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PubMed2005

Physical properties of four acrylic denture base resins.

Resistance to impact fracture and high flexural strength are desirable properties of denture base acrylics. The purpose of this laboratory study was to determine the Izod impact strength, the flexural strength, the flexural modulus, and the yield distance for four premium denture resins. Bar specimens 86 x 11 x 3 mm of Lucitone 199, Fricke Hi-I, ProBase Hot, and Sledgehammer Maxipack were fabricated following the manufacturer's instructions for heat processing. The bars were surface finished using silicon carbide paper to 600 grit. Ten specimens from three lots of each material were made (n=30). Flexural strength, flexural modulus, and yield distance were determined by testing the specimens to failure using a three-point test fixture. Izod impact strength was determined using an Izod tester on un-notched specimens generated from the flexural test (n=60). Analysis of variance (ANOVA) and post-hoc Tukey's test were used for statistical comparison of each property. There were significant differences in the physical properties among the denture acrylics tested. Lucitone 199 demonstrated the highest impact strength, flexural strength, and yield distance (p<0.05). Lucitone 199 with an Izod impact strength of 5.5+/-1.2 N'm, a flexural strength of 99.5+/-4.5 MPa, and yield distance of 9.9+/-0.76 mm exhibited statistically greater results than Fricki Hi-I, ProBase Hot, and Sledgehammer Maxipack. Fricki Hi-I with a yield distance of 7.3+/-1.1 mm was statically greater than ProBase Hot and Sledgehammer Maxipack. Fricki Hi-I, ProBase Hot, and Sledgehammer Maxipack were statistically similar for the Izod impact strength and flexural strength tests performed. ProBase Hot and Sledgehammer Maxipack yielded statistically similar results for all tests performed. Flexural modulus had an inverse relationship to the impact strength, flexural strength, and yield distance.

Acrylic Resins↗
PubMedDate not supplied

An aspect of denture base retention: direct measurement of force due to surface tension.

A fixed-volume drop of liquid between a pair of parallel surfaces has been a common model for the denture-mucosa system. The reported one-term equation for the model, the derivation of which is suspect, implies that the acting force is inversely proportional to the square of the separation. Direct measurement of the force, however, showed that a better approximation is given by a two-term equation, with force varying as the inverse of the separation. The need for rigorous theoretical derivation is thereby emphasized. The experimental data suggest that a maximum retention force might occur for denture bases at separations of about 15 microns.

Acrylic Resins↗
PubMed2005

Influence of chemical and mechanical polishing on water sorption and solubility of denture base acrylic resins.

Influence of polishing methods on water sorption and solubility of denture base acrylic resins was studied. Eighty samples were divided into groups: Classico (CL), and QC 20 (QC) - hot water bath cured; Acron MC (AC), and Onda Cryl (ON) - microwave cured; and submitted to mechanical polishing (MP) - pumice slurry, chalk powder, soft brush and felt cone in a bench vise; or chemical polishing (CP) - heated monomer fluid in a chemical polisher. The first desiccation process was followed by storage in distilled water at 37 +/- 1 degrees C for 1 h, 1 day, 1, 2, 3 and 4 weeks. Concluding each period, water sorption was measured. After the fourth week, a second desiccation process was done to calculate solubility. Data were submitted to analysis of variance, followed by Tukey test (p<or=0.05). Means of water sorption (%) and solubility (%), respectively, were: CL-MP: 1.92 and 0.02; CL-CP: 1.98 and 0.52; QC-MP: 2.31 and -0.05; QC-CP: 2.32 and 0.25; AC-MP: 2.45 and -0.07; AC-CP: 2.43 and 0.41; ON-MP: 2.32 and -0.06; ON-CP: 2.34 and 0.27. Mechanical polishing promoted significantly lower solubility of acrylic resins; initially, water sorption values were higher for chemically polished samples, however, after 4 weeks all groups were similar.

Absorption↗
PubMedDate not supplied

Effect of the major connector on abutment tooth and denture base movement: an in vitro study.

This in vitro study investigated the effect of the major connector on distal abutment tooth and denture base movements when loads were applied to a partial denture with extracoronal attachments. A brass mechanism was constructed for load application, and the abutment and base movements were measured in three planes using a kinesiograph. It was determined that cutting the major connector affected the degree of abutment tooth movement but not the direction. After cutting the major connector, the base movement increased in all three planes with the different forces applied. The direction of the base movement changes only in the buccolingual plane.

Dental Abutments↗
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

[A comparative study of mechanical properties of microwave-cured and conventional water bath-cured denture base resins].

OBJECTIVE: To study the mechanical properties of microwave-cured polymethyl methacrylate (PMMA) denture base resins. METHODS: Using experiment research, the mechanical properties of microwave-cured and water bath-cured PMMA materials were compared. RESULTS: The microwave-cured acrylic strips had equal or better mechanical properties than conventionally processed strips. CONCLUSION: The microwave-cured denture materials satisfies the requirements of the prosthetic clinic.

Biomechanical Phenomena↗
PubMedDate not supplied

Effects of denture teeth on the dimensional accuracy of acrylic resin denture bases.

The Michigan Computer-Graphics Coordinate Measurement System was used to determine the effects of artificial denture teeth on the accuracy of acrylic resin denture bases. Two poly(methyl methacrylate) acrylic resins and two processing techniques were tested. Groups processed with denture teeth reproduced more accurate points than groups processed without denture teeth. Groups processed with a conventional heat-polymerized acrylic resin reproduced more accurate points than groups polymerized with an injection pressing type of acrylic resin.

Acrylic Resins↗
PubMed1991

Measurement methods used for the determination of dimensional accuracy and stability of denture base materials.

The literature relating to methods of measurement of dimensional accuracy and stability of denture base materials is reviewed. The papers are presented chronologically together with information on the measurement technique used and the reported level of accuracy. Most authors utilized optical measuring apparatus, with the use of calipers being the second most popular method.

Dental Materials↗
PubMed1992

Further observations on high impact strength denture-base materials.

Previous studies have shown that high impact strength can be conferred on denture-base poly(methyl methacrylate) polymers by modification with acrylic-terminated butadiene-styrene block copolymers, and that the acrylic end-group was necessary for effective reinforcement. It is now shown that, by solvent extraction studies, grafting of the copolymer occurs both with acrylic-terminated and non-terminated block copolymers. It is therefore concluded that the mode of grafting is different, and some possible mechanisms are discussed.

Acetone↗
PubMed1989

Impact properties of acrylic denture base resin. 3. Impact properties of cross-linked polymers.

The impact properties in acrylic denture base resins cross-linked using 6 diacrylates, such as ethylene glycol dimethacrylate (EDMA) and rho-divinyl benzene (DVB), were investigated and discussed. In addition, the creep characteristics of these cross-linked resins were examined and related with their impact characteristics. From these results, it was seen that both characteristics deteriorated with an increase in the diacrylate concentration from 2 mol% to 10 mol%. On the other hand, an increase in the repeated number (n) of (--CH2--CH2--O--)n promoted a flexibility in the materials which resulted in a higher impact strength and toughness. But, there was no a significant difference in the resilience of these materials.

Acrylic Resins↗