Fabrication of complete denture bases reinforced with polyethylene woven fabric

An overview of development and status of fiber-reinforced composites as dental and medical biomaterials

Fibr-reinforced composites (FRC) have been used successfully for decades in many fields of science and engineering applications. Benefits of FRCs relate to physical properties of FRCs and versatile production methods, which can be utilized. Conventional hand lamination of prefabricated FRC prepregs is utilized still most commonly in fabrication of dental FRC devices but CAD-CAM systems are to be come for use in certain production steps of dental constructions and medical FRC implants. Although metals, ceramics and particulate filler resin composites have successfully been used as dental and medical biomaterials for decades, devices made out of these materials do not meet all clinical requirements. Only little attention has been paid to FRCs as dental materials and majority of the research in dental field has been focusing on particulate filler resin composites and in medical biomaterial research to biodegradable polymers. This is paradoxical because FRCs can potentially resolve many of the problems related to traditional isotropic dental and medical materials. This overview reviews the rationale and status of using biostable glass FRC in applications from restorative and prosthetic dentistry to cranial surgery. The overview highlights also the critical material based factors and clinical requirement for the succesfull use of FRCs in dental reconstructions.

Influence of reinforcing materials on strain of maxillary complete denture

OBJECTIVE

A maxillary complete denture has been a common prosthetic treatment for people with edentulous maxillas. The fracture and deformation of dentures are recurrent and common problems for denture-wearers. Consequently, reinforcement materials are embedded in the denture base to prevent fracture and deformation. The purpose of this study was to examine the influence of reinforcing materials on the strain within the acrylic base of a maxillary complete denture.

MATERIALS AND METHODS

Three reinforcements (cast cobalt-chromium bar; glass fibers; and cobalt-chromium wire) were embedded in the bases and a strain-gauge was attached at three positions (labial, middle and posterior) at the mid-line of the polished surface of each denture. A vertical occlusal load of 49 N was applied to the left and right side in the region of the 1st premolar and the 1st molar. Comparisons of the strain were made via ANOVA.

RESULTS

The strain of the denture base with a cast cobalt-chromium reinforcement was significantly (p < 0.05) smaller than that with the other reinforcements.

CONCLUSIONS

This result suggested that a cast cobalt-chromium reinforcement helps to reduce the risk of fracture and deformation of a maxillary complete denture.

Effect of short-term water storage on the elastic properties of some dental restorative materials—A resonant ultrasound spectroscopy study

OBJECTIVES

This study was aimed to determine if short-term water storage would change elastic properties of dental composite materials.

METHODS

Particulate filler composite resin and continuous unidirectional E-glass FRC materials were photopolymerized and additionally post-polymerized by heat for testing elastic properties with the Resonance Ultrasound Spectroscopy method as a function of time in water storage. The test specimens were stored in 37 degrees C water for up to 30 days.

RESULTS

About 1% weight increase due to water sorption was observed in both materials with both polymerization methods. Water sorption did not change the resonance frequencies towards lower values, indicating no significant decrease in elastic properties in these materials. Because of high damping of the polymer composite materials leading to wide resonance peaks and low number of the recorded peaks, accurate determination of the elastic properties was not possible.

SIGNIFICANCE

Results suggest that the most likely explanation for the previously observed decrease in bending stiffness of FRC materials is the decreased yield limit of the hydrated polymer matrix. It is important to recognize that water sorption has the effect on mechanical properties of dental composite materials by changing the yield limit of the matrix rather than by changing the elastic properties of the material.

Static strength of molar region direct technique glass fibre-reinforced composite fixed partial dentures

The aim of this study was to determine static fracture force of fibre-reinforced composite (FRC) fixed partial dentures (FPD) with different retainer designs. The fabrication simulated the process to make directly made 3-unit maxillary molar FPD. Four types of retainers were tested (n = 5): conventional crown preparation (1.2 mm axially and 2.0 mm occlusally), slot preparation (3.5 mm high x 3.5 mm wide x 1 mm deep), no preparation with broad fibre abutment contact, and combination of the slot and broad fibre contact were performed. The FPD contained unidirectional E-glass FRC veneered with particulate reinforced composite. Dimensions of the FPDs were homogenized. FPDs were stored at 1 week 37 degrees C deionized water, thermocycled between 5 degrees C and 55 degrees C (5000 cycles, dwell time 10 s) and statically loaded to failure. The slot retainer design yielded the lowest mean load to initial and final failure (FF) (1284 and 1313 N, respectively), the crown retainer the highest mean load to initial failure at 1755 N, and the combination retainer resulted in the highest mean load to FF (1836 N) (anova, P < 0.001; Tukey multiple comparisons, 0.05 significance level). The results of this study suggest that the fabrication of direct FRC FPD does not necessarily require extensive preparation for the retainers.

Flexural strengths of denture base resin repaired with autopolymerizing resin and reinforcements after thermocycle stressing

PURPOSE

Fracture of an acrylic denture base is a common problem in prosthodontic practice. Although various reinforcement methods have been used, when a fractured denture base is repaired with autopolymerizing resin recurrent fractures frequently occur at the repairing interface or adjacent areas. The purpose of this study was to evaluate the maximum flexural load of denture base resin repaired with autopolymerizing resin and several reinforcement systems after thermocycle stressing.

MATERIALS AND METHODS

Rectangular (10 x 70 x 3 mm) flexural specimens were fabricated by repairing a pair of heat-cured denture base resin specimens using autopolymerizing resin and a series of reinforcement materials. The materials included 4 metal wires and a woven glass fiber. Each reinforcement was embedded in the center of the specimens. Flexural specimens repaired without reinforcement were prepared as controls. Specimens were subjected to 50,000 thermocycles (4 approximately 60 degrees C, 1-minute dwell time). A 3-point flexural test was carried out by loading the center of the repaired site at 5 mm/minute crosshead speed with 50 mm span jig supports. The load necessary to cause fracture was recorded for each specimen. All data were statistically analyzed using ANOVA and the Bonferroni/Dunn test (alpha < 0.05).

RESULTS

The average load to fracture of specimens repaired with nonreinforced autopolymerizing resin was 68.4 N after 50,000 thermocycles. Specimens reinforced with 1.2 mm diameter stainless steel wire exhibited the highest value (89.8 N). The value for specimens reinforced with 1.2 mm diameter Co-Cr-Ni wire was 86.6 N. These fracture loads were significantly higher than those for specimens without reinforcement (p < 0.05). Low elasticity reinforcement, such as pure titanium wires, woven metal wire, and woven glass fiber were not effective in increasing the load to fracture values of flexural specimens.

CONCLUSIONS

Specimens reinforced with 1.2 mm diameter stainless steel wires or Co-Cr-Ni wires resulted in significantly higher loads to fracture as compared to specimens without reinforcement. The use of pure titanium wire, woven metal wire, and woven glass fiber did not improve the fracture loads.

Numerical failure analysis of glass-fiber-reinforced composites

The purpose of this work was to propose a new numerical model for glass-fiber-reinforced composites. The proposed numerical model was constructed with orthotropic shell, isotropic shell, and beam elements representing glass fiber cloth, silica filler, and the remaining matrix resin, respectively. The proposed model was applied to failure analysis under three-point bending conditions. The validity of the numerical model was checked through comparisons with experimental results. Four types of specimens were used: composite resin, and composite resin with neutral, upper, and lower glass-fiber cloth reinforcement insertions. For all types, close agreement between the analytical and experimental results was confirmed. This indicates that the proposed numerical model is effective for evaluating the mechanical behaviors of glass-fiber-reinforced composites.