ultrasonographic eveluation of rapid palatal expansion zone
DESCRIPTION
Rapid palatal expansion zone is eveluated by ultrasonography in this study.TRANSCRIPT
Ibrahim Sevki BayrakdarIsmail Gumussoy
Ozkan MilogluYasin Yasa
COMPARATIVE EVALUATION OF THE RAPID PALATAL EXPANSION ZONE USING ULTRASONOGRAPHY AND
CONVENTIONAL RADIOGRAPHYDepartment of Oral Diagnosis and Dentomaxillofacial Radiology, ERZURUM
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.
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.
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.
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.
Methods and materials
2-banded Haas appliance
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.
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.
Radiographic examination
technique
Radiographic examination technique
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
Ultrasound scanning technique
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.
Radiological 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.
Ultrasonography evaluation
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.
AT THE BEGINNING OF THE TREATMENT (T1)
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.
AT THE 10th DAY OF TREATMENT (T2)
AT THE 20th DAY OF TREATMENT (T3)
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.
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.
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.
Conclusion
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