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At least 199 records · Page 11Linked to original sources
PubMed1995

Repair strength of denture base resins using various methods.

The object of this study was to measure the repair strength of denture base resins repaired using, (a) standard heat activated polymerising resin, (b) a denture base resin especially formulated for microwave-activated polymerisation, and (c) an autopolymerising resin. Comparisons were made between conventional water bath and microwave curing and autopolymerised resin repairs, using transverse bend and impact tests. Repairs with the two heat-activated denture base resins were carried out using conventional dental flasking procedures, whereas autopolymerised resin repairs were carried out in open gypsum moulds. The results indicate that the transverse strength, and impact resistance of the resin specimens repaired with microwave irradiation were generally superior to specimens repaired by using a water bath curing cycle or the use of an autopolymerising resin.

Acrylic Resins↗
PubMed1993

Use of the final denture base for the intermaxillary registration in an implant-supported overdenture: technical note.

A method of implant-retained overdenture treatment based on the early use of the final denture base during registration of the maxillomandibular jaw relation is described. Using this stable denture base, an accurate recording of jaw relation and an adequate try-in procedure are facilitated without displacement of the base, especially in the situation of an unfavorable flat edentulous mandibular residual ridge.

Alveolar Bone Loss↗
PubMed1995

Dimensional changes of relined denture bases with heat-cured, microwave-activated, autopolymerizing, and visible light-cured resins. A laboratory study.

The dimensional changes of relined denture bases were evaluated in a laboratory study. Heat-cured resin, two autopolymerizing resins, microwave-activated resin and a new visible light-cured resin were used as relining materials in this study. The gaps between the metal die and the relined denture bases were measured immediately after the relining procedure and subsequently on the first day, first week, fourth week, and eight week. The relined denture bases were stored in distilled water at 37 degrees C between measurements. It was shown that dimensional changes in relined denture bases were influenced by the relining materials and procedures, and that heat-cured resin proved to have the smallest dimensional change as well as the greatest dimensional stability in comparison with the other relining materials and procedures.

Acrylic Resins↗
PubMed1998

Stress relaxation of heat-activated acrylic denture base resin in the mold after processing.

STATEMENT OF PROBLEM: Stress relaxation of polymethyl methacrylate has been reported, but no studies have investigated residual stress relaxation in heat-activated acrylic denture base resin fabricated by the polymer-monomer mixture method. PURPOSE: This study evaluated the development of residual stress relaxation and clarified how restricted time in the stone mold influenced stress relaxation of heat-activated acrylic denture base resin after processing. MATERIAL AND METHODS: Flat, dumbbell-shaped specimens were used. Thermocouples and strain gauges were embedded in resin for measuring temperature and strain at the dough-stage of resin packing. To clarify the stress relaxation in the stone mold, specimens were removed from the mold by deflasking at 4 hours after from the start of bench cooling (immediately after reaching room temperature; control), and 1 day, 3, 5, and 10 days from the start of bench cooling. RESULTS: Shrinkage strains at deflasking were two thirds for 1 day restriction, one half for 3 and 5 days restriction, as compared with the control. CONCLUSIONS: This study suggested that removing a denture base fabricated by heat-activated acrylic denture base resin from the stone mold only after keeping it in stone mold for at least 1 day or more was effective for reducing deformation of the denture base.

Acrylic Resins↗
PubMed1996

Color stability: denture base resins processed with the microwave method.

Several quick heat-cured denture base resin systems and microwave processing resins have been introduced to provide easier and faster processing. The microwave processing method is the fastest of the heat-cured processing methods. Conventional acrylic resins processed with the microwave method seem to possess adequate physical properties, and one study indicated that a microwave acrylic resin was reasonably color stable under conditions of accelerated aging, although manufacturers do not recommend using them for microwave processing. The purpose of this study was to evaluate the color stability of seven conventional and one microwave heat-cured denture base materials processed with the microwave method. The samples were subjected to conditions of accelerated aging to test for color stability. The color stability was quantitatively measured and color measurements were made before weathering and at 300, 600, and 900 hours. The mean color change for each sample group was statistically analyzed with polynomial regression to determine the pattern of color change over time. The differences in color change for the acrylic resins were significant for all materials, but the color change for Lucitone Hy-pro was not noticeable on visual examination. The results of this study revealed that color changes occurred after accelerated aging in heat-cured denture base resins and Acron GC microwave acrylic resins processed with the microwave method. Hy-pro and TruTone materials exhibited the least color change; Hy-pro material was the most color stable material.

Acrylic Resins↗
PubMed2001

Repair of denture base resins with visible light-polymerized reline material: effect on tensile and shear bond strengths.

STATEMENT OF PROBLEM: Triad visible light-polymerized (VLP) reline resin has the potential to repair denture bases from other resin systems with the elimination of flasking/deflasking procedures. PURPOSE: This study measured the tensile and shear bond strengths of Triad VLP, PMMA, and glass-fiber-reinforced PMMA (GF-PMMA) acrylic resins before and after repair with Triad VLP reline material. MATERIAL AND METHODS: Fifty-six specimens were fabricated from Triad VLP, PMMA, and GF-PMMA denture base resins. Both Triad VLP reline material and autopolymerizing acrylic resins were used to repair identical laboratory fabricated resin joints. Twenty-eight rectangular specimens (in 4 different groups of 7 each) were prepared to study the shear bond strength of Triad reline material used to repair different denture base resin joints. RESULTS: Statistically significant differences (P< .0001) were found between the tensile strengths of specimens repaired with the Triad VLP reline resin used as a repair agent and those repaired with the autopolymerizing resin. The tensile strength of the Triad VLP denture base resin was found to be higher than that of both the PMMA and GF-PMMA acrylic resins. CONCLUSION: The low tensile and shear bond strengths found after the repair of PMMA and GF-PMMA acrylic resins with Triad VLP reline material were attributed to a lack of cohesion/adhesion between the Triad VLP reline material and the interfaces of the treated sites. The use of Triad VLP reline material to repair Triad VLP denture base resin produced the highest strengths.

Acrylic Resins↗
PubMed2005

Effect of direct relining on stresses at the denture base and the metal frame of removable partial dentures.

The Kennedy Class I removable partial denture (RPD) can cause stress to supporting hard and soft tissues and may lead to harmful effects. The purpose of this study is to investigate the pattern of these stresses in three different positions before and following a relining procedure. Ten patients, five males and five females, with a lower distal extension RPD and an opposing upper class III type RPD were selected for this study. Strain gauges together with a strain gauge indicator were used to study the pattern of stresses in three selected positions. Some changes were significantly different at the site of the denture base and at the metal frame near the direct retainer. After relining, the stresses were shared partially by the abutments and partially by the tissues. Maximum stresses were reported during swallowing. No significant difference was noticed between males and females.

Adult↗
PubMed1991

A comparison of mandibular denture base extension in conventional and implant-retained dentures.

A border outline for mandibular implant-retained dentures is described. The lingual extension of the impression is greatly reduced compared with a conventional mandibular denture. Because of the implant attachment, the shortened border is more comfortable and does not compromise denture retention. Improper implant position is also discussed with respect to denture extension.

Dental Implants↗
PubMed1993

Effect of microwave polymerisation on indentation creep, recovery and hardness of acrylic denture base materials.

With the advent of newer methods of activation of the polymerisation of denture base resins, there is a need to compare their physical properties using various modes of activation. Indentation creep, recovery and hardness of denture base resins polymerised either by microwave irradiation or heat were compared. A microwave curing cycle of 3 minutes at 500W was used. The Wallace microhardness tester and an indentation creep test were employed in order to evaluate the denture base resins. Under the experimental conditions of the study the results indicated that indentation creep, recovery and cyclic loading-deloading were similar in the resins polymerised by the two methods. Hardness was either similar or a softer produce was produced by microwave irradiation for two of the resins used. Hardness seems to be more sensitive to residual monomer levels, and for this reason a suitable microwave curing cycle should be employed to optimise all the physical properties.

Acrylic Resins↗
PubMed1991

[Accuracy of fit of the denture base depending on various jaw geometries. Biotechnical analysis].

Good function of full dentures is closely related to an accurate fit of the denture bases. The shape of these bases depend again on the polymerization technique applied. Methods of biotechnical analysis were employed to determine the effects of the alveolar ridge, defined as an angle with the vertical plane, on the accuracy of fit. Both the expansion of castings and the curing contraction of acrylics were taken into consideration in this analysis. The relationships between an increase or reduction of the full denture base and the mechanism of adhesion to the denture-bearing area were computed and their practical implications are discussed.

Alveolar Process↗
PubMedDate not supplied

Influence of thickness on the linear dimensional change, warpage, and water uptake of a denture base resin.

This study examined the influence of thickness on changes (linear dimensions, warpage, and water uptake) in a denture base resin following two processing methods (heat polymerization and microwave activation). Changes were influenced by both processing method and thickness. These findings suggested that the processing method and denture base resin thickness are important factors in the dimensional change of acrylic resin dentures, and that the overall dimensional denture base changes are the result of localized changes.

Acrylic Resins↗
PubMed1991

Polymerization shrinkage, impact strength and roughness of montmorillonite-modified denture base resins.

Montmorillonite (MMT) was added to two commercial denture base resins, Lucitone (LU) and Accelar (AC) in amounts varying from 0-8 weight percent (wt%). The linear polymerization shrinkage, impact strength and average roughness or polishability were measured after specimens were processed using standard methods. The linear polymerization shrinkage was 1.37 and 1.02% for the unmodified denture base resins and the impact strength was 37.36 and 20.02 J/m; while the average roughness after polishing was 0.026 and 0.047 microns for LU and AC, respectively. The addition of MMT significantly (P less than 0.05) reduced the linear polymerization shrinkage and impact strength, while increasing the roughness of LU and AC.

Acrylic Resins↗
PubMed1989

[Suitability of denture base by light-cured resin for reline].

With a view to evaluating the dimensional accuracy of the light-cured relining resin from the viewpoint of the suitability of the mucosal surface of the denture base, an experiment by direct relining technique was made using a total of 12 materials, i.e. 2 kinds of denture base material, 3 kinds of relining material and 2 kinds of denture base mold; cured, refined test sample interposed by impression material was adapted to the prototype and was measured for the thickness of impression material by means of stereoscopic microscope. The results obtained were as follows: 1) Lifting discrepancies averaged 0.5, 0.8 and 1.2mm for E (Eporex-E), R (Rebaron) and T (Triad), respectively, indicating a significant difference in lifting discrepancy according to the kind of relining materials. 2) In terms of the different molds of denture base, 2 kinds of R and E tended to show a little greater lifting discrepancies for thick samples of the alveolar ridge area, compared with the opposite tendency in case of T. 3) In terms of the different materials, combination of A and E (Acron.Eporex-E), and that of B and E (Triad.Eporex-E) showed values of the same order without difference. 4) Standard deviation for T showed a value of about 0.5mm or so, with a greater variation than others.

Acrylic Resins↗
PubMed1991

Bonding of plastic teeth to denture base resins.

This study evaluated the bond strengths of some new and traditional resin denture teeth and denture base resins. It included regular monolithic acrylic resin teeth (Bioform), monolithic acrylic resin-IPN teeth (Bioform IPN), and multilithic acrylic resin-composite resin teeth (Vivosit), with relatively new light-activated resin (Triad), conventional heat-cured resin (Lucitone 199), and autopolymerizing resin (Hygenic) denture base materials. The results of four-point flexure testing showed that the traditional materials gave the highest bond strength values. The autopolymerizing resin systems demonstrated interfacial failure with all resin denture teeth, showing that the common practice of treating teeth with the respective autopolymerizing monomer failed to produce adequate bond strength. Combinations of acrylic resin, IPN, and multilithic denture teeth with light-activated resins gave results calling for improvements in basic bonding system design, since interface debonding was prevalent. No failures occurred between the lap-ridge region of the multilithic tooth system and conventional heat-cured denture base resin.

Acrylic Resins↗
PubMed1989

Comparative bond strengths of plastic teeth to microwave-curing, heat-curing and 4-META containing denture base resins.

Bond strength of hardened plastic teeth or acrylic resin teeth to microwave-curing, conventional heat-curing and 4-META-containing denture base resins were comparatively investigated in this study. Effects of grinding and monomer coating of the tooth ridge lap were also studied. Bond strength of plastic denture teeth to microwave-curing denture base resin was slightly higher than the other two resins. With all denture base resins used, an increased bond strength was obtained with hardened plastic teeth by treatment of tooth ridge lap but not with acrylic resin teeth. However, scattering of the bond strength was reduced by treatment of tooth ridge lap in acrylic resin teeth specimens. With hardened plastic teeth specimens, fracture in the base resin was increased by monomer coating. With acrylic resin teeth specimens, no specific fracture patterns were demonstrated by treatment of tooth ridge lap. Fracture occurred mostly in the acrylic resin teeth. These results suggest that bond strength of both denture teeth to microwave-curing or 4-META-containing denture base resin was increased or solidified by grinding or monomer coating of tooth ridge lap.

Acrylic Resins↗
PubMed2005

Use of metal conditioners to improve bond strengths of autopolymerizing denture base resin to cast Ti-6Al-7Nb and Co-Cr.

OBJECTIVE: The shear bond strengths of an autopolymerizing denture base resin to cast Ti-6Al-7Nb and Co-Cr alloys using three metal conditioners were investigated. METHODS: Ti-6Al-7Nb alloy and Co-Cr alloy discs were cast. The disc surfaces were air-abraded with 50 microm alumina particles and treated with three metal conditioners (Alloy Primer; Cesead II Opaque Primer; Metal Primer II). An autopolymerizing denture base resin was applied on the discs within a hole punched in a piece of sticky tape and a Teflon ring to define the bonding area. All specimens were immersed in 37 degrees C water for 24 h. Half of the specimens were thermocycled up to 20,000 cycles. The shear bond strengths were determined at a crosshead speed of 1.0 mm/min. RESULTS: Specimens treated with the three metal conditioners had significantly (p<0.05) improved shear bond strengths of the autopolymerizing denture base resin to both Ti-6Al-7Nb and Co-Cr. Although the bond strengths of the bonded Ti-6Al-7Nb specimens were higher than those of the Co-Cr alloy before thermocycling, the decrease in the bond strength of Ti-6Al-7Nb was considerably greater than that of the Co-Cr after thermocycling. CONCLUSION: Significant improvements in bond strength of the autopolymerizing denture base resin to cast Ti-6Al-7Nb alloy and Co-Cr alloy were achieved through the application of Alloy Primer, Cesead II Opaque Primer and Metal Primer II. The bond durability to Ti-6Al-7Nb alloy was inferior to that to Co-Cr.

Chromium Alloys↗
PubMed1992

Comparison of bond strength of six soft denture liners to denture base resin.

The bond strength of six commercial soft denture liners was evaluated using a modified tensile test. The soft denture liners investigated were Prolastic, VinaSoft, Flexor, Molloplast-B, Novus, and Super-Soft. The samples were processed according to the manufacturers' instructions to cured denture base resin (polymethyl methacrylate; PMMA). The soft denture liners were 10 x 10 x 3 mm and were processed between two PMMA blocks. The samples were placed in tension until failure. The mode of failure, cohesive or adhesive, was also recorded. The results of this study showed that the bond strength is related to the components of the materials. Prolastic, VinaSoft, and Flexor had the lowest bond strength to cured PMMA and ranged from 9.6 to 11.3 kg/cm2. Super-Soft, Novus, and Molloplast-B demonstrated better bond strengths and ranged from 16.7 to 17.6 kg/cm2. The bond strength of Novus could be improved by using the recommended bonding agent and bonded Novus at 26.1 kg/cm2 had the highest bond strength of all materials tested.

Adhesiveness↗
PubMed1989

[Studies on the influences of the indirect retainers on the displacements of the denture bases and the abutment teeth. 2. The forms and locations of indirect retainers used for cross arch stabilizations].

The purpose of this experimental study is to investigate and evaluate characteristic movements of the denture bases and the abutment teeth, when the forms and locations of the indirect retainers used for the cross arch stabilization are altered. The results are as follows: 1. Under the vertical forces, the increases of abutment tooth excursion and denture base movement are observed, when the fulcrum line crosses the "loading axis" at nearly right angle. 2. When the vertical forces are applied, the displacements of abutment tooth and denture base with two indirect retainers are more reduction than that with one. 3. The distances between two indirect retainers used for cross arch stabilization increase, the less displacements of abutment tooth and denture base are. 4. When the partial denture has only one indirect retainer used for the cross arch stabilization, it is important that the positive rest is located on the anterior tooth and the indirect retainer is placed on as distal tooth as possible. 5. If the occlusal forces are supported by the residual ridge, it may be better designs that the positive rest is located on the anterior tooth and the Akers clasp with mesial rest or the double Akers clasp is located on the premolars.

Dental Abutments↗