Ionomer Group Research Articles

Sealants revisited: An efficacy battle between the two major types of sealants – A randomized controlled clinical trial

The aim of this study is comparing the retention and caries preventive effect of the glass-ionomer fissure sealant and resin-based fissure sealant. A randomized-controlled split-mouth study was conducted to compare the retention and the caries preventive effect of light-cured resin-based sealant (3M ESPE) and glass ionomer sealant (Fuji VII). The sealants were applied to either the right or the left lower mandibular molars (7-9 yrs of age) in 120 school children, based on the randomization process. They were recalled for assessment of clinical retention at intervals of 3, 6, and 12 months. The caries-preventive effect between the two materials was tested statistically by the McNemar's test for matched pairs, and the differences observed with regard to the retention of the materials was tested by Chi-square tests. The level of significance was set to be at P < 0.05. At the end of 12th month, sealant retention is found to be higher in the resin-based sealant group compared to the glass ionomer group. In the glass ionomer sealants placed, 101 (91%) were caries-free and 10 (9%) had caries. In the resin-based sealant, 105 (94.60%) had sound teeth and 6 (5.4%) had dental caries (P = 0.34). The glass ionomer sealant was less retentive when compared to resin sealants. The caries incidence between the glass ionomer and resin-based sealants was not statistically significant.

Effect of mouthwashes on the integrity of composite resin and resin modified glass ionomer: In vitro study.

BackgroundThe constant search for an improved esthetic dental material has led investigators to realize that its performance depends on the conditions where the material is used. It has been probed that the contact with mouth rinses triggers alterations, reason why the aim of this study was to identify their possible effects of it on the integrity of nanohybrid composite resin and resin modified glass ionomer.Material and MethodsA total of 144 samples were manufactured with two nanohybrid composite resins and two resin modified glass ionomer restorative materials. The specimens were immersed in one of the three mouthwashes used in the study, for a total of 1092 minutes, with intervals of contact with artificial saliva. This strategy simulates three years of constant use of mouthwashes. The samples weight and surface roughness measurement was recorded with a precision scale and profilometer, at different stages: At the beginning of the study, after 546 minutes (simulating one and a half year), and after 1092 minutes (simulating three years).ResultsThe collected data on surface roughness and weight were submitted to the analysis of variance (ANOVA), with repeated measures of three factors. The results determined shifts in values in terms of weight and roughness in all the samples. The composite resin “Grandio” group was the one that showed bigger shifts, while the glass ionomer group “Vitremer” showed stability on its structure. The evaluated mouthwashes displayed similar behavior between each other.ConclusionsThe use of mouthwashes triggered changes on the structure of both dental materials: composite resin and resin modified glass ionomer mostly associated with surface roughness. Key words:Glass ionomer, composite resin, mouthwash, roughness, degradation.

Assessment of Microleakage Using Dye Penetration Method in Primary Teeth Restored with Tooth-colored Materials: An In Vitro Study

The present study aimed to assess the microleakage in primary teeth restored with tooth-colored materials using the dye penetration method. A total of 60 healthy primary molar teeth were included in this study and standardized class II mesio-occlusal cavities were prepared on the samples. Consequently, these teeth were randomly divided into three experimental groups (n = 20 each group) such as group I: nano-filled resin-modified glass-ionomer, group II: nanocomposite resin, and group III: Cention N. After completing all the restorations, the restored teeth were subjected to 100 cycles of thermocycling. Next, all the surfaces of the tooth, except the restoration and a 1-mm zone adjacent to the restoration's margins, were covered with two coats of nail varnish. The coated teeth were then submerged in a 0.5% basic fuchsin dye solution. The teeth were then sectioned along the center of each restoration mesiodistally. Each part was visualized under a stereomicroscope at ×40 magnifications to assess microleakage. Out of all the included restorative materials, the least microleakage was demonstrated by teeth restored by the nano-filled resin-modified glass-ionomer (RMGI) group (1.05 ± 0.21) followed by the Cention N group (1.84 ± 0.14) and the nanocomposite resin group (3.10 ± 0.03). A statistical method involving the analysis of variance revealed a statistically significant difference among the different restorative materials. Multiple comparisons among the restorative materials showed a statistically significant difference between groups I and II and groups II and III restorative materials (p < 0.05). The dye penetration score 1 was more [11(55%)] for the nano-filled RMGI group, score 3 was more [12(60%)] for the nanocomposite resin group, and score 2 was more [9(45%)] for the Cention N group. The present study showed significantly less microleakage associated with the nano-filled resin-modified glass ionomer group than nanocomposite resin and Cention N groups. Since many years, dentists have encountered a challenging problem with cervical lesions. Thus, an interdisciplinary treatment approach is the appropriate option in the management of carious teeth that involve gingival recession and cervical extension.

Comparative efficacy of nanofilled and microfilled resin-modified glass ionomer as pits and fissure sealant in permanent molar teeth

The purpose of the present study was to compare the efficacy of nanofilled and microfilled resin- modified glass ionomer as pits and fissure sealants in permanent molar teeth. Ninety six teeth having fissure at the occlusal surface were randomly divided into two groups: Group I: Treated by nanofilled resin-modified glass ionomer sealant and Group II: Treated by microfilled resin- modified glass ionomer sealants. Clinical assessment was performed by modified Ryge´s criteria by means of retention, color match, marginal adaptation at 3, 6, and 12 months follow-up visit. Chi-square test was used for testing differences between the two groups; a value of p&lt;0.05 was considered as statistically significant. The results revealed that at 12 months observation period, nanofilled resin-modified glass ionomer sealant showed better retention, color stability and marginal adaptation than that of microfilled resin-modified glass ionomer sealants. Furthermore, the differences between two groups in respect to marginal adaptation and color match were statistically significant (p&lt;0.05). It can be concluded that nanofilled resin-modified glass ionomer sealant could be a better alternative to microfilled resin- modified glass ionomer sealant.

Influence of Hand Instrumentation and Ultrasonic Scaling on the Microleakage of various Cervical Restorations: An in vitro Study.

In cervical lesions, various restorative materials can be inserted, which can be affected by the application of periodontal scalers. This study evaluated and compared the marginal seal of class V glass ionomer, composite resin, and amalgam restorations after subjecting them to hand instrumentation and ultrasonic scaling. In this experimental study, 30 sound human first premolars were selected. In each tooth, buccal and lingual cavities (4 mm mesiodistal width, 3 mm occlusogingival height, and 2 mm depth) were made. The teeth were randomly assigned to three groups of 10 teeth: (1) Glass ionomer group, (2) composite group, and (3) amalgam group. Teeth were subjected to thermocycling procedure for 1,000 cycles between 5 and 55°C water baths and a 1-minute dwell time. Then, each group was randomly subdivided: (1) Margins of 30 restorations were exposed to hand instrumentation procedures by applying 10 working strokes, (2) margins of 30 restorations were exposed to a periodontal tip mounted on a piezoelectric ultrasonic handpiece working at 25 kHz for 10 seconds. The specimens were serially sectioned mesiodistally. Each section was examined under a stereomicroscope. The extent of microleakage was ranked using a 0 to 4 scale at both occlusal and cervical margins of the restorations. Data were analyzed initially using the Kruskal-Wallis test, followed by multiple comparisons using the Mann-Whitney and Wilcoxon test. The type of restorative material had a significant influence on dye penetration, whether in the enamel margin or in the dentinal margin (p < 0.001). The microleakage of glass ionomer group was the highest. No statistical differences were found in dye penetration between scaling groups (hand instrumentation and ultrasonic scaling) (p > 0.05). Type of restorative material had a significant influence on microleakage. No statistical differences were found in dye penetration between scaling groups. The microleakage of glass ionomer restoration is greater than amalgam and composite restorations after subjecting them to hand instrumentation and ultrasonic scaling.

A Clinical and Laboratory Evaluation of Different Remineralizing Agents Used for Treatment of Carious Posterior Teeth

Objective: The purpose of this study is to 1) evaluate clinically and radiographically the carious dentin treated with Ozone, Casein Phosphopeptide - Amorphous Calcium Phosphate (Tooth Mousse) mixed with Glass Ionomer and Glass Ionomer Cement only in primary molars of 4 - 8 years old children (In vivo study), and 2) Compare the microhardness of carious dentin treated with Ozone, Casein Phosphopeptide - Amorphous Calcium Phosphate (Tooth Mousse) mixed with Glass Ionomer and Glass Ionomer Cement only in extracted primary molars (In vitro study). Design: Forty five primary molars with proximal caries in children, ranging in their age from 4-8 years old. They were equally divided into three groups (15 each) according to the materials were used for restoration. The first group was restored with glass ionomer cement, the second group was restored with Casein Phosphopeptide – Amorphous Calcium Phosphate(CPP-ACP ) incorporated with glass ionomer cement, and the third group was pretreated with ozonized olive oil then restored with glass ionomer cement. Also this study was carried out on forty five freshly extracted carious primary molars, which divided equally into three groups and restored as mentioned before in clinical cases and examinedfor microhardness assessment. Results: the greatest value of mean radiodensity was recorded in Tooth Mousse group followed by Glass ionomer group then Ozone group. However there was no statistically significant difference between the three groups. Conclusion: Casein phosphopeptide - Amorphous Calcium Phosphate (Tooth Mousse) mixed with Glass ionomer cement as well as glass ionomer alone seemed to be successful as a remineralizing agent in primary molars.

Marginal Adaptation Evaluation of Biodentine and MTA Plus in "Open Sandwich" Class II Restorations.

This study aimed at evaluation of two different commercially available calcium silicate materials (Biodentine and mineral trioxide aggregate [MTA] Plus) used as dentin substitute. Sixty Class II cavities were prepared in extracted mandibular third molars, with margins extending 1 mm below the cementum-enamel junction. The samples were divided into three groups on the basis of dentin substitute used: resin modified glass ionomer cement, Biodentine, and MTA Plus. Cavities were restored with composite resins in an "open sandwich" technique. The samples were subjected to alternate aging in phosphate buffered saline and cyclic loading. Marginal adaptation was evaluated in terms of "continuous margin" at the gingival margin, using a low vacuum scanning electron microscope. Statistical analysis was done with two-way analysis of variance with Holm-Sidak's correction for multiple comparisons. The glass ionomer group and Biodentine group presented an overall 83% and 91% of continuous margins, with no difference between them. MTA Plus showed least values of continuous margins. Granular deposits were seen over the surface of Biodentine and MTA Plus. Biodentine and resin-modified glass ionomer cement, when used as a dentin substitute under composite restorations in open sandwich technique, gave satisfactory marginal adaptation values. Contemporary calcium silicate materials can be used as dentin substitute materials in "open sandwich" Class II restorations. This study evaluates the marginal adaptation of Biodentine, MTA Plus, and resin modified glass ionomer cement used as dentin substitutes and reports better adaptation obtained with Biodentine and glass ionomer cement.

Effect of desensitizers on retention of castings cemented to anatomically prepared teeth

Context : The extensive use of desensitizing agents to control incidences of post-cementation sensitivity can variably affect the forces required for debonding of the prosthesis. The available literature offers inconsistent results and is generally carried out using a flat occlusal preparation. Aims: Evaluation of effect of desensitizing agents-nonpolymerizable (Systemp) and polymerizable (Clearfil SE Bond)-on retention of complete veneer castings luted to anatomically prepared teeth with zinc phosphate and glass ionomer cement (ZPC and GIC). Materials and Methods: Seventy maxillary second premolars were prepared conforming to the anatomic form to receive complete veneer castings. Two sets of dies were prepared; one for obtaining castings and second to permit mathematical calculation of the surface area. The specimens were divided into four experimental groups of 15 samples each and two control groups of 5 samples each. Two desensitizers and two luting cements were used. After cementation, the samples were tested at crosshead speed of 0.5 mm/min on universal testing machine (UTM) using a customized self-aligning device. Minimum load required to debond the specimens was recorded. Force value for each specimen was divided by its surface area to obtain the tensile bond strength. Results: Significant reduction in tensile bond strength was noted for all the experimental groups, irrespective of luting cement used. Conclusion: Systemp-glass ionomer group exhibited highest bond strength followed by Systemp-zinc phosphate, Clearfil SE Bond-glass ionomer and Clearfil SE Bond-zinc phosphate group.

Sulfonated Poly(Fluorenyl Ether Ketone) Membranes with Suppressed Semi-Interpenetrating Crossover and Enhanced Proton Selectivity for Vanadium Redox Flow Batteries

A series of hybrid membranes with special microstructure, based on sulfonated poly (fluorenyl ether ketone) ionomer (SPFEK, IEC=1.74 mequiv.g-1) and secondary amine group containing SiO2 (SiO2–NH–NH2), has been successfully designed and prepared for vanadium redox flow battery (VRB) application. The hybrid membranes are prepared by simply adding KH792 into the SPFEK solution in N,N’-dimethylacetamide (DMAc), followed by dispersion, co-condensation and solvent casting. The water uptake, mechanical property, proton conductivity, (VO)2+ permeability and single cell performance are investigated in order to understand the relationship between morphology and property of the membranes. The hybrid membranes show dramatically improved proton selectivity when compared with SPFEK. The vanadium ion (VO)2+ permeability through the hybrid membrane is about 10 times lower than that of virgin SPFEK. The columbic efficiency and energy efficiency of the single cell of the hybrid membrane are higher than the SPFEK membrane. The results inidicate that hybrid membranes of this type are promising for VRBs.

Effect of tooth preparation and bonding agents on cementation of metal full crown

Objective To find out the effect of tooth preparation and bonding agents on cementation of metal full crown,to provide research basis for clinical practice of full crown restoration .Methods 60 dissociation teeth were randomly divided into six groups ,10 teeth in each group .Different adhesive materials or different polymerization angle were used in different groups ,the six groups were 3 polymerization angle zinc group ,3 polymerization angle glass ionomer group,3 polymerization angle resin cement group ,5 polymerization angle zinc group ,5 polymerization angle glass ionomer group ,and 5 polymerization angle resin cement group .In the first three groups ,polymerization angle was 3,and in the latter three groups ,polymerization angle was 5.The retentive force values of all groups were tested and compared.Results The metal crown retentive force of 3 polymerization angle zinc group[（198.5 ±11.6）N]was sig-nificantly better than that of 5 polymerization angle zinc group[（138.2 ±14.1）N]（t=7.46,P〈0.05）.Polymeriza-tion angle showed no statistically significant effect on metal crown retentive force values of glass ionomer groups and resin cement groups （t=1.52,2.03,all P〉0.05）.Bonding zinc retention of 3 degree of polymerization group was （198.5 ±11.6）N,glass ionomer and resin cements were （302.7 ±19.2） N and （352.7 ±21.8） N.Bonding zinc retention of 5 degree of polymerization group was （138.2 ±14.1）N,glass ionomer and resin cements were （317.4 ± 23.8）N and （362.9 ±22.6） N.Different adhesives showed statistically significant effects on metal crown retentive force values of 3 polymerization angle groups and 5 polymerization angle groups （F=7.88,8.42,all P〈0.05）. Conclusion A suitable adhesive,standard operation can get the best cementation effect ,and improve clinical repair effect. Key words: Tooth preparation; Dental cements; Crowns; Metals; Cementation

Comparison of the sealing ability of different types of glass ionomer cements in temporary restoration

Glass ionomer cement has been used for temporary restoration; however, several formulations are available. Objective: The aim of this study was compare the linear leakage of different types of glass ionomer cement – R, F, N and C. Material and methods: Forty-four third molars were used and prepared with standardized class I cavity preparations. By using gutta-percha, the cavity height was standardized in 5 mm. The samples were divided into 4 experimental groups (R, N, F and C), and 2 control groups (positive – not restored, and negative – restored using resin). The teeth were waterproofed and immersed in 2% methylene blue. After 7 days, they were sectioned and the measurement of the dye leakage was performed by stereomicroscopy (40X) using a calibrated periodontal probe. Results: Data were analysed by Kruskal Wallis and Dunn tests. There was statistically significant differences (p = 0.002) between R and C, and R and N glass ionomer groups. C and N glass ionomer groups were similar. F glass ionomer group was similar to all other groups. Conclusion: It can be concluded that different types of glass ionomer formulations can influence the peripheral sealing of the restorative material. R glass ionomer was the most effective, while C and N glass ionomers were the least ones.

Synthesis of Nafion/CeO2 hybrid for chemically durable proton exchange membrane of fuel cell

Abstract Nafion/CeO 2 hybrid composites prepared through a self-assemble route are proposed for chemically durable electrolyte membrane of fuel cell. Self-assembly of Nafion and CeO 2 nanoparticles between the positively charged CeO 2 and the negatively charged SO 3 − end groups of Nafion ionomers gives the composite structure a good compatibility on the interface. As a result, the Nafion/CeO 2 hybrid proton exchange membranes present conductivities slightly lower than that of the pristine Nafion membrane at 100 RH% condition, whereas much higher than the later when humidification is below 75 RH%. The Nafion/CeO 2 hybrid membranes also display excellent radical scavenge ability under hydroxyl radical corrosion condition. With Fenton reagent of 30 wt% H 2 O 2 solution containing 20 ppm FeCl 2 at 85 °C, the fluoride emission rates for the self-assembled Nafion/CeO 2 membranes with ceria content of 1, 3, 5, 10 wt% are 43.05, 8.67, 6.01, 4.47 mg h −1 , respectively, much lower than that for pristine Nafion membrane (55.78 mg h −1 ) and Nafion/CeO 2 membrane prepared from the conventional sol–gel method (11.64 mg h −1 ). Another important aspect of the self-assembled Nafion/CeO 2 membrane contributed to the durability is the low humidity-induced stress and dimensional stability. The humidity-induced stress of the self-assembled Nafion/CeO 2 membranes with ceria content of 1–10 wt% was 1.22–1.93 MPa, in comparison to 2.25 MPa of pristine Nafion membrane. Thus, the proton exchange membranes prepared from self-assembled Nafion/CeO 2 present high durability under the fuel cell operating conditions. In the open circuit voltage accelerated test under in situ accelerating RH cyclic test, the OCV reduction rate of self-assembled Nafion/CeO 2 membrane with ceria content of 5 wt% is 1.13×10 −4 mV/s, much lower than 11.7×10 −4 mV/s of the pristine Nafion membrane and 5.78×10 −4 mV/s of the Nafion/CeO 2 hybrid membrane prepared from the conventional sol–gel method.

Twenty-four month clinical evaluation of fissure sealants on partially erupted permanent first molars: Glass ionomer versus resin-based sealant

Glass ionomer sealants are an alternative to resin-based sealants, especially for use in partially erupted permanent molars. The authors conducted a study to compare the retention, marginal staining and cariostatic properties of a glass ionomer sealant with those of a resin-based sealant during a 24-month period. We included in this study 39 patients aged 5 through 9 years who had bilateral partially erupted first permanent molars. One of us (S.B.) placed a resin-based sealant (Delton Plus FS+, Dentsply Professional, York, Pa.) (group D) on a partially erupted first molar in one quadrant of the maxilla or mandible and a glass ionomer sealant (GC Fuji Triage White, GC America, Alsip, Ill.) (group T) in the other quadrant. Two masked and calibrated investigators (S.A.A., J.C.) evaluated the sealants for retention, marginal staining and carious lesions at three, six, 12 and 24 months. The authors used a multinomial regression for statistical analysis (P < .05). The recall rate was 69.2 percent at 24 months. Two sealants from group D and three from group T were lost completely. Complete retention rates at 24 months were 40.7 and 44.4 percent for groups D and T, respectively. The authors found no statistically significant difference in retention rates between groups at each recall examination (P > .05). For marginal staining, sealants in the resin-based group exhibited statistically higher marginal staining than did sealants in the glass ionomer group (P < .05). Although the authors detected no caries in teeth in group T, teeth in group D in which the sealant was lost completely experienced demineralization. Resin-based and glass ionomer sealants exhibited similar retention rates at 24 months. However, marginal staining was lower in the glass ionomer group, and the authors found no caries in teeth in this group. Consequently, glass ionomer sealants may be a better choice when salivary contamination is expected. Sealing during tooth eruption presents a particular challenge owing to difficulty in isolating the tooth. Glass ionomers may be a better material for sealing partially erupted molars.

The Efficacy Of Glass Ionomer Hybrid As Orthodontic Brackets Adhesives To Inhibit Calsium Released Of The Enamel

Composite resins are predominantly used to bond orthodontic brackets onto teeth. These can lead to calcium released of the enamel surrounding the brackets. Purpose : To observe calcium release during the use of adhesives which release fluoride Method : This experimental study was design to determine the calcium released after soaking in the acid solution. This in vitro study used forty extracted human premolars (20 teeth were bonded with glass ionomer, and 20 teeth were bonded with glass ionomer hybrid). Half of the teeth in each group were treated with fluoride application and the other half were not treated fluoride application topically. Calcium released of the enamel was evaluated using Spectrofotometer. Result : The results showed that there was a significant difference between glass ionomer group without and with fluoride application (p 0,005) in the group of glass ionomer hybrid without and with fluoride application topically. Conclusion : The adhesive glass ionomer hybrid could prevent calcium released with or without the usage of sodium fluoride.

QLF(Quantitative light-induced fluorescence)를 이용한 글라스 아이오노머 수복물의 인접면 우식 재광화 효과에 관한 연구

This in vitro study compared the remineralization of incipient interproximal caries in the presence of three glass ionomer cements(highly-filled glass ionomer cement, resin-modified glass ionomer cement, compomer) and a resin composite(control). Thirty-two extracted premolars were selected based upon the lack of any visible demineralization. The teeth were coated in a transparent acid resistant nail varnish leaving mm square. The teeth were subjected to the demineralizing buffer for 3 days and quantitative light-induced fluorescence(QLF) images of the subjects were taken. Proximal restoration was simulated by placing tooth specimens and the various glass ionomer cements in closed containers with artificial saliva at and pH 7.0 with constant circulation. Further QLF images were subsequently taken at 30, 60, and 90 days. The changes of mineral loss() were evaluated by QLF and the change of () were compared between groups in order to evaluate the effects of remineralization. All data were analyzed using ANOVA and the post-HOC Dunnett C multiple comparison test at p(changes of mineral loss) increased for all treatments, the increases for three glass ionomer groups were significantly higher than that for the resin group at first month period. As time went on, the amount of decreased.

Can hygroscopic expansion compensate polymerization shrinkage? Part I. Deformation of restored teeth

Objective Restorative materials exhibit contraction and expansion due to polymerization and water absorption. Each process deforms and stresses a restored tooth structure in opposite direction. This study evaluated the tooth deformations during these competing processes. Methods Large MOD cavities were prepared in 10 extracted molars. Five were restored with a hydrophobic resin composite (Filtek Supreme, 3M ESPE) and the others with a hydrophilic resin-modified glass-ionomer (Ketac Nano, 3M ESPE). The restored molars and two unrestored controls were stored in water for 24 weeks. The molars were digitized with an optical scanner at baseline, after preparation, restoration, and at 1, 2, 4, 8, 16, and 24 weeks water immersion. The digitized buccal, lingual, and restoration surfaces were analyzed to determine their deformation patterns. The results were statistically analyzed using ANOVA followed by Student–Newman–Keuls post hoc tests ( p = 0.05). Results The buccal and lingual tooth surfaces moved 13–14 μm inward after restoration. After water immersion, cuspal deformation in the resin composite group gradually decreased, reversing the shrinkage deformation within four weeks. The immersed resin-modified glass ionomer group reversed shrinkage deformation within one week, and continued to expand further to 28 μm after 24 weeks. Cuspal deformations after water immersion were significantly different with the two restoratives. Restoration surfaces also expanded after water immersion, while the control teeth showed no significant deformation. Significance Polymerization shrinkage deformation was compensated by hygroscopic expansion within 4 weeks in teeth restored with a hydrophobic resin composite, while a hydrophilic restorative over-compensated polymerization shrinkage within 1 week causing tooth expansion.

Neutron study of self-organization in solutions of ionomers based on sulfonated polystyrene

Processes of self-organization of ionomers based on sulfonated PS containing ionogenic groups in the salt form (SO3Na) in chloroform have been studied by small-angle neutron scattering. At a small content of ionogenic groups SO3Na (1.35 mol %), the conformation of PS chains changes from coil-like to globular due to electrostatic interactions between them. An increase in the share of ionogenic groups to 2.6 mol % brings about the assembly of ionomer chains into a hollow spherical structure with the solvent inside. In the shell of a micelle, polar groups are densely packed and shielded from the solvent by nonpolar fragments of adjoining chains. At a low content of ionogenic groups in ionomers, two-thirds of macromolecules in solution are not incorporated in any structures. With an increase in the content of polar groups to 2.6 mol %, almost all chains are organized to small clusters—the stable pairs of macromolecules.

Poly(Ethylene Oxide)/Styrene Ionomers Blends: Crystallization of Poly (Ethylene Oxide) Component Studied by Wide-Angle X-Ray Diffraction

Wide-angle X-ray diffraction (WAXD) and the scanning electron microscopy (SEM) were used to determine the morphology of crystalline phase of blends of poly(ethylene-oxide) (PEO) and styrene-acrylic acid (S-AA) copolymers neutralized with sodium ions (Na+). In this study, we investigated the effects of blend composition and the content of ionic groups in amorphous ionomers on the degree of crystallinity and the crystallite sizes. It was found that the degree of crystallinity of PEO in the blends decreases both with increasing S-ANa(6.4) content and with increasing ANa content. The sizes of PEO crystallites, measured both in the direction perpendicular and parallel to the polymer axis, are almost independent of ionic groups content in the amorphous component of the blends but they decrease with increasing S-ANa(6.4) content. For the blends containing small amounts of PEO the confined crystallization of this polymer were observed. The final crystalline morphology of these blends, observed by SEM method, is different in comparison to that formed without spatial confinement.

Comparison between effectiveness of a low-viscosity glass ionomer and a resin-based glutaraldehyde containing primer in treating dentine hypersensitivity—a 25.2-month evaluation

The null-hypothesis tested was; there is no difference in effectiveness between a new low-viscosity glass ionomer and a resin-based glutaraldehyde containing primer in treating hypersensitive teeth after 2 years. Using a split-mouth design, hypersensitive teeth in 14 adult patients were randomly assigned to 2 treatment groups. Hypersensitive tooth surfaces were covered with a low-viscosity glass ionomer (Fuji VII) and a resin-based glutaraldehyde containing primer (Gluma Desensitizer). The discomfort interval scale (DIS) ranging from 0 to 4 was used to test the level of hypersensitivity before and after treatment, and at 3 months using compressed air blown for 2 s, and at 1 and 25.2 months using a telephone interview. Differences between and within the treatment groups were tested using the sign rank test. Evaluations in the gluma group were discontinued after 3 months. The mean DIS score for hypersensitive teeth in the glass ionomer group was statistically significantly lower than that in the gluma group, immediately after application (p=0.0005), after 1 month (p=0.02) and after 3 months (p=0.003). After 3 months, 11/14 of the hypersensitive teeth in the glass ionomer group and 2/14 in the gluma group were free of sensitivity. The mean DIS score for hypersensitive teeth in the glass ionomer group remained low after 19.2 months (0.25: S.E.=0.13) and 25.2 months (0.22: S.E.=0.15). The null-hypothesis was rejected. The low-viscosity glass ionomer (Fuji VII) is more effective in treating hypersensitive teeth than Gluma Desensitizer after 3 months. The positive treatment effect of the glass ionomer continued until 25.2 months.

Influence of ionic groups on the crystallization and melting behavior of segmented polyurethane ionomers

AbstractThe isothermal crystallization kinetics and melting behavior of the soft segment in polyurethane (PU) ionomer/nonionomer based on PCL‐4000 (poly(ε‐caprolactone)) were investigated using polarizing optical microscopy (POM) and differential scanning calorimetry (DSC). In general, the presence of ionic groups in PU ionomers can promote the formation of a more stable crystalline structure and lower the equilibrium melting temperature of the crystallizable phase. Comparison between the crystallization characteristics of PU nonionomers and ionomers suggests that the Coulombic Forces between ionic groups within hard segment can increase the crystallization rate and decrease the crystal size of soft segment when the total molecular weight (Mw) of PU ionomer is higher than ∼71,000. On the other hand, the opposite effect of ionic groups on the crystallization rate is observed in PU ionomers with Mw below ∼20,000. The DSC thermograms illustrate that the ionic groups can significantly enhance the microphase separation in PU ionomers with higher Mw values. By the control and manipulation of crystallization and microstructure formation in PU ionomer, it is possible to achieve shape memory PUs with superior physical property. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 4603–4613, 2006