A preclinical model links osseo‐densification due to misfit and osseo‐destruction due to stress/strain

Abstract

Objective Primary stability is a prerequisite for implant osseointegration. Some degree of misfit between an implant and its osteotomy is required to ensure primary stability, and this is typically achieved by undersizing an implant osteotomy. In this preclinical study, we aimed at understanding the relationship between misfit, insertion torque, implant stability, and their cumulative short‐ and longer‐term effects on peri‐implant bone. Materials and methods We placed implants in maxillary extraction sites of a rat; in the control group, these implants had minimal misfit while those in the test group had a high degree of misfit and therefore osseo‐densified the peri‐implant bone. Results Compared to controls, the misfit‐induced stresses produced by osseo‐densification led to micro‐fractures in the peri‐implant bone and an extensive zone of dying osteocytes. High interfacial pressures produced a pro‐resorptive environment as shown by tartrate‐resistant acid phosphatase activity and cathepsin K immunostaining (IHC). The lack of alkaline phosphatase activity and collagen I IHC supported the absence of new bone formation. Collectively, micro‐computed tomography imaging, quantification of bone–implant contact (BIC), vimentin, and IL1‐β IHCs demonstrated that implant failure occurred soon afterward, which presented as a crater‐like lesion filled with fibrous, inflamed granulation tissue around the test implants. Conclusion By controlling every other risk indicator, we confirmed how excessive osseo‐densification can lead directly to osseo‐destruction.

Can Bone Compaction Improve Primary Implant Stability? An In Vitro Comparative Study with Osseodensification Technique

“…Because most of the studies on the osseodensification technique are not clinical, some reviews have shown the effectiveness of this method in improving primary stability in medullary bone [31,32]; however, it is still unclear whether secondary stability is positively or negatively affected by this surgical technique [3,33]. Further clinical studies are required to analyze how implant stability varies during the healing period subsequent to the two surgical procedures.…”

“…Moreover, recently a preclinical study analyzed misfit and osteodestruction due to stress/strain linked to the osseodensification technique [33]. One of the most common questions about the osseodensification protocol involves micro-fractures in the peri-implant bone that cause a huge zone of dying osteocytes [40].…”

“…In fact, high interfacial pressures and mechanical preparation seem to produce a pro-resorptive environment as indicated by the lack of alkaline phosphatase activity and collagen I. Although several authors assessed whether the osseodensification technique produces bone chips usable as autografts during implant site preparation [41], the mechanical movement and heat generation on the bone walls could negatively influence the osseointegration phenomenon [33].…”

Bone formation around unstable implants is enhanced by a WNT protein therapeutic in a preclinical in vivo model

“…For example, in a previous study we created a situation where an implant was placed into an undersized osteotomy. Inserting the implant produced compressive strains that severely damaged the peri‐implant bone, resulting in sustained resorption and implant loosening and ultimately, fibrous encapsulation (Coyac et al., 2019). Here, we created a situation where an implant was placed into an oversized osteotomy, and in this case, immediate loading of the implants was a key to their failure: loading generated high strains in the gap interface (Figure 1), resulting in an unfavorable environment for osteogenic cell differentiation (Figure 2).…”

A novel system exploits bone debris for implant osseointegration

“…In an effort to identify areas for potential improvement, we and other groups have studied the biomechanical features of osteotomy site preparation and implant placement. [1][2][3] The historical literature advises the careful preparation of an implant bed, followed by a healing period to allow the remodeling of bone damaged by drilling. 4 Even with copious irrigation, osteotomy site preparation produces mechanical and thermal damage 5 that culminates in a peri-implant "zone of death."…”