Background:
Implant-supported prostheses offer one possibility to provide an adequate prosthetic restoration for edentulous patients. For the mandible, the All-On-Four concept presents a well-established protocol for the implant positions, while the number of studies of the same concept in the maxilla is still limited. The number of implants for such a full arch restoration as well as their position is strongly affected by the bone quality and the anatomical situation, but still leaves some flexibility for the dentist. Nonetheless, number and position of the implants have a crucial influence on the biomechanical load transfer from the restoration into the surrounding alveolar bone.
Aim/Hypothesis:
It was the aim of the presented study to determine biomechanical loading patterns of the All-On-Four concept transferred to the maxilla using numerical methods. A special focus was on the change of these loading patterns depending on the positioning of the implants.
Material and Methods:
Finite element (FE) models of an edentulous maxilla were created based on a CT scan. On top of this maxilla mucosa was modelled using an optical scan of the corresponding mucosa of the same patient. Four implants (tioLogic®, length 13 mm, diameter 4.2 mm, Dentaurum, Germany) were modelled from CAD data and were placed in the model according to the All-On-Four concept: Two in the region of the upper lateral incisors, and two at the location of the upper second premolars. Three different FE models were created, each with a different insertion direction for the posterior implants, such that the implant heads were tilted distally in an angle of 30°, 35°, and 40°, respectively. An idealised framework was modelled on top of these implants for each of the FE models, and between implants and framework angled abutments were modelled. To investigate the loading pattern of each of the models, different loading situations were simulated: Total loads of 100 N and 400 N, respectively, were applied directly onto the framework, either equally distributed across all implant locations, only above the two anterior implants or above a single posterior implant. All simulations were performed twice, first assuming immediate loading (sliding contact between bone and implants), and second assuming full osseointegration of the implants. Stresses and displacements in the prosthetic restoration as well as stresses in the cortical and strains in the trabecular bone were registered.
Results:
Loading of the framework resulted in displacements of up to 35 µm (400 N on one lateral implant). Full osseointegration decreased the calculated displacements of the framework by 10% compared to immediate loading for the same model, and resulted in a noticeable reduction of stresses in the surrounding cortical bone (from 119 to 16 MPa for 400 N equally distributed on all implants) as well as in strains in the bone (from 5,840 to 850 µstrains). Especially for loading single posterior implants, the immediate loading resulted in strains of up to 48,800 µstrain, which is tenfold the typically assumed non-pathological load. With immediate loading, the different implant angulations resulted in different loading behaviour (stress in cortical bone: 81 MPa, 273 MPa and 65 MPa for 30°, 35° and 40°, respectively, for 400 N on the two anterior implants), but did not show different behaviour after osseointegration in the same model (16 MPa for all implant angulations).
Conclusions and clinical implications:
While the load determined for the immediate loading situation within the bone is rather high, the assumed maximum load of 400 N is not a common load regularly observed in the patient’s mouth. Special care has to be taken to ensure that full osseointegration can be obtained. The influence of the angulation of the posterior implants seems to decline after full osseointegration has been achieved.
Background:
Implant-supported prostheses offer one possibility to provide an adequate prosthetic restoration for edentulous patients. For the mandible, the All-On-Four concept presents a well-established protocol for the implant positions, while the number of studies of the same concept in the maxilla is still limited. The number of implants for such a full arch restoration as well as their position is strongly affected by the bone quality and the anatomical situation, but still leaves some flexibility for the dentist. Nonetheless, number and position of the implants have a crucial influence on the biomechanical load transfer from the restoration into the surrounding alveolar bone.
Aim/Hypothesis:
It was the aim of the presented study to determine biomechanical loading patterns of the All-On-Four concept transferred to the maxilla using numerical methods. A special focus was on the change of these loading patterns depending on the positioning of the implants.
Material and Methods:
Finite element (FE) models of an edentulous maxilla were created based on a CT scan. On top of this maxilla mucosa was modelled using an optical scan of the corresponding mucosa of the same patient. Four implants (tioLogic®, length 13 mm, diameter 4.2 mm, Dentaurum, Germany) were modelled from CAD data and were placed in the model according to the All-On-Four concept: Two in the region of the upper lateral incisors, and two at the location of the upper second premolars. Three different FE models were created, each with a different insertion direction for the posterior implants, such that the implant heads were tilted distally in an angle of 30°, 35°, and 40°, respectively. An idealised framework was modelled on top of these implants for each of the FE models, and between implants and framework angled abutments were modelled. To investigate the loading pattern of each of the models, different loading situations were simulated: Total loads of 100 N and 400 N, respectively, were applied directly onto the framework, either equally distributed across all implant locations, only above the two anterior implants or above a single posterior implant. All simulations were performed twice, first assuming immediate loading (sliding contact between bone and implants), and second assuming full osseointegration of the implants. Stresses and displacements in the prosthetic restoration as well as stresses in the cortical and strains in the trabecular bone were registered.
Results:
Loading of the framework resulted in displacements of up to 35 µm (400 N on one lateral implant). Full osseointegration decreased the calculated displacements of the framework by 10% compared to immediate loading for the same model, and resulted in a noticeable reduction of stresses in the surrounding cortical bone (from 119 to 16 MPa for 400 N equally distributed on all implants) as well as in strains in the bone (from 5,840 to 850 µstrains). Especially for loading single posterior implants, the immediate loading resulted in strains of up to 48,800 µstrain, which is tenfold the typically assumed non-pathological load. With immediate loading, the different implant angulations resulted in different loading behaviour (stress in cortical bone: 81 MPa, 273 MPa and 65 MPa for 30°, 35° and 40°, respectively, for 400 N on the two anterior implants), but did not show different behaviour after osseointegration in the same model (16 MPa for all implant angulations).
Conclusions and clinical implications:
While the load determined for the immediate loading situation within the bone is rather high, the assumed maximum load of 400 N is not a common load regularly observed in the patient’s mouth. Special care has to be taken to ensure that full osseointegration can be obtained. The influence of the angulation of the posterior implants seems to decline after full osseointegration has been achieved.
Background:
Implant-supported prostheses offer one possibility to provide an adequate prosthetic restoration for edentulous patients. For the mandible, the All-On-Four concept presents a well-established protocol for the implant positions, while the number of studies of the same concept in the maxilla is still limited. The number of implants for such a full arch restoration as well as their position is strongly affected by the bone quality and the anatomical situation, but still leaves some flexibility for the dentist. Nonetheless, number and position of the implants have a crucial influence on the biomechanical load transfer from the restoration into the surrounding alveolar bone.
Aim/Hypothesis:
It was the aim of the presented study to determine biomechanical loading patterns of the All-On-Four concept transferred to the maxilla using numerical methods. A special focus was on the change of these loading patterns depending on the positioning of the implants.
Material and Methods:
Finite element (FE) models of an edentulous maxilla were created based on a CT scan. On top of this maxilla mucosa was modelled using an optical scan of the corresponding mucosa of the same patient. Four implants (tioLogic®, length 13 mm, diameter 4.2 mm, Dentaurum, Germany) were modelled from CAD data and were placed in the model according to the All-On-Four concept: Two in the region of the upper lateral incisors, and two at the location of the upper second premolars. Three different FE models were created, each with a different insertion direction for the posterior implants, such that the implant heads were tilted distally in an angle of 30°, 35°, and 40°, respectively. An idealised framework was modelled on top of these implants for each of the FE models, and between implants and framework angled abutments were modelled. To investigate the loading pattern of each of the models, different loading situations were simulated: Total loads of 100 N and 400 N, respectively, were applied directly onto the framework, either equally distributed across all implant locations, only above the two anterior implants or above a single posterior implant. All simulations were performed twice, first assuming immediate loading (sliding contact between bone and implants), and second assuming full osseointegration of the implants. Stresses and displacements in the prosthetic restoration as well as stresses in the cortical and strains in the trabecular bone were registered.
Results:
Loading of the framework resulted in displacements of up to 35 µm (400 N on one lateral implant). Full osseointegration decreased the calculated displacements of the framework by 10% compared to immediate loading for the same model, and resulted in a noticeable reduction of stresses in the surrounding cortical bone (from 119 to 16 MPa for 400 N equally distributed on all implants) as well as in strains in the bone (from 5,840 to 850 µstrains). Especially for loading single posterior implants, the immediate loading resulted in strains of up to 48,800 µstrain, which is tenfold the typically assumed non-pathological load. With immediate loading, the different implant angulations resulted in different loading behaviour (stress in cortical bone: 81 MPa, 273 MPa and 65 MPa for 30°, 35° and 40°, respectively, for 400 N on the two anterior implants), but did not show different behaviour after osseointegration in the same model (16 MPa for all implant angulations).
Conclusions and clinical implications:
While the load determined for the immediate loading situation within the bone is rather high, the assumed maximum load of 400 N is not a common load regularly observed in the patient’s mouth. Special care has to be taken to ensure that full osseointegration can be obtained. The influence of the angulation of the posterior implants seems to decline after full osseointegration has been achieved.
Background:
Implant-supported prostheses offer one possibility to provide an adequate prosthetic restoration for edentulous patients. For the mandible, the All-On-Four concept presents a well-established protocol for the implant positions, while the number of studies of the same concept in the maxilla is still limited. The number of implants for such a full arch restoration as well as their position is strongly affected by the bone quality and the anatomical situation, but still leaves some flexibility for the dentist. Nonetheless, number and position of the implants have a crucial influence on the biomechanical load transfer from the restoration into the surrounding alveolar bone.
Aim/Hypothesis:
It was the aim of the presented study to determine biomechanical loading patterns of the All-On-Four concept transferred to the maxilla using numerical methods. A special focus was on the change of these loading patterns depending on the positioning of the implants.
Material and Methods:
Finite element (FE) models of an edentulous maxilla were created based on a CT scan. On top of this maxilla mucosa was modelled using an optical scan of the corresponding mucosa of the same patient. Four implants (tioLogic®, length 13 mm, diameter 4.2 mm, Dentaurum, Germany) were modelled from CAD data and were placed in the model according to the All-On-Four concept: Two in the region of the upper lateral incisors, and two at the location of the upper second premolars. Three different FE models were created, each with a different insertion direction for the posterior implants, such that the implant heads were tilted distally in an angle of 30°, 35°, and 40°, respectively. An idealised framework was modelled on top of these implants for each of the FE models, and between implants and framework angled abutments were modelled. To investigate the loading pattern of each of the models, different loading situations were simulated: Total loads of 100 N and 400 N, respectively, were applied directly onto the framework, either equally distributed across all implant locations, only above the two anterior implants or above a single posterior implant. All simulations were performed twice, first assuming immediate loading (sliding contact between bone and implants), and second assuming full osseointegration of the implants. Stresses and displacements in the prosthetic restoration as well as stresses in the cortical and strains in the trabecular bone were registered.
Results:
Loading of the framework resulted in displacements of up to 35 µm (400 N on one lateral implant). Full osseointegration decreased the calculated displacements of the framework by 10% compared to immediate loading for the same model, and resulted in a noticeable reduction of stresses in the surrounding cortical bone (from 119 to 16 MPa for 400 N equally distributed on all implants) as well as in strains in the bone (from 5,840 to 850 µstrains). Especially for loading single posterior implants, the immediate loading resulted in strains of up to 48,800 µstrain, which is tenfold the typically assumed non-pathological load. With immediate loading, the different implant angulations resulted in different loading behaviour (stress in cortical bone: 81 MPa, 273 MPa and 65 MPa for 30°, 35° and 40°, respectively, for 400 N on the two anterior implants), but did not show different behaviour after osseointegration in the same model (16 MPa for all implant angulations).
Conclusions and clinical implications:
While the load determined for the immediate loading situation within the bone is rather high, the assumed maximum load of 400 N is not a common load regularly observed in the patient’s mouth. Special care has to be taken to ensure that full osseointegration can be obtained. The influence of the angulation of the posterior implants seems to decline after full osseointegration has been achieved.