Enhancement of Implant Osseointegration by High-Frequency Low-Magnitude Loading

Abstract

BackgroundMechanical loading is known to play an important role in bone remodelling. This study aimed to evaluate the effect of high- and low-frequency axial loading, applied directly to the implant, on peri-implant bone healing and implant osseointegration.MethodologyTitanium implants were bilaterally installed in rat tibiae. For every animal, one implant was loaded (test) while the other one was not (control). The test implants were randomly divided into 8 groups according to 4 loading regimes and 2 experimental periods (1 and 4 weeks). The loaded implants were subject to an axial displacement. Within the high- (HF, 40 Hz) or low-frequency (LF, 8 Hz) loading category, the displacements varied 2-fold and were ranked as low- or high-magnitude (LM, HM), respectively. The strain rate amplitudes were kept constant between the two frequency groups. This resulted in the following 4 loading regimes: 1) HF-LM, 40 Hz-8 µm; 2) HF-HM, 40 Hz-16 µm; 3) LF-LM, 8 Hz-41 µm; 4) LF-HM, 8 Hz-82 µm. The tissue samples were processed for resin embedding and subjected to histological and histomorphometrical analyses. Data were analyzed statistically with the significance set at p<0.05.Principal FindingsAfter loading for 4 weeks, HF-LM loading (40 Hz-8 µm) induced more bone-to-implant contact (BIC) at the level of the cortex compared to its unloaded control. No significant effect of the four loading regimes on the peri-implant bone fraction (BF) was found in the 2 experimental periods.ConclusionsThe stimulatory effect of immediate implant loading on bone-to-implant contact was only observed in case of high-frequency (40 Hz) low-magnitude (8 µm) loading. The applied load regimes failed to influence the peri-implant bone mass.

Direct Radial LMHF Microvibration Induced Bone Formation and Promoted Implant Osseointegration

“…However, in recent studies by Zhang, direct LMHF (8 Hz, 42 μm; 40 Hz, 16 μm; 60 Hz) vibration on the implant did not show any increase in BF or BIC. Our study did not show any change in the 40 Hz (15 μm) group either, but we found that bone formation and osseointegration increased in the 10, 20, and 30 Hz groups.…”

“…In earlier studies, whole‐body LMHF vibration promoted osseointegration, local LMHF vibration promoted osseointegration, and low‐frequency 1‐Hz microvibration loaded directly on the implant in the rabbit tibia and beagle mandible increased the BIC . However, direct LMHF (8, 40, and 60 Hz) vibration did not yield any change in osseointegration …”

“…Low‐frequency (1 Hz) microvibration applied directly to titanium implants in rabbit femurs and tibiae increased bone ingrowth, bone volume, volumetric density, and bone formation, whereas the direct application of 1 Hz microvibration in beagle mandibles increased the bone density around the implant . However, when the LMHF vibration was directly loaded on the implant, neither the 60 Hz vibration on the rabbit tibiae nor the 40 Hz or 80 Hz vibration on the rat tibiae altered the BF …”

“…Local axial vibrations (0.5 N, 40 Hz; and 20 N, 2 Hz) on Wistar rat tibiae for 4 weeks (10 minutes per day) increased the BIC and BF around the implants. 24 However, when the LMHF vibration was directly loaded on the implant, none of the treatments (40, 60, or 80 Hz) on rat tibiae altered the BIC or BF 25,26 (they did, over 40 should cause failure).…”

Bone remodeling and mechanobiology around implants: Insights from small animal imaging

“…Considering small animal models, mechanical stimulation can be (a) applied directly to the implant through miniaturized devices, (b) administered to the single implanted bone through loads coming from adjacent bones or joints, and (c) delivered through generalized whole body vibrations. Figures modified from with permission.…”