritic condition as is seen in human OA is an excellent system to study the involvement of MMP-1 in the pathogenesis of OA. To date, however, no report is available regarding canine MMP-1 promoter and the regulatory mechanism by which increased synthesis of MMP-1 protein might be regulated. To gain an insight, we have investigated the promoter region of canine MMP-1. MMP-1 synthesis in the resident cells of arthritic joints is regulated via two major cytokines, IL-1beta and TNF-alpha. By using a series of progressively deleted reporter constructs, multiple cytokine-responsive elements were identified in the proximal promoter region of canine MMP-1. These include DNA-binding elements of AP-1 and SAF-1 transcription factors. Mutation of AP-1 or SAF-1 element resulted in marked reduction in the cytokine responsiveness of MMP-1 promoter. We show that AP-1 and SAF-1 DNA-binding activities are increased in cytokine-stimulated cells as well as in osteoarthritic cartilage tissues. In correlation, immunohistochemical analysis indicated higher levels of MMP-1, SAF-1 and AP-1 proteins in osteoarthritic but not in the normal cartilage tissue. These results show that induction and activation of AP-1 and SAF-1 transcription factors are involved in the regulation of MMP-1 expression in the chondrocytes which could be used as therapeutic targets to combat pathogenesis of OA.

Calcium transport in human salivary glands: a proposed model of calcium secretion into saliva

Salivary calcium plays a vital role in bio-mineralization of dental enamel and exposed dentin. In order to elucidate the yet unknown cellular and molecular mechanisms of calcium secretion in human salivary glands the presence of various relevant plasma membrane transport systems for calcium were investigated. Using an RT-PCR approach, expression of the epithelial calcium channel (CaT-Like), the calcium binding protein (calbindin-2), the endoplasmic reticulum pumps (SERCA-2 and -3), and the plasma membrane calcium ATPases (PMCA-1, -2, and -4), were found in parotid and submandibular glands. Immunohistochemistry revealed that CaT-Like is located in the basolateral plasma membrane of acinar cells; while calbindin-2, SERCA-2 and SERCA-3 were found inside the acinar cells; and PMCA-2 was found in the apical membrane and in the secretory canaliculi between the cells. Based on these findings, we propose the following model of calcium secretion in human salivary glands: (1) calcium enters the acinar cell at the basolateral side via calcium channel CaT-Like (calcium influx); (2) intracellular calcium is taken up into the endoplasmic reticulum by SERCA-2 and possibly SERCA3 or bound to calbindin-2 (intracellular calcium pool); and (3) calcium is secreted by PMCAs at the apical plasma membrane (calcium efflux).

Two-hybrid analysis of human salivary mucin MUC7 interactions

MUC7 is a low molecular weight monomeric mucin secreted by submandibular, sublingual and minor salivary glands. This mucin has been implicated in the non-immune host defense system in the oral cavity since it binds and agglutinates a variety of oral microbes. To investigate interactions between this mucin and other secretory salivary proteins, a submandibular gland prey library was screened with baits encoding the N- and C-terminal regions of MUC7 in the yeast two-hybrid system. The N-terminal region interacted with several secretory salivary proteins, whereas the C-terminal region did not. Interacting proteins included amylase, acidic proline-rich protein 2, basic proline-rich protein 3, lacrimal proline-rich protein 4, statherin and histatin 1. Formation of complexes between these proteins and the N-terminal region of MUC7 was confirmed in Far Western blotting experiments. Interactions between mucin and non-mucin proteins in saliva could protect complex partners from proteolysis, modulate the biological activity of complexed proteins or serve as a delivery system for distribution of secretory salivary proteins throughout the oral cavity.

Effect of a Calcium Carbonate-Based Dentifrice on in situ Enamel Remineralization

This crossover study evaluated the effect of calcium carbonate (CaCO(3))-based monofluorophosphate dentifrice on enamel remineralization. Ten volunteers wore palatal appliances containing four enamel blocks with caries-like lesions, two of them covered by a test plaque of mutans streptococci. The following treatments were evaluated: a negative control, a silica-based or a CaCO(3)-based dentifrice, and the percentage of enamel surface microhardness recovery was determined. The CaCO(3)-based dentifrice was more effective than the negative control on the enhancement of enamel remineralization, either in the presence or absence of test plaque. This efficacy was also shown by the silica-based dentifrice but only in the presence of test plaque.

Serum amyloid A-activating factor-1 (SAF-1) transgenic mice are prone to develop a severe form of inflammation-induced arthritis

The transcription factor serum amyloid A-activating factor-1 (SAF-1) has been identified as a regulator of a number of cellular genes. To assess the pleiotropic role of SAF-1 in vivo, we generated SAF-1 transgenic mice, in which CMV immediate-early promoter was used to direct expression of the SAF-1 transgene in multiple organs. Our study shows that overexpression of SAF-1 predisposes animals to arthritis. Although SAF-1 transgenic mice do not spontaneously develop arthritis, they develop a severe form of arthritis when challenged with the Lyme disease agent Borrelia burgdorferi, which is known to promote arthritis development in both humans and mice. CMV-SAF-1 transgenic mice, upon B. burgdorferi infection, showed increased joint swelling and synovial inflammation compared with nontransgenic littermates. Immunohistochemical analysis of joint tissues collected 21 days after B. burgdorferi infection revealed colocalization of matrix metalloproteinase-1, a degradative enzyme that destroys type II collagen, a major architectural component of articular cartilage, and SAF-1 in both SAF-1 transgenic and nontransgenic mice. Further analysis by RNase protection assay and Western immunoblot demonstrated the presence of higher levels of matrix metalloproteinase-1 and SAF-1 in the inflamed joints of SAF-1 transgenic mice compared with their levels in nontransgenic mice. Consistent with these findings, reduced levels of proteoglycans were detected in the inflamed joint cartilage of transgenic mice, indicating damage to the cartilage structure. Together these results suggest a role of SAF-1 in the pathogenesis of inflammation-induced arthritis.

Reduced gingival fluid flow: a peripheral marker of the pharmacological effect of roquinimex

OBJECTIVE

Roquinimex is a drug with effects on inflammation and tumors. The pharmacological effect is not fully understood, and the molecular mechanism most characterized in vitro is an increase of plasminogen activator inhibitor type 2 (PAI-2) in human peripheral blood monocytes. The aims were to investigate peripheral pharmacological effects of roquinimex on peripheral blood monocytes and dog gingival fluid (GCF).

DESIGN

Six dogs were used in a cross-over study. The amount of GCF was determined with a Periotron. The PAI-2 concentration in GCF was determined with ELISA. Monocytes were isolated from peripheral blood.

RESULTS

Dogs treated with the drug had significantly lower GCF flow values and the PAI-2 concentration in GCF was higher, but no effect was seen on peripheral monocytes.

CONCLUSION

Roquinimex treatment led to a consistently decreased flow rate of GCF and a higher local concentration of PAI-2 in GCF.

Cyclic strain stimulates early growth response gene product 1-mediated expression of membrane type 1 matrix metalloproteinase in endothelium

SUMMARY

Matrix metalloproteinases (MMPs) are hypothesized to be involved in the processes of endothelial cell (EC) migration and matrix remodeling during angiogenesis. Although hemodynamic forces (such as blood pressure, wall tension, and shear stress) are considered to be strong stimuli for angiogenesis, the role of hemodynamic forces on the regulation of MMPs including membrane type 1 matrix metalloproteinase (MT1-MMP) has not been fully elucidated. To study this, rat microvascular EC were exposed to 60 cycles/minute of 24% maximum strain for up to 24 hours. MT1-MMP mRNA and protein increased in a time-dependent manner through 24 hours of exposure to cyclic strain. Cyclic strain induced early growth response gene product (Egr-1) mRNA and protein within 1 hour. A specific nucleoprotein complex was formed when an oligonucleotide containing binding sites for Sp1 and Egr-1 was incubated with nuclear extracts from EC exposed to 1 hour of cyclic strain. Antibodies to Egr-1 completely supershifted this complex. Increased binding of Egr-1 by cyclic strain to the MT1-MMP promoter correlated with enhanced transcriptional activity. These results suggest that cyclic strain up-regulates the Egr-1-mediated expression of MT1-MMP in rat microvascular EC, emphasizing the importance of hemodynamic forces in the regulation of MT1-MMP in vivo.

Acid resistance of human enamel in vitro after bicarbonate application during remineralization

OBJECTIVES

The aim of this study was to investigate the acid resistance of subsurface enamel lesions remineralized with bicarbonate solutions during remineralization.

METHODS

Two experiments were carried out. In experiment 1, mineral uptake and acid resistance of remineralized enamel lesions were analyzed quantitatively by microradiography for mineral changes. Bicarbonate solutions of 0.5, 5.0 and 50.0 mM were used. In experiment 2, to clarify acid resistance mechanisms, the pH changes in demineralizing solutions on the remineralized enamel surfaces were measured continuously. Only a bicarbonate solution of 5.0 mM was used.

RESULTS

In experiment 1, the bicarbonate-treated groups were more acid resistant than the non-treated groups (p<0.05). However, no statistically significant difference was observed among the different concentrations of bicarbonate. In experiment 2, the pH rise of the bicarbonate group was greater than the other groups.

CONCLUSION

It was found that bicarbonate-treated enamel lesions were resistant to acid. It would suggest that bicarbonate ions applied during remineralization may have penetrated into the subsurface lesions. These ions may have worked as buffer agents against the acid challenge and inhibited the decrease in pH.

Human chromosomal localization, tissue/tumor expression, and regulatory function of the ets family gene EHF

Ets factors are members of an ancient multigene family of transcription factors including oncoproteins and possibly tumor suppressors. We previously characterized a novel divergent ets gene, Ehf (ets homologous factor) in mice. Here we report the cDNA sequence, chromosomal location, and tissue/tumor expression patterns of the human EHF gene and the regulatory activity of the EHF protein. EHF maps to 11p12, which is deleted in many prostate, breast, and lung carcinomas and is a hot spot for inherited deletion- or amplification-associated developmental defects. EHF is differentially expressed in normal tissues and carcinomas and between tumor stages and is most highly expressed in the organs known to form carcinomas upon 11p12 deletion. EHF protein represses the ETS-2 induced activity of both stromelysin-1 and collagenase-1 promoters. These data suggest that EHF may contribute to human development and carcinogenesis and is a candidate for the 11p12 tumor suppressor gene.

Salivary factors in caries models

Consideration of salivary factors in caries models rarely extends beyond viewing saliva as a sink or diluent for plaque metabolic products, or as a source of buffering, for neutralizing plaque acids. In reality, saliva has a complex chemistry and a wide range of biochemical activities that may significantly affect plaque chemistry and microbiology. Thus, saliva is a major source of microbial nutrients, without which bacterial acid production is diminished. Buffering by salivary bicarbonate, and base production from urea and basic amino acids and peptides, significantly affect Stephan curves. Saliva is supersaturated with respect to basic calcium phosphate salts and contains novel inhibitors of calcium phosphate precipitation, while specific salivary proteins bind calcium. It seems important to consider if this system is reflected in plaque. Saliva, with contributions from serum and bacterial constituents, provides most of the precursors for the acquired enamel pellicle, which acts to slow demineralization during caries attack. Pellicle constituents appear to influence initial bacterial colonization of tooth surfaces and, therefore, may affect the microbial composition of plaque, but their detailed effects on plaque are poorly understood. Microbial adaptations to the anti-bacterial systems also seem important but are poorly investigated. Thus, saliva possesses an array of activities that have substantial actual or potential impact on plaque and, therefore, merit consideration for inclusion in systems intended to model dental caries.

In situ caries models

By using in situ models, we have the potential to study both fundamental aspects of the caries process as well as more applied research problems such as the effect of food on dental caries and the role of fluoride in caries prevention in human subjects without actually causing caries in the natural dentition. The key experimental parameters that need to be considered in the development of an in situ model are the characteristics of the subject panel, the physical design of the model, the type of hard tissue substrate and the method of assessing mineral status, and the study design and clinical protocol. Each parameter must be carefully considered in relation to the objectives of the research, study design requirements, ethical considerations, impact on clinical relevance, and impact on the control of variation. The major source of variation associated with in situ models should be of biological and not experimental origin. The design and conduct of proper in situ model studies require a clear understanding of the caries process, sound analytical support, and a knowledge of how to work with research subjects to achieve a high level of compliance. Given the complex nature of caries, a combination of hard tissue substrates--including sound, surface-softened lesions and subsurface lesions--may be necessary to model all aspects of caries progression and prevention successfully. Internal validation of in situ models using fluoride dose-response controls is considered to be necessary for studies evaluating the efficacy of new fluoride dentifrice formulations.