• Journal of Technologic Dentistry
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• v.30 no.2
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• pp.47-56
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• 2008

This is a research for thickness change of denture base according to the shape of sprue & investment position of denture base in flask when injecting polyamid base resin for flexible partial denture as a part of study for Valplast among the flexible partial denture with a nylon base. It has been introduced several kinds of flexible partial denture product with a nylon base, but Valplast is the most widely used product among them. Valplast has been the most generally used material today since developed in 1950s in the United States as a material for flexible partial denture. Valplast is much more aesthetic than general metal-acrylic partial denture due to its translucent pink color and biocompatibility in terms of material characteristic. It keeps its flexibility for a long time after production, imposes a less burden on the teeth used as abutment, and it can be easily insert and remove due to its particular suppleness. Moreover, it is felt like real teeth more than metal-acrylic partial denture when being put in and takes alveolar bone under good protection since it receives occlusal force equally under the denture base. The most outstanding feature of Valplast is flexibility. The extent of its flexibility is determined by width & thickness of denture base. Considering general working procedure of Valplast, it can be seen that the thickness of denture base formed out of wax is increasing by the pressure while injecting resin. This research is to decide and test on the thickness increasing of Valplast by injecting pressure and the hypothesis upon that and is to prepare the basis estimating the increasing extent of thickness of denture base on the basis of the test result. In this test, it is expected occlusal malposition & thickness increasing of denture base by injecting pressure according to 4 kinds of test data which are to select 3 types of sprue method settling the forefront position at which the test material of fixed standard can be invested and to position the test material at the rearmost part keeping the minimum distance to set sprue. For 4 kinds of injecting test by investment position & sprue type, 20 test materials, 5 for each test were produced and a pressure of 1,180Kg was given with automatic injector of air cylinder type. The results are as follows: 1. For the amount of thickness increasing of denture base by investment position, the thickness of front investment is less increasing than the one of rear investment. 2. For the amount of thickness increasing of denture base by sprue type, the thickness of straight decompression sprue type which can absorb the injecting pressure after injecting polyamide base resin is less increasing than the other sprue types.

• The Journal of Korean Academy of Prosthodontics
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• v.36 no.1
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• pp.18-25
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• 1998

The purpose of this study was to determine how to use soft relining material by observing an amount of denture displacement according to the different base area of residual ridge and thickness of soft relining material under masticatory force. Stone models that simulated residual ridge were made with different amount of denture base area and denture was fabricated by conventional heat curing resin with usual manner on the model and relined by silicone type soft relining material with different thickness. Specimen was examined the amount of denture displacement by Instron within range of normal occlusal force. The results were as following : 1. The increasing rate of denture displacement was higher than that of soft relining material thickness. 2. The amount of denture displacement decreased 1.7 times when base area became double at same thickness of soft relining material 3. The increasing rate of denture displacement was higher than that of occlusal force

• The Journal of Korean Academy of Prosthodontics
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• v.37 no.6
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• pp.782-790
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• 1999

The purpose of this study was to evaluate the effect of proportional thickness of various reline materials on the transverse strength of denture base. The denture base resin used in this study was Vertex $RS^{(R)}$ (Dentimex Zeist., Holland). The reline resins used were Tokuso $rebase^{(R)}$ normal set (Tokuyama Corp., Japan), $Rebaron^{(R)}$ (GC Corp., Japan), $Kooliner^{TM}$ (GC INC., U.S.A), New $truliner^{TM}$(Harry J. Bosworth Co., U.S.A). The bulk specimens with 2.5mm thickness of denture base were prepared as the control group. Group 1 was fabricated with 2.0mm thickness of denture base and 0.5mm reline material, group 2 with 1.5:1.0mm, group 3 with 1.0:1.5mm, group 4 with 0.5:2.0mm composition. Measurements of transverse strength were taken for each specimens The results were as follows: 1. Regardless of the reline resin type, the transverse strength of denture base was decreased after reline procedure. 2. The transverse strength according to the reline resin type was decreased in the following order : Rebaron, Tokuso rebase, Kooliner, and then New truliner and there was a significant difference among the reline materials (P<0.05). 3. The strength of the relined denture base generally decreased as the proportional thickness of the denture reline material increased. These results suggest that increasing the proportional thickness of the reline material progressively decreased the strength of the relined denture base. Thus, the denture base should not be unnecessarily altered during the reline procedure.

• Journal of Dental Rehabilitation and Applied Science
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• v.36 no.3
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• pp.183-195
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• 2020

Purpose: The purpose of this study is to compare the flexural strength of CAD/CAM denture base resins with conventional denture base resins based on their thicknesses. Materials and Methods: For the conventional denture base resins, Lucitone 199^® (C-LC) was used. DIOnavi - Denture (P-DO) and DENTCA Denture Base II (P-DC) were taken for the 3D printing denture base resins. For the prepolymerized PMMA resins, Vipi Block Gum (M-VP) and M-IVoBase^® CAD (M-IV) were used. The final dimensions of the specimens were 65.0 mm x 12.7 mm x 1.6 mm / 2.0 mm / 2.5 mm. The 3-point bend test was implemented to measure the flexural strength and flexural modulus. Microscopic evaluation of surface of fractured specimen was conducted by using a scanning electron microscope (SEM). After testing the normality of the data, one-way ANOVA was adopted to evaluate the differences among sample groups with a significance level of P = 0.05. The Tukey HSD test was performed for post hoc analysis. Results: Under the same thicknesses, there are significant differences in flexural strength between CAD/CAM denture base resins and conventional denture base resins except for P-DO and C-LC. M-VP showed higher flexural strength than conventional denture base resins, P-DC and M-IV displayed lower flexural strength than conventional denture base resins. Flexural modulus was highest in M-VP, followed by C-LC, P-DO, P-DC, M-IV, significant differences were found between all materials. In the comparison of flexural strength according to thickness, flexural strength of 2.5 mm was significantly higher than that of 1.6 mm in C-LC. Flexural strength of 2.5 mm and 2.0 mm was significantly higher than that of 1.6 mm in P-DC and M-VP. In M-IV, as the thickness increases, significant increase in flexural strength appeared. SEM analysis illustrates different fracture surfaces of the specimens. Conclusion: The flexural strength of different CAD/CAM denture base resins used in this study varied according to the composition and properties of each material. The flexural strength of CAD/CAM denture base resins was higher than the standard suggested by ISO 20795-1:2013 at a thickness of 1.6 mm or more though the thickness decreased. However, for clinical use of dentures with lower thickness, further researches should be done regarding other properties at lower thickness of denture base resins.

• The Journal of Advanced Prosthodontics
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• v.13 no.4
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• pp.226-236
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• 2021

PURPOSE. This study aimed to evaluate the effect of incorporating zirconium oxide nanoparticles (nano-ZrO₂) in polymethylmethacrylate (PMMA) denture base resin on flexural properties at different material thicknesses. MATERIALS AND METHODS. Heat polymerized acrylic resin specimens (N = 120) were fabricated and divided into 4 groups according to denture base thickness (2.5 mm, 2.0 mm, 1.5 mm, 1.0 mm). Each group was subdivided into 3 subgroups (n = 10) according to nano-ZrO₂ concentration (0%, 2.5%, and 5%). Flexural strength and elastic modulus were evaluated using a three-point bending test. One-way ANOVA, Tukey's post hoc, and two-way ANOVA were used for data analysis (α = .05). Scanning electron microscopy (SEM) was used for fracture surface analysis and nanoparticles distributions. RESULTS. Groups with 0% nano-ZrO₂ showed no significant difference in the flexural strength as thickness decreased (P = .153). The addition of nano-zirconia significantly increased the flexural strength (P < .001). The highest value was with 5% nano-ZrO₂ and 2 mm-thickness (125.4 ± 18.3 MPa), followed by 5% nano-ZrO₂ and 1.5 mm-thickness (110.3 ± 8.5 MPa). Moreover, the effect of various concentration levels on elastic modulus was statistically significant for 2 mm thickness (P = .001), but the combined effect of thickness and concentration on elastic modulus was insignificant (P = .10). CONCLUSION. Reinforcement of denture base material with nano-ZrO₂ significantly increased flexural strength and modulus of elasticity. Reducing material thickness did not decrease flexural strength when nano-ZrO₂ was incorporated. In clinical practice, when low thickness of denture base material is indicated, PMMA/nano-ZrO₂ could be used with minimum acceptable thickness of 1.5 mm.

• The Journal of Korean Academy of Prosthodontics
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• v.34 no.4
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• pp.816-822
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• 1996

The purpose of this study was to determine whether there was any difference in the mean porosity of denture base resin cured by microwave energy, when the liquid monomers of denture resin(K-33 : methyl methacrylate for conventional water bath curing or Acron MC : special monomer for microwave curing) and/or the thicknesses of denture base($5{\times}10{\times}60mm\;or\;10{\times}10{\times}60mm$) were varied. The mean porosities of k-33 specimens cured in water bath with two different thicknesses were used as control. The results were as follows : 1. Regardless of specimen thickness, Acron MC cured by microwave energy showed the least mean porosity, followed by K-33 cured by water bath heat, and K-33 cured by microwave energy showed the highest level of mean porosity(P<0.05). 2. In both K-33 and Acron MC cured by microwave energy the mean porosities of 5mm thickness groups were lower than those of 10mm thickness groups(P<0.05). But no significant difference was found in mean porosity between 5mm thickness and 10mm thickness of water bath heat cured groups made of K-33(P>0.05).

• Journal of Technologic Dentistry
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• v.36 no.1
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• pp.1-7
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• 2014

Purpose: The aim of this study was analyzed by comparing the effect of glass fiber reinforcement addition on the strength of resin denture base. It was intended to provide a reference data useful for clinical application. Methods: The test specimens (length $64.0{\pm}0.1mm$, width $10.0{\pm}0.1mm$, thickness $1.0{\pm}0.1mm$, $1.5{\pm}0.1mm$, and $2.0{\pm}0.1mm$ respectively) were made. In the experimental groups resin denture base reinforced with glass fiber were fabricated. In the control groups resin denture base were fabricated by conventional method. After specimen fabrication was completed, transverse test was performed using a universal testing machine. Results: The transverse strength value in CON group was $83.08{\pm}9.07MPa$ for 1.0 mm, which ranked the highest in value. On the other hand, the value was $56.07{\pm}5.15MPa$ for 2.0mm, which ranked the lowest in value. And CON+SES group was $119.80{\pm}30.70MPa$ for 1.0mm, which ranked the highest in value. On the other hand, the value was $84.00{\pm}7.97MPa$ for 2.0mm, which ranked the lowest in value. Also, the flexural modulus value in CON group was $2,983.10{\pm}506.92MPa$ for 1.0mm, which ranked the highest in value. On the other hand, the value was $1,257.64{\pm}230.48MPa$ for 2.0mm, which ranked the lowest in value. And CON+SES group was $4,679.41{\pm}1578.29MPa$ for 1.0mm, which ranked the highest in value. On the other hand, the value was $2,512.36{\pm}527.09MPa$ for 2.0mm, which ranked the lowest in value. Conclusion: The reinforced glass fiber increased the strength of resin denture base, effected to reduce the thickness of resin denture base.

• The Journal of Korean Academy of Prosthodontics
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• v.42 no.4
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• pp.344-355
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• 2004

Statement of problem: For a long time, many of denture base acrylic resins have been used for edentulous and partial edentulous patients because of easy manipulation and good mechanical properties, but its esthetic aspect has not been commented enough. Denture base acrylic resins also has caused esthetic problems due to discoloration or staining as in esthetic restoration. Many researches and reports have treated the problems and accomplished esthetic improvement. But these researches and reports dealt with general food colors or beverages, not with fermented foods. Purpose: This study is designed to assess what fermented foods, such as soy sauce, gochujang, and toenjang that many of Koreans have taken in, influence on the color and hardness variation of denture base acrylic resins. Materials and methods: For the procedure, twelve disks per 4 denture base acrylic resins were fabricated with a thickness of 2mm and 16mm in diameter. Each seven specimen were measured for discoloration with spectrophotometer, while the others, five specimen, for surface hardness change with Barcol hardness tester, over time. Each 12 specimen were immersed into the 4 beakers of fermented foods(soy sauces, gochujangs, toenjangs, deionized water), and $L^{*},a^{*}$, and $b^*$ values were measured for the color difference$({\Delta}E^*)$, on the 1st, 7th, and 28th day with spectrophotometer, with the measurement of surface hardness change. Each data observed was processed statistically. Results: The findings are as follows; Discoloration 1. All of denture base resins was not influenced by the kind of fermented foods, except for $QC20^{(R)}$ 2. Soy sauce and red pepper paste caused more change for denture base resins than deionized water and soy bean paste, except for Perform$^{(R)}$ 3. Most significant change was shown in Lucitone 199$^{(R)}$, whereas Perform$^{(R)}$ results in the least change for all immersed solution, with no statistical significance. Hardness change 1. Barcol hardness values in deposited specimens have been changed low degree, but with significant statistical change according to the kind of food and duration. 2. Lucitone$^{(R)}$ 199 as significantly lower Barcol hardness value than others do. Conclusion: Based on the above results, it suggests that the habitual intake of fermented foods is not helpful for the color stability of denture base acrylic resins because Soy sauce and red pepper paste mainly caused discoloration and surface hardness change. Particularly $Lucitone199^{(R)}$ shows specific discoloration and low surface hardness values. Therefore, it is recommended giving caution patients with denture of $Lucitone199^{(R)}$ especially against the habitual intake of fermented foods like soy sauce and red pepper paste.

• The Journal of Korean Academy of Prosthodontics
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• v.27 no.2
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• pp.79-100
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• 1989

The Purpose of this study was to investigate material differences in stress transmission among various artificial teeth and denture base materials. For this study, a two-dimensional finite element model and a two-dimensional photoelastic model of a mandible with complete denture were made. A resin tooth and a porcelain tooth were used as artificial teeth, and a resin base, a metal lined base, and a soft-liner lined base were used as denture bases. An occlusal load was applied and principal stresses generated in the supporting tissues were compared. To test the impact stress transmission, strain gauge attached to the denture base specimens made of the different materials were made in thick and thin groups. Voltage outputs from hitting the specimen with a steel ball were compared. The results were as follows : 1. In FEM, increasing the mucosal thickness reduced the maximum principal stresses in the supporting tissues, but altering the tooth materials and the base materials induced no difference in the stresses. 2. In photoelastic model study, no difference in fringe order among the specimens were observed, but the thick mucosa group and the soft-liner lined group revealed a more uniform distribution of the load. 3. In strain measuring, the impact force transmission was highest in the soft-liner lined group, and was the lowest in the metal lined group(p<0.01). 4. In the thin group using the resin base, the porcelain tooth showed higher impact stress transmission than the resin tooth(p<0.01), but no difference was observed between them in the thick group. In the soft-liner lined group, the porcelain tooth showed higher impact stress transmission than the resin tooth(p<0.01), but no difference was observed between them in the metal lined group. 5. The thick group showed lower impact stress transmission than the thin group(p<0.01).

• Journal of Technologic Dentistry
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• v.37 no.4
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• pp.205-212
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• 2015

Purpose: The objective of this study was to compare the surface roughness according to polishing process in conventional laboratory techniques used for polishing three different acrylic denture base resins. Materials and methods: Specimen preparation and surface polishing procedures were conducted to manufacturer's recommendation with three heat-polymerized denture base resins. Surface roughness and gloss were measured by a contact type tester and a LED gloss checker using thickness 2 mm and diameter 10 mm. There were five specimens for each acrylic resin material and polishing procedures. Mean average surface roughness (Ra) values of each specimen group were analyzed using a one-way ANOVA analysis of variance and Scheffe's post hoc test. Surfaces after surface roughness and gloss testing according to each polishing process were evaluated under a stereoscopic microscope. Results: The highest mean average surface roughness was measured($Ra=2.43{\pm}0.47$) for surfaces finished with a denture tungsten carbide bur in Triplex. The lowest surface roughness values ($Ra=0.11{\pm}0.07$) were determined in Vertex polished with a lathe. In addition, all materials revealed that surface roughness determined highly in HP1 and HP2 than other procedures. All correlation between surface roughness and gloss showed highly with three heat-polymerized resins. Specially, topmost correlation revealed than other material in Triplex. Significant differences in mean average surface roughness were found between polishing process used high speed lathe and low speed hand-piece. Conclusion: Laboratory polishing used to high speed was found to produce the smoothest surface of heat-polymerized denture base acrylic resin. Therefore, we recommended that high polishing process need to get smooth surface.