Novel polymer-ceramic composites for protection against ballistic fragments

For the first time, internally reinforced aggregate polymer ceramic composites were evaluated against fragment simulating projectiles (FSPs) of various calibers to investigate their ballistic impact response. Samples were prepared by mechanically mixing B4C and cBN over a range of ratios and combinations with either thermosetting phenolic or epoxy resin and aramid pulp. Dry mixtures were then molded in a closed die using a heated platen press. The resulting tiles were then mounted as ‘‘strike faces’’ to an aramid backing material using an epoxy resin. Backed targets were tested in a fully instrumented firing range against 5.56 mm FSPs to test ballistic limit. A further series of tests using 7.62, 12.5, and 20 mm FSPs was conducted to examine round deformation across a range of fragments calibers. Round deformations were measured after impact and plotted against shot velocity. It was found that the polymer ceramic composite materials were effective round deformers and, like sintered ceramic strike faces, demonstrated improved ballistic performance at an equivalent areal density and impressive multihit capability.

Periodontal tissue response to coverage of root cavities restored with resin materials: A histomorphometric study in dogs

Background: the purpose of this study was to histomorphometrically evaluate the response of periodontal tissues covering Class V resin restorations in dogs.Methods: After raising a mucoperiosteal flap, bony defects measuring 5 x 5 mm were created on the buccal aspect of the canines of five dogs followed by cavity preparations on the root surface measuring 3 x 3 x 1 mm. Before repositioning the flap to cover the bone defect, the cavities were restored with composite resin (CR) or resin-modified glass ionomer cement (RMGIC) or were left unrestored as control (C). The dogs were euthanized 90 days after surgery. Specimens comprising the tooth and periodontal tissues were removed, processed routinely, cut into longitudinal serial sections in the bucco-lingual direction, and stained with hematoxylin and eosin (H&E) or Masson's trichrome. The most central sections were selected for histomorphometric analysis.Results: Histomorphometric analysis revealed apical migration of epithelial tissue onto the restorative materials (RMGIC and CR). The C group presented significantly longer connective tissue attachment (P < 0.05) than the RMGIC and CR groups and significantly higher bone regeneration (P < 0.05) compared to the RMGIC group. Histologically, the cervical third (CT) of all groups had the most marked chronic inflammatory infiltrate.Conclusions: Within the limits of this study, it can be concluded that the restorative materials used exhibit biocompatibility; however, both materials interfered with the development of new bone and the connective tissue attachment process.

In situ effect of an erosive challenge on different restorative materials and on enamel adjacent to these materials

Objectives: This in situ study evaluated the effect of an erosive challenge on different restorative materials and on enamel restored with these materials, as well as the ability of these materials to protect the adjacent enamel against erosion.Methods: Ten volunteers wore palatal devices with eight bovine enamel blocks, randomly selected and distributed into two vertical rows, corresponding to the following groups: GI/GV, resin-modified glass ionomer; GII/GVI, conventional glass ionomer; GIII/GVII, composite resin; GIV/GVIII, amalgam. one row (corresponding to groups I-IV) was immersed in a cola drink and the other row (corresponding to groups V-VIII) was subjected to saliva only. The palatal device was continuously worn for 7 days and only half of the appliance (groups I-IV) was immersed in the soft drink (Coca-Cola (R), 150 mL) for 5 min, three times a day. The study variables comprised the wear (profilometry, mu m) and the percentage of surface microhardness change (%SMHC). Data were tested for significant differences by two-way ANOVA and Tukey's tests (p < 0.05).Results: Considering the restorative materials, for %SMHC and wear, there were no differences among the materials and between the saliva and the erosive challenge. For enamel analyses, the erosive challenge promoted a higher wear and %SMHC of the enamel than did the saliva. There were no significant differences in wear and %SMHC of the enamel adjacent to the different restorative materials.Conclusion: This research data suggest that there is little %SMHC and wear of the studied restorative materials and none of them had a preventive effect against erosion on adjacent enamel, which showed a pronounced wear. (c) 2007 Elsevier Ltd. All rights reserved.

Cytotoxicity and biocompatibility of direct and indirect pulp capping materials

There are several studies about the cytotoxic effects of dental materials in contact with the pulp tissue, such as calcium hydroxide (CH), adhesive systems, resin composite and glass ionomer cements. The aim of this review article was to summarize and discuss the cytotoxicity and biocompatibility of materials used for protection of the dentin-pulp complex, some components of resin composites and adhesive systems when placed in direct or indirect contact with the pulp tissue. A large number of dental materials present cytotoxic effects when applied close or directly to the pulp, and the only material that seems to stimulate early pulp repair and dentin hard tissue barrier formation is CH.

Tissue response to experimental dental cements prepared from a modified power glass composition

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Shear bond strength of metal-ceramic repair systems

Statement of problem. When clinical fractures of the ceramic veneer on metal-ceramic prostheses can be repaired, the need for remake may be eliminated or postponed. Many different ceramic repair materials are available, and bond strength data are necessary for predicting the success of a given repair system.Purpose. This study evaluated the shear bond strength of different repair systems for metal-ceramic restorations applied on metal and porcelain.Material and methods. Fifty cylindrical specimens (9 X 3 mm) were fabricated in a nickel-chromium alloy (Vera Bond 11) and 50 in feldspathic porcelain (Noritakc). Metal (M) and porcelain (P) specimens were embedded in a polyvinyl chloride (PVC) ring and received I of the following bonding and resin composite repair systems (n=10): Clearfil SE Bond/Clearfil AP-X (CL), Bistite II DC/Palfique (BT), Cojet Sand/Z100 (Q), Scotchbond Multipurpose Plus/Z100 (SB) (control group), or Cojet Sand plus Scotchbond Multipurpose Plus/Z100 (CJSB). The specimens were stored in distilled water for 24 hours at 37 degrees C, thermal cycled (1000 cycles at 5 degrees C to 55 degrees C), and stored at 37 degrees C for 8 days. Shear bond tests between the metal or ceramic specimens and repair systems were performed in a mechanical testing machine with a crosshead speed of 0.5 mm/min. Mean shear bond strength values (MPa) were submitted to 1-way ANOVA and Tukey honestly significant difference tests (alpha=.05). Each specimen was examined under a stereoscopic lens with X 30 magnification, and mode of failure was classified as adhesive, cohesive, or a combination.Results. on metal, the mean shear bond strength values for the groups were as follows: MCL, 18.40 +/- 2.88(b); MBT, 8.57 +/- 1.00(d); MCJ, 25.24 +/- 3.46(a); MSB, 16.26 +/- 3.09(bc); and MCJSB, 13.11 +/- 1.24(c). on porcelain, the mean shear bond strength values ofeach group were as follows: PCL, 16.91 +/- 2.22(b); PBT, 18.04 +/- 3.2(ab); PCJ, 19.54 +/- 3.77(ab); PSB, 21.05 +/- 3.22(a); and PCJSB, 16.18 +/- 1.71(b). Within each substrate, identical superscript letters denote no significant differences among groups.Conclusions. The bond strength for the metal substrate was significantly higher using the Q system. For porcelain, SB, Q, and BT systems showed the highest shear bond strength values, and only SB was significantly different compared to CL and CJSB (P <.05).

Cytotoxicity of monomers, plasticizer and degradation by-products released from dental hard chairside reline resins

Objectives. The aim of this study was to evaluate the cytotoxic effect of the monomers isobutyl methacrylate (IBMA) and 1,6-hexanediol dimethacrylate (1,6-HDMA), the plasticizer di-n-butyl phthalate (DBP), and the degradation by-products methacrylic acid (MA) and benzoic acid (BA) on L929 cells. Based on previous investigations on the release of these compounds from hard chairside reline resins, a range of concentrations (mu mol/L) were selected for the cytotoxicity tests (IBMA, 5.491406.57; 1,6-HDMA, 1.2239.32; DBP, 1.12143.8; MA, 9.07581; BA, 3.19409).Methods. Cytotoxic effects were assessed using MTT and 3H-thymidine assays after the cells had been exposed to the test compounds at the given concentrations for 24h. Cytotoxicity was rated based on cell viability relative to controls (cells exposed to medium without test substances).Results. DNA synthesis activity was inhibited by all compounds. Mitochondrial dehydrogenase activity decreased in cells treated with monomers, plasticizer and MA by-product, whereas no cytotoxic effect was observed on contact with BA at the majority of concentrations tested. The ranges of suppression for 3H-thymidine assay were: IBMA, 2595%; 1,6-HDMA, 9598%; DBP, 4098%; MA, 9799%; BA, 5471%. For MTT assay, the ranges of suppression were: IBMA, 096%; 1,6-HDMA, 2689%; DBP, 1780%; MA, 5266%; BA, 027%. The 3H-thymidine assay was more sensitive than the MTT assay.Significance. This study evaluated the cytotoxicity of a wide range of concentrations of monomers (IBMA and 1,6-HDMA), plasticizer (DBP) and degradation by-products (MA and BA), including those expected to be released from hard chairside reline resins. The differences observed in the cytotoxicity of these compounds, along with other properties, may assist the dental practitioners in the selection of reline materials with improved service life performance and low risk of adverse reactions in patients who wear relined dentures.

Determination of the properties of an experimental glass polyalkenoate cement prepared from niobium silicate powder containing fluoride

Objectives. The purpose of this paper is to modify the conventional calcium fluoro-aluminosilicate glass, which is used in the formation of glass ionomer cements (CIGs) by the niobium addition and to study the properties of GICs obtained.Materials and methods. Sol-gel process was used to prepare the powder at lower temperature than fusion method. Glass-ceramic powder obtained in this way was used to prepare the GICs. The properties such as working and setting times, microhardness and diametral tensile strength were evaluated for the experimental GICs and a commercial luting cement.Results. The ideal powder:liquid (P:L) ratio determined to prepare the experimental GICs was equal to 1:1. The cements prepared using this ratio showed working and setting times similar to the commercial GICs. in mechanical tests it was observed that microhardness and diametral tensile strength of the experimental GICs decreased significantly with the reduction of P:L ratio. on the other hand, the results obtained in microhardness tests indicated that the presence of niobium was a positive factor.Significance. The chemical process allows the development of glass-ceramic powder at 600 degrees C which is the goal of the present paper. It was concluded that GICs containing niobium might be used in dental applications and these results encourage further researches on other compositions. (c) 2007 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

Evaluation of interface characterization and adhesion of glass ceramics to commercially pure titanium and gold alloy after thermal- and mechanical-loading

Objectives. This study evaluated the effect of thermal- and mechanical-cycling on the shear bond strength of three low-fusing glassy matrix dental ceramics to commercial pure titanium (cpTi) when compared to conventional feldspathic ceramic fused to gold alloy.Methods. Metallic frameworks (diameter: 5 min, thickness: 4 mm) (N = 96, n = 12 per group) were cast in cpTi and gold alloy, airborne particle abraded with 150 mu m aluminum oxide. Low-fusing glassy matrix ceramics and a conventional feldspathic ceramic were fired onto the alloys (thickness: 4mm). Four experimental groups were formed; Gr1 (control group): Vita Omega 900-Au-Pd alloy; Gr2: Ticeram-cpTi; Gr3: Super Porcelain Ti-22-cpTi and G4: Vita Titankeramik-cpTi. While half of the specimens from each ceramic-metal combination were randomly tested without aging (water storage at 37 C for 24h only), the other half were first thermocycled (6000 cycles, between 5 and 55 C, dwell time: 13 s) and then mechanically loaded (20,000 cycles under SON load, immersion in distilled water at 37 C). The ceramic-alloy interfaces were loaded under shear in a universal test machine (cross-head speed: 0.5 mm/min) until failure occur-red. Failure types were noted and the interfaces of the representative fractured specimens from each group were examined with stereo microscope and scanning electron microscope (SEM). in an additional study (N = 16, n = 2 per group), energy dispersive X-ray spectroscopy (EDS) analysis was performed from ceramic-alloy interfaces. Data were analyzed using ANOVA and Tukey's test.Results. Both ceramic-metal combinations (p < 0.001) and aging conditions (p < 0,001) significantly affected the mean bond strength values. Thermal- and mechanical-cycling decreased the bond strength (MPa) results significantly for Gr3 (33.4 +/- 4.2) and Gr4 (32.1 +/- 4.8) when compared to the non-aged groups (42.9 +/- 8.9, 42.4 +/- 5.2, respectively). Gr1 was not affected significantly from aging conditions (61.3 +/- 8.4 for control, 60.7 +/- 13.7 after aging) (p > 0.05). Stereomicroscope images showed exclusively adhesive failure types at the opaque ceramic-cpTi interfacial zone with no presence of ceramic on the substrate surface but with a visible dark titanium oxide layer in Groups 2-4 except Gr1 where remnants of bonder ceramic was visible. EDS analysis from the interfacial zone for cpTi-ceramic groups showed predominantly 34.5-85.1% O(2) followed by 1.1-36.7% Aland 0-36.3% Si except for Super Porcelain Ti-22 where a small quantity of Ba (1.4-8.3%), S (0.7%) and Sn (35.3%) was found. In the Au-Pd alloy-ceramic interface, 56.4-69.9% O(2) followed by 15.6-26.2% Si, 3.9-10.9% K, 2.8-6% Na, 4.4-9.6% Al and 0-0.04% Mg was observed.Significance. After thermal-cycling for 6000 times and mechanical-cycling for 20,000 times, Triceram-cpTi combination presented the least decrease among other ceramic-alloy combinations when compared to the mean bond strength results with Au-Pd alloy-Vita Omega 900 combination. (c) 2008 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

Surface degradation of glass ceramics after exposure to acidulated phosphate fluoride

Objective: This study evaluated the surface degradation effect of acidulated phosphate fluoride (APF) gel exposure on the glassy matrix ceramics as a function of time. Material and methods: Disc-shaped ceramic specimens (N = 120, 10/per ceramic material) were prepared in stainless steel molds (inner diameter: 5 mm, height: 2 mm) using 6 dental ceramics: 3 indicated for ceramic-fused-to-metal (Vita Omega 900, Carmen and Vita Titankeramik), 2 for all-ceramic (Vitadur Alpha and Finesse (R) Low Fusing) and 1 for both types of restorations (IPS d. SIGN). The specimens were wet ground finished, ultrasonically cleaned and auto-glazed. All specimens were subjected to calculation of percentage of mass loss, surface roughness analysis and topographical description by scanning electron microscopy (SEM) before (0 min) and after exposure to 1.23 % APF gel for 4 min and 60 min representing short-and long-term etching effect, respectively. The data were analyzed using two-way ANOVA with repeated measures and Tukey` s test (alpha=0.05). Results: Significant effect of the type of the ceramics (p=0.0000, p=0.0031) and exposure time (p=0.0000) was observed in both surface roughness and percentage of mass loss values, respectively. The interaction factor between both parameters was also significant for both parameters (p=0.0904, p=0.0258). Both 4 min (0.44 +/- 0.1-0.81 +/- 0.2 mu m) and 60 min (0.66 +/- 0.1 - 1.04 +/- 0.3 mu m) APF gel exposure created significantly more surface roughness for all groups when compared to the control groups (0.33 +/- 0.2-0.68 +/- 0.2 mu m) (p<0.05). There were no significant differences in percentage of mass loss between the ceramics at 4 min (p>0.05) but at 60 min exposure, IPS d. SIGN showed the highest percentage of mass loss (0.1151 +/- 0.11). The mean surface roughness for Vita Titankeramik (0.84 +/- 0.2 mu m) and Finesse (R) Low Fusing (0.74.+/- 0.2 mu m) was significantly higher than those of the other ceramics (0.59 +/- 0.1 mu m - 0.49 +/- 0.1 mu m) and Vita Titankeramik (p<0.05) regardless of the exposure time. A positive correlation was found between surface roughness and percentage of mass loss for all ceramic materials [(r=0.518 (Vitadur Alpha), r=0.405 (Vita Omega 900), r=0.580 (Carmen), r=0.687 (IPS d. SIGN), r=0.442 (Finesse (R) Low Fusing), r=0.572 (Vita Titankeramik), Pearson's correlation coefficient)]. The qualitative SEM analysis showed evidence of corrosive attack on all of ceramics at varying degrees. Conclusions: The ceramics indicated for either metal-ceramic or all-ceramic restorations were all vulnerable to surface texture changes and mass loss after short-term and long-term APF gel exposure.

Mechanical and thermal cycling effects on the flexural strength of glass ceramics fused to titanium

This study evaluated the effects of mechanical and thermal cycling on the flexural strength (ISO 9693) of three brands of ceramics fused to commercially pure titanium (cpTi). Metallic frameworks of 25 x 3 x 0.5 mm dimensions (N = 84) were cast in cpTi, followed by 150-mu m aluminum oxide airborne particle abrasion at a designated area of the frameworks (8 x 3 mm). Bonder and opaque ceramic were applied on the frameworks, and then the corresponding ceramic (Triceram, Super Porcelain Ti-22, Vita Titankeramik) was fired onto them (thickness: 1 mm). Half of the specimens from each ceramic-metal combination were randomly tested without aging (only water storage at 37 degrees C for 24 hours), while the other half were mechanically loaded (20,000 cycles under 10 N load, immersion in distilled water at 37 degrees C) and thermocycled (3,000 cycles, between 5-55 degrees C, dwell time of 13 seconds). After the flexural strength test, failure types were noted. Mechanical and thermal cycling decreased the mean flexural strength values significantly (p<0.05) for all the three ceramic-cpTi combinations tested when compared to the control group. In all the three groups, failure type was exclusively adhesive at the opaque ceramic-cpTi interfacial zone with no presence of ceramic on the substrate surface except for a visible oxide layer.

Effect of multiple firing and silica deposition on the zirconia-porcelain interfacial bond strength

Objectives. To test the hypothesis that multiple firing and silica deposition on the zirconia surface influence the bond strength to porcelain.Materials and methods. Specimens were cut from yttria-stabilized zirconia blocks and sintered. Half of the specimens (group S) were silica coated (physical vapor deposition (PVD)) via reactive magnetron sputtering before porcelain veneering. The remaining specimens (group N) had no treatment before veneering. The contact angle before and after silica deposition was measured. Porcelain was applied on all specimens and submitted to two (N2 and S2) or three firing cycles (N3 and S3). The resulting porcelain-zirconia blocks were sectioned to obtain bar-shaped specimens with 1 mm(2) of cross-sectional area. Specimens were attached to a universal testing machine and tested in tension until fracture. Fractured surfaces were examined using optical microscopy. Data were statistically analyzed using two-way ANOVA, Tukey's test (alpha = 0.05) and Weibull analysis.Results. Specimens submitted to three firing cycles (N3 and S3) showed higher mean bond strength values than specimens fired twice (N2 and S2). Mean contact angle was lower for specimens with silica layer, but it had no effect on bond strength. Most fractures initiated at porcelain-zirconia interface and propagated through the porcelain.Significance. The molecular deposition of silica on the zirconia surface had no influence on bond strength to porcelain, while the number of porcelain firing cycles significantly affected the bond strength of the ceramic system, partially accepting the study hypothesis. Yet, the Weibull modulus values of S groups were significantly greater than the m values of N groups. (C) 2012 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

Comparison of two bond strength testing methodologies for bilayered all-ceramics

Objectives. This study compared the shear bond strength (SBS) and microtensile (MTBS) testing methodologies for core and veneering ceramics in four types of all-ceramic systems.Methods. Four different ceramic veneer/core combinations, three of which were feldspathic and the other a fluor-apatite to their respectively corresponding cores, namely leucitereinforced ceramic ((IPS)Empress, Ivoclar), low leucite-reinforced ceramic (Finesse, Ceramco), glass-infiltrated alumina (In-Ceram Alumina, Vita) and lithium disilicate ((IPS)Empress 2, Ivoclar) were used for SBS and MTBS tests. Ceramic cores (N = 40, n = 10/group for SBS test method, N=5blocks/group for MTBS test method) were fabricated according to the manufacturers' instructions (for SBS: thickness, 3 mm; diameter, 5 mm and for MTBS: 10 mm x 10 mm x 2 mm) and ultrasonically cleaned. The veneering ceramics (thickness: 2 mm) were vibrated and condensed in stainless steel moulds and fired onto the core ceramic materials. After trying the specimens in the mould for minor adjustments, they were again ultrasonically cleaned and embedded in PMMA. The specimens were stored in distilled water at 37 degrees C for 1 week and bond strength tests were performed in universal testing machines (cross-head speed: 1mm/min). The bond strengths (MPa +/- S.D.) and modes of failures were recorded.Results. Significant difference between the two test methods and all-ceramic types were observed (P < 0.05) (2-way ANOVA, Tukey's test and Bonferroni). The mean SBS values for veneering ceramic to lithium disilicate was significantly higher (41 +/- 8 MPa) than those to low leucite (28 +/- 4 MPa), glass-infiltrated (26 +/- 4 MPa) and leucite-reinforced (23 +/- 3 MPa) ceramics, while the mean MTBS for low leucite ceramic was significantly higher (15 +/- 2 MPa) than those of leucite (12 +/- 2 MPa), glass-infiltrated (9 +/- 1 MPa) and lithium disilicate ceramic (9 +/- 1 MPa) (ANOVA, P < 0.05).Significance. Both the testing methodology and the differences in chemical compositions of the core and veneering ceramics influenced the bond strength between the core and veneering ceramic in bilayered all-ceramic systems. (c) 2006 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

Reactionary dentinogenesis after applying restorative materials and bioactive dentin matrix molecules as liners in deep cavities prepared in nonhuman primate teeth

Objective: the aim of this in vivo study was to evaluate the response of the pulp-dentin complex following application of resin-modified glass-ionomer cement, calcium hydroxide hard-setting cement and EDTA-soluble preparation of dentine matrix proteins (ESDP) in deep cavities prepared in non-human primate teeth. Methods: Eighteen deep Class V buccal cavities were prepared in premolars of four capuccin monkeys. In Groups 1 and 2, the cavity floor was lined with ESDP or a resin-modified glass-ionomer cement (Vitrebond - 3M ESPE), respectively. In Group 3 (control), the cavity was lined with a hard setting calcium hydroxide cement (Dycal - Dentsply). The cavities were subsequently filled with amalgam. After 6 months, the animals were sacrificed and the teeth were prepared for microscopic assessment. Six-micron thick serial sections were stained with H/E, Masson's trichrome and Brown & Brenn techniques. Results: No inflammatory pulpal response was observed for all experimental and control Groups. However, the amount of reactionary dentin deposition differed between groups in the rank order ESDP (Group 1) > calcium hydroxide (Group 3) > resin-modified glass-ionomer (Group 2). These differences were statistically significant. Conclusions: All materials were biocompatible when applied in deep cavities. ESDP stimulated higher deposition of reactionary dentin matrix than Vitrebond and Dycal.

The effect of mold temperature on castability of CPTi and Ti-6Al-4V castings into phosphate bonded investment materials

Objective. The aim of this study was to evaluate the castability of CP titanium and Ti-6Al-4V alloy castings into Rematitan Plus investment at three different mold temperatures.Methods. A nylon mesh pattern (20 mm with 64 squares and wire of 0.7 mm in diameter) was used for the castability testing. Initially, an image of the wax pattern was obtained by means of a digital camera and the total extension of filaments (mm) was then measured, using the Leica Qwin image analysis system. The mesh sprued was placed in the Rematitan Plus investment material and the castings were made in a Discovery Plasma machine at three different mold temperatures: 430 degrees C (control group), 480 degrees C or 530'C. Ten castings were made for each temperature. The images of the castings were analyzed (Leica Qwin) and the castability index determined by the number of the completely cast segments as a percentage of the wax pattern. Data were analyzed by two-way ANOVA and Tukey's multiple comparison test (a = 0.05) using materials and temperatures as discriminating variables.Results. The Ti-6Al-4V alloy (60.86%) presented a better castability index than CP Ti (48.44%) (p < 0.000001). For CP Ti, the temperature of 530 degrees C (23.96%) presented better castability than at other temperatures, 480 degrees C (14.66%) and 430 degrees C (12.54%), with no difference between them (p < 0.001). For Ti-6Al-4V alloy, there was a statistically significant difference among the three temperatures: 530 degrees C (28.36%) > 480 degrees C (19.66%) > 430 degrees C (15.97%) (p < 0.002).Significance. Within the limitations of this study, the increase in the mold temperature of the Rematitan Plus investment resulted in a better castability index for both materials, and Ti-6Al-4V presented a better castability index than CP Ti. (c) 2005 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.