Hounsfield Units: a new indicator showing maxillary resistance in rapid maxillary expansion cases?
OBJECTIVE
To determine if density measurements of several maxillary regions in Hounsfield Units (HU) and outcomes of rapid maxillary expansion (RME) are correlated. Is correlation powerful enough to give us direct information about maxillary resistance to RME?


METHODS
Twenty-two computed tomographic (CT) scans (14 years) are used in this archive study. Two CT records were collected, one before RME (T1) and one after 3 months of retention period (T2). Maxillary measurements were made using dental and skeletal landmarks in first molar and first premolar slides to measure the effects of RME. Density of midpalatal suture (MPSD) and segments of maxillary bone is measured in HU at T1. Correlation analysis was conducted between density measurements and maxillary variables. Regression analysis was then performed for variables that showed positive correlation.


RESULTS
There was no correlation between density and skeletal measurements. Intermolar angle (ImA) in molar slice showed statistically significant correlation with density measurements. The ImA variable showed the highest correlation with MPSD in frontal section (r  =  0.669, P < .01).


CONCLUSIONS
There is correlation of 32.1-43.3% between density measurements and ImA increase. Our density measurements explain a certain percentage of ImA increase, but density is not the only and definitive indicator of changes after RME.
a  Resident, Department of Orthodontics, School of Dentistry, University of Marmara, Istanbul, Turkey.
Yasemin Bahar
YB
Acar
Melih
M
Motro
A Nejat
AN
Erverdi
D000293:Adolescent; D000465:Algorithms; D000539:Alveolar Process / Q000000981:diagnostic imaging; D059925:Anatomic Landmarks / Q000000981:diagnostic imaging; D001641:Bicuspid / Q000000981:diagnostic imaging; D015519:Bone Density / Q000502:physiology*; D002648:Child; D003393:Cranial Sutures / Q000000981:diagnostic imaging; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008297:Male; D008310:Malocclusion / Q000628:therapy; D008437:Maxilla / Q000000981:diagnostic imaging*; D008963:Molar / Q000000981:diagnostic imaging; D009295:Nasal Bone / Q000000981:diagnostic imaging; D016382:Orthodontic Appliance Design; D010155:Palatal Expansion Technique / Q000295:instrumentation; D010159:Palate / Q000000981:diagnostic imaging; D012189:Retrospective Studies; D014057:Tomography, X-Ray Computed / Q000379:methods; D019227:Tooth Apex / Q000000981:diagnostic imaging; D019228:Tooth Crown / Q000000981:diagnostic imaging; D016896:Treatment Outcome
Hounsfield Units; Rapid maxillary expansion; Suture density