Korean J Orthod.  2019 Mar;49(2):97-105. 10.4041/kjod.2019.49.2.97.

In-vitro assessment of the accuracy and reliability of mandibular dental model superimposition based on voxel-based cone-beam computed tomography registration

• Han G
• Li J
• Wang S
• Liu Y
• Wang X
• Zhou Y

• KMID: 2453973
• DOI: http://doi.org/10.4041/kjod.2019.49.2.97

Abstract

OBJECTIVE
This study was performed to evaluate the accuracy and reliability of a newly designed method to achieve mandibular dental model superimposition, using voxel-based cone-beam computed tomography (CBCT) registration.
METHODS
Fourteen dry cadaveric mandibles and six teeth extracted from patients with severe periodontitis were used to establish 14 orthodontic tooth-movement models. The protocol consisted of two steps: in the first step, voxel-based CBCT mandible superimposition was performed; the reference comprised the external portion of the symphysis, extending to the first molar. The laser-scanned dental model image was then integrated with the CBCT image to achieve mandibular dental model superimposition. The entire process required approximately 10 minutes. Six landmarks were assigned to the teeth to measure tooth displacement, using tooth displacement on the superimposed laser-scanned mandibles as the reference standard. Accuracy was evaluated by comparing differences in tooth displacement based on the method and the reference standard. Two observers performed superimposition to evaluate reliability.
RESULTS
For three-dimensional tooth displacements, the differences between the method and the reference standard were not significant in the molar, premolar, or incisor groups (p > 0.05). The intraclass correlation coefficients for the inter- and intra-observer reliabilities of all measurements were > 0.92.
CONCLUSIONS
Our method of mandibular dental model superimposition based on voxel registration is accurate, reliable, and can be performed within a reasonable period of time in vitro, demonstrating a potential for use in orthodontic patients.

Keyword

Computed tomography; Digital models; Tooth movement; Orthodontic treatment

MeSH Terms

Bicuspid
Cadaver
Cone-Beam Computed Tomography*
Dental Models*
Humans
In Vitro Techniques
Incisor
Mandible
Methods
Molar
Periodontitis
Tooth
Tooth Movement

Figure

• 

  Figure 1 Dry mandible model acquisition. A, Six teeth were inserted into the tooth sockets of each dry cadaveric mandible to establish a dry mandible model. B, Laser-scan of a dry mandible model.

• 

  Figure 2 Flowchart of the method and evaluation process. 3D, Three-dimensional; CBCT, cone-beam computed tomography.

• 

  Figure 3 Steps comprising the mandibular dental model superimposition method. A–D, Step 1: Voxel-based cone-beam computed tomography (CBCT) mandible superimposition. The red frame indicates the registration reference area. D, Results of voxel-based CBCT mandible superimposition. E–H, Step 2: registration of the laser-scanned dental model and CBCT images. Selected reference points on the CBCT (E) and laser-scanned dental model (F) images; G, initial registration of the two images according to the reference points; H, completion of the two steps yields mandibular dental model superimposition.

• 

  Figure 4 Color-coded map of the registration procedure. A–D, Color-coded visualization charts show the differences between the two images after the registration procedure. Results of (A) voxel-based cone-beam computed tomography (CBCT) superimposition and (B) registration of the laser-scanned dental model image onto the CBCT image; C, the reference standard: laser-scanned mandible superimposition; D, color-coded visualization chart showing the superimposition error.

• 

  Figure 5 Landmark assignment and three-dimensional (3D) tooth displacement measurements. A, Landmarks were assigned to the bilateral molar mesio-buccal cusps, premolar buccal cusps, and midpoints of the incisor edges. B, Red circle: landmark transferred using crown superimposition to avoid errors in assignment. C, The 3D coordinate system.

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