Korean J Orthod.  2009 Apr;39(2):95-104. 10.4041/kjod.2009.39.2.95.

Effect of cutting flute length and shape on insertion and removal torque of orthodontic mini-implants

• Yun SD
• Lim SH

• KMID: 1975814
• DOI: http://doi.org/10.4041/kjod.2009.39.2.95

Abstract

OBJECTIVE
The purpose of this study was to evaluate the effect of length and shape of cutting flute on mechanical properties of orthodontic mini-implants. METHODS: Three types of mini-implants with different flute patterns (Type A with 2.6 mm long flute, Type B with 3.9 mm long and straight flute, Type C with 3.9 mm long and helical flute) were inserted into the biomechanical test blocks (Sawbones Inc., USA) with 2 mm and 4 mm cortical bone thicknesses to test insertion and removal torque. RESULTS: In 4 mm cortical bone thickness, Type C mini-implants showed highest maximum insertion torque, then Type A and Type B in order. Type C also showed shortest total insertion time and highest maximum removal torque, but Type A and B didn't showed statistically significant difference in insertion time and removal torque. In 2 mm cortical bone thickness, there were no significant difference in total insertion time and maximum removal torque in three types of mini-implants, but maximum insertion torque of Type A was higher than two other Types of mini-implants. CONCLUSIONS: Consideration about length and shape of cutting flute of mini-implant is also required when the placement site has thick cortical bone.

Keyword

Cutting flute; Total insertion time; Maximum insertion torque; Maximum removal torque

MeSH Terms

Torque

Figure

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  Fig 1 Three types of mini-implants used in this study (unit: mm).

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  Fig 2 Torque tester (Biomaterials Korea Inc., Seoul, Korea).

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  Fig 3 Graph showing the definition of maximum insertion torque and total insertion time.

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  Fig 4 Graph showing the definition of maximum removal torque.

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  Fig 5 Microscopic evaluation of removed mini-implant to check for any distortion of screw tip and threads. Type A (left); Type B (center); Type C (right).

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  Fig 6 Total insertion time for each type of mini-implant. Type A, 2.6 mm long flute; Type B, 3.9 mm long and straight flute; Type C, 3.9 mm long and helical flute.

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