Effects of natural products-based dentifrices on acrylic resin for denture bases: A simulated period of 4 years.

PURPOSE: To evaluate the antimicrobial activity of dentifrices based on Malva sylvestris and propolis and the effect on the acrylic resin. METHODS: The inhibitory effect against Candida albicans, Enterococcus faecalis and Streptococcus mutans was determined. The specimens of resin were divided into groups: Control (brushing with distilled water); brushing with Colgate; brushing with Protex; brushing with Malvatricin, brushing with Proporalcare Dental Gel and brushing with Green Propolis Dental Gel. Brushing was carried out in a brushing machine. Roughness and color were assessed. The data were analyzed by ANOVA, followed by the Bonferroni post test (α= 0.05). RESULTS: The products evaluated showed antimicrobial activity against all microorganisms (P< 0.05), except Proporalcare Dental Gel, which was not effective against E. faecalis. Greater roughness (P< 0.05) was observed in the samples treated with Colgate. The samples from control and Protex groups showed the lowest color variation and the highest luminosity, with a difference in relation to the others (P< 0.05), which showed higher values, although clinically acceptable. CLINICAL SIGNIFICANCE: The dentifrices based on natural products can be indicated for cleaning prostheses, since they showed antimicrobial activity and did not cause perceptible color changes of the resin tested. The dentifrices did not produce adverse effects on the surface of the resin or did so less than the conventional dentifrice.

Antibacterial activity of barbatimão (Stryphnodendron adstringens) against periodontopathogens and cytotoxic effects on fibroblasts.

This in vitro study aimed to evaluate the growth-inhibitory effects against periodontal disease-causing bacteria and cytotoxic effects against mouse fibroblast cells of the Stryphnodendron adstringens (barbatimão) hydroalcoholic extract. The contents of phenols and tannins in the extract were determined. The growth-inhibitory activity of the barbatimão was evaluated by determining the minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC). The viability of fibroblast cells was analyzed using the 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyl-tetrazolium bromide assay at 24 and 48 h post-treatment. The MIC values of the extract against Prevotella intermedia, Porphyromonas gingivalis, and Fusobacterium nucleatum were 0.05, 0.125, and 2 mg mL-1, respectively, while the MBC values were 4, 2, and 2 mg mL-1, respectively. The viability rate of barbatimão (0.25 mg mL-1)-treated L929 cells was higher than that of chlorhexidine (0.12%)-treated L929 cells at 48 h post-treatment. The contents of total phenolics and total tannins in the extract were 837.39 ± 0.10 and 785.82 ± 0.14 mg of tannic acid equivalent per gram of the extract, respectively. These findings indicate that the barbatimão hydroalcoholic extract, which exerted potent growth-inhibitory effects against the test microbial species and low cytotoxic effects on fibroblasts, has potential applications in the development of novel mouthwash products.

Dental mini-implant designs to support overdentures: Development, biomechanical evaluation, and 3D digital image correlation.

STATEMENT OF PROBLEM: Custom mini-implants are needed for edentulous patients with extensive mandibular deficiencies where endosteal placement is not possible. However, the best design for these mini-implants is unclear. PURPOSE: The purpose of this in vitro study was to develop 2 dental mini-implant designs to support mandibular overdentures and evaluate the effect of their geometries on primary stability and stress distribution. MATERIAL AND METHODS: Two mini-implant designs were developed with changes in the shape, size, and arrangement of threads and chamfers. The experimental mini-implants were made of Grade V titanium alloy (Ti-6Al-4V), (Ø2.0×10 mm) and submitted to a nanoscale surface treatment. Thirty mini-implants (n=10) were placed into fresh swine bones: experimental-threaded, experimental-helical, and a commercially available product model (Intra-Lock System) as the control. The biomechanical evaluations of the experimental mini-implants were compared with those of the control in terms of primary stability, through insertion torque (IT), and with the pullout test. The analysis of stress distribution was performed by using the method of 3D digital image correlation under 250-N axial load and 100-N oblique (30-degree angled model) load. The data were analyzed by ANOVA and the Tukey HSD test (α=.05). RESULTS: The IT and pullout test presented a statistically significant difference for all mini-implants (P<.05), with higher IT for the experimental-threaded and maximum pullout force for the control, followed by threaded (P=.001) and helical (P=.001). Regarding the 3D digital image correlation, a lower incidence of stress was found in the cervical third for all mini-implants. No statistically significant differences were found between the designs evaluated (P>.05). CONCLUSIONS: Comparing the experimental mini-implants with the commercially available control, the experimental-threaded model presented greater primary stability, and all mini-implants showed less stress in the cervical third.

Influence of surface treatment on the fluorescence of composite resins subjected to in situ bleaching.

OBJECTIVE: Use fluorescence analysis to evaluate the effect of polishing and surface sealant on the color of composite resin bleached with carbamide peroxide and subjected to staining. MATERIALS AND METHODS: Forty-eight composite resin specimens (Z250/Z350XT) were fabricated. After 24 hours stored in distilled water, all specimens were submitted to in situ bleaching with 16% home peroxide for 8 hours daily for a period of 14 days. Subsequently specimens were separated in three groups according to surface treatment proposed (group 1-polishing Sof-Lex; group 2-BisCover; group 3-control). After this, all the specimens were stained with red wine. A spectrofluorometer was used to evaluate the fluorescence in two readouts (L0-after surface treatment and L1-after staining).Data were analyzed by applying ANOVA using a statistical software program. RESULTS: No differences were shown for the factor treatment and other interactions. The lowest mean fluorescence value was found for Z350XT resin (1759.18 ± 0.13) when compared with Z250 (6863.92 ± 0.13). There was significant difference in the mean fluorescence values for all surface treatments between the two different readouts L0 (4820.93 ± 0.05) and L1 (3802.17 ± 0.05). CONCLUSION: The results suggested that all surface treatments proposed did not influenced the results of wine staining of bleached resins when compared with the control evaluated by the fluorescence method. CLINICAL SIGNIFICANCE: The purposes of this research was to find solutions, by means of surfaces treatment, to achieve restorations with a satisfactory and similar final aspect in relation to the teeth, and avoid discrepancies related to the esthetics and longevity of the restoration.

Development of an Impression Material with Antimicrobial Properties for Dental Application.

PURPOSE: To evaluate the antimicrobial activity and physico-mechanical properties of an irreversible hydrocolloid in which nanostructured silver vanadate decorated with silver nanoparticles (AgVO3 ) was added at various concentrations (0% - control, 2.5%, 5%, and 10% by weight). MATERIALS AND METHODS: The agar diffusion method (n = 10) was used to evaluate the inhibitory effect on the following species: Streptococcus mutans, Staphyloccocus aureus, Pseudomonas aeruginosa, Escherichia coli, and Candida albicans. The gelation time, flow capacity and plastic deformation were verified (n = 10). The data were analyzed using the Kruskal-Wallis test followed by the Dunn post-test, or via one-way ANOVA with multiple comparisons with a Bonferroni adjustment depending on the distribution (α = 0.05). RESULTS: All percentages of the nanomaterial were able to promote the antimicrobial activity of a hydrocolloid, with the formation of an inhibition zone (p < 0.05). In general, there was a dose-dependent effect on antimicrobial activity: higher concentrations of the nanomaterial promoted greater action except in the cases of P. aeruginosa (p < 0.001; F = 51.74) and S. aureus (p < 0.001), where the highest inhibition was for the 2.5% group. No difference was found in the gelation time when the control was compared with the groups with AgVO3 (p > 0.05). The difference was between the 5% and 10% groups (p = 0.007), and the latter promoted an increase in time. The flow capacity of the hydrocolloid with 5% of AgVO3 was significantly lower when compared with the control (p = 0.034). The AgVO3 influenced the plastic deformation (p < 0.001) in such a way that concentrations of 5% (p = 0.010) and 10% (p < 0.001) promoted an increase in this property when compared with the control. CONCLUSIONS: AgVO3 can be incorporated into an irreversible hydrocolloid as an antimicrobial agent without promoting adverse effects on physical-mechanical properties when used in concentrations of 2.5%.

Denture Liners: A Systematic Review Relative to Adhesion and Mechanical Properties.

PURPOSE: The objective of this systematic review is to compare results concerning the properties of adhesion, roughness, and hardness of dental liners obtained in the last ten years. METHODS: Searches on the databases LILACS, PubMed/Medline, Web of Science, and Cochrane Database of Systematic Reviews were supplemented with manual searches conducted between February and April of 2018. The inclusion criteria included experimental in vitro and in vivo, clinical, and laboratory studies on resilient and/or hard liners, assessment of hardness, roughness, and/or adhesion to the denture base, and physical/mechanical changes resulting from the disinfection process and changes in liners' composition or application. RESULTS: A total of 406 articles were identified and, from those, 44 are discussed. Twenty-four studies examined the bond strength, 13 surface roughness, and 19 the hardness. Of these 44 studies, 12 evaluated more than one property. Different substances were used in the attempt to improve adhesion. Considering roughness and hardness, the benefits of sealants have been tested, and the changes resulting from antimicrobial agents' incorporation have been assessed. CONCLUSION: Adhesion to the prosthesis base is improved with surface treatments. Rough surfaces and changes in hardness compromise the material's serviceability.

Retention force and deformation of an innovative attachment model for mini-implant-retained overdentures.

STATEMENT OF PROBLEM: The gradual loss of retention and the need for periodic replacement of attachment-system components are the most frequent complications in implant-supported overdentures. PURPOSE: The purpose of this in vitro study was to develop a new attachment system for overdentures with polymeric materials and compare its retention and deformation with a conventional O-ring attachment system. MATERIAL AND METHODS: A matrix with 2 mini-implants with ball abutments was used to simulate the mandibular border during a fatigue resistance test. A total of 60 polyacetal (n=20), polytetrafluoroethylene (n=20), and conventional O-ring (n=20) attachments were captured in pairs with acrylic resin and subjected to 3625 insertion and removal cycles, simulating 30 months of overdenture use. The internal and external deformations of the attachments were assessed using an optical stereomicroscope. One-way ANOVA and the Tukey honestly significant difference tests were used for statistical evaluation (α=.05). RESULTS: The polyacetal attachment system showed the highest retention (P<.001), followed by the O-ring and polytetrafluoroethylene attachments. The O-ring attachments exhibited the lowest deformation (P<.001), and the polyacetal attachments had the highest internal deformation (P<.001). CONCLUSIONS: The newly developed polyacetal attachment model increased the retention of mini-implant-retained overdentures, and despite the deformation experienced, the retention period appears to be better than that of conventional systems.

Effect of casting atmosphere on the marginal deficiency and misfit of Ni-Cr alloys with and without beryllium.

STATEMENT OF PROBLEM: The marginal adaptation of prosthetic crowns is still a significant clinical problem. PURPOSE: The purpose of this in vitro study was to evaluate the marginal deficiency and misfit of Ni-Cr alloys with and without beryllium under different casting conditions. MATERIAL AND METHODS: Four casting conditions were selected: flame-torch, induction/argon, induction/vacuum, and induction/air; and 2 alloys were used, Ni-Cr-Be and Ni-Cr. For each group, 10 metal specimens were prepared. Silicone indirect impressions and analysis of the degree of rounding were used to evaluate the marginal deficiencies of metal copings, and a standardized device for the setting pressure associated with optical microscopy was used to analyze the marginal misfit. Results were evaluated with 2-way ANOVA (α=.05), followed by the Tukey honest significant difference post hoc test, and the Pearson correlation test (α=.05). RESULTS: Alloy (P<.001) and casting technique (P<.001) were shown to affect marginal deficiencies. The Ni-Cr cast using the torch technique showed the highest marginal deficiency, and the Ni-Cr-Be cast in a controlled argon atmosphere showed the lowest (P<.001). Alloy (P=.472) and casting techniques (P=.206) did not affect the marginal misfit, but significant differences were found in the interaction (P=.001); the lowest misfit was achieved using the Ni-Cr-Be, and the highest misfit occurred with the molten Ni-Cr, using the cast torch technique. No correlation was found between deficiency and marginal misfit (r=.04, P=.69). CONCLUSIONS: The interactions demonstrated that the alloy containing beryllium that was cast in an argon atmosphere led to reduced marginal deficiency. Improved marginal adaptation can be achieved for the same alloy by using the torch technique.

Evaluation of antibiofilm and mechanical properties of new nanocomposites based on acrylic resins and silver vanadate nanoparticles.

OBJECTIVE: The purpose of this study was evaluate, for the first time, the impact of incorporation of nanostructured silver vanadate (ß-AgVO3) in antibiofilm and mechanical properties of dental acrylic resins (poly(methyl methacrylate), PMMA). DESIGN: The ß-AgVO3 was synthesized and characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy, and microanalysis (SEM/EDS). Resins specimens were prepared with 0-10% wt.% ß-AgVO3 and characterized by SEM, XRD and optical microscopy. The antibiofim activity of the samples against Candida albicans and Streptococcus mutans was investigated by XTT reduction test, colony-forming units (CFUs), and confocal laser scanning microscopy (CLSM). The flexural strength, hardness, and surface roughness of the samples containing ß-AgVO3 were compared with the pure PMMA matrix. RESULTS: The incorporation of 10% ß-AgVO3 significantly reduced the metabolic activity of C. albicans and S. mutans (p<0.05). There was a reduction in microbial load (CFU/mL) of microorganisms for the different concentrations used (p<0.05), which was confirmed by confocal microscopy. The addition of ß-AgVO3 did not change the mechanical properties of hardness and surface roughness of the resins (p>0.05). However, flexural strength decreased with the addition of amounts greater than 1% (p<0.05). CONCLUSIONS: ß-AgVO3 additions in dental acrylic resin may have an impact on inhibition of biofilm of main microorganisms associated with dental prostheses. However, the viability of clinical use should be evaluated in function of changed promoted in some mechanical properties.

In vitro study of the antibacterial properties and impact strength of dental acrylic resins modified with a nanomaterial.

STATEMENT OF PROBLEM: The accumulation of bacteria on the surface of dental prostheses can lead to systemic disease. PURPOSE: The purpose of this in vitro study was to evaluate the growth of Staphylococcus aureus and Pseudomonas aeruginosa on the surface of autopolymerizing (AP) and heat-polymerizing (HP) acrylic resins incorporated with nanostructured silver vanadate (ß-AgVO3) and its impact strength. MATERIAL AND METHODS: For each resin, 216 circular specimens (9 × 2 mm) were prepared for microbiologic analysis and 60 rectangular specimens (65 × 10 × 3.3 mm) for mechanical analysis, according to the percentage of ß-AgVO3: 0%, control group; 0.5%; 1%; 2.5%; 5%; and 10%. After a biofilm had formed, the metabolic activity of the bacteria was measured using the XTT reduction assay (2,3-bis-(2-methoxy-4-nitro-5-sulfophenyl)-2H-tetrazolium-5-carboxanilide) (n=8), and the number of viable cells was determined by counting colony forming units per milliliter (CFU/mL) (n=8). Confocal laser scanning microscopy (CLSM) was used to complement the analyses (n=2). The mechanical behavior was evaluated by impact strength assays (n=10). Data were analyzed by 2-way ANOVA, followed by the Tukey honestly significant difference (HSD) post hoc test (α=.05). RESULTS: The addition of 5% and 10% ß-AgVO3 significantly decreased the metabolic activity of P. aeruginosa for both resins (P<.05). The HP resin promoted a greater reduction in metabolic activity than the AP resin (P<.05). No difference was found in the metabolic activity of S. aureus according to the XTT (P>.05). The number of CFU/mL for S. aureus and P. aeruginosa decreased significantly when 5% and 10% ß-AgVO3 were added (P<.001). These concentrations significantly reduced the impact strength of the resins (P<.001) because the system was weakened by the presence of clusters of ß-AgVO3. CONCLUSION: The addition of ß-AgVO3 can provide acrylic resins with antibacterial activity but reduces their impact strength. More efficient addition methods should be investigated.