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At least 253 records · Page 14Linked to original sources
PubMedDate not supplied

Denture base reinforcement using woven polyethylene fiber.

Reinforcement of acrylic denture base resin with high-performance polyethylene fiber in woven form produced a substantial improvement of stiffness and impact strength, as well as reducing the sensitivity of the material to notches that mimic anatomic features. The mechanical properties of the new systems were not affected by water immersion. Reinforced complete maxillary and mandibular dentures having good appearance and satisfactory fiber/resin integration were achieved using conventional laboratory techniques. These prostheses are undergoing clinical trials with encouraging results.

Analysis of Variance↗
PubMed1994

Cytotoxicity of eluates from light-polymerized denture base resins.

This study examined the metabolic effects of eluates from four light-polymerized denture base resins and one heat-polymerized denture base resin on oral epithelial cells in vitro. The eluate was cell culture medium that contained either or both of apparently nonpolymerized components and reaction products that diffused out of the resin samples. Eluates were prepared by daily transfer of sample disks in a cell culture medium over 10 days. Toxicity of eluates was tested immediately after transfer (fresh) and after storage for 30 days (aged) by use of radioisotope incorporation and cell viability studies. The fresh eluates inhibited cell metabolism, whereas the aged eluates stimulated then inhibited the responses. Results suggest that the components that leach out of the tested materials do so at different rates and have prolonged toxic effects on cells. Thus soaking prosthesis in water before insertion may be beneficial.

Acrylic Resins↗
PubMed2000

In vitro colonisation of acrylic resin denture base materials by Streptococcus oralis and Actinomyces viscosus.

AIM: The aim of the study was to compare the attachment of two typical strains of oral bacteria to four denture base materials. DESIGN: In vitro study. METHOD: Discs of acrylic resin denture base materials (Paladon 65, polished and unpolished; Palapress; Microbase, polished and unpolished, and Triad VLC) were placed into Petri dishes with Schaedler's medium, inoculated with Streptococcus oralis 34 or Actinomyces viscosus T14V. MAIN OUTCOME MEASURES: After 24 h or 48 h the numbers of adhering bacteria were measured. RESULTS: The bacteria adhered to all discs in similar numbers: 3-9 x 10(6)/ml (viable cell count) and 9-22 x 10(8)/ml (total cell count) for T14V, and 2-6 x 10(6)/ml (viable cell count) and 1.5-3 x 10(8)/ml (total cell count) for 34. CONCLUSIONS: Polishing had little effect on adherence. Denture base materials are not resistant against adherence and possible surface damage by oral bacteria. Therefore, thorough oral hygiene is important for denture wearers.

Acrylic Resins↗
PubMed1989

[Superplastic forming of titanium alloy denture base].

Ti-6Al-4V alloy has both excellent biocompatibility and superior mechanical properties. This Ti-6Al-4V can be deformed greatly and easily at the superplastic temperature of 800 degrees C to 900 degrees C. The superplastic forming of Ti-6Al-4V was made to apply to fabrication of denture base. Almost the same procedure as for dental casting mold was employed in producing the superplastic forming die by the improved phosphate bonded investment. In the pressure vessel of heat resistant alloy, Ti-6Al-4V plate was formed superplastically on the die by argon gas pressure at 850 degrees C. The fit of superplactic forming Ti-6Al-4V denture base was better than that of casting Co-Cr alloy denture bases. The Ti-6Al-4V alloy might react a little with the die. Because micro Vikers hardness of the cross-section did not go up too much near the surfaces. Even just after being formed, the surfaces were much smoother than that of Co-Cr alloy casting. The tensile strength and yield strength of superplastic forming Ti-6Al-4V were higher than those of Co-Cr castings. The elongation was about 10%. These results show that superplastic forming of Ti-6Al-4V would be suitable for a denture base.

Dental Alloys↗
PubMed1979

Skin sensitivity to denture base materials in the burning mouth syndrome.

The significance of sensitizing compounds in the denture base for the etiology of the burning mouth syndrome (BMS) has been studied in 53 denture-wearing persons, seven males and 46 females. Epicutaneous patch tests were performed with standard concentrations of benzoyl peroxide, dibutylphthalate, dimethyl-p-toluidine, formaldehyde, hydroquinone, methylmethacrylate, p-phenylendiamine and with cadmium sulfate, potassium dichromate, cobalt chloride and nickel sulfate. Furthermore, patch testing was performed with filings from the denture mixed with the patient's own saliva. In cases with an inflamed oral mucosa, the presence of hyphae of Candida albicans was assessed by a smear technique. Positive skin reactions were observed in 15 persons to dimethyl-p-toluidine, hydroquinone, formaldehyde, methylmethacrylate, p-phenylendiamine, potassium dichromate, cobalt chloride and nickel sulfate, including three cases with reactions to filings from their dentures, and one patient who after subsequent testing showed skin sensitivity to balsam of Peru. In 12 cases an etiological connection could be traced between the oral symptoms and the denture base, indicating that contact sensitivity to base materials or to allergens and microbial antigens on the denture plate plays a greater role in the pathogenesis of BMS in edentulous persons than previously suggested.

Adult↗
PubMedDate not supplied

The significance of adhesive denture base resin.

This article reviews the problems that occur at the metal-resin interface of removable partial dentures. The absence of a chemical bond between the denture base resin and the base metal alloy results in a potential for microleakage and bond failure at the junction. Recent development of a denture base resin that incorporates 4-META has been reported, primarily in the Japanese dental literature. The primary advantage of the 4-META resin system involves its bond to base metal alloys used in removable partial prosthodontics.

Acrylic Resins↗
PubMed1990

[Transverse strength and acoustic emission characteristics of commercial denture base resins].

Transverse strength and acoustic emission (AE) characteristics were measured by the transverse test in deionized water at 37 degrees C on commercial denture base resins (five heat-cured type resins and one polysulfone). Difference in flexural property of five heat-cured denture base resins was not shown from the transverse deflection according to JIS, but high toughness of polysulfone was recognized in transverse deflection, flexural strength, flexural modulus, flexural rigidity, flexural proof stress, and fracture energy. The five heat-cured denture base resins showed a low AE activity, but the polysulfone resin high AE activity. Significant rates of AE for polysulfone were detected at a kgf of approximately 50-60% the maximum load. The presence of Kaiser effect in its cycle transverse test was confirmed.

Acoustics↗
PubMed1983

Influence of tooth-to-denture-base discrepancy on space closure following premature loss of deciduous teeth.

Influence of tooth-to-denture-base discrepancy on so-called physiologic migration of the first molar was studied on serial dental casts of 116 boys and girls, obtained through a dental health program for school children in an area in which there was no dentist. The alteration of spaces following premature loss of deciduous molars was examined comparing the anterior to posterior discrepancies between tooth and denture base. Modes of space alteration showed positive correlation with the size of the discrepancy, especially in the mandibular dental arches. The space deficiency in the posterior region seemed to have a positive effect on the mesial migration of the first molar. Mesial migration of the first molar seems to be pathologic rather than physiologic and is strongly affected by tooth-to-denture-base discrepancies. Space maintenance does not seem to be useful, because it is not necessary in minimum discrepancy cases and is not effective in severe discrepancy cases.

Adolescent↗
PubMedDate not supplied

Adherence of Candida species to newly polymerized and water-stored denture base polymers.

PURPOSE: The aim of this in vitro study was to examine the adherence of yeasts to newly polymerized and water-stored denture base polymers using four Candida strains with different cell surface hydrophobicities. MATERIALS AND METHODS: Thirty-two autopolymerized denture base polymer specimens were stored in distilled water at 37 degrees C for 7 days and 32 were newly polymerized. Sixteen specimens of each group were pretreated with unstimulated mixed saliva (saliva group), and 16 were pretreated with phosphate-buffered saline ([PBS] PBS group) at 37 degrees C for 1 hour. Hydrophobicity of the newly polymerized and water-stored specimen surfaces was determined by contact angle measurements. C guilliermondii, C albicans, C glabrata, and C tropicalis were grown on tryptic soy agar. They were pretreated either with saliva or PBS and suspended in PBS. Four parallel test specimens were incubated without agitation in each yeast suspension at 37 degrees C for 1 hour, washed, and allowed to dry in air. Adherent cells were fixed, gram stained, and counted from 10 high-power light-microscopy fields of each specimen. RESULTS: Enhanced adherence of yeasts was observed in water-stored test specimens in comparison to newly polymerized test specimens. Salivary pellicle reduced the hydrophobicity of test specimens and the adherence of yeasts. No differences in contact angles of distilled water between newly polymerized and water-stored polymers were observed. CONCLUSION: Yeasts seem to adhere less to newly polymerized than water-stored denture base polymer. This may be due to the release of residual monomer from the newly polymerized material.

Adhesiveness↗
PubMed2002

Quantitative determination of salivary components in the pellicle on PMMA denture base material.

The formation of a salivary pellicle is a protective mechanism of the body for all surfaces in the oral cavity. The nature of the substrate may influence the composition of the pellicle. The aim of this study was to investigate the quantitative composition and individual variation of the salivary pellicle formed on denture base material (PMMA). Cylindrical specimens of PMMA were carried in the mouth and then desorbed with a 0.5-M sodium chloride solution. The solution was analysed for total protein, alpha-amylase, total proteases, protease inhibitors, secretory immunoglobulin A, immunoglobulin G, peroxidases, thiocyanate, lysozyme, and calcium content. All investigated salivary components could be found unequivocally in the desorption solution, indicating that a salivary pellicle had formed on the surface of the PMMA. Large coefficients of variation indicate large individual variations in the adsorbed amounts. The data also point to large intraindividual variations for the bound salivary components. Only the protease inhibitors revealed a strong positive correlation of the bound activity to the salivary activity. It is hypothesised that differences in the bound amounts of antimicrobial components might influence the microbial colonisation of denture bases and that protease inhibitors could be meaningful for the spread of the yeast Candida albicans from denture base material to the oral mucosa and thus might be an explanation for different susceptibility to denture base stomatitis.

Adolescent↗
PubMed1980

Fatigue test machine for denture base polymers.

A description of a single station fatigue test machine suitable for denture base polymers is given. This machine has been especially designed for dental purposes. A group of representative denture base polymers has been tested, which includes dental poly(methylmethacrylate) of the standard heat polymerized type, autopolymerizing pour type and a heat polymerized rubber graft polymer. These materials were compared and some preliminary results are given. These show that the rubber demonstrated the most satisfactory fatigue life and the pour types were least satisfactory.

Dental Stress Analysis↗
PubMedDate not supplied

[Water absorption by denture base resins].

In a review of the international literature about water absorption of denture base resins any effect on the physical properties of these polymers has been considered. The authors discuss the possibilities of controlling the final results on denture base function.

Absorption↗
PubMed1993

A comparison of the dimensional accuracy of microwave and conventionally polymerized denture base materials.

This study compares the dimensional changes of microwave and conventionally polymerized denture bases and also establishes the degree of monomer conversion using gas-liquid chromatography. Dimensional changes of three denture base materials were assessed using an optical comparator and the results showed no significant differences between the materials employed or the curing method used. Efficient monomer conversion was demonstrated with levels of residual monomer of less than 1% for all materials.

Chromatography, Gas↗
PubMed1991

The effects of hollow microsphere fillers on density and impact strength of denture base resins.

The addition of 20 vol% and 40 vol% filler significantly (p less than 0.05) reduced the density and impact strength of the denture base resin when compared with resin without filler. There was no significant difference in the density or impact strength between 20 vol% and 40 vol% filled specimens. Desiccation significantly (p less than 0.05) decreased the density and impact strength of denture base resin regardless of the presence or amount of filler added. The addition of microsphere filler decreased the denture base resin density by 8% to 9%, which may not reduce the weight of prostheses enough to be clinically significant. The impact strength was reduced by approximately 30%.

Analysis of Variance↗
PubMedDate not supplied

Resin denture bases: review of accuracy and methods of polymerization.

Traditional compression molding and heat-activation methods for polymerization of denture base resins have been widely used. Studies have shown that stresses introduced during processing can lead to the distortion of denture bases. Chemical-, microwave-, and light-energy activation, and various combinations (including polymerization under pressure) have been offered as alternative ways to make dentures. These methods have been attempts to improve the accuracy of fit of the dentures, but sometimes the goal has also been to provide a more convenient laboratory technique. This extensive review covers studies that have investigated the accuracy of acrylic and other types of resins for making dentures using the known range of fabrication methods.

Acrylic Resins↗
PubMed1989

Impact properties of acrylic denture base resin. 2. Effect of temperature and residual monomer on impact characteristics.

The temperature dependence of the impact strength, resilience, and toughness of the acrylic denture base resins on temperature changes was examined by using a modified impact testing machine. In addition, the creep properties and the residual monomer of their resins were measured; and considering these properties, the impact characteristics of the denture base resins were discussed. With an increase in temperature, the impact properties of all the acrylic denture base resins tested decreased. Furthermore, there was an adequate correlation between the impact characteristics and the amount of the residual monomer. The coefficient of correlation was 0.92 for the impact strength, -0.95 for the resilience and 0.94 for the toughness. For the cold cured acrylic resins, both elastic moduli obtained by the impact test and by the creep test increased obviously according to an increase in the time which elapsed after polymerization.

Acrylic Resins↗
PubMed1992

Linear dimensional variability of three denture base resins after processing and in water storage.

It has been shown that denture base resins shrink during curing and expand during storage in water. This investigation measured and compared linear dimensional changes of three denture base resins that occurred during processing and after storage in water for 30, 60, and 90 days. Triad, Accelar 20, and Lucitone 199 long- and short-cured resins were studied, and it was found that Accelar 20 resin exhibited the least curing shrinkage and Lucitone 199 resin short-cured exhibited the most. However, no significant differences occurred between the groups. After 90 days of water storage, the only resin that exhibited a shrinkage from the processed state was Accelar 20. All of the expansion or shrinkage changes were so small that they were not statistically significant and should not be clinically detectable.

Acrylic Resins↗
PubMed1979

[Properties of polyfluoroethylene-copolymers for the denture base lining material (author's transl)].

Silicone rubber is conventionally used as a lining soft material for denture base. However it still has some properties to be improved, such as poor adhesive strenth with acrylic resin, discoloration, degradation and growth of candida. We attempted to apply chemically-stable polyfluoroethylene-copolymers for this purpose. The terpolymers consisting of difluoroethylene, tetrafluoroethylene and chlorotrifluoroethylene (or hexafluoropropylene) were prepared and tested for tensile strenth, adhesive strength to acrylic resin, water sorption, contact angle, shore hardness, and toxicity by hemolysis test, cell culture test and extraction test. One of the selected terpolymer showed less water sorption (0.1 mg/cm2), stronger tensile strength (160 kg/cm2) and adhesive strength (110 kg/cm2) than the silicone rubber lining material. The toxicity test results suggested that the terpolymer will pose a low potential acute toxicity in vivo. All the test results seem to suggest that the polyfluoroethylene elastomer described here is a promising soft liner material for denture base.

Acrylic Resins↗