Andréa Candido dos Reis

Analysis of primary stability of dental implants inserted in different substrates using the pullout test and insertion torque.

The aim of the study was to evaluate mechanical behavior of implants inserted in three substrates, by measuring the pullout strength and the relative stiffness. 32 implants (Master Porous-Conexao, cylindrical, external hexagon, and surface treatment) were divided into 4 groups (n = 8): pig rib bone, polyurethane Synbone, polyurethane Nacional 40 PCF, and pinus wood. Implants were installed with the exact distance of 5 mm of another implant. The insertion torque (N·cm) was quantified using the digital Kratos torque meter and the pullout test (N) was performed by an axial traction force toward the long axis of the implant (2 min/mm) through mount implant devices attached to a piece adapted to a load cell of 200 Kg of a universal testing machine (Emic DL10000). Data of insertion torque and maximum pullout force were submitted to one-way ANOVA and Bonferroni tests (α = 0.05). Polyurethane Nacional 40 PCF and pinus wood showed the highest values of insertion torque and pullout force, with significant statistical difference (P < 0.05) with other groups. The analysis showed stiffness materials with the highest values for primary stability.

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 (β-AgVO3) in antibiofilm and mechanical properties of dental acrylic resins (poly(methyl methacrylate), PMMA). DESIGN The β-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.% β-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 β-AgVO3 were compared with the pure PMMA matrix. RESULTS The incorporation of 10% β-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 β-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 β-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.

Microstructure and Mechanical Properties of Composite Resins Subjected to Accelerated Artificial Aging

The aim of this study was to investigate the influence of accelerated artificial aging (AAA) on the microstructure and mechanical properties of the Filtek Z250, Filtek Supreme, 4 Seasons, Herculite, P60, Tetric Ceram, Charisma and Filtek Z100. composite resins. The composites were characterized by Fourier-transform Infrared spectroscopy (FTIR) and thermal analyses (Differential Scanning Calorimetry - DSC and Thermogravimetry - TG). The microstructure of the materials was examined by scanning electron microscopy. Surface hardness and compressive strength data of the resins were recorded and the mean values were analyzed statistically by ANOVA and Tukeys test (α=0.05). The results showed significant differences among the commercial brands for surface hardness (F=86.74, p<0.0001) and compressive strength (F=40.31, p<0.0001), but AAA did not affect the properties (surface hardness: F=0.39, p=0.53; compressive strength: F=2.82, p=0.09) of any of the composite resins. FTIR, DSC and TG analyses showed that resin polymerization was complete, and there were no differences between the spectra and thermal curve profiles of the materials obtained before and after AAA. TG confirmed the absence of volatile compounds and evidenced good thermal stability up to 200 °C, and similar amounts of residues were found in all resins evaluated before and after AAA. The AAA treatment did not significantly affect resin surface. Therefore, regardless of the resin brand, AAA did not influence the microstructure or the mechanical properties.

Influence of torsional strength on different types of dental implant platforms.

Aim:The study assessed deformation of implant components submitted to torsion tests of 80 and 120 N·cm using an optical stereomicroscope. Material and Methods:The following 3 types of Titaniumfix conical implant connections (n = 5) measuring Ø 4.0 × 11.5 mm were used: external, internal hexagon and Morse taper connections. The diagonal and lateral measurements of the hexagon implant platform were measured before and after the torsion test. Results:The torsion test using torque of 80 and 120 N·cm altered the implant dental platforms. All groups presented deformation of implant component after torque of 80 N·cm with no statistical difference among them. During torque of 120 N·cm, a difference in the Morse taper connection in relation to the internal and external hexagon connection was observed. The Morse taper connection implant, followed by the internal hex implant, underwent less deformation. Greater deformation occurred in the external hex implants. Conclusion:For all the implants, high insertion torques deformed the implant platform preventing long-term maintenance and stability of implants.

Influence of the Ultimate Torsion on the Geometry of Dental Implants

This study evaluated the profile of implants subjected to torsion test. Four types of implants (Conexão®) were analyzed: Master Porous (MP - external hexagon, cylindrical, double-porous surface implants; 11.5 X 3.75 mm), Master Screw (MS - external hexagon, cylindrical, machined implants; 11.5 X 3.75 mm), Conect Conic (CC - external hexagon, cylindrical, machined implants; 11.5 X 3.5 mm) and Master Conect AR (CA - internal hexagon, cylindrical, double-porous surface implants; 11.5 X 3.75 mm). The Nikon® model C profile projector was used for the analysis before and after torsion test with a Mackena® model MK-20XX digital torque meter. The measures analyzed in the profile of implants were: diameter and height of the platform, diameter of the screw/platform connection, angle of the screw/platform connection, external diameter, internal diameter, thread pitch, height and length of the thread. Statistical analysis was performed using ANOVA and Tukey test at 5% significance level. The torsion test caused a visible deformity on the external implant profile. There was a statistical difference among the implants before and after torsion (p<0.05) for the variables: platform diameter, platform height, diameter of the screw/platform connection and length. Changes were observed in platform height of CC and CA, fracture of CA implants, fracture of the MP and MS assembler/connectors, and internal thread stripping of CC. Thus, it was concluded that excessive or some unadvised torque by the manufacturer can lead to changes in different geometric measurements of implants.

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 (&agr;=.05), followed by the Tukey honest significant difference post hoc test, and the Pearson correlation test (&agr;=.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.

In Vitro Microstructural Analysis of Dental Implants Subjected to Insertion Torque and Pullout Test

The change in the implant microstructure during handling may reduce the potential of surface treatment on the osteoinduction and, therefore, on the osseointegration. The aim of this study was to evaluate by energy-dispersive X-ray spectroscopy (EDX) the effect of insertion torque and pullout test on the microstructure of dental implants with different shapes. Four shapes of implants (n=8) were selected: conical with surface treatment (COTS), cylindrical with surface treatment (CTS), cylindrical with double surface treatment (CTSD) and cylindrical with machined surface (CSU). Before and after performing the mechanical tests, the screw surfaces were subjected to analysis of chemical composition by EDX. The results obtained by the microstructural analysis showed presence of three main chemical elements: Ti, C and O. There was a significant change in the concentration of Ti and C. The implant with double surface treatment (CTSD) showed the greatest Ti reduction and the greatest C increase. It may be concluded that the mechanical manipulation may alter the implant surfaces as regards their microstructure. Therefore, surgical planning should take into consideration the choice of surface treatment because the characteristics of the implants may be modified as they are inserted and removed from the bone site.

Estudo in vitro da influência do formato e do tratamento de superfície de implantes odontológicos no torque de inserção, resistência ao arrancamento e frequência de ressonância

OBJECTIVE: The purpose of the study was to evaluate the influence of the shape and surface treatment on the primary stability of dental implants inserted in different substrates through association methods such as insertion torque, pullout strength and resonance frequency. MATERIAL AND METHOD: 32 implants were used with 8 cylindrical treatment Porous (CA), 8 machined cylindrical (MS), 8 cylinder dual treatment Porous (MP) and 8 tapered untreated (CC). The substrates used for inclusion were: pork rib;

Bioglass® and resulting crystalline materials synthesized via an acetic acid-assisted sol–gel route

In this study, we report on the synthesis of a bioactive glass powder with the original 45S5 composition (Bioglass®) by means of an acetic acid-assisted sol–gel route. A glassy material was obtained after the gels underwent a thermal stabilization treatment at 600 °C for 3 h. Above this temperature, the heat-treated gels crystallized partially, forming a sodium-calcium-silicate Na2CaSi2O6 phase. Even after crystallization, this material showed in vitro bioactivity in simulated body fluid after 12 h, when the formation of hydroxycarbonate apatite on the material surface was identified by X-ray diffraction. Not surprisingly, microbiological assays revealed that these gel-derived materials appear to have an antibacterial effect against Pseudomonas aeruginosa (ATCC 27853)—a Gram-negative bacterium that is noted for its environmental survival versatility, ability to produce biofilm and resistance to some antibiotics. Thus, using common precursors that are widely available, relatively cheap, simple to use, and which result in gels with low stabilization temperature, it was possible to explore the versatility of sol–gel processing to obtain the golden standard 45S5 bioglass.Graphical Abstract

Traumatic ulcerative granuloma with stromal eosinophilia around mini dental implants without the protection of a denture base.

This is a report of a case of an unusual oral lesion after the placement of mini implants for the retention of a mandibular overdenture. A patient received four 2-mm-wide dental implants in the anterior mandible and had her mandibular denture relined with a soft material. After 3 months, she was not wearing her mandibular denture, and two nodular ulcerated lesions were observed near the mini implants. The lesions ceased following excision and regular denture wearing. Clinical and microscopic examination led to the diagnosis of traumatic ulcerative granuloma with stromal eosinophilia (TUGSE). TUGSE is rare lesion with a benign course that may occur following injury of the oral mucosa by mini implants under certain circumstances.