CBCT Evaluation of Mid-palatine Suture Maturation for Optimum Expansion Mechanics
1Orthodontic Clinic, Pulse Hospital, Ahmedabad, Gujarat, India
2-4Department of Orthodontics, Ahmedabad Dental College, Ahmedabad, Gujarat, India
Corresponding Author: Alka Banker, Orthodontic Clinic, Pulse Hospital, Ahmedabad, Gujarat, India, e-mail: email@example.com
Received on: 23 June 2022; Accepted on: 02 January 2023; Published on: 02 March 2023
Objective: The purpose of this study was to evaluate the maturation of mid-palatine suture (MPS) in Indian adolescents between 11 and 18 years using cone-beam computed tomography (CBCT).
Materials and methods: Cone-beam computed tomography (CBCT) images in axial sections of MPS from 80 adolescents (43 males and 37 females) were classified using a scale denoting the maturation stage of MPS (A, B, C, D, and E). The chi-squared test was applied to evaluate suture stages by sex and age-groups.
Results: Stage A was observed in only four subjects of 11 years. Stage B was present in all age subjects but was more prevalent in subjects <14 years of age. Stage C was the most prevalent in subjects up to 16 years of age. Stages D and E showed low prevalence rates and were found more in subjects in the 17–18-year age-group.
Conclusion: Although the maturation of MPS increases with age, age cannot be considered the only factor. The satisfactory prognosis of orthopedic expansion mechanics can be expected up till stage C, as the bony fusion of MPS begins from stage D.
How to cite this article: Banker A, Andani AG, Trivedi B, et al. CBCT Evaluation of Mid-palatine Suture Maturation for Optimum Expansion Mechanics. CODS J Dent 2022;14(1):11-15.
Source of support: Nil
Conflict of interest: None
Keywords: Cone-beam computed tomography, Expansion, Mid-palatine suture, Rapid maxillary expansion, Slow maxillary expansion, Transverse.
Expansion of the maxilla is one of the most effective orthopedic approaches used for the correction of the transverse maxillary deficiency. Various malocclusions, such as posterior crossbites, dental crowding due to arch perimeter deficiency, and buccally placed canines, are caused due to transverse maxillary deficiency. Expansion can be a rapid maxillary expansion (RME), semi-RME (SRME), or slow maxillary expansion (SME) and is done by gradually opening the MPS and separating the two halves of the maxillary bone with the help of orthopedic expansion devices. The bone formation takes place subsequently between the two separated halves and expands the maxilla transversely. However, expansion can only be performed in patients whose MPS is not completely fused. There is significant variation in the skeletal maturation timing among individuals as the fusion is poorly correlated with the patient’s age and sex.1-3 Consequently, expansion treatment has unpredictable outcomes in still growing but older patients, namely late adolescents and young adults. Failure to properly predict the degree of mid-palatine fusion in these patients can lead to the choosing of the least favorable and potentially damaging expansion modality. Iatrogenic effects, such as acute pain, gingival recession, mucosal necrosis, buccal tipping of teeth, and poor stability, can result if expansion mechanics and appliance is incorrectly selected for a patient with a partial or fully fused palate. Conversely, prematurely committing a patient to surgically assisted RME (SARME) creates a burden of increased cost, pain, and healing time for the patient. Since the successful expansion of the palate is dependent upon the degree of palatal fusion and carefully chosen modality, the orthodontist needs a guideline to establish a more accurate prognosis.
This study was carried out to evaluate the morphology as well as the degree of closure of the MPS of 11–18-year age-groups, in both genders using CBCT.
MATERIALS AND METHODS
For the evaluation of skeletal maturation stages of MPS, our study included axial sections CBCT scans of 80 patients (37 females and 43 males) between the age-group 11 and 18 years taken from a dental diagnostic imaging center in Ahmedabad, Gujarat, India. Subjects were included in the study on the basis of the following criteria:
Cone-beam computed tomography (CBCT) scans of subjects between ages 11 and 18 years.
Cone-beam computed tomography (CBCT) scans of subjects having a history of trauma, surgeries, previous orthodontic treatment, or cleft lip and palate.
All CBCT images used were taken using a CBCT Kodak unit (model CS 9300; Carestream Health, Rochester, New York, USA), 16-bit grayscale CBCT scans were performed at 90 kV, 8 mA, field of view of 17 × 13 cm, 0.3 mm voxel size, and a scan time of 11.30 seconds. All scans were taken by a single technician using the same machine. To standardize the head positioning of all subjects, the vertical laser beam (aimed at the midsagittal plane) and a horizontal laser beam (aimed at Frankfort horizontal) were used during radiographic acquisition. In the multiplanar reconstruction, the screen skull image was manipulated, so that vertical and horizontal lines overlay MPS in the axial and frontal cuts (Fig. 1), and in the sagittal section, the horizontal reference line coincided with the median region of the palate. This area of the palate is the cancellous bone between the upper and lower cortical bones.
The method suggested by Angelieri et al.4 (Fig. 1) was used to classify the maturation stages of MPS. In cases where the palate was very curved and difficult to visualize in one plane, two axial sections were made—one section was in front of the autonomic nervous system (ANS) and the other from the rear of the palate passing through the peripheral nervous system (PNS) (Fig. 2). The skeletal maturation stages of MPS were differentiated using the image in Figure 3.
All the axial cross-sectional slices used for the assessment of MPS were arranged in a presentation (Microsoft Office PowerPoint 2016) with a black background and displayed on a computer screen. Care was taken to keep the contrast of the images constant. They were then reviewed by two examiners, one radiologist and one orthodontist and the best images were selected.4 This was considered the main evaluation. Evaluation by another blinded examiner, an orthodontist, was done to verify interexaminer error using Κ statistics. This was found to be perfect.
Data are presented in tables by relative (percentage) as well as absolute (number) frequencies. The chi-squared test was used to analyze the suture stages by sex and age-groups, and to compare the data with those of Angelieri et al.4 A significance level of 5% (p < 0.05) was used (Table 1).
|% within age||15.4%||61.5%||23.1%||0.0%||0.0%||100.0%|
|% within age||0.0%||36.4%||45.5%||18.2%||0.0%||100.0%|
|% within age||15.4%||30.8%||53.8%||0.0%||0.0%||100.0%|
|% within age||0.0%||35.7%||50.0%||14.3%||0.0%||100.0%|
|% within age||0.0%||11.1%||55.6%||33.3%||0.0%||100.0%|
|% within age||0.0%||14.3%||71.4%||14.3%||0.0%||100.0%|
|% within age||0.0%||16.7%||16.7%||33.3%||33.3%||100.0%|
|% within age||0.0%||14.3%||14.3%||57.1%||14.3%||100.0%|
|% within age||5.0%||31.3%||42.5%||17.5%||3.8%||100.0%|
The development of a protocol enabling clinicians to make reliable treatment planning decisions as it pertains to the modality of palatal expansion has been elusive till date. Skeletal maturation of the MPS from adolescence into young adulthood involves progressive closure, which causes an increase in impedance and a decrease in skeletal response to expansion mechanics and, eventually, failure to separate hemimaxillae. The predictor of success will be a personalized assessment of the patient’s stage of skeletal maturation. This retrospective study has offered insight into the efficacy of implementing Angelieri et al.4 protocol to predict the success of the skeletal expansion of maxilla. In this study, the degree of maturation of MPS and its relationship with developmental stage, age, and gender in the Indian population are evaluated (Table 2).
|% within gender||9.3%||39.5%||30.2%||16.3%||4.7%||100.0%|
|% within gender||0.0%||21.6%||56.8%||18.9%||2.7%||100.0%|
|% within gender||5.0%||31.3%||42.5%||17.5%||3.8%||100.0%|
There was a higher prevalence of stages A, B, and C in young adolescents, while stages D and E were seen in late adolescents, particularly at 17–18 years of age.
Stage A, which is normally found in young adolescents, was found only in four samples of our study; this is consistent with the results of Angelieri et al.4
Stage B was observed more commonly in the 12–14 years (31.3%) age-group. It was observed in 11 (61.5%), 12 (36.4%), 13 (30.8%), and 14 years (35.7%). Similar results were also seen in other studies in which stage B was observed mainly up to 13 years of age.4,6
Treatment given at this stage of maturation (stages A and B) can be effective, with both skeletal as well as dental expansion possible. Any expansion modalities could be considered, depending upon the clinician’s preference. But in SME, only dentoalveolar changes could be expected (Table 3 and 4).7
|% within age-group||10.8%||43.2%||40.5%||5.4%||0.0%||100.0%|
|% within age-group||0.0%||35.7%||50.0%||14.3%||0.0%||100.0%|
|% within age-group||0.0%||13.8%||41.4%||34.5%||10.3%||100.0%|
|% within age-group||5.0%||31.3%||42.5%||17.5%||3.8%||100.0%|
|A||Relatively straight high-density line at the midline|
|B||Scalloped high-density line at the midline|
|C||Two parallel, scalloped high-density lines close to each other and separated in some areas by small low-density spaces|
|D||Two scalloped high-density lines at the midline on the maxillary portion of the palate that cannot be visualized in the palatine bone|
|E||It cannot be identified|
In stage C, “bony islands” can be seen in tomographic images of the subjects. Stage C was found mainly in the 12–16-year age-group and was 13 (53.8%), 14 (50.0%), 15 (55.6%), and 16 years (71.4%). Stage C was found more commonly in females (56.8%) than males (30.2%) in our study. Similar results were seen in other studies, which means maturation of MPS occurs earlier in women than in men.8 Since this is a transition stage where there is a beginning of fusion, it would be preferable to use lighter, more physiological forces to avoid damage to the anchor teeth. SRME could be a treatment of choice here, where the forces are not so high so as to cause damage and trauma, and at the same time not so light that it does not have any effect on the sutural opening.9
Stage D was seen mainly in the 15–18-year age-group, particularly after 15 years. It was seen in 17 (33.3%) and 18 years (57.1%). So the highest prevalence of stage D was seen in 18-year-old. However, it was equally distributed between both sexes (seven females and seven males). As the age of the group increased, a progressively higher percentage of stage D was seen.4,6
In the age-group 11–15 years, a lower percent (13.1%) of stage D was seen with equal distribution between the sexes (six girls and five boys). This suggests that the prevalence of stage D increases with increasing age.6
With the maturation of MPS, there is an increase in interdigitation,10,11 which begins in the posterior region and subsequently progresses toward the anterior.1,11
Expansion mechanics at this stage may show diastema or spacing in the anterior region and dental expansion in the posterior region. When the expansion is done for relieving anterior crowding and not for correction of posterior crossbite, the treatment will be successful at this stage. An expansion protocol using the RME approach would not be a viable option for patients at this stage, as increased forces may likely cause molar or premolar extrusion and periodontal damage. The option of mini-implant assisted rapid palatal expander using the palate as an anchorage could be considered here.12 Stage E in which complete ossification of MPS was observed only 3.8% of total samples in 17–18 years of age. Patients with a thinner palate are usually classified as stage E because the upper and lower cortical bones are close together.4 The parasutural bone density is increased, with the same level as in other regions of the palate.13 At this stage, only dental tipping movements because of expansion mechanics could be expected. SARME could be considered as the treatment of choice during this stage if skeletal expansion is needed.14
There were no significant differences between males and females in suture morphology which is consistent with the results of other studies.6,7,15
Studies have shown that rather than the presence or lack of fusion, it is the percentage of fusion in each subject that is more critical.1,10 Hence, choosing the expansion technique should depend not on age or dentition but on the maturation stage. Different expansion modalities depending upon the stage of maturation, could help the clinician choose the most favorable appliance with the potential for minimum damage. In this way, a customized treatment can be given to every patient depending on his MPS maturation stage.
Though the maturation of MPS increases with age, it is not the only criteria to be considered. Rather than age or dentition, the percentage of maturation or fusion is more critical. A favorable prognosis of expansion mechanics can be expected till stage C of MPS maturation, while dentoalveolar changes can be expected in stage D. Thus, depending on which stage of maturation the patient is in, appliances, as well as the forces of expansion, can be chosen to diminish potential damage and deliver most favorable prognosis.
Alka Banker https://orcid.org/0000-0001-8446-8011
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