Type Of Denture Base Material Research Articles

Evaluation of Color Stability for Two Types of Denture Base Materials: Heat Cured Acrylic and Flexible Resin.

Commonly consumed beverages used by human being daily (Tea & Cola) caused external staining. This study is done to evaluate the color stability for two different types of denture base materials against this external staining caused by (Tea & Cola). Sixty (60) samples were prepared, divided into two groups, 30 samples of heat cure acrylic material & 30 samples of flexible resin material (Valplast). Each group divided into three subgroups 10 samples in each, according to the type of staining solution that immersed in it, (synthetic saliva & tea), (synthetic saliva & Cola), and (synthetic saliva alone as a control). Tea & Cola were mixed with synthetic saliva in order to create intraoral environment to certain extent. Color measurement was made at Baghdad University, Collage of Engineering, using reflected spectrophotometer before immersion (at baseline) & after immersion, at intervals of (24 hours) & (1 week) respectively. The result was a highly significant difference between, heat cure acrylic & flexible resin a t baseline & the (flexible samples) were the higher value in discol oration than (heat cure acrylic samples) regardless the type of s taining solution. Maximum discoloration was seen in (synthetic sal iva & tea) solution for both denture base materials. Followed by (synthetic saliva & Cola) & (synthetic saliva alone) respectively . Both denture base mater ials had a color changes after immersion in staining solution (tea , Cola & synthetic saliva). The color changes, for two materi als, were increased with the increase of immersion time.

Effect of adding a hard-reline material on the flexural strength of conventional, 3D-printed, and milled denture base materials

Statement of problemNovel 3-dimensionally printed resin and milled polymethyl methacrylate materials have been marketed for computer-aided design and computer-aided manufacturing (CAD-CAM) denture base fabrication. However, information on the flexural strength of digitally fabricated denture base material is limited, and little is known about how they are affected by a hard-reline procedure. PurposeThe purpose of this in vitro study was to assess the flexural strength of 6 digitally manufactured denture base materials and to assess the effect of a hard-reline procedure on their flexural strength. Material and methodsA total of 140 strips of denture base material were fabricated from a conventional heat-polymerized polymethyl methacrylate (L199), 3 brands of milled polymethyl methacrylate (IBC, DSL, and ADH), and 3 brands of 3D-printed resin (DFD, ADB, and DrFD) (n=20). Ten specimens in each group did not receive any treatment, and 10 were relined with a hard-reline material (ProBase Cold Trial Kit). Specimens were then subjected to a 3-point flexural strength test using a universal testing machine at a crosshead speed of 5.0 mm/min. A 1-way ANOVA test followed by the Tukey multiple comparison test was used to detect the difference in flexural strength and the strain at fracture of the different types of denture base materials (α=.05). The comparison of flexural strength between with and without hard-reline was analyzed using an unpaired t test (α=.05). ResultsAll materials, with or without the hard-reline, met the International Organization for Standardization (ISO) 20 795-1:2013 standard for flexural strength (65 MPa). The milled materials (DSL>IBC≈ADH) showed higher flexural strength than the 3D-printed or conventional materials (DrFD>DFD≈ADB≈L199) without a hard-reline. No statistical difference in flexural strength was found among the hard-relined denture base materials (P=.164). All 3 milled materials showed reduced flexural strength after relining, while the relined conventional (L199) and 3D-printed materials (DFD and ADB) showed notably higher flexural strength; printed DrFD showed no significant difference (P=.066). In terms of strain at fracture, the milled materials displayed higher values than those of the conventional or 3D-printed materials (P<.05). ConclusionsAll digitally fabricated denture base materials were within acceptable limits for clinical use, even after hard relining. Flexural strength was highly dependent on the type of material. Hard relining affected the flexural strength of most of the digitally fabricated denture base materials.

The Effect of Disinfection Methods on C. Albicans in Three Types of Denture Base Materials

This study aimed to evaluate the efficacy of disinfectant solutions on Candida albicans (C. albicans) for different types of denture materials. A total of 144 specimens (10x10x2 mm) were obtained from three different materials: autopolymerized acrylic resin, heat-cured acrylic resin, and hard relining material (n = 6). Three disinfectant solutions were used: 100% white vinegar, 2% chlorhexidine digluconate (Saver) and denture cleaning tablets (Corega). The specimens were placed on Eliza plates and 1.5 mL of Yeast Extract Peptone (YPD) was added to each well. Then, 30�L of candida culture was added to the wells. Next, the specimens were incubated at 37�C at 80 rpm for 48 h. Disinfectants were added to the Eliza plates. For all specimens, the disinfectants were replaced with 2 mL of sterile water and kept at 100 rpm for 30 min. Then, 0.1 mL of the liquid was taken and inoculated into the pads containing YPD medium. After incubation, the candida colony growth on the pads was measured. Scanning electron microscope (SEM) images were taken from randomly selected specimens from each group. Statistically significant differences (𝑃 [ 0.05) were found between the disinfectant method groups and the control group for the three types of denture materials. The 2% chlorhexidine gluconate (Saver) disinfectant was the most effective for C. Albicans ATCC 60193 and oral isolate of C. Albicans for all three of the tested denture materials. The effect of cleaning of tabs (Corega) and white vinegar was found to be similar.

Evaluation of efficiency of complete dentures using bps, lecutonite &amp; acrylic materials

Introduction: Type of materials used in fabrication of denture base has an effect on dimension during denture base material processing and other factors related to clinical use. The study aims were to assess the efficiency of complete dentures made using bps, lecutonite &amp; acrylic materials. Material and Methods: Ninety patients were selected to construct complete dentures with bps, lecutonite &amp; acrylic materials denture base materials. They were randomly divided into three groups: group 1, patients with bps; group 2, patients with heat curing acrylic resin fabricated by injection moulding technique and conventional methods; and group 3, patients with lecutonite. The dimensional changes were assessed using digital caliper. Results: After the twelfth month, injection moulding acrylic resin had significantly the highest dimensional change followed by the lecutonite. There were no significant differences in the dimensions between the three types of denture base materials at normal mouth temperature, while, after hot tea drinking at 45∘C, the dimensional change was significantly the highest in cobalt chrome metallic denture base group. Conclusion: BPS denture base has stable dimension compared to denture bases fabricated of lecutonite, acrylic resin but it was more affected by altered mouth temperature.

Flexural Properties and Hardness of CAD-CAM Denture Base Materials.

To compare flexural strength, elastic modulus, and surface hardness of computer aided design and computer aided manufacturing CAD-CAM milled, 3D-printed, and heat-polymerized denture base resins. A total of 120 specimens were fabricated from heat-polymerized acrylic resin (HP), milled resin (Avadent and IvoCad), and 3D-printed resin (ASIGA, FormLabs, and NextDent). The specimens were divided into 6 groups according to the type of denture base material (n = 20/material) (10/flexural properties and 10/hardness). Flexural strength and elastic modulus of the specimens were evaluated by 3-point bending test and surface hardness by Vickers hardness test. To test flexural properties, the specimens were fabricated according to ISO 20795-1:2013 standards (64 × 10 × 3.3 ± 0.2 mm). The dimensions for hardness test were 15 × 10 × 2.5 ± 0.2 mm. Scanning electron microscope was used to evaluate the surface morphology of the fractured specimens. The means and standard deviations were calculated, followed by one-way ANOVA and Tukey post-hoc test (α = 0.05). Milled resins showed significantly higher values for flexural strength, elastic modulus, and surface hardness, followed by HP and then 3D-printed resins (p < 0.001). Withinmilled groups, flexural strength of AvaDent was significantly higher than IvoCad (p < 0.001), while elastic modulus and hardness didn't show significant difference. Within3D-printed resins, ASIGA showed the highest flexural strength and elastic modulus, insignificantly with FormLabs (p = 0.595) and significantly with NextDent (p = 0.008). ASIGA also showed significantly the highest hardness among the 3D-printed groups. No significant difference was found between FormLabs and NextDent in flexural strength (p = 0.357), elastic modulus (p = 1.00), or surface hardness (p = 0.987). CAD-CAM milled resins had greater flexural properties and hardness compared to heat-polymerized acrylic resin and 3D-printed resins. Although 3D-printed samples showed the lowest values of tested properties, the flexural strength and modulus were above clinically acceptable values.

Effect of denture cleansers on the surface properties and color stability of 3D printed denture base materials

ObjectivesTo evaluate the effect of denture cleansers on surface roughness, hardness and color stability of 3D printed resins compared to heat-polymerized resin. MethodsAcrylic specimens (N = 160) were prepared using one heat-polymerized (HP) and three 3D printed denture base resins. Specimens per material were randomly divided into four groups (n = 10) according to immersion solutions as follows: distilled water (DW), sodium hypochlorite (NaOCl), effervescent tablet 1 or effervescent tablet 2. Color changes (∆E) were measured using a spectrophotometer. Surface roughness (Ra, µm) and microhardness were evaluated. The results were analyzed using one- and three-way ANOVA with Tukey's post hoc test (α = 0.05). ResultsAfter 360 days of cleaning protocols, we observed a significant increase in the surface roughness of tested materials (P<0.001). Hardness values significantly decreased in all groups (P<0.001), except HP and ND specimens, cleaned with effervescent tablet 1 (P>0.05) and AS specimens with effervescent tablet 2 (P = 0.051). According to the National Bureau of Standards (NBS) score, all denture base specimens had ‘perceivable’ to ‘extremely marked’ color change after immersion in NaOCl, while immersion in effervescent tablets 1 and 2 resulted in a ‘slight’ to ‘marked’ color change. Conclusion3D printed denture bases exhibited changes in surface roughness, hardness and color similar to HP denture base material. The use of denture cleansers resulted in a time-dependent increase in surface roughness and a decrease in hardness. The color change was significant with NaOCl, while effervescent denture cleansers produced a minimal color difference. Clinical significanceDenture cleansers seem to influence surface properties over time. The degree of impact is mainly dependent on the type of cleanser selected, regardless of the type of denture base material.

Photoelastic Stress Analysis for Mandibular Implant Supported Overdenture with Two Types of Denture Base Materials: A Comparative in vitro Study

Photoelastic Stress Analysis for Mandibular Implant Supported Overdenture with Two Types of Denture Base Materials: A Comparative in vitro Study

Effect of Denture Adhesives on Adhesion of Candida albicans to Denture Base Materials: An In Vitro Study

This study aimed to investigate the adhesion of Candida albicans (CA) to the surface of the denture base using two different types of resins after exposure to denture adhesives (DAs). Twenty-five samples of polymethyl methacrylate (PMMA) and 25 samples of urethane dimethacrylate (UDMA) (10 mm × 10 mm × 2 mm) were prepared and allocated to 10 groups (five samples in each group). For each type of denture base materials, four test groups were immersed for 30 days in four commercially available DAs in addition to water as control group. Specimens were then in vitro evaluated for CA adhesion using light microscopy under × 1,000 magnification. The results showed that the mean number of CA per specimen in the adhesive-exposed groups was higher than that in the control group for both UDMA and PMMA resins. However, this difference was not statistically significant. No association between the type of denture base material and Candida count was identified following immersion in different types of DA and distilled water (p >0.05). Candida count was not associated with the type of DA when UDMA specimens were compared (p >0.05). PMMA resin specimens that were immersed in Corega cream showed significantly higher counts of Candida compared to control specimens that were immersed in distilled water (p <0.05). The study found no association between the type of denture base materials and CA adhesion. No clear impact was identified for the type of DA on CA adhesion to acrylic denture bases. Using DAs would likely not increase the incidence of denture stomatitis in completely edentulous patients.

Effect of Denture Cleansers on Color Stability and Flexural Strength of Heat Polymerized Acrylic Resin an In-Vitro Study

Heat polymerized poly methyl methacrylate is the most commonly used denture base material. Selecting a denture cleanser, compatibility between various type of denture base material and cleanser must be considered to avoid harmful effects. Study objective was to evaluate the changes in flexural strength and colour change of heat cured denture base resins when treated using denture cleansers. Method: The disk shaped specimens15mm in diameter and 4mm in thickness and rectangular shaped specimens 65mm x 10mm x 3.3mm were fabricated using split mould technique. A total of 60 standardized specimens were fabricated and stored in distilled water for 24hrs. After 1 day, the specimens were appropriately labelled and immersed in groups of 20 to prepared denture cleanser solutions for treatment. Solutions were prepared and immersed according to manufactures instructions (Corega tab: one tablet to 200ml of water and immersion time is 15min; Fitty dent: one tablet to 200ml of water and immersion time is 30min). After immersion, the resin specimens will be removed, thoroughly cleanedunder running water, dried with absorbent paper, and then the procedure of immersion will be repeated. This procedure will be performed for a total of 30 times over a period of 6 days simulating patients180 days of cleansing. 10 specimens of each group where tested for flexural strength using universal testing machine. Specimens were loaded until fracture occurred. The peak load was recorded in Newton and the flexural strength was calculated from peak load and another 10 specimens were tested for colour change using spectrophotometer .The specimens were tested on the measuring head of the spectrophotometer. The colour characteristics, tristimulus values X, Y, Z, and CIE (Lab) of specimens, were evaluated. The findings were statistically analysed using ONE -WAY ANOVA and students T test. Results: Heat cure denture base resin used for this study showed significant difference in flexural strength and..... , , , , , Sch J Dent Sci | - DOI :

Effect of Two Different Types of denture Base Materials on the Supporting Structures of Mandibular Mini Implant Supported Over denture

Effect of Two Different Types of denture Base Materials on the Supporting Structures of Mandibular Mini Implant Supported Over denture

Comparative evaluation of three types of denture base materials with saliva substitute before and after thermocycling: An in vitro study

Statement of problemXerostomia refers to the decrease in the quality and quantity of saliva. In denture wearers, xerostomia affects the retention of the denture because of lack of wettability of the denture base. However, which denture base resin materials are best wetted by artificial salivary substitutes is unclear. PurposeThe purpose of this in vitro study was to determine the wetting properties of 3 different commercially available denture base resin materials with artificial salivary substitute by using contact angle measurements and to compare these properties before and after thermocycling. Material and methodsA total 120 specimens were fabricated with 3 different denture base materials (n=40): heat-polymerized polymethylmethacrylate (DenTek), injection-molded nylon polyamide (Valplast), and microwave polymerized (VIPI WAVE). The advancing and receding contact angles were measured with a goniometer by using the WinDrop++ software program. The contact angle hysteresis was calculated from the advancing and receding contact angles values. The same specimens were subjected to thermocycling to measure the advancing and receding contact angles values. The comparative evaluation was carried out before and after thermocycling. ResultsThe mean ±standard deviation contact angles of the microwave-polymerized material were (62.40 ±1.21 degrees) advancing contact angle, (32.12 ±0.66 degrees) receding contact angle, and (30.28 ±1.40 degrees) contact angle of hysteresis. It was followed by the injection-molded nylon polyamide material, whose mean ±standard deviation contact angle values were (68.57 ±1.72 degrees) advancing contact angle, (43.02 ±1.39 degrees) receding contact angle, (26.27 ±2.05 degrees) contact angle hysteresis and high impact strength heat-polymerized polymethylmethacrylate material, whose mean ±standard deviation contact angle values were (69.81 ±0.16 degrees) advancing contact angle, (41.90 ±1.02 degrees) receding contact angle, and (27.91 ±0.97 degrees) contact angle hysteresis. The statistical analysis showed significant differences among contact angle values of the microwave-polymerized material as compared with the heat-polymerized polymethylmethacrylate and injection-molded nylon polyamide materials (P<.001). ConclusionsThe microwave-polymerized material showed better wettability with artificial saliva substitute than heat-polymerized polymethylmethacrylate and injection-molded nylon polyamide.

Water sorption and solubility of two acrylic resin denture base materials polymerized by Infrared radiation

Aims: To determine the effect of different curing times of a new method of polymerization by infrared radiation on the absorption and solubility in water of acrylic resin materials for denture base. Materials and Methods: In this study two types of denture base materials cured by heat were used (Traditional or Conventional and High Impact), the entire number of prepared specimens were (80) which grouped into: A- Control group: Consisted of two types of acrylic resin specimens polymerized by conventional water bath .B- Experimental group: Consisted of two types acrylic resin specimens polymerized by infrared radiation (IR) at different times of curing cycles. In each group; specimens were divided equally, some related to water sorption test others for solubility test. The mean of mass change of the material after they saturated with water and dried out of it was used, then analysis of data was done using one-way analysis of variance and Duncan test. Results: Statistically, no significant differences existed between Traditional and High Impact acrylic resin cured by water bath in water sorption and solubility tests. The means values for previously mentioned tests in two types of acrylic resin had been decreased significantly by changing type of curing from conventional water bath to (IR) method. Conclusions: The selection of appropriate time and type of curing method may optimize the level of absorption and solubility in water for previously mentioned materials.

The influence of base resin of removable dentures on the planktonic growth of individual representatives of oral microflora

Introduction. Microbiological researches of the role of denture base materials in violation of the oral cavity micro ecology were conducted. Aim. Therefore, the purpose of research is to study the effect of different polymeric materials on denture bases, on the intensity of planktonic growth of resident and transient representatives of oral cavity microflora in a periodic culture on the basis of registration of its optical density. Material and methods. 7 types of denture base materials and their influence on the planktonic growth of microorganisms have been studied. Results. The planktonic growth of the S. oralis strain was suppressed by all base materials: SYNMA (by 35.5%), Bre.Flex (by 27.5%) and Protacryl-M (by 25.7%), in the smallest – Nylon (by 5.4%), Villacryl (by 9.5%). Conclusions. Through experimental research, we have proved the direct involvement of basic resin materials in changes in the oral cavity micro ecology and the process of occurrence of prosthetic stomatitis.

EFFECT OF TWO POLISHING TECHNIQUES ON SURFACE ROUGHNESS OF THREE DIFFERENT DENTURE BASE MATERIALS (AN IN VITRO STUDY)

INTRODUCTION: A direct link was found between surface roughness, the accumulation of plaque and the adherence of microorganisms concerning acrylic resins. However, the surface properties of the new thermoplastic materials remain questionable especially after using the conventional finishing and polishing techniques. Studying surface properties of each material makes the recommendation of the proper techniques easier. OBJECTIVES: This in vitro study intended to compare three types of denture base materials in regarding to the effect of different polishing techniques on their surface roughness. MATERIALS AND METHODS: 36 specimens were incorporated in this study. 12 specimens were in each group. 3 groups were formed: Group A: Heat cured Polymethylmethacrylate (PMMA). Group B: Thermoplastic Polyamides. Group C: Thermoplastic Acetal. Dimensions of specimens were (20×20×3 mm) with projection at the side. Statistical analysis was carried out using two way analysis of variance (ANOVA). Statistical significance was defined at P≤0.05. RESULTS: Technique no. 1 showed a high significant value in compared to technique no.2 for polishing the tested materials. CONCLUSIONS: PMMA was the highest affected group followed by thermoplastic acetal and the last affected group was thermoplastic polyamide. Prepolishing rubberizing with rubber bur improves the polishing procedure. RESULTS: Remarkable improvement in the histology and the ultrastructure of the alveolar bone of rats in Group III was observed. Moreover, hematological values revealed significant decrease in the inflammatory condition of rats with induced RA after fish oil treatment. CONCLUSIONS: Rheumatoid arthritis is an important risk factor for alveolar bone loss. The treatment of the RA induced rats with fish oil not only prevented the alveolar bone resorption and stimulated new bone formation, but also reduced relatively the level of rheumatoid factor in the blood.

Effect of Surface Treatments and Adhesive Materials on the Shear Bond Strength of Artificial Denture Teeth to Denture Base Resins

The purpose of the current study was intended to evaluate the effect of different surface modifications and different adhesive materials on the shear bond strength of artificial teeth to heat-polymerized and thermoplastic denture base materials using different repair techniques. Forty cross-linked artificial teeth used to construct different types of acrylic based denture prosthesis were selected to be bonded to two types of denture base materials, heat-polymerized acrylic resin denture base material, and thermoplastic acrylic resin denture base material. The specimens were divided into four subgroups according to the repair technique and adhesive material used. The base surfaces of all acrylic teeth then were moistened with monomer prior to bonding to the denture base specimens. Then, the specimens were tested using Universal Testing Machine for shear bond strength. The results were analyzed by using two-way analysis of variance (ANOVA) statistical analysis and multiple comparison tests, α ≤ 0.05. The effect of the types of denture base materials vs the surface conditioning methods displayed a statistically significant difference. This study concluded that monomer surface treatment of the bonded surface of artificial denture teeth and the use of cyanoacrylate adhesive followed by additional microwave polymerization displayed better shear bond strength when compared with other repair techniques. Artificial teeth debonding from their denture bases is a common complication in dental practice. The current study evaluates different repairing techniques. Within the limitation of this study, the use of cyanoacrylate adhesive in combination with microwave polymerization is one of the best techniques of repairing denture teeth debonding.

Comparison of Flexural Strength and Surface Roughness of two Different Flexible and Heat Cure Denture Base Material: An in Vitro Study

To Compare and Evaluate the Flexural Strength and Surface Roughness of Lucitone-FRS, Valplast (Flexible Denture Base Materials) and Trevalon (Heat Cure Denture Base Material). Three stainless steel master dies of dimension 65 × 20 × 3 mm were fabricated and were invested in standard metal denture flask. A total of 60 specimens were fabricated with 20 specimens of each type of denture base material. Fabrication of a Heat Cure Acrylic Denture Base Resin Specimen was Done Followed by Fabrication of Flexible Denture Base Resins Specimen. In the same manner, samples were fabricated for Lucitone-FRS, and Valplast. These specimens were further divided into two subsets; containing 10 specimens each from each group. In one subset, Flexural Strength was Measured while in the other subset, Surface Roughness was measured. The Surface Roughness values were measured using a surface testing machine Mitutoyo-SJ-Series 201 (Japan). The flexural strength of specimens was measured using a 3-point bending test device on universal testing machine. All the results were compiled and Analyzed by SPSS software. Flexural strength was found maximum in the VALPLAST and minimum in LUCITONE. Surface Roughness Test was done on total 10 samples of each material, i.e. Lucitone-FRS, Valplast and Trevalon. Results for Surface Roughness Test are Valplast has maximum Surface-Roughness followed by Trevalon and minimum in Lucitone-FRS on both polished and unpolished surface. Trevalon can be ideal in cross-arch stabilization cases and Valplast and Lucitone FRS can be successfully used in cases of small arch complete dentures and removable partial dentures. The selection of the right denture base material is imperative as it largely affects the overall clinical outcomes and comforts. Results of the present study would aid the dentist in the selection of ideal denture base materials for specific cases like those requiring Cross Arch Stabilization, Small Arch Complete Dentures, and Removable Partial D entures.

EFFECTIVENESS OF DIFFERENT CHEMICAL CLEANSERS AND DISINFECTANTS ON THE TRANSVERSE STRENGTH OF DIFFERENT DENTURE BASE MATERIALS

Denture wearers are strongly urged to practice regular oral and denture hygiene to maintain good oral and general health. Denture cleansing by chemical agents is an easily practiced method that requires simply the immersion of the denture in a commercially available solution according to the manufacturer’s instructions. In selecting a disinfectant for dental prosthesis, compatibility between the disinfectant and the type of denture base material must be considered to avoid adverse effects in it. The aim of this study is to evaluate the effect of over the counter denture cleansers on the transvers strength of three denture base materials. Heat cure acrylic rein, self cure acrylic rein and the Thermoplastic groups specimens were immersed for one week (5 hours per a day) in peroxide effervescent denture cleansers (Corega Tabs, & Fittydent) and finally 2% Chlorhexidine. Distilled water was used as the control group. Transvers strength was measured using three-point bending test in a universal testing machine. Data were analyzed with ANOVA and Post-hoc Tukey’s tests. The results showed multi variance analysis revealed high significance p ≤ 0.005 for solutions and resin types, and the interaction of these factors on transverse strength. Conclusion: transverse strength of denture base material can be altered by the disinfectant solutions tested as well as by the type of resin.

Evaluation of Retention for Implant RetainedMandibular over Denture using Two Different Denture Base Materials

Objectives: This study was made for measuring and comparing the Retention of implant retained mandibular overdenture using resilient attachment with two different denture base materials (flexible and conventional acrylic resins). Methods/ Statistical Analysis: Twenty male patients selected for this study with completely edentulous mandible and divided according to the type of denture base material used into two equal groups, both groups received implant retained overdenture with resilient attachment. Group I; denture base made from conventional acrylic, Group II; denture base from thermo-elastic flexible acrylic, retention evaluation was made zero time, two months and four months after insertion. Findings: In this study, there was no statistical significance of difference between the groups, at time of insertion, 2 and 4 months after insertion. The highest values of retention were enlisted with the overdenture made from them oplastic acrylic resin and that may due to high inter facial surface tension recorded values of thermoplastic acrylic resin. Strong tension increase retention of the prosthesis in place. Flexible acrylic denture base showed better retention values and function than denture base made from heat cured acrylic resin material and it is agreed with another study which proved that retention values of Thermo-elastic resin was higher than conventional resin as the Thermo-elastic resins have greater flexibility, adaptation and fitting values than conventional resin. So, it has an improved retention because of inter-facial surface tension effect. Application/Improvements: Using overdenture base made of thermo-elastic acrylic resin clinically better than using overdenture base made of conventional acrylic denture base in retention and function.

Influence of Adhesive on Shear Bond Strength Between Denture Base Materials and Self-Cured Silicon Soft Liner

Background: Soft lining materials play an important role in modern prosthodontics because of their capability of restoring health of inflamed and distorted mucosa. Gradual changes of oral tissues require that complete or partial dentures be relined to improve their adaptation to the supporting tissue. This study aimed to evaluate the shear bond strength (SBS) of heat cured acrylic and injection-molded ValplastTM denture base materials to silicone self-cure soft lining materials, with and without adhesive, after storage in two different times in artificial saliva. Materials and Methods: 40 rectangularspecimens were prepared from two types of self-cured silicone soft lining material,one with adhesive and the other without adhesive were applied to two types of denture base materials ( heat polymerized Polymethyl methacrylate and injection-molded nylon denture base materials). Shear bond strength of the specimens was measured, after immersionin artificial saliva for different periods (72 hours or 10 weeks), using Lloyd universal testing machine. Results: Acrylic denture base bonded to soft liner with adhesive at 72 hours of immersion in artificial saliva showed the highest shear bond strength. Comparing SBS values of the tested soft lining materials revealed significant differences between adhesively bonded and non-adhesively bonded types. Conclusions: This study concluded that the bond strength of the silicone soft lining materials with denture base materials increased with adhesive. Silicone soft lining materials are affected by artificial saliva storage.

Chewing efficiency and occlusal forces in PMMA, acetal and polyamide removable partial denture wearers.

Thermoplastic materials, such as acetal (AC) and polyamide (PA), constitute an alternative to polymethyl methacrylate (PMMA) based resins as the materials for removable partial dentures. However, none of the previous studies compared chewing efficiency and occlusal forces in the wearers of dentures made of various materials. Therefore, the aim of this study was to determine and compare the chewing efficiency and occlusal forces in PMMA, PA and AC RPDs' wearers. The hypothesis was that the type of denture base material shows a significant effect on chewing efficiency (expressed as a degree of food fragmentation) and occlusal force. The experiment included the group of 30 patients using removable partial dentures. The dentures made of PMMA, acetal and polyamide were tested in each patient. Each denture was worn for 90 days, with a random sequence of the denture manufacturing and insertion. After 7, 30 and 90 days of each denture wear, chewing efficiency coefficient was determined with the aid of a sieving method, and occlusal force was measured with a dynamometer. The use of dentures made of PMMA or acetal was reflected by a marked increase in chewing efficiency and occlusal force. None of these parameters changed significantly with the time of denture wear. Moreover, no significant correlation was found between chewing efficiency and occlusal forces. Denture base material exerts significant effects on the degree of food fragmentation and the level of occlusal forces. The use of dentures and clasps made of materials with lower modulus of elasticity is associated with lower chewing efficiency and lower occlusal forces.