Unfilled Acrylic Resin Research Articles

Nanofilled bis-acryl composite resin materials: Is it necessary to polish?

Statement of problemManufacturers of the recently introduced nanofilled bis-acryl composite resins no longer recommend polishing to produce interim restorations; however, whether this advice is appropriate is unclear. PurposeThe purpose of this in vitro study was to evaluate the effect of the type of interim resin material, polishing procedure, and artificial staining on surface roughness, gloss, and color. Material and methodsDisk-shaped specimens were prepared from 1 unfilled acrylic resin (Duralay) and 3 bis-acryl composite resins (Structur 3—nanofilled, Systemp C&B—microhybrid, Proviplast—microhybrid). The specimens of each material were assigned to 2 subgroups (n=15): polished and unpolished. Surface roughness (Ra—μm), gloss (UB), and color (ΔE) were analyzed at baseline and after 14 days of artificial staining. Roughness and gloss data were separately analyzed by 3-way ANOVA and color by 2-way ANOVA, followed by the post hoc Tukey test (α=.05). ResultsThe baseline roughness of all materials was significantly reduced by the polishing procedure, whereas the baseline gloss was increased (P<.001). Only the unpolished Proviplast had a significant increase in Ra values after aging. Structur 3 had higher gloss than Systemp C&B and Proviplast. The acrylic resin had the lowest color change after staining. ConclusionsThe polishing procedure produced smother and glossier surfaces for all the materials tested. The nanofilled bis-acryl composite resin material had higher gloss than the microhybrid bis-acryls tested, but it was not different from the acrylic resin. The 14 days of artificial staining did not promote significant changes in Ra or gloss values, except for Ra in the unpolished Proviplast subgroup, indicating excellent performance of the materials. The acrylic resin had the highest color stability.

The effect on the flexural strength, flexural modulus and compressive strength of fibre reinforced acrylic with that of plain unfilled acrylic resin - an in vitro study.

The aim of this in vitro study was to compare the flexural strength, the flexural modulus and compressive strength of the acrylic polymer reinforced with glass, carbon, polyethylene and Kevlar fibres with that of plain unfilled resin. A total of 50 specimens were prepared and divided into 10 specimens each under 5 groups namely group 1- control group without any fibres, group 2 - carbon fibres, group 3- glass fibres, group 4 - polyethylene, group 5- Kevlar. Universal testing machine (Tinius olsen, USA) was used for the testing of these specimens. Out of each group, 5 specimens were randomly selected and testing was done for flexural strength using a three point deflection test and three point bending test for compressive strength and the modulus was plotted using a graphical method. Statistical analysis was done using statistical software. The respective mean values for samples in regard to their flexural strength for PMMA plain, PMMA+ glass fibre, PMMA+ carbon, PMMA+ polyethylene and PMMA+ Kevlar were 90.64, 100.79, 102.58, 94.13 and 96.43 respectively. Scheffes post hoc test clearly indicated that only mean flexural strength values of PMMA + Carbon, has the highest mean value. One-way ANOVA revealed a non-significant difference among the groups in regard to their compressive strength. The study concludes that carbon fibre reinforced samples has the greatest flexural strength and greatest flexural modulus, however the compressive strength remains unchanged.

An in vitro study of the effect of different restorative materials on the reliability of a veneering porcelain

Implant-supported, porcelain veneered restorations experience a greater rate of porcelain fracture than tooth-supported restorations. For completely edentulous patients, one approach to minimizing porcelain fracture is touse acrylic resin in the mandible, although its efficacy is unknown. The purpose of this study was to evaluate the reliability of a veneering porcelain fatigued with different restorative materials invitro. Fifty-nine veneering porcelain disk specimens were fabricated by layering veneering porcelain on nickel-chromium base metal alloy disks. Four groups of different indenter materials fatigued the porcelain specimens: group WC, tungsten carbide served as a control; group FC, pressed leucite glass ceramic; group NHC, nanohybrid composite resin denture tooth; and group AR, unfilled acrylic resin denture tooth. Porcelain specimens were randomly divided into 4 groups (n=14). A step-stress accelerated life-testing model was used. Use-level probability Weibull plots were generated, and the reliability of each group was estimated for a theoretical completion of 50 000 cycles at 150 N. Nanohybrid composite resin and unfilled acrylic resin denture tooth groups had higher reliability than tungsten carbide and leucite glass ceramic groups. No significant differences existed between the reliability of the tungsten carbide and leucite glass ceramic groups and the nanohybrid composite resin and acrylic resin denture tooth groups. Veneering porcelain disk specimens fatigued with the unfilled acrylic resin and nanohybrid composite resin denture tooth indenters exhibited higher reliability than the specimens fatigued with either the tungsten carbide or leucite glass ceramic indenters. All of the veneering porcelain disk specimens failed with the same mode of fracture, although thesurface posttest exhibited different fracture characteristics among specimens fatigued with the 4 different materials.

Localized three-body wear of six types of composite resin veneering materials

The wear resistance of six types of composite resin veneering materials was determined in vitro by use of a three-body wear-testing device. This investigation examined the wear characteristics of the veneering composite resins in heavy occlusal contact areas. After repeated cyclic loading, wear values were measured with a profilometer, and surface textures were evaluated with a scanning electron microscope. All of the composite resin veneering materials were significantly more wear resistant than unfilled acrylic resin; but the composite resin materials demonstrated rougher surfaces than unfilled resin. Three of the composite resins exhibited fractures in the contact areas.

Direct post and core pattern made with light-curing composite resin

An unfilled Bis-GMA composite resin can be used advantageously for making an accurate cast post and core pattern. The technique is faster and easier than normal pattern fabrication methods using an unfilled acrylic resin, wax, or a combination of the two.

Restoration of Class IV and VI defects in anterior teeth with an unfilled resin

The etched resin technique with unfilled acrylic resin has been successful for Class IV and VI defects on anterior incisor teeth and has proven more useful than alternatives in the immediate treatment of traumatized teeth. The advantages of this approach are (1) ease of operation, (2) excellent retention, (3) conservative tooth preparation, (4) excellent esthetics, (5) lower cost to patient, (6) reduced additional insult to recently traumatized teeth in stabilizing them, (7) stable color, and (8) lack of trauma to opposing teeth (Fig. 10).

Fracture Toughness of Composite and Unfilled Restorative Resins

Fracture toughness, critical strain energy release rate, and critical stress intensity factor were determined for experimental and commercial restorative resins. A composite resin had lower resistance to crack initiation than an unfilled acrylic resin. The data were consistent with surface failure observed in single-pass wear studies of these resins.

Thermal properties of nonmetallic restorative materials.

Thermal capacity, diffusivity, and conductivity were determined for nonmetallic restorative materials. Thermal characteristics were affected by composition, powder-liquid ratio, and water sorption. Diffusivity and conductivity followed the same order of values. The least conductive material investigated was an unfilled acrylic resin. Highest diffusivities and conductivities were exhibited by a resin composite. Values obtained with the composite were about the same as those obtained for a thick mix of unmodified zinc oxide-eugenol cement.

Physical and mechanical properties of composite restorative materials

Unfilled acrylic resin was compared with three composite filling materials for setting time, stability, thermal expansion, color stability, smoothness, and strength.