9. The Inclination Angle on the Axial
Surface of Coping affects the stress distribution of the abutment tooth for Overdentures
D.Yamanaka1, T.Ohyama1,2,
Y.Katakura1, E.Nagai1,2, S. Nakabayashi1 and
T.Ishigami1,2
1 Department of Partial Denture Prosthodontics, Nihon University School of Dentistry, Japan
2 Division of
Clinical ResearchCDental Research CenterCNihon University School of Dentistry, Japan
Introduction
In case of
minority residual teeth, the overdenture is designed
for maintenance of the abutment tooth and the residual ridge and stability of
occlusion. When a coping is applied to the abutment tooth for overdenture, the shape of coping may affect the stress
distribution of an abutment tooth and the circumferencial
tissue. In this study, the interaction between the difference of the
inclination angle on the axial surface and the stress distribution and displacement
direction on the abutment tooth under the vertical load was examined by using three-dimensional
finite element method.
Materials and Methods
The complete overdenture model with the coping was setting on the mandibular right canine, was evaluated. The abutment tooth
was assembled of inclined 15 degrees from occlusal
plane. The outline of the abutment tooth and mandible were modeled based on the
data from multi detector CT (Asteion Super4 Edition,
Toshiba, Japan). Periodontal ligament, cortical bone, cancellous
bone, and alveolar mucosa shapes were modeled referred to anatomical
measurement. The analysis models were constructed tooth, cortical bone, cancellous bone, periodontal ligament, alveolar mucosa,
denture base and coping. This study was used the Rhinoceros (Version 1.0,
Robert McNeil & Associates, USA) and ANSYS (Version 11.0, Ansys Inc, USA).
Table 1 shows the
Young modulus and Poissonfs ratio. Three kinds of the inclination angle (0, 30,
45 degrees) on the axial surface of the coping were designed. The height of the
coping was 1 mm from the lingual alveolar crest, and the top surface was set to
the parallel of occlusal plane (Fig.1). The loading
condition was set up the vector of muscular contraction of the chewing
movement.
Table 1
Fig.1
Table 2 shows the quantity of loading conditions.
Table 2
Fig.2 shows the loading directions with arrows. Ten occlusal stops at the intercuspal position and the upper part of the condyle bilaterally was restrained completely on the designed models. Fig.3 shows the restricted positions with circles. Stress levels were calculated under the minimum principal stress on the surface of cortical bone. Vector of the movements were calculated on the six points of the surface of abutment tooth.
Fig.2
Fig.3
Results
Fig.4 shows the
stress distribution of the abutment tooth (2D stress contour plots) and the
stress distribution graph of the top surface of cortical bone. The stress
concentration was detected on the labial and lingual side of the abutment
tooth, but there were no significant differences about the stress distribution
and displacement direction on three kinds of analysis models. The displacement
of abutment tooth was correlated the elevated inclination angle on the axial
surface was increased slightly.
Fig.4
Discussions
The influence of
the difference of the inclination angle on axial surface of the coping was no
apparent, because the load was vertical for the attractive surface of coping
and the height of the coping was short.
Conclusions
According to the results, there were no significant differences about both the stress distribution and displacement direction on three kinds of the inclination angle (0, 30, 45 degrees) on the axial surface of the coping under the vertical load.
Acknowledgement
This study was
supported in part by Sato Fund, Nihon University School of Dentistry (2007).
References
1. Korioth TW, Hannam AG Deformation of the human mandible during simulated tooth clenching, J Dent Res 73:56-66, 1994
2.
Yuusuke Katakura,
Influence of the Angle of Attractive Surface of Root Cap Affect Abutment Tooth
for Overdenture, JJ Mag
Dent 17(2): 31-34,2008