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Research Papers

Remodeling of the Mandibular Bone Induced by Overdentures Supported by Different Numbers of Implants

[+] Author and Article Information
Kai Li

State Key Laboratory of Military Stomatology,
Department of Prosthodontics,
Stomatology School,
Fourth Military Medical University,
145 Changle Xi Road,
Xi'an 710032, China
e-mail: 54918808@qq.com

Haitao Xin

State Key Laboratory of Military Stomatology,
Department of Prosthodontics,
Stomatology School,
Fourth Military Medical University,
145 Changle Xi Road,
Xi'an 710032, China
e-mail: xhthmj@fmmu.edu.cn

Yanfang Zhao

State Key Laboratory of Military Stomatology,
Department of Prosthodontics,
Stomatology School,
Fourth Military Medical University,
145 Changle Xi Road,
Xi'an 710032, China
e-mail: 245561054@qq.com

Zhiyuan Zhang

State Key Laboratory of Military Stomatology,
Department of Prosthodontics,
Stomatology School,
Fourth Military Medical University,
145 Changle Xi Road,
Xi'an 710032, China
e-mail: 295095130@qq.com

Yulu Wu

State Key Laboratory of Military Stomatology,
Department of Prosthodontics,
Stomatology School,
Fourth Military Medical University,
145 Changle Xi Road,
Xi'an 710032, China
e-mail: 331617386@qq.com

1Corresponding author.

Manuscript received April 25, 2015; final manuscript received February 16, 2016; published online March 21, 2016. Assoc. Editor: Guy M. Genin.

J Biomech Eng 138(5), 051003 (Mar 21, 2016) (8 pages) Paper No: BIO-15-1197; doi: 10.1115/1.4032937 History: Received April 25, 2015; Revised February 16, 2016

The objective of this study was to investigate the process of mandibular bone remodeling induced by implant-supported overdentures. computed tomography (CT) images were collected from edentulous patients to reconstruct the geometry of the mandibular bone and overdentures supported by implants. Based on the theory of strain energy density (SED), bone remodeling models were established using the user material subroutine (UMAT) in abaqus. The stress distribution in the mandible and bone density change was investigated to determine the effect of implant number on the remodeling of the mandibular bone. The results indicated that the areas where high Mises stress values were observed were mainly situated around the implants. The stress was concentrated in the distal neck region of the distal-most implants. With an increased number of implants, the biting force applied on the dentures was almost all taken up by implants. The stress and bone density in peri-implant bone increased. When the stress reached the threshold of remodeling, the bone density began to decrease. In the posterior mandible area, the stress was well distributed but increased with decreased implant numbers. Changes in bone density were not observed in this area. The computational results were consistent with the clinical data. The results demonstrate that the risk of bone resorption around the distal-most implants increases with increased numbers of implants and that the occlusal force applied to overdentures should be adjusted to be distributed more in the distal areas of the mandible.

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Copyright © 2016 by ASME
Topics: Bone , Density
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References

Figures

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Fig. 4

The distribution of the occlusal force recorded by a T-Scan III digital occlusal system. (a) Recordings of two-implant supported overdentures and (b) recordings of four-implant supported overdentures.

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Fig. 3

Three-dimensional FE models of mandibular overdentures supported by different numbers of implants. (a) Two-implant model: two implants at the position of the mandibular bilateral lateral incisors; (b) three-implant model: one implant in the mandibular midline and the other two implants at the position of the canines; and (c) four-implant model: two implants at the position of the mandibular bilateral incisor and two located at the bilateral mandibular first premolar.

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Fig. 2

Pretreatment CT image

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Fig. 1

Pretreatment intraoral view

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Fig. 5

Flowchart of the remodeling program

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Fig. 6

Stress contours of the mandibular bone in the 24th month. (a) Stress contour of cortical bone for the two-implant model; (b) stress contour of cortical bone for the three-implant model; (c) stress contour of cortical bone for the four-implant model; (d) stress contour of cancellous bone for the two-implant model; (e) stress contour of cancellous bone for the three-implant model; and (f) stress contour of cancellous bone for the four-implant model.

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Fig. 7

Density contours of the mandibular bone in the 24th month. (a) Density contour of cortical bone for the two-implant model; (b) density contour of cortical bone for the three-implant model; (c) density contour of cortical bone for the four-implant model; (d) density contour of cancellous bone for the two-implant model; (e) density contour of cancellous bone for the three-implant model; and (f) density contour of cancellous bone for the four-implant model.

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Fig. 10

Clinical X-ray data from implant-supported overdenture restoration. (a) X-ray image of an implant in the left side of the mandibular bone from a patient with a two-implant supported overdenture in the 12th month; (b) X-ray image of an implant in the left side of the mandibular bone from a patient with a two-implant supported overdenture in the 24th month; (c) X-ray image of an implant in the left side of the mandibular bone from a patient with a four-implant supported overdenture in the 12th month; and (d) X-ray image of an implant in the left side of the mandibular bone from a patient with a four-implant supported overdenture in the 24th month.

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Fig. 8

Bone remodeling process for the three models

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Fig. 9

Post-treatment intraoral view: (a) two implants and (b) four implants

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