Korean J Orthod.  2021 Jul;51(4):231-240. 10.4041/kjod.2021.51.4.231.

Root proximity of the anchoring miniscrews of orthodontic miniplates in the mandibular incisal area: Cone-beam computed tomographic analysis

• Jeong DM
• Oh SH
• Choo H
• Choi YS
• Kim SH
• Lee JS
• Hwang EH

• KMID: 2518516
• DOI: http://doi.org/10.4041/kjod.2021.51.4.231

Abstract

Objective
This outcome analysis study evaluated the actual positions of the orthodontic miniplate and miniplate anchoring screws (MPASs) and the risk factors affecting adjacent anatomic structures after miniplate placement in the mandibular incisal area.
Methods
Cone-beam computed tomographic images of 97 orthodontic miniplates and their 194 MPASs (diameter, 1.5 mm; length, 4 mm) in patients whose miniplates provided sufficient clinical stability for orthodontic treatment were retrospectively reviewed. For evaluating the actual positions of the miniplates and analyzing the risk factors, including the effects on adjacent roots, MPAS placement height (PH), placement depth (PD), plate angle (PA), mental fossa angle (MA), and root proximity were assessed using the paired t-test, analysis of variance, and generalized linear model and regression analyses.
Results
The mean PDs of MPASs at positions 1 (P1) and 2 (P2) were 2.01 mm and 2.23 mm, respectively. PA was significantly higher in the Class III malocclusion group than in the other groups. PH was positively correlated with MA and PD at P1. Of the 97 MPASs at P1, 49 were in the no-root area and 48 in the dentulous area; moreover, 19 showed a degree of root contact (19.6%) without root perforation. All MPASs at P2 were in the no-root area.
Conclusions
Positioning the miniplate head approximately 1 mm lower than the mucogingival junction is highly likely to provide sufficient PH for the P1-MPASs to be placed in the no-root area.

Keyword

Cone-beam computed tomography; Miniplate; Anchorage; Orthodontic treatment

Figure

• 

  Figure 1 Clinical application of the orthodontic miniplate (OMP) used in this study. A, OMP for lower intrusion and molar protraction. Intraoral photographs and panoramic radiographs show multidirectional tooth movement achieved using a bendable OMP. B, Schematic illustration of an OMP combined with a reverse curve NiTi application for lower posterior uprighting with intrusion.

• 

  Figure 2 Placement protocol of the orthodontic miniplate (OMP). A, The I-type OMP with two holes and a tube-shaped head. B, The OMP is placed with self-drilling miniplate anchoring screws (MPASs). C, The OMP is placed in the incised area. D, MPASs are fixed to the cortical bone under the mucosa by using a manual screwdriver. E, The incised area is sutured with 4-0 silk. P1, position 1; P2, position 2.

• 

  Figure 3 Schematic illustration and actual cone-beam computed tomographic image of the orthodontic miniplate (OMP) in the anterior mandible. A, The vertical distance from the cementoenamel junction to the center of the miniplate anchoring screw (MPAS) at position 1 (P1) (placement height, PH). B, Distance from the outer surface of the labial cortical bone to the tip of the MPASs at P1 (PD1) and P2 (PD2). C, The angle of the step-up bend on the OMP that was made by an orthodontist based on the soft- and hard-tissue anatomic features of the incision site (plate angle, PA). D, The angle made by the two tangents on the sagittal plane, with one from the most prominent midpoint of the chin and the other from the most prominent point on the labial root surface (mental fossa angle, MA).

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  Figure 4 Schematic illustration showing the classification of root proximity according to the location of the miniplate anchoring screw (MPAS) at position 1. A, Frontal view: group 1, frontal overlap (no contact [1a], frontal contact [1b, the MPAS contacts the labial surface of the mandibular incisor], and root perforation [1c]); group 2, interdental space; group 3, lateral contact; and group 4, no-root area. B, Axial view: 1a, no contact; 1b, frontal contact; 1c, root perforation; 2, interdental space; 3, lateral contact.

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  Figure 5 Cone-beam computed tomographic image of the orthodontic miniplate according to the classification of root proximity. A, Group 1 with subdivision a, no contact. B, Group 1 with subdivision b, frontal contact. C, Group 3, lateral contact. D, Group 2, interdental space. E, Group 4, no-root area.

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