The 8 × 21 mm Tutofix® screw (Tutogen, Neunkirchen am Brand, Germany) had a thread length of 18 mm, a thread depth of 0.7 mm, a thread infeed of 2.1 mm per turn and a hexagonal drive head.
The cage screen had an opening size of 0.65 mm and thread diameter of 0.29 mm.
A screw made of titanium with a length of 1 mm and thread M 0.7, was then screwed in place (Fig. 1).
For threaded cups, this corresponds to an outer diameter of 50 mm plus thread flanks.
Under batch conditions, the SDS enrichment ratio obtained with SIC of thread pitch 30 mm and inclined angle 30° was about 2.4 times of that obtained without SIC.
The Chapman's formula has the following form: The symbols in the formula were respectively denoted as: F pullout = predicted pullout strength (N), S shear = ultimate shear strength of synthetic bone (MPa), L = length of thread engagement in synthetic bone (mm), D o = thread outer diameter (mm), d = thread depth (mm), and p = thread pitch (mm).
In group A, the pullout strength and maximum torque of common anterior screws (diameter, 5.5 mm; thread length, 30 mm) was tested.
In group B, the pullout force and maximum torque of the expandable anterior fixation screw (diameter, 12 mm; thread length, 30 mm) unexpanded was tested.
Micromotion of identical implants, with a constant pitch of 0.8 mm but different thread helices (Angle Group), was compared.
The effect of thread pitch (coarse and fine threads) on fatigue life of ISO bolts within the range of 10≤D≤24 mm (D=outside diameter) and American Unified bolts within the range of 7/16″≤D≤1″ was studied.
