L-mimosine increases the production of vascular endothelial growth factor in human tooth slice organ culture model.

AIM To assess the pro-angiogenic and pro-inflammatory capacity of the dentine-pulp complex in response to the prolyl hydroxylase inhibitor L-mimosine in a tooth slice organ culture model. METHODOLOGY Human teeth were sectioned transversely into 600-μm-thick slices and cultured in medium supplemented with serum and antibiotics. Then, pulps were stimulated for 48 h with L-mimosine. Pulps were subjected to viability measurements based on formazan formation in MTT assays. In addition, histological evaluation of pulps was performed based on haematoxylin and eosin staining. Culture supernatants were subjected to immunoassays for vascular endothelial growth factor (VEGF) to determine the pro-angiogenic capacity and to immunoassays for interleukin (IL)-6 and IL-8 to assess the pro-inflammatory response. Interleukin-1 served as pro-inflammatory control. Echinomycin was used to inhibit hypoxia-inducible factor-1 (HIF-1) alpha activity. Data were analysed using Student's t-test and Mann-Whitney U test. RESULTS Pulps within tooth slices remained vital upon L-mimosine stimulation as indicated by formazan formation and histological evaluation. L-mimosine increased VEGF production when normalized to formazan formation in the pulp tissue of the tooth slices (P < 0.05). This effect on VEGF was reduced by echinomycin (P < 0.01). Changes in normalized IL-6 and IL-8 levels upon treatment with L-mimosine did not reach the level of significance (P > 0.05), whilst treatment with IL-1, which served as positive control, increased IL-6 (P < 0.05) and IL-8 levels (P < 0.05). CONCLUSIONS The prolyl hydroxylase inhibitor L-mimosine increased VEGF production via HIF-1 alpha in the tooth slice organ culture model whilst inducing no prominent increase in IL-6 and IL-8. Pre-clinical studies will reveal if these in vitro effects translate into dental pulp regeneration.

Interactions between dodecyl phosphates and hydroxyapatite or tooth enamel: relevance to inhibition of dental erosion.

Tooth surface modification is a potential method of preventing dental erosion, a form of excessive tooth wear facilitated by softening of tooth surfaces through the direct action of acids, mainly of dietary origin. We have previously shown that dodecyl phosphates (DPs) effectively inhibit dissolution of native surfaces of hydroxyapatite (the type mineral for dental enamel) and show good substantivity. However, adsorbed saliva also inhibits dissolution and DPs did not augment this effect, which suggests that DPs and saliva interact at the hydroxyapatite surface. In the present study the adsorption and desorption of potassium and sodium dodecyl phosphates or sodium dodecyl sulphate (SDS) to hydroxyapatite and human tooth enamel powder, both native and pre-treated with saliva, were studied by high performance liquid chromatography-mass Spectrometry. Thermo gravimetric analysis was used to analyse residual saliva and surfactant on the substrates. Both DPs showed a higher affinity than SDS for both hydroxyapatite and enamel, and little DP was desorbed by washing with water. SDS was readily desorbed from hydroxyapatite, suggesting that the phosphate head group is essential for strong binding to this substrate. However, SDS was not desorbed from enamel, so that this substrate has surface properties different from those of hydroxyapatite. The presence of a salivary coating had little or no effect on adsorption of the DPs, but treatment with DPs partly desorbed saliva; this could account for the failure of DPs to increase the dissolution inhibition due to adsorbed saliva.

Impact of Acquired Pellicle Modification on Adhesion of Early Colonizers

New preventive approaches against dental erosion caused by acidic drinks and beverages include fortification of beverages with natural polymers. We have shown that the mixture of casein and mucin significantly improved the erosion-inhibiting properties of the human pellicle layer. This study aimed to investigate the effect of pellicle modification by casein, mucin and a casein-mucin mixture on the adhesion of early bacterial colonizers. Test specimens of human tooth enamel were prepared, covered with saliva and coated with 0.5% aqueous (aq.) casein, 0.27% aq. mucin or with 0.5% aq. casein-0.27% aq. mucin, after which the adhesion of Streptococcus gordonii, Streptococcus oralis, and Actinomyces odontolyticus was measured after incubation for 30 min and 2 h. log10 colony-forming units were compared by nonparametric tests. All three bacterial strains adhered in higher number to pellicle-coated enamel than to native enamel. The protein modifications of pellicle all decreased the counts of adhering bacteria up to 0.34 log10/mm2, the most efficient being the casein-mucin mixture. In addition to the recently shown erosion-reducing effect by casein-mucin, modification of the pellicle may inhibit bacterial adherence compared to untreated human pellicle.

Influence of the condition of the adjacent tooth surface on fluorescence measurements for the detection of approximal caries

The aim of this study was to test whether the status of the adjacent tooth surface has an influence on the signal of a new laser fluorescence (LF) device for the detection of approximal caries. Seventy-eight teeth were selected from a pool of extracted permanent human molars, frozen at -20 degrees C until use. Before being measured the teeth were defrosted, cleaned, and any calculus removed. As a control, a defined approximal surface of each tooth was measured with the LF device holding the tip with the detecting- and the reverse-side on it, but without a neighboring tooth contacting the surface. The proximal site under examination was then placed adjacent to a tooth, which had deep dentinal caries, a composite restoration, a provisional ZnO-Eugenol restoration, or a ceramic restoration. The adjacent tooth with the ZnO-Eugenol restoration, the composite restoration, and the dentinal caries all demonstrated a statistically significant increase of LF readings on sound tooth surfaces. Teeth with enamel or dentinal caries were only slightly (and not statistically significantly) influenced by the different types of neighboring surfaces compared with the control LF readings. It can be concluded that caries detection of approximal tooth surfaces with the new LF system might be influenced by the condition of the adjacent tooth surface.

Immunodetection of bone-related proteins in microcalcifications of human dental pulp

Objective: Root canal obliterations may pose esthetic and clinical problems or may even be a risk factor for tooth survival. Microcalcifications in the pulp can be so extensive that the entire root canal system becomes obliterated. Since bone sialoprotein (BSP) and osteopontin (OPN) are involved in both physiological and pathological mineralization processes, our hypothesis was that these two bone-related noncollagenous proteins are present in microcalcifications of the pulp. The purpose of this study was, therefore, to characterize the nature of microcalcifications in the pulp of aged human teeth. Methods: From a large collection of human teeth, 10 were found to exhibit pulpal microcalcifications. The teeth were extracted for periodontal reasons from 39-60 year old patients. After fixation in aldehydes and decalcification, teeth were processed for embedding in LR White resin for analysis in the light and transmission electron microscope. For the detection of BSP and OPN, post-embedding high resolution immunocytochemistry was applied. Results: The microcalcifications were round or elongated, occasionally coalescing, and intensely stained with toluidine blue. Collagen fibrils were found in most but not all microcalcifications. All microcalcifications were immunoreactive for both antibodies and showed an identical labeling pattern. Gold particle labeling was extensively found throughout the interfibrillar ground substance of the microcalcifications, whereas the dentin matrix lacked immunolabeling. Conclusion: BSP and OPN appear to be major matrix constituents of pulp microcalcifications and may thus, like in other mineralized tissues, be involved in their mineralization process.

CO2 laser-irradiation through topically applied fluoride increases acid resistance of demineralised human enamel in vitro

PURPOSE: To evaluate the effect of CO2 laser treatment through topically applied amine fluoride solution on demineralised enamel. MATERIALS AND METHODS: Sixty extracted human molar crowns were selected and cut longitudinally into half. One half was subjected to a 10-day pH-cycling procedure to create caries-like lesions, whereas the other was left non-demineralised. The following treatments were randomly assigned (one treatment per tooth, on respective non-demineralised and demineralised matched specimens): exposure to a 1% amine fluoride solution for 15 s without irradiation (group I), irradiation for 15 s with a continuous-wave CO2 laser (group II), or laser-treatment for 15 s through the amine fluoride solution applied immediately beforehand (group III). Fluoride uptake (n = 30) and acid resistance (n = 30) were determined after treatment. Enamel surface alterations after laser irradiation were monitored using scanning electron microscopy. RESULTS: In groups I and III, an increased fluoride uptake was detected (p < or = 0.05). Laser irradiation through topical fluoride resulted in an increased acid resistance of sound and demineralised enamel specimens in deeper layers (p < or = 0.05). In addition, less surface alterations were observed in SEM examination of specimens irradiated through the amine fluoride solution compared with counterparts treated with laser only. CONCLUSIONS: CO2 laser light application through an amine fluoride solution may be instrumental in enhancing acid resistance of sound and demineralised enamel.

Human and feline invasive cervical resorptions: the missing link?--Presentation of four cases

This report describes 4 patients presenting with multiple teeth affected by invasive cervical resorption (ICR). The cases came to our attention between 2006 and 2008; previously, no cases of multiple ICR (mICR) had been reported in Switzerland. Characteristics common to all 4 cases included progression of disease over time, similar clinical and radiographic appearance of lesions, and obscure etiology. The histologically assessed teeth showed a similar pattern of tooth destruction, with resorptive lesions being confined to the cervical region. Howship's lacunae and multinucleated, tartrate-resistant acid phosphatase-positive odontoclasts were detected. None of the teeth presented with internal resorption. The positive pulp sensitivity corresponded to the histologic findings, indicating that the pulp tissue resisted degradation even in advanced stages of resorptive lesions. Although mICR is rare in humans, a similar disease known as feline odontoclastic resorptive lesions (FORL) is common in domestic, captive, and wild cats. The etiology of FORL, like that of mICR, remains largely unknown. Because FORL has been associated with feline viruses, we asked our mICR patients whether they had had contact with cats, and interestingly, all patients reported having had direct (2 cases) or indirect (2 cases) contact. In addition, blood samples were taken from all patients for neutralization testing of feline herpes virus type 1 (FeHV-1). Indeed, the sera obtained were able to neutralize (2 cases) or partly inhibit (2 cases) replication of FeHV-1, indicating transmission of feline viruses to humans. Future studies on mICR (and FORL) should evaluate the possible role of a (feline) virus as an etiologic (co-)factor in this disease.

Leptin effects on the regenerative capacity of human periodontal cells

Obesity is increasing throughout the globe and characterized by excess adipose tissue, which represents a complex endocrine organ. Adipose tissue secrets bioactive molecules called adipokines, which act at endocrine, paracrine, and autocrine levels. Obesity has recently been shown to be associated with periodontitis, a disease characterized by the irreversible destruction of the tooth-supporting tissues, that is, periodontium, and also with compromised periodontal healing. Although the underlying mechanisms for these associations are not clear yet, increased levels of proinflammatory adipokines, such as leptin, as found in obese individuals, might be a critical pathomechanistic link. The objective of this study was to examine the impact of leptin on the regenerative capacity of human periodontal ligament (PDL) cells and also to study the local leptin production by these cells. Leptin caused a significant downregulation of growth (TGFβ1, and VEGFA) and transcription (RUNX2) factors as well as matrix molecules (collagen, and periostin) and inhibited SMAD signaling under regenerative conditions. Moreover, the local expression of leptin and its full-length receptor was significantly downregulated by inflammatory, microbial, and biomechanical signals. This study demonstrates that the hormone leptin negatively interferes with the regenerative capacity of PDL cells, suggesting leptin as a pathomechanistic link between obesity and compromised periodontal healing.

Regulation of NAMPT in human gingival fibroblasts and biopsies

Adipokines, such as nicotinamide phosphoribosyltransferase (NAMPT), are molecules, which are produced in adipose tissue. Recent studies suggest that NAMPT might also be produced in the tooth-supporting tissues, that is, periodontium, which also includes the gingiva. The aim of this study was to examine if and under what conditions NAMPT is produced in gingival fibroblasts and biopsies from healthy and inflamed gingiva. Gingival fibroblasts produced constitutively NAMPT, and this synthesis was significantly increased by interleukin-1β and the oral bacteria P. gingivalis and F. nucleatum. Inhibition of the MEK1/2 and NFκB pathways abrogated the stimulatory effects of F. nucleatum on NAMPT. Furthermore, the expression and protein levels of NAMPT were significantly enhanced in gingival biopsies from patients with periodontitis, a chronic inflammatory infectious disease of the periodontium, as compared to gingiva from periodontally healthy individuals. In summary, the present study provides original evidence that gingival fibroblasts produce NAMPT and that this synthesis is increased under inflammatory and infectious conditions. Local synthesis of NAMPT in the inflamed gingiva may contribute to the enhanced gingival and serum levels of NAMPT, as observed in periodontitis patients. Moreover, local production of NAMPT by gingival fibroblasts may represent a possible mechanism whereby periodontitis may impact on systemic diseases.

Toothbrushing after an erosive attack: will waiting avoid tooth wear?

The purpose of this study was to determine if storage for up to 4 h in human saliva results in a decrease of erosive tooth wear (ETW) and in an increase of surface microhardness (SMH) of enamel samples after an erosive attack with subsequent abrasion. Furthermore, we determined the impact of individual salivary parameters on ETW and SMH. Enamel samples were distributed into five groups: group 1 had neither erosion nor saliva treatment; groups 2-5 were treated with erosion, then group 2 was placed in a humid chamber and groups 3-5 were incubated in saliva for 30 min, 2 h, and 4 h, respectively. After erosion and saliva treatments, all groups were treated with abrasion. Surface microhardness and ETW were measured before and after erosion, incubation in saliva, and abrasion. Surface microhardness and ETW showed significant changes throughout the experiment: SMH decreased and ETW increased in groups 2-5, regardless of the length of incubation in saliva. The results of groups 3-5 (exposed to saliva) were not significantly different from those of group 2 (not exposed to saliva). Exposure of eroded enamel to saliva for up to 4 h was not able to increase SMH or reduce ETW. However, additional experiments with artificial saliva without proteins showed protection from erosive tooth wear. The recommendation to postpone toothbrushing of enamel after an erosive attack should be reconsidered.

Can stable isotope analysis and tooth histology assist in detecting stillbirth? An approach using neonatal remains from the Roman settlement Studen Petinesca

Infant burials in Roman settlements are a common observation. Even though ancient authors provide information many questions remain uncertain. For instance, the burial ritual for stillbirth and infanticide neonates is not specifically mentioned. This study therefore aimed to investigate the application of stable nitrogen (δ15N) and carbon (δ13C) isotopes from neonatal bone collagen in differentiating between a breastfeeding signal and stillbirth or a short survival of less than ten days. For this purpose collagen of 11 human and 14 non-human bones from the Roman settlement Petinesca (1st - 3rd century AD, Switzerland) was extracted and analysed for δ15N and δ13C. Tooth histology was performed for the central incisor and canine of the right mandible in order to investigate the presence of a neonatal line. According to the length of the long bones the age varied between 8.5 lunar months to 2 months ex utero. The stable isotope results provided a breastfeeding signal for all except one individual where the breastfeeding signal was absent. The tooth histological analysis of this individual exhibited no neonatal line. It is concluded that stable isotope analysis could indicate stillbirth or a short survival after birth. The tooth histology confirmed the stable isotope results. Furthermore, this might indicate that the burial ritual did not differentiate between stillbirth and neonates, who died within the time span stated by ancient authors of up to 40 days of age or the appearance of teeth. However, for further justifications additional research is going to be conducted.

Biomaterials for promoting periodontal regeneration in human intrabony defects: a systematic review

Intrabony periodontal defects are a frequent complication of periodontitis and, if left untreated, may negatively affect long-term tooth prognosis. The optimal outcome of treatment in intrabony defects is considered to be the absence of bleeding on probing, the presence of shallow pockets associated with periodontal regeneration (i.e. formation of new root cementum with functionally orientated inserting periodontal ligament fibers connected to new alveolar bone) and no soft-tissue recession. A plethora of different surgical techniques, often including implantation of various types of bone graft and/or bone substitutes, root surface demineralization, guided tissue regeneration, growth and differentiation factors, enamel matrix proteins or various combinations thereof, have been employed to achieve periodontal regeneration. Despite positive observations in animal models and successful outcomes reported for many of the available regenerative techniques and materials in patients, including histologic reports, robust information on the degree to which reported clinical improvements reflect true periodontal regeneration does not exist. Thus, the aim of this review was to summarize, in a systematic manner, the available histologic evidence on the effect of reconstructive periodontal surgery using various types of biomaterials to enhance periodontal wound healing/regeneration in human intrabony defects. In addition, the inherent problems associated with performing human histologic studies and in interpreting the results, as well as certain ethical considerations, are discussed. The results of the present systematic review indicate that periodontal regeneration in human intrabony defects can be achieved to a variable extent using a range of methods and materials. Periodontal regeneration has been observed following the use of a variety of bone grafts and substitutes, guided tissue regeneration, biological factors and combinations thereof. Combination approaches appear to provide the best outcomes, whilst implantation of alloplastic material alone demonstrated limited, to no, periodontal regeneration.