Substance P regulates the expression of matrix metalloproteinases and tissue inhibitors of metalloproteinase in cultured human gingival fibroblasts

Background and Objective: Substance P may play a role in the pathogenesis of periodontal disease; however, its mechanisms of modulation are not clear. This study evaluated the effect of two concentrations of Substance P on the expression of matrix metalloproteinases (MMPs) and tissue inhibitors of metalloproteinases (TIMPs) in cultured human gingival fibroblasts. Materials and Methods: Fibroblasts were stimulated for 48 h with 10(-4) or 10(-9) m Substance P; untreated fibroblasts served as controls. The expression of MMP-1, -2, -3, -7 and -11 and of TIMP-1 and -2 was evaluated using real-time polymerase chain reaction and western blotting. Resulsts: There was a significant, concentration-dependent stimulatory effect of Substance P on MMP-1, -2, -3 and -7 and TIMP-2 gene expression (p < 0.05), and a probable effect on MMP-11 (p = 0.06). At the higher concentration (10(-4) m Substance P), MMP-1, -2, -3, -7 and -11 and TIMP-2 showed the greatest up-regulation; at the lower concentration (10(-9) (M) Substance P), MMP-1, -3 and -7 and TIMP-2 exhibited diminished up-regulation, with MMP-2 and -11 showing down-regulation (p < 0.05). Expression of TIMP-1 was not affected by Substance P (p > 0.05). Western blotting confirmed that Substance P up-regulated MMP-1, -2, -3 and -11 and TIMP-2. MMP-1, -3 and -11 and TIMP-2 showed greater up-regulation at the higher Substance P concentration and diminished up-regulation at the lower concentration. MMP-2 was up-regulated to a similar degree at both Substance P concentrations. Conclusion: In gingival fibroblast cells, Substance P at the higher concentration (10(-4) m) induced greater up-regulation of MMP-1, -3 and -11 and TIMP-2 expression, but at the lower concentration (10(-9) (M)) induced diminished up-regulation, which may represent a mechanism for modulating periodontal breakdown.

STAT3 expression in salivary gland tumours

The aim of the present study was to evaluate the signal transducer and activator of transcription (STAT3) expression, which is constitutively active in different types of malignant tumours, in salivary gland tumours. Fifty biopsies of salivary gland tumours (9 pleomorphic adenomas, 12 adenoid cystic carcinomas, 7 epithelial-myoepithelial carcinomas, 10 polymorphous low-grade adenocarcinomas and 12 mucoepidermoid carcinomas) and 10 normal. salivary glands were immunohistochemically labeled for STAT3 and Phospho-STAT3 (STAT3P). The labeled sections were quatitatively and quantitatively evaluated. The results showed that, in normal salivary gland, STAT3 was expressed in cytoplasm and STAT3P in nuclei of all tissue cells, except in large mucous acinar cells for which both antibodies were negative. In pleomorphic adenoma, the expression was the same as in normal glands. In malignant tumours, there were variations in the expression of these antibodies. The most important one was the presence of STAT3 in the nuclei of the malignant tumour cells, most evident in the cribriform-type of adenoid cystic carcinoma. Both toss and variation of STAT3P expression were also observed. The presence of STAT3 in the nuclei of malignant salivary gland tumours may represent an important event in oncogenesis probably contributing to tumour cell proliferation white blocking apoptosis. However, further investigation will. be necessary to support this hypothesis. (c) 2007 Pubtished by Elsevier Ltd.

EFFECT OF METAL PRIMERS ON MICROTENSILE BOND STRENGTH BETWEEN ZIRCONIA AND RESIN CEMENTS

Statement of problem. There are no established clinical procedures for bonding zirconia to tooth structure using resin cements. Purpose. The purpose of this study was to evaluate the influence of metal primers, resin cements, and aging on bonding to zirconia. Material and methods. Zirconia was treated with commercial primers developed for bonding to metal alloys (Metaltite, Metal Primer II, Alloy Primer or Totalbond). Non-primed specimens were considered as controls. One-hundred disk-shaped specimens (19 x 4 mm) were cemented to composite resin substrates using Panavia or RelyX Unicem (n=5). Microtensile bond strength specimens were tested after 48 hours and 5 months (150 days), and failure modes were classified as type 1 (between ceramic/cement), 2 (between composite resin/cement) or 3 (mixed). Data were analyzed by 3-way ANOVA and Multiple Comparison Tukey test (alpha=.05). Results. The interactions primer/luting system (P=.016) and luting system/storage time (P=.004) were statistically significant. The use of Alloy Primer significantly improved the bond strength of RelyX Unicem (P<.001), while for Panavia, none of the primers increased the bond strength compared to the control group. At 48 hours, Panavia had statistically higher bond strength (P=.004) than Unicem (13.9 +/- 4.4MPa and 10.2 +/- 6.6MPa, respectively). However, both luting systems presented decreasing, statistically similar; values after aging (Panavia: 3.6 +/- 2.2MPa; Unicem: 6.1 +/- 5.3MPa). At 48 hours, Alloy Primer/Unicem had the lowest incidence of type 1 failure (8%). After aging, all the groups showed a predominance of type 1 failures. Conclusions. The use of Alloy Primer improved bond strength between RelyX Unicem and zirconia. Though the initial values obtained with Panavia were significantly higher than RelyX Unicem, after aging, both luting agents presented statistically similar performances. (J Prosthet Dent 2011;105:296-303)

Clinical versus laboratory adhesive performance to wet and dry demineralized primary dentin

Purpose: To evaluate the influence of dentin moisture on bond strengths of an etch-and-rinse bonding agent to primary dentin clinically and in the laboratory. Methods: The sample consisted of two groups of 20 caries-free primary second molars: molars in exfoliation period (clinical group) and extracted molars (laboratory group). Class I cavities were prepared in all specimens leaving a flat dentin surface on the pulpal floor. A two-step etch-and-rinse adhesive was vigorously rubbed on either dry (n= 5) or wet demineralized dentin (n= 5) under clinical or laboratory conditions. After restorative procedures, the teeth from the clinical group were extracted after 20 minutes. All samples were processed and underwent microtensile bond strength test and silver nitrate uptake evaluation under scanning electron microscopy. Results: Statistically higher bond strength values were observed when the bonding was performed under laboratory conditions and on a wet demineralized dentin. Most of the failures were adhesive and mixed irrespective of the experimental condition. Silver nitrate uptake occurred in all groups irrespective of the experimental condition. Resin-dentin bond strengths produced in the laboratory in primary teeth may overestimate those produced under clinical circumstances. (Am J Dent 2011;24:221-225).

Effects of adhesive temperature on the early and 6-month dentin bonding

Objectives: The aim of this study was to test the effect of adhesive temperature on the bond strength to dentin (mu TBS) and silver nitrate uptake (SNU) of an ethanol/water (Adper Single Bond 2 [SB]) and an acetone-based (Prime&Bond 2.1 [PB]) etch-and-rinse adhesive system. Methods: The bottles of each adhesive were kept in various temperatures (5 degrees C, 20 degrees C, 37 degrees C and 50 degrees C) for 1 h previously to its application in the occlusal demineralized dentin of 40 molars. Bonded sticks (0.8 mm(2)) were tested in tension (0.5 mm/min) immediately (IM) or after 6 months (6 M) of water storage. Two bonded sticks from each hemi-tooth were immersed in silver nitrate and analyzed by SEM. Data were analyzed by two-way repeated measures ANOVA and Tukey`s test (alpha = 0.05). Results: No significant difference in mu TBS was detected for both adhesives at 5 degrees C and 20 degrees C. The highest bond strength for PB was observed in the 37 degrees C group while for SB it was in the 50 degrees C. Significant reductions of bond strengths were observed for PB at 37 degrees C and SB at 50 degrees C after 6 M of water storage. Silver nitrate deposition was seen in all hybrid layers, irrespective of the group. Lower silver nitrate deposition (water trees) in the adhesive layer was seen for PB and SB at higher temperatures. Conclusions: The heating or refrigeration of the adhesives did not improve their resin-dentin bond resistance to water degradation over time. (C) 2009 Elsevier Ltd. All rights reserved.

Can the durability of one-step self-etch adhesives be improved by double application or by an extra layer of hydrophobic resin?

Objectives: This study evaluated the immediate and 6-month resin-dentin mu-bond strength (mu TBS) of one-step self-etch systems (Adper Prompt L-Pop [AD] 3M ESPE; Xeno III [XE] Dentsply De Trey; iBond [iB] Heraeus Kulzer) under different application modes. Materials and methods: Dentin oclusal surfaces were exposed by grinding with 600-grit SiC paper. The adhesives were applied according to the manufacturer`s directions [MD], or with double application of the adhesive layer [DA] or following the manufacturer`s directions plus a hydrophobic resin layer coating [HL]. After applying the adhesive resins, composite crowns were built up incrementally. After 24-h water storage, the specimens were serially sectioned in ""x"" and ""y"" directions to obtain bonded sticks of about 0.8 mm 2 to be tested immediately [IM] or after 6 months of water storage [6M] at a crosshead speed of 0.5 mm/min. The data from each adhesive was analyzed by a two-way repeated measures ANOVA (mode of application vs. storage time) and Tukey`s test (alpha = 0.05). Results: The adhesives performed differently according to the application mode. The DA and HL either improved the immediate performance of the adhesive or did not differ from the MD. The resin-dentin bond strength values observed after 6 months were higher when a hydrophobic resin coat was used than compared to those values observed under the manufacturer`s directions. Conclusions: The double application of one-step self-etch system can be safety performed however the application of an additional hydrophobic resin layer can improve the immediate resin-dentin bonds and reduce the degradation of resin bonds over time. (c) 2008 Elsevier Ltd. All rights reserved.

Effect of prolonged application times on the durability of resin-dentin bonds

Objectives. To examine the effect of prolonged application time on the early and 3-year resin-dentin microtensile bond strength. Methods. Water/ethanol (Single Bond [SB]) and acetone-based systems (One Step [OS]) were employed. A flat superficial dentin surface was exposed in third human molars by wet abrasion. The adhesives were applied to a delimited area of 52 mm(2) on wet surfaces, for 40, 90, 150 and 300s. Four teeth were assigned for each experimental condition. Composite build-ups were constructed incrementally After water storage at 37 degrees C for 24 h, teeth were sectioned to obtain sticks with cross-sectional areas of 0.8 mm(2) to be tested in tension (0.5 mm/min) either immediately (IM) or after 3 years (3Y) of water storage. The microtensile bond strength (mu TBS) values were analyzed by two way repeated measures ANOVA and Tukey`s test (alpha = 0.05). Results. The 90- and 150-s groups achieved the highest IM mu TBS for OS (p < 0.01). For SB, the highest IM mu TBS values were observed after 300-s application (p < 0.01). Significant decreases in mu TBS were observed for OS in the 40- and 90-s groups after 3Y, except for the 150-s group. With regard to SB, after 3Y significant drops in mu TBS values were observed for the 40- and 150-s groups, except for the 300-s group. Significance. Prolonged application times can increase the immediate LTBS of two-step etch-and-rinse adhesive systems and make the adhesive layer more stable over time. (c) 2007 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

Do Low-shrink Composites Reduce Polymerization Shrinkage Effects?

Progress in polymer science has led to continuous reduction of polymerization shrinkage, exemplified by a new generation of ""low-shrink composites"". The common inference that shrinkage stress effects will be reduced in teeth restored with such restoratives with lower shrinkage was tested in extracted human premolars. Mesio-occluso-distal slot-shaped cavities were cut and restored with a conventional (SupremePlus) or low-shrink (RefleXions, Premise, Kalore, and LS) composite (N = 5). We digitized the coronal surfaces before and 10 min after restoration to determine cuspal deflection from the buccal and lingual volume change/area. We also determined the main properties involved (total shrinkage, post-gel shrinkage, degree of conversion, and elastic modulus), as well as microleakage, to verify adequate bonding. It was shown that, due to shrinkage stresses, buccal and lingual surfaces pulled inward after restoration (9-14 microns). Only Kalore and LS resulted in significantly lower tooth deformation (ANOVA/Student-Newman-Keuls post hoc, p = 0.05). The other two low-shrink composites, despite having the lowest and highest total shrinkage values, did not cause significant differences in cuspal deflection. Deflection seemed most related to the combination of post-gel shrinkage and elastic modulus. Therefore, even for significantly lower total shrinkage values, shrinkage stress is not necessarily reduced.

Slow crack growth and reliability of dental ceramics

Objective. To determine the slow crack growth (SCG) and Weibull parameters of five dental ceramics: a vitreous porcelain (V), a leucite-based porcelain (D), a leucite-based glass-ceramic (E1), a lithium disilicate glass-ceramic (E2) and a glass-infiltrated alumina composite (IC). Methods. Eighty disks (empty set 12mm x 1.1mm thick) of each material were constructed according to manufacturers` recommendations and polished. The stress corrosion susceptibility coefficient (n) was obtained by dynamic fatigue test, and specimens were tested in biaxial flexure at five stress rates immersed in artificial saliva at 37 degrees C. Weibull parameters were calculated for the 30 specimens tested at 1MPa/s in artificial saliva at 37 degrees C. The 80 specimens were distributed as follows: 10 for each stress rate (10(-2), 10(-1), 10(1), 10(2) MPa/s), 10 for inert strength (10(2) MPa/s, silicon oil) and 30 for 10(0) MPa/s. Fractographic analysis was also performed to investigate the fracture origin. Results. E2 showed the lowest slow crack growth susceptibility coefficient (17.2), followed by D (20.4) and V (26.3). E1 and IC presented the highest n values (30.1 and 31.1, respectively). Porcelain V presented the lowest Weibull modulus (5.2). All other materials showed similar Weibull modulus values, ranging from 9.4 to 11.7. Fractographic analysis indicated that for porcelain D, glass-ceramics E1 and E2, and composite IC crack deflection was the main toughening mechanism. Significance. This study provides a detailed microstructural and slow crack growth characterization of widely used dental ceramics. This is important from a clinical standpoint to assist the clinician in choosing the best ceramic material for each situation as well as predicting its clinical longevity. It also can be helpful in developing new materials for dental prostheses. (c) 2010 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

Micro-Shear Bond Strength of Different Adhesives to Human Dental Enamel

The aim of this study was to evaluate the micro-shear bond strength of 5 adhesive systems to enamel, one single-bottle acid-etch adhesive (O), two self-etching primers (P) and two all-in-one self-etching adhesives (S). Method: Sixty premolar enamel surfaces (buccal or lingual) were ground flat with 400- and 600-grit SiC papers and randomly divided into 5 groups (n=12), according to the adhesive system.. SB2 - Single Bond 2 (O); CSE - Clearfil SE Bond (P); ADS - AdheSE (P); PLP - Adper Prompt L-Pop (S); XE3 - Xeno III (S). Tygon tubing (inner diameter of 0.8mm) restricted the bonding area to obtain the resin composite (Z250) cylinders. After storage in distilled water at 37 degrees C for 24h and thermocycling, micro-shear testing was performed (crosshead speed of 0.5mm/min). Data were submitted to one-way ANOVA and Tukey test (a=5%). Samples were also subjected to stereomicroscopic and SEM evaluations after micro-shear testing. Mean bond strength values (MPa +/- SD) and the results of Tukey test were: SB2: 36.36(+/- 3.34)a; ADS: 33.03(+/- 7.83)a; XE3: 32.76(+/- 5.61)a; CSE: 30.61(+/- 6.68)a; PLP: 22.17(+/- 6.05)b. Groups with the same letter were not statistically different. It can be concluded that no significant difference was there between SB2, ADS, XE3 and CSE, in spite of different etching patterns of these adhesives. Only PLP presented statistically lower bond strengths compared with others. J Clin Pediatr Dent 35(3): 301-304, 2011

Understanding Contradictory Data in Contraction Stress Tests

The literature shows contradictory results regarding the role of composite shrinkage and elastic modulus as determinants of polymerization stress. The present study aimed at a better understanding of the test mechanics that could explain such divergences among studies. The hypothesis was that the effects of composite shrinkage and elastic modulus on stress depend upon the compliance of the testing system. A commonly used test apparatus was simulated by finite element analysis, with different compliance levels defined by the bonding substrate (steel, glass, composite, or acrylic). Composites with moduli between 1 and 12 GPa and shrinkage values between 0.5% and 6% were modeled. Shrinkage was simulated by thermal analogy. The hypothesis was confirmed. When shrinkage and modulus increased simultaneously, stress increased regardless of the substrate. However, if shrinkage and modulus were inversely related, their magnitudes and interaction with rod material determined the stress response.

Scanning Electron Microscopy In Vitro Study on the Effect of Carisolv Application on Periodontally Diseased Root Surfaces

The purpose of this study was to evaluate the characteristics of diseased root surfaces treated by the association of scaling and the application of Carisolv. Twenty-four uniradicular periodontally involved teeth were used in this study The teeth were divided randomly into three groups: eight teeth were scaled and root planed until there was a complete visible removal of calculus (group 1), Carisolv was applied on the root surfaces of eight teeth twice for 30 seconds before scaling with a sharp curette (group 2), and eight teeth received the same treatment as in group 2 but with a blunt curette (group 3). Specimens were examined using scanning electron microscopy The superficial aspect of the roots from group 1 presented scratches that mirrored the curette cutting edge, and the smear layer completely covered the surface. Root surfaces from groups 2 and 3 also presented a smear layer that covered the surface completely but it was somewhat smoother than group 1. The use of Carisolv as an adjunct to scaling and root planing presented no advantage for smear layer removal over scaling alone, suggesting that no benefit is obtained by the use of Carisolv during periodontal mechanical treatment. (Int J Periodontics Restorative Dent 2011;31:91-95.)

Polymerization stress, shrinkage and elastic modulus of current low-shrinkage restorative composites

Objective. To compare currently available low-shrinkage composites with others regarding polymerization stress, volumetric shrinkage (total and post-gel), shrinkage rate and elastic modulus. Methods. Seven BisGMA-based composites (Durafill/DU, Filtek Z250/FZ, Heliomolar/HM, Aelite LS Posterior/AP, Point 4/P4, Filtek Supreme/SU, ELS/EL), a silorane-based (Filtek LS, LS), a urethane-based (Venus Diamond, VD) and one based on a dimethacrylate-derivative of dimer acid (N`Durance, ND) were tested. Polymerization stress was determined in 1-mm high specimens inserted between two PMMA rods attached to a universal testing machine. Total volumetric shrinkage was measured using a mercury dilatometer. Maximum shrinkage rate was used as a parameter of the reaction speed. Post-gel shrinkage was measured using strain-gages. Elastic modulus was obtained by three-point bending. Data were submitted to one-way ANOVA/Tukey test (p = 0.05), except for elastic modulus (Kruskal-Wallis). Results. Composites ranked differently for total and post-gel shrinkage. Among the materials considered as ""low-shrinkage"" by the respective manufacturers, LS, EL and VD presented low post-gel shrinkage, while AP and ND presented relatively high values. Polymerization stress showed a strong correlation with post-gel shrinkage except for LS, which presented high stress. Elastic modulus and shrinkage rate showed weak relationships with polymerization stress. Significance. Not all low-shrinkage composites demonstrated reduced polymerization shrinkage. Also, in order to effectively reduce polymerization stress, a low post-gel shrinkage must be associated to a relatively low elastic modulus. (C) 2010 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

Ethanol Wet-bonding Challenges Current Anti-degradation Strategy

The long-term effectiveness of chlorhexidine as a matrix metalloproteinase (MMP) inhibitor may be compromised when water is incompletely removed during dentin bonding. This study challenged this anti-bond degradation strategy by testing the null hypothesis that wet-bonding with water or ethanol has no effect on the effectiveness of chlorhexidine in preventing hybrid layer degradation over an 18-month period. Acid-etched dentin was bonded under pulpal pressure simulation with Scotchbond MP and Single Bond 2, with water wet-bonding or with a hydrophobic adhesive with ethanol wet-bonding, with or without pre-treatment with chlorhexidine diacetate (CHD). Resin-dentin beams were prepared for bond strength and TEM evaluation after 24 hrs and after aging in artificial saliva for 9 and 18 mos. Bonds made to ethanol-saturated dentin did not change over time with preservation of hybrid layer integrity. Bonds made to CHD pre-treated acid-etched dentin with commercial adhesives with water wet-bonding were preserved after 9 mos but not after 18 mos, with severe hybrid layer degradation. The results led to rejection of the null hypothesis and highlight the concept of biomimetic water replacement from the collagen intrafibrillar compartments as the ultimate goal in extending the longevity of resin-dentin bonds.