Abstract
Aim: To assess the effect of length and insertion angle on stability of mini screw in synthetic bone replica used for retraction of anterior teeth. Materials and Methods: A total of 120 titanium miniscrews (SK Surgicals) were equally divided into two groups based on their insertion in synthetic replica of bone (ORTHOBONES, 3B scientific, Germany) i.e. maxillary (Group I) or mandibular (Group II) bone. Both the groups were further divided into 8 subgroups based on length and angulation i.e. Ia60 (8mm, 60o), Ia90 (8mm, 90o), Ib60(11mm, 60o), Ib90(11mm, 90o), IIa60(6mm 60o), IIa90(6mm 90o), IIb60(8mm 60o) and IIb90(8mm 90o). Two customized angulation guiding jigs, at 60o and 90o angle were fabricated. Miniscrew was driven into the bone using the screwdriver. A Universal testing machine was used to conduct Shear Compressive Strength test on all the Miniscrews. Data was collected and ANOVA and Post Hoc Test were applied to get the results. Result: For maxillary bone analogue (Group I), 11 mm miniscrew inserted at 90o angulation had maximum values and 8 mm screws at 60ohad minimum values of SCS. The trend for SCS of miniscrews in Group I was Ib90>Ib60>Ia90>Ia60. In mandibular bone analogue, 8 mm miniscrews inserted at 90o angulation showed maximum stability and 6mm at 60oshowed minimum SCS. The trend for SCS in Group II was IIb90>IIa90>IIb60>IIa60. Intergroup comparison revealed that statistical difference for IIb60>Ia60, IIb90>Ia90, IIb90>Ia60 and IIb60>Ia90 which suggest that MS inserted in mandibular analogue had better SCS than in maxilla irrespective of angulation. Conclusion: Longer miniscrews inserted perpendicular to the bone gives maximum stability. It is also found that stability increases with increase in cortical bone thickness. Keywords: Miniscrews, Bone, Shear compressive strength, Primary stability, TAD, Bone analogue.
Highlights
Anchorage control is an important factor in the successful outcome of any Orthodontic treatment
The results of this study showed that, in maxillary bone analogue (Group I), 8 mm screw inserted at 90 degrees angulation showed a mean value of shear compressive strength (SCS) as 82.60+12.040 N, whereas 8 mm screw inserted at 60 degree angulation showed a value of 74.07+9.714 N
In mandibular bone analogue (Group II), 6 mm screw at 90 degrees showed a mean value of SCS as 103.53+ 14.788N, whereas 6 mm screw at 60 degree angulation showed a mean value of SCS as 84.00+- 16.423N. 8 mm screw at 90 degrees showed a value of 109.27+10.437N, whereas 8 mm screw at 60 degree angulation showed a value of 101.40+-13.146N
Summary
Anchorage control is an important factor in the successful outcome of any Orthodontic treatment. Toward the end of the 1980s, a number of clinicians focused on the use of standard dental implants as permanent abutments[8,9,10,11,12] for tooth replacement and skeletal anchorage for orthodontic tooth movement. The disadvantages of dental implants are the need for an invasive surgical procedure, the time required for Osseo integration prior to force application, and cost.[8] To obviate these limitations, implants were designed for use in orthodontics and were termed as TAD (Temporary Anchorage Device). It is decided to assess the two most important mechanical factors i.e. optimal length and angle of insertion for the stability of mini screw as Temporary anchorage device in orthodontics
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