Mouthguard Biomechanics for Protecting Dental Implants from Impact: Experimental and Finite Element Impact Analysis.

PURPOSE: The purpose of this study was to evaluate mouthguard shock absorption ability, strain, and stress generation during impact on dental implants placed in the anterior maxilla. The mouthguard material was also characterized. MATERIALS AND METHODS: Sixty experimental models were created and divided into six groups (n = 10): implant type, external hexagon (EH) and Morse taper (MT); without and with two mouthguards (MTG), EVA custom-fitted (Ct-MTG) and standard self-adapted (St-MTG). The Shore A hardness, EVA sheet and mouthguard thickness, and elastic modulus were measured to characterize the mouthguard material. A strain gauge was attached to the palatal surface of the implant abutment, which was subjected to an impact test. Distortion of the abutment and implant was determined after impact from centroid displacements in standardized radiographic images. Two-dimensional finite element models were created to represent the six groups and were submitted to nonlinear dynamic impact analysis. The data were statistically analyzed using analysis of variance (ANOVA) and Tukey test (α = .05). RESULTS: Ct-MTG resulted in higher Shore A hardness (P < .001). After the heat-forming process, the St-MTG maintained the original thickness, but the Ct-MTG thickness had decreased. The elastic modulus of EVA was 18.1 ± 0.5 MPa. The mouthguard presence reduced strain values significantly (P < .001), particularly for Ct-MTG. There was no significant difference between implant connection types EH and MT (P = .547). CONCLUSION: The external hexagon abutment resulted in higher stress and micro-displacement values. The mouthguard was able to absorb 40% to 46% of the energy caused by the impact on the dental implant.

Bone Remodeling Around Implants with External Hexagon and Morse-Taper Connections: A Randomized, Controlled, Split-Mouth, Clinical Trial.

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.

Influence of Connection Types and Implant Number on the Biomechanical Behavior of Mandibular Full-Arch Rehabilitation.

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.

Avaliação da estabilidade dos tecidos duros e moles em implantes imediatos com carga imediata em área estética: estudo clínico prospectivo longitudinal / Soft and hard tissue maintenance following placement of immediate-loaded implants in the aesthetic zone: a prospective longitudinal clinical trial

O objetivo desse trabalho foi avaliar, clínica e radiograficamente (bi/tridimensional), as alterações em tecidos moles e duros encontradas após a colocação de implantes imediatos com carga imediata em alvéolos pós-extração. Dez pacientes tratados com implantes imediatos com carga imediata nos incisivos central e lateral superiores foram incluídos. Parâmetros clínicos foram avaliados em fotografias padronizadas tiradas após a instalação do implante ( baseline ) e 1, 3 e 6 meses após. Parâmetros bi- e tridimensionais foram medidos em tomografias Cone-Beam, para avaliar a estabilidade do tecido ósseo na região vestibular. Também foram realizadas análises clínicas e fotográficas dos tecidos moles, para avaliar a sua estabilidade durante o período de avaliação. Não houve variações estatisticamente significativas nos parâmetros clínicos e radiográficos avaliados, tendo sido demonstrada uma manutenção de 94% do volume do osso vestibular. Implantes imediatos com carga imediata apresentam boa estabilidade dos tecidos moles e duros peri-implantares...

To evaluate by clinical and radiographic bi- and tridimensional means the soft and hard tissues alterations following immediate implant placement and loading in postextraction sockets in theanterior maxilla. Ten patients, treated with immediate-loaded implants in the maxillary central or lateral incisors, were evaluated in this study. Clinical parameters were evaluated in standardized pictures taken at baseline (immediately after), and 1, 3, and 6 months after provisional implant-supported single crown placement. Bi- and tridimensional radiographic parameters were evaluated from standardized digital periapical radiographies and from CBCT images. The volume of the buccal bone wall covering the central millimeter of the implant was also assessed in the CBCT images. The variation for all clinical, bi- and tridimensional parameters assessed was non-statistically significant. There was 94% maintenance of bone volume. The parameters assessed showed good clinical, bi- and tridimensional radiographic stability of soft and hard tissues for implants immediately placed and loaded in aesthetic zones...

Remodelação óssea de implantes com conexão hexágono externo e elementos de retenção no módulo da crista sob carregamento imediato – estudo clínico prospectivo longitudinal de um ano / Bone remodeling of implants with external hexagon connection and retention elements at the crestal module under immediate loading – a 1-year longitudinal prospective clinical trial

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.

Biomechanical evaluation of platform switching: different mismatch sizes, connection types, and implant protocols.

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.

Método de elementos finitos aplicado à Implantodontia / Applicability of finite element methods in Implantology

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...

Influence of implant design on the biomechanical environment of immediately placed implants: computed tomography-based nonlinear three-dimensional finite element analysis.

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.

Characterization of five different implant surfaces and their effect on osseointegration: a study in dogs.

BACKGROUND: Chemical modification of implant surface is typically associated with surface topographic alterations that may affect early osseointegration. This study investigates the effects of controlled surface alterations in early osseointegration in an animal model. METHODS: Five implant surfaces were evaluated: 1) alumina-blasting, 2) biologic blasting, 3) plasma, 4) microblasted resorbable blasting media (microblasted RBM), and 5) alumina-blasting/acid-etched (AB/AE). Surface topography was characterized by scanning electron microscopy and optical interferometry, and chemical assessment by x-ray photoelectron spectroscopy. The implants were placed in the radius of six dogs, remaining 2 and 4 weeks in vivo. After euthanization, specimens were torqued-to-interface failure and non-decalcified-processed for histomorphologic bone-implant contact, and bone area fraction-occupied evaluation. Statistical evaluation was performed by one-way analysis of variance (P <0.05) and post hoc testing by the Tukey test. RESULTS: The alumina-blasting surface presented the highest average surface roughness and mean root square of the surface values, the biologic blasting the lowest, and AB/AE an intermediate value. The remaining surfaces presented intermediate values between the biologic blasting and AB/AE. The x-ray photoelectron spectroscopy spectra revealed calcium and phosphorus for the biologic blasting and microblasted RBM surfaces, and the highest oxygen levels for the plasma, microblasted RBM, and AB/AE surfaces. Significantly higher torque was observed at 2 weeks for the microblasted RBM surface (P <0.04), but no differences existed between surfaces at 4 weeks (P >0.74). No significant differences in bone-implant contact and bone area fraction-occupied values were observed at 2 and 4 weeks. CONCLUSION: The five surfaces were osteoconductive and resulted in high degrees of osseointegration and biomechanical fixation.

Biomechanical evaluation of platform switching in different implant protocols: computed tomography-based three-dimensional finite element analysis.

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.

Influence of implant connection type on the biomechanical environment of immediately placed implants - CT-based nonlinear, three-dimensional finite element analysis.

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.

Effects of platelet-rich plasma on healing of alveolar socket: split-mouth histological and histometric evaluation in Cebus apella monkeys.

CONTEXT: The prediction of implant treatment is directly influenced by the quality of the remaining bone after tooth extraction. AIMS: The purpose of this experimental study was to, histologically and histometrically, evaluate the bone repair process in the central areas of extraction sockets filled with platelet-rich plasma. MATERIALS AND METHODS: Four young adult male Cebus apella monkeys were used. The extraction of both right and left inferior second premolars was accomplished. After extraction, in one of the extraction sockets, coagulum was maintained while in the other it was removed; the alveolus was dried with gauze compress and filled up with platelet concentrate. For PRP production, Sonnleitner's protocol was followed. The specimens for histological and histometric assessment were obtained in 30, 90, 120 and 180 days intervals. RESULTS: In 30 days new bone formation was intense in both experimental and control sockets and no significant differences were observed between the two groups. After 90 days of the extraction, while the control group showed signs of decrease in osteogenesis, in the experimental unit, the process of bone formation and fibroblast-like cell proliferation remained intense. After 120 days, the PRP treated socket was occupied by large trabeculae of bone. After 180 days, the control unit was occupied mostly with bone marrow. The experimental unit remained occupied with large amounts of bone tissue. CONCLUSIONS: It was possible to conclude that bone repair was enhanced by the use of platelet- rich plasma in alveolar sockets.