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Implantable enzyme capsules for cancer chemotherapy from bakers' yeast cytosine deaminase immobilized on epoxy-acrylic resin and urethane prepolymer.

For trial use in the local chemotherapy of cancer by a combination of cytosine deaminase (EC 3.5.4.1) and 5-fluorocytosine (J. Biotechnol., (1985), 2, 13-21), 40 U of partially purified cytosine deaminase was obtained from 500 g of commercial compressed bakers' yeast. The enzyme, which is unstable, was immobilized to stabilize it by the use of commercial epoxy-acrylic beads (Eupergit C). The immobilized enzyme was made into enzyme capsules with cellulose tubing for dialysis to encapsulate it or urethane polymer to entrap it, which materials are biocompatible. The activity of the intact cellulose capsules thus made was 0.4% that of the immobilized enzyme inside. The enzyme capsules also were stable. Ten days after the cellulose capsules were implanted in rats, 25% of the starting activity remained. When the polyurethane capsules were tested in vitro for 9 mo for thermostability at 37 degrees C, the activity decreased rapidly (with a half-life of 28 d) during the first 4 mo, and then slowly (half-life, about 100 d) during the next 5 mo. A calculation to transform the biphasic decline into a sum of the exponential decline of two components of enzymic activities with different strengths and half-lives showed that the larger half-life was 5 mo.

Antineoplastic Agents↗

Physical and chemical factors influencing the release of drugs from acrylic resin films.

An investigation was conducted to evaluate the factors influencing the release of salicylic acid and chlorpheniramine maleate from polymethacrylate amino-ester copolymer films (Eudragits RL PM and RS PM). Differential scanning calorimetry was performed on the films to study the solubility of drug in the polymer and to determine the effect of added drug on the thermal properties of the film. Incorporation of drug into the polymers decreased the glass transition temperature of the polymers. Dissolution of drug from monolithic slabs was followed as a function of temperature, drug concentration in the films, and ionic strength of the release media. In addition, adsorption studies were conducted with each drug:polymer combination to help explain release results and further characterize the drug:polymer interactions that occurred. The rate of drug release increased with increasing temperature. Adsorption of salicylic acid by the polymers was believed to influence the drug release profiles observed for different drug loadings and ionic strengths. Eudragit RL was found to adsorb salicylic acid to a greater extent than the Eudragit RS. Chlorpheniramine maleate was not found to be adsorbed by either polymer.

Acrylates↗

Cranioplasty utilizing a preserved autogenous bone flap coated with acrylic resin.

Cranioplasty utilizing a resin-coated preserved autogenous skull flap was devised and used in 36 cases, 14 of them being followed up radiologically. It has been confirmed that this method is advantageous in that it repairs the skull defect satisfactorily both from surgical and cosmetic points of view. Furthermore this method causes no anxiety to the patient because of the autogenous origin of the bone flap. We recommend this method for cranioplasty when an autogenous bone flap is preserved.

Adolescent↗

Effect of chilled monomer on working time and transverse strength of three autopolymerizing acrylic resins.

Samples of three commercially available poly(methyl-methacrylate) autopolymerizing resins were made by using room temperature and chilled monomer. Working and setting times and transverse strengths were determined. The following conclusions can be drawn: 1. Working and setting times increased approximately 2 to 4 minutes when chilled monomer was used. This could be advantageous in certain situations. 2. Transverse strength decreased approximately 17% with the use of chilled monomer. The clinical significance of this decrease is not known.

Chemical Phenomena↗

Effects of thermocycling on the margins of transitional acrylic resin crowns.

Transitional resin crowns were subjected to thermocycling and examined for marginal integrity since disturbance of the marginal seal is detrimental. Two groups of 10 crowns, one with a chamfer and the second with a shoulder finish line, were subjected to two series of 2500 thermocycles. In the first series, the crowns received cold thermocycling and in the second, hot thermocycling. Impressions were made of the facial margins before thermocycling, after cold thermocycling, and after hot thermocycling. The impressions were analyzed for loss of marginal integrity and changes in axial contour. Cold thermocycling resulted in only limited deterioration, but the changes after hot thermocycling were more pronounced. Tooth preparation designs did not influence the effects of thermocycling.

Cold Temperature↗

Laboratory-processed acrylic resin provisional restoration with cast metal substructure for immediately loaded implants.

Most methods of immediate loading of implants reported in the literature involve retrofitting a pre-existing denture to the implants. This article describes and illustrates clinical and laboratory procedures for immediate loading of implants in the edentulous mandible with the use of a laboratory-processed, provisional, screw-retained, implant-supported fixed complete denture that incorporates a cast metal reinforcement.

Dental Alloys↗

The effect of surface treatment of denture acrylic resin on the residual monomer content and its release into water.

The test specimens were processed by autopolymerizing poly(methylmethacrylate) (PMMA), and their surfaces were untreated, polished in a conventional manner with a rag wheel, or coated with a light-curing resin. The residual methylmethacrylate (MMA) content and its release into water from the specimens were measured with high-performance liquid chromatography. The light-curing resin coating reduced most effectively the release of residual MMA into water during a 2-day storage, but conventional polishing of the PMMA surface had a similar effect when the mean values of groups were tested by means of one-way ANOVA (p < 0.001). The residual MMA content was lowest in the test specimens coated with a light-curing resin, whereas only a slight difference was seen when the untreated and polished test specimens were compared. This study suggests that not only light-curing resin coating but also the conventional polishing of the denture PMMA reduces residual MMA release into water in vitro.

Analysis of Variance↗