The Effect of a Keratin Hydrogel Coating on Osseointegration: An Histological Comparison of Coated and Non-coated Dental Titanium Implants in an Ovine Model

Abstract

Bioactive substances may be used to enhance the rate and quantity of bone healing during osseointegration of titanium dental implants. A pilot observational study was undertaken to assess a novel keratin hydrogel in six adult sheep utilising the femoral condyles as the surgical site to assess osseointegration. Implants and osteotomy sites were coated with the keratin gel prior to implant placement (test implants) whereas the opposite knee received unmodified control implants in each animal. Fifty 3.5 mm × 7 mm Neoss dental implants were surgically implanted with a range of 3–5 Neoss dental implants placed per surgical site in each knee and allowed to heal for 5 days or 2, 4, 8, 12 and 16 weeks prior to the sheep being sacrificed. Of the 50 placed implants, 24 were used for this study and analysed via resin-embedded, undemineralised sections from test and control implants to assess the range of healing around the unloaded dental implants. These dental implants were analysed using histomorphometric methods for the best 3 consecutive threads on each side and the percentage of bone to implant contact (%BIC) was used to determine the degree of osseointegration between test and control dental implants at each time point. All implants appeared osseointegrated at the time of sacrifice. One each of the pairs of control implants at 2, 4 and 12 weeks demonstrated minimal integration histologically, with %BIC <10 %. No test implants had %BIC <35 % at any time point. Mean %BIC for test implants was higher than controls at all time points except 5 days and 2 weeks. The range from 2 to 16 weeks healing was 39.7 % [SD 25.5 %] to 85.4 % [14.2 %] for test implants and 35.6 % [43.4 %] to 46.6 % [23.1 %] for controls. %BIC appeared to increase earlier in the test implants (from 4 weeks onwards) compared to controls. After 16 weeks, %BIC was almost twice as great in test implants as controls. This pilot observational study suggests that keratin hydrogel may promote earlier osseointegration around titanium dental implants. Further cross-sectional studies with larger sample sizes are warranted. The most marked difference between test and control implants was seen after 4 weeks. It is recommended that future studies in this model focus on healing after 4 weeks.