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PubMed2006

Effect of relining, water storage and cyclic loading on the flexural strength of a denture base acrylic resin.

OBJECTIVES: This study investigated the effect of relining, water storage and cyclic loading on the ultimate flexural strength (FS(U)) and on the flexural strength at the proportional limit (FS(Pl)) of a denture base acrylic resin (Lucitone 550-L). METHODS: Rectangular bars of L were made (64 mm x 10 mm x 2 mm) and relined (1.3mm) with four relining resins (Kooliner-K, Ufi Gel Hard-UGH, Tokuso Rebase Fast-TR and New Truliner-NT). In addition, specimens relined with L and intact L specimens were made (64 mm x 10 mm x 3.3 mm). A three-point flexural test was applied on the specimens (n=10) after (1) polymerization; (2) water storage (30 days); (3) cyclic loading (10,000 cycles at 5 Hz) and (4) water storage (30 days)+cyclic loading. Data (MPa) were analyzed with three-way ANOVA and Tukey's HSD tests (alpha=0.05). To test for a possible correlation between FS(U) and FS(Pl), a linear regression coefficient "r" was calculated. RESULTS: After water storage, L-UGH and L-TR demonstrated an increased FS(U) (41.49-50.64 MPa and 49.95-57.36 MPa, respectively) (P<0.05). Only L-TR demonstrated an increased FS(Pl) (20.58-24.21 MPa) after water storage (P<0.05). L-L had the highest FS(U) (between 78.57 and 85.09 MPa) and FS(Pl) (between 31.30 and 34.17 MPa) (P<0.05). The cyclic loading decreased the FS(U) and FS(Pl) of all materials (P<0.05). Regression analysis showed a strong linear correlation between the two variables (r=0.941). CONCLUSIONS: Water storage improved the FS(U) of L-UGH and L-TR and the FS(Pl) of L-TR. L-L produced the highest FS(U) and FS(Pl). The FS(U) and FS(Pl) of all materials were detrimentally influenced by cyclic loading.

Acrylic Resins↗

PubMed1997

The effect of surface treated UHMWPE beads on some properties of acrylic resin denture base material.

UHMWPE in the form of experimental surface treated beads was added to acrylic resin denture base material in various percentages to form a composite material. The influence on doughing and manipulation times, and transverse and impact strength was examined. The results indicated that the manipulation times, were not significantly affected as the percentage of UHMWPE beads in the acrylic resin powder increased. Increasing the percentage of incorporated UHMWPE beads resulted in an inconsistent decrease in the modulus of rupture and no effect on the impact fracture resistance. It was concluded that the use of treated UHMWPE beads is of no significant benefit to the properties of acrylic resin.

Acrylic Resins↗

PubMed1995

The effect of the slope inclination of buccal polished surface of mandibular denture base on food retention.

The accumulation of food debris in the buccal vestibule can inhibit normal mastication and appears to be a factor that can cause patient discomfort. This study focused on the effect of the slope inclination of the buccal polished surface of the mandibular denture base on the ability to expel test-food particles from the buccal vestibule. It was revealed that an inclination of the slope steeper than 80 degrees markedly inhibits the normal ability to expel foods from the vestibule. It was revealed that the most appropriate inclination of the buccal slope is approximately 60 degrees or 70 degrees. These results could be utilized for constructing a denture prosthesis.

Adult↗

PubMed2000

[The effect of long-term water storage on some mechanical properties of denture base material].

Flexural strength and Hounsfield impact resistance of a denture base material were yearly tested in a time scale of 5 years. Impact energy for fracture was continuously stable during the 5-year-long storage in water. Forces caused fracture in wet circumstances were between 60-80 N during the observation period. A significantly (p < 0.001) higher forces were measured at fractures for dry specimens in comparison to the wet polymer material in some years.

Biomechanical Phenomena↗

PubMed2005

An in vitro investigation of water sorption and solubility of two acetal denture base materials.

Acetal resins have been used as an alternative denture base and clasp material recently. The aim of this study was to compare water sorption and water solubility of pink and white acetal resins as compared to a heat-polymerized polymethyl methacrylate resin (PMMA). The tests were performed in accordance with International Standards Organization specification No: 1567. Pink acetal resin showed significantly lower water sorption than heat-polymerized acrylic resin and white acetal resin. PMMA showed significantly higher solubility than pink and white acetal resin. Water sorption and solubility of PMMA, pink and white acetal resins were within the ISO specification limit.

Polymethyl Methacrylate↗

PubMed1983

The level of residual monomer in self-curing denture-base materials.

Because residual monomer may cause tissue irritation, we investigated two self-curing acrylic denture-base materials--one a compression type, and the other a pourable material--by means of gas-liquid chromatography. Both exhibited higher residual monomer levels than did heat-cured acrylics, with thick sections having lower values than did thin sections. The pourable material showed lower values than did the compression variety.

Acrylic Resins↗

PubMed1990

Rheology of acrylic denture-base polymers.

The aim of this study was to investigate the changing rheological behavior of a denture-base polymer from mixing to setting. In addition, monomer evaporation and exothermic behavior of the mix were evaluated. The results show that the material behaves as a pseudoplastic fluid. It is shown that the viscosity increases at different rates with respect to lapsed time, and increases with higher temperature. Also, it is shown that polymerization and monomer evaporation both play a part in dough formation.

Acrylic Resins↗

PubMed1980

Compressive creep of denture base polymers.

The creep characteristics of heat-polymerized and auto-polymerized dough and pour type denture base materials were measured at 23,37, and 50 degrees C with emphasis on secondary steady state creep rates. The creep rates were correlated to the processing conditions and material composition. Two different creep mechanisms were evident, depending on the stress levels. Below 20-40 M Nm-2 at 37 degrees C, the creep was due to a homogeneous deformation. At higher stress levels the creep was ascribed to an inhomogeneous deformation mechanism. The lowest creep rates were found for the heat-polymerized materials. Variations in the creep rates for the other materials could generally be related to composition differences.

Acrylic Resins↗

PubMed2002

Durability of acrylic tooth bond to polymeric denture base resins.

The effect of ageing in simulated mouth conditions on bond strength between acrylic teeth and denture base resins was evaluated. Bonding was tested in tension according to ADA specification No. 15. The data was analysed using two-way analysis of variance and Tukey test at P < 0.05. The ageing effect on bond strength became significant after six months of exposure when bonding of acrylic teeth to heat-cured and autopolymerised resins was significantly reduced, P = 0.001 and P = 0.03 respectively. The bond strength value of the autopolymerised resin to acrylic tooth after one year in test environment was half the acceptable value of 31.0 MPa suggested by the ADA specification No. 15, whereas tooth bond strength to heat-cured resin was acceptable even after one year of exposure.

Acrylic Resins↗

PubMed1974