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PubMed2003

Effect of storage time on microtensile strength of polyacid-modified resin composites.

OBJECTIVE: The purpose of this study was to determine the cohesive microtensile strength of four polyacid-modified resin composites (PAMRC: Dyract, Dyract AP, Freedom and F2000) after 24h and 6 months of storage in water using the microtensile technique. METHODS: Blocks measuring 1.5 cm x 1.5 cm x 1.0 cm were constructed incrementally for each material using a silicone matrix. The blocks were stored in distilled water at 37 degrees C for 24 h and were then serially sectioned in both x and y directions to obtain several beams measuring 1.0 cm x 1.0 mm x 1.0 mm. Each beam was gently trimmed from two sides with ultra-fine diamond burs to reduce the cross-sectional area to a 'neck' of approximately 0.4mm(2) located in the middle of their length. The beams (18-22 per material) were randomly divided and tested in tension either after 24 h or after 6 months of storage in water at 37 degrees C in a Vitrodyne testing machine at 0.6 mm/min. RESULTS: Mean microtensile strengths (MPa) at 24 h were: 48.7+/-13.8 for Dyract AP; 36.5+/-14.1 for Dyract; 38.2+/-14.5 for Freedom and 48.6+/-7.2 for F2000. There was no statistically significant difference among the materials (p>0.05). At 6 months, only Dyract AP showed significant increase in microtensile strength (p<0.05) while the other materials showed no differences in microtensile strength with time (p>0.05). SIGNIFICANCE: The results indicate that storage in water for 6 months caused no reduction of the microtensile strength of PAMRC materials.

Analysis of Variance↗
PubMed2003

A 6-year clinical evaluation of Class I poly-acid modified resin composite/resin composite laminate restorations cured with a two-step curing technique.

OBJECTIVE: Polymerization shrinkage is still one of the main disadvantages of resin composite restorations (RC). Especially in cavities with a high C-factor, debonding can occur. A laminate restoration including a base with a more elastic behavior might result in a better adaptation. The purpose of this study was to evaluate the durability of a combination of two techniques suggested to counter the stress formation in direct RC restorations in cavities with the highest C-factor. METHODS: Each of the 29 patients received one or two pair(s) of Class I restorations. The first restoration was a poly-acid modified resin composite/resin composite (PMRC/RC) sandwich restoration and the second a direct RC restoration. Both restorations, except for the PMRC layer, were placed with oblique layering and two-step curing technique. Ninety restorations, 23 premolar and 67 molars, were evaluated annually with slightly modified USPHS criteria during 6 years. RESULTS: At 6 years, 41 pairs were evaluated. A cumulative failure rate of 2.4% was observed for both the RC and the laminate restorations. One laminate restoration showed non-acceptable color match, but was not replaced and one RC restoration showed non-acceptable marginal adaptation. Two cases of slight postoperative sensitivity were observed in one patient. Three restorations were partially replaced due to primary proximal caries. SIGNIFICANCE: A high durability for and no differences, were observed between both restorative techniques in Class I cavities.

Adult↗
PubMed2003

Strengthening effect of aluminum fluoride added to resin composites based on polyacid-containing polymer.

OBJECTIVES: The study investigates the possible strengthening effect of aluminum ions liberated during long-time water storage of experimental resin composites containing a polymer with carboxylic acid groups. METHODS: The organic part of the resin composites was formed by photopolymerization of methacrylate monomers. The monomer mixture was composed of UEDMA, HEMA or TEGDMA, and 0-40 mol% HEMAN (the adduct of HEMA and maleic anhydride). The filler part of the resin composites consisted of a conventional silanated glass filler and 1 or 5 wt% of AlF3 x 3H2O. The rupture strength and bending modulus were measured without water storage and after 1 month, 1 year, and 3 years of water storage at 37 degrees C of the resin composite. RESULTS: The experimental composites that had been stored in water had lower rupture strength and modulus than the composites that were tested without water storage. Specimens containing 30 or 40 mol% HEMAN increased in strength, and specimens containing 20, 30, or 40 mol% HEMAN increased in modulus during the period of water storage. Depending on composition, values for strength and modulus obtained after 3 years of water storage was up to 50% higher than the values obtained after 1 month. SIGNIFICANCE: The strengthening effect of aluminum fluoride may be interpreted as the result of increased crosslinking by aluminum ions and carboxylate groups. The results may serve as a basis for the improvement of the mechanical properties of polyacid-modified resin composites.

Aluminum Compounds↗
PubMed2004

Marginal and flexural integrity of three classes of luting cement, with early finishing and water storage.

OBJECTIVES: The aims of this investigation were to clarify the effects of finishing-time and 24 h water-storage on mechanical properties and marginal adaptation to dentin of seven modern luting cements, representing three chemical types. METHODS: Bistite II, Chemiace II, Compolute, XenoCem, PermaCem, Fuji Cem and Fuji Plus were investigated with specimen sub-groups (N=10) for each property measured. The principal series of experiments was conducted in dentin cavities with interfacial polishing either immediately (3 min) after setting or after 24 h water-storage. After the finishing procedure, the maximum marginal gap width and the opposing width (if any) per cavity were measured microscopically, and summed. Then the overall sum of gap-widths (per group; N=10) was calculated. Marginal gaps were similarly measured in Teflon cavities, together with shear-bond-strengths to dentin and early flexural strengths, moduli and swelling data. RESULTS: For specimen-sets polished immediately after setting, summed marginal gaps of 23-121 microm were observed, for all luting cements except Compolute. A significantly different (p<0.05) result of either no gap or 6-28 microm summed gap-widths occurred in specimens polished after 24 h. For all materials, their shear-bond-strengths, flexural strength and moduli significantly increased after 24 h storage. SIGNIFICANCE: The marginal behavior can be interpreted in terms of the contributions of bonding, shrinkage, swelling and compliance of components, along with compositional features of the cements. With these types of cement it is generally inadvisable to polish the interfacial luting surface immediately after cementing. The polishing procedures should be carried out not less than 24 h later. One resin-cement was able to withstand immediate finishing.

Bicuspid↗
PubMed1996

Resin-modified glass ionomer cements: bonding to enamel and dentin.

OBJECTIVES: This study was designed to investigate the effect of storage in water on bonding efficacy to enamel and dentin of four resin-modified (Dyract, De Trey Dentsply; Fuji II LC, GC Dental Corp.; Photac Fil, ESPE; Vitremer, 3M Dental Products), one conventional glass ionomer filling material (Ketac Fil, ESPE) and a resin composite system (Pekafill/Gluma bonding system, Bayer). The hypothesis was that water storage would lead to an adverse effect on bond strength of resin-modified glass ionomer cements to enamel and dentin. METHODS: The shear bond strength of each material was determined after storage periods of 24 h, 1 wk, 1 mon, 3 mon and 6 mon. The data were subjected to one-way ANOVA. Significant differences were determined by multiple comparison testing (significance level 5%). The failure modes of the debonded specimens were analyzed with a dissecting microscope. RESULTS: Shear bond strengths to enamel for Dyract, Photac Fil and Pekafill were 5.2 +/- 1.3, 9.9 +/- 1.6 and 17.0 +/- 2.3 MPa, irrespective of storage time (p > 0.05). For Ketac Fil, the average shear bond strength between 1 wk and 6 mon was 4.5 +/- 1.7 MPa, the mean value for Fuji II LC between 24 h and 3 mon was 10.3 +/- 3.9 MPa and after 6 mon was 19.8 +/- 4.4 MPa, while Vitremer showed increasing shear bond strengths between 24 h (2.4 +/- 0.8 MPa) and 1,3 and 6 mon (13.8 +/- 4.3 MPa). Shear bond strengths to dentin were not adversely affected by storage throughout the 6 mon for Dyract (13.0 +/- 2.6 MPa), Fuji II LC (12.7 +/- 1.7 MPa) and Pekafill (14.6 +/- 3.1 MPa), when tested by ANOVA (p > 0.05). Ketac Fil showed 4.9 +/- 1.2 MPa between 1 wk and 6 mon and lower shear bond strength after 24 h. The average shear bond strengths up to 1 mon for Vitremer were 5.4 +/- 2.5 MPa (p > 0.05). However, at 3 and 6 mon immersion in water, three specimens had loosened spontaneously. With Photac Fil, no adhesion to dentin was registered. Most samples showed cohesive failure patterns in the restorative materials. Adhesive or mixed failures were registered only for Vitremer on dentin and enamel up to 1 wk and for Dyract on enamel. SIGNIFICANCE: Long-term water storage generally had no adverse effect on bonding efficacy of resin-modified glass ionomer cements to dentin and enamel.

Acid Etching, Dental↗
PubMed1996

Long-term mechanical characteristics of resin-modified glass ionomer restorative materials.

OBJECTIVES: The purpose of this study was to compare the effects of long-term water storage on the mechanical characteristics of four resin-modified glass ionomer restorative materials with those of a conventional glass ionomer cement and a resin composite material. METHODS: Cylindrical specimens were prepared and stored in water for 1 h, 24 h, 1 wk, 1 mon, 3 mon and 6 mon prior to determination of diametral tensile strength (DTS) and depth of surface indentation both under 1 N load and after removal of the load. RESULTS: Diametral tensile strength was lowest for the conventional glass ionomer cement and highest for the composite; the resin-modified glass ionomer cements were intermediate between the reference materials. Water storage reduced DTS between 24 h and 1 wk or 1 mon but then remained unaffected until the final measurements after 6 mon. The materials showed a trend toward a slight increase in the depth of indentation both under load and after removal of the load with increasing storage time. These mechanical properties indicate the position of four resin-modified glass ionomer cements on a continuum with conventional glass ionomer cement and resin composite as the end points. SIGNIFICANCE: The mechanical properties of resin-modified glass ionomers show that this group of materials is weaker than resin composite but stronger than conventional glass ionomer cement. Water storage for 6 mon has little adverse effect on the mechanical properties.

Analysis of Variance↗
PubMed1998

Marginal adaptation and retention of a glass-ionomer, resin-modified glass-ionomers and a polyacid-modified resin composite in cervical Class-V lesions.

OBJECTIVES: An 18-month follow-up clinical trial of one conventional glass-ionomer (HIFI Master Palette), three resin-modified glass-ionomers (Fuji II LC, Vitremer, 3M Exp. 155) and one polyacid-modified resin composite (Dyract) was conducted to evaluate their clinical effectiveness in Class-V cervical lesions. In addition, the interface between dentin and two resin-modified glass-ionomers and one polyacid-modified resin composite was examined by scanning electron microscopy (SEM). METHODS: After evaluation of the restorations immediately following placement (baseline), all patients were subjected to a strict recall schedule with controls at 6, 12 and 18 months. The clinical effectiveness was recorded in terms of retention and marginal integrity, clinical microleakage, caries recurrence, and tooth vitality. A chi 2-test (p < 0.05) was used to test for significant differences between materials. In case of restoration loss or special defects, a replica was made to examine the surface texture and restoration margins by SEM. In vitro, the interface was examined by SEM after an argon-ion-beam etching technique was used to enhance surface relief and disclose interfacial substructures. RESULTS: Retention appeared to be good for all the materials tested. Marginal discrepancies were localized at the incisal enamel and/or the cervical dentin margin, except for the polyacid-modified resin composite that showed most of the defects at the incisal enamel margin. None of the systems could guarantee margins free of microleakage for a long time. In vitro, the type of dentin pre-treatment defines to a great extent the morphology of the resultant interface between dentin and the restorative material tested. SIGNIFICANCE: In this clinical study, the retention rate of the tested materials was good and even excellent for some products. Perfect marginal adaptation deteriorated too fast. The marginal adaptation of the polyacid-modified resin composite at the enamel site would probably have been better by the use of selective enamel or total acid etching. Marginal sealing remains a problem. Future research should concentrate on improving the marginal adaptation and sealing capacities before a broader clinical use can be advocated.

Acrylic Resins↗
PubMed1999

Comparative study of the physical properties of a polyacid-modified composite resin and a resin-modified glass ionomer cement.

OBJECTIVES: The physical properties of the resin-modified composite resin Dyract (Detrey Dentsply) and the resin-modified glass ionomer cement Fuji II LC (GC) were compared, and the effect of water sorption on these properties was studied. METHODS: Compressive, diametral compressive and flexural strengths were measured using specimens aged up to three months. The Vickers hardness and the water erosion were also determined. The specimens were stored at 37 degrees C under five different conditions, chosen to vary the water sorption of the samples. The results were analyzed using a multi-factor analysis of variance. RESULTS: Dry specimens of Dyract and Fuji II LC showed similar properties. However, the two materials behaved differently when stored in presence of water. In contrast to Fuji II LC, Dyract showed very little expansion for the first 24 h (1.5 +/- 0.3 and 0.03 +/- 0.01%, respectively), leached small quantities of ions and retained its mechanical strength. Those differences are related to their chemical composition. Fuji II LC is hydrophilic, as it contains polyHEMA. In the presence of water, Fuji II LC behaves like a hydrogel, but the network resulting from the copolymerization of acidic and UDMA monomers is less hydrophilic, and the effect of water on Dyract is retarded. SIGNIFICANCE: The significant properties of Dyract are determined by its composite character. This certainly represents some advantages, for instance, a higher mechanical strength, a better protection against initial dehydration and subsequent water effects. However, Dyract shows some disadvantages over Fuji II LC, like a lower amount of fluoride release or the interference of oxygen during polymerization.

Absorption↗
PubMed1999

Measurement at low strain rates of the elastic properties of dental polymeric materials.

OBJECTIVE: To evaluate a simple static test (i.e. a slow strain rate test) designed to measure Young's modulus and the bulk modulus of polymeric materials (The NOL Test). Though it is a 'mature' test as yet it has never been applied to dental materials. METHODS: A small cylindrical specimen is contained in a close-fitting steel constraining ring and compressive force applied to the ends by steel pistons. The initial (unconstrained) deformation is controlled by Young's modulus. Lateral spreading leads to constraint from the ring and subsequent deformation is controlled by the bulk modulus. A range of dental materials and reference polymers were selected and both moduli measured. From these data Poisson's ratios were calculated. RESULTS: The test proved be a simple reliable method for obtaining values for these properties. For composite the value of Young's modulus was lower, bulk modulus relatively similar and Poisson's ratio higher than that obtained from high strain rate techniques (as expected for a strain rate sensitive material). SIGNIFICANCE: This test does fulfil a requirement for a simple test to define fully the elastic properties of dental polymeric materials. Measurements are made at the strain rates used in conventional static tests and values reflect this test condition. The higher values obtained for Poisson's ratio at this slow strain rate has implications for FEA, in that analysis is concerned with static or slow rate loading situations.

Benzophenones↗
PubMed2000

Effect of maturation on the fluoride release of resin-modified glass ionomer and polyacid-modified composite resin cements.

The effect of an early water contact on the fluoride release is studied for the resin-modified glass ionomer cements (RM-GIC) GC Lining LC, PhotacBond, Vitremer and Vitrebond and for the polyacid-modified composite resins (PAM-C) Variglass and Dyract. Six months fluoride release profiles were determined in regularly renewed water (37 degrees C), for the products directly after light curing and after 24 h maturation in a humid atmosphere (85% RH). ANOVA shows that both the short-term and the long-term fluoride release of a RM-GIC are influenced by this maturation. This indicates that direct water contact for this material should be avoided. For the RM-GIC a correlation is found between the initial fluoride release process and the long-term process. For the PAM-C materials, no differences in the fluoride release are found as a function of maturation, indicating that early water contact has no effect. The amounts of fluoride released by PAM-C are low compared to RM-GIC, which can affect their caries preventive potential. The results are explained on the basis of the setting reaction of both types of materials.

Acrylic Resins↗
PubMed2000

Effect of a neutral citrate solution on the fluoride release of resin-modified glass ionomer and polyacid-modified composite resin cements.

The effect of 0.01 mol/l citrate solution at pH = 7 on the fluoride release is compared for the resin-modified glass ionomer cements (RM-GIC) GC Lining LC, PhotacBond, Vitremer and Vitrebond and for the polyacid-modified composite resins (PAM-C) Variglass and Dyract by means of the six-month fluoride release profiles at 37 degrees C. The fluoride release of both RM-GIC and PAM-C increases in the neutral citrate solution as compared to water, which can be explained by the ability of citrate to complex metal ions and hence to degrade the glass as well as the polysalt matrix of the cement. Although RM-GIC release more fluoride than PAM-C in water as well as in citrate solution, the relative increase in fluoride release upon immersion in citrate solution is most pronounced for PAM-C. Whereas for the latter citrate affects both the short-term and long-term fluoride release, for RM-GIC only the long-term fluoride release is affected. This suggests that the action of citrate increases with decreasing importance of the polysalt formation in the hardening of the material. This could be explained on the basis of the difference in the chemical properties of the cement matrix.

Acrylic Resins↗
PubMed1999

Blood-compatibility of polyurethane/liquid crystal composite membranes.

Polyurethane/liquid crystal composite membranes were first suggested to be used as biomaterials. In our work, three series of polyurethane/liquid crystal composite membranes based on three different kinds of liquid crystal compounds [N-(-4-methyoxybenzylidene)-4'-heptylaniline, 4-pentyl-4'-nitrile-biphenyl and cholesteryl oleyl carbonate] were prepared by casting on glass plates from a tetrahydrofuran (THF) solution of polymer and liquid crystal at room temperature. In our opinion, the formation of liquid crystal phase on the composite membrane surface is the basic requirement for getting better biomaterial. The result of this work is in accordance with our opinion. The effect of liquid crystal content on the formation of liquid crystal phase was identified by the observation of optical polarization microscopy (OPM). The results showed that the content of liquid crystal in composite membrane must be more than 30% (wt) in order to form liquid crystal phase on the composite membrane surface. The blood-compatibility of the composite membranes was assessed from SEM observation of the platelet's adhesion to membrane's surface, blood clotting time and haemolysis ratio. The observation of platelet's adhesion showed that the platelets gathered together on the pure polyurethane films, but the amount of platelets which were adherent on the surface covered by the liquid crystal phase was fewer than that of pure polyurethane film when platelet-rich plasma was allowed to be in contact with the membranes for 1 h at room temperature. The determination of blood clotting time and haemolysis ratio showed that these polyurethane/liquid crystal composite membranes, in which the content of liquid crystal was more than 30% (wt), appear to be beneficial in improving the blood compatibility and reducing the thrombogenicity.

Biocompatible Materials↗
PubMed2001

Mineralization in bovine dentin adjacent to glass-ionomer restorations.

OBJECTIVES: To assess the uptake of fluoride as well as the increase in mineralization by bovine dentin after restoring an experimentally made cavity with conventional glass-ionomer cement or a polyacid resin composite. METHODS: Cylindrical cavities were prepared on the labial root surfaces in bovine dentin. The cavities were restored with the test material. The restored teeth were individually suspended in distilled water at 37 degrees C for 30 days. The teeth were sectioned and the superficial dentin cavity walls were analyzed for fluoride, calcium, and phosphorus by an EPMA device. The effects of the different fluoride-releasing materials on the hardness of the dentin were determined by indentation (20-microm intervals below the filled surface into the underlying sound dentin from the surface to a depth of 100microm). RESULTS: Conventional glass-ionomer cement had a significant effect on fluoride uptake. In addition, the calcium and phosphorus scan revealed the elevation of calcium and phosphorus levels in a deeper zone corresponding to the locations of the fluoride uptake at the surface of axial wall. However, the polyacid resin composite did not exhibit a zone of calcium and phosphorus elevation. The average dentin hardness under conventional glass-ionomer cement in the studied five distances ranged from 84.3 to 61.3KHN, however, that of the polyacid resin composite ranged from 62.5 to 64.9KHN. Analysis of variance for these data demonstrated a significant difference in hardness between the 20-microm depth and the other depths (P<0.01, ANOVA Fisher's PSLD). CONCLUSION: The present paper indicates that the fluoride penetrated deeper into the dentin with conventional glass-ionomer cement than the polyacid resin composite. Conventional glass-ionomer cement had a significant effect on fluoride uptake. In addition, hypermineralization occurred within the superficial dentin cavity wall region of conventional glass-ionomer cement.

Analysis of Variance↗
PubMedDate not supplied

Cariostatic effect of fluoride-containing restorative systems associated with dentifrices on root dentin.

OBJECTIVE: The aim of this in vitro study was to evaluate the interaction between two sources of fluoride (restorative systems and dentifrices) in inhibiting artificial root caries development. METHODS: One hundred and eighty tooth segments were embedded in polyester resin, and sanded flat. Cylindrical cavities 1.0mm-deep and 1.5mm-diameter were prepared in root dentin and randomly restored by fluoride-containing restorative systems: Ketac-fil/Espe (Ke), Fuji II LC/GC Corp (Fj), F2000/3M (F2), Surefil/Dentsply (Su) or a control: Filtek Z250/3M (Z2). Ten experimental groups were made to test the association among the five restorative systems and two dentifrices: with F(-) (Sensodyne Baking Soda) or without F(-) (Sensodyne Original) (n=18). After surface polishing, a 1mm-wide margin around the restorations was demarcated and initial dentin surface Knoop microhardness values (KHN(i)) were obtained. The specimens were submitted to a pH-cycling model, and to applications of slurries of dentifrice. Afterwards the final dentin surface Knoop microhardness values (KHN(f)) were measured. RESULTS: The differences between KHN(i) and KHN(f), and the covariate KHN(i) were considered by the ANCOVA and Tukey's test (alpha=0.05). The interaction between restorative system and dentifrice was statistically significant (p=0.0026). All restorative systems provided some protection against artificial caries challenge when associated with the fluoride-containing dentifrice treatment. The means (standard deviation) of reductions in Knoop hardness values for systems associated with the fluoride-containing dentifrice were: Ke: 40.0(1.02)(a), Fj: 41.9(1.02)(b), F2: 43.3(1.04)(c), Su: 43.5(1.00)(c), Z2: 44.0(1.02)(c); and with the non-fluoride-containing dentifrice were: Ke: 42.9(1.02)(a), Fj: 44.7(1.01)(b), F2: 45.2(1.09)(bc), Su: 46.0(0.99)(c), Z2: 46.6(0.99)(c) (statistical differences were expressed by different letters). CONCLUSION: The cariostatic effect shown by the fluoride-containing dentifrice could enhance that shown by Ketac-fil and Fuji II LC, and could mask that shown by F2000.

Analysis of Variance↗
PubMed2003

Sorption and solubility of resin-based restorative dental materials.

OBJECTIVES: To measure the water sorption and solubility of different resin-based restorative dental materials. METHODS: Eight commercial restorative materials were selected: two resin composites (Z100 and Prodigy), four polyacid-modified resin composites (Compoglass, Compoglass F, Dyract and Dyract AP), and two light-cured glass ionomers (Vitremer and Fuji II LC). Five disc specimens were prepared of each material, following the manufacturer's instructions, and were grounded wet with silicon carbide paper. Water sorption and solubility of the different materials were calculated by means of weighting the samples before and after water immersion and desiccation. Data were analyzed by one-way ANOVA and Student-Newman-Keuls tests (P<0.05). RESULTS: Compoglass and Compoglass F showed the lowest values of water sorption and solubility, while Vitremer and Fuji II LC displayed the highest values. Solubility values of Prodigy, Z100, Dyract and Dyract AP did not show significant differences among them, while their water sorption values attained some differences and were lower for Prodigy followed by Dyract and Z100. CONCLUSIONS: The attained water sorption and solubility values are mainly influenced by the generic type of material and variations occurring between materials of the same type may result from differences in resin matrix compositions.

Absorption↗
PubMed2003

Fluoride release from orthodontic cements-effect of specimen surface area and depth.

OBJECTIVE: The aims of this in vitro study were firstly to compare fluoride release from a disc model of two orthodontic cements with various surfaces varnished, reducing the surface area by 25, 50 and 75%; secondly, to measure the fluoride release from previously exhausted discs of the same cements following removal of various depths of surface material. METHODS: Forty discs of each cement, Fuji Ortho LC and Ultra Band-Lok, (6mm diameter by 3mm) were divided into two groups of 20 discs each. For each material, the first group was divided further into four groups of five discs, one group acting as control, while the other three groups were varnished reducing the surface area by 25, 50 and 75%, respectively. The second group was exhausted initially over a 60 day pre-experimental period and was subsequently divided into four groups of five discs, one group acting as control. The other three groups had material ground from one of the flat surfaces, to depths of 10, 100 or 1000 microm, to reveal a fresh surface. In both studies, the discs were immersed either daily (up to day 20) or twice weekly (up to day 60) in fresh 2ml aliquots of deionised water. The fluoride concentration in the deionised water was measured at the end of the experimental period. RESULTS: For each cement, the relationship between the cumulative fluoride release and the percentage of the surface covered was clearly non linear at both 5 and 60 days. Fuji Ortho LC proved to release significantly greater amounts of fluoride at both 5 days and 60 days compared with Ultra Band-Lok. The results for Ultra Band-Lok were also significant when compared to the control group, but significantly less fluoride was released when compared with Fuji Ortho LC. When comparing the 25 and 50% covered discs, the amount of fluoride released was not significantly different for both cements. Furthermore, the relationship between fluoride release and depth was clearly non linear for both cements. CONCLUSIONS: For the materials tested in this study, reducing the surface area of the discs did not reduce the cumulative fluoride release in a linear fashion. In addition, the previously exhausted discs began to release fluoride again, but this fell to concentrations similar to the control discs after the initial 5-day period for both cements. This suggests that further traces of previously unreleased fluoride had become available from the subsurface of these cements. The pattern of fluoride release was similar for all models tested.

Acrylic Resins↗
PubMed2003

Fluoride release from orthodontic band cements-a comparison of two in vitro models.

OBJECTIVES: To compare, in vitro, the fluoride release from a conventional glass ionomer cement (Ketac-Cem), a resin-modified glass ionomer cement (3M-Multicure) and a polyacid modified composite (Ultra Band-Lok) using a banded tooth model and a disc model with the same mean cement weight. METHODS: Forty pairs of caries-free third molars were collected and divided into two groups, each of 20 teeth. One tooth from each pair was banded with Ketac-Cem and the other with Ultra Band-Lok or 3M-Multicure; the average band size for each cement group was the same. Two coats of nail varnish were painted on each tooth to within 1mm of the band margin. Five discs (4.5mm diameter and 2mm depth) were prepared for each cement, these dimensions having been calculated so that the mean cement weight of the banded tooth model matched that of the disc model for each cement. The fluoride released into 2ml of deionised water, from each banded tooth or disc, was measured at regular intervals over 30 days using an Orion ion-selective electrode connected to an ion analyser. RESULTS: At 30 days, for both banded tooth and disc models, the mean cumulative fluoride release was greatest from 3M-Multicure followed by Ketac-Cem, which in turn released more fluoride than Ultra Band-Lok. These differences were all significant (p<0.05). Despite having the same mean cement weight, the banded tooth model for Ketac-Cem and 3M-Multicure released approximately 3-4 times more cumulative fluoride than the disc model after 30 days (p<001). For Ultra Band-Lok, both models released comparable levels of fluoride (p>0.05). CONCLUSIONS: Cement type, specimen geometry and surface area appear to influence significantly fluoride release characteristics.

Cariostatic Agents↗
PubMed2000

Three-year clinical evaluation of a polyacid-modified resin composite in minimally invasive occlusal cavities.

OBJECTIVE: The aim of this study was to evaluate the 3-year clinical performance of one polyacid-modified resin composite material (PMRC). Dyract, in minimally invasive occlusal cavities and its neighbouring fissures. METHODS: One hundred and sixteen restorations of the material investigated were placed by a single operator in a group of selected children under controlled conditions. Isolation of the restorations was accomplished with the use of cotton rolls and aspiration. Using modified US Public Health Service (USPHS) codes and criteria, the restorations were reviewed clinically within 1 week of placement (baseline), and thereafter at 6 months, 1, 2 and 3 years. RESULTS: After 3 years, marginal discolouration was present in 8.6% of the restorations. The marginal adaptation was rated as partly sealed (Oscar-Alpha) in 107 (92.2) of the restorations. Five restorations had lost their sealant components, while four restorations were partly sealed with explorer-catch after 3 years. Although wear of the restorations was considerable, restorations rated as 'partly sealed' had at least two-thirds of their sealant components fully retained. Recurrent caries was associated with four (3.4%) restorations. CONCLUSION: In this clinical study, the retention rate of the tested PMRC material was good, although a marked occlusal wear was evident. The marginal adaptation of the PMRC at the enamel site would probably have been better by the use of enamel-etching. Provided the marginal adaptation and wear resistance of the material is further improved, clinical use of PMRCs in minimally invasive occlusal cavities can be advocated.

Child↗