Comparative Study on Color Stability of Denture Reline Polymers when Using Microwave and Chemical Disinfection

This study investigated the color stability of reline resin after two methods of disinfection i.e microwave disinfection and chemical disinfection. A stainless steel moldwith a breakaway compartment (10 mm in diameter by 0.7 mm thickness) was made to fabricate specimens of various resins. Each material was mixed according to manufacturer’s instructions and applied into the mold. Prior to color stability testing, specimenswere cleaned in distilled water for 20 minutes to kill any microorganisms that may had contaminated the discs during fabrication. And then specimens were immersed in Sodium Perborate Monohydrate 200 ml of solution for 15 days and microwaved for 15 days sothat it is comparable to chemical disinfection soaking. The color stability of each specimen was measured again using spectrophotometer and values were obtained. The data of ∆E, ∆L, ∆b, ∆a were analysed by 2 way repeated measures ANOVAs test. Significant statistic changes in color parameters ∆L, ∆a, ∆b of the reline resin DPI, Ufi Gel Hard And Kooliner were observed when dentures were disinfected by Sodium Perborate Monohydrate 2% solutions. The color stability of the reline resin was influenced by time, regardless of disinfection or non disinfection. This can be attributed to bleaching (whitening) effect of reline material. Discoloration Original Research Article of resin based materials may be caused by intrinsic or extrinsic factors. Intrinsic factors are related to internal alterations in material resulting from physicochemical reactions or residual monomer oxidation with time. Thus the initiator, quantity and type of monomer and the polymerisation efficiency can affect the color stability of resin based materials. The color stability deviation value ∆E significantly increased to maximum for chemical disinfectant, least for Control group and intermediate for microwaved group. Ufi Gel showed the highest deviation ∆E and Control Group showed the lowest deviation according to results

Effect of microwave postpolymerization treatment on residual monomer content and the flexural strength of autopolymerizing reline resin.

Background : Microwave postpolymerization has been suggested as a method to improve the flexural strength of an autopolymerizing denture reline resin. However, the effect of microwave postpolymerization on the residual monomer content and its influence on flexural strength have not been investigated. Objectives : This study analyzed the effect of microwave postpolymerization on the residual monomer content and its influence on the flexural strength of an autopolymerizing reline resin (Denture Liner). Materials and Methods : A total of 70 specimens (64 Χ 10 Χ 3.3 mm) were polymerized according to the manufacturer's instructions and divided into 7 groups (n = 10). Control group specimens were not subjectedto any further processing. Before testing, the specimens were subjected to postpolymerization in a microwave oven using different power (550 and 650 W) and time (3, 4, and 5 min) settings. Two specimens of each group were then manually ground into fine powder and samples extracted from the specimens using reflux method. The samples were then subjected to gas chromatography for residual monomer determination in area%. Eight specimens were subjected to a three-point bending device with a span of 50 mm and crosshead speed of 5 mm/min, and the flexural strength was determined in MPa. Data analyses included Student's t-test and one-way analysis of variance. Results : For the Denture Liner reline resin, the residual monomer content decreased and the flexural strength increased significantly with the application of microwave irradiation using different time/power combinations. The specimens with the lowest residual monomer content were the similar specimens which presented with the highest flexural strength. Conclusion : Microwave postpolymerization irradiation can be an effective method for increasing the flexural strength of denture liner (at 650 W for 5 min) by reducing the residual monomer content by further polymerization at free radical sites.

The color stability of direct denture reline resins / 대한치과보철학회지

STATEMENT OF PROBLEM: Direct denture reline resins tend to discolor during service in the oral environment by intrinsic and extrinsic factor. PURPOSE: This study was designed to evaluate the color stability of direct denture reline resins. MATERIAL AND METHODS: Mild Rebaron(GC Corp., Japan), Meta Base M(Sun medical Co., Japan), Mild Rebaron LC(GC Corp., Japan) and as a control group, Vertex SC(Dentimex Zeist, Holland) were chosen for this study. Ten specimens of each direct denture reline resins were fabricated. Treatment methods designed for this study were the coffee staining test(7days) and the accelerated aging test(100hours). The color changes before and after treatment were measured by Tristimulous colorimeter(Yasuda seiki seisakusho, Ltd. Japan) and analyzed. RESULTS: All the direct denture reline resins subjected to the coffee staining test and the accelerated aging test showed noticible difference in color change. After coffee staining test, Meta Base M showed the highest color change followed by Vertex SC, Mild Rebaron LC and Mild Rebaron. There were no statistical differences between Meta Base M and Vertex SC and between Mild Rebaron LC and Mild Rebaron(p>0.05). After accelerated aging test, Mild Rebaron LC showed the highest color change followed by Vertex SC, Meta Base M and Mild Rebaron. There were no statistical differences only between Mild Rebaron and Mata Base M(p>0.05) but among the others, there were statistical differences(p<0.05). CONCLUSION: Within the limitation of this study, all the direct denture reline resins subjected to the extrinsic and intrinsic factors showed noticible difference in color change, and there were differences among manufacturers.

The effect of denture cleansers on the bond strength and the surface hardness of reline resin to denture base resin / 대한치과보철학회지

STATEMENT OF PROBLEM: Removable partial denture and complete denture often require denture base relines to improve the fittness against tissue-bearing mucosa because of the gradual change in edentulous ridge contour and resorption of underlyng bony structure. Self-curing hard reline resins offers the immediate and relatively inexpensive means to be recondition the surface of denture base directly. However weak bond between denture base resin and reline material can harbor bacteria, promote staining, or result in complete separation of the two materials. PURPOSE: The purpose of this study was to evaluate the effect of denture cleansers on bond strength and surface hardness of reline resin to denture base resin Denture base resin beams(60.0x15.0x3.0 mm) were made with Lucitone 199. MATERIAL AND METHODS: 10mm section was removed from the center of each specimen. The samples were replaced in the molds and the space of 10mm sections were packed with Tokuso Rebase reline material. The specimens were immersed in denture cleansers(Polident, Cleadent) and were evaluated after 1week, 2weeks, and 4weeks. The bond strength and surface hardness of self-curing hard reline materials to heat-curing denture base resin were measured using an UTM(universal testing machine). RESULTS AND CONCLUSION: 1) There was no significant difference of usage, kind, and denture cleaner by application time on the bonding strength of self-curing hard reline resin to denture base resin. 2) There was no significant difference of usage, kind, and denture cleaner by application time on the surface hardness, but the surface hardness showed decreasing tendency, as the time of immersion was extended 3) The failure modes of the specimens was initially adhesive failure and finally cohesive failure of self-curing hard reline resin.

Effects Of Metal Surface Treatments On The Shear Bond Strength Between Ni-Cr Denture Base And Reline Resins / 대한치과보철학회지

The purpose of this study was to evaluate the effects of four metal surface treatments on the shear bond strength of reline resin to Ni-Cr alloy. The denture base metal used in this study was Ni-Cr alloy(Ticonium Premium 100, Ticonium Co., U.S.A.). 120 specimens were divided into five metal surface treatments:sandblasting only, MR.BOND(Tokuyama Corp., Japan), Cesead Opaque Primer(Kuraray Co., Japan), METALPRIMER II(GC Corp., Japan)and Super-Bond C&B(Sun Medical Co., Japan) after sandblasting. They were bonded with one of three reline resins: Mild Rebaron(GC Corp., Japan), Mild Rebaron LC(GC Corp., Japan) and Meta Base M(Sun Medical Co.,Japan).Then they were thermocycled 1,000 times at temperature of 4 celsius degrees and 60 celsius degrees. The shear bond strengths were measured using the universal testing machine(Instron,Model 4301, England)with a cross-head speed of 2 mm/min. The results were as follows: 1.All metal primers and adhesive cement significantly improved the bond strength of reline resin to Ni-Cr alloy compared with sandblasted specimens. 2.In Mild Rebaron and Mild Rebaron LC,Cesead Opaque Primer showed the highest bond strength, but the differences among Cesead Opaque Primer,MR.BOND and METALPRIMER II were not significant.The bond strength of Cesead Opaque Primer was significantly different with that of Super-Bond C&B. 3.In Meta Base M,Super-Bond C&B showed the highest bond strength,but there was no difference between Super-Bond C&B and three metal primers. 4.There was no difference in the bond strength between Mild Rebaron and Mild Rebaron LC when metal surface was treated with the same method. 5.The bond strengths of Mild Rebaron and Mild Rebaron LC treated with Cesead Opaque Primer were higher than that of Meta Base M.The bond strengths of Mild Rebaron treated with MR. BOND and METALPRIMER II was higher than that of Meta Base M.However,there was no difference among three reline resins treated with Super-Bond C&B.