Polyethylene fibre reinforced poly(methylmethacrylate)--water sorption and dimensional changes during immersion

Behaviour of PMMA Resin Composites Incorporated with Nanoparticles or Fibre following Prolonged Water Storage

When PMMA denture base acrylics are exposed to oral environments for prolonged periods, the denture base absorbs water, which has a negative influence on the denture material and the degree to which the denture base will be clinically effective. This study assessed the water sorption, desorption, and hygroscopic expansion processes within PMMA denture-base resins reinforced with nanoparticles or fibre in comparison to the non-reinforced PMMA. The surfaces of the fillers were modified using a silane coupling agent (y-MPS) before mixing with PMMA. Group C consisted of specimens of pure PMMA whereas groups Z, T, and E consisted of PMMA specimens reinforced with ZrO₂, TiO₂ nanoparticles, or E-glass fibre, respectively. The reinforced groups were subdivided into four subgroups according to the percentage filler added to the PMMA resin by weight (1.5%, 3.0%, 5.0%, or 7.0%). Five specimens in disc shape (25 ± 1 mm × 2.0 ± 0.2 mm) were tested for each group. To assess water sorption and hygroscopic expansion, specimens from each group were individually immersed in water at 37 ± 1 °C for 180 days. The samples were then desorbed for 28 days at 37 ± 1 °C, to measure solubility. Water sorption and solubility were calculated using an electronic balance in accordance with ISO Standard 20795-1, and hygroscopic expansion was measured using a laser micrometre. Statistical analysis was undertaken at a p ≤ 0.05 significance level using a one-way ANOVA followed by Tukey post-hoc tests. The results demonstrated that the values of sorption (W_sp), mass sorption (M_s%), and % expansion within the tested groups reached equilibrium within 180 days. A noticeable difference was observed in groups Z and E for (W_sp)/(M_s%) compared to the Group C, but this was not significant. However, the difference between Group C and Group T for these measurements was significant. Non-significant differences also existed between each respective reinforced group and the control group in terms of hygroscopic expansion % values. During the 28-day desorption period, there were no differences in the values of solubility (W_sl)/mass desorption (M_d%) between Group C and each of the reinforced tested groups. The findings indicate that the inclusion of ZrO₂ nanoparticles or E-glass fibres does not increase the water solubility/sorption of the PMMA. However, modifying the PMMA with TiO₂ did significantly increase the water sorption level.

Histopathological evaluation of the effects of fiber reinforced acrylic resins on living tissues

OBJECTIVE

The aim of this study was the histopathological evaluation of the effects of the fiber reinforced acrylic resins on living tissues.

MATERIALS AND METHODS

The study was performed on 21 rabbits. Three groups, each including seven subjects, were formed. There was no applied plate in the control group. For the second group, heat-polymerized acrylic resin plates were inserted. For the third group, heat-polymerized acrylic resin plates containing proportionally 5% chopped silanated E type glass fiber were inserted. Plates were fixed to the palatine bone of the rabbits with titanium screws. Before the implementation of the plates and 1 month after the plates were applied, soft tissue samples were taken from the buccal mucosa of the rabbits. Also, tissue samples were taken from the control group. All samples were evaluated histopathologically.

RESULTS

In the control group, only a focal atrophy was observed. In the acrylic group, large decomposition containing erythrocytes under the parahyperkeratotic region and micro-vesicle like spongiotic tissue reactions were observed. In the fiber reinforced acrylic group, widespread focal atrophy, bulgy look of the epithelium cells similar to apoptosis, over-distension and sub-corneal decomposition had been observed. In terms of atrophy and hyperkeratosis there were no statistically significant differences among groups. However, in respect to sub-corneal decomposition, there was a statistically significant difference in the fiber reinforced group (p < 0.01).

CONCLUSIONS

The statistically significant difference in the sub-corneal decomposition of the fiber reinforced group had made us think that fiber edges had a traumatic effect on the reaction.

Effects of mica and glass on surface hardness of acrylic tooth material

The purpose of this study was to evaluate the effects of four different ratios of silanized mica filler and milled glass fiber on the surface hardness of an acrylic denture tooth material. Acrylic resin disks made of polymethyl methacrylate (PMMA) used in fabrication of denture teeth were used as the control group. Eight test groups were prepared by adding a ratio of 5%, 10%, 15%, or 20% by weight of silane-treated mica filler or milled glass fibers to the PMMA resin of denture teeth. Surface hardness test was performed for each group. There were statistically significant differences in surface hardness between the control group and 5%, 10%, and 15% mica- and glass-containing test groups (p<0.05). It was determined that addition of 5%, 10%, and 15% of silane-treated mica filler or silane-treated milled glass fiber to the PMMA resin of denture teeth resulted in significantly improved surface hardness.

Dimensional stability and dehydration of a thermoplastic polycarbonate-based and two PMMA-based denture resins

This study compared the dimensional stability and dehydration of a thermoplastic polycarbonate denture base resin with two conventional polymethyl methacrylate denture base resins. Maxillary complete dentures were fabricated from the three denture materials and the accuracy of fit along the posterior palatal border of the cast used in processing was measured. Measurements were conducted at five palatal locations immediately after processing and at 7 and 30 days during immersion in water (23 degrees C) and at 7 and 30 days during dehydration (23 degrees C, 65-75% relative humidity). Percentage mass loss during dehydration was determined with an electronic balance. The thermoplastic material was separately compared with each of the conventional resins using a modified Welch two-sample t-test, with a Bonferroni correction for P values. For mean palatal dimensional change, the thermoplastic resin was generally not statistically different from the conventional resins after processing and during immersion (P > or = 0.06), but was generally less than the conventional resins during dehydration (P < or = 0.02). For mean percentage mass loss, the thermoplastic resin consistently showed much smaller, statistically significant values compared with the conventional resins (P < 0.001). It was concluded that the thermoplastic resin should show dimensional changes in service comparable with the conventional resins, but less dimensional change caused by dehydration.

Water sorption, solubility and dimensional changes of denture base polymers reinforced with short glass fibers

The aim of this study was to determine water sorption, solubility and dimensional stability of injection and compression-molded polymethyl methacrylate based denture base polymer that was reinforced with various concentrations and lengths of E-glass fibers. For water sorption and solubility, 20 test groups with different fiber contents and lengths of fibers were prepared. Test specimens without fibers were used as a control. The water sorption and solubility was measured after 90 days water storage. For dimensional stability, rhombic test specimens were prepared and the dimensional changes were measured after processing, drying and storing in water for 4 days and 30 days and were compared with those on the brass model. The water sorption and solubility of injection-molded denture base polymer was lower compared to compression-molded specimens (p < 0.05). The dimensional accuracy of denture base polymer was not affected with fiber reinforcement (p > 0.05).

The influence of short-term water storage on the flexural properties of unidirectional glass fiber-reinforced composites

OBJECTIVE

The aim of this study was to determine flexural properties of unidirectional E-glass fiber-reinforced composite (FRC) with polymer matrices of different water sorption properties.

METHODS

Rhombic polymer and FRC test specimens made of three commercially available diacrylate resin (Sinfony Activator, Triad Gel, 3M Scotchbond Adhesive) and different volume fractions of fibers were tested with three-point bending test according to ISO 10477 after storing in water for 30 days. Water sorption of specimens was also measured.

RESULTS

Flexural strength of specimens with 45 vol% fraction E-glass fibers varied from 759 to 916 MPa in dry conditions. Water-stored specimens showed flexural strengths of 420-607 MPa. ANOVA analysis revealed that the fiber-volume fraction and the water sorption of the polymer matrix had a significant effect (p < 0.001) on the flexural properties. Dehydration of specimens recovered the mechanical properties. Decrease of flexural properties after water immersion was considered to be mainly caused by the plasticizing effect of water and the decrease depended on water sorption.

SIGNIFICANCE

Use of polymers with low-water sorption seems to be beneficial in order to optimize the flexural properties of FRC.

Flexural properties and impact strength of denture base polymer reinforced with woven glass fibers

OBJECTIVES

The present investigation was undertaken to determine the reinforcing effect of woven glass fibers on deflection, flexural strength, flexural modulus and impact strength of acrylic denture base polymer.

METHODS

Three silanized or unsilanized woven glass fibers were used. Specimens were made by heating the denture cure resin dough containing glass fibers, which were sheathed in the dough. Specimens with four different thicknesses and of five different types were made, incorporating the glass fiber. Three-point flexural test and flywheel type impact test were employed to determine the flexural properties and impact strength.

RESULTS

When specimens contained unsilanized glass fiber, the flexural strength in specimens of 1 and 2 mm thickness and the impact strength in specimens of 2 mm thickness were higher than those of specimens without glass fiber (p < 0.01). On the contrary, the flexural strength and deflection in specimens reinforced with silanized glass fiber of 1 mm thickness were significantly higher (p < 0.01, p < 0.05) than those of unreinforced specimens. Further, the impact strength in specimens reinforced with silanized glass fiber of 2 mm thickness was significantly higher (p < 0.01) than that of unreinforced specimens. Statistically significant differences were found in the flexural strength (p < 0.05) and in the impact strength (p < 0.01) when specimens of 4 mm thickness were reinforced with two or three unsilanized glass fibers.

SIGNIFICANCE

The reinforcement with glass fiber was effective in thin specimens, and the reinforcing effect increased with the increase of the number of glass fibers in the case of thick specimens.

Fabrication of complete denture bases reinforced with polyethylene woven fabric

Incorporation of 5 layers of woven, high-modulus polyethylene fiber into acrylic resin denture bases produces substantial improvements in mechanical properties and dimensional changes. A modified split-pack technique has been developed using conventional dental-laboratory compression molding to accommodate multiple layers of woven fabric in complete denture bases. A recess formed in the resin by a spacer allows the reinforcement to be embedded in the denture base without exposing the fibers. Embedded fibers do not compromise the esthetics of complete dentures.

Reinforcement of denture base resin with glass fillers

PURPOSE

This study evaluated the effect of short glass fibers on the transverse strength of a heat-polymerized acrylic resin denture base material.

MATERIALS AND METHODS

Four groups of specimens (n = 10) were fabricated according to the ISO standard for the transverse strength test. E-glass fibers were triturated to produce short fibers of different lengths. Specimens for Group 1 (control) were made of unfilled polymethylmethacrylate (PMMA). For group 2, the PMMA powder was modified with 0.1 g of dry glass fibers. For group 3, the PMMA powder was modified with 0.1 g of silanized glass fibers. For group 4, the PMMA powder was modified with 0.2 g of silanized glass fibers. A three-point loading test was used to determine the transverse strength of the tested specimens. The fracture surface of each specimen was evaluated using SEM.

RESULTS

The addition of untreated glass fibers increased the transverse strength by 11% but produced some porosity in the polymeric matrix. The addition of silane-treated glass fibers increased the transverse strength of PMMA by 28% for group 3 and by 26% for group 4, and produced a dense structure for the polymer-fiber composite.

CONCLUSION

The transverse strength of PMMA can be slightly increased by the addition of short glass fibers.

Development and clinical applications of a light-polymerized fiber-reinforced composite

STATEMENT OF PROBLEM

After 0 years of intermittent reports in the literature, the use of fiber reinforcement is just now experiencing rapid expansion in dentistry.

PURPOSE

This article describes the development and use of a continuous, unidirectional fiber reinforced composite as a framework for the fabrication of fixed prostheses.

METHODS

By using various matrix materials and fibers, a number of fiber-reinforced composite formulations were evaluated with the goal of creating a system with optimized mechanical properties and handling characteristics. Fiber-reinforced composite based on a light polymerized BIS-GMA matrix has been used clinically to make 2-phase prostheses comprised of an internal glass fiber-reinforced composite substructure covered by a particulate composite. The clinical and laboratory procedures required for the fabrication and use of reinforced composite fixed prostheses are described for laboratory-fabricated complete or partial coverage fixed prosthesis and chairside prosthesis.

RESULTS

Although additional clinical experience is needed, fiber-reinforced composite materials can be used to make metal-free prostheses with excellent esthetic qualities.