Flexural strength of rebased denture polymers

The properties of denture base and reline resins may be affected by daily changes between room temperature and mouth temperature. The purpose of the study was to evaluate the effect of thermocycling on the flexural strength of the relined denture base polymer with reline resin. Three denture base resins, three hard reline resins and their combinations were tested. Fourteen specimens, 65x10x2.5 mm, were fabricated for each material. Polymer combination specimens were made using 1.5 mm hard reline resin on 1.0 mm cured denture base resins. Half of the specimens were stored for 50+/-2 h in distilled water at 37 degrees C, while the other half were thermocycled for 20 000 cycles between 4 and 60 degrees C. Three point bending tests were conducted on a universal testing machine at a cross-head speed of 0.5 cm/s. The flexural strengths were measured and a statistical analysis was performed on the data using three-way ANOVA (P<0.05). The results showed that the flexural strength of relined denture base polymer was significantly higher than that of hard reline polymer. Thermocycling did not affect the flexural strength of the relined denture base polymers, whereas the denture base polymer and reline polymer alone showed a decrease in strength after thermocycling.     

Basic studies on hard direct reline resins. Part 1. Adhesive strength

Direct relining methods has come to occupy an important position in removable denture prosthodontics. The purpose of this study was to investigate the effect of various experimental conditions on the adhesive strength of hard direct reline resins to denture base resin. The experimental conditions were as follows: 1) immersion time of denture base resin before relining, 2) amount of load at relining, 3) roughness of adhesive surface, 4) immersion time of relined resin. The following results were obtained: 1. The adhesive strength of Rebaron was the highest, followed by that of TRIAD and KOOLiner. 2. The immersion times of denture base resin did not appreciably affect the adhesive strength. 3. With the rougher adhesive surface, Rebaron and KOOLiner showed a tendency to increase adhesive strength. 4. The adhesive strength was not appreciably affected by load. 5. We did not find a definitive correlation between adhesive strength and immersion times of relined resin.     

Strength of relined denture base polymers subjected to long-term water immersion

PURPOSE: This study was undertaken to characterize the long-term equilibrium flexural strength at proportional limit (FSp) of 4 denture reline polymers processed onto 4 denture base polymers. MATERIALS AND METHODS: A 3-point flexural test was applied on rectangular specimens of each denture base polymer-denture reline polymer. Each specimen was immersed in water for 4 months prior to and 4 months after reline. RESULTS: Significant differences existed among the relined specimens because of the denture base polymer variable, the denture reline polymer variable, and their interaction (P < 0.05). The descending order in FSp according to the denture base polymer, arranged in terms of statistical significance was: Acron approximately Acron MC > Triad > Palapress Vario, where approximately denotes no significant difference between Acron and Acron MC. The descending order in FSp according to the denture reline polymer, arranged in terms of statistical significance was: Triad > Rebaron > Rebaron LC > Tokuso Rebase. Significant difference existed among all of the denture reline polymers. CONCLUSION: The present study showed that the long-term equilibrium strengths of 4 denture reline polymers processed onto 4 denture base polymers were different. The strength of the relined specimen of a denture base is dependent on the strength of the denture base polymer and that of the reline polymer.     

Shear bond strength of denture reline polymers to denture base polymers

PURPOSE: This study was undertaken to characterize the shear bond strength established between four denture base polymers and four denture reline polymers. MATERIALS AND METHODS: Cylindric columns of denture reline polymers were bonded to columns of denture base polymers. Specimens were immersed in water for 4 months and then thermocycled. The strength at which the bond failed under shear stress was recorded. RESULTS: Significant differences in bond strength existed among the specimens because of the denture base polymer variable, the denture reline polymer variable, and their interaction (P < .05). A light-activated denture base polymer (Triad) bonded adequately with a light-activated reline polymer (Triad) but less well with the other reline polymers tested. The bond strength established between some denture base polymers and a different light-activated reline polymer (Rebaron LC) was relatively low. CONCLUSION: The type of denture base polymer and denture reline polymer affected the shear bond strength between them.     

Assessment of shear bond strength between three denture reline materials and a denture base acrylic resin

PURPOSE: This study reports the effect of five surface treatments on the bond strength established between three denture reline materials and a denture base resin. MATERIALS AND METHODS: Cylindric columns of denture reline materials were bonded to columns of denture base resins that received one of the surface treatments: application of dichloromethane, the monomer of the denture base resin, the recommended bonding agent or the monomer of the denture reline material, polishing with 240-grit silicone carbide paper, and air abrasion. A control group without surface treatment was included for each material. Specimens were immersed in water for 1 day and then thermocycled. The strength at which the bond failed under shear was recorded. RESULTS: None of the surface treatments significantly improved the bond strength of Kooliner. Triad bonding agent and denture base monomer applications most significantly improved the bond strengths of Triad and GC reline, respectively. CONCLUSION: Triad bonding agent and denture base monomer should be used in conjunction with Triad and GC reline, respectively, when relining a denture base resin.     

Dimensional changes of processed denture bases after relining with three resins.

This study compared the dimensional change of simulated processed denture bases after relining with three resins. Thirty simulated denture bases 1.5 to 2 mm thick were processed from Lucitone 199 resin following the manufacturer's instructions using the long-cure method. Ten bases were relined with Lucitone 199 (long-cure), 10 were relined with Triad resin, and 10 were relined with Accelar 20 resin. The relined bases were processed on a metal die using a reline jig, and three measurements (from distobuccal flange to distobuccal flange) were made with a traveling microscope immediately before and after relining. Each relined simulated denture base showed a significant dimensional shrinkage after processing. The mean dimensional change values of the Triad resin relined bases were significantly greater than those of the other two resin relined bases. All of the dimensional change values, however, would probably be insignificant in a clinical situation.     

A new polyisoprene-based light-curing denture soft lining material

OBJECTIVES: The purpose of this study was to investigate some clinically relevant properties of Clearfit LC, a newly developed polyisoprene-based light-curing lining material. Its properties were compared with those of other four commercial products. MATERIALS AND METHODS: Five soft lining materials, Clearfit LC, two plasticised acrylics (Super-soft, Soften) and two silicones (Molloplast B, Sofreliner) were used to determine water sorption, solubility, staining resistance, Shore A hardness and shear bond strength to denture base. Five specimens for each test were fabricated. The results of each test among the five materials were compared by one-way ANOVA and Scheffe's post-hoc test at alpha=0.05. RESULTS: One-way ANOVA of each test showed that the differences among five materials were significant (P<0.05). Clearfit LC showed the intermediate water sorption and solubility (10.07; 1.72 microg/mm(3)). It also showed the lowest color change in beta-carotene/olive oil solution and instant coffee solution (DeltaE=1.19, 5.48, respectively). The shear bond strength of Clearfit LC was 1.56MPa, and no adhesive failure was found. Its Shore A hardness value (56.2) was located between two acrylics and silicones. It was also found that the softer materials tend to failure cohesively. CONCLUSIONS: The polyisoprene-based lining material showed low water sorption and solubility, moderate softness, high staining resistance and satisfactory shear bond strength to denture base resin. It also provides clinicians sufficient working time due to its light-curing property. It would be an attractive alternative as a relining material.     

The effect of chemical surface treatments of different denture base resins on the shear bond strength of denture repair

STATEMENT OF PROBLEM: Fracture of a repaired denture base often occurs at the junction of the base and repair materials rather than within these materials. PURPOSE: The purpose of the study was to evaluate the shear bond strengths of 4 denture base acrylic resins following the use of 3 chemical solvents and to examine treated acrylic resin surfaces under a field emission scanning electron microscope (SEM). MATERIAL AND METHODS: Forty discs (15 mm in diameter and 3 mm thick) were fabricated for each denture base material (a conventionally molded, heat-polymerized [Meliodent, M], an injection-molded, heat-polymerized [SR-Ivocap, I], and a microwave-polymerized [Acron MC, A]) repaired with an autopolymerizing acrylic resin (Meliodent), for a total of 120 specimens, processed according to manufacturers' instructions, embedded in acrylic resin blocks, and divided into 4 groups of 10. One of the groups served as control and had no surface treatment. In the 3 experimental groups, specimen surfaces were treated with chemical etchants by immersion in acetone (ac) for 30 seconds, in methylene chloride (mc) for 30 seconds, or in MMA (mo) for 180 seconds, respectively. Then autopolymerizing acrylic resin (Meliodent) was placed on the treated surfaces using a brass ring (6 mm in diameter and 2 mm in height) to confine the material to a standardized dimension. After 24 hours of storage at 37 degrees C, the shear bond strength (MPa) of the specimens was measured in a universal testing machine. A 2-way analysis of variance and the Tukey HSD test were performed to identify significant differences (alpha=.05). The nature of the failure was noted as adhesive, cohesive, or mixed. The effect of the chemical treatments on the surface of base resins was examined under an SEM. RESULTS: Chemical treatments increased the bond strength of repair material significantly. Significant differences were found between the control and experimental groups (P<.001). In the control group, M showed the highest (16.7 MPa) bond strength, and A showed the lowest (9.4 MPa). No significant differences were detected between M (18.9 MPa) and A (19.9 MPa) with acetone treatment, or between M (19.3 MPa) and A (20.3 MPa) with methylene chloride treatment. The SEM observations showed that application of chemical etchants produced smoother surfaces than controls. CONCLUSION: Chemical treatment prior to denture base repair showed significant improvement on the bond strength of the base materials. Although the microwave-polymerized acrylic resin, A, showed the lowest shear bond strength compared to the control groups, the highest percentage increase was obtained with A after chemical treatments.     

Evaluation of adhesion of chairside hard relining materials to denture base polymers

STATEMENT OF PROBLEM: Removable denture bases are made of modified poly(methyl methacrylate) (PMMA), which has reliable bond strength with resins containing methyl methacrylate (MMA). However, some hard relining materials with different chemical compositions have been reported to have less than adequate bond strength to PMMA denture base polymers. PURPOSE: This in vitro study evaluated the initial bonding properties of chairside hard relining materials to different removable denture base polymers, as well as the structure of the interface. MATERIAL AND METHODS: The tensile strength (MPa) of adhesion of 8 chairside hard relining materials (Original Truliner, GC Reline Hard, Ufigel Hard, Triad Reline, New Truliner, Light Liner, Astron LC Hard, and Flexacryl Hard) was tested against 3 denture base polymers (Ivocap Plus, Paladon 65, and Palapress Vario). Dumbbell-shaped specimens with a 6-mm diameter of bonding surface were used for tensile testing of bond strength (n=5). An MMA containing hard relining material (Original Truliner) was used as a control. Tensile strength of the bond was calculated using the bonding area and maximum force under tension. Statistical analyses of data were conducted with 2-way analysis of variance (alpha=.05). The influence of the bonding agents and the relining materials on the PMMA denture base surface layer and its structure were investigated. The depths of the swollen layers were measured with a transmission light microscope. Fracture surfaces after testing were also visually evaluated. Chemical analyses of all materials prior to testing were performed using high-performance liquid chromatography. RESULTS: Significant differences were found among tensile bond strengths of chairside hard relining materials to PMMA denture base polymers forming 3 different groups (P<.001). No significant difference among different denture base polymers was found with regard to tensile strength of adhesion (P=.918), but the interaction term between hard relining material and denture base polymer was found to be significant (P<.001). The tensile bond strength of the relining materials and denture base polymers was found to range from 8% to 60% of the strength of the PMMA denture base polymers. CONCLUSION: The chemical composition of the bonding agents and the relining materials and their combinations affected the depth of the swollen layers of the denture base polymers and the tensile strength of adhesion.     

Factors affecting the bond strength of denture base and reline acrylic resins to base metal materials

Objective

The shear bond strengths of two hard chairside reline resin materials and an auto-polymerizing denture base resin material to cast Ti and a Co-Cr alloy treated using four conditioning methods were investigated.

Material and Methods

Disk specimens (diameter 10 mm and thickness 2.5 mm) were cast from pure Ti and Co-Cr alloy. The specimens were wet-ground to a final surface finish of 600 grit, air-dried, and treated with the following bonding systems: 1) air-abraded with 50-70-µm grain alumina (CON); 2) 1) + conditioned with a primer, including an acidic phosphonoacetate monomer (MHPA); 3) 1) + conditioned with a primer including a diphosphate monomer (MDP); 4) treated with a tribochemical system. Three resin materials were applied to each metal specimen. Shear bond strengths were determined before and after 10,000 thermocycles.

Results

The strengths decreased after thermocycling for all combinations. Among the resin materials assessed, the denture base material showed significantly (p<0.05) greater shear bond strengths than the two reline materials, except for the CON condition. After 10,000 thermocycles, the bond strengths of two reline materials decreased to less than 10 MPa for both metals. The bond strengths of the denture base material with MDP were sufficient: 34.56 MPa for cast Ti and 38.30 for Co-Cr alloy.

Conclusion

Bonding of reline resin materials to metals assessed was clinically insufficient, regardless of metal type, surface treatment, and resin composition. For the relining of metal denture frameworks, a denture base material should be used.     

The bond strength of a visible light-cured reline resin to acrylic resin denture base material

The introduction of Triad visible light-cured denture resin has led to several applications. Among them is direct intraoral relining of complete and partial dentures. This study investigated the bonding characteristics of Triad reline resin to four commonly used heat-cured denture base resins. The shear and tensile bond strengths of Triad resin and four denture base resins were determined and compared with intact tensile strengths. The findings of this study indicate that the bond strength of Triad resin to denture base resin is sufficiently high to suggest its clinical applicability.     

不同表面处理对义齿软衬树脂黏结强度的影响

目的:探讨4种不同表面处理对义齿软衬树脂与硬质树脂之间黏结强度影响。方法:制作热凝硬质基托树脂试件(直径8mm,长度15mm)和热凝义齿软衬树脂试件(厚4mm,直径10mm),然后将2个硬质树脂试件黏结在软衬树脂正反两面的中心。采用4种不同表面处理方式——第1组,对照组,不加任何处理;第2组,喷砂粗化处理;第3组,专用黏结剂涂布表层;第4组,表层涂布 喷砂粗化。每组各10个试件,分别测定黏结强度,采用SPSS10.0软件进行单因素方差分析。结果:第1、2、3、4组的平均黏结强度分别为3.518、2.834、4.077和3.852MPa。F=6.40,P<0.0014。表层涂布组的黏结强度最高,而喷砂组的黏结强度最低。结论:使用专用黏结剂表层涂布,可显著增强义齿软衬树脂的黏结强度;而进行喷砂处理,反而会使黏结强度下降。     

Tensile bond strengths of hard chairside reline resins as influenced by water storage

Due to gradual resorption of the edentulous ridge bone, removable prostheses often require denture base relines to improve fit and stability. This research evaluated the bond strength between one heat-cured acrylic resin (Lucitone 550(R)) and two hard chairside reline resins, after two different periods of storage in water (50 h and 30 days). The bond strength was evaluated using a tensile test. The mode of failure, adhesive or cohesive, was also recorded. The results submitted to the Kruskal-Wallis test indicated that the highest tensile strengths were achieved with intact Lucitone 550(R) denture base resin in both periods of storage in water. After 50 h of storage in water, Duraliner II(R) reline material exhibited the highest bond strength to the denture base resin. After 30 days of storage in water, Duraliner II(R) reline resin demonstrated a significant reduction in adhesion, showing lower tensile bond strength than Kooliner(R) material. Both hard chairside reline materials failed adhesively across Lucitone 550(R) denture base resin, in both periods of time.     

Shear bond strength of visible-light-cured resin relative to heat-cured resin

One promising clinical application of visible-light-cured (VLC) denture resin is for relining complete and partial dentures. Typically, a VLC resin would be used to reline an existing prosthesis fabricated from heat-cured resin (HCR). This study measured the shear bond strength of a VLC resin bonded to HCR specimens by different bonding agents. For comparison, we measured the shear bond strengths of VLC resin bonded to VLC resin specimens and of autopolymerizing resin (APR) to HCR specimens. Cylindrical specimens of HCR (n = 126) and VLC (n = 24) were thermocycled to simulate aging, and the bonding surfaces were prepared by being sanded to approximate clinical roughness. The specimens were divided into seven groups of approximately 20 each, and test materials were bonded by different bonding agents. Statistical analysis by ANOVA and the Student-Newman-Keuls test showed significant differences (p less than 0.05) among all groups except APR to HCR/no bonding agent, VLC to HCR/VLC bonding agent, or VLC to HCR/VLC and HCR bonding agent. The traditional bond of APR to HCR with HCR bonding agent was significantly stronger (p less than 0.05) than the strongest bond of VLC to HCR with HCR and VLC bonding agents.     

Influence of thermal and mechanical stresses on the strength of intact and relined denture bases

STATEMENT OF PROBLEM: Denture bases may become increasingly weaker as a result of thermal stress and flexural cyclic loading. Information regarding this potential problem and its relationship to the denture base reline is limited. PURPOSE: This study evaluated the influence of thermal and mechanical stresses on the strength of intact and relined denture bases. MATERIAL AND METHODS: Twenty-eight microwave-polymerized (Acron MC) intact denture bases were prepared in the shape of a 3-mm-thick maxillary denture. Additionally, fifty-six 2-mm-thick denture bases were relined with 1 mm of autopolymerizing resin (Tokuyama Rebase Fast II or New Truliner) (n=28). Intact and relined specimens were divided into 4 groups (n=7) as follows: without stress (control); a mechanical stress at 0.8 Hz for 10,000 cycles; 5000 thermal cycles between 5 degrees C and 55 degrees C; or a combination thermo-mechanical stress. The specimens were vertically loaded in compression with a rounded rod at 5 mm/min until failure, using a universal testing machine. Data on maximum fracture load (N), deflection at fracture (%), and fracture energy (N.mm) were analyzed by 2-way analysis of variance and Student-Newman-Keuls tests (alpha=.05). RESULTS: The strength of the denture bases relined with New Truliner was not significantly affected by any of the experimental conditions, but comparing the control groups, New Truliner exhibited the lowest maximum fracture load values. The maximum fracture load of intact denture bases (P=.002) and those relined with Tokuyama Rebase Fast II (P=.01) showed a significant decrease after thermal stress. Additionally, cyclic loading significantly decreased the maximum fracture load (P<.001), deflection at fracture (P=.025), and fracture energy (P<.001) of intact denture bases and those relined with Tokuyama Rebase (P values of .002, .039, and .001, respectively). CONCLUSION: Thermal and mechanical stresses exert deleterious effects on the strength of intact and/or relined denture bases, which vary according to the relining material used.     

Bond strength of three chairside crown reline materials to milled polymethyl methacrylate resin

Statement of problemInformation on the bond strength of milled polymethyl methacrylate interim restorations when relined with chairside reline materials is lacking.PurposeThe purpose of this in vitro study was to measure the shear bond strength of various combinations of 3 different chairside reline materials bonded to milled polymethyl methacrylate blocks with 3 different types of surface treatments.Materials and methodsUniform blocks (10×10×22 mm) were milled from tooth-colored polymethyl methacrylate disks (Vivid PMMA; Pearson Dental Supply Co). The surface treatments tested were airborne-particle abrasion with 50-μm particle size aluminosilicate, application of acrylic resin monomer (Jet Liquid; Lang Dental Manufacturing Co) for 180 seconds, and airborne-particle abrasion with monomer application. The control groups were blocks with no surface treatment. The chairside reline materials tested were Jet acrylic resin (Jet Powder; Lang Dental Manufacturing Co), bis-acryl resin (Integrity; Dentsply Sirona), and flowable composite resin (Reveal; Bisco). All materials were applied through a Ø1.5×3-mm bonding ring. Ten specimens for each of the 12 groups were tested in a universal testing machine. Load was applied at a crosshead speed of 1 mm/min. Fracture surfaces were then analyzed for cohesive versus adhesive or mixed failure. Data were analyzed using 2-way ANOVA and Tukey-Kramer post hoc analysis (α=.05).ResultsThe mean shear bond strength values ranged from 1.77 ±0.79 MPa to 28.49 ±5.75 MPa. ANOVA revealed that reline material (P<.05), surface treatment (P<.05), and their interactions (P<.05) significantly affected the shear bond strength among the experimental groups. The strongest combination was Jet acrylic resin applied on specimens treated with airborne-particle abrasion and monomer. All 3 failure modalities (adhesive, cohesive, and mixed modes) were observed.ConclusionsOf the materials tested, the most reliable material to bond to milled polymethyl methacrylate was Jet acrylic resin, and the bond strength values were increased substantially when the milled polymethyl methacrylate surface was airborne-particle abraded and monomer was applied.     

Shear bond strengths of polymethyl methacrylate to cast titanium and cobalt-chromium frameworks using five metal primers

STATEMENT OF PROBLEM: Poor chemical bonding of a denture base resin to cast titanium frameworks often introduces adhesive failure and increases microleakage. PURPOSE: This study examined the shear bond strengths of a denture base resin to cast pure titanium, Ti-6Al-4V, and a cobalt-chromium alloy using various adhesive primers. MATERIAL AND METHODS: Disks (6.0 mm diameter, 2.5 mm thick) were cast of the 3 alloys. The disk surfaces were grit-blasted with 50 microm alumina and treated with 5 different metal primers (Metal Primer II ?MP]; Cesead Opaque primer ?OP]; Meta Base ?MB]; experimental primer ?EP]; Siloc bonding system ?SI]). A denture base resin (Palapress Vario) was then applied on the disks with hole-punched sticky tape (bonding area of 5.0 mm) and a Teflon (PTFE, New Age Industries Inc, Willow Grove, Pa.) ring (6.0 mm diameter x 2.0 mm thick). Specimens without primer were also prepared as controls. All specimens were immersed in 37 degrees C water and thermocycled up to 2,000 cycles. Shear bond strength values were determined at a crosshead speed of 0.5 mm/min. Data were statistically analyzed using 3-way ANOVA, followed by 1-way ANOVA and the Scheffé multiple range test. RESULTS: Primers significantly (P <.05) improved shear bond strengths of denture base resin to all metals, among which no significant differences were found. Specimens primed with OP, MP, and EP showed higher bond strengths than did those primed with MB. After thermocycling, the bond strengths of MB and SI decreased substantially; MB showed the least durability (22.8% to 35.5% decrease) among the primers. CONCLUSION: The application of 5 primers significantly improved the shear bond strengths of a denture base resin to cast CP titanium, Ti-6Al-4V, and Co-Cr alloy. OP and MP primers exhibited greater bond strength and durability than did MB and SI.     

Comparative study of the transverse strength of three denture base materials

OBJECTIVES: Fracture resistance of recently introduced denture base resins has not been compared to traditional denture base materials. This study compared the transverse strength of three denture base materials, namely, Lucitone 199, Triad VLC, and the newly introduced Eclipse. MATERIALS AND METHODS: A total of 30 specimens (50mmx25mmx2.5mm) were fabricated, 10 from each material. The specimens were loaded until failure on an Instron universal testing machine using a three point flexural test. One-way analysis of variance (ANOVA) was used to compare the mean transverse strength between the three materials tested. RESULTS: The transverse strength values showed significant differences between the three denture base materials (P<0.0001). The mean transverse strength and standard deviations (MPa) were as follows: Eclipse 116.13+/-17.7, Lucitone 87.12+/-8.1, and Triad VLC 57.96+/-7.3. CONCLUSIONS: Within the limitations of this study, Eclipse showed the highest transverse strength among the materials tested. Eclipse denture base material may provide a stronger alternative to traditional denture base resins.     

The Effect of Water Immersion on the Shear Bond Strength Between Chairside Reline and Denture Base Acrylic Resins

PURPOSE: The effect of water immersion on the shear bond strength (SBS) between 1 heat-polymerizing acrylic resin (Lucitone 550-L) and 4 autopolymerizing reline resins (Kooliner-K, New Truliner-N, Tokuso Rebase Fast-T, Ufi Gel Hard-U) was investigated. Specimens relined with resin L were also evaluated. MATERIALS AND METHODS: One hundred sixty cylinders (20 x 20 mm) of L denture base resin were processed, and the reline resins were packed on the prepared bonding surfaces using a split-mold (3.5 x 5.0 mm). Shear tests (0.5 mm/min) were performed on the specimens (n = 8) after polymerization (control), and after immersion in water at 37 degrees C for 7, 90, and 180 days. All fractured surfaces were examined by scanning electron microscopy (SEM) to calculate the percentage of cohesive fracture (PCF). Shear data were analyzed with 2-way ANOVA and Tukey's test; Kruskall-Wallis test was used to analyze PCF data (alpha= 0.05). RESULTS: After 90 days water immersion, an increase in the mean SBS was observed for U (11.13 to 16.53 MPa; p < 0.001) and T (9.08 to 13.24 MPa, p= 0.035), whereas resin L showed a decrease (21.74 MPa to 14.96 MPa; p < 0.001). The SBS of resins K (8.44 MPa) and N (7.98 MPa) remained unaffected. The mean PCF was lower than 32.6% for K, N, and T, and higher than 65.6% for U and L. CONCLUSIONS: Long-term water immersion did not adversely affect the bond of materials K, N, T, and U and decreased the values of resin L. Materials L and U failed cohesively, and K, N, and T failed adhesively.     

Clinical evaluation of a chemically cured hard denture relining material

The purpose of the current study was to evaluate the clinical performance of a chemically cured denture relining material after 1-year service period. A powder–liquid material designed for denture base relining (Tokuso Rebase Normal-set, Tokuyama Corp., Tokyo, Japan.) was assessed. Fifty adult patients, who required denture reline treatment, participated in the current project. Adaptation of each denture was examined with a silicone elastomeric material, and the surface to be relined was reduced by means of a rotary cutting instrument, then conditioned with dichloromethane. The relining material was spatulated, poured into the relining area, inserted and adjusted after setting. Each relined denture was subjected to base line evaluation immediately after relining and end evaluation after 1 year. Standardized criteria were used for direct evaluation of the material. After an observation period of 1 year, the rate of the relining cases considered to be in clinically ideal condition (Alfa) was 90% for staining, 90% for discoloration, 94% for peeling, 96% for adaptation and 100% for irritation to oral tissue. Only one case was judged as clinically unacceptable (Charlie), and this was for staining. On the basis of a 1-year observation, the Tokuso Rebase material is considered to be a clinically reliable hard denture relining agent.