Korean J Orthod.  2008 Dec;38(6):397-406. 10.4041/kjod.2008.38.6.397.

Cortical bone thickness and root proximity at mandibular interradicular sites: implications for orthodontic mini-implant placement

• Lim JE
• Lim WH
• Chun YS

• KMID: 2273971
• DOI: http://doi.org/10.4041/kjod.2008.38.6.397

Abstract

OBJECTIVE
The purpose of this study was to provide clinical guidelines to indicate the best location for mini-implants as it relates to the cortical bone thickness and root proximity.
METHODS
CT images from 14 men and 14 women were used to evaluate the buccal interradicular cortical bone thickness and root proximity from mesial to the central incisor to the 2nd molar. Cortical bone thickness was measured at 4 different angles including 0degrees, 15degrees, 30degrees, and 45degrees.
RESULTS
There was a statistically significant difference in cortical bone thickness between the second premolar/ first permanent molar site, central incisor/central incisor site, between the first/second permanent molar site and in the anterior region. A statistically significant difference in cortical bone thickness was also found when the angulation of placement was increased except for the 2 mm level from the alveolar crest. Interradicular spaces at the 1st/2nd premolar, 2nd premolar/1st permanent molar and 1st/2nd permanent molar sites are considered to be wide enough for mini-implant placement without root damage.
CONCLUSIONS
Given the limits of this study, mini-implants for orthodontic anchorage may be well placed at the 4 and 6 mm level from the alveolar crest in the posterior region with a 30degrees and 45degrees angulation upon placement.

Keyword

Mini-implant; Cortical bone thickness; Root proximity

MeSH Terms

Bicuspid
Female
Humans
Incisor
Male
Molar

Figure

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  Fig 1 A, 3D reconstructed CT image using V-works 4.0™; B, bisect the image along a line that passes the contact point and perpendicular to the occlusal plane; C, bisected and 90° right-rotated sagittal image between Lt. and Rt. mandibular central incisors.

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  Fig 2 Measurement of cortical bone thickness. Cortical bone thickness was measured in 4 different angles (0°, 15°, 30°, 45°) at 2, 4, 6 mm height from the alveolar crest.

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  Fig 3 Measurement of root proximity. 'Central' means the closest distance between the tangent lines, each one tangent to the proximal root surface. 'Buccal' means the distance between the intersecting points which are made by two tangent lines, one is tangent to proximal root surface and the other is tangent to buccal root surface. 'Horizontal' means the closest distance from 'buccal' to 'central'.

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  Fig 4 Mean value of cortical bone thickness in the mandible. Inter-bar connecting lines mean significant differences between one and the other (p < 0.05). 1, Central incisor; 2, lateral incisor; 3, canine; 4, first premolar; 5, second premolar; 6, first molar; 7, second molar.

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  Fig 5 Cortical bone thickness with different angulations at the 2 mm level. Inter-bar connecting lines mean significant differences between one and the other (p < 0.05). 1, Central incisor; 2, lateral incisor; 3, canine; 4, first premolar; 5, second premolar; 6, first molar; 7, second molar.

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  Fig 6 Cortical bone thickness with different angulations at the 4 mm level. Inter-bar connecting lines mean significant differences between one and the other (p < 0.05). 1, Central incisor; 2, lateral incisor; 3, canine; 4, first premolar; 5, second premolar; 6, first molar; 7, second molar.

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  Fig 7 Cortical bone thickness with different angulations at the 6 mm level. Inter-bar connecting lines mean significant differences between one and the other (p < 0.05). 1, Central incisor; 2, lateral incisor; 3, canine; 4, first premolar; 5, second premolar; 6, first molar; 7, second molar.

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  Fig 8 Mean value of root proximity in the mandible. 1, Central incisor; 2, lateral incisor; 3, canine; 4, first premolar; 5, second premolar; 6, first molar; 7, second molar.

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