RESUMEN

OBJECTIVES: To evaluate clinical, radiographic, microbiologic, and biomechanical parameters related to bone remodeling around implants with external hexagon (EH) and Morse-taper (MT) connections. MATERIALS AND METHODS: Twelve totally edentulous patients received four custom-made implants in the interforaminal region of the mandible. Two of those implants had the same macroscopic design, but different prosthetic connections. All patients received an immediate implant-supported prosthesis. Clinical parameters (periimplant probing pocket depth (PPD), modified gingival index (mGI), and mucosal thickness (MTh)) were evaluated at 12 months follow-up. The distance between the top of the implant and the first bone-to-implant contact (IT-FBIC) was evaluated on standardized digital peri-apical radiographs acquired at 1, 3, 6, and 12 months follow-up. Samples of the subgingival microbiota were collected 1, 3, and 6 months after implant loading and used for the quantification of Tanerella forsythia, Porphyromonas gingivalis, Aggragatibacter actinomycetemcomitans, Prevotella intermedia, and Fusobacterium nucleatum. Further, 36 computerized-tomography based finite element (FE) models were accomplished, simulating each patient under three loading conditions. RESULTS: The evaluated clinical parameters were equal for EH and MT implants. Mean IT-FBIC was significantly different between the tested connections (1.17 ± 0.44 mm for EH, and 0.17 ± 0.54 mm for MT, considering all evaluated time periods). No significant microbiological differences could be observed between tested connections. FE analysis showed a significantly higher peak of equivalent (EQV) strain (p = 0.005) for EH (mean 3,438.65 µÎµ) compared to MT (mean 840.98 µÎµ) connection. CONCLUSIONS: Radiographic periimplant bone loss depends on the implant connection type. MT connections showed less periimplant bone loss, compared to EH connections.

Asunto(s)

RESUMEN

PURPOSE: To evaluate the influence of different implant numbers and connection types on the biomechanical behavior of mandibular full-arch implant-supported rehabilitation. MATERIALS AND METHODS: Computed tomography-based finite element models comprising a totally edentulous mandible and 3.8 × 13-mmdiameter implants, abutments, abutment screws, bar retaining screw, and bar were constructed. Different implant numbers (three, four, and five implants) and loading conditions (symmetrical/balanced, unilateral, and posterior with diverse loading magnitudes) were simulated for both external hex and Morse-taper connections. The peak equivalent strain (EQV strain) in the bone and the peak of von Mises stress (EQV stress) in the abutment screw and bar retaining screw were evaluated. RESULTS: Lower strain values were observed for a symmetrical loading distribution. Considering the same loading conditions, significantly higher bone strain levels were observed for external hex, compared with the Morse-taper connection. The number of implants had no significant influence on strain levels in bone, irrespective of the connection types. Compared with the external hex connection, the Morse-taper connection type presented significantly lower EQV stress values in abutment screws, but significantly higher stress in the bar retaining screw. Increasing the number of implants significantly reduced the EQV stress in the abutment screw and bar retaining screw. CONCLUSION: The Morse-taper connection type significantly decreased the strain levels in peri-implant bone, while increasing the stress in bar retaining screws. A smaller number of implants in an inferior full-arch rehabilitation slightly increased the stress in the abutment and bar retaining screws. Balanced adjustments of the loading improve the biomechanics of a mandibular full-arch rehabilitation.

Asunto(s)

RESUMEN

OBJECTIVES: The objective of the study was to evaluate the effectiveness of a short fibre-reinforced composite (FRC) applied in combination with a conventional filler composite (CFC) on the fatigue resistance, fracture strength, failure mode and stress distribution, for restorations of premolars under two loading angles. MATERIAL AND METHODS: Thirty-two inferior premolars received extensive cavities with removal of the lingual cusp. Teeth were restored directly using 'FRC (EverX Posterior, GC) + CFC (G-aenial, GC)' or 'CFC only' and received two fatigue/fracture loadings at two different angles (0°/45°) (n = 8). Data were submitted to two-way ANOVA (α = 5 %) and Tukey test. Failure mode was analysed using SEM. Four 3D finite element (FE) models were constructed and static, linear and elastic analyses were performed. Maximum principal and von Mises stresses were evaluated. RESULTS: All specimens survived the mechanical fatigue simulation. No statistical difference in fracture resistance was recorded between FRC + CFC and CFC only, considering both loading angles (p = 0.115). However, the 0° loading showed a statistical significant higher strength than the 45° loading (p = 0.000). Failure mode analysis revealed more repairable fractures upon 0° loading, versus more root fractures (unrepairable) upon 45° loading. FE revealed a higher amount of stress upon 45° loading, with tensile stress being imposed to the lingual cervical area. CONCLUSION: The fracture strength was not increased using the FRC. Loading at a 45° decreased significantly the fracture resistance. CLINICAL RELEVANCE: The restoration of extensive cavities in posterior tooth is a challenge for the clinicians and the choice of the material that increases the fracture strength of tooth-restoration complex is required.

Asunto(s)

RESUMEN

Telehealth has become a very important tool that allows the monitoring of heart failure patients in a home environment. However, little is known about the effect that such monitoring systems have on patients' compliance, evolution and self-care behaviour. In particular, the effect that the selected user interface has on these factors is unknown. This study aims to investigate this, and to determine some practicalities that must be considered when designing and implementing a telehealth programme for heart failure. To achieve this, daily measurements of blood pressure, pulse, SpO2 and weight were collected from 534 patients suffering from heart failure. In addition, they were asked to fill in the European heart failure self-care behaviour scale questionnaire and the EQ-5D quality of life questionnaire, before and after the monitoring period. Two telehealth systems were used, the Motiva platform provided by Philips and the standalone unit provided by Docobo, the Doc@Home system. Significant differences were found between both systems concerning the compliance and adherence of patients. Moreover, a general, positive effect of telehealth was identified due to the fact that patients showed an increased self-awareness when managing their condition. These findings are supported by behavioural changes and a better understanding of heart failure from the patients' perspective.

Asunto(s)

RESUMEN

Objetivo: avaliar a remodelação óssea radiográfica ao redor de implantes hexágono externo (EH) que possuem roscas no módulo da crista. Material e métodos: doze pacientes desdentados totais receberam quatro implantes (Ø 3,8 mm x 13 mm) customizados na região interforaminal. Doze desses implantes foram hexágono externo com roscas no módulo da crista. Todos os pacientes receberam uma prótese implantossuportada imediata. A distância entre o topo do implante e o primeiro contato osso/implante (IT-FBIC) foi avaliada em radiografias periapicais digitais padronizadas adquiridas em um, três, seis e 12 meses de acompanhamento. A comparação entre vários períodos de observação foi realizada utilizando análise de variância (Anova) para medidas repetidas, seguida pelo teste post-hoc de Tukey. Resultados: a variação radiográfica da perda óssea peri-implantar foi significativamente diferente entre os períodos de acompanhamento (p < 0,001). A média de IT-FBIC foi de 1,17 ± 0,44 mm, depois de 12 meses de carregamento funcional. Conclusão: a remodelação óssea peri-implantar ocorrerá para implantes com hexágono externo, independentemente da presença de elementos de retenção no módulo da crista do implante

Objective: to evaluate the radiographic bone remodeling around implants using external hexagon (EH) with a threaded implant crestal module. Material and methods: twelve patients with totally edentulous mandibles received four custom-made (Ø 3.8 x 13 mm) implants in the interforaminal region. Twelve of the implants were external hexagon with a threaded implant crestal module. All patients received an immediate implant-supported prosthesis. The distance between the top of the implant and the first bone-to-implant contact (IT-FBIC) was evaluated on standardized digital periapical radiographs acquired at one, three, six, and 12 months of follow-up. Comparison among multiple observation periods was performed using repeated-measures analysis of variance (Anova), followed by a Tukey post-hoc test. Results: the radiographic periimplant bone loss was significantly different among the follow-up periods (p < 0.001). Mean IT-FBIC was 1.17 mm ± 0.44 mm, at 12 months follow-up period. Conclusions: radiographic periimplant bone remodeling will occur for implants using external hexagon, regardless of the presence of retention elements at the implant crestal module.

Asunto(s)

RESUMEN

OBJECTIVES: To explore the feasibility of a 3D-microleakage protocol for the evaluation of various configurations of adhesive-tooth interfaces. METHODS: Three different kinds of specimens were prepared: (1) a Class-I composite restoration placed without any bonding to maximize gap formation at the interface; (2) a glass-fiber post cemented with a self-adhesive composite cement into a prepared root canal; and (3) inlay MOD composite restorations placed with either a 1-step self-adhesive or a 2-step etch-and-rinse composite cement. After silver-nitrate (AgNO3) infiltration, the specimens were scanned using a Skyscan 1172 X-ray microtomograph (µCT; Skyscan Bruker) at 100kV, 100µA and 7.8-9.5µm resolution. Projection images were reconstructed, after which maximum-intensity projections (MIPs) and 3D-volumetric renderings were produced. For the inlays, an additional conventional stereomicroscopic (SM) microleakage evaluation was accomplished after specimen sectioning. RESULTS: MIPs and 3D-renderings from specimens (1) and (2) revealed strongly varying microleakage patterns along the marginal gap/interface. For the specimens of setup (3), the high radiopacity of the 2-step composite cement hindered evaluation of the MIPs. MIP-microleakage patterns along the enamel margin of the restoration cemented with the 1-step composite cement corresponded well to the stereomicroscopic images. SIGNIFICANCE: The reported µCT-protocol revealed good sensitivity to detect AgNO3 infiltration at the adhesive-tooth interface when considerable microleakage was present. When microleakage was less apparent and spread in a more diffuse pattern, evaluation with µCT was less sensitive compared to stereomicroscopic evaluation.

Asunto(s)

RESUMEN

BACKGROUND: It is not yet well understood to what extent different implant-abutment mismatch sizes and implant-abutment connection types may influence the peri-implant biomechanical environment of implants in different clinical situations. METHODS: Computed tomography-based finite element models comprising a maxillary central incisor socket and 4.5 × 13 mm outer-diameter implants with external and internal hex connection types were constructed. The abutments were designed with diameters of 3.5 mm (platform switching [PS] with 1 mm of diametral mismatch [PS - 1]), 4.0 mm (PS with 0.5 mm of diametral mismatch [PS - 0.5]), and 4.5 mm (conventional matching implant-abutment design [CD]). Analysis of variance at the 95% confidence interval was used to evaluate peak equivalent strain (EQV strain) in the bone, bone volume affected by a strain >4,000 µÎµ (EQV strain >4,000 µÎµ), the peak von Mises stress (EQV stress) in abutment screw, and the bone-implant relative displacement. RESULTS: Similar bone strain levels (EQV strain and EQV strain >4,000 µÎµ) were encountered in PS - 1, PS - 0.5, and CD models for immediately placed implants, independent of the connection type. For immediately loaded implants, slightly smaller peak EQV strain and EQV strain >4,000 µÎµ were found for PS - 1. However, for both connection types in osseointegrated models, the higher the mismatch size, the lesser the amount of strain found. CONCLUSIONS: The increase in mismatch size of PS configuration results in a significant decrease of strain levels in bone for osseointegrated implants, principally for external hex connections. No significant effect of PS could be noted in immediately placed implants.

Asunto(s)

RESUMEN

The long-term success of a cementless total hip arthroplasty depends on the implant geometry and interface bonding characteristics (fit, coating and ingrowth) and on stem stiffness. This study evaluates the influence of stem geometry and fitting conditions on the evolution and distribution of the bone-stem contact, stress and strain during and after the hip stem insertion, by means of dynamic finite element techniques. Next, the influence of the mechanical state (bone-stem contact, stress and strain) resulted from the insertion process on the stem initial resistance to subsidence is investigated. In addition, a study on the influence of bone-stem interface conditions (friction) on the insertion process and on the initial stem stability under physiological loading is performed. The results indicate that for a stem with tapered shape the contact in the proximal part of the stem was improved, but contact in the calcar region was achieved only when extra press-fit conditions were considered. Changes in stem geometry towards a more tapered shape and extra press fit and variation in the bone-stem interface conditions (contact amount and high friction) led to a raise in the total insertion force. A direct positive relationship was found between the stem resistance to subsidence and stem geometry (tapering and press fit), bone-stem interface conditions (bone-stem contact and friction interface) and the mechanical status at the end of the insertion (residual stress and strain). Therefore, further studies on evaluating the initial performance of different stem types should consider the parameters describing the bone-stem interface conditions and the mechanical state resulted from the insertion process.

Asunto(s)

RESUMEN

BACKGROUND: Strain, frequency, loading time, and strain rate, among others, determine mechanical parameters in osteogenic loading. We showed a significant osteogenic effect on bone mass (BM) by daily peri-implant loading at 1.600µÎµ.s(-1) after 4 weeks. PURPOSE: To study the peri-implant osteogenic effect of frequency and strain in the guinea pig tibia by in vivo longitudinal micro-computed tomography (CT) analysis. MATERIAL AND METHODS: One week after implant installation in both hind limb tibiae, one implant was loaded daily for 10' during 4 weeks, while the other served as control. Frequencies (3, 10, and 30Hz) and strains varied alike in the three series to keep the strain rate constant at 1.600µÎµ.s(-1) . In vivo micro-CT scans were taken of both tibiae: 1 week after implantation but before loading (v1) and after 2 (v2) and 4 weeks (v3) of loading as well as postmortem (pm). BM (BM (%) bone-occupied area fraction) was calculated as well as the difference between test and control sides (delta BM) RESULTS: All implants (n=78) were clinically stable at 4 weeks. Significant increase in BM was measured between v1 and v2 (p<.0001) and between v1 and v3 (p<.0001). A significant positive effect of loading on delta BM was observed in the distal peri-implant marrow 500 Region of Interest already 2 weeks after loading (p=.01) and was significantly larger (11%) in series 1 compared with series 2 (p=.006) and 3 (p=.016). CONCLUSIONS: Within the constraints of constant loading time and strain rate, the effect of early implant loading on the peri-implant bone is strongly dependent on strain and frequency. This cortical bone model has shown to be most sensitive for high force loading at low frequency.

Asunto(s)

RESUMEN

Um fator-chave para a previsibilidade dos protocolos de utilização de implantes é o desenvolvimento de designs de implantes, conexões protéticas e materiais de próteses que sejam capazes de promover estabilidade sob as cargas mastigatórias regulares. Entretanto, o elaborado design dos implantes e sua relação com os tecidos de suporte e as restaurações protéticas impedem o uso de fórmulas analíticas simples para avaliação dos efeitos de cargas externas sob as tensões internas e deslocamentos. Nestes tipos de análises, o método em elementos finitos (MEF) tem proporcionado informações valiosas, a um custo operacional e investimento de tempo relativamente baixos. Na Implantodontia, a análise em elementos finitos (AEF) tem sido aplicada para prever o comportamento biomecânico de diversos designs de implantes, cenários clínicos e designs de próteses. Estas informações podem ser posteriormente aplicadas na otimização de designs de implantes em função dos parâmetros biomecânicos benéficos ao osso peri-implantar. Neste sentido, considerando especialmente as recentes mudanças nos protocolos clínicos de uso dos implantes, AEF individualizadas ou com modelagens complexas e detalhadas podem contribuir na tomada de decisões clínicas mais precisas, minimizando os riscos de falha dos tratamentos...

A key factor for the predictability and long-term success of implant treatment is the development of implants and prosthesis designs providing sufficient biomechanical stability, under masticatory standard loading. However, the intricate design of the implants and their relationship with the supporting tissues and prosthetic restoration prevent the use of simple analytical formulas for the evaluation of the effect of external loading on the internal stresses and displacements. In these analysis types, the fi nite element method has provided valuable data, for a relatively low operational cost and time investment. In Implantology, FEA has been applied to predict the biomechanical behavior of various implant designs, clinical scenarios and prosthesis designs. This information may be further applied in the optimization of implant designs as a function of the biomechanical parameters beneficial to the peri-implant bone. In this way, especially considering the recent changes in osseointegrated implant usage clinical protocols, individualized FEA can contribute to more accurate treatment decisions, diminishing the risks of implant failure...

Asunto(s)

RESUMEN

PURPOSE: To evaluate the influence of different implant designs on the biomechanical environment of immediately placed implants. MATERIALS AND METHODS: Computed tomography (CT)-based finite element models comprising a maxillary central incisor socket and four commercially available internal-connection implants (SIN SW, 3i Certain, Nobel Replace, and ITI Standard) of comparable diameters and lengths were constructed. Biomechanical scenarios of immediate placement, immediate loading, and delayed loading protocols were simulated. Analysis of variance at the 95% confidence level was used to evaluate peak equivalent strain (EQV strain) in bone and bone-to-implant relative displacement. RESULTS: Loading magnitude (77.6%) and the clinical situation (15.0%) (ie, presence or absence of an extraction socket defect, condition of the bone-to-implant interface) presented the highest relative contributions to the results. Implant design contributed significantly to strains and displacements in the immediate placement protocol. Whereas a greater contribution of implant design was observed for strain values and distributions for immediately placed and immediately loaded protocols, a smaller contribution was observed in the delayed loading scenario. CONCLUSION: Implant design contributes significantly to changing biomechanical scenarios for immediately placed implants. The results also suggest that avoiding implant overloading and ensuring high primary implant stability are critical in encouraging the load-bearing capability of immediately placed implants.

Asunto(s)

RESUMEN

Elastic modulus and strength of trabecular bone are negatively affected by osteoporosis and other metabolic bone diseases. Micro-computed tomography-based beam models have been presented as a fast and accurate way to determine bone competence. However, these models are not accurate for trabecular bone specimens with a high number of plate-like trabeculae. Therefore, the aim of this study was to improve this promising methodology by representing plate-like trabeculae in a way that better reflects their mechanical behavior. Using an optimized skeletonization and meshing algorithm, voxel-based models of trabecular bone samples were simplified into a complex structure of rods and plates. Rod-like and plate-like trabeculae were modeled as beam and shell elements, respectively, using local histomorphometric characteristics. To validate our model, apparent elastic modulus was determined from simulated uniaxial elastic compression of 257 cubic samples of trabecular bone (4mm×4mm×4mm; 30µm voxel size; BIOMED I project) in three orthogonal directions using the beam-shell models and using large-scale voxel models that served as the gold standard. Excellent agreement (R(2)=0.97) was found between the two, with an average CPU-time reduction factor of 49 for the beam-shell models. In contrast to earlier skeleton-based beam models, the novel beam-shell models predicted elastic modulus values equally well for structures from different skeletal sites. It allows performing detailed parametric analyses that cover the entire spectrum of trabecular bone microstructures.

Asunto(s)

RESUMEN

PURPOSE: To evaluate the influence of platform switching on the biomechanical environment of implants in different placement and loading protocols. MATERIALS AND METHODS: A computed tomography-based finite element model of a maxillary central incisor extraction socket was constructed containing a conical 13-mm external-hex implant with a 4.3-mm-diameter shoulder. Abutment models that were 4.3 mm and 3.8 mm in diameter were then imported and aligned to the implant. The 4.3-mm abutment edge matched perfectly the edge of the implant shoulder, while the 3.8-mm abutment assumed a platform-switching configuration. Then, immediately placed, immediately loaded, and osseointegrated (ie, conventional delayed loaded) protocols were simulated. Analysis of variance was used to interpret the data for peak equivalent strain (EQV strain) in the bone, bone-to-implant relative displacement, peak von Mises stress (EQV stress) in the abutment screw, and implant-abutment gap. RESULTS: In the same clinical situation, the differences in the values of the assessed results were minor for abutments of different diameters. In addition, no statistically significant influence of the abutment diameter was seen on any of the evaluated biomechanical parameters, except for the bone-to-implant displacement, although this was observed in a rather low percentage. Nevertheless, a slightly higher EQV stress in the abutment screw was seen in all cases for the 3.8-mm-diameter abutment, although this was not statistically significant. CONCLUSION: Within the limitation of this finite element analysis, it can be concluded that a circumferential horizontal mismatch of 0.5 mm does not make an important contribution to the biomechanical environment of implants. Also, there seems to be no significant biomechanical drawback to the design rationale of reducing the abutment diameter to move the implant-abutment gap area away from the implant-bone interface.

Asunto(s)

RESUMEN

OBJECTIVES: To optimize a microtomographic (micro-CT) technique to quantitatively evaluate the effectiveness of contemporary caries-excavation techniques. METHODS: A beam-hardening curve was obtained from an initial reconstruction of a wedge-shaped hydroxyapatite (HAp) block and fitted with a 5th order polynomial function, after which each micro-CT tooth slice was corrected accordingly. Calibration of the 8-bit gray values into mineral-density values was obtained by scanning, reconstructing and processing volume of interests (VOIs) of HAp phantoms with different mineral densities (0.25, 0.75, 3.14g/cm(3)). One carious tooth was scanned before and after caries removal with an experimental enzyme-based gel. After reconstruction, a 3D-median filter was applied to each micro-CT slice, and a connected threshold grower algorithm was used to blank-out undesired structures in each slice. Volume rendering with a look-up-table (LUT), based on mineral densities, was accomplished for the tooth before and after caries removal. Finally, the actual volume of excavated tissue was quantified. RESULTS: Correction for beam hardening produced tooth slices with relatively homogeneous gray values along the whole area of enamel and dentin. Accurate mineral-density values were obtained for enamel, dentin and carious regions (2.89, 1.74 and 0.27g/cm(3), respectively). After pre-processing (3D-median filtering and connected threshold grower algorithm), acceptable segmentation of carious dentin based on gray values was accomplished (Otsu method, gray value=75 or mineral density=1.12g/cm(3)), from which quantitative volumetric parameters were calculated. SIGNIFICANCE: Accurate calibration, standardization of scanning and reconstruction steps and adequate pre-processing of micro-CT slices allowed detailed volumetric calculation of caries-excavation techniques.

Asunto(s)

RESUMEN

The first objective of this computational study was to assess the strain magnitude and distribution within the three-dimensional (3D) trabecular bone structure around an osseointegrated dental implant loaded axially. The second objective was to investigate the relative micromotions between the implant and the surrounding bone. The work hypothesis adopted was that these virtual measurements would be a useful indicator of bone adaptation (resorption, homeostasis, formation). In order to reach these objectives, a microCT-based finite element model of an oral implant implanted into a Berkshire pig mandible was developed along with a robust software methodology. The finite element mesh of the 3D trabecular bone architecture was generated from the segmentation of microCT scans. The implant was meshed independently from its CAD file obtained from the manufacturer. The meshes of the implant and the bone sample were registered together in an integrated software environment. A series of non-linear contact finite element (FE) analyses considering an axial load applied to the top of the implant in combination with three sets of mechanical properties for the trabecular bone tissue was devised. Complex strain distribution patterns are reported and discussed. It was found that considering the Young's modulus of the trabecular bone tissue to be 5, 10 and 15GPa resulted in maximum peri-implant bone microstrains of about 3000, 2100 and 1400. These results indicate that, for the three sets of mechanical properties considered, the magnitude of maximum strain lies within an homeostatic range known to be sufficient to maintain/form bone. The corresponding micro-motions of the implant with respect to the bone microstructure were shown to be sufficiently low to prevent fibrous tissue formation and to favour long-term osseointegration.

Asunto(s)

RESUMEN

PURPOSE: The purpose of the present study was to evaluate the biomechanical environment of immediately placed implants, before and after osseointegration, by comparing three different implant-abutment connection types. MATERIALS AND METHODS: A computer tomography-based finite element model of an upper central incisor extraction socket was constructed containing implants with either external hex, internal hex, or Morse-taper connection. Frictional contact elements were used in the bone, implant, abutment, and abutment screw interfaces in the immediately placed simulations. In osseointegrated simulations, the repair of bone alveolar defect and a glued bone-to-implant interface were assumed. By analysis of variance, the influence was assessed of connection type, clinical situation, and loading magnitude on the peak equivalent strain in the bone, peak von Mises stress in the abutment screw, bone-to-implant relative displacement, and abutment gap. RESULTS: The loading magnitudes had a significant contribution, regardless of the assessed variable. However, the critical clinical situation of an immediately placed implant itself was the main factor affecting the peak equivalent strain in the bone and bone-to-implant displacement. The largest influence of the connection type in this protocol was seen on the peak equivalent stress in the abutment screw. On the other hand, a higher influence of the various connection types on bone stress/strain could be noted in osseointegrated simulations. CONCLUSIONS: The implant-abutment connection design did not significantly influence the biomechanical environment of immediately placed implants. Avoiding implant overloading and ensuring a sufficient initial intraosseous stability are the most relevant parameters for the promotion of a safe biomechanical environment in this protocol.

Asunto(s)

RESUMEN

O objetivo deste trabalho foi avaliar a influência do desenho do implante nas micromovimentações de implantes imediatos com carga imediata. Modelos em elementos finitos de um alvéolo de extração de um incisivo central superior e quatro desenhos de implantes de conexão interna, disponíveis comercialmente (SIN SW®, 3i Certain®, Nobel ReplaceTM e RN synOcta® ITI Standard), com diâmetros e comprimentos semelhantes foram construídos. Cargas de 50, 100 e 200 N foram aplicadas sobre os implantes. ANOVA com nível de 95% de significância foi utilizada para avaliar os dados da micromovimentação dos implantes. O design do implante influencia significativamente (31,21%) a micromovimentação de implantes imediatos com carga imediata. Não obstante, a intensidade da carga aplicada (68,80%) é o fator mais importante na estabilidade dos implantes neste protocolo.

The purpose of this paper was to evaluate the influence of different implant designs on the micromovements of immediately placed implants. CT-based finite element models comprising an upper central incisor socket and four commercially available internal connection implant designs (SIN SW®, 3i Certain®, Nobel ReplaceTM, and RN synOcta® ITI Standard) of comparable diameter and length were constructed. 50, 100 and 200N magnitude loads were applied over the implant. ANOVA at 95% level of significance was used to evaluate bone to implant relative displacement (micromovements). The implant design (68,80%) greatly influences the micromovement of immediately placed implants. However, the loading magnitude (68,80%) is the most important factor regarding the implant stability in this protocol.

Asunto(s)

RESUMEN

Objetivo: o objetivo do presente estudo foi analisar o ambiente biomecânico de implantes imediatos com carga imediata, comparando 3 diferentes magnitudes de carga. Material e Métodos: um modelo em elementos finitos de um incisivo central superior contendo um implante cônico de 13 mm de comprimento e 4,5 mm de plataforma, hexágono interno, foi construído. Elementos de contato friccional foram utilizados para simular as interfaces entre o osso, implante, abutment e parafuso do abutment. Foram aplicadas forças de 50, 100 e 200 N na extremidade superior do abutment. Os dados para a deformação equivalente no osso, as tensões equivalentes no parafuso, deslocamento relativo osso-implante e gap do abutment foram calculados. Resultados/Conclusão: a magnitude das cargas aplicadas sobre os implantes imediatos com carga imediata influenciam significativamente o ambiente biomecânico deste protocolo.

Objective: the purpose of the present study was to evaluate the biomechanical environment of immediately placed implants, by comparing three different loading magnitudes. Material and Methods: a CT-based finite element model of an upper central incisor extraction socket was constructed containing a conical internal hex 13-mm implant. Frictional contact elements were used in the bone, implant, abutment and abutment screw interfaces. Forces of 50, 100 and 200 N were applied on the superior central region of the abutment. Data for the peak equivalent strain in the bone, peak Von Mises stress in the abutment screw, bone-to-implant relative displacement and abutment gap were calculated. Results/Conclusion: the loading magnitudes applied over the implants are capable to greatly influence the biomechanical environment in immediately placed protocol.

Asunto(s)

RESUMEN

PURPOSE: The objective of this study was to examine whether one-step self-etching adhesives (1-SEAs) really have an advantage over multistep systems. MATERIALS AND METHODS: Nine one-step self-etching adhesives (Absolute, Adper Prompt L-Pop, Clearfil S3 Bond, G-Bond, Hybrid Bond, iBond, One-up Bond F Plus, Optibond All-in-one and Xeno III) were included in this study. One two-step self-etching adhesive (Clearfil SE Bond) and one three-step etch-and-rinse adhesive (Optibond FL) served as controls. Their microtensile bond strength to bur-cut enamel and dentin was determined using a standardized protocol and the respective adhesive/dentin interface of these adhesives was characterized by transmission electron microscopy. Statistical analysis was performed with the Kruskal-Wallis nonparametric test. RESULTS: Regarding bond strength, the control adhesives tended to perform superior to the one-step adhesives. However, a significant difference between the control adhesives and some one-step adhesives could not always be demonstrated, partly due to the statistical setup of this study. Interface analysis by electron microscopy showed wide variation among the one-step adhesives, depending on their composition and their acidity. 1-SEAs also exhibited two different kinds of droplets, depending on their hydrophilicity. Hydrophobic HEMA-free 1-SEAs such as G-Bond were prone to phase separation, while especially HEMA-containing hydrophilic 1-SEAs, such as Clearfil S3 Bond and Xeno III were predisposed to forming osmosis-induced droplets. Hybrid bond, Absolute, and iBond featured both phase separation as well as osmosis. Optibond All-in-one exhibited a clustering reaction of the filler particles upon solvent evaporation. All adhesives including the control adhesives showed signs of nanoleakage, indicating that all adhesives are to some extent permeable to water. A definitive conclusion with regard to quantitative assessment of nanoleakage was much hindered by inconsistencies in the silver deposition. The application procedure of some 1-SEAs sometimes proved as elaborate and time consuming as those of the two-step adhesive Clearfil SE Bond. CONCLUSION: Considering bond strength and application procedure, 1-SEAs are not always a better alternative to multistep adhesives.

Asunto(s)

RESUMEN

BACKGROUND: The per-operative assessment of primary stem stability may help to improve the performance of total hip replacement. Vibration analysis methods have been successfully used to assess dental implant stability, to monitor fracture healing and to measure bone mechanical properties. The objective of the present study was to evaluate in vivo a vibration analysis-based endpoint criterion for the insertion of the stem by successive surgeon-controlled hammer blows. METHODS: A protocol using a vibration analysis technique for the characterisation of the primary bone-prosthesis stability was tested in 83 patients receiving a custom-made, intra-operatively manufactured stem prosthesis. Two groups were studied: one (n = 30) with non cemented and one (n = 53) with partially cemented stem fixation. Frequency response functions of the stem-femur system corresponding to successive insertion stages were compared. RESULTS: The correlation coefficient between the last two frequency response function curves was above 0.99 in 86.7% of the non cemented cases. Lower values of the final correlation coefficient and deviations in the frequency response pattern were associated with instability or impending bone fracture. In the cases with a partially cemented stem an important difference in frequency response function between the final stage of non cemented trial insertion and the final cemented stage was found in 84.9% of the cases. Furthermore, the frequency response function varied with the degree of cement curing. CONCLUSION: The frequency response function change provides reliable information regarding the stability evolution of the stem-femur system during the insertion. The protocol described in this paper can be used to accurately detect the insertion end point and to reduce the risk for intra-operative fracture.