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PubMed2004

Dimensional accuracy of acrylic resin maxillary denture base polymerized by a new injection pressing method.

The purpose of this study was to confirm the dimensional accuracy of a newly developed injection pressing method for resin polymerization by making use of the internal electric resistance of resin to determine the optimal timing for resin injection. A new injection pressing polymerization pot with a built-in system to measure the internal electric resistance of resin was used for resin polymerization. Fluid-type resin was injected into the mold of a maxillary complete denture base under nine different conditions: three different timings for resin injection according to the electric resistance of resin dough (early stage: 11 Mohms; intermediate stage: 16 Mohms; final stage: 21 Mohms) and three different motor powers for resin injection (2000 N, 4000 N, and 6000 N). In the best polymerization condition (injected during the early stage of resin dough under a motor power of 6000 N), the adaptation of the denture base showed a statistically significant improvement compared with the conventional pouring method.

Acrylic Resins↗

PubMed1999

Cholestyramine protection against ochratoxin A toxicity: role of ochratoxin A sorption by the resin and bile acid enterohepatic circulation.

We have shown that the addition of cholestyramine (CHA, a resin known to bind bile salts in the gastrointestinal tract) to ochratoxin A (OTA)-contaminated rat diets reduced plasma levels of the toxin and prevented OTA-induced nephrotoxicity. To elucidate the mechanism of action of CHA, we carried out in vitro experiments to determine whether the resin may bind the toxin. For comparative purposes, binding of bile salts to the resin was also examined. Results showed that CHA binds both OTA and bile salts (taurodeoxycholate [TDC] and taurocholate [TCA]). Also, CHA showed greater affinity for OTA and TDC than for TCA. At 1 mM concentration, 96% of OTA and 80% of TDC were bound to the resin, while for TCA binding was only 50%. However, saturation of the resin was reached at higher levels with bile acids compared to OTA (3.67 mmol/g resin for TCA and 3.71 mmol/g resin for TDC versus 2.85 mmol/g resin for OTA). To characterize the nature of the binding of the toxin to CHA, NaCl (0 to 200 mM) was added to a fixed amount of OTA or bile acids. As expected, TCA absorption was decreased by the addition of NaCl (<50 mM), indicating electrostatic binding. However, OTA and TDC sorption was decreased only at high concentrations of NaCl (>150 mM), suggesting a stronger binding to the resin than that shown with TCA. Sequential competitive studies demonstrated that CHA binds more OTA than TCA. The results of the in vivo study show the role of bile salts in OTA absorption. The toxin's plasma levels at 1 and 3 h after a single oral dose of OTA were significantly decreased in bile salt-depleted rats compared to the control. Thus, the alteration of the bile salt biliary pool and OTA enterohepatic circulation may be an additional mechanism of action of the resin against mycotoxin toxicity.

Animals↗

PubMedDate not supplied

Effects of light-curing time on the cytotoxicity of a restorative resin composite applied to an immortalized odontoblast-cell line.

This in vitro study evaluated the cytotoxic effects of a restorative resin composite applied to an immortalized odontoblast-cell line (MDPC-23). Seventy-two round resin discs (2-mm thick and 4 mm in diameter) were light-cured for 20 or 40 seconds and rinsed, or not, with PBS and culture medium. The resin discs were divided into four experimental groups: Group 1: Z-100/20 seconds; Group 2: Z-100/20 seconds/rinsed; Group 3: Z-100/40 seconds; Group 4: Z-100/40 seconds/rinsed. Circular filter paper was used as a control material (Group 5). The round resin discs and filter papers were placed in the bottom of wells of four 24-well dishes (18 wells for each experimental and control group). MDPC-23 cells (30,000 cells/cm2) were plated in the wells and allowed to incubate for 72 hours. The zone of inhibition around the resin discs was measured under inverted light microscopy; the MTT assay was carried out for mitochondrial respiration and cell morphology was measured under SEM. The scores obtained from inhibition zone and MTT assay were analyzed with the Kruskal-Wallis followed by Dunnett tests. In Groups 1, 2, 3 and 4, the thickness of the inhibition zone was 1,593 +/- 12.82 microm, 403 +/- 15.49 microm, 1,516 +/- 9.81 microm and 313 +/- 13.56 microm, respectively. There was statistically significant difference among the experimental and control groups at the 0.05 level of significance. The MTT assay demonstrated that the resin discs of the experimental groups 1, 2, 3 and 4 reduced the cell metabolism by 83%, 40.1%, 75.5% and 24.5%. Only between the Groups 2 and 4 was there no statistically significant difference for mitochondrial respiration. Close to the resin discs, the MDPC-23 cells exhibited rounded shapes, with only a few cellular processes keeping the cells attached to the substrate or, even disruption of plasma membrane. Adjacent to the inhibition zone, the cultured cells exhibited multiple fine cellular processes on the cytoplasmic membrane organized in epithelioid nodules, similar to the morphology observed to the control group. Based on the results, the authors may conclude that the Z-100 resin composite light cured for 20 seconds was more cytopathic to MDPC-23 cells than Z-100 light cured for 40 seconds. The cytotoxic effects of the resin discs decreased after rinsing them with PBS and culture medium. This was confirmed by MTT assay and upon evaluation of the inhibition zone, which was narrower following rinsing of the resin discs.

Cell Line, Transformed↗

PubMed1990

[Transmittance of light-cured composite resins. 1. Measurement of transmittance with time].

The factors that influence the change of the transmittance of light-cured composite resins during polymerization were examined. Six experimental composite resins such as used organic composite filler and fourteen commercial composite resins were investigated using the experimental device for measurement of the transmittance. The transmittance of the experimental composite resins were from 25 to 73%. The transmittance of the experimental composite resins changed with time; a group with increasing transmittance (G1), a group giving a maximum transmittance (G2), and a group with decreasing transmittance (G3). These changes of transmittance were influenced by the difference in the refractive indices between matrix resin and filler, but the refractive index that indicated a maximum transmittance of matrix resin during polymerization could not be observed when the refractive index of the matrix resin and filler was same. The light transmitted through the commercial composite resins was less than half of the irradiation light. This change of transmittance could also be classified into the three groups mentioned above. The commercial composite resins belonged to the group with increasing transmittance (G1).

Composite Resins↗

PubMed1989

[Chromatic study of composite resins. Report 1. The influence of the color measuring instruments and the background colors on the chromatic values].

The purpose of this study was to investigate the influence of the structural difference of the color measuring instruments and the background colors on the chromatical values of the composite resins. Composite resin disks which were 10 mm in diameter and 1 mm and 2 mm in thickness, and made by the light-cured composite resin Silux Plus (3M Co.) were chromatically measured. The colors of the composite resin used in this study were universal, yellow, dark-yellow and light. The color measuring instruments used in this study were the Murakami Color Research Laboratory Fast Spectrophotometer CMS-500 used with the Flexible Sensor FS-1, FS-2 and FS-3, and the Murakami Color Research Laboratory Color Difference Meter CD-270 used with the Improved Light Guide CD-270. The diameters of the head which receives the light from the object were: FS-1 (2 mm), FS-2 (3 mm), FS-3 (5 mm) and Improved Light Guide CD-270 (2 mm). The chromatical values of the resin specimens were measured without back color, backed by a white plate and backed by a black plate. The chromatical values of the composite resin disks were measured with the different color measuring instruments under the different background colors. The XYZ, L*a*b* and xy values were compared and the following results were obtained. 1) The chromatical XYZ, L*a*b* and xy values of the composite resins showed different value patterns among the color measuring instruments. 2) Different influences of the background colors on the chromatical values of the composite resins were obtained among the different colors and different thicknesses of the resins in the cases of some color measuring instruments were used. 3) The most precise color measuring instrument for chromatical measuring of the composite resins among the instruments used in this study was the Fast Spectrophotometer CMS-500 used with the FS-3. 4) Prior to the comparison of the chromatical values measured by the different color measuring instruments, the chromatical values obtained by measurement with the same specimens should be compared and the structural differences, the precision and the sensitivities of the instruments should be understood.

Color↗

PubMed1989

[Chemical durability of composite resins].

To evaluate their chemical durability, samples of posterior composite resins were stored in NaOH (0.1 mol, 1 mol), HCl (0.1 mol, 1 mol), acetone (99%), and distilled water at 37 degrees C for a week and subjected to the direct tensile test, measurement of surface roughness and SEM observation. NaOH caused the degradation of composite resins, decrease of tensile strength and increase of surface roughness. The SEM photograph of fractured surface of tensile specimens revealed the degradation zone under the surface. It was considered that NaOH caused the hydrolysis of silan coupling of composite resins. HCl also caused the degradation of composite resins, but some resins showed the durability in this condition. More examination is needed to clarify the mechanism of degradation. Acetone caused the degradation of matrix resin and some composite resins. It was considered to dissolve the low degree of polymerized matrix resin of composite resins. Immersion in chemicals of composite resins was thought to be useful to evaluate the chemical durability and to accelerate the degradation in water.

Composite Resins↗

PubMed1987

Wear patterns and rates of posterior composite resins.

The use of composite resins as posterior restorative materials has been growing at a rapid rate. In spite of major improvements in both physical and mechanical characteristics secondary caries and resistance to wear are still major concerns. This paper deals with the wear rate and patterns of wear of posterior composite resins. Results of long term clinical studies show that a major difference exists between composites containing submicron or supramicron sized filler particles. In general, the wear rates of the larger filler particles composite resins decrease with time. On the other hand, the microfilled posterior composite resins appear to exhibit a linear rate of wear. The wear patterns of the two different types of posterior composite resins are also dissimilar. Composite resins containing filler particles larger than 1 micron tend to undergo a generalized loss of material. The microfilled composite resins also lose material generally but to a lesser degree. Furthermore, the submicron filled posterior composite resins tend to exhibit localized wear, particularly in centric holding areas. Such a change does not, as a rule, occur with composite resins containing larger filler particles. Finally, the microfilled composite resins tend to develop continuous marginal fractures at tooth restoration interfaces.

Composite Resins↗

PubMed1993

Composite resins in the 21st century.

Human enamel and dentin should be used as the physiologic standards with which to compare composite resins, especially in the posterior region. The intrinsic surface roughness of composite resins must be equal to or lower than the surface roughness of human enamel on enamel-to-enamel occlusal contact areas (Ra = 0.64 microns). Roughness determines the biologic strength of composite resins. The nanoindentation hardness value of the filler particles (2.91 to 8.84 GPa) must not be higher than that of the hydroxyapatite crystals of human enamel (3.39 GPa). Composite resins intended for posterior use should have a Young's modulus at least equal to, and preferably higher than, that of dentin (18.500 MPa). The compressive strength of enamel (384 MPa) and dentin (297 MPa) and the fracture strength of a natural tooth (molar = 305 MPa; premolar = 248 MPa) offer excellent mechanical standards to select the optimal strength for posterior composite resins. The in vivo occlusal contact area wear rate of composite resins must be comparable to the attritional enamel wear rate (about 39 microns/y) in molars. Differential wear between enamel and composite resin on the same tooth is a new criterion for visualizing and quantifying the wear resistance of composite resins in a biologic way. Posterior resins must have a radiographic opacity that is slightly in excess of that of human enamel (198% Al). Based on these standard criteria, it can be concluded that in the 21st century the ultrafine compact-filled composite resins may be the materials of choice for restoring posterior cavities.

Analysis of Variance↗

PubMed1994

Water sorption by maxillary acrylic resin denture base and consequent changes in vertical dimension.

Many kinds of materials have been tried in the Laboratory and to some extent clinically prior to introduction of acrylic resin. With the introduction of acrylic resin as denture base material, continuous attempts have been made to evaluate its physical properties. To observe the changes in vertical measurements of acrylic resin dentures due to water sorption and to assess variations of vertical movements of individual teeth within dentures due to water sorption; present study was carried out on 25 maxillary acrylic dentures. From results, the maximum water sorption appears to take place within 24 hours and after 28 day of water sorption; there is no change in vertical dimension if the denture is placed for further more time. With the introduction of acrylic resin as denture base material continued attempts have been made to evaluate physical properties so as to determine its suitability as an ideal nonmetalic denture base materials. Several investigations have been carried out on physical properties of this material such as compressive strength, tensile strength, solubility and colour stability. These have proved their superiority over other nonmetalic denture base materials used so far. Also several studies have been carried out to assess dimensional changes that occur in acrylic resin during processing, but very few studies have been carried out about the water sorption changes in the acrylic resin and still few about the vertical dimensional changes in acrylic resin due to water sorption. While fabricating the denture base from the acrylic resin, it comes in contact with water during polishing as well as cleaning, consequently during the use of denture it is constantly wetted by oral fluids. It is the hypothesis that water sorption by denture base acrylic may effect the retention and stability of the denture. It has been shown that water molecules act according to the laws of diffusion. The diffusion presumably occurs between the macromolecules which are forced slightly apart. This separation renders the molecules mobile and the inherent stresses created during heat curing of the acrylic resin can be relieved with consequent intermolecular relaxation and possible changes in the shape of the denture. Exposure time also plays a significant role in water sorption. The present investigation was therefore, carried out by keeping the following objectives: (1) The primary objective was to observe the changes in vertical measurements of acrylic resin dentures due to water sorption. (2) To assess the variations of vertical movement of individual teeth within the dentures due to water sorption.

Absorption↗

PubMed2003

Fracture toughness of resin-modified glass ionomer restorative materials: effect of powder/liquid ratio and powder particle size reduction on fracture toughness.

OBJECTIVES: The objectives of the current investigation were two-fold: (1) to examine the effect of different powder/liquid (P/L) ratios on the fracture toughness of commercial resin-modified glass ionomer cement and conventional glass ionomer cement, and (2) to evaluate the effect of powder size reduction on the fracture toughness of experimental resin-modified glass ionomers in order to improve their physical properties. METHODS: The P/L ratios of the glass ionomer and resin-modified glass ionomers were varied from the manufacturer's recommended ratio to 2.0 and 1.0 by weight. The powder particle sizes for the experimental resin-modified glass ionomers tested were 2, 5, 10 and 25 micro m in diameter. Fracture toughness was determined on ring-shaped specimens with a fatigued pre-crack. RESULTS: The fracture toughness of the resin-modified glass ionomers was significantly higher (p<0.005) than that of the glass ionomer and was not greatly influenced by the P/L ratio. For the experimental resin-modified glass ionomers, it was observed that fracture toughness gradually decreased as the powder particle size became finer. SIGNIFICANCE: The resin components in the liquid play an important role in the improvement of the physical properties of the resin-modified glass ionomer. A reduction in the powder particle size of up to 10 micro m, which resulted in a smoother surface, can maintain high fracture toughness. The high fracture toughness values of the resin-modified glass ionomer may be one of the factors contributing to a favorable clinical outcome in high stress-bearing areas.

Analysis of Variance↗

PubMed1997

In vitro toothbrush-dentifrice abrasion of resin-modified glass ionomers.

OBJECTIVES: This study was conducted to compare the rate of abrasive wear and change in surface roughness of resin-modified and conventional acid-base glass ionomers when subjected to toothbrush-dentifrice abrasion. METHODS: Two resin-modified and two conventional glass ionomers were used. Samples of a high-copper amalgam and a hybrid resin composite were used as reference materials. Specimens of each material were prepared and subjected to toothbrush-dentifrice abrasion using 20,000 strokes of brushing. The amount of vertical loss of material was determined by profilometry (Surfcom-4A, Tokyo-Seimitsu, Tokyo, Japan). The surface characteristics after abrasion were evaluated on secondary electron images by SEM, and the surface hardness (KHN) was also measured for all materials. Data were analyzed by one-way ANOVA (p < 0.05), followed by a multiple comparisons test using LSD (Least-significant difference) at a level of p < 0.05. RESULTS: The abrasion resistance of resin-modified glass-ionomers was statistically lower for the amalgam and the resin composite reference materials. Statistically lower abrasion resistance and surface hardness were observed for the resin-modified glass ionomers than for their conventional acid-base counterparts when two forms of products from the same manufacturer were compared. SEM observations made after abrasion testing showed a significantly rougher surface for all glass ionomer materials than for the amalgam and the resin composite. SIGNIFICANCE: When comparisons were made between products from the same manufacturers, it was found that in vitro resistance to toothbrush-dentifrice abrasion of the resin-modified glass ionomers is inferior to that of the conventional acid-base glass ionomers. The lower abrasion resistance found in the resin-modified products appears to be related to their lower surface hardness.

Aluminum Hydroxide↗

PubMed1984

Detection of bacteremia with the BACTEC 16B resin blood culture medium.

A new blood culture medium (16B) containing adsorbent and cationic exchange resins has become available for use with the BACTEC instrument (Johnston Laboratories, Towson, MD). Its purpose is to enhance the detection of bacteremia through binding of antimicrobials. The performance of the BACTEC 16B resin medium was compared with the routine BACTEC 6B medium in patients with suspected sepsis receiving antibiotics. A total of 1,227 blood specimens were inoculated in 6B and 16B media and yielded 93 positive cultures from 43 clinically septic patients. Of 103 bacterial isolates recovered, 63 (61.2%) were recovered in both media, 14 (13.6%) in the routine 6B medium only, and 26 (25.2%) in the resin medium only (P greater than 0.05). Staphylococci, both coagulase positive and negative, were recovered much more frequently in resin medium (P less than 0.01). When the results of all the blood culture sets collected for each patient on any given day were considered, the routine 6B medium was the only source of isolation for seven bacterial species in six patients, and the resin medium was the only source of isolation for nine species in nine patients. However, of the nine organisms whose sole isolation source was the resin medium, eight were recovered early in the course of antibiotic therapy (6 within 24 to 36 hours and 2 within 36 to 48 hours of the first antibiotic dose) and had been isolated previously in routine 6B medium. In no instance was the antibiotic regimen changed as a result of the persistence of the organism in resin medium in the early phases of treatment. The use of resin medium did not improve overall detection time for 63 isolates recovered in both media. In conclusion, although the 16B resin medium did recover a greater number of bacterial isolates, it contributed very little information that might be of use in modifying and improving the treatment of septic patients receiving antimicrobials.

Anti-Bacterial Agents↗

PubMed1994

Use of an adhesive resin for bonding orthodontic brackets.

To date, most successful bonding agents used in orthodontics rely on mechanical retention to both the enamel and bracket base. Chemical adhesion to enamel as seen with glass ionomer cements, and to the silanated base of ceramic brackets have been tried. Recent developments in resin formulation have led to the production of adhesive diacrylate resins capable of forming adhesive bonds to certain metals including stainless steel. The aim of this experiment was to compare such a resin, Panavia EX, with a more conventional 'no-mix' orthodontic bonding resin. Two different base retention mechanisms were used, and the effect of rebonding and differing environmental conditions were also investigated. The results indicated that Panavia EX could produce greater bond strengths than the more conventional bonding resin. Of the two base retention systems tested, braised mesh bases gave consistently greater bond strengths than the cast base, although no base/resin specificity could be detected. Re-using the same brackets showed rebound strengths to be significantly lower than initial bond strength although the results indicated the adhesive resin was still able to bond more effectively to these used brackets than the conventional resin. Environment had the greatest effect on bond strength, such that following environmental exposure there was no significant difference between the two resins. This latter factor, and in particular the more complex bonding technique required for the adhesive resin, means that Panavia EX cannot be recommended for orthodontic use in its present form.

Acrylic Resins↗

PubMed1993

A new method of attaching cast gold occlusal surfaces to acrylic resin denture teeth.

Historically, cast gold occlusal surfaces for complete or removable partial dentures have been fabricated with retentive loops or beads and luted to prepared denture teeth with acrylic resin or attached to tooth-colored, heat-processed acrylic resin. At present, alternatives to mechanical retention for attaching resin to metal include chemical bonding of the resin after placement of intermediate ceramic or tin layers and the use of chemically adhesive resin cements. Compared to mechanical retention, the chemical bonding of resin to metal requires less gold and allows more room for properly contoured and esthetic resin. Additionally, this chemical bond limits microleakage at the resin-metal interface. In the following technique, cast gold occlusal surfaces are fitted to onlay preparations of acrylic resin denture teeth set in a processed denture base. The castings are air-abraded, tin plated, and luted to the denture teeth with Panavia dental adhesive. This method is quick, easy, and economical.

Acrylic Resins↗

PubMed2005

GC-MS analysis of penta- and tetra-cyclic triterpenes from resins of Pistacia species. Part I. Pistacia lentiscus var. Chia.

Pistacia species contain oleoresins with bioactive triterpenes. In this study triterpenes, including minor components, were identified and quantified in both neutral and acidic fraction of Pistacia lentiscus var. Chia resin, grown exclusively in Chios island (Greece), collected traditionally, as well as by the use of stimulating agents (liquid collection). It was proved that these two resin samples were composed of several different minor triterpenes. In the traditional collection of the resin, 36 triterpenes were identified, 23 of which are new minor compounds (five in the acidic and eighteen in the neutral fraction). In the liquid collection resin eight compounds were identified in the acidic and 11 in the neutral fraction, while seven compounds were not contained in resin traditionally collected. The main triterpenes in both resin samples collected traditionally and by use of stimulating agents were in the following order: isomasticadienonic acid (24 and 22.5% w/w of triterpenic fraction respectively), masticadienonic acid (9.3 and 14.7% w/w of triterpenic fraction) and 28-norolean-17-en-3-one (19 and 36% w/w of triterpenic fraction respectively). The aim of this study was to compare the qualitative and quantitative composition of triterpenes in the resin samples collected using the traditional and new liquid techniques, and examine whether the collection technique influences the contained triterpenes in P. lentiscus var. Chia resin samples. Finally, since there is confusion on interpreting mass spectra of triterpenes we present an analytical review on the base peaks, main fragments and fragmentation mechanism/pattern of several skeleton penta- and tetra- cyclic triterpenes reported in P. lentiscus resin. Also, a biosynthetic route for triterpene skeletons contained in P. lentiscus resin was approached.

Gas Chromatography-Mass Spectrometry↗

PubMed2004

Comparison of depth of dentin etching and resin infiltration with single-step adhesive systems.

OBJECTIVES: Adhesion of resin composites to dentin is currently believed to result from impregnation of adhesive resin into superficially demineralized dentin. The purpose of this study was to use micro-Raman spectroscopy and scanning electron microscopy (SEM) to investigate the extent of resin penetration into etched dentin with single-step adhesive systems. METHODS: Adhesive systems used were One-Up Bond F (Tokuyama Dental) and Reactmer Bond (Shofu, Inc.). A self-etching primer system Mac Bond II (Tokuyama Dental) was employed as a control. Resin composites were bonded to bovine dentin with the adhesive systems, and specimens were sectioned parallel to dentinal tubules. Raman spectra were successively recorded along a line perpendicular to the dentin-adhesive interface in steps of 0.2 microm and the spectra were obtained. SEM observations of the resin-dentin interface were also conducted. RESULTS: The dentin-resin interface of single-step adhesive systems showed a gradual transition in the relative amount of adhesive from the resin side to dentin side. The widths of resin penetration into demineralized dentin detected by Raman microscopy were greater than those obtained by the morphological analysis using SEM. CONCLUSIONS: From the results of this study, a gradual variation in the composition of the dentin-resin interface was detected, and the degree of resin impregnation observed with SEM observation was less than that detected with the Raman microscopy.

Animals↗

PubMedDate not supplied

Influence of resin cross-linking on solid-phase chemistry.

A range of PS-DVB resins were prepared by suspension polymerization with styrene, p-chloromethyl styrene, and DVB. Yields of polymerization increased (from 40% to almost 80%) with increasing cross-linking. The beads exhibited the expected swelling characteristics, with the 0.3% resin swelling to almost 9 times its dry volume in CHCl3. Kinetics of cleavage of the dye Methyl Red from the range of Rink linked resins showed rate enhancements of up to 500% between the 6.0 and the 0.3% cross-linked resins. Total synthesis of Kawaguchipeptin B was carried out on the resins, and their performance during the syntheses was investigated. Contrary to expectations, the purities of the cyclic peptide product increased with increasing resin cross-linking doubling from the 0.3-6.0% resin. A Suzuki reaction showed the half-lives of reaction increased with increasing resin cross-linking with an 11-fold increase in half-life between the 0.3-2.7% resin. Surprisingly, we observed very little reaction in the case of the 3.0 and 6.0% cross-linked resins.

Anti-Bacterial Agents↗

PubMedDate not supplied

Tailoring ultraresins based on the cross-linking of polyethylene imines. Comparative investigation of the chemical composition, the swelling, the mobility, the chemical accessibility, and the performance in solid-phase synthesis of very high loaded resins.

Ultraresins have been prepared from polyethyleneimines and cross-linking molecules and have been provided with various degrees of cross-linking. The total nitrogen loading and the loading with secondary and with tertiary amines have been determined in all products. Nitrogen loadings of the novel resins were up to 15 mmol/g, reactive secondary amines up to 13.8 mmol/g. In addition to the exceptionally high loading, the novel resins displayed efficient swelling volumes in polar and nonpolar solvents. The mobility of resin-bound species as determined by EPR-spectroscopy, depending on the amount of cross-linker, indicated good flexibility and reactivity of this resin type. The novel, high-loaded resins have been investigated subsequently in solid-phase synthesis. The Rink amide linker and two different hydroxy linkers (hydroxyacetamide, HMPB) have been attached to the resin. Despite the high loadings, the secondary amines were easily accessible and could be functionalized exhaustively. Reactivity of the linker-coupled resins was found to be closely related to the resin composition. Increased resin cross-linking led to reduced swelling, reduced mobility, and reduced reactivity in the synthesis of a medium-sized model peptide. As the result of the systematic investigation of structure-property relations in Ultraresins, a support material was identified that combined high reactivity and a mobility in the range of the extremely flexible Tentagel supports. In the optimized Ultraresin, >95% of all available secondary nitrogens could be coupled with Rink linker or with the small 2-hydroxyacetamide anchor, resulting in loadings from 2.7 to 6.8 mmol/g, respectively. A resin with an attached HMPB linker and spacer delivered analytically pure peptides in solid-phase synthesis, fully exploiting the exceptionally high loadings.

Journal Article↗