In this study, low-level laser therapy promoted the osseointegration of implants with poor initial stability, particularly in the initial stages of bone healing.

ObjectiveThis study aimed to evaluate the bending moments, and compressive and tensile forces in implant-supported prostheses with three, four or five abutments.Material and MethodsTen Pd-Ag frameworks were tested over two master models with: 1) parallel vertical implants, and 2) tilted distal implants. Strain gauges were fixed on the abutments of each master model to measure the deformation when a static load of 50 N was applied on the cantilever (15 mm). The deformation values were measured when the metallic frameworks were tested over three, four or five abutments, and transformed into force and bending moment values. Data were analyzed by ANOVA and Tukey’s test for multiple comparisons at 5% level of significance.ResultsAbutment #1 (adjacent to the cantilever) had the highest values of force and sagittal bending moment for all tests with three, four or five abutments. Independently from the number of abutments, axial force in abutment #1 was higher in the vertical model than in the tilted model. Total moment was higher with three abutments than with four or five abutments. Independently from the inclination of implants, the mean force with four or five abutments was lower than that with three abutments.ConclusionThe results suggest that in the set-ups with four or five abutments tilted distal implants reduced axial force and did not increase bending moments.

T he objective of this research was to evaluate, by three-dimensional (3D) finite element analysis (FEA), the stress distribution in three different fiveimplant mandibular protocol prosthesis models, when these three undergo a simulated occlusal load of 100 N in the area of the cantilever: (1) model A, temporary all-acrylic resin; (2) model B, metal-acrylic; and (3) model C, metal-ceramic. Materials and Methods Modeling of the External and Internal Portions of the MandibleThe external 3D modeling of the mandible was acquired from the laser digitization of a natural edentulous mandible in the sagittal, horizontal, and frontal planes (0.01mm precision) using Digimil 3D (Technodrill). The first 3D model was created using Geomatic Studio version 7.0, and then a continuous model was obtained using Rhynoceros 3D version 3.0.A tomographic image (70 transversal vertical slices, 1-mm thickness) of the same edentulous mandible was obtained using Helicoidal Tomographic Hispeed CTI System Series 6.3 (GE Healthcare). This image was superimposed over the external mandible model to develop the internal model (Rhynoceros 3D version 3.0). Modeling of Implants and Prosthetic ComponentsThe 3D shapes of implant and prosthetic components were obtained by manual measurements (eg, length, diameter, thread pitch) with magnifying lens and a digital caliper. These dimensions were used for generating digital surfaces (Rhynoceros 3D version 3.0), and then solid shapes were obtained (SolidWorks 2012, SolidWorks).

Objectives: This nonlinear three-dimensional finite element analysis (FEA) study evaluated the effect of the number of implants, distal implant inclination, and use of angled abutments on stress magnitude and distribution in cortical bone (CB), abutment screw (AS), and prosthetic screw (PS) of implant-supported fixed complete dentures. Methods: Nonlinear 3D FEA models of mandibular fixed complete dentures were created with five, four, or three parallel straight implants (5S, 4S, 3S) and with tilted distal implants (5T, 4T, 3T). In addition, the 5T model was tested using angled abutments over the tilted distal implants to re-align the implant inclination. A 100-N axial load was applied over the first molar region (cantilever) to analyze the von Mises stresses in selected points (CB, AS, and PS). Results: The implant adjacent to the load showed the highest stresses in CB, AS, and PS. The model with three implants showed higher stresses than the ones with four and five implants. Peak stresses in the AS increased 40% from five to four implants and 100% from five to three implants. Tilting the distal implants increased stresses in CB. Peak stress in the PS increased 150% from 5S to 5T models and 100% from 4S to 4T models. Angled abutments generated lower stresses on CB and AS but higher stresses on PS. Conclusions: The results suggest that stresses in the cortical bone, abutment screw, and prosthetic screw increase when tilting the posterior implants and reducing the number of implants. The use of angled abutments decreased stresses at the bone-implant interface and in abutment screws but increased stresses on prosthetic screws.

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