Korean J Orthod.  2021 Jul;51(4):260-269. 10.4041/kjod.2021.51.4.260.

Quantitative cone-beam computed tomography evaluation of hard and soft tissue thicknesses in the midpalatal suture region to facilitate orthodontic mini-implant placement

• Oh SH
• Lee SR
• Choi JY
• Kim SH
• Hwang EH
• Nelson G

• KMID: 2518519
• DOI: http://doi.org/10.4041/kjod.2021.51.4.260

Abstract

Objective
To identify the most favorable sites that optimize the initial stability and survival rate of orthodontic mini-implants, this study measured hard and soft tissue thicknesses in the median and paramedian regions of the palate using cone-beam computed tomography (CBCT) and determined possible sexand age-related differences in these thicknesses.
Methods
The study sample comprised CBCT images of 189 healthy subjects. The sample was divided into four groups according to age. A grid area was set for the measurement of hard and soft tissue thicknesses in the palate. Vertical lines were marked at intervals of 0, 1.5, and 3.0 mm lateral to the midpalatal suture, while horizontal lines were marked at 2-mm intervals up to 24 mm from the posterior margin of the incisive foramen. Measurements were made at 65 points of intersection between the horizontal and vertical lines.
Results
The palatal hard tissue thickness decreased from the anterior to the posterior region, with a decrease in the medial-to-lateral direction in the middle and posterior regions. While the soft tissue was rather thick around the lateral aspects of the palatal arch, it formed a constant layer that was only 1–2-mm thick throughout the palate. Statistically significant differences were observed according to sex and age.
Conclusions
The anterolateral palate as well as the midpalatal suture seem to be the most favorable sites for insertion of orthodontic mini-implants. The thickness of the palate differed by age and sex; these differences should be considered while planning the placement of orthodontic mini-implants.

Keyword

Cone-beam computed tomography; Midpalatal suture; Thickness; Mini-implant

Figure

• 

  Figure 1 A, A schematic illustration of the area for measuring the hard tissue and soft tissue thicknesses of the palate (so-called I-bar). B, Measuring grid for the palatal hard and soft tissue heights at the 65 evaluated sites, starting from the posterior border of the incisive foramen (occlusal view). C, Reference points and lines for measuring the palatal hard and soft tissue heights (sagittal view). AP, anterior-posterior; ML, midline-lateral.

• 

  Figure 2 A sagittal section of a cone-beam computed tomography image of the palate. The image shows the measurement of the height of the soft (A) and hard (B) tissues of the palate at one reference point (the midpalatal suture [ML = 0], 4 mm from incisive foramen posteriorly [AP = 4]). AP, anterior-posterior; ML, midline-lateral.

• 

  Figure 3 Mean palatal hard and soft tissue thicknesses (mm) at the 65 evaluated sites. Midline, the line at the midpalatal suture; Left 1.5 and 3.0, the lines from left 1.5 and 3.0 mm from the midline; Right 1.5 and 3.0, the lines from right 1.5 and 3.0 mm from the midline.

• 

  Figure 4 Mean palatal hard (A) and soft (B) tissue thicknesses (mm) at the 65 evaluated sites in male and female patients. Hard and soft tissue thicknesses showing significant sex-related differences (*) are marked in blue and orange color, respectively. Midline, the line at the midpalatal suture; Left 1.5 and 3.0, the lines from left 1.5 and 3.0 mm from the midline; Right 1.5 and 3.0, the lines from right 1.5 and 3.0 mm from the midline. In each line, the left and right rows indicate thickness in male and female patients, respectively.

• 

  Figure 5 Mean palatal hard and soft tissue thicknesses (mm) at the 65 evaluated sites were marked with a target shape. The inner circle color indicated the thickness of the hard tissue, and the outer circle color indicated the thickness of the soft tissue, referring to the color scale bar on the left. A, Whole group. B, Male and female groups. C, Mixed and permanent dentition groups.

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