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

Soon-dong Yun; Sung-hoon Lim

doi:10.4041/kjod.2009.39.2.95

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

Original Article

Korean Journal of Orthodontics

Korean Journal of Orthodontics 2009; 39(2): 95-104.

Published online: 30 April 2009

DOI: https://doi.org/10.4041/kjod.2009.39.2.95

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

Soon-dong Yun, DDS^a, Sung-hoon Lim, DDS, MSD, PhD^b

^aGraduate Student, Department of Orthodontics, School of Dentistry, Chosun University, Korea.

^bAssociate Professor, Department of Orthodontics, School of Dentistry, Chosun University, Korea.

Corresponding author: Sung-hoon Lim. Department of Orthodontics, School of Dentistry, Chosun University, 421, Seoseok-dong, Dong-gu, Gwangju 501-825, Korea. +82 62 220 3876; shlim@chosun.ac.kr

Received 5 August 2008 Revised 30 October 2008 Accepted 2 November 2008

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.

Keywords: Cutting flute, Total insertion time, Maximum insertion torque, Maximum removal torque

Figures and Tables

Fig 1

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

Fig 2

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

Fig 3

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

Fig 4

Graph showing the definition of maximum removal torque.

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).

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.

Table 1

Mechanical properties of the biomechanical test block

Table 2

Mean results and standard deviation (cortical bone thickness 2.0 mm)

Type A, mini-implant with 2.6 mm long flute; Type B, mini-implant with 3.9 mm long and straight flute; Type C, mini-implant with 3.9 mm long and helical flute; NS, not significant; ^*Statically significant, p < 0.05; Significance determined by Tukey's test.

Table 3

Mean results and standard deviation (cortical bone thickness 4.0 mm)

Type A, mini-implant with 2.6 mm long flute; Type B, mini-implant with 3.9 mm long and straight flute; Type C, mini-implant with 3.9 mm long and helical flute. Significance determined by Tukey's test. ^*Statically significant, p < 0.05.

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