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Modified direct relining method produces an accurate adaptation of denture.

The purpose of this study was to examine if a modified direct relining method could result in excellent denture adaptation compared to a conventional method. Direct relining was done using heat-polymerized acrylic resin base on a maxillary cast with two times of three seconds of cooling using dichloro-difluoro-methane coolant. Discrepancy between cast and intaglio surface at residual ridge and center of palate was measured at 12 minutes after mixing of resin (Time 0) and at 24 hours or seven days after water immersion (36 degrees C). At Time 0 (with three seconds of cooling), the discrepancy at ridge (0.39 +/- 0.27) and palate (0.66 +/- 0.31) was significantly lower compared to that of control (ridge = 0.93 +/- 0.51; palate = 1.14 +/- 0.13, P < 0.05); and the same observations occurred at 24 hours and seven days too. On intaglio side (with three seconds of cooling), the peak temperature was 5 degrees C lower than that of control and it occurred at a delay of about 60 seconds. Based on the results of this study, we therefore suggested that this delayed and lowered temperature served to improve the adaptability of denture base.

Acrylic Resins↗

Unpolymerized layer on autopolymerizing, hard reline materials.

PURPOSE: The purpose of this study was to clarify certain properties of the resulting unpolymerized surface layer on 6 hard, autopolymerizing reline resins. MATERIALS AND METHODS: Two of the resins examined were the conventional type with a base monomer composition of mainly methyl methacrylate, and the other four were cross-linked reline materials containing difunctional monomers. For curing, the materials were polymerized in air at 24 and 37 degrees C, and in distilled water at 37 degrees C. The powder-to-liquid ratio was changed by +/- 20 wt% of the manufacturer's specified ratio. The inhibition depth processed under these conditions was measured with an optical microscope. Each sample was then immersed in methylene blue dye bath for 3 weeks before its surface was observed. RESULTS: Especially on cross-linked reline materials, the unpolymerized layer was significantly reduced with higher temperature, lower oxygen presence, and lower powder-to-liquid ratio (P < 0.01). The unpolymerized layer was stained in all materials. There were tiny, stained voids in the polymerized region on the conventional type of reline resins, whereas no staining was found in the polymerized region on the cross-linking reline resins. CONCLUSION: The inhibition depth was strongly affected by the temperature, the presence of air, and viscosity. The unpolymerized layer was easily contaminated in all materials. However, the highly polymerized, cross-linked reline materials might be harder to contaminate than the conventional type of reline resins.

Analysis of Variance↗

Color stability of visible light-cured, hard direct denture reliners: an in vitro investigation.

PURPOSE: Previous studies have disclosed the unsatisfactory color stability of autopolymerizing, hard direct denture reliners (HDDR). The present study investigated the color stability of the newly introduced visible light-cured and dual-cured HDDRs. MATERIALS AND METHODS: Five HDDRs were evaluated after 1 hour, 1 day, 7 days, and 30 days of immersion in coffee, tea, and water. Color measurements were obtained with a tristimulus colorimeter, and color differences (delta E*) were calculated. RESULTS: After 30 days of immersion one visible light-cured material exhibited the highest delta E* value (17.8). The other materials showed acceptable color stability in water and coffee. However, tea strongly affected their color. CONCLUSION: Reliners, staining solutions, and immersion time are significant factors that affect color stability. After 7 days of immersion, all of the materials showed perceptible color differences. Tea exhibited higher staining capacity than coffee.

Analysis of Variance↗

[Denture lining].

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Denture Liners↗

Equilibrium strengths of denture polymers subjected to long-term water immersion.

PURPOSE: This study characterized the effect of water immersion on the strength of denture polymers. MATERIALS AND METHODS: Four denture-base polymers and four denture-reline polymers were tested for flexural strength at proportional limits (FSpl) at 24 hours and at monthly intervals. The equilibrium strength of each polymer was estimated. RESULTS: The denture polymers took from 24 hours to 4 months to reach their equilibrium strength. The equilibrium strengths of the denture polymers were significantly different. CONCLUSION: Water immersion affected the strength of most denture polymers. Different denture polymers behaved differently in response to water immersion.

Analysis of Variance↗

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.

Acrylic Resins↗

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.

Acrylic Resins↗

Effect of surface treatment on the bonding of an autopolymerizing soft denture liner to a denture base resin.

PURPOSE: This in vitro study evaluated the effects of surface treatments and thermocycling on the bonding of autopolymerizing silicone soft denture liner (Sofreliner) to denture base resin. MATERIALS AND METHODS: The bonding surfaces of denture base cylinders were polished with 600-grit silicon carbide paper and pretreated with applications of Sofreliner Primer, Sofreliner Primer after air abrasion, Reline Primer, or Reline Primer after air abrasion. Failure loads and elongation at failure were measured after subjecting specimens to 0, 10,000, 20,000, and 30,000 thermocycles. Failure modes were assessed for all specimens. Seven specimens were fabricated for each of 16 groups, including four pretreatments and four thermocycle groups. RESULTS: Failure loads of the Sofreliner Primer group were significantly higher than those of the air-abrasion group up to 20,000 thermocycles; both groups showed cohesive failures of the soft denture liner. Failure loads of the Reline Primer group were significantly higher than with Reline Primer after air abrasion up to 10,000 thermocycles. Failure mode after 10,000 thermocycles was cohesive for the Reline Primer group and mixed cohesive/adhesive for Reline Primer after air abrasion. Failure loads of the Sofreliner Primer group were significantly higher than those of the Reline Primer group at each thermocycling interval. Elongation values decreased after 10,000 thermocycles for all groups. CONCLUSION: Air abrasion on the denture base resin surface was not effective in enhancing failure load. Cyclic thermal stress is one factor degrading the bond between soft denture liner and acrylic resin denture base.

Acrylic Resins↗

Denture repairs in different regions of Croatia in relation to prosthodontic teams.

The purpose of this paper is to evaluate the incidence of denture repairs in different districts of Croatia through the year of 2002. and to analyse the percentage of different repairs (relinings, simple repairs up to 2 elements and complicated repairs-more than 2 elements) in relation to prosthodontic teams. Data on the number of dentures, and the number and types of denture repairs delivered in the Croatian regions of Zagreb, Rijeka, Split and Karlovac were obtained from the Croatian Institute for Health Insurance for the whole of the year 2002. Information of the number of prosthodontic teams operating in those regions was also obtained. Proportionally more denture repairs were carried out in Karlovac (18%) than Split (5%). The smallest percantage of dentures that required relining was registered in Split and the highest in Rijeka (chi2 = 36.7, p < 0.01). The smallest percentage of simple repairs was registered in Rijeka and the highest in Split (chi2 = 24.3, p < 0.01). The smallest percentage of complicated repairs was registered in Split and the highest in Karlovac. In each region the proportion of denture repairs and types of repairs were correlated with a number of prosthodontic teams in that region. Karlovac had the smallest percentage of specialistic prosthodontic teams and the highest rate of denture repairs.

Croatia↗

In vitro properties of light-polymerized reline materials.

One premixed and three powder-liquid light-polymerized, hard denture reline materials were evaluated for Knoop hardness, transverse strength, and tensile strength when bonded to a heat-activated denture resin. The chemical compositions of the components of the reline materials were analyzed. The premixed light-activated liner was harder, had a higher tensile bond strength to the heat-activated denture resin, and was somewhat stronger than the power-liquid reline materials. Properties of the resins were related to their compositions.

Acrylic Resins↗

[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.

Acrylic Resins↗