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ABSTRACT: The aim of this study was to assess the color alteration and sensitivity of teeth throughout and following in-office bleaching. Twenty-two volunteers participated in this clinical trial of bleaching treatment (35% hydrogen peroxide bleaching gel and placebo) applied on maxillary incisors and canines. According to a split-mouth design, the volunteers' maxillary hemi-arches received either the bleaching or placebo agent, applied four times, at 1-week intervals. Color alteration and tooth sensitivity were assessed throughout and following bleaching. Statistical calculations were performed using gamma distribution and repeated-measures ANOVA. There was a statistically significant difference between teeth submitted to a bleaching agent and placebo (P < .001). At the end of the first, second, third, and fourth sessions, the bleached teeth presented color scores statistically lower than those observed immediately before bleaching. There was no difference in the color scale scores of the bleached teeth between bleaching sessions. The sensitivity data test showed a significant difference among treatments (P < .0001). Color alteration and dental sensitivity were altered by the bleaching agent.
The International journal of periodontics & restorative dentistry 03/2013; 33(2):209-215. · 1.20 Impact Factor
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ABSTRACT: Abstract Purpose: The aim of this study was to evaluate stress distribution on the peri-implant bone, simulating the influence of Nobel Select implants with straight or angulated abutments on regular and switching platform in the anterior maxilla, by means of 3D finite elements analysis. Materials and Methods: Four mathematical models of a central incisor supported by external hexagon implant (13mm x 5mm) were created varying the platform (R - regular or S - switching) and the abutments (S - straight or A - angulated 15º). The models were created by using Mimics 13 and Solid Works 2010 software programs. The numerical analysis was performed by ANSYS Workbench 10.0. Oblique forces (100 N) were applied to the palatine surface of the central incisor. The bone/implant interface was considered perfectly integrated. Maximun (σmax) and minimum (σmin) principal stress values were obtained. Results: For the cortical bone the highest stress values (σmax) were observed in the RA (regular platform and angulated abutment, 51 MPa), followed by SA (platform switching and angulated abutment, 44.8 MPa), RS (regular platform and straight abutment, 38.6 MPa) and SS (platform switching and straight abutment, 36.5 MPa). For the trabecular bone, the highest stress values (σmax) were observed in the RA (6.55 MPa), followed by RS (5.88 MPa), SA (5.6 MPa) and SS (4.82 MPa). Conclusions: The regular platform generated higher stress in the cervical peri-implant region on the cortical and trabecular bone than the platform switching, irrespective of the abutment used (straight or angulated).
Journal of Oral Implantology 10/2012; · 1.53 Impact Factor
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ABSTRACT: The non-homogenous aspect of periodontal ligament (PDL) has been examined using finite element analysis (FEA) to better simulate PDL behavior. The aim of this study was to assess, by 2-D FEA, the influence of non-homogenous PDL on the stress distribution when the free-end saddle removable partial denture (RPD) is partially supported by an osseointegrated implant.
Six finite element (FE) models of a partially edentulous mandible were created to represent two types of PDL (non-homogenous and homogenous) and two types of RPD (conventional RPD, supported by tooth and fibromucosa; and modified RPD, supported by tooth and implant [10.00x3.75 mm]). Two additional Fe models without RPD were used as control models. The non-homogenous PDL was modeled using beam elements to simulate the crest, horizontal, oblique and apical fibers. The load (50 N) was applied in each cusp simultaneously. Regarding boundary conditions the border of alveolar ridge was fixed along the x axis. The FE software (Ansys 10.0) was used to compute the stress fields, and the von Mises stress criterion (svM) was applied to analyze the results.
The peak of svM in non-homogenous PDL was higher than that for the homogenous condition. The benefits of implants were enhanced for the non-homogenous PDL condition, with drastic svM reduction on the posterior half of the alveolar ridge. The implant did not reduce the stress on the support tooth for both PDL conditions. Conclusion: The PDL modeled in the non-homogeneous form increased the benefits of the osseointegrated implant in comparison with the homogeneous condition. Using the non-homogenous PDL, the presence of osseointegrated implant did not reduce the stress on the supporting tooth.
Journal of applied oral science: revista FOB 06/2012; 20(3):362-8. · 0.39 Impact Factor
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ABSTRACT: PURPOSE: To evaluate the stress distribution in peri-implant bone by simulating the effect of an implant with microthreads and platform switching on angled abutments through tridimensional finite element analysis. The postulated hypothesis was that the presence of microthreads and platform switching would reduce the stress concentration in the cortical bone. METHODS: Four mathematical models of a central incisor supported by an implant (5.0mm×13mm) were created in which the type of thread surface in the neck portion (microthreaded or smooth) and the diameter of the angled abutment connection (5.0 and 4.1mm) were varied. These models included the RM (regular platform and microthreads), the RS (regular platform and smooth neck surface), the SM (platform switching and microthreads), and the SS (platform switching and smooth neck). The analysis was performed using ANSYS Workbench 10.0 (Swanson Analysis System). An oblique load (100N) was applied to the palatine surface of the central incisor. The bone/implant interface was considered to be perfectly integrated. Values for the maximum (σ(max)) and minimum (σ(min)) principal stress, the equivalent von Mises stress (σ(vM)), and the maximum principal elastic strain (ɛ(max)) for cortical and trabecular bone were obtained. RESULTS: For the cortical bone, the highest σ(max) (MPa) were observed for the RM (55.1), the RS (51.0), the SM (49.5), and the SS (44.8) models. The highest σ(vM) (MPa) were found for the RM (45.4), the SM (42.1), the RS (38.7), and the SS models (37). The highest values for σ(min) were found for the RM, SM, RS and SS models. For the trabecular bone, the highest σ(max) values (MPa) were observed in the RS model (6.55), followed by the RM (6.37), SS (5.6), and SM (5.2) models. CONCLUSION: The hypothesis that the presence of microthreads and a switching platform would reduce the stress concentration in the cortical bone was partially rejected, mainly because the microthreads increased the stress concentration in cortical bone. Only platform switching reduced the stress in cortical bone.
Journal of prosthodontic research. 05/2012;
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ABSTRACT: The aim of this study was to evaluate stress distribution on peri-implant bone simulating the influence of implants with different lengths on regular and switching platforms in the anterior maxilla by means of three-dimensional finite element analysis.
Four mathematical models of a central incisor supported by an external hexagon implant (diameter, 5.0 mm) were created, varying the length (15.0 mm for long implants [L] and 7.0 mm for short implants [S]) and the diameter of the abutment platform (5.0 mm for regular models [R] and 4.1 mm for switching models [S]). The models were created using the Mimics 11.11 (Materialise) and SolidWorks 2010 (Inovart) software. Numerical analysis was performed using ANSYS Workbench 10.0 (Swanson Analysis System). Oblique forces (100 N) were applied to the palatine surface of the central incisor. The bone/implant interface was considered perfectly integrated. Maximum (σ(max)) and minimum (σ(min)) principal stress values were obtained.
For the cortical bone, the highest stress values (σ(max)) were observed in the SR (73.7 MPa) followed by LR (65.1 MPa), SS (63.6 MPa), and LS (54.2 MPa). For the trabecular bone, the highest stress values (σ(max)) were observed in the SS (8.87 MPa) followed by the SR (8.32 MPa), LR (7.49 MPa), and LS (7.08 MPa).
The influence of switching platform was more evident for the cortical bone in comparison with the trabecular bone for the short and long implants. The long implants showed lower stress values in comparison to the short implants, mainly when the switching platform was used.
The Journal of craniofacial surgery 05/2012; 23(3):678-81. · 0.81 Impact Factor
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ABSTRACT: The aim of this study was to assess the contributions of some prosthetic parameters such as crown-to-implant (C/I) ratio, retention system, restorative material, and occlusal loading on stress concentrations within a single posterior crown supported by a short implant.
Computer-aided design software was used to create 32 finite element models of an atrophic posterior partially edentulous mandible with a single external-hexagon implant (5 mm wide x 7 mm long) in the first molar region. Finite element analysis software with a convergence analysis of 5% to mesh refinement was used to evaluate the effects of C/I ratio (1:1; 1.5:1; 2:1, or 2.5:1), prosthetic retention system (cemented or screwed), and restorative material (metal-ceramic or all ceramic). The crowns were loaded with simulated normal or traumatic occlusal forces. The maximum principal stress (stressmax) for cortical and cancellous bone and von Mises stress (stressvM) for the implant and abutment screw were computed and analyzed. The percent contribution of each variable to the stress concentration was calculated from the sum of squares analysis.
Traumatic occlusion and a high C/I ratio increased stress concentrations. The C/I ratio was responsible for 11.45% of the total stress in the cortical bone, whereas occlusal loading contributed 70.92% to the total stress in the implant. The retention system contributed 0.91% of the total stress in the cortical bone. The restorative material was responsible for only 0.09% of the total stress in the cancellous bone.
Occlusal loading was the most important stress concentration factor in the finite element model of a single posterior crown supported by a short implant.
The International journal of oral & maxillofacial implants 05/2012; 27(3):e13-8. · 1.78 Impact Factor
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ABSTRACT: In view of reports in the literature on the benefits achieved with the use of platform switching, described as the use of an implant with a larger diameter than the abutment diameter, the goal being to prevent the (previously) normal bone loss down to the first thread that occurs around most implants, thus enhancing soft tissue aesthetics and stability and the need for implant inclination due to bone anatomy in some cases, the aim of this study was to evaluate bone stress distribution on peri-implant bone, by using three-dimensional finite element analysis to simulate the influence of implants with different abutment angulations (0 and 15 degrees) in platform switching.
Four mathematical models of an implant-supported central incisor were created with varying abutment angulations: straight abutment (S1 and S2) and angulated abutment at 15 degrees (A1 and A2), submitted to 2 loading conditions (100 N): S1 and A1-oblique loading (45 degrees) and S2 and A2-axial loading, parallel to the long axis of the implant. Maximum (σmax) and minimum (σmin) principal stress values were obtained for cortical and trabecular bone.
Models S1 and A1 showed higher σmax in cortical and trabecular bone when compared with S2 and A2. The highest σmax values (in MPa) in the cortical bone were found in S1 (28.5), followed by A1 (25.7), S2 (11.6), and A2 (5.15). For the trabecular bone, the highest σmax values were found in S1 (7.53), followed by A1 (2.87), S2 (2.85), and A2 (1.47).
Implants with straight abutments generated the highest stress values in bone. In addition, this effect was potentiated when the load was applied obliquely.
The Journal of craniofacial surgery 03/2012; 23(2):415-8. · 0.81 Impact Factor
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ABSTRACT: OBJECTIVES: This study evaluated the reliability and failure modes of implants with a microthreaded or smooth design at the crestal region, restored with screwed or cemented crowns. The postulated null hypothesis was that the presence of microthreads in the implant cervical region would not result in different reliability and strength to failure than smooth design, regardless of fixation method, when subjected to step-stress accelerated life-testing (SSALT) in water. MATERIALS AND METHODS: Eighty four dental implants (3.3 × 10 mm) were divided into four groups (n = 21) according to implant macrogeometric design at the crestal region and crown fixation method: Microthreads Screwed (MS); Smooth Screwed (SS); Microthreads Cemented (MC), and Smooth Cemented (SC). The abutments were torqued to the implants and standardized maxillary central incisor metallic crowns were cemented (MC, SC) or screwed (MS, SS) and subjected to SSALT in water. The probability of failure versus cycles (90% two-sided confidence intervals) was calculated and plotted using a power law relationship for damage accumulation. Reliability for a mission of 50,000 cycles at 150 N (90% 2-sided confidence intervals) was calculated. Differences between final failure loads during fatigue for each group were assessed by Kruskal-Wallis along with Benferroni's post hoc tests. Polarized-light and scanning electron microscopes were used for failure analyses. RESULTS: The Beta (β) value (confidence interval range) derived from use level probability Weibull calculation of 1.30 (0.76-2.22), 1.17 (0.70-1.96), 1.12 (0.71-1.76), and 0.52 (0.30-0.89) for groups MC, SC, MS, and SS respectively, indicated that fatigue was an accelerating factor for all groups, except for SS. The calculated reliability was higher for SC (99%) compared to MC (87%). No difference was observed between screwed restorations (MS - 29%, SS - 43%). Failure involved abutment screw fracture for all groups. The cemented groups (MC, SC) presented more abutment and implant fractures. Significantly higher load to fracture values were observed for SC and MC relative to MS and SS (P < 0.001). CONCLUSION: Since reliability and strength to failure was higher for SC than for MC, our postulated null hypothesis was rejected.
Clinical Oral Implants Research 03/2012; · 2.51 Impact Factor
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ABSTRACT: This study aimed to evaluate stress distribution on peri-implant bone simulating the influence of platform switching in external and internal hexagon implants using three-dimensional finite element analysis.
Four mathematical models of a central incisor supported by an implant were created: External Regular model (ER) with 5.0 mm × 11.5 mm external hexagon implant and 5.0 mm abutment (0% abutment shifting), Internal Regular model (IR) with 4.5 mm × 11.5 mm internal hexagon implant and 4.5 mm abutment (0% abutment shifting), External Switching model (ES) with 5.0 mm × 11.5 mm external hexagon implant and 4.1 mm abutment (18% abutment shifting), and Internal Switching model (IS) with 4.5 mm × 11.5 mm internal hexagon implant and 3.8 mm abutment (15% abutment shifting). The models were created by SolidWorks software. The numerical analysis was performed using ANSYS Workbench. Oblique forces (100 N) were applied to the palatal surface of the central incisor. The maximum (σ(max)) and minimum (σ(min)) principal stress, equivalent von Mises stress (σ(vM)), and maximum principal elastic strain (ε(max)) values were evaluated for the cortical and trabecular bone.
For cortical bone, the highest stress values (σ(max) and σ(vm) ) (MPa) were observed in IR (87.4 and 82.3), followed by IS (83.3 and 72.4), ER (82 and 65.1), and ES (56.7 and 51.6). For ε(max), IR showed the highest stress (5.46e-003), followed by IS (5.23e-003), ER (5.22e-003), and ES (3.67e-003). For the trabecular bone, the highest stress values (σ(max)) (MPa) were observed in ER (12.5), followed by IS (12), ES (11.9), and IR (4.95). For σ(vM), the highest stress values (MPa) were observed in IS (9.65), followed by ER (9.3), ES (8.61), and IR (5.62). For ε(max) , ER showed the highest stress (5.5e-003), followed by ES (5.43e-003), IS (3.75e-003), and IR (3.15e-003).
The influence of platform switching was more evident for cortical bone than for trabecular bone, mainly for the external hexagon implants. In addition, the external hexagon implants showed less stress concentration in the regular and switching platforms in comparison to the internal hexagon implants.
Journal of Prosthodontics 02/2012; 21(3):160-6. · 1.01 Impact Factor
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ABSTRACT: This study used the 3D finite element (FE) method to evaluate the mechanical behavior of a maxillary central incisor with three types of dowels with variable heights of the remaining crown structure, namely 0, 1, and 2 mm.
Based on computed microtomography, nine models of a maxillary central incisor restored with complete ceramic crowns were obtained, with three ferrule heights (0, 1, and 2 mm) and three types of dowels (glass fiber = GFD; nickel-chromium = NiCr; gold alloy = Au), as follows: GFD0--restored with GFD with absence (0 mm) of ferrule; GFD1--similar, with 1 mm ferrule; GFD2--glass fiber with 2 mm ferrule; NiCr0--restored with NiCr alloy dowel with absence (0 mm) of ferrule; NiCr1--similar, with 1 mm ferrule; NiCr2--similar, with 2 mm ferrule; Au0--restored with Au alloy dowel with absence (0 mm) of ferrule; Au1--similar, with 1 mm ferrule; Au2--similar, with 2 mm ferrule. A 180 N distributed load was applied to the lingual aspect of the tooth, at 45° to the tooth long axis. The surface of the periodontal ligament was fixed in the three axes (x = y = z = 0). The maximum principal stress (σ(max)), minimum principal stress (σ(min)), equivalent von Mises (σ(vM)) stress, and shear stress (σ(shear)) were calculated for the remaining crown dentin, root dentin, and dowels using the FE software.
The σ(max) (MPa) in the crown dentin were: GFD0 = 117; NiCr0 = 30; Au0 = 64; GFD1 = 113; NiCr1 = 102; Au1 = 84; GFD2 = 102; NiCr2 = 260; Au2 = 266. The σ(max) (MPa) in the root dentin were: GFD0 = 159; NiCr0 = 151; Au0 = 158; GFD1 = 92; NiCr1 = 60; Au1 = 67; GFD2 = 97; NiCr2 = 87; Au2 = 109.
The maximum stress was found for the NiCr dowel, followed by the Au dowel and GFD; teeth without ferrule are more susceptible to the occurrence of fractures in the apical root third.
Journal of Prosthodontics 02/2012; 21(4):304-11. · 1.01 Impact Factor
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ABSTRACT: This three-dimensional finite element analysis study evaluated the effect of different material combinations on stress distribution within metal-ceramic and all-ceramic single implant-supported prostheses.
Three-dimensional finite element models reproducing a segment of the maxilla with a missing left first premolar were created. Five groups were established to represent different superstructure materials: GP, porcelain fused to gold alloy; GR, modified composite resin fused to gold alloy; TP, porcelain fused to titanium; TR, modified composite resin fused to titanium; and ZP, porcelain fused to zirconia. A 100-N vertical force was applied to the contact points of the crowns. All models were fixed in the superior region of bone tissue and in the mesial and distal faces of the maxilla section. Stress maps were generated by processing with finite element software.
Stress distribution and stress values of supporting bone were similar for the GP, GR, TP, and ZP models (1,574.3 MPa, 1,574.3 MPa, 1,574.3 MPa, and 1,574.2 MPa, respectively) and different for the TR model (1,838.3 MPa). The ZP model transferred less stress to the retention screw (785 MPa) than the other groups (939 MPa for GP, 961 MPa for GR, 1,010 MPa for TP, and 1,037 MPa for TR).
The use of different materials to fabricate a superstructure for a single implant-supported prosthesis did not affect the stress distribution in the supporting bone. The retention screw received less stress when a combination of porcelain and zirconia was used.
The International journal of oral & maxillofacial implants 11/2011; 26(6):1202-9. · 1.78 Impact Factor
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ABSTRACT: Ceramics have been widely used for esthetic and functional improvements. The resin cement is the material of choice for bonding ceramics to dental substrate and it can also dictate the final esthetic appearance and strength of the restoration. The correct use of the wide spectrum of resin luting agents available depends on the dental tooth substrate. This article presents three-year clinical results of a 41 years old female patient B.H.C complaining about her unattractive smile. Two all-ceramic crowns and two laminates veneers were placed in the maxillary incisors and cemented with a self-adhesive resin luting cement and conventional resin luting cement, respectively. After a three-year follow-up, the restorations and cement/teeth interface were clinically perfect with no chipping, fractures or discoloration. Proper use of different resin luting cements shows clinical appropriate behavior after a three-year follow-up. Self-adhesive resin luting cement may be used for cementing all-ceramic crowns with high predictability of success, mainly if there is a large dentin surface available for bonding and no enamel at the finish line. Otherwise, conventional resin luting agent should be used for achieving an adequate bonding strength to enamel.
European journal of dentistry. 08/2011; 5(4):478-85.
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ABSTRACT: The cementation procedure of metal-free fixed partial dentures exhibits special characteristics about the porcelains and cementation agents, which turns the correct association between these materials necessary. Our purpose in this literature review was to point the main groups of cements associated to metal-free restoration and discuss about the advantages, disadvantages, and recommendations of each one. Our search was confined to the electronic databases PubMed and SciELO and to books about this matter. There are essentially 3 types of hard cement: conventional, resin, or a hybrid of the two. The metal-free restorations can be fixed with conventional or resin cements. The right choice of luting material is of vital importance to the longevity of dental restorative materials. Conventional cements are advantageous when good compressive straight, good film thickness, and water dissolution resistance are necessary. However, they need an ideal preparation, and they are not acid dissolution resistant. Conventional cements are indicated to porcelains that cannot be acid etched. Resin cements represent the choice to metal-free restoration cementation because they present better physical properties and aesthetic than conventional agents.
The Journal of craniofacial surgery 05/2011; 22(3):952-8. · 0.81 Impact Factor
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ABSTRACT: Based on a maxillary premolar restored with laminate veneer and using the 3-D finite element analysis (FEA) and μCT data, the aim of this study was to evaluate the influence of different types of buccal cusp reduction on the stress distribution in the porcelain laminate veneer and in the resin luting cement layer.
Two 3-D FEA models (M) of a maxillary premolar were built from μCT data. The buccal cusp reduction followed two configurations: Mt - buccal cusp completely covered by porcelain laminate veneer; and Mp - buccal cusp partially covered by porcelain laminate veneer. The loading (150 N in 45°) was performed on the top of the buccal cusp. The finite element software (Ansys Workbench 10.0) was used to obtain the maximum shear stress (τ(max)) and maximum principal stress (σ(max)).
The Mp showed reduced the stress (σ(max)) in porcelain laminate veneer (from -2.3 to 24.5 MPa) in comparison with Mt (from -5.3 to 27.4 MPa). The difference between the peak and lower stress values of σ(max) in Mp (-6.8 to 26.7 MPa) and Mt (-5.3 to 27.4 MPa) was similar for the resin luting cement layer. The structures not exceeded the ultimate tensile strength or the shear bond strength.
Cusp reduction did not affect significant increase in σ(max) and τ(max). The Mt showed better stress distribution (τ(max)) than Mp.
Journal of prosthodontic research. 04/2011; 55(4):221-7.
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ABSTRACT: The fracture or chipping of ceramic veneers is a common problem for zirconia-based restorations.
This study evaluated the stress distribution in the veneer of a maxillary central incisor restored with a complete crown using a zirconia core with a feldspathic ceramic veneer, simulating an incomplete bond between the veneer and zirconia substructure.
Based on a microcomputed tomography of a maxillary central incisor, 3 finite element models (M) for a complete crown were developed: Mf, a complete crown based on feldspathic ceramic; Mlz, a zirconia-based complete crown with a complete bond at the zirconia/veneer interface; and Mnzl, similar to Mlz, but with an incomplete bond at the zirconia/veneer interface created by using a contact element with a frictional coefficient of 0.3. A distributed load of 1 N was applied to the lingual surface at 45 degrees to the long axis of the tooth.
The zirconia core in the Mnzl model showed peak stresses for maximum principal stress (σ(max)) and shear stress of 9.02 and 8.81 MPa, respectively. The ceramic veneer in the Mnlz model showed peak stresses for σ(max), minimum principal stress (compressive), and von Mises stresses of 5.4 MPa, 61.23 MPa, and 35.19 MPa, respectively.
The incomplete bond increased the σ(max) in the ceramic veneer in comparison to the perfect bond condition.
The Journal of prosthetic dentistry 01/2011; 105(1):14-20. · 1.22 Impact Factor
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ABSTRACT: The aim of this study was to evaluate the influence of different Young moduli of the ceramic crown on the distribution of tensions in the region of the abutment-crown interface by making use of 2D finite element analysis.
Two representative models of a sagittally sectioned maxilla were built through AutoCad program showing an implant in the region of the upper central incisor and were restored by means of IPS e.max Press or Procera AllCeram on zircon abutment. Numerical analysis (Ansys 10.0) was performed under 2 loading conditions (50 N): on the lingual face, at 45 degrees with the implant's long axis (L1) and perpendicular to the incisal edge (L2). The von Mises equivalent stress (σvM) and maximum principal stress (σmax) were obtained.
It was noticed that, independent of the restoring system, the maximum σvM values were in the incisal region of the cementation interface for both loading conditions. The IPS e.max Press system showed higher σvM on the adhesive interface with higher L1 influence. The same behavior was also observed as regards the σmax variation.
It was concluded that a restoring system with a lower Young modulus shows higher stress concentration on the abutment-crown interface when cemented on an abutment with a high Young modulus. Thus, IPS e.max Press system provides higher stress concentration in the resin cement layer than Procera AllCeram system, suggesting that the resin cement layer shows lower failure risk when the Procera crown is used.
Implant dentistry 12/2010; 19(6):539-48. · 1.51 Impact Factor
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ABSTRACT: The aim of this study was to evaluate the effect of unilateral angular misfit of 100 μm on stress distribution of implant-supported single crowns with ceramic veneering and gold framework by three-dimensional finite element analysis. Two three-dimensional models representing a maxillary section of premolar region were constructed: group 1 (control)-crown completely adapted to the implant and group 2-crown with unilateral angular misfit of 100 μm. A vertical force of 100 N was applied on 2 centric points of the crown. The von Mises stress was used as an analysis criterion. The stress values and distribution in the main maps (204.4 MPa for group 1 and 205.0 MPa for group 2) and in the other structures (aesthetic veneering, framework, retention screw, implant, and bone tissue) were similar for both groups. The highest stress values were observed between the first and second threads of the retention screw. Considering the bone tissue, the highest stress values were exhibited in the peri-implant cortical bone. The unilateral angular misfit of 100 μm did not influence the stress distribution on the implant-supported prosthesis under static loading.
The Journal of craniofacial surgery 11/2010; 21(6):1683-7. · 0.81 Impact Factor
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ABSTRACT: To evaluate stress distribution in different horizontal mandibular arch formats restored by protocol-type prostheses using three-dimensional finite element analysis (3D-FEA).
A representative model (M) of a completely edentulous mandible restored with a prefabricated bar using four interforaminal implants was created using SolidWorks 2010 software (Inovart, São Paulo, Brazil) and analyzed by Ansys Workbench 10.0 (Swanson Analysis Inc., Houston, PA) to obtain the stress fields. Three mandibular arch sizes were considered for analysis, regular (M), small (MS), and large (ML). Three unilateral posterior loads (L) (150 N) were used: perpendicular to the prefabricated bar (L1); 30° oblique in a buccolingual direction (L2); 30° oblique in a lingual-buccal direction (L3). The maximum and minimum principal stresses (σ(max), σ(min)), the equivalent von Mises (σ(vM)), and the maximum principal strain (σ(max) ) were obtained for type I (M.I) and type II (M.II) cortical bones.
Tensile stress was more evident than compression stress in type I and II bone; however, type II bone showed lower stress values. The L2 condition showed highest values for all parameters (σ(vM), σ(max), σ(min), ɛ(max)). The σ(vM) was highest for the large and small mandibular arches.
The large arch model had a higher influence on σ(max) values than did the other formats, mainly for type I bone. Vertical and buccolingual loads showed considerable influence on both σ(max) and σ(min) stresses.
Journal of Prosthodontics 11/2010; 20(1):29-34. · 1.01 Impact Factor
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ABSTRACT: The aim of the present study was to conduct a critical literature review about the technique of computer-guided surgery in implantology to highlight the indications, purposes, immediate loading of implants and complications, protocol of fabrication, and functioning of virtual planning software. This literature review was based on OLDMEDLINE and MEDLINE databases from 2002 to 2010 using the key words "computer-guided surgery" and "implant-supported prosthesis." Thirty-four studies regarding this topic were found. According to the literature review, it was concluded that the computer-assisted surgery is an excellent treatment alternative for patients with appropriate bone quantity for implant insertion in complete and partially edentulous arches. The Procera Nobel Guide software (Nobel Biocare) was the most common software used by the authors. In addition, the flapless surgery is advantageous for positioning of implants but with accurate indication. Although the computer-guided surgery may be helpful for virtual planning of cases with severe bone resorption, the conventional surgical technique is more appropriate. The surgical guide is important for insertion of the implants regardless of the surgical technique, and the success of immediate loading after computer-guided surgery depends on the accuracy of clinical and/or laboratorial steps.
The Journal of craniofacial surgery 11/2010; 21(6):1917-21. · 0.81 Impact Factor
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ABSTRACT: This study aimed to evaluate the influence of loading on a maxillary central incisor with the periodontal ligament (PDL) represented by 2D elastic beam elements using a 2D finite element analysis. Two models (M) were built varying the PDL representation: Mh (homogeneous PDL) and Mht (heterogeneous PDL with beam3 elements). Stress and displacements were determined for three loading conditions (L): Ll, lingual face loading at 45° with the tooth long axis; Li, perpendicular to the incisal edge; and Lip, on the incisal edge, parallel to the tooth long axis. Evaluation was performed on ANSYS software. Lip provided lower stress variation on the tooth and support structures when compared to Ll and Li. PDL's influence on stress values was lower for Lip. Oblique loading showed stress and displacement not observed in parallel loading condition through PDL's heterogeneous representation and it is probably incompatible with the in vivo condition.
Computer Methods in Biomechanics and Biomedical Engineering 10/2010; 13(5):515-21. · 0.85 Impact Factor
