Wnt expression during osseointegration of titanium dental implants

Abstract

Background: The Wnt 1, 7b and 10b proteins come from a family of 19 signalling molecules. These proteins initiate the Wnt/Beta-catenin signalling pathway to promote osteoblast differentiation and bone formation and thus, might be important during osseointegration of titanium dental implants. We hypothesized that these Wnt genes will be expressed during osseointegration.

Aims: (i) To investigate osseointegration around Neoss implants with ProActive or Bimodal surfaces (Neoss Implant System, Neoss Ltd., Harrogate, UK). (ii) To determine the expression of Wnt genes during osseointegration.

Methods: Twenty 3.5 mm x 7 mm titanium dental implants were used. One ProActive implant and one Bimodal implant, with the dimensions of 3.5 mm x 7 mm, were placed bilaterally into the mandibular diastema of 10 sheep. Two animals per time interval were sacrificed after 6 hours, 1, 2, 4 and 6 weeks of unloaded healing. A small bone sample from the mesial aspect of each implant was extracted for RNA extraction. RT-PCR was conducted to detect the expression of Wnt 1, 7b and 10b genes using redundant primers and PCR products were cloned and sequenced. The implants were sectioned en bloc with surrounding bone and embedded in resin. Digitised images were collected of two bucco-lingual and one mesio-distal orientated ground-section from each block. Mean bone-implant contact (BIC) measurements were obtained from 16 to 32 thread images per implant using the program NIH ImageJ (ImageJ, USA).

Results: Fifteen implants were present at the time of sacrifice. Five implants failed to integrate. BIC significantly increased from 1 week to all subsequent time intervals (P < 0.05). BIC for ProActive and Bimodal implants did not differ significantly at 6 hours, 1 week and 6 weeks. At 2 weeks, Bimodal implants had a significantly higher BIC (P = 0.01). cDNA of the expected size for Wnt 10b, 7b and GAPDH were amplified using redundant primers.

Conclusion: These results suggest that osseointegration was occurring around Neoss implants over the experimental timeframe. However, osseointegration was not significantly enhanced by the ProActive implant surface. The expression of Wnt 10b, but not Wnt 7b or Wnt 1, was demonstrated during osseointegration. Additionally, the ovine Wnt 10b was sequenced and confirmed.