- Email: [email protected]
INFLUENCE OF IMPLANT POSITION ON THE BEHAVIOUR OF A MANDIBULAR IMPLANT-RETAINED OVERDENTURE
Presentation O-215
S218
Dental Biomechanics
INFLUENCE OF IMPLANT POSITION ON THE BEHAVIOUR OF A MANDIBULAR IMPLANT-RETAINED OVERDENTURE Anne-Sophie Bonnet (1), Guillaume Dubois (2), Marwan Daas (3), Paul Lipinski (1)
1. Laboratory of Mechanical Reliability, ENIM, France; 2. Laboratory of Physics and Mechanics of Materials, ENIM, OBL, France; 3. Department of Prosthetic Dentistry, René Descartes University, France.
Introduction
Results
A possible solution to total edentulism is the mandibular implant-retained overdenture. This one is supported by two implants linked to the overdenture by specific attachments. Among the numerous prosthetic parameters that have to be defined to optimize the therapeutic solution, implant positioning is of major importance. The most common position is situated around canines as a high bone volume is associated to a sufficient lingual prosthetic one in this area. However, when this choice in not possible, an incisor or a premolar position is adopted. The aim of the present work is to analyse the effect of this positioning on the global and local behaviour of the overdenture.
As already mentioned in previous studies [Daas, in press], the main interest of this type of overdenture is the significant part of the mastication force transiting through the mucosa, leading thus to a weak loading of the implants. Figure 1 illustrates the force repartition between the implants and the mucosa for each implant position. 30
Vertical force (N)
10 -10 -30
work.side imp. non work.side imp
-50 -70 -90
Methods The geometry of a willed edentulous patient’s mandible and overdenture was obtained, thanks to a computered tomography exam. The geometry was meshed with HyperMesh software. The bone was modelled as an isotropic material after a preliminary study indicating that the influence of anisotropy was neglectable for this type of overdenture. A constant layer of cortical bone around a cancellous bone core was considered in the interforaminal region. Care was taken at the mesh size and quality in the bone surrounding implant areas. In the rest of the mandible, the bone was modelled as a homogeneous material considering the proportions of cortical and cancellous bone. The mucosa, the implants and the ball attachments were also added to the model and meshed. Contact was managed between the mucosa and the overdenture, between both parts of the attachments and at the temporo-mandibular joint. The muscular action was provided according to the previous study of [Daas, in press] to engender a mastication force of 100N on the food-simulating obstacle placed on first molar. Three different implant positions were considered: around incisors, canines and premolars. All calculations were carried out with MSC/Marc software.
mucosa
-110
incisor canine premolar
Figure 1: Repartition of mastication force between implants and mucosa. The values of maximal axial stress in the bone surrounding implant (on the working side) are also reported in Table 1. The smallest bending and compression stresses are obtained in the canine configuration. Stresses inside Incisor Canine Premolar bone (MPa) Bending 63 44,5 60,5 Compression -2 -1,5 -12,5 Total -65/+61 -46/+43 -73/+48 Table 1:Values of maximal bending, compression and total axial stresses at bone-implant interface(working side)
Discussion The calculations reveal that the canine position is the most favourable for implants position in terms of bone stresses and part of mastication force transiting through mucosa. Other results highlight a great difference in the overdenture mobility as a function of implants position.
References Daas et al, Med. Eng. & Physics, In Press, 2007.
Journal of Biomechanics 41(S1)
16th ESB Congress, Oral Presentations, Wednesday 9 July 2008
S218
Dental Biomechanics
INFLUENCE OF IMPLANT POSITION ON THE BEHAVIOUR OF A MANDIBULAR IMPLANT-RETAINED OVERDENTURE Anne-Sophie Bonnet (1), Guillaume Dubois (2), Marwan Daas (3), Paul Lipinski (1)
1. Laboratory of Mechanical Reliability, ENIM, France; 2. Laboratory of Physics and Mechanics of Materials, ENIM, OBL, France; 3. Department of Prosthetic Dentistry, René Descartes University, France.
Introduction
Results
A possible solution to total edentulism is the mandibular implant-retained overdenture. This one is supported by two implants linked to the overdenture by specific attachments. Among the numerous prosthetic parameters that have to be defined to optimize the therapeutic solution, implant positioning is of major importance. The most common position is situated around canines as a high bone volume is associated to a sufficient lingual prosthetic one in this area. However, when this choice in not possible, an incisor or a premolar position is adopted. The aim of the present work is to analyse the effect of this positioning on the global and local behaviour of the overdenture.
As already mentioned in previous studies [Daas, in press], the main interest of this type of overdenture is the significant part of the mastication force transiting through the mucosa, leading thus to a weak loading of the implants. Figure 1 illustrates the force repartition between the implants and the mucosa for each implant position. 30
Vertical force (N)
10 -10 -30
work.side imp. non work.side imp
-50 -70 -90
Methods The geometry of a willed edentulous patient’s mandible and overdenture was obtained, thanks to a computered tomography exam. The geometry was meshed with HyperMesh software. The bone was modelled as an isotropic material after a preliminary study indicating that the influence of anisotropy was neglectable for this type of overdenture. A constant layer of cortical bone around a cancellous bone core was considered in the interforaminal region. Care was taken at the mesh size and quality in the bone surrounding implant areas. In the rest of the mandible, the bone was modelled as a homogeneous material considering the proportions of cortical and cancellous bone. The mucosa, the implants and the ball attachments were also added to the model and meshed. Contact was managed between the mucosa and the overdenture, between both parts of the attachments and at the temporo-mandibular joint. The muscular action was provided according to the previous study of [Daas, in press] to engender a mastication force of 100N on the food-simulating obstacle placed on first molar. Three different implant positions were considered: around incisors, canines and premolars. All calculations were carried out with MSC/Marc software.
mucosa
-110
incisor canine premolar
Figure 1: Repartition of mastication force between implants and mucosa. The values of maximal axial stress in the bone surrounding implant (on the working side) are also reported in Table 1. The smallest bending and compression stresses are obtained in the canine configuration. Stresses inside Incisor Canine Premolar bone (MPa) Bending 63 44,5 60,5 Compression -2 -1,5 -12,5 Total -65/+61 -46/+43 -73/+48 Table 1:Values of maximal bending, compression and total axial stresses at bone-implant interface(working side)
Discussion The calculations reveal that the canine position is the most favourable for implants position in terms of bone stresses and part of mastication force transiting through mucosa. Other results highlight a great difference in the overdenture mobility as a function of implants position.
References Daas et al, Med. Eng. & Physics, In Press, 2007.
Journal of Biomechanics 41(S1)
16th ESB Congress, Oral Presentations, Wednesday 9 July 2008