1. COMPARATIVE EVALUATION OF THE RAPID PALATAL
EXPANSION ZONE USING ULTRASONOGRAPHY AND
CONVENTIONAL RADIOGRAPHY
Ibrahim Sevki Bayrakdar
Ismail Gumussoy
Ozkan Miloglu
Yasin Yasa

2. Rapid palatal expansion (RPE) was first introduced in the 1860s
by Angell for the treatment of maxillary constriction. It later
became a conventional orthodontic treatment. RPE is used in
orthodontic practice to correct posterior crossbite and dental
crowding and to facilitate correction of Angle Class II and Class III
malocclusions. The overall objective of RPE is to widen the maxilla
by separating the midpalatal suture and the circummaxillary
sutural system.

3. Oral radiographs and computed tomography (CT) are commonly
used methods to assess the palatal expansion zone. However,
Sumer et al. indicated that ultrasonography (US) might be a useful
and accurate method to evaluate bone fill in the midpalatal suture
in patients undergoing surgically assisted RPE. In the orthopedic
literature, US has been shown to be accurate and reliable for the
evaluation of distraction osteogenesis wounds in long bones. Studies
also showed that US was useful for the evaluation of mandibles
treated with distraction osteogenesis.

4. The purpose of this study was to assess the accuracy of US in
evaluating the sutural opening in a series of patients undergoing
RPE, verifying the reliability of the method against those of oral
radiographic findings.

5. Methods and materials
The study sample consisted of 29 nonsurgical patients (mean age, 13.9 years;
range, 11-20 years; 12 males, 17 females) with mixed or permanent dentition
who underwent RPE therapy as part of comprehensive orthodontic treatment.
Subjects with craniofacial anomalies that would have required any type of
surgical intervention were not included in the study. Individuals with prior
orthodontic treatment history, such as phase I treatment, were also excluded
from the sample. Each patient had a 2-banded Haas appliance, which was
supported by the bilateral maxillary first molars, with extension of the
expansion arms along the gingiva of the premolars.

6. 2-banded Haas appliance

7. Maxillary expansion started at the beginning of the orthodontic treatment for
all the patients, and the appliance was activated by one turn per day until the
maxillary constriction was corrected. Depending on the amount of expansion,
the activation period ranged from 21 to 25 days. All evaluations, including
occlusal radiographs and US examinations, were performed immediately after
appliance practice (T1), 10 turns (T2), and 20 turns (T3) during the expansion
period. In total, 87 US images and 87 occlusal radiographies of 29 patients
were evaluated.

8. Radiographic examination technique
Maxillary occlusal radiographs were taken using a Belmont Photo X-II
dental X-ray machine, set at 60 kVp and 7 mA with an exposure time of 0.50 s.
Vista scan phosphor plate system was used. To ensure standardization of the
occlusal radiographs of the maxillary region, the patient sat upright, with the
sagittal plane perpendicular to the floor and the occlusal plane horizontal. The
receptor was placed with the long dimension perpendicular to the sagittal
plane, crosswise in the mouth. The central ray was directed at a vertical
angulation of +65 degrees and a horizontal angulation of 0 degrees, the bridge
of the nose just below the nasion, and toward the middle of the receptor. The
central ray entered the patient’s face through the bridge of the nose.

9. Radiographic examination technique

10. Two experienced radiologists performed the US examinations.
Sonograms were obtained in the axial planes using an Applio 300 (Toshiba,
Tokyo, Japan) 8 MHz linear array transducer. The ultrasound probe was
positioned outside the mouth on the skin overlying the midpalatal suture,
and the US beam was oriented perpendicular to the bone surface. A real-time
survey was then performed of the midpalatal suture, producing axial
slices.
Ultrasound scanning technique

11. Ultrasound scanning technique

12. Radiological evaluation
The radiographs revealed a normal anatomical structure at the beginning
of the treatment prior to expansion of the midpalatal sutural opening. As the
midpalatal suture was opened, the radiographic image showed a larger
radiolucid area, parallel to the suture or triangular shaped, with its base
toward the anterior region of the face.

13. Ultrasonography evaluation
Using US, the surfaces of the bone segments were easily identified, and
assessments in the expansion zone could be performed accurately during the
active phase of expansion. The area was characterized by a nonhomogeneous
and hyperechoic, sharply demarcated zone. A real-time US survey of the sutural
expansion was performed in all 29 patients. The duration of the study was
approximately 3 min.

14. Pre-expansion, the median palatin suture appears on occlusal radiographs
as a thin radiolucent line in the midline between the two portions of the
premaxilla. It extends from the alveolar crest between the central incisors
superiorly through the anterior nasal spin and continues posteriorly between
the maxillary palatin processes to the posterior aspect of the hard palate. The
suture is limited by two parallel radiopaque borders of thin cortical bone on
each side of the maxilla. US cannot be used to evaluate the sutural opening
at this stage due to the presence of intact and thick vestibular cortical bone,
which reflects ultrasound beams, making it impossible for the beams to
penetrate the bone structure.

15. AT THE BEGINNING OF THE TREATMENT (T1)

17. During the RPE period, as patients turn the screw, the midpalatal suture is
opened and appears on occlusal radiographs as a thick radiolucent line in the
midline between the two portions of the maxilla. The thickness of the
radiolucent line increases over time. Likewise, on the US examination, this
structure appears as a hyperechoic line because the ultrasound beam is not
reflected and can easily penetrate the expansion gap.

18. AT THE 10th DAY OF TREATMENT (T2)

20. AT THE 20th DAY OF TREATMENT (T3)

22. The US and occclusal radiography findings were comparable
with regard to the assessment of the sutural opening at the
beginning, 10th, and 20th days of the expansion period.

23. In the current study, US was used to assess the midpalatal suture in patients
undergoing RPE. To the best of our knowledge, there are no published
quantitative or semiquantitative sonographic comparisons of sutural expansion
with oral radiographies and US in RPE patients. US was used in one study of
three surgically assisted RPE patients, where it proved accurate in the
measurement of the gap across the osteotomy and in the evaluation of callus
formation. In that study, which is similar to our evaluation, callus formation was
examined after expansion. In contrast, we compared US findings of midpalatal
sutural expansion during the active RPE period with those of radiographic
examinations.

24. Conclusion
US is an easy-to-use, inexpensive tool that can provide accurate information
on midpalatal sutural expansion in patients undergoing RPE. In the present
study, the accuracy of US was as high as that of radiography in the
determination of sutural expansion. A major advantage of US is that it is a real-time
imaging tool with no ionizing radiation.

25. Thank you for your attention ....