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The accuracy of computer-aided design and manufacturing surgical-guide for infrazygomatic crest miniscrew placement

Objectives:

Infrazygomatic crest (IZC) surgical guides have been employed to prevent any avoidable complications during miniscrew insertion. The purpose of this study was to evaluate the accuracy of IZC miniscrew placement when using a surgical-guide developed by computer-aided design and manufacturing (CAD/CAM) techniques.

Materials and Methods:

Ten patients were scanned with cone-beam computed tomography for three-dimensional (3D) planning of IZC miniscrew placements. The upper arches were scanned separately, and virtual miniscrews were placed in the position planned by 3D software. The CAD/CAM surgical guides were designed and fabricated individually to enable accurate miniscrew placement. Subsequently, 20 self-drilling miniscrews were inserted at the right and left IZC areas using 5 CAD/CAM surgical guides (CS group, n = 10) and direct insertion (DI group, n = 10), respectively. Pre- and post-operative digital model images were compared, actual and planned miniscrew positions were superimposed and measured for 3D angular and distance deviations in the two groups. Comparisons between groups were made using the Kruskal–Wallis test.

Results:

In the CS group, the median coronal and sagittal angular deviations were 2.95 degrees (range 0.34–5.26 degrees) and 2.05 degrees (range 0.38–4.08 degrees), respectively, while the median coronal and apical deviations were 0.39 mm (range 0.24–0.51 mm) and 0.50 mm (range 0.16–0.66 mm). These deviations differed significantly from those of the DI group.

Conclusion:

The IZC CAD/CAM surgical guide has made it possible to control miniscrew placement with high precision.

Accuracy of miniscrew surgical guides assessed from cone-beam computed tomography and digital models

INTRODUCTION

Several methods are available to enhance the precision of miniscrew placement. The use of surgical guides based on cone-beam computed tomography is indicated especially in patients with risky or difficult anatomic situations. The purpose of this study was to evaluate the accuracy of miniscrew placement by using surgical guides developed with computer-aided design and manufacturing techniques.

METHODS

Miniscrews were placed in cadaver maxillae using stereolithographic computer-aided design and manufacturing techniques with assistance from surgical guides (surgical guide group, n = 25) or periapical x-rays (control group, n = 20). Insertion sites were selected using a 3-dimensional surgical planning program by fusing maxillary digital model images and cone-beam computed tomography images. Deviations between actual and planned placements were measured as 3-dimensional angular deviations and distance (coronal and apical) deviations.

RESULTS

In the surgical guide group, the angular deviation was a median of 3.14° (range, 1.02°-10.9°), and the mesiodistal deviations in the coronal and apical areas were medians of 0.29 mm (range, 0.03-0.73 mm) and 0.21 mm (range, 0.03-0.97 mm), respectively. The deviations differed significantly between operators in the control group, but not in the surgical guide group. In the surgical guide group, there was no root damage from miniscrew placement, and 84% of the miniscrews were placed without contacting adjacent anatomic structures. In the control group, 50% of the miniscrews were placed between the roots (P <0.05).

CONCLUSIONS

Surgical guide accuracy was improved when digital model imaging was used. Miniscrews were placed more accurately when using surgical guides than when using a direct method.