Investigation of bone healing around immediately loaded and unloaded dental implants using sika deer antlers as implant bed

Background

The use of sika deer (Cervus nippon) antlers offers the possibility to study the remodelling process around implants in multiple times without sacrificing the animal. The antler of deer is the only mammalian organ that can fully grow back once lost from its pedicle, the base from which it regrows each summer after shedding it in spring annually. This annually growth is very fast rate and completes in just 3–4 months.

Aim/Hypothesis

This study aimed to compare biomechanical characteristics of immediately loaded and osseointegrated dental implants inserted into Sika deer antler and lay a foundation for developing an alternative animal model for dental implants studies.

Material and Methods

Two implants per antler were inserted with a distance of 2.5 cm. One implant was loaded immediately via a self-developed loading device; the other was submerged and unloaded as a control implant. The immediately loaded implants and surrounding tissue were harvested after 3, 4, 5 and 6 weeks. The unloaded implants were collected after the shedding of antler. Specimens were scanned by μCT scanner and bone mineral density was analysed. Moreover, a histological analysis of all specimens was done. Sections obtained from the grinding system were stained using toluidine blue without removing the plastic medium and were evaluated under a Zeiss-Axio-Imager light microscope at original magnifications ranging between 5 and 50x. Finally, finite element models were generated for loaded and unloaded specimens. A vertical force of 10 N was applied on the implant. The mean values of maximum displacements and strains were recorded and compared.

Results

During the healing time, the density of antler tissue around the implant was increased. The bone mineral density of the antler around immediately loaded implants was much higher than that around unloaded ones after full osseointegration. Specimens carrying unloaded implants collected after antler shedding displayed signs of excellent osseointegration. The peri-implant bone was mostly compact and periapically more cancellous with few fat marrow spaces. Osseointegration appeared to be insufficient in the specimens obtained at 3, 4 and 5 post-operative weeks. Peri-implant spaces with diameters up to 100 μm were observed along the implant bodies. The highest displacement of implants (6.2 μm) was observed after 3-week immediate loading. The model of 6-week osseointegrated implant showed the lowest displacement (0.3 μm). As the healing time increased, the deformation of antler tissue around the implants was reduced.

Conclusion and Clinical Implications

Our findings showed that antler tissue has similar biomechanical properties as human bone and can be used as a novel model for studying bone remodelling around dental implants.