Guilherme Elias Pessanha Henriques

University of Campinas, Conceição de Campinas, São Paulo, Brazil

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Publications (57)52.15 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: Abstract The aim of this study was to evaluate three transfer techniques used to obtain working casts of implant-supported prostheses through the marginal misfit and strain induced to metallic framework. Thirty working casts were obtained from a metallic master cast, each one containing two implant analogues simulating a clinical situation of three-unit implant-supported fixed prostheses, according to the following transfer impression techniques: Group A, squared transfers splinted with dental floss and acrylic resin, sectioned and re-splinted; Group B, squared transfers splinted with dental floss and bis-acrylic resin; and Group N, squared transfers not splinted. A metallic framework was made for marginal misfit and strain measurements from the metallic master cast. The misfit between metallic framework and the working casts was evaluated with an optical microscope following the single-screw test protocol. In the same conditions, the strain was evaluated using strain gauges placed on the metallic framework. The data was submitted to one-way ANOVA followed by the Tukey's test (α=5%). For both marginal misfit and strain, there were statistically significant differences between Groups A and N (p<0.01) and Groups B and N (p<0.01), with greater values for the Group N. According to the Pearson's test, there was a positive correlation between the variables misfit and strain (r=0.5642). The results of this study showed that the impression techniques with splinted transfers promoted better accuracy than non-splinted one, regardless of the splinting material utilized.
    The Journal of oral implantology. 12/2014;
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    ABSTRACT: Although various abutment connections and materials have recently been introduced, insufficient data exist regarding the effect of stress distribution on their mechanical performance. The purpose of this study was to investigate the effect of different abutment materials and platform connections on stress distribution in single anterior implant-supported restorations with the finite element method. Nine experimental groups were modeled from the combination of 3 platform connections (external hexagon, internal hexagon, and Morse tapered) and 3 abutment materials (titanium, zirconia, and hybrid) as follows: external hexagon-titanium, external hexagon-zirconia, external hexagon-hybrid, internal hexagon-titanium, internal hexagon-zirconia, internal hexagon-hybrid, Morse tapered-titanium, Morse tapered-zirconia, and Morse tapered-hybrid. Finite element models consisted of a 4 × 13-mm implant, anatomic abutment, and lithium disilicate central incisor crown cemented over the abutment. The 49 N occlusal loading was applied in 6 steps to simulate the incisal guidance. Equivalent von Mises stress (σvM) was used for both the qualitative and quantitative evaluation of the implant and abutment in all the groups and the maximum (σmax) and minimum (σmin) principal stresses for the numerical comparison of the zirconia parts. The highest abutment σvM occurred in the Morse-tapered groups and the lowest in the external hexagon-hybrid, internal hexagon-titanium, and internal hexagon-hybrid groups. The σmax and σmin values were lower in the hybrid groups than in the zirconia groups. The stress distribution concentrated in the abutment-implant interface in all the groups, regardless of the platform connection or abutment material. The platform connection influenced the stress on abutments more than the abutment material. The stress values for implants were similar among different platform connections, but greater stress concentrations were observed in internal connections.
    The Journal of prosthetic dentistry 05/2014; · 1.22 Impact Factor
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    ABSTRACT: Abstract This study evaluated the effects of axial and oblique occlusal loading on implant-supported partial dentures with different connection systems (external-hexagon, internal-hexagon, and Morse-taper). Upon axial loading, all systems presented similar stress values. Stress values increased under oblique loading. Stress distribution changed for some of the internal-connection structures. It can be concluded that oblique load increases stress on bone structures and prosthetic components. Internal-connection system implants present more favorable stress distribution patterns than do external-connection system implants.
    Journal of Oral Implantology 04/2013; · 1.15 Impact Factor
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    ABSTRACT: Objective: To evaluate stress values and distribution patterns lower jaw posterior partial dentures supported by tilted implants. Method: Three-dimensional finite element models were built simulating a three-element fixed partial denture supported by two implants of external-hexagon or morse-taper connection. Models were built with implants placed parallel to each other or with the distal implant mesially tilted. The models with parallel implants were built with straight abutments, while the tilted models were built with a 17o angled abutment. Screw retained frameworks were loaded with oblique force of 180N on first premolar and first molar and 280N on second premolar. Maximum stress values (von Mises equivalent stress) and distribution patterns were obtained for all modeled structures of each model. Strain measurements were obtained for both bone structures. Result: Stress distribution on cortical bone was similar on all models. Maximum stress values on cortical bone ranged from 123-138MPa, presenting little variation. The same pattern was observed on trabecular bone. Mesial tilting of the distal implant increased higher stress concentration on trabecular bone around the straight implant. Strain ranged from 776-796με on cortical bone and 589-840με on trabecular bone. Morse-taper prosthetic components presented higher maximum stress on abutment and prosthetic screw. Angled abutments presented stress distribution and maximum stress values similar to those presented by the straight abutments. Prosthetic screws were not affected by the presence of angled abutments. Conclusion: Both external-hexagon and morse-taper connection systems presented similar stress distribution on the supporting bone, and maximum stress values within the ultimate compressive and tensile strength of bone. Tilting of the distal implant does not promote deleterious changes on stress and strain of bone structures.
    IADR General Session 2012; 06/2012
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    ABSTRACT: Objective: this work evaluated the influence of length, splinting and implant/abutment joint designs using a study photoelastic. Method: eight models were made from silicone molds in photoelastic resin (Araldite - Huntsman, Brazil), distributed one to each group composed as: G1 three splintted crowns over external hexagon implants of 5 x 7mm (Neodent - Brazil); G2 three-unit crowns over external hexagon implant of 5 x 7mm; G3 three splintted crowns over external hexagon implants of 5 x13mm; G4 three-unit crowns over implants of 5 x 13mm; G5 three splintted crowns over Cone Morse implants of 5 x 7mm; G6 three-unit crowns over Cone Morse implants of 5 x 7mm; G7 three splintted crowns over Cone Morse implants of 5 x 13mm and G8 three-unit crowns over Cone Morse implants of 5 x 13mm. The edge adaptation, in all of the metallic structures, was inicially analised in optical microscopy and showed results under 40µm. After, they were analysed through photoelastic analysis and it was possible to observe that all of the structures showed similar patterns of passivity. An occlusal loading of 100N was aplied in three points individually: A (occlusal region of the first pre molar), B (occlusal region of the second pre molar) and C (occlusal region of the first molar). Through the photoelastic technique it was possible to evaluate the influence of the length, of the splinttation and of the kind of connection of implants in the tensions distribution in posterior rehabilitations of mandible. Result: G2 and G4 showed significantly higher quantity and location of photoelastic fringes. Conclusion: the length of the implant seems not to influence in the tensions distribution, while splintation and the Cone Morse connection influenced in a positive way the tensions distribution in posterior rehabilitation of mandible.
    IADR General Session 2012; 06/2012
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    ABSTRACT: Objective: This study evaluated, by means of three dimensional finite element analyses, stress values and distribution pattern of axial and oblique occlusal loading of three-element fixed implant-supported prostheses manufactured with different implant connection systems. Method: Virtual models of a lower posterior partial denture were obtained using three implant connections systems (external-hexagon, internal-hexagon and morse-taper) with conical abutments and screwed titanium frameworks. In order to perform the finite element analyses all materials were considered to be homogeneous, isotropic and linearly elastic. Implant was considered to be completely osseointegrated and prosthetic structures were forged together. Both oblique and axial loads were standardized at 180 N for first premolar and molar, and 280 N for second premolar. Result: Similar stress values and distribution patterns were observed for all connection systems submitted to axial loading. Under oblique loading maximum stress values presented significant increase. Internal connection models presented lower stress on trabecular bone, implants and abutments. High stress areas were concentrated on the surface of cortical and trabecular bone. Conclusion: Based on the results this study, it can be concluded that oblique loads generate increased stress on bone structures and also on prosthetic components. Internal connection implant systems present more favorable stress distribution pattern than external connection.
    IADR General Session 2012; 06/2012
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    ABSTRACT: Objectives: The aim of this study was to evaluate the precision of four different mold filling techniques and verify an accurate methodology to evaluate these techniques. It was obtained 40 casts using four from a metallic matrix simulating three unit implant retained prosthesis. Methods: The molds were filled using four different techniques (n=10) following the four groups (n=10): Group 1- casts obtained with a single portion filling technique; Group 2- by using a two-step filling technique; Group 3- by using the latex cylinder technique; Group 4- by joining the implant analogues previously to the mold filling. A titanium framework was obtained used as reference to evaluate the marginal misfit and tension forces in each cast. The vertical misfit was measured with an optical microscope with an increase of 120 times following the single screw test protocol. The strain was quantified using strain gauges. Data were analyzed by ANOVA- 1 way and Tukey test (α=0,05). The correlation presence between strain and vertical misfit was evaluated by Pearson test. Results: The misfit values did not present statistic difference (p=0,979). The strain results showed statistic difference between groups 3 and 4 (p=0,027).The Pearson correlation presented no correlation between misfit and strain (r=-0,0403). Conclusions: The splinting technique was considered as efficient as the conventional technique. The strain gauges methodology was accurate on strain measurements and cast distortion evaluation. There was no correlation between strains and marginal misfit.
    IADR General Session 2012; 06/2012
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    ABSTRACT: Objective: The aim of this experimental in vitro study was to evaluate the behavior of the stresses induced in the supporting structures of denture through the photoelastic method in the following conditions: Group 1- conventional denture, 2- conventional denture relined with acrylic soft liner and 3- conventional denture relined with resilient material silicone-based. Method: For this experiment were made three lower dentures and a maxillary one. The photoelastic tests were conducted with the prosthesis in position of maximum intercuspation. Loads were made in axial position. The mandibular photoelastic model was loaded with 10, 20 and 30 kgf/cm² in each specimen. Result: The Group 1 showed stresses all along the model, with greater emphasis on the anterior and left lateral and less strain on the right side. In the left lateral surface, Group 2 showed similar as Group 1 , with stresses in the region of premolar and retromolar trigone. The Group 3 exhibited decreased of fringe orders and homogeneous distribution of induced stresses. Conclusion: It was concluded that the first and the second groups generated constrained tensions, which may cause increased bone resorption. The relining material based on silicone provided more homogeneous distribution of the stresses induced by the prosthesis.
    IADR General Session 2012; 06/2012
  • L. LUTHI, Piracicaba SP, M.A. RODRIGUES, G.E.P. HENRIQUES
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    ABSTRACT: Objective: This study aimed to evaluate the marginal misfit of implant supported frameworks and the stress transmitted to the supporting implants. Method: The structures were distributed into two groups (n = 10): Group 1 - premachined Ni-Cr-Ti UCLA abutment and Group 2 casted Ni-Cr-Ti UCLA abutment. Marginal misfit was measured following the single screw protocol, strain gauge was used to analyze the strains developed in the implants. Marginal misfit and strain data were obtained before and after 1 million mechanical cycles. All data was submitted to Mauchlys’ sphericity test and latter tested using mixed model analysis for repeated measurements, followed by Tukey-Kramer test (p≤0.05). Result: Marginal misfit levels presented to be higher for the completely calcinable group than for the overcastted group, regardless of the number of cycles evaluated. Also, in both groups marginal misfit significantly increased after the cyclic loading simulation. As for strain analyses, the completely calcinable group presented higher strain values than the overcastted group on both initial and final (1 million loading cycles) testing. In addition, both groups presented increased stress when tested after every 500 thousand cycles Conclusion: Manufacturing Ni-Cr-Ti implant supported frameworks with overcasted UCLA components generated better marginal fit and, consequently lower stress on the supporting structures.
    IADR General Session 2012; 06/2012
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    ABSTRACT: Abstract Objective. This study aimed to evaluate the influence of the casting procedure and cyclic loading of prosthetic frameworks on detorque of prosthetic screws and marginal misfit of single unit implant-supported prostheses. Materials and methods. Twenty specimens were obtained, each one consisting of a set of an implant (external hexagon 3.75 × 13 mm - Branemark type), a prosthetic abutment (entirely calcinable or overcasted UCLA) and a prosthetic screw. After the specimens were obtained, the prosthetic screws were tightened with 30 Ncm torque and released 24 h later in order to evaluate initial detorque. The screws were retightened and marginal gaps were assessed. All specimens were submitted to 10(6) loading cycles, performed with 2 Hz frequency and 130 N load. The specimens were re-evaluated for marginal misfit and detorque after the mechanical loading (final marginal misfit/final detorque). The results were submitted to analysis of variance for repeated measurements, followed by Tukey HSD test (α = 0.05). Results. No statistically significant differences were found on detorque values of the prosthetics screws for all groups and intervals evaluated (p = 0.8922). The entirely calcinable abutments showed higher initial marginal misfit compared to the overcasted ones (p = 0.0438). There was no statistically significant difference on marginal misfit before and after mechanical loading for both groups (p > 0.05). Conclusions. It can be concluded that the overcasted abutments showed lower misfit values when compared to the entirely casted abutments. No difference was observed on detorque values of prosthetic screws. After mechanical loading there was no difference on marginal misfit and detorque between the groups.
    Acta odontologica Scandinavica 05/2012; · 1.41 Impact Factor
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    ABSTRACT: Objective: The aim of this study was to assess by photoelastic analysis and through a test of flexural resistance, welding techniques, Laser and TIG (Tungsten Inert Gas) in the manufacturing of NiCrTi implant frameworks. Method: Three groups were formed with 5 samples each: framework cast in one piece, Laser welded and TIG welded. The photoelastic model was made with flexible resin, from the transfer impression of a stainless steel matrix with 4 similar implants with regular diameter and hexagonal external connection. The tensions caused by the installation of the frameworks with 20 Ncm torque on the photoelastic model, were analyzed in a circular polariscope and recorded by camera. Later, the resistance test was performed on the mechanical universal testing machine (Model 4411, Instron corp., Canton, MA). The frameworks were positioned in the mechanical testing machine which was set to move 2mm per minute until the occurrence of fracture of the cantilever. Result: The results were tabulated and submitted to ANOVA and Tukey's test at 5% significance. The results showed no statistical difference of maximum shear stress between any of the techniques used, however, the highest stresses were found along the implants of the right side. The one piece frameworks showed higher fracture resistance when compared to the TIG welded. Conclusion: The stresses around the implants were similar among the diffferent framework manufacturing techniques and among all evaluated areas. And one-piece casting framework and Laser welded showed better resistance, than the TIG welding techniques.
    AADR Annual Meeting 2012; 03/2012
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    ABSTRACT: Objective: Aiming to obtain frameworks with better fit, this study compared one-piece casted frameworks with frameworks obtained by two different soldering techniques: Laser-welding and TIG (Tungsten Inert Gas). Method: Thru photoelastic analysis and flexural strength tests, the stress distribution around implants and the mechanical resistance of the frameworks were evaluated. Fifteen commercially pure titanium frameworks were obtained using a steel matrix, with four external-hexagon (3.75x13mm) implants. The frameworks were divided into three groups: GI or control - one-piece casted frameworks; GII - Laser welded frameworks; GIII - TIG welded frameworks. For stress analyses a photoelastic model, reproducing the steel matrix was manufactured with photoelastic flexible resin. Each framework was screwed with 20Ncm torque to the photoelastic models implants. Using a circular polariscope the order of the isochromatic fringes around the implants was obtained. Maximum sheer stress was determined through the “stress optical law”. A mechanical test of flexural strength was performed at the hanging arms joints of each framework, using a universal testing machine (Instron 4411 Corp.Canton, Mass.) with a speed of 2 mm/min, load cell 500Kgf and maximum length of 5.00mm. The data were submitted to ANOVA followed by Tukey test (p=0.05). Result: No difference was observed on shear stress of the welding techniques. The casted group showed lower stress values than the TIG welded group. On the mechanical test the casted group presented higher compressive resistance (291,91N/mm2), followed by laser (224,20N/mm2) and TIG welded ones (123,65N/mm2). Conclusion: It is concluded that the conventional casting technique provides more mechanically resistant infrastructures than the welding techniques, with similar or lower stress to the supporting implants.
    AADR Annual Meeting 2012; 03/2012
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    ABSTRACT: Objective: The aim of this study was to evaluate the influence of photoinitiator type and curing light on the Knoop Hardness (KHN), cross-link density (CLD) and yellowing of experimental resins. Method: Three resins were prepared containing BisGMA, UDMA, BisEMA and TEGDMA. The photoinitiators used were camphorquinone (CQ), Phenyl-propanedione (PPD) and the association (CQ/PPD). These photoinitiators were used in combination with an aliphatic amine (DMAEMA). The Ninety cylindrical specimens (n=10) were made and photocured by different curing lights: Quartz-halogen-tungsten light (XL3000), a second generation LED (Radii Cal) and a polywave LED (Valo). The energy dose was standardized at 32J. After 24hs, the yellowing effect was analyzed by spectrophotometer and the initial KHN in a microhardener tester. Next, specimens were immersed in 100% ethanol for 24hs and the KHN was measured again. The cross-link density was measured as the softening effect of the resins (decrease of KHN). Data were submitted to two-way ANOVA and Tukey test (α = 0.05). Result: For the KHN, the presence of CQ and photocuring with Valo unit provided higher KHN values compared to the other groups. For the CLD, there were no difference among the groups tested (p ≥ 0.05). In general, the yellowing effect, analyzed by the b* axis of the CIELAB color system was higher when the resin blend contained CQ or the association CQ/PPD, compared to the resin with only PPD as the photoinitiator. Conclusion: The use of CQ as photoinitiator promoted higher hardness values, however allowed a higher yellowing of the resin material. The light curing unit Valo promoted better results of Knoop hardness, even with the resin contained PPD in its formulation.
    AADR Annual Meeting 2012; 03/2012
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    ABSTRACT: Objectives: This study aimed to evaluate the influence of the casting procedure and cyclic loading of prosthetic frameworks on detorque of prosthetic screws, in the marginal misfit and stress of single unit implant-supported prostheses. Methods: Twenty specimens were obtained, each one consisting in a set of an implant (external hexagon 3.75 x 13mm), a prosthetic abutment (entirely calcinable or overcastted UCLA) and a prosthetic screw. After the specimens were obtained, the prosthetic screws were tightened with 30Ncm torque and released 24h later in order to evaluate initial detorque. The stress analysis was performed using strain gauges. The screws were retightened and marginal gaps and were assessed. All specimens were submitted to 106 loading cycles, performed with 2Hz frequency and 130N load. The specimens were reevaluated for marginal misfit, detorque, and stress after the mechanical loading (final measurements). The results were submitted to analysis of variance for repeated measurements, followed by Tukey HSD test (α=0.05). Results: No differences were found on detorque values of the prosthetics screws for all groups and intervals evaluated (p=0.8922). The entirely calcinable abutments showed higher initial marginal misfit compared to the overcastted ones (p=0.0432). Mechanical loading did not affect the marginal misfit of both groups (p>0.05). There was no significant difference on stress of the abutments (p=0.2114). Stress decreased after mechanical loading on both groups (p<0.05). Conclusions: The overcastted abutments showed lower misfit when compared to the entirely casted abutments. The mechanical loading did not influence the marginal misfit and detorque of either groups. Nonetheless, it influenced the stress of single unit implant-supported prostheses.
    AADR Annual Meeting 2012; 03/2012
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    ABSTRACT: The purpose of this study was to evaluate the effects of adhesive primer applications on the bond strength of resin cements to cast titanium. Four adhesive primers - Metaltite, Metal Primer II, Alloy Primer and Ceramic Primer - and their respective resin cements - Bistite II DC, Link Max, Panavia F 2.0, RelyX Unicem and RelyX ARC - were tested. Cast plates were prepared from titanium ingots (n=6 specimens/cement) and had their surfaces airborne-particle abraded with Al2O3 (50 μ m). Three resin cement cylinders were built on each bonded titanium surface, using a cylindrical translucent tubing mold and were subjected to micro-shear testing. Data were analyzed statistically by two-way ANOVA and Tukey's post-hoc test (α=0.05). The application of Metal Primer II and Ceramic Primer resulted in significant higher bond strength for Link Max and RelyX Unicem resin cements, respectively, than nonuse of adhesive primers. Panavia F 2.0 and RelyX ARC yielded high bond strength means with or without adhesive primers. The use of adhesive primers might increase the bond strength to cast titanium depending on the resin cement used.
    Brazilian dental journal 01/2012; 23(3):218-22.
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    ABSTRACT: This study verified the surface microroughness of denture acrylic resins submitted to toothbrushing, chemical disinfection and thermocycling procedures. Samples were prepared according to conventional, microwaved and boiled resins and submitted to microroughness measurements before and after procedures using a profilometer (Ra). Data were subjected to anova and Tukey's test (5%). Before thermocycling, a difference was found among treatments for microwaved and boiled resins, with greater values for toothbrushing and lower values for Efferdent and hypochlorite; control was intermediate. Differences among resins were observed for treatments, with higher values for boiled resin and lower values for conventional and microwaved resins. After thermocycling, differences were found for microwaved resin, with a higher value for toothbrushing and a lower value for Efferdent and hypochlorite; control was intermediate. Tooth-brushed boiled resin presented higher values and hypochlorite lower values; control and Efferdent were intermediates. Differences among resins were seen for treatments, with higher values for boiled resin and lower values for conventional and microwaved resins. Boiled resin presented differences for toothbrushing and hypochlorite, before and after thermocycling procedures were compared. For microwaved and boiled resins, toothbrushing and chemical disinfection promoted different levels of surface microroughness when associated or not with thermocycling.
    Gerodontology 11/2011; 29(2):e891-7. · 1.83 Impact Factor
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    ABSTRACT: The aim of this study was to evaluate the distribution of generated stress around implants and adjacent bone tissue using different implant-retained overdenture designs through photoelastic analysis. Over an edentulous human mandible, achieved from a human model, 2 or 4 microunit analog abutments were embedded (Master; Conexao Systems Prosthodontics, São Paulo, Brazil), settled in the interforaminal region. Three models of photoelastic resin (Araltec Chemicals Ltda, Hunstman, Guarulhos, São Paulo, Brazil), with 2 or 4 incorporated implants and microunit abutments, were obtained from molds using silicone for duplication. Inclusion, finishing, and polishing procedures were applied on the frameworks. This study was based on 3 different mechanisms of implant-retained mandibular overdentures: O'ring (GI), bar-clip (GII) (both with 2 implants), and their association (GIII) (with 4 implants). After the adaptation of each overdenture system on the photoelastic models, 100-N alternate occlusal loads were applied on back-side and front-side regions. The photoelastic analysis was made with the aid of a plain polariscope linked to a digital camera, Sony Cybershot α100, which allowed visualization of the fringes and registration of images on digital photographs. The results demonstrated higher tension concentrated over the GIII, with a flat distribution of stress to the posterior ridge and overload on the posterior implants. GI showed the smaller stress level, and GII, intermediate level; there was distribution of stress to the posterior ridge in these 2 groups. The use of bar attachment proved to be a better alternative, because it showed a moderate level of tension with a more uniform stress distribution and possessed higher retention than did the ball system.
    The Journal of craniofacial surgery 11/2011; 22(6):2332-6. · 0.81 Impact Factor
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    ABSTRACT:   Titanium frameworks are frequently indicated for implant supported prostheses; however, voids are usually encountered inside cast titanium. Objective:  This study aimed to confirm the efficacy of a radiographic technique for inspection of porosity in commercially pure titanium castings with different diameter.   Sixty dumbbell rods (n=20) with a central 1.5, 2.0 and 3.5mm diameter were prepared by lost-wax casting. Cast specimens were finished and polished and submitted to radiographic examination (90kV, 15mA, 0.6s and 10-13mm of distance) using periapical film. The radiographs were visually analysed for the presence of porosity in the extension of the dumbbell or in the central portion of the rods. Data were submitted to Pearson Chi-square test (5%).   The tested radiographic method proved to be suitable for the evaluation of cast frameworks. Internal porosities were observed in most of the specimens (91.7%) (p=0.0005); however, only 20% occurred on the central portion of the rods (p=0.612).   Internal porosities can be visualised through radiographs and occur mostly in small diameter structures. The radiographic evaluation of metal structures can improve the quality of frameworks and thereby potentially increase the longevity of the rehabilitation.
    Gerodontology 09/2011; 28(3):233-7. · 1.83 Impact Factor
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    ABSTRACT: Objectives: This study verified the influence of room temperature and water storage on tooth displacement in complete maxillary dentures. Methods: Thirty complete maxillary dentures were made according to the long, fast or microwaved polymerization cycles. Commercially available acrylic resins (Classico and Onda-Cryl/Classico; and QC-20/Dentsply) were used according to manufacturers' recommendations. In order to measure the displacement of the tooth, reference metallic pins were fixed on the median region of the incisal border of the central incisors, buccal cusp of the first premolar and distobuccal cusp of the second molars. Transverse (incisor to incisor, premolar to premolar and molar to molar) and anteroposterior (right incisor to right molar and left incisor to left molar) distances were measured with a linear optical microscope with a significant level of 0.0005 mm. After measuring procedure, the dentures were stored in dry conditions in plastic containers at room temperature for 24 weeks. After storage, the distances were measured again and the dentures stored in water in an oven at 37C for 24 weeks, when the distances were re-evaluated. Data were submitted to ANOVA and Tukey's test (5%). Results: Anteroposterior distances showed contraction in all types of acrylic resins, with different percentual levels. Changes on incisor to incisor (room = -8.5% and water = -7.0%) and molar to molar (room = -1.8% and water = -1.1%) distances were greater in the Onda-Cryl resin, whereas premolar to premolar (room = -2.2% and water = -1.7%) distance was greater in the QC-20 resin. Conclusion: The distances between teeth were adversely affected by different storages. Water sorption was not sufficient to compensate the distortion that occurs during denture deflasking and at room temperature storage. Tooth displacement is still a complex factor that can influence the vertical dimension of occlusion and denture stability.
    IADR General Session 2011; 03/2011
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    ABSTRACT: The lack of passivity of the implant supported prosthesis may lead to mechanical and biological disorders such as loosening and breakage of screws, due to the tensions generated by prosthetic frameworks. The increasing use of laser welding and TIG welding (tungsten inert gas) for construction of infrastructure on implants raises issues as to the forces applied to the prosthesis-implant system and alveolar bone. Objectives: the aim of this study was to evaluate by using photoelasticity stresses generated by welding and TIG Laser in the union of cylindrical rods of titanium cp (Ti cp) to the abutment of the same metal and casting frameworks. Methods: on a steel matrix with four implants (Signovinces) was connecting the transfers abutments with acrylic resin and obtaining working model on which the laser welding were carried out (G 1), TIG welding (G 2), and casting frameworks in one-piece(G 3). The specimens were bolted on a photoelastic model with manual torque of 20 Ncm, and put into a round polariscope and took standardized digital photographs. Measurement points for the fringe order were defined. Results: tensions was present in all groups, the highest fringe order in group 1 was N = 1 and to groups 2 and 3 the higher order fringe was N = 2, with Group 3 showing more points with N = 2. Conclusions: it was concluded that the Laser welding exhibited the best passivity, followed by TIG welding in implant supported framework on 4 implants.
    IADR General Session 2011; 03/2011

Publication Stats

336 Citations
52.15 Total Impact Points

Institutions

  • 2005–2014
    • University of Campinas
      • Faculty of Dentistry from Piracicaba
      Conceição de Campinas, São Paulo, Brazil
    • Universidade Federal de Goiás
      Goianá, Goiás, Brazil
    • São Paulo State University
      • Departamento de Materiais Odontológicos e Prótese (Araçatuba)
      São Paulo, Estado de Sao Paulo, Brazil
  • 2004
    • University of São Paulo
      San Paulo, São Paulo, Brazil