Abstract
The aims of this study were to measure the three-dimensional (3-D) loads exerted on the implants supporting an overdenture during function in vivo and to clarify the effect of the number of the implants on the loads. The load-measuring devices were mounted on the implants inserted in the mandible of a 62 aged female subject. Either two or four implants connected with a bar were used for supporting her overdenture. The loads on the implants were expressed three dimensionally as load vectors and were analyzed in the coordinates based on the Frankfort horizontal plane and sagittal plane. The tasks examined were maximum voluntary clenching (MVC) and gum chewing (GC). The total load exerted on the implants with a four-implant supported overdenture (4I-Od) was larger than that with a two-implants supported overdenture (2I-Od) at MVC. The maximum occlusal force on the overdenture showed the same manner (p<0.01). The directions of the loads were posterior and lateral at MVC. The total load exerted on the implants located on the working side, was larger than that on the implants located on the non-working side during GC in the case of 4I-Od. The similar manner was also observed in the 2I-Od. The tensile loads were registered during GC. The functional loads exerted on the individual implants in the case of 4I-Od were smaller than those in the 2I-Od. The loads on the implants during function are thus affected by the number of implants supporting the overdenture.
