Surface Of Denture Base Research Articles

Adherence of Candida to complete denture surfaces in vitro: A comparison of conventional and CAD/CAM complete dentures.

PURPOSEThe goal of this study was to compare the adhesion of Candida albicans to the surfaces of CAD/CAM and conventionally fabricated complete denture bases.MATERIALS AND METHODSTwenty discs of acrylic resin poly (methyl methacrylate) were fabricated with CAD/CAM and conventional procedures (heat-polymerized acrylic resin). The specimens were divided into two groups: 10 discs were fabricated using the CAD/CAM procedure (Wieland Digital Denture Ivoclar Vivadent), and 10 discs were fabricated using a conventional flasking and pressure-pack technique. Candida colonization was performed on all the specimens using four Candida albicans isolates. The difference in Candida albicans adhesion on the discs was evaluated. The number of adherent yeast cells was calculated by the colony-forming units (CFU) and by Fluorescence microscopy.RESULTSThere was a significant difference in the adhesion of Candida albicans to the complete denture bases created with CAD/CAM and the adhesion to those created with the conventional procedure. The CAD/CAM denture bases exhibited less adhesion of Candida albicans than did the denture bases created with the conventional procedure (P<.05).CONCLUSIONThe CAD/CAM procedure for fabricating complete dentures showed promising potential for reducing the adherence of Candida to the denture base surface. Clinical Implications. Complete dentures made with the CAD/CAM procedure might decrease the incidence of denture stomatitis compared with conventional dentures.

Finite Element Analysis of Implant-Assisted Removable Partial Denture Attachment with Different Matrix Designs During Bilateral Loading.

The aim of this study was to investigate the effect of different matrix designs on resilient attachment on an implant-assisted removable partial denture (IARPD) using finite element analysis (FEA). A laser scanner was used to extract the geometrical data of a human partially edentulous mandible. A 12-mm-long and 4.8-mm-diameter-wide implant was modeled, and two types of intradental attachment of snap fastener principle (elliptical) and resilient attachment (titanium) matrices were modeled along with tooth roots and periodontal ligaments. The modeling was performed with a combination of reverse engineering and solid modeling. The model incorporated a removable partial denture and was loaded with realistic bilateral forces. The FEA was used to analyze the stress and strain distributions in the IARPD and in the metal framework. Stresses and deformations in the metal framework and resin denture base surfaces were analyzed for the elliptical and titanium matrix designs. The maximum von Mises stresses were 605.85 and 614.96 MPa in the metal framework surface and 10.35 and 10.63 MPa in the resin denture base surface, respectively, for the elliptical and titanium matrix designs. The maximum deformations (displacements) were 418.5 and 428.3 μm in the metal framework surface for the elliptical and titanium matrix designs, respectively. The corresponding values of displacements for the resin denture base surface were 325.52 and 249.22 μm for the elliptical and titanium matrix designs, respectively. The maximum displacements in the matrixes were, however, nearly the same (229.51 and 229.47 μm) for both the elliptical and titanium matrixes. The titanium matrix design was a more favorable design compared with the elliptical design, because it had lower lateral deformation as indicated by the maximum displacement.

Biofilm formation on complete denture liners

AIM: To clinically evaluate biofilm growth on 4 liners in complete denture base surfaces of 20 geriatric patients. MATERIAL AND METHODS: Patients received new complete maxillary dentures prepared with 4 chambers (10x10x2 mm) in the tissue surface of acrylic denture base. Each of the 4 chambers was randomly filled with the following denture liners: Eversoft (M1); Kooliner (M2); GC Reline Extra Soft (M3); Elite Soft Relining (M4). Patients were randomly separated into 2 treatment groups: T1- sanitization with soft brush and dentifrice; T2- similar to T1 with daily immersion in cleansing chemical solution (Ortoform). Patients had 8 follow-up sessions over a 3-month period. The internal denture surface was stained with a dental plaque dye at each of the follow-up visits. Standardized photographs were taken, and biofilm growth was scored. Data were tabulated and submitted to Analysis of Variance. Means were compared by Tukey (p&lt;0.05) and T tests. RESULTS: Kooliner (M2) means were significantly different from the others for both groups T1 and T2. Treatment 1 promoted higher biofilm growth scores than treatment 2. The highest score after treatment 1 was Kooliner (M2) and the lowest was Elite Soft Relining (M4). As for treatment 2, Eversoft (M1) was statistically different from Elite Soft Relining (M4). Again, Kooliner (M2) presented the highest score and Elite Soft Relining (M4) the lowest. Kooliner (M2) was statistically different from both GC Reline Extra Soft (M3) and Elite Soft Relining (M4). CONCLUSION: Of the materials and treatments studied, the best clinical selection for lower biofilm growth scores would be Elite Soft Relining (M4) with treatment 2.

Effect of gypsum separating media on the appearance of stone cast surfaces

Several well-known parameters influence the appearance of the denture base surface, including proper isolation of the dental stone. There is lack of data describing the influence of this parameter on the appearance of the denture base surface. The purpose of this study was to evaluate the effectiveness of 2 dental stone separating media on the surface of the denture base. A conventional flasking technique for fabricating a denture base was used. Twenty casts were poured with Type III yellow dental stone to produce 20 identical denture bases. Each cast was sectioned into halves. One half of the cast was treated with Al-Cote (control group) and the other half with Iso-K separating material. Once the denture base was finished, a single examiner, blinded to the experiment, visually compared the 2 surfaces of each cast (right and left part of the cast) under natural light to determine which surface was glossier. The McNemar test (.05 significance level) was used to compare the discordant pairs (20 discordant pairs). Two pairs (10%) were glossier than the Iso-K treatment, and 18 pairs (90%) within the Iso-K treatment were glossier than the treatment with Al-Cote. A statistically significant difference was found between the 2 treatments (P<.001). The odds ratio was 9.00, with a 95% confidence interval of 2.155 to 79.981. When used according to the manufacturer's instructions, denture surfaces treated with Iso-K appeared glossier than when treated with Al-Cote separating material.

Antifungal Effect of Some Medicinal Plant Extracts On Candida Albicans Adherence on Acrylic Resin Denture Base Material. An In Vitro Study

Evaluate the antifungal effect of some medicinal plant extracts (peppermint, rue, pomegranate and garlic) and their anti–adherent effect on C. albicans cells that attached on the fitting surface of acrylic resin denture base. Materials and Methods: This study evaluated the antifungal effect of plant extracts, using broth micro dilution method at two concentrations for each one. The visualization, in-spection and enumeration of adherent C. albicans cells and the detection of the anti–adherent effect of these plant extracts was achieved by using fluorescent microscope. For each plant extract, two concen-trations in addition to the time of immersion at three different intervals (1 h, 24 hrs and 48 hrs) were evaluated for the anti–adherent effect. Result: Antifungal effect of plant extracts on candida albicans cells, was measured by spectrophotometer which showed that both rue and pomegranate extracts had the best antifungal effect at first concentration, while in the second concentration, pomegranate and garlic extracts had the best antifungal effect . The mean number of remaining C. albicans cells which adhered on acrylic resin samples after treatment by immersion in the first concentration of plant ex-tracts for one hour was (3.1), (3.7), (3.7) and (4.7)] cells /mm2 respectively; while after treatment with second concentration of plant extracts for one hour was [ (4), (4.4), (4.4) and (4)] cells / mm2 respec-tively for the above mentioned plant Conclusion: All examined medicinal plant extracts were signifi-cantly effective in dislodging C. albicans cells from acrylic resin samples at their different concentra-tions and statistically there was no significant difference among the different times of immersion.

Effect of surface treatments on the bond strength of soft denture lining materials to an acrylic resin denture base

Adhesive failure between acrylic resin and resilient liner material is commonly encountered in clinical practice. The purpose of this study was to evaluate the effect of different surface treatments on the bond strength of 2 different resilient lining materials to an acrylic resin denture base. Ninety-six dumbbell-shaped specimens were fabricated from heat-polymerized acrylic resin, and 3 mm of the material was cut from the thin midsection. The specimens were divided into 6 groups according to their surface treatments: no surface treatment (control group), 36% phosphoric acid etching (acid group), erbium:yttrium-aluminum-garnet (Er:YAG) laser (laser group), airborne-particle abrasion with 50-μm Al2O3 particles (abrasion group), an acid+laser group, and an abrasion+laser group. The specimens in each group were divided into 2 subgroups according to the resilient lining material used: heat-polymerized silicone based resilient liner (Molloplast B) and autopolymerized silicone-based resilient liner (Ufi Gel P). After all of the specimens had been polymerized, they were stored in distilled water at 37°C for 1 week. A tensile bond strength test was then performed. Data were analyzed with a 2-way ANOVA, and the Sidak multiple comparison test was used to identify significant differences (α=.05). The effects of the surface treatments and resilient lining materials on the surface of the denture base resin were examined with scanning electron microscopy. The tensile bond strength was significantly different between Molloplast B and Ufi Gel P (P<.001). The specimens of the acid group had the highest tensile bond strength, whereas those of the abrasion group had the lowest tensile bond strength. The scanning electron microscopy observations showed that the application of surface treatments modified the surface of the denture base resin. Molloplast B exhibited significantly higher bond strength than Ufi Gel P. Altering the surface of the acrylic resin denture base with 36% phosphoric acid etching increased bond strength.

Study of celluar toxicity and antibacterial property of nano-silver coating modified denture base

To investigate celluar toxicity and antibacterial property of nano-silver coating modified denture base and to provide a theortical basis for clinical application. The samples were divided into coating group and denture base group. Samples in coating groups were treated with silver ion sputtering and were further divided into the 10, 20, 40, 60, 80, 100 s subgroups according to their sputtering time. Surface microstructure of samples in coating groups and denture base group were observed by scanning electron microscopy (SEM), and composition of material surface were determined with energy dispersive spectrum (EDS) analysis. Methyl thiazolyl terazolium (MTT) method was used to analysis L929 cells proliferation rate and cell toxicity grade while the coating groups (n = 6) and group test specimens (n = 6), negative control (polyethylene, PE) (n = 6) and positive control group (PVC-org.Sn) (n = 6) were co-cultured with L929 cells. The antibacterial properties of coating groups were investigated by using the bacterial membrane adhering method with Streptococcus mutans and Candida albicans. SEM observation showed that the surface of control group specimens were smooth, whereas dense and uniform distributed nano silver particles were visible on the surface of coating group specimens. The silver particles were round, and the diameter size was 10 nm. MTT assay showed that after being co-cultured with specimens in control group, L929 cell had higher proliferation rate than 100% at 24, 48, 72 h, and cytotoxicity were graded 0. The membrane adhering method results showed that all of bacterial colonies were found in control group, but without anything at the coating groups. Deposition of nano silver on the denture base surface by ion sputtering method is a viable method. There's no cytotoxicity of series Ag-coating material. Nano-silver modified denture base material benefits L929 cell surface proliferation and has antibacterial action.

Complete denture fabricated by Jiro Abe's method for edentulous patient with severe alveolar ridge resorption: a case report

Fabrication of complete denture by Jiro Abe's method was introduced that enhance the retention and stability of denture by sealing around the denture border with mucous membrane to make negative pressure at the inner surface of denture base when swallowing or occlusion. In this case, taking impression and fabricating complete denture by the Jiro Abe's method for an edentulous patient with severe mandibular alveolar bone resorption allowed us to obtain clinically enhance stability of denture and improve satisfaction of patient. (J Korean Acad Prosthodont 2014;52:338-45)

Effect of different denture cleaning methods on roughness in resin denture base

To determine the effect of different denture cleaning methods on surface roughness in resin denture base. We established 20 wafer samples of fuser base resin (14 mm×14 mm×3 mm), and then randomly divided them into 4 groups: group A was the control group, which were placed in water, while group B, C and D were the experimental groups, whose cleaning methods were toothbrush and water, toothbrush and toothpaste, denture cleaning tablets, respectively. Each procedure in group B and C lasted for 3 seconds, but group D lasted 5 min and repeated for 1080 times. We cleaned twice a day to simulate the method of cleaning dentures. Surface roughness was checked after different procedures by laser scanning confocal microscopy. Significant difference on surface roughness was found between group B, C and A (P<0.05), while no significant difference in the surface roughness between group A and D (P>0.05). Significant surface roughness alterations have been observed in toothbrush and toothpaste group, but no change has been found in denture cleaning tablets group, which does not produce scratches on the surface of resin denture base.

Effect of surface treatments and thermocycling on shear bond strength of various artificial teeth with different denture base materials

Background: Separation and deboning of artificial teeth from denture bases present a major clinical and labortory problem which affect both the patient and the dentist. The optimal bond strength of artificial teeth with denture base reinforced with nanofillers and flexible denture bases and the effect of thermo cycling should be evaluated. This study was conducted to evaluate and compare the shear bond strength of artificial teeth (acrylic and porcelain) with denture bases reinforced by 5% Zirconium oxide nanofillers and flexible bases under the effect of different surface treatments and thermo cycling and comparing the results with conventional water bath cured denture bases. Material and methods: Two types of artificial teeth; acrylic and porcelain were used and prepared for this study. Five specimens of each tooth type were processed to each denture base materials after the application of different surface treatments; these teeth were bonded to heat polymerized, nano composite resin and flexible denture bases. Specimens were thermo cycled and tested for bond strength until fracture with an Instron universal testing machine. Data were analyzed with analysis of variance and student T-test. Photomicrographic examinations were used to identify adhesive and cohesive failures within debonded specimens. Results: The mean force required to fracture the specimens were obviously larger for nanocomposite specimens compared with the heat cured and flexible specimens. The most common failure was cohesive within the tooth or the denture base. With each base material, the artificial teeth which were treated with thinner exhibited highest shear bond strength. Thermocycling had deleterious effect on the flexible denture base specimens. In general, nanocomposite and heat cured groups failed cohesively within the artificial tooth. While the valplastic groups failed adhesively at the tooth denture base interface. Conclusions: Within the limitations of this study, the type of denture base materials and surface treatments of the tooth selected for use may influence the shear bond strength of the tooth to the base. Selection of more compatible combinations of base and artificial teeth may reduce the number of prosthesis fractures and resultant repairs. Key words: acrylic teeth, porcelain teeth, Nano composite denture base, thermo cycling, flexible denture, thinner,

Effect of biofilm formation, and biocorrosion on denture base fractures

PURPOSEThe aim of this study was to investigate the destructive effects of biofilm formation and/or biocorrosive activity of 6 different oral microorganisms.MATERIALS AND METHODSThree different heat polymerized acrylic resins (Ivocap Plus, Lucitone 550, QC 20) were used to prepare three different types of samples. Type "A" samples with "V" type notch was used to measure the fracture strength, "B" type to evaluate the surfaces with scanning electron microscopy and "C" type for quantitative biofilm assay. Development and calculation of biofilm covered surfaces on denture base materials were accomplished by SEM and quantitative biofilm assay. According to normality assumptions ANOVA or Kruskal-Wallis was selected for statistical analysis (α=0.05).RESULTSSignificant differences were obtained among the adhesion potential of 6 different microorganisms and there were significant differences among their adhesion onto 3 different denture base materials. Compared to the control groups after contamination with the microorganisms, the three point bending test values of denture base materials decreased significantly (P<.05); microorganisms diffused at least 52% of the denture base surface. The highest median quantitative biofilm value within all the denture base materials was obtained with P. aeruginosa on Lucitone 550. The type of denture base material did not alter the diffusion potential of the microorganisms significantly (P>.05).CONCLUSIONAll the tested microorganisms had destructive effect over the structure and composition of the denture base materials.

Studying the Effect of Different Separating Medium on the Roughness of the tissue surface of Acrylic Denture Base (In Vitro Study)

Objective: In order to evaluate the effect of different typed of Separating Medium on the roughness of the fittedtissue surface of acrylic denture base.Methodology: Chosen three types of separating medium (Group A Tin foil), (Group B Detery Isolant),(Group CCold Mould Seal),used 30 samples of hot cure acrylic resin ,10 samples for each group, after complete curing ofthese samples , Profilometer device was used to measure the surface roughness of each sample in all groups.Results: Using One Way ANOVA Test and LSD test, the results were highly significant in differences among allgroups. Although (Group A) showing lest roughness, (Group B) showing a satisfactory result of roughness, While(Group C) Showing the highest unsatisfactory surface roughness of acrylic denture base.Recommendations: make other studies on the effect of different separating medium on other properties ofthe fitted tissue surface of acrylic denture base such as hardness.

Effect of the microwave irradiation on disinfection of complete denture lined with soft resilient liner

BackgroundThe fitting surface of denture base promotes accumulation of micro-organisms. The microwave irradiation is used for denture disinfection. It is important therefore to study the effect of different intensities and the exposure time of the microwave irradiation preventing or promoting the accumulation of micro-organisms. The objective of this study aimed to evaluate the effect of microwave irradiation on disinfection of complete denture lined with soft resilient liner. MethodTwenty one edentulous patients were selected from the outpatient clinic of prosthodontics Department, Faculty of Oral and Dental Medicine, Cairo University. Every patient had received upper and lower acrylic complete dentures lined with soft resilient liner which were constructed following the conventional technique. The disinfection of the dentures with microwave for the fitting surfaces of denture bases and mucosa beneath them were swabbed at insertion visit, one week, two weeks & three weeks after denture insertion. Microbial adhesion was determined by counting the colonies forming units (CFU) of the micro-organisms in the collected specimens. Data were tabulated, and statistically analyzed. ResultsThe number of adhering microorganism on denture lined with soft resilient liner was more than number of adhering microorganism to the mucosa. The three different watts used for denture disinfection were effective in decreasing the number of microorganism in both mucosal swabs and denture swabs. ConclusionsIncreasing the watt intensity leads to decreasing the CFU. In mucosal swabs the decrease was non-significant. The adhesion of micro-organisms increases by time on mucosa and the denture base.

Recording ‘Sublingual Crescents’ in Lower Complete Dentures: A Technique so Effective but still Esoteric and Arcane

To achieve retention in severely resorbed mandibular ridges during impression making and to maintain the retention and stability of these dentures during function. No good method with adequate clinical photographs that will empower the dentist with the necessary skill has been reported in the literature. The technique involves making a preliminary impression in alginate to record the denture bearing area clearly, doing a border moulding procedure with excess width to fill the wide sulcus present; except in the area of anterior lingual flange from second premolar to second premolar area. The anterior lingual border of the impression is then extended sublingually without interfering with the tongue function or blocking the opening of the ducts of the sublingual gland; to maintain contact with the surrounding sublingual tissue in both protruded and retruded positions of the tongue, thereby creating good peripheral seal in the most vulnerable area in the lower denture, where the seal is easily broken during tongue movements. This impression technique, combined with arrangement of teeth on the center of the ridge in the posterior part, use of flattened cusp posterior teeth and contoured polish surface of denture base (Fisch concept) provide sufficient retention and stability to the dentures made on these severely resorbed ridges. Patients with severely resorbed ridges cannot be rehabilitated with implants also and so normally suffer with loose lower denture fabricated with normal border moulding procedures. These patients can be rehabilitated to a great extent properly.

Review of adhesive techniques used in removable prosthodontic practice

There are several benefits in using adhesive technique in removable prosthodontics as well as fixed prosthodontics. Previous studies have examined denture-base surface treatments that improve bond strength between a denture base resin and autopolymerizing repair resin. Dichloromethane and ethyl acetate are organic solvents that swell the denture base surface, thereby permitting diffusion of the acrylic resin. The optimal treatment duration is 5-10 s for dichloromethane and 120 s for ethyl acetate. It was reported that the bond durability of dichloromethane was superiorto that of ethyl acetate. Bonding between metal components and the denture base resin has an important role in the longevity of removable prostheses. The combination of metal conditioners and alumina air-abrasion is effective in fabricating and repairing removable dentures. Acidic monomers (4-META and MDP) are appropriate for base metal alloys, including Co-Cr alloy and titanium alloy, while thione monomers (MTU-6 and VBATDT) are suitable for noble metal alloys such as gold alloy and silver-palladium-copper-gold (Ag-Pd-Cu-Au) alloy. As an alternative to conventional restorations, resin-bonded restorations can provide precisely parallel guide planes with well-made rest seats. Careful consideration should be paid to stabilizing loosened teeth by fixing them with resin-bonded splints or fixed partial dentures.

Comparative evaluation of tensile bond strength of a polyvinyl acetate-based resilient liner following various denture base surface pre-treatment methods and immersion in artificial salivary medium: An in vitro study.

Background and Aim:This study was formulated to evaluate and estimate the influence of various denture base resin surface pre-treatments (chemical and mechanical and combinations) upon tensile bond strength between a poly vinyl acetate-based denture liner and a denture base resin.Materials and Methods:A universal testing machine was used for determining the bond strength of the liner to surface pre-treated acrylic resin blocks. The data was analyzed by one-way analysis of variance and the t-test (α =.05).Results:This study infers that denture base surface pre-treatment can improve the adhesive tensile bond strength between the liner and denture base specimens. The results of this study infer that chemical, mechanical, and mechano-chemical pre-treatments will have different effects on the bond strength of the acrylic soft resilient liner to the denture base.Conclusion:Among the various methods of pre-treatment of denture base resins, it was inferred that the mechano-chemical pre-treatment method with air-borne particle abrasion followed by monomer application exhibited superior bond strength than other methods with the resilient liner. Hence, this method could be effectively used to improve bond strength between liner and denture base and thus could minimize delamination of liner from the denture base during function.

Peel bond strength of two silicone soft liners to a heat-cured denture base resin.

This study investigated the peel strength of two different soft liners to a polymethylmethacrylate (PMMA) denture base resin before and after thermocycling. The silicone-based soft liner materials tested were Molloplast B and Permaflex; the denture base material was a heat-cured acrylic resin, Meliodent. A total of 40 specimens was prepared using rectangular molds with dimensions of 100 x 10 x 2 mm for PMMA and 150 x 10 x 2 mm for soft liners, as described in ASTM-D903-93. For each of the liner materials, 10 specimens were packed against a cured PMMA denture base surface as recommended by the manufacturers. The other 10 specimens were packed against PMMA denture base dough and processed together. In each group, 5 of the specimens were tested directly, while the other 5 were thermocycled in a water bath (5°C to 55°C; 3000 cycles) before testing. Peel testing was performed using an Instron testing machine. The results revealed that peel strength values of the Permaflex specimens prepared according to the manufacturer's recommendations were significantly higher than those of Molloplast B (p < 0.05). However, when packing was done against uncured PMMA dough, the difference between the specimens of two liners was not significant. Thermocycling led to significant decreases in the peel strength of both Permaflex liner specimens packed against cured/uncured PMMA resin surfaces (p < 0.05), whereas this process did not affect the strength of Molloplast B specimens. Results indicated that the material Molloplast B was superior to the material Permaflex in terms of peel strength when the specimens were simultaneously polymerized with PMMA and thermocycled.

The effect of denture base surface pretreatments on bond strengths of two long term resilient liners

PURPOSEPurpose of this study was to evaluate effect of two surface treatments, sandblasting and monomer treatment, on tensile bond strength between two long term resilient liners and poly (methyl methacrylate) denture base resin.MATERIALS AND METHODSTwo resilient liners Super-Soft and Molloplast-B were selected.Sixty acrylic resin (Trevalon) specimens with cross sectional area of 10×10 mm were prepared and divided into two groups of 30 specimens each. Each group was surface treated (n = 10) by sandblasting (250 µ alumina particles), monomer treatment (for 180 sec) and control (no surface treatment). Resilient liners were processed between 2 poly(methyl methacrylate) surfaces, in the dimensions of 10×10×3 mm. Tensile strength was determined with Instron Universal testing machine, at a crosshead speed of 5 mm/min; and the modes of failure (adhesive, cohesive or mixed) were recorded. The data were analyzed using one-way ANOVA, followed by Tukey HSD test (α = 0.05).RESULTSMonomer pretreatment of acrylic resin produced significantly higher bond strengths when compared to sandblasting and control for both resilient liners (P < .001). Sandblasting significantly decreased the bond strength for both the liners when compared to monomer pretreatment and control (P < .001). Mean bond strength of Super-Soft lined specimens was significantly higher than Molloplast-B in various surface treatment groups (P < .05).CONCLUSIONSurface pretreatment of the acrylic resin with monomer prior to resilient liner application is an effective method to increase bond strength between the base and soft liner. Sandblasting, on the contrary, is not recommended as it weakens the bond between the two.

Effect of reline material and denture base surface treatment on the impact strength of a denture base acrylic resin

In this study, the effect of relining and surface treatment on the impact strength (IS) of a heat-polymerising denture base acrylic resin (Lucitone 550-L) was evaluated. Rectangular bars of L were made (60 x 6 x 2 mm) and relined (2 mm) with the relining resins Ufi Gel Hard (UH) and Tokuso Rebase Fast (TR). Specimens relined with L and intact L, TR and UH specimens were also made (60 x 6 x 4 mm), for comparison. Before relining, the L surface was left untreated or wetted with methyl methacrylate monomer and/or the bonding agents (BA) supplied by manufacturers of the reline resins. V-notches were machined at the midpoint of the length of all specimens. The notches were made either across the width (Nw) or across the thickness of the specimens (Nth). The Charpy impact test was performed using a 0.5-J pendulum, which had been specially designed and constructed. Data were analysed separately for each notch position using one-way analysis of variance and Tukey honestly significant difference post-hoc test (p = 0.05). The IS of L was similar to that of L/L. For the Nw notch, treating the denture base L with TR BA and relining with TR reline material produced the highest IS. The IS of specimens made from heat polymerising acrylic resin Lucitone 550 was increased after relining using the hard chairside reline resin TR with its proprietary BA.

The Effect of Denture Base Surface Treatments on Microlekage of Soft Lining Materials

Aims: To evaluate the effect of two acrylic resin denture base surface trearments on microleakage of 4 soft denture lining materials (Tru–soft, Bony plus, UfiGel–P and Molloplast–B after 2 periods of storage and thermalcycling. Materials and methods: One hundred eighty specimens for microleakage were prepared in a disc shape 30 mm diameter and 4 mm thickness (2 mm for acrylic resin part and 2 mm for soft lining material part). Soft lining materials were bonded to three different groups of acrylic resin surface pretreatments (untreated, sandblasted and monomer treated denture base). These specimens underwent two aging procedures: Storage with two periods (one week and one month), and 500 cycles of thermalcycling inside 2% methylene blue dye. Results: Statistical analysis showed that treating the acrylic resin denture base by sandblasting increased microleakage of silicone–based linings (UfiGel–P and Molloplast–B)and decreased microleakage of acrylic–based linings (Tru–soft and Bony plus) in comparison to untreated denture base, while treating the denture base with MMA monomer positively decreased microleakage for all tested soft lining materials in relation to untreated and sandblasted denture base at one week storage, one month storage and at thermalcycling. Conclusions: For all types of denture base surface treatments, microleakage was inevitable, however, wetting the acrylic resin denture base with MMA monomer was more effective in reducing microkeakage than sandblasted and untreated denture bases.