Influence of implant distribution on the biomechanical behaviors of mandibular implant-retained overdentures: a three-dimensional finite element analysis

Abstract

Objective: To assess stress distribution in peri-implant bone and attachments of mandibular overdentures retained by small diameter implants, and to explore the impact of implant distribution on denture stability.

Methods: Through three-dimensional Finite Element Analysis (3D FEA), four models were established: three models of a two mandibular implants retained overdenture (IOD) and one model of a conventional complete denture (CD). The three IOD models consisted of one with two implants in the bilateral canine area, another with implants in the bilateral lateral incisor area, and the third with one implant in the canine area, and another in the lateral incisor area. Three types of loads were applied on the overdenture for each model: a 100 N vertical load and a inclined load on the left first molar, and a100N vertical load on the lower incisors. The stress distribution in the peri-implant bone, attachments, and the biomechanical behaviors of the overdentures were analyzed.

Results: Despite different distribution of implants, the maximum stress values in peri-implant bone remained within the physiological threshold for all models across three loading conditions. The dispersed implant distribution design (implant in the canine area) exhibited the highest maximum stress in peri-implant bone (822.8 µe) and the attachments (275 MPa) among the three IOD models. The CD model demonstrated highest peak pressure on mucosa under three loading conditions (0.8188 Mpa). The contact area between the denture and mucosa of the CD model was smaller than that in the IOD models under molar loading, yet it was larger in the CD model compared to the IOD model under anterior loading. However, the contact area between the denture and mucosa under anterior loading in all models was significantly smaller than those under molar loading. The IOD in all three models exhibited significantly less rotational movement than the complete denture. Different implant positions had minimal impact on the rotational movement of the IOD.

Conclusion: IOD with implants in canine area exhibited the highest maximum stress in the peri-implant bone and attachments, and demonstrated increased rotational movement. The maximum principal stress was concentrated around the neck of the small diameter one-piece implant, rather than in the abutment. An overdenture retained by two implants showed better stability than a complete denture.

Keywords: Distribution of implants; Implant overdenture; Three dimensional finite element analysis.

Fig. 1

Tixos Nano OVD SDI and ball-attachment model

Fig. 2

The diagram of the three-dimensional finite element models

Fig. 3

The three types of load applied on the denture

Fig. 4

Distribution of maximum pressure on mucosa (1) in Model 00 under VI load, (2) in Model 22 under VI load, (3) in Model 23 under VI load, (4) in Model 33 under VI load, (5) in Model 00 under VM load, (6) in Model 22 under VM load, (7) in Model 23 under VM load, (8) in Model 33 under VM load, (9) in Model 00 under IM load, (10) in Model 22 under IM load, (11) in Model 23 under IM load, (12) in Model 33 under IM load

Fig. 5

Distribution of contact area between the denture and mucosa under VM load. The cold tone represents the area where contact with the denture was close and tight, whereas the warm tone indicates the area where the denture tilted and separated from the mucosa.

Fig. 6

Distribution of contact area between the denture and mucosa under IM load

Fig. 7

Distribution of contact area between the denture and mucosa under VI load