Flexural Properties of Heat-Polymerized PMMA Denture Base Resins Reinforced with Fibers with Different Characteristics.

Polymethylmethacrylate (PMMA) has been the most-widely used denture base material in prosthetic dentistry for the last 80 years. It is still one of the best alternatives when new methods are inapplicable. Due to the lack of some physical inadequacies occurring during cyclic use and accidental situations, various reinforcement strategies such as using nanoparticles, wires, fibers, and meshes have been investigated and reported. In this study, it was aimed to conduct a comparative investigation of the effect of fiber additives with different characteristics on the flexural properties of heat-cured PMMA denture base resins. Glass fibers (GFs), polypropylene fibers (PPFs), and carbon fibers (CFs) having 3, 6, and 12 mm lengths and 0.25, 0.50, and 1.0% concentrations (v/v) were used for the reinforcement of PMMA denture base resins. The flexural properties (flexural strength, flexural modulus, and maximum deformation) were determined using a three-point bending test, and three-way ANOVA analyses with Bonferroni corrections were performed on the test results. The morphologies of the fracture surfaces were analyzed using scanning electron microscopy. All three fibers exhibited reinforcement in the flexural strength (p < 0.001) and flexural modulus (p < 0.001) regardless of their length and concentration. The group with 1.0% 12 mm CF-reinforced PMMA exhibited the greatest flexural strength (94.8 ± 8.8 MPa), and that with 1.0% 3 mm GFs displayed the lowest flexural strength (66.9 ± 10.4 MPa) among the fiber-reinforced groups. The greatest value of the flexural modulus was displayed by the 1.0% 3 mm CF-reinforced resin (3288.3 ± 402.1 MPa). Although the CF-reinforced groups exhibited better flexural properties, CFs are not favorable for use as reinforcement in practice due to the dark gray discoloration of the denture base resin. It was concluded that PPF is a promising material for the reinforcement of heat-cured PMMA denture base resins.

Investigation on the Potential Use of Polypropylene Mesh for the Reinforcement of Heat-Polymerized PMMA Denture Base Resin.

The aim of this study was to investigate the potential use of polypropylene (PP) hernia mesh as a reinforcement of PMMA denture base resin in comparison with metal and glass fiber meshes, with the expectation of enhancing the mechanical stability of the PMMA dentures in oral conditions. The control group with no mesh, the aluminum metal mesh (Al) group, the PP1 (PP mesh used on top) group, the PP2 (PP mesh used on both the top and bottom) group, the orthopedic casting tape with self-curing resin (DP0) group, and the flushed form (DPA) group were fabricated in a chromium mold. A total of 144 specimens were divided into three equal portions and subjected to: first, no treatment; second, thermal cycling only; and third, thermal cycling and chewing simulation. The flexural strength, maximum deformation, and flexural modulus were determined by a three-point bending test to compare mechanical properties. Fracture surfaces were evaluated by scanning electron microscopy. The obtained data were statistically analyzed by a two-way ANOVA test with Bonferroni corrections. The non-treated Al mesh reinforcement group exhibited the highest (82.66 ± 6.65 MPa) flexural strength, and the PP2 group treated with chewing simulation displayed the lowest (56.64 ± 4.59 MPa) flexural strength. The Al group showed the highest (7.25 ± 1.05 mm) maximum deformation and the PP2 group showed lowest (3.64 ± 0.28 mm) maximum deformation when both groups were not subjected to any treatment. The control group with no treatment exhibited the lowest (1556.98 ± 270.62 MPa) flexural modulus values, and the Al group with no treatment exhibited the highest (3106.07 ± 588.68 MPa) flexural modulus values. All the mesh groups displayed intact fractures. Any type of mesh used for reinforcement exhibited a significant change in all flexural properties (p < 0.001). The PP1 reinforcement group did not exhibit a significant change in mechanical properties when the effect of treatment was compared. Using PP hernia mesh on top enhanced the mechanical properties despite the weakening when it was used on both the top and bottom. The mechanical stability provided by the PP hernia mesh indicated it to be a promising candidate to be used for reinforcement.

Color stability of hybrid ceramics exposed to beverages in different combinations.

BACKGROUND: The aim of this study is to evaluate the color stability of hybrid ceramics stored in different combinations of beverages that are routinely consumed. METHODS: The specimens were prepared with resin nano-ceramic (Lava Ultimate, 3M Espe, USA) and hybrid ceramic (Vita Enamic, Vita Zahnfabrik, Germany). The specimens were aged in a thermocycler machine for 10,000 cycles. They were stored in different combinations of beverages (water, tea, coke, coffee, red wine, pomegranate juice, and turnip juice) for 12 + 12 h. Surface roughness measurements were performed using a profilometer. The specimen colors were measured using a spectrophotometer. The color values (L-a-b) of the specimens and mean surface roughness values (Ra) were recorded at the end of the 1st (D1), 7th (D7), 14th (D14) and 28th (D28) d. RESULTS: When the solution groups were examined, significant color changes were observed in the Lava coffee-tea, Enamic coffee-tea, Lava coffee-wine, and Enamic coffee-wine groups compared with the other groups (p < 0.01). Except for the samples in the Lava coffee-wine 28th day (D28) and Enamic coffee-wine 28th day (D28) groups, more color changes were observed in the Lava samples than in the Enamic samples across all groups and periods. CONCLUSION: Greater color changes (except for the samples stored in coffee-wine) were observed in the Lava samples than in the Enamic samples across all groups and periods. It was observed that the coffee-tea and coffee-wine beverage combinations produced the greatest color change in hybrid ceramics within the limitations of this study.

Effect of Clinically Relevant Smear Layers and pH of Universal Adhesives on Dentin Bond Strength and Durability.

PURPOSE: To evaluate the effects of different smear layers on the microtensile bond strength (µTBS) of a reference two-step self-etch adhesive and two universal adhesives. MATERIALS AND METHODS: Mid-coronal dentin of 90 teeth was exposed and divided into three bur groups (coarse diamond, fine diamond, or tungsten carbide). Each bur-prepared group was further divided into three adhesive groups: Clearfil SE Bond (SE, Kuraray Noritake), Single Bond Universal (SB; 3M Oral Care), and G-Premio Bond (GP, GC). After adhesive application, 4-mm-thick resin composites were built up. Half of the teeth in each bur-adhesive group were used in immediate µTBS testing, and the others were tested after thermal aging (n = 5). Rectangular sticks were prepared using a low-speed diamond saw. For each tooth, 6 central sticks were used in the µTBS test. Statistical analysis was performed using three-way ANOVA and Bonferroni tests (α = 0.05). RESULTS: SE presented higher µTBS than universal adhesives and SB presented higher µTBS than GP regardless of dentin surface preparation and thermal aging (p ˂ 0.05). For SE and SB, the tungsten carbide bur demonstrated higher immediate and aged µTBS than did the extra-fine diamond bur (p ˂ 0.05). The immediate µTBS was similar for GP with all bur types (p ˃ 0.05); the tungsten carbide and extra-fine diamond burs presented higher µTBS than did the coarse-diamond bur after thermal aging (p ˂ 0.05). CONCLUSION: Dentin surface preparation and adhesive type had significant effects on µTBS. The smear layer created with an extra-fine diamond or tungsten carbide bur is favorable when mild and ultra-mild self-etch adhesives are used.

Analysis of Interleukin-1 Receptor Antagonist Variable Number Tandem Repeat Variant in Recurrent Aphthous Stomatitis.

BACKGROUND/AIMS: Recurrent aphthous stomatitis (RAS) is one of the common oral inflammatory diseases. As immunological and genetic factors have been held responsible for the pathogenesis of RAS, the objective of this study was to determine whether the interleukin-1 receptor antagonist (IL-1Ra) gene variable number tandem repeat (VNTR) variant is a risk factor for the development of RAS in Turkish patients and to define its contribution to the increased risk. METHODS: The IL-1Ra VNTR variant was evaluated in 169 RAS patients and 171 healthy controls by the polymerase chain reaction (PCR) method. RESULTS: No statistically significant difference was found in the genotype distributions and allele frequencies of IL-1Ra VNTR variant between RAS patients and healthy controls. CONCLUSION: Lack of association between IL-1Ra VNTR variant and RAS could indicate that IL-1Ra has no significant role in the pathophysiology of RAS. However, it still appears to be very worthwhile to continue to search for cytokine gene variants in order to predict the development of such disease.

Effect of a functional variant of tumor necrosis factor-ß gene in temporomandibular disorders: A pilot study.

BACKGROUND: Temporomandibular disorders (TMD) are a group of conditions that cause chronic orofacial pain. The tumor necrosis factor ß (TNF-ß) is a proinflammatory cytokine that is involved in the various aspects of the inflammatory process including organization and maintenance, and in the arrangement of cells at the inflammation site. The purpose of this study was to evaluate the correlation between TNF-ß +252A/G (rs909253) variant and susceptibility to TMD in a Turkish cohort. METHODS: The study included 104 patients (26 males, 78 females) with TMD and 126 healthy controls (44 males, 82 females). The TNF-ß +252A/G variant analysis was based on Polymerase Chain Reaction-Restriction Fragment Length Polymorphism (PCR-RFLP). RESULTS: There was no deviation from HWA for TNF-ß +252A/G variant in patient and control groups. There was significant difference in genotype and allele frequencies between patient group and control group in terms of TNF-ß +252A/G variant, respectively (P = 0.010, 0.015). A significant increase in the TNF-ß +252 AG genotype and G allele frequencies were observed in TMD patients compared to healthy controls. The individuals with GG genotype and G allele had an increased risk of developing TMD. A statistically significant association was observed when the patients were compared with the controls according to AA genotype vs AG+GG genotypes (P = 0.002, OR: 2.23, 95% CI:1.31-3.82). TNF-ß +252A/G genotype distribution was associated with chewing problems (P = 0.046). CONCLUSIONS: In conclusion, our results provided evidence that TNF-ß +252A/G variant may contribute to TMD development in a Turkish cohort. Further studies are needed to confirm this observation.

Effect of surface finishing on the colour stability and translucency of dental ceramics.

BACKGROUND: The purpose of this study was to investigate the effects of staining solutions and surface finishing on the colour stability and translucency of hybrid ceramic (HC) and resin nanoceramic (RNC) materials. METHODS: Twenty four groups consisting of 10 specimens (240 specimens in total) were created out of HC and RNC, including six groups to be stored in distilled water served as the controls groups. The Vita Enamic technical set, Shofu polishers, medium and fine rubber wheels and Sof-Lex polishing discs were used as polishing instruments. Cola, tea, and coffee were used as staining solutions. The colour differences (∆E*) and translucency parameter (TP) were evaluated by a spectrophotometer. Data were analysed by a One-way Analysis of Variance (ANOVA) and Mann-Whitney U test. RESULTS: There was a statistically significant difference between the ∆E* values of the HC specimens in the coffee groups and the ∆E* values of the other HC groups (p < 0.05). The ∆E* values of the RNC specimens in the coffee and tea groups were not different from the specimens in the cola groups (p > 0.05). The TP values of the polished groups were higher than the Sof-Lex groups and the Shofu groups on both HC and RNC materials (p < 0.05). CONCLUSIONS: Increased ∆E* values were observed in HC specimens stored in a coffee solution compared to the specimens stored in a tea or cola solution. Both of the RNC specimens stored in coffee and tea had higher ∆E* values than the RNC specimens stored in the cola. The TP values of both HC and RNC specimens stored in the coffee solution decreased.

The IL-1Ra gene variable number tandem repeat variant is associated with susceptibility to temporomandibular disorders in Turkish population.

BACKGROUND: Temporomandibular joint disorders (TMD) are a group of disorders involving temporomandibular joint and related structures. Interleukine-1 receptor antagonist (IL-1Ra) is an important anti-inflammatory molecule that competes with other interleukin-1 molecules. This study was designed to investigate the possible association of the IL-1Ra VNTR variant with the risk of TMD in the Turkish population. METHODS: Peripheral blood samples were collected from 100 patients with TMD (23 males, 77 females) and 110 healthy individuals (35 males, 75 females). Genotyping of IL-1Ra 86 bp VNTR variant was evaluated by gel electrophoresis after polymerase chain reaction (PCR). RESULTS: Our results show that there is a statistically significant difference between TMD patients and control group with respect to IL-1Ra genotype distribution and allele frequencies. 1.2, 1.4, and 4.4 genotypes were more common in patients, while 2.2 and 3.3 genotypes were rarer (P<.000). Frequency of alleles 1 and 4 was higher in patient groups (P<.000), whereas alleles 2 and 3 had a lower frequency in patients with TMD (P<.000). CONCLUSIONS: This is the first correlation study that evaluates the association between IL-1Ra gene VNTR variant and TMD. The VNTR variant related to IL-1Ra gene showed a strong pattern of association with TMD that may have a potential impact on disease counseling and management. Larger studies with various ethnicities are needed to establish the impact of IL-1Ra VNTR variant on risk of developing TMD.

Investigation of CD40 gene rs4810485 and rs1883832 mutations in patients with recurrent aphthous stomatitis.

OBJECTIVES: Recurrent aphthous stomatitis (RAS) is a common painful disorder affecting oral health, mucosa and overall quality of life. The etiopathogenesis of RAS remains unclear. RAS shows a large genetic diversity among the patients. In present study, we investigated whether CD40 gene rs4810485 and rs1883832 are associated with RAS and its clinical findings in Turkish patients. MATERIALS AND METHODS: Genomic DNA obtained from 387 individuals (160 patients with RAS and 227 healthy controls) were used in the study. CD40 gene rs4810485 and rs1883832 mutations were determined by using polymerase chain reaction with the specific primers. RESULTS: There was no statistically significant difference between the groups with respect to genotype and allele distribution (p>0.05, OR 0.94, 95% CI 0.70-1.28, OR 1.01 95% CI 0.75-1.37, respectively). Additionally, there was no statistically significant difference in the combined genotype analysis of CD40 gene rs4810485 and rs1883832 mutations (p>0.05). CONCLUSIONS: According to our results, we found that CD40 gene mutations are not associated with RAS. We are convinced that CD40 gene mutations do not predispose to develop RAS in Turkish population. To our knowledge, this is the first study regarding CD40 gene rs4810485 and rs1883832 mutations investigated in RAS patients.