Cj. Ivanoff et al., INFLUENCE OF IMPLANT DIAMETERS ON THE INTEGRATION OF SCREW IMPLANTS -AN EXPERIMENTAL-STUDY IN RABBITS, International journal of oral and maxillofacial surgery, 26(2), 1997, pp. 141-148
The influence of diameter on the integration of titanium screw-shaped
implants was studied in the rabbit tibia by means of removal torque me
asurements and histomorphometry. Implants 3.0, 3.75, 5.0, and 6.0 mm i
n diameter and 6.0 mm long were inserted through one cortical layer in
the tibial metaphyses of nine rabbits and allowed to heal for 12 week
s. The implants were then unscrewed with a torque gauge, and the peak
torque required to shear off the implants was recorded. The histologic
analysis in undemineralized ground sections comprised (1) a gross des
cription of the implant sites and assessments of (2) the total implant
length in bone and (3) in the cortical passage, as well as (4) the th
ickness of the cortical bone adjacent to the implants. From the remova
l torque values obtained and morphometric measurements, a mean shear s
tress value was calculated for each implant type. The biomechanical te
sts showed a statistically significant increase of removal torque with
increasing implant diameter. The resistance to shear seemed to be det
ermined by the implant surface in supportive cortical bone, whereas th
e newly formed bone at the periosteal and endosteal surfaces did not s
eem to have any supportive properties after 12 weeks. It is suggested
that wide diameter implants may be used clinically to increase implant
stability.