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ABSTRACT: The aim of this study was to evaluate the biocompatibility of mineral trioxide aggregate mixed with selective hydration accelerators such as calcium chloride (CaCl2), citric acid (CA), and calcium lactate gluconate solution (CLG).
Inductively coupled plasma-atomic emission spectrometry analysis was used to measure calcium ions in the extracts of test materials. The 2,3-bis(2-methoxy-4-nitro-5-sulfophenyl)-5-[(phenylamino)carbonyl]-2H-tetrazolium hydroxide assay was performed using MG-63 cells to examine the cytotoxicity of the test materials. The surface of each sample and the growth pattern of the attached cells were observed using scanning electron microscopy (SEM).
MTA mixed with 10 wt% CaCl2 and MTA mixed with 43.4 wt% CLG released a higher amount of calcium ions than the other groups. The 2,3-bis(2-methoxy-4-nitro-5-sulfophenyl)-5-[(phenylamino)carbonyl]-2H-tetrazolium hydroxide assay revealed that the cell viability of MTA mixed with 0.1 wt% CA was significantly higher than pure MTA on 7-day extract (P < .05). MTA mixed with 43.4 wt% CLG showed significantly higher cell viability than the other groups on 1-day extract (P < .05). MTA mixed with 10 wt% CaCl2 in all groups showed the lowest cell viability at all time points (P < .05). Under SEM, elongated and confluent cells were observed in all samples except in samples of MTA mixed with 10 wt% CaCl2.
MTA mixed with 0.1 wt% CA showed good biocompatibility. MTA mixed with 43.4 wt% CLG showed favorable biocompatibility on 1 day. MTA mixed with 10 wt% CaCl2 in all groups showed the lowest cell viability at every time point and poor cell attachment under SEM.
Journal of endodontics 04/2013; 39(4):497-500. · 2.95 Impact Factor
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ABSTRACT: Abstract Objectives. The objective of this study was to compare the caries risk profiles obtained from the simplified Cariogram models and the conventional Cariogram model of Korean dental patients. Materials and methods. Data required for a caries risk assessment with the Cariogram were collected from 80 young adult patients (mean: 23 years old). Three different simplified Cariogram models were produced with exclusion of either or both salivary secretion rate and lactobacilli count: group 1, conventional model; group 2, both salivary secretion rate and lactobacilli count excluded; group 3, salivary secretion rate excluded; group 4, lactobacilli count excluded. Results. The mean chance of avoiding caries in group 1 (55.5%) was not significantly different from those in groups 2 and 3. Also four caries-related sectors of the Cariogram (diet, bacteria, susceptibility and circumstance) in group 1 were not significantly different than in groups 2 and 3. Group 4 showed significant differences from group 1 in the mean chance of avoiding caries and the diet, susceptibility and circumstance sectors (p < 0.05). Significant correlations were detected between all risk factors and their corresponding risk sectors (p < 0.05). Also there were significant correlations between each risk factor and the chance of avoiding caries, except for the amount of plaque, in groups 1, 2 and 3 (p < 0.05). Conclusions. The simplified Cariogram model without salivary secretion rate and lactobacilli count did not significantly change the outcome produced from the conventional model. However, single exclusion of lactobacilli count noticeably changed the caries risk profile.
Acta odontologica Scandinavica 10/2012; · 1.41 Impact Factor
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ABSTRACT: The purpose of this study was to evaluate the effects of different desensitizing agents on the prevention of root caries when applied to root surfaces.
Thirty human roots were sectioned into quarters with a 3 × 4 mm window. A desensitizer (VX, Clinpro™ XT Varnish; SP, Seal & Protect®; or PB, Clearfil™ Protect Bond) was applied to three of the quarters in each window. Teeth were stored separately in water for one day, 30 days, or 60 days. The remaining quarter, without the application of desensitizer, served as a control. After storage in water, all specimens were subjected to pH cycling. Scanning electron microscopy was used to observe the demineralization bands created on the subsurface layer. The weight percentages of fluorine (F), silica, and calcium (Ca) were determined using electron probe microanalysis to quantify the elemental distributions in the root dentin. The concentrations of F released during a pH cycling were measured.
For the control group, the average lesion depth was 18.92 ± 5.42 μm, and the average Ca loss was 15.66% ± 6.80% in the superficial layer and 30.44% ± 9.61% in the subsurface layer. No Ca loss occurred in the desensitizer-treated groups. All desensitizing agents remained intact for at least 60 days. F levels were increased in the hybrid layer but not in the subhybrid area. Outward release of F diminished with time.
The F-containing resin-based desensitizers protected exposed root surfaces from demineralization. F liberated from the desensitizers was detected only at minimal levels.
Operative Dentistry 02/2012; 37(3):306-15. · 1.24 Impact Factor
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ABSTRACT: OBJECTIVES: The purpose of this study was to determine the color of white spot lesions. MATERIALS AND METHODS: Human premolars were subjected to a pH cycling to produce artificial caries lesions and classified into groups (n = 10/group): group 1, immersion in deionized water; group 2, pH cycling without fluoride (F) application; group 3, pH cycling with immersion in 1,000 ppm NaF solution; and group 4, pH cycling with immersion in 5,000 ppm NaF solution. CIE L*a*b* color parameters of the tooth were determined using a spectroradiometer at baseline, after demineralization and after pH cycling. The extent of demineralization was evaluated by scanning electron microscopy (SEM) and electron microprobe analysis (EPMA). RESULTS: Significant degrees of color change (ΔE*) were observed after demineralization (p < 0.05). The changes were mainly due to an increase in lightness (L*) and a decrease in yellowness (b*). F application induced a significantly large ΔE* in group 4 (p < 0.05). The color reversal after remineralization was mostly due to the recovery of L*. SEM and EPMA verified that net mineral gains occurred in the subsurface lesions. CONCLUSIONS: The initially white appearance of enamel caries was a result of changes of L* and b*. F treatment partially restored the color of white spot lesions. CLINICAL RELEVANCE: F-driven remineralization induced both mineral gains and esthetic enhancement of artificially produced enamel white spot lesions. The increase of L* and the decrease of b* contributed to the color changes.
Clinical Oral Investigations 01/2012; · 2.36 Impact Factor
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ABSTRACT: Mineral trioxide aggregate (MTA) is used widely in endodontic therapy. This study examined the setting time, compressive strength, and pH of MTA mixed with several hydration accelerators (calcium chloride, low-dose citric acid, calcium lactate gluconate solution).
Group 1 (control) was obtained by mixing MTA with distilled water. In group 2, MTA containing 10% calcium chloride was mixed with distilled water. In group 3, MTA was mixed with 0.1% citric acid. In group 4, MTA was mixed with a calcium lactate gluconate solution. The setting time, compressive strength, and pH were examined.
The setting time of MTA mixed with hydration accelerators was significantly shorter than that of MTA mixed with water (P < .01). In particular, replacing distilled water with a calcium lactate gluconate solution provided a significant decrease in setting time. The compressive strengths of MTA mixed with hydration accelerators were significantly lower than that of MTA mixed with water (P < .01), but those values increased with time. The pH of MTA mixed with hydration accelerators was significantly lower than that of MTA mixed with water (P < .01) but stable at a high level (pH 11-12).
Hydration accelerators improved the setting time of MTA. Nevertheless, more study will be needed to improve MTA without impairing its preexisting advantages.
Journal of endodontics 10/2011; 37(10):1433-6. · 2.95 Impact Factor
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ABSTRACT: An experimental Portland cement was manufactured with pure raw materials under controlled laboratory conditions. The aim of this study was to compare the chemical constitution, physical properties, and biocompatibility of experimentally manufactured Portland cement with those of mineral trioxide aggregate (MTA) and Portland cement.
The composition of the cements was determined by scanning electron microscopy (SEM) and energy-dispersive x-ray analysis (EDAX). The setting time and compressive strength were tested. The biocompatibility was evaluated by using SEM and XTT assay.
SEM and EDAX revealed the experimental Portland cement to have a similar composition to Portland cement. The setting time of the experimental Portland cement was significantly shorter than that of MTA and Portland cement. The compressive strength of the experimental Portland cement was lower than that of MTA and Portland cement. The experimental Portland cement showed a similar biocompatibility to MTA.
The experimental Portland cement might be considered as a possible substitute for MTA in clinical usage after further testing.
Journal of endodontics 01/2011; 37(1):58-62. · 2.95 Impact Factor
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ABSTRACT: Odontogenic ameloblast-associated protein (ODAM) has been shown to be specifically expressed in ameloblasts and odontoblasts and has been suggested to play a role in the mineralization of the enamel, possibly through the regulation of matrix metalloproteinase 20. However, its function in dentin is not clear. The purpose of this study was to evaluate the effect of ODAM on tertiary dentin formation.
MDPC-23 odontoblastic cells were cultured, and the effect of recombinant ODAM (rODAM) on mineralized nodule formation was evaluated. Pinpoint pulp exposures were made in rat teeth and then capped with rODAM mixed with a carrier (rODAM group), carrier only (Carrier group), or white mineral trioxide aggregate (WMTA group). After 1, 2, and 4 weeks, odontoblasts and tertiary dentin were investigated histologically and immunohistochemically.
Nodule formation in MDPC-23 cells was enhanced by rODAM treatment. Odontoblasts were polarized and showed a palisade arrangement in the remaining pulp from the rODAM group, but not the Carrier or WMTA groups. In the WMTA group, extensive tertiary dentin along the entire pulp-dentin border obliterated the pulp chamber. In contrast, in the rODAM group, limited reaction of odontoblasts resulted in normal pulp tissue appearance without excessive tertiary dentin formation and obliteration of the pulp cavity. In the Carrier and WMTA groups, bone sialoprotein was immunostained in most of the tertiary dentin, whereas in the rODAM group, dentin sialoprotein expression was immunostained primarily in newly formed reactionary dentin.
These results suggest that rODAM accelerates reactionary dentin formation close to the pulp exposure area, thereby preserving normal odontoblasts in the remaining pulp.
Journal of endodontics 12/2010; 36(12):1956-62. · 2.95 Impact Factor
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ABSTRACT: To elucidate how dentists access knowledge sources when choosing adhesive agents for bonded restoration and whether these resources influenced the selection of materials.
A national survey was carried out involving dentists in South Korea. The questionnaire included the status of the operator, clinical techniques, and materials. A total of 12,193 e-mails were distributed, 2632 were opened by recipients, and 840 responses were collected.
For primary information resources in material selection, 55.8% (n = 469) of the responders mentioned continuing education. This selection criteria varied according to the working status of the clinician (p < 0.0001). The choice of bonding system was influenced by of the length of the career (p < 0.0001), and the preferred bonding systems differed according to the source of the information (p = 0.035).
The popular bonding systems were not ranked according to the bonding strategy, but a preference was found for specific brands or manufacturers. To decrease the confusion of clinicians related to the selection of bonding materials, evidence-based guidelines need to be comprehensibly organized and efficiently approached in clinics.
The journal of adhesive dentistry 11/2009; 11(6):439-46. · 1.11 Impact Factor
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ABSTRACT: Our previous studies have demonstrated that nuclear factor I-C (NFI-C) null mice developed short molar roots that contain
aberrant odontoblasts and abnormal dentin formation. Based on these findings, we performed studies to elucidate the function
of NFI-C in odontoblasts. Initial studies demonstrated that aberrant odontoblasts become dissociated and trapped in an osteodentin-like
mineralized tissue. Abnormal odontoblasts exhibit strong bone sialoprotein expression but a decreased level of dentin sialophosphoprotein
expression when compared with wild type odontoblasts. Loss of Nfic results in an increase in p-Smad2/3 expression in aberrant odontoblasts and pulp cells in the subodontoblastic layer in vivo and primary pulp cells from Nfic-deficient mice in vitro. Cell proliferation analysis of both cervical loop and ectomesenchymal cells of the Nfic-deficient mice revealed significantly decreased proliferative activity compared with wild type mice. In addition, Nfic-deficient primary pulp cells showed increased expression of p21 and p16 but decreased expression of cyclin D1 and cyclin
B1, strongly suggesting cell growth arrest caused by a lack of Nfic activity. Analysis of the pulp and abnormal dentin in Nfic-deficient mice revealed an increase in apoptotic activity. Further, Nfic-deficient primary pulp cells exhibited an increase in caspase-8 and -3 activation, whereas the cleaved form of Bid was hardly
detected. These results indicate that the loss of Nfic leads to the suppression of odontogenic cell proliferation and differentiation and induces apoptosis of aberrant odontoblasts
during root formation, thereby contributing to the formation of short roots.
Journal of Biological Chemistry 06/2009; 284(25):17293-17303. · 4.77 Impact Factor
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ABSTRACT: Our previous studies have demonstrated that nuclear factor I-C (NFI-C) null mice developed short molar roots that contain aberrant odontoblasts and abnormal dentin formation. Based on these findings, we performed studies to elucidate the function of NFI-C in odontoblasts. Initial studies demonstrated that aberrant odontoblasts become dissociated and trapped in an osteodentin-like mineralized tissue. Abnormal odontoblasts exhibit strong bone sialoprotein expression but a decreased level of dentin sialophosphoprotein expression when compared with wild type odontoblasts. Loss of Nfic results in an increase in p-Smad2/3 expression in aberrant odontoblasts and pulp cells in the subodontoblastic layer in vivo and primary pulp cells from Nfic-deficient mice in vitro. Cell proliferation analysis of both cervical loop and ectomesenchymal cells of the Nfic-deficient mice revealed significantly decreased proliferative activity compared with wild type mice. In addition, Nfic-deficient primary pulp cells showed increased expression of p21 and p16 but decreased expression of cyclin D1 and cyclin B1, strongly suggesting cell growth arrest caused by a lack of Nfic activity. Analysis of the pulp and abnormal dentin in Nfic-deficient mice revealed an increase in apoptotic activity. Further, Nfic-deficient primary pulp cells exhibited an increase in caspase-8 and -3 activation, whereas the cleaved form of Bid was hardly detected. These results indicate that the loss of Nfic leads to the suppression of odontogenic cell proliferation and differentiation and induces apoptosis of aberrant odontoblasts during root formation, thereby contributing to the formation of short roots.
Journal of Biological Chemistry 05/2009; 284(25):17293-303. · 4.77 Impact Factor
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ABSTRACT: We reported previously that Nfic-deficient mice exhibit short and abnormal molar roots and severely deformed incisors. The objective of this study is to address the mechanisms responsible for these changes using morphological, IHC, and RT-PCR analysis. Nfic-deficient mice exhibited aberrant odontoblasts and abnormal dentin formation in molar roots and the labial crown analog of incisors. The most striking changes observed in these aberrant odontoblasts were the loss of intercellular junctions and the decreased expression of ZO-1 and occludin. As a result, they became dissociated, had a round shape, and lost their cellular polarity and arrangement as a sheet of cells. Furthermore, the dissociated odontoblasts became trapped in dentin-like mineralized tissue, resembling osteodentin in the overall morphology. These findings suggest that loss of the Nfic gene interferes with the formation of intercellular junctions that causes aberrant odontoblast differentiation and abnormal dentin formation. Collectively, these changes in odontoblasts contributed to development of molars with short and abnormal roots in Nfic-deficient mice.
Journal of Histochemistry and Cytochemistry 02/2009; 57(5):469-76. · 2.72 Impact Factor
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ABSTRACT: This study compared the chemical constitution, radiopacity, and biocompatibility of Portland cement containing bismuth oxide (experimental cement) with those of Portland cement and mineral trioxide aggregate (MTA).
The chemical constitution of materials was determined by scanning electron microscopy and energy-dispersive X-ray analysis. The radiopacity of the materials was determined using the ISO/6876 method. The biocompatibility of the materials was tested by MTT assay and tissue reaction.
The constitution of all materials was similar. However, the Portland cement and experimental cement were more irregular and had a larger particle size than MTA. The radiopacity of the experimental cement was similar to MTA. The MTT assay revealed MTA to have slightly higher cell viability than the other materials. However, there were no statistically significant differences between the materials, with the exception of MTA at 24 h. There was no significant difference in the tissue reaction between the experimental groups.
These results suggest that the experimental cement may be used as a substitute for MTA.
Oral surgery, oral medicine, oral pathology, oral radiology, and endodontics 02/2009; 107(3):e96-102. · 1.50 Impact Factor
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ABSTRACT: The aims of this study were to evaluate the adequate thickness of opaque resins for situations such as an oral black cavity and discolored tooth structure, as well as the translucency of each opaque material at various thicknesses.
Six opaque-shade composite resins (Z-350 OA3, Amelogen Universal A2O, Esthet-X A2O, Esthet-X A4O, Charmfil UO, and Aelite Universal OA3) were prepared in metal molds with a hole of 8mm in diameter and various thicknesses (0.5mm, 1.0mm, 1.5mm, 2.0mm, 2.5mm, 3.0mm and 4.0mm). Four backgrounds (white tile, black tile, C4 shade porcelain and opaque resin itself) were used to determine the translucency parameter (TP) (between black and white backgrounds), and to mimic a black oral cavity (between black and opaque resin backgrounds) and a discolored tooth structure (between C4 and opaque resin backgrounds). Color measurements were made by a colorimeter to determine the CIELAB values of each specimen with each background and to calculate the TP and DeltaE* value difference among the specimens on the backgrounds.
TP and DeltaE* obtained between black and opaque resin backgrounds decreased in similar pattern as thickness increased. A C4 background was masked by resin thicknesses of 0.5-1.0mm, while a black background required thicknesses of 1.0-2.0mm.
This study can provide helpful guidelines for the esthetic restoration of discolored tooth structures or 'through and through' class III and IV cavities with composite resin materials.
Journal of Dentistry 12/2008; 37(2):102-7. · 2.95 Impact Factor
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ABSTRACT: Rheumatoid arthritis is an autoimmune disease with an unknown etiology. Azathioprine is an immunosuppressive drug that is used to treat rheumatoid arthritis. This case report describes the rapid periapical bone destruction that occurred during the endodontic treatment of a rheumatoid arthritis patient taking azathioprine and a corticosteroid. The cause of the rapid destruction is unclear. However, severe side effects can occur after administering azathioprine to rheumatoid arthritis patients. Therefore, dentists should check the patient's medical state thoroughly in order to prevent side effects when performing endodontic treatment.
Journal of endodontics 11/2008; 34(10):1261-3. · 2.95 Impact Factor
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ABSTRACT: Reparative dentin has a wide variety of manifestations ranging from a regular, tubular form to an irregular, atubular form. However, the characteristics of reparative dentin have not been clarified. This study hypothesized that the level of bone sialoprotein (BSP) expression will increase if the newly formed reparative dentin is bone-like but the dentin sialophosphoprotein (DSPP) level will decrease. In order to test this hypothesis, the expression of BSP and DSP was examined by immunohistochemistry and the expression of BSP was measured by in situ hybridization in an animal model. The pulps of 12 maxillary right first molars from twelve male rats were exposed and capped with MTA. In addition, in order to understand the role of transforming growth factor-beta 1 (TGF-beta1) during reparative dentinogenesis, the expression of BSP and DSPP mRNA was analyzed by RT-PCR in a human dental pulp cell culture, and the transforming growth factor-beta 1 receptors (TbetaRI) and Smad 2/3 were examined by immunofluorescence in an animal model. DSP was expressed in the normal odontoblasts and odontoblast-like cells of the reparative dentin. Interestingly, BSP was strongly expressed in the odontoblast-like cells of reparative dentin. The level of the TbetaRI and Smad 2/3 proteins was higher in the reparative dentin than in the normal dentin. TGF-beta1 up-regulated BSP in the human pulp cell cultures. This suggests that reparative dentin has both dentinogenic and osteogenic characteristics that are mediated by TGF-beta1.
Journal of Molecular Histology 05/2008; 39(2):153-60. · 1.48 Impact Factor
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ABSTRACT: The purpose of this study was to investigate the viscoelastic properties related to the handling characteristics of composites.
A custom-designed vertical oscillation rheometer (VOR) was used for the rheological measurements of composites. The VOR consists of three parts: (1) a measuring unit, (2) a deformation induction unit, and (3) a force-detecting unit. Two medium-viscous composites, Z100 and Z250, and two packable composites, P60 and SureFil, were tested. A dynamic oscillatory test was used to evaluate the storage modulus (E'), loss modulus (E''), and loss tangent (tan delta) of the composites as a function of frequency (omega) from 0.1 to 20Hz at 23 degrees C.
The E' and E'' increased with increasing frequency and showed differences in magnitude among brands. The complex moduli E* of the composites at omega=2 Hz, normalized to that of Z100, were 2.16 (Z250), 4.80 (P60), and 25.21 (SureFil). The magnitudes and frequency characteristic of loss tangent differed significantly among brands. The relationship among the complex modulus E*, the phase angle delta, and the frequency omega was represented by the frequency domain phasor form E*(omega)e(idelta)=E*(omega) angledelta.
The viscoelasticities of composites, which influence handling characteristics, are significantly different among brands. The VOR is a relatively simple device for the dynamic rheological measurement of dental composites. The loci of the frequency domain phasor plots in a complex plane are a valuable method of representing the viscoelastic properties of composites.
Dental Materials 05/2007; 23(4):425-32. · 3.13 Impact Factor
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ABSTRACT: This study investigated the expression and localization of APin (which was previously identified and cloned from a rat odontoblast cDNA library), during ameloblast differentiation in rat incisors, by using in situ hybridization and immunohistochemistry. The subcellular localization of APin varied during ameloblast differentiation, but was stage-specific. APin mRNA was not expressed in pre-ameloblasts, was weakly expressed in secretory ameloblasts, and was strongly expressed in maturation-stage ameloblasts as well as in the junctional epithelium attached to the enamel of erupted molars. In the maturation-stage ameloblasts, APin protein was conspicuous in the supranuclear area (Golgi complex) of smooth-ended ameloblasts as well as in both the supranuclear area and the ruffle end of ruffle-ended ameloblasts. During ameloblast-lineage cell culture, APin was expressed at a low level in the early stages of culture, but at a high level in the late stage of culture, which was equivalent to the maturation stage. APin protein was efficiently secreted from transfected cells in culture. Furthermore, its overexpression and inactivation caused an increase and decrease in matrix metalloproteinase-20 (MMP-20) and tuftelin expression, respectively. These findings indicate a functional role for APin in the mineralization and maturation of enamel that is mediated by the expression of MMP-20 and tuftelin.
European Journal Of Oral Sciences 05/2007; 115(2):153-60. · 1.88 Impact Factor
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ABSTRACT: The aim of this study was to measure the cusp deflection by polymerization shrinkage during composite restoration for mesio-occluso-distal (MOD) cavities in premolars, and to examine the influence of cavity dimension, C-factor and restoration method on the cusp deflection.
Thirty extracted maxillary premolars of similar size were prepared with four different sizes of MOD cavity, and divided into six groups. The width and depth of the pulpal wall of the cavity were as follows: group 1: 1.5x1 mm, group 2: 1.5x2 mm, group 3: 3x1 mm, and groups 4-6: 3x2 mm. Groups 1-4 were restored using a bulk filling with a composite. Group 5 was restored incrementally, and group 6 was restored with an indirect composite inlay. Cusp deflections were measured using LVDT transducers. The cusp deflections were compared between groups using ANOVA and Scheffe tests, and a correlation analysis was done.
The cusp deflections of groups 1-4 were 12.1 (2.2), 17.2 (1.9), 16.2 (0.8) and 26.4 (4.2) microm, respectively. There was a strong positive correlation between the length cubed divided by the thickness cubed of the remaining cusp (L3/T3) and cusp deflection. The C-factor was related to the % flexure (100xcusp deflection/cavity width). The cusp deflections of groups 5 and 6 were 17.4 (2.0) and 17.9 (1.4) microm, respectively, which were much lower values than those of group 4.
The cusp deflection increased with increasing cavity dimension and C-factor. Use of an incremental filling technique or an indirect composite inlay restoration could reduce the cuspal strain.
Dental Materials 04/2007; 23(3):288-95. · 3.13 Impact Factor
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ABSTRACT: The purpose of this study was to monitor the expression of matrix metalloproteinase-1 (MMP-1) and tissue inhibitor of metalloproteinase-1 (TIMP-1) produced by an osteoblastic cell line MG63 stimulated with Prevotella nigrescens lipopolysaccharides (LPS), and to compare the level of secretion before and after the P. nigrescens LPS was treated with calcium hydroxide [Ca(OH)2]. The underlying hypothesis is that the balance between MMP and TIMP secretion is the key to an understanding of the host degradative pathways involved in the pathogenesis of bacterial derived pulpal and periapical diseases. Confluent monolayers of MG63 human osteosarcoma cells were exposed to varying concentrations of P. nigrescens or Escherichia coli LPS. Alternately, confluent cultures were exposed to 10 microg/ml of bacterial LPS pretreated with Ca(OH)2 (12.5 mg/ml) for 72 hours. At the end of the experimental period, total RNA was extracted and real-time quantitative polymerase chain reaction (PCR) was performed for MMP-1, TIMP-1, and glyceraldehyde-3-phosphate dehydrogenase (GAPDH). The results showed that the expression of MMP-1 mRNA was low and invariant for the experimental period in the negative controls. However, exposure to P. nigrescens LPS increased expression after 48 hours. Expression of TIMP-1 mRNA was highly increased at 24 and 48 hours with lower concentrations of LPS in contrast to a suppression with a concentration of 10 microg/ml. Treatment of P. nigrescens LPS with Ca(OH)2 resulted in a down-regulation of MMP-1, whereas pretreated E. coli LPS demonstrated no stimulatory activity for MMP-1 gene expression. Both types of LPS when pretreated with Ca(OH)2 induced slightly up-regulated expression of TIMP-1.
Journal of Endodontics 01/2007; 32(12):1142-5. · 2.88 Impact Factor
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ABSTRACT: This study investigated the effect of the consistency, specimen geometry and adhesion on the measurements of axial polymerization shrinkage of light cured composite resins using an axial shrinkage-measuring device.
Four commercially available composites were examined: an anterior posterior hybrid composite Z100, a posterior packable composite P60 and two flowable composites, Filtek flow and Tetric flow. The axial polymerization shrinkage of the composites was determined using a 'bonded disc method' and 'non-bonded' free shrinkage method at varying C-factors by altering the specimen geometry. These measured axial shrinkages were compared with the free volumetric shrinkages. The consistency of the composites was also compared using a squeeze test.
Using the non-bonded method, the axial shrinkage was approximately one third of the true volumetric shrinkage as a result of isotropic contraction. However, in the bonded disc method, the axial shrinkage increased up to the volumetric shrinkage by anisotropic contraction as the bonded surface increased. The axial shrinkage increased with the increasing C-factor. It approached the true volumetric shrinkage and reached a plateau at near a C-factor of 5-6. However, in flowable composites, a lower level of axial shrinkage was measured by the compensational radial flow.
When estimating the volumetric shrinkage from the axial shrinkage measured using the bonded disc method, the C-factor of the specimen should be higher than 5 and the consistency of the composite is also an important factor that needs to be considered.
Dental Materials 12/2006; 22(11):1071-9. · 3.13 Impact Factor
