الفهرس 
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Abstract
The aim of the study was to measure the maximum insertion and removal torques of three different types of miniscrews inserted in two groups of artificial bone resembling maxillary and mandibular bone of the posterior region.
A sample of sixty miniscrews from three different companies were grouped into three groups (20 screw in each group), all miniscrews had same dimensions (1.4mm diameter and 8 mm length).
Miniscrews were divided equally into three groups according to the manufacturing company. Twenty miniscrews for each group.
group A: Hubit
group B: Dentos
group C: Neo anchor plus
Each groupwas sub-divided equally into two sub-groups according to bone density. Ten miniscrews for each sub-group.
As bone quality is an eminent factor in screw success, two artificial bone blocks (Sawbones) with different properties were used to mock the posterior maxilla and posterior mandible.
MIT and MRT of each screw in each group was recorded and compared in the maxillary and mandibular bone. In order to maximize the accuracy of measuring procedure a device (Torque tester MC) was used to insert and remove the miniscrews in the bone with same speed and weight.
The angle of insertion and removal for all miniscrews was unified (90 degrees) and proper statistical analysis tests where used to study the results. Effect of cortical bone thickness and cancellous bone density of maxillary and mandibular artificial bone on miniscrew MIT and MRT were studied and the relation between MIT and MRT was also studied.
The following conclusions were drawn from the current study:
1- Increase in the cortical bone thickness increases the maximum insertion and maximum removal torques.
2- Increase in the bone density increases both maximum insertion and maximum removal torques.
3- Increase in the maximum insertion torque results in an increase in the maximum removal torque as both significantly correlated.
4- Since maximum insertion torque was high in the mandibular bone, it is advised to use pre-insertion drilling technique in the mandible to reduce maximum insertion torque to acceptable limits.