*Article* **Mechanical and Biological Advantages of a Tri-Oval Implant Design**

**Xing Yin 1,2, Jingtao Li 1,2, Waldemar Hoffmann 3, Angelines Gasser 3, John B. Brunski <sup>2</sup> and Jill A. Helms 2,\***


Received: 2 February 2019; Accepted: 25 March 2019; Published: 28 March 2019

**Abstract:** Of all geometric shapes, a tri-oval one may be the strongest because of its capacity to bear large loads with neither rotation nor deformation. Here, we modified the external shape of a dental implant from circular to tri-oval, aiming to create a combination of high strain and low strain peri-implant environment that would ensure both primary implant stability and rapid osseointegration, respectively. Using in vivo mouse models, we tested the effects of this geometric alteration on implant survival and osseointegration over time. The maxima regions of tri-oval implants provided superior primary stability without increasing insertion torque. The minima regions of tri-oval implants presented low compressive strain and significantly less osteocyte apoptosis, which led to minimal bone resorption compared to the round implants. The rate of new bone accrual was also faster around the tri-oval implants. We further subjected both round and tri-oval implants to occlusal loading immediately after placement. In contrast to the round implants that exhibited a significant dip in stability that eventually led to their failure, the tri-oval implants maintained their stability throughout the osseointegration period. Collectively, these multiscale biomechanical analyses demonstrated the superior in vivo performance of the tri-oval implant design.

**Keywords:** dental implant; osseointegration; alveolar bone remodeling/regeneration; bone biology; finite element analysis (FEA); biomechanics
