Evaluation Of Deflection Characteristics Of Orthodontic Mini Implants Following Placement- An Ex-Vivo Study

Abstract

Aim: To Radiographically Evaluate And Compare The Deflection Characteristics Of Self-Drilling

Titanium Alloy Mini Implants When Inserted Into Bone Similar To The Human Mandible.

Method: 80 Self Drilling Titanium Alloy Implants Of The Following Sizes Were Used: 1.3mm,

1.4mm, 1.5mm And 1.6mm Diameters And 10mm, 8mm, 7mm And 6mm Lengths. 5 Mini

Implants Of Each Of The Possible Combinations Of Lengths And Diameters Were Tested For Study.

The Implants Were Inserted Perpendicularly Into Bovine Rib Bone Held In A Custom Made Stand.

The Rib Bone Was Made Into Segments 1.5cm Wide Using An Osteotome And Embedded In

Autopolymerising Acrylic Resin Blocks With Four Bone Segments In Each Block. Thus A Total Of

Twenty Resin Blocks Were Made. Insertion Torque Was Set At 1kgf In The Long Handle Implant

Driver With Attached Torque Gauge. Each Resin Block Contained One Implant Per Bone Segment

And Individual Blocks Contained Implants Of Identical Lengths But Varying Diameter. The Resin

Blocks Were Then Radiographically Exposed And The Deviation Of The Long Axis Of The Implant

From A True Vertical Line Drawn Through The Centre Of Entry Of The Implant Into Cortical Bone

Was Measured.

Results: There Was An Increase In Deflection Of The Mini Implant With Increase In Length. On

The Other Hand, Increase In Diameter Resulted In Decrease In The Amount Of Deflection Observed.

Conclusion: Selecting An Implant Depends On Anatomical Limitations Like Cortical Bone

Thickness, Proximity To Adjacent Roots, Or Any Other Vital Structures And Implant Design. For

Insertion Into Thicker Bone Such As The Mandible, It Is Preferable To Use A Thicker And Shorter

Mini Implants As They Exhibit Lesser Deflection.  In Areas Of Lesser Cortical Bone, A Thinner And

Longer Mini Implant Can Be Considered As The Resistance Offered By The Bone Will Be Lesser.