Original article
Computed tomographic analysis of tooth-bearing alveolar bone for orthodontic miniscrew placement

https://doi.org/10.1016/j.ajodo.2007.05.019Get rights and content

Introduction

When monocortical orthodontic miniscrews are placed in interdental alveolar bone, the safe position of the miniscrew tip should be ensured. This study was designed to quantify the periradicular space in the tooth-bearing area to provide practical guidelines for miniscrew placement.

Methods

Computerized tomographs of 30 maxillae and mandibles were taken from nonorthodontic adults with normal occlusion. Both mesiodistal interradicular distance and bone thickness over the narrowest interradicular space (safety depth) were measured at 2, 4, 6, and 8 mm from the cementoenamel junction.

Results

Mesiodistal space greater than 3 mm was available at the 8-mm level in the maxillary anterior region, between the premolars, and between the second premolar and the first molar at 4 mm. In the mandible, sufficient mesiodistal space was found between the premolars, between the molars, and between the second premolar and the first molar at the 4-mm level. Safety depth greater than 4 mm was found in the maxillary and mandibular intermolar regions, and between the second premolar and the first molar in both arches.

Conclusions

Subapical placement is advocated in the anterior segment. Premolar areas appear reliable in both arches. Angulated placement in the intermolar area is suggested to use the sufficient safety depth in this area.

Section snippets

Material and methods

The accuracy of the CT and the measuring software was preliminarily assessed by using a dry human skull with an intact alveolar bone structure before actual measurement (Fig 1). A 1.0 x 125 mm Duran (Scheu-Dental GmbH, Iserlohn, Germany) plate was fixed with sticky wax parallel to the occlusal plane on the alveolar crest of the skull. Gutta percha markers were attached on the plate at 5 points. The skull was then placed in a custom-made acrylic box 5 mm thick filled with distilled water to

Results

Linear CT measurements compared with the actual measurements from the skull showed a mean ratio of 0.993 (SD, 0.08), indicating excellent reliability of the CT.

In the maxilla, the greatest interroot distance was observed between the first molar and the second premolar at the 8-mm level from the CEJ. The areas with the greatest mean interradicular space at the 4-mm level were the second premolar and the first molar followed by the first and second premolars, and the lateral incisor and the

Discussion

The amount of periroot space can be affected by the shape and length of adjacent roots and their arrangements, ie, tips and torques. When the root shape is conical or pipette shaped, the operator can take advantage of the larger interdental space in the middle or apical portion. Since the periroot space is generally only 2 to 3 mm, accuracy was critical in this study. Although the high accuracy and the reliability of the CT are known, the preliminary study on the dry skull was performed to

Conclusions

This study was designed to evaluate the periroot space in the tooth-bearing area to provide practical guidelines for miniscrew placement. The results and its clinical implications are summarized as follows.

  • 1.

    In the maxilla, between the central incisors at 8 mm from CEJ, between the lateral incisor and the canine at 8 mm, between the canine and the first premolar at 6 mm, between the first and second premolars at 4 mm, and between the second premolar and the first molar at 4 mm showed adequate

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  • Cited by (0)

    Supported by the 2004 research fund of the College of Dentistry, Yonsei University.

    The authors report no commercial, proprietary, or financial interest in the products or companies described in this article.

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