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The solar selective absorber coating (SSAC) are at the core of the efficient solar-thermal system. In this paper, for the first time, the Chromium-iron oxidation mixture cermet was successfully prepared on the surface of ultra-pure ferritic stainless steel by chemical coloring as SSAC. The coating surface has an optical trap structure, and the chromium-iron oxidation mixture cermet is used as an absorption layer to realize solar-thermal conversion. The solar absorptance (AM1.5) of the coating reached 93.66, and the thermal emittance was less than 13. After thermal shock tests at 25/300 &deg, C done 32 times (accumulated 812.8 h), the Performance Criterion (PC) of the coating was 0.01375 &lt, 0.05, showing outstanding thermal stability.

The present work studies the microstructure and mechanical performance of tricalcium phosphate (TCP) based cermet toughened by iron particles. A novelty arises by the employment of spark plasma sintering for fabrication of the cermet. Results showed partial transformation of initial alpha TCP matrix to beta phase and the absence of oxidation of iron particles, as well as a lack of chemical reaction between TCP and iron components during sintering. The values of compressive and tensile strength of TCP/Fe cermet were 3.2 and 2.5 times, respectively, greater than those of monolithic TCP. Fracture analysis revealed the simultaneous action of crack-bridging and crack-deflection microstructural toughening mechanisms under compression. In contrast, under tension the reinforcing mechanism was only crack-bridging, being the reason for smaller increment of strength. Elastic properties of the cermet better matched values reported for human cortical bone. Thereby the new TCP/Fe cermet has potential for eventual use as a material for bone fractures fixation under load-bearing conditions.

SUMMARY Objective: The purpose of this study was to evaluate the influence of thermal cycling on the flexural properties and simulated wear of computer-aided design/computer-aided manufacturing (CAD/CAM) resin composites. Methods: The six CAD/CAM resin composites used in this study were 1) Lava Ultimate CAD/CAM Restorative (LU); 2) Paradigm MZ100 (PM); 3) CERASMART (CS); 4) Shofu Block HC (SB); 5) KATANA AVENCIA Block (KA); and 6) VITA ENAMIC (VE). Specimens were divided randomly into two groups, one of which was stored in distilled water for 24 hours, and the other of which was subjected to 10,000 thermal cycles. For each material, 15 specimens from each group were used to determine the flexural strength and modulus according to ISO 6872, and 20 specimens from each group were used to examine wear using a localized wear simulation model. The test materials were subjected to a wear challenge of 400,000 cycles in a Leinfelder-Suzuki device (Alabama machine). The materials were placed in custom-cylinder stainless steel fixtures, and simulated localized wear was generated using a stainless steel ball bearing (r=2.387 mm) antagonist in a water slurry of polymethyl methacrylate beads. Simulated wear was determined using a noncontact profilometer (Proscan 2100) with Proscan and AnSur 3D software. Results: The two-way analysis of variance of flexural properties and simulated wear of CAD/CAM resin composites revealed that material type and thermal cycling had a significant influence (p0.05) between the two factors. The flexural properties and maximum depth of wear facets of CAD/CAM resin composite were different (p0.05) by thermal cycling, except in the case of VE. The volume losses in wear facets on LU, PM, and SB after 10,000 thermal cycles were significantly higher (p Conclusion: The results of this study indicate that the flexural properties and simulated wear of CAD/CAM resin composites are different depending on the material. In addition, the flexural properties and simulated wear of CAD/CAM resin composites are influenced by thermal cycling.

Author(s): Mohammad, Noorjahan; Pattanaik, Snigdha; Reddy, Thimma Bv; Animireddy, Dwitha; Ankireddy, Swetha | Abstract: Purpose:This study evaluates the fracture strength of pulpotomized primary molars restored with amalgam, miracle mix, cermet, resin-modified glass ionomer cement, and nanocomposites. Materials and methods:Fifty primary first and second molars were collected for this study. All the teeth were randomly divided into five groups (n = 10). Standard pulpotomy cavities were prepared. Teeth were air dried and the canal orifices were capped with a layer of zinc oxide eugenol. A lining of calcium hydroxide was placed over it. Amalgam, miracle mix, cermet, resin-modified glass ionomer cement, and nanocomposite were placed in groups I, II, III, IV, and V, respectively. All the samples were then subjected to the fracture strength test using the universal testing machine and the results were statistically analyzed. Results:All the groups were compared by the ANOVA one-way test which indicated that there were statistically significant differences among the five groups. Conclusion:Nanocomposites can be considered to be the best restorative material in terms of fracture strength among amalgam, miracle mix, cermet, and resin-modified glass ionomer cement. How to cite this article:Mohammad N, Pattanaik S, et al. Comparative Evaluation of the Fracture Strength of Pulpotomized Primary Molars: An In Vitro Study. Int J Clin Pediatr Dent 2019;12(1):5-9.

Background: Microleakage may cause tooth sensitivity, secondary caries, discoloration and even failure of the restoration. In order to overcome these potential problems, materials that are able to bind to the tooth structure have been developed, such as composite resin and glass ionomer cement. The purpose of the study was to compare microleakage arising from amalgam (Am), composite resin (CR), glass ionomer (GI), Ketac-Silver (KS), and GI filling with banding (GI+B) when these materials are used for class II restoration of a primary molar. Methods: Fifty primary molars were collected and class II cavities were prepared on each tooth. The teeth were randomly divided into five groups (Am, CR, GI, KS, and GI+B), each of which received a different material as part of the restoration. The restored teeth then underwent 100 cycles of thermocycling that consisted of 55°C for 30 seconds, 19°C for 20 seconds, and 5°C for 30 seconds. The teeth were then immersed in 0.5% basic fuchsin solution for 24 hours. Afterwards, the teeth were embedded and sectioned mesiodistally through the center of each restoration. Dye penetration associated with the occlusal and cervical margins of each restoration was then assessed. Results: Cervical leakage was greater than occlusal leakage in the CR, GI and KS groups (p

Alumina-titanium materials (cermets) of enhanced mechanical properties have been lately developed. In this work, physical properties such as electrical conductivity and the crystalline phases in the bulk material are evaluated. As these new cermets manufactured by spark plasma sintering may have potential application for hard tissue replacements, their biocompatibility needs to be evaluated. Thus, this research aims to study the cytocompatibility of a novel alumina-titanium (25 vol. % Ti) cermet compared to its pure counterpart, the spark plasma sintered alumina. The influence of the particular surface properties (chemical composition, roughness and wettability) on the pre-osteoblastic cell response is also analyzed. The material electrical resistance revealed that this cermet may be machined to any shape by electroerosion. The investigated specimens had a slightly undulated topography, with a roughness pattern that had similar morphology in all orientations (isotropic roughness) and a sub-micrometric average roughness. Differences in skewness that implied valley-like structures in the cermet and predominance of peaks in alumina were found. The cermet presented a higher surface hydrophilicity than alumina. Any cytotoxicity risk associated with the new materials or with the innovative manufacturing methodology was rejected. Proliferation and early-differentiation stages of osteoblasts were statistically improved on the composite. Thus, our results suggest that this new multifunctional cermet could improve current alumina-based biomedical devices for applications such as hip joint replacements.

Aim The purpose of the present study was to determine the influence of glass ionomer cement and amalgam restoration on the level of Streptococcus mutans in the interproximal plaque at periodic intervals and also to compare these values. Materials and methods Seventeen adult patients having two proximal carious lesions on any quadrant of the jaw (either opposing or contralateral) were selected for this study. Carious lesions were diagnosed clinically and from bitewing radiographs. Of the two carious lesions, one was restored with glass ionomer cermet cement and another with amalgam. Plaque samples were collected from interproximal areas before and at 1 month and 3 months post-treatment in a test tube containing 5 ml of modified Stuart's liquid transport fluid. Identification of organisms in the colony was done after Gram staining. Results Comparison of values before restoration and after restoration at 1 month interval showed a statistically significant decrease (p < 0.001). Similarly, comparison of values before and after restorations at 3 months also showed statistically significant decrease (p < 0.02). But comparison of restorations of 1 and 3 months intervals showed no statistical significant difference (p > 0.05). Conclusion Glass ionomer restorations have definite advantage over the amalgam, as the tunnel preparation is more conservative and fluoride release from the glass ionomer inhibits the growth of S. mutans in the plaque. Clinical significance Glass ionomer cement should be preferred over amalgam in conservatively prepared restorations as it reduces the microbial activities due to fluoride release. How to cite this article Tegginmani VS, Goel B, Uppin V, Horatti P, Kumar LSV, Nainani A. Comparison of Antibacterial Activity of Glass-ionomer Cement and Amalgam in Class Two Restorations by Streptococcus mutans Count Analysis at Fixed Intervals: An in vivo Study. J Contemp Dent Pract 2013;14(3):381-386.

Objectives The purpose of this in vitro study is to compare the compressive strength (CS) and diametral tensile strength (DTS) of the zirconia-reinforced restorative material (Zirconomer®) with conventional glass ionomers (Fuji 1X) and amalgam. Materials and methods Specimens (n = 120) were fabricated from silver amalgam, reinforced glass ionomer cement (GIC) (glass ionomer, Fuji 1X GC Corp.), and zirconia-reinforced glass ionomer (Zirconomer, Shofu Inc.) for testing the CS and DTS. The results were analyzed using analysis of variance, followed by a Tukey post hoc test. Results Both CS and DTS were found to be significantly higher for the zirconia-reinforced GIC and silver amalgam compared with GIC (p < 0.001). Conclusion A newer class of restorative material like Zirconomer helps to overcome the potential hazard of mercury, but retains the strength and durability of amalgam as well as the sustained high-fluoride release of GICs. Furthermore, long-term studies are required to confirm its use as an alternative to the currently available posterior restorative material. How to cite this article Chalissery VP, Marwah N, Almuhaiza M, AlZailai AM, Chalisserry EP, Bhandi SH, Anil S. Study of the Mechanical Properties of the Novel Zirconia-reinforced Glass Ionomer Cement. J Contemp Dent Pract 2016;17(5):394-398.

Introduction: The purpose of this study was to investigate the association between dye and bacterial penetration through interim restorations used during endodontic treatment. Methods: Sixty-four extracted human teeth were used, with 2 teeth each as positive and negative controls. Endodontic access with a mesio– occluso–distal cavity was prepared. Palatal cusps of maxillary molars and buccal cusps of mandibular molars were removed. Cotton was placed over the canals and covered with Cavit. Thirty teeth were restored with Ketac Silver (KS) and 30 with KS reinforced with a stainless steel band (KSSB). Samples were submersed in India ink mixed with brain heart infusion broth containingStreptococcus gordonii. After 3 months of simulated chewing, structural integrity and dye and bacterial penetration were assessed. Results: Positive controls had both dye and bacterial penetration. Negative controls had no dye or bacterial penetration. All KS restorations debonded, whereas 18 KSSB restorations (60%) debonded. KS restorations were 1.67 times more likely to debond than KSSB restorations (Fisher exact test). KS was 1.3 times more likely to have dye penetration than KSSB (Fisher exact test) and 3 times more likely to have bacterial penetration, although not statistically significant (c 2 test). Overall, 88.3% of specimens had dye penetration, and 20% had bacterial penetration. This 68.3% difference indicated no association between dye and bacterial penetration (exact McNemar test). Conclusions: Stainless steel bands helped maintain structural integrity of KS restorations under masticatory function. Bands helped prevent dye penetration but not bacterial penetration. There was no association between dye and bacterial penetration. (J Endod 2009;35:1017–1022)

The unique combination of mechanical properties such as excellent wear resistance and good chemical stability at elevated temperature helps titanium carbonitride based (Ti (C, N)-based) cermets to play an important roles in metal cutting operations. Nowadays, cermets cutting tools are widely used for semi-finishing and finishing works on steel and cast iron. However, their brittleness is still an unavoidable limitation for their utilization. With the development of nano-technology, nano-modified cermets have received more attention due to the high toughening enhancements. In this review, the development of nano-modified Ti(C,N) cermets is discussed including the fabrication, microstructure, mechanical properties, cutting performance and the practical applications in different fields. Many patents having important effect on the development of cermets were noticed, too.

Objective: This study compares the quality of class I restorations made with the atraumatic restorative treatment (ART) technique and conventional class I amalgam restorations. Methods: The study was carried out among secondary school students in Mzuzu, Malawi. First-year students in 1987 who needed at least two class I restorations were selected. Based on a split-mouth design, each participant received both ART and conventional restorations. The 89 pairs of class I cavities were divided randomly into two groups, since two different cermet ionomer cement (CIC) filling materials were used. Impressions of the restorations and subsequent models were made shortly after restoration, after six months, one year, two years, and three years. The quality of the restorations was determined on the models following the US Public Health Service criteria. Bulk fracture, contour, marginal integrity, and surface texture of the restorations were recorded and evaluated separately. Survival rates were determined by the resultant score of all criteria. Results: Though conventional amalgam restorations performed better on all criteria, this difference was significant only for the contour criterion. The survival rates of ART restorations after three years (81.0%) were lower than those of amalgam restorations (90.4%) (P=.067). Conclusions: The quality of ART class I restorations is competitive with that of conventional amalgam restorations.

Electrochemical sensors composed of a ceramic–metallic (cermet) solid electrolyte are used for the detection of gaseous sulfur compounds SO 2 , H 2 S, and CS 2 in a study involving 11 toxic industrial chemical (TIC) compounds. The study examines a sensor array containing four cermet sensors varying in electrode–electrolyte composition, designed to offer selectivity for multiple compounds. The sensors are driven by cyclic voltammetry to produce a current–voltage profile for each analyte. Raw voltammograms are processed by background subtraction of clean air, and the four sensor signals are concatenated to form one vector of points. The high-resolution signal is compressed by wavelet transformation and a probabilistic neural network is used for classification. In this study, training data from one sensor array was used to formulate models which were validated with data from a second sensor array. Of the 11 gases studied, 3 that contained sulfur produced the strongest responses and were successfully analyzed when the remaining compounds were treated as interferents. Analytes were measured from 10 to 200% of their threshold-limited value (TLV) according to the 8-h time weighted average (TWA) exposure limits defined by the National Institute of Occupational Safety and Health (NIOSH). True positive classification rates of 93.3, 96.7, and 76.7% for SO 2 , H 2 S, and CS 2 , respectively, were achieved for prediction of one sensor unit when a second sensor was used for modeling. True positive rates of 83.3, 90.0, and 90.0% for SO 2 , H 2 S, and CS 2 , respectively, were achieved for the second sensor unit when the first sensor unit was used for modeling. Most of the misclassifications were for low concentration levels (such 10–25% TLV) in which case the compound was classified as clean air. Between the two sensors, the false positive rates were 2.2% or lower for the three sulfur compounds, 0.9% or lower for the interferents (eight remaining analytes), and 5.8% or lower for clean air. The cermet sensor arrays used in this analysis are rugged, low cost, reusable, and show promise for multiple compound detection at parts-per-million (ppm) levels.

Purpose: This in vitro study determined the fracture strength of five core materials supported by two different endodontic dowels. Diametral tensile strength and microhardness of the three resin composite core materials used in this study were also tested. Material and Methods: The fracture strength study used one lanthanide-reinforced flowable resin composite (Ti-Core Auto E), one titanium- and lanthanide-reinforced composite (Ti-Core), one lanthanide-reinforced composite (Ti-Core Natural), and two metal-reinforced glass ionomer core materials (Ketac Silver and GC Miracle Mix). Two types of dowels were used: a multitiered, split-shank threaded dowel with a flange (#1 Flexi-Flange) and one without a flange design (#1 Flexi-Post). The specimens were divided into ten groups. Each tooth/dowel and core specimen was placed in a special jig at 45° and subjected to a load by a universal testing machine. The diametral tensile strength and the microhardness of the three resin composite core materials were measured by a universal testing machine and Barcol hardness tester, respectively. All test groups contained ten specimens. Results: The fracture strength value of the resin composite core materials was significantly larger ( p < 0.0001) than those for the metal-reinforced glass-ionomer core materials. Analysis of variance (ANOVA) also showed that the Flexi-Flange dowel interacted with Ti-Core and Ti-Core Auto E to significantly ( p < 0.0013) increase the fracture strength relative to the Flexi-Post. One-way ANOVA revealed that there were no significant differences between them in terms of diametral tensile strength. The Barcol hardness values of the composite core materials were statistically different ( p < 0.0001), with the Ti-Core the highest, followed by Ti-Core Natural, then Ti-Core Auto E. Conclusions: Resin composite core material performed better than glass ionomer material in this in vitro study. The flowable composite core material performed about the same in terms of fracture strength and diametral tensile strength compared with nonflowable composites. Combined with certain core materials, the flange design increased the fracture strength of the tooth/dowel and core combination.

To investigate polyalkenoate reaction rates in conventional glass-ionomer cement (GIC) and resin-modified glass ionomer (RMGI) restorative materials using infrared spectroscopy.Nine conventional GIC and six RMGI restorative materials were prepared according to manufacturer's directions and placed on a FTIR (Fourier transform infrared spectroscopy) diamond ATR (attenuated total reflectance) surface. FTIR spectra (700 to 1800 cm-1) were obtained each minute for 3 h. VLC specimens were light polymerized after 1 min; at 5 min, all samples were covered with gauze saturated with deionized water. Polyalkenoate reaction was determined by measuring area growth (Å/cm-1) between 1375 and 1500 cm-1. Mean peak areas were determined at 5, 15, 30, 90, and 180 min and compared using ANOVA (p = 0.05) RESULTS: For all RMGI materials, VLC polymerization inhibited the polyalkenoate reaction rate. Compared to conventional GIC, RMGI materials demonstrated less polyalkenoate reaction. Compared to dark curing, RMGI light polymerization significantly inhibited the polyalkenoate reaction rate.The addition of resin components to glass-ionomer products significantly retards and impedes the polyalkenoate reaction. The polyalkenoate reaction rate of RMGI products was significantly lower than that of self-curing GIC restorative materials. Furthermore, light activation of RMGI products further retards the polyalkenoate rate. When clinicians require the therapeutic benefit of a polyalkenoate product, perhaps a conventional GIC restorative product should be the first material of choice.

Venturi M. Evaluation of canal filling after using two warm vertical gutta-percha compaction techniques in vivo: a preliminary study. International Endodontic Journal, 39, 538‐546, 2006. Aim To evaluate the quality of root canal filling when comparing two warm gutta-percha filling techniques in vivo. Methodology Human teeth were randomly divided into two equal groups, with 30 canals each. The root canals were shaped by hand and ProFile 0.04 rotary instrumentstosize20‐40attheend-pointandthenfilled with gutta-percha cones and AH-Plus. In group A, a traditional warm vertical compaction technique was performed using the Touch’n Heat, and back-filling with the Obtura II. In group B, a modified warm vertical compactiontechniquewasused:smallamountsofguttapercha were removed, and the remaining most apical 3 mm were compacted with a 1 mm movement; then thermomechanicalback-fillingwasperformed.Theteeth were extracted, stored in dye, cleared, and the distance betweentheapexandapicallimitofthefilling,lineardye penetration, and voids were measured from the buccal, lingual, mesial and distal perspective.The homogeneity of variance and means was verified using Levene’s test and t-test. anova and Dunnett post hoc test were used to establish the significance and to analyse the effects through multiple comparisons. Results Compared with the specimens of group A, the specimens of group B exhibited less mean linear dye penetration (P < 0.05), smaller void length (P £ 0.05) and maximal width (P £ 0.05) when examined in all four views, and a more precise filling when viewed from the buccal aspect (P < 0.05). Conclusions The modified warm vertical compaction technique with apical back-filling produced a more effective and precise three-dimensional filling.

A dowel-and-core restoration may fail due to failure at either the dowel-tooth or dowel head-core material interface. Long-term clinical success of a dowel-and-core restoration depends on retention of both the dowel to the tooth and the dowel head to the core material. Thus, strengthening of the dowel head-core interface is important.This study evaluated the retention between a prefabricated dowel and 3 different core materials with or without a dual-polymerized adhesive resin luting agent.Sixty prefabricated dowels (Gold Plated Anchorage Post) were divided into 3 groups (n=20) consisting of 1 of 3 core materials, amalgam (Standalloy F), light-polymerized resin composite (Clearfil Ray), or glass ionomer (Chelon-Silver). Each core group was divided into 2 subgroups (n=10), and a dual-polymerized adhesive resin luting agent (Panavia F) was applied to the dowel heads of 1 of these subgroups before application of the core material. The manufacturing procedure was standardized by using a plastic index (4.5-mm internal diameter and 5-mm height) and a custom-made dowel holder, which held the dowel head. Prepared specimens were stored in water at room temperature for 3 months and then loaded to fracture in a universal testing machine with a crosshead speed of 0.05 mm/min until failure. Bond strengths were recorded (MPa). Data were analyzed with 2-way analysis of variance (ANOVA) in a 2 x 3 factorial randomized design (alpha=.05). Afterward, core material differences were computed with 1-way ANOVA for both of the bonded and nonbonded groups. Post hoc multiple comparisons were made with the Dunnett C multiple range test.Dowel-head retention values (MPa) of the tested core materials (mean +/- SD) from the highest to the lowest were as follows: bonded amalgam core, 296.1 +/- 108; bonded composite core, 284.3 +/- 38.3; nonbonded composite core, 177.0 +/- 53.7; nonbonded amalgam core, 128.5 +/- 35.0; bonded glass-ionomer core (GIC), 128.0 +/- 24.5; nonbonded GIC, 61.8 +/- 13.3. Two-way ANOVA revealed significant differences between the core material groups and between the bonded and nonbonded groups (P.001). The interaction between the core material and bond variables was also significant (P =.018). One-way ANOVA revealed statistically significant differences between the bonded (P.001) and also between the nonbonded core material groups (P.001). Post hoc multiple comparisons showed that the dowel-head retention of the GIC was significantly weaker than the post-head retention for amalgam and resin composite, whether bonded or not.Within the limitations of this study, the adhesive resin luting agent tested appeared to have a significant strengthening effect on the dowel-head retention of the core materials.

Objectives: Conventional and resin-modified glass-ionomer cements (GIC, RM-GIC) are available for clinical use as restorative materials or as liners and bases. This study was conducted to compare the effect of a 12-month storage period in water on the surface microhardness, measured in Vickers units (VH), between a GIC and a RM-GIC group and to determine if the addition of resins improved the GIC microhardness. Method: VH microhardness was assessed in three GIC: Ketac-Fil, Ketac-Molar and Ketac-Silver (KF, KM, KS) and three RM-GIC: Photac-Fil, Fuji II LC and Vitremer (PF, FU, VI) stored in distilled water at 37 °C for 12 months. Measurements were taken at 1, 7, 15, 30, 90, 180 and 365 days. The statistical evaluation was done by means of one-way analysis of variance (ANOVA) and Tukey's multiple comparison tests. Results: There are significant VH differences among the materials studied and within each material over storage time. GICs, except for KS, showed a higher VH throughout the study period. Among the RM-GIC, VI showed a significantly higher VH at 12 months than at 1 day. The VH of PF diminished in the final stage of the study, whereas that of FU stabilized. Significance: The results suggest that the addition of resins to the GIC did not appear to improve the surface microhardness of these materials. Furthermore, the surface microhardness of both the conventional and resin-modified glass-ionomers suffered variations over time. However, these materials should not be deemed inadequate for use in clinical applications. Probably, conventional and resin-modified GICs placed in the oral environment would not be affected to the same extent as in in vitro tests.

Ceramic/metal composites, cermets, arise from the idea to combine the dissimilar properties in the pure materials. This work aims to study the biocompatibility of new micro-nanostructured 3 Y-TZP/Ti materials with 25, 50 and 75 vol.% Ti, which have been successfully obtained by spark slasma sintering technology, as well as to correlate their surface properties (roughness, wettability and chemical composition) with the osteoblastic cell response. All samples had isotropic and slightly waved microstructure, with sub-micrometric average roughness. Composites with 75 vol.% Ti had the highest surface hydrophilicity. Surface chemical composition of the cermets correlated well with the relative amounts used for their fabrication. A cell viability rate over 80% dismissed any cytotoxicity risk due to manufacturing. Cell adhesion and early differentiation were significantly enhanced on materials containing the nanostructured 3 Y-TZP phase. Proliferation and differentiation of SaOS-2 were significantly improved in their late-stage on the composite with 75 vol.% Ti that, from the osseointegration standpoint, is presented as an excellent biomaterial for bone replacement. Thus, spark plasma sintering is consolidated as a suitable technology for manufacturing nanostructured biomaterials with enhanced bioactivity.

The fabrication of cermet biocompatible coatings by means Cold Gas Spray (CGS) provides prosthesis with outstanding mechanical properties and the required composition for enhancing the bioactivity of prosthetic materials. In this study, hydroxyapatite/Titanium coatings were deposited by means of CGS technology onto titanium alloy substrates with the aim of building-up well-bonded homogeneous coatings. Powders were blended in different percentages and sprayed; as long as the amount of hydroxyapatite in the feedstock increased, the quality of the coating was reduced. Besides, the relation between the particle size distribution of ceramic and metallic particles is of significant consideration. Plastic deformation of titanium particles at the impact eased the anchoring of hard hydroxyapatite particles present at the top surface of the coating, which assures the looked-for interaction with the cells. Coatings were immersed in Hank's solution for 1, 4 and 7 days; bonding strength value was above 60 MPa even after 7 days, which enhances common results of HAp coatings obtained by conventional thermal spray technologies.

Thermocycling has been shown to cause surface degradation of many dental materials, but its effect on the fracture toughness and hardness of direct core buildup materials is unknown.This study was designed to determine the effect of thermocycling on the fracture toughness and hardness of 5 core buildup materials.Fifteen specimens were prepared from each of the following materials: Fluorocore, VariGlass VLC, Valiant PhD, Vitremer, and Chelon-Silver. American Standard for Testing Materials guidelines for single-edge notch, bar-shaped specimens were used. Ten specimens of each material were thermocycled for 2000 cycles; the other 5 specimens were not thermocycled. All specimens were subjected to 3-point bending in a universal testing machine. The load at fracture was recorded, and the fracture toughness (K(IC)) was calculated. Barcol hardness values were also determined. Data were analyzed with 1-way analysis of variance and compared with the Tukey multiple range test (P.05). Pearson's correlation coefficient was also calculated to measure the association between fracture toughness and hardness.Fluorocore had the highest thermocycled mean K(IC) and Valiant PhD the highest non-thermocycled K(IC). Chelon-Silver demonstrated the lowest mean K(IC) both before and after thermocycling. One-way analysis of variance demonstrated significant differences between conditions, and the Tukey test showed significant differences (P.05) between materials for both conditions. Most specimens also showed significant hardness differences between conditions. Pearson's correlation coefficient indicated only a mild-to-moderate correlation between hardness and fracture toughness.Within the limitations of this study, the thermocycling process negatively affected the fracture toughness and hardness of the core buildup materials tested.

PURPOSE The present in vitro study examined 3 mechanical properties, namely compressive, flexural, and diametral tensile strength, of various commercially available cements and core materials as a function of time after mixing. MATERIALS AND METHODS The examined materials were 2 cermet cements (Ketac Silver [ESPE, Seefeld, Germany] and Chelon Silver [ESPE]), 1 metal-reinforced glass ionomer cement (Miracle Mix [GC Dental Industrial Corp, Tokyo, Japan]), 2 conventional glass ionomer cements (Ketac Bond [ESPE] and Ketac Cem [ESPE]), 1 standard cure zinc phosphate cement (Harvard Cement [Richter and Hoffmann, Berlin, Germany]), and 1 zinc phosphate cement with the addition of 30% silver amalgam alloy powder (Harvard Cement 70% with Dispersalloy 30% [Richter and Hoffmann/Johnson and Johnson, East Windsor, NJ]). Properties were measured using a universal testing machine at 15 minutes, 1 hour, and 24 hours after first mixing. RESULTS Compressive strengths varied widely between the 3 times of measurement from 5.8 +/- 6.6 MPa for Ketac Cem to 144.3 +/- 10.2 MPa for Ketac Silver. Twenty-four hours after mixing, the Bonferroni test showed significant (p

Statement of problem. New glass ionomer cements exhibit better mechanical properties than their older counterparts. However, there is concern about their use as a core material in post-and-core applications. Purpose. This in vitro study evaluated the fatigue resistance of 2 new glass ionomer cements, Shofu Hi-Dense and Fuji IX GP, and compared their mechanical behavior as a core material under masticatory load with a silver-reinforced glass ionomer (ESPE Ketac-Silver) and a silver amalgam (Cavex Avaloy LC). Material and methods. A total of 100 commercial plastic teeth were divided into 4 groups of 25 specimens each. Titanium posts were placed in the prepared root canals, and cores were built up in amalgam, silver-reinforced glass ionomer cement, and the 2 new glass ionomer cements. The post-and-core specimens were prepared for full cast metal crowns, which were fabricated and cemented with glass ionomer cement. Twenty specimens from each group were placed in a mastication simulator and cyclically loaded with a 400 N force for 1.5 million cycles. The 5 remaining specimens were used as controls. The specimens were sectioned and observed macroscopically and microscopically to determine the number of defects (alterations) in each material. Observed defects were verified with the Kruskal-Wallis test, and the 4 core materials were ranked with the Tukey multiple comparisons test. Results. The mean rank sum values of the defects were as follows: Cavex Avaloy LC Amalgam (16.75), Fuji IX GP (38.50), Shofu Hi-Dense (39.53), and ESPE Ketac-Silver (67.22). The amalgam alloy was significantly different ( P Conclusion. Under the conditions of this study, the 2 new glass ionomer cements used as core materials showed a higher number of defects than amalgam. These results suggest that their fatigue resistance may be inadequate for post-and-core applications. (J Prosthet Dent 2001;86:149-55.)

This in vitro study on fluoride (F) release from conventional and metal-reinforced glass ionomer investigated the following: (1) the release of F in deionized water compared to artificial saliva, (2) the effect of various surface coatings on F release, (3) the uptake of released F by hydroxyapatite, (4) the expression of the release data in a mathematical model, (5) F content in the powders and set materials, and (6) surface morphology of varnished and resin-coated specimens.Glass ionomer Ketac-Fil (KF), Fuji II (FJ), and Ketac-Silver (KS) were mixed according to the manufacturers' instructions, and prepared into specimens of 137.8 mm2 surface area. All three specimens were suspended in 50 ml of deionized water, artificial saliva, or aqueous solution of hydroxyapatite and submitted to constant agitation at 37 degrees C. In a separate experiment, the specimens were coated with varnish or light-cured bonding resin and tested for F release in solutions similar to those for uncoated specimens. The release of F occurred for 28 days. The concentration of F was measured with F-ion-specific electrode.All tested products showed a strong initial rate of F release which decreased with time until it reached a relatively steady rate after two weeks. The F released from KF and FJ was comparable in both pattern and magnitude. They released approximately four times more F than KS. In all cases, the release of F in artificial saliva was significantly (p0.001) less than in deionized water. Surface coating the specimens significantly reduced the F release ( p0.05 top0.001, depending on the product and type of coating). The inhibitory effect of coating markedly decreased with time. Resin coating reduced F release more than varnish in KF and KS, but not for FJ. Essentially, all F released in aqueous solution was taken up by the hydroxyapatite, with FJ ranking the highest in increasing hydroxyapatite F concentration. Over the 28 days, the quantities of F released from FJ, KF, and KS were, respectively, 3.8, 2.3, and 1.0% of the total F content in the specimens. The F concentration in the set KS was 53.9 and 72.5% of that found in KF and FJ, respectively. The release data as a function of time were best described by the power curve. Micromorphological examinations revealed remnants of surface coatings on specimens after 14 days storage in artificial saliva.Glass ionomer cements released significantly less F in artificial saliva than in deionized water. Surface coating the specimens substantially reduced F release. These clinically relevant factors were not considered by many in vitro release studies which overestimate the F availability from glass ionomers. A recall appointment 24 h after the placement of glass ionomer restoration should be given for surface finishing.

Objective Aim of the present study was to evaluate the clinical suitability of the condensable metal-reinforced glass ionomer cement Hi-Dense in classes I and II cavities of primary molars. Methods Seventeen children received a total of fifty four Hi-Dense fillings (nineteen class I and thirty five class II). The restorations were clinically assessed at baseline, after one and after two years of clinical service according to modified USPHS codes and criteria. The restorations were replicated in each recall and representative samples were qualitatively analysed under a SEM. Results Over the observation period of two years, five restorations failed due to total retention loss, two fillings needed replacement because of persisting hypersensitivity, one filling was lost because of an unsuccessful endodontic treatment, and four restorations remained intact until natural exfoliation (Two year survival rate: 92% for Class I and 66% for Class II). The SEM analysis of surfaces and marginal areas exhibited an inferior adhesive performance primarily in proximal areas, whereas a negative step formation due to wear was frequently observed in occlusal parts. Conclusions The results clearly indicate that the condensable, metal-reinforced GIC Hi-Dense reveals no enhanced performance and lifetime expectancy for class II restorations in primary molars when compared to other non-resin-modified GICs.

Growth kinetics of SV40 large T-antigen-transfected bovine pulp-derived cells on dentin were investigated. These cells were used in a dentin barrier test device, and the system was evaluated by testing a set of dental filling materials. Cells (120 cells/mm2) were seeded on dentin slices and incubated for up to 21 days. Cell proliferation was recorded using MTT assay. For cytotoxicity tests 3500 cells/mm2 were seeded on dentin discs, which were then incorporated into the dentin barrier test device. After 72 h preincubation test materials were applied. After a 24 h exposure with or without perfusion of the pulpal part of the test device, cell survival was evaluated using MTT assay. The cells revealed similar growth kinetics on dentin slices and on tissue culture plates. In cytotoxicity tests the cells were more sensitive toward the test materials than previously used three-dimensional cultures of human foreskin fibroblasts and as anticipated from clinical experience. Further improvement is expected by using three-dimensional cultures of pulp-derived cells.

Objective To evaluate the tissue responses to implants of Ketac Silver and Super EBA cement in the guinea pig mandible. Study design. Sixteen guinea pigs were used for 2 experimental periods of 4 and 12 weeks. Both materials were placed in Teflon applicators and implanted into surgically prepared sites in the mandible. A histologic examination for reaction to the material occurred after the animals were killed and processed. Results. After 4 weeks, minimal inflammatory reactions were observed in Ketac Silver implants, whereas the Super EBA implants showed minimal to moderate inflammation. Localized foreign body reaction was present in areas of fragmented small particles of Ketac Silver. At 12-weeks observation, no inflammatory reactions were present around either material. Direct bone contact was observed in 1 Ketac Silver implant. Conclusions. Ketac Silver and Super EBA cement elicited mild reactions under the conditions of this model. From a biologic point of view, these 2 materials may offer equal utility in endodontic surgery.

Objective: In reinforced materials, interfacial bonding is critical for efficient transfer of stress from the matrix to the reinforcement. The goal of this study was to characterize the physical and chemical nature of this interface in three metal-reinforced glass ionomers. Two of them were commercial, ESPE-Ketac Silver (KS) and GC-Miracle Mix (MM), and the third, EX, was experimental. Methods: The techniques of scanning electron microscopy (SEM) and infrared spectroscopy (IR) were used to accomplish the stated goal. SEM analysis utilized polished sections of set cylindrical specimens of each material prepared from their respective powder and liquid components. The glass and the liquid in EX were the same as in MM. The reinforcing agent in EX, 50% by weight, was an Ag-base spherical alloy similar in composition to that in MM. For EX, the alloy was oxidized to promote its bonding to the matrix. The specimens for IR study were prepared as follows. The metallic powders of each material were mixed with the corresponding liquid in excess, stored at 37°C for 1 h, washed with warm water (60°C), filtered and dried. The untreated metallic powders served as controls for IR analysis. Results: SEM revealed a distinct halo shaped internal reaction layer surrounding each alloy particle in EX. A similar layer was not seen in MM and KS. The alloy–matrix interface was continuous and gap-free in EX. In contrast, gaps separating matrix from respective reinforcements were conspicuous features in MM and KS. The IR spectrum of the liquid treated EX alloy powder showed absorbency bands characteristic of unreacted carboxyl groups and carboxylate salts. These bands were absent in the IR spectra of all other powders—treated and untreated. Significance: The absence of interfacial bonding in MM and KS demonstrated in this study provides a reason why these two materials, in spite of metal addition, have not proved to be any stronger or more durable than their metal-free counterparts. A means of creating interfacial bonding presented here could be useful in the design of improved reinforced glass ionomer materials.

Objective: To compare a silver-reinforced glass ionomer material (cermet) with a resin-modified glass ionomer in minimal Class II preparations in primary teeth. Methods : Matched pairs of primary molars with approximal caries that required operative treatment were used. Each cavity was filled with either Vitremer or Ketac-Silver. The restorations were followed for at least 36 months and examined annually using bitewing radiographs and clinical inspections. Impressions were taken at each recall and models were examined microscopically. Results: After 36 months, one of the resin-modified glass ionomer (RMGI) restorations and 13 (26.5%) of the silver cermet restorations had failed. The RMGI failed because of secondary caries, while most of the failures of the silver cermet fillings were marginal defects alone or in combination with secondary caries. The median survival time (MST) for the silver cermet restorations was 37 months. The RMGI restorations had a MST exceeding 42 months, but MST could not be calculated exactly because of the low failure rate during the study period. Conclusions: The resin-modified glass ionomer had the overall best performance of the two materials under comparison. The silver cermet material cannot be recommended for Class II restorations in primary teeth.

Dental glass-ionomer cements (GIC) set by an acid-base reaction between a polyalkenoic acid and an ion-leachable glass. The exact relationship between the glass composition and the setting and final properties of GIC is not yet fully elucidated. As part of a systematic study of this relationship, we studied the leaching stoichiometry of glasses used in commercial formulations to correlate the glass composition with its leaching properties. The leaching experiments were performed in acetic acid solutions at pH = 3.4 by means of a pH-stat method. After predetermined time intervals, the suspension was filtered and the filtrate was analyzed for the glass constituents. The usefulness of the pH-stat method for the determination of glass reactivity was corroborated. The deviation of the leaching stoichiometry with respect to the pure glass stoichiometry decreased with increasing relative content of mono- and bivalent glass network dwellers and modifiers. Indications were found that the latter can be leached out independently and preferentially, while the leaching of network dwellers is coupled with the aluminum release. The F content as well as the reactivity of the glass affect the amount of fluoride available for release from a set GIC. It could be concluded that the leaching stoichiometry of GIC glasses can be correlated with their absolute and relative composition.

Objective. This work was undertaken to measure mechanical properties of a diverse group of materials used for direct core build-ups, including a high copper amalgam, a silver cermet cement, a VLC resin composite and two composites specifically developed for this application. Methods. Compressive strength, elastic modulus, diametral tensile strength and flexural strength and modulus were measured for each material as a function of time up to 3 months, using standard specification tests designed for the materials. Results. All the materials were found to meet the minimum specification requirements except in terms of flexural strength for the amalgam after 1 h and the silver cermet at all time intervals. Significance. There proved to be no obvious superior material in all respects for core build-ups, and the need exists for a specification to be established specifically for this application.

The strength of a modern, low metal:glass ratio, metal-reinforced glass-ionomer cement was measured evaluating a number of protective barriers: one light-cured resin, two solvent-based dental varnishes and petroleum jelly. The cement was exposed to water at 10 and 60 min from start of mix. The results obtained with these protecting agents were compared with those obtained where no protection was applied. A comparison of uniaxial flexural strength and biaxial flexural strength showed the latter to be more discriminating. Proprietary dental varnishes were superior to petroleum jelly, producing similar strengths of 50 MPa. Petroleum jelly was, however, preferable to no protection. Moisture protection during the first 30 min was found to be beneficial, thereafter no further strength increase was found. A second material, a cement which has a high metal:glass ratio, was found to be more moisture resistant but weaker in strength than the modern material, with a biaxial strength of 39 MPa.

This study was designed to investigate the effect of retaining coronal tooth substance on the performance of post-retained core materials, and to compare the fracture resistance of the system with an intact tooth prepared to similar dimensions. Ten teeth restored with post-retained silver amalgam, and 10 teeth restored with silver-glass cermet, all with a retained single wall of coronal tooth substance, were compared with 10 unrestored teeth prepared to similar dimensions when subjected to a shearing load. The results showed no statistically significant difference between the unrestored teeth and those restored with a silver-glass cermet. Whilst the teeth restored with silver amalgam had a significantly higher fracture resistance (P > 0.01) there was greater tendency to root fracture.

Purpose. This pilot study examined the cyclic fatigue of five endodontic post systems (AccessPost, Flexi-Flange, Flexi-Post, ParaPost, and Vlock) with four core materials (Tytin silver amalgam, Ti-Core, Ketac-Silver and G-C Miracle Mix). Material and methods. In vitro cyclic fatigue was performed with a machine designed to simulate masticatory fatigue forces. An instantaneous force of 22.2 N (5 pounds) was applied to each post and core combination for a test configuration of 4,000,000 repetitions, or until failure occurred. The type of failure and number of repetitions at failure was recorded for each sample tested. Two-way analysis of variance (ANOVA) was used to compare groups. Results. All posts/core samples with Ti-Core composite and Tytin silver amalgam completed the test with no failures. All posts/core samples with Ketac-Silver material failed before the 4,000,000 test cycle configuration and all failures were core failures. All posts/core samples with G-C Miracle Mix material failed in a similar manner. Newman-Keuls multiple comparison test illustrated that, with this simulated fatigue test, Ti-Core material and Tytin silver amalgam were superior to both G-C Miracle Mix and Ketac-Silver materials. (J Prosthet Dent 1997;78: 458-64.)

O objetivo deste estudo foi verificar a resistência à remoção por tração e a infiltração marginal de coroas totais fundidas cimentadas com cimento de ionômero de vidro, em dentes reconstruídos com duas formulações de cimento de ionômero de vidro, ou seja, Cermet e "mistura milagrosa", em comparação às coroas totais cimentadas em dentes com preparo para coroa total (sem reconstrução). Foram selecionados trinta molares superiores recém-extraídos, dez para cada condição experimental. Uma liga do sistema prata/estanho (M3) foi utilizada para obtenção das coroas totais. As amostras foram submetidas a ciclagens térmicas nas temperaturas de 5ºC, 37ºC e 55ºC, por sessenta minutos, durante sete dias. Para a última ciclagem térmica, foi utilizado o corante Rhodamina B a 0,1%, em solução aquosa. A seguir, as amostras foram lavadas e mantidas em condições ambientais por vinte e quatro horas, para serem levadas à máquina de ensaios universal, para os testes de remoção por tração axial. A análise de variância mostrou diferença estatisticamente significante, no nível de 5%, dos dentes sem reconstrução (controle), com relação aos dentes reconstruídos com "mistura milagrosa" e dentes reconstruídos com Cermet. Os dentes sem reconstrução apresentaram maior média aos testes de resistência por tração. Verificou-se, pela comparação individual entre as condições avaliadas, que o grupo reconstruído com "mistura milagrosa" e Cermet não mostrou diferença estatisticamente significante. Da mesma forma, foram elaboradas comparações individuais entre as condições avaliadas dos escores de infiltração, em que se pôde observar que houve significância entre os grupos de "mistura milagrosa" e Cermet com o grupo controle (dentes sem reconstrução). Os dentes reconstruídos com "mistura milagrosa" e Cermet não mostraram diferenças estatisticamente significantes entre siThe aim of this work was to measure tensile strength and microleakage of full cast crowns cemented on built-up cores using two formulations of glass-ionomer cement, Cermet and "miracle-mix", as compared to full cast crowns cemented exclusively on tooth structure. Thirty freshly extracted upper molars were selected, ten for each experimental condition. An alloy of the silver/tin system (M3) was employed to obtain the full crowns. The samples were thermocycled at 5ºC, 37ºC and 55ºC, for 60 minutes, during 7 days. For the last thermal cycle, 1% Rhodamine B aqueous solution dye was used. After that, the samples were washed and kept at room temperature for 24 hours, and taken to a universal testing machine for testing. The data were analyzed by parametric and non parametric statistical methods and the following conclusions were drawn: 1 - there was a statistically significant difference in removal resistance of cemented full crowns under the various conditions; 2 - the crowns cemented on the "miracle-mix" and Cermet reconstructed teeth showed statistically significant lower removal resistances than controls (teeth which had not been reconstructed); 3 - no statistically significant difference was found comparing teeth reconstructed either with "miracle-mix" or Cermet; 4 - no statistically significant differences were found between microleakage patterns in teeth rebuilt with the "miracle-mix" and with Cermet; 5 - statistically significant differences were found between microleakage patterns in teeth rebuilt with "miracle-mix" and Cermet cores as compared to the non reconstructed group (control)

The aims of the present study were to measure the fluoride release of 1 glass ionomer cement, 1 cermet cement, 3 resin-modified glass ionomer cements and 1 compomer, and to determine the influence of each material on bacterial growth. Test specimens were eluted in saline for 180 days. Every 2 days, the specimens were transferred into fresh saline and the fluoride content of the solution was measured. Furthermore, 48-h, 14-d, 90-d, and 180-d eluates were inoculated with Streptococcus mutans and bacterial growth was recorded nephelometrically. Fluoride release dropped significantly over time for each material with values between 6.2 (Ketac-Silver) and 29.3 (Photac-Fil) ppm after 48 h to values between 0.6 (Ketac-Silver) and 1.7 (Ketac-Fil, Vitremer) ppm after 180 days. Each material reduced bacterial growth at each time of examination, but the effect decreased significantly over time with a maximum growth of 71.7% (Ketac-Fil) to 85.6% (Ketac-Silver) after 48 h and 94.7 (Vitremer) to 99.0% (Ketac-Silver) after 180 days (growth control = 100%). Both Ketac-Silver and Dyract showed a significantly lower inhibiting effect on bacterial growth than the other materials. The tested materials showed a good correlation between fluoride release and influence on bacterial growth. However, both effects dropped dramatically over the 180-days period.

The purpose of this in vitro study was to determine the fractural load of four core materials supported by five post designs. This study was divided into 20 groups with 10 samples per group. Specimens were placed in a special jig at a 45-degree angle, and the fracture load values, in pounds, were obtained with the use of a universal testing machine. A 5 x 4 factorial design was used to assess and compare the fractural strength, and a two-way analysis of variance was used to determine whether the buccolingual, mesiodistal, and height dimensions differed across groupings. Mean fracture load values were obtained. Flexi-Post dowel/Ti-Core material at 277.1 pounds and ParaPost dowel/ Tytin silver amalgam at 277.3 pounds recorded the greatest mean values. These values were not statistically different. ParaPost dowel/Ketac-Silver material had the lowest mean value (49.6 pounds). For all posts Tytin silver amalgam and Ti-Core material were significantly stronger than Ketac-Silver and G-C Miracle Mix material. Ketac-Silver and G-C Miracle Mix materials did not differ from each other. Results indicated that Ti-Core composite material is at least as strong as Tytin silver amalgam.

An in vivo clinical study was performed to evaluate the healing of a new approach to the repair of incomplete vertical root fractures. The two-stage surgical procedure incorporated ultrasonic fracture cleaning, bonding of the fracture repair with silver glass-ionomer cement, placement of a bone graft material, and application of guided-tissue regeneration. Of the six roots in the study, five failed within 2 to 11 months. One root continued to be symptom-free, without periodontal pocket formation for 1 yr, but then failed because of extension of the incomplete root fracture to the lingual of the root.

Tunnel restorations (n = 161) performed by 4 dentists were evaluated after a mean of 35 months in situ. Demineralized enamel was to be spared during preparation. The preparations were filled with a cermet glass ionomer (polyalkenoate) cement. Evaluation was carried out using clinical and radiographical criteria. During the observation period, approximately 16% of the restorations were replaced due to caries in dentin and 14% due to marginal ridge fracture. Cavitation in the approximal surface and/or increased radiolucency of the approximal enamel were observed in 34% of the remaining tunnel-restored teeth. A significantly higher frequency of failures were registered when treating patients with a high caries activity, where the initial lesion was large, and where the restoration did not reach the approximal surface.

The two-body and three-body wear of glass-ionomers (GIC), visible light cured glass-ionomers (VLC-GIC), and composites were compared. The wear simulations were performed for the two-body wear in an artificial mouth and for the three-body wear with the so-called ACTA machine. The tested materials were different conventional glass-ionomers, light cured glass-ionomers, composites, and amalgam. The wear rates of 8 specimens of each material for the two-body and 16 for the three-body wear test were compared. After 10(5) cycles with each testing device, the wear shapes were measured. All measurements were related to the wear rate of amalgam. For the two-body wear method, the worn materials were qualitatively judged by scanning electron microscopy. The two different wear testing methods lead to similar results with slight differences in ranking. Amalgam showed the lowest wear rates with both methods. Photac Fil, a newly developed VLC-GIC, showed dramatically lower wear resistance than composites and conventional GIC with both methods. Further investigations are necessary to identify the material-specific parameters influencing the wear behaviour of a material in relation to different wear testing methods.

Pairs of extracted premolar teeth were prepared with MOD cavities reducing the lingual cusp at its base to one of five widths: 1.25-2.25 mm. One of each pair was then restored with one of five adhesive restorative techniques and the weakened cusp of both teeth fractured by a force applied to the cusp at an angle of 30 degrees to the long axis of the tooth. At all cusp widths a layered restorative technique in which the cavities were filled to the enamel-dentine junction with glass-ionomer cement and the enamel replaced by composite, reinforced the weakened cusp more than the other restorative materials tested. This combination of materials to reinforce weakened cusps is worth considering as a cost effective alternative to removing the cusp entirely and making a crown or protecting the cusp with a cuspal coverage gold inlay.

Objectives. The short-term fluoride release/uptake of four glass ionomer restoratives was measured and compared to the fluoride release after exposure to three commercial fluoride gels. Methods. Materials tested were: 1) Ketac-Fil (ESPE GmbH); 2) Ketac-Silver (ESPE GmbH); 3) Photac-Fil (ESPE GmbH); and 4) Fuji II LC (GC Corp.). Twenty discs of each material were fabricated and stored in deionized water at 37°C. Initial fluoride release was measured at 24 h intervals for 7 d, and 24 h intervals at the end of each week for 5 wk. After 6 wk, samples were divided into groups and each group was treated for 6 min with one of the following commercial fluoride gels: acidulated phosphate fluoride (APF), neutral sodium fluoride (NaF), and stannous fluoride (SnF2). Control specimens were placed in deionized water. After exposure, fluoride measurements were carried out at 24 h intervals for 7 d, and 24 h intervals at the end of 2 wk. Fluoride exposure was repeated, and measurements were again recorded over 3 wk. Results. Initial fluoride release by all materials was highest during the first 24 h and decreased sharply over the first week. After exposure to APF, fluoride release increased significantly for all materials. Exposure to NaF also resulted in increased fluoride release for all materials although it was not as high as the increase recorded after exposure to APF. Exposure to SnF2 did not result in significant fluoride release by any material. Significance. The results of this study suggest that certain fluoride gels may replenish fluoride within some glass ionomers and thus prolong their cariostatic potential.

• Objective. Several methacrylate/glass ionomer hybrid materials are now available for clinical use as restorative filling materials. However, the long-term resistance of these materials to physical degradation in the humid oral condition is not known. The objective of this investigation was to determine the mechanical properties, e.g., ultimate compressive strength and diametral tensile strength, of several glass ionomer materials as a function of time after aging in water at oral temperature. • Methods. Eight glass ionomer filling materials indicated for restorative or core build-up applications were studied. Three conventional glass ionomers, two metal-containing conventional glass ionomers and three methacrylate-modified systems were included in the study. Cured specimens of each were aged in distilled water at 37°C for 24 h, 1 wk, 4 wk, 12 wk, 24 wk and 52 wk. • Results. Like the conventional glass ionomers, the methacrylate-modified glass ionomers of this study, with one exception, did not exhibit a decrease in compressive strength, modulus and diametral tensile strength as a result of prolonged storage in water at oral temperature. Some differences among the various groups were apparent. The compressive strengths of the conventional glass ionomers were lower than the methacrylate-modified system, except for one material, Fuji II (GC Dental Corp.), of the former group. A significant difference in the compressive strength was seen between the encapsulated and hand-mixed versions of the same commercial brand product. The compressive modulus was higher and the diametral tensile strength was lower for the conventional systems indicating that, as a group, these materials are more brittle than the methacrylate-modified hybrid ionomers. With the exception of VariGlass VLC (L.D. Caulk), most of the materials studied showed little decrease in mechanical properties after aging in water for 52 wk. • Significance. These materials could, therefore, be indicated for use in applications where they are in contact with oral fluids under physiological conditions.

Objectives. The early strength of glass ionomer cements was investigated previously (Cattani et al., 1993). Using the same set of glass ionomer cements, this study was designed to determine if mechanical property degradation occurred after an extended period of storage in water. Methods. In the present study, the effect of aging in water on the compressive, tensile and flexural strengths of twelve commercial glass ionomer cements was evaluated at different time intervals after the beginning of the setting reaction. The aging periods varied from 24 h to 12 mon. Results. The results show that the mechanical properties of the tested materials are in some cases affected by long-term aging in water. The evolution of strength follows distinct patterns of change. It has been established that the glass ionomer cements are neither characterized by a continuous increase nor a continuous decrease in strength. Most of the materials tested maintained a constant strength. However, several of them first display an improvement of the mechanical strength followed by a reduction. In this case, the 24h and the 12 mon strengths are usually similar. Significance. The aging mechanisms of glass ionomers are complex. Strengthening probably results from additional crosslinking and build-up of a silica gel phase, whereas weakening may result from erosion and plasticizing effect of water.

The aim of this study was to investigate the effect of acidic agents on surface roughness and characteristics of four restorative materials. Fifty-two discs were created from each restorative material: metal-reinforced glass ionomer cement (Ketac-S), resin-modified glass ionomer cement (Fuji II LC), resin composite (Filtek Z250), and amalgam (Valiant-PhD); each disc was 12 mm in diameter and 2.5 mm thick. The specimens were divided into four subgroups (n=13) and immersed for 168 hours in four storage media: deionized water (control); citrate buffer solution; green mango juice; and pineapple juice. Surface roughness measurements were performed with a profilometer, both before and after storage media immersion. Surface characteristics were examined using scanning electron microscopy (SEM). Statistical significance among each group was analyzed using two-way repeated ANOVA and Tukey's tests. Ketac-S demonstrated the highest roughness changes after immersion in acidic agents (p0.05), followed by Fuji II LC. Valiant-PhD and Filtek Z250 illustrated some minor changes over 168 hours. The mango juice produced the greatest degradation effect of all materials tested (p0.05). SEM photographs demonstrated gradual surface changes of all materials tested after immersions. Of the materials evaluated, amalgam and resin composite may be the most suitable for restorations for patients with tooth surface loss.

The purpose of this study was to determine the wear of stainless steel crowns (SSCs) in children, and compare the extent of microleakage in SSCs that had been repaired using either a cermet glass-ionomer cement (GIC) or a packable composite resin (CR).For the first aim, the occlusal surface thickness of 31 harvested SSCs (21 primary first and 10 second molars) and 18 unused SSCs was measured, and then examined under scanning electron microscopy. For the second aim, standardised holes were prepared on the occlusal surfaces of 20 SSCs, and then repaired using either a cermet GIC or packable CR. After their repair, the extent of microleakage was determined using 0.5% basic fuchsin and stereomicroscopy.The thickness of all the harvested SCCs was 5.3 μm less than that of the unused SCCs (p0.02), and there were no significant differences between the thickness and occlusal wear rates of harvested SSCs from the first and second primary molars. Although neither of the two repair materials completely prevented microleakage, the number of specimens in which microleakage occurred after repair with a cermet GIC was significantly lower than the number of specimens in which a packable CR was used (p0.05).We concluded that the occlusal surfaces of SSCs for first and second primary molars display wear. Although perforated SSCs can be repaired using either a cermet GIC or a packable CR, less microleakage occurs in SSCs that were repaired with a cermet GIC than those with a packable CR.

The aim of this study was to compare the clinical performance of an amalgam, a glass polyalkenoate (ionomer) cerment material and a resin-based composite material used in small Class II cavities in permanent teeth. All restorations were inserted under rubber dam. They were examined yearly for 3 years. One clinician continued the study up to 5 years. The clinical examination focused on two criteria: clinically acceptable and failure. In addition, impressions were taken of the prepared cavities immediately before restoration and at each clinical examination using an elastomeric material. The study comprised 274 Class II restorations (88 amalgams, 95 cerments and 91 resin composites) placed in 142 adolescent patients. One hundred and sixty-seven restorations were in molar and 107 in premolar teeth. Patient dropout after 5 years resulted in the loss of 161 restorations, evenly distributed for restorative material and type of tooth involved. Four amalgam restorations, 22 glass ionomer cerment and nine resin composite restorations failed. The glass ionomer cerment and amalgam restorations failed primarily due to bulk fractures, while the resin composite restorations failed due to secondary caries and bulk fractures.