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Artificial Saliva (artificial + saliva)
Selected AbstractsEnvironmental damage and occlusal contact area wear of composite restorativesJOURNAL OF ORAL REHABILITATION, Issue 1 2002A. U. J. Yap The chemical environment is one aspect of the oral environment, which could have an appreciable influence on the in-vivo degradation of composite resins. The resin matrix can be softened and fillers constituents can be leached out when composites are exposed to certain chemicals/food-simulating liquids (FSLs). A reciprocal compression sliding wear device was used to study the effects of the chemical environment on occlusal contact area (OCA) wear of four composite restoratives (Silux Plus, Z100, Ariston pHc and Surefil). The effects of FSL on hardness was also investigated and correlated to wear. Thirty-six hardness/wear specimens of each material were made and stored in artificial saliva at 37 °C for 24 h. The specimens were then divided into six groups of six specimens and stored in the following FSL for 1 week at 37 °C: distilled water (W), 0·02 N citric acid (C), 0·02 N lactic acid (L), heptane (H) and 75,25% ethanol,water solution (E). Conditioning in artificial saliva (S) was used as control. After conditioning, the specimens were wear tested at 20 MPa contact stress against SS304 counter-bodies in the respective FSL/artificial saliva up to 20 000 cycles. Wear depth (lm, n=6) was measured using profilometry. Change in hardness (,KHN, Knoop hardness number) was determined by microhardness testing pre- and post-conditioning. Results of statistical analyses (ANOVA/Scheffe's at significance level 0·05) of wear data were as follows: Silux , S, W > L, H, E and C, L > H; Z100 , S, W > all other mediums and E > H; Ariston , all other mediums > H; Surefil , W, C > S, L, H, E (> indicates significantly more wear). With the exception of Surefil, the greatest wear was observed with conditioning and wear testing in water. This ranged from 93·18 ± 21·96 lm for Z100 to 31·43 ± 2·80 lm for Surefil. For all materials, conditioning in heptane resulted in the least wear. This ranged from 8·9 ± 2·2 ,m for Ariston to 16·5 ± 5·9 lm for Silux. The effects of the different FSL on OCA wear were material dependent. No correlation was observed between ,KHN and wear. [source] Corrosion of some selected ceramic alloys used in fixed partial dentures and their postsolder joints in a synthetic neutral salivaEUROPEAN JOURNAL OF ORAL SCIENCES, Issue 1 2009Pascal De March The electrochemical behavior of several alloys used in the frameworks of fixed partial dentures and their corresponding postsolders was studied in artificial saliva as a function of chemical composition. Open circuit potentials and polarization resistances were measured. The general electrochemical behaviors between the cathodic domain and the oxidation of solvent were characterized using cyclic polarization. The possible galvanic corrosion of coupled parent and postsolder alloys was also studied. The polarization resistances were high or very high. During immersion, the noblest alloys stayed in the immunity domains of their base elements, whereas Ni,Cr alloys were quickly passivated. The oxidation of the noble elements occurred only when the alloys were exposed to very high potentials solely achievable by artificial means. However, problems of galvanic corrosion may occur between an alloy and its postsolder joint if they are both exposed to saliva. Such corrosion may lead to a weakening of the framework. The parent alloy was often potentially affected by such corrosion but with low exchange currents. [source] Influence of the mineral content and morphological pattern of artificial root caries lesion on composite resin bond strengthEUROPEAN JOURNAL OF ORAL SCIENCES, Issue 1 2004Anderson T. Hara Dentine substrates with different mineral contents and morphological patterns were created by submitting root slabs to the following treatments: (A) immersion in artificial saliva during the experimental period (control), (B) demineralization for 32 h to induce caries lesion (demineralized group), and (C) demineralization for 32 h followed by remineralization for 8 d (remineralized group). The slabs were longitudinally sectioned, the mineral content was determined by cross-sectional microhardness, and the bond strength of an adhesive system/composite resin was assessed using a microtensile bond strength test. The dentine morphology after the treatments as well as the failure pattern of the debonded specimens was examined by scanning electron microscopy. Statistically significant differences were found in mineral content. Morphological analysis showed marked differences between the patterns of demineralized and remineralized substrates. The bond strength mean value of the control A did not differ from the group B, but was statistically higher than the group C. Since no linear relationship was found between dentine mineral content and bond strength values, it could be suggested that the morphological pattern may be more relevant than the mineral content to explain the bond strength of composite resin to dentine. [source] Solubility of root-canal sealers in water and artificial salivaINTERNATIONAL ENDODONTIC JOURNAL, Issue 10 2003E. Schäfer Abstract Aim, To compare the weight loss of eight different root-canal sealers in water and in artificial saliva with different pH values. Methodology, For standardized samples (n = 12 per group), ring moulds were filled with epoxy resin (AH 26, AH Plus)-, silicone (RSA RoekoSeal)-, calcium hydroxide (Apexit, Sealapex)-, zinc oxide,eugenol (Aptal-Harz)-, glass-ionomer (Ketac Endo)- and polyketone (Diaket)-based sealers. These samples were immersed in double-distilled water or artificial saliva with different pH values (7.0, 5.7 and 4.5) for 30 s, 1 min, 2 min, 5 min, 10 min, 20 min, 1 h, 2 h, 10 h, 24 h, 48 h, 72 h, 14 days and 28 days. Mean loss of weight was determined and analysed statistically using a one-way anova and Student,Newman,Keuls test for all pairwise comparisons. Results, Most sealers were of low solubility, although Sealapex, Aptal-Harz and Ketac Endo showed a marked weight loss in all liquids. Even after 28 days of storage in water, AH 26, AH Plus, RSA RoekoSeal, and Diaket showed less than 3% weight loss. At exposure times greater than 14 days, Sealapex showed the significantly greatest weight loss of all sealers tested (P < 0.05). Aptal-Harz and Ketac Endo were significantly more soluble in saliva (pH 4.5) than in water (P < 0.05). Conclusions, Under the conditions of the present study, AH Plus showed the least weight loss of all sealers tested, independent of the solubility medium used. Sealapex, Aptal-Harz and Ketac Endo had a marked weight loss in all liquids. [source] Effect of conditioning films and a novel anti-adherent agent on bacterial adherence to dentineINTERNATIONAL ENDODONTIC JOURNAL, Issue 4 2001A. Maglad Aim,Adherence of bacteria to dentine is a prerequisite to infection of the root canal system, yet adherence of root canal bacteria to dentine is poorly understood. The aim of this study was to evaluate the effect of conditioning films and anti-adherent compounds on bacterial adherence to dentine. Methodology,Freshly extracted molar teeth were prepared and sectioned to give 225 discs of predetermined dimensions. The discs were allocated to two groups. Group 1 (n = 189) was divided into three subgroups (n = 63) and coated with one of three conditioning agents (artificial saliva, serum, or distilled water) prior to bacterial inoculation. Group 2 discs (n = 36) were treated with either a novel anti-adherent agent (PC1036, Biocompatibles) (n = 18) or distilled water (n = 18) prior to conditioning with artificial saliva. Monospecies bacterial biofilms were generated on the dentine discs by incubating them in brain heart infusion broth (37 gL,1) containing Streptococcus intermedius (Si), Enterococcus faecalis (Ef) or Lactobacillus fermentum (Lf) (originally isolated from infected root canals). The number of bacteria adhering to the discs in each of the groups was determined using standard serial dilution protocols. Additional discs were prepared under all conditions for scanning electron microscopy. Where appropriate, statistical analysis by one way anova, post hoc Bonferroni, and independent t -test were used. Results,Si adhered significantly better to dentine when conditioned with serum compared with artificial saliva (P = 0.005) or distilled water (P = 0.009). Conversely, Ef adhered significantly better to the control discs (distilled water) compared with serum conditioned discs (P = 0.016). The conditioning films had no effect on the adherence of Lf, which adhered to the dentine discs significantly less (P = 0.001) than either Si or Ef. The anti-adherent coating significantly reduced the number of Si adhering to the dentine compared with the control (P = 0.012). Conclusion,Given the importance of adherence in root canal infection it is conceivable that an anti-adherent compound, could be used to prevent bacterial recontamination of cavities or the root canal system. [source] Measurement of stain on extracted teeth using spectrophotometry and digital image analysisINTERNATIONAL JOURNAL OF DENTAL HYGIENE, Issue 3 2007DL Lath Abstract:, Aim:, The aim of this study was to assess the reliability and validate a customized image analysis system, designed for use within clinical trials of general dental hygiene and whitening products, for the measurement of stain levels on extracted teeth and to compare it with reflectance spectrophotometry. Method:, Twenty non-carious extracted teeth were soaked in an artificial saliva, brushed for 1 min using an electric toothbrush and a standard toothpaste, bleached using a 5.3% hydrogen peroxide solution and cycled for 6 h daily through a tea solution. CIE L* values were obtained after each treatment step using the customized image analysis system and a reflectance spectrophotometer. A statistical analysis was carried out in SPSS. Results:, Fleiss' coefficient of reliability for intra-operator repeatability of the image analysis system and spectrophotometry was 0.996 and 0.946 respectively. CIE L* values were consistently higher using the image analysis compared with spectrophotometry, and t -tests for each treatment step showed significant differences (P < 0.05) for the two methods. Limits of agreement between the methods were ,27.95 to +2.07, with a 95% confidence of the difference calculated as ,14.26 to ,11.84. The combined results for all treatment steps showed a significant difference between the methods for the CIE L* values (P < 0.05). Conclusion:, The image analysis system has proven to be a reliable method for assessment of changes in stain level on extracted teeth. The method has been validated against reflectance spectrophotometry. This method may be used for pilot in vitro studies/trials of oral hygiene and whitening products, before expensive in vivo tests are carried out. [source] R1 Effect of brushing on dental erosionINTERNATIONAL JOURNAL OF PAEDIATRIC DENTISTRY, Issue 2006A. Z. ABDULLAH Objectives:, To compare the effect of brushing versus dipping using three different concentrations of fluoridated toothpastes on enamel erosion in vitro using surface profilometry. Methods:, In a randomised, blinded experiment six groups of seven enamel slabs each were cut and mounted into resin blocks, ground and checked for surface flatness using a scanning profilometer (Scantron Proscan 2000). Each slabs' surface was covered with nail varnish except for a small window (1 x 2 mm). Each group was immersed under static conditions for 2 minutes, five times daily in fresh 200 ml aliquots of citric acid 0.3% (pH = 3.6). In addition, three groups were immersed in three different fluoridated toothpastes (0 ppm F, 1100 ppm F, or 1450 ppm F) twice daily morning and evening for 2 minutes each time. The other three groups were brushed using the same toothpastes twice daily for 2 minutes each time. The total cycling period lasted 16 days during which the slabs were incubated overnight and between erosive challenges in artificial saliva at 37oC. A 60-minute gap was left between daytime immersions. Before and after dipping in the erosive solutions the slabs were rinsed with de-ionised water. After the cycling period, the slabs were analysed with the scanning profilometer to measure the amount of surface loss at day 4, 8, 12, and 16. Results:, Surface loss ± SD of enamel at day 16 caused by citric acid combined with dipping using non-fluoridated toothpaste was 61.19 ± 8.50 ,m, 1100 ppm F was 43.44 ± 10.94 ,m or 1450 ppm F was 34.98 ± 4.29 ,m. Surface Loss ± SD of enamel at day 16 caused by citric acid combined with brushing using 0 ppm F, 1100 ppm F, or 1450 ppm F toothpastes was 75.62 ±10.64, 63.51 ± 5.27 and 48.94 ± 13.67 ,m, respectively. Conclusion:, Enamel erosion was increased significantly (CI 95%) using brushing with toothpastes compared to dipping. In addition, enamel erosion showed a dose-response to fluoridated toothpastes. Acknowledgment:, This project was supported by GlaxoSmithKline. [source] Solubility, salivary sorption and degree of conversion of dimethacrylate-based polymeric matrixesJOURNAL OF BIOMEDICAL MATERIALS RESEARCH, Issue 2 2008Luana Gonçalves Abstract This study investigated the relationship between the solubility, salivary sorption, and degree of conversion of dimethacrylate-based polymeric matrixes. Six polymeric matrixes produced by mixing bis-GMA, TEGDMA and UDMA dimethacrylate monomers were studied. Photoactivation was induced by camphoroquinone/ethyl N,N-dimethyl-4-aminobenzoate. The specimens were light-cured using an irradiance of 850 mW/cm2 for 20 s. The solubility and sorption (,g/mm3) were measured after immersion in artificial saliva (neutral pH) for 7 days. The degree of conversion (%) was obtained by using a FT-IR spectrometer equipped with an attenuated total reflectance crystal (ATR). The degree of conversion varied from 39.15 ± 6.30 to 65.57± 4.80, and was influenced by the viscosity of the monomers present in the polymeric matrixes. The solubility of polymeric matrixes varied between 13.64 ± 0.39 and 25.08 ± 0.83, and was strongly influenced by the degree of conversion (Pearson, r = ,0.9587, p < 0.01). No correlation was found between salivary sorption and the degree of conversion (p = 0.3918). Salivary sorption was only dependent on the chemical and physical structures of the monomers presented in the polymeric matrixes. © 2007 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 2008 [source] In vitro cytotoxicity of dental composites based on new and traditional polymerization chemistries,JOURNAL OF BIOMEDICAL MATERIALS RESEARCH, Issue 2 2007M. Goël Brackett Abstract The biological response to dental restorative polymer composites is mediated by the release of unpolymerized residual monomers. Several new composite formulations claim to reduce unpolymerized residual mass. The current study assessed the cytotoxic responses to several of these new formations and compared them with more traditional formulations. Our hypothesis predicted that if these new polymerization chemistries reduce unpolymerized residual mass, the cytotoxicity of these materials also should be reduced relative to traditional formulations. Methods: Materials (HerculiteXRV, Premise, Filtek Supreme, CeramxDuo, Hermes, and Quixfil) were tested in vitro in direct contact with Balb mouse fibroblasts, initially, then after aging in artificial saliva for 0, 1, 3, 5, or 8 weeks. The toxicity was determined by using the MTT assay to the estimate SDH activity. Knoop hardness of the materials also was measured at 0 and 8 weeks to determine whether surface breakdown of the materials in artificial saliva contributed to cytotoxic responses. Results: Materials with traditional methacrylate chemistries (Herculite, Premise, Filtek Supreme) were severely (>50%) cytotoxic throughout the 8-week interval, but materials with newer chemistries or filling strategies (Hermes, CeramXDuo, and Quixfil) improved over time of aging in artificial saliva. Hermes showed the least cytotoxicity at 8 weeks, and was statistically equivalent to Teflon® negative controls. Hardness of the materials was unaffected by exposure to artificial saliva. Conclusions: Newer polymerization and filling strategies for dental composites show promise for reducing the release of unpolymerized components and cytotoxicity. © 2006 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 2006 [source] Sorption and solubility testing of orthodontic bonding cements in different solutionsJOURNAL OF BIOMEDICAL MATERIALS RESEARCH, Issue 2 2006Manuel Toledano Abstract To evaluate and compare the solubility and sorption of orthodontic bonding cements after immersion in different solutions, five different cements were used: a fluoride-containing resin composite, a light-cured glass ionomer cement, a light-cured resin composite, a paste,paste chemically cured resin composite, and a liquid,paste chemically cured resin composite. Five different solutions were employed: distilled water, artificial saliva, an alcohol-free mouthrinse solution (Orthokin), a 5% alcohol mouthrinse solution (Perioaid), and a 75% ethanol/water solution. Five disc specimens (15 mm × 0.85 mm) were used for each experimental condition. Materials were handled following manufacturers' instructions and were ground wet with silicon carbide paper. Solubility and sorption of the materials were calculated by means of weighing the samples before and after immersion and desiccation. Data were analyzed by two-way ANOVA and Student,Newman,Keuls test (p < 0.05). The light-cured glass ionomer cement showed the lowest solubility and the highest sorption values. When using alcohol-containing solutions as storage media, solubility of the paste,paste chemically cured resin composite increased, and sorption values for the tested chemically cured resin composites were also increased. The use of alcohol-free mouthrinses does not affect sorption and solubility of orthodontic cements. The chemically cured (paste,paste) composite resin cement, requiring a mixing procedure, was the most affected by immersion in alcohol-containing solutions. © 2005 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 2006 [source] Influence of storage regime prior to abrasion on surface topography of restorative materialsJOURNAL OF BIOMEDICAL MATERIALS RESEARCH, Issue 2 2003Cecilia Pedroso Turssi Abstract This investigation was carried out to evaluate the effect of storage conditions prior to brushing simulation on surface texture of restorative materials. One resin-modified glass ionomer (Fuji II LC Improved/GC Corp.), one polyacid-modified composite resin (Dyract AP/Denstply), one microfill composite (Durafill VS/Kulzer), and one hybrid (Filtek,Z250/3M) composite were tested. Forty-five standardized cylindrical specimens of each material were made and randomly divided into three groups according to their subsequent storage conditions: distilled deionized water, artificial saliva, or pH-cycling regime. After 24 h, the experimental units were finished and polished and the surface roughness was measured to obtain Ra baseline values (Bv). Samples were subjected to their assigned storage regime and brushed afterwards. By the end of 10 repetitions of this protocol, final surface roughness readings (Fv) were taken. The analysis of covariance (, = 0.05), considering the covariate Bv showed a significant interaction between restorative material and storage condition (pvalue = 0.0002). Tukey's test revealed that the pH-cycling model provided a significantly lower surface roughness for Fuji II LC and Dyract AP than did the other media. For both composites no significant difference among storage regimes was detected. Under a condition simulating dynamic variation in pH prior to abrasion, the resultant surface texture may be either smoothed down or unchanged, depending on the restorative material, when compared to the effect provided by artificial saliva and distilled deionized water. © 2003 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 65B: 227,232, 2003 [source] Bleaching Agents with Varying Concentrations of Carbamide and/or Hydrogen Peroxides: Effect on Dental Microhardness and RoughnessJOURNAL OF ESTHETIC AND RESTORATIVE DENTISTRY, Issue 6 2008JULIANA JENDIROBA FARAONI-ROMANO DDS ABSTRACT Purpose:, To evaluate the effect of low and highly concentrated bleaching agents on microhardness and surface roughness of bovine enamel and root dentin. Methods:, According to a randomized complete block design, 100 specimens of each substrate were assigned into five groups to be treated with bleaching agents containing carbamide peroxide (CP) at 10% (CP10); hydrogen peroxide (HP) at 7.5% (HP7.5) or 38% (HP38), or the combination of 18% of HP and 22% of CP (HP18/CP22), for 3 weeks. The control group was left untreated. Specimens were immersed in artificial saliva between bleaching treatments. Knoop surface microhardness (SMH) and average surface roughness (Ra) were measured at baseline and post-bleaching conditions. Results:, For enamel, there were differences between bleaching treatments for both SMH and Ra measurements (p = 0.4009 and p = 0.7650, respectively). SMH significantly increased (p < 0.0001), whereas Ra decreased (p = 0.0207) from baseline to post-bleaching condition. For root dentin, the group treated with CP10 exhibited the significantly highest SMH value differing from those groups bleached with HP18/CP22, HP7.5, which did not differ from each other. Application of HP38 resulted in intermediate SMH values. No significant differences were found for Ra (p = 0.5975). Comparing the baseline and post-bleaching conditions, a decrease was observed in SMH (p < 0.0001) and an increase in Ra (p = 0.0063). Conclusion:, Bleaching agents with varying concentrations of CP and/or HP are capable of causing mineral loss in root dentin. Enamel does not perform in such bleaching agent-dependent fashion when one considers either hardness or surface roughness evaluations. CLINICAL SIGNIFICANCE Bleaching did not alter the enamel microhardness and surface roughness, but in root dentin, microhardness seems to be dependent on the bleaching agent used. [source] Effects of a 10% Carbamide Peroxide Bleaching Agent on Roughness and Microhardness of Packable Composite ResinsJOURNAL OF ESTHETIC AND RESTORATIVE DENTISTRY, Issue 4 2005ROBERTA TARKANY BASTING DDS ABSTRACT Purpose:: Bleaching agents containing 10% carbamide peroxide may be applied to the surface of preexisting packable resin-based composite restorations. The aim of this in vitro study was to evaluate the effect of a 10% carbamide peroxide bleaching agent (Review, SS White, Rio de Janeiro, Brazil) on surface roughness and microhardness of three packable resin-based composites (Fill Magic condensable, Vigodent, Rio de Janeiro, Brazil; Alert, Jeneric Pentron, Wallingford, CT, USA; Definite, Degussa, Hanau, Germany). Materials and Methods: For the control (no bleaching) and experimental (bleaching treatment) groups, 12 specimens of each material were prepared in cylindrical acrylic molds. The experimental specimens were exposed to the bleaching agent for 6 hours a day for 3 weeks. During the remaining time (18 h), they were stored in artificial saliva. The control specimens remained immersed in artificial saliva throughout the experiment. Surface roughness and microhardness measurements were performed on the top surface of each specimen. Results: Analysis of variance and the Tukey test showed no significant differences in roughness among the packable composites evaluated (p=.18), but those submitted to the treatment with a 10% carbamide peroxide bleaching agent displayed significantly higher mean surface roughness than did the corresponding control group for each material. For the microhardness tests, there were significant differences among materials (p < .0001). Alert showed the highest microhardness values followed by Definite and Fill Magic condensable. Conclusions: Ten percent carbamide peroxide bleaching agents may change the surface roughness of packable composites, but they do not alter their microhardness. [source] Shear Bond Strength of Enamel Treated with Seven Carbamide Peroxide Bleaching AgentsJOURNAL OF ESTHETIC AND RESTORATIVE DENTISTRY, Issue 4 2004ROBERTA TARKAN. ABSTRACT Purpose:: Lower average values of bond strength of adhesive systems to enamel bleached with 10% carbamide peroxide agents have been reported, but the effects of higher concentrations of carbamide peroxide bleaching agents are still unknown. The aim of this in vitro study was to evaluate the shear bond strength of enamel treated with different concentrations of carbamide peroxide to an adhesive system after a postbleaching period of storage in artificial saliva for 15 days. Materials and Methods: Seven carbamide peroxide bleaching agents with concentrations varying from 10 to 22% were analyzed. A placebo agent was used as a control group. The agents were applied on the enamel fragments for 8 h/d for 42 days. During the remaining time, the specimens were stored in artificial saliva. After that time, the fragments were stored individually in artificial saliva for 15 days. An adhesive system was used to bond resin-based composite cylinders on the enamel surface. Shear bond strength tests were performed and the fractured surfaces of the specimens were visually examined with a stereomicroscope at ×30. Results: The analysis of variance did not show differences in shear bond strength among the treatment agents. The fractures for all treatment agents were predominantly adhesive. Conclusion: After 15 days storage in artificial saliva, different concentrations of carbamide peroxide bleaching agents and a placebo agent had the same enamel shear bond strength values. [source] Corrosion behaviour of high copper dental amalgamsJOURNAL OF ORAL REHABILITATION, Issue 6 2004A. U. J. Yap summary, This study evaluated the corrosion behaviour of two high copper dental amalgam alloys [Dispersalloy (Dentsply-Caulk) and Tytin (Kerr)] in different electrolytes. Amalgam specimens were prepared, coupled to a copper wire, cemented into glass tubes and polished to a 600-grit finish. A corrosion cell was prepared using a carbon counter-electrode, a standard calomel electrode as the reference and amalgam as the working electrode. The alloys were tested in the following mediums at 37 °C: (i) artificial saliva based on Fusayama's solution (FS), (ii) artificial saliva with citric acid adjusted to pH 4·0 (FC) and (iii) 1% sodium chloride solution (SC). Corrosion potentials (Ecorr) and corrosion rates (Icorr) were determined using potentiostatic and impedance spectroscopy methods. Data was subjected to anova/Scheffe's post hoc test at 0·05 significance level. For both alloys, the corrosion potential in FS was significantly greater than in SC. Corrosion potential of Tytin in FS and SC was also significantly greater than in FC. The corrosion rate of Dispersalloy in FC was significantly greater than in FS and SC. For Tytin, corrosion rate in SC was significantly greater than in FS and FC. Although no significant difference in corrosion potential/rate was observed between the alloys when tested in FS, significant differences were observed when electrochemical testing was carried out in FC and SC. The corrosion behaviour of high copper amalgam alloys are both material and environment dependent. Certain food substances may increase the corrosion of high copper amalgams. [source] Occlusal contact area (OCA) wear of two new composite restorativesJOURNAL OF ORAL REHABILITATION, Issue 2 2002A. U. J. Yap The occlusal contact area wear resistance of two new composite restoratives (Z250 and P60) was investigated and compared with two existing materials (Silux and Z100) using a reciprocal compression-sliding test apparatus. Six wear specimens were made for each material and subjected to wear testing at 20 MPa with artificial saliva as lubricant. Wear depth (,m) was measured using profilometry every 20 000 cycles up to 120 000 cycles. Results were analysed using ANOVA/Scheffe's test (P < 0·05) and Pearson's correlation. The effects of cyclic loading on wear and counter-body loss were material dependent. Silux had the lowest wear at all cyclic intervals. At 20 000 and 40 000 cycles, Silux had significantly less wear than all the other composites evaluated, and Z100 had significantly less wear than Z250 and P60. After 60 000 cycles, significant differences in wear was observed only between Silux and the other composites. Correlation between number of cycles and wear/counter-body loss, and between wear and counter-body were significant and positive. The microfilled composite Silux had significantly better OCA wear resistance than the minifilled composites Z100, Z250 and P60. [source] Environmental damage and occlusal contact area wear of composite restorativesJOURNAL OF ORAL REHABILITATION, Issue 1 2002A. U. J. Yap The chemical environment is one aspect of the oral environment, which could have an appreciable influence on the in-vivo degradation of composite resins. The resin matrix can be softened and fillers constituents can be leached out when composites are exposed to certain chemicals/food-simulating liquids (FSLs). A reciprocal compression sliding wear device was used to study the effects of the chemical environment on occlusal contact area (OCA) wear of four composite restoratives (Silux Plus, Z100, Ariston pHc and Surefil). The effects of FSL on hardness was also investigated and correlated to wear. Thirty-six hardness/wear specimens of each material were made and stored in artificial saliva at 37 °C for 24 h. The specimens were then divided into six groups of six specimens and stored in the following FSL for 1 week at 37 °C: distilled water (W), 0·02 N citric acid (C), 0·02 N lactic acid (L), heptane (H) and 75,25% ethanol,water solution (E). Conditioning in artificial saliva (S) was used as control. After conditioning, the specimens were wear tested at 20 MPa contact stress against SS304 counter-bodies in the respective FSL/artificial saliva up to 20 000 cycles. Wear depth (lm, n=6) was measured using profilometry. Change in hardness (,KHN, Knoop hardness number) was determined by microhardness testing pre- and post-conditioning. Results of statistical analyses (ANOVA/Scheffe's at significance level 0·05) of wear data were as follows: Silux , S, W > L, H, E and C, L > H; Z100 , S, W > all other mediums and E > H; Ariston , all other mediums > H; Surefil , W, C > S, L, H, E (> indicates significantly more wear). With the exception of Surefil, the greatest wear was observed with conditioning and wear testing in water. This ranged from 93·18 ± 21·96 lm for Z100 to 31·43 ± 2·80 lm for Surefil. For all materials, conditioning in heptane resulted in the least wear. This ranged from 8·9 ± 2·2 ,m for Ariston to 16·5 ± 5·9 lm for Silux. The effects of the different FSL on OCA wear were material dependent. No correlation was observed between ,KHN and wear. [source] Influence of Artificial Accelerated Aging on Dimensional Stability of Acrylic Resins Submitted to Different Storage ProtocolsJOURNAL OF PROSTHODONTICS, Issue 6 2010Lucas da Fonseca Roberti Garcia DDS Abstract Purpose: The aim of this study was to evaluate the influence of artificial accelerated aging on dimensional stability of two types of acrylic resins (thermally and chemically activated) submitted to different protocols of storage. Materials and Methods: One hundred specimens were made using a Teflon matrix (1.5 cm × 0.5 mm) with four imprint marks, following the lost-wax casting method. The specimens were divided into ten groups, according to the type of acrylic resin, aging procedure, and storage protocol (30 days). GI: acrylic resins thermally activated, aging, storage in artificial saliva for 16 hours, distilled water for 8 hours; GII: thermal, aging, artificial saliva for 16 hours, dry for 8 hours; GIII: thermal, no aging, artificial saliva for 16 hours, distilled water for 8 hours, GIV: thermal, no aging, artificial saliva for 16 hours, dry for 8 hours; GV: acrylic resins chemically activated, aging, artificial saliva for 16 hours, distilled water for 8 hours; GVI: chemical, aging, artificial saliva for 16 hours, dry for 8 hours; GVII: chemical, no aging, artificial saliva for 16 hours, distilled water for 8 hours; GVIII: chemical, no aging, artificial saliva for 16 hours, dry for 8 hours GIX: thermal, dry for 24 hours; and GX: chemical, dry for 24 hours. All specimens were photographed before and after treatment, and the images were evaluated by software (UTHSCSA , Image Tool) that made distance measurements between the marks in the specimens (mm), calculating the dimensional stability. Data were submitted to statistical analysis (two-way ANOVA, Tukey test, p= 0.05). Results: Statistical analysis showed that the specimens submitted to storage in water presented the largest distance between both axes (major and minor), statistically different (p < 0.05) from control groups. Conclusions: All acrylic resins presented dimensional changes, and the artificial accelerated aging and storage period influenced these alterations. [source] Confocal Examination of Subsurface Cracking in Ceramic MaterialsJOURNAL OF PROSTHODONTICS, Issue 7 2009MMedSc, Maged K. Etman DDS Abstract Purpose: The original ceramic surface finish and its microstructure may have an effect on crack propagation. The purpose of this study was to investigate the relation between crack propagation and ceramic microstructure following cyclic fatigue loading, and to qualitatively evaluate and quantitatively measure the surface and subsurface crack depths of three types of ceramic restorations with different microstructures using a Confocal Laser Scanning Microscope (CLSM) and Scanning Electron Microscope (SEM). Materials and Methods: Twenty (8 × 4 × 2 mm3) blocks of AllCeram (AC), experimental ceramic (EC, IPS e.max Press), and Sensation SL (SSL) were prepared, ten glazed and ten polished of each material. Sixty antagonist enamel specimens were made from the labial surfaces of permanent incisors. The ceramic abraders were attached to a wear machine, so that each enamel specimen presented at 45 degrees to the vertical movement of the abraders, and immersed in artificial saliva. Wear was induced for 80K cycles at 60 cycles/min with a load of 40 N and 2-mm horizontal deflection. The specimens were examined for cracks at baseline, 5K, 10K, 20K, 40K, and 80K cycles. Results: Twenty- to 30-,m deep subsurface cracking appeared in SSL, with 8 to 10 ,m in AC, and 7 ,m close to the margin of the wear facets in glazed EC after 5K cycles. The EC showed no cracks with increasing wear cycles. Seventy-,m deep subsurface cracks were detected in SSL and 45 ,m in AC after 80K cycles. Statistically, there was significant difference among the three materials (p < 0.05). Bonferroni multiple comparison of means test confirmed the ANOVA test and showed that there was no statistical difference (p > 0.05) in crack depth within the same ceramic material with different surface finishes. Conclusions: The ceramic materials with different microstructures showed different patterns of subsurface cracking. [source] Survival of mycobacterial species in aerosols generated from artificial salivaLETTERS IN APPLIED MICROBIOLOGY, Issue 3 2000M.S. Lever Tuberculosis is transmitted primarily by the aerosol route and the aim of this study was to measure the ability of pathogenic mycobacteria to survive in aerosols generated from artificial saliva. Aerosols of Mycobacterium avium, Mycobacterium intracellulare and Mycobacterium tuberculosis were generated and maintained in air under controlled conditions using a Henderson apparatus and a rotating drum. There were no differences in aerosol survival between the three species, and all had a poor survival rate over a period of 1 h. These data confirm epidemiological studies that close and prolonged contact with a TB patient is required for transmission of infection. [source] Chemical and morphological features of dental composite resin: Influence of light curing units and immersion mediaMICROSCOPY RESEARCH AND TECHNIQUE, Issue 3 2010Patrícia Aleixo Dos Santos Abstract Aims: The study evaluated the influence of light curing units and immersion media on superficial morphology and chemistry of the nanofilled composite resin Supreme XT (3M) through the EDX analysis and SEM evaluation. Light curing units with different power densities and mode of application used were XL 3000 (480 mW/cm2), Jet Lite 4000 Plus (1230mW/cm2), and Ultralume Led 5 (790 mW/cm2) and immersion media were artificial saliva, Coke®, tea and coffee, totaling 12 experimental groups. Specimens (10 mm × 2 mm) were immersed in each respective solution for 5 min, three times a day, during 60 days and stored in artificial saliva at 37°C ± 1°C between immersion periods. Topography and chemical analysis was qualitative. Findings: Groups immersed in artificial saliva, showed homogeneous degradation of matrix and deposition of calcium at the material surface. Regarding coffee, there was a reasonable chemical degradation with loss of load particles and deposition of ions. For tea, superficial degradation occurred in specific areas with deposition of calcium, carbon, potassium and phosphorus. For Coke®, excessive matrix degradation and loss of load particles with deposition of calcium, sodium, and potassium. Conclusion: Light curing units did not influence the superficial morphology of composite resin tested, but the immersion beverages did. Coke® affected material's surface more than did the other tested drinks. Microsc. Res. Tech., 2010. © 2009 Wiley-Liss, Inc. [source] Changes in the mechanical properties of tooth-colored direct restorative materials in relation to timePOLYMERS FOR ADVANCED TECHNOLOGIES, Issue 9 2003Gülbin Sayg Abstract The objective of this study was to determine the flexural strength, flexural modulus, Vickers hardness of a packable composite (Surefil), and an ormocer (Definite) in comparison with a microhybrid composite (Z-100), a microfil composite (Silux Plus) and a polyacid-modified composite resin (Dyract). Flexural strength and flexural modulus were determined using a three-point bending device. Microhardness was measured with a Vickers indentor. The specimens of each material were prepared according to manufacturer's instructions. The specimens were stored in artificial saliva at pH 6, all at 37°C. The groups were tested at the beginning of the test, at 3 months and at 6 months. Flexural strength values of Surefil and Definite showed a progressive increase. The highest MPa values were determined for Surefil (134.4,MPa) and the lowest MPa values were obtained for Dyract (59.6,MPa). The highest flexural modulus values were revealed for Surefil (10.000 GPa). Z-100, Silux Plus and Definite showed a tendency to decline in relation to time for their flexural modulus. GPa values of Silux Plus were stable at 3 and 6 months. Vickers hardness numbers showed that Surefil was the hardest and Dyract was the weakest material. Copyright © 2003 John Wiley & Sons, Ltd. [source] Increased blood concentration of isopropanol in ketotic dairy cows and isopropanol production from acetone in the rumenANIMAL SCIENCE JOURNAL, Issue 4 2009Hiroshi SATO ABSTRACT To evaluate acetone and isopropanol metabolism in bovine ketosis, the blood concentrations of isopropanol, acetone, plasma 3-hydroxybutyrate (3-HB) and other metabolites were analyzed in 12 healthy controls and 15 ketotic dairy cows including fatty liver and inferior prognosis after laparotomy for displaced abomasum. In ruminal fluid taken from 6 ketotic cows, ruminal isopropanol and acetone were also analyzed. Ketotic cows showed higher concentrations of isopropanol, acetone, 3-HB and nonesterified fatty acid, and higher activities of aspartate transaminase and ,-glutamyl transferase than control cows. Blood samples had higher concentration of isopropanol accompanied by increased acetone. In the ketotic cows, acetone was detected not only in blood but also in ruminal fluid, while higher ruminal isopropanol did not necessarily accompany its elevation in the blood. Using 2 steers with rumen cannula, all ruminal content was emptied and then substituted with artificial saliva to evaluate the importance of ruminal microbes in isopropanol production. Under each condition of intact and emptied rumen, acetone was infused into the rumen and blood isopropanol was analyzed. The elevation in the blood isopropanol concentration after acetone infusion was markedly inhibited by the emptying. Here, increased blood concentrations of isopropanol and acetone were observed in ketotic cows, and the importance of ruminal microbes in isopropanol production was confirmed. [source] Preventive effect of iron gel with or without fluoride on bovine enamel erosion in vitroAUSTRALIAN DENTAL JOURNAL, Issue 2 2010MG Bueno Abstract Background:, The aim of this study was to evaluate the preventive effect in vitro of experimental gel containing iron and/or fluoride on the erosion of bovine enamel. Methods:, To standardize the blocks (n = 80), specimens (4 × 4 mm) were previously selected to measure the initial microhardness. The blocks were randomly allocated into four groups of 20 samples each: C (control, placebo gel); F (fluoride gel, 1.23% NaF); Fe (iron gel, 10 mmol/L FeSO4) and F + Fe (fluoride + iron gel). The gels were applied and removed after 1 minute. The blocks were then submitted to six alternating remineralization and demineralization cycles. The beverage Coca-Cola® (10 minutes, 30 mL) was used for demineralization, and artificial saliva (1 hour) for remineralization. The effect of erosion was measured by wear analysis (profilometry). Data were analysed by ANOVA and the Tukey test for individual comparisons (p <0.05). Results:, The mean wear (± SD, ,m) was C: 0.94 ± 0.22; F: 0.55 ± 0.12; Fe: 0.49 ± 0.11 and F + Fe: 0.55 ± 0.13. When the experimental gels were used, there was statistically significant reduction in enamel wear in comparison with the control (p <0.001). However, the experimental gels did not differ significantly among them. Conclusions:, The gels containing iron with or without fluoride are capable of interfering with the dissolution dental enamel in the presence of erosive challenge. [source] | ||||||||||||||||