Recently, osseointegrated dental implants have come to be used more and more in the treatment of edentulism. Osseointegration has been found to achieve better results than fibro osseous integration however, it has been suggested that excessive and/or concentrated stresses may cause resorption of the surrounding bone.
To address this problem, the IMZ implant system incorporates stress-absorbing elements, such as the intramobile element (IME). There are varying reports regarding the characteristics of the IME, however, and its effectiveness is still controversial.
This study compares the stress-transfer characteristics around a single freestanding IMZ implant with three types of internal elements: an IME made of polyoxymethylene, an intramobile connector (IMC) consisting of a polyoxymethylene head and titanium screw, and a metal element (Metal-E) made of stainless steel. An IMZ implant (4×13mm) and five strain gauges (Kyowa Inc.) around the implant were embedded in an acrylic resin block (3×3×3cm). The vertical (10 and 15kgf) and horizontal (3 and 5kgf) static forces applied to the surface of the superstructure and the strain values around the implant were measured.
The results are as follows:
1. Under vertical forces, among the three types of elements no significant difference in the stresses around a single freestanding implant was found.
2. Under horizontal forces, a more uniform stress around a single freestanding implant with the Metal-E was observed. When using the IME, there was a greater stress concentration on the upper-oppressive side of the implant. The action of the IMC appeared to be midway between the IME and the Metal-E.
3. The IME fractured after several applications of 5-kgf horizontal force.