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PubMed2003

Evaluation of a new 2-paste glass ionomer cement.

A new 2-paste resin-reinforced glass ionomer cement, Fuji Ortho Band Paste Pak (GC Corporation, Tokyo, Japan), for the placement of orthodontic bands, has been developed for easier handling. The aim of this study was to compare the fluoride release and uptake characteristics of this cement with that of 3 others commonly used to cement orthodontic bands: a conventional resin-reinforced glass ionomer cement, a polyacid-modified composite resin, and a conventional glass ionomer cement. Fluoride release was measured during a 28-day period. After the measurement on day 28, experimental samples were exposed to 1000 ppm sodium fluoride solution for 5 minutes, and fluoride release was then measured for 7 days. Initially, the new 2-paste resin-reinforced glass ionomer cement released the greatest amount of fluoride; the polyacid-modified composite resin released the least initially, and it continued to show the lowest values throughout the study. The fluoride uptake and release values of the new 2-paste resin-reinforced glass ionomer cement were statistically significantly higher than those of the conventional resin-reinforced glass ionomer cement or the conventional glass ionomer cement. The new 2-paste resin-reinforced glass ionomer cement might be a good alternative to conventional products for cementing orthodontic bands.

Absorption↗
PubMed2003

Long-term in vitro fluoride release and rerelease from orthodontic bonding materials containing fluoride.

The purpose of this study was to compare in vitro long-term (30 month) fluoride release and rerelease rates (after fluoride exposure) from 3 orthodontic bonding materials containing fluoride and 1 without fluoride. Ten samples of each material (Python, TP Orthodontics, LaPorte, Ind; Assure, Reliance Orthodontic Products, Itasca, Ill; Fuji Ortho LC, GC America, Alsip, Ill; and Transbond XT, 3M Unitek, Monrovia, Calif) were fabricated and stored in deionized distilled water at 37 degrees C. Five samples had fluoride-release rates measured at days 546, 637, 730, 821, and 913 after initial fabrication, and 5 samples were exposed to fluoride (Nupro 2% NaF gel, Dentsply Canada, Woodbridge, Ontario, Canada) for 4 minutes at day 535 and had measurements taken on days 546, 548, 552, 575, 637, 730, 821, and 913. To prevent cumulative measurements, the storage solutions were changed 24 hours before measurement. Statistically significant differences were found in fluoride-release rates (P <.0001), with Fuji Ortho LC releasing the most fluoride, followed by Python and Assure at all time points in the nonfluoride exposed group. In the fluoride-exposed group, there were significant differences in fluoride release (P <.0001), with Fuji Ortho LC releasing the most fluoride. A "burst-effect" pattern of fluoride release was seen after fluoride exposure for all materials. It was concluded that Fuji Ortho LC, Assure, and Python might have sufficient long-term fluoride-release rates to reduce white spot formation, and all are recommended as suitable fluoride-releasing orthodontic bonding materials.

Acrylic Resins↗
PubMed2006

Modeling and experimental investigation of rheological properties of injectable poly(lactide ethylene oxide fumarate)/hydroxyapatite nanocomposites.

Injectable multiphasic polymer/ceramic composites are attractive as bioresorbable scaffolds for bone regeneration because they can be cross-linked in situ and are osteoconductive. The injectability of the composite depends on the nanoparticle content and the energetic interactions at the polymer/particle interface. The objective of this research was to determine experimentally the rheological properties of the PLEOF/apatite composite as an injectable biomaterial and to compare the viscoelastic response with the predictions of a linear elastic dumbbell model. A degradable in situ cross-linkable terpolymer based on low molecular weight poly(L-lactide) and poly(ethylene oxide) linked by unsaturated fumarate groups is synthesized. The poly(L-lactide-co-ethylene oxide-co-fumarate) (PLEOF) terpolymer interacts with the surface of the apatite nanoparticles by polar interactions and hydrogen bonding. A kinetic model is developed that takes into account the adsorption/desorption of polymer chains to/from the nanoparticle surface. Rheological properties of the aqueous dispersion of PLEOF terpolymer reinforced with nanosized hydroxyapatite (HA) particles are investigated using mechanical rheometry. To this end, we performed a series of rheological experiments on un-cross-linked PLEOF reinforced with different volume fractions of HA nanoparticles. The results demonstrate that the observed nonlinear viscoelasticity at higher shear rates is controlled by the energetic interactions between the polymer chains and dispersed particle aggregates and by the rate of the adsorption/desorption of the chains to/from the surface of the nanoparticles.

Animals↗
PubMed2006

Molecular, seasonal, and spatial distributions of organic aerosols from fourteen Chinese cities.

Organic aerosols were studied at the molecular level in 14 coastal and inland mega-cities in China during winter and summer 2003. They are characterized by the abundant presence of n-alkanes (annual average, 340 ng m(-3)), fatty acids (769 ng m(-3)), sugars (412 ng m(-3)), and phthalates (387 ng m(-3)). In contrast, fatty alcohols, polyols/polyacids, lignin and resin products, sterols, polycyclic aromatic hydrocarbons (PAHs), and hopanes were detected as relatively minor components. n-Alkanes show a weak odd/even carbon predominance (CPI = 1.1) and PAHs show a predominance of benzo(b)fluoranthene, suggesting a serious contribution from fossil fuel (mainly coal) combustion. Their concentrations (except for phthalates and polyols/polyacids) were 2-15 times higher in winter than summer due to a significant usage of coal burning and an enhancement of atmospheric inversion layers. Phthalates were found to be more abundant in summer than winter, probably due to enhanced vaporization from plastics followed by adsorptive deposition on the pre-existing particles. Concentrations of total quantified compounds are extremely high (approximately 10 microg m(-3)) in the midwest (Chongqing and Xi'an) where active industrialization/urbanization is going on. This study shows that concentrations of the compounds detected are 1-3 orders of magnitude higher than those reported from developed countries.

Aerosols↗
PubMed2000

Determination of changes on tooth-colored cervical restorations in vivo using a three-dimensional laser scanning device.

The present study aimed at the determination of changes of tooth-colored cervical restorations in vivo using an optical 3-dimensional laser scanning device. The study was performed on 197 cervical restorations placed on incisors, canines, and premolars. Four different tooth-colored restoration materials, a composite, a polyacid-modified resin composite, and two resin-modified glass ionomer cements, were used for the restoration of the lesions. For the determination of changes, images were taken at baseline and 15, 24 and 36 months after the placement of the fillings using a 3D-laser scanning device. The images were superimposed automatically, and digital subtraction was made by a specially developed image analysis software. The total substance loss on the entire filling surface at 36 months for the resin-modified glass ionomer Photac-Fil was 44 (+/-23) microm, for Fuji II LC 45 (+/-26) microm, for Dyract 71 (+/-47) microm and for Tetric 18 (+/-12) microm. Differentiating between the class of lesion, a higher wear rate was observed at 36 months on restorations which had been placed in erosion/non-carious cervical cavities (66 (+/-33) microm). In conclusion, the composite material demonstrated a distinctly lower surface wear rate over time in comparison to the resin-modified glass ionomer cements and the polyacid-modified resin composite.

Adult↗
PubMed2002

Hardness and in vitro wear of a novel ceramic restorative cement.

The aim of the present work was to compare a new ceramic restorative cement for posterior restorations, DoxaDent, with other types of tooth-colored materials for direct use as regards hardness and in vitro wear. Four hybrid resin composites, one polyacid-modified resin composite, one resin-modified glass ionomer cement, one conventional glass ionomer cement, one zinc phosphate cement, an experimental version as well as the marketed version of the ceramic restorative cement, were investigated. Hardness of the materials was tested with the Wallace indentation tester and wear was tested with the ACTA wear machine. All tests were carried out on 2-wk-old specimens. DoxaDent was as hard as the zinc phosphate cement and the hardest resin composite. The ceramic restorative cement wore significantly more than the resin composites, the same as the zinc phosphate cement, and less than the glass ionomer cements. No correlation between hardness and wear was found. It can be concluded that the ceramic restorative cement is a rather hard material but with a relatively low wear resistance.

Aluminum Compounds↗
PubMed2003

In vitro evaluation of marginal and internal adaptation after occlusal stressing of indirect class II composite restorations with different resinous bases.

Composite inlays are indicated for large cavities, which frequently extend cervically into dentin. The purpose of this study was to compare in vitro the marginal and internal adaptation of class II fine hybrid composite inlays (Herculite, Kerr) made with or without composite bases, having different physical properties. Freshly extracted human molars were used for this study. The base extended up to the cervical margins on both sides and was made from Revolution (Kerr), Tetric flow (Vivadent), Dyract (Detrey-Dentsply) or Prodigy (Kerr), respectively. Before, during and after mechanical loading (1 million cycles, with a force varying from 50 to 100 N), the proximal margins of the inlay were assessed by scanning electron microscopy. Experimental data were analysed using non-parametric tests. The final percentages of marginal tooth fracture varied from 30.7% (no base) to 37.6% (Dyract). In dentin, percentages of marginal opening varied from 9.2% (Tetric Flow) to 30.1% (Prodigy), however, without significant difference between base products. Mean values of opened internal interface with dentin varied from 11.06% (Tetric Flow) to 28.15% (Prodigy). The present results regarding dentin adaptation confirmed that the physical properties of a base can influence composite inlay adaptation and that the medium-rigid flowable composite Tetric Flow is a potential material to displace, in a coronal position, proximal margins underneath composite inlays.

Compomers↗
PubMed1998

Evidence-based research in the primary dental care setting.

Evidence based practice is now recognised as an important topic for all health professionals, and rightly so. It is essential that clinical procedures we offer to our patients or drugs that we prescribe have been scientifically proven to be of benefit.

Child↗
PubMed2006

Application of HS-SPME in the determination of potentially toxic organic compounds emitted from resin-based dental materials.

Leaching of volatile substances from resin-based dental materials may have a potential impact on the biocompatibility as well as safety of these materials. Information from manufacturers on ingredients in the materials is very often incomplete. Patients and dentists may be in contact with components emitted from cured dental fillings or from substrates applied in their preparation. Therefore, determination of the components of these materials is necessary for better prevention from possible harmful effects caused by dental fillings. The aim of this work was the isolation and identification of organic compounds evolved from four commercial resin-modified glass-ionomer cements (resin-based dental materials applied in dentistry) by using an alternative method of volatile compounds analysis-HS-SPME (headspace-solid phase microextraction). Dental materials were heated in closed vial at various temperatures and volatile substances released into the headspace phase above the sample were isolated on a thin polymeric fibre placed in SPME syringe. Identification was performed by using the GC-MS (gas chromatography-mass spectrometry) technique. Almost 50 RMGIC (resin-modified glass-ionomer cement) components (monomers and additives) were identified. The main identified leachables were: iodobenzene (DPICls-diphenyliodonium chloride degradation product), camphorquinone (photo-initiator), tert-butyl-p-hydroxyanisole (inhibitor), 4-(dimethylamino)ethyl benzoate (co-initiator), ethylene glycol dimethacrylate (monomer).

Compomers↗
PubMed2000

A comparison of shear-peel band strengths of 5 orthodontic cements.

The objective of this study was to compare the shear-peel band strength of 5 orthodontic cements using both factory and in-office micro-etched bands. The 5 orthodontic cements evaluated were a zinc phosphate (Fleck's Cement), 2 resin-modified glass ionomer cements (RMGI)(3M Multicure glass ionomer and Optiband), and 2 polyacid-modified composite resin cements (PMCR)(Transbond Plus and Ultra Band Lok). Salivary contamination was examined with a polyacid-modified composite resin (Transbond Plus). Two hundred and eighty extracted human molar teeth were embedded in resin blocks and each was randomly assigned to the following 7 groups: 6 groups with factory etched bands, 5 cement groups and salivary contaminated group, and 1 in-office micro-etched group. The cemented teeth were put in deionized water at 37 degrees C for 30 days and thermocycled for 24 hours. The force required to break the cement bond was used as a measure of shear-peel band retention. With the use of an Instron testing machine, a shear-peel load was applied to each cemented band. Data were analyzed with a one-way analysis of variance (ANOVA) with a Tukey test for the multiple comparisons. The RMGIs and PMCRs demonstrated significantly greater shear-peel band strengths compared to the zinc phosphate cement. No statistically significant differences were noted between the RMGI cement and PMCR cements and within the RMGI groups, however, there was a statistically significant difference within the PMCR groups. Significantly lower band strengths were noted with the saliva contaminated PMCR cement group (Transbond Plus) and the inpractice sandblasted PMCR group. Both RMGIs and PMCRs were found to demonstrate favorable banding qualities. The lower band strength with saliva-contaminated bands suggests that moisture control is critical when using a PMCR. The variability noted in the in-office micro-etched bands might be technique related.

Compomers↗
PubMed2006

Light curing the primer-beneficial when working in problem areas?

The purpose of this study was to investigate whether Transbond XT with MIP and Assure were affected by light curing the primers before contamination with blood or saliva. The study material consisted of 180 human premolars. The teeth were assigned into 12 groups of 15 specimens each. Metal brackets were bonded to each tooth under five different enamel surface conditions: dry, contaminated with blood or contaminated with saliva after primer application without light curing the primer, and contaminated with blood or contaminated with saliva after primer application with light curing the primer. The shear bond strengths of the two adhesive groups were not significantly different from each other within the same surface condition. There was no statistically significant difference between the groups bonded under dry conditions. On the other hand, curing the primer before adhesive application enhanced the bond strength in the contamination groups. Saliva and blood behaved similarly, showing higher bond strength values when the primer was light cured before contamination. However, they revealed bond strengths of different magnitudes because of the differences in the type and amount of inorganic and organic substances they contained. Under ideal conditions, light curing the primer did not introduce any advantages. However, curing the primer before contamination revealed higher bond strengths. To minimize the negative effect of contamination on bond strength, it would be appropriate for clinicians to light cure immediately after the application of the primer.

Analysis of Variance↗
PubMed2004

Clinical performance of a resin-modified glass-ionomer and two polyacid-modified resin composites in cervical lesions restorations: 1-year follow-up.

The aim of this study was to assess the clinical performance of a resin-modified glass-ionomer cement (Vitremer) and two polyacid-modified resin composites (F2000 and Freedom) over 1 year. Nineteen patients with at least three cervical lesions were selected, providing an initial sample size of 87 restorations (29 per material), being 78 to non-carious and nine to carious lesions. Restorations were evaluated at baseline, 6 months and 1 year after placement, using modified US Public Health Service criteria: colour match, marginal discoloration, caries, anatomical form, marginal integrity and surface texture. At baseline, restorations were considered as acceptable for all criteria. At 1-year recall, 21 restorations per material were re-examined. Freedom was rated Bravo or Charlie for all the examined criteria and Vitremer earned an Alfa rating solely for the criterion caries. On the contrary, F2000 showed the best overall results, although presenting significant alteration in colour match. Statistical analysis of data was performed using chi-square and Mc Nemar tests. As to the evaluated periods, significant difference was observed solely between baseline and 1-year recall. Freedom and Vitremer were statistically different (P < 0.01) as to anatomical form and surface texture. For F2000, significant difference (P < 0.05) was noticed as to colour match and anatomical form. After 1-year follow-up, F2000 showed the most acceptable results as to the analysed criteria.

Adult↗
PubMed1999

Organic leachables from polymer-based dental filling materials.

Results are reported from a study on the in vitro separation and identification of leachables from three different polymer-based dental filling materials by using a combined method of gas chromatography and mass spectrometry. The median number of separable organic leachables in these materials was between 14 and 22. Of these organic leachables the following were identified and quantified: DL-camphorquinone, 4-dimethylaminobenzoic acid ethyl ester (DMABEE), drometrizole, 1,7,7-trimethylbicyclo[2,2,1]heptane, 2,2-dimethoxy[1,2] diphenyletanone (DMBZ), ethyleneglycol dimethacrylate (EGDMA), and triethyleneglycol dimethacrylate (TEGDMA). Three of the leachables have previously been shown to provoke allergy. The range of log P(ow) values (representing the lipophilicity of these compounds) varied between 1.09 and 4.20. By multivariate data analysis, selected leachables from the tested materials were shown to separate into characteristic patterns. The results contribute to a characterization of potential hazardous compounds in polymer-based dental filling materials.

4-Aminobenzoic Acid↗
PubMed1998

Effects of finishing/polishing time on surface characteristics of tooth-coloured restoratives.

This study compared the effects of immediate and delayed finishing/polishing procedures on the surface characteristics (surface roughness and hardness) of tooth-coloured restoratives including a microfilled, a heavily filled and a polyacid-modified composite resin and a resin-modified glass-ionomer cement. Eighty-four specimen discs were made for each material; the first 12 were used as controls and the remaining 72 specimens were randomly divided into two equal groups. The first group was finished/polished immediately after light polymerization and stored for 1 week in distilled water at 37 degrees C while the second group was finished/polished after 1 week storage in distilled water at 37 degrees C. Finishing and polishing was carried out using the following systems: Enhance system, white stones with Vaseline and Super-snap disks system. The finished/polished surfaces were subjected to profilometric evaluation and microhardness testing. The effects of delayed finishing/polishing procedures on surface roughness and hardness appear to be both material and technique dependent. Delayed finishing/polishing of polyacid-modified composite resins and resin-modified glass-ionomer cements generally resulted in a smoother surface. The surface roughness of composite resins after finishing/polishing procedures were generally not influenced by the finishing/polishing time. For all materials, delayed finishing/polishing with the various techniques generally resulted in a surface of similar hardness to or harder than that obtained with immediate finishing/polishing and the control group.

Bisphenol A-Glycidyl Methacrylate↗
PubMed1998

Marginal leakage in class II-restorations after use of ceramic-inserts luted with different materials.

The efficiency of using prefabricated ceramic inlays to prevent microleakage has been discussed in different investigations. The purpose of this study was to evaluate the marginal microleakage of a new glass ceramic inlay system in combination with two different composite luting materials and one polyacid-modified composite, respectively. Standardized class II cavities (n = 60) were filled with (1) Empress inlays fixed with a highly viscous luting composite as a control group, and with glass ceramic inlays (Cerana) in combination with (2) a highly viscous luting composite, (3) a low-viscous luting composite and (4) a polyacid-modified composite, respectively. After thermocycling the marginal quality was analysed with scanning electron microscopy, and the dye penetration along the cavity walls was measured. The use of the Cerana inlays with a polyacid-modified composite resin did not reveal a good marginal adaptation. However, the combination of the Cerana and the Empress inlays with the highly viscous composite exhibited a comparable marginal fit. Within the limitations of an in vitro study it is concluded that the combination of the new glass ceramic inlays with a polyacid-modified composite cannot be recommended for clinical use.

Aluminum Silicates↗
PubMed1998

Changes on storage of polyacid-modified composite resins.

Two polyacid-modified composite resins, Dyract and Compoglass, have been studied for water-uptake on storage in three aqueous media, namely pure water, 0.9% NaCl and 1 M NaCl at 37 degrees C, and the results compared with those of a conventional composite resin, Pekafill. The equilibrium water-uptake of Dyract and Compoglass varied depending on time of cure and ionic strength of the storage medium. This latter finding contrasted with that for Pekafill, where equilibrium water content showed almost no variation with ionic strength of the storage medium. Uptake of water was always greater in Dyract and Compoglass than in Pekafill, reflecting the role of water in promoting the later neutralization reaction in these materials and its further role in hydrating the ionic products of that reaction. Despite this and other evidence of neutralization, specimens of Dyract and Compoglass stored in wet conditions (0.9% NaCl) showed no change in compressive strength on storage from 24 h to 30 days, a result similar to that reported previously for Dyract alone for flexural strength for times up to 1 year. By contrast, specimens of Dyract and Compoglass stored in dry air at 37 degrees C, and therefore unable to undergo any neutralization, showed an increase in compressive strength of between 40 and 70 MPa by 30 days that was significant at P < 0.01.

Air↗
PubMed1999

The properties of polymerizable luting cements.

The properties of a polyacid-modified composite resin and two resin-modified luting cements have been studied. The polyacid-modified composite resin had the slowest setting reaction and, in this respect, it did not conform to the current international standard for luting cements. The compressive strength of all of the materials was studied after varying periods of storage from 24 h to 1 year. The polyacid-modified composite resin showed a distinct dip in strength at 1 month in all of the storage media, but otherwise it showed no significant variation with either age or storage medium. The resin-modified glass-ionomers showed variation at 24 h with storage medium (deionized water, 0.9% NaCl or 20 mmol dm(-3) lactic acid), but thereafter they showed little variation, until 1 year, when Vitremer luting showed a significant decline in strength in pure water. However, at 24 h and when stored in water, all of the materials had strengths that easily exceeded the minimum requirement of the current standard (70 MPa). They all took up water on storage, with diffusion coefficients ranging from 1.32 to 17. 19x10(-7) cm2 s(-1). These values were found to depend on whether the specimens were stored in pure water or in physiological saline. However, equilibrium water contents varied only slightly between water and saline. The polyacid-modified composite resin, Dyract-Cem, took up the least water, as well as showing the smallest variation in strength with age. By contrast, it was more difficult to mix than the other materials and the high viscosity of the paste led to the formation of voids and other imperfections in the specimens.

Compomers↗
PubMed2000

The effect of polishing systems on microleakage of tooth-coloured restoratives. Part 2: composite and polyacid-modified composite resins.

The purpose of this in vitro study was to investigate the effect of polishing systems on the microleakage of composite and polyacid-modified composite resins. Class V cavities were prepared at the cemento-enamel junction of 80 freshly extracted posterior teeth. The prepared teeth were randomly divided into two groups and restored with conventional or polyacid-modified composite resins. The restored teeth were stored in distilled water at 37 degrees C for 1 week after removal of excess restorative with diamond finishing burs. The restored teeth were then divided into four groups of ten and finished/polished using the following systems: Two Striper micron finishing system (MFS), Sof-Lex XT (Sof-Lex), Enhance composite finishing and polishing system (Enhance), and Shofu composite finishing kit (Shofu). The finished restorations were subjected to dye penetration testing. Results showed that the microleakage resistance at both enamel and dentin margins of composite and polyacid-modified composite resins are not significantly affected by the different polishing systems.

Adhesives↗