System for application of controlled forces on dental implants in rat maxillae: Influence of the number of load cycles on bone healing

Abstract

Experimental studies on the effect of micromotion on bone healing around implants are frequently conducted in long bones. In order to more closely reflect the anatomical and clinical environments around dental implants, and eventually be able to experimentally address load‐management issues, we have developed a system that allows initial stabilization, protection from external forces, and controlled axial loading of implants. Screw‐shaped implants were placed on the edentulous ridge in rat maxillae. Three loading regimens were applied to validate the system; case A no loading (unloaded implant) for 14 days, case B no loading in the first 7 days followed by 7 days of a single, daily loading session (60 cycles of an axial force of 1.5 N/cycle), and case C no loading in the first 7 days followed by 7 days of two such daily loading sessions. Finite element modeling of the peri‐implant compressive and tensile strains plus histological and immunohistochemical analyses revealed that in case B any tissue damage resulting from the applied force (and related interfacial strains) did not per se disturb bone healing, however, in case C, the accumulation of damage resulting from the doubling of loading sessions severely disrupted the process. These proof‐of‐principle results validate the applicability of our system for controlled loading, and provide new evidence on the importance of the number of load cycles applied on healing of maxillary bone.

Cellular and Molecular Dynamics during Early Oral Osseointegration: A Comprehensive Characterization in the Lewis Rat

“…Fortunately, oral implantation models in rodents are not a novel concept. A number of studies have employed two particular types of maxilla implantation in the rodent: those which involve extraction of one or more of the first molars before placement of the implant (extraction models) − or direct implantation into the maxillary diastema without tooth extraction (nonextraction models). − Further examination of either of these models will uncover a large variety in methodology. In extraction models, the placement of the implant is reported to be either immediately following tooth extraction − ,, or up to 30 days after. ,− , Placement is also inconsistent, in bed of the first molar, ,− ,, anywhere between the first and second molar, or the socket where the mesial root of the first molar is located before extraction. , In nonextraction models, implantation into the maxillary diastema can occur anywhere anterior to the first molar and posterior of the incisor roots. ,, Finally, both models have a large variety of implant dimensions ranging from 0.67 to 1.7 mm in diameter and 2.0–4.5 mm in length. ,,,, One could argue that these variations in implantation procedures, implant size, and bone quality at different locations may reflect what happens in the clinic.…”