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.     

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.     

Wettability of denture relining materials under water storage over time

STATEMENT OF PROBLEM

Poor wettability of denture relining materials may lead to retention problems and patient discomfort.

PURPOSE

Purpose of this study is to compare and evaluate wettability of nine denture relining materials using contact angle measurements under air and water storage over time.

MATERIAL AND METHODS

Nine denture relining materials were investigated in this study. Two heat-curing polymethyl-methacrylate (PMMA) denture base materials: Vertex RS, Lang, one self-curing polyethyl-methacrylate (PEMA) chairside reline resin: Rebase II, six silicone relining materials: Mucopren soft, Mucosoft, Mollosil® plus, Sofreliner Touch, GC Reline™ Ultrasoft, Silagum automix comfort were used in this experiment. Contact angles were measured using high-resolution drop shape analysis system (DSA 10-MK2, KRUESS, Germany) under three conditions (in air after setting, 1 hour water storage, and 24 hours water storage). Nine materials were classified into three groups according to material composition (Group 1: PMMA, Group 2: PEMA, Group 3: Silicone). Mean values of contact angles were compared using independent samples t-test and one-way ANOVA, followed by a Scheffe''s post hoc analysis (α= 0.01).

RESULTS

Contact angles of materials tested after air and water storage increased in the following order: Group 1 (PMMA), Group 2 (PEMA), Group 3 (Silicone). Heat-cured acrylic denture base resins had more wettability than silicone relining materials. Lang had the highest wettability after 24 hours of water storage. Silicone relining materials had lower wettability due to their hydrophobicity. Wettability of all denture relining materials, except Rebase II and Mollosil® plus, increased after 24 hours of water storage.

CONCLUSIONS

Conventional heat-cured resin showed the highest wettability, therefore, it can be suggested that heat-cured acrylic resin is material of choice for denture relining materials.     

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.     

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.     

上颌全口义齿铸造腭托后堤区的网状设计与临床观察

目的：评价上颌全口义齿铸造金属腭侧基托后堤区网状设计的临床效果。方法：采用刮除石膏的方法形成后堤区,在上颌基托硬腭区采用金属板设计,牙槽嵴及基托后缘10mm（后堤区）范围采用金属网加强塑料基托设计。在戴牙后1个月对上颌义齿固位效果进行评价。对由于后堤区封闭不佳造成的固位不良者,进行后堤区重衬后再次评价。结果：158例患者中,139例固位佳,15例固位一般,4例固位差。单纯由后堤区边缘封闭不良造成的固位一般11例,固位差3例,经后堤区重衬后对此14例再次评价,固位佳9例,固位一般5例。结论：上颌全口义齿铸造金属腭侧基托后堤区的网状设计,既保持了常规设计的优点,又克服了其不能重衬的缺点,减少了全口义齿的失败率。     

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.     

Color stability: Denture base resins processed with the microwave method

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

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.     

Three-dimensional analysis of maxillary denture displacement during reline impression procedure

The contourmeter was used to determine quantitatively the denture displacements caused by various impression materials and techniques during the relining of a maxillary denture. This study indicated the following conclusions. Tissue-conditioning material used with closed-mouth impression technique or light-bodied polysulfide used with either open- or closed-mouth technique caused the least denture displacement in the three dimensions when compared with regular-bodied polysulfide or zinc oxide and eugenol impression materials. Comparing the same impression materials used with either open- or closed-mouth technique showed no significant difference in maxillary denture displacements. A relined complete denture should be remounted on the articulator and the occlusion refined to eliminate occlusal mismatches resulting from three-dimensional denture displacements during relining.     

抗菌涂层材料对义齿基托吸水性和溶解性与单体渗出的影响

目的研究义齿基托树脂表面抗菌涂层对基托吸水性和溶解性以及单体渗出的影响。方法根据YY 0270-2003 标准,测量4种基托树脂涂膜前、后的吸水值和溶解值,应用索氏提取法测量固化后基托树脂的交联度;利用气相色谱法测量基托树脂涂膜前、后的单体渗出量。采用SPSS17.0软件包对数据进行统计学分析。结果具有抗菌涂层的基托材料的吸水值、溶解值和单体渗出量明显减少。4种材料中,贺利氏树脂的交联度最高,日进和山八树脂次之,新世纪树脂最低。结论义齿基托树脂的吸水值、交联度和单体渗出量之间存在一定联系,即交联度较大时,吸水值减少,甲基丙烯酸单体渗出量也相应降低。抗菌涂层可以提高树脂基托的综合性能。     

The effect of glass fiber reinforcement on the residual monomer content of two denture base resins.

OBJECTIVE: The amount of residual monomer is one of the principal factors affecting the properties of acrylic resin denture bases. In recent years, glass fibers have been used to strengthen denture base resins. The purpose of this study was to investigate the effect of glass fiber reinforcement on the amount of residual methyl methacrylate released from two different denture base resins (heat cured and autopolymerized). METHOD AND MATERIALS: Continuous unidirectional and woven preimpregnated glass fiber reinforcements (Stick and Stick Net) were used to reinforce heat-curing and autopolymerizing denture base resins. RESULTS: The release of residual methyl methacrylate from heat-cured and autopolymerized test specimens reinforced with glass fibers was significantly higher than that from unreinforced test specimens. Stick Net glass fiber reinforcement resulted in significantly higher residual monomer release than did Stick glass fiber reinforcement. Test specimens made from heat-cured denture polymethyl methacrylate released less residual methyl methacrylate than did specimens made from autopolymerized polymethyl methacrylate. CONCLUSION: Glass fiber reinforcement increases the residual monomer content of denture base resins. The level of residual monomer ranged from 0.11% to 0.37% in heat-cured resin and from 0.18% to 0.46% in autopolymerized denture base resin.     

Evaluation of the properties of a new pour denture base material utilizing a modified technique and initiator system

A new denture base system, Provac, has been developed for complete and partial dentures, and for relining. The Provac material is methyl methacrylate, which cures with the aid of barbituric acid. In this study the physical and mechanical properties of the new resin were investigated and compared with those of a conventional autopolymerizing material (Croform) and a conventional heat polymerizing material (Trevalon). It was found that the dimensional accuracy of Provac was better than that of the conventional heat-curing material, Trevalon, and the denture was finished more easily and quickly. The physical and mechanical properties of Provac resin were found to be similar to those of the other two materials, and conformed to the International Specifications for denture base materials. The residual monomer levels in Provac material were always higher than the minimal obtainable values associated with conventional heat-cured materials when these were polymerized with a terminal boil during the curing cycle.     

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.     

总义齿不同材料垫底前后咀效能的比较

目的：探讨总义齿不同材料垫底前后咀嚼效能的变化。方法：选择需作衬垫的总义齿30付,分成两组,分别用软衬材料和热凝塑料垫底,用722型光栅分光光度计吸光光度法测定衬垫前后的咀嚼效能。结果：软衬前后吸光度值有显著性差异。结论：总义齿软衬垫后咀嚼效能有很大提高。     

Immediate maxillary denture base extension for posterior palatal seal

A procedure for extension of the maxillary denture base for development of a posterior palatal seal is described. The technique involves provisional extension with paraffin wax and adding direct relining resin supported by a silicone putty core. This simple, quick procedure achieves immediate recovery of retention for underextended maxillary dentures without additional laboratory procedures.     

微波消毒对甲基丙烯酸树脂全口义齿稳定性的影响

目的 探讨微波消毒对甲基丙烯酸树脂全口义齿稳定性的影响.方法 制作20件上颌无牙颌丙烯酸树脂基托并定点,测量微波消毒前后标志点间距离.收集20例戴甲基丙烯酸树脂全口义齿患者,对上颌半口义齿进行微波消毒,消毒前后对义齿进行评分,请患者填写问卷调查表进行主观评价.结果 微波消毒后,丙烯酸树脂基托尺寸稳定,基托光滑面近远中标志点间距离（t=-0.463,P=0.649）、基托光滑面颊舌向标志点间距离（t =0.650,P=0.523）消毒前后差异无统计学意义.微波消毒前后,患者对义齿的各项满意率相同,语言功能、稳定性、咀嚼能力和舒适度满意率分别为90％ （18/20）、80％（16/20）、85％ （17/20）和95％（19/20）;微波消毒前后对义齿的评分也无变化：60％ （12/20）为3分,（6/20） 30％为2分,（2/20）10％为1分.结论 微波消毒对甲基丙烯酸树脂全口义齿稳定性无明显影响.     

Improvement of a removable complete denture by relining or rebasing

When the fit of a removable complete denture is diminished as a result of progressive alveolar bone reduction, relining or rebasing might be indicated. In clinical practice, a degree of confusion exists concerning the concepts relining, and rebasing. Relining is resurfacing the tissue side of a denture with a new material to fill the space which exists between the original denture contour and the altered tissue contour. Rebasing is resurfacing the fitting surface of a denture by replacing the entire denture base with new material, also to fill the space which exists between the original denture contour and the altered tissue contour. In particular, attention is given to 3 specific forms ofrelining and rebasing which serve to restore the maxillomandibular relationship, to extend effectively the palatal denture surface of the maxillary denture and to reline or rebase an implant-supported overdenture.     

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.     

Current concepts for relining complete dentures: a survey

Reline procedures for complete dentures have received scant attention in the literature. Fifty-seven dental colleges responded to an 11-item survey on reline procedures. According to the tabulated data, most dental schools recommended the following (not necessarily our recommendations). Leave the denture(s) out of the mouth for at least 24 hours prior to fabrication of the reline impressions. Use tissue-conditioning material only on selected patients. Use Coe Comfort as the tissue-conditioning material of choice. Place either none or one relief hole in the maxillary denture, and place no relief holes in the mandibular denture prior to the impression(s). Place relief holes along the palatal midline of the maxillary denture. No specific size is recommended for the palatal relief holes. Place 1 mm of basal surface relief and 1 to 2 mm of border relief before the reline impression is made. Use a polysulfide rubber base material as the material of choice for reline impressions. Use a closed mouth impression technique. Remove the palate from the maxillary denture prior to processing. Use heat-cured resin (Lucitone) for processing. Use pressure-indicator paste prior to delivery of the denture(s). Remount the complete denture(s) on an articulator after processing for making occlusal corrections.