Short dental implants: a literature review and rationale for use

Implant prostheses are often used to restore partially or completely edentulous patients. The posterior regions of the mouth often have less available bone height than the anterior regions. The bone density of the remaining bone after tooth loss is often less in the posterior regions than the anterior region of the mouth. A review of the literature reveals implants shorter than 10 mm often have a higher failure rate than longer implants. These complications may be related to an increase in crown height, higher bite forces in the posterior regions, and less bone density. As a result, biomechanical methods to decrease stresses to the implant-bone interface are warranted. The forces to the implants may be reduced by eliminating lateral contacts in mandibular excursions and eliminating cantilevers on the prosthesis. The area of forces applied to the prosthesis may be increased by increasing the implant number, increasing the implant diameter, increasing the implant design surface area, and splinting the implants together. As a result of these biomechanical methods to decrease stress, Misch, et al reported a 99% implant survival with 7-mm and 9-mm implants in the posterior regions of the jaws. It is interesting to note that the natural teeth follow a similar biomechanical approach to accommodate the higher bite forces in the posterior regions of the mouth. The molar teeth do not become longer than the anterior teeth. The diameter is increased, the design of the roots is different, and the roots are splinted together. The anterior teeth have incisal guidance and eliminate posterior lateral forces to the posterior teeth in all mandibular excursions. A similar biomechanical approach is logical for posterior implants, especially when shorter implants are used to support the prosthesis.