Introduction
This study aimed to evaluate the maturation of the midpalatal suture (MPS), zygomaticomaxillary suture, and zygomaticotemporal suture (ZTS) (right and left) through density by multislice computed tomography in patients categorized by age groups.
Methods
We evaluated tomographic images of 192 participants (aged 7-30 years), divided into 3 groups by age. To analyze the maturation of the sutures, the density scores of MPS, zygomaticomaxillary, and ZTS were determined in Hounsfield units, within an area corresponding to 1 mm in width and length, referring to the longest length of each suture, in 3 regions: central, right adjacent, and left adjacent sites. A density cutoff point in MPS for performing rapid maxillary expansion was established using the receiver operating characteristic curve.
Results
The length of the sutures has a positive correlation with age and density. Density in all measurements showed a positive and significant correlation with age. All sutures had lower density in central sites than in adjacent sites (except in group 3: left adjacent sites of MPS and zygomatic site of ZTS sutures). There was no significant difference between the sexes. The density cutoff point in MPS was 294.4 Hounsfield units.
Conclusions
Density increases with age, showing a significant correlation. Central sites have lower density than adjacent sites, especially in younger patients. Sex does not have any relevant effects on the final measurement values, and density appears to be correlated with the degree of sutures maturation.
Highlights
-
•
Density in the bony sutures involved in rapid maxillary expansion increases with age.
-
•
The sutures presented lower density at the central sites than at the adjacent sites.
-
•
Suture density may be a possible predictor for the decision to perform rapid maxillary expansion.
Transverse maxillary deficiency stands out as a frequent diagnosis among orthodontic patients. Posterior crossbite, unilateral or bilateral, is the malocclusion most commonly associated with this deficiency, with an incidence between 8% and 22% in deciduous and early mixed dentitions.
Rapid maxillary expansion (RME) has been the treatment of choice among orthodontists to correct this discrepancy. The maxillary disjunction procedure was first described by Angell, but Haas was the one who popularized the benefits of separating the midpalatal suture (MPS).
During the RME process, however, it has been suggested that the opening of the MPS does not represent an isolated event, as it is associated with side effects on soft tissues and support structures. ,,,
Difficulties and diverse side effects have been associated with nonsurgical RME in late adolescents and young adults, ,,,, contrary to the satisfactory results obtained during the period of pubertal growth. ,, The decision of which procedure to choose to treat late adolescents and young adults has historically been a challenge. ,, However, individual assessment of the maturation of the MPS and circummaxillary sutures may be a promising method for predicting the best expansion technique to be used. ,
Despite the success of the RME protocol, there is still no consensus regarding the age limit for performing midpalatal disjunction. Furthermore, several studies question age as a limiting factor. ,,,,,,,,,,, It has been reported by several authors that age alone cannot be a reliable indicator for predicting the fusion or maturation of the PMS, because, even in adults, patients with immature sutures have been found. ,,, This is mainly because of the great physiological variability among patients who may present the palatine suture with more obliteration or with more interdigitation, both early and at more advanced ages, without there being a precise method and diagnosis for such assessment. ,,,,,
Recent studies ,,, have associated density in the MPS and circummaxillary sutures with the outcome of RME, and sought to correlate this density with the outcome of palatal disjunction. However, more details about the maturational stages are necessary to guide the clinician in the safest indication of the RME protocol.
This study aimed to develop and evaluate an objective density-based method to determine the degree of maturation of the MPS, zygomaticomaxillary suture (ZMS), and zygomaticotemporal suture (ZTS) and define a cutoff point for MPS density to indicate nonsurgical treatment in adult and late adolescent patients.
Material and methods
The research was approved by the Research Ethics Committee of the Federal University of Juiz de Fora, according to the criteria for research on human beings (document No. 5.960.602).
On the basis of previous studies, ,,,,,,, a sample of 192 examinations was calculated to compare 3 groups of equal sizes, with assumed Gaussian distributions, standardized difference (effect size), and intended power values. The parameters adopted were an effect size of 0.30, test power of 0.80, and an α value of 0.05.
From a database of multislice computed tomography (MSCT) examinations of the skull and face, tomographic examinations of patients aged 7-30 years without cranial malformation and/or bone pathology and without signs of rhinosinusitis were randomly selected. The 192 MSCT examinations were allocated into 3 groups, with a homogeneous distribution between males and females (97 women and 95 men), according to age range (n = 64 per group): group 1, aged 7-13 years; group 2, aged 13-20 years; group 3, aged 21-30 years.
MSCT images were acquired with a 128-channel computed tomography scanner (Somatom Definition AS; Siemens Medical Systems, Erlangen, Germany). The automatic tube modulation system (CARE 4D; Siemens Medical Systems) was used in all examinations. The field of view used comprised the entire skull, and the axial sections were performed with 100 kV/mA (40 mA) and a reconstruction thickness of 2 mm.
The degree of skeletal density of the MPS, right and left ZMS, and right and left ZTS was determined in all sample examinations using the OnDemand 3D program (Cybermed Inc, Seoul, South Korea). The positioning of the skull image was reoriented, adjusting the median sagittal line (union of the anterior nasal spine and Nasion points) in a vertical position and the Frankfurt plane in a horizontal position.
Subsequently, the axial section in which the MPS presents the greatest anteroposterior extension was identified, in which the length of the MPS was determined through the distance between the anterior nasal spine and the posterior nasal spine.
On the MPS image, using the region of interest (ROI) tool, the density values in Hounsfield units (HU) were measured within a 1-mm wide ROI and the length of the MPS, determining the central site (CS) ( Fig 1 ). Next, 2 ROIs with the same width (1 mm) were determined juxtaposed to the CS, 1 on the right side (right adjacent site [ADS]) and one on the left side (left ADS) ( Fig 1 ). All ROIs respected the anterior and posterior limits of the maxilla. For each examination, the average density value in the MPS area was determined in the CS, right ADS, and left ADS.
Delimitation of the left CS and ADS in the axial section to determine the density in the MPS.
For the evaluation of the right and left ZMS, the measurements were made in the coronal plane, with the same skull positioning criteria and ROI construction methodology adopted for MPS. In the ZMS were determined the CS, the zygomatic ADS (ZADS; on the zygomatic bone side), and the maxillary ADS (MADS; on the maxilla side) were determined, being evaluated the average density in each site being evaluated ( Fig 2 ).
Delimitation of the CS in the coronal section to determine the density in the ZMS.
To measure the right and left ZTS, measurements were made in the coronal plane, with the same skull positioning criteria and ROI construction methodology adopted for MPS. In ZTS, the CS, ZADS (on the side of the zygomatic bone), and temporal ADS (TADS; on the side of the temporal bone) were determined, and the average density was evaluated at each site ( Fig 3 ).
Delimitation of the zygomatic CS and ADS in the coronal section to determine the density in the ZTS.
To evaluate the examiner’s calibration and determine the method error, the average density of the 3 sutures was determined twice (in 30 examinations), with a 30-day interval between measurements, and then compared.
Statistical analysis
The intraclass correlation coefficient was applied to evaluate method error. The distribution of continuous variables was verified using the Kolmogorov-Smirnov test.
Comparison of suture length and density between sexes was performed using the Mann-Whitney test. For comparisons of suture density among the 3 age groups, the Kruskal-Wallis analysis was applied, followed by the Bonferroni post-hoc test.
Spearman analysis verified the degree of correlation between suture length, density in CS and ADS, age, and sex. Multiple linear regression was performed between the density of the CS and ADS in each suture.
For all analyses, the α level was established at 0.05, with a 95% confidence interval, and was performed in Stata software (version 15; Stata Corp, College Station, Tex).
Density values of the CS of MPS were subjected to receiver operating characteristic (ROC) curve analysis to determine a density value at which it is possible to safely perform RME, taking as a cutoff point the density of patients aged 13 years (up to 14 years old).
Results
Interclass correlation coefficient values were >0.98 for all measurements, indicating excellent intrarater reliability. The Kolmogorov-Smirnov test indicated nonnormal distribution of variables, with the exception of density at the CS of the left ZMS suture ( P = 0.077).
Among the 192 participants in the study, 97 (50.5%) were female and 95 (49.5%) were male ( Table I ).
Table I
Average ages by age groups
| Groups | Female | Male | Total |
|---|---|---|---|
| 1 (aged 7-13 y) | 9.93 ± 1.99 | 10.79 ± 1.93 | 10.39 ± 2.00 |
| 2 (aged 14-20 y) | 16.54 ± 2.04 | 16.59 ± 1.91 | 16.56 ± 1.97 |
| 3 (aged 21-30 y) | 24.94 ± 2.84 | 25.28 ± 2.95 | 25.11 ± 2.87 |
Note. Values are presented as mean ± standard deviation.
The total length and density of the CS and ADS for men and women are shown in Table II . There was no significant difference between men and women.
Table II
Average length values and densities by gender
| Variables | Female | Male | P value |
|---|---|---|---|
| MPS | |||
| Total length | 46.6 ± 3.9 | 47.2 ± 4.0 | 0.346 |
| CS | 336.7 ± 145.9 | 336.4 ± 158.1 | 0.994 |
| Right ADS | 482.4 ± 131.4 | 523.8 ± 110.9 | 0.122 |
| Left ADS | 394.6 ± 188.9 | 394.5 ± 112.7 | 0.263 |
| Right ZMS suture | |||
| Total length | 22.4 ± 4.0 | 22.9 ± 4.0 | 0.646 |
| CS | 496.5 ± 210.2 | 456.3 ± 174.6 | 0.078 |
| MADS | 667.6 ± 142.6 | 685.2 ± 161.8 | 0.468 |
| ZADS | 626.6 ± 116.1 | 643.1 ± 109.7 | 0.255 |
| Left ZMS suture | |||
| Total length | 21.7 ± 4.6 | 22.8 ± 4.6 | 0.121 |
| CS | 462.3 ± 201.6 | 460.0 ± 169.4 | 0.967 |
| ZADS | 728.8 ± 189.4 | 714.2 ± 155.8 | 0.730 |
| MADS | 509.9 ± 258.2 | 605.2 ± 194.9 | 0.025 |
| Right ZTS | |||
| Total length | 12.8 ± 3.0 | 13.3 ± 2.8 | 0.256 |
| CS | 563.5 ± 281.2 | 595.0 ± 258.5 | 0.587 |
| ZADS | 595.6 ± 278.7 | 631.9 ± 272.2 | 0.291 |
| TADS | 671.2 ± 198.6 | 668.4 ± 243.0 | 0.811 |
| Left ZTS | |||
| Total length | 13.0 ± 3.2 | 13.2 ± 3.0 | 0.624 |
| CS | 635.9 ± 310.6 | 676.0 ± 336.9 | 0.461 |
| TADS | 691.3 ± 313.8 | 719.6 ± 320.4 | 0.597 |
| ZADS | 673.3 ± 304.3 | 715.0 ± 336.9 | 0.457 |
Note. Values are presented as mean ± standard deviation.
Table III presents the values for the total length and densities of the CS and ADS divided by age groups. With the exception of the density of the ZADS of the right ZMS and the right ADS of the MPS, all variables showed a significant difference among the 3 groups, with the greatest absolute difference between groups 1 and 2, except in the right ZTS. In group 1, the CS presented the lowest density values in relation to the ADS, which was observed only in the MPS and right ZMS in group 2.
Table III
Comparison of the mean values of total length and density in the CS and ADS of the sutures among the 3 age groups
| Variables | Groups | P value | Group difference | ||||
|---|---|---|---|---|---|---|---|
| 1 | 2 | 3 | 2 − 1 | 3 − 2 | 3 − 1 | ||
| MPS | |||||||
| Total length (mm) | 43.2 ± 1.8 | 47.3 ± 2.9 | 50.1 ± 3.3 | <0.001 | 4.1 | 2.8 | 6.9 |
| CS (HU) | 174.1 ± 62.7 | 381.3 ± 117.4 | 454.2 ± 95.4 | <0.001 | 207.2 | 72.9 | 280.1 |
| Right ADS (HU) | 479.0 ± 113.2 | 515.7 ± 114.6 | 513.9 ± 138.4 | 0.075 | 36.7 | −1.8 | 34.8 |
| Left ADS (HU) | 290.1 ± 179.8 | 455.3 ± 136.5 | 438.1 ± 74.6 | <0.001 | 165.2 | −17.2 | 148.0 |
| Right ZMS | |||||||
| Total length (mm) | 18.5 ± 3.4 | 24.4 ± 2.3 | 25.0 ± 2.5 | <0.001 | 5.9 | 0.6 | 6.54 |
| CS (HU) | 269.6 ± 121.8 | 537.4 ± 141.0 | 622.9 ± 101.3 | <0.001 | 267.8 | 85.5 | 353.3 |
| MADS (HU) | 641.0 ± 117.0 | 638.1 ± 143.1 | 749.9 ± 166.9 | <0.001 | −2.9 | 111.8 | 108.9 |
| ZADS (HU) | 623.1 ± 115.9 | 623.5 ± 116.9 | 657.6 ± 104.1 | 0.193 | 0.4 | 34.1 | 34.4 |
| Left ZMS | |||||||
| Total length (mm) | 18.0 ± 3.7 | 24.6 ± 3.2 | 24.1 ± 2.9 | <0.001 | 6.6 | −0.5 | 6.0 |
| CS (HU) | 271.4 ± 108.3 | 526.5 ± 152.4 | 585.6 ± 114.8 | <0.001 | 255.1 | 59.1 | 314.2 |
| ZADS (HU) | 628.7 ± 153.0 | 776.8 ± 154.6 | 759.2 ± 174.3 | <0.001 | 148.1 | −17.6 | 130.6 |
| MADS (HU) | 560.3 ± 174.9 | 416.6 ± 269.6 | 694.3 ± 150.7 | <0.001 | −143.7 | 277.7 | 133.9 |
| Right ZMS | |||||||
| Total length (mm) | 10.3 ± 1.9 | 14.0 ± 2.3 | 14.8 ± 2.5 | <0.001 | 3.7 | 0.8 | 4.4 |
| CS (HU) | 319.4 ± 154.9 | 559.5 ± 169.3 | 858.3 ± 142.2 | <0.001 | 240.1 | 298.8 | 538.8 |
| ZADS (HU) | 423.2 ± 158.8 | 539.2 ± 239.0 | 878.3 ± 184.4 | <0.001 | 116.0 | 339.1 | 455.0 |
| TADS (HU) | 491.6 ± 145.9 | 633.9 ± 159.2 | 883.9 ± 146.4 | <0.001 | 142.3 | 250.0 | 392.2 |
| Left ZMS | |||||||
| Total length (mm) | 10.2 ± 1.4 | 14.5 ± 2.9 | 14.7 ± 2.3 | <0.001 | 4.3 | 0.2 | 4.5 |
| CS (HU) | 312.7 ± 120.4 | 705.4 ± 262.1 | 949.0 ± 158.1 | <0.001 | 392.7 | 243.6 | 636.3 |
| TADS (HU) | 533.3 ± 279.5 | 677.6 ± 300.7 | 905.1 ± 252.8 | <0.001 | 144.3 | 227.5 | 371.8 |
| ZADS (HU) | 478.6 ± 185.1 | 629.8 ± 338.7 | 973.4 ± 179.4 | <0.001 | 151.2 | 343.6 | 494.8 |
Stay updated, free articles. Join our Telegram channel
Full access? Get Clinical Tree
