Changes in the midpalatal and pterygopalatine sutures induced by micro-implant-supported skeletal expander, analyzed with a novel 3D method based on CBCT imaging

Abstract

BackgroundMini-implant-assisted rapid palatal expansion (MARPE) appliances have been developed with the aim to enhance the orthopedic effect induced by rapid maxillary expansion (RME). Maxillary Skeletal Expander (MSE) is a particular type of MARPE appliance characterized by the presence of four mini-implants positioned in the posterior part of the palate with bi-cortical engagement. The aim of the present study is to evaluate the MSE effects on the midpalatal and pterygopalatine sutures in late adolescents, using high-resolution CBCT. Specific aims are to define the magnitude and sagittal parallelism of midpalatal suture opening, to measure the extent of transverse asymmetry of split, and to illustrate the possibility of splitting the pterygopalatine suture.MethodsFifteen subjects (mean age of 17.2 years; range, 13.9–26.2 years) were treated with MSE. Pre- and post-treatment CBCT exams were taken and superimposed. A novel methodology based on three new reference planes was utilized to analyze the sutural changes. Parameters were compared from pre- to post-treatment and between genders non-parametrically using the Wilcoxon sign rank test. For the frequency of openings in the lower part of the pterygopalatine suture, the Fisher’s exact test was used.ResultsRegarding the magnitude of midpalatal suture opening, the split at anterior nasal spine (ANS) and at posterior nasal spine (PNS) was 4.8 and 4.3 mm, respectively. The amount of split at PNS was 90% of that at ANS, showing that the opening of the midpalatal suture was almost perfectly parallel antero-posteriorly. On average, one half of the anterior nasal spine (ANS) moved more than the contralateral one by 1.1 mm. Openings between the lateral and medial plates of the pterygoid process were detectable in 53% of the sutures (P < 0.05). No significant differences were found in the magnitude and frequency of suture opening between males and females. Correlation between age and suture opening was negligible (R 2 range, 0.3–4.2%).ConclusionsMidpalatal suture was successfully split by MSE in late adolescents, and the opening was almost perfectly parallel in a sagittal direction. Regarding the extent of transverse asymmetry of the split, on average one half of ANS moved more than the contralateral one by 1.1 mm. Pterygopalatine suture was split in its lower region by MSE, as the pyramidal process was pulled out from the pterygoid process. Patient gender and age had a negligible influence on suture opening for the age group considered in the study.

Asymmetric nasomaxillary expansion induced by tooth‐bone‐borne expander producing differential craniofacial changes

“…The borders of the midpalatal suture and midsagittal bony landmarks become difficult to be clearly defined over time after expansion due to the immediate surface remodeling and consequent CBCT image blurring . Second, the midpalatal suture was not always fully separated from the ANS to the PNS, in consistence with previous systematic review reporting 14.2% partial separation from the ANS to the transverse palatal suture . Third, irregular splits of some parts of circum‐maxillary sutures may be combined with asymmetric expansion, irrespective of the symmetry of midpalatal split .…”

“…To determine the symmetry of maxillary expansion, we utilized the right‐left difference of lateral expansion at the level of anterolateral maxillary walls instead of the symmetry of the midpalatal split for several reasons. First, the method of measuring the borders of separated midpalatal suture was highly time‐dependent and skill‐sensitive . The borders of the midpalatal suture and midsagittal bony landmarks become difficult to be clearly defined over time after expansion due to the immediate surface remodeling and consequent CBCT image blurring .…”

“…The chin deviation was evaluated based on 3 mm or more distance between point 18 and midsagittal plane. Utilizing the Fusion module of the OnDemand3DTM software, T1 and T2 volume‐rendered images were superimposed by using the stable anatomical structures of the whole anterior cranial base, based on the voxel grey scale . The 3D‐coordinated superimposition system was constructed by common X, Y and Z planes with the zero point (0, 0, and 0) at the nasion (Figure E).…”

“…Asymmetric nasomaxillary expansion may occur with TBB‐RPE, producing different craniofacial changes from symmetric expansion. Primarily, one‐half of the separated maxilla may move more than the contralateral one, resulting in asymmetric palatal expansion . Even with symmetrical midpalatal separation, incomplete midpalatal sutural split may be combined with unilateral transpalatal sutural split, creating palatal arch distortion.…”

<p>A New Methodology for the Digital Planning of Micro-Implant-Supported Maxillary Skeletal Expansion</p>

“…In addition, MARPE devices are used in association with the facemask to enhance the maxillary protraction, especially in patients older than 8-9 years of age. [17][18][19][20] The present paper aims to describe a novel procedure to position a particular type of MARPE appliance, the Maxillary Skeletal Expander (MSE), [20][21][22][23][24][25][26] in the patient's oral cavity through digital planning and workflow.…”