Some Biomechanical and Histologic Characteristics of Early‐Loaded Locking Pin and Expandable Implants: A Pilot Histologic Canine Study

Abstract

A two-stage approach with a 3- to 6-month healing period is recommended for the "conventional" osseointegration technique with oral implants. This may induce inconvenience and discomfort for patients, and immediate early loading protocols are preferable. To compare a new type of implant with two locking pins, designed to allow immediate loading, with an expandable implant design with regard to bone tissue response and implant stability. The molars and premolars of two beagle dogs were extracted in the mandible, and two types of implants (an apically expandable implant and a locking pin implant) were immediately placed in the sockets. The dogs received at least four implants (two of each type) in each side of the mandible. Implants were loaded with gold-palladium bridges 15 days later. The loaded implants were left for 3 months, and the dogs were sacrificed. Resonance frequency analysis (RFA) was performed at placement and sacrifice. Ground sections for histomorphometry were produced for each implant. Implant stability as measured by RFA was similar for the two types of implants before healing. At termination of the study, stability was higher for the locking pin implants. Bone histomorphometry showed that both types of implant were anchored by the same amount of bone and that bone-titanium interfaces did not differ. The locking pin implant showed better secondary stability than did the expandable implant, probably because of a better transmission of strains to bone.