Preliminary cone-beam computed tomography study evaluating dental and skeletal changes after treatment with a mandibular Schwarz appliance.
BACKGROUND
The purpose of this study was to evaluate the efficacy of the Schwarz appliance with a new method of superimposing detailed cone-beam computed tomography (CBCT) images.


METHODS
The subjects were 28 patients with Angle Class I molar relationships and crowding; they were randomly divided into 2 groups: 14 expanded and 14 nonexpanded patients. Three-dimensional Rugle CBCT software (Medic Engineering, Kyoto, Japan) was used to measure 10 reference points before treatment (T0) and during the retention period of approximately 9 months after 6 to 12 months of expansion (T1). Cephalometric and cast measurements were used to evaluate the treatments in both groups. Also, the mandibular widths of both groups were measured along an axial plane at 2 levels below the cementoenamel junction from a CBCT scan. Differences between the 2 groups at T0 and T1 were analyzed by using the Mann-Whitney U test.


RESULTS
The dental arch (including tooth root apices) had expanded; however, alveolar bone expansion was only up to 2 mm below the cementoenamel junction. There was a statistically significant (P <0.05) difference between the groups in terms of crown, cementoenamel junction, root, and upper alveolar process. However, no significant (P >0.05) differences were observed in the interwidths of the mandibular body, zygomatic bones, condylar heads, or mandibular antegonial notches. In the mandibular cast measurements, arch crowding and arch perimeter showed statistically significant changes in the expanded group. The buccal mandibular width and lingual mandibular width values had significant changes as measured from a point 2 mm below the cementoenamel junction.


CONCLUSIONS
The findings suggest that the Schwarz appliance primarily affected the dentoalveolar complex, but it had little effect on either the mandibular body or any associated structures. In addition, the molar center of rotation was observed to be below the root apex.
Tai
Kiyoshi
K
A. T. Still University, Mesa, Arizona 85206, USA.
Hotokezaka
Hitoshi
H
Park
Jae Hyun
JH
Tai
Hisako
H
Miyajima
Kuniaki
K
Choi
Matthew
M
Kai
Lisa M
LM
Mishima
Katsuaki
K
D000539:Alveolar Process / Q000000981:diagnostic imaging; D002508:Cephalometry / Q000379:methods*; D002648:Child; D054893:Cone-Beam Computed Tomography / Q000379:methods*; D003724:Dental Arch / Q000000981:diagnostic imaging; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods; D021621:Imaging, Three-Dimensional / Q000379:methods; D008297:Male; D008311:Malocclusion, Angle Class I / Q000000981:diagnostic imaging / Q000628:therapy*; D008334:Mandible / Q000000981:diagnostic imaging*; D008335:Mandibular Condyle / Q000000981:diagnostic imaging; D008437:Maxilla / Q000000981:diagnostic imaging; D008963:Molar / Q000000981:diagnostic imaging; D016382:Orthodontic Appliance Design; D009967:Orthodontic Appliances; D010155:Palatal Expansion Technique; D019227:Tooth Apex / Q000000981:diagnostic imaging; D019237:Tooth Cervix / Q000000981:diagnostic imaging; D019228:Tooth Crown / Q000000981:diagnostic imaging; D014092:Tooth Root / Q000000981:diagnostic imaging; D016896:Treatment Outcome; D015050:Zygoma / Q000000981:diagnostic imaging