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The rupture lengthening test demonstrated the addition of fiberglass to acrylic resin tends to make the test bodies more rigid, making them fracture with a shorter lengthening than unloaded resin. The greatest rigidity was observed with a 20% load.
Microencapsulation of ketoprofen using Eudragit E, L and S (acrylic resins) was investigated. The preparation is based on the dispersion of acetone containing ketoprofen in liquid paraffin. Aluminium tristearate was used as an additive for the preparation of microcapsules. In the preparation of microcapsules, the reproducibility of the Eudragit E microcapsule was better than that of Eudragit L and S microcapsules. The microcapsules obtained were uniform and free-flowing particles. From the phase diagram of ketoprofen-Eudragit E or S-aluminium tristearate, it became clear that the region in which the spherical microcapsules ranging from 250 to 1000 microns in size could be prepared was limited. The dissolution patterns of ketoprofen from Eudragit E, L and S microcapsules were dependent on the pH of the dissolution medium.
This study evaluated the effectiveness of three different disinfectant solutions against denture bioburden absorbed within the depth of acrylic resin. Specimens were taken from dentures that had been worn by the patients for 15 to 20 years and were scheduled for replacement.
Some clinical observations have brought the authors to suspect a corrosion of acrylic resins by an alcaline peroxide (Steradent) proposed as a denture cleanser. By way of a laboratory simulation they have shown that standardized samples of Lucitone 199 are corroded by the main active agents issuing from Steradent: oxygen and a high level of alcalinity. A daily use of Steradent can thus badly affect the physical properties of denture acrylic bases.
The effects of four liquid components of denture acrylic resin on host cell activity and fungal adhesion were investigated in this study. The low concentration (1 micromol l(-1)) of the liquid components caused no change in the activities and morphologies of the gingival fibroblast cells, compared with control and dimethylsulphoxide-exposed cells. However, when the cells were exposed to high concentrations (1 mmol l(-1)) of benzqyl peroxide, morphological change was observed, implying that the exposure of the cells to high concentrations of the liquid components of denture acrylic causes the loss of adhesion proteins from the cells. Thus the amount of Candida adhesion to human gingival cells was analysed, and the adherence of fungi to the cell was significantly reduced when the cells were pre-exposed to methyl methacrylate, hydroquinone and benzoyl peroxide at a concentration of 1 micromol l(-1) (P < 0.01), which did not affect either the cell viability or the cell morphology. These results, taken together, suggested that the renewal of dentures could be a possible therapeutic and/or preventive aid for oral candidosis in denture-wearing patients.
The purpose of this study was to evaluate the color stability of two acrylic resin adhesives with different activation systems: a benzoyl peroxide (BPO)-amine redox system and a tri-n-butylborane (TBB) derivative system. The colorimetric values of the two resins in different shades (Clear and Ivory) were determined (n=5) 24 hours after polymerization as a baseline using the L*a*b* system of the Commission Internationale de l'Eclairage (CIE). The specimens were thereafter immersed in distilled water, and the color difference (deltaE*) values were calculated. After 24 weeks, the TBB-initiated material showed a significantly (p<0.05) lower color change than the BPO-amine-initiated material. The deltaE* values for the BPO-amine-initiated materials were 6.9 for Clear and 15.8 for Ivory, whereas those for the TBB-initiated materials were 1.3 and 1.8 respectively. Thus, it was concluded that the TBB-initiated material had superior color stability to that of the BPO-amine-initiated material.
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Microencapsulation of ketoprofen using Eudragit RS and RL (acrylic resins) was investigated based on the dispersion system of ketoprofen-containing acetone in liquid paraffin. Aluminium tristearate was used as an additive for the preparation of microcapsules. Good reproducibility was observed in the microencapsulation and the resulting microcapsules were uniform, free-flowing particles. The phase diagram of ketoprofen-Eudragit RS or RL-aluminium tristearate indicated that it is only in a very limited region that spherical microcapsules ranging from 250 to 1000 microns in diameter could be prepared. Instrumental analysis using an energy dispersive-type X-ray microanalyser and a scanning electron microscope showed that aluminium tristearate was localized near the surface of the microcapsules. From these results, it was presumed that aluminium tristearate reduces the phase tension between Eudragit microcapsules and liquid paraffin. The dissolution patterns of ketoprofen from Eudragit RS and RL microcapsules were independent of the pH of the dissolution medium, and the dissolution rates were considerably lower than those from ketoprofen powders.
PURPOSE: This study investigated the influence of hard and resilient polymerized acrylic resin base materials on the blood flow of the supporting underlying mucosa of mandibular denture wearers during different denture-wearing periods. MATERIALS AND METHODS: Measurements were carried out on 20 complete denture wearers, 10 with hard bases and 10 with soft ones. The mucosal blood flow underlying the dentures was measured bilaterally in the canine and molar regions using a laser Doppler flowmeter. Baseline measurements were performed before denture wearing and after the dentures were worn for 1 week, 1 month, 3 months, and 6 months. RESULTS: Mean blood flow to the mucosa after 1 week was significantly lower in the measured regions than that obtained before the dentures were worn. Blood flow in the canine region returned to almost normal levels 6 months after beginning to wear complete dentures. However, blood flow in the molar region of the denture wearers in the hard base group increased after 6 months, whereas blood flow values did not return to the levels recorded before denture insertion in the soft lining group. CONCLUSION: It appears that wearing dentures hinders blood flow to denture-supporting tissues, even when soft liners are used.
The effect of incorporated CaF2 (2.04%), NaF (2.27%) and amine fluoride (0.71%) in acrylic resin plates, on bending strength and fluoride release by rinsing and immersion in synthetic saliva, was determined. Bending strength was reduced by 6.7, 9.5 and 20% respectively. The most elevated release of fluoride from the NaF containing--and the most protracted from the CaF2 containing--plates may be related to the solubilities of the compounds. It appears that the organic molecule of the AmF compound affects the strength of the acrylic plates most significantly. The F- concentrations released in the in vitro rinsing experiment may be presumed to occur in vivo at some higher level due to the larger size of dental appliances.
A case history is presented of a patient who fabricated 3 prostheses from autopolymerizing acrylic resin intended for fingernail augmentation and then cemented them into her mouth with super glue. Patients must be warned not to attempt self-treatment for esthetics with self-fabricated prostheses because severe adverse and irreversible hard and soft tissue reactions may occur.
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Marsupialization is a surgical technique that may be preferred to enucleation in treatment of benign cysts. The acrylic resin obturator maintains the surgical opening during healing and assures success of the surgery. Two basic techniques to construct a stable and retentive obturator prosthesis were described.
A one-session technique for preparing a temporary space maintainer has been described. The technique consists of attaching an acrylic resin pontic to etched surfaces of natural adjacent teeth by means of a composite resin. The main advantages of this technique are elimination of premature tooth preparation, good esthetics, fair strength, low cost, and rapid completion of the restoration without the need of a dental laboratory.
A technique has been described for the fabrication of strong, esthetic, and periodontally considerable provisional restorations. The technique involves cast nonprecious metal frameworks and heat-processed acrylic resin.
The tensile and shear strength for a polyalkeonate luting cement (AquaCEM) and a no-mix acrylic resin (Unite) in orthodontic bracket bonding were compared in an in vitro test. Brackets bonded/cemented to extracted premolar teeth were subjected to loads in a universal testing apparatus and the dislodging forces were recorded. The possible influences of setting time and of bracket base design were also studied. No significant differences between the cement and the resin were found after allowing 24 hours of setting time. This in contrast to the significantly stronger tensile strength but inferior shear strength for the polyalkeonate cement when stress was applied after 15 minutes. A significantly higher tensile strength value was recorded for a foil-meshed bracket base type compared to an integral base type with cut grooves after 15 minutes, but not after 24 hours. While the polyalkeonate cement adhesion mostly fractured within the cement layer, the acrylic bond more often failed in the enamel-adhesive interface. The results support the use of the fluoride-containing cement as an alternative to acrylic adhesives in orthodontic bracket bonding, especially in high-risk caries patients.
The clinical usefulness of continuous E-glass partial fiber reinforcement of acrylic resin removable dentures was evaluated an average 13 months after the insertion of the fibers. Twelve removable complete dentures and ten removable partial dentures with a history of recurrent fracture were selected for this study. The partial fiber reinforcement was incorporated into the denture at the time of repair. One complete denture and one removable partial denture fractured in the region of reinforcement during the examination period. These fractures were most likely caused by faulty placement of the fiber reinforcement in the denture in the dental laboratory. In six dentures, new fractures occurred in regions without partial fiber reinforcement. The results revealed the importance of both the correct positioning of the partial fiber reinforcement in the denture and the use of accurate laboratory techniques.