Effect of degradation of denture base resin on bond strength to relining resins

The purpose of this study was to evaluate the effect of degradation of a denture base resin on bond strength to relining resins. Denture base resin specimens were immersed under various conditions to simulate degradation. Tensile bond strength of denture base resin after immersion to relining resins was measured with or without surface grinding. The bond strength of denture base resin without grinding after immersion to relining resin was significantly lower than that before immersion. However, bond strength was improved by surface grinding before bonding. These results suggest that bonding efficiency of denture base resin to relining resins was affected by immersion condition, which caused potential degradation of the denture base resin.     

Shear Bond Strength of Two Chemically Different Denture Base Polymers to Reline Materials

Purpose: This study evaluated the shear bond strengths of light-polymerized urethane dimethacrylate (Eclipse) and heat-polymerized polymethylmethacrylate (Meliodent) denture base polymers to intraoral and laboratory-processed reline materials.
Materials and Methods: Thirty disks measuring 15 mm diameter and 2 mm thick were prepared for each denture base material following the manufacturers' recommendation. They were relined with Meliodent RR, Kooliner, and Secure reline materials after 1 month of water immersion. Ten additional Eclipse specimens were relined using the same Eclipse resin. A shear bond test was carried out on an Instron machine at a crosshead speed of 1.0 mm/min 24 hours after relining. Data were analyzed using two-way and one-way ANOVAs and post hoc Dunnett's T3 test ( p = 0.05). The nature of failure was analyzed under a stereomicroscope. The effect of dichloromethane adhesive on the two denture polymer surfaces and the failed interfaces of mixed and adhesive failures were analyzed under a SEM (scanning electron microscope).
Results: Two-way ANOVA showed significant differences in the shear bond strength values as a function of the denture base polymers, reline materials, and their interaction ( p < 0.05). One-way ANOVA showed significant differences in shear bond strength values among denture base-reline combinations ( p < 0.05) except for Meliodent-Kooliner and Eclipse-Meliodent RR relines. Meliodent showed the highest shear bond strength value when relined with Meliodent RR (14.5 ± 0.5 MPa), and Eclipse showed the highest value with Eclipse relining (11.4 ± 0.6 MPa). Meliodent denture base showed adhesive, cohesive, and mixed failure, while all Eclipse showed adhesive failure with various reline materials.
Conclusion: The two chemically different denture base polymers showed different shear bond strength values to corresponding reline materials.     

Properties of a new light-polymerized relining material

This study evaluated a newly developed light-polymerized relining material. The material had lower values for bending strength than conventional resins, but laminating the denture base and the relining material increased the plasticity and thus the toughness. The fit of dentures relined with the new material was similar to that of the autopolymerizing resin. A strong adhesion was obtained between the relining material and the denture base when a new light-activated bonding agent was used.     

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.     

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 eighth week. The relined denture bases were stored in distilled water at 37°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.     

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.     

The effect of relining on the accuracy and stability of maxillary complete dentures--an in vitro and in vivo study.

A technique was developed for evaluating in vitro the accuracy or fit of experimental denture bases using a low-viscosity impression material for determining the space between the master die and the processed denture base. These measurements indicated that relining heat-cured maxillary denture bases with autopolymerizing acrylic resin improved their adaptation to the ridges. Interestingly, if no teeth were present in the heat-cured denture base, markedly less distortion occurred after processing. Limited clinical measurements on the stability of maxillary dentures in function showed no statistically significant change in stability after relining, but the trend was toward increased stability with the relined denture.     

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.     

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.     

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.     

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.     

衬特舒用于全口义齿重衬的临床效果观察

目的:观察衬特舒软衬材料、热凝树脂、自凝树脂对全口义齿重衬修复的临床效果。方法:分别采用软衬材料、热凝树脂、自凝树脂对不同牙槽嵴和黏膜条件的无牙颌患者进行全口义齿重衬,衬垫1年后复查。比较3种材料重衬义齿的舒适度、固位性、咀嚼功能恢复的满意度及清洁情况。结果:对于牙槽嵴或黏膜条件差的患者,软衬材料重衬义齿的成功率明显高于热凝、自凝树脂重衬义齿(P<0.05);对于牙槽嵴和黏膜条件尚好的患者,3种材料重衬义齿的成功率无显著差异(P>0.05)。结论:衬特舒软衬材料重衬义齿稳固、舒适、咀嚼功能提高,适用于牙槽嵴或黏膜条件差的患者。     

Comparative evaluation of sodium hypochlorite and microwave disinfection on dimensional stability of denture bases

PURPOSE

To compare the effect of sodium hypochlorite and microwave disinfection on the dimensional stability of denture bases without and with relining.

MATERIALS AND METHODS

A brass die was prepared by simulating an edentulous maxillary arch. It was used to fabricate 1.5 mm and 3 mm of thickness denture bases (n = 40). The 1.5 mm of thickness-specimens (n = 20) were relined with 1.5 mm of autopolymerizing relining resin. Five holes were prepared over crest of ridge of brass die with intimately fitting stainless steel pins which were transferred to the intaglio surface of specimens during fabrication of denture bases. For calculation of dimensional changes in denture bases, differences between the baseline area before and after disinfection of the specimens were used. The denture bases without and with relining were divided into 2 groups (each n = 20). Data were analyzed using student paired ''t'' and unpaired ''t'' test.

RESULTS

Microwave disinfection produces significant shrinkage in both denture bases without relining (t = 17.16; P<.001) and with relining (t = 14.9; P<.001). Denture bases without relining showed more shrinkage when compared with relined denture bases after microwave disinfection (t = 6.09; P<.001). The changes in dimensional stability after sodium hypochlorite disinfection were not significant for both denture bases without relining (t = 2.19; P=.056) and denture bases with relining (t = 2.17; P=.058).

CONCLUSION

Microwave disinfection leads to increased shrinkage of denture bases without and with relining. Chemical disinfection with sodium hypochlorite seems to be a safer method of disinfection with regards to physical properties such as changes in dimensional stability.     

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.     

Physical properties of a new denture lining material containing a fluoroalkyl methacrylate polymer

STATEMENT OF PROBLEM: A new fluoride-containing, methacrylate-based denture lining material has been introduced. Because of the fluoride content, this material is expected to demonstrate low water sorption and solubility and high stain resistance, but these attributes remain untested. PURPOSE: This study investigated a wide range of clinically relevant properties for a new fluoroalkyl methacrylate denture base liner product (Maxfit) and compared these properties with those of 3 other commercial products. MATERIAL AND METHODS: Four denture lining materials were tested: Maxfit, Kooliner, Tokuyama Rebase (fast set), and Denture Liner. Water sorption (microg/mm(3)) and solubility (microg/mm(3)) were tested according to International Organization for Standardization (ISO) Standard No. 1567. Stain resistance was evaluated by measuring color change (DeltaE) after immersion in 2 solutions (coffee and turmeric solution). Microhardness was determined using Knoop indentation testing according to American National Standards Institute/American Dental Association Specification No. 17. Relined denture fit was evaluated by measuring the gap (mm) occurring between the relined denture base and the cast after polymerization. Shear bond strength (MPa) to denture base materials (polymethyl methacrylate, cobalt-chromium alloy, and titanium) was tested according to ISO Standard No. 11405. Data were statistically analyzed using nonparametric Kruskal-Wallis (alpha=.05) and Mann-Whitney U tests combined with the Bonferroni correction (alpha=.008). RESULTS: Maxfit showed the lowest water sorption and solubility (8.0 +/- 0.1, 0.5 +/- 0.1 microg/mm(3), respectively). The color change from coffee immersion of Maxfit was significantly less than Tokuyama Rebase and Denture Liner, and significantly less than Tokuyama Rebase and Denture Liner in a turmeric solution (P<.001). Knoop hardness of Maxfit (8.66 +/- 0.51) was higher than Kooliner and Tokuyama Rebase (P<.001). The relined denture fit using Maxfit was not different from other materials. Significantly higher shear bond strength to denture base resin was noted for Maxfit compared to Tokuyama Rebase and Denture Liner (P<.008). CONCLUSIONS: The new fluoroalkyl methacrylate-based denture liner (Maxfit) showed the lowest water sorption and solubility, and superior stain resistance. In spite of the addition of the fluoride content, this product exhibited no deterioration in physical properties, such as surface hardness, fit of the relined denture, and shear bond strengths to denture base materials tested.     

Application of electrolyzed acid water to sterilization of denture base part 1. Examination of sterilization effects on resin plate

Bactericidal activities of electrolyzed strong and weak acid waters for acrylic denture base resin were evaluated in order to discuss the applicability of these waters for sterilization of denture base. Only 1-minute immersion in the electrolyzed strong or weak acid water could completely eliminate the attached bacteria, Staphylococcus aureus 209P, on the resin plate. When the resin was relined with tissue conditioner, 5-minute immersion or 1- to 2-minute ultrasonic cleaning reduced the number of the bacteria from 10(5)/cm2 level to 10(1)/cm2 and no surviving bacteria could be detected after 10-minute treatment. These findings suggest that both the electrolyzed strong and weak acid waters are well applicable to the disinfectant for acrylic denture base showing excellent bactericidal activities in a significantly shorter treatment as compared with the conventional denture cleaning.     

Evaluation of hard direct reline resins

Peak curing temperatures of hard, direct, autopolymerizing reline resin materials tested were all within ADA specification guidelines. A temperature range of 10 degrees C was demonstrated among materials, with the highest polymerization temperatures recorded for Perm and Lang's Self-Curing Rebase Acrylic, and the lowest for KOOLiner, Flexacryl, and COE-Rect. This temperature difference is probably clinically detectable. However, intraoral testing of polymerization temperatures yielded lower peak values than those observed with specification testing, and the temperature peaks occurred earlier with intraoral conditions. There were significant color changes with simulated aging for three of the products tested: Flexacryl, COE-Rect, and Lang's Self-Curing Rebase Acrylic. The color changes occurred after only 24 hours of accelerated aging. Although there was only a small change in color with aging for Perm and KOOLiner, there was a moderate shift in the color of KOOLiner (delta E = 2.2) before aging. Thus only Perm demonstrated little color change with simulated aging. Of the reline products, one material, KOOLiner, demonstrated lower bond tensile strengths to denture base materials. However, the clinical significance of this was not known. One denture base material (Astron) recorded significantly higher bond strength values for all reline products and failure always took place within the denture base.     

义齿清洁剂对热固化型基托树脂物理及机械性能的影响

目的 评价5种义齿清洁剂对热固化型基托树脂颜色稳定性、表面粗糙度、弯曲强度的影响。方法 热固化型基托树脂试样浸泡于保丽净、澳多—C、Protefix、0.2%葡萄糖酸氯己定、雅克菱义齿清洁剂以及蒸馏水中,后测量试样颜色的改变(ΔE)、粗糙度值、弯曲强度。结果 0.2%葡萄糖酸氯己定、雅克菱义齿清洁剂的颜色改变较对照组显著较大;将ΔE值用NBS（美国国家标准局）单位来表示,所有组对应的人色差感觉程度均为感觉轻微。对于表面粗糙度和弯曲强度,不同浸泡处理组间无统计学差异。结论 热固化型基托树脂使用义齿清洁剂180 d后,0.2%葡萄糖酸氯己定、雅克菱浸泡后颜色稳定性较差,但为临床可接受。保丽净、澳多—C、Protefix对材料均无影响。     

Comparison of adhesiveness of chewing gum to hard and soft denture base materials

PurposeThe purpose of this study was to compare the adhesiveness of chewing gum to hard and soft denture base materials to investigate food retention associated with the basal surface of the denture.MethodsTest specimens were fabricated using acrylic resin[Re], cobalt-chromium alloy[Co], zirconia[Zr], silicone soft relining material[SS], and acrylic soft relining material[AS]. Samples were set on a top-and-bottom pair lifting platform equipped with a digital force gauge. The experimenter chewed 3.0 g of chewing gum for 5 min. After surface saliva was wiped off, the chewing gum was placed on the lower test fragment and compressed until the distance between the upper and lower test fragments decreased to 1 mm. The upper test fragment was pulled at a crosshead speed of 100 mm/min. Adhesiveness was measured under dry conditions, and under wet conditions with inter-positioned artificial saliva.ResultsUnder dry conditions, the adhesive strength was 17.04 ± 1.99 N for Re, 12.88 ± 2.20 N for Co, 3.80 ± 1.03 N for Zr, 5.76 ± 1.41 N for SS, and 12.54 ± 2.44 N for AS. Under wet conditions, the adhesive strength was 5.26 ± 1.64 N for Re, 0.96 ± 0.21 N for Co, 3.32 ± 0.40 N for Zr, 5.20 ± 1.35 N for SS, and 6.78 ± 1.97 N for AS.ConclusionsAmong the hard denture base materials, zirconia recorded low adhesiveness and Re recorded high adhesiveness under both wet and dry conditions. The adhesiveness of Co was low under wet conditions but high under dry conditions. Among the soft denture base materials, SS under dry conditions recorded lower adhesiveness than that of AS. The adhesiveness of SS was low under both wet and dry conditions.     

Effect of surface treatment on shear bond strength of relining material and 3D-printed denture base

PURPOSEThis study aimed to analyze the shear bond strength between the 3D-printed denture base and the chairside relining material, according to the surface treatment.MATERIALS AND METHODSCylindrical specimens were prepared using DENTCA Denture Base II. The experimental groups were divided into 6 (n = 10): no surface treatment (C), Tokuyama Rebase II Normal adhesive (A), sandblasting (P), sandblasting and adhesive (PA), sandblasting and silane (PS), and the Rocatec system (PPS). After bonding the chairside relining material to the center of the specimens in a cylindrical shape, they were stored in distilled water for 24 hours. Shear bond strength was measured using a universal testing machine, and failure mode was analyzed with a scanning electron microscope. Shear bond strength values were analyzed using one-way analysis of variance, and Tukey’s honest significant difference test was used for post-hoc analysis (P < .05).RESULTSGroup PPS exhibited significantly higher shear bond strength than all other groups. Groups P and PA displayed significantly higher bond strengths than the control group. There were no significant differences between groups PS and A compared to the control group. Regarding the failure mode, adhesive failure occurred primarily in groups C and A, and mixed failure mainly in groups P, PA, PS, and PPS.CONCLUSIONThe shear bond strength between the 3D-printed denture base and the chairside relining material exhibited significant differences according to the surface treatment methods. It is believed that excellent adhesive strength will be obtained when the Rocatec system is applied to 3D-printed dentures in clinical practice.