Nontraumatic Implant Explantation: A Biomechanical and Biological Analysis in Sheep Tibia
Preclinical research in a sheep tibia model has been conducted to evaluate the underlying mechanisms of the nontraumatic implant explantation of failed implants, which allow placing a new one in the bone bed. Twelve dental implants were placed in sheep diaphysis tibia and once osseointegrated they were explanted using a nontraumatic implant explantation approach. Implant osseointegration and explantation were monitored by means of frequency resonance, removal torque, and angle of rotation measurement. The host bone bed and the explanted implant surface were analyzed by conventional microscopy and scanning electron microscope. Results show that osseointegration was broken with an angular displacement of less than 20°. In this situation the implant returns to implant stability quotient values in the same range of their primary stability. Moreover, the explantation technique causes minimal damage to the surrounding bone structure and cellularity. This nontraumatic approach allows the straightforward replacement of failed implants and emerges as a promising strategy to resolve clinically challenging situations.
Implant surgery in sheep tibia. The holes made with the initial drill (a), guide the subsequent drilling sequence (b), and place the implants (c). Once the implants have been placed (d), primary stability is measured with Osstell ISQ (e). The surgical wound is closed in layers, starting with the periosteum (f).
Implant osseointegration: radiographic follow up (a–c) and histological images (d–e). Examples of craniocaudal radiographs taken after placement of the implants (a), four weeks after surgery (b), and 22 weeks after surgery prior to explantation (c). Additionally, samples from the tibia were collected to confirm histologically the osseointegration at 22 weeks of implant placement (a and b). Photomicrograph (d) shows a panoramic view of the implant and the peri-implant bone, and (e) shows in detail the bone implant contact and the newly-formed bone between the implant threads.
Resonance frequency analysis. Implant stability quotient (ISQ) was measured at the day of implantation, 22 weeks postimplantation, before and after osseointegration breakage. *Statistically significant differences (P < 0.05).
(a) Custom-made device for implant removal torque and angular displacement measurement. (b) Average removal angle corresponding to the maximum removal torque during explantation (data are expressed as mean + SD). (c) Removal torque vs angular displacement curves of 9 explantations. The experimental points have been linked together for better viewing.
(a) Scanning electron micrographs showing the surface state of an implant after explantation. Only the apical region accumulates macroscopic remnants of bone. (b) EDX mapping of carbon (red) and titanium (green) on scanning electron micrographs taken at the implant neck after explantation. Cells on the surface present spread morphology, which is characteristic of attachment and differentiation. (c) Close-up scanning electron micrograph on the surface showing the bare implant surface: purple EDX spectrum at the purple cross, organic remnants: yellow EDX spectrum at the yellow cross and calcium phosphate remnants of bone: red EDX spectra at the red cross.
Characterization of the bone at explant sites. (a) Image of 2 implant sites after explantation. (b) Cross-section of the tibia showing the bone bed. Note the marks left by both the neck and the threads of the implant. (c) SEM micrograph showing the structure of the bone at the explant site. (d) At higher magnifications, both the Haversian canals (arrowheads) and the Volkmann canals (arrows) can be distinguished. (e, f) Optical micrographs showing the cellularity at the explant site (MGG staining). Viable osteocytes were observed within lacunae (blue staining).
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