Three-dimensional finite element analysis of three internal tapered implant-abutment designs / Análise tridimensional de elementos finitos de três geometrias implante-abutment cônicos internos

ABSTRACT Objective: The aim of this study was to compare the stress distribution in internal tapered connection implants with different adaptation geometries submitted to oblique load simulation using the Finite Element Analysis (FEA) method. Methods: Three different internal tapered implant-abutment assemblies were modeled by varying only the diameter of the abutment body in the cone region. The dimensions of the implants were 4.0 mm in diameter and 13 mm in length. Oblique loads of 210 N angled 30 degrees to the long axis of the implant were applied to a hemispherical body positioned over the abutments simulating a dental crown. The stress generated by the implant-abutment assembly was analyzed by the FEA method using the von Mises criterion. Results: A higher concentration of stress in the coronal region (collar) and implant body on the opposite side of the load application was shown, as well as in the body region of the abutments and in the screw threads. The cervical region of the implants showed the highest von Mises stress values, the highest values being observed in G3 (1034 MPa), followed by G2 (841 MPa) and G1 (702 MPa). Conclusion: According to the results presented, it can be concluded that the stress distribution was more homogeneous and less concentrated in the G1 implant-abutment assembly. Therefore, the use of abutments with dimensions standardized by the implant manufacturer is recommended.

RESUMO Objetivo: O objetivo deste estudo foi comparar a distribuição de tensões em implantes de conexão cônica interna com diferentes geometrias de adaptação submetidos à simulação de carga oblíqua pelo método de Análise de Elementos Finitos (FEA). Métodos: Três diferentes conjuntos implante-pilar cônicos internos foram modelados variando apenas o diâmetro do corpo do pilar na região do cone. As dimensões dos implantes foram de 4,0 mm de diâmetro e 13 mm de comprimento. Cargas oblíquas de 210 N anguladas 30 graus em relação ao longo eixo do implante foram aplicadas sobre um corpo hemisférico posicionado sobre os pilares simulando uma coroa dentária. A tensão gerada pelo conjunto implante-pilar foi analisada pelo método FEA utilizando o critério de von Mises. Resultados: Foi evidenciada maior concentração de tensões na região coronal (colar) e corpo do implante no lado oposto da aplicação da carga, assim como na região do corpo dos pilares e nas roscas dos parafusos. A região cervical dos implantes apresentou os maiores valores de tensão de von Mises, sendo os maiores valores observados em G3 (1034 MPa), seguido de G2 (841 MPa) e G1 (702 MPa). Conclusão: De acordo com os resultados apresentados, pode-se concluir que a distribuição de tensões foi mais homogênea e menos concentrada no conjunto implante-pilar do G1. Portanto, recomenda-se o uso de pilares com dimensões padronizadas pelo fabricante do implante.

Influence of Different Screw Torque Levels on the Biomechanical Behavior of Tapered Prosthetic Abutments.

PURPOSE: To study the force used for tightening tapered one-piece prosthetic abutments and their influence on the removal torque value and stress level of the prosthetic abutment after cyclic loading. MATERIALS AND METHODS: Fourteen implants and prosthetic abutments were divided into two groups (n = 7): G1, 20 Ncm; and G2, 32 Ncm (manufacturer recommended). A 20-mm T-shaped horizontal bar was adapted to the abutments. A 12-Hz cyclic loading was applied to the specimens in an electrodynamic testing system with the maximum number of cycles set to 106. Specimens were inclined by 15 degrees from the vertical axis, and a 5-mm off-center vertical load was applied to generate a combination of bending and torquing moments on the tapered connections. Progressive loads (from 164.85 to 362.85 N) were applied when the previous sample survived 106 cycles. The paired t test compared the screw removal torque with the initial tightening torque for each group (α = .05). A finite element analysis (FEA) of the mechanical testing analyzed the regions of stress concentration. RESULTS: No specimens failed after 106 cyclic loadings. The mean screw removal torque for both groups was similar to the initial abutment torque value applied for each group (G1, 20.36 ± 8.73 Ncm; and G2, 35.61 ± 6.99 Ncm) (P > .05). FEA showed similar stress behavior for both groups in the study despite the different simulated screw preloads (G1: 200 N; G2: 320 N). The coronal region of the implant body presented the highest strain values in both groups. CONCLUSION: Tightening tapered one-piece prosthetic abutments at 20 and 32 Ncm maintains a stable connection after cyclic loading. The stresses generated by the different tightening forces during cyclic loading are highest at the coronal level of the connection.

Influence of the Prosthetic Index on Fracture Resistance of Morse Taper Dental Implants.

PURPOSE: Manufacturers have inserted a prosthetic index, an internal hexagon to guide prosthetic components inside Morse taper implants. However, it is still unclear if this mechanism could decrease the mechanical strength of Morse taper implants. The aim of this study was to evaluate the influence of the prosthetic index inside Morse taper implants on fracture resistance compared with nonindexed implants. MATERIALS AND METHODS: Fifty-seven Morse taper implants, with 11.5-degree angulation of the internal conical portion, were divided into three groups: implants without the prosthetic index and solid Morse taper universal post (group 1), implants with the prosthetic index and solid Morse taper universal post (group 2), and implants and abutments with the prosthetic index (group 3). All groups were modeled for finite element stress analysis (FEA), simulating force application of a perpendicular load to the abutments. Fracture resistance (n = 10) was determined under the same condition. Dynamic loading (n = 9) was also performed. The statistical analysis was performed using one-way analysis of variance (ANOVA), and the Tukey test was applied (α = .05). The metallographic analysis was used to identify the fracture distribution and the microstructure of the titanium alloy. RESULTS: There was no statistically significant difference between the values of all tested groups. According to the FEA, the prosthetic index region was out of stress. The mean fracture resistances and loading test were 353.7 N and 200 N for group 1, 397.3 N and 170 N for group 2, and 372.0 N and 160 N for group 3, respectively. Metallographic analysis showed a macroscopic failure pattern just as demonstrated by FEA. CONCLUSION: The presence of the prosthetic index on Morse taper implants did not decrease its resistance to fracture for the tested implants.

Comparative Analysis of Cutting Efficiency and Surface Maintenance Between Different Types of Implant Drills: An In Vitro Study.

INTRODUCTION: This study evaluated cutting efficiency (CE) and linear wear of dental implant drills after 450 standardized osteotomies on bovine ribs. Diamond-like carbon-coated steel drills (SG), acid-treated steel drills (EG), and ceramic drills (ZG) were divided into 6 subgroups according to the number of uses. MATERIALS AND METHODS: A robot-controlled program performed systematic instrumentation, timing, axial loading, and managed feed rate. CE was recorded in a polyurethane resin blank and end wear (VBBmax) was analyzed under stereo microscopy. RESULTS: After osteotomies in beef ribs, CE for the Ø2.0-mm drill decreased 10.2% in SG and 10.9% in ZG; for the Ø3.0-mm drill, CE decreased 30.6% in SG, 8.5% in ZG, and improved in EG. The greatest wear occurred in Ø2.0-mm drills; ZG drills (Ø3.0 mm) exhibited only edge frittering, as confirmed on scanning electron microscopy. CONCLUSION: After 50 exposures to mechanical loads, steel and ceramic drills lost CE. Whereas cutting and thermal performance improved in experimental drills, the Ø2.0-mm drill exhibited the most signs of wear proportional to use. These findings suggest that, with the methodology employed, the life of these drills exceeds 50 osteotomies.