Comparison of Thermal Conductivity, Flexural Strength, and Surface Hardness of Alumina Incorporated and Conventional Heat-Activated Denture Base Resins

Introduction: Commonly used polymethyl methacrylate (PMMA) denture base material cannot be considered as ideal due toinferior thermal and mechanical properties.Aim: The aim of the study was to evaluate and compare the thermal conductivity, flexural strength, and surface hardness ofheat cure acrylic resin incorporated with 10 wt.% and 15 wt.% alumina and conventional denture base resin.Materials and Methods: A total of 108 specimens were prepared. Specimens were divided into three main groups. Group Aspecimens were disk shaped (50 mm × 5 mm) and used for measuring thermal conductivity. Groups B and C specimens wererectangular shaped (65 mm × 10 mm × 3 mm) and were used for measuring flexural strength and surface hardness, respectively.Each group was further divided into three subgroups (1, 2, and 3) depending on the concentration, namely, PMMA without filler(control), PMMA + 10 wt.% of Al2O3, and PMMA + 15 wt.% of Al2O3 containing 12 samples each. Thermal conductivity wasmeasured using a modified guarded hot plate apparatus. Flexural strength was assessed with a three-point bending test usinga universal testing machine. Hardness testing was conducted using a Vickers Hardness Tester. The results were analyzedusing one-way ANOVA followed by post hoc comparison by Tukey’s method.Results: Mean values of thermal conductivity were (in W/mK) 0.190, 0.231, and 0.275 for subgroups A1, A2, and A3, respectively.The mean flexural strength values were (in MPa) 56.62, 66.73, and 74.24 for subgroups B1, B2, and B3, respectively. Meanvalues of surface hardness was calculated to be (in HV) 15.17, 16.51, and 17.91 for subgroup C1, C2, and C3, respectively.There was statistically significant improvement in thermal conductivity, flexural strength, and surface hardness after incorporationof alumina and the increase was in proportion to the weight percentage of alumina filler.Conclusion: Incorporation of alumina into heat cure denture base resin significantly improved the thermal conductivity, flexuralstrength, and surface hardness.

Nonthermal plasma on the shear bond strength of relining resin to thermoplastic denture base resin / 대한치과보철학회지

PURPOSE: This study evaluated the effect of nonthermal plasma treatment on the bond strength of autopolymerizing relining resin to the injection molded thermoplastic denture base resins (TDBRs) with different surface treatments. MATERIALS AND METHODS: Acrylic Resin (Acrytone), Polyester (Estheshot-Bright), Polyamide (Valplast) and Polypropylene (Weldenz) were subjected to various surface treatments: No treatment, Nonthermal plasma, Sandblasting, Sandblasting and nonthermal plasma. Specimens were bonded using an autopolymerizing relining resin. Shear bond strength was tested using universal testing machine with crosshead speed of 1 mm/min. Statistical analysis by two-way analysis of variance with Tukey's test post hoc was used. RESULTS: Acrytone showed significantly higher shear bond strength value among other TDBR group while Weldenz had the lowest. The sandblasting and nonthermal plasma condition had significantly higher shear bond strength value in all of the resin groups (P < .05). CONCLUSION: The use of nonthermal plasma treatment showed limited effect on the shear bond strength between TDBRs and relining resin, and combination of nonthermal plasma and sandblasting improved the shear bond strength between TDBR and reline material.

Effects of incorporation of 2.5 and 5 wt% TiO₂ nanotubes on fracture toughness, flexural strength, and microhardness of denture base poly methyl methacrylate (PMMA)

PURPOSE: The aim of this preliminary study was to investigate, for the first time, the effects of addition of titania nanotubes (n-TiO2) to poly methyl methacrylate (PMMA) on mechanical properties of PMMA denture base. MATERIALS AND METHODS: TiO2 nanotubes were prepared using alkaline hydrothermal process. Obtained nanotubes were assessed using FESEM-EDX, XRD, and FT-IR. For 3 experiments of this study (fracture toughness, three-point bending flexural strength, and Vickers microhardness), 135 specimens were prepared according to ISO 20795-1:2013 (n of each experiment=45). For each experiment, PMMA was mixed with 0% (control), 2.5 wt%, and 5 wt% nanotubes. From each TiO2:PMMA ratio, 15 specimens were fabricated for each experiment. Effects of n-TiO2 addition on 3 mechanical properties were assessed using Pearson, ANOVA, and Tukey tests. RESULTS: SEM images of n-TiO2 exhibited the presence of elongated tubular structures. The XRD pattern of synthesized n-TiO2 represented the anatase crystal phase of TiO2. Moderate to very strong significant positive correlations were observed between the concentration of n-TiO2 and each of the 3 physicomechanical properties of PMMA (Pearson's P value ≤.001, correlation coefficient ranging between 0.5 and 0.9). Flexural strength and hardness values of specimens modified with both 2.5 and 5 wt% n-TiO2 were significantly higher than those of control (P≤.001). Fracture toughness of samples reinforced with 5 wt% n-TiO2 (but not those of 2.5% n-TiO2) was higher than control (P=.002). CONCLUSION: Titania nanotubes were successfully introduced for the first time as a means of enhancing the hardness, flexural strength, and fracture toughness of denture base PMMA.

Effect of Surface Treatment on Shear Bond Strength between Artificial Resin Teeth and Denture Base Resin / 대한치과재료학회지

The purpose of this study was to investigate the effect of retaining holes on the denture base, as well as primer application, on the shear bond strength of denture base resin to the denture base. Using Trubyte Biotone artificial teeth, we selected a maxillary first molar and prepared a total of 80 teeth. Each prepared tooth was polished flat using a dental bar. The polished specimens were placed in the center of a silicon mold (diameter 30 mm, height 23 mm) and were embedded with clear acrylic resin (Ortho Jet, Lang Dental, USA). Forty specimens were shaped, using Fisher bar # 701 at the central part of the alveolar surface, to form retention holes. Each denture base resin was transferred to the resin after surface treatment, as instructed by the manufacturer. The highest shear bond strength (36.2 MPa) was achieved by heat-polymerized resin, when the retention hole and the primer were applied to the artificial tooth. The lowest shear bond strength (11.8 MPa) was achieved by auto-polymerized resin, when the primer was applied to the artificial tooth. The combination of heat-polymerized resin and artificial tooth resulted in a complex fracture pattern, whereas auto-polymerized resin and artificial tooth showed an adhesive fracture pattern.

The effects of plasma treatment on the wettability and adhesion properties of the surface of aged denture base resin / 实用口腔医学杂志

Objective:To investigate the effects of plasma treatment on the surface element,wettability and adhesion properties of aged denture base resin.Methods:42 pieces of 10 mm × 10 mm × 1 mm and 100 cubes of 8 mm × 10 mm × 30 mm polymethyl methacrylate specimens were prepared and thermocycled at 5-55 ℃ for 5 000 cycles.40 pieces were used for surface contact angle measurement and 2 for X-ray photoelectron spectroscopy analysis.The 100 cubes were randomly divided into 5 groups:Control(A) and 4 experimental groups in which the samples were exposed to plasma for 1 min (B),2 min (C),3 min (D) and 4 min (E) (n =20) respectively.After plasma treatment,silicone-based soft liner (3 mm) was packed against 2 resin cubes.Thus,50 tensile test specimens were obtained(n =10),and the tensile bond strength was tested by a universal testing machine.Results:The contact angle (°) of group A,B,C,D,E was 63.60 ± 10.81,46.79 ± 5.08,44.13 ± 4.17,40.11 ± 6.01 and 41.03 ± 8.61 respectively (A vs B,C,D or E,P ＜ 0.05).After plasma treatment,the contents of O =C-O and C-O in the samples were increased from 14.17％ and 20.58％ to 18.32％ and 29.32％,respectively.The tensile bond strength(MPa) of group A,B,C,D and E was 0.884 ±0.130,1.281 ±0.086,1.419 ±0.103,1.871 ± 0.248 and 1.904 ± 0.223 respectively (A vs B,C,D or E,P ＜ 0.05;B or C vs D or E,P ＜ 0.05;B vs C,P ＞ 0.05;D vs E,P ＞ 0.05).Conclusion:Plasma treatment can improve the wettability and adhesion properties of aged denture base resin.

Evaluation and comparison of transverse and impact strength of different high strength denture base resins.

Aim: The present study was undertaken to evaluate and compare the impact strength and transverse strength of the high‑impact denture base materials. A conventional heat polymerized acrylic resin was used as a control. Materials and Methods: The entire experiment was divided into four main groups with twenty specimens each according to denture base material selected Trevalon, Trevalon Hi, DPI Tuff and Metrocryl Hi. These groups were further subgrouped into the two parameters selected, impact strength and flexural strength with ten specimens each. These specimens were then subjected to transverse bend tests with the help of Lloyds instrument using a three point bend principle. Impact tests were undertaken using an Izod–Charpy digital impact tester. Results: This study was analyzed with one‑way analysis of variance using Fisher f‑test and Bonferroni t‑test. There was a significant improvement in the impact strength of high‑impact denture base resins as compared to control (Trevalon). However, in terms of transverse bend tests, only DPI Tuff showed higher transverse strength in comparison to control. Trevalon Hi and Metrocryl Hi showed a decrease in transverse strength. Conclusions: Within the limits of this in vitro study, (1) There is a definite increase in impact strength due to the incorporation of butadiene styrene rubber in this high strength denture base materials as compared to Trevalon used as a control. (2) Further investigations are required to prevent the unduly decrease of transverse strength. (3) It was the limitation of the study that the exact composition of the high‑impact resins was not disclosed by the manufacturer that would have helped in better understanding of their behavior.

The effect of Zirconium Nitride coating on shear bond strength with denture base resin in Co-Cr alloy and titanium alloy

PURPOSE: The purpose of this study was to evaluate of Zirconium Nitride (ZrN) coating on shear bond strength with denture base resin in Co-Cr and Ti-6Al-4V alloy. MATERIALS AND METHODS: Co-Cr and Ti-6Al-4V alloy disks (10 mm in diameter, 2.5 mm in thickness; each other: n = 14) were prepared and divided with 2 groups each other by ZrN coating. After primer was applied to disks surface, denture base resin with diameter 6 mm, height 5 mm was bonded on metal disk surface. After surface roughness was measured by Profiler, shear bond strength was determined with Universal testing machine and analyzed with two-way ANOVA. The specimen surfaces and failure mode were examined using a scanning electron microscope. RESULTS: ZrN coated groups showed significantly higher rough surface than non-coated groups (P < 0.05). Irrespective of alloy materials, shear bond strength of ZrN coated groups were lower than non-coated groups (P < 0.001). The scanning electron microscope (SEM) of ZrN coated groups showed mixed and adhesive fractures. CONCLUSION: ZrN coating weakened bonding strength between denture base resin and Co-Cr, Ti-6Al-4V alloy.

Mechanical properties of denture base resins with organic-inorganic hybrid coating after long-term water im-mersion / 实用口腔医学杂志

The durability of denture base resins with a new type of organic-inorganic hybrid coating was examined after long-term water im-mersion.After water immersion for 1 80 days at constant temperature of 37 ℃ the flexural strength and elastic modulus of the samples with the coating were qualified with the national standerds,the controls were not.

Research progress on nano-silver base inorganic antibacterial agents used in denture resin base / 实用口腔医学杂志

In recent years,nano-silver base inorganic antibacterial agents have been widely used in medicinal and biological fields.The recent research progress on nano-silver base inorganic antibacterial agents used in denture resin base,antibacterial effects,biocompatibility and the influence of the agents on the mechanical properties and color of the resin are introduced.

Evaluation of shear bond strength of three different types of artificial teeth to heat cure denture base resin: An in vitro study.

Context: Bonding of artificial teeth and denture base material remained a significant problem for successful prosthetic treatment. Aim: The purpose of this in vitro study was to evaluate shear bond strength of three different artificial teeth with heat cure denture base material after various surface conditioning methods and thermocycling. Materials and Methods: Ninety mandibular first molar denture teeth were selected. They were divided into three groups, Group I: Nanocomposite resin (Veracia), Group II: Composite teeth (Endura), and Group III: Cross-linked acrylic denture teeth (Acry rock). All groups were further subdivided into subgroups based on surface conditioning methods. Subgroup A: No surface conditioning (control group), Subgroup B: Surface conditioning with methyl methacrylate-based bonding agent (Vitacoll), and Subgroup C: Air abrasion with 50 μm aluminum oxide powder particles plus silane-coupling agent (Monobond-S) and Vitacoll bonding agent. Evaluation of shear bond strength of all the specimens was done using universal testing machine. Results: Mean shear bond strength of Group I, Subgroup B (6.87 ± 0.934) showed higher value when compared with Group II, Subgroup B (6.76 ± 1.84) and Group III, Subgroup B (5.66 ± 2.18). The control group (untreated surface) of all three types of artificial teeth used in this study showed significantly lower shear bond strength values than experimental groups (surface conditioning methods; P < 0.05). Conclusion: The results of this study suggest that there were significant differences in shear bond strength among control group and surface treatment groups of denture teeth bonded to heat cure denture base resin.

Assessment of the impact strength of the denture base resin polymerized by various processing techniques.

Aim : To measure the impact strength of denture base resins polymerized using short and long curing cycles by water bath, pressure cooker and microwave techniques. Materials and Methods: For impact strength testing, 60 samples were made. The sample dimensions were 60 mm × 12 mm × 3 mm, as standardized by the American Standards for Testing and Materials (ASTM). A digital caliper was used to locate the midpoint of sample. The impact strength was measured in IZOD type of impact tester using CEAST Impact tester. The pendulum struck the sample and it broke. The energy required to break the sample was measured in Joules. Data were analyzed using Student's " t" test. Results: There was statistically significant difference in the impact strength of denture base resins polymerized by long curing cycle and short curing cycle in each technique, with the long curing processing being the best. Conclusion: The polymerization technique plays an important role in the influence of impact strength in the denture base resin. This research demonstrates that the denture base resin polymerized by microwave processing technique possessed the highest impact strength.

The effect of bur preparation on the surface roughness and reline bond strength of urethane dimethacrylate denture base resin.

Background: The clinical success of relining depends on the ability of reline resin to bond to denture base. Surface preparations may influence reline bond strength of urethane-based dimethacrylate denture base resin. Aim: To investigate the effect of bur preparation on the surface roughness (R a ) of eclipse denture base resin and its shear bond strength (SBS) to an intra-oral self-curing reline material. The mode of reline bonding failure was also examined. Materials and Methods: Twenty-four cylindrical Eclipse™ specimens were prepared and separated into three groups of eight specimens each. Two groups were subjected to mechanical preparation using standard and fine tungsten carbide (TC) burs and the third group (control) was left unprepared. The R a of all specimens was measured using a contact stylus profilometer. Subsequently, relining was done on the prepared surface and SBS testing was carried out a day later using a universal testing machine. Results: One-way ANOVA revealed significant differences (P<0.05) in R a and SBS values for all the groups. Post-hoc Tukey's HSD test showed significant differences (P<0.05) between all the groups in the R a values. For SBS also there were significant differences (P<0.05), except between standard bur and control. Conclusions: 1) There was a statistically significant difference in the R a of Eclipse™ specimens prepared using different carbide burs (P<0.05). 2) There was a statistically significant difference in the relined SBS (P<0.05) when prepared using different burs, but the difference between the standard bur and the control group was not statistically significant.

Effect of adhesive primers on bonding strength of heat cure denture base resin to cast titanium and cobalt-chromium alloy

STATEMENT OF PROBLEM: The poor chemical bonding of a denture base resin to cast titanium framework often introduces adhesive failure and increases microleakage. PURPOSE: This study evaluated the shear bond strengths of a heat cure denture base resin to commercially pure titanium, Ti-6Al-4V alloy and a cobalt-chromium alloy using two adhesive primers. MATERIAL AND METHODS: Disks of commercially pure titanium, Ti-6Al-4V alloy and a cobalt-chromium alloy were cast. Specimens without the primer were also prepared and used as the controls. The shear bond strengths were measured on a screw-driven universal testing machine. RESULTS: The primers significantly (P < .05) improved the shear bond strengths of the heat cure resin to all metals. However, the specimens primed with the Alloy primer(R) (MDP monomer) showed higher bond strength than those primed with the MR bond(R) (MAC-10 monomer) on titanium. Only adhesive failure was observed at the metal-resin interface in the non-primed specimens, while the primed specimens showed mixed failure of adhesive and cohesive failure. CONCLUSIONS: The use of appropriate adhesive metal primers makes it possible not only to eliminate the need for surface preparation of the metal framework before applying the heat cure resins, but also reduce the need for retentive devices on the metal substructure. In particular, the Alloy primer(R), which contains the phosphoric acid monomer, MDP, might be clinically more acceptable for bonding a heat cure resin to titanium than a MR bond(R), which contains the carboxylic acid monomer, MAC-10.

Effect of denture base surface pretreatments on the tensile bond strength between a resilient liner and a processed denture base resin / 대한치과보철학회지

STATEMENT OF PROBLEM: The failure of adhesion between the resilient denture liner and the denture base is a serious problem in clinic. PURPOSE: The PURPOSE of this study was to evaluate the effect of denture base resin surface pretreatments (mechanical and/or chemical) on the tensile bond strength between a resilient liner and processed denture resin. MATERIAL AND METHOD: Acrylic-based resilient liners (Soft liner; GC co., Japan & Coe-Soft; GC America Inc. USA) and silicone-based resilient liners (Mucosoft; Parkell Inc., USA & Dentusil; Bosworth co., USA) were used. Specimens in each soft lining material were divided two groups with or without mechanical pretreatment. Each denture base specimen received 1 of 4 chemical pretreatments including: (1) no treatment, (2) 30-s acetone treatment, (3) 15-s methylene chloride treatment, (4) 180-s methyl methacrylate treatment. All specimens were thermocycled and placed under tension until failure in a universal testing machine. RESULTS: 1. Silicone-based resilient liners exhibited significantly higher tensile bond strengths than acrylicbased resilient liners (P<.05). 2. Grinding the denture base resin improved tensile bond strengths of silicone-based resilient liners, but reduced tensile bond strengths of acrylic-based resilient liners (P<.05). 3. In acrylic-based resilient liners, treating with acetone significantly increased the bond strength of Soft liner and treating with methyl methacrylate significantly increased the bond strength of Coe-Soft (P<.05). However they were not effective compared to silicone-based resilient liner. 4. In silicone-based resilient liners, treating with all chemical etchants significantly increased the bond strength of Mucosoft to denture base, and treating with methylene chloride and methyl methacrylate increased the bond strength of Dentusil to denture base (P<.05). CONCLUSION: Although chemical and mechanical pretreatments were not effective on tensile bond strength of acrylic-based resilent liner to denture base, treating the denture base resin surface with appropriate chemical etchants after mechanical pretreatment significantly increased the tensile bond strength of silicone-based resilient liner to denture base.

Shear bond strength of heat-cured denture base resin to surface treated Co-Cr alloy with different methods / 대한치과보철학회지

STATEMENT OF PROBLEM: For the long-term success of removable partial dentures, the bonding between metal framework and denture base resin is one of the important factors. To improve bonding between those, macro-mechanical retentive form that is included metal framework design has been generally used. However it has been known that sealing at the interface between metal framework and denture base resin is very weak, because this method uses mechanical bonding. PURPOSE: Many studies has been made to find a simple method which induces chemical bond, now various bonding system is applied to clinic. In this experiment, shear bond strengths of heat-cured denture base resin to the surface-treated Co-Cr alloy were measured before and after thermocycling. Chemically treated groups with Alloy Primer(TM), Super-Bond C&B(TM), and tribochemically treated group with Rocatec(TM) system were compared to the beadtreated control group. The data were analyzed with two-way ANOVA. RESULT: 1. Shear bond strength of bead-treated group is highest, and Alloy Primer(TM) treated group, Super-Bond C&B(TM) treated group, Rocatec(TM) system treated group were followed. Statistically significant differences were found in each treated group(p0.05). 3. Shear bond strengths of bead-treated group and Alloy Primer(TM) treated group showed no statistically significant difference before and after thermocycling(p>0.05), and those of Super-Bond CBTM treated group and RocatecTM system treated group showed statistically significant difference after thermocycling(p<0.05).

A comparative study on the dimensional change of the different denture bases / 대한치과보철학회지

STATEMENT OF PROBLEM: Acrylic resin is most commonly used for denture bases. However, acrylic resin has week points of volumetric shrinkage during polymerization that reduces denture fit. The expandability of POSS (Polyhedral Oligomeric Silsesquioxane) containing polymer could be expected to reduce the polymerization shrinkage of denture bases and would increase the adaptability of the denture to the tissue. PURPOSE: The purpose of this study was to compare the dimensional stability in the conventional acrylic resin base, POSS-containing acrylic resin base, and metal bases. MATERIALS AND METHODS: Thirty six maxillary edentulous casts and dentures of different base were fabricated. Tooth movement and tissue contour change of denture after processing (resin curing, deflasking, decasting and finishing without polishing) and immersion in artificial saliva at 37 degrees C for 1 week and 4 weeks were measured using digital measuring microscope and threedimensional laser scanner. RESULTS: The results were as follows: 1. The conventional resin group showed significant (p<0.01) dimensional change throughout the procedure (processing and immersion in artificial saliva). 2. After processing, the metal group and POSS resin group showed lower linear and 3-dimensional change than conventional resin group (p<0.01). 3. There was no statistically significant linear and 3-dimensional change after immersion for 1 week and 4 weeks in metal and POSS resin group. 4. In all groups, the midline and alveolar ridge crest area presented smaller 3-dimensional change compared with vestibule and posterior palatal seal area after processing and soaking in artificial saliva for 1 week and 4 weeks (p<0.01). CONCLUSION: In this study, a reinforced acrylic-based resin with POSS showed good dimensional stability.

Fracture toughness of self-curing denture base resins with different polymerizing conditions / 대한치과보철학회지

PURPOSE: The intent of this study was to evaluate the effects of curing conditions on selfcuring denture base resins to find out proper condition in self-curing resin polymerization. MATERIALS AND METHODS: In this study, 3 commercial self-curing denture base resins are used: Vertex SC, Tokuso Rebase and Jet Denture Repair Acrylic. After mixing the self curing resin, it was placed in a stainless steel mold(3x6x60mm). The mold containing the resin was placed under the following conditions- in air at 23 degrees C, or in water at 23degrees C; or in water at 23degrees C under pressure(20psi); or in water at 37degrees C under pressure(20psi); or in water at 50degrees C under pressure(20psi); or in water at 65degrees C under pressure(20psi), respectively. Also heatcuring denture base resin is polymerized according to manufacturers' instructions as control. Fracture toughness was measured by a single edge notched beam(SENB) method. Notch about 3mm deep was carved at the center of the long axis of the specimen using a dental diamond disk driven by a dental micro engine. The flexural test was carried out at a crosshead speed 0.5mm/min and fracture surface were observed under measuring microscope. RESULTS AND CONCLUSION: The results obtained were summarized as follows : 1. The fracture toughness value of self-curing denture base resins were relatively lower than that of heat-curing denture base resin. 2. In Vertex SC and Jet Denture Repair Acrylic, higher fracture toughness value was observed in the curing environment with pressure but in Tokuso Rebase, low fracture toughness value was observed but there was no statistical difference. 3. Higher fracture toughness value was observed in the curing environment with water than air but there was no statistical difference. 4. Raising the temperature in water showed the increase of fracture toughness.

Physical Properties Of Relining Denture Base Resins With Different Polymerizing Methods / 대한치과보철학회지

This study would like to measure and compare water sorption and solubility of acrylic resins, with 3 different polymerizing methods, and tensile strength between denture base resin and relining resins. For this experiment, 3 different acrylic resins were used; heat polymerizing resin: Vertex (Dentmex, Zeist,Holland), autopolymerizing resin: Tokuso Rebase (Tokuyama Corp, Tokyo, Japan), and light curing resin: Mild Rebaron LC (GC Corp, Tokyo, Japan) The results were as follows; 1. Tokuso Rebase showed the lowest water sorption, followed by Mild Rebaron LC and Vertex. Among resins, there were some signigicant differences (P0.05). About 50% of Rebaron LC showed cohesive fracture. 4. Tensile strength has more decreased after thermocycling than before, but there was no statistical difference (P>0.05).

Cytotoxicity Of Denture Base Resins / 대한치과보철학회지

The purpose of this study was to investigate the cytotoxicity and mutagenicity of denture ase resins. According to manufacturer's instructions, resin specimens were made. Group 1: heat-polymerizing acrylic resin (Luciton 199(R)). Group 2: heat-polymerizing acrylic resin containing polyhedraloligosilsesquioxane(POSS esin). Group 3: auto-polymerizing acrylic resin (Repair Acrylic(R)). Group 4: direct relining auto-polymerizing acrylic resin (Tokuso Rebase(R)). Fresh specimens, 24 hrs. and 72 hrs. soaked specimens in distilled water were made. Responses with metabolic assay and mutagenesis assay to eluates from resin specimens were measured. Cultures with medium alone provided controls. Cytotoxicity was assessed with agar overlay test. The results were as follows: 1. Group 4 showed higher cytotoxicity than Group 1, Group 2 and Group 3 in fresh, 24-and 72-hour immersion cases (p<.05). Group 3 showed higher cytotoxicity than Group 2 in fresh cases and showed higher cytotoxicity than Group 1 and Group 2 in 24-and 72-hour immersion cases (p<.05). Group 1 and Group 2 showed no significant difference. 2. All acrylic denture base resins showed significant increase of cell activity as immersion time increased (p<.05). 3. Auto-polymerizing acrylic denture base resins showed higher cytotoxicity than heat-polymerizing acrylic denture base resins (p<.05). 4. All acrylic denture base resins showed lower mutagenicity than controls (p<.05).