SEARCH · Search PubMed
Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.
Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.
There is an ever-growing demand for esthetic dental treatment. Treatment modalities include crowns, bleaching, and ceramic or composite veneers. A more conservative treatment option, enamel microabrasion, may be indicated in certain clinical scenarios. The purpose of this clinical report is to describe the use of enamel microabrasion for a patient with discolored anterior teeth.
PURPOSE: The retention forces of a newly developed compomer cement (Dyract Cem), a glass ionomer cement (Ketac Cem Aplicap), and a resin cement (F21) were examined. MATERIAL AND METHODS: Cemented cast gold crowns were removed along the path of insertion with a Zwick universal testing device. The impact of both a cured and a noncured additional bonding layer that were applied to the inner surface of the crowns was examined across the Dyract Cem group. RESULTS: The mean adhesive strength was measured at 2.36 +/- 0.69 N/mm2 in the Ketac Cem group, at 0.60 +/- 0.28 N/mm2 in the F21 group, and at 1.85 +/- 0.94 N/mm2 in the Dyract Cem group, respectively. The application of an additional bonding layer to the inner surface of the crowns did not significantly improve the retentive strength of Dyract Cem; the respective mean strengths were observed at 1.46 +/-0.33 N/mm2 for the uncured and at 1.70 +/- 0.76 N/mm2 for the cured bonding layers. CONCLUSIONS: Dyract Cem and Ketac Cem showed significantly higher retentive strengths than F21 (p < 0.001, Wilcoxon test, 5% level). No significant difference was found in bond strength between Ketac Cem and Dyract Cem.
STATEMENT OF PROBLEM: "Compomers" are being used with increasing frequency in Europe and North America. PURPOSE: This study evaluated the marginal seal of two compomers in vivo. MATERIAL AND METHODS: Periodontally involved teeth, scheduled for extraction, were selected. Four groups of a combination of materials were used (Dyract with Dyract-PSA primer, group 1; Dyract with Prime and Bond 2.0, group 2; Compoglass with SCA primer, group 3; and Compoglass with Syntac Single Component, group 4). The restorations were made in a standardized shaped cavity, across the cementoenamel junction, and the teeth were extracted after 2 to 3 months of clinical service. The specimens were kept in a solution of 2% methylene blue for 24 hours. After being embedded in epoxy resin, sections were made with a low speed saw along the longitudinal axis of the teeth. The examination of dye penetration was made with a microscope at a magnification of x20 and scoring was done at both coronal and apical sites. Kruskal-Wallis statistical analysis was performed at 5% significance level. RESULTS: Groups 2 and 4 scored significantly less than groups 1 and 3 and for groups 2 and 4, 30% of the restorations exhibited leakage. CONCLUSION: These restoration systems did not completely prevent leakage either at the incisal or the cervical margins. Therefore the use of an enamel-dentin bonding system in combination with the proprietary compomer is recommended.
Explore the source record for details and available documents.
Bleaching has been suggested by several authors in order to treat the unaesthetic aspect of dental fluorosis. Many results are, however, unsatisfactory. A different method, based on the structural characteristics of the fluorotic tooth and the organic and exogenous nature of fluorotic enamel stains, includes three principal stages: 1--enamel etching with 12% HCl in order to eliminate the posteruptive calcified layer that covers the fluorotic enamel surface and to denude the microcavities containing the organic elements; 2--application of pure manufactured sodium hypochlorite to remove these organic stains; and 3--filling the chemically opened microcavities with a light-cured dental adhesive to provide the tooth with a smooth and even surface and to prevent restaining. To improve the aesthetic aspect of intensely discolored teeth, it is possible to use a variety of tints available in several composite resin kits. Teeth with a rough enamel surface react more positively than ones with a smooth surface. The enamel adhesives provide better results than the amelo-dentinal ones.
OBJECTIVES: To find a predictive formula of stress, considering the surfaces (free, adhered) involved, the volume and characteristics of material and the deformation of the measuring system. MATERIALS AND METHODS: 231 samples of five chemically cured restoratives (Silar (SIL, 23), Clearfil F2 (CLE, 39), P10 (P10, 33), Concise (CON, 30), Isopast (ISO, 28)) and four luting (3M Experimental 241 (EXM, 20), Variolink II (VAR, 13), Vitremer LC (VTM, 20) and Dyract Cem (DYR, 25)) materials were allowed to polymerize until they reached a maximum tension (T(max), 25 min) between six pairs (null 5.81, 8.5, 11.26, 12.42, 17.02, 23.14 mm) of polished metallic discs (range of distances: 0.02-5.9 mm) mounted in a tension machine. The deformation of the measuring system was measured for the recorded forces. RESULTS: A descriptive non-linear formula T(max)=KVol(-3.267)FS(3.283)AS(0.642)Def(0.561) was found that individualizes the material's characteristics (K) that considers volume (Vol), free (FS) and adhered (AS) surfaces and deformation (Def) of the system for each force. This formula renders good correlation (material K (r(2) coefficient)): SIL 0.9998 (0.995), CLE 1.0062 (0.989), P10 1.0224 (0.990), CON 0.9908 (0.992), ISO 0.9648 (0.974), EXM 1.0083 (0.991), VAR 0.9777 (0.996), VTM 0.9925 (0.993), DYR 0.9971 (0.997) between actual T(max) and calculated Tension. There are statistically significant differences (p=0.002) between K values of both (restorative and luting) groups. SIGNIFICANCE: Predictive parameters have influence in a different way to what is actually considered, if the system is allowed to have deformation, as occurs naturally and volume and material's characteristics are considered.
OBJECTIVES: The aim of this study was to investigate the influence of the proprietary bonding agents Hytac OSB (OSB) (Espe), Prime&Bond 2.1 (PB) (Dentsply DeTrey) and Syntac Single Component (SSC) (Vivadent) on the fluoride release of the corresponding polyacid-modified composite resins Hytac (HTC), Dyract AP (DAP) and Compoglass F (CGF), respectively. METHODS: Ten cylindrical specimens (6mm diameter and 3mm thick) of each polyacid-modified composite were prepared according to the manufacturers' instructions: five with bonding agent applied and five without bonding agent as a control. The specimens were immersed individually in 10ml ultra-pure water at 37 degrees C immediately after light-curing of the polyacid-modified composite resins. Over 140 days, the water was regularly renewed and the fluoride concentration eluted during each period was determined with a combined fluoride ion selective electrode. RESULTS: The fluoride release decreases according to the sequence: CGF>DAP>HTC. The bonding agent significantly reduces the fluoride released by DAP and CGF, respectively, by a factor 2-3 and +/-1.4. For HTC, the bonding agent reduces the fluoride released initially by a factor of +/-2, but the difference between the fluoride release with and without bonding agent becomes insignificant after approximately 3 weeks. SIGNIFICANCE: It can be concluded that the use of bonding agent can significantly reduce fluoride release of polyacid-modified composite resins in the long-term, and especially in the short-term. The decrease in fluoride release might reduce the material's potential to prevent recurrent caries.
OBJECTIVE: The aim of this study was to compare the shear bond strengths and fracture characteristics of two compomers bonded with a single step bonding agent with two modern composites, a microfil and hybrid, bonded with a fourth generation bonding agent. METHODS: Freshly extracted human third molars were sectioned parallel to the occlusal surface to expose midcoronal dentin, prepared with 320-grit surface finish, and bonded (N = 11 samples/group) following manufacturer's directions with the compomers (Dyract, DeTrey Konstanz, Germany or Compoglass, Vivadent, Schaan Liechtenstein) or the dentin bonding agent SMP+ (Scotchbond Multi-Purpose Plus, 3M Dental Products, St. Paul MN) with Silux Plus or Z100 (3M Dental Products, St. Paul, MN). The samples were tested using a single plane lap shear bond strength test at 5 mm/min until failure. Statistical analysis was performed using ANOVA with Scheffe multiple comparison testing. Fracture surfaces of the debonded surfaces were examined using SEM to determine the failure mode of each specimen. RESULTS: Bond strengths for the compomers were 12.7 +/- 2.9 MPa for Dyract and 8.9 +/- 4.1 MPa for Compoglass and were not significantly different. Bond strengths for the dentin bonded composites were significantly stronger than the compomer Compoglass, but were not different from one another, despite the use of different composites. The averages values for SMP + /Silux Plus and SMP + /Z100 were 15.7 +/- 4.5 MPa and 15.2 +/- 5.6 MPa, respectively. SEM analysis showed that all materials exhibited mixed failure patterns. Compoglass specimens exhibited 5 of 11 failures classified as adhesive, while each of the other materials showed only 1 of 11 adhesive failures. SIGNIFICANCE: Compomers have undergone rapid development over the last several years, but their bond strengths have not yet reached the same level as modern dentin bonded composites. Difference in composite filler type and amount had little influence on the bond strength determined in this work.
OBJECTIVES: To quantify the width of the cement interface between ceramic inlays generated by the CEREC-2 CAD-CAM system and the tooth, and to determine the effect of cement viscosity on the interface width. METHODS: Standardised MOD cavities were cut in 15 human premolar teeth using a custom paralleling device. A ceramic inlay was made with a CEREC-2 CAD-CAM machine for each tooth. The inlays were cemented using one of three resin-based composite systems of varying viscosity; a hybrid microfilled posterior composite, a compomer restorative and a dual-cure luting composite. The teeth were subsequently sectioned and measurements were taken at 21 key points with the aid of an image-analysis light microscopy system. RESULTS: Statistical significance tests were applied to examine for difference in interface dimensions at specific points within each of the cement-groups and amongst groups. The interface space at the occlusal walls has a distinct wedge shape, being narrower at the external interface (50 microns, SD 15) than internally (211 microns, SD 38). There is no statistically significant difference in the interface dimensions of the gingival floor between the boxes that lie above and below the CEJ. There is no statistically significant difference in the width of the interface at any given point between the three cement groups. SIGNIFICANCE: There is a significant improvement in the fit of CEREC-2 restorations when compared with the original CEREC system. Cements of varying viscosity (within the measured range) may be used for cementation of these inlays, without adversely affecting the width of the interface. Caution must be exercised with light-activated composite cements to ensure adequate transmission of light through the ceramic and the underlying composite cement.
OBJECTIVES: The development of a micro plate assay for cytotoxicity testing of dental materials based on a bioassay using brine shrimp larvae (artemia salina) as sensitive organisms. METHODS: Brine shrimp larvae are commonly used for cytotoxicity assays in pharmacology. These larvae are sensitive to toxic substances. The ratio between dead larvae (no motility) and living larvae (high motility) in comparison to a control without any toxic substances is used to estimate the toxicity of the test solutions. The test materials (Arabesk((R)), Solitaire((R)), Pertac((R)) II, Tetric((R)), Herculite((R)) and the compomer materials Dyract((R)), Hytac((R)), Compoglass((R))) were polymerized and consecutively milled. After incubation of 1g in 4ml distilled water at 37 degrees C for 48h, the solid materials were separated by centrifugation. The solutions were equibrilated with NaCl to a salt content of 25g/l. Aliquots of 200microl were distributed in eight micro wells and 50microl of a artemia salina containing (n=8-14) solution were added to each well. As controls eight wells with 250microl salt solution containing a comparable number of brine shrimp were used. At baseline, after 2, 5, 24 and 48h, the dead shrimp were counted using a stereo microscope. Finally all shrimps were sacrificed using Na-acid (5%) and counted to get the number of shrimps per well. RESULTS: All compomers and Solitaire caused 100% brine shrimp lethality after 24h and showed significantly (p<0.01, signed rank test) higher toxicities than the remaining composites. With the exception of Pertac II, all composites showed significantly higher toxic values than the control. Pertac II did not show any differences from the controls used. CONCLUSIONS: This new technique has some advantages for toxicity testing of restorative materials, because it can quickly be carried out at low costs. The disadvantage is the high quantity of material used and the low sensitivity.
OBJECTIVES: The aim of this study was to evaluate the effect of hydrostatic pressure on the regional bond strengths of compomers to dentine. METHODS: Thirty freshly extracted molars were ground flat to expose the dentine and randomly divided into two groups for bonding: no hydrostatic pressure and hydrostatic pressure of 15cm H(2)O. Xeno CF, Dyract AP and F 2000 were applied to dentine surfaces pretreated by the respective bonding systems following the manufactures' instructions, and then restored with Clearfil AP-X. After 24h storage in water, the teeth were sectioned into 0.7-mm thick slabs and visually divided into three regional subgroups: the region communicating with the pulp through dentinal tubules (pulp horn); the region between the pulp horns (center); and the region between the pulp horn and DEJ (periphery). The specimens were trimmed to a cross-sectional area of 1mm(2) and subjected to the micro-tensile bond test. The data were analyzed by one- and three-way ANOVA, and Fisher's PLSD (p<0.05). RESULTS: There were no significant regional differences of bond strengths for all the compomers tested (p>0.05). However, hydrostatic pressure significantly decreased the bond strength of F 2000 to all regions (p<0.05), while the bond strength of Dyract AP significantly decreased only at the pulp horn region (p<0.05). On the other hand, the bond strengths of Xeno CF seemed not to be affected by hydrostatic pressure (p>0.05). For Dyract AP and F 2000, the fracture modes were affected by hydrostatic pressure, while, for Xeno CF, there were no significant differences between the fracture modes with non- or positive hydrostatic pressure. SIGNIFICANCE: Simulated pulpal pressure of 15cm H(2)O had a greater influence on the bond strengths of compomers to dentine than did dentine regions. Therefore, when measuring the bond strengths of compomers to dentine under the simulated in vivo conditions, the wetness of the dentine surface, as well as the intrinsic properties of each material should be seriously considered.
The aim of this in vitro study was to compare fluoride release from two cement disc models (partially varnished and unvarnished) of three orthodontic bonding materials with fluoride release from the same materials when used to bond an orthodontic bracket onto a tooth surface. A resin-modified glass ionomer cement (Vitremer) and a compomer material (Dyract Ortho) were compared with a conventional resin adhesive (Right-On). Ten discs (3.0 mm diameter and 1.5 mm thick) of each material were manufactured in a silicone mould and ten premolar teeth were bonded with orthodontic brackets using each material. All the premolar teeth were covered with nail varnish up to the bracket periphery and five of the discs for each material were coated with nail varnish on both upper and lower surfaces which halved the surface area. The fluoride released into 2 ml of deionised water, from each tooth or disc, was measured at regular intervals over 60 days. At 60 days, cumulative fluoride release was highest from the unvarnished discs, less for the varnished discs and least from the tooth-bracket model for both test materials. Despite having twice the surface area, the unvarnished disc model released only 1.2 to 1.5 times more fluoride than the varnished disc model. Compared with the tooth-bracket model, the unvarnished discs released 3.0 to 4.5 times more fluoride, whereas the varnished discs released only 2.2 to 3.7 times more fluoride. For the materials tested in this study, halving the surface of the discs did not reduce the cumulative fluoride release by half. The tooth/bracket model with minimal bonding material demonstrated substantial cumulative fluoride release. The pattern of fluoride release was similar for all models tested.
OBJECTIVES: The aim of this study was to evaluate the marginal adaptation of direct Class II sandwich restorations with resin-modified glass-ionomer cements and compomers in comparison to base and total bond restorations. For sandwich restorations with a triple cure resin-modified glass-ionomer cement the influence of different light curing techniques was also evaluated. METHODS: Large butt-joint class II cavities with cervical margins 1 mm below the cemento-enamel junction were cut into 120 extracted human molars. The cavities (15 groups, n = 8) were filled using a sandwich, base or total bond technique with materials from five different manufacturers. A three-sited light curing technique was used in 13 groups. For the material combination Vitremer/Z100 two additional groups with a different wand positioning and a metal matrix were evaluated. After water storage for 21 days and thermocycling (2000x, 5-55 degrees C), replicas were quantitatively analysed in the SEM. Statistical analysis was performed with the Kruskal-Wallis test and the Bonferroni test at p < 0.05. RESULTS: The marginal adaptation of vertical enamel margins was not dependent on the restorative technique. For margins in dentine, marginal adaptation was significantly better with the sandwich technique than with a base or total bond technique for all materials. There were no significant differences between the base and total bond technique. Overall, resin-modified glass-ionomer cements showed somewhat better results than compomers in sandwich restorations, though differences were not significant for some criteria. Vitremer/Z100 sandwich restorations applied with a metal matrix showed the highest mean percentage of excellent margins of all experimental groups. CONCLUSIONS: Both resin-modified glass-ionomer cements and compomers can improve the marginal quality when used in a sandwich technique. Further research is necessary to determine the ideal material combination for sandwich restorations.
Pumice prophylaxis has long been accepted as a prerequisite for achieving adequate enamel etching during orthodontic bonding procedures. Three methods were used in this study to examine the effects of pumice prophylaxis on the bond strength of orthodontic brackets: (1) shear bond strength of brackets that were bonded to extracted premolars after surface preparation procedures, which either included or did not include prior pumice prophylaxis, was evaluated; (2) scanning electron microscopy (SEM) was used to examine the surface characteristics of teeth that had been etched with and without prior pumice prophylaxis; and (3) rate of bracket failure in patients who had had brackets bonded with and without prior pumice prophylaxis was recorded during an average treatment time of 18 months. No significant differences were noted in bond strength, general etched enamel surface characteristics, or bracket retention rates. Some specific differences, however, were noted on SEM in localized areas of the etched enamel surfaces, although these did not appear to affect the bond strength or bracket retention rates ultimately attained.
In the cement industry, the extrusion technique is used to produce flat shapes with improved resistance to compression. Extrusion is a plastic-forming process that consists of forcing a highly viscous plastic mixture through a shaped die. The material should be fluid enough to be mixed and to pass through the die, and on the other hand, the extruded specimen should be stiff enough to be handled without changing in shape or cracking. These characteristics are industrially obtained by adding cellulosic polymers to the mixture. The aim of this work is to understand the action mechanism of these additives on the major pure phases constituting a typical Portland cement: tricalcium silicate (C(3)S), dicalcium silicate (C(2)S), tricalcium aluminate (C(3)A), and tetracalcium iron-aluminate (C(4)AF). In particular, a methylhydroxyethyl cellulose (MHEC) was selected from the best-performing polymers for further study. The effect of this additive on the hydration kinetics (rate constants, activation energies, and diffusional constants) was evaluated by means of differential scanning calorimetry (DSC) while the hydration products were studied by using thermogravimetry-differential thermal analysis (TG-DTA), X-ray diffraction (XRD), and scanning electron microscopy (SEM). MHEC addition in calcium silicate pastes produces an increase in the induction time without affecting the nucleation-and-growth period. A less dense CSH gel was deduced from the diffusional constants in the presence of MHEC. Moreover, CSH laminar features and poorly structured hydrates were noted during the first hours of hydration. In the case of the aluminous phases, the additive inhibits the growth of stable cubic hydrated phases (C(3)AH(6)), with the advantage of the metastable hexagonal phases being formed in the earliest minutes of hydration.
Explore the source record for details and available documents.
Explore the source record for details and available documents.