Assessment of Palatine Suture Maturation By “Black Bone” Rmi-A Preliminary Feasibility Study

Transverse maxillary deficiency is a common orthodontic problem and is often accompanied by unilateral or bilateral posterior crossbite and dental crowding [1]. The best time to do the palatal expansión is in the anterior phase or during adolescence [2-7], since after this phase theremay be a need for a complementary surgery [8] to weaken the bony bases, allowing the expansion.The most common approach is the use of a tooth-supported expander, with or without acrylic [9,10]. Some undesirable effects related to the age are: exaggerated inclination of the posterior teeth and lack of expansion of the middle third of the faceas a result of the palatine and maxillary sutures ossification [3].

The ossification of the medial palatine suture starts from the palatine part and extends to the incisive foramen showing histological and radiographic changes [11]. The knowledge of the mat uration stage of the medial palatine suture has great importance for the success of the palatine disjunction so that the verification of local conditions can only be done by imaging methods.The ideal pattern for studying the effects of palatine disjunction is concomitant computed tomography, since the morphological aspects and even the volume of the structures before and after the procedure can be evaluated [12,13].

Recently, a method of prognosis of palatal disjunction was described by the evaluation of ossification stages in concomitant computed tomography scans that help predict the success of this operation [14]. Despite the practicality and lower costs, the use of ionizing radiation in tomographies has been questioned by orthodontists [15] and the possibility of evaluating images of the ossification of the median palatine suture using nuclear magnetic resonance seems a promising field.The soft part of the sutures is formed by a layer of vascularized connective tissue that diverges from the calcified cortical of the bones that compose it. The relaxation times of these tissues in T1 and T2 produce the necessary contrast in the generated images [16], through the off-line post-processing in workstation of the previously obtained images of these patients.

Recently, a new regimen of examination has been described [17] in order to shorten the time and accentuate the contrast between skull sutures and other structures [18], called Black Bone RMI. There gimen in question allows the suppression of the sign of fat and wáter present in soft tissues and accentuates the visualization of the cortical bone, which appears in black. In addition, it is not necessary to injectra diological contrast that isinvasive and can be dangerous for some patients. This method allow sthe visualization of pointsused in radio graphic cephalometry [19] and allows the obtaining of 2D and 3D images with ease of accessto the cranial sutures [20] and the acquisition time is small erthan the conventional resonance (around 4minutes), whichis beneficial to the patient, especially in children. Regarding Otorhinolaryngology, the treatment of transversed eficiency seems to have favorable effects in several aspects. Improvement in oral breathing and head posture [21] was verified in children treated with this methodology.

Improvement in hearingloss was verified in children subject to expansión by the influenceon the muscular function of the auditory tube and improvement in themobility of the tympanicmembrane [22]. In addition, other general health benefits of children are related to treatment with palatal expansion, such as improvement of sleepquality and nocturnal enuresis [23-25]. Palatine atresia was present in 72.9% of patients who presented episodes considered to be a risk of death by parents orguardians related to the combination of apnea, color change, muscletone, choking or coughing when compared to another group of transverse consctriction depends on the maturation stage of the median of children who did not had these episodes [26]. Since the treatment palatine suture, which in turn may contribute too to rhinolaryngological treatment, seems important toestablish previously the bestoccasion for its application.

Forth is reason we propose a method of evaluation of the median palatine suture without the use of ionizingradiation that can be used to establish the best moment for the treatment of expansione specially in circumpubertal individuals.The purpose of this research is to evaluate the possibility of using “Black Bone” magnetic resonance imaging for the planning of the palatal disjunction procedure without the use of ionizing radiation from CT.

Patients Ethical approval was granted by the Brazil Educational Association (Associação Educativa do Brasil) Research Ethics Committ (Sao Paulo, Brazil)48278115.8.0000.5141, for MRI examination in patients aged five years and older in whom coventionalface/ cranial base RMI were nedded for other problems than diseases that could interfere in the sutural or bone maturation. Written informed consent from the participants and/or their parents was obtained. Patients who had previously undergone surgery, had completed orthodontic treatment or had fixed orthodontic appliances were excluded. For this time, two volunteers with ages, were selectedby age and sex to match the most approximated mean according to [1,27].

Both convencional and “Black Bone Imaging awere acquiredon a 1.5T magnetressonanse machine (Philiips). Sagittal T1, T2 weighted spin echo and “Black Bone” image swereobtainedwith image acquisitioncentredon the middle axial structur estopermit visualization of the palatine suture.

1. Sagittal T1 SE (includeskull and face)
2. Axial T1 SE 4/1mm (thickness/space): fromthe chin tothe top of the frontal sinus
3. Axial T2 FSE withfatsat 4/1mm (thickness /space): fromthe chin tothe top of the sinus front
4. Coronal T1 4/1mm (thickness /space): fromthe bridge tothe anterior wall of thesinusjaw
5. Coronal T2 FSE withfatsat 4/1mm fromthe bridge tothe anterior wall of thesinusJaw

For “Black Bone” RRMI has been used the followingprotocol:

Repetition time: 8.6ms, Echo Time: 4.2ms, FlipAngle: 5º, Scan FOV: 24cm, PhaseEncode: 256, Frequency Encode: 256, Receive Bandwidth: 31.25,ZIP: 2,512,NEX: 2,ETL: 1,Slicewidth: 2.4mm, Space between slices: 1,2mm.

The mean acquisition time in the conventional in the “Black Bone” protocol was 3.5minutes. Head orientation: Natural head position in all 3 planes of space with the image analysis software cursor positioned at the patient´s midsagital plane in both coronal and axial views, the long axis of the palate horizontal in the sagital view.

The cross-sectional slice was used for sutural assessment after placing the horizontal line of the software along the palate. For subjects with more curved palate the suture was evaluated in two central cross-sectional slices.

Positioning parameters were used to evaluate the axial sections of the maxillary bones, palatine bones and the medial palatine suture.Through the software Radiant DICOM viewer (Mexidant, Poland) the DICOM files were processed for adjusting brightness, contrast and zoom and exported to the Jpeg file format.The images were evaluated by three researchers (RCR, NJCR, BCR) after a calibration for the parameters of interest and the images selected to illustrate the maturation phases. For this purpose the flowchart adapted from [15,28] was used, as can be seen in the flowchart.

At this time two patients could be identified at the center of the mean age and maturation stage of the suture1, both in conventional MRI and in the “Black Bone”.

The Black Bone RMI protocol offers an advantage in relation to the time of acquisition of the conventional protocol and it is not intended to the emission of ionizing radiation from the computed to mography, being a viable alternative to establish the best alternativef or the orthodontic expansion procedure of the palate. Based on this preliminar study. We are know continuing the research to a large patients in different stages and sexes to validate this method.

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